JPH11110807A - Optical head device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical head device which is capable of surely removing an offset component incorporated in a track error signal. SOLUTION: A photodetector for detecting a track-jumping signal, which is applied to this track head device, has a pair of light receiving regions 23a, 23b for detecting the track-jumping signal which are arranged by being away from each other, and simultaneously. A blind region 24 is provided in a region which is irradiated with light beams of a high intensity area, in which all of a 0-order diffracted light beam, a 1st-order diffracted light beam and a -1st- order diffracted light beam among reflected light beams reflected from an optical disk between this pair of light receiving regions are superposed, to remove the offset component incorporated in the track-jumping signal. As a result, the offset component incorporated in the track-jumping signal, i.e., an influence on the track signal by the lens shift is removed. Consequently, the stabilized tracking control is achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical head device for recording information on an optical disk as a recording medium and reproducing information from the optical disk.

[0002]

2. Description of the Related Art An optical disk device includes an optical head device having an objective lens for irradiating a recording surface of an optical disk as a recording medium with a light beam having a cross-sectional beam diameter set to a predetermined size. By irradiating the beam, reflected light corresponding to the information recorded on the optical disk is taken out to reproduce the information.

The above-described optical head device has a semiconductor laser device (hereinafter simply referred to as a laser device) as a light source for generating a light beam and a light beam radiated from the laser device on a recording surface of an optical disk as a recording medium. An objective lens for converging and extracting a reflected light beam reflected by the recording surface, a photodetector for photoelectrically converting the reflected light beam extracted by the objective lens and outputting a reproduction signal corresponding to information recorded on the optical disc; Each element is formed by a plurality of optical members or the like constituting an optical path of a light beam. The optical head device has an objective lens mounted on an actuator (movable part) in order to enable high-speed access, and a laser element, a photodetector, and an optical member forming an optical path are fixed units separated from the actuator. (Fixed part) is widely used.

On the recording surface of the optical disk, a guide groove called a groove is provided so that the condensed spot of the light beam condensed by the objective lens can always follow a predetermined radial position. I have.

In order to always match the center of the condensed spot converged by the objective lens with the center of the groove,
The objective lens is moved in the radial direction of the optical disk by the well-known tracking control.

In this case, the amount by which the objective lens should be moved, that is, the tracking control amount, is determined based on a track error signal obtained using, for example, a known push-pull method.
Is set. In the push-pull method, a light beam reflected and diffracted by a groove is received by a photodetector having a light-sensitive portion divided into two, and photoelectrically converted, and a difference between the photoelectrically converted signals is used as a track error signal. Is a method used as
For example, pages 86 to 88 of "Optical Disk Technology" (Noboru Murayama et al., Radio Technology, 1989) and FIGS.
9 described elsewhere.

[0007]

However, when a track error signal is obtained by using the above-described push-pull method, as described in "Optical Disc Technology", due to the offset component of the track error signal, Even though no tracking error has occurred, there is a problem that a tracking error signal is output as if the tracking error occurred.

That is, when it is necessary to read information at another radial position on the optical disk or to record new information at another radial position, the actuator in which the objective lens is mounted is driven in the radial direction. Further, by appropriately combining and controlling the displacement of the objective lens in the tracking direction, the focused spot is moved at a high speed from the current radial position to the target radial position.

When such control is performed, the center of the objective lens is displaced, so that the light beam reflected and diffracted by the groove of the optical disc has an asymmetric positional relationship with respect to the division line of the photodetector. Light enters the sensing part. Then, a difference occurs between two signal levels obtained by photoelectrically converting the light beam incident on the light receiving unit. This is because the difference signal obtained from the photodetector does not become 0 even though the condensing spot is located at the center of the track to be traced, and as a result, an offset component occurs in the tracking error signal. The shift of the center of the objective lens is called a lens shift.

[0010] Further, the occurrence of such an offset component in the tracking error signal brings about an inconvenience of promoting unstable tracking control. Since the above-described lens shift is caused by moving the actuator at a high speed in the radial direction of the optical disc, it is difficult to substantially eliminate the lens shift from the viewpoint of increasing the speed of reading or writing information. is there. For this reason, there is a problem that the offset component contained in the track shift signal must be reliably removed.

An object of the present invention is to provide an optical head device capable of reliably removing an offset component contained in a track shift signal and obtaining a stable tracking characteristic.

[0012]

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above-mentioned problems. According to the first aspect, a light source for emitting a light beam and a light beam emitted from the light source are recorded on a recording medium. A light condensing unit for condensing light on the recording surface of the recording medium, and a photoelectric conversion unit for converting a reflected light beam reflected and diffracted on the recording surface of the recording medium into an electric signal, wherein the recording medium comprises: A guide groove for guiding a condensed spot obtained by condensing the light beam by the condensing unit in a circumferential direction of the recording medium, wherein the photoelectric conversion unit is condensed by the condensing unit; When the condensed spot obtained by moving the recording medium in the radial direction of the recording medium, the recording medium is substantially orthogonal to the direction in which the reflected light beam reflected by the condensing spot is projected onto the photoelectric conversion means and moves. Do A photoelectric conversion region divided into a plurality of light receiving regions by at least one division line defined in a direction, wherein the first light receiving region is formed of a light beam reflected and diffracted by the guide groove of the recording medium. A light beam mainly containing a part or all of a light beam in which only the zero-order light component and the first-order light component overlap with each other is received, and the second light receiving region is formed of the light beam reflected and diffracted by the recording medium. A light beam mainly containing a part or all of a light beam in which only the zero-order light component and the -1st-order light component overlap is received, and the zero-order light component of the light beam reflected and diffracted by the recording medium is received. An insensitive area that does not receive a light beam is provided in an area where the intensity center is irradiated, a first signal is generated by photoelectrically converting the light beam received in the first light receiving area, and a light beam received in the second light receiving area To the second signal Is generated, and the difference signal between the first signal and the second signal is matched with the center of the guide groove formed in advance on the recording surface of the recording medium and the center of the light beam passing through the light condensing means. An optical head device is provided, wherein the optical head device is used as a track error signal used for tracking control for moving the light condensing means in a direction crossing the guide groove in order to cause the light to converge.

According to the second aspect, the light source for emitting the light beam, the light condensing means for condensing the light beam emitted from the light source on the recording surface of the recording medium, and the reflection and reflection on the recording surface of the recording medium. A photoelectric conversion unit that converts the diffracted reflected light beam into an electric signal, wherein the recording medium records the condensed spot obtained by condensing the light beam by the condensing unit. A guide groove for guiding the recording medium in a circumferential direction, wherein the photoelectric conversion unit is configured to perform the recording when a condensed spot obtained by being condensed by the condensing unit moves in a radial direction of the recording medium. The medium is divided into a plurality of light receiving areas by at least one division line defined in a direction substantially orthogonal to a direction in which a reflected light beam reflected by the condensing spot is projected onto the photoelectric conversion means and moves. The first light receiving region is a part of a light beam in which only the zero-order light component and the primary light component of the light beam reflected and diffracted by the guide groove of the recording medium overlap or The second light receiving region receives a light beam mainly including all of the light beam, and the second light receiving region is a part of the light beam in which only the 0th-order light component and the -1st-order light component of the light beam reflected and diffracted by the recording medium overlap. Alternatively, the first light receiving region and the second light
The 0th-order light component, the 1st-order light component, and -1 of the light beam reflected and diffracted by the recording medium between the light receiving region and the light receiving region.
An insensitive area for receiving no light beam is provided in an area where the next light component overlaps, a first signal is generated by photoelectrically converting the light beam received in the first light receiving area, and a light beam received in the second light receiving area To generate a second signal, and passes a difference signal between the first signal and the second signal through the center of a guide groove formed in advance on a recording surface of the recording medium and the light condensing means. An optical head device is provided, wherein the optical head device is a track error signal used for tracking control for moving the condensing means in a direction crossing the guide groove so as to match the center of the light beam.

According to the third aspect, a light source for emitting a light beam, a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium, and a light source for reflecting and reflecting the light beam on the recording surface of the recording medium A photoelectric conversion unit that converts the diffracted reflected light beam into an electric signal, wherein the recording medium records the condensed spot obtained by condensing the light beam by the condensing unit. A guide groove for guiding the recording medium in a circumferential direction, wherein the photoelectric conversion unit is configured to perform the recording when a condensed spot obtained by being condensed by the condensing unit moves in a radial direction of the recording medium. The medium is divided by at least one division line defined in a direction substantially orthogonal to the direction in which the reflected light beam reflected from the condensing spot is projected onto the photoelectric conversion means and moves. A pair of first and second light receiving regions arranged at intervals corresponding to a region irradiated with the intensity center of the zero-order light component of the light beam reflected and diffracted by the guide groove of the recording medium is formed. And the first light receiving region has 0 of light beams reflected and diffracted by the recording medium.
A light beam mainly composed of a part or all of a light beam in which only the primary light component and the primary light component overlap is received, and the second light receiving region is provided with a light beam reflected by the recording medium and diffracted by 0%. A light beam mainly containing a part or all of a light beam in which only the first light component and the minus first light component overlap is received, and the light beam received in the first light receiving region is photoelectrically converted to generate a first signal. The light beam received by the second light receiving area is photoelectrically converted to generate a second signal, and a difference signal between the first signal and the second signal is formed in advance on a recording surface of the recording medium. A track error signal used for tracking control for moving the light condensing means in a direction crossing the guide groove so that the center of the guide groove and the center of the light beam passing through the light condensing means coincide with each other. Optical head device provided That.

According to the fourth aspect, a light source for emitting a light beam, a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium, and a light source for reflecting and reflecting the light beam on the recording surface of the recording medium A photoelectric conversion unit that converts the diffracted reflected light beam into an electric signal, wherein the recording medium records the condensed spot obtained by condensing the light beam by the condensing unit. A guide groove for guiding the recording medium in a circumferential direction, wherein the photoelectric conversion unit is configured to control the recording medium when a condensed spot obtained by being converged by the condensing unit moves in a radial direction of the recording medium. Is divided into a plurality of light receiving areas by at least one division line defined in a direction substantially orthogonal to a direction in which a reflected light beam reflected by the condensing spot is projected on the photoelectric conversion means and moves. The first light receiving region is a part of a light beam in which only the zero-order light component and the primary light component of the light beam reflected and diffracted by the guide groove of the recording medium overlap or The second light receiving region receives a light beam mainly including all of the light beam, and the second light receiving region is a part of the light beam in which only the 0th-order light component and the -1st-order light component of the light beam reflected and diffracted by the recording medium overlap. Or receive a light beam having a major component as a main component, and provide a dead area that does not receive the light beam in a region where the intensity center of the zero-order light component of the light beam reflected and diffracted by the recording medium is irradiated, A first signal is generated by photoelectrically converting the light beam received by the first light receiving region, a second signal is generated by photoelectrically converting the light beam received by the second light receiving region, and the first signal is generated. And the second signal are the signals of the respective signals. L1 and L2, (L1−L2) pp is the maximum value of the amplitude of the difference signal between the first signal and the second signal, (L1 + L2) a is the area where the information on the recording surface is not recorded, and Assuming that the sum signal of the first signal and the second signal for the reflected light beam reflected from the area where the guide groove is not formed is 0.35 ≦ [(L1−L2) pp / (L1 + L2) )
a], [(L1-L2) pp / (L1 + L2) a] ≦ 1.05, and [(L1-L2) / (L1 + L)
2)] When pp is the maximum value of the amplitude obtained by dividing the instantaneous value of the signal level (L1−L2) by the instantaneous value of the signal level (L1 + L2) regardless of the presence or absence of information on the recording surface. 1.10 ≦ [(L1−L2) / (L1 + L2)] pp, [(L1−L2) / (L1 + L2)] pp ≦ 1.65, and [(L1−L2) / (L1 + L2) ]
[(L1-L2) / (L1 + L) indicating the maximum value of pp
2)] ppmax and [(L1-L2) / (L1 + L
2)] The minimum value of pp [(L1−L2) / (L1 +
L2)] ppmin, [(L1-L2) / (L1 + L2)] ppmin /
[(L1-L2) / (L1 + L2)] ppmax ≧ 0.
70, the difference signal between the first signal and the second signal is used to match the center of the guide groove formed in advance on the recording surface of the recording medium with the center of the light beam passing through the light condensing means. An optical head device is provided, wherein the optical head device is a track error signal used for tracking control for moving the light condensing means in a direction crossing the guide groove.

According to claim 5, the wavelength is approximately 650 nm.
With a light source that emits a light beam and a numerical aperture of approximately 0.6,
Lens means for condensing a light beam emitted from the light source on a recording surface of a recording medium; and photoelectric conversion means for converting a reflected light beam reflected and diffracted on the recording surface of the recording medium into an electric signal. In the optical head device, the recording medium includes a guide groove having a spiral shape or a plurality of concentric circles whose center-to-center distance is substantially set to 1.48 μm,
Information can be recorded substantially at the center of the guide groove or between the guide grooves, and the photoelectric conversion unit is configured to: when a condensed spot obtained by being converged by the lens unit moves in a radial direction of the recording medium, The recording medium is divided into a plurality of light receiving regions by at least one division line defined in a direction substantially orthogonal to a direction in which the reflected light beam reflecting the condensed spot is projected onto the photoelectric conversion means and moves. A light beam having a photoelectric conversion region and having as a main component a part or all of a light beam in which only the zero-order light component and the primary light component of the light beam reflected and diffracted by the guide groove of the recording medium overlap; A first signal is generated by photoelectrically converting the beam, and a part or all of the light beam in which only the 0th-order light component and the -1st-order light component of the light beam reflected and diffracted by the recording medium overlap. A second signal is generated by photoelectrically converting the light beam as a main component, and the light beam is received in a region where the intensity center of the zero-order light component of the light beam reflected and diffracted by the recording medium is irradiated. An insensitive area is provided, and the difference signal between the first signal and the second signal is converted into a center of a guide groove formed in advance on a recording surface of the recording medium and a center of a light beam passing through the light condensing means. The optical head device is provided with a track error signal used for tracking control for moving the light condensing means in a direction crossing the guide groove in order to match.

According to the sixth aspect, a light source for emitting a light beam, a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium, and a light source for reflecting and reflecting the light beam on the recording surface of the recording medium A photoelectric conversion unit that converts the diffracted reflected light beam into an electric signal, wherein the recording medium records the condensed spot obtained by condensing the light beam by the condensing unit. A guide groove for guiding the recording medium in a circumferential direction, wherein the photoelectric conversion unit is configured to perform the recording when a condensed spot obtained by being condensed by the condensing unit moves in a radial direction of the recording medium. The medium is divided into a plurality of light receiving areas by at least one division line defined in a direction substantially orthogonal to a direction in which a reflected light beam reflected by the condensing spot is projected onto the photoelectric conversion means and moves. The first light receiving region is a part of a light beam in which only the zero-order light component and the primary light component of the light beam reflected and diffracted by the guide groove of the recording medium overlap or The second light receiving region receives a light beam mainly including all of the light beam, and the second light receiving region is a part of the light beam in which only the 0th-order light component and the -1st-order light component of the light beam reflected and diffracted by the recording medium overlap. Or receive a light beam having a major component as a main component, and provide a dead area that does not receive the light beam in a region where the intensity center of the zero-order light component of the light beam reflected and diffracted by the recording medium is irradiated, The light beam received by the first light receiving area is photoelectrically converted to generate a first signal, and the light beam received by the second light receiving area is photoelectrically converted to generate a second signal. With the center of the guide groove pre-formed The gain of at least one of the first signal and the second signal is adjusted so that the signal level of the first signal and the signal level of the second signal match when the center of the light beam that has passed through the light condensing means matches. Adjusting the difference signal between the first signal and the second signal whose gain has been adjusted, by using the light collecting means to match the center of the guide groove with the center of the light beam passing through the light collecting means. An optical head device is provided, which is used as a track error signal used for tracking control for moving in a direction crossing a guide groove.

According to claim 7, a light source for emitting a light beam, a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium, and a light source for reflecting and reflecting the light beam on the recording surface of the recording medium. A photoelectric conversion unit that converts the diffracted reflected light beam into an electric signal, wherein the recording medium records the condensed spot obtained by condensing the light beam by the condensing unit. A guide groove for guiding the recording medium in a circumferential direction, wherein the photoelectric conversion unit is configured to perform the recording when a condensed spot obtained by being condensed by the condensing unit moves in a radial direction of the recording medium. The medium is divided into a plurality of light receiving areas by at least one division line defined in a direction substantially orthogonal to a direction in which a reflected light beam reflected by the condensing spot is projected onto the photoelectric conversion means and moves. The first light receiving region is a part of a light beam in which only the zero-order light component and the primary light component of the light beam reflected and diffracted by the guide groove of the recording medium overlap or The second light receiving region receives a light beam mainly including all of the light beam, and the second light receiving region is a part of the light beam in which only the 0th-order light component and the -1st-order light component of the light beam reflected and diffracted by the recording medium overlap. Alternatively, the third light receiving region receives the light beam mainly composed of all the light beams, and the third light receiving region receives the intensity center of the zero-order light component of the light beam reflected and diffracted by the recording medium, and A first signal is generated by photoelectrically converting the received light beam, and a second signal is generated by photoelectrically converting the light beam received by the second light receiving region;
The difference signal between the first signal and the second signal is used to match the center of a guide groove formed in advance on the recording surface of the recording medium with the center of a light beam that has passed through the light collecting means. An optical head device for generating an information signal by performing a photoelectric conversion of a light beam received by the third light receiving area as a track error signal used for tracking control for moving a light condensing means in a direction crossing the guide groove; Is provided.

According to the eighth aspect, a light source for emitting a light beam, a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium, and a light source for reflecting and reflecting the light beam on the recording surface of the recording medium. A photoelectric conversion unit that converts the diffracted reflected light beam into an electric signal, wherein the recording medium records the condensed spot obtained by condensing the light beam by the condensing unit. A guide groove for guiding the recording medium in a circumferential direction, wherein the photoelectric conversion unit is configured to perform the recording when a condensed spot obtained by being condensed by the condensing unit moves in a radial direction of the recording medium. The medium is divided by at least one division line defined in a direction substantially orthogonal to the direction in which the reflected light beam reflected from the condensing spot is projected onto the photoelectric conversion means and moves. A pair of first and second light receiving regions disposed at intervals corresponding to a region irradiated with the intensity center of the zero-order light component of the light beam reflected and diffracted by the guide groove of the recording medium; , The pair of first and second
A third light receiving area disposed between the light receiving areas;
The light receiving area receives a light beam mainly composed of a part or all of a light beam in which only the zero-order light component and the primary light component of the light beam reflected and diffracted by the recording medium overlap, The light receiving region receives a light beam mainly composed of a part or all of a light beam in which only the 0th-order light component and the -1st-order light component of the light beam reflected and diffracted by the recording medium overlap, The third light receiving area receives the intensity center of the zero-order light component of the light beam reflected and diffracted by the recording medium, and photoelectrically converts the light beam received by the first light receiving area to generate a first signal. A second signal is generated by photoelectrically converting the generated light beam received by the second light receiving area to generate a second signal, and a difference signal between the first signal and the second signal is formed in advance on a recording surface of the recording medium. Of light passing through the center of the guide groove The track error signal used for tracking control for moving in a direction transverse to the guiding groove of the focusing means in order to match the center of the over arm, the third
An optical head device is provided, wherein an information signal is generated by photoelectrically converting a light beam received in a light receiving region.

According to the ninth aspect, a light source for emitting a light beam, a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium, and a light source for reflecting and reflecting the light beam on the recording surface of the recording medium. A photoelectric conversion unit that converts the diffracted reflected light beam into an electric signal, wherein the recording medium records the condensed spot obtained by condensing the light beam by the condensing unit. A guide groove for guiding the recording medium in a circumferential direction, wherein the photoelectric conversion unit is configured to perform the recording when a condensed spot obtained by being condensed by the condensing unit moves in a radial direction of the recording medium. The medium is divided into a plurality of light receiving areas by at least one division line defined in a direction substantially orthogonal to a direction in which a reflected light beam reflected by the condensing spot is projected onto the photoelectric conversion means and moves. The first light receiving region is a part of a light beam in which only the zero-order light component and the primary light component of the light beam reflected and diffracted by the guide groove of the recording medium overlap or The second light receiving region receives a light beam mainly including all of the light beam, and the second light receiving region is a part of the light beam in which only the 0th-order light component and the -1st-order light component of the light beam reflected and diffracted by the recording medium overlap. Alternatively, the third light receiving region receives the light beam mainly composed of all the light beams, and the third light receiving region receives the intensity center of the zero-order light component of the light beam reflected and diffracted by the recording medium, and A first signal is generated by photoelectrically converting the received light beam, and a second signal is generated by photoelectrically converting the light beam received by the second light receiving region;
The signal levels of the first signal and the second signal match when the center of the guide groove formed in advance on the recording surface of the recording medium matches the center of the light beam that has passed through the condensing means. Adjusting the gain of at least one of the first signal and the second signal, and adjusting the gain of the first signal.
Tracking control for moving a difference signal between a signal and the second signal so that the center of the guide groove coincides with the center of a light beam passing through the light collecting means in a direction crossing the guide groove. Track error signal used for
An optical head device is provided, wherein an information signal is generated by photoelectrically converting a light beam received by the third light receiving region.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the optical head device according to the present invention will be described below in detail with reference to the drawings. First, an optical head device according to the first embodiment will be described.

FIG. 1 is a block diagram schematically illustrating an optical disk device in which an optical head device according to an embodiment of the present invention is incorporated. As shown in FIG. 1, an optical disk device 1 includes an optical head device 3 that records information on a recording surface of an optical disk D as a recording medium or reads information already recorded on the recording surface, and an optical head device 3. A signal processor 5 for transmitting a signal corresponding to information to be recorded toward the optical head and converting the information read by the optical head device 3 into an electric signal; and rotating the optical head device 3 and the optical disk D at a predetermined speed. Control section 9 for controlling motor 7
And An external device 99 such as a host computer is connected to the signal processing unit 5 via an interface (not shown).

In FIG. 1, the optical head device 3 transmits and receives electric signals to and from the signal processing unit 5 while controlling the irradiation position of the light beam irradiating the optical disc D by the control signal from the control unit 9. A light beam is exchanged with the optical disc D.

The signal processing unit 5 converts information read from the optical disk D by the optical head device 3 into an electric signal based on an instruction from the external device 99, and reproduces the information as recorded information. A recording signal is generated to make the information to be recorded correspond to the change in the light intensity of the light beam emitted from the optical head device 3.

The controller 9 controls the light intensity of the light beam emitted from the optical head device 3 to the optical disk D, the position of the light beam on the optical disk, the rotation speed of the optical disk D rotated by the motor 7, and the like.

Hereinafter, the operation of the optical disk apparatus 1 shown in FIG. 1 will be briefly described. First, the signal processing unit 5 is connected to the external device 9.
9 for reproducing or recording information on the optical disk D.

Based on the command signal, the signal processing unit 5
Exchanges electrical signals with the optical head device 3 and transmits control signals to the control unit 9. Based on the transmitted control signal, the control unit 9 controls the irradiation position of the light beam on the optical disc D irradiated by the optical head device 3 and the rotation speed of the motor 7.

As described above, the optical head device 3 transmits and receives a light beam to and from the optical disk D based on the electric signal exchanged with the signal processing unit 5 under the control of the control unit 9. To reproduce or record information.

When the information is reproduced or recorded, the optical head device 3 obtains an electric signal corresponding to the information recorded on the optical disk D and the information on the light beam irradiation position, and converts the electric signal into a signal processing unit. 5 is transmitted.

The signal processing unit 5 sends a control signal for changing the position of the optical head device 3 to the control unit 9 based on the electric signal corresponding to the information on the irradiation position of the light beam from the electric signal. After performing processing such as decoding on the electric signal corresponding to the recorded information, the processed electric signal (reproduced signal) is transmitted to the external device 99.

The external device 99 receiving the reproduction signal from the signal processing unit 5 refers to the reproduction signal and
Then, the instruction signal as the next instruction is transmitted to the signal processing unit 5 again.

The optical disk device 1 reproduces information recorded on the optical disk D or records information on the optical disk D by repeating a series of operations as described above. Next, the structure of the optical head device 3 will be described with reference to FIGS.

As shown in FIG. 2, the optical head device 3
Are a laser light emitting / receiving unit (hereinafter, referred to as a fixed optical system) 3a fixed on the base 31 and a fixed optical system 3a
And an actuator 3b for irradiating the recording surface of the optical disk D with the laser beam from the optical disk D and guiding the reflected laser beam reflected on the recording surface of the optical disk D again to the fixed optical system 3a. The actuator 3b includes, as shown in FIG. 3, a carriage 33 movably formed on a pair of guide rails 32, 32 extending in the radial direction of the optical disc D, and is integrally formed with the carriage 33. The guide rails 32, 34 are formed by a pair of radial drive coils 34, 34 and a magnetic field supplied from a magnetic field supply mechanism (not shown).
32 is formed so as to be movable in the radial direction of the optical disc D.

The fixed optical system 3a has a housing 10 made of, for example, aluminum, as shown in FIG. At one end of the housing 10, a laser element (semiconductor laser) 11 for generating a laser beam of a predetermined wavelength, for example, approximately 650 nanometers (hereinafter referred to as nm) is provided.
Has been fixed.

The divergent laser beam Rf is emitted in the direction in which the laser beam Rf emitted from the semiconductor laser 11 travels.
A collimator lens 12 for collimating f is arranged.

In the direction in which the laser beam Rf collimated by the collimator lens 12 is guided, the cross-sectional beam shape of the laser beam Rf emitted in an ellipse is changed from an ellipse to a circle in relation to an aspect ratio specific to the laser beam Rf. An elliptical correction prism 13 to be corrected and a laser beam Rf formed integrally with the elliptical correction prism 13 and having a substantially circular cross-sectional shape are passed toward the actuator 3b, that is, the optical disk D, and are reflected by a recording surface (not shown) of the optical disk D. A beam splitter 14 for separating the reflected laser beam Rr from the laser beam Rf heading for the optical disc D, and changing the direction of the polarization plane of the laser beam Rf passed through the beam splitter 14 and directed to the actuator 3b from linearly polarized light to circularly polarized light. Convert and anti-disc on optical disc D By direction of the polarization direction of the polarization plane of the reflected laser beam Rr from circular polarization to the direction of the plane of polarization of the laser beam Rf directed to actuator 3b is 9
A λ / 4 plate (phase delay plate) 15 for converting into linearly polarized light rotated by 0 ° is arranged in order. Note that the beam splitter 14 is a polarization beam splitter.

The optical disk D by the beam splitter 14
The reflected laser beam Rr separated from the laser beam Rf toward
With two further reflected laser beams Rra and Rrb
Half-mirror type beam splitter 16
Is arranged.

In the direction in which one of the two reflected laser beams Rra split by the beam splitter 16 is guided, a converging lens 17 for giving a predetermined imaging characteristic and convergence to the reflected laser beam Rra is arranged. I have.

In the direction in which the reflected laser beam Rra given convergence and predetermined imaging characteristics by the converging lens 17 travels, the reflected laser beam Rra
Lens 1 for improving aberration due to convergence given to lens
8. Reflected laser beam Rra passed through concave lens 18
Next, a cylindrical lens 19 for providing a predetermined imaging characteristic for detecting a focus shift described later, a reflected laser beam Rra given a predetermined imaging characteristic by the cylindrical lens 19, and the reflected laser beam Rra The photodetectors 20 that output output signals corresponding to the light intensities are arranged in order.

In a direction in which the reflected laser beam Rrb split into two by the beam splitter 16 is guided, a mirror 21 for guiding the reflected laser beam Rrb reflected on the optical disk D in a predetermined direction is arranged.

In the direction in which the reflected laser beam Rrb bent by the mirror 21 travels, a converging lens 22 for giving a predetermined convergence to the reflected laser beam Rrb is arranged.

In the direction in which the reflected laser beam Rrb given a predetermined convergence by the converging lens 22 is guided, a photodetector 23 used for detecting a track shift and an offset amount described later is arranged. I have.

The carriage 33 of the actuator 3b has
As shown in FIG. 5, the laser beam Rf emitted from the fixed optical system 3a after passing through the beam splitter 14 and the λ / 4 plate 15 of the fixed optical system 3a is bent so as to be incident on an objective lens described below. A rising mirror 35 is provided.

The predetermined direction of the recording surface of the optical disc D is set between the rising mirror 35 and the optical disk D in a direction in which the laser beam Rf, which is guided by the rising mirror 35 and bent by approximately 90 ° by the rising mirror 35, is directed. An objective lens 36, which is bent by the rising mirror 35 to converge the laser beam Rf and takes out the reflected laser beam Rr reflected by the recording layer of the optical disc D, is disposed on the recording layer (not shown). The objective lens 36
5 is a guide groove formed in advance in the recording surface of the optical disk D in a direction parallel to the recording surface of the optical disk D described in detail later with reference to FIG. It is movably held in a tracking direction substantially orthogonal to the groove g and a focus direction orthogonal to the recording surface of the optical disc D. The aperture ratio of the objective lens 36 is approximately 0.6 with respect to a wavelength of 650 nm of the laser beam emitted by the semiconductor laser 11.

As shown in FIG. 5, the lens holder 37
Has a bearing portion 37a substantially at the center, and a lens holding surface 37b holding the objective lens 36 on a circumference of a concentric circle having a predetermined radius centered on the bearing portion 37a, and a direction perpendicular to the lens holding surface 37b. A bearing portion 37a is provided on a shaft 39 having a cylindrical surface 37c formed in a partially cut-out cylindrical shape, and extending substantially from the center of a lens holder base 38 fixed at a predetermined position of the carriage 33. By being engaged, it is formed to be rotatable around the shaft 39.

On the cylindrical surface 37c of the lens holder 37, two sets of coils 4 are provided at positions defined so as to divide the outer periphery of the cylindrical surface 37c into approximately four equal parts along the axis passing through the bearing 37a.
0, 40 and 41, 41 are provided.

The lens holder base 38 has an arbitrary radius whose radius is increased as compared with the cylindrical surface 37c of the lens holder 37 with the axis 39 as the center axis, at a position corresponding to the circumference of the concentric circle at one position. A yoke 42 having a notched portion is formed. At a predetermined position on the inner wall of the yoke 42, two sets of magnets 43, 43 and 44, which provide a magnetic field in a predetermined direction toward the cylindrical surface 37c of the lens holder 37,
44 are provided. The magnets 43, 43 are magnetized to have N and S poles in a form that is divided into two by a plane orthogonal to the optical axis of the objective lens 36. The N and S poles are magnetized in such a manner that the N and S poles are divided into two parts by a plane parallel to.

Next, the flow of the laser beam in the optical head device 3 described with reference to FIGS. 2 to 5 will be described. Laser beam R emitted from semiconductor laser 11
f is converted into a parallel light beam by the collimator lens 12, the cross-sectional shape is corrected to a substantially circular shape by the elliptical correction prism 13, and the light passes through the beam splitter 14.

The laser beam Rf transmitted through the beam splitter 14 is converted from linearly polarized light into circularly polarized light by passing through a quarter-wave plate 15, and is emitted toward a rising mirror 35 of the actuator 3b. Is done.

The laser beam Rf guided to the rising mirror 35 is bent by approximately 90 ° by the rising mirror 35 and guided to the objective lens 36 held by the lens holder 37.

The laser beam Rf is guided to the objective lens 36 and converged, and then radiated to the optical disk D as a spot. The reflected laser beam Rr, which is the laser beam Rf applied to the optical disk D and reflected by the guide groove on the recording surface of the optical disk D, that is, the groove g, is returned to the objective lens 36 and the rising mirror 35 in order, and the quarter-wave plate 15
Then, the polarization state is converted from circularly polarized light to linearly polarized light again, and guided to the beam splitter 14. Reflected laser beam Rr
Is rotated by exactly 90 ° with respect to the polarization direction of the original laser beam Rf emitted from the semiconductor laser 11, so that the reflected laser beam Rr
Are now reflected by the polarization plane of the beam splitter 14.

The reflected laser beam Rr separated from the laser beam Rf from the semiconductor laser 11 toward the objective lens 36 by the beam splitter 14 is converted by the beam splitter 16 into two reflected laser beams Rra and Rrb having substantially equal light intensities. Is divided.

The reflected laser beam Rra transmitted through the beam splitter 16 is given predetermined imaging characteristics and convergence by the converging lens 17, then the aberration characteristics are improved by the concave lens 18, and the focus error is detected by the cylindrical lens 19. The photodetector 20 is irradiated with the astigmatism for

The reflected laser beam Rra applied to the photodetector 20 is converted by the photodetector 20 into an electric signal having a magnitude corresponding to the light intensity, and is used as a focus error signal and a reproduction signal. In this example, the detection of the focus error signal is a well-known astigmatism method, and a detailed description thereof will be omitted.

On the basis of the focus error signal generated by the photodetector 20, focus control, that is, focusing, for eliminating a deviation between the focus of the spot converged by the objective lens 36 and the recording surface of the optical disk D in the optical axis direction is performed. You. In focusing, the coils 40, 40 are controlled based on the focus error signal.
Is supplied with a current in a predetermined direction, so that the magnets 43, 4
As a result of the attraction or repulsion due to the electromagnetic interaction with the magnetic field provided by 3, the lens holder 37 (objective lens 36) is moved either in a direction toward or away from the recording surface of the optical disc D.

The remaining reflected laser beam Rrb reflected by the beam splitter 16 passes through the optical path 9
It is bent by 0 °, given a predetermined convergence by the converging lens 22, and guided to a photodetector 23 used for detecting a track shift and an offset amount. In addition,
As described in detail in FIG. 7, the photodetector 23 includes two light receiving regions 23a and 23b arranged at predetermined intervals and symmetrically with respect to the dividing line 23c.

The two light receiving areas 2 of the photo detector 23
Each of the signals photoelectrically converted by 3a and 23b is used for generating a track shift signal by applying a well-known push-pull method, as will be described later in detail with reference to FIG.

A track error signal is generated by the signal processing section shown in FIG. 8 based on the track shift signal generated by the photodetector 23, and the focus of the spot converged by the objective lens 36 and the groove on the recording surface of the optical disc D are recorded. Track control, ie, tracking, is performed to eliminate the deviation from the center of g. In the tracking, current is supplied to the coils 41, 41 in a predetermined direction based on a track shift signal, which is a difference between outputs of the light receiving areas 23a and 23b of the photodetector 23, so that the magnets 44, 44 provide the tracking. As a result of attraction or repulsion due to electromagnetic field interaction with the applied magnetic field, the lens holder 37 (objective lens 36) is shifted toward the center of the optical disc D in the radial direction in the direction orthogonal to the groove g along the recording surface of the optical disc D or the outer periphery. Moved closer to one.

Incidentally, an optical disk (DVD) for high-density digital recording, which has a higher recording density than that of a conventionally used music optical disk (CD) and also records video information, has been put into practical use. A DV capable of writing and reproducing information at the same recording density as DVD
A D-RAM (a distance between grooves g is approximately 1.48 micrometers (hereinafter, referred to as μm)) is being put into practical use, and the distance between adjacent grooves g has been reduced. Since the crosstalk between the adjacent groove g and the adjacent groove g is increased, the offset component included in the track shift signal must be reliably removed.

For this reason, in this embodiment, a dead area 24 where no light receiving area is formed is formed between the light receiving areas 23a and 23b of the photodetector 23. More specifically, although the 0th-order diffracted light of the reflected laser beam Rrb applied to the photodetector 23 has its outer peripheral portion blurred by the objective lens 36, as described below with reference to FIG. Has a sufficient light intensity.
In the photodetector 24, a dead area 24 is formed at a position where the central area of the zero-order diffracted light is irradiated.

Here, the width of the dead area 24 between the light receiving areas 23a and 23b in the direction orthogonal to the dividing line 23c, that is, the distance between the light receiving area 23a and the light receiving area 23b is determined according to the specifications of the optical disc D, the semiconductor laser 11 From the wavelength of the laser beam Rf emitted by the lens, the aperture ratio and the imaging characteristics of the objective lens 36, and the optical design specifications of the fixed optical system 3a.
Easily sought. As an example, when the center-to-center (inter-interval) distance of the grooves g formed on the recording surface of the optical disk D is approximately 1.48 μm, the beam spot diameter of the reflected laser beam reflected by the optical disk D (0 (Original light component). Note that this setting
When information is recorded on the recording surface of the optical disc D, the information can be recorded either between the grooves g or at the center of the groove g.

FIG. 6 shows that the 0th-order diffracted light, 1st-order diffracted light and -1st-order diffracted light of the reflected laser beam Rr reflected on the recording surface of the high-density optical disc D for DVD and DVD-RAM are guided to the objective lens 36. FIG. 3 is a schematic diagram schematically illustrating a state in which the operation is performed.

As shown in FIG. 6, the reflected laser beam Rr reflected by the groove g on the recording surface of the optical disc D
Are the 0th-order diffracted light that passes through substantially the entire area of the objective lens 36, the 1st-order diffracted light that partially overlaps the 0th-order diffracted light, and −
The light is incident on the objective lens 36 as an aggregate of the first-order diffracted light, the high-order diffracted light including the second-order not shown, and the high-order diffracted light including the second-order.

As is apparent from FIG. 6, each of the first-order diffracted light and the -1st-order diffracted light has a portion overlapping with the 0th-order diffracted light. That is, as described above, the DVD-R
In a high-density optical disc for AM, a well-known music C
D, the distance between adjacent grooves g is smaller than that of D, the wavelength is short (for example, 780 nm → 650 nm), and the numerical aperture N of the objective lens is
A is large (for example, 0.45 → 0.6
From 0), each of the 1st-order diffracted light and the -1st-order diffracted light partially overlaps with the 0th-order diffracted light, and further partially overlaps with each other.

More specifically, since each of the 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light is partially blocked by the opening of the objective lens 36, only a part of the reflected laser beam Rr passes through the objective lens 36. The light is returned to the fixed optical system 3a.

That is, the zero-order diffracted light is guided to the two light receiving areas 23a and 23b of the photodetector 23 shown in FIG. 7, for example, with the peripheral portion of the reflected laser beam before incidence on the objective lens 36 being cut off. On the other hand, the first-order diffracted light and the -1st-order diffracted light respectively enter the two light receiving regions 23a and 23b of the photodetector 23 while overlapping with the 0th-order diffracted light. That is, a difference between the photoelectric conversion signals from the two light receiving regions 23a and 23b is a track shift signal.

Therefore, if there is a condensed spot at a position where the center of the condensed spot of the laser beam converged on the optical disc D by the objective lens 36 and the center of the groove g, the radial direction of the groove g Since a symmetrical diffracted light is generated, the difference signal between the output signals from the two light receiving regions is at the 0 level, and when they do not match, the intensity of one of the diffracted lights increases, and the difference signal level becomes 0 Will shift.

FIG. 7 is a plan view showing the light receiving surface of the photodetector 23. As shown in FIG. 7, the photodetector 23 is used for generating a well-known track error signal, and has two light receiving regions 23a and 23b divided by a dividing line 23c.
A dead area 24 is formed between 3a and 23b. The dividing line 23c is formed by the groove g of the optical disc D.
Are arranged so as to be substantially parallel to the direction in which the shadow is projected.

In other words, the above-mentioned tracking shift signal can be said to be a signal that captures a change in the phase difference between the first-order diffracted light and the -1st-order diffracted light with respect to the 0th-order diffracted light. Therefore, as much as possible, the first-order diffracted light and the -1st-order diffracted light, which greatly contribute to the generation of the tracking shift signal, are taken as much as possible, centering on the portion where the intensity is high. It is important to reduce the track offset as much as possible at the center.

Therefore, as shown in FIG. 7, the light receiving surface of the photodetector 23 has a light receiving area 23a for receiving a part where the intensity of the first-order diffracted light is high or a part where the zero-order diffracted light and the first-order diffracted light overlap. A light receiving region 23b for receiving a portion where the intensity of the -1st order diffracted light is high or a portion where the 0th order diffracted light and the -1st order diffracted light overlap, and a portion where the intensity of the 0th order diffracted light is high or the 0th order diffracted light and the 1st order diffracted light , -1st-order diffracted light has an insensitive area 24 to be irradiated, which is effective in reducing track offset.

FIGS. 8A and 8B show the positional relationship of the reflected laser beam from the optical disk to the photodetector 23 with and without lens shift, respectively. Things.

The photodetector 2 having the structure described above
3, the light receiving area of the light receiving areas 23a and 23b for receiving the condensed spot of the reflected laser beam is
Since the dead area 24 is provided between the light receiving areas 23a and 23b, the light receiving quantity is reduced.
b captures the first-order diffracted light and the -1st-order diffracted light, respectively. Further, since the intensity center of the 0th-order diffracted light related to the generation of the tracking offset component is located in the insensitive region 24, the difference between the signals obtained by photoelectrically converting the amounts of light received in the light receiving regions 23a and 23b while removing the tracking offset. Thus, a stable tracking signal can be generated.

As shown in FIG. 8B, the photodetector 23 of the condensed spot is shifted by the lens shift.
Even when the irradiation position on the light is relatively shifted, the intensity center of the 0th-order diffracted light is not located in any of the light receiving regions 23a and 23b, but is located in the dead region 24. Therefore, the tracking offset component can be reduced even at the time of lens shift.

FIG. 9 is a schematic block diagram showing an example of a signal processing unit and a control unit which can be used for the signal processing unit 5 and the control unit 9 of the optical disk device 1 shown in FIG. As shown in FIG. 9, the signal processing unit 5 is connected to the main control circuit 50, and reproduces information recorded on the optical disc D based on outputs from four light receiving areas (not shown) of the photo detector 20. The circuit 51 is provided. In addition,
The information reproducing circuit 51 includes, for example, a threshold circuit (not shown), a binarizing circuit, a data expanding circuit, a buffer memory, and the like, and a current-voltage converting circuit described in detail later.
The information corresponding to the output from each light receiving area converted into a voltage signal by the differential amplifier and the adder is transmitted to the main control circuit 50.
And outputs it to the external device 99 via.

On the other hand, the control section 9 includes a linear motor control circuit 61 for supplying a current in a predetermined direction to the radial drive coil 34 for moving the actuator 3b in the radial direction of the optical disc D, and an objective lens 36 for controlling the recording surface of the optical disc D. A focus error detection circuit 62 for setting a current value to be supplied to the two coils 40, 40 on the cylindrical surface of the lens holder 37 in order to move in a direction perpendicular to the direction of movement of the lens holder 37, and removing a focus error detected by the focus error detection circuit 62. A focus control circuit 63 for supplying a focus control current to the coils 40 and 40, and a cylindrical surface 2 of the lens holder 37 for moving the objective lens 36 in a direction intersecting the tangent to the groove g on the recording surface of the optical disc D. Track deviation control circuit 64 for setting a current value to be supplied to the two coils 41, 41; The track control circuit 65 that supplies a track control current to the coils 41 and 41 and the light intensity of the laser beam radiated from the semiconductor laser 11 to remove the track shift and the offset output from the rack shift control circuit 64 are adjusted to a predetermined value. A laser drive circuit 66 for setting the intensity is provided. Each circuit is connected to the main control circuit 50.

The information reproducing circuit 51 is connected to each of four light-receiving regions (not shown) of the photodetector 20 and converts the output current output from each light-receiving region into a voltage. The added output of the adder 72 for obtaining the sum of the voltage signals output from each of 71a to 71d is input. By obtaining the sum of these four voltage signals, an information signal, that is, an RF signal is formed.

The focus error detection circuit 62 has the first
And first and second differential amplifiers 73a and 73a for obtaining a differential output between two predetermined outputs among the output voltages output from the fourth to fourth current-voltage converters 71a to 71d.
An output obtained by adding each output of 73b by an adder 74 is input.

Each of the track shift control circuit 64 and the linear motor control circuit 61 has a photodetector 2
The current output from each of the third light receiving regions 23a and 23b is subjected to current-to-voltage conversion by the fifth and sixth current-to-voltage converters 81a and 81b to obtain a differential output of a signal obtained. The output of the amplifier 83 is input.

As described above, according to the optical head device 3 shown in FIGS. 2 to 8, the track shift of the objective lens 36 is caused by the output from the light receiving area 23a of the photodetector 23 and the light receiving area 23b of the photodetector 23. Is subtracted from the output from the first and second signals.

Since the above-described embodiment can be applied to an optical disk for DVD-RAM as described above, the output level of the light receiving area 23a of the photodetector 23 is set to L1, and the light receiving area 2 of the photodetector 23 is set to L1.
The output level of 3b is L2, the maximum value of the amplitude of the difference signal between L1 and L2 is (L1-L2) pp, the area where the information on the recording surface of the optical disc D is not recorded, and the area where the groove g is not formed. Assuming that the sum signal of L1 and L2 with respect to the reflected light beam reflected from is represented by (L1 + L2) a, 0.35 ≦ [(L1−L2) pp / (L1 + L2)
a], [(L1−L2) pp / (L1 + L2) a] ≦ 1.05.

The maximum value of the amplitude obtained by dividing the instantaneous value of the signal level (L1−L2) by the instantaneous value of the signal level (L1 + L2) regardless of the presence or absence of information on the recording surface of the optical disc D is [ (L1-L2) / (L1 + L
2)] pp, 1.10 ≦ [(L1−L2) / (L1 + L2)] pp, [(L1−L2) / (L1 + L2)] pp ≦ 1.65. Further, [(L1-L2) / (L1 + L
2)] indicates the maximum value of pp [(L1-L2) / (L1 +
L2)] ppmax and [(L1-L2) / (L1 + L
2)] The minimum value of pp [(L1−L2) / (L1 +
L2)] ppmin, [(L1-L2) / (L1 + L2)] ppmin /
[(L1-L2) / (L1 + L2)] ppmax ≧ 0.
70 are satisfied.

As described above, the tracking control signal is calculated by the track shift control circuit 64 on the basis of the output signal output from the differential amplifier 83. It is possible to compensate for the offset amount acting as a track error, that is, the influence of the offset component included in the track shift signal. Therefore, DVD and DVD-RA
Crosstalk in a high-density optical disk represented by an optical disk for M can be significantly reduced.

FIG. 10 is a graph showing an output from the conventional photodetector and a track error signal provided from the signal processing unit and the control unit shown in FIG. The horizontal axis represents the detrack amount, which is the shift between the center of the condensed spot and the center of the groove, and shows the amount of detrack from the center of 0 to half of the groove pitch toward the inner and outer circumferences of the optical disk. I have. The vertical axis represents the level of the tracking error signal, and the levels of 1.0 and -1.0 correspond to one of the two light receiving regions of the photodetector when all the light incident on the optical disk is reflected by the optical disk. This corresponds to the case where all of the converging spots are incident on one side.

As is apparent from FIG. 10, the photodetector 23 is formed by using the dead area 24 of the photodetector 23.
By removing the offset component included in the track shift signal output from the light receiving areas 23a and 23b by the track shift control circuit 64, the conventional track error including the effect of the lens shift indicated by the dotted line in FIG. Compared with the signal, it is recognized that the center value of the track shift signal indicated by the solid line input to the track control circuit 65 approaches 0 and that the track offset is reduced.

Next, an optical head device according to a second embodiment will be described. The detailed description of the same configuration as that of the above-described first embodiment is omitted. FIG.
FIG. 10 is a schematic block diagram illustrating another example of the signal processing unit and the control unit illustrated in FIG. 9.

As shown in FIG. 11, the current-voltage converter 8
A gain controller 88 that matches the output signal level from the current-to-voltage converter 81a with the output signal level from the current-to-voltage converter 81b is provided between the differential amplifier 83 and 1a or 81b. . In the embodiment shown in FIG. 11, the current-voltage converter 81a and the differential amplifier 8
3, a gain controller 88 is provided.

The gain controller 88 has, for example,
This is to cope with the case where the tracking error signal which should be at the 0 level when there is no lens shift does not become 0 due to a component precision error of the optical head device, an assembly error, or an inclination of the optical disk. One of the two light receiving regions, for example, the light receiving region 23
By adjusting the magnitude of the signal from a by the gain controller 88, the output signal levels from the two light receiving regions can be matched.

As a result, the effect of reducing the offset component included in the track shift signal is further ensured. Therefore, it is possible to prevent an output as if an offset occurs or does not exist due to a difference between output signal levels of the light receiving regions 23a and 23b.

Next, an optical head device according to a third embodiment will be described. The detailed description of the same configuration as that of the above-described first embodiment is omitted. The optical head device according to the third embodiment has a light receiving area for generating an information signal, that is, an RF signal, in addition to the structure of the photodetector for generating the tracking error signal described in the first embodiment. It is.

FIGS. 12A and 12B are plan views showing a light receiving surface of a photodetector in an optical head device according to the third embodiment, and show an optical disk with and without a lens shift, respectively. FIG. 6 shows the positional relationship of the reflected laser beam from the photodetector 23 with respect to the photodetector 23.

As shown in FIG. 12A, the light receiving surface of the photodetector includes a pair of spaced light receiving regions 23a and 23b for generating a tracking signal described in the first embodiment. A pair of light receiving areas 23a and 23b
And a light receiving region 25 provided in a band shape between the two.

The pair of light receiving areas 23a and 23b greatly contribute to the generation of the tracking error signal.
A position where light is received as much as possible around a portion where the intensity of the first-order diffracted light and the −1st-order diffracted light is high, and conversely, the 0th-order diffracted light is arranged at a position where the portion whose intensity is high is excluded. A tracking error signal with a reduced track offset component can be generated.

On the other hand, the center of the spot where the intensity of the 0th-order diffracted light is high is received by the light receiving region 25 provided between the pair of light receiving regions 23a and 23b. Then, an RF signal is generated by photoelectrically converting the light amount of a part of the condensed spot received by the light receiving region 25 and performing current-voltage conversion. In general, when an RF signal is generated using a part of a light beam that has reached a photodetector, the resolution tends to decrease. In the third embodiment, however, in the light receiving region 25, the high intensity of the zero-order diffracted light is high. Since the portion is received and the peripheral portion having relatively low intensity in the 0th-order diffracted light is ignored, the influence is small, and accurate reproduction or recording of information is enabled.

Further, as shown in FIG. 12B, even when the center of the condensed spot is shifted due to the lens shift, the high-intensity portion of the zero-order diffracted light can be received by the light receiving region 25. Thus, it is possible to provide an information signal that enables highly reliable and accurate information reproduction or recording.

FIG. 13 is a schematic block diagram showing an example of a signal processing unit and a control unit which can be used for the signal processing unit and the control unit of the optical disk device having the photodetector shown in FIGS. 12 (a) and 12 (b). is there.

As shown in FIG. 13, the signal processing section 5 is connected to the main control circuit 50, and reproduces information recorded on the optical disc D based on the output from the light receiving area 25 of the photodetector 23. The circuit 51 is provided.

The information reproducing circuit 51 is connected to the light receiving region 25 of the photodetector 23, and converts a current output from the light receiving region 25 into a voltage.
The voltage signal which is the output from c is input. This voltage signal corresponds to an information signal, that is, an RF signal.

The focus error detection circuit 62 includes the first
And first and second differential amplifiers 73a and 73a for obtaining a differential output between two predetermined outputs among the output voltages output from the fourth to fourth current-voltage converters 71a to 71d.
An output obtained by adding each output of 73b by an adder 74 is input.

Each of the track shift control circuit 64 and the linear motor control circuit 61 has a photodetector 2
The current output from each of the third light receiving regions 23a and 23b is subjected to current-to-voltage conversion by the fifth and sixth current-to-voltage converters 81a and 81b to obtain a differential output of a signal obtained. The output of the amplifier 83 is input.

As described above, according to the optical head device shown in FIGS. 12A and 12B, the objective lens 36
The track deviation of the light receiving area 2 of the photodetector 23
3a and the light receiving area 2 of the photodetector 23
3b is detected as a difference signal obtained by subtracting the output from
A tracking signal is generated based on the detection result. Further, an RF signal is generated by an output from the light receiving region 25 of the photodetector 23.

In the first embodiment, in order to obtain an RF signal, light beams incident on the four light receiving regions of the photodetector 20 are photoelectrically converted, and further, the current-voltage converters 71a to 71d perform current-voltage conversion. Convert and adder 7
2, an arithmetic process of generating a sum signal of these signals is required inside the circuit.

On the other hand, in the third embodiment, an RF signal can be generated by photoelectrically converting a part of a high-intensity condensed spot received by the photodetector 25 and performing current-voltage conversion. Therefore, the capacity of the integrated circuit can be reduced and the number of pins of the integrated circuit can be reduced, so that the demand for miniaturization can be satisfied.
In addition, since the circuit size can be reduced, power consumption and heat generation can be reduced, which also has a great advantage in this respect.

Next, an optical head device according to a fourth embodiment will be described. Note that a detailed description of the same configuration as that of the above-described third embodiment is omitted. FIG.
FIG. 14 is a schematic block diagram illustrating another example of the signal processing unit and the control unit illustrated in FIG. 13.

As shown in FIG. 14, the current-voltage converter 8
A gain controller 89 for matching the output signal level from the current-voltage converter 81a with the output signal level from the current-voltage converter 81b is provided between the differential amplifier 83 and 1a or 81b. . In the embodiment shown in FIG. 14, the current-voltage converter 81a and the differential amplifier 8
3, a gain controller 89 is provided.

As in the second embodiment, the gain controller 89 is set to 0 when there is no lens shift due to, for example, a component accuracy error of the optical head device, an assembly error, or an inclination of the optical disk. This is to cope with the case where the tracking error signal to be the level does not become 0, and by adjusting the magnitude of the signal from one of the two light receiving areas, for example, the light receiving area 23a by the gain controller 89, the 2
The output signal levels from the two light receiving areas can be matched.

As a result, the effect of reducing the offset component included in the track shift signal becomes more reliable. Therefore, it is possible to prevent an output as if an offset occurs or does not exist due to a difference between output signal levels of the light receiving regions 23a and 23b.

Further, the characteristics realized by the configuration of the third embodiment can be made more stable. As described above, according to the optical head device of the present invention, the photodetector that receives the reflected laser beam from the optical disk includes a pair of spaced light receiving regions that detect a track error signal, and A region where the intensity center position of the reflected laser beam for generating the offset component is irradiated, that is, a region between the pair of light receiving regions and a dead region where the beam is not received is provided.

As a result, since the zeroth-order diffracted light, the first-order diffracted light, and the −1st-order diffracted light of the reflected laser beam reflected from the optical disk do not receive the overlapping portion, the offset component included in the track error signal is not received. That is, the influence of the lens shift on the track error signal can be removed, and stable tracking control can be performed.

Further, according to the optical head device of the present invention,
Each output of the light receiving area for detecting a track deviation is set to an appropriate size by a gain controller. Therefore, a photodetector capable of removing the offset component can be provided at low cost, and the offset component can be prevented from being detected or changing in size due to the output of the photodetector.

Further, according to the optical head device of the present invention, an inherent difference component which may occur due to a difference between the areas of the two light receiving regions, component accuracy of elements of the optical head device, or assembly of the optical head device. Is set to an appropriate size by the gain controller. Accordingly, there is no increase in assembly cost and component cost due to removal of the offset component.

Further, according to the optical head device of the present invention,
A photodetector that receives the reflected laser beam from the optical disc is provided between a pair of spaced light receiving regions for detecting a track error signal and a region irradiated with the intensity center position of the reflected laser beam, that is, a pair of light receiving regions. A light receiving area for receiving the beam in the area and generating an RF signal.

Thus, the part of the reflected laser beam reflected from the optical disk, which is the part where the 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light all overlap, is not received, but based on the difference signal between the pair of light receiving regions. Therefore, the influence of the offset component included in the track error signal, that is, the lens shift, on the track error signal can be removed, and stable tracking control can be performed. In addition, it is possible to generate an RF signal without requiring a complicated signal processing circuit at the same time, which is advantageous for miniaturization of the device.

In the above-described embodiment, a case has been described in which a high-density optical disk for DVD-RAM in which the distance between grooves is configured to be small is assumed, but a conventional CD system having grooves, for example, a CD-R. Like, DV
The present invention can be applied to an optical disc in which the distance between grooves is wider than that of a D-RAM.

As shown in FIG. 6, in a high-density optical disc for DVD-RAM, since the groove interval is small, the 0th-order diffracted light is applied to the photodetector in addition to the 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light. And a first-order diffracted light, a beam in which the 0th-order diffracted light and the -1st-order diffracted light overlap, and a beam in which the 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light overlap.

The optical head device of the present invention is applied to a light beam including such a diffracted light. However, the conventional optical disk of the groove type has the specifications of the conventional wavelength, track pitch, NA, etc. The optical head device according to the present invention is also effective for such a device.

That is, as shown in FIGS. 15A and 15B, in an optical disk such as a CD-R having a smaller groove pitch than a DVD-RAM, a zero-order diffracted light and a first-order diffracted light are applied to the photodetector. , -1st order diffracted light, 0th order diffracted light and 1st order diffracted light,
A beam in which the first-order diffracted light and the -1st-order diffracted light are overlapped is incident, and a beam in which the 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light are superposed is not generated, and therefore does not enter the photodetector.

Even if the reflected light beam including the diffracted light from such an optical disk is incident on the photodetector applied to the optical head device of the present invention, the signal output from the pair of light receiving areas 23a and 23b is not reflected. By detecting the difference, a tracking error signal can be generated.

As described above, in an optical disk having a CD-type groove, there is no occurrence of light in which all of the 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light of the reflected laser beam reflected from the optical disc overlap. For this reason, the present invention can be applied to a CD-type optical disk, and can remove the influence of the offset component included in the track error signal, that is, the lens shift, on the track error signal. Tracking control can be performed.

[0119]

As described above, according to the present invention, it is possible to provide an optical head device capable of reliably removing an offset component contained in a track error signal.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an optical disk device having an optical head device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a configuration of an optical head device incorporated in the optical disk device shown in FIG.

FIG. 3 is a schematic diagram illustrating an example of an actuator of the optical head device illustrated in FIG. 2;

FIG. 4 is a schematic diagram illustrating an example of a fixed optical system of the optical head device illustrated in FIG. 2;

FIG. 5 is a schematic view illustrating a lens holder of the actuator shown in FIG. 3 and its vicinity.

FIG. 6 is a schematic diagram illustrating a state of a reflected laser beam from an optical disk returned to an objective lens of the actuator shown in FIGS. 3 and 5;

FIG. 7 is a schematic plan view showing a light receiving area of a photodetector used for detecting a track shift capable of removing an offset component included in the reflected laser beam shown in FIG. 6 in the fixed optical system shown in FIG. 4; FIG.

8 (a) and 8 (b) show a state of a reflected laser beam from an optical disk incident on a light receiving area of the photodetector shown in FIG. 7 in a case where there is no lens shift and in a case where there is a lens shift, respectively. FIG.

FIG. 9 is a schematic block diagram illustrating an example of a signal processing unit and a control unit that can be used in the signal processing unit and the control unit of the optical disc device illustrated in FIG. 1;

FIG. 10 is a graph showing an output from a conventional photodetector and a track shift signal provided by a signal processing unit and a control unit shown in FIG. 9;

FIG. 11 is a schematic block diagram illustrating a modified example of the signal processing unit and the control unit illustrated in FIG. 9;

FIGS. 12A and 12B are plan views showing modified examples of the photodetector, and show a case where there is no lens shift and a case where there is no lens shift, respectively. FIG. 3 is a diagram illustrating a state of a laser beam.

FIG. 13 is a schematic block diagram showing an example of a signal processing unit and a control unit of an optical disc device to which the photodetector shown in FIGS. 12A and 12B is applied.

FIG. 14 is a schematic block diagram illustrating another example of the signal processing unit and the control unit illustrated in FIG. 13;

15 (a) and (b) show a case where there is no lens shift and a case where there is no lens shift, respectively. FIG. It is a figure showing a situation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical disk apparatus 3 ... Optical head apparatus 3a ... Fixed optical system 3b ... Actuator 5 ... Signal processing part 7 ... Motor 9 ... Control part 10 ... Housing 11 ... Semiconductor laser 12 ... Collimator lens 13 ... Elliptical correction prism 14 ... Beam splitter ( Polarization) 15 λ / 4 plate (phase delay element) 16 Beam splitter (half mirror) 17 Convergent lens 18 Concave lens 19 Cylindrical lens 20 Photodetector 21 Mirror 22 Convergent lens 23 Photodetector 23a Light receiving area (Track error detection) 23b ... Light receiving area (Track error detection) 24 ... Dead area 25 ... Light receiving area (RF signal generation) 31 ... Base 32 ... Guide rail 33 ... Carriage 34 ... Radial drive coil 35 ... Start-up mirror 36 ... Objective Lens 37 ... Lens Ruder 50 ... Main control circuit 51 ... Information reproduction circuit 61 ... Linear motor control circuit 62 ... Focus error detection circuit 63 ... Focus control circuit 64 ... Track shift control circuit 65 ... Track control circuit 66 ... Laser drive circuit 71 (ad) ... current-voltage converter 72 ... adder 73 (a, b) ... differential amplifier 74 ... adder 81 (ac) ... current-voltage converter 83 ... differential amplifier 88 ... gain controller 89 ... gain controller D ... optical disk g ... groove

Claims (9)

[Claims] A light source for emitting a light beam; a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium; and reflected light reflected and diffracted on the recording surface of the recording medium. An optical head device comprising: a photoelectric conversion unit configured to convert a beam into an electric signal; wherein the recording medium is configured to focus a light spot obtained by condensing the light beam by the condensing unit in a circumferential direction of the recording medium. A guide groove for guiding the recording medium; and wherein the photoelectric conversion unit is configured such that when a condensed spot obtained by being condensed by the condensing unit moves in a radial direction of the recording medium, the recording medium At least one defined in a direction substantially orthogonal to the direction in which the reflected light beam reflecting the spot is projected onto the photoelectric conversion means and moves.
A photoelectric conversion region divided into a plurality of light receiving regions by one dividing line, and the first light receiving region has a zero-order light component and a first-order light component of the light beam reflected and diffracted by the guide groove of the recording medium. A light beam mainly containing a part or the whole of the light beam where only the light component overlaps is received.
A light beam mainly containing a part or all of a light beam in which only the 0th-order light component and the -1st-order light component of the light beam reflected and diffracted by the recording medium overlaps, and is reflected by the recording medium. And providing an insensitive area that does not receive the light beam in an area where the intensity center of the 0th-order light component of the diffracted light beam is irradiated, photoelectrically converting the light beam received in the first light receiving area to generate a first signal And generating a second signal by photoelectrically converting the light beam received by the second light receiving region, and forming a difference signal between the first signal and the second signal on a recording surface of the recording medium in advance. A track error signal used for tracking control for moving the light condensing means in a direction crossing the guide groove so that the center of the guide groove and the center of the light beam passing through the light condensing means coincide with each other. Characteristic light head Device. 2. A light source for emitting a light beam, a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium, and reflected light reflected and diffracted on the recording surface of the recording medium. An optical head device comprising: a photoelectric conversion unit configured to convert a beam into an electric signal; wherein the recording medium is configured to focus a light spot obtained by condensing the light beam by the condensing unit in a circumferential direction of the recording medium. A guide groove for guiding the recording medium; and wherein the photoelectric conversion unit is configured such that when a condensed spot obtained by being condensed by the condensing unit moves in a radial direction of the recording medium, the recording medium At least one defined in a direction substantially orthogonal to the direction in which the reflected light beam reflecting the spot is projected onto the photoelectric conversion means and moves.
A photoelectric conversion region divided into a plurality of light receiving regions by one dividing line, and the first light receiving region has a zero-order light component and a first-order light component of the light beam reflected and diffracted by the guide groove of the recording medium. A light beam mainly containing a part or the whole of the light beam where only the light component overlaps is received.
A first light receiving area for receiving a light beam mainly composed of a part or all of a light beam in which only a zero-order light component and a minus first-order light component of the light beam reflected and diffracted by the recording medium overlap; And between the second light receiving region and
0 of the light beams reflected and diffracted by the recording medium
A dead area in which the light beam is not received is provided in an area where the next light component, the first light component, and the -1st light component overlap, and a first signal is generated by photoelectrically converting the light beam received in the first light receiving region. A second signal is generated by photoelectrically converting the light beam received by the second light receiving region, and a difference signal between the first signal and the second signal is formed in advance on a recording surface of the recording medium. A track error signal used for tracking control for moving the light condensing means in a direction crossing the guide groove so that the center of the guide groove coincides with the center of the light beam passing through the light condensing means. Optical head device. 3. A light source for emitting a light beam, a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium, and reflected light reflected and diffracted on the recording surface of the recording medium. An optical head device comprising: a photoelectric conversion unit configured to convert a beam into an electric signal; wherein the recording medium is configured to focus a light spot obtained by condensing the light beam by the condensing unit in a circumferential direction of the recording medium. A guide groove for guiding the recording medium; and wherein the photoelectric conversion unit is configured such that when a condensed spot obtained by being condensed by the condensing unit moves in a radial direction of the recording medium, the recording medium At least one defined in a direction substantially orthogonal to the direction in which the reflected light beam reflecting the spot is projected onto the photoelectric conversion means and moves.
And at intervals corresponding to a region irradiated with the intensity center of the zero-order light component of the light beam reflected and diffracted by the guide groove of the recording medium. A pair of first and second light receiving regions, wherein the first light receiving region is a part of a light beam in which only the zero-order light component and the primary light component of the light beam reflected and diffracted by the recording medium overlap. Alternatively, the second light receiving region receives a light beam mainly composed of all the light beams, and the second light receiving region is a light beam reflected and diffracted by the recording medium, in which only the 0th-order light component and the -1st-order light component overlap. Receiving a light beam mainly or partially of the light beam, photoelectrically converting the light beam received in the first light receiving region to generate a first signal, and photoelectrically converting the light beam received in the second light receiving region. To generate a second signal, The difference signal between the signal and the second signal, the light collecting means for matching the center of the guide groove formed in advance on the recording surface of the recording medium with the center of the light beam passing through the light collecting means. An optical head device which is used as a tracking error signal used for tracking control for moving the control signal in a direction crossing the guide groove. 4. A light source for emitting a light beam, a light condensing means for converging a light beam emitted from the light source on a recording surface of a recording medium, and reflected light reflected and diffracted on the recording surface of the recording medium. An optical head device comprising: a photoelectric conversion unit configured to convert a beam into an electric signal; wherein the recording medium is configured to focus a light spot obtained by condensing the light beam by the condensing unit in a circumferential direction of the recording medium. A guide groove for guiding the recording medium; and the photoelectric conversion unit, when the condensed spot obtained by being converged by the condensing unit moves in the radial direction of the recording medium, the recording medium At least one defined in a direction substantially orthogonal to the direction in which the reflected light beam reflecting the light is projected onto the photoelectric conversion means and moves.
A photoelectric conversion region divided into a plurality of light receiving regions by one dividing line, and the first light receiving region has a zero-order light component and a first-order light component of the light beam reflected and diffracted by the guide groove of the recording medium. A light beam mainly containing a part or the whole of the light beam where only the light component overlaps is received.
A light beam mainly containing a part or all of a light beam in which only the 0th-order light component and the -1st-order light component of the light beam reflected and diffracted by the recording medium are overlapped, is reflected by the recording medium. And 0 of the diffracted light beam
An insensitive area that does not receive a light beam is provided in an area irradiated with the intensity center of the next light component, a first signal is generated by photoelectrically converting the light beam received in the first light receiving area, and a second signal is generated in the second light receiving area. The received light beam is photoelectrically converted to generate a second signal, and the first signal and the second signal have respective signal levels L1, L
2 and (L1−L2) pp is the first signal and the second signal.
The maximum value of the amplitude of the signal difference signal is represented by (L1 + L2) a, where the first signal and the first signal corresponding to the reflected light beam reflected from the area of the recording surface where the information is not recorded and the area where the guide groove is not formed. Assuming that the sum signals of the second signals are indicated respectively, 0.35 ≦ [(L1−L2) pp / (L1 + L2)
a], [(L1-L2) pp / (L1 + L2) a] ≦ 1.05, and [(L1-L2) / (L1 + L)
2)] When pp is the maximum value of the amplitude obtained by dividing the instantaneous value of the signal level (L1−L2) by the instantaneous value of the signal level (L1 + L2) regardless of the presence or absence of information on the recording surface. 1.10 ≦ [(L1−L2) / (L1 + L2)] pp, [(L1−L2) / (L1 + L2)] pp ≦ 1.65, and [(L1−L2) / (L1 + L2) ]
[(L1-L2) / (L1 + L) indicating the maximum value of pp
2)] ppmax and [(L1-L2) / (L1 + L
2)] The minimum value of pp [(L1−L2) / (L1 +
L2)] ppmin, [(L1-L2) / (L1 + L2)] ppmin /
[(L1-L2) / (L1 + L2)] ppmax ≧ 0.
70, the difference signal between the first signal and the second signal is used to match the center of the guide groove formed in advance on the recording surface of the recording medium with the center of the light beam passing through the light condensing means. An optical head device for generating a track error signal used for tracking control for moving the light converging means in a direction crossing the guide groove. 5. A light source that emits a light beam having a wavelength of about 650 nm, lens means having a numerical aperture of about 0.6, and condensing a light beam emitted from the light source on a recording surface of a recording medium; A photoelectric conversion means for converting a reflected light beam reflected and diffracted on the recording surface of the recording medium into an electric signal, wherein the recording medium has a center-to-center distance of approximately 1.48 μm. A guide groove having a shape of a circle or a plurality of concentric circles, and information can be recorded substantially at the center of the guide groove or between the guide grooves, and the photoelectric conversion means is a condensed spot obtained by being converged by the lens means. When the recording medium moves in the radial direction of the recording medium, a direction substantially perpendicular to the direction in which the reflected light beam reflected by the recording medium on the condensing spot is projected onto the photoelectric conversion unit and moves. At least one defined for
A light beam having a photoelectric conversion region divided into a plurality of light receiving regions by one dividing line, wherein only a zero-order light component and a first-order light component of a light beam reflected and diffracted by the guide groove of the recording medium overlap with each other; A first signal is generated by photoelectrically converting a light beam mainly or partially of the beam, and a 0th-order light component and a -1st-order light component of the light beam reflected and diffracted by the recording medium. A second signal is generated by photoelectrically converting a light beam mainly or partly or wholly of the light beam that only overlaps, and 0 of the light beams reflected and diffracted by the recording medium is generated.
A dead area that does not receive a light beam is provided in a region where the intensity center of the next light component is irradiated, and a difference signal between the first signal and the second signal is formed in advance on a recording surface of the recording medium. The light is a track error signal used for tracking control for moving the light condensing means in a direction crossing the guide groove so that the center of the guide groove coincides with the center of the light beam passing through the light condensing means. Head device. 6. A light source for emitting a light beam, a light condensing means for condensing a light beam emitted from the light source on a recording surface of a recording medium, and reflected light reflected and diffracted on the recording surface of the recording medium. An optical head device comprising: a photoelectric conversion unit configured to convert a beam into an electric signal; wherein the recording medium is configured to focus a light spot obtained by condensing the light beam by the condensing unit in a circumferential direction of the recording medium. A guide groove for guiding the recording medium; and wherein the photoelectric conversion unit is configured such that when a condensed spot obtained by being condensed by the condensing unit moves in a radial direction of the recording medium, the recording medium At least one defined in a direction substantially orthogonal to the direction in which the reflected light beam reflecting the spot is projected onto the photoelectric conversion means and moves.
A photoelectric conversion region divided into a plurality of light receiving regions by one dividing line, and the first light receiving region has a zero-order light component and a first-order light component of the light beam reflected and diffracted by the guide groove of the recording medium. A light beam mainly containing a part or the whole of the light beam where only the light component overlaps is received.
A light beam mainly containing a part or all of a light beam in which only the 0th-order light component and the -1st-order light component of the light beam reflected and diffracted by the recording medium are overlapped, is reflected by the recording medium. And 0 of the diffracted light beam
An insensitive area that does not receive a light beam is provided in an area irradiated with the intensity center of the next light component, a first signal is generated by photoelectrically converting the light beam received in the first light receiving area, and a second signal is generated in the second light receiving area. A second signal is generated by photoelectrically converting the received light beam, and the center of the guide groove formed in advance on the recording surface of the recording medium coincides with the center of the light beam passing through the light condensing means. Sometimes the first
The gain of at least one of the first signal and the second signal is adjusted so that the signal levels of the signal and the second signal match, and the difference signal between the gain-adjusted first signal and the second signal is obtained. A track error signal used for tracking control for moving the light condensing means in a direction crossing the guide groove so that the center of the guide groove coincides with the center of the light beam passing through the light condensing means. Optical head device. 7. A light source for emitting a light beam, a light condensing means for converging a light beam emitted from the light source on a recording surface of a recording medium, and reflected light reflected and diffracted on the recording surface of the recording medium. An optical head device comprising: a photoelectric conversion unit configured to convert a beam into an electric signal; wherein the recording medium is configured to focus a light spot obtained by condensing the light beam by the condensing unit in a circumferential direction of the recording medium. A guide groove for guiding the recording medium; and wherein the photoelectric conversion unit is configured such that when a condensed spot obtained by being condensed by the condensing unit moves in a radial direction of the recording medium, the recording medium At least one defined in a direction substantially orthogonal to the direction in which the reflected light beam reflecting the spot is projected onto the photoelectric conversion means and moves.
A photoelectric conversion region divided into a plurality of light receiving regions by one dividing line, and the first light receiving region has a zero-order light component and a first-order light component of the light beam reflected and diffracted by the guide groove of the recording medium. A light beam mainly containing a part or the whole of the light beam where only the light component overlaps is received.
Receiving a light beam mainly or partly or entirely of a light beam in which only the 0th-order light component and the -1st-order light component of the light beam reflected and diffracted by the recording medium overlap;
The light receiving area receives the intensity center of the zero-order light component of the light beam reflected and diffracted by the recording medium, and photoelectrically converts the light beam received by the first light receiving area to generate a first signal. A second signal is generated by photoelectrically converting the light beam received by the second light receiving region, and a difference signal between the first signal and the second signal is formed in advance on a recording surface of the recording medium. A track error signal used for tracking control for moving the light condensing means in a direction transverse to the guide groove so that the center of the guide groove coincides with the center of the light beam passing through the light condensing means; An optical head device, wherein an information signal is generated by photoelectrically converting a light beam received by the optical head. 8. A light source for emitting a light beam, a light condensing means for converging a light beam emitted from the light source on a recording surface of a recording medium, and reflected light reflected and diffracted on the recording surface of the recording medium. An optical head device comprising: a photoelectric conversion unit configured to convert a beam into an electric signal; wherein the recording medium is configured to focus a light spot obtained by condensing the light beam by the condensing unit in a circumferential direction of the recording medium. A guide groove for guiding the recording medium; and wherein the photoelectric conversion unit is configured such that when a condensed spot obtained by being condensed by the condensing unit moves in a radial direction of the recording medium, the recording medium At least one defined in a direction substantially orthogonal to the direction in which the reflected light beam reflecting the spot is projected onto the photoelectric conversion means and moves.
And at intervals corresponding to a region irradiated with the intensity center of the zero-order light component of the light beam reflected and diffracted by the guide groove of the recording medium. A pair of first and second light receiving regions,
A third light-receiving element disposed between the pair of first and second light-receiving areas;
A first light receiving region, wherein the first light receiving region includes, as a main component, a part or all of a light beam in which only the zero-order light component and the first-order light component of the light beam reflected and diffracted by the recording medium overlap. And the second light receiving region includes, as a main component, a part or all of the light beam in which only the 0th-order light component and the -1st-order light component of the light beam reflected and diffracted by the recording medium overlap. The third light receiving area receives the intensity center of the zero-order light component of the light beam reflected and diffracted by the recording medium, and the light beam received by the first light receiving area To generate a first signal, photoelectrically convert a light beam received by the second light receiving region to generate a second signal, and generate a difference signal between the first signal and the second signal, Center and front of guide groove formed in advance on the recording surface of the recording medium A track error signal used for tracking control for moving the light condensing means in a direction crossing the guide groove so as to match the center of the light beam passing through the light condensing means; An optical head device for generating an information signal by photoelectrically converting a signal. 9. A light source for emitting a light beam, a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium, and reflected light reflected and diffracted on the recording surface of the recording medium An optical head device comprising: a photoelectric conversion unit configured to convert a beam into an electric signal; wherein the recording medium is configured to focus a light spot obtained by condensing the light beam by the condensing unit in a circumferential direction of the recording medium. A guide groove for guiding the recording medium; and wherein the photoelectric conversion unit is configured such that when a condensed spot obtained by being condensed by the condensing unit moves in a radial direction of the recording medium, the recording medium At least one defined in a direction substantially orthogonal to the direction in which the reflected light beam reflecting the spot is projected onto the photoelectric conversion means and moves.
A photoelectric conversion region divided into a plurality of light receiving regions by one dividing line, and the first light receiving region has a zero-order light component and a first-order light component of the light beam reflected and diffracted by the guide groove of the recording medium. A light beam mainly containing a part or the whole of the light beam where only the light component overlaps is received.
Receiving a light beam mainly or partly or entirely of a light beam in which only the 0th-order light component and the -1st-order light component of the light beam reflected and diffracted by the recording medium overlap;
The light receiving area receives the intensity center of the zero-order light component of the light beam reflected and diffracted by the recording medium, and photoelectrically converts the light beam received by the first light receiving area to generate a first signal. A second signal is generated by photoelectrically converting the light beam received by the second light receiving area, and the center of a guide groove formed in advance on the recording surface of the recording medium and the light beam passing through the light collecting means When the center coincides with the first
The gain of at least one of the first signal and the second signal is adjusted so that the signal levels of the signal and the second signal match, and the difference signal between the gain-adjusted first signal and the second signal is obtained. A track error signal used for tracking control for moving the light condensing means in a direction crossing the guide groove so that the center of the guide groove coincides with the center of the light beam passing through the light condensing means; An optical head device for generating an information signal by photoelectrically converting a light beam received in a light receiving region.