JPH0512698A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To provide an optical information recording and reproducing device which eliminates an offset caused by a light spot fluctuation due to optical axis deviation without generating a light quantity loss, without increasing parts number and with a simple method. CONSTITUTION:A light spot motion adjustment mechanism is provided to move a light spot, which is converged on the surface of an optical information recording medium 29 by an objective lens 28, in an approximately 45 degree direction with respect to the radial direction of the track in accordance with the motion of a galvanometer mirror 15. Light receiving elements 24 and 25, which receive reflected light from the optical information recording medium 29, are at least bi-sected and the bi-secting line is arranged to coincide with the direction of the optical axis deviation caused by the motion of the galvanometer mirror 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus for performing tracking control using a galvanometer mirror.

[0002]

2. Description of the Related Art Conventionally, as an optical information recording / reproducing apparatus for performing tracking control using a galvano mirror, for example,
There is one disclosed in JP-A-61-194647. This will now be described with reference to FIG. The laser light emitted from the semiconductor laser 1 is collimated by the collimate lens 2 and the polarized beam splitter (PB
S) 3, reflected by the quarter-wave plate 4 into circularly polarized light, reflected by the galvano mirror 5, reflected by the optical path conversion mirror 7 in the movable part 6, and condensed by the objective lens 8 to obtain optical information. The surface of the recording medium 9 is irradiated in the form of a light spot, whereby information recording and the like are performed. Further, the reflected light obtained by reading the signal of the optical information recording medium 9 (optical disc or the like) follows the same path as the incident path, returns to the quarter wavelength plate 4, is linearly polarized and converted, and this time passes through the polarization beam splitter 3. Detected by the light receiving element 10, information reproduction, focus error signal, track error signal, etc. are detected. In this case, the light receiving element 10 has a light receiving surface divided into four parts a, b, c, d. For example, in the signal detection of the track error signal Tr, the output of Tr = (a + c)-(b + d) The value can be obtained from the sign of the value, and tracking control can be performed using this value.

In this case, when a galvanometer mirror, which is a tracking actuator, is moved, an optical axis shift occurs due to the tilt, a light spot on the light receiving element 10 fluctuates, and an offset occurs, so that an accurate track error signal can be detected. Disappear. Therefore, in the conventional configuration as shown in FIG. 6, two photodetectors 11 and 12 are arranged in the optical path between the objective lens 8 and the optical path conversion mirror 7 to detect the optical axis deviation amount. Then, the detected value is fed back to the track error signal to eliminate the offset, thereby reducing the adverse effect on the track error signal due to the deviation of the optical axis.

[0004]

In the conventional device as described above, the photodetectors 11 and 12 are arranged in the optical path of the reflected light from the optical information recording medium 9 so that the light amount of the optical axis deviation occurs. Is being compensated by sensing
When the optical axis shift occurs, a light amount loss occurs, and the light amount detected by the light receiving element 10 decreases, so that C /
Problems such as a decrease in N and an increase in error rate will occur. Further, by newly adding the photodetectors 11 and 12 as described above, problems such as complication of an electric circuit of an optical system, increase of assembly adjustment, and deterioration of stability with respect to secular change occur. .

[0005]

According to a first aspect of the present invention, a laser beam emitted from a laser light source in an emission optical system is condensed by an objective lens via a galvanometer mirror and is then formed on the surface of an optical information recording medium. Information is recorded by irradiating, and the reflected light from the optical information recording medium is recorded on the optical information recording medium by guiding the reflected light from the optical information recording medium to the light receiving element in the signal detection optical system through the galvanomirror again. In an optical information recording / reproducing apparatus for reproducing information, detecting a focus error signal, and detecting a track error signal, a light spot focused on the surface of the optical information recording medium by the objective lens is moved according to the movement of the galvanometer mirror. Before a reflected light from the optical information recording medium is received, provided with a light spot movement adjusting mechanism that moves in a direction of about 45 ° with respect to the radial direction of the track. Dividing line that divides with at least two-split light receiving element is arranged so as to match the direction of the optical axis deviation caused by the movement of the galvanometer mirror.

According to a second aspect of the present invention, in the first aspect of the present invention, there is provided a light spot movement adjusting mechanism for moving the light spot in a direction of about 45 ° with respect to the radial direction of the track according to the movement of the galvanometer mirror. A beam shaping mechanism for beam shaping was added.

[0007]

According to the first aspect of the invention, the light spot movement adjusting mechanism is used to move the light spot in a direction of approximately 45 ° with respect to the radial direction of the track for tracking, and the movement of the light spot caused by the tracking is performed. Accordingly, by providing the dividing line in the same direction as the movement of the light spot generated on the light receiving element, it is possible to reduce the offset of the track error signal due to the optical axis shift.

According to the second aspect of the present invention, the beam shaping mechanism is used to provide about 45 in the radial direction of the track.
By performing the tracking by moving the light spot in the direction of °, it is possible to improve the light utilization efficiency and perform signal detection with low noise.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. First, FIG. 1 shows the overall configuration of the apparatus. This device is roughly divided into a fixed part 13, a movable part 14, and a galvano mirror 15 provided between them. The fixed portion 13 includes an emission optical system 16 and a signal detection optical system 17. The emitting optical system 16 includes
A laser light source 18, a collimator lens 19, and a beam splitter 20 are provided. The signal detection optical system 17 includes a half-wave plate 21 and a condenser lens 22.
, The polarization beam splitter 23, and the two light receiving elements 2
4, 25 are provided. Further, the movable portion 14 is provided with an optical path deflecting mirror 26, a rising mirror 27, and an objective lens 28. An optical disc 29 as an optical information recording medium is arranged above the objective lens 28.

Then, in this case, the light spot P focused on the surface of the optical disk 29 by the objective lens 28 is directed at a direction of about 45 ° with respect to the radial direction of the track according to the movement of the galvano mirror 15. An optical spot movement adjusting mechanism (not shown) for moving is provided. Also,
The light receiving elements 24 and 25 that receive the reflected light from the surface of the optical disc 29 are divided into three, as shown in FIGS. 2A and 2B, whereby the light receiving surfaces a, b, and c.
And light receiving surfaces d, e, f are formed. In this case, the direction of the dividing line 30 that divides the galvano mirror 1
It is arranged so as to coincide with the direction of the optical axis shift caused by the movement of 5.

Further, here, in the light spot movement adjusting mechanism, the light spot P on the surface of the optical disc 29 is moved in a direction of about 45 ° with respect to the radial direction of the track according to the movement of the galvano mirror 15. In addition, a beam shaping mechanism (not shown) that performs beam shaping is added.

In such a structure, first, the light emitted from the laser light source 18 becomes parallel light by the collimator lens 19, passes through the beam splitter 20, and goes toward the movable portion 14 via the galvanometer mirror 15. . The light that has entered the movable portion 14 is reflected by the optical path changing mirror 26, enters the rising mirror 27 from a direction approximately 45 ° from the radial direction, is reflected upward, and is condensed by the objective lens 28. To form a light spot on the surface of the optical disc 29. Then, the reflected light obtained by reading the information signal recorded on the optical disc 29 passes through a path similar to the incident path and again the beam splitter 20 in the fixed portion 13.
Back to the half wave plate 21,
The polarization beam splitter 2 is sequentially transmitted through the condenser lens 22.
The polarized light is separated at 3, and the light is transmitted or reflected.
The reflected light is detected by the light receiving element 24, and one of the transmitted light is detected by the light receiving element 25.

The light receiving elements 24 and 25 are shown in FIGS.
As shown in FIG.
c, d, e, and f, and the direction of the dividing line 30 and the direction of the track pattern of the light spot on the surface of the optical disc 29 are arranged to be approximately 45 °. At this time, the track error signal Tr can be detected by using the well-known push-pull method, but the conventional detection method causes an offset due to the optical axis shift of the galvano mirror 15. Such a phenomenon is
This is caused by the movement of the galvanometer mirror 15 causing the light spot to be swung in the direction of an angle of 45 ° with respect to the track direction on the surface of the optical disc 29, as shown in FIG. Therefore, in the present embodiment, the optical disc 29 is
The beam of the light spot oscillated at 45 ° on the surface of the light is guided to the surface of the light receiving elements 24 and 25 through the galvano mirror 15, and the light spot 31 irradiated on the surface.
Also focuses on being swung in the direction of 45 ° with respect to the track direction. That is, by making the direction of the dividing line 31 on the surfaces of the light receiving elements 24 and 25 coincide with the direction of the optical axis shift caused by the movement of the galvanometer mirror 15,
As shown in FIG. 4, since the light spots 31 on the light receiving elements 24 and 25 move along the direction of the dividing line 31, no offset occurs, which allows stable detection of the track error signal Tr. .. In this case, the value of the track error signal Tr can be calculated by the following formula: Tr = a−c = d−f = (a + f) − (c + d). Therefore, even in the CCS (Continuous Servo) system, the separated galvanomirror single-axis actuator system can be applied, and high-speed access can be achieved.

The optical path changing mirror 26 may have a beam shaping function. The reproduction signal, that is, the M / O signal can be obtained by the difference method, and the focus error signal can be obtained by the beam size method.

Next, a modified example of the above embodiment will be described with reference to FIG. Here, the configuration inside the movable portion 14 is changed. That is, the means for changing the optical path is changed by using the prism 32 as the optical path changing member as shown in FIG. 5A or by using the diffraction grating 33 as the optical path changing member as shown in FIG. 5B. Is. Although the optical path is changed by the reflection by the mirror in the above-mentioned embodiment, the operation principle is not changed even if the optical path is changed by using the refraction and the diffraction.

Although only two light receiving elements are used in the signal detection optical system 17 in consideration of simplification of the optical system,
The same effect can be obtained when the focus error signal is changed to another method, a large number of light receiving elements are used due to tolerances or devices, or the light receiving elements are packaged.

[0017]

According to the first aspect of the present invention, the laser light emitted from the laser light source in the emission optical system is condensed by the objective lens through the galvanometer mirror and applied to the surface of the optical information recording medium. While recording information, etc., reproduction of information recorded on the optical information recording medium by guiding the reflected light from the optical information recording medium again to the light receiving element in the signal detection optical system via the galvanomirror, In an optical information recording / reproducing apparatus for detecting a focus error signal and a track error signal, a light spot focused on the surface of the optical information recording medium by the objective lens is moved in the radial direction of the track according to the movement of the galvano mirror. A light spot movement adjusting mechanism that moves in a direction of about 45 ° with respect to the optical information recording medium is provided to reduce the number of the light receiving elements. Both of them are divided into two parts, and the dividing lines are arranged so as to coincide with the direction of the optical axis shift caused by the movement of the galvano mirror. Therefore, by using the light spot movement adjusting mechanism, about 45 in the radial direction of the track. Tracking is performed by moving the light spot in the direction of °, and the track error due to the optical axis shift is provided by providing the dividing line in the same direction as the movement of the light spot on the light receiving element due to the movement of the light spot caused by the tracking. It is possible to reduce the signal offset, and thus it is possible to realize an optical pickup that is compatible with CCS even by the separation type uniaxial galvanometer actuator method.

According to a second aspect of the present invention, in the first aspect of the invention, there is provided a light spot movement adjusting mechanism for moving the light spot in a direction of about 45 ° with respect to the radial direction of the track according to the movement of the galvanometer mirror. Since a beam shaping mechanism for performing beam shaping is added, it is possible to improve the light utilization efficiency by moving the light spot in the direction of approximately 45 ° with respect to the radial direction of the track for tracking by using the beam shaping mechanism. In addition to the above, it is possible to detect signals with low noise.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a front view showing the shape of a light receiving element.

FIG. 3 is an operation explanatory diagram showing how the light spot fluctuates on the optical disc surface.

FIG. 4 is an operation explanatory diagram showing how the light spot fluctuates on the surface of the light receiving element.

5A is a plan view showing a state where a prism is used as an optical path changing member, and FIG. 5B is a plan view showing a state where a diffraction grating is used as an optical path changing member.

FIG. 6 is a configuration diagram showing a conventional example.

[Explanation of symbols]

15 galvo mirror 16 Output optical system 17 Signal detection optical system 18 Laser light source 24,25 light receiving element 29 Optical information recording medium 31 dividing line P light spot

Claims (2)

[Claims] 1. Information recording and the like are performed by converging laser light emitted from a laser light source in an emission optical system with an objective lens through a galvano mirror and irradiating the surface of an optical information recording medium. By reproducing the reflected light from the optical information recording medium to the light receiving element in the signal detection optical system through the galvano mirror again, reproduction of information recorded on the optical information recording medium, focus error signal, and track error signal In an optical information recording / reproducing apparatus for detection, a light spot focused on the surface of the optical information recording medium by the objective lens is directed at a direction of about 45 ° with respect to a radial direction of a track according to the movement of the galvano mirror. An optical spot movement adjusting mechanism for moving the optical information recording medium, and dividing the light receiving element for receiving the reflected light from the optical information recording medium into at least two parts. The optical information recording and reproducing apparatus characterized by dividing lines for dividing is arranged to coincide with the direction of the optical axis deviation caused by the movement of the galvanometer mirror. 2. A beam shaping mechanism for performing beam shaping is added to a light spot movement adjusting mechanism for moving the light spot in a direction of approximately 45 ° with respect to the radial direction of the track according to the movement of the galvano mirror. The optical information recording / reproducing apparatus according to claim 1.