JPH0684185A - Optical disk apparatus - Google Patents

Abstract

PURPOSE:To detect a track with good accuracy by a method wherein a binary- coded focusing sum signal is generated from a focusing sum signal on which an information signal written on a disk is hardly superposed and a seek operation is controlled by using the sum signal. CONSTITUTION:A target track is accessed by a seek control circuit 25 by using a tracking difference signal Trd and a focusing sum signal Toa from a focus detection circuit 51. The tracking difference signal Trd and the tracking sum signal Toa from the detection circuit 51 are filtered by filters 15, 16, a high-frequency noise is removed, and both signals are then binary-coded by binary- coding circuits 17, 18. They are input respectively to a direction detection circuit, a track counter 21, a speed detection circuit 23 and a sum-signal correction circuit 19. The correction circuit 19 averages the binary-coded focusing sum signal during a prescribed period, shapes a waveform and removes a noise remaining in the binary-coded sum signal. The binary-coded sum signal which has been corrected by the correction circuit is input to the direction detection circuit and the speed detection circuit 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device such as a magneto-optical disk device for reading information recorded on a magneto-optical disk.

[0002]

2. Description of the Related Art As is well known, as a recording medium signal processing device using a recording medium (disc), there are, for example, an optical disc device and a magneto-optical disc device. This type of device has a hole (concavo-convex) called a physical bit on an information track of a disc having an information track called a concentric circle or a spiral groove, a region where magnetic characteristics are changed, or a metal Information is written (recorded) or information is read (reproduced) by arranging the areas whose states are changed.

Conventionally, in an apparatus for recording / reproducing information along a recording track, for example, an optical head is controlled so that a light spot is irradiated right above the track. When information is read from or written to a target track away from the track where the current optical head is located, the optical head is moved to access the target track. The operation for this track access is called a seek operation.

In the above seek operation, Japanese Patent Laid-Open No. 2-1
As described in Japanese Patent No. 4430, by moving a head carriage assembly holding an optical head in the radial direction of the disk while controlling the speed, an optical spot emitted from the optical head onto the optical disk moves a recording track. Promptly moved across to the target track.

In order to perform this speed control, the speed of the optical head must be detected, and the speed at that time is detected as follows. That is, the light reflected from the optical disc is received by the 4-division photodiode for generating the tracking control signal. The difference between the two electric signals generated by the photodiodes from the adders 30a and 30b of the above publication is detected, the difference signal indicating the difference is binarized at a predetermined level, and the cycle of the binarized signal is determined. By counting using a predetermined clock and obtaining the reciprocal of the counting result,
The speed of the optical head is detected.

In order to allow the light spot to reach the target track quickly and surely across the recording track, the moving direction of the optical head (from the inner circumference to the outer circumference of the disk or vice versa) during the speed control described above. It is also necessary to detect The reason is explained below.

For example, when the light spot is moving from the inner circumference to the outer circumference of the disc at a low speed, the groove of the disc is in the same direction as the light spot due to eccentricity or the like.
If they move faster than the light spots, their relative velocities temporarily reverse. That is, the moving direction of the light spot is reversed due to the eccentricity of the disc.

Therefore, in an apparatus using a disk in which some eccentricity cannot be avoided, it is necessary to quickly and surely determine in which direction the light spot is moving. This determination is performed by the speed control described above. This is an essential operation.

The moving direction of the light spot is the above-mentioned adder 30.
and a difference signal (hereinafter, a tracking difference signal) indicating a difference between the tracking control electric signals indicated by a and 30b,
The sum signal indicating the sum (hereinafter, the tracking sum signal) can be detected by using the phase difference between the binarized signals.

That is, the signal level of the binarization difference signal is held at the timing of the rising edge of the binarization sum signal during the movement of the optical head, and the moving direction of the light spot is judged by the level of the held signal. To be done. In other words, if the held signal is at high level,
The light spot is moving from the outer circumference to the inner circumference of the disc,
If the signal is at a low level, it is moving from the inner circumference to the outer circumference.

As described above, the speed is detected using the tracking difference signal, and the direction is detected from the phase difference between the sum signal and the difference signal, whereby accurate speed control can be performed, and the number of remaining tracks up to the target track can be increased. A high-speed seek operation based on can be realized.

[0012]

However, since the information signal is superimposed on the tracking signal when the optical head moves on the track in which the information is written, an accurate binary sum signal cannot be obtained. Sometimes. Traditionally, such information signals in the tracking sum signal used for seek operations are ignored. Therefore, in such a case, the relative movement direction of the disc and the light spot cannot be detected, and the speed control becomes extremely difficult.

An object of the present invention is to accurately and reliably detect the light spot, that is, the relative speed between the optical head carriage and the optical disk, and the moving direction of the light spot, without being affected by the information written on the disk. It is an object of the present invention to provide an optical disk device capable of achieving the above.

[0014]

In order to achieve the above object, an optical disk device according to the present invention comprises means for irradiating an optical disk with a polarized beam having a first polarization direction and moving the optical disk in the radial direction of the optical disk. Means for splitting a polarized reflected light beam having a second polarization direction reflected from the optical disc according to the polarization direction of the reflected light beam, and receiving the reflected light beam before entering the spectroscopic means, A first light receiving means for generating an electrical signal corresponding to the beam; and a second light receiving means for receiving the spectral beam split by the spectral means and generating a deviation signal corresponding to the spectral beam.
A means for detecting a moving direction of the irradiation means by using an electric signal from the first light receiving means and a deviation signal from the second light receiving means when the light receiving means and the irradiation means are moving; And means for driving the irradiation means according to the detection result of the detection means.

Since the electric signal obtained from the first light receiving means does not include a signal component, the direction of movement of the light spot during seek is accurately determined, and therefore a reliable seek operation is performed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a main part of the configuration of an optical disk device according to the present invention. The disk 11 is, for example, a magneto-optical (M
O) This disk 11 is rotationally driven by a spindle motor (not shown) whose speed is controlled at a constant angular velocity or a constant linear velocity. The disk 11 is provided with information tracks called grooves in, for example, a spiral shape or a concentric shape. In this information track, a plurality of sector marks (header information) are recorded in advance at predetermined intervals. This sector mark is composed of a combination of a plurality of physical holes (emboss bits) and indicates the address (track number, sector number, etc.) of the information recording area that follows it.

The optical head 13 irradiates the disk 11 with a laser beam, and the laser beam is condensed as a light spot on the disk 11. This laser beam is a polarized beam having a first polarization direction that is polarized in a predetermined angle direction with respect to its optical axis. By this light spot, writing of information to or reading of information from a predetermined track on the disk 11 is performed.

The movable portion 13b of the optical head 13 is driven by an actuator 27 of the head carriage assembly, and at the time of track seek, in the direction of the arrow (disk 11).
Is moved freely in the radial direction of (i.e., across the tracks on the disk). That is, the actuator 2
By driving 7, the light spot from the optical head 13 accesses the target track.

The optical head 13 is provided with a plurality of photodiodes, and the laser beam reflected light from the disk 11 is detected by these photodiodes. As shown in FIG. 2, the optical head 13 includes a light source, that is, a semiconductor laser 31,
Collimator lens 32, beam splitter 33, beam shift correction plate 34, galvano mirror
(Rotating mirror) 35, detection optical system 36, photodiode 37, two-divided photodiode 38, four-divided photodiode 39, APC detector 40, and the like, and a movable portion 13 including a rising mirror 41.
It consists of b, etc.

With the above structure, the light beam from the semiconductor laser 31 is converted into a parallel beam by the collimator lens 32 and is incident on the beam splitter 33. The prism on the incident side of the beam splitter 33 converts the light beam having an elliptical cross section into a circular light beam.

The light beam which has passed through the beam splitter 33 passes through the beam shift correction plate 34 and is reflected by the galvano mirror 35 which is rotated in the direction indicated by the arrow I around the axis.

The light beam reflected by the galvanometer mirror 35 is directed to the movable portion 13b, reflected by the internal raising mirror 41, and a parallel light beam is formed as a light spot on the disk surface of the disk 11 by an objective lens (not shown). Collected. The divergent light beam reflected by the disk 11 is polarized light having a second polarization direction different from the laser beam emitted from the optical head 13 having the first polarization angle. This reflected light beam is again converted into a parallel light beam by the objective lens, reflected by the rising mirror 41, and returned to the beam splitter 33 via the galvanometer mirror 35 and the beam shift correction plate 34 again.

The reflected light beam from the disk 11 guided to the beam splitter 33 is separated by a detection optical system 36 including a focus detection optical system and detected by photodiodes 37, 38 and 39. The detection optical system 36 includes a polarization beam splitter 36a, a non-polarization beam splitter 36b, and an optical element 3 forming a focus detection optical system.
6c.

Then, the non-polarization beam splitter 36b
The light reflected by is passed through the optical element 36c and detected by the four-division photodiode 39. This detection signal Fo1, F
O2 is processed by the focus / track detection circuit 51 of FIG. 1 to generate a focusing control signal (hereinafter, focusing sum signal) Fod. That is, since the detection signals Fo1 and Fo2 from the four-division photodiode 39 are signals obtained by the light that has not passed through the polarization beam splitter 36a, the information component on the disk 11 is not included.

The light passing through the non-polarization beam splitter 36b is transmitted through the polarization beam splitter 36a and detected by the two-divided photodiode 38. The detection signals Tr1 and Tr2 are the focus / track detection circuit 51 shown in the figure.
And the track difference signal Trd is generated. The detection signals Tr1 and Tr2 are also called deviation signals, and indicate the deviation between the optical beam irradiated on the optical disk and the track.
Here, the detection signal T from the two-division photodiode 38
Since r1 and Tr2 are signals obtained by the light that has passed through the polarization beam splitter 36a, the information components on the disk 11 are included.

Further, by processing the signal from the two-divided photodiode 38 and the signal transmitted through the non-polarization beam splitter 36b and reflected by the polarization beam splitter 36a and detected by the detector 37, the disk 11 is processed.
The information recorded in is reproduced.

At the time of recording and reproducing information, the focus signal Fod from the focus / track detection circuit 51.
In response to this, the focusing servo mechanism 61 is driven. As a result, the objective lens is moved along the optical axis direction and maintained in a focused state. As a result, the light beam from the objective lens forms a minimum beam spot on the disk 11.

Similarly, the tracking servo mechanism 71 is driven in response to the track signal Trd from the focus / track detection circuit 51. As a result, the objective lens is maintained in the combined track state. As a result, the convergent light beam from the objective lens follows the desired tracking guide on the disk 11.

FIG. 3 shows a configuration example of the focus / track detection circuit 51 of FIG. The focus / track detection circuit 51 detects the detection signals Tr1, Tr2, F from the optical head 13.
A tracking difference signal Trd used in the tracking servo mechanism 61 and the seek control circuit 25, a focusing difference signal Fod used in the focusing servo mechanism 61, and a focusing sum signal Foa used in the seek control circuit 25 are generated from o1 and Fo2.

The detection signals Tr1 and Tr2 are subtracted from each other by the subtracter 51a to obtain the tracking difference signal trd.
The tracking difference signal trd is normalized by the AGC circuit 51b, and the tracking difference signal Trd is generated. The detection signals Fo1 and Fo2 are subtracted from each other by the subtracter 51c to obtain the focusing difference signal fod. The focusing difference signal fod is normalized by the AGC circuit 51d to generate the focusing difference signal Fod. The detection signals Tr1 and Tr2 are added to each other by the adder 51e to obtain the tracking sum signal tra. The tracking sum signal tra is filtered by the filter 51f, peak-held by the peak-hold circuit 51g during seek, and then input to the AGC circuits 51d to 51i.
The detection signals Fo1 and Fo2 are added to each other by the adder 51h to obtain the focusing sum signal foa. The focusing sum signal is normalized by the AGC circuit 51i to generate the focusing sum signal Foa.

The amplitude of the tracking difference signal and the amplitude of the focusing sum signal are reduced due to variations in the reflection characteristics of the disk 11, the four-division photodiode 39 for focusing, and the two-division photodiode for tracking 38, and a binary signal is correctly generated. In order to prevent the information from being disabled, the switch SW is closed during reading or writing (or erasing) of information, and the focusing difference signal f
The od and the tracking difference signal trd are normalized by dividing by the tracking sum signal tra.
rd, which are used for tracking control and focusing control, respectively. When seeking, the SW is closed,
Each signal is normalized by the peak value of the tracking sum signal so that a constant amplitude can be secured.

As shown in FIG. 1, track seek,
In other words, access to the target track is
Using the tracking difference signal Trd and the focusing sum signal Foa from the track detection circuit 51, a feedback loop control system constituted by the seek control circuit 25 including the circuit elements 15 to 24, 26 and 27 of FIG. 1 is used.

That is, the focus / track detection circuit 51
The tracking difference signal Trd and the focusing sum signal Foa are filtered by filters 15 and 16, respectively, and high frequency noises in these signals are removed.

The filtered difference signal and sum signal are binarized by binarization circuits 17 and 18, respectively. This binarization is performed using, for example, the maximum value and the minimum intermediate level of the input signal levels as threshold values.

FIG. 4A shows a groove on the disc, FIG.
(B) Focusing sum signal fo corresponding to the groove
FIG. 4C shows a binarized focusing sum signal obtained by binarizing the sum signal. As previously mentioned,
In the focusing sum signal foa, the reflected light that does not pass through the polarization beam splitter 36 a is reflected by the photodiode 39.
Since it is generated based on the detection signals Fo1 and Fo2 obtained by being incident on
The information signal written on the disk 11 is hardly superimposed. Therefore, as shown in FIG. 4C, the binarized sum signal does not include the information signal, so that the binarized sum signal having an ideal waveform can be obtained.

FIGS. 5A, 5B and 5C are respectively shown in FIG.
It is a drawing corresponding to (A), 4 (B), 4 (C),
FIG. 5A shows the groove on the disk 11, but FIG.
FIG. 5B shows a tracking sum signal tra which has been conventionally used for a seek operation, and FIG. 5C shows a binarized tracking sum signal obtained by binarizing the sum signal tra. As described above, the tracking sum signal tra is a signal generated using the signals Tr1 and Tr2 obtained by the light reflected from the disk 11 passing through the polarization beam splitter 36a and then entering the photodiode 38. . These signals Tr1 and Tr2 contain information components. Therefore, FIG.
As shown in (B), the tracking sum signal tra also contains an information component. As a result, as shown in FIG. 5C, when the tracking sum signal is binarized, the information component is superimposed, so that the groove cannot be accurately detected by the binarized tracking sum signal.

Returning to the description of FIG. 1, the binarized difference signal binarized by the binarization circuit 17 is input to the direction detection circuit 20, the track counter 21, and the speed detection circuit 23. The binarized sum signal binarized by the binarization circuit 18 is input to the sum signal correction circuit 19.

The sum signal correction circuit 19 has a function of averaging the binarized focussing sum signal for a predetermined period and then shaping the waveform to remove noise remaining in the binarized sum signal. The binarized sum signal corrected by the sum signal correction circuit 19 is input to the direction detection circuit 20 and the speed detection circuit 23.

Before the seek operation is started, the CPU 10 presets in the track counter 21 data indicating the number of cross tracks that should cross (intersect) from the track where the current light spot is located to the target track. For example, if the target track is an outer track than the current track, a positive value is preset,
In the case of the inner circumference, a negative value is preset. or,
Each time the optical head 13 moves to the track counter 21 and the light spot crosses one track on the disk 11,
The binarization circuit 17 supplies a one-pulse binarization difference signal.

The direction detection circuit 20 detects the moving direction of the moving optical head 13b. For example, a low level is output when the optical head 13b is moving outside the disk, and a high level is output when the optical head 13b is moving inside. When the signal from the direction detection circuit 20 is at low level, the track counter 21 counts down the preset value using the output of the binarization circuit 17. When the signal is at high level, the track counter 21 counts up the preset value. Then, as the light spot approaches the target track, the absolute value of the count value of the counter 21 decreases, and when the light spot reaches the target track, the count value becomes "0".

The direction detection circuit 20 performs the following operation in order to detect the track seek direction of the optical head 13.
That is, when the light spot moves from the outer circumference to the inner circumference of the disk 11, as shown in FIGS. 6 (A) and 6 (B), the direction detection circuit 20 outputs the binary signal at the rising edge of the binary focusing sum signal. A high level signal is generated by sampling / holding the signal level of the digitalized tracking difference signal. When the light spot moves from the inner circumference to the outer circumference of the disk 11, as shown in FIGS. 7 (A) and 7 (B),
The direction detection circuit 20 samples and holds the signal level of the binarized tracking difference signal at the rising edge of the binarized focusing sum signal to generate a low level signal. In this way, the direction detection circuit 20 outputs a signal whose logical level changes depending on the moving direction (seek direction) of the light spot, and the output is given to the up-count / down-count designating input terminal of the track counter 21.

For example, assume that the optical head 13b is moved to a track outside the disk 11. A positive value is preset in the track counter 21 by the CPU 10. The reference speed signal generator 22 has a counter 2
The preset value of 1 is input, and the analog value corresponding to this preset value is output to the differential amplifier 24. As a result, the actuator 27 moves the optical head 13b to the outside of the disk 11 at high speed. The direction detection circuit 20 detects the direction and outputs a low level, and as a result, the track counter 21 counts down the preset value using the pulse output of the binarization circuit 17. While the optical head 13b is moving to the outside of the disk 11, the disk 1
When the inversion of the relative speed occurs temporarily due to the eccentricity of 1, the direction detection circuit 20 outputs a high level for that period. As a result, the counter 21 counts up only during that period, and the count value is corrected. By this count correction operation, an accurate number of cross tracks can be detected regardless of whether the disk 11 is eccentric.

The track counter output is input to the reference speed signal generation circuit 22 as described above. The reference speed signal generation circuit 22 generates reference speed data according to the number of remaining tracks up to the target track. Therefore, when the current light spot is far away from the target track and the number of remaining tracks is large, the reference speed signal generation circuit 22 generates a high speed reference speed, and the reference speed gradually decreases as it approaches the target track.

Based on the binarization difference signal from the binarization circuit 17 and the sum signal from the sum signal correction circuit 19, the speed detection circuit 23 uses a differential amplifier to output a signal indicating the speed of the currently moving light spot. It is provided to the circuit 24.

The differential amplifier 24 generates a signal proportional to the difference between the reference value from the reference speed signal generation circuit 22 and the detection value from the speed detection circuit 23. This signal is generated by the drive circuit 2.
Given to 6.

The drive circuit 26 drives the actuator 27 in response to the signal from the differential amplifier 24, whereby the optical head 13b is moved. As a result, the speed of the optical head 13 is controlled so that the light spot moves at a speed that minimizes the difference between the reference value and the detected value.

That is, by the above speed control, when there are many remaining tracks, seek is performed at a high reference speed, and as the number of remaining tracks decreases, the reference speed decreases, and thus the seek speed decreases.

[0048]

As described above, according to the present invention, the binarized focusing sum signal is generated from the focusing sum signal in which the information signal written on the disc is less likely to be superimposed, and the seek operation is controlled using this sum signal. There is. This allows
It becomes possible to detect a track more accurately than when using the tracking sum signal. That is, the speed and direction of movement of the light spot can be detected more accurately without being affected by writing information.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing the configuration of an embodiment of a magneto-optical disk device according to the present invention.

FIG. 2 is a diagram schematically showing a configuration of the optical head shown in FIG.

FIG. 3 is a block diagram showing a configuration example of a focus / track detection circuit of FIG.

4A shows a groove provided on a disc, FIG. 4B shows a focusing sum signal corresponding to the groove, and FIG. 4C shows a binarized focusing sum signal. The signal is used for seek operation.

5A shows a groove provided on the disc, FIG. 5B shows a tracking sum signal corresponding to the groove, and FIG. 5C shows a binarized tracking sum signal. The signal is used for conventional seek operations.

6A is a binarized tracking difference signal, and FIG.
(B) shows each binarized focusing sum signal, and these figures are diagrams for explaining the direction detecting operation, and show when the light spot is moving inside the disc.

7 (A) is a binarized tracking difference signal, FIG.
(B) shows each binarized focusing sum signal, and these figures are diagrams for explaining the direction detecting operation, and show when the light spot is moving to the outside of the disc.

[Explanation of symbols]

11 ... Magneto-optical disk, 13 ... Optical head, 15.16 ...
Filter, 17/18 ... Binarization circuit, 19 ... Sum signal correction circuit, 20 ... Direction detection circuit, 21 ... Track counter, 22 ... Reference speed signal generation circuit, 23 ... Speed detection circuit, 24 ... Differential operation amplification circuit, 25 ... seek control circuit, 26 ... drive circuit, 27 ... actuator, 3
6 ... Detection optical system, 36a ... Polarizing beam splitter, 3
6b ... Non-polarizing beam splitter, 36c ... Focus detection optical element, 37.38.39 ... Detector, 51 ... Focus / track detection circuit, 61 ... Focusing servo mechanism, 71 ... Tracking servo mechanism.

Claims (2)

[Claims] 1. An optical disk apparatus for accessing a target track on an optical disk having a track formed therein and information recorded along the track, wherein a means for irradiating the optical disk with a polarized beam, wherein the polarized beam is Polarized light having a first polarization direction at a predetermined angle with respect to the optical axis, wherein the irradiation means can move toward the target track along the optical disk in a direction traversing the track, and reflected light reflected from the optical disk. Means for splitting the beam according to the polarization direction of the reflected light beam, wherein the reflected light beam is polarized light having a second polarization direction different from the first polarization direction, and is incident on the spectroscopy means. A first light receiving means for receiving the reflected light beam before being generated and generating an electrical signal corresponding to the reflected light beam; and the spectroscopic means. Spectroscopic spectroscopic beam received Te,
Second light receiving means for generating a deviation signal corresponding to the spectral beam, wherein the deviation signal indicates a deviation between the light beams incident on the disk and the track, and when the irradiation means is moving, the second light receiving means 1 means for detecting the moving direction of the irradiation means using an electric signal from the light receiving means and a deviation signal from the second light receiving means, and means for driving the irradiation means according to the detection result of the detection means An optical disc device comprising: 2. An optical disk apparatus for accessing a target track of an optical disk having a track formed and information recorded on the track, wherein light for irradiating the optical disk with a polarized beam and inputting a reflected beam reflected by the optical disk is inputted. The head, wherein the polarized beam is polarized light having a first polarization direction at a predetermined angle with respect to its optical axis, and the reflected beam is the first polarized direction.
And a non-polarization beam splitter for splitting the reflected light beam reflected from the optical disc into a first light beam and a second light beam, and a first light beam A photodiode that receives and generates an electric signal corresponding to the first light beam; a first binarization circuit that generates a first binarization signal corresponding to the electric signal; The binarized signal has a rising edge, receives a polarized light beam splitter that splits the second light beam according to the polarization direction of the second light beam, and receives a spectral light beam that is split by the polarized light beam splitter. A two-divided photodiode that generates a deviation signal corresponding to each of the spectral light beams, wherein the deviation signal is a light beam emitted to the optical disc and the track. A subtraction circuit that generates a difference signal that indicates a difference and that indicates a difference between the deviation angle signals from the two-division photodiode; and a second binarization circuit that generates a second binarization signal corresponding to the difference signal. An actuator for moving the optical head in a direction traversing a track of the optical disk toward the target track, and a sampled at a rising edge of the first binarization signal when the optical head is moved by the actuator. A direction detection circuit that detects the moving direction of the optical head based on the signal level of the second binarized signal; and a drive circuit that drives the actuator according to the detection result of the detection circuit. An optical disk device characterized by the above.