JP2003045044A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably attain the setting operation to the tracking control even in the state where a focus lens is shifted after the seek operation is finished, in an optical disk device. SOLUTION: The detection offset of a track deviation detecting signal generated by the shift of a focus lens at the time when the seek operation is finished, is removed by a binary circuit, an averaging circuit and an amplifier circuit, then the setting operation to the tracking control is carried out, and an offset removing circuit is separated after the setting of the tracking control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc device for recording or reproducing information on an optical information medium such as an optical disc having a track, and more particularly to an optical spot for recording or reproducing information. The present invention relates to an optical disk device that can easily achieve an initial operation of tracking control for positioning on a track, that is, an operation of pulling in tracking control.

[0002]

2. Description of the Related Art In an optical disk device, a laser beam is focused by a focus lens using an optical head, irradiated onto the information recording surface of the optical disk as a light spot, and information is recorded by modulating the light intensity of the laser beam,
Alternatively, information is reproduced by receiving reflected light from the optical disc with a photodetector and converting the intensity of the reflected light into an electric signal. On the information recording surface of the optical disc, a track is formed in advance by an uneven pit row, a groove, a land, or the like so that the light spot can scan a predetermined position. When the light spot emitted from the optical head deviates from the track, the optical intensity distribution of the optical disk reflected light changes, so the track deviation detection signal is obtained by receiving the reflected light with a multi-division photodetector and performing signal processing. be able to. The track deviation detection signal is supplied to a lens actuator equipped with a focus lens after performing signal processing such as phase compensation and current amplification, and the lens actuator drives the focus lens according to the track deviation detection signal. Therefore, the position of the light spot deviated from the track center can be automatically corrected, and so-called tracking control can be achieved. Further, when recording or reproducing information at different information recording surface positions of the optical disc, the above tracking control is temporarily suspended, and after moving the optical head to a desired position along the radial direction of the optical disc, Tracking control is started again. The operation of moving the optical head in the radial direction of the optical disk is called access or seek.

Normally, the tracks are periodically arranged along the radial direction of the optical disk, so that the track deviation detection signal has a periodic waveform such as a sine function centered on the zero level. However, if the set positions of the laser light source, the focus lens, the photodetector, etc. are displaced within the optical head, the amplitude center of the track displacement detection signal deviates from the zero level, and so-called offset occurs. In particular, since the focus lens is supported by the spring of the lens actuator so as to be movable in the radial direction of the optical disc, when a sudden braking force is applied to the optical head at the end of the seek operation or when an external force is applied to the optical disc device or the optical head. Occurs, or when an overcurrent flows through the lens actuator due to an inadvertent malfunction of tracking control, the focus lens is displaced or vibrates in the optical head, and an offset occurs in the track deviation detection signal. When the tracking control is restarted when the track deviation detection signal is offset, the detection sensitivity decreases near the zero level of the track deviation detection signal, and the margin range for the overshoot that passes the focus target position of the control is reduced. Is narrow, there is a high possibility that tracking control pull-in will fail.

Therefore, in Japanese Patent Laid-Open No. 10-308024, a displacement amount of a focus lens is measured using a position sensor, a signal component corresponding to an offset is created from a focus lens displacement signal, and an offset is obtained from a track deviation detection signal. A technique for removing a signal component corresponding to is disclosed. Further, Japanese Patent Laid-Open No. 2000-187855 discloses a TZC using a track zero cross (TZC) detection circuit, a digital signal processor (DSP) and an MPU.
A technique of measuring a rising time interval and a falling time interval of an output signal of a detection circuit, creating a correction signal so that the two time intervals are equal, and removing a signal component corresponding to an offset from a track deviation detection signal is disclosed. ing.

[0005]

However, in the case of using the position sensor, the position sensor or the light shielding plate or the like is arranged so that the focus lens displacement signal becomes zero level when the focus lens is in the neutral position of the lens actuator spring. I had to adjust the position. In addition, it is necessary to obtain the conversion coefficient for converting the focus lens displacement signal into the offset component of the track deviation detection signal in advance, and to determine the gain of the amplifier, etc. There is a problem that the conversion coefficient may change due to dust adherence to a plate or the like or a change in sensor sensitivity, and a stable offset removal effect cannot be obtained for a long period of time.

Further, when the TZC detection circuit, the DSP and the MPU are used, the DSP or MPU during the seek operation monitors the track count and the automatic focus control and the optical head feed amount by the seek mechanism. Moreover, adding digital measurement processing of the rising time interval and the falling time interval and calculation of the correction signal can be performed by the DSP or MPU.
The burden on In particular, in order to improve the measurement accuracy of the rising time interval and the falling time interval, the sampling time interval, which is the unit of the measurement time, must be made fine, and a redundant number of bytes is required for digitizing the measured values. There is a problem that a high-speed DSP or MPU is required because the number of calculations by the DSP or MPU rapidly increases.

It is an object of the present invention to provide an optical disk device capable of correcting an offset generated in a tracking error signal due to a fluctuation of a light spot for recording or reproducing information at the end of seek. The present invention provides an optical disc device that does not require the introduction or adjustment of new measuring means, does not increase the processing load of the MPU or the like in the device, and can easily achieve a stable pull-in operation for a long period of time. You can do it.

[0008]

In order to achieve the object of the present invention, in the first invention, the optical disk device uses a binary track deviation detection signal generated by detecting a light spot reflected from the optical disk. A binarizing circuit for binarizing, and an averaging circuit for obtaining an average signal of the binarized signals by the binarizing circuit,
When an offset occurs in the track deviation detection signal,
A subtraction circuit that subtracts the averaged signal from the track deviation detection signal so as to remove the offset.

According to a second aspect of the invention, an optical disk device has a light collecting means for collecting a laser beam as a light spot on the optical disk and a track deviation detecting means for detecting a positional deviation between a track on the optical disk and the light spot. Drive means for moving the light collecting means in a direction substantially perpendicular to the direction of the track, tracking control means for controlling the drive means by a track deviation detection signal output from the track deviation detection means, A first switch means for controlling the operation of the tracking control means, a binarizing means for binarizing the track deviation detection signal with a predetermined level, and a binary value output from the binarizing means. Averaging means for obtaining a rough average level using the averaging signal, amplification means for amplifying the averaging signal output from the averaging means, and output from the amplification means. A second switch means for opening and closing the amplified signal, a signal output from the second switching means and a subtraction means for subtracting from said tracking error detection signal.

In a second aspect of the present invention, the switch control is such that when the first switch means is cut off, the second switch means is made conductive, and when the first switch means is made conductive, the second switch means is cut off. Provide means. Further, in the present invention, a delay means for delaying signal transmission is provided between the switch control means and the second switch means, and after the first switch means is turned on, a predetermined period of time elapses between the switch control means and the second switch means. The switch means of 2 is cut off.

In the second invention, there is provided subtraction processing means for subtracting a constant level offset which the track deviation detection signal output by the track deviation detection means has regardless of the position of the light converging means. Further, the averaging means is composed of a capacitor and a resistor or a choke coil.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an optical disk device according to the present invention will be described below with reference to the drawings using some examples. FIG. 1 shows a first optical disc device according to the present invention.
FIG. 3 is a configuration diagram showing an embodiment of the above, which is an embodiment when a tracking error signal is detected by a push-pull method.
In the figure, 1 is an optical disk device, 2 is an optical disk, 3
Rotates the optical disk 2 with a disk motor. An optical head 4 is composed of a semiconductor laser 5, a half mirror 6, a prism mirror 7, a two-dimensional lens actuator 8, a focus lens 9 and a four-division photodetector 10. The two-dimensional lens actuator 8 can move the focus lens 9 in two directions. A differential circuit 11 subtracts two signals output from the four-division photodetector 10 and outputs a track deviation detection signal 12. Reference numeral 13 is a comparison circuit, for example, which compares the level of the track deviation detection signal 12 with a zero level and outputs a positive constant voltage when it is positive and a negative constant voltage when it is negative as a binarized signal 14. Reference numeral 15 is an averaging circuit, which outputs an almost average level of the binarized signal 14 in time as an average signal 16. Reference numeral 17 denotes an amplifier circuit, which amplifies the average signal 16 with a predetermined amplification factor and outputs an offset signal 18. Reference numeral 19 is a switch circuit. Reference numeral 20 denotes a differential circuit which outputs a track deviation detection signal 21 corrected by subtracting the offset signal 18 from the track deviation detection signal 12. The corrected track deviation detection signal 21 is supplied to the two-dimensional lens actuator 8 through the switch circuit 22 and the tracking control circuit 23 including a phase compensation circuit and a current amplification circuit.

Reference numeral 24 denotes an MPU, which controls the entire optical disk device. The MPU 24 is a disk motor control circuit 25.
To control the rotation of the disk motor 3 and to the laser drive circuit 26 to control the amount of light emitted from the semiconductor laser 5. Reference numeral 27 denotes a head feeding mechanism, which is composed of, for example, a rail fixed to the optical disk device 1, a pulley provided on the optical head 4 and a coil or magnet for generating an electromagnetic force. Can be moved to. The MPU 24 sends a command to the head feed control circuit 28, and the head feed control circuit 28 moves the optical head 4 in the radial direction of the optical disc 3 by passing an electric current through the coil of the head feed mechanism 27 to generate an electromagnetic force. Further, the MPU 24 issues a command 29 for canceling the automatic tracking control at the start of the seek to cut off the switch circuit 22 and makes the switch circuit 19 conductive through the delay circuit 30. At the end of the seek, a command 29 is issued to start the automatic tracking control to make the switch circuit 22 conductive, and the delay circuit 3
The switch circuit 19 is cut off through 0. The delay circuit 30 keeps the switch circuit 19 conductive even after the servo is turned on, corrects the offset of the tracking signal for a while, and shuts off the switch circuit 19 when the tracking control becomes stable.

Next, the operation of the optical disk device 1 shown in FIG. 1 will be described. First, when the optical disk 2 is inserted and fixed to the disk motor 3, the MPU 24 sends a command to the disk motor control circuit 25 to rotate the disk motor 3 and the optical disk 2. Next MPU24
Sends a command to the head feed control circuit 28 and causes the head feed mechanism 27 to move the optical head 4 to an arbitrary position in the radial direction of the optical disc 3. After that, the MPU 24 sends a command to the laser drive circuit 26 to cause the semiconductor laser 5 to emit light. The laser beam emitted from the semiconductor laser 5 is reflected by the half mirror 6 and the prism mirror 7, and is focused by the focus lens 9 as a light spot on the recording surface of the optical disc 2. The laser beam reflected by the recording surface of the optical disc 2 is again condensed by the focus lens 9, reflected by the prism mirror 7, and transmitted through the half mirror 6. The half mirror 6 is a parallel plate and is obliquely arranged, and therefore imparts astigmatism to the transmitted focused beam. Therefore, the laser beam transmitted through the half mirror 6 is added with astigmatism and focused on the surface of the four-division photodetector 10.

FIG. 2 is a block diagram showing an embodiment of the signal detection circuit of the optical disk device shown in FIG. 1, showing the shape of the light receiving element on the surface of the four-division photodetector 10 and the connection of the electric circuits around it. The four-division photodetector 10 includes four light receiving elements D1 and D1.
It consists of 2, D3 and D4. Circle 41 indicates the laser beam. In this embodiment, the astigmatism method is used for defocus detection, and the output signal d1 of the light receiving element D1 and the output signal d3 of the light receiving element D3 are added by the adding circuit 43 to obtain the light receiving element D.
The output signal d2 of 2 and the output signal d4 of the light receiving element D4 are added by the adder circuit 44, the output of the adder circuit 43 and the output of the adder circuit 44 are subtracted by the differential circuit 45, and (d1 + d
3) -defocus detection signal 46 represented by (d2 + d4)
To get Automatic focus control can be achieved by supplying the defocus detection signal 46 to the two-dimensional lens actuator 8 shown in FIG. 1 through a phase compensation circuit and a current amplification circuit not shown. Further, the push-pull method is used for detecting the track deviation, and when the light spot deviates from the track, the light intensity distribution of the laser beam 41 changes at the dividing line 42 of the four-division photodetector 10 as a boundary. The output signal d1 of D1 and the output signal d2 of the light receiving element D2 are added by the adding circuit 47, the output signal d3 of the light receiving element D3 and the output signal d4 of the light receiving element D4 are added by the adding circuit 48, and the output of the adding circuit 47 and the adding circuit are added. 48
1 is subtracted by the same differential circuit 11 as shown in FIG. 1 to obtain the track deviation detection signal 12 represented by (d1 + d2)-(d3 + d4). The track deviation detection signal 12 is supplied to the two-dimensional lens actuator 8 through the differential circuit 20, the switch corridor 22, the tracking control circuit 23 including a phase compensation circuit, a current amplification circuit, and the like in FIG. 1, and automatic tracking control is achieved. To be done. When automatic focus control and automatic tracking control are achieved, MPU2
4 receives data to be recorded from an external computer or the like not shown in the figure, and sends modulated data to the laser drive circuit 26 based on the data to be recorded. The amount of emitted light is modulated, and data is recorded on the track of the optical disc 2. When reproducing the recorded data, when the light spot scans the data recorded on the track of the optical disc 2, the total amount of light of the laser beam 41 shown in FIG. The outputs of the adder circuit 48 are added by the adder circuit 49 to obtain (d1 + d2 + d3
A reproduction signal 50 represented by + d4) is obtained. Playback signal 50
Is sent to the MPU 24, demodulated into original information data by the MPU 24, and sent to an external computer or the like not shown in the figure. Recording or reproduction of information is achieved by the above operation.

Next, the operation of recording or reproducing information on tracks at different positions on the optical disc 2 will be described. First, the offset correction operation of the track deviation detection signal according to the present embodiment will be described with reference to FIG. FIG. 3 is a waveform diagram for explaining a processing operation for correcting an offset due to a seek of the track shift detection signal, FIG. 3A is a waveform diagram showing the detected track shift detection signal, and FIG. 3B. Is 2 of the signal shown in FIG.
FIG. 3C shows a waveform diagram of the binarized signal, FIG. 3C shows an average signal of the binarized signal of FIG. 3B, and FIG. 3D shows a waveform diagram of the corrected track deviation detection signal. In each of the waveform diagrams, the horizontal axis represents time and the vertical axis represents voltage. More specifically, FIG. 3A shows the track deviation detection signal 12 output by the differential circuit 11 of FIG. 1, and FIG. 3B shows the binarized signal output by the comparison circuit 13 of FIG. 14 is shown in FIG.
1C shows the average signal 16 output from the averaging circuit 15 in FIG. 1, and FIG. 3D shows the corrected track deviation detection signal 21 output from the differential circuit 20 in FIG.

When a sudden braking force acts on the optical head during the seek operation or at the end of the seek operation, the focus lens 9 supported by the spring of the two-dimensional lens actuator 8 is displaced or vibrated, and the laser beam shown in FIG. 41 is displaced or vibrated in the vertical direction of the paper surface. First, the case where the focus lens 9 is at the neutral position of the support spring of the two-dimensional lens actuator 8 will be described. The laser beam 41 is located at the center of the four-division photodetector as shown in FIG. 2, and the output signal d1 of the light receiving element D1 and the output signal d2 of the light receiving element D2.
(D1 + d2) and the output signal d3 of the light receiving element D3 and the output signal d4 of the light receiving element D4 (d3 + d4) are equal on average, and the track deviation detection signal 12 is the track deviation detection signal TE- of FIG. Center of amplitude A as indicated by A
VA becomes a zero level waveform. Comparing circuit 13 of FIG.
Can be achieved by a simple circuit as shown in FIG. 4, for example.

FIG. 4 is a block diagram showing an embodiment of the comparison circuit. In this circuit, the track deviation detection signal 12 is input to the plus input terminal of the differential operational amplifier 61, and the minus input terminal is grounded to zero level. However, it is used without a feedback resistor. The difference of the track deviation detection signal 12 with respect to the zero level of the minus input terminal is amplified with an infinite gain, and the binarized signal 14 corresponding to the supply voltage ± Vcc of the operational amplifier 61 is output. Since the track deviation detection signal TE-A shown in FIG. 3A has almost the same time intervals at which it passes the zero level, the binarized signal 14 is positive as shown by the binarized signal S1-A in FIG. 3B. Level time interval a
And the time interval b at which the negative level is reached is equal.

The averaging circuit 15 shown in FIG. 1 is, for example, as shown in FIG.
Alternatively, it can be achieved by a simple circuit as shown in FIG. 5 (a) and 5 (b) are circuit diagrams showing an embodiment of the binarization circuit. In the circuit of FIG. 5 (a), two resistors R1 and R2 and two capacitors C1 and C2 are provided, A signal 16 having an average voltage level of the input binarized signal 14 can be obtained by repeating charging and discharging by the two capacitors C1 and C2 through the resistor R2. Also,
In the circuit of FIG. 5B, a choke coil CH and two capacitors C1 and C2 are provided, and two capacitors C1
By repeating charging and discharging through the choke coil CH, C2 and C2 can obtain an average voltage level signal 16 of the input binarized signal 14.

In the binarized signal SI-A of FIG. 3 (b), the plus level time interval a and the minus level time interval b are equal, so the average signal 16 is the average signal S2- of FIG. 3 (c).
As shown in A, the level becomes zero. Therefore, the average signal 1
6 is input to the differential circuit 20 as it is at the zero level when it passes through the amplifier circuit 17 of FIG. 1 and the switch circuit 19 is connected, and the corrected track deviation detection signal 21 is shown in FIG. It does not change from the original track deviation detection signal TE-A (see FIG. 3A) as indicated by TE'-A.

Next, the focus lens 9 is displaced from the neutral position of the support spring of the two-dimensional lens actuator 8,
The case where the laser beam 41 indicated by is shifted upward with respect to the dividing line 42 will be described. Sum of output signal d1 of light receiving element D1 and output signal d2 of light receiving element D2 (d1 +
d2) becomes larger on average than the sum (d3 + d4) of the output signal d3 of the light receiving element D3 and the output signal d4 of the light receiving element D4, and the track deviation detection signal 12 is the track deviation signal TE- of FIG. As shown by B, the center of amplitude AV−
B shifts to the plus side by Vb, and an offset occurs. When this track deviation detection signal TE-B is compared with the zero level, as shown by the binarized signal S1-B in FIG.
The time interval a at which the binary signal 14 has a positive level is longer than the time interval b at which it has a negative level, and the average signal 1
6 is the average signal S2-B of FIG. 3 (c), which is a positive level. Therefore, by setting the amplification factor of the amplifier circuit 17 of FIG. 1 to a predetermined value, the offset amount Vb of the track deviation detection signal TE-B is generated from the average signal S2-B, and the switch circuit 19 is connected. In this case, it is input to the differential circuit 20. Therefore, the offset of the corrected track deviation detection signal 21 is removed as shown by the corrected track deviation detection signal TE'-B in FIG.

On the contrary, when the focus lens 9 is displaced in the opposite direction and the laser beam 41 shown in FIG. 2 is displaced downward in the drawing with respect to the dividing line 42, the output signal d1 of the light receiving element D1.
And the output signal d2 of the light receiving element D2 (d1 + d2) is the output signal d3 of the light receiving element D3 and the output signal d of the light receiving element D4.
4 is smaller than the sum (d3 + d4) of 4 on average, and the track deviation detection signal 12 has the amplitude center AV-C of Vc as shown by the track deviation detection signal TE-C of FIG.
However, it shifts to the minus side, and the opposite offset occurs. When the track deviation detection signal TE-C is compared with the zero level, the time interval a at which the binarized signal 14 has a positive level becomes a negative level, as shown by the binarized signal S1-C in FIG. 3B. It becomes shorter than the time interval b, and the average signal 16 becomes a negative level as shown by the average signal S2-C in FIG. Therefore, by setting the amplification factor of the amplifier circuit 17 of FIG. 1 to a predetermined value, the offset amount Vc of the track deviation detection signal TE-C is generated from the average signal 16,
The differential circuit 20 when the switch circuit 19 is connected
Entered in. Therefore, the offset of the corrected track deviation detection signal 21 is removed as shown by the corrected track deviation detection signal TE'-C in FIG.

When information is recorded on or reproduced from tracks at different positions on the optical disc 2, first, MP is recorded.
U24 gives a command 2 to cancel the automatic tracking control.
9 to disconnect the switch circuit 22 and cause the switch circuit 19 to conduct through the delay circuit 30. After that, the MPU 24 sends a command to the head feed control circuit 28, and the head feed mechanism 27 performs a seek operation of moving the optical head 4 to a predetermined position in the radial direction of the optical disc 3. During the seek operation or at the end of the seek operation, a sudden propulsive force or a braking force is applied to the optical head, and the focus lens 9 supported by the spring of the two-dimensional lens actuator 8 is displaced or vibrated, and the laser beam shown in FIG. 41 is displaced or vibrated in the vertical direction of the paper surface, and an offset occurs in the track deviation detection signal 12.

However, by the comparison circuit 13, the averaging circuit 15, and the amplification circuit 17 according to the present invention, the differential circuit 20 always outputs the track deviation detection signal 21 from which the offset is removed as described above. Therefore, the MPU 24
After the optical head 4 has moved to a predetermined position in the radial direction of the optical disc 3, the automatic tracking control is restarted.
9 to make the switch circuit 22 conductive, and a stable pull-in operation can be achieved by the track shift detection signal 21 from which the offset is removed. When the pull-in operation is achieved and the automatic tracking control is started, the displacement of the focus lens is reduced and the offset amount generated in the track shift detection signal 12 is also reduced. Therefore, the switch circuit 19 is cut off through the delay circuit 30. As mentioned above, automatic tracking control is achieved again at a different track position,
Information can be recorded or information can be reproduced.

Track deviation detection signal 12 and binary signal 1
Although the circuit shown in FIG. 2 and FIG. 4 has been used as the generating means of No. 4, various ICs and LSIs are currently on the market for RF signal processing and servo control of CD players and the like. Is the input of the output of the light receiving element for detecting the track deviation and the track deviation detection signal or the binarized signal 1
There are some which can output a track number count signal equivalent to four. When such an IC or LSI is used, the present invention can be implemented only by adding a simple averaging circuit using inexpensive parts shown in FIG. 5, an inexpensive DC amplifier circuit, a switch circuit and a delay circuit.

In the above embodiment, the optical disc device using the push-pull method for detecting the track deviation is described, but the present invention is also applied to the optical disc apparatus using the three-spot method track deviation detecting method using the diffraction grating. It goes without saying that you can do it. Further, as a track shift detecting method, there is a phase difference detecting method as described in, for example, Japanese Patent Laid-Open Nos. 57-181433 and 62-165737. In the phase difference detection method, when a light spot scans a concave-convex pit array on an optical disc information recording surface, a phenomenon in which a temporal change of a reflected light intensity distribution varies depending on a place is used, for example, reflected light is detected by four-division light detection. Then, the outputs of the two light receiving elements at the diagonal positions are added to each other, and the phase difference of the time change of the two added signals is detected to obtain the track deviation detection signal. The present invention can also be applied to an optical disk device using the track shift detection method of this phase difference detection method.

A second embodiment in which the present invention is applied to an optical disk device which uses a phase difference detection method for detecting track deviations,
This will be described with reference to FIGS. In the second embodiment, the optical disc rotating means, the automatic focus control means, the information recording / reproducing means and their operations are the same as those of the optical disc device 1 described with reference to FIG. 1, and the track deviation detecting means and the output signal processing means thereof. Is different. Therefore, the same components as those of the optical disc device 1 described with reference to FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 6 shows a second optical disk device according to the present invention.
It is a block diagram which shows the Example of. The track deviation detection signal by the phase difference detection method is a signal (d1 + d3) obtained by adding the output signal d1 of the light receiving element D1 and the output signal d3 of the light receiving element D3 of the four-division photodetector 10 described in FIG. 2 and the light receiving element D2. Is generated from the signal (d2 + d4) that is obtained by adding the output signal d2 of the above and the output signal d4 of the light receiving element D4. In FIG. 6, reference numeral 81 denotes an adding circuit, which is a signal (d1 + d) obtained by adding the output signal d1 of the light receiving element D1 and the output signal d3 of the light receiving element D3.
3) is output, and the addition circuit 82 outputs a signal (d2 + d4) obtained by adding the output signal d2 of the light receiving element D2 and the output signal d4 of the light receiving element D4. Reference numeral 83 is a capacitor that cuts the DC component of the output signal (d1 + d3) of the adder circuit 81 and passes the AC component signal 84, and 85 is an AC component signal that cuts the DC component of the output signal (d2 + d4) of the adder circuit 82. It is a capacitor that allows 84 to pass through. 87
Is a track shift detection signal generation circuit, and the signal (d1 + d
A track deviation detection signal 88 is generated from the AC component signal 84 of 3) and the AC component signal 86 of the signal (d2 + d4).
Reference numeral 90 denotes a comparison circuit, which compares the level of the track deviation detection signal 88 with a zero level and outputs a positive constant voltage when it is positive and a negative constant voltage when it is negative as a binarized signal 91. The resistor R1, the resistor R2, the capacitor C1, and the capacitor C2 form an averaging circuit, which outputs an almost average level in time of the binarized signal 91 as an average signal 92. 93
Is a differential circuit, which amplifies with a predetermined amplification factor determined by the resistors Rf and Rs and outputs an offset signal 94. Reference numeral 95 is a switch circuit. A differential circuit 96 subtracts the offset signal 94 from the track deviation detection signal 88 and outputs a corrected track deviation detection signal 97. The corrected track deviation detection signal 97 passes through the switch circuit 98 and the tracking control circuit 99 including a phase compensation circuit, a current amplification circuit, etc., and becomes the signal 100 supplied to the two-dimensional lens actuator 8 shown in FIG.

Reference numeral 101 denotes an MPU, which at the start of a seek cancels the automatic tracking control, issues a command 102 to cut off the switch circuit 98 and at the same time issues a command 103 to make the switch circuit 95 conductive, and at the end of the seek the automatic tracking control. At the beginning, the command 102 is issued to turn on the switch circuit 98, and after receiving the notification 104 of the tracking control achievement from the tracking control circuit 99, the command 103 is issued to shut off the switch circuit 95.

First, the track shift detection signal generation circuit 87.
The configuration and operation of will be described. FIG. 7 is a block diagram showing an embodiment of the track deviation detection signal generation circuit. In the figure, 111 is a differentiating circuit, which outputs a time differential signal 112 of the AC component signal 84 of the signal (d1 + d3). 1
Reference numeral 13 denotes a comparator, which compares the level of the AC component signal 84 of the signal (d1 + d3) with a zero level, sends a positive constant voltage to the output gate only while the signal 84 is at a positive level, and uses the differential signal 112 output from the differentiating circuit 111. The output gate is opened to output the zero-cross signal 114. Reference numeral 115 denotes a pulse width forming circuit, which outputs a signal (d) from the instant when the zero-cross signal 114 output from the comparator 113 rises.
The high-level pulse signal 116 is output for a fixed time corresponding to a half cycle of (1 + d3) or (d2 + d4). 11
7 is a differentiating circuit, which is an AC component signal 8 of the signal (d1 + d3)
The time differential signal of 6 is output. Reference numeral 118 denotes a comparator, which compares the level of the AC component signal 86 of the signal (d1 + d3) with the zero level, sends a positive constant voltage to the output gate only while the signal 86 is at a positive level, and outputs it by the differential signal output from the differential circuit 117. Open the gate and output the zero-cross signal. 119 is a pulse width forming circuit, which is a comparator 1
The high-level pulse signal 120 is output for a certain period of time from the instant of the rising edge of the zero-cross signal output from 18. Reference numeral 121 denotes a delay circuit, which outputs a pulse signal 122 obtained by delaying the pulse signal 120 by a fixed time corresponding to a quarter cycle of the signals (d1 + d3) and (d2 + d4).
An AND circuit 123 outputs a high level signal 124 only when both the pulse signal 116 and the pulse signal 122 are high level. Reference numeral 125 is an averaging circuit, which is constituted by a simple circuit as shown in FIG. 5A or FIG. 5B, for example, and outputs a signal 126 of an average voltage level of the input signal 124. 127 is a differential circuit, and the signal 12
The reference voltage Vo indicated by 128 is subtracted from 6 and the track deviation detection signal 88 is output.

FIG. 8 is a waveform diagram for explaining the operation of the track deviation detection signal generation circuit. The AC component signal 84 of the signal (d1 + d3) shown in FIG.
1 is time-differentiated to be a differential signal 112 as shown in FIG. 8B, whereby the output gate of the comparator 113 is opened only while the differential signal 112 is at a positive level as shown in FIG. 8C. . At the same time, the (d1 + d3) signal 84 shown in FIG. 8A is compared with the zero level inside the comparator 113, and a positive constant voltage is sent to the output gate only during the positive level. Therefore, the comparator 11
The zero-cross signal 114 output by 3 becomes a pulse that rises at the moment when the (d1 + d3) signal 84 zero-crosses from the negative level to the positive level, as shown in FIG. 8 (d).
The zero-cross signal 114 output from the comparator 113 rises by the pulse width forming circuit 115 at the moment when the (d1 + d3) signal 84 zero-crosses from the negative level to the positive level as shown in FIG. 8E, and a half cycle of the (d1 + d3) signal. Becomes the high-level pulse signal 116 for a fixed time corresponding to.

Similarly, the AC component signal 86 of the signal (d2 + d4) is similarly processed by the differentiating circuit 117, the comparator 118 and the pulse width forming circuit 119. For example, if the (d2 + d4) signal 86 has the same phase as the (d1 + d3) signal 84 as shown in FIG. 8F, the pulse signal 120 has the same waveform as the pulse signal 116 shown in FIG. The circuit 121 delays a constant time corresponding to a quarter period of the (d1 + d3) signal or the (d2 + d4) signal, and the constant pulse width signal 12 as shown in FIG.
It becomes 2. Therefore, the output signal 124 of the AND circuit 123
Is the (d2 + d4) signal 86 as shown in FIG.
Rises at the instant of zero crossing of the signal and falls at the instant of zero crossing of the (d1 + d3) signal 84. Also, signal 12
The duty of the pulse width of 4 is (d2 + d4) signal 8
25% if the phase of 6 matches the (d1 + d3) signal 84
And the phase of the (d2 + d4) signal 86 becomes (d1 + d
3) It becomes smaller than 25% when delayed from the signal 84, and becomes larger than 25% when advanced. The averaging circuit 125 outputs the reference voltage Vo when the pulse width duty of the signal 124 is 25%, outputs a voltage lower than Vo when the pulse width duty is smaller than 25%, and outputs a voltage higher than Vo when the pulse width duty is larger than 25%. Since the signal 126 is offset by the reference voltage Vo, the reference voltage V is changed by the differential circuit 127.
subtract o. As described above, when the light spot deviates from the track, (d1 + d3) signal 84 and (d2 + d)
4) The phase of the signal 86 changes, the duty of the pulse width of the output signal 124 changes, and the signal level output from the averaging circuit 125 deviates from the reference voltage Vo.
The track deviation detection signal 88 can be obtained by subtracting o.

Next, the second optical disk device according to the present invention
The operation of the embodiment will be described. First, similarly to the first embodiment, when the optical disc is inserted and rotated and the automatic focus control is achieved, the output of each light receiving element is output from the four-division photodetector of the optical head to the addition circuit 81 of FIG. 82 is input.
A track shift detection signal generation circuit 87 generates a track shift detection signal 88 from the AC component signal 84 of the output signal (d1 + d3) of the addition circuit 81 and the AC component signal 86 of the output signal (d2 + d4) of the addition circuit 82. The track deviation detection signal 88 passes through the differential circuit 96, the switch circuit 98, and the tracking control circuit 99 including a phase compensation circuit, a current amplification circuit, etc. in FIG. 6, and outputs the signal 100 to the two-dimensional lens actuator 8 shown in FIG. By supplying
Automatic tracking control is achieved. When automatic focus control and automatic tracking control are achieved, MPU101
Receives data to be recorded from an external computer or the like (not shown), records the data on the track of the optical disc, or reproduces the recorded data and sends it to the computer or the like.

Next, the operation for recording or reproducing information on tracks at different positions on the optical disk will be described. First, the offset correction operation of the track deviation detection signal according to the present invention will be described. When a sudden braking force is applied to the optical head during the seek operation or at the end of the seek operation, the focus lens supported by the spring of the two-dimensional lens actuator 8 is displaced or vibrates, and a detection error occurs in the track deviation detection signal 88.

FIG. 9 is a waveform diagram for explaining the processing operation for correcting the offset of the track deviation detection signal due to seek or the like, and FIG. 9A is a track output by the track deviation detection signal generation circuit 87 of FIG. 9B shows the shift detection signal 88, FIG. 9B shows the binarized signal 91 output from the comparison circuit 90 of FIG. 6, and FIG. 9C shows the resistance R1 and the resistance R of FIG.
2 shows the average signal 92 output from the averaging circuit composed of the capacitors C1 and C2, and FIG. 9D shows the corrected track deviation detection signal 97 output from the differential circuit 96 in FIG. First, the case where the focus lens is at the neutral position of the support spring of the two-dimensional lens actuator 8 and there is no detection error in the track deviation detection signal 88 will be described. The track deviation detection signal 88 has an amplitude center AV- as shown by the track deviation detection signal TE-A in FIG.
When A is at zero level, it becomes a roughly triangular waveform. Since the track deviation detection signal TE-A has almost the same time interval for passing the zero level, the binarized signal 91 output from the comparison circuit 90 of FIG. 6 is the binarized signal S1-A of FIG. 9B. As shown, the time interval a at which the level is positive and the time interval b at which the level is negative are equal. Therefore, the average signal 92 is shown in FIG.
As shown by the average signal S2-A in (c), the level becomes zero. Therefore, when the average signal 92 passes through the amplifier circuit 93 of FIG. 6 and the switch circuit 95 is connected, the average signal 92 is input to the differential circuit 96 as it is at the zero level, and the corrected track deviation detection signal 97 is shown in FIG. As shown by the corrected track deviation detection signal TE′-A in FIG.
It is the same as the track deviation detection signal TE-A shown in (a).

The focus lens 9 is displaced from the neutral position of the support spring of the two-dimensional lens actuator 8 and an offset is generated in the track deviation detection signal 88, and the amplitude of the track deviation detection signal TE-B shown in FIG. Central AV
When −B shifts to the plus side by Vb, when the track shift detection signal TE-B is compared with the zero level, FIG.
As shown by the binarized signal S1-B, the time interval a of the binarized signal 91 having the positive level is longer than the time interval b of the binarized signal 91, and the average signal 92 is the average signal of FIG. 9C. It becomes a positive level as indicated by S2-B. Therefore, by setting the amplification factor of the amplifier circuit 93 of FIG. 6 to a predetermined value, the offset amount Vb of the track deviation detection signal TE-B is generated from the average signal 92, and the switch circuit 9 is generated.
When 5 is connected, it is input to the differential circuit 96.
Therefore, the corrected track deviation detection signal 97 is shown in FIG.
The offset is removed as shown by the corrected track deviation detection signal TE'-B in (d).

On the contrary, the track deviation detection signal 88 is shown in FIG.
When the center AV-C of the amplitude shifts to the minus side by Vc as shown by the track shift detection signal TE-C in (a),
When the track deviation detection signal TE-C is compared with the zero level, as shown by the binarized signal S1-C in FIG. 9B, the time interval a at which the binarized signal 91 has a positive level becomes a negative level. It becomes shorter than the interval b, and the average signal 92 becomes a negative level as shown by the average signal S2-C in FIG. 9C. Therefore, by setting the amplification factor of the amplifier circuit 93 in FIG. 6 to a predetermined value, the offset amount Vc of the track deviation detection signal TE-C is generated from the average signal 92,
Differential circuit 96 when the switch circuit 95 is connected
Entered in. Therefore, the corrected track deviation detection signal 97 has the offset removed as shown by the corrected track deviation detection signal TE'-C in FIG. 9D.

When recording or reproducing information on tracks at different positions on the optical disk, first, the MPU
101 is a command 1 for canceling the automatic tracking control
02, the switch circuit 98 is cut off, and the command 103 is issued to make the switch circuit 95 conductive. After that, the MPU 101 sends a command to the head feed control circuit 28 described with reference to FIG. 1, and the head feed mechanism 27 performs a seek operation of moving the optical head 4 to a predetermined position in the radial direction of the optical disc 3. During the seek operation or at the end of the seek operation, a sudden propulsive force or a braking force acts on the optical head, and the focus lens supported by the spring of the two-dimensional lens actuator 8 is displaced or vibrated, and the track deviation detection signal 88 is offset. Occurs. However, due to the comparison circuit 90, the averaging circuit, and the amplification circuit 93 according to the present embodiment, the differential circuit 96 always outputs the track deviation detection signal 97 from which the offset is removed as described above. So M
The PU 101 issues a command 102 to start the automatic tracking control again after the optical head 4 has moved to a predetermined position in the radial direction of the optical disc 3 to make the switch circuit 98 conductive, and the track deviation detection signal with the offset removed. 97
As a result, a stable pull-in operation can be achieved. When the pull-in operation is achieved and the automatic tracking control starts, the displacement of the focus lens decreases and the offset amount generated in the track deviation detection signal 88 also decreases.
01 receives the notification 104 of achievement of tracking control from the tracking control circuit 99 and then issues a command 103 to cut off the switch circuit 95. As described above, the automatic tracking control is achieved again at a different track position, and information can be recorded or information can be reproduced.

As described above, according to the present invention, a new measuring means is introduced in the optical disk device for performing the pulling operation to the tracking control for positioning the optical spot for recording or reproducing information on the track of the optical disk. It is possible to easily achieve a stable retracting operation over a long period of time without requiring any adjustment or adjustment and without increasing the processing load of the MPU or the like in the apparatus.

[0040]

As described above, according to the present invention, there is no need to introduce or adjust new measuring means, and the processing load of the MPU or the like in the apparatus is not increased, and it is possible to achieve a long period of time. A stable pull-in operation can be easily achieved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of an optical disk device according to the present invention.

2 is a configuration diagram showing an embodiment of a signal detection circuit of the optical disc device shown in FIG.

FIG. 3 is a waveform diagram for explaining a processing operation for correcting an offset due to a seek of a track deviation detection signal.

FIG. 4 is a configuration diagram showing an embodiment of a comparison circuit.

FIG. 5 is a circuit diagram showing an embodiment of a binarization circuit.

FIG. 6 is a configuration diagram showing a second embodiment of an optical disk device according to the present invention.

FIG. 7 is a configuration diagram showing an embodiment of a track deviation detection signal generation circuit.

FIG. 8 is a waveform diagram for explaining the operation of the track deviation detection signal generation circuit.

FIG. 9 is a waveform diagram for explaining a processing operation of correcting an offset due to a seek or the like of a track deviation detection signal.

[Explanation of symbols]

1 ... Optical disc device, 2 ... Optical disc, 4 ... Optical head,
8 ... Two-dimensional lens actuator, 9 ... Focus lens, 10 ... 4-division photodetector, 12 ... Track deviation detection signal, 13 ... Comparison circuit, 15 ... Average circuit, 17 ... Amplification circuit, 19 ... Switch circuit, 20 ... Difference Moving circuit, 22 ... Switch circuit, 24 ... MPU, 27 ... Head feeding mechanism.

Claims (6)

[Claims] 1. A track shift detection signal generated by detecting a light spot reflected from an optical disc is binarized.
A binarizing circuit, an averaging circuit that obtains an average signal of the binarized signal by the binarizing circuit, and when an offset occurs in the track deviation detection signal, the offset is removed.
An optical disc apparatus comprising: a subtraction circuit that subtracts the averaged signal from the track deviation detection signal. 2. A light collecting means for collecting laser light as a light spot on an optical disk, a track deviation detecting means for detecting a positional deviation between a track on the optical disk and the light spot, and the light collecting means. Driving means for moving in a direction substantially perpendicular to the direction of the track, tracking control means for controlling the driving means by a track deviation detection signal output from the track deviation detecting means, and operation of the tracking control means are controlled. By comparing the track shift detection signal with a predetermined level by the first switch means,
Binarizing means for binarizing, and 2 output from the binarizing means
Averaging means for obtaining a rough average level using the binarized signal, amplifying means for amplifying the averaged signal output from the averaging means, and a second switch for opening / closing the amplified signal output from the amplifying means. And an subtraction unit for subtracting the signal output from the second switch unit from the track deviation detection signal. 3. The optical disk device according to claim 2,
An optical disk characterized by comprising switch control means for turning on the second switch means when the first switch means is turned off, and for turning off the second switch means when the first switch means is turned on. apparatus. 4. The optical disk device according to claim 3,
A delay means for delaying signal transmission is provided between the switch control means and the second switch means, and the second switch means is shut off after a predetermined time has passed after the first switch means is turned on. An optical disk device characterized in that. 5. The optical disc apparatus according to claim 2, wherein the track deviation detection signal output by the track deviation detection means subtracts an offset of a constant level which is independent of the position of the light condensing means. An optical disk device, characterized in that a subtraction processing unit is provided. 6. The optical disk device according to claim 1, wherein the averaging means comprises a capacitor and a resistor or a choke coil.