JP4048690B2 - Optical disc tilt detection method, optical pickup device, and optical disc device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical disc tilt detection method, an optical pickup device, and an optical disc device. For example, an optical disc (MO), a compact disc (CD), a write-once compact disc (CD-R), a digital video disc (DVD) as a disc-shaped recording medium. ) Can be applied to disc tilt detection when recording or reproducing information recorded on the disc.
[0002]
[Prior art]
In the field of optical discs in recent years, in addition to the conventional CD format, various types such as write-once optical discs (CD-R), magnetic discs (MO), and phase change optical discs (DVD-RAM) coated with an organic dye-based dye film. There are various types of optical discs.
[0003]
In such an optical disc recording / reproducing apparatus, a radial tilt angle indicating a radial tilt of the optical disc with respect to a light spot irradiated from an optical pickup is controlled. As the recording density is improved, there is a large demand for accurately detecting the radial tilt of the optical disc and ensuring the reliability by the radial tilt control of the optical disc.
[0004]
In such an optical disk recording / reproducing apparatus, when performing radial tilt detection on an optical disk, for example, a tilt sensor using a reflective sensor is mounted on the optical pickup, and the optical pickup is moved in the radial direction of the optical disk. The radial tilt was detected from the difference in the amount of reflected light.
[0005]
Japanese Patent Laid-Open No. 8-255360 discloses that a reflected signal from an optical disk is detected by two photodetecting elements to generate a difference signal and an envelope of the detected signal is detected to detect a differential component. An optical disc apparatus is disclosed in which a DC offset can be removed by performing tracking control from these differences.
[0006]
Japanese Patent Laid-Open No. 9-212891 discloses that a laser beam is divided into a main light beam and a sub light beam, and push-pull signals are individually generated from them, and a tilt signal corresponding to a disc tilt is generated from these push-pull signals. An optical head device is disclosed. Japanese Patent Laid-Open No. 9-245357 discloses a servo control device for an optical disc recording / reproducing apparatus that controls tracking servo and thread servo by converting a detracking signal and a radial tilt signal from a push-pull signal and a phase difference detection signal. Has been.
[0007]
[Problems to be solved by the invention]
In the optical disk recording / reproducing apparatus using the conventional tilt sensor described above, the optical pickup and the tilt sensor cannot be placed at the same position in the radial direction of the optical disk. Therefore, the radial position of the optical disk detected by the tilt sensor and the optical pickup Unlike the focal position, there is a disadvantage that a correct disc tilt angle with respect to the optical pickup cannot be obtained. Further, since the tilt sensor is mounted on the optical pickup, there is a disadvantage that the optical pickup becomes large.
[0008]
In Japanese Patent Laid-Open No. 8-255360, it is necessary to finely adjust the gain when subtracting the push-pull signal of one beam in order to remove the DC offset component, so that adjustment is complicated. If the adjustment is not appropriate, there is a disadvantage that the accuracy decreases. Further, in Japanese Patent Laid-Open No. 9-212891, the gain is adjusted after adding two push-pull signals of the sub-beam, and this is added to the push-pull signal of the main beam to generate an offset signal. There is an inconvenience that the adjustment of the gain is complicated and the accuracy is lowered if the adjustment is not appropriate. In Japanese Patent Laid-Open No. 9-245357, since the push-pull signal of one beam and the phase difference detection signal are each amplified to a predetermined level to convert the radial tilt signal, the adjustment of the gain is complicated and the adjustment is difficult. If it is not appropriate, there is an inconvenience that accuracy decreases.
[0009]
The present invention has been made in consideration of the above points, and it is not necessary to divide the beam into a plurality of parts in order to use one light beam. The return light from the beam is received by the divided detectors, and the tilt signal can be obtained by calculating the detection output from each divided detector, so even if there are scratches or dust on the disk surface, the same light spot can be used. Optical disc tilt detection method, optical pickup device, and optical disc apparatus having the advantage of being able to detect the radial tilt of a disc with high accuracy with a simple configuration, as well as the advantage of not being affected by the above signals Is to try to propose.
[0010]
Further, an optical disc tilt detection method capable of detecting a radial tilt of a disc with high accuracy without causing an error in recording / reproduction of a disc having a large amount of eccentricity, or when tracking of a signal recording track of an optical pickup is poor, An optical pickup device and an optical disk device are proposed.
[0011]
[Means for Solving the Problems]
In order to solve such a problem, the optical disc tilt detection method of the present invention is provided on an optical disc. Using an optical pickup with an objective lens In the optical disc tilt detection method for detecting the tilt angle of the optical disc with respect to the light spot in order to record information or reproduce information by irradiating the light spot, with respect to the reflected light from the optical disc, A first signal is generated by subtracting a detection signal from the divided light receiving unit in the track crossing direction of the light spot, and the first signal is generated from the divided light receiving unit in the direction perpendicular to the track crossing direction and the track crossing direction of the light spot. A second signal is generated by phase comparison of the detection signals; A third signal corresponding to the displacement of the objective lens in the track crossing direction is generated, and the calculation result of the first signal to the third signal is generated. The tilt angle of the optical disk is detected based on the above.
[0016]
Another optical pickup device according to the present invention is an objective for detecting an inclination angle of the optical disc with respect to the light spot in order to record information or reproduce information by irradiating a laser spot on the optical disc. In the optical pickup device provided with a lens, a first signal generating means for generating a first signal by subtracting a detection signal from a divided light receiving unit in the track transverse direction of the light spot with respect to the reflected light from the optical disk A second signal generating means for generating a second signal by phase comparison of the detection signal from the divided light receiving section in the cross-track direction of the light spot and the direction orthogonal to the cross-track direction, and the cross-track direction of the objective lens A third signal generating means for generating a third signal corresponding to the displacement of the first signal, and an operation for calculating the first signal to the third signal. Means for detecting the tilt angle of the optical disc based on the calculated value, and correcting the tilt angle of the optical disc with respect to the light spot according to the tilt angle. The correction part to perform is provided.
[0018]
Further, another optical disc apparatus of the present invention detects the tilt angle of the optical disc with respect to the light spot in order to record information or reproduce information by irradiating the optical spot with a laser spot on the optical disc. In the optical disc apparatus, the optical pickup includes an objective lens having a fixed relative positional relationship and a divided light receiving unit, and the first signal is obtained by subtracting the detection signal from the divided light receiving unit in the track crossing direction of the light spot. First signal generating means for generating, second signal generating means for generating a second signal by phase comparison of detection signals from the divided light-receiving units in the track transverse direction and the direction perpendicular to the track transverse direction of the light spot, Third signal generating means for generating a third signal corresponding to the displacement of the objective lens in the cross-track direction; To the third signal, an inclination angle detection unit for detecting the inclination angle by detecting the inclination angle of the optical disk based on the calculated value, and the above-mentioned according to the inclination angle. And a correction unit that corrects the tilt angle of the optical disc with respect to the light spot.
[0020]
According to the optical disk apparatus of the present invention, the following operations are performed.
A laser beam is irradiated from an optical pickup of an optical system onto an optical disk whose rotation is controlled by a spindle servo system. Further, focus servo is performed by a focus coil of a biaxial actuator of an optical system controlled by the focus servo system. Also, tracking servo is performed by the tracking coil of the biaxial actuator.
[0021]
The reflected light from the optical disk is detected by each divided light receiving unit of the servo signal detection system, and the first signal and the second signal are generated by using the detection signal from each divided light receiving unit. To calculate the tilt angle of the disk. Then, the detected tilt angle of the disc is corrected by the correction unit.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an optical disk device according to an embodiment of the present invention will be described in detail with reference to the drawings as appropriate.
[0023]
FIG. 1 is a diagram showing a configuration of an optical system of an optical pickup of the optical disc apparatus according to the present embodiment.
In FIG. 1, light emitted from a laser 1 is converted into parallel light by a collimator lens 2, an elliptical light beam is shaped into a circular light beam by an anamorphic prism 3, and astigmatism is simultaneously corrected. Further, after passing through the beam splitter (1) 5, it is condensed by the objective lens 6 and incident on the optical disk 7.
[0024]
The optical path of the light reflected by the optical disc 7 is divided into a servo signal detection system 9 by reflection and a RF signal detection system 10 by transmission after being reflected by the beam splitter (1) 5 and then by the beam splitter (2) 8. . In the servo signal detection system 9, the light beam is condensed by the condenser lens 11 and further condensed on the photodetector 13 by the multilens 12. Similarly, in the RF signal detection system 10, the light beam is condensed by the condenser lens 14 and further condensed on the photodetector 16 by the concave lens 15.
[0025]
FIG. 2 shows detector patterns and spots according to the present embodiment. In FIG. 2, the track crossing direction is a radial direction, and the direction orthogonal to the track crossing direction is a tangential direction. In FIG. 2, the detector comprises a four-divided light receiving portion of detectors A23, B24, C25, and D26. The light spot 27 is incident on the four-divided light receiving portions of the detectors A23, B24, C25, and D26.
[0026]
FIG. 3 is a diagram illustrating generation of a one-spot push-pull signal (hereinafter abbreviated as PP signal) and a DPD signal according to the present embodiment.
First, generation of a PP signal will be described. When there is a mark on which an embossed groove or pit is recorded on the disc, the PP signal is generated as follows.
[0027]
The outputs of the detectors A23 and D26 of the four-divided light receiving units of the detectors A23, B24, C25, and D26 are input to the addition input terminal of the adder 32, and the adder 32 performs the calculation (A + D). The outputs of the detectors B24 and C25 are input to the addition input terminal of the adder 33, and the adder 33 performs an operation (B + C). (A + D) is input to the non-inverting input terminal of the subtractor 34, (B + C) is input to the inverting input terminal of the subtractor 34, and the subtractor 34 performs an operation of {(A + D)-(B + C)}. A signal output from the subtractor 34 to the terminal 105 is a PP signal.
[0028]
Next, generation of a DPD signal will be described. If the disc has embossed pits or recorded marks, the DPD signal is generated as follows.
In FIG. 3, the outputs A, B, C, and D of the four-divided light receiving units of the detectors A23, B24, C25, and D26 are respectively input to the equalization circuits 44A, 44B, 44C, and 44D, and after equalization processing, 2 Binarization is performed by the value conversion circuits 45A, 45B, 45C, and 45D. The outputs of the binarization circuits 45A and 45B are compared by a phase comparison circuit 46 to generate a pulse train P (AB), shaped by an LPF (low-pass filter) 48, and input to one input terminal of an adder 50 To do. The outputs of the binarization circuits 45D and 45C are compared by the phase comparison circuit 47 to generate a pulse train P (DC), shaped by the LPF (low-pass filter) 49, and the other input terminal of the adder 50 To enter. The adder 50 calculates {P (A−B) + P (D−C)} and outputs a DPD signal = {P (A−B) + P (D−C)} to the terminal 51.
[0029]
As another DPD signal generation method, as shown in FIG. 13, the signals from the four-divided light receiving sections A23, B24, C25, and D26 are added by adders 200 and 201 separately from A + C and B + D. Then, after the equivalent processing is performed by the equalizers 202 and 203, the binarization circuits 204 and 205 binarize it. The outputs of the binarization circuits 204 and 205 are phase-compared by the phase comparison circuit 206, and the positive phase component and the negative phase component of the phase comparison are applied to LPFs (low pass filters) 207 and 208, respectively. The DPD signal can be obtained from the terminal 210 by subtracting the output signals from the LFP 207 and the LPF 208 by the adder 209.
[0030]
FIG. 4 is a diagram illustrating the PP signal level with respect to the position of the light spot according to the present embodiment. The figure shown in FIG. 4 shows the calculated value of the PP signal with respect to the position of the light spot when there is no disc tilt indicated by the solid line and when there is a dotted line. In FIG. 4, when there is no radial tilt on the disk indicated by the solid line, the PP signal is 0 as shown on the vertical axis when the light spot is at the 0 position indicating directly above the track center as shown on the horizontal axis. Become. However, when there is a radial tilt indicated by a dotted line, an offset occurs, and when the light spot is right above the track center, the PP signal becomes 0.4 and does not become 0, and the light spot becomes 0. 0 from right above the track center. The PP signal becomes 0 at a position shifted by about 05 μm.
[0031]
FIG. 5 is a diagram showing the DPD signal level with respect to the position of the light spot according to the present embodiment. The diagram shown in FIG. 5 shows the calculated value of the DPD signal with respect to the position of the light spot when there is no disc tilt indicated by a solid line and when there is a dotted line. In FIG. 5, when there is no radial tilt on the disk indicated by the solid line, the DPD signal is 0 as shown on the vertical axis when the light spot is at the 0 position showing the position directly above the track center as shown on the horizontal axis. Become. However, when there is a radial tilt indicated by a dotted line, an offset occurs, and when the light spot is directly above the track center, the DPD signal becomes 0.09 and does not become 0, and the light spot becomes 0. 0 from directly above the track center. The DPD signal becomes 0 at a position shifted by about 02 um. Thus, in the case of the DPD signal, it can be seen that the offset amount due to the tilt of the disk is considerably smaller than that in the case of the PP signal.
[0032]
For example, when an optical pickup having a wavelength of 650 nm and NA (aperture ratio) 0.7 is used, and the disc thickness is 0.6 mm, the track pitch is 0.8 μm, and the mark length is 0.5 μm, the radial tilt of the disc is 0.5 degrees. When the light spot is directly above the center of the track, if the amplitude of each of the PP signal and the DPD signal is 1, the PP signal is 0.40 and the DPD signal is 0.09.
[0033]
Accordingly, when the disc has a radial tilt, a difference occurs between the PP signal and the DPD signal normalized by the respective amplitudes. Since the difference between the PP signal and the DPD signal increases as the disc tilt angle increases, this difference can be used to detect the disc radial tilt angle with respect to the optical pickup.
[0034]
FIG. 6 is a diagram illustrating a difference between the PP signal and the DPD signal with respect to the radial tilt according to the present embodiment. The diagram shown in FIG. 6 shows experimental values of the difference between the PP signal and the DPD signal with respect to the radial tilt of the disc. In FIG. 6, as the radial tilt of the disc shown on the horizontal axis increases, the difference between the PP signal and the DPD signal shown on the vertical axis increases so as to be substantially proportional. Here, tracking is applied using a DPD signal.
[0035]
FIG. 7 is a diagram showing the detection of the disc tilt in the read-only disc of the present embodiment. When reproducing a read-only disc made up of the entire surface pit row 73 as shown in FIG. 7, the difference between the DPD signal obtained from the light spot 70 and the PP signal obtained from the light spot 70 is detected to detect the disc with respect to the optical pickup. Disc tilt can be detected.
[0036]
FIG. 8 is a diagram showing the detection of the disc tilt in the groove disc of the present embodiment. As shown in FIG. 8, the groove 83 is formed by using a light spot 85 with respect to a groove disk comprising recording portions 80 and 82 for recording information signals only in the groove 83 and an address portion 81 of a pit row 84 of embossed pits. The PP signal is detected, and the DPD signal is detected from the address unit 81 using the light spot 85. Then, the tilt of the disc with respect to the optical pickup can be detected by detecting the difference between the PP signal and the DPD signal.
[0037]
FIG. 9 is a diagram showing detection of a disc tilt in the land / groove disc of the present embodiment. Information signals are recorded on a land / groove disc composed of recording portions 90 and 93 for recording information signals on both lands 95 and grooves 94 and address portions A91 and B92 of embossed pit rows 96 as shown in FIG. In the case of recording or reproducing the land 95, the DPD signal and the PP signal {(A + D)-(B + C)} when the light spot 100 passes through the address part B92 of the track (1) 97 are detected and the PP signal By detecting the difference between the DPD signal and the DPD signal, the tilt of the disc relative to the optical pickup can be detected. When the groove 94 is recorded or reproduced, the DPD signal and the PP signal {(A + D) − (B + C)} when the spot 100 passes the address part A91 of the track (2) 98 are detected, and the PP signal By detecting the difference between the DPD signals, the tilt of the disc with respect to the optical pickup can be detected.
[0038]
In the above-described embodiment, the example in which the radial tilt of the disc is detected by obtaining the difference between the PP signal and the DPD signal has been described.
[0039]
The normal playback operation in the optical disc apparatus is performed as follows.
A laser beam is irradiated from the optical pickup of the optical system onto the optical disk 7 rotated by the spindle motor 2 servo-controlled by the spindle servo system of the servo circuit. After turning on the focus servo controlled by a focus servo system (not shown), the drive signal from the tracking servo system of the servo circuit is amplified by an amplifier and applied to the tracking coil of the biaxial actuator of the optical pickup of the optical system, When the actuator is moving in the track direction, a detection signal is detected from the photodetector 13 of the optical system by the reflected light from the optical disc 7.
[0040]
The tracking error signal generated by the servo circuit is amplified by an amplifier to be a tracking actuator drive signal, and is applied to the tracking coil of the biaxial actuator of the optical pickup of the optical system.
[0041]
In the optical pickup of the optical system, the objective lens is independent of the focusing direction (direction approaching or separating from the optical disk 7) and the tracking direction (direction crossing the track of the optical disk) by a biaxial actuator using electromagnetic force. Moved.
[0042]
The optical pickup of this optical system is sequentially moved in the outer peripheral direction of the optical disc 7 in synchronization with the rotation of the optical disc 7 by a slide (thread) motor (not shown), thereby sequentially changing the irradiation position by the laser beam to the outer periphery of the optical disc 7. Displace in the direction.
[0043]
The RF amplifier generates a reproduction RF signal from the reflected light from the optical disc 7. The reproduced RF signal is demodulated in the data signal processor, and after error correction code is detected and error correction is performed, deinterleave processing and EFM-PLUS demodulation processing are performed, and the demodulated signal can be output. Amplified to level and output.
[0044]
Here, in the present embodiment, the optical system is provided with a tilt angle correction unit that controls the tilt angle of the optical disc 7 with respect to the light spot from the optical pickup (not shown).
[0045]
The control unit generates a control signal to be sent to the servo circuit based on the RF signal from the RF amplifier, a gain setting control signal to be sent to the gain setting unit of the servo circuit, etc. Control the operation of each part.
[0046]
The disc tilt detection operation is performed as follows.
First, when the control unit recognizes that the optical disk 7 has been inserted into a predetermined position of the apparatus, it instructs the start of focus servo and spindle servo. Specifically, a laser beam is irradiated from the optical pickup of the optical system onto the optical disk 7 rotated by a spindle motor servo-controlled by the spindle servo system of the servo circuit. Further, focus servo is performed by a focus coil of a biaxial actuator of an optical system controlled by a focus servo system of a servo circuit.
[0047]
The control unit detects the radial tilt of the disc. Specifically, the reflected light from the optical disc is detected by the detector 13 of the servo signal detection system 9, and the PP signal and the DPD signal are generated using the detection signals from the detectors A to D, and the PP signal and the DPD signal are generated. Calculate the disc tilt by calculating the difference.
[0048]
The control unit causes the tilt angle correction unit of the servo circuit to correct the tilt angle. Specifically, the tilt angle is corrected for each medium supported by the optical disc drive system.
[0049]
When detecting the radial tilt of the disk, the position of the sled is changed. Specifically, the optical pickup of the optical system is sequentially moved in the outer peripheral direction of the optical disc 7 in synchronization with the rotation of the optical disc 7 by a slide (thread) motor (not shown), and thereby the irradiation position by the laser beam is sequentially changed to the optical disc 7. Displace in the outer circumferential direction.
[0050]
The optical disk tilt detection method of the present embodiment detects the tilt angle of the optical disk 7 with respect to the light spot in order to record information or reproduce information by irradiating the optical spot on the optical disk 7 with an optical pickup. In the optical disk tilt detection method for performing the above, the PP signal as the first signal is obtained by subtracting the detection signal from each of the divided light receiving portions A to D in the track crossing direction of the light spot 27 with respect to the reflected light from the light spot 27. And a DPD signal as a second signal is generated by comparing the phases of the detection signals of the divided light receiving portions A to D in the track crossing direction and the direction orthogonal to the track crossing direction of the light spot 27, and the first signal Since the difference calculation value between the first signal and the second signal is obtained and the tilt angle of the optical disk is detected based on the difference calculation value, no adjustment is made. Since the radial tilt angle of the optical disk relative to the optical pickup can be automatically detected by calculating the difference between the first signal and the second signal, the tilt of the optical pickup or disk is corrected using a radial tilt servo. In this case, the optical pickup or the optical disk can be corrected to an optimum angle.
[0051]
Further, in the optical disk tilt detection method of the present embodiment, the first signal obtained from the light spot 70 when the information recording / reproduction is performed using the light spot 70 with respect to the optical disk composed of the entire surface pit row in the above description. Since the difference between the PP signal as the second signal and the DPD signal as the second signal is detected, the disc tilt can be detected easily and reliably in the reproduction of the reproduction-only disc made of the entire pit row. be able to.
[0052]
In addition, the optical disk tilt detection method of the present embodiment uses a light spot 85 for an optical disk composed of the recording units 80 and 82 capable of recording information only in the groove 83 and the address unit 81 of the embossed pit row 84. When recording / reproducing information, the recording unit 80, 82 detects the PP signal as the first signal, and the address unit 81 detects the second signal, the DPD signal. In the case of recording and reproducing information using one spot in a groove disc composed of a recording portion for recording a signal and an address portion of a pit row of embossed pits, the disc tilt can be detected easily and reliably.
[0053]
Also, the optical disk tilt detection method of the present embodiment is applied to an optical disk composed of recording units 90 and 93 capable of recording information on both the land 95 and the groove 94 and address portions A91 and B92 of the embossed pit row 96. When recording / reproducing information using only the light spot 100, the DPD signal as the second signal and the PP signal as the first signal when passing through the address portion A91 as the first address portion of the predetermined track Since the PP signal {(A + D)-(B + C)} of the light spot 100 used for generating the signal is detected and the difference between the first signal and the second signal is detected, information is provided to both the land and the groove. An information signal is recorded using one spot on a land groove disc composed of a recording section for recording a signal and address portions A and B of embossed pit rows. In case, it is possible to detect the disk tilt easily and reliably.
[0054]
The optical disc tilt detection method of the present embodiment is a detection method that can detect the radial tilt angle with high accuracy even when the disc has a large eccentricity. This embodiment can improve the above-mentioned drawbacks.
[0055]
It is known that the PP signal (one-spot push-pull signal) generates an offset signal in accordance with the positional relationship between the objective lens and the photo detector. For example, as shown in FIGS. 12A, 12B, and 12C, when the objective lens follows the eccentricity of the optical disk, the position of the light spot on the detector moves with the eccentricity. In such a case, a non-negligible offset is generated and the radial tilt detection is performed. The accuracy will drop significantly.
[0056]
Therefore, in such a case, if the configuration of the objective lens and the detector is taken into consideration so that no offset is generated even if there is eccentricity, or the processing for removing the offset generated by the eccentricity is not performed, a sufficient radial tilt is achieved. The detection performance cannot be demonstrated.
[0057]
Therefore, the present embodiment intends to propose an optical disc tilt detection method, an optical pickup device, and an optical disc device, which have the advantage that the radial tilt can be detected even when the eccentricity is large.
[0058]
FIG. 10 shows the configuration of the optical pickup according to the present embodiment.
In FIG. 10, the objective lens 101 performs a tracking operation by moving in the direction of the arrow in the figure. The objective lens 101 is attached to an actuator (not shown) provided in the optical block 108 and is moved in the tracking direction by this actuator. The objective lens 101 is also moved in the focus direction by the actuator, and focus servo is performed.
[0059]
Further, the movement of the objective lens 101 is detected by the midpoint sensor 103. In FIG. 10, the midpoint sensor 103 is provided on the optical block 108.
[0060]
The objective lens 101 performs a tracking operation by moving in the track crossing direction (radial direction) of the optical disc 102 according to the eccentricity of the optical disc 102 or according to the movement of the optical block 108.
[0061]
The relative positional relationship between the objective lens 101 and the photo detector 114 is moved by the tracking operation, and accordingly, the position of the light spot on the photo detector 114 is also moved as shown in FIGS. An offset accompanying the movement occurs.
[0062]
An offset amount S3 is obtained by amplifying the lens shift amount S2 from the midpoint sensor 103 by the amplifier 104. Since this offset amount S3 corresponds to the lens shift amount S2 that is a detection signal from the midpoint sensor 103, the above-described offset included in the PP signal S1 is subtracted from the PP signal S1 by the subtractor 106. It is possible to remove the signal and extract only the sum component S4 of the tilt component and the original tracking error.
[0063]
By subtracting the above-described sum component S4 from the DPD signal S5 by the subtractor 107, only the radial tilt signal S6 can be obtained, and detection from the DPD signal S5 to the PP signal S1 and the midpoint sensor 103 is performed without any adjustment. By obtaining the signal difference, the radial tilt angle of the optical disc with respect to the optical pickup can be automatically detected.
[0064]
Therefore, when correcting the tilt of the optical pickup or the disk using the radial tilt servo, the optical pickup can be corrected to an optimum angle.
[0065]
Further, the optical pickup device of the present embodiment irradiates the laser spot on the optical disc 7 to detect the tilt angle of the optical disc with respect to the light spot in order to record information or reproduce information. In the apparatus, the first signal is generated by subtracting the detection signal from the divided light receiving unit in the cross-track direction of the light spot with respect to the reflected light from the optical disc, and orthogonal to the cross-track direction and the cross-track direction of the light spot. The second signal is generated by phase comparison of the detection signals from the divided light receiving units in the direction to obtain the difference calculation value between the first signal and the second signal, and the tilt angle of the optical disk is calculated based on the difference calculation value. A tilt angle detector that detects the tilt angle by performing detection, and a correction that corrects the tilt angle of the optical disc with respect to the light spot according to the tilt angle Therefore, the radial tilt angle of the optical disc relative to the optical pickup can be automatically detected by obtaining the difference between the first signal and the second signal without any adjustment. When correcting the tilt of an optical pickup or disc using a radial tilt servo, the optical pickup or optical disc can be corrected to an optimum angle and a radial tilt sensor is not required, so the optical pickup can be downsized. Can do.
[0066]
In addition, the optical pickup according to the present embodiment can cope with poor tracking characteristics of a disk having a large eccentricity or an optical pickup by providing a midpoint sensor, and can detect a radial tilt with high accuracy.
[0067]
The optical disk apparatus according to the present embodiment also detects an inclination angle of the optical disk with respect to the light spot in order to record information or reproduce information by irradiating the optical spot with a laser spot on the optical disk. In the apparatus, the first signal is generated by subtracting the detection signal from the divided light receiving unit in the cross-track direction of the light spot with respect to the reflected light from the optical disc, and orthogonal to the cross-track direction and the cross-track direction of the light spot. The second signal is generated by phase comparison of the detection signals from the divided light receiving units in the direction to obtain the difference calculation value between the first signal and the second signal, and the tilt angle of the optical disk is calculated based on the difference calculation value. A tilt angle detector that detects the tilt angle by performing detection, and corrects the tilt angle of the optical disc with respect to the light spot according to the tilt angle. When correcting the tilt of the optical pickup or disc using the radial tilt servo, the optical pickup or the optical disc can be corrected to the optimum angle and the radial tilt sensor is unnecessary. Therefore, the optical pickup can be miniaturized and the optical disc apparatus can be miniaturized.
[0068]
In addition, the optical disk apparatus according to the present embodiment can cope with poor tracking characteristics of a disk having a large eccentricity or an optical pickup by providing a midpoint sensor, and can detect a radial tilt with high accuracy. When correcting the tilt of an optical pickup or disk using a servo, the optical pickup or optical disk can be corrected to an optimal angle, and a radial tilt sensor is not required, so the optical pickup is downsized and the optical disk device is downsized. Can be
[0069]
Further, as shown in FIG. 11, in the optical disk apparatus of the present embodiment, the relative positions of the objective lens 109 and the optical detector 111 are fixed on the optical block 112, and the entire optical block 112 is used by using the slide mechanism 113. Is moved in the radial direction indicated by the arrow, so-called uniaxial feed structure. According to this, as described above, the radial tilt can be accurately detected without causing an offset, and when the tilt of the optical pickup or the disk is corrected using the radial tilt servo, the optical pickup or the optical disk is at an optimum angle. Since the radial tilt sensor is not necessary, the optical pickup can be downsized and the optical disc apparatus can be downsized.
[0070]
In the present embodiment described above, only the example applied to the detection of the radial tilt of the optical disc apparatus is shown. However, the radial tilt detection apparatus of the card reader or other electronic apparatus having a plate-like recording medium such as a hard disk is shown. Needless to say, the above may be applied.
[0071]
【The invention's effect】
The optical disk tilt detection method of the present invention is provided on an optical disk, Using an optical pickup with an objective lens In the optical disc tilt detection method for detecting the tilt angle of the optical disc with respect to the light spot in order to record information or reproduce information by irradiating the light spot, with respect to the reflected light from the optical disc, A first signal is generated by subtracting a detection signal from the divided light receiving unit in the track crossing direction of the light spot, and the first signal is generated from the divided light receiving unit in the direction perpendicular to the track crossing direction and the track crossing direction of the light spot. A second signal is generated by phase comparison of the detection signals; A third signal corresponding to the displacement of the objective lens in the track crossing direction is generated, and the calculation result of the first signal to the third signal is generated. Because the tilt angle of the optical disc is detected based on Easily and reliably detect disc tilt with high accuracy even for optical discs with large eccentricity There is an effect that can be.
[0077]
Further, the optical pickup device of the present invention includes an objective lens that detects an inclination angle of the optical disc with respect to the light spot in order to record information or reproduce information by irradiating a laser spot on the optical disc. In the provided optical pickup device, a first signal generating means for generating a first signal by subtracting a detection signal from a divided light receiving unit in the cross-track direction of the light spot with respect to the reflected light from the optical disc; Second signal generating means for generating a second signal by phase comparison of the detection signal from the divided light receiving section in the cross-track direction of the light spot and the direction orthogonal to the cross-track direction; and displacement of the objective lens in the cross-track direction And a third signal generating means for generating a third signal corresponding to the first signal, and an operator for calculating the first signal to the third signal. And an inclination angle detector that detects the inclination angle of the optical disk based on the calculated value, and corrects the inclination angle of the optical disk with respect to the light spot according to the inclination angle. Since the correction unit is provided, when correcting the tilt of the optical pickup or the disk using the radial tilt servo, the optical pickup or the optical disk can be corrected to an optimum angle even when an optical disk having a large eccentricity is mounted. Since the radial tilt sensor is not required, the optical pickup can be reduced in size.
[0079]
The optical disc apparatus of the present invention also detects an inclination angle of the optical disc with respect to the light spot in order to record information or reproduce information by irradiating the optical spot on the optical disc with a laser spot. In the apparatus, the optical pickup includes an objective lens having a fixed relative positional relationship and a divided light receiving unit, and generates a first signal by subtracting a detection signal from the divided light receiving unit in the cross-track direction of the light spot. First signal generation means, second signal generation means for generating a second signal by phase comparison of detection signals from the divided light receiving sections in the cross-track direction of the light spot and the direction orthogonal to the cross-track direction, and the objective Third signal generating means for generating a third signal in accordance with the displacement of the lens in the cross-track direction, and the first signal A calculation means for calculating the third signal, a tilt angle detection unit for detecting the tilt angle by detecting the tilt angle of the optical disk based on the calculated value, and the light according to the tilt angle. And a correction unit that corrects the tilt angle of the optical disk with respect to the spot. When correcting the tilt of the optical pickup or the disk using a radial tilt servo, the optical pickup or the optical disk is mounted even when an optical disk having a large eccentricity is mounted. Since the angle can be corrected to an optimum angle and a radial tilt sensor is not required, the optical pickup can be miniaturized and the optical disk apparatus can be miniaturized.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of an optical system according to an embodiment.
FIG. 2 is a diagram showing detector patterns and spots according to the present embodiment.
FIG. 3 is a diagram illustrating generation of a PP signal and a DPD signal according to the present embodiment.
FIG. 4 is a diagram illustrating a PP signal level with respect to a position of a light spot according to the present embodiment.
FIG. 5 is a diagram showing a DPD signal level with respect to the position of a light spot according to the present embodiment.
FIG. 6 is a diagram illustrating a difference between a PP signal and a DPD signal with respect to radial tilt according to the present embodiment.
FIG. 7 is a diagram showing detection of a disc tilt in the read-only disc of the present embodiment.
FIG. 8 is a diagram showing detection of a disc tilt in the groove disc according to the present embodiment.
FIG. 9 is a diagram illustrating detection of disc tilt in the land / groove disc of the present embodiment;
FIG. 10 is a diagram showing an optical pickup using the midpoint sensor of the present embodiment.
FIG. 11 is a diagram illustrating a single-axis feeding optical pickup according to the present embodiment;
FIG. 12 is a diagram showing movement of spots on the photodetector due to eccentricity of the optical disc.
FIG. 13 is a diagram illustrating generation of another DPD signal.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Laser, 2 ... Collimator lens, 3 ... Anamorphic prism, 5 ... Beam splitter 1, 6 ... Objective lens, 7 ... Disc, 8 ... Beam splitter 2, 9 ... Servo signal detection system, DESCRIPTION OF SYMBOLS 10 ... RF signal detection system, 11 ... Condensing lens, 12 ... Multi lens, 13 ... Photo detector, 23 ... Detector A, 24 ... Detector B, 25 ... Detector C, 26 ... Detector D, 27... Light spot 1, 32, 33... Adder, 44A, 44B, 44C, 44D... Equalization circuit, 45A, 45B, 45C, 45D ... Binary circuit, 46, 47. , 48, 49... LPF, 50... Adder, 51... Terminal, 70... Light spot, 73 .. pit row, 80, 82. 84... Pit row, 85... Light spot, 90, 93... Recording portion, 91... Address portion A, 92... Address portion B, 94. 97... Track 1, 98... Track 2, 99... Track 3, 100... Light spot, 101... Objective lens, 102. ...... Subtractor, 108 ...... Optical block, 109 ...... Objective lens, 110 ...... Disc, 111 ...... Detector, 112 ...... Optical block, 113 ...... Slide mechanism, 200, 201 ...... Adder, 202, 203 ...... Equalizer, 204, 205 ... Binary circuit, 206 ... Phase comparison circuit, 207,208 ... LPF, 209 ... Adder, 210 ... Terminal,

Claims (3)

An optical disc tilt that detects the tilt angle of the optical disc with respect to the optical spot in order to record information or reproduce the information by irradiating the optical spot on the optical disc using an optical pickup provided with an objective lens In the detection method,
For reflected light from the optical disc,
A first signal is generated by subtracting the detection signal from the divided light receiving section in the track crossing direction of the light spot,
A second signal is generated by phase comparison of detection signals from the divided light receiving units in the track crossing direction and the direction orthogonal to the track crossing direction of the light spot,
Generating a third signal corresponding to the displacement of the objective lens in the cross-track direction;
An optical disc tilt detection method, wherein the tilt angle of the optical disc is detected based on the calculation results of the first signal to the third signal . In an optical pickup device provided with an objective lens for detecting an inclination angle of the optical disc with respect to the light spot in order to record information or reproduce information by irradiating a laser spot on the optical disc,
For reflected light from the optical disc,
First signal generating means for generating a first signal by subtraction operation of the detection signal from the divided light receiving section in the track transverse direction of the light spot;
Second signal generating means for generating a second signal by phase comparison of detection signals from the divided light receiving sections in the track transverse direction and the direction perpendicular to the track transverse direction of the light spot;
Third signal generating means for generating a third signal according to the displacement of the objective lens in the cross-track direction;
Computing means for computing the first signal to the third signal;
A tilt angle detector that detects the tilt angle by detecting the tilt angle of the optical disc based on the calculated value;
A correction unit for correcting the tilt angle of the optical disc with respect to the light spot according to the tilt angle;
The optical pickup apparatus is characterized in that as comprising a. In an optical disc apparatus for detecting an inclination angle of the optical disc with respect to the light spot in order to record information or reproduce information by irradiating a laser spot on the optical disc with an optical pickup,
The optical pickup has an objective lens with a fixed relative positional relationship and a divided light receiving unit,
First signal generating means for generating a first signal by subtraction operation of the detection signal from the divided light receiving section in the track transverse direction of the light spot;
Second signal generating means for generating a second signal by phase comparison of the detection signals from the divided light receiving portions in the track transverse direction and the direction perpendicular to the track transverse direction of the light spot;
Third signal generating means for generating a third signal according to the displacement of the objective lens in the cross-track direction;
Computing means for computing the first signal to the third signal;
An inclination angle detector that detects the inclination angle by detecting the inclination angle of the optical disk based on the calculated value;
A correction unit that corrects the tilt angle of the optical disc with respect to the light spot according to the tilt angle;
An optical disc apparatus characterized by comprising:

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