JP2005353226A - Skew detecting device, skew correction controller and optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly and directly detect a skew generated at the time of optical disk recording, including the direction in which the skew is generated. <P>SOLUTION: When a skew is generated due to warpage or the like of an optical disk, focusing on difference produced in a photoelectric conversion amount between left and right regions in the direction of extending tracks of a photodetector 1, sample and hold circuits 4 to 7 and dividers 8 and 9 normalize photoelectric conversion signals at the time of writing obtained from left and right, that is, A + B and C + D of the photodetector 1 to photoelectric conversion signals at the time of reading, and a skew detection output 300 is obtained by a subtracter 10 obtains a difference between the normalized photoelectric conversion signals. This output can quickly and directly detect a skew generated at the time of optical disk recording, including the direction in which the skew is generated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical disc apparatus that records information on a reflectance change type optical disc, and more particularly, to a skew detection device and a skew correction control device that detect skew caused by warpage or distortion of an optical disc.

  2. Description of the Related Art In recent years, various optical discs such as reflectivity-changing CDs and DVDs for recording and reproducing video information and music information have become widespread, and optical disc apparatuses for recording and reproducing these optical discs have been developed. The optical disk apparatus collects laser light on a recording surface of an optical disk that is rotated by a pickup, and receives the reflected light to perform recording / reproduction. At this time, if the incident angle of the laser beam incident on the recording surface of the optical disc is deviated, the aberration of the laser beam on the recording surface increases, and the recording quality during recording deteriorates. Therefore, in the optical disc apparatus, it is necessary that the incident angle of the laser beam incident on the recording surface of the optical disc is always a predetermined angle.

  For example, if the optical disk is warped or distorted during formation, the optical disk is warped by the chucking pressure, or the outer periphery of the optical disk hangs down due to the weight of the optical disk itself, the optical disk is irradiated vertically. A so-called skew occurs in which the amount of reflected light is reduced when the laser beam that is supposed to be emitted is obliquely inclined, which hinders accurate reproduction of recorded data.

  For this reason, a skew canceling mechanism is installed to prevent a decrease in recording quality due to skew. For example, a method of measuring a warp amount of an optical disk by providing a skew sensor that measures a mechanical amount is generally performed (see, for example, Patent Document 1). Becomes higher.

  Therefore, as a simpler method, for example, there is a method of measuring a skew amount by processing a signal generated from return light during recording, for example, a method of detecting skew using a pit (PIT) level during recording. It has been devised.

However, in the pit skew detection method, the signal detected by the skew detection is output according to the recording quality. However, since the coma aberration caused by the skew affects the recording quality, the detected information is just skew (just Draws a quadratic curve symmetrically with respect to (skew) and has no polarity. Therefore, a change in skew can be detected, but it cannot be determined whether the skew has changed to the plus side or the minus side.
JP 2000-195079 A (page 3-4, FIG. 1)

  Therefore, as an actual operation method, an open loop control method has been devised in which the skew is changed to look at the change in the pit level to find the bottom from the curve. However, since the direction in which the skew is changed is not known, the lens may be shaken in a worsening direction, and writing quality at that time may be deteriorated. To solve this problem, there is an improvement method in which the skew direction is predicted in advance so as not to swing in a worsening direction. However, since the skew values at several places are predicted using amplitude information such as tracking errors before recording, it is not perfect.

  In addition, because the target direction of the skew is detected using the relative relationship of the pit level with respect to the skew angle, it is difficult to obtain the relative relationship of the output due to the skew unless the influence of surface blurring, which is a fluctuation in the circumference, is removed. In order to eliminate this, it was necessary to compare with the maximum value for one round, and thus the detection speed was limited.

  The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a skew detection apparatus that can quickly and directly detect a skew that occurs during optical disk recording, including the direction of the occurrence. Another object of the present invention is to provide a skew correction control device and an optical disk device equipped with the skew correction control device.

  In order to achieve the above object, the present invention provides a skew detection device for detecting a skew from a return light of a laser beam irradiated on a rotating optical disc, the photoelectric conversion element divided into two in the track direction of the optical disc, And a calculation means for calculating a difference between two photoelectric conversion signals respectively output from the two divided regions of the photoelectric conversion element, wherein a calculation result of the calculation means is used as a detected skew amount.

  Further, the present invention includes a normalizing unit that normalizes the two photoelectric conversion signals, normalizes the two photoelectric conversion signals obtained by the arithmetic unit by the normalizing unit, and The difference between the converted photoelectric conversion signals is used as a detection skew amount.

  Further, the present invention provides a lens for condensing laser light on a disk, moving means for moving the position of the lens, a light receiving element in which a light receiving surface for photoelectrically converting return light from the disk is divided into four parts, A skew detection device that detects the skew amount of the disk based on a photoelectric conversion signal of the light receiving element, and the lens by controlling the moving means so that the skew amount detected by the skew detection device becomes a target value. The skew detecting device includes a photoelectric conversion element that is divided into two in the track direction of the optical disc and a difference between two photoelectric conversion signals that are respectively output from the two divided regions of the photoelectric conversion element. And a calculation result of the calculation means as a detected skew amount.

  Further, the present invention provides a lens for condensing laser light on a disk, moving means for moving the position of the lens, a light receiving element in which a light receiving surface for photoelectrically converting return light from the disk is divided into four parts, A skew detection device that detects the skew amount of the disk based on a photoelectric conversion signal of the light receiving element, and the lens by controlling the moving means so that the skew amount detected by the skew detection device becomes a target value. The skew detection device adds the photoelectric conversion signals obtained from the four divided photoelectric conversion elements and two of the four divided areas of the photoelectric conversion elements to the optical disc. Adding means for creating two photoelectric conversion signals equivalent to signals obtained from the two regions of the photoelectric conversion element across the track direction, and the two calculated photoelectric conversion signals Comprising a calculating means for calculating a difference signal, characterized by a detecting skew quantity calculation results of the calculating means.

  The present invention also provides an optical disc apparatus for condensing laser light from an optical pickup onto an optical disc and receiving return light from the optical disc with the optical pickup to record information on the optical pickup, A skew detecting device for detecting a skew amount of the disk based on a photoelectric conversion signal obtained by photoelectrically converting the return light by a light receiving element whose light receiving surface is divided into four, and a skew amount detected by the skew detecting device And a control means for moving the lens in the optical pickup so that the value becomes a target value, and the skew detection device receives photoelectric conversion signals obtained from two of the four divided areas of the photoelectric conversion element. Two signals equivalent to the signals obtained from the two regions of the photoelectric conversion element that are added and straddle the track direction of the optical disc Adding means for creating a photoelectric conversion signal, comprising a calculating means for calculating the difference between two photoelectric conversion signals the calculated, characterized by a detecting skew quantity calculation results of the calculating means.

  As described above, in the present invention, when skew occurs due to the warp of the optical disk or the like, it is noted that there is a difference in the photoelectric conversion amount in the left and right regions in the direction across the track of the light receiving element. By obtaining the difference between the obtained photoelectric conversion signals and detecting the skew amount, it is possible to quickly and directly detect the skew amount according to the actually generated skew including the direction of the occurrence.

  Further, when obtaining the difference between the photoelectric conversion signals obtained from the left and right sides of the light receiving element, the skew amount that is not affected by the field shake and the laser power fluctuation can be detected by normalizing each signal component.

According to the present invention, attention is paid to the fact that there is a difference in the photoelectric conversion amount in the left and right regions in the direction straddling the track of the light receiving element when skew occurs due to the warp of the optical disk, etc. By detecting the difference between the photoelectric conversion signals to be detected and detecting the skew amount, it is possible to quickly and directly detect the skew generated during recording on the optical disk, including the direction of the occurrence.
Also, since a direct value corresponding to the skew that occurs during optical disc recording is detected as the skew amount, there is no need to find the bottom while swinging the skew during writing. An adverse effect can be prevented.
In addition, since a direct value corresponding to the skew generated at the time of optical disk recording is obtained as a skew amount including the direction of the skew generation, an inexpensive skew correction control system can be configured with a simple feedback circuit, and this skew Skew correction with good responsiveness can be performed by the correction control system.
Since the skew detection speed is high and the operation speed of the skew correction control system is high, it is possible to cope with a change in one track and to improve the writing performance of the optical disk apparatus.

  The purpose of quickly and directly detecting the skew that occurs during optical disk recording, including the direction of the occurrence, when the skew occurs due to warping of the optical disk, etc. Focusing on the fact that there is a difference in the photoelectric conversion amount of the light receiving element, it was easily realized by obtaining the difference between the photoelectric conversion signals obtained from the left and right of the light receiving element and detecting the skew amount.

  FIG. 1 is a block diagram showing the configuration of the skew detection apparatus according to the first embodiment of the present invention. The skew detection apparatus includes a light receiving element 1 that photoelectrically converts return light from the optical disc, an adder 2 that adds signals output from the light receiving surface dividing portions A and B of the light receiving element 1, and a light receiving surface division of the light receiving element 1. Adder 3 for adding the signals output from parts C and D, sample hold circuits (S / H) 4 and 5 for sample-holding the output of adder 2, and sample-and-hold for sample-holding the output of adder 3 Circuits (S / H) 6 and 7, a divider 8 that divides the outputs of the sample and hold circuits 4 and 5, a divider 9 that divides the outputs of the sample and hold circuits 6 and 7, and a divider 8 A subtracter 10 for subtracting the output of the divider 9 from the output, a sampling clock generation circuit 11 for supplying a write clock to the sample hold circuits 4 and 6, and a write clock for the sample hold circuits 5 and 7 are provided. Configured with a sampling clock generating circuit 12.

  Next, the operation of the present embodiment will be described. First, when the laser beam irradiated from the optical pickup of the optical disk apparatus forms a spot on the track of the disk, the image formed is ideally a clean circle if there is no skew as shown in FIG. become. However, if skew occurs due to the tilt of the relationship between the optical disk and the lens, coma appears and the image gradually deforms as shown in FIGS. The difference between FIG. 2 (B) and FIG. 2 (C) is due to the difference in whether the lens is tilted clockwise or counterclockwise with respect to the track. For example, the lens is rotated clockwise. FIG. 2B shows the case of falling in the direction, and FIG. 2C shows the case of falling in the counterclockwise direction.

  The light receiving element 1 has a light receiving region divided into A, B, C, and D, and A, B, C, and D are arranged so as to straddle the track. When the skew is zero, as shown in FIG. 3 (A), a clear image formation point is formed and writing is performed symmetrically. However, if there is a skew, as shown in FIG. 3 (B), the conspicuous point is deformed, and the density of the light spot collected on the left and right changes depending on the location, so writing is performed symmetrically. It will not be. In this embodiment, the occurrence of skew is detected based on this non-symmetrical result (difference between the A + B photoelectric conversion signal and the C + D photoelectric conversion signal of the light receiving element).

  Therefore, the photoelectric conversion signals from A and B of the light receiving element 1 are added by the adder 2, and the photoelectric conversion signals from C and D of the light receiving element 1 are added by the adder 3. The addition result of the adder 2 and the addition result of the adder 3 are sampled and held by the sampling clock output from the write sampling clock circuit 12 by the sample hold circuit 4 and the sample hold circuit 6. The addition result of the adder 2 and the addition result of the adder 3 are sampled and held by the sampling clock circuit 12 output from the sampling clock circuit 12 by the sample hold circuit 5 and the sample hold circuit 7.

  FIG. 4 is a waveform diagram for explaining the sample and hold operation of the sample and hold circuit. FIG. 4A shows the writing level and reading level of the laser beam when writing data to the optical disc. FIG. 4B shows, for example, an A + B output signal (RF signal) of the light receiving element 1. FIG. 4C shows timing for sampling the RF signal shown in FIG. The read sampling timing is 101, and the write sampling timing is 102. Incidentally, the read sampling timing 101 and the write sampling timing 102 coincide with the periods of the read sampling clock and the write sampling clock, respectively.

  When the hold values of the sample hold circuits 4, 5, 6, and 7 are (C + D) WRITE, (C + D) READ, (A + B) WRITE, (A + B) READ, the divider 8 is (A + B) WRITE / (A + D) READ. The divider 9 calculates (C + D) WRITE / (C + D) READ, and the subtractor 10 uses {(A + B) WRITE / (A + D) READ}-{(C + D) WRITE / (C + D). ) READ} is subtracted to obtain the skew detection output 300.

  The above-described processing has the purpose of removing the fluctuation of the visual field and the laser power fluctuation by normalizing the light reception level at the time of writing with the light reception level at the time of reading. Basically, the return light at the time of reading is not affected by the generated pits as at the time of writing, so it can be considered that the emitted light returns. If writing is not affected by pit shaping, return light at the time of reading and writing is represented only by the power ratio of the incident light. Actually, at the time of writing, a portion with a high power density contributes to the formation of pits, so that it is difficult to return, and a portion with a low density cannot be formed with pits, so the return rate is high. In particular, when coma occurs due to skew or the like, the density distribution of the laser light is not symmetrical, and therefore the return rate changes due to the density difference between the left and right. Therefore, the influence received by pit molding differs on the left and right.

  Next, the return light falls on the light receiving element 1, but a part of the return light does not return onto the light receiving element due to the aperture and the optical path. At this time, the return light returns to left-right symmetry if there is no influence of aberration, but does not return to left-right symmetry under the influence of aberration. However, if there is no influence of pits generated at the time of writing, only the ratio expressed by power is obtained at the time of reading and writing, so the relationship of the ratio becomes symmetrical. However, as described above, pits are generated in the portion where the density of the laser beam is high, and pits are not generated where the density is low, so the relationship between reading and writing does not become symmetrical on the left and right.

  Therefore, {(A + B) WRITE / (A + D) READ} − {(C + D) WRITE / (C + D) READ} indicates the skew amount 300, and its sign indicates the direction in which the skew amount is generated. The skew amount 300 is a value that is not affected by the field of view fluctuation and the laser power fluctuation.

  FIG. 5 is a diagram showing characteristics of typical values handled in the above processing. In the figure, 51 is the (A + B) WRITE characteristic, and 52 is the (C + D) WRITE characteristic, both of which can be approximated by a quadratic curve. 53 is a straight line with a characteristic of the skew amount 300. When the skew amount 300 is 0, there is no skew. When the skew amount is +, the skew is caused to fall clockwise with respect to the track from the lens and fall clockwise. In the case of,-, for example, it indicates that the skew has occurred by tilting counterclockwise from the lens with respect to the track.

  According to the present embodiment, attention is paid to the fact that there is a difference in the photoelectric conversion amount between the left and right regions of the light receiving element 1 when a skew occurs. Specifically, the difference between the A + B and C + D photoelectric conversion signals of the light receiving element 1 By detecting the skew amount and detecting the skew amount, the skew amount corresponding to the actual skew generation can be directly determined including the direction of the skew generation.

  FIG. 6 is a block diagram showing the configuration of the skew detection apparatus according to the second embodiment of the present invention. However, the same parts as those in the first embodiment will be described with the same reference numerals. The skew detection device outputs the PIT signal output from the light receiving element 1, adders 2 and 3, sample and hold circuits (S / H) 14 and 15, sampling clock generation circuit 12, adder 16, and adder 16. The CPU 17 to be processed, the multiplier 18 that multiplies the hold value of the sample hold circuit 14 by the coefficient K1, the multiplier 19 that multiplies the hold value of the sample hold circuit 15 by the coefficient K2, and the difference between the outputs of the multiplier 18 and the multiplier 19 The difference from the first embodiment is that the method of normalizing the A + B and C + D photoelectric conversion signals obtained from the light receiving element 1 is different.

  Next, the operation of the present embodiment will be described. The photoelectric conversion signals obtained in the A and B regions of the light receiving element 1 are added by the adder 2, sampled and held by the sample hold circuit 14 by the sampling clock read from the sampling clock generating circuit 12, and C and D of the light receiving element 1. The photoelectric conversion signals obtained in the region are added by the adder 3 and sampled and held by the sample hold circuit 15 by the read sampling clock from the sampling clock generation circuit 12. The hold values of the sample and hold circuits 14 and 15 are added by the adder 16 and output to the CPU 17 as a pit signal output.

  Here, the characteristic curve of (A + B) WRITE, the characteristic curve of (C + D) WRITE, and the characteristic curve of (A + B) WRITE + (C + D) WRITE are shown at 41, 42 and 43 in FIG. The CPU 17 obtains a point that becomes the minimum value of (A + B) WRITE + (C + D) WRITE as indicated by 41 in FIG. These points are 401 and 402 in FIG. 7, and the values are (A + B) WRITEref and (C + D) WRITEref. The CPU 17 sets the reciprocals of (A + B) WRITEref and (C + D) WRITEref at these points as coefficients K1 and K2. When K1 = 1 / (A + B) WRITEref, K2 = 1 / (C + D) WRITEref, and the CPU 17 sets the multipliers 18 and 19.

  Thereafter, the sample hold value of the sample hold circuit 14 is multiplied by K1 by the multiplier 18, the sample hold value of the sample hold circuit 15 is multiplied by K2 by the multiplier 19, and normalized. Is subtracted by the subtracter 10, and a skew amount (SKEW detection output) 400 is detected. In this case, the skew amount 400 is {(A + B) WRITE / (A + B) WRITEref} − {(C + D) WRITE / (C + D) WRITEref}, as shown in FIG. In FIG. 8, 44 indicates (A + B) WRITE × K1, and 45 indicates (C + D) WRITE × K2.

  This embodiment differs only in the normalization method when calculating the skew amount 400, and the effect is the same as the effect of the first embodiment.

  The normalization method for calculating the skew amount is not limited to the above. The minimum value of the (A + B) WRITE characteristic curve and the minimum value of the (C + D) WRITE characteristic curve are (A + B) WRITEmin, (C + D) WRITEmin. The same effect can be obtained by normalizing with these values. In this case, the skew amount is {(A + B) WRITE / (A + B) WRITEmin} − {(C + D) WRITE / (C + D) WRITEmin}.

  FIG. 9 is a block diagram showing a configuration of a skew correction control apparatus according to the third embodiment of the present invention. The skew correction control device 30 according to the present embodiment includes the light receiving element 1, the skew detection device 20, the controller 22, and the skew actuator 222. However, the skew detection apparatus 20 has the same configuration as that of the first or second embodiment. The skew detection device 20 processes a photoelectric conversion signal from the light receiving element 1 in the pickup 21 and outputs a skew amount 300. The skew amount 300 is compared with a target value, and the difference is input to the controller 22. If the target value is zero, the controller 22 controls the skew actuator 222 to move the lens (not shown) so that the skew amount 300 becomes zero, and performs correction so that the skew becomes zero. For example, when the skew amount 300 has a certain value of +, the skew actuator 222 moves the lens (not shown) clockwise with respect to the track to make the skew amount zero, and when the skew amount 300 has a certain value of − The skew actuator 222 moves the lens counterclockwise with respect to the track so that the skew amount is zero.

  According to the present embodiment, since the skew detection apparatus 20 has the same configuration as that of the first or second embodiment, the skew amount and the generation direction thereof are output as the skew amount 300. The skew generated by such a simple feedback circuit can be corrected quickly and accurately, and good signal recording characteristics can be obtained at low cost.

  Note that the skew correction control device 30 shown in FIG. 9 is mounted on an optical disk device that records an optical disk, and can correct skew caused by warpage of the optical disk without being affected by field fluctuations or laser power fluctuations. In addition, the writing performance of the optical disk apparatus can be improved without increasing the cost.

  In addition, the present invention is not limited to the above-described embodiment, and can be implemented in various other forms in specific configurations, functions, operations, and effects without departing from the gist thereof. For example, in the above-described embodiment, the light receiving element is divided into four parts. This is because the light receiving element for obtaining the RF signal from the return light is also used for skew detection. In this case, the adder is omitted and the number of parts can be reduced, but a light receiving element dedicated to skew detection is required.

It is the block diagram which showed the structure of the skew detection apparatus which concerns on the 1st Embodiment of this invention. It is the figure which showed the form of the spot which the laser beam irradiated from an optical pick-up connects on the track | truck of a disk. It is a figure explaining the difference in the spot density on the light receiving element divided into four. It is a wave form diagram explaining the sample hold operation of the sample hold circuit shown in FIG. FIG. 2 is a characteristic diagram showing a characteristic curve of typical values handled in the process shown in FIG. 1. It is the block diagram which showed the structure of the skew detection apparatus which concerns on the 2nd Embodiment of this invention. FIG. 7 is a characteristic diagram showing a characteristic curve of typical values handled in the process shown in FIG. 6. FIG. 7 is a characteristic diagram showing a characteristic curve of typical values handled in the process shown in FIG. 6. It is the block diagram which showed the structure of the skew correction control apparatus which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Light receiving element 2, 3, 16 ... Adder 4, 5, 6, 7, 14, 15 ... Sample hold circuit (S / H), 8, 9 ... Divider, 10 ... Subtractor 11, 12 ... Sampling clock generation circuit, 17 ... CPU, 18, 19 ... Multiplier, 20 ... Skew detection device, 21 ... Pickup, 22 ... Controller, 222 ... Skew actuator.

Claims (9)

A skew detection device for detecting skew from a return light of a laser beam irradiated on a rotating optical disk,
A photoelectric conversion element divided into two in the track direction of the optical disc;
Calculating means for calculating a difference between two photoelectric conversion signals respectively output from the two divided regions of the photoelectric conversion element;
A skew detection apparatus characterized in that a calculation result of the calculation means is a detected skew amount. A skew detection device for detecting skew from a return light of a laser beam irradiated on a rotating optical disk,
A photoelectric conversion element divided into four;
Two signals equivalent to the signals obtained from the two regions of the photoelectric conversion element across the track direction of the optical disc by adding the photoelectric conversion signals obtained from two regions of the four divided regions of the photoelectric conversion element Adding means for generating a photoelectric conversion signal of
Calculating means for calculating a difference between the two photoelectric conversion signals calculated;
A skew detection apparatus characterized in that a calculation result of the calculation means is a detected skew amount.   A normalizing unit for normalizing the two photoelectric conversion signals; and normalizing the two photoelectric conversion signals obtained by the arithmetic unit by the normalizing unit, and normalizing the normalized photoelectric conversion 3. The skew detection apparatus according to claim 1, wherein a difference between signals is set as a detected skew amount.   In the writing mode for writing information to the optical disc, the normalizing means outputs the first and second photoelectric conversion signals when the laser power is at the writing level from the two divided regions of the photoelectric conversion element and 2 of the photoelectric conversion element. The third and fourth photoelectric conversion signals when the laser power is at the reading level are obtained from the divided area, the first photoelectric conversion signal is divided by the second photoelectric conversion signal, and the third photoelectric conversion signal is obtained. 4. The skew detection apparatus according to claim 3, wherein the signal is normalized by dividing by the fourth photoelectric conversion signal.   The normalizing means is a characteristic curve of the added value of the first and second photoelectric conversion signals obtained when the laser power is at the write level from the two-divided region of the photoelectric conversion element in the write mode for writing information on the optical disc. 4. The skew according to claim 3, wherein the first and second photoelectric conversion signals are normalized by the values of the first and second photoelectric conversion signals at the time of the minimum value. Detection device.   The normalizing means calculates a minimum value of each of the first and second photoelectric conversion signal characteristic curves when the laser power is at a write level from a two-divided region of the photoelectric conversion element in a write mode for writing information to the optical disc. 4. The skew detection apparatus according to claim 3, wherein normalization is performed by obtaining and dividing the first and second photoelectric conversion signals by these minimum values. A lens for condensing the laser beam on the optical disc;
Moving means for moving the position of the lens;
A light receiving element in which a light receiving surface for photoelectrically converting return light from the disk is divided into two in the track direction of the optical disk;
A skew detection device that detects a skew amount of the optical disk based on a photoelectric conversion signal of the light receiving element;
A control circuit that moves the lens by controlling the moving means so that the skew amount detected by the skew detection device becomes a target value;
The skew detection apparatus includes a calculation unit that calculates a difference between two photoelectric conversion signals respectively output from the two divided regions of the photoelectric conversion element, and uses a calculation result of the calculation unit as a detected skew amount. A skew correction control device. A lens for condensing the laser beam on the disk;
Moving means for moving the position of the lens;
A light receiving element in which a light receiving surface for photoelectrically converting return light from the disk is divided into four parts;
A skew detection device for detecting a skew amount of the disk based on a photoelectric conversion signal of the light receiving element;
A control circuit that moves the lens by controlling the moving means so that a skew amount detected by the skew detecting device becomes a target value;
The skew detection device is obtained from the two regions of the photoelectric conversion element that straddle the track direction of the optical disk by adding the photoelectric conversion signals obtained from two of the four divided regions of the photoelectric conversion element. An adding means for creating two photoelectric conversion signals equivalent to the signal, and a calculating means for calculating a difference between the two calculated photoelectric conversion signals, and calculating the calculation result of the calculating means as a detected skew amount And a skew correction control device. An optical disc apparatus that focuses laser light on an optical disc from an optical pickup, receives return light from the optical disc by the optical pickup, and records information on the disc,
A skew detection device that detects a skew amount of the disk based on a photoelectric conversion signal obtained by photoelectrically converting the return light by a light receiving element in which a light receiving surface in the optical pickup is divided into four parts;
Control means for moving the lens in the optical pickup so that the skew amount detected by the skew detection device becomes a target value;
The skew detection device is obtained from the two regions of the photoelectric conversion element straddling the track direction of the optical disk by adding the photoelectric conversion signals obtained from the two regions among the four divided regions of the photoelectric conversion element. An adding means for creating two photoelectric conversion signals equivalent to the signal, and a calculating means for calculating a difference between the two calculated photoelectric conversion signals, and calculating a calculation result of the calculating means as a detected skew amount An optical disc apparatus characterized by:

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