JP2004146061A - Optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device which detects appropriately the quantity of cross talk from its adjacent track to a read signal for one track from a read signal for the track without recording a special signal. <P>SOLUTION: The recording signals of at least three respective tracks being adjacent on a recording medium are read simultaneously, individually, and optically, and read signal values for tracks of one end, center, the other end out of three tracks are generated respectively as first, second, and third read-out signal values. When the first read signal value is larger than a second threshold value and the third read signal value is also larger than the second threshold value, a third gate signal is generated. When the first read signal value is smaller than a first threshold value and the third read signal value is also smaller than the first threshold value, a fourth gate signal is generated. The difference between the second read signal value at the time of generation of the third gate signal and the second read-out signal value at the time of generation of the fourth gate signal is generated as a value indicating the quantity of cross talk to the second read signal. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to an optical pickup device that writes or reads an information signal such as a video signal, an audio signal, or a computer data signal on an optical recording medium such as an optical disk.

Research on high-density recording of information signals including not only audio signals but also video signals and computer data on optical discs has been advanced. For example, if an information signal including a video signal of a movie for about two hours is recorded on an optical disk having a size of a known compact disk on which only an audio signal is recorded, the recording density of the optical disk must be considerably high. For high-density recording, it is conceivable to reduce a track interval for recording an information signal. When the track interval, that is, the track pitch is reduced, the problem is that the amount of crosstalk mixed into the information signal increases to degrade the quality of the reproduced information signal. In particular, when the optical disk is inclined with respect to the optical axis, the amount of crosstalk from one adjacent track increases, and good signal reproduction may not be performed.

Conventional pickup devices can read information signals well on an optical disk with a large track pitch set, but can read information from an optical disk with a small track pitch due to high recording density without being adversely affected by crosstalk. It is impossible to read the signal well. However, even if the optical disc has a large track pitch, as described above, if the optical disc is inclined with respect to the optical axis, the amount of crosstalk from one adjacent track increases. Therefore, the conventional pickup device includes a disk tilt detector for detecting the tilt of the disk, and controls the optical axis to the optical disk according to the detected tilt amount detected by the disk tilt detector. .

FIG. 1 shows a disk tilt detector used in a conventional pickup device. In this disk tilt detector, the light emitting diode 11 generates a beam light for disk tilt detection with respect to the disk 12, and the light receivers 13 and 14 are provided in the disk radial direction with the light emitting diode 11 interposed therebetween. The reflected light is respectively received. Each light receiving level signal of the light receiving units 13 and 14 is supplied to a differential amplifier 15 and the difference is obtained. For example, when the right side of the disk 12 is tilted downward in the drawing, the output level of the light receiver 13 increases, and the output level of the light receiver 14 decreases. Therefore, the inclination of the disk can be detected from this level difference. The output signal of the differential amplifier 15 is supplied to a drive mechanism for adjusting the tilt of the entire pickup, and the tilt of the entire pickup is automatically adjusted so as to correct the tilt detected by the disc tilt detector.

However, such a tilt detector and a driving mechanism increase the size of the pickup device, so that it is difficult to move the pickup itself at a high speed, and as a result, it is difficult to access the target track at a high speed. In addition, since the angle of installation of the tilt detector needs to be adjusted accurately, there is a disadvantage that it takes time and effort in assembling the apparatus. Furthermore, although the crosstalk from adjacent tracks can be balanced from the output of the tilt detector, the amount of crosstalk itself cannot be measured by the tilt detector, so that the track interval cannot be made extremely small. . On the other hand, a method has been proposed in which a mark for measuring crosstalk is previously recorded on a track. However, such a mark uses a certain amount of the disk recording capacity irrespective of the information to be recorded by the user, so that there is a disadvantage that the recording capacity on the disk is reduced.

The present invention has been made in view of the above points, and has as its object to reduce the amount of crosstalk from a track adjacent to a read signal for one track without recording a special signal. To provide an optical pickup device that appropriately detects a read signal from the read signal.

2. The optical pickup device according to claim 1, wherein the optical pickup device optically reads a signal recorded on a track of a recording medium, wherein the recording signal of each of at least three adjacent tracks on the recording medium is recorded. Signal reading means for reading each of the three tracks simultaneously and individually and optically to generate respective read signal values for the tracks at one end, the center and the other end of the three tracks as first, second and third read signal values. Comparing means for individually comparing the first and third read signal values with a first threshold value and a second threshold value which is larger than the first threshold value; and wherein the first read signal value is larger than the second threshold value and Means for generating a third gate signal when the third read signal value is greater than the second threshold value; and wherein the first read signal value is less than the first threshold value and the third read signal value is less than the first threshold value. Means for generating a fourth gate signal at a small point in time; and calculating a difference between the second read signal value when the third gate signal is generated and the second read signal value when the fourth gate signal is generated. (2) a crosstalk amount detecting means for generating a value indicating the crosstalk amount to the read signal.

An optical pickup device according to a seventh aspect of the present invention is an optical pickup device for optically reading a signal recorded on a track of a recording medium, wherein the recording signal of each of three adjacent tracks on the recording medium is read. Each of the three signals is read individually and optically at the same time, and the read signal values for one end of the preceding read, the center and the other end of the delayed read of the three tracks are defined as first, second, and third read signal values. A signal reading means for generating, a first comparing means for generating a fifth gate signal when the first read signal value is smaller than a first threshold value, and the first read signal value being larger than the first threshold value. A second comparing means for generating a sixth gate signal when it is larger than a second threshold value; a delay means for individually delaying the fifth and sixth gate signals; and a second delay means for delaying the fifth and sixth gate signals. A fifth sample and hold circuit that holds and outputs the second read signal value when the gate signal is generated, and a fifth sample and hold circuit that holds and outputs the second read signal value when the sixth gate signal is generated and delayed by the delay unit. A 6-sample and hold circuit, and obtaining a held output value of the fifth sample and hold circuit when the third read signal value is smaller than the first threshold value, wherein the third read signal value is larger than the second threshold value. A selection means for obtaining a held output value of the sixth sample and hold circuit, and a difference between each of the held output values of the fifth and sixth sample and hold circuits obtained by the selection means being crossed to the second read signal. And a crosstalk amount detecting means for generating a value indicating the talk amount.

An optical pickup device according to a tenth aspect of the present invention is an optical pickup device for optically reading a signal recorded on a track of a recording medium, wherein the optical pickup device optically reads a recording signal of one track on the recording medium. A signal reading means for reading and outputting as a first read signal value; a memory for storing the first read signal value output from the signal read means at a predetermined cycle; Means for reading, as second and third read signal values, a plurality of the first read signal values stored in the memory from the plurality of first read signal values corresponding to the respective read points adjacent to each other by one track and two tracks on the other side. Comparing means for individually comparing the first and third read signal values with a first threshold value and a second threshold value which is larger than the first threshold value; and comparing the first read signal value with the second threshold value. Means for generating a third gate signal when the third read signal value is greater than the second threshold value and when the first read signal value is less than the first threshold value and the third read signal value is greater than the first threshold value; Means for generating a fourth gate signal at a time smaller than a threshold value, and a difference between the second read signal value when the third gate signal is generated and the second read signal value when the fourth gate signal is generated. Crosstalk amount detecting means for generating a value indicating the crosstalk amount to the second read signal.

An optical pickup device according to claim 11, wherein the optical pickup device optically reads a signal recorded on a track of a recording medium, wherein the recording signal is recorded on at least three adjacent tracks on the recording medium. Signal reading means for reading each of the three tracks simultaneously and individually and optically to generate respective read signal values for the tracks at one end, the center and the other end of the three tracks as first, second and third read signal values. Comparing means for individually comparing the first and third read signal values with a first threshold value and a second threshold value which is larger than the first threshold value; and when the first read signal value is smaller than the first threshold value. Means for generating a first gate signal; means for generating a second gate signal when the first read signal value is greater than the second threshold value; and means for generating a second gate signal when the third read signal value is less than the first threshold value. Means for generating a third gate signal, means for generating a fourth gate signal when the third read signal value is greater than the second threshold value, and means for generating the second gate signal when the first gate signal is generated. First crosstalk amount detection means for generating a difference from the second read signal value when the second gate signal is generated as a value indicating a crosstalk amount from the one end track to the center track; The difference between the second read signal value when the gate signal is generated and the second read signal value when the fourth gate signal is generated is used as a value indicating the amount of crosstalk from the other track to the center track. And a second crosstalk amount detecting means for generating.

An optical pickup device according to a thirteenth aspect of the present invention is an optical pickup device for optically reading a signal recorded on a track of a recording medium, wherein the recording signal of each of three adjacent tracks on the recording medium is read. Each of the three signals is read individually and optically at the same time, and the read signal values for one end of the preceding read, the center and the other end of the delayed read of the three tracks are defined as first, second, and third read signal values. A signal reading means for generating, a comparing means for individually comparing the first and third read signal values with a first threshold value and a second threshold value which is larger than the first threshold value, and wherein the first read signal value is Means for generating a first gate signal when less than one threshold value, means for generating a second gate signal when the first read signal value is greater than the second threshold value, and means for generating a third gate signal when the third read signal value is greater than the second threshold value. Means for generating a third gate signal when less than a threshold value, means for generating a fourth gate signal when the third read signal value is greater than the second threshold value, and means for generating the second read signal when the first gate signal is generated. First crosstalk amount detection means for generating a difference between the signal value and the second read signal value when the second gate signal is generated as a value indicating a crosstalk amount from the one end track to the center track; The difference between the second read signal value when the first gate signal is generated and the second read signal value when the second gate signal is generated is calculated by the amount of crosstalk from the track at the other end to the center track. And a second crosstalk amount detecting means for generating a value indicating

An optical pickup device according to a fifteenth aspect of the present invention is an optical pickup device for optically reading a signal recorded on a track of a recording medium, wherein the optical pickup device optically reads a recording signal of one track on the recording medium. A signal reading means for reading and outputting as a first read signal value; a memory for storing the first read signal value output from the signal read means at a predetermined cycle; Reading means for reading, as the second and third read signal values, from the plurality of first read signal values stored in the memory, the read signal values corresponding to the read points adjacent to each other by one track and two tracks on the other side. Comparing means for individually comparing the first and third read signal values with a first threshold value and a second threshold value which is larger than the first threshold value; and wherein the first read signal value is the first threshold value. Means for generating a first gate signal when less than the first threshold value; means for generating a second gate signal when the first read signal value is greater than the second threshold value; and means for generating a third gate signal value when the third read signal value is less than the first threshold value. Means for generating a third gate signal at a time; means for generating a fourth gate signal when the third read signal value is greater than the second threshold value; and means for generating a fourth gate signal when the first gate signal is generated. A first crosstalk amount detection for generating a difference from the second read signal value when the second gate signal is generated as a value indicating a crosstalk amount from one track of one of three adjacent tracks to a center track; Means for calculating a difference between the second read signal value when the third gate signal is generated and the second read signal value when the fourth gate signal is generated from the other one of the three adjacent tracks. Said A second crosstalk amount detecting means for generating a value indicating the amount of crosstalk to track central, is characterized by having a.

An optical pickup device according to claim 17, wherein the optical pickup device optically reads a signal recorded on a track of a recording medium, wherein the recording signal of at least three adjacent tracks on the recording medium is recorded. Signal reading means for reading each of the three tracks simultaneously and individually and optically to generate respective read signal values for the tracks at one end, the center and the other end of the three tracks as first, second and third read signal values. Comparing means for individually comparing the first and third read signal values with a first threshold value or a second threshold value which is larger than the first threshold value; and when the first read signal value is smaller than the first threshold value. Or a means for generating a first gate signal when the third read signal value is smaller than the first threshold value or when the third read signal value is larger than the second threshold value. Means for generating a fourth read signal value by extracting only an AC component of the second read signal value; and means for converting the fourth read signal value when the first gate signal is generated from the track at one end to the center. A first crosstalk amount detecting means for generating a value indicating a crosstalk amount to the first track, and a fourth cross signal from the other end track to the center track when the second gate signal is generated. And a second crosstalk amount detecting means for generating a value indicating the amount of talk.

An optical pickup device according to claim 19 is an optical pickup device for optically reading a signal recorded on a track of a recording medium, wherein the recording signal of each of three adjacent tracks on the recording medium is read. Each of the three signals is read individually and optically at the same time, and the read signal values for one end of the preceding read, the center and the other end of the delayed read of the three tracks are defined as first, second, and third read signal values. Signal reading means for generating, a comparing means for individually comparing the first and third read signal values with a first threshold value or a second threshold value which is larger than the first threshold value, and wherein the first read signal value is Means for generating a first gate signal when the third read signal value is smaller than the first threshold value or larger than the second threshold value; Means for generating a second gate signal, means for obtaining a fourth read signal value by extracting only the AC component of the second read signal value, and means for applying the fourth read signal value when the first gate signal is generated to the one end. A first crosstalk amount detecting means for generating a value indicating a crosstalk amount from the track to the center track, and the fourth read signal value when the second gate signal is generated from the track at the other end to the center. And a second crosstalk amount detecting means for generating a value indicating the amount of crosstalk to the track.

An optical pickup device according to claim 21 is an optical pickup device for optically reading a signal recorded on a track of a recording medium, wherein the optical pickup device optically reads a recording signal of one track on the recording medium. A signal reading means for reading and outputting as a first read signal value; a memory for storing the first read signal value output from the signal read means at a predetermined cycle; Reading means for reading, as the second and third read signal values, from the plurality of first read signal values stored in the memory, the read signal values corresponding to the read points adjacent to each other by one track and two tracks on the other side. Comparing means for individually comparing the first and third read signal values with a first threshold value or a second threshold value which is larger than the first threshold value; and wherein the first read signal value is the first threshold value. Means for generating a first gate signal when the third read signal value is smaller than the second threshold value or when the third read signal value is smaller than the first threshold value or when the third read signal value is larger than the second threshold value. Generating means, obtaining a fourth read signal value by extracting only an AC component of the second read signal value, and outputting the fourth read signal value when the first gate signal is generated among three adjacent tracks. First crosstalk amount detecting means for generating a value indicating the crosstalk amount from one end track to the center track; and the fourth read signal value when the second gate signal is generated, among the three adjacent tracks. And a second crosstalk amount detecting means for generating a value indicating the crosstalk amount from the other track to the center track.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 shows an optical system of an optical pickup device used in an optical disk player according to the present invention. In this pickup device, the light source 21 is driven by a drive circuit (not shown) to emit laser light, and the laser light emitted from the light source 21 is reflected by the beam splitter 22 and reaches the objective lens 24. The objective lens converges the laser beam on the recording surface of the optical disk. Three or more tracks are irradiated on the recording surface of the optical disk 26. The light beam reflected on the recording surface of the optical disk 16, that is, the reflected light is converted into a parallel laser beam by the objective lens 24, then passes straight through the beam splitter 22 and reaches the light receiver 27.

The light receiver 27 has three light receiving elements 34 to 36 as shown in FIG. 3, and these light receiving elements 34 to 36 are linearly arranged at predetermined intervals in the disk radial direction. When a track image (pit image) of one track to be read on the optical disk 26 is formed on the light receiving element 35, the light receiving element 34 is formed such that track images of adjacent tracks of the one track are formed on the light receiving elements 34 and 36. The interval between ~ 36 is defined.

FIG. 4 shows a crosstalk detection circuit connected to the output of the light receiver 27. In this crosstalk detection circuit, an inverter 49 is connected to the light receiving element 35. The inverter 49 inverts the output level of the light receiving element 35. Two comparators 41 and 43 are connected to the light receiving element 34, and two comparators 42 and 44 are connected to the light receiving element 36. The comparator 41 compares the output level of the light receiving element 34 with the first threshold value Th1, and outputs a high-level output signal when the output level of the light receiving element 34 is smaller than Th1. The comparator 42 compares the output level of the light receiving element 36 with the first threshold value Th1, and outputs a high-level output signal when the output level of the light receiving element 36 is smaller than Th1. The comparator 43 compares the output level of the light receiving element 34 with the second threshold value Th2, and outputs a high-level output signal when the output level of the light receiving element 34 is greater than Th2. The comparator 44 compares the output level of the light receiving element 36 with the second threshold Th2, and outputs a high-level output signal when the output level of the light receiving element 36> Th2. A logic circuit including AND circuits 45 to 48 is formed at the outputs of the comparators 41 to 44. The AND circuit 45 calculates the logical product of the output levels of the comparators 41 and 42, the AND circuit 46 calculates the logical product of the output levels of the comparators 41 and 44, and the AND circuit 47 calculates the logical product of the output levels of the comparators 42 and 43. The AND circuit 48 calculates the logical product of the output levels of the comparators 43 and 44.

サ ン プ ル Sample hold (S / H) circuits 51 to 54 are connected to the outputs of the AND circuits 45 to 48, respectively. The sample hold circuit 51 holds the output signal of the inverter 49 in response to the fourth gate signal which is the high level signal output of the AND circuit 45, and the sample hold circuit 52 outputs the third gate signal which is the high level signal output of the AND circuit 48. The sample and hold circuit 53 holds the output signal of the light receiving element 35 in response to the first gate signal which is the high level signal output of the AND circuit 46, and the sample and hold circuit 54 The output signal of the inverter 49 is held in accordance with the second gate signal which is a high-level signal output of the AND circuit 47. An integrating and adding circuit 55 is connected to the sample and hold circuits 51 and 52, and an integrating and adding circuit 56 is connected to the sample and hold circuits 53 and 54. The integrating and adding circuit 55 obtains a crosstalk amount by adding the output values of the sample and hold circuits 51 and 52 and further integrating them. The integration and addition circuit 56 obtains a crosstalk balance level by adding the output values of the sample and hold circuits 53 and 54 and further integrating them.

FIG. 5 shows an example of a measured waveform of a read signal obtained from the light receiving element 35, that is, an example of an eye pattern when a digital video disk is used as the optical disk 26. It can be seen from this eye pattern that the read signal amplitudes differ between pits formed on the optical disc 26 having different lengths due to differences in spatial frequency transfer characteristics. Therefore, the above-described first threshold value Th1 and second threshold value Th2 are set in consideration of the fact that the amplitudes are different from each other. That is, as shown in FIG. 5, the first threshold value Th1 is set to be larger than the magnitude of the amplitude value for the shortest pit, and the second threshold value Th2 is set to a value larger than the first threshold value Th1. In the case of FIG. 5, the absolute values of the first threshold Th1 and the second threshold Th2 are equal to each other. It should be noted that the read signal amplitudes differ from each other depending on the pit length, which is the same for other optical disks such as a compact disk.

First, as an operation of the crosstalk detection circuit having the above configuration, a crosstalk balance level detection operation will be described. When the light receiving element 36 receives the reflected light from the land on the track and the light receiving element 35 receives the reflected light from the pit on the track, the light reflected from the land is more reflected than the light reflected from the pit. Therefore, the output level of the light receiving element 34 is smaller than the first threshold value Th1, and the output level of the light receiving element 36 is larger than the second threshold value Th2. As a result, the output levels of the comparators 41 and 44 become high and the output levels of the comparators 42 and 43 become low, so that the output level of the AND circuit 46 becomes high and the other AND circuits 45 and 44 become high. The output levels of 47 and 48 are low. At this time, the sample hold circuit 53 is activated in response to the high level output of the AND circuit 46, that is, the first gate signal, and the sample hold circuit 53 holds and outputs the output signal of the light receiving element 35. This held output is supplied to the integrating and adding circuit 56.

On the other hand, when the light receiving element 34 receives the reflected light from the land on the track and the light receiving element 36 receives the reflected light from the pit on the track, the output level of the light receiving element 34 is larger than the second threshold value Th2, The output level of the light receiving element 36 becomes smaller than the first threshold Th1. As a result, the output levels of the comparators 42 and 43 become high and the output levels of the comparators 41 and 44 become low, so that the output level of the AND circuit 47 becomes high and the other AND circuits 45 and 43 become high. The output levels of 46 and 48 are low. At this time, the sample hold circuit 54 is activated in response to the high level output of the AND circuit 47, that is, the second gate signal, and the sample hold circuit 54 holds and outputs an inverted signal of the output signal of the light receiving element 35 by the inverter 49. This held output is supplied to the integrating and adding circuit 56.

The integration and addition circuit 56 integrates the signals supplied from the sample and hold circuits 53 and 54, adds the integration results, and outputs the result. Since this operation is continuously performed, the average value of the signal levels supplied from the sample and hold circuits 53 and 54 is added in the integration and addition circuit 56. Since the inverter 49 is provided, when the output level of the light receiving element 34 is actually smaller than the first threshold value Th1 and the output level of the light receiving element 36 is larger than the second threshold value Th2, the output level of the light receiving element 34 becomes The difference between the average values of the output signals of the light receiving element 35 when the output level of the light receiving element 36 is smaller than the first threshold value Th1 is larger than the second threshold value Th2.

When the crosstalk balance is maintained, when the output level of the light receiving element 34 is lower than the first threshold Th1 and the output level of the light receiving element 36 is higher than the second threshold Th2, the output level of the light receiving Since the ratio between when the output level of the light receiving element 36 is smaller than the first threshold value Th1 and when the output level of the light receiving element 36 is smaller than the first threshold value Th2 is substantially equal, the addition output of the integration and addition circuit 56 has a small value of almost 0. However, when the crosstalk balance is not maintained, for example, if the amount of crosstalk to the light receiving element 35 from the track to the light receiving element 34 is larger than that from the track to the light receiving element 36, the light receiving element 34 When the light receiving element 36 receives the reflected light from the upper land portion and the light receiving element 36 receives the reflected light from the pit portion on the track, the light receiving element 35 is less affected by the crosstalk than in the opposite case. As a result, the average value of the output level of the inverter 49 increases, and the addition output of the integration and addition circuit 56 becomes negatively large. On the other hand, if the amount of crosstalk to the light receiving element 35 is larger from the track to the light receiving element 36 than from the track to the light receiving element 34, the light receiving element 36 receives the reflected light from the land portion on the track and receives the light. When the element 34 receives the reflected light from the pit portion on the track, the average value of the output level of the light receiving element 35 increases due to the influence of the crosstalk as compared with the opposite case. As a result, the addition output of the integration and addition circuit 56 becomes positive.

That is, the addition output of the integration and addition circuit 56 indicates the imbalance of the crosstalk amount, and from this value, the influence of the crosstalk due to the inclination of the optical disk 26 can be known. Next, the operation of the crosstalk detection circuit for detecting the amount of crosstalk will be described. When the light receiving element 34 receives the reflected light from the land on the track and the light receiving element 36 also receives the reflected light from the land on the track, each output level of the light receiving elements 34 and 36 is larger than the second threshold Th2. Become. As a result, each output level of the comparators 43 and 44 becomes high level, and each output level of the comparators 41 and 42 becomes low level. Therefore, the output level of the AND circuit 48 becomes high level and the other AND circuits 45 to 45 become high. Each output level of 47 becomes a low level. At this time, the sample and hold circuit 52 is activated in response to the high level output of the AND circuit 48, that is, the third gate signal, and the sample and hold circuit 52 holds and outputs the output signal of the light receiving element 35. This held output is supplied to the integrating and adding circuit 55.

When the light receiving element 34 receives the reflected light from the pit portion on the track and the light receiving element 36 also receives the reflected light from the pit portion on the track, each output level of the light receiving elements 34 and 36 is smaller than the first threshold Th1. Become. As a result, each output level of the comparators 43 and 44 becomes low level, and each output level of the comparators 41 and 42 becomes high level. Therefore, the output level of the AND circuit 45 becomes high level and the other AND circuits 46 to Each of the 48 output levels is low. At this time, the sample hold circuit 51 is activated in response to the high level output of the AND circuit 45, that is, the fourth gate signal, and the sample hold circuit 51 holds and outputs an inverted signal of the output signal of the light receiving element 35 by the inverter 49. This held output is supplied to the integrating and adding circuit 55.

The integration and addition circuit 55 integrates the signals supplied from the sample and hold circuits 51 and 52, adds the integration results, and outputs the result. Since this operation is continuously performed, the average value of the signal levels supplied from the sample and hold circuits 51 and 52 is added in the integration and addition circuit 55. Since the inverter 49 is provided, the light receiving elements when the output levels of the light receiving elements 34 and 36 are actually larger than the second threshold value Th2 and when the output levels of the light receiving elements 34 and 36 are smaller than the first threshold value Th1 are actually provided. This means that the difference between the average values of the 35 output signals is obtained. If there is no crosstalk in the light reception of the light receiving element 35, the average value is almost the same regardless of the brightness of the adjacent tracks, so that the difference is almost zero. This affects the light reception of the element 35. Therefore, the addition output of the integration and addition circuit 55 indicates the amount of crosstalk due to the brightness.

When the eye pattern of the read signal obtained from the light receiving element 35 is asymmetric with respect to the eye opening unlike the eye pattern shown in FIG. 5, the output signal of the inverter 49 is corrected by multiplying it by an appropriate coefficient. be able to. In the crosstalk detection circuit shown in FIG. 4, since the output signal of the light receiving element 35 is inverted by the inverter 49 and then supplied to the sample and hold circuits 51 and 54, it is supplied to the integration and addition circuits 55 and 56. Although it is supposed that the two signals are added to result in a subtraction, instead of providing the inverter 49, as shown in FIG. 6, the output signals of the light receiving element 35 are sampled and held by all the sample and hold circuits 51 to 54. It is apparent that the output signals of the sample hold circuits 51 to 54 may be supplied to the integration circuits 57 to 60 and subtracted by the differential amplifiers 88 and 89.

FIG. 7 shows a pickup device having a crosstalk removing function for removing crosstalk according to the crosstalk amount and the crosstalk balance level obtained from the above-described crosstalk detecting circuit. In this pickup device, the light receiver 61 has five light receiving elements, and these light receiving elements are linearly arranged at predetermined intervals in the disk radial direction. On the recording surface of the optical disk, a light beam emitted from a light source (not shown) irradiates five or more tracks in the radial direction of the disk, and the reflected light reaches five light receiving elements of a light receiver 61, and each light receiving element A track image is formed on the element by one of five consecutive tracks. An inverse matrix operation circuit 62 is connected to the output of the light receiver 61. The inverse matrix calculation circuit 62 converts the output signal of the light receiver 61 into an inverse matrix using the crosstalk amount and the crosstalk balance level output from the crosstalk detection circuit 64. A signal extraction circuit 63 is connected to an output of the inverse matrix operation circuit 62. The signal extraction circuit 63 extracts three signals p ₂ , p ₃ , and p ₄ among the signals p _{1 to} p ₅ as the operation result of the inverse matrix operation circuit 62 and supplies the signals to the crosstalk detection circuit 64. The crosstalk detection circuit 64 has, for example, the configuration shown in FIG.

If the signals output from the light receiving elements of the light receiver 61 are s ₁ to s _{5 in the} arrangement order, the crosstalk amount output from the crosstalk detection circuit 64 is a, and the crosstalk balance level is c, There is a matrix relationship expressed by equation (1) between the signals p _{1 to} p ₅ of the operation result of the matrix operation circuit 62. Here, the influence of crosstalk from tracks other than the five tracks formed as track images on the light receiver 61 is ignored.

受光器６１の出力信号ｓ₁〜ｓ₅、クロストーク検出回路６４の出力信号ａ，ｃ、及び逆行列演算回路６２の出力信号ｐ₁〜ｐ₅の行列をベクトルＳ，Ｃ，Ｐとすると、その間には

Assuming that the matrices of the output signals s _{1 to} s _{5 of} the light receiver 61, the output signals a and c of the crosstalk detection circuit 64, and the output signals p _{1 to} p ₅ of the inverse matrix operation circuit 62 are vectors S, C, and P, In the meantime

(Equation 2)
S = CP
There is a relationship. In order to restore the original signal recorded on the disk from the output signals s _{1 to} s ₅ of the light receiver 61, an inverse matrix C ⁻¹ of the matrix C is obtained,

(Equation 3)
P = C ^-1 · S
Can be calculated. This is equivalent to actually forming a linear combination of the output signals s _{1 to} s ₅ of the light receiver 61 by the coefficients obtained from a and c. Three signals p ₂ , p ₃ and p ₄ of the signals p _{1 to} p ₅ resulting from the inverse matrix operation of the inverse matrix operation circuit 62 are extracted by the signal extraction circuit 63 and applied to the crosstalk detection circuit 64. The crosstalk amount a and the crosstalk balance level c obtained by the crosstalk detection circuit 64 are fed back to the inverse matrix calculation circuit 62 to perform crosstalk removal control so that the crosstalk amount a and the crosstalk balance level c decrease. It is.

In the embodiment for performing the inverse matrix operation, this means subtracting the adjacent track signal from the signal of the center track in accordance with the amount of crosstalk, and this can be configured using a VCA (Voltage Control Amplifier). it can. FIG. 8 shows an example of this configuration. In FIG. 8, reference numeral 111 denotes a differential amplifier for calculating the difference between the crosstalk amount and the crosstalk balance detected by the above-described configuration, and 112 denotes an adder for calculating the sum of these. Now, the sum C2 + C3 of the crosstalk amount C2 from the input 2 to which the read signal for one adjacent track is supplied and the crosstalk amount C3 from the input 3 to which the read signal is supplied to the other adjacent track is the differential amplifier 111. If the balance C2-C3 is supplied to the other input of each of the differential amplifier 111 and the adder 112, a signal obtained by adding these signals represents C2, These differences represent the magnitude of C3. Therefore, the crosstalk is removed by subtracting the signals of the adjacent tracks from the detection signal of the center track of 118 by the voltage control differential amplifiers 113 and 114 at an appropriate ratio by the gate adjusters 121 and 122. Here, if a servo system is configured such that this signal is checked again by the crosstalk detection circuit 115, a signal is obtained at the output of the voltage-controlled differential amplifier 114 such that the crosstalk amount and the balance become zero. By sending this signal to the demodulation circuit, it is possible to always obtain a signal from which the amount of crosstalk has been removed even if the amount of crosstalk changes.

Note that s only _three of the signal by the inverse matrix operation circuit 62 performs the calculation of the crosstalk cancellation, s _2, p _3, crosstalk detection circuit 64 a signal s ₄ as an input signal in the output signal of the photodetector 61 It is also possible to operate. FIG. 9 shows a crosstalk detecting circuit of a three-beam type pickup device as an embodiment of the present invention. This crosstalk detection circuit is applicable to a case where a three-beam type optical system is used as the optical system of the pickup device. The optical system of the pickup device includes three light receiving elements 71 to 73. The light receiving elements 71 to 73 are arranged on the disk so as to receive the reflected light of the spot light illuminated by three beams on three mutually adjacent three tracks. As shown in FIG. 10, three spot lights 65 to 67 are formed on the disk, a spot light 66 is formed on one track located at the center of the three tracks, and a spot light 65 is formed on the one track. The spot light 67 is formed at a position preceding the spot light 66 on one of two adjacent tracks, and the spot light 67 is formed at a position later than the spot light 66 on the other of the two adjacent tracks adjacent to the one track. The light receiving element 71 receives the reflected light of the spot light 65, the light receiving element 72 receives the reflected light of the spot light 66, and the light receiving element 73 receives the reflected light of the spot light 67.

In this crosstalk detection circuit, two comparators 74 and 75 are connected to the output of the light receiving element 71. The comparator 74 compares the output level of the light receiving element 71 with the first threshold value Th1, and outputs a high-level output signal when the output level of the light receiving element 71 <Th1. The comparator 75 compares the output level of the light receiving element 71 with the second threshold value Th2, and outputs a high-level output signal when the output level of the light receiving element 71> Th2. Delay elements 76 and 77 are connected to the outputs of the comparators 74 and 75, respectively. The delay elements 76 and 77 correspond to the time during which the spot lights 65 to 67 move by the distance L between the spot lights 65 and 66 or the spot lights 66 and 67 in the tangential direction of the disk. A sample hold (S / H) circuit 78 is connected to the output of the delay element 76, and a sample hold circuit 79 is connected to the delay element 77. The sample and hold circuit 78 holds the output level of the light receiving element 72 in accordance with the output signal of the delay element 76 and supplies the held output to the selector 80. The sample and hold circuit 79 sets the light receiving element in accordance with the output signal of the delay element 77. The output level 72 is held and the held output is supplied to the selector 81. Each of the selectors 80 and 81 receives the delayed output signal of the light receiving element 72 from the delay elements 76 and 77 at the input IN, receives the output signal of the light receiving element 73, and outputs the output level of the light receiving element 73 and the first level. It has a comparison function of comparing the threshold value Th1 with the second threshold value Th2. Each of the selectors 80 and 81 further has first and second outputs OUT1 and OUT2, and outputs a signal input to the input IN from the first output OUT1 when the output level of the light receiving element 73 is smaller than the first threshold Th1. When the output level of the light receiving element 73 is higher than the second threshold Th2, the signal input to the input IN is output from the second output OUT2. The first output OUT1 of each of the selectors 80 and 81 is connected to integrating circuits 82 and 83, and the second output OUT2 of each of the selectors 80 and 81 is connected to integrating circuits 84 and 85. A differential amplifier 86 is connected to the integration circuits 82 and 85, and a crosstalk amount is obtained from the differential amplifier 86. A differential amplifier 87 is connected to the integrating circuits 83 and 84, and a crosstalk balance level is obtained from the differential amplifier 87.

In the operation of the crosstalk detecting circuit, when the output level of the light receiving element 71 is smaller than the first threshold value Th1, the output level of the comparator 74 becomes a high level. It is supplied to the hold circuit 78. The sample hold circuit 78 holds and outputs the output signal of the light receiving element 72 according to the high level signal. On the other hand, when the output level of the light receiving element 71 is higher than the second threshold value Th2, the output level of the comparator 75 becomes a high level, and this high level is delayed by the delay element 77 and supplied to the sample hold circuit 79. The sample hold circuit 79 holds and outputs the output signal of the light receiving element 72 according to the high level signal from the delay element 77. Since the light receiving element 71 is ahead of the light receiving element 72 in the tangential direction of the disc by the time corresponding to the distance L because of the three-beam type pickup device, the comparators 74 and 75 change from the low level to the high level. After a lapse of time corresponding to the distance L, the output signals of the light receiving element 72 are held in the sample and hold circuits 78 and 79.

When the output level of the light receiving element 73 is smaller than the first threshold Th1, the selector 80 supplies the output signal of the sample and hold circuit 78 to the integration circuit 82, and the selector 81 supplies the output signal of the sample and hold circuit 79 to the integration circuit 83. I do. When the output level of the light receiving element 73 is larger than the second threshold value Th2, the selector 80 supplies the output signal of the sample hold circuit 78 to the integration circuit 84, and the selector 81 supplies the output signal of the sample hold circuit 79 to the integration circuit 85. I do.

As a result, the integration circuit 82 integrates the output signal of the light receiving element 72 when the output level of the light receiving element 71 is smaller than the first threshold value Th1 and the output level of the light receiving element 73 is smaller than the first threshold value Th1. The integration circuit 85 integrates the output signal of the light receiving element 72 when the output level of the light receiving element 71 is higher than the second threshold value Th2 and the output level of the light receiving element 73 is higher than the second threshold value Th2. The difference between the output levels of the integrating circuits 85 and 82 is obtained by a differential amplifier 86, and the output signal of the differential amplifier 86 indicates the amount of crosstalk. The integration circuit 83 integrates the output signal of the light receiving element 72 when the output level of the light receiving element 71 is higher than the second threshold value Th2 and the output level of the light receiving element 73 is lower than the first threshold value Th1. At 84, the output signal of the light receiving element 72 when the output level of the light receiving element 71 is smaller than the first threshold Th1 and the output level of the light receiving element 73 is larger than the second threshold Th2 is integrated. The difference between the output levels of the integrating circuits 84 and 83 is obtained by the differential amplifier 87, and the output signal of the differential amplifier 87 indicates the crosstalk balance level.

That is, the crosstalk amount and the crosstalk balance level obtained from the differential amplifiers 86 and 87 are the same as those of the crosstalk detection circuit shown in FIG. In the circuit of FIG. 9, the differential amplifier 86 is connected to the outputs of the integrating circuits 82 and 85, and the differential amplifier 87 is connected to the outputs of the integrating circuits 83 and 84. The amplifiers 86 and 87 may be directly connected, and their differential outputs may be integrated by individual integration circuits. Further, an inverter may be provided as shown in FIG. 4 so that an inverted signal is supplied to one of the integrating circuits, and the output values of the respective integrating circuits may be added.

When a delay element is used as in the embodiment of FIG. 9, one circuit cannot take in the next signal during the delay time, so that there is a sampling interval. Since it does not change abruptly, it still has sufficient speed. If it is necessary to cope with a steep crosstalk change, the response speed can be increased by facilitating several circuits in FIG. 9 and simultaneously using them.

The present invention can be applied to a pickup device that reads a signal of only one track and is used more often than before. Next, FIG. 11 shows an embodiment in which a signal detected by one light spot is once stored in the memory 103 to be configured. In FIG. 11, reference numeral 101 denotes a detector as a light receiving element for receiving light reflected from a light spot for one track on a disk. A read signal, which is an output signal of the detector 101, is digitized by the A / D converter 102 and stored in the memory 103. When one digitized read signal value, one sample value, is input to the memory 103, the memory controller 104 outputs the data collected at the reading point one track and two tracks next to the digitized read signal value. . In FIG. 11, X is the first read signal value at the current read point, Y is the second read signal value at the read point one track before the current read point in the disk radial direction, and Z is the disk value from the current read point. This is the third read signal value at the read point two tracks before in the radial direction. The storage positions of these data in the memory 103 can be calculated from the scanning speed of the medium and the sampling interval. The three signal values thus obtained at adjacent points are compared with the threshold values Th1 and Th2 by the comparators 41 to 44, and the memory value at the intermediate time point is determined by the AND condition as in the above-described embodiment. Are averaged by adding. Here, it is also possible to perform processing such as dividing by the number of samples to prevent overflow. The averaged signal is subtracted by the differential amplifier 88 or 89, and is used as a crosstalk amount or a signal for balancing this. Here, it is also possible to adopt a configuration in which the difference is obtained and then averaged. In the circuit of FIG. 11, the same parts as in FIG. 6, that is, comparators 41 to 44, AND circuits 45 to 48, S / H circuits 51 to 54, integrating circuits 57 to 60, and differential amplifiers 88 and 89 convert digital signals. It is a circuit for processing.

サ ー ボ By subtracting the output value of the memory according to the value of the amount of crosstalk obtained in the above-described example, a servo operation for setting the crosstalk to 0 can be performed. In each of the above embodiments, the case where the first threshold value Th1 is smaller than the second threshold value Th2 has been described. However, the same value may be used, or the second threshold value Th2 may be smaller. It is also possible to operate. For example, as shown in FIG. 12, when the same threshold value Th is used simply (near 0 in FIG. 5), the influence of noise is increased, but the processing circuit can be simplified. In the circuit of FIG. 12, inverters 93 and 94 for inverting the output signals of the comparators 91 and 92 are provided. This is the same for the following embodiments.

FIG. 13 further shows a crosstalk detecting circuit of an imaging detection type pickup device as an embodiment of the present invention. In this crosstalk detecting circuit, each of the light receiving elements 131 to 133 receives an image of one track out of three tracks adjacent to each other, similarly to the light receiving elements 34 to 36 of the light receiver 27 shown in FIGS. An image is formed on a surface, and a voltage value corresponding to the amount of received light is generated as a read signal value. The light receiving element 131 generates a read signal for one of the three tracks, the light receiving element 132 generates a read signal for the central track of the three tracks, and the light receiving element 133 reads the other track of the three tracks. Generate a signal. The comparators 135 and 136 are connected to the light receiving element 131, and the comparators 137 and 138 are connected to the light receiving element 133. The comparator 135 compares the output level of the light receiving element 131 with the first threshold Th1, and outputs a high-level output signal when the output level of the light receiving element 131 is smaller than Th1. The comparator 136 compares the output level of the light receiving element 131 with the second threshold value Th2, and outputs a high-level output signal when the output level of the light receiving element 131> Th2. The comparator 137 compares the output level of the light receiving element 133 with the first threshold value Th1, and outputs a high-level output signal when the output level of the light receiving element 133 is smaller than Th1. The comparator 138 compares the output level of the light receiving element 133 with the second threshold value Th2, and outputs a high-level output signal when the output level of the light receiving element 133 is greater than Th2.

サ ン プ ル Sample hold (S / H) circuits 139 to 142 are connected to the outputs of the comparators 135 to 138, respectively. The sample and hold circuit 139 holds the output level of the crosstalk cancel circuit 150 described below in accordance with the high level signal of the comparator 135, and the sample and hold circuit 140 operates in response to the high level signal of the comparator 136. The sample and hold circuit 141 holds the output level of the crosstalk cancel circuit 150 in accordance with the high level signal of the comparator 137, and the sample and hold circuit 142 holds the output level of the crosstalk in accordance with the high level signal of the comparator 138. The output level of the cancel circuit 150 is held. A differential amplifier 147 is connected to the sample and hold circuits 139 and 140 via integration circuits 143 and 144. The differential amplifier 147 subtracts the output signal of the integration circuit 143 from the output signal of the integration circuit 144, and the amount of crosstalk from one end track where the light receiving element 131 receives an image to the center track where the light receiving element 132 receives an image. Is output from the differential amplifier 147. Similarly, a differential amplifier 148 is connected to the sample and hold circuits 141 and 142 via integration circuits 145 and 146. The differential amplifier 148 subtracts the output signal of the integration circuit 145 from the output signal of the integration circuit 146, and the signal indicating the amount of crosstalk from the other track to the center track from which the light receiving element 133 receives the image as an image is a differential amplifier. 148.

The crosstalk cancel circuit 150 is a circuit that removes a crosstalk component included in a read signal for the center track to be actually read output from the light receiving element 132, and includes VCAs (voltage control amplifiers) 151 and 152 and a differential amplifier 153. , 154. The VCA 151 amplifies the output signal of the light receiving element 131 with a gain according to the output signal of the differential amplifier 147, and the VCA 152 amplifies the output signal of the light receiving element 133 with a gain according to the output signal of the differential amplifier 148. The differential amplifier 153 subtracts the output signal of the VCA 151 from the output signal of the light receiving element 132, and the differential amplifier 154 subtracts the output signal of the VCA 152 from the output signal of the differential amplifier 153. The output signal of the differential amplifier 154 is a signal from which the crosstalk component included in the read signal for the center track has been removed, and is supplied to the sample and hold circuits 139 to 142.

In the crosstalk circuit having such a configuration, the read signals of both tracks adjacent to the center track are discriminated by the comparators 135 to 138 into three values by two threshold values Th1 and Th2. The sample and hold circuit 139 removes the read signal value from the light receiving element 132 to the central track when the read signal value from the light receiving element 131 to one end track is smaller than Th1 (exactly, the crosstalk component is removed by the crosstalk cancel circuit 150). The same holds true for the sample and hold circuits 140 to 142), and the held read signal value is integrated by the integration circuit 143. The sample and hold circuit 140 holds the read signal value from the light receiving element 132 to the central track when the read signal value from the light receiving element 131 to one end track is larger than Th2, and integrates the held read signal value by the integration circuit 144. Is done. The sample hold circuit 141 holds the read signal value for the center track from the light receiving element 132 when the read signal value for the other track from the light receiving element 133 is smaller than Th1. Is integrated. The sample hold circuit 142 holds the read signal value for the center track from the light receiving element 132 when the read signal value for the other track from the light receiving element 133 is greater than Th2. Is integrated.

Assuming that a value smaller than Th1 among the above three values is L and a value larger than Th2 is H, the output signal A of the integrating circuit 144 is the read signal of the central track when the read signal value of one track is H. The output signal B of the integration circuit 143 is an integrated value of the read signal value of the center track when the read signal value of one track is L. The differential amplifier 147 sequentially generates the difference AB as a signal CL indicating the amount of crosstalk. Similarly, the output signal C of the integration circuit 146 is the integration value of the read signal value of the center track when the read signal value of the other track is H, and the output signal D of the integration circuit 145 is the output signal D of the other track. This is an integrated value of the read signal value of the center track when the read signal value is L. The differential amplifier 148 sequentially generates the difference CD as a signal CR indicating the amount of crosstalk.

The signal A indicates the average value of the read signal of the central track when one of the adjacent tracks is bright, and the signal B indicates the average value of the read signal of the central track when the one track is dark. If there is no crosstalk from the adjacent track to the center track, each of the signals A and B represents the average level of the read signal of only the center track irrespective of the signal of the adjacent track, and both have the same value. However, if there is crosstalk, the signal A increases due to the influence of the adjacent track (one end track), and the signal B decreases due to the influence of the one end track. Therefore, the difference signal CL indicates a value corresponding to the amount of crosstalk from one track.

The signal C indicates the average value of the read signal of the central track when the other track as the adjacent track is bright, and the signal D indicates the average value of the read signal of the central track when the other track is dark. If there is no crosstalk from the adjacent track to the center track, each of the signals C and D represents the average level of the read signal of the center track only irrespective of the signal of the adjacent track, and both have the same value. However, if there is crosstalk, the signal C becomes large under the influence of the adjacent track (the other end track), and the signal D becomes small under the influence of the other end track. Therefore, the difference signal CR indicates a value corresponding to the amount of crosstalk from the other track.

Here, if the crosstalk is detected from the read signal of the center track and the disc tilt is controlled by the difference of the crosstalk signal, the crosstalk can be controlled so as to balance the aberration including the lens aberration. Also, a good signal can be obtained. In addition, by using the liquid crystal pickup and this crosstalk detection circuit together, it is possible to control the wavefront so as to minimize the crosstalk.

The crosstalk is reduced to zero by multiplying the read signal of the adjacent track by a coefficient, subtracting the result from the read signal of the center track, performing the crosstalk detection on the result of the subtraction, and controlling the coefficient. You can apply servos as you do. For example, as shown in FIG. 13, the gain of the VCA 151 is controlled according to the signal CL, and the level of the read signal from the light receiving element 131 is amplified by the gain of the VCA 151. That is, in the VCA 151, the read signal from the light receiving element 131 is multiplied by a coefficient corresponding to the signal CL. The output value of the VCA 151 corresponds to a crosstalk component from one end track in the read signal of the center track. On the other hand, the gain of VCA 152 is controlled according to signal CR, and the level of the read signal from light receiving element 133 is amplified by the gain of VCA 152. That is, in the VCA 152, the read signal from the light receiving element 133 is multiplied by a coefficient corresponding to the signal CR. The output value of the VCA 152 corresponds to a crosstalk component from the other track in the read signal of the center track. In the differential amplifier 153, by subtracting the output signal of the VCA 151 from the read signal from the light receiving element 132, the crosstalk component from one end track is reduced. Further, by subtracting the output signal of the VCA 152 from the output signal of the differential amplifier 153 in the differential amplifier 154, the crosstalk component from the other end track is also reduced. Therefore, the output signal of the differential amplifier 154 becomes a read signal of the central track in which the crosstalk components from both adjacent tracks are reduced. The read signal is supplied to the sample and hold circuits 139 to 142, and a feedback system for generating the signals CL and CR is formed. As a result, the read signal of the center track is controlled so that the crosstalk component becomes zero. It is done.

The configuration having two thresholds, such as Th1 and Th2, has two purposes. One is to increase the detection sensitivity. When the modulation degree of the adjacent track is small, the influence of the crosstalk is small, and averaging including all the influences causes a decrease in sensitivity.Therefore, addition integration is performed only on a signal having a certain amplitude or more. By doing so, the sensitivity is improved. The other is to increase the allowance of the gate time. For short pits / lands such as 3T and 4T, the amplitude is smaller than the MTF characteristic, and the threshold is set to a value that does not exceed this length. As a result, since the gate is limited to the pits / lands for operating the gate, there is an effect that the permissible amount of delay time shift is increased particularly when the gate is applied due to a signal delay.

FIG. 14 shows an embodiment in which the crosstalk detection circuit of FIG. 13 is applied to a three-beam type pickup device. In this embodiment, the optical system of the pickup device includes three light receiving elements 161 to 163. As shown in FIG. 10, three spot lights are formed on the disk, and the light receiving element 162 receives the reflected light of the spot light formed on the track to be read on the disk, that is, the center track. The light receiving element 163 receives the reflected light of the preceding spot light on one adjacent track and receives the reflected light of the delayed spot light on the other adjacent track. The read signal from the light receiving element 163 is supplied to the comparators 135 and 136 and the crosstalk canceling circuit 150 as it is, while the read signal from the light receiving element 161 is supplied via the delay element 164 to the comparators 137 and 138 and the crosstalk canceling circuit. The read signal from the light receiving element 162 is supplied to the crosstalk cancel circuit 150 via the delay element 165. The delay element 164 sets a time corresponding to twice the distance L shown in FIG. 10 as a delay time, and the delay element 165 sets a time corresponding to the distance L as a delay time. The other configuration of the crosstalk detection circuit is the same as that of FIG. 13, and the same operation as that described above is performed.

FIG. 15 shows an embodiment in which the crosstalk detection circuit of FIG. 13 is applied to a one-beam type pickup device. In this embodiment, the optical system of the pickup device is provided with one light receiving element 166, and a read signal, which is an output signal of the light receiving element 166, is digitized by an A / D converter 167 and stored in a memory 168. . When one digitized read signal value, one sample value, is input to the memory 168, a memory controller (not shown) outputs the data collected at the reading point one track and two tracks next to the digitized read signal value. I do. The first read signal value at the current read point is supplied to the comparators 135 and 136 and the crosstalk cancel circuit 150. The second read signal value at the read point one track before in the disk radial direction from the current read point previously stored in the memory 168 is read from the memory 168 and supplied to the crosstalk cancel circuit 150. The third read signal value at the read point two tracks ahead in the disk radial direction from the current read point further stored in the memory 168 is supplied to the comparators 137 and 138 and the crosstalk cancel circuit 150. The storage location of these data in the memory 168 can be calculated from the scanning speed of the medium and the sampling interval. The other configuration of the crosstalk detection circuit is the same as that of FIG. 13, and the same operation as that described above is performed. In the case of FIG. 15, the crosstalk detection circuit is a circuit for processing digital signals.

FIG. 16 shows a configuration in which a read signal for the central track is supplied to the sample and hold circuits 139 and 141 via the inverter 171 in the crosstalk circuit of FIG. The output signals of the sample and hold circuits 139 and 140 are individually integrated by the integration and addition circuit 172 and then added to each other. The output signals of the sample and hold circuits 141 and 142 are individually integrated by the integration and addition circuit 173, Are added to each other. The integration addition circuits 172 and 173 output signals indicating the amount of crosstalk from adjacent tracks. The output signals of the integration / addition circuits 172 and 173 are supplied to a crosstalk cancellation circuit as shown in FIG. 13, and the read signal of the center track in which the crosstalk component is reduced, which is the output signal of the crosstalk cancellation circuit. May be supplied to the sample / holds 140 and 142 and the inverter 171. The configuration shown in FIG. 16 can be applied to a three-beam type pickup device and a one-beam type pickup device.

FIG. 17 further shows a crosstalk detection circuit of an imaging detection type pickup device as an embodiment of the present invention. The light receiving elements 181 to 183 are similar to the light receiving elements 131 to 133 in FIG. Capacitors 184 to 186 are connected to outputs of the light receiving elements 181 to 183, respectively. The capacitors 184 to 186 are for extracting an AC component in a read signal which is an output signal of the light receiving elements 181 to 183. The AC component passing through the capacitor 184 is compared with the threshold value Th2 in the comparator 187, and the AC component passing through the capacitor 186 is compared in the comparator 188 with the threshold value Th2. When the AC component passing through the capacitor 184 is larger than the threshold Th2, the sample and hold circuit 189 holds the AC component passing through the capacitor 185, and the held AC component is integrated by the integration circuit 191 and accumulated by the accumulation circuit 193. You. That is, since the DC component of the read signal is cut by the capacitor 185, the average value of the read signal of the center track becomes 0, and the signal obtained from the accumulation circuit 193 indicates the amount of crosstalk from one adjacent track to the center track. It shows. Similarly, when the AC component passing through the capacitor 186 is larger than the threshold Th2, the sample-and-hold circuit 190 holds the AC component passing through the capacitor 185, and the held AC component is integrated by the integration circuit 192 and is accumulated by the accumulation circuit 194. Accumulated. The signal obtained from the accumulating circuit 194 indicates the amount of crosstalk from the other adjacent track to the center track.

In this embodiment, the capacitors 184 to 186 are used to extract the AC component in the output signals of the light receiving elements 181 to 183. However, the present invention is not limited to this. For example, a high-pass filter including an operational amplifier may be used. May be. FIG. 18 shows an example in which a crosstalk cancel circuit 195 for removing a crosstalk component included in a read signal for the center track in accordance with a signal indicating the amount of crosstalk obtained by the configuration of FIG. 17 is provided. The crosstalk cancel circuit 195 includes VCAs 196 and 197 and differential amplifiers 198 and 199, similarly to the crosstalk cancel circuit 150 shown in FIG.

FIG. 19 shows an embodiment in which the crosstalk detection circuit of FIG. 18 is applied to a three-beam type pickup device. In this embodiment, the optical system of the pickup device includes three light receiving elements 201 to 203. The light receiving elements 201 to 203 are similar to the light receiving elements 161 to 163 shown in FIG. The read signal from the light receiving element 203 is supplied to the capacitor 184 as it is, but the read signal from the light receiving element 201 is supplied to the capacitor 186 via the delay element 204, and the read signal from the light receiving element 202 is also supplied via the delay element 205. Is supplied to the capacitor 185. The delay element 204 sets a time corresponding to twice the distance L shown in FIG. 10 as a delay time, and the delay element 205 sets a time corresponding to the distance L as a delay time. Other configurations of the crosstalk detection circuit are the same as those in FIG. 17 or FIG. 18, and the same operation as that described above is performed.

FIG. 20 shows an embodiment in which the crosstalk detection circuit of FIG. 18 is applied to a one-beam type pickup device. In this embodiment, the optical system of the pickup device is provided with one light receiving element 206, and a read signal as an output signal of the light receiving element 206 is digitized by an A / D converter 207 and stored in a memory 208. . When one digitized read signal value, which is one sample value, is input to the memory 208, a memory controller (not shown) outputs data collected at a reading point one track and two tracks adjacent to the digitized read signal value. I do. The first read signal value at the current read point is supplied to the capacitor 184. The second read signal value at the read point one track ahead in the disk radial direction from the current read point previously stored in the memory 208 is read from the memory 208 and supplied to the capacitor 185. The third read signal value at the read point two tracks ahead in the disk radial direction from the current read point further stored in the memory 208 is supplied to the capacitor 186. The storage positions of these data in the memory 208 can be calculated from the scanning speed of the medium and the sampling interval. Other configurations of the crosstalk detection circuit are the same as those in FIG. 17 or FIG. 18, and the same operation as that described above is performed. In the case of FIG. 20, the crosstalk detection circuit is a circuit for processing digital signals.

In each of the embodiments shown in FIGS. 17 to 20, Th2 is used as the threshold value of the comparators 187 and 188. However, in the comparators 187 and 188, the input signal from the capacitor is smaller than the threshold value Th1. Sometimes, a gate signal may be generated, and the sample and hold circuits 189 and 190 may perform a holding operation.

In each of the embodiments described above, a system in which the read signal of the center track is mostly processed in an analog manner has been described. In any of the embodiments, the read signal is converted into a digital value and the processing is performed so as to satisfy the same function. It is also possible to form a circuit such as the above-described crosstalk detection circuit in the pickup device together with a processing circuit having other functions such as signal demodulation.

Further, in each of the above-described embodiments, only the read signal of the center track is output. However, crosstalk can be similarly removed from the signal of an adjacent track. It can also be configured. Further, the present invention can of course be used in combination with other conventionally known crosstalk and tilt detecting devices, or using a tilt detection signal (crosstalk balance) obtained by the present invention to drive a conventional driving mechanism. It can be configured to adjust and cancel the tilt. Further, it is possible to check the substrate thickness of the disk based on the determination result of the amount of crosstalk, or to correct the influence of the error of the substrate thickness.

The value of the threshold value in each of the above-described embodiments can be appropriately changed depending on the type of the disc, the manner of making the disc, the wavelength of the light source used, the numerical aperture, and the like. Various configurations are possible, for example, checking from the above, or varying according to the error rate at the time of signal demodulation. In the embodiment, the example in which the optical disk is used as the recording medium has been described. However, the shape of the recording medium is not limited to the disk, but may be a card shape.

As described above, according to the present invention, one track obtained by an optical pickup device using a relatively simple circuit and a cross signal from a read signal for one track to a read signal for one track from the adjacent track are obtained. The user can know the amount of talk and the balance level thereof, and can operate to remove the crosstalk. Therefore, good signal reproduction is possible even when reproducing a disk having an inclination. Further, since there is no need to put a specific crosstalk detection pattern on the disk, it is possible to achieve a high density without sacrificing the signal capacity.

FIG. 9 is a diagram showing a disc tilt detector used in a conventional pickup device. FIG. 2 is a schematic diagram showing an optical system of the optical pickup device according to the present invention. It is a figure showing the light receiving surface of a light receiver. FIG. 3 is a diagram showing a crosstalk detection circuit of the pickup device according to the present invention. FIG. 4 is a diagram illustrating an eye pattern of a read signal. FIG. 3 is a diagram showing a crosstalk detection circuit of the pickup device according to the present invention. FIG. 3 is a block diagram showing a configuration of a crosstalk removing portion of the pickup device according to the present invention. FIG. 3 is a block diagram illustrating a specific configuration of an inverse matrix operation circuit. FIG. 3 is a diagram showing a crosstalk detection circuit of a pickup device using three beams according to the present invention. FIG. 3 is a diagram showing a positional relationship between three beam spot lights on a disk. FIG. 3 is a diagram illustrating a crosstalk detection circuit of a pickup device using one beam according to the present invention. FIG. 9 is a diagram illustrating a modified example of the crosstalk detection circuit of the pickup device according to the present invention. FIG. 3 is a diagram illustrating a crosstalk detection circuit of the pickup device of the imaging detection system according to the present invention. FIG. 3 is a diagram showing a crosstalk detection circuit of a pickup device using three beams according to the present invention. FIG. 3 is a diagram illustrating a crosstalk detection circuit of a pickup device using one beam according to the present invention. FIG. 14 is a diagram illustrating a modified example of the crosstalk detection circuit of FIG. 13. FIG. 3 is a diagram illustrating a crosstalk detection circuit of the pickup device of the imaging detection system according to the present invention. FIG. 18 is a diagram illustrating a configuration in which a crosstalk cancellation circuit is provided in the crosstalk detection circuit in FIG. 17. FIG. 3 is a diagram showing a crosstalk detection circuit of a pickup device using three beams according to the present invention. FIG. 3 is a diagram illustrating a crosstalk detection circuit of a pickup device using one beam according to the present invention.

Explanation of reference numerals

13, 14, 27, 61 Photodetectors 41 to 44, 74, 75, 91, 92 Comparator 49, 93, 94, 171 Inverter 62 Inverse matrix operation circuit 63 Signal extraction circuit 64 Crosstalk detection circuit 80, 81 Selector 150, 195 Crosstalk cancel circuit

Claims (22)

An optical pickup device that optically reads a signal recorded on a track of a recording medium,
The recording signals of at least three adjacent tracks on the recording medium are read individually and optically simultaneously and in parallel, and the read signal values for the tracks at one end, the center and the other end of the three tracks are first, Signal reading means for generating as second and third read signal values;
Comparing means for individually comparing the first and third read signal values with a first threshold value and a second threshold value which is larger than the first threshold value;
Means for generating a third gate signal when the first read signal value is greater than the second threshold value and the third read signal value is greater than the second threshold value;
Means for generating a fourth gate signal when the first read signal value is smaller than the first threshold value and the third read signal value is smaller than the first threshold value;
A difference between the second read signal value when the third gate signal is generated and the second read signal value when the fourth gate signal is generated is generated as a value indicating the amount of crosstalk to the second read signal. An optical pickup device, comprising: The optical pickup device according to claim 1, wherein the signal reading means corrects and outputs a crosstalk amount of each read signal according to an output value of the crosstalk amount detecting means. The crosstalk amount detecting means includes: a third sample and hold circuit that holds and outputs the second read signal value in accordance with the third gate signal; an inverter that inverts the second read signal; A fourth sample-and-hold circuit for holding and outputting the output signal value of the inverter, and adding a value obtained by integrating the output signal of the third sample-hold circuit and a value obtained by integrating the output signal of the fourth sample-hold circuit. 2. The optical pickup device according to claim 1, further comprising: an integrating and adding circuit that obtains a value indicating the crosstalk amount. The crosstalk amount detecting means includes: a third sample and hold circuit that holds and outputs the second read signal value in accordance with the third gate signal; an inverter that inverts the second read signal; A fourth sample-and-hold circuit for holding and outputting the output signal value of the inverter, and adding the output signal of the third sample-and-hold circuit and the output signal of the fourth sample-and-hold circuit, and obtaining the sum. 2. The optical pickup device according to claim 1, further comprising: an addition and integration circuit that integrates a value to obtain a value indicating the crosstalk amount. The crosstalk amount detecting means holds and outputs the second read signal value in response to the third gate signal, and holds and outputs the second read signal value in response to the fourth gate signal. A fourth sample-and-hold circuit to perform integration and subtraction, wherein a difference between a value obtained by integrating the output signal of the third sample-and-hold circuit and a value obtained by integrating the output signal of the fourth sample-and-hold circuit is a value indicating the amount of crosstalk. The optical pickup device according to claim 1, further comprising a circuit. The crosstalk amount detecting means holds and outputs the second read signal value in response to the third gate signal, and holds and outputs the second read signal value in response to the fourth gate signal. Calculating a difference between an output signal of the third sample and hold circuit and an output signal of the fourth sample and hold circuit, and integrating the difference to obtain a value indicating the amount of crosstalk. The optical pickup device according to claim 1, further comprising an integrating circuit. An optical pickup device that optically reads a signal recorded on a track of a recording medium,
The recording signals of each of three adjacent tracks on the recording medium are simultaneously and individually and optically read by three beams, and read signals for one of the leading tracks, the center of the three tracks, and the other end of the lag reading among the three tracks Signal reading means for generating values as first, second and third read signal values;
First comparing means for generating a fifth gate signal when the first read signal value is smaller than a first threshold value;
A second comparing unit that generates a sixth gate signal when the first read signal value is larger than a second threshold value that is larger than the first threshold value;
Delay means for individually delaying the fifth and sixth gate signals;
A fifth sample and hold circuit for holding and outputting the second read signal value at the time of generation of the fifth gate signal delayed by the delay means;
A sixth sample-and-hold circuit for holding and outputting the second read signal value when the sixth gate signal delayed by the delay unit is generated;
When the third read signal value is smaller than the first threshold value, the held output value of the fifth sample hold circuit is obtained, and when the third read signal value is larger than the second threshold value, the sixth sample is obtained. Selecting means for obtaining a hold output value of the hold circuit;
Crosstalk amount detection means for generating a difference between each held output value of the fifth and sixth sample and hold circuits obtained by the selection means as a value indicating a crosstalk amount to the second read signal. An optical pickup device characterized by the following. The crosstalk amount detecting means includes a first integrating means for integrating a held output value of the fifth sample and hold circuit obtained by the selecting means, and a held output of the sixth sample and hold circuit obtained by the selecting means. A second integration means for integrating the values, and a subtraction means for calculating a difference between the output signal values of the first and second integration means to obtain a value indicating the crosstalk balance. The optical pickup device according to claim 7. The crosstalk amount detection means includes a subtraction means for calculating a difference between the held output values of the fifth and sixth sample-and-hold circuits obtained by the selection means, and an output signal of the subtraction means for integrating the crossover signal. 8. The optical pickup device according to claim 7, further comprising integrating means for obtaining a value indicating a talk balance. An optical pickup device that optically reads a signal recorded on a track of a recording medium,
Signal reading means for optically reading a recording signal of one track on the recording medium and outputting as a first reading signal value;
A memory for storing the first read signal value output from the signal reading means at a predetermined cycle;
From the plurality of first read signal values stored in the memory, each read signal value corresponding to each read point adjacent by one track and two tracks on the side already read from the current read point by the signal read means is read from the plurality of first read signal values. Means for reading as second and third read signal values;
Comparing means for individually comparing the first and third read signal values with a first threshold value and a second threshold value which is larger than the first threshold value;
Means for generating a third gate signal when the first read signal value is greater than the second threshold value and the third read signal value is greater than the second threshold value;
Means for generating a fourth gate signal when the first read signal value is smaller than the first threshold value and the third read signal value is smaller than the first threshold value;
A difference between the second read signal value when the third gate signal is generated and the second read signal value when the fourth gate signal is generated is generated as a value indicating the amount of crosstalk to the second read signal. An optical pickup device, comprising: An optical pickup device that optically reads a signal recorded on a track of a recording medium,
The recording signals of at least three adjacent tracks on the recording medium are read individually and optically simultaneously and in parallel, and the read signal values for the tracks at one end, the center and the other end of the three tracks are first, Signal reading means for generating as second and third read signal values;
Comparing means for individually comparing the first and third read signal values with a first threshold value and a second threshold value which is larger than the first threshold value;
Means for generating a first gate signal when the first read signal value is less than the first threshold value;
Means for generating a second gate signal when the first read signal value is greater than the second threshold value;
Means for generating a third gate signal when the third read signal value is less than the first threshold value;
Means for generating a fourth gate signal when the third read signal value is greater than the second threshold value;
The difference between the second read signal value when the first gate signal is generated and the second read signal value when the second gate signal is generated indicates a crosstalk amount from the one end track to the center track. First crosstalk amount detecting means for generating a value as a value;
The difference between the second read signal value at the time of generation of the third gate signal and the second read signal value at the time of generation of the fourth gate signal is determined by calculating the amount of crosstalk from the track at the other end to the center track. An optical pickup device comprising: a second crosstalk amount detecting means for generating a value as an indicated value. The optical pickup device according to claim 11, wherein the signal reading unit corrects and outputs the second read signal in accordance with an output value of the first and second crosstalk amount detecting units. An optical pickup device that optically reads a signal recorded on a track of a recording medium,
A recording signal of each of three adjacent tracks on the recording medium is simultaneously and individually and optically read by three beams, and each of the read signals for one of the leading read, the middle, and the other of the delayed read of the three tracks Signal reading means for generating values as first, second and third read signal values;
Comparing means for individually comparing the first and third read signal values with a first threshold value and a second threshold value which is larger than the first threshold value;
Means for generating a first gate signal when the first read signal value is less than the first threshold value;
Means for generating a second gate signal when the first read signal value is greater than the second threshold value;
Means for generating a third gate signal when the third read signal value is less than the first threshold value;
Means for generating a fourth gate signal when the third read signal value is greater than the second threshold value;
The difference between the second read signal value when the first gate signal is generated and the second read signal value when the second gate signal is generated indicates a crosstalk amount from the one end track to the center track. First crosstalk amount detecting means for generating a value as a value;
The difference between the second read signal value at the time of generation of the first gate signal and the second read signal value at the time of generation of the second gate signal is determined by calculating the amount of crosstalk from the track at the other end to the center track. An optical pickup device comprising: a second crosstalk amount detecting means for generating a value as an indicated value. 14. The optical pickup device according to claim 13, wherein the signal reading unit corrects and outputs the second read signal in accordance with an output value of the first and second crosstalk amount detecting units. An optical pickup device that optically reads a signal recorded on a track of a recording medium,
Signal reading means for optically reading a recording signal of one track on the recording medium and outputting as a first reading signal value;
A memory for storing the first read signal value output from the signal reading means at a predetermined cycle;
From the plurality of first read signal values stored in the memory, each read signal value corresponding to each read point adjacent by one track and two tracks on the side already read from the current read point by the signal read means is read from the plurality of first read signal values. Reading means for reading as second and third read signal values;
Comparing means for individually comparing the first and third read signal values with a first threshold value and a second threshold value which is larger than the first threshold value;
Means for generating a first gate signal when the first read signal value is less than the first threshold value;
Means for generating a second gate signal when the first read signal value is greater than the second threshold value;
Means for generating a third gate signal when the third read signal value is less than the first threshold value;
Means for generating a fourth gate signal when the third read signal value is greater than the second threshold value;
The difference between the second read signal value at the time of generation of the first gate signal and the second read signal value at the time of generation of the second gate signal is calculated from one end of three adjacent tracks to the center track. First crosstalk amount detection means for generating a value indicating the crosstalk amount,
The difference between the second read signal value at the time of generation of the third gate signal and the second read signal value at the time of generation of the fourth gate signal is calculated from the other one of the three adjacent tracks to the center. An optical pickup device comprising: a second crosstalk amount detection unit that generates a value indicating a crosstalk amount to a track. 16. The optical pickup device according to claim 15, wherein the reading unit corrects and outputs the second read signal in accordance with an output value of the first and second crosstalk amount detecting units. An optical pickup device that optically reads a signal recorded on a track of a recording medium,
The recording signals of at least three adjacent tracks on the recording medium are read individually and optically simultaneously and in parallel, and the read signal values for the tracks at one end, the center and the other end of the three tracks are first, Signal reading means for generating as second and third read signal values;
Comparing means for individually comparing the first and third read signal values with a first threshold value or a second threshold value which is larger than the first threshold value;
Means for generating a first gate signal when the first read signal value is smaller than the first threshold value or larger than the second threshold value;
Means for generating a second gate signal when the third read signal value is smaller than the first threshold value or larger than the second threshold value;
Means for obtaining a fourth read signal value by extracting only the AC component of the second read signal value;
First crosstalk amount detection means for generating the fourth read signal value at the time of generation of the first gate signal as a value indicating a crosstalk amount from the one end track to the center track;
Second crosstalk amount detection means for generating the fourth read signal value at the time of generation of the second gate signal as a value indicating a crosstalk amount from the track at the other end to the center track. Optical pickup device. 18. The optical device according to claim 17, wherein the means for obtaining the fourth read signal value corrects and outputs the fourth read signal in accordance with an output value of the first and second crosstalk amount detecting means. Type pickup device. An optical pickup device that optically reads a signal recorded on a track of a recording medium,
A recording signal of each of three adjacent tracks on the recording medium is simultaneously and individually and optically read by three beams, and each of the read signals for one of the leading read, the middle, and the other of the delayed read of the three tracks Signal reading means for generating values as first, second and third read signal values;
Comparing means for individually comparing the first and third read signal values with a first threshold value or a second threshold value which is larger than the first threshold value;
Means for generating a first gate signal when the first read signal value is smaller than the first threshold value or larger than the second threshold value;
Means for generating a second gate signal when the third read signal value is smaller than the first threshold value or larger than the second threshold value;
Means for obtaining a fourth read signal value by extracting only the AC component of the second read signal value;
First crosstalk amount detection means for generating the fourth read signal value at the time of generation of the first gate signal as a value indicating a crosstalk amount from the one end track to the center track;
And a second crosstalk amount detecting means for generating the fourth read signal value at the time of generation of the second gate signal as a value indicating a crosstalk amount from the other track to the center track. Optical pickup device. 20. The optical device according to claim 19, wherein the means for obtaining the fourth read signal value corrects and outputs the fourth read signal in accordance with an output value of the first and second crosstalk amount detecting means. Type pickup device. An optical pickup device that optically reads a signal recorded on a track of a recording medium,
Signal reading means for optically reading a recording signal of one track on the recording medium and outputting as a first reading signal value;
A memory for storing the first read signal value output from the signal reading means at a predetermined cycle;
From the plurality of first read signal values stored in the memory, each read signal value corresponding to each read point adjacent by one track and two tracks on the side already read from the current read point by the signal read means is read from the plurality of first read signal values. Reading means for reading as second and third read signal values;
Comparing means for individually comparing the first and third read signal values with a first threshold value or a second threshold value which is larger than the first threshold value;
Means for generating a first gate signal when the first read signal value is smaller than the first threshold value or larger than the second threshold value;
Means for generating a second gate signal when the third read signal value is smaller than the first threshold value or larger than the second threshold value;
Means for obtaining a fourth read signal value by extracting only the AC component of the second read signal value;
First crosstalk amount detection means for generating the fourth read signal value at the time of generation of the first gate signal as a value indicating a crosstalk amount from one end track of the three adjacent tracks to a center track;
A second crosstalk amount detecting means for generating the fourth read signal value at the time of generation of the second gate signal as a value indicating a crosstalk amount from the other track of the three adjacent tracks to the center track; An optical pickup device comprising: 22. The optical device according to claim 21, wherein the means for obtaining the fourth read signal value corrects and outputs the fourth read signal in accordance with an output value of the first and second crosstalk amount detecting means. Type pickup device.

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