JP2006134449A - Track cross detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a track cross detector for an optical disk for detecting a slice level for the binarization of a tracking error signal, without deteriorating following capability. <P>SOLUTION: In the track cross detector, an error detection means 10 detects the tracking error signal. A relative velocity detection means 12 detects the relative velocity between an optical disk track and an optical pickup. A comparison determination means 13 performs the comparison with a reference value, operates a control means 14 according to the relationship, and controls a cutoff frequency of a low-pass filter 11 capable of varying the cutoff frequency. Accordingly, the DC level of the tracking error signal at the cutoff frequency corresponding to the relative velocity is detected, and the track cross signal is detected by a binarization circuit 15. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a track cross detection device used in a tracking control system of an optical disk device.

  Tracking control in a conventional optical disc apparatus is performed using signals output by multi-divided photodetectors mounted on an optical pickup or the like of the optical disc apparatus in accordance with the amount of received light.

  Of the tracking control, a phase error detection method (DPD method), a push-pull method, a three-beam method, and the like are generally widely used as means for detecting the tracking error amount of the optical disk. (For example, see Non-Patent Document 1)

By using the phase relationship between the binarized signal of the tracking error signal (hereinafter referred to as the track cross signal) and the off-track signal indicating that the optical pickup is at the off-track position, the optical pickup is relative to either the inner or outer periphery. The direction of travel is detected and used for tracking control. Also, the number of track crossings is monitored by counting track cross signals and used to control seek operations. Here, the track cross signal has no noise and is required to be detected while maintaining the phase relationship between the track cross detection signal and the off-track signal.
A conventional detection device for detecting a track cross signal from a tracking error signal will be described below.

FIG. 17 is a block diagram showing a track cross detection apparatus according to the conventional method.
In FIG. 17, reference numeral 1001 denotes an error amount detection means for detecting a tracking error amount based on the output of the multi-split light detector. Reference numeral 1002 denotes a high frequency component removing unit that removes high frequency components such as noise of the tracking error amount output from the error amount detecting unit 1001 and outputs a tracking error signal. Reference numeral 1003 denotes a low-pass filter that detects the DC level of the tracking error signal output from the high-frequency component removing unit 1002 and outputs it as a slice level.

  Reference numeral 1004 denotes hysteresis binarization means for binarizing the tracking error signal by giving hysteresis characteristics to the slice level.

FIG. 18 is a diagram illustrating the relationship between the outputs of the conventional tracking cross detection apparatus.
In FIG. 18, the tracking error signal (A) that is the output of the high-frequency component removing means 1002, the output signal (B) of the low-pass filter 1003, and the rise (C) and fall (D) with hysteresis characteristics. ) Represents the relationship between each slice level and the track cross signal (E).

  FIG. 19 is a diagram showing the relationship between the tracking error signal in the conventional track cross detection apparatus, the threshold level with hysteresis by the hysteresis binarization means, and the track cross signal.

The operation of the track cross detection apparatus configured as described above will be described below.
A tracking error amount is detected by the error amount detection means 1001 using the phase error detection method, push-pull method, three-beam method, or the like, with the signal output from the multi-segment light detector as an input. Although the tracking error amount depends on the tracking error detection method to be used, it includes a lot of unnecessary high frequency components due to the influence of information signal components and noise. Therefore, the high frequency component removing means 1002 limits the high frequency components. Suppressed and output as tracking error signal. A DC level is detected by the low-pass filter 1003 with respect to the tracking error signal. The hysteresis binarizing means 1004 gives the DC level detected by the low-pass filter 1003 a hysteresis characteristic that is not easily affected by noise and the like, and the tracking error signal is binarized by setting the slice level to a slice level. Get.
Heitaro Nakajima and Hiroshi Ogawa, “Illustrated Compact Disc Reader”, revised 3rd edition, Ohmsha, May 1996, p.1-296

  However, as shown in FIG. 19A, the period of the tracking error signal becomes longer near the peak of the eccentricity of the optical disk in the tracking off state. For this reason, as shown in FIG. 19B, the low-pass filter 1003 that should originally detect the DC level of the tracking error signal follows the tracking error signal itself, not the DC level, and an accurate DC level is detected. Disappear. Therefore, binarization is performed at a position different from the original DC level, and a phase shift occurs. Further, as shown in FIG. 19C, if the tracking error signal itself is followed, it is easily affected by noise components that cannot be suppressed by the high frequency component removing means 1002, and a binarized track cross signal is obtained. In addition, the noise component gets on. As a result, the direction detection with the off-track signal is not accurately performed, and tracking pull-in or the like is not correctly performed.

  Furthermore, if a low-pass filter with a low cutoff frequency is realized in consideration of a long-period tracking error signal near the peak of the eccentricity of the optical disk, the circuit scale increases. Further, it becomes impossible to follow the fluctuation of the DC level of a relatively fast cycle due to a light defect or the like, and the fluctuation of the DC level of a fast cycle due to a lens shift or the like during seeking, resulting in deterioration of followability and responsiveness.

  The present invention has been made to solve the above-described problem, and does not lower the cut-off frequency of the low-pass filter for detecting the DC level more than necessary with respect to the frequency of the tracking error signal that is an input signal. An object of the present invention is to provide a track cross detection device that detects a stable track cross signal without impairing the performance and responsiveness.

  In order to solve the above problems, a track cross detection apparatus according to claim 1 of the present invention includes an error detection means for detecting a tracking error signal based on a signal output from an optical pickup in an optical disc apparatus, and the optical pickup. Output from the error detection means according to the relative speed between the optical disk track and the optical pickup, and relative speed detection means for detecting the relative speed between the optical disk track and the optical pickup. A low-pass filter that switches a cut-off frequency for detecting a DC level of a tracking error signal, a comparison determination unit that compares an output of the relative speed detection unit and a preset reference value, and a comparison determination unit Control means for controlling the cut-off frequency of the low-pass filter according to the output; The binarizing the tracking error signal outputted from said error detecting means the output of the low-pass filter as a slice level, characterized in that it comprises a binarizing means for outputting a track cross signal.

  According to a second aspect of the present invention, there is provided a track cross detection apparatus based on an error detection means for detecting a tracking error signal based on a signal output from an optical pickup in an optical disc apparatus, and on the signal from the optical pickup. A relative speed detecting means for detecting a relative speed between the track of the optical disk and the optical pickup; a low-pass filter for detecting and outputting a DC level of the tracking error signal output from the error detecting means; and a track of the optical disk; Sample hold means for holding the output value of the low-pass filter according to the relative speed with the optical pickup, comparison determination means for comparing the output of the relative speed detection means with a preset reference value, Depending on the output of the comparison judgment means, the output of the low pass filter and the sample filter A control means for controlling the output of the value held by the threshold means, and a tracking error signal output from the error detection means with the output signal switched by the control means as a slice level, and a track cross signal As a binarization means for outputting as follows.

  According to a third aspect of the present invention, there is provided a track cross detection apparatus based on an error detection means for detecting a tracking error amount based on a signal output from an optical pickup in an optical disc apparatus and a signal from the optical pickup. A relative speed detecting means for detecting a relative speed between a track of the optical disc and the optical pickup; a low-pass filter having an output hold means for detecting a DC level of a tracking error signal output from the error detecting means; Comparison determination means for comparing the output of the speed detection means with a preset reference value, control means for controlling switching of the output hold means of the low-pass filter according to the output of the comparison determination means, and the low-pass filter Output from the error detection means with the output of the slice as the slice level Binarizing means for binarizing the error signal and outputting it as a track cross signal, wherein the low-pass filter detects the tracking error from the error detecting means according to the relative speed of the track of the optical disc and the optical pickup. The DC level of the signal is held in the output hold means.

  A track cross detection apparatus according to a fourth aspect of the present invention is the track cross detection apparatus according to the second aspect, wherein the output of the control means and the control indicating whether the tracking on state or the tracking off state is present. A low-pass filter that receives a control signal from the logic circuit and prevents the sample-and-hold means from operating regardless of the output of the control means in a tracking-on state. The output of the low-pass filter is controlled to be the slice level of the binarization means.

  The track cross detection apparatus according to claim 5 of the present invention is the track cross detection apparatus according to claim 3, wherein the control means indicates whether the control means is in a tracking-on state or a tracking-off state. A low-pass filter that receives a control signal from the logic circuit and operates the output hold means of the low-pass filter regardless of the output of the control means when in a tracking-on state. It is characterized by controlling so that it does not occur.

  The track cross detection apparatus according to claim 6 of the present invention is the track cross detection apparatus according to claim 4 or 5, wherein the relative speed detection means receives the signal for controlling the seek of the optical pickup and immediately after the start of seek. A reset means for clearing the detected value is provided.

  The track cross detection apparatus according to claim 7 of the present invention is the track cross detection apparatus according to claim 2 or 3, wherein the hold value is previously set in the positive or negative direction depending on the polarity of the detected track cross signal. A correction means for correcting at a predetermined rate of change is provided.

  The track cross detection apparatus according to claim 8 of the present invention is characterized in that, in the track cross detection apparatus according to claim 7, the rate of change of the correction means is changed according to the output of the relative speed detection means. .

  According to a ninth aspect of the present invention, there is provided a track cross detection device comprising: error detection means for detecting a tracking error amount based on a signal output from an optical pickup in an optical disc device; and an optical disc based on a signal from the optical pickup. A low speed filter having a relative speed detecting means for detecting a relative speed between the track and the optical pickup, an output holding means for detecting a DC level of a tracking error signal output from the error detecting means, and the relative speed A pulse train generating means for outputting a pulse train according to the relative speed between the track of the optical disc detected by the detecting means and the optical pickup, and limiting the input of the low pass filter; and the low pass according to the output of the pulse train generating means Control means for controlling the output hold means of the filter; Serial binarizing the tracking error signal outputted from said error detecting means the output of the low-pass filter as a slice level, characterized in that it comprises a binarizing means for outputting a track cross signal.

  The track cross detection apparatus according to claim 10 of the present invention is characterized in that, in the track cross detection apparatus according to claim 9, the pulse train generation means is load hold means by a BSDA (Bit Stream D / A) system. To do.

  The track cross detection apparatus according to an eleventh aspect of the present invention is the track cross detection apparatus according to the ninth aspect, wherein the pulse train generation means is load hold means based on a PWM (Pulse Width Modulation) system.

  The track cross detection device according to claim 12 of the present invention is the track cross detection device according to claim 9, wherein the pulse train generation means converts a pulse train having a length corresponding to the relative speed detection means to both edges of the track cross signal. A load hold means for closing the gate for a certain period of rising and falling of the pulse train is used according to a method of outputting each time.

  A track cross detection device according to claim 13 of the present invention receives a control signal indicating whether the track cross detection device according to claim 9 is in a tracking on state or a tracking off state, In the tracking-on state, control is performed so that the output of the relative speed detection means is maximized and the input of the low-pass filter is not limited.

  A track cross detection apparatus according to a fourteenth aspect of the present invention is the track cross detection apparatus according to the thirteenth aspect, receives a signal for controlling the seek of the optical pickup, and outputs the detection value of the relative speed detection means immediately after the start of the seek. A reset means for clearing is provided, and the input of the low-pass filter is limited.

  According to the track cross detection device of the present invention, it is necessary to lower the cut-off frequency more than necessary by providing means for holding the input / output of the low-pass filter or limiting the input in accordance with the track position and the relative speed of the optical pickup. However, it is possible to eliminate the increase in circuit scale and to ensure followability and responsiveness.

  According to the track cross detection apparatus of the first aspect, the cutoff frequency for detecting the DC level of the tracking error signal output from the error detection means is switched according to the relative speed between the track of the optical disc and the optical pickup. A low-pass filter is provided. Thereby, it is possible to prevent the slice level from following the tracking error signal itself in a place where the track loss is slow, such as near the return of the disk eccentricity. In addition, since the cutoff frequency of the low-pass filter is not set lower than necessary with respect to the input tracking error signal, it is possible to ensure followability and quick response to fluctuations in the DC level.

  According to the track cross detection apparatus of the second aspect, the output value of the low-pass filter is held in the sample hold means according to the relative speed between the track of the optical disk and the optical pickup, and the relative speed is set in advance. The output of the low-pass filter and the value held by the sample and hold means are switched according to the output of the comparison / determination means for comparing the reference values. As a result, the slice level can be prevented from following the tracking error signal itself at a slow track cross, such as near the return of the disk eccentricity. In addition, since the cutoff frequency of the low-pass filter is not set lower than necessary with respect to the input tracking error signal, it is possible to ensure followability and quick response to fluctuations in the DC level.

  According to the track cross detection apparatus of the third aspect, the DC level of the tracking error signal from the error detection means, which is the input (internal value) of the low-pass filter, according to the relative speed of the optical disc track and the optical pickup. Is held in the output hold means, and switching control of the output hold means is performed. As a result, the slice level can be prevented from following the tracking error signal itself at a slow track cross, such as near the return of the disk eccentricity. In addition, since the cutoff frequency of the low-pass filter is not set lower than necessary with respect to the input tracking error signal, it is possible to ensure followability and quick response to fluctuations in the DC level.

  Further, according to the track cross detection device according to claim 4 or claim 5, in the tracking on state, a function for turning off the hold function of the hold means is added so that the hold means is not always operated. . As a result, it is possible to improve a decrease in followability and quick response to fluctuations in DC level due to unnecessary operation of the holding means in the tracking-on state.

  According to the track cross detection apparatus of the sixth aspect, the relative speed detection value is cleared at the start or immediately before the seek, and the forced hold state is set. Thereby, it is possible to improve the follow-up performance of the slice level with respect to the tracking error signal in a low speed state immediately after the start of seeking.

  According to the track cross detection apparatus of the seventh aspect, the correcting means for correcting the hold value of the holding means is added. As a result, it is possible to improve the decrease in the followability and responsiveness to the DC level due to the hold in a place where the tracking on state where the relative speed becomes zero is not necessary.

  According to the track cross detection apparatus of the eighth aspect, the change rate of the correction means is changed according to the relative speed. Thereby, the follow-up performance of the DC level can be improved by adjusting the rate of change of the correction means according to the relative speed.

  According to the track cross detection apparatus of the ninth aspect, pulse train generation means for outputting a pulse train according to the relative speed between the track of the optical disc and the optical pickup and limiting the input of the low-pass filter is added. As a result, the cut-off frequency can be equivalently lowered at a slow track cross, such as near the return of the disk eccentricity. In addition, since the cutoff frequency of the low-pass filter is not set lower than necessary with respect to the input tracking error signal, it is possible to ensure followability and quick response to fluctuations in the DC level.

  According to the track cross detection device of the thirteenth aspect, the relative speed detection value is fixed to the maximum value so that the input of the low-pass filter is not limited in the tracking-on state, and the on-state in which the hold unit does not always operate. It was made to become. As a result, it is possible to improve the followability and responsiveness to the DC level in the tracking-on state (= zero relative speed).

  According to the track cross detection apparatus of the fourteenth aspect, the relative speed detection value is cleared at the start or immediately before the seek, and the input restriction of the low-pass filter is forcibly increased. Thereby, it is possible to improve the follow-up performance of the slice level with respect to the tracking error signal which is unnecessary in the low speed state immediately after the start of seeking.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a track cross detection apparatus according to Embodiment 1 of the present invention.
In FIG. 1, reference numeral 10 denotes error detection means for detecting a tracking error signal. Reference numeral 11 denotes a low-pass filter capable of switching a cutoff frequency for detecting the DC level of the tracking error signal in accordance with the relative speed between the track of the optical disc and the optical pickup. Reference numeral 12 denotes a relative speed detecting means for detecting the relative speed between the track of the optical disk and the optical pickup. Reference numeral 13 denotes comparison determination means for comparing the relative speed output from the relative speed detection means 12 with a preset reference value. Reference numeral 14 denotes control means for controlling the cut-off frequency of the low-pass filter 11 in accordance with the output of the comparison / determination means 13. Reference numeral 15 denotes binarizing means for setting the output of the low-pass filter 11 to a slice level and binarizing the tracking error signal.

FIG. 2 is an example showing a configuration diagram of the low-pass filter 11 of the track cross detection apparatus according to Embodiment 1 of the present invention.
In FIG. 2, reference numeral 20 denotes a first low-pass filter having a cutoff frequency in consideration of a long-period tracking error signal near the peak of the eccentricity of the optical disk. Reference numeral 21 denotes a second low-pass filter having a cutoff frequency higher than that of the first low-pass filter 20 in consideration of a DC fluctuation with a relatively fast cycle. Reference numeral 22 denotes a selector that switches between the first low-pass filter 20 and the second low-pass filter 21.

  FIG. 3 is a diagram showing the relationship between outputs in the vicinity of the peak of disk eccentricity in the track cross detection apparatus according to Embodiment 1 of the present invention.

  3, the tracking error signal (a) near the peak of the eccentricity of the optical disk and the output (b) of the first low-pass filter 20 when the configuration of the low-pass filter 11 is configured as shown in FIG. The output (c) of the second low-pass filter 21, the output (d) of the low-pass filter 11, the relative speed (e) detected by the relative speed detection means 12, and the reference value (f) of the comparison determination means 13 And the relationship between the output (g) of the control means.

The operation of the track cross detection apparatus configured as described above will be described below.
Based on the output of the multi-split optical detector of the optical pickup, the error detection means 10 detects the tracking error amount by using a phase error detection method, a push-pull method, a three-beam method, etc., and an unnecessary high frequency due to noise or the like. A tracking error signal from which components have been removed is output and input to the low-pass filter 11 and the binarizing means 15.

  Here, as shown in FIG. 3A, the period of the tracking error signal becomes longer as it approaches the vicinity of the peak of the eccentricity of the optical disk, and after the peak, the period becomes shorter again.

  The low-pass filter 11 detects the DC level of the tracking error signal by selecting the output of the internal first low-pass filter 20 or the second low-pass filter 21 by the selector 22 that is switched using the control means 14. The detection result is output to the binarization means 15.

  Here, as shown in FIG. 3B, since the first low-pass filter 20 has a low cut-off frequency, a tracking error that is also input to a long-period tracking error signal near the peak of the eccentricity of the optical disk. The slice level does not follow the signal itself and a stable DC level is detected, but it cannot follow the fluctuation of the DC level of the tracking error signal having a relatively fast period. On the other hand, as shown in FIG. 3C, the second low-pass filter 21 has a higher cut-off frequency than the first low-pass filter 20, so that the long-period tracking error signal near the peak of the eccentricity of the optical disk is detected. The slice level follows the input of the tracking error detection signal itself, and an accurate DC level cannot be detected. However, it can accurately follow the fluctuation of the DC level of the tracking error signal in a relatively fast cycle.

  The relative speed detection means 12 detects the relative speed between the track of the optical disk and the optical disk pickup, and the comparison determination means 13 compares the relative speed output by the relative speed detection means 12 with a preset reference value, The magnitude relationship between the speed and the reference value is output to the control means 14.

As described above, the control unit 14 outputs a signal for switching the selector 22 and controls switching of the first and second low-pass filters 20 and 21 in the low-pass filter 11. Here, it is assumed that the selector 22 selects the first low-pass filter 20 when the output of the control means 14 is Low, and the selector 22 selects the second low-pass filter 21 when the output is High.
Here, as shown in FIG. 3 (e), the relative speed approaches zero near the peak of the eccentricity of the optical disk, and increases again after the peak. The comparison determination means 13 compares the relative speed (e) with the reference value (f). If the relative speed is slower than the reference value as shown in (g), the output of the control means 14 is output. Set to Low and set to High when the relative speed is faster than the reference value. By controlling the selector 22 as described above, the output of the low-pass filter 11 is the second low-pass filter when the relative speed (e) is faster than the reference value (f) as shown in FIG. 21 (c), and when it is slow, the output (b) of the first low-pass filter 20.

  In the binarizing means 15, the output of the low-pass filter 11 is set to a slice level, the tracking error signal is binarized, and a track cross signal is generated.

  As described above, according to the track cross detection apparatus according to the first embodiment, when the relative speed of the optical disk track and the optical pickup detected by the relative speed detection means 12 is slower than a preset reference speed. Since the control means controls to switch the cut-off frequency of the low-pass filter 11 for detecting the DC level to the low-pass filter 20 having a low cut-off frequency considering the disc eccentricity, the optical disc eccentricity is controlled. The slice level for binarization does not follow the long-period tracking error signal itself in the vicinity of the peak, and track cross signal detection can be performed at a stable slice level. In addition, when the relative speed is high, the cutoff frequency is not set lower than necessary for the input tracking error signal. Will not get worse.

In the first embodiment, a configuration in which two low-pass filters as shown in FIG. 2 are switched as an example of the low-pass filter 11 is shown. However, the low-pass filter 11 is not a two-stage switching cutoff frequency, but a multi-stage switching. By switching the cut-off frequency in stages, the followability and responsiveness of DC level detection can be improved.
The same effect can be obtained by configuring the low-pass filter 11 with one low-pass filter and switching the cutoff frequency by arbitrarily switching the filter coefficient of the low-pass filter.

(Embodiment 2)
FIG. 4 is a block diagram showing the configuration of the track cross detection apparatus according to Embodiment 2 of the present invention.
In FIG. 4, reference numeral 40 denotes a low-pass filter having output hold means for detecting the DC level of the tracking error signal. Here, the cut-off frequency of the low-pass filter 40 is a cut-off frequency in consideration of the DC fluctuation of the relatively early period of the tracking error signal, like the second low-pass filter 21 of FIG. The low-pass filter 40 holds the DC level of the tracking error signal in the output hold means according to the relative speed of the optical disk track and the optical pickup. In addition, the same code | symbol is used about the same component as embodiment mentioned above, and the description is abbreviate | omitted. However, the control means 14 does not control the cut-off frequency of the low-pass filter 11, but controls the operation of the output hold means of the low-pass filter 40.

FIG. 5 is an example showing a configuration diagram of a low-pass filter 40 having output hold means in the track cross detection apparatus according to Embodiment 2 of the present invention.
In FIG. 5, 50 is a first filter coefficient, 51 is a second filter coefficient, 52 is an adder, 53 is a flip-flop, 54 is an output of the adder 52 and the flip-flop 53. This is a selector whose output is input to the switching flip-flop 53. In the second embodiment, the selector 54 selects the output of the flip-flop 53 when the output of the control means 14 is Low, and the selector 54 selects the output of the adder 52 when it is High. Further, the flip-flop 53 and the selector 54 constitute output holding means.

FIG. 6 is a diagram illustrating the relationship between outputs in the vicinity of the peak of disk eccentricity in the track cross detection apparatus according to Embodiment 2 of the present invention.
6, the tracking error signal (a) near the peak of the eccentricity of the optical disk when the configuration of the low-pass filter having the output hold unit is the configuration of FIG. 5, for example, and the hold unit is not operated in the low-pass filter 40. The relationship between the output (b) when the hold means is operated, the output (c) when the hold means is operated, the output (d) of the relative speed detection means 12 and the reference value (e) of the comparison judgment means 13, and the control The relationship of means output (f) is shown.

The operation of the track cross detection apparatus configured as described above will be described below.
Based on the output of the multi-split optical detector of the optical pickup, the error detection means 10 detects the tracking error amount by using a phase error detection method, a push-pull method, a three-beam method, etc., and an unnecessary high frequency due to noise or the like. A component is removed and a tracking error signal is output and input to the low-pass filter 40 and the binarizing means 15.

  Here, in the vicinity of the peak of the eccentricity of the optical disk, as shown in FIG. 6A, the period of the tracking error signal becomes longer as it approaches the vicinity of the peak, and after the peak, the period becomes shorter again.

  The low-pass filter 40 operates the output hold means by the selector 54 that is arbitrarily switched by the control means 14, detects the DC level of the tracking error signal output from the error detection means 10, and binarizes the detection result. Output to.

  Here, as shown in FIG. 6B, when the internal hold function is not operated, the cut-off frequency of the low-pass filter 40 itself takes into account the DC fluctuation of the tracking error signal in a relatively early cycle. For a long-period tracking error signal near the peak of the eccentricity of the optical disk, the tracking error signal follows the tracking error signal itself, and an accurate DC level cannot be detected. Can be followed accurately.

  The relative speed detection means 12 detects the relative speed between the track of the optical disk and the optical disk pickup, and the comparison determination means 13 compares the relative speed output by the relative speed detection means 12 with a preset reference value, The magnitude relationship between the speed and the reference value is output to the control means 14.

  As described above, the control unit 14 outputs a signal for switching the selector 54 and controls the operation switching of the output hold unit in the low-pass filter 40.

  Here, as shown in FIG. 6 (d), the relative speed approaches zero near the peak of the eccentricity of the optical disk, and increases again after the peak. The comparison determination means 13 compares the relative speed (d) with the reference value (e). If the relative speed is slower than the reference value as shown in (f), the output of the control means 14 is set to Low. If the relative speed is faster than the reference value, the output of the control means 14 is set to High. By controlling the selector 54 as described above, the output of the low-pass filter 40 is held when the relative speed is slower than the reference value, as shown in FIG. 6C.

  In the binarizing means 15, the output of the low-pass filter 40 is set to a slice level, the tracking error signal is binarized, and a track cross signal is generated.

  As described above, according to the track cross detection apparatus according to the second embodiment, when the relative speed between the optical disk track and the optical pickup detected by the relative speed detection unit 12 is lower than a preset reference speed. Since the control means 14 performs control so as to operate the output hold means of the low-pass filter 40 for detecting the DC level, the long-period tracking error signal itself near the peak of the eccentricity of the optical disk is binary. Thus, the track cross signal can be detected with a stable slice level without the follow-up slice level. In addition, since the cutoff frequency is not set lower than necessary with respect to the input tracking error signal, it is possible to improve the deterioration of the followability and responsiveness to fluctuations in the DC level.

  As shown in FIG. 7, the same effect can be obtained even if the low-pass filter 40 is a general low-pass filter 70 having no output hold function and the sample hold means 71 is used for the output of the low-pass filter 70.

  FIG. 8 shows an example of a configuration diagram of the sample hold means 71. The sample hold means 71 holds the output value of the low-pass filter 70 in accordance with the relative speed between the track of the optical disc and the optical pickup. Reference numeral 80 denotes a holding unit, and 81 denotes a selector that switches between an input and a holding value and outputs it. Here, when the output of the control means 14 is Low, the selector 81 selects the holding means 80 and holds the slice level of the binarizing means 15, and when High, the selector 81 selects the output of the low-pass filter 70. Similar to the second embodiment, when the relative speed is low, the same effect can be obtained by holding the slice level of the binarizing means 15.

(Embodiment 3)
FIG. 9 is a block diagram showing the configuration of the track cross detection apparatus according to Embodiment 3 of the present invention.
In FIG. 9, reference numeral 90 denotes a control signal indicating whether the tracking is on or the tracking is off. Reference numeral 91 denotes an OR circuit that outputs a logical sum of the control signal 90 and the control means 14. In addition, the same code | symbol is used about the same component as embodiment mentioned above, and the description is abbreviate | omitted. Here, it is assumed that the control signal 90 is a control signal that is High in the tracking-on state and Low in the tracking-off state.

FIG. 10 is a diagram illustrating the relationship between outputs in the vicinity of the transition from the tracking off state to the tracking on state of the tracking cross detection apparatus according to the third embodiment of the present invention.
In FIG. 10, the tracking error signal (a) when the transition is made from the tracking-off state to the tracking-on state, the output (b) of the low-pass filter 40, the output (c) of the relative speed detection means 12, and the comparison judgment means 13 The relationship with the reference value (d), the output (e) of the control means 14, the output signal (f) of the control signal 90, and the state of the output (g) of the OR circuit 91 are shown.

The operation of the track cross detection apparatus configured as described above will be described below.
Based on the output of the multi-split optical detector of the optical pickup, the error detection means 10 detects the tracking error amount by using a phase error detection method, a push-pull method, a three-beam method, etc., and an unnecessary high frequency due to noise or the like. A component is removed and a tracking error signal is output and input to the low-pass filter 40 and the binarizing means 15.

  The low-pass filter 40 operates the output hold means according to the output of the OR circuit 91, detects the DC level of the tracking error signal output from the error detection means 10, and outputs the detection result to the binarization means 15. Here, the output hold means of the low-pass filter 40 does not operate when the output of the OR circuit 91 is High, and operates when the output is Low, and holds the output of the low-pass filter 40.

  The relative speed detection means 12 detects the relative speed between the track of the optical disk and the optical disk pickup, and the comparison determination means 13 compares the relative speed output by the relative speed detection means 12 with a preset reference value, The magnitude relationship between the speed and the reference value is output to the control means 14.

The control unit 14 receives the output of the comparison / determination unit 13 and outputs Low to the OR circuit 91 when the relative speed is slower than the reference value and High when the relative speed is faster.
The control signal 90 outputs High to the OR circuit 91 in the tracking on state and Low in the tracking off state.

  As shown in FIG. 10 (f), the control signal 90 outputs High in the tracking on state. Further, as shown in (c), since the relative speed is zero in the tracking-on state in the relative speed detecting means 12 and the comparison result of the comparison judging means 13 is necessarily slower than the relative speed, as shown in (e). The output of the control means 14 is Low. However, since the logical sum of the control signal 90 and the control means 14 becomes High in the OR circuit 91 as shown in (g), the output hold means of the low-pass filter 40 is always in the tracking on state as shown in (b). The output is not held without operation.

  In the binarizing means 15, the output of the low-pass filter 40 is set to a slice level, the tracking error signal is binarized, and a track cross signal is generated.

  As described above, according to the track cross detection apparatus according to the third embodiment, the OR circuit 91 outputs the logical sum of the control signal 90 indicating the tracking state and the output of the control means 14, and when the tracking on state, the low pass Since the hold means of the filter 40 is not operated, for example, when the relative speed is detected by counting the track cross signal period that is generally used, and the hysteresis binarization means is used as the binarization means. Thus, it is possible to improve the follow-up and responsiveness to DC level fluctuations caused by unnecessary operation of the holding means in the tracking-on state. Even when the track cross signal is not used for the relative speed detection, the relative speed is zero in the tracking on state, so that the tracking of the DC level fluctuation in the tracking on state due to the operation of the slice level output hold means operates. It can improve the decline of sex and responsiveness.

  In the configuration diagram of FIG. 7, an OR circuit is provided between the control means 14 and the sample-and-hold means 71, and the control means 14 outputs a logical sum of the control signal 90 and the output of the control means in the tracking-on state. Regardless of the output, the same effect as in the third embodiment can be obtained by controlling the sample hold means 71 not to operate and controlling so as not to hold the slice level of the binarization means 15.

  In the third embodiment, not only the control signal 90 but also a reset means for clearing the detected value of the relative speed detecting means 12 until a new relative speed is detected in response to the seek command. As a result, the relative speed detection result is always set to zero immediately after the seek command, so that the comparison / determination means 13 determines that the relative speed is slower than the reference value, and the output of the control means 14 is set to Low to binarize. By holding the slice level of the means 15, it is possible to prevent the slice level from following a tracking error signal having a slow cycle immediately after seeking, and to obtain a more stable track cross signal.

(Embodiment 4)
FIG. 11 is a block diagram showing the configuration of the track cross detection apparatus according to Embodiment 4 of the present invention.
In FIG. 11, reference numeral 110 denotes correction means for correcting the value of the holding means 80 at a predetermined rate of change in the positive or negative direction depending on the polarity of the track cross signal. Here, as the holding means 80, for example, a flip-flop having the same function as the flip-flop 53 of FIG. The configuration diagram of the sample hold means 71 in the present embodiment is shown in FIG. The same components as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted.

FIG. 12 is a diagram illustrating a relationship between outputs in the vicinity of the peak of disk eccentricity in the track cross detection apparatus according to the fourth embodiment of the present invention.
In FIG. 12, the tracking error signal (a) near the peak of the eccentricity of the optical disk, the output (b) of the sample and hold means 71, the output (c) of the relative speed detecting means 12, and the reference value ( d) and the output (e) of the control means.

The operation of the track cross detection apparatus configured as described above will be described below.
Based on the output of the multi-split optical detector of the optical pickup, the error detection means 10 detects the tracking error amount by using a phase error detection method, a push-pull method, a three-beam method, etc., and an unnecessary high frequency due to noise or the like. A tracking error signal from which components have been removed is output and input to the low-pass filter 70 and the binarizing means 15.

  The low-pass filter 70 detects the DC level of the tracking error signal output from the error detection means 10 and outputs it to the sample hold means 71.

  In the sample and hold means 71, when the output of the control means 14 is Low, the selector 81 outputs the value of the holding means 80, and when it is High, the selector 81 selects the output of the low-pass filter 70 and outputs it to the binarization means 15. Is done.

  The relative speed detection means 12 detects the relative speed between the track of the optical disk and the optical disk pickup, and the comparison determination means 13 compares the relative speed output by the relative speed detection means 12 with a preset reference value, The magnitude relationship between the speed and the reference value is output to the control means 14.

  As described above, the control unit 14 outputs a signal for switching the selector 81 and controls the output of the sample hold unit 71.

  Here, as shown in FIG. 12 (c), the relative speed approaches zero near the peak of the eccentricity of the optical disk, and increases again after the peak. The comparison determination means 13 compares the relative speed (c) with the reference value (d). If the relative speed is slower than the reference value as shown in (e), the output of the control means 14 is set to Low. If the relative speed is faster than the reference value, the selector 81 is controlled by setting the output of the control means 14 to High.

  Further, the correction means 110 is a positive direction when the track cross signal output from the binarization means 15 is High, and a negative direction when the track cross signal is Low. The hold value is corrected. Thereby, as shown in FIG. 12B, the output of the sample hold means 71 in FIG. 12 does not become a complete hold state even when the control means 14 is in the low state, and the output of the DC level according to the tracking error signal Output while making corrections.

  In the binarizing means 15, the output of the sample hold means 71 is set to a slice level, the tracking error signal is binarized, and a track cross signal is generated.

  As described above, according to the track cross detection apparatus according to the fourth embodiment, even if the slice level of the binarization unit 15 is held by the control unit 14, the correction unit 110 performs the track cross signal. When the polarity is high, the correction value is corrected in the correction means in the negative direction when the polarity is low, so that the holding value of the holding means 80 is corrected, so that the slice level is in the hold state. In addition, by performing correction to follow the DC level of the tracking error signal, the followability in the hold state is improved, and unnecessary hold means operation due to noise or the like and the hold means in the tracking on state where the relative speed becomes zero It is possible to improve the DC level followability and quick response due to the above operation.

  Although the correction amount of the correction unit 110 is constant in the above-described fourth embodiment, the change rate of the correction unit 110 is changed according to the output of the relative speed detection unit 12, and when the relative speed is high, the correction unit By adjusting the change rate of 110 to be large and to be small when it is slow, the strength of the slice level hold can be adjusted stepwise, so that the followability of the DC level can be further improved.

  In the configuration shown in FIG. 4 instead of correcting the hold value of the sample hold means 71, the hold value of the flip-flop 53 in the low-pass filter 40 having the output hold means is the same as that of the correction means 110. The same effect can be obtained even when the correction is performed by the correction means having a function.

(Embodiment 5)
FIG. 13 is a block diagram showing the configuration of the track cross detection apparatus according to Embodiment 5 of the present invention.
In FIG. 13, reference numeral 130 denotes a pulse train generating means for outputting a pulse train in accordance with the output of the relative speed detecting means 12 and limiting the input of the low-pass filter. In addition, the same code | symbol is used about the same component as embodiment mentioned above, and the description is abbreviate | omitted. However, the control means 14 does not control the cut-off frequency of the low-pass filter 12, but controls the operation of the hold means of the low-pass filter 40.
In the fifth embodiment of the present invention, the configuration shown in FIG. 5 is used as an example of the low-pass filter 40. Here, in the fifth embodiment, the selector 54 selects the output of the flip-flop 53 when the output of the control means 14 is Low, and the selector 54 selects the output of the adder 52 when it is High.

  Further, as an example of the pulse train generation means, it is assumed that a load hold means using a PWM (Pulse Width Modulation) method for generating a pulse having a duty according to a set value is used.

FIG. 14 is a diagram illustrating the relationship between outputs near the peak of the eccentricity of the optical disc in the track cross detection apparatus according to the fifth embodiment of the present invention.
In FIG. 14, the tracking error signal (a) near the peak of the eccentricity of the optical disk, the output (b) of the low-pass filter 40, and the output (c) of the relative speed detecting means 12 are shown.
FIGS. 15A to 15C show outputs of the pulse train generation means 130 at points indicated by arrows 140 to 142 in FIG.

The operation of the track cross detection apparatus configured as described above will be described below.
Based on the output of the multi-split optical detector of the optical pickup, the error detection means 10 detects the tracking error amount by using a phase error detection method, a push-pull method, a three-beam method, etc., and an unnecessary high frequency due to noise or the like. The component is removed and a tracking error signal is output.

  The low-pass filter 40 operates the output hold means by the selector 54 switched by the control means 14, detects the DC level of the tracking error signal output from the error detection means 10, and outputs the detection result to the binarization means 15. To do.

  The relative speed detection means 12 detects the relative speed between the track of the optical disk and the optical disk pickup, and outputs it to the pulse train generation means 130.

  As shown in FIG. 15, the pulse train generation means 130 has a lower duty of the output pulse signal as the relative speed is lower, and is output to the control means 14. However, the frequency of the output pulse of the pulse train generation means 130 by the PWM method used in this embodiment is sufficiently short with respect to the period of the tracking error signal.

  The control means 14 outputs a signal for switching the selector 54 as described above in accordance with the pulse train generation means 130, and controls the operation switching of the output hold means in the low-pass filter 40.

  As described above, since the duty of the output signal of the pulse train generation means becomes lower as the relative speed is lower, the period during which the output hold means of the low-pass filter 40 is operated becomes longer as the relative speed is lower, equivalently the low-pass filter. The cut-off frequency of 40 becomes lower. As a result, in FIG. 14, the output of the low-pass filter 40 is as shown in FIG.

  In the binarizing means 15, the output of the low-pass filter 40 is set to a slice level, the tracking error signal is binarized, and a track cross signal is generated.

  Thus, according to the track cross detection apparatus according to the fifth embodiment, the pulse train is generated by the pulse train generator 130 according to the output of the relative speed detector 12, and the output hold means of the low-pass filter 40 is generated by the pulse train. Since the control means 14 controls to operate, the cutoff frequency can be equivalently changed according to the relative speed without changing the filter coefficient of the low-pass filter, and near the peak of the eccentricity of the optical disk. The tracking error signal itself having a long period of time does not follow the slice level for binarization, and the track cross signal can be detected with a stable slice level. Further, since the low-pass filter does not have a low cut-off frequency characteristic considering a long period, an increase in circuit scale can be improved. In addition, since the cutoff frequency is not set lower than necessary with respect to the input tracking error signal, it is possible to improve the deterioration of the followability and responsiveness to fluctuations in the DC level.

  As described above, the case where the load hold means by the PWM method for changing the duty of the pulse according to the relative speed is used as the pulse train generation means has been described, but the load by the BSDA (Bit Stream D / A) method is used as the pulse train generation means. Even if the holding means is used, the same effect can be obtained.

FIG. 16 shows a configuration example of the pulse train generation means by the BSDA method in the track cross detection apparatus according to the fifth embodiment of the present invention.
In FIG. 16, reference numeral 160 denotes a set value, which is set according to the relative speed in the fifth embodiment. Reference numeral 161 denotes an adder with an overflow flag. 162 is a flip-flop.

The operation of the pulse train generating means based on the BSDA system configured as described above will be described below.
The set value 160 and the output of the flip-flop 162 are added by the adder 161. When the adder 161 overflows, an overflow flag is set and this is used as the output of BSDA. The larger the set value, the more easily the adder overflows, and signals are frequently output. In this way, if the set value is changed according to the relative speed, the higher the relative speed, the shorter the output pulse interval, and the slower the relative speed, the wider the pulse output interval. As described above, the cutoff frequency of the low-pass filter 40 can be equivalently changed according to the relative speed.

  Note that the pulse train generation means 130 uses a load hold means that closes the gate for a certain period of rise and fall of the pulse train by a method in which a pulse is output as the relative speed is higher for each edge of the track cross signal and the delay time is shorter as the pulse speed is slower. However, the same effect can be obtained.

  In the fifth embodiment, the control signal indicating whether the tracking is on or the tracking off is received, and in the tracking on state, the output of the controller 14 is fixed to High regardless of the output of the pulse generator. As a result, the output hold means of the low-pass filter 40 is not operated and the cut-off frequency is not lowered, so that the followability to the DC level due to the drop of the output pulse of the pulse train generation means in the tracking on state (= relative speed zero) The deterioration of quick response can be improved.

  In the tracking-on state, the output of the control means 14 is not fixed to High, but the detection value of the relative speed detection means 12 is fixed to the maximum value, so that the output of the pulse train generation means 130 is maximized and controlled. By maximizing the period during which the output of the means 14 is in the high state, the period during which the output holding means of the low-pass filter 40 operates is minimized, and the input of the low-pass filter 40 is not restricted so that the cutoff frequency is not lowered. However, the same effect can be obtained.

  In addition, a signal for controlling the seek of the optical pickup may be received and reset means for clearing the detection value of the relative speed detection means 12 immediately after the start of seek may be provided to limit the input of the low-pass filter 40. Immediately after the start of seek, the cut-off frequency of the low-pass filter 40 is equivalently reduced by minimizing the output pulse of the pulse train generation means 130, and a stable DC level can be detected without following a slow tracking error signal immediately after the start of seek. Is possible.

  The first to fifth embodiments of the present invention can be realized by either hardware or software, and the same effect can be obtained.

  The track cross detection device according to the present invention is useful in that stable optical disk operation can be ensured and stable control of the optical disk device can be performed.

It is a block diagram showing the structure of the track cross detection apparatus which concerns on Embodiment 1 of this invention. It is a block diagram showing an example of a structure of the low pass filter 11 of the track cross detection apparatus which concerns on Embodiment 1 of this invention. It is a figure showing the relationship of each output in the peak vicinity of the disk eccentricity of the track cross detection apparatus concerning Embodiment 1 of this invention. It is a block diagram showing the structure of the track cross detection apparatus which concerns on Embodiment 2 of this invention. It is a block diagram showing an example of a structure of the low-pass filter 40 of the track cross detection apparatus which concerns on Embodiment 2 of this invention. It is a figure showing the relationship of each output in the peak vicinity of the disk eccentricity of the track cross detection apparatus concerning Embodiment 2 of this invention. It is a block diagram showing another structure of the track cross detection apparatus which concerns on Embodiment 2 of this invention. It is a block diagram showing an example of a structure of the sample hold means 71 of the track cross detection apparatus concerning Embodiment 2 of this invention. It is a block diagram showing the structure of the track cross detection apparatus which concerns on Embodiment 3 of this invention. It is a figure showing the relationship of each output of the vicinity which transfers to the tracking-on state from the tracking-off state of the track cross detection apparatus concerning Embodiment 3 of this invention. It is a block diagram showing the structure of the track cross detection apparatus which concerns on Embodiment 4 of this invention. It is a figure showing the relationship of each output in the peak vicinity of the disc eccentricity of the track cross detection apparatus concerning Embodiment 4 of this invention. It is a block diagram showing the structure of the track cross detection apparatus which concerns on Embodiment 5 of this invention. It is a figure showing the relationship of each output in the peak vicinity of the disk eccentricity of the track cross detection apparatus concerning Embodiment 5 of this invention. It is a figure ((a)-(c)) showing the output of the pulse-train production | generation means by the PWM system in each point shown in FIG. 14 of the track cross detection apparatus which concerns on Embodiment 5 of this invention. It is a block diagram showing an example of a structure of the pulse train production | generation means by the BSDA system of the track cross detection apparatus which concerns on Embodiment 5 of this invention. It is a block diagram showing the structure of the conventional track cross detection apparatus. It is a figure showing the relationship of each output of the conventional track cross detection apparatus. It is a figure showing the relationship between the tracking error signal in the conventional track cross detection apparatus, the threshold level with hysteresis by the hysteresis binarization means, and the track cross signal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Error detection means 11 Low pass filter which can change cut-off frequency arbitrarily 12 Relative speed detection means 13 Comparison determination means 14 Control means 15 Binarization means 20 1st low pass filter 21 2nd low pass filter 40 Output hold means Low pass filter 50 first filter coefficient 51 second filter coefficient 52 adder 53 flip-flop 54 selector 70 low pass filter 71 sample hold means 80 holding means 81 control means 90 control signal 91 OR circuit 110 correction means 130 pulse train generation means 160 Set value 161 Adder with overflow flag output 162 Flip-flop 1001 Error amount detection means 1002 High frequency component removal means 1003 Low pass filter 1004 Hysteresis binarization means

Claims (14)

Error detection means for detecting a tracking error signal based on a signal output from an optical pickup in the optical disc apparatus;
Based on a signal from the optical pickup, a relative speed detecting means for detecting a relative speed between a track of the optical disc and the optical pickup;
A low-pass filter that switches a cut-off frequency for detecting a DC level of a tracking error signal output from the error detection unit according to a relative speed between a track of the optical disc and the optical pickup;
Comparison determination means for comparing the output of the relative speed detection means with a preset reference value;
Control means for controlling the cut-off frequency of the low-pass filter in accordance with the output of the comparison determination means;
A binarizing unit that binarizes a tracking error signal output from the error detection unit using the output of the low-pass filter as a slice level and outputs it as a track cross signal;
A track cross detection device characterized by the above. Error detection means for detecting a tracking error signal based on a signal output from an optical pickup in the optical disc apparatus;
Based on a signal from the optical pickup, a relative speed detecting means for detecting a relative speed between a track of the optical disc and the optical pickup;
A low-pass filter that detects and outputs a DC level of the tracking error signal output from the error detection means;
Sample hold means for holding the output value of the low-pass filter according to the relative speed between the track of the optical disc and the optical pickup;
Comparison determination means for comparing the output of the relative speed detection means with a preset reference value;
Control means for performing control to switch between the output of the low-pass filter and the output of the value held by the sample hold means according to the output of the comparison determination means;
A binarization unit that binarizes the tracking error signal output from the error detection unit using the output signal switched by the control unit as a slice level and outputs the signal as a track cross signal;
A track cross detection device characterized by the above. Error detection means for detecting a tracking error amount based on a signal output from an optical pickup in the optical disc apparatus;
Based on a signal from the optical pickup, a relative speed detecting means for detecting a relative speed between a track of the optical disc and the optical pickup;
A low-pass filter having output hold means for detecting the DC level of the tracking error signal output from the error detection means;
Comparison determination means for comparing the output of the relative speed detection means with a preset reference value;
Control means for performing switching control of the output hold means of the low-pass filter according to the output of the comparison determination means;
A binarizing unit that binarizes the tracking error signal output from the error detecting unit using the output of the low-pass filter as a slice level, and outputs the tracking error signal as a track cross signal;
The low-pass filter is
According to the relative speed of the optical disc track and the optical pickup, the output hold means holds the DC level of the tracking error signal from the error detection means,
A track cross detection device characterized by the above. The track cross detection device according to claim 2,
A logic circuit that receives an output of the control means and a control signal indicating whether the tracking is on or the tracking is off;
The low-pass filter receives a control signal from the logic circuit. When the tracking-on state is established, the low-pass filter does not operate the sample-and-hold means regardless of the output of the control means, and the output of the low-pass filter is the binary value. To control the slice level of the conversion means,
A track cross detection device characterized by the above. In the track cross detection device according to claim 3,
A logic circuit that receives an output of the control means and a control signal indicating whether the tracking is on or the tracking is off;
The low-pass filter receives a control signal from the logic circuit, and controls the output hold means of the low-pass filter not to operate regardless of the output of the control means in a tracking-on state.
A track cross detection device characterized by the above. In the track cross detection device according to claim 4 or 5,
A reset means for receiving a signal for controlling the seek of the optical pickup and clearing the detection value of the relative speed detection means immediately after the start of seeking;
A track cross detection device characterized by the above. In the track cross detection device according to claim 2 or 3,
Compensating means for correcting the hold value at a predetermined rate of change in the positive or negative direction depending on the polarity of the detected track cross signal,
A track cross detection device characterized by the above. In the track cross detection device according to claim 7,
Changing the rate of change of the correcting means according to the output of the relative speed detecting means;
A track cross detection device characterized by the above. Error detection means for detecting a tracking error amount based on a signal output from an optical pickup in the optical disc apparatus;
Based on a signal from the optical pickup, a relative speed detecting means for detecting a relative speed between a track of the optical disc and the optical pickup;
A low-pass filter having output hold means for detecting the DC level of the tracking error signal output from the error detection means;
A pulse train generating means for outputting a pulse train in accordance with a relative speed between the track of the optical disc detected by the relative speed detecting means and the optical pickup, and for limiting an input of the low-pass filter;
Control means for controlling the output hold means of the low-pass filter according to the output of the pulse train generation means;
A binarizing unit that binarizes a tracking error signal output from the error detection unit using the output of the low-pass filter as a slice level and outputs it as a track cross signal;
A track cross detection device characterized by the above. The track cross detection device according to claim 9,
The pulse train generation means is load hold means by a BSDA (Bit Stream D / A) system.
A track cross detection device characterized by the above. The track cross detection device according to claim 9,
The pulse train generation means is a load hold means by a PWM (Pulse Width Modulation) system.
A track cross detection device characterized by the above. The track cross detection device according to claim 9,
The pulse train generation means is a load hold means that closes the gate for a certain period of rise and fall of the pulse train by a method of outputting a pulse train having a length corresponding to the relative speed detection means for each edge of the track cross signal.
A track cross detection device characterized by the above. The track cross detection device according to any one of claims 9 to 12,
Receiving a control signal indicating whether it is in a tracking-on state or a tracking-off state, and in a tracking-on state, controls the relative speed detection means to maximize the output and not limit the input of the low-pass filter;
A track cross detection device characterized by the above. The track cross detection device according to claim 13,
Receiving a signal for controlling the seek of the optical pickup, and provided with reset means for clearing the detection value of the relative speed detection means immediately after the start of seeking, limiting the input of the low-pass filter;
A track cross detection device characterized by the above.

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