JPH11203787A - Optical disc playback device with equalizer characteristic control circuit - Google Patents

Abstract

(57) Abstract: An RF signal is properly binarized, and an error rate and a jitter amount are maintained at predetermined values or less. A cutoff frequency characteristic control signal corresponding to a reproduction position of an optical disk is supplied to an equalizer to change a gain characteristic of the equalizer. The synchronization detection circuit 16 separates the data and the synchronization information, the sector head detection circuit 18 detects the ID indicating the head of the sector from the synchronization information, and the ID detection circuit 19 controls the gain characteristic of the equalizer with the sector number obtained from the data. I do. Further, the gain characteristic of the equalizer 4 is controlled or switched by detecting an error rate or a jitter amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk reproducing apparatus provided with an equalizer characteristic control circuit, and more particularly to a method of converting data recorded by CLV (constant linear velocity) to CAV (constant rotational velocity).
The present invention relates to an optical disk reproducing apparatus provided with an equalizer characteristic control circuit of an apparatus for reproducing data on a disc.
It is suitable for use in VD devices and DVD-ROM devices.

[0002]

2. Description of the Related Art When reading an optical disk recorded by the CLV method at high speed, it is necessary to increase the motor torque to increase the response speed of the motor. For this purpose, it is necessary to increase the size of the motor and supply a large current to the motor. However, since the power of the optical disk device is limited, a large current cannot be supplied to the motor, and the size of the motor is limited.
When the optical pickup is randomly accessed at high speed, the optical pickup is reciprocated at high speed in the radial direction of the optical disk, and the rotation speed of the optical disk must be changed each time. Therefore, a considerable time is required until the rotation speed of the optical disk becomes stable. During this time, data cannot be reproduced and access cannot be performed efficiently.

In order to solve this drawback, it is conceivable to reproduce data recorded by the CLV method by the CAV method. However, data recorded in the CLV format is
When the data is reproduced by the V method, the reproduction speed becomes higher as it reaches the outer periphery of the optical disk. For example, in a DVD disk, if the minimum channel length is T, the minimum pit length is 3T. During playback, 3T on the pit surface, 3T on the mirror surface
, The frequency of the RF signal is the highest, and this is the 3T frequency. When the data is reproduced at a bit standard rotation speed, the 3T frequency at the innermost circumference is 4.4 MHz, while the 3T frequency at the outermost circumference is 10.6 MHz.
In order to properly binarize the reproduced signal, it is necessary to provide an equalizer to increase the gain near the 3T frequency. If the equalizer is configured to increase the gain near the 3T frequency near the inner circumference of the optical disk, the gain of the 3T frequency near the middle and outer circumference of the optical disk is insufficient, and the vertical amplitude of the eye pattern is insufficient. Cannot be binarized correctly, the jitter amount increases, and the error rate increases. Further, depending on the configuration of the equalizer, the flat part of the group delay characteristic is not sufficient for the required frequency band, so that the amount of group delay of a reproduced signal having a high frequency near the outer periphery changes. The fact that the amount of group delay of the signal changes means that the rising and falling timings of the pulse are shifted, thereby increasing the jitter. The amount of jitter in the lateral direction of the eye pattern increases, and thus the error rate increases. As the jitter increases, the error rate increases,
Data or signals cannot be reproduced faithfully.

[0004] For this reason, as an example, as an equalizer, the gain difference from the direct current to the 3T frequency is set within about 3 dB, and the group delay characteristic is 14T frequency (when the pit surface has a length of 14T and the mirror surface has a length of 14T). It is necessary to design flat from the frequency of the reproduction RF signal) to about 1.5 times the 3T frequency.

[0005] However, it is difficult to design an equalizer that satisfies the above conditions. That is, no matter how the gain characteristic curve of the equalizer is determined, if the reproduction speed is changed by CAV reproduction with the same equalization characteristic, the above characteristics cannot be satisfied over the entire area of the disc, and the 3T frequency gain is insufficient. As a result, binarization cannot be correctly performed, and a disadvantage occurs that an error rate and a jitter amount increase. Also, depending on how the gain characteristic curve of the equalizer is determined, the group delay characteristic cannot be designed to be flat from the 14T frequency to about 1.5 times the 3T frequency. There is a disadvantage that the phase of the wave changes and the amount of jitter and the error rate increase.

[0006]

When an optical disk recorded in the CLV system is reproduced in the CAV system, it is difficult to design an equalizer that satisfies the above requirements. An object of the present invention is to convert an optical disc recorded by the CLV method into a CA.
An object of the present invention is to provide an optical disc reproducing apparatus provided with an equalizer characteristic control circuit capable of controlling the characteristics of the equalizer so as to satisfy the conditions required for the equalizer even when reproducing data in the V system.

[0007]

An optical disk reproducing apparatus provided with an equalizer characteristic control circuit according to the present invention detects information on a reproduction position of an optical disk and controls a cutoff frequency of the equalizer based on the reproduction position of the optical disk. ing. As information on the reproduction position of the optical disk, the position of a sector can be used. In order to achieve the above object, in an optical disc reproducing apparatus provided with an equalizer characteristic control circuit according to the present invention, an error rate is detected and a cutoff frequency of the equalizer is set to be equal to or less than a predetermined error rate. Controlling. Further, in the optical disk reproducing apparatus provided with the equalizer characteristic control circuit according to the present invention, the amount of jitter or error rate of the reproduced data is detected, and the equalizer is cut so that the amount of jitter or error rate does not exceed a predetermined value. Off frequency is controlled.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an optical disk reproducing apparatus provided with an equalizer characteristic control circuit according to the present invention will be described in detail with reference to some embodiments.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described by taking reproduction of a DVD disk as an example.

FIG. 1 is a characteristic curve diagram of an equalizer used in an optical disk reproducing apparatus provided with an equalizer characteristic control circuit according to the present invention. FIG. 1A shows the frequency characteristic of the gain of the equalizer circuit, and FIG. 1B shows the frequency characteristic of the group delay of the equalizer. 1 (a) and 1 (b),
The horizontal axis indicates frequency. FIG. 1C shows a data error rate with respect to the 3T frequency when the optical disk recorded by the CLV method is reproduced by the CAV method at a rotation speed that becomes a standard speed on the inner circumference. In FIG. 1C, the 3T frequency on the horizontal axis is proportional to the disc radius at the reproduction position. Therefore, FIG.
In (c), the horizontal axis can be replaced with the disk position.

The vertical axis shows three types of characteristic curves of the equalizer. The vertical axis of FIG. 1A is a gain (decibel), and as a result of being controlled by the equalizer characteristic control circuit according to the present invention, the equalizer has three gain characteristic curves. In the figure, reference numeral 71 denotes a gain characteristic curve obtained by boosting the gain near the 3T frequency (about 4.4 MHz) at the innermost circumference of the optical disc. The gain characteristic curve 72 shows the 3T frequency (about 7.5M) at the middle position of the optical disc.
Hz), and the gain characteristic curve 73 is boosted near the outermost 3T frequency (about 11 MHz). The vertical axis of FIG. 1B is the group delay amount (n
s), which is a group delay characteristic curve in the case where the gain characteristic curve of the equalizer is determined as shown in FIG. 1 (a), wherein the group delay characteristic curve 75 corresponds to the gain characteristic curve 71, and the group delay characteristic curve 76 and 77 are gain characteristic curves 72 and 7 respectively.
3 is supported. The vertical axis in FIG. 1 (c) is the error rate,
Error rate characteristic curves 78, 79, and 80 correspond to gain characteristic curves 71, 72, and 73, respectively.

In the gain curve shown in FIG. 1, 3T frequencies near 4.4 MHz, 7.5 MHz, and 10.6 MHz, which are the innermost, middle, and outermost 3T frequencies of the optical disk, are raised. In one embodiment of the present invention, the three gain characteristic curves 71, 72, 73 are controlled by controlling the cutoff frequency or the cutoff frequency and the gain of the equalizer.
Is set, and the cutoff frequency of the equalizer is controlled by the reproduction position of the optical disc, the error rate or the amount of jitter,
One gain characteristic curve is selected from the gain characteristic curves 71, 72, 73. By selecting the gain characteristic curve of the equalizer, the group delay characteristic is also selected, and the flat part of the group delay characteristic can be used, so that the error rate and the jitter amount can be kept in good ranges. That is, in the present invention, when the gain boost amount is kept constant in each gain characteristic curve, the cutoff frequency of the equalizer is changed according to the reproduction position of the optical disc, the error rate, or the amount of jitter, and the cutoff frequency is changed. Gain characteristic curves 7 according to
1, 72 and 73 can be provided. The gain control signal of the equalizer may be made variable in order to make the gain boost amount of each of the gain characteristic curves 71 to 73 variable.

In the present invention, the gain characteristic curves 71 to 7
3, the group delay characteristic curve is switched as shown by curves 75 to 77. Further, error rate characteristic curves 78 to 80 indicating error rates corresponding to the gain characteristic curves 71 to 73 are obtained. In the case of the gain characteristic curve 71, the innermost 3T frequency (4.4M
Hz), the error rate at this point is the lowest. At a point where the frequency is slightly higher than 4.4 MHz, the gain of the curve 71 is increased. However, since the group delay characteristic curve 75 corresponding to the gain characteristic curve 71 has a small frequency band in the flat portion, the phase of the reproduced signal of the high frequency is low. And the error rate and the amount of jitter increase. In the case of the gain characteristic curve 72, see 7.
At frequencies below 5 MHz, the error rate increases due to the decrease in gain. The gain of the curve 72 is 7.5 MH
The gain is maximum at a frequency slightly higher than z, but also in this case, the error rate increases for the reasons described above. Also, the group delay characteristic curve 7 corresponding to the gain characteristic curve 72
In No. 6, since the frequency from 14T to 1.5 times the 3T frequency cannot be flattened, the phase of the high-frequency reproduced signal changes, and the error rate and the amount of jitter increase. In the case of the gain characteristic curve 73, 4.4 MHz and 7.5 MH
Since the gain near z is insufficient, the reproduced signal (RF signal) cannot be properly binarized, so that the error rate of the RF signal near these frequencies increases, and the gain characteristic shown by the curve 72 cannot be used. . At frequencies higher than 11 MHz, the gain is even higher, but the error rate increases for the reasons described above. Since the group delay characteristic curve 77 corresponding to the gain characteristic curve 73 is kept flat in the required band, the error rate and the jitter amount do not increase due to the group delay characteristic. Therefore, if the gain characteristic curves 71 to 73 are switched according to the reproduction position of the optical disk or the error rate or the amount of jitter, a good gain characteristic curve can be always selected. In this case, the group delay characteristics 75 to 77 are also determined by the selected gain characteristic curves 71 to 73, and by shifting to a gain curve in which a high frequency gain is boosted, a flat portion of the group delay characteristic is held up to a high frequency. Therefore, the error rate and the amount of jitter can be kept below a predetermined value.

In the prior art, since one gain characteristic curve is used, the error rate and the amount of jitter increase due to lack of gain or lack of a flat part of the group delay characteristic, so that it is impossible to reproduce the optical disk satisfactorily. The number of gain characteristic curves to be switched and used is not limited to three as shown in FIG. 1, but may be any number. The point at which the gain is increased is not necessarily limited to the innermost, middle, and outermost 3T frequencies. For example, 1/4 and 3 from the innermost circumference of the optical disc
An equalizer with an increased gain near the 3T frequency at the / 4 position may be used. In the present invention, in order to obtain good equalizer characteristics from the innermost circumference to the outermost circumference of the optical disc 1, attention is paid to the fact that the reproduction speed of the optical disc 1 changes depending on the track position or sector position of the optical disc 1, What is necessary is just to change the characteristic of the equalizer 4 at a predetermined sector position. Also, the characteristics of the equalizer may be changed by focusing on the error rate or the jitter amount. To change the characteristics of the equalizer 4, there are a method of changing the cutoff frequency of the equalizer 4, a method of changing the boost level and the cutoff frequency of the equalizer 4, and the like.

FIG. 2 is a block diagram showing an embodiment of an optical disk reproducing apparatus using the equalizer characteristic control device according to the present invention. In the figure, an optical disc 1, for example, DV
Data is recorded on the D disk by the CLV method. Data recorded on the optical disk 1 is detected by the optical pickup 2, converted into an electric signal by a photoelectric conversion element, amplified by an amplifier circuit 3, and supplied to an equalizer 4. The equalizer 4 amplifies the signal so as to increase the gain around a predetermined 3T frequency, and outputs RF signals of data and video signals after keeping the group delay characteristic flat in a required frequency band. . This RF signal is binarized by the data slice circuit 5. The tracking control signal and the focus control signal amplified by the amplification circuit 3 and detected by the detection circuit of the servo processor 6 are phase-compensated by the phase compensation circuit of the servo processor 6 and then supplied to the drive circuit 7, and output from the drive circuit 7. Is supplied to a focus coil (not shown) and a tracking coil (not shown) of the optical pickup 2 to control focusing and tracking. Further, a slider control signal and a motor speed control signal from the microcomputer 8 are supplied to the drive circuit 7 through the servo processor 6. The slider 9 mounted with the optical pickup 2 controls the movement of the optical disk 1 in the radial direction by a slider control signal output from the drive circuit 7. The rotation speed of the spindle motor 10 is controlled by a motor rotation control signal from the drive circuit 7. In this embodiment, as described above, the spindle motor control will be described as CAV control.

As the equalizer 4, for example, a 7th-order Bessel type low-pass filter can be used as described later. However, as described in the section of the prior art, since the equalizer 4 must be designed to satisfy various conditions, the optical disk 1 recorded by the CLV method can be used with a single equalizer designed in advance by the CAV method. Cannot be reproduced well. In the embodiment shown in the figure, a predetermined sector number is detected, and at this position, the characteristics of the equalizer 4 are controlled or switched by the output of the microcomputer 8. Hereinafter, a circuit configuration for detecting identification information indicating a sector number will be described with reference to FIG. First, the data configuration recorded on the DVD optical disk will be described. DV
The optical disk for D is divided into a plurality of sectors.
One sector is composed of 26 frames. Synchronization information is arranged at the head of each frame, and data is arranged thereafter. Synchronization information is 8 from SY0 to SY7
It is composed of different types of synchronization information, and is arranged at the beginning of each frame according to a predetermined rule. The synchronization information at the head of each sector is predetermined.
The data of the first frame of the sector includes identification information (ID information) indicating the sector number.

In FIG. 2, after the synchronization information and the data are binarized in the data slice circuit 5, the data is supplied to a phase comparison circuit of a PLL circuit 15 composed of a phase comparison circuit and a voltage controlled oscillator. It is supplied to the detection circuit 16. The phase comparison circuit of the PLL circuit 15 compares the binary signal with the synchronous clock from the voltage controlled oscillator,
This synchronous clock is controlled so that the phase matches the binary signal. The synchronization clock extracted from the PLL circuit 15 is supplied to a synchronization detection circuit 16. The synchronization detection circuit 16 uses the synchronization clock to strobe the binarized data to obtain a binary code, and demodulates the data from the binary code into a demodulation circuit 17.
, And the synchronization information is supplied to the sector head detection circuit 18. Here, the binary code data supplied to the demodulation circuit 17 is converted from 16 bits to 8 bits and then supplied to the ID detection circuit 19. The sector head detection circuit 18 detects synchronization information indicating the head of the sector from the supplied synchronization information. The synchronization information arranged at the head of the sector, that is, the synchronization information arranged at the beginning of the frame at the head of the sector, forms a special pattern. Therefore, in order to detect this, for example, a reference pattern memory for generating the same pattern as the above-mentioned pattern and a register are provided in the sector head detection circuit 18, and when the synchronization information is sent by the register and coincides with the output of the reference pattern memory, By configuring so that a pulse (hereinafter referred to as a head pulse) is generated, the synchronization information at the head of the sector can be detected. In the ID detection circuit 19, the I pulse in the data supplied from the demodulation circuit 17 is
D information is detected. The ID information indicating the sector number is supplied to the microcomputer 8. The microcomputer constantly or intermittently monitors the ID information, and supplies a control signal for changing the characteristics of the equalizer 4 to the equalizer when the ID information of a predetermined sector number comes.
When the optical pickup 2 jumps over a predetermined sector number, such as at the time of access, since the microcomputer has access destination data, it is detected from this data that the predetermined sector number has jumped. Then, the same control signal as when the predetermined number is detected is generated to control the equalizer 4. Note that the data output from the demodulation circuit 17 is a deinterleave circuit (rearranges the data and parity into an array capable of error correction), an error correction circuit, and a descrambling circuit (data that is arrayed according to a certain rule and recorded on an optical disk). The output is supplied to an external device such as a computer through an interface circuit.

FIG. 3 is a block diagram showing an embodiment of an equalizer used in an optical disk reproducing apparatus provided with an equalizer characteristic control circuit according to the present invention. The figure shows a 7th-order Bessel-type equalizer, which includes second-order low-pass filters 31, 32, and 33 and a first-order low-pass filter. Q (resonance constant or resonance sharpness) of the second-order low-pass filters 31, 32, 33
ctor) and ω (the angular frequency of the cutoff frequency of each low-pass filter) are (Q1, ω1), (Q2,
ω2), (Q3, ω3), and ω of the first-order low-pass filter 34 is ω4. In this low-pass filter, the values of Q1, Q2, and Q3 are determined in advance, and only the cutoff frequency ω of each of the filters 31 to 34 is controlled. Secondary low-pass filter 31, 3
2 and 33 are filter cutoff control circuits 35 and
Each filter 31 is controlled by a control signal from 36, 37, 38.
, And the cutoff frequency is controlled so as to maintain the seventh-order Bessel characteristic of the entire low-pass filter. The second-order differentiation circuit 39 and the inverting amplification circuit 40 constitute a high-pass filter, and a high-pass filter is provided by performing the second-order differentiation of the RF signal by the second-order differentiation circuit 39. The frequency characteristic output from the high-pass filter changes according to the control signal from the filter cutoff control circuit 35. The second-order differentiated RF signal is supplied to the inverting amplifier circuit 40. The signal output from the second-order differentiating circuit 39 is inverted and amplified by the inverting amplifier circuit 40, and the boost amount of the wide-range gain of the equalizer is determined. The gain of the inverting amplifier circuit 40 changes according to a control signal from the gain control circuit 41. That is, the boost amount of the boost section is controlled by the gain (boost amount) control signal from the gain control circuit 41. Therefore, by controlling the second-order differentiating circuit 39 and the inverting amplifying circuit 40, the frequency at which the gain is boosted and the boost amount are controlled.

The output of the secondary low-pass filter 31 and the output of the inverting amplifier circuit 40 are added by an adder circuit 44 and output to the data slice circuit 5 through the secondary low-pass filter circuits 32 and 33 and the primary low-pass filter circuit 34.
The gain data set in the register of the microcomputer 8 is D / A
The data is converted into an analog amount by the converter 42 and supplied to the gain control circuit 41. The gain control signal or the boost amount control signal from the gain control circuit 41 is supplied to the inverting amplifier circuit 40 and controls the gain of the amplifier circuit 40. In the seventh-order Bessel type low-pass filter of this embodiment, the gain control signal is set to a predetermined value in advance. Therefore, the gain of the inverting amplifier circuit 40 is predetermined. The boosted frequency or the frequency at which the gain is increased depends on the filter cutoff frequency control circuit 35.
Is supplied to the second-order differentiating circuit 39. That is, the second-order differentiating circuit 39 and the inverting amplifier 40 constitute a high-pass filter, and the cut-off frequency of the high-pass filter is obtained by controlling the cut-off frequency of the second-order differentiating circuit. It is obtained by controlling the gain of the inverting amplifier circuit 40. The output of the high-pass filter is added to the signal controlled by the low-pass characteristic of the secondary low-pass filter 31 to obtain a gain characteristic having a boost section.

The cutoff frequency control data set in the register of the microcomputer 8 is converted into an analog quantity by the D / A converter 43 and supplied to the filter cutoff control circuits 35 to 38 as a cutoff frequency control signal.
The control signals from the filter cutoff frequency control circuits 35 to 38 are supplied to the respective secondary low-pass filters 31 to 33 and the primary low-pass filter 34. Each low pass filter 3
By changing the cutoff frequency characteristics 2 to 34, the cutoff frequency of the gain characteristic obtained at the output of the adder circuit 44 is determined. Low-pass filters 31 to 34
Is changed so as to maintain the characteristics of the 7th-order Bessel as a whole. By determining the gain characteristic of the equalizer, the group delay characteristic of the seventh-order Bessel type low-pass filter is determined. When ID information is supplied from the ID detection circuit 19 shown in FIG. 2 to the microcomputer 8 and a predetermined sector number is detected, cutoff frequency control data is output from the microcomputer 8 to the equalizer 4, and the filter cutoff frequency control circuit is output. The frequency for boosting the gain is determined by the control signal from 35, the cutoff frequency of each of the low-pass filters 31 to 34 is controlled, and as a whole the low-pass filter,
The gain characteristic and the group delay characteristic change, that is, are switched, so that the gain characteristic and the group delay characteristic suitable for the frequency of the RF signal according to the reproduction position of the optical disk can be selected. Therefore, by controlling or switching the gain characteristic of the equalizer 4, the RF signal can be reproduced well.

FIG. 4 is a block diagram showing another embodiment of the equalizer characteristic control circuit according to the present invention. In the present embodiment, the error rate is detected, and when the error rate exceeds a predetermined value, a control signal for switching the characteristics of the equalizer is generated from the microcomputer 8 to control the equalizer to maintain a required gain, and The group delay characteristics can be made flat in a required frequency range. In the figure, demodulation circuit 1
7 is supplied to a deinterleave circuit 45, where the data and parity are rearranged so that errors can be corrected.
6. In the error detection circuit 46, if there is an error in the data, an error pulse is output to the counter 46,
This counter 47 counts. The counter 47 is reset by a reset signal from the microcomputer 8 at predetermined time intervals. The output of the counter 47 is supplied to the microcomputer 8. The microcomputer 8 supplies cut-off control data to the equalizer 4 when the number of error pulses exceeds a predetermined number within a predetermined time. However, it is unclear which of the gain characteristics 71 to 73 shown in FIG. Regarding this point, the equalizer information currently in use is taken in, and when the error rate exceeds a predetermined error rate, the characteristics of the equalizer 4 are switched to the next reproduction position, that is, the setting suitable for reproduction at the outer peripheral position. Just do it. In the figure, the output of the error detection circuit 46 is corrected by an error correction circuit 48, then rearranged in an order in which data is reproduced by a descrambling circuit 49, and output to the next-stage interface circuit.

FIG. 5 is a block diagram showing a third embodiment of the optical disk reproducing apparatus provided with the equalizer characteristic control circuit according to the present invention. In this embodiment, the amount of jitter, which is the time lag between the output of the data slicer circuit 5 and the output of the voltage controlled oscillator 52, is measured, and when the absolute value of the amount of jitter exceeds a predetermined amount, the equalizer is used. 4 are switched. The binarized data output from the data slice circuit 5 is supplied to the phase comparison circuit 51 of the PLL circuit 15. The synchronous clock is supplied from the voltage controlled oscillator 52 constituting the PLL circuit 15 to the phase comparison circuit 5.
1 and the phase of the synchronous clock is compared with the phase of the binarized signal from the data slicer circuit 5.

FIG. 6 is a signal waveform diagram for explaining the embodiment of the present invention shown in FIG. In the figure, the binarized signal 6
The phase of the rising edge of the edge detection signal 67 generated from both edges is compared with the phase of the falling edge of the synchronous clock 62. The pulse width of the edge detection signal 67 is equal to a half cycle of the synchronous clock. If the falling edge of the synchronous clock does not exist when the edge detection signal 67 is L, the phase of the synchronous clock 62 is ahead of the phase of the binarized signal 61, and the synchronous clock is shifted from the rising edge of the edge detection signal 67. Until the fall of 62
If a PU signal (charge pump charge pulse) 63 is generated and a falling edge of the synchronous clock exists when the edge detection signal 67 is L, the phase of the synchronous clock 62 is advanced as compared with the binary signal 61. Will be
From the falling edge of the synchronous clock 62, the edge detection signal 67
Until the rise, a PD signal (charge pump discharge pulse) 64 is generated. These PU signal 63 and PD
The signal 64 is supplied to the charge pump circuit 53 of FIG.
The charge / discharge of the charge pump circuit 53 is controlled, and a voltage corresponding to the phase difference is generated at its output. This voltage is supplied to the voltage controlled oscillator 52 through the filter circuit 54, and the phase of the voltage controlled oscillator 52 is controlled so that the phase of the synchronous clock 62 matches the phase of the binary signal 61.

The PU signal 63 and the PD signal 64 extracted from the phase comparison circuit 51 are supplied to a T / V conversion circuit 56 through an OR circuit 55. In this circuit, the PU signal 63 and the PD signal 64 are integrated to form an integrated signal 65, which is then peak-held, and a peak hold voltage 66
Occurs. This voltage indicates the phase difference between the binary signal 61 and the synchronous clock 62. Since the jitter is proportional to the phase difference between the binarized signal and the synchronous clock, the output voltage of the T / V conversion circuit 56 indicates the amount of the jitter. T indicating the amount of jitter
The output of the / V conversion circuit 56 is converted into a digital signal by the A / D conversion circuit 57 and supplied to the microcomputer 8. The microcomputer 8 outputs data for controlling the cutoff frequency for changing the characteristics of the equalizer 4 when the jitter amount exceeds a predetermined amount, as in the case of the error rate. In the case of the jitter amount, similarly to the case of the error rate, control data including the position information of the optical pickup 2 is output from the microcomputer 8.

In the above embodiment, the case where the optical disk recorded by the CLV system is reproduced at the rotation speed of the standard speed on the inner circumference of the CAV system has been described. The present invention can also be applied to a case where reproduction is performed at a multiple of the number or an arbitrary multiple of the number of rotations. In this case, the purpose can be achieved by changing the point at which the gain is raised by increasing the gain characteristic of the equalizer, or by increasing the number of points at which the gain is raised.

[0026]

As described above, in the present invention,
Since the gain characteristic is controlled by a predetermined position between the innermost circumference and the outermost circumference of the optical disk, and the sector number is detected to switch the gain characteristic, the optical disk recorded by the CLV method is reproduced by the CAV method. At this time, the reproduction signal can be correctly binarized, and the group delay characteristic in a required frequency band can be kept flat.
Further, in the present invention, by switching the characteristics of the equalizer based on the error rate or the amount of jitter and the position information of the slider in addition to the sector number, the same effect as in the case of the sector number can be obtained.

[Brief description of the drawings]

FIG. 1 is a characteristic curve diagram of an equalizer used in an optical disk reproducing device including an equalizer characteristic control circuit according to the present invention.

FIG. 2 is a block diagram showing an embodiment of an optical disk reproducing apparatus provided with an equalizer characteristic control circuit according to the present invention.

FIG. 3 is a block diagram showing an embodiment of an equalizer used in an optical disc reproducing apparatus provided with an equalizer characteristic control circuit of the present invention.

FIG. 4 is a block diagram showing an embodiment of an error rate detection circuit used in an optical disk reproducing device provided with an equalizer characteristic control circuit according to the present invention.

FIG. 5 is a block diagram showing an embodiment of a jitter amount detection circuit used in an optical disk reproducing apparatus provided with an equalizer characteristic control circuit according to the present invention.

FIG. 6 is a characteristic curve diagram for explaining FIG. 5;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Optical pickup, 4 ... Equalizer, 5 ... Data slice circuit, 8 ... Microcomputer, 15 ... P
LL circuit, 16: synchronization detection circuit, 17: demodulation circuit, 18
... Sector top detection circuit, 19 ... ID detection circuit, 20 ... Signal processing circuit, 31, 32, 33 ... Secondary low-pass filter circuit, 34 ... Primary low-pass filter circuit, 35, 36,
37, 38: filter cutoff frequency control circuit, 39
... second order differentiation circuit, 40 ... inverting amplifier circuit, 42, 43 ... D
/ A converter, 44 addition circuit, 45 deinterleave circuit, 46 error detection circuit, 47 counter, 48
... Error correction circuit, 49 ... Descramble circuit, 51 ... Phase comparison circuit, 52 ... Voltage controlled oscillator, 53 ... Charge pump circuit, 54 ... LPF, 55 ... OR circuit, 56 ... T /
V conversion circuit, 57 ... A / D converter.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Endo 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Visual Information Media Division, Hitachi, Ltd. (72) Inventor Hiroyuki Tanaka Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa No. 292 In the Visual Information Media Division of Hitachi, Ltd.

Claims (16)

[Claims] 1. An optical disk recorded in a CLV format is read by a CA.
An optical disc reproducing apparatus for reproducing in the V system, comprising: an equalizer for controlling a gain of an RF signal read from an optical pickup; and a cutoff control signal generating circuit for controlling a cutoff frequency of the equalizer, wherein the cutoff control is performed. An optical disc reproducing apparatus provided with an equalizer characteristic control circuit, wherein a cutoff frequency of an equalizer gain characteristic is controlled by a control signal from a signal generation circuit. 2. An optical disc reproducing apparatus provided with an equalizer characteristic control circuit according to claim 1, further comprising a reproducing position detecting means for detecting a reproducing position of the optical disk, wherein said cut-off control signal is generated at a predetermined reproducing position. An optical disc reproducing apparatus provided with an equalizer characteristic control circuit, wherein a cutoff frequency of the equalizer is controlled by changing a control signal from a circuit. 3. An optical disk reproducing apparatus provided with an equalizer characteristic control circuit according to claim 1, further comprising a data error rate detecting means, wherein an error rate is set to a predetermined value by an output from said error rate detecting means. An optical disc reproducing apparatus provided with an equalizer characteristic control circuit, wherein the control signal from the cutoff control signal generating circuit is changed when the frequency exceeds the limit, and the cutoff frequency of the equalizer is switched. 4. An optical disk reproducing apparatus provided with an equalizer characteristic control circuit according to claim 1, further comprising means for detecting a jitter amount of data, wherein the amount of jitter is determined in advance by an output from said jitter amount detecting means. An optical disc reproducing apparatus provided with an equalizer characteristic control circuit, wherein the control signal from the cutoff control signal generating circuit is changed when the frequency exceeds the limit, and the cutoff frequency of the equalizer is switched. 5. An optical disk recorded in the CLV format is read by a CA.
In an optical disc reproducing apparatus for reproducing in the V system, an equalizer for controlling a gain in a frequency band and a cutoff frequency of an RF signal read from an optical pickup, a boost amount control signal generating circuit for controlling a boost amount of the equalizer, and A cutoff control signal generation circuit that controls a cutoff frequency of the equalizer, and controls a boost amount of the gain of the equalizer by a control signal from the boost amount control signal generation circuit; An optical disc reproducing apparatus provided with an equalizer characteristic control circuit, which controls a frequency at which a gain of the equalizer is boosted. 6. An optical disk reproducing apparatus provided with an equalizer characteristic control circuit according to claim 5, wherein a control signal from said boost amount control signal generation circuit is constant even when a cutoff frequency of said equalizer is changed. An optical disc reproducing apparatus provided with an equalizer characteristic control circuit characterized by the above-mentioned. 7. An optical disk reproducing apparatus provided with an equalizer characteristic control circuit according to claim 5, wherein said cutoff control signal generation circuit outputs synchronization information and data from an RF signal and a synchronization clock. A detection circuit, a sector head detection circuit for detecting the head of the sector from the synchronization information, and an ID detection circuit for detecting sector number information from the data by using the sector head detection circuit. An optical disc reproducing apparatus provided with an equalizer characteristic control circuit, wherein a cutoff frequency of an equalizer and a frequency for boosting a gain are controlled by a corresponding cutoff frequency control signal. 8. An optical disk reproducing apparatus provided with an equalizer characteristic control circuit according to claim 5, wherein said cutoff control signal generation circuit includes a deinterleave circuit for rearranging data and parity so that errors can be corrected, And a counter for counting error pulses from the error detection circuit, and controls a cutoff frequency of the equalizer and a frequency for boosting the gain according to a predetermined error rate. An optical disc reproducing apparatus provided with an equalizer characteristic control circuit. 9. An optical disk reproducing apparatus provided with an equalizer characteristic control circuit according to claim 8, wherein said cut-off control signal generating circuit cuts off said equalizer in accordance with a plurality of predetermined reproduction positions of said optical disk. The frequency is controlled to a predetermined value, and when the error rate detected from the error rate detection circuit exceeds a predetermined error rate, a control signal capable of selecting a predetermined cutoff frequency is generated. An optical disc reproducing apparatus provided with an equalizer characteristic control circuit. 10. An optical disk reproducing apparatus provided with an equalizer characteristic control circuit according to claim 5, wherein said cutoff control signal generation circuit includes a data slicer circuit for binarizing an RF signal, and a phase of a synchronous clock of two. A PLL circuit for synchronizing with the digitized data, a jitter amount detection circuit that converts an absolute value of the phase error signal output from the PLL circuit into a voltage, and outputs a voltage corresponding to the absolute value of the phase error signal. An optical disc reproducing apparatus having an equalizer characteristic control circuit, characterized in that the cutoff frequency of the equalizer is controlled according to a predetermined amount of jitter. 11. An optical disk reproducing apparatus provided with an equalizer characteristic control circuit according to claim 10, wherein said cutoff control signal generation circuit cuts off said equalizer in response to a plurality of predetermined reproduction positions of said optical disk. The frequency is controlled to a predetermined value, and a control signal capable of selecting a predetermined cutoff frequency is generated when the amount of jitter detected from the jitter amount detection circuit exceeds a predetermined amount of jitter. An optical disc reproducing apparatus provided with an equalizer characteristic control circuit. 12. An optical disk recorded in the CLV system is
In an optical disc reproducing apparatus for reproducing in an AV system, an equalizer including a plurality of secondary low-pass filters, a second-order differentiating circuit, and an amplifier circuit, a boost amount control signal generating circuit for controlling a boost amount of the equalizer, and the equalizer And a cutoff control signal generation circuit for controlling a cutoff frequency of the cutoff control signal.The control circuit supplies a control signal from the boost amount control signal generation circuit to the amplification circuit to control a gain boost amount. The control signal from the generation circuit is supplied to the second-order differentiation circuit to control the frequency at which the gain is boosted, and the control signal from the cutoff control signal generation circuit is supplied to the second-order low-pass filter to obtain the gain characteristic. An optical disc reproducing apparatus including an equalizer characteristic control circuit for controlling a cutoff frequency. 13. An optical disk reproducing apparatus provided with an equalizer characteristic control circuit according to claim 12, wherein the control signal from said boost amount control signal generation circuit is constant even when the cutoff frequency of said equalizer is changed. An optical disc reproducing apparatus provided with an equalizer characteristic control circuit characterized by the above-mentioned. 14. An optical disk reproducing apparatus provided with an equalizer characteristic control circuit according to claim 12, wherein said cutoff control signal generation circuit includes a synchronization detection circuit for outputting synchronization information and data from an RF signal and a synchronization clock. A sector head detection circuit for detecting the head of a sector from the synchronization information, and an ID detection circuit for detecting sector number information from the data using the sector head detection circuit, according to a predetermined sector number. An optical disc reproducing apparatus provided with an equalizer characteristic control circuit, wherein a cutoff frequency of an equalizer is controlled by a cutoff frequency control signal. 15. An optical disk reproducing apparatus provided with an equalizer characteristic control circuit according to claim 12, wherein said cut-off control signal generation circuit comprises: a deinterleave circuit for rearranging data and parity so that errors can be corrected; And a counter for counting the number of error pulses from the error detection circuit, and controlling a cutoff frequency of the equalizer according to a predetermined error rate. An optical disc reproducing device provided with a circuit. 16. An optical disk reproducing apparatus provided with an equalizer characteristic control circuit according to claim 12, wherein said cut-off control signal generation circuit includes a data slicer circuit for binarizing an RF signal, and a phase of a synchronization clock of two. A PLL circuit for synchronizing with the digitized data, and a T / V converter for converting a pulse width of a charge pump charge pulse and a charge pump discharge pulse output from the PLL circuit into a voltage and outputting a voltage corresponding to a jitter amount. An optical disc reproducing apparatus comprising an equalizer characteristic control circuit, comprising: a circuit for controlling a cutoff frequency of the equalizer according to a predetermined amount of jitter.