JP2001243714A - Optical disk drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve seek to an unrecorded area and address detection accuracy when subsequent pulling is caused to flow after the seek and to accelerate a pulling operation by calculating a channel period from the time in which a light spot passes an address area and setting an equalizer circuit for address detection to an optimum value in accordance with the calculated channel period in the case of reproducing an optical disk where address information is intermittently recorded at constant angular velocity(CAV). SOLUTION: The start and the end of an address area are detected, and an address area pulse in generated and counted by a reference clock. When the counted value is divided by 2048, the current channel clock frequency can be detected, and the cut-off frequency of the equalizer circuit and the detection center frequency of a wobble detection circuit are set by using the value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk drive, and more particularly to a constant angular velocity reproduction (Constant) of a recordable optical disk on which address information is intermittently recorded.
In the case of ant angular velocity reproduction (hereinafter, referred to as “CAV reproduction”), a signal processing means capable of accurately detecting an address immediately after a seek even in an unrecorded area is characterized.

[0002]

2. Description of the Related Art In recent years, with the advent of digital versatile discs (hereinafter referred to as "DVDs"), large-capacity optical disc apparatuses have started to attract attention, and not only read-only disc apparatuses but also recordable optical discs ( The following "DVD-RA
M ”. Competition for the development of disk devices for) is also intensifying. Therefore, first, the configuration of the address detection circuit in the disk device for DVD-RAM reproduction will be described.

FIG. 8 is a block diagram of an address detection circuit in a conventional disk device for DVD-RAM reproduction. In FIG. 8, reference numeral 101 denotes an optical disk having a thin film of a phase-change recording material, in which tracks are formed in a spiral or concentric shape at a predetermined interval. Reference numeral 102 denotes a spindle motor for rotating the optical disk 101 at a predetermined linear velocity. Reference numeral 104 denotes an optical pickup, which includes a four-segment photodetector 105 for detecting a tracking error signal, a two-segment photodetector 106 for detecting a focus error signal, and an actuator 103 for focusing a light spot and scanning the track. . As shown, the four-divided photodetector 105 is divided into four regions a to d by a track direction axis and an axis perpendicular to the axis. Then, the signals of a to d divided into four are processed to detect a tracking error signal. 107, 108, 109, 11
Reference numeral 0 denotes an I / V converter for performing current-voltage conversion of a detection current output from the four-divided detector 105;
Reference numerals 3 and 114 denote I / V converters for current-to-voltage conversion of the detection current output from the two-divided detector 106. Reference numerals 111 and 112 denote adders for adding signals of two regions parallel to the track direction of the four-divided photodetector 105 in order to obtain a push-pull tracking error signal. And the adder 111 adds the signals of the area a and the area b, respectively. Reference numeral 115 denotes an adder for adding the outputs of the I / V converters 113 and 114 and the outputs of the adders 111 and 112.
And a total addition RF signal obtained by adding all the optical signals received by the two-divided photodetector 106.

The output of the adder 115 is the peak value detection circuit 1
16 and the bottom value detection circuit 117, and the peak value detection circuit 116 outputs a continuous peak value of the full addition RF signal, while the bottom value detection circuit 117 outputs a continuous bottom value of the full addition RF signal. Is output.

Reference numeral 118 denotes a circuit for calculating an envelope signal (RFENV) of the total addition RF signal from the signals output from the peak value detection circuit 116 and the bottom value detection circuit 117. The envelope signal (RFENV) is sent to the controller 130. Is entered. 119 is a voltage control type gain control amplifier, 120 is an equalizer, 122 is an offset canceller for removing an offset from the output of the equalizer 120, and 121 is an offset canceler 1
22 is a control voltage generator for controlling the voltage control type gain control amplifier 119 using the envelope detected from the output of the control signal 22 and the voltage control type gain control amplifier 119 or the offset canceller 122
AGC circuit is configured by a loop configured by
The control is performed so that the signal voltage amplitude output from the signal 20 becomes a predetermined value. Reference numeral 123 denotes a data slice circuit for binarizing the output of the equalizer 120. The binarized data is input to the controller 130 and demodulated. 124
Is a balance adjustment circuit for changing the combined balance of the outputs of the adders 111 and 112, and 125 is a differential amplifier for generating a push-pull signal from the output adjusted by the balance adjustment circuit 124.

[0006] Since the push-pull signal (TEDIF) output from the differential amplifier 125 contains high frequency components, the LPF 12 is controlled so that it can be handled in the servo band.
6 to detect only the low frequency component, and the controller 130
Is input as a push-pull tracking error signal (TEPP). The balance adjustment circuit 124 is adjusted by the controller 130 while observing the waveform of the push-pull tracking error signal (TEPP) while controlling the control signal (TBAL).
PP).

The push-pull signal (TEDIF) is also input to an equalizer 128 and a wobble detector 129. The equalizer 128 equalizes the waveform so that the address can be easily detected, and then inputs the same to an address detector 127. The wobble detector 129 detects a wobble signal (WBL) carved along the track of the optical disc 101 and outputs a binarized signal to the controller 130. 1
Reference numeral 32 denotes a traverse driving circuit for a traverse mechanism (not shown) for moving the optical pickup 104 along an axis substantially perpendicular to the track direction axis. Reference numeral 131 denotes an actuator drive circuit for controlling the actuator 103 so that the light spot is focused and scanned on a track.

Next, details of the address detection section 127 will be described with reference to FIG.
This will be described with reference to FIG. In FIG. 9, reference numerals 201 and 202 denote comparators, which binarize an address signal (TEDIF) with respect to respective threshold values. An OR gate 204 adds the outputs of the comparators 201 and 202. Reference numerals 203 and 205 denote retriggerable mono-multis, a function of receiving pulses from the comparators 201 and 202 and outputting a pulse for an appropriate time, and a function of outputting a pulse again from the time when a trigger input is received during pulse output. And 206 and 209 are current sources; 207 and 208 are analog switches;
6, 207, 208, and 209 constitute a charge pump circuit. Reference numeral 210 denotes an analog switch that opens and closes according to an address gate signal. The analog switch 210 charges and discharges the capacitor 111 when the address gate signal is “H”. Reference numeral 212 denotes an inverter, and the comparator 20
The voltage obtained by inverting the threshold voltage of
It is given as a threshold voltage to 1.

The operation of reproducing the DVD-RAM by the tracking control circuit configured as described above will be briefly described. First, a track format of a DVD-RAM will be briefly described. A track is composed of a land and a groove. Here, the land is a concave track when viewed from the laser light incident surface, and the groove is a convex track when viewed from the laser light incident surface. The land track and the groove track are alternately connected at a fixed position every one turn. Meanwhile, one track is formed from the inner circumference to the outer circumference. Also, the groove depth between the land and the groove should be set to (laser wavelength /
6). Since the land track and the groove track have different phase shifts of the reflected light, the light spot received by the four-divided photodetector 105 is symmetric with respect to the track axis, so that the polarity of the push-pull tracking error signal is inverted.

[0010] The disk is divided into a plurality of zones, and sectors are provided for each round of the disk by the number unique to each zone (here, "n"). A sector is composed of an address area for forming an address when a disc is created, and a recording area in which a user can record data. As shown in FIG. 10, in the groove,
At the portion where the (m-1) sector is switched to the (m) sector, the address of the (m) sector behind the header portion is valid, and in the land, (m + n-
In the portion where the sector 1) is switched to the sector (m + n), the address of the sector (m + n) in front of the header portion is valid.

FIG. 11 shows a push-pull tracking error signal when a light spot moves on a land track or a groove track and an input / output signal to the address detection section 127. When the upper part is reproduced and the land track is reproduced, the waveform passing through the header area is vertically symmetrical, and the phase between CPDET1 and CPDET2 is reversed.

Here, the reproduction of the address area will be briefly described. When the TEDIF signal including the address signal is input to the comparators 201 and 202, the comparator 201
Is binarized using a threshold (−) as a threshold voltage, and the comparator 202 uses a threshold (+) as a threshold voltage. Here, the threshold value (-) is a voltage obtained by inverting the threshold value (+) by the inverter 212 with reference to the reference voltage. Therefore, the threshold value (-) and the threshold value (+) are the reference voltage. Are symmetrical with respect to.

In FIG. 12, an upper address obtained by binarizing the upper side of the reference voltage of the TEDIF signal is an upper address.
The lower address is the lower address, and the lower address is added by the OR gate 204 to obtain the CAPA.
The lower address is input to the mono multi 203 as a trigger signal, the mono multi 203 outputs a lower address detection signal, the upper address is input to the mono multi 205 as a trigger signal, and the mono multi 205 is an upper address detection signal. Is output. The lower address detection signal and the upper address detection signal are added by the controller and used as an IDGT signal for identifying a header field, as a gate signal of the analog switch 210.

The CAPA is an input signal of a charge pump constituted by the current sources 206 and 209 and the analog switches 207 and 208. When the address gate signal is "H" and the analog switch 210 is turned on, the binary address signal "CAPA" is output. The charging current flows into the capacitor 211 during the “H” period, and the discharging current flows from the capacitor 211 during the “L” period of the binary address signal. With this configuration, the capacitor 211 is charged / discharged only during the header field period. Therefore, the threshold value (−) is set so that the pulse duty of the binary address signal gated by the address gate signal is set to 50%. , The threshold value (+) is fed back, so that the address detection accuracy is improved and accurate binarization is possible.

[0015] The controller 130 detects the address information from the CAPA, thereby ascertaining the exact position of the light spot. Further, using the detected address information, the number of remaining sectors up to the land / groove switching point is calculated as an expected value. This calculation is performed every time the address is read normally. In accordance with the expected value, a land / groove switching signal for switching the tracking polarity at the land / groove switching point is supplied to the tracking control circuit to switch the polarity. In this way, the DVD-RAM alternately reproduces the address area and the recording area while switching the polarity of the push-pull tracking error signal between the land track and the groove track every round.

[0016]

However, according to the prior art, if a large flow occurs after a seek failure to an unrecorded area during constant angular velocity reproduction (CAV reproduction), the characteristics of the equalizer circuit must be determined in order to perform address detection. In order to optimize, the tap switching operation must be sequentially tried to detect the optimal set value, and to detect the wobble signal,
The switching operation of the center frequency of the detection band-pass filter must be sequentially tried to detect the optimum set value, so that it has a disadvantage that the address detection operation takes time.

That is, a DVD-RAM disk has a mixture of a recording area and an unrecorded area, and naturally seeks to the recording area at the time of reproduction. Since the PLL cannot be locked by RF, it is necessary to set an optimum equalizer for the address signal only by the signal of the address section. The address part is pre-pitted intermittently,
If the setting is performed using only the signals in this portion, the adjustment in a short time is performed intermittently, and as a result, it takes time to detect the address.

If the address cannot be read, the optical disk device cannot not only calculate the expected value of the land / groove switching point, but also output a switching signal at an erroneous point.
Land / groove cannot be switched smoothly,
In the worst case, the state in which tracking is lost is repeated, and reproduction becomes impossible.

[0019]

According to a first aspect of the present invention, there is provided an optical disk apparatus for holding an optical disk having address information intermittently recorded on an information recording surface. Holding means, disk rotation control means for rotating the optical disk, laser light generating means for generating laser light, and converging the laser light generated by the laser light generating means on the information recording surface of the optical disk to form a light spot. A light spot forming means for forming, a photodetector for detecting reflected light of the light spot, a reproduction signal detection means for detecting a reproduction RF signal from an optical signal received by the photodetector, and a voltage amplitude of the reproduction RF signal being a predetermined value. Voltage gain control means for controlling the voltage amplitude so that the voltage amplitude is controlled to a predetermined value by the voltage gain control means. Equalizing means capable of changing the frequency characteristic of the RF signal after in-control, data slicing means for binarizing the RF signal after waveform equalization output from the equalizing means, and a low frequency of the reproduced RF signal RF envelope detecting means for detecting components, wobble detecting means for detecting undulation of a track from an optical signal received by the photodetector, a positional deviation amount between the light spot and the center of the track, a track direction axis and this axis. A push-pull tracking error detecting means for detecting by comparing the addition result of two areas parallel to the track direction among the areas of the photodetector divided into four by an axis perpendicular to the axis; Tracking control amount detecting means for obtaining a tracking control amount, Tracking control means for controlling the light spot in the direction of the track center based on the control amount of the laser, and an optical pickup comprising the laser light generating means, the light spot forming means and the photodetector, substantially perpendicular to the track direction axis. In an optical disc apparatus having traverse control means for moving in an axial direction intersecting with the light source and address detection means for extracting an address signal from a reproduction signal obtained from reflected light of the light spot, a cutoff frequency and a boost amount of the equalizer means Equalizer setting means for changing the address area passing signal detecting means for detecting a state where the light spot passes through the address area; and a pulse number for measuring the address area passing signal with a reference pulse to obtain the address passing period pulse number. Detecting means, and the address passing period pal Means for calculating the channel clock frequency from the
Wherein the set value of the equalizer setting means is changed in accordance with the value of the channel clock frequency.

According to a second aspect of the present invention, in the optical disk device of the first aspect, the setting value of the equalizer setting means is set to a length of time for which the light spot passes through the address area. Correspondingly, so that the minimum data frequency read from the optical disc is the cutoff frequency of the equalizer setting means,
Change.

According to a third aspect of the present invention, in the optical disk device of the first aspect, the pulse number detecting means counts the number of pulses counted at each end timing of the pulse detected by the address area detecting means. Is reset after storing.

According to a fourth aspect of the present invention, in the optical disk device of the first aspect, the channel clock frequency calculating means is configured to output one of the reference pulses.
A value obtained by dividing a product of a cycle time and the pulse value of the address passing period by a predetermined value is defined as a one-channel clock cycle time.

According to a fifth aspect of the present invention, there is provided an optical disk apparatus comprising: an optical disk holding unit that holds an optical disk having address information intermittently recorded on an information recording surface; and a disk rotation control unit that rotates the optical disk. Laser light generating means for generating laser light, light spot forming means for converging the laser light generated by the laser light generating means on the information recording surface of the optical disc to form a light spot, and reflected light of the light spot A photodetector for detecting a signal, a reproduction signal detection means for detecting a reproduction RF signal from an optical signal received by the photodetector,
Voltage gain control means for controlling the voltage amplitude of the reproduced RF signal to a predetermined value; and frequency characteristics of the RF signal after gain control in which the voltage amplitude is controlled to a predetermined value by the voltage gain control means. Equalizer means,
Data slicing means for binarizing an RF signal after waveform equalization output from the equalizer means, RF envelope detecting means for detecting a low frequency component of the reproduced RF signal, and tracking from an optical signal received by the photodetector A wobble detecting means for detecting undulation, and the position difference between the light spot and the track center is divided into four parts by a track direction axis and an axis perpendicular to the track direction. Push-pull tracking error detection means for comparing and detecting the result of addition of two areas parallel to each other, tracking control amount detection means for obtaining a tracking control amount according to the positional deviation amount, and based on the tracking control amount. Tracking control means for controlling the light spot in the track center direction Traverse control means for moving an optical pickup, comprising the laser light generating means, the light spot forming means, and the photodetector, in an axial direction substantially perpendicular to the track direction axis, and reflecting the light spot. An optical disc device having address detection means for extracting an address signal from a reproduction signal obtained from light; an address area passage signal detection means for detecting a state in which the light spot passes through an address area; A number-of-pulses detecting means for measuring an address passing period pulse value by measuring with a reference pulse, and a channel clock frequency calculating means for calculating a channel clock frequency from the address passing period pulse value; Corresponding to the detection center frequency of the wobble detection means Was set to be changed, characterized in that.

According to a sixth aspect of the present invention, in the optical disk device of the fifth aspect, the wobble detecting means is constituted by at least one or more high-pass filter means or low-pass filter means,
The cut-off frequency of the high-pass filter means or the low-pass filter means is independently changed.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. The first embodiment of the present invention corresponds to the first, second, third, and fourth aspects of the present invention. By the operation of the above means, the address area passing signal is used as a reference in the case of CAV reproduction. Measure the pulse to determine the transit time, divide this by the number of channel bits in the address area specified by the disc standard to determine the channel period, and optimize the equalizer cutoff frequency and boost amount according to this value. Set to a value. As a result, the address detection speed can be increased even in an unrecorded area.

According to a second embodiment of the present invention,
According to the sixth aspect of the present invention, by the operation of the above means, CA
In the case of V reproduction, the passage time is obtained by measuring the address area passing signal with a reference pulse, and this is divided by the number of channel bits of the address area defined by the disc standard to obtain the channel period. To set the center frequency of the wobble detection circuit to an optimum value. As a result, the wobble detection speed can be increased. Note that the embodiment shown here is merely an example, and is not necessarily limited to this embodiment.

(Embodiment 1) An optical disk device according to a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram of the address detection circuit according to the first embodiment. In FIG. 1, reference numeral 1 denotes an optical disk having a thin film of a phase-change recording material, in which tracks are spirally or concentrically formed at predetermined intervals. Reference numeral 2 denotes a spindle motor for rotating the optical disk 1 at a predetermined linear speed.

Reference numeral 4 denotes an optical pickup, which includes a four-part photodetector 5 for detecting a tracking error signal, a two-part photodetector 6 for detecting a focus error signal, and an actuator 3 for scanning a track by focusing a light spot. I have it. As shown, the four-divided photodetector 5 is divided into four regions a to d by a track direction axis and an axis perpendicular to this axis. Then, the signals of a to d divided into four are processed to detect a tracking error signal. 7, 8,
Reference numerals 9 and 10 denote I / V converters for current-to-voltage conversion of the detection current output from the quadrant detector 5, and 1
Reference numerals 3 and 14 are I / V converters for current-voltage conversion of the detection current output from the two-divided detector 6.

Numerals 11 and 12 denote adders for adding signals in two areas parallel to the track direction of the four-divided photodetector 5 in order to obtain a push-pull tracking error signal. The signal of d
The adder 111 adds the signals of the area a and the area b, respectively. Reference numeral 15 denotes an adder for adding the outputs of the I / V converters 13 and 14 and the outputs of the adders 11 and 12, whereby an optical signal received by the 4-split photodetector 5 and the 2-split photodetector 6 is Fully added RF with all added
Get the signal. The output of the adder 15 is a peak value detection circuit 16
And the bottom value detection circuit 17, the peak value detection circuit 16 outputs a continuous peak value of the full addition RF signal, while the bottom value detection circuit 17 outputs a continuous bottom value of the full addition RF signal Is done.

Numeral 18 is for calculating the envelope signal (RFENV) of the total addition RF signal from the signals output from the peak value detection circuit 16 and the bottom value detection circuit 17, and the envelope signal (RFENV) is sent to the controller 30. Is entered. 19 is a voltage control type gain control amplifier, 20 is an equalizer, 22 is an offset canceller for removing an offset from the output of the equalizer 20, and 21 is a voltage control type gain control amplifier 19 using an envelope detected from the output of the offset canceler 22. Is a control voltage generator for controlling the voltage control type gain control amplifier 19 or an offset canceller 22 in a loop.
A GC circuit is configured to perform control so that the signal voltage amplitude output from the equalizer 20 becomes a predetermined value.

Reference numeral 23 denotes a data slice circuit for binarizing the output of the equalizer 20, and the binarized data is input to the controller 30 and demodulated. Reference numeral 24 denotes a balance adjustment circuit for changing the combined balance of the outputs of the adders 11 and 12, and reference numeral 25 denotes a differential amplifier for calculating a push-pull signal from the output adjusted by the balance adjustment circuit 24. Since the push-pull signal (TEDIF) output from the differential amplifier 25 contains a high-frequency component, the LPF 26 can be handled in the servo band.
Only the low-frequency component is detected, and is input to the controller 30 as a push-pull tracking error signal (TEPP). The controller 30 adjusts the balance adjustment circuit 24 by a push-pull tracking error signal (TEP).
This is performed by the control signal (TBALPP) while observing the waveform P).

The push-pull signal (TEDIF) is also input to an equalizer 28 and a wobble detector 29. After the equalizer 28 performs waveform equalization so as to improve the address detection performance, the signal is input to an address detector 27. The wobble detector 29 detects a wobble signal (WBL) carved along the track of the optical disc 1 and outputs a binarized signal to the controller 30. Reference numeral 31 denotes a traverse drive circuit for a traverse mechanism (not shown) for moving the optical pickup 4 along an axis substantially perpendicular to the track direction axis. Reference numeral 32 denotes an actuator drive circuit for controlling the actuator 3 so that the light spot is focused and scanned on a track. Address detector 2
7 is the same as the operation of the address detection unit 127 described in the conventional example.

FIG. 2 is a block diagram showing the internal configuration of the address area detecting section 33. In the figure, 304, 30
Reference numerals 5 and 306 denote AND circuits for generating timing signals using the signals of the shift register constituted by 301, 302 and 303. A signal obtained by adding the CPDET1 signal and the CPDET2 signal by the OR circuit 310 is input to the input of the shift register. Reference numeral 307 denotes a set / reset circuit which is set at the output of the AND circuit 304 to make the output “H”, and reset by the output of the AND circuit 306 to make the output “L”. Reference numeral 308 denotes a counter that counts the pulses of the clock terminal, and reference numeral 309 denotes a latch circuit that captures and holds the count value of the counter 308. CLK1 signal is C
The speed is set to about several tens of MHz at a speed sufficient to count the pulse widths of PDET1 and CPDET2.

The operation of the optical disk device according to the first embodiment configured as described above, when the light spot scans a groove track, will be briefly described with reference to FIGS. I do. As shown in FIG. 3, at the point where the light spot enters the address area, the rising edge of the output signal of the OR circuit 310 for generating the logical OR signal of CPDET1 and CPDET2 is detected, and the set / reset circuit 307 is detected by the start signal.
Is set and the clear terminal of the counter 308 is set to “H” to start the counting operation. At the point where the light spot completes passing through the address area, CPDET1 and CPDET
When the falling edge of the logical sum signal of ET2 is detected,
A latch signal is generated to latch the count value of the counter 308. After the latch, the set / reset circuit 307 is reset by the clear signal, and the clear terminal of the counter 308 is set to "L" to initialize. Since this operation is performed every time the light spot passes through the address area, the count value latched by the latch signal is the time when the light spot passes through the address area. The controller 30 also detects the fall of the logical sum signal of CPDET1 and CPDET2, and sets ADR_
The count value is read using the TME signal line.

Next, a method of setting the equalizer 28 to an optimum value using the address area transit time will be described. The characteristics of the equalizer 28 can be changed by a control signal from the controller 30, and the cutoff frequency is changed by the FC2 signal, and the boost amount is changed by the BOOST2 signal.

FIG. 4 shows the data format of the address area.
This figure shows the number of bytes in each area.
You. VFO1 and VFO2 are composed of 4T signal patterns.
With this signal, the bit clock for PLL lock is
Generate. AM (Address Mark) is the address mark signal
No., and found the beginning of PID (Physical ID)
This is a synchronizing signal. PID1 to 4 are 4 bytes each
Information, the first byte is sector information and the remaining 3 bytes
Is the sector number, which is 8-16 modulated.
Recorded. IED1-4 are each PID
Is an error detection code. PA1 and PA2 are PA direct
This is for recognizing the demodulation state of the previous data.
You. As shown in FIG. 4, the total number of bytes in the address area is 1
It is 28 bytes. One byte is 16 channel bits.
Therefore, the address area consists of 2048 channel bits
It will be. Here, the address area transit time
To T _adr(Sec) One channel bit time is T_ch(S
If ec), the following relationship is established. T_ch = T_adr÷ 2048 (sec)… (1) T_chFirst, the cutoff frequency of the equalizer 28
Is calculated. Cutoff frequency is 3 of channel clock
To set the 3T signal frequency, which is the period,
It is calculated using the formula. Fc = 1１ {((T_ch{3)} 2} (Hz) ... (2)

Next, the configuration of the equalizer 28 will be described, and a method of changing the cutoff frequency will be described. FIG.
(A) is a configuration example of the equalizer 28, and 401 and 40.
3 and 404 are secondary low-pass filters, 405 is a primary low-pass filter, 402 is a secondary high-pass filter, 406
Is an adder, and 407 is a multiplier. These constitute a 7th-order equiripple filter.

First, the operation of the secondary low-pass filter will be described with reference to FIG. 501 and 502 are + terminals and-
This shows a transconductance amplifier in which an output current changes according to a voltage difference between terminals, and 503 and 504 are capacitors. Assuming that the gains of the transconductance amplifiers 501 and 502 are gm, the output of the transconductance amplifier 501 is V11, the current flowing through the capacitor 503 is i ₁ , and the current flowing through the capacitor 504 is i ₂ , the following equation is established. _{i 2 = (V 11 -V 2} ) gm ... (3) V 2 = i 2 / sC 2 ... (4) i 1 = (V 1 -V 2) gm ... (5) V 11 = i 1 / sC 1 … (6)

When the transfer functions of V ₂ / V ₁ are obtained by solving the equations (3) to (6), the following is obtained.

V ₂ / V ₁ = (gm ² / C ₁ C ₂ ) / {s ² + sgm / C ₂ + gm ² / C ₁ C ₂ } (7)

The standard transfer function of the second-order low-pass filter can be expressed by the following equation, where ωn is the resonance angular frequency, Q is the resonance peak value, and G ₀ is the gain constant. _{H (s) = G 0 ·} ωn 2 / {s 2 + s (ωn / Q) + ωn 2} ... (8) (7) As can be seen by comparing equation (8), the resonance by changing the gm The angular frequency can be changed, thus changing the cutoff frequency.
Generally, transconductance amplifiers 501, 502
Is composed of a differential amplifier using two transistors. As an example of changing the gain, a method of linearly changing the current source of the differential amplifier by the FC2 signal from the controller 30 is used. Thus, when the current value of the current source is increased by N times, the gain is increased by N times.
The cutoff frequency can be changed by the signal.

FIG. 5D shows a configuration example in which the current source is switched by giving FC2 as a digital value. 512, 5
13, 514, 515 are current sources, 516, 517, 51
8, 519 are switches, 520 is a data latch,
The current sources are weighted by powers of two. Now, when the digital signal of N bits are inputted to the FC2 signals, all switches corresponding to the bits of the output of the data latch 520 "1" is set is turned ON so as to generate an I ₀ cage, using the I ₀ as a current source of the aforementioned differential amplifier. Therefore, depending on the input digital value,
The current source can be controlled almost linearly.

Next, the operation of the equalizer circuit composed of the low-pass filter 401, the high-pass filter 402, and the integrator 407 will be described with reference to FIG. 50
5, 506 and 507 indicate transconductance amplifiers, and 509, 510 and 511 are capacitors.
When obtaining the transfer function of the IN and V ₁ of the FIG. 5 (c), the expressed by the following equation. V ₁ / IN = (gm ² −s ² KC ₃ C ₄ ) / {s ² C ₃ C ₄ + sC ₃ gm + gm ² } (9)

As can be seen from equation (9), the characteristic is a combination of a high-pass filter and a low-pass filter. As is clear from this equation, changing gm can change the frequency characteristics. As described above, the current source of the differential amplifier constituting the transconductance amplifier can be changed linearly by the FC2 signal from the controller 30, and the cutoff frequency can be changed.

Next, the boost amount is set.
The setting of the boost amount can be realized by changing K in the equation (9). That is, the BOOS from the controller 30
What is necessary is just to change the gain of the multiplier 508 by the T2 signal. In the first embodiment, the appropriate value of the boost amount is obtained in advance by an experiment, and stored in the controller 30 as a table value corresponding to the cutoff frequency. After calculating the cutoff frequency, the controller 30 searches the table and changes the BOOST2 signal so that the optimum boost value can be set.

In such an optical disk device according to the first embodiment, in the case of CAV reproduction of a DVD-RAM, a transit time is obtained by measuring a pass signal of an address area with a reference pulse, and the transit time is determined by the DVD-RAM standard. The channel period is obtained by dividing by the number of channel bits in the predetermined address area, and the cutoff frequency and the boost amount of the equalizer are set to optimal values in accordance with this value. By optimizing the setting value of the equalizer circuit in the area as described above, the address detection speed can be increased, and the effect of increasing the pull-in operation can be obtained.

(Embodiment 2) An optical disk apparatus according to Embodiment 2 of the present invention will be described with reference to the drawings. An object of the second embodiment is to quickly set the center frequency of the wobble detection circuit to an optimum value after a seek or after a tracking flow during CAV reproduction to increase the wobble detection speed.

FIG. 6 is a block diagram of an address detection circuit according to the second embodiment. The hardware shown in FIG. 6 is almost the same as the configuration shown in FIG.
9A is different in that it has a configuration in which the detection center frequency can be adjusted. Address area transit time _Tadr (s
ec) measures the one channel bit time T _{c h} (se
The process is the same as that of the first embodiment until c) is obtained by using the expression (1).

When T _ch is known, the detection center frequency of the wobble detector 29 is calculated. The wobble frequency when the DVD-RAM is reproduced at 1 × speed is about 158 (KHz), and this frequency changes according to the reproduction speed. The 1x 1 channel bit time for reproduction to calculate the set frequency by the T _{RE F} (10) equation. _{FCNT = (T ch ÷ T REF} ) × 158 (KHz) ... (10)

FIG. 7 shows an example of the wobble detection circuit. The detection circuit is constituted by a band-pass filter, and the detection center frequency can be changed by setting from the controller 30. The band-pass filter has a configuration in which a second-order high-pass filter and a second-order low-pass filter are connected in series, and the transconductance amplifiers 601 and 602 and the capacitors 605 and 606 form the second-order high-pass filter and the transconductance amplifier 60
3, 604 and capacitors 607, 608 constitute a secondary low-pass filter. 609 is a buffer,
It is inserted between the first and second stage filters. The operation of the secondary low-pass filter is the same as that shown in FIG.

The secondary high-pass filter has two stages of primary high-pass filters connected in series. First, a primary high-pass filter composed of a transconductance amplifier 601 and a capacitor 605 will be described. The following equation is established assuming that the output current of the transconductance amplifier 601 is i. i = (V ₆₁ −V _ref ) gm (11) V ₆₀ −V ₆₁ = i / sC ₆ (12)

When the transfer function is obtained from the equations (11) and (12), the following is obtained. V ₆₁ / V ₆₀ = sC ₆ / (sC ₆ + gm) (13)

When the transfer function of the secondary high-pass filter is obtained in consideration of the equation (13), the following is obtained. V ₆₂ / V ₆₀ = s ² C ₆ C ₇ / {s ² C ₆ C ₇ + s (C ₆ + C ₇ ) gm + gm ² } (14) The standard transfer function of the secondary high-pass filter has a resonance angular frequency of ωn, Assuming that the resonance peak value is Q and the gain constant is G ₀ ,
It can be expressed by the following equation. H (s) = G ₀ · s ² / {s ² + s (ωn / Q) + ωn ² } (15) As apparent from comparison of equations (14) and (15), gm
Can be changed to change the resonance angular frequency, and thus the cutoff frequency of the high-pass filter.

The gain is changed by the FC from the controller 30 as in the low-pass filter of the first embodiment.
A method is used in which the current source of the differential amplifier is changed linearly by the ON signal. Thus, when the current value of the current source is increased by N times, the gain is increased by N times, so that the cutoff frequency can be changed by the FCON signal. FCO
The setting method using the N signal is the same as the FC signal described in the first embodiment.
The description is omitted because it is the same as the setting method using two signals.

In general, the cutoff frequency of the high-pass filter is slightly lowered from the detection center frequency obtained by the equation (10), and the cutoff frequency of the low-pass filter is set to the detection center frequency obtained by the equation (10). Increase the frequency slightly upward. As a result, it is possible to prevent the gain from decreasing at the detection center frequency.

In the case of a DVD-RAM, the recording area is divided into zones, and each zone has a zone CLV for CAV reproduction.
(ZCLV) method. Therefore, the process of optimizing the detection center frequency of the wobble detection circuit may be performed at least in units of zones.

In the optical disk device according to the second embodiment, when performing CAV reproduction of a DVD-RAM,
The transit time is obtained by measuring the address area passing signal with a reference pulse, and this is divided by the number of channel bits in the address area defined by the DVD-RAM standard to obtain a channel period. Wobble detection is performed in accordance with this value. By setting the center frequency of the circuit to the optimum value, the detection center frequency of the wobble detection circuit can be optimized,
Address detection can be performed quickly, and the pull-in operation can be performed quickly.

[0058]

As described above, according to the optical disk apparatus of the first aspect of the present invention, in the case of the CAV reproduction of the DVD-RAM, the passing time is obtained by measuring the address area passing signal with the reference pulse. Is divided by the number of channel bits in the address area defined by the DVD-RAM standard to obtain the channel period, and the cutoff frequency and the boost amount of the equalizer are set to optimal values in accordance with this value. As a result, the address detection speed can be increased even in an unrecorded area.

Further, according to the optical disk apparatus of the present invention, in the case of CAV reproduction of a DVD-RAM,
The transit time is obtained by measuring the address area passing signal with a reference pulse, and this is divided by the number of channel bits in the address area defined by the DVD-RAM standard to obtain a channel period. Wobble detection is performed in accordance with this value. Since the center frequency of the circuit is set to the optimum value, the wobble detection speed can be increased even in the case of a flow after seek or in an unrecorded area. As a result, the address detection speed can be increased.

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical disc device according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating an internal configuration of an address area detection unit according to the first embodiment of the present invention.

FIG. 3 is a timing chart illustrating an operation of an address area detection unit according to the first embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of an address area of the DVD-RAM.

FIG. 5 is a block diagram illustrating an operation of the equalizer circuit according to the first embodiment of the present invention.

FIG. 6 is a block diagram of an optical disc device according to a second embodiment of the present invention.

FIG. 7 is a block diagram of a wobble detection circuit in an operation according to the second embodiment of the present invention;

FIG. 8 is a block diagram of a conventional example.

FIG. 9 is a block diagram of an address detection unit.

FIG. 10 is a block diagram showing the relationship between lands and grooves.

FIG. 11 is a timing chart showing an operation of a block diagram of a conventional example.

FIG. 12 is a timing chart showing the operation of the conventional address detection unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical disk 2 ... Spindle motor 3 ... Actuator 4 ... Optical pick-up 5 ... 4-split photodetector 6 ... 2-split photodetector 7, 8, 9, 10, 13, 14 ... I / V converters 11, 12, 15 ... adder 16 ... peak value detection circuit 17 ... bottom value detection circuit 18, 25 ... differential amplifier 19 ... voltage control type gain control amplifier 20, 28: Equalizer 21: Control voltage generator 22: Offset canceller 23: Data slice circuit 24: Balance adjuster 26: LPF 27: Address detector 29 ..Wobble detector 30 Controller 31 Traverse drive circuit 32 Actuator drive circuit 33 Address area detector

Claims (6)

[Claims] 1. An optical disk holding means for holding at least an optical disk on which address information is intermittently recorded on an information recording surface; a disk rotation control means for rotating the optical disk; and a laser light generating means for generating a laser light A light spot forming means for forming a light spot by converging a laser light generated by the laser light generating means on an information recording surface of the optical disc; a photodetector detecting reflected light of the light spot; and receiving light by the photodetector. Reproduction signal detection means for detecting a reproduction RF signal from the obtained optical signal, voltage gain control means for controlling the voltage amplitude of the reproduction RF signal to a predetermined value, and setting the voltage amplitude to a predetermined value by the voltage gain control means. Equalizer means capable of changing the frequency characteristic of the RF signal after controlled gain control; Data slicing means for binarizing the RF signal after waveform equalization output from the equalizer means, RF envelope detecting means for detecting a low frequency component of the reproduced RF signal, and a track from the optical signal received by the photodetector. A wobble detecting means for detecting undulation; and, in the track direction, of the photodetector region obtained by dividing the amount of displacement between the light spot and the track center into four by a track direction axis and an axis perpendicular to the axis. A push-pull tracking error detecting means for comparing and detecting an addition result of two areas parallel to each other; a tracking control amount detecting means for obtaining a tracking control amount according to the positional deviation amount; Tracking control means for controlling the light spot in the direction of the track center A step, the laser light generating means, the light spot forming means,
Traverse control means for moving an optical pickup constituted by the photodetector in an axis direction substantially perpendicular to the track direction axis; address detection means for extracting an address signal from a reproduction signal obtained from reflected light of the light spot An optical disc device having: a cutoff frequency of the equalizer means, an equalizer setting means for changing a boost amount, an address area passing signal detecting means for detecting a state in which the light spot passes through an address area, and A pulse number detecting unit for measuring an address passing period pulse number by measuring an address area passing signal with a reference pulse, and a channel clock frequency calculating unit for calculating a channel clock frequency from the address passing period pulse value; Depending on the value of the clock frequency, And to vary the set value of the serial equalizer setting means, the optical disk apparatus characterized by. 2. The minimum data frequency read out from the optical disk according to claim 1, wherein a setting value of the equalizer setting means corresponds to a length of time for which the light spot passes through the address area. The optical disk device is changed so that the cutoff frequency is equal to the cutoff frequency of the equalizer setting means. 3. The optical disk device according to claim 1, wherein the pulse number detecting means resets after storing the pulse number counted at each end timing of the pulse detected by the address area detecting means. Optical disk device. 4. The optical disk device according to claim 1, wherein the channel clock frequency calculating means calculates a value obtained by dividing a product of one cycle time of the reference pulse and the address passing period pulse value by a predetermined value for one channel. An optical disc device characterized by having a clock cycle time. 5. An optical disk holding means for holding an optical disk having address information intermittently recorded on an information recording surface, a disk rotation control means for rotating the optical disk, and a laser light generating means for generating a laser beam. A light spot forming means for forming a light spot by converging a laser light generated by the laser light generating means on an information recording surface of the optical disc; a photodetector detecting reflected light of the light spot; and receiving light by the photodetector. Reproduction signal detection means for detecting a reproduction RF signal from the obtained optical signal, voltage gain control means for controlling the voltage amplitude of the reproduction RF signal to a predetermined value, and setting the voltage amplitude to a predetermined value by the voltage gain control means. Equalizer means capable of changing the frequency characteristic of the RF signal after controlled gain control; Data slicing means for binarizing the RF signal after waveform equalization output from the equalizer means, RF envelope detecting means for detecting a low frequency component of the reproduced RF signal, and a track from the optical signal received by the photodetector. Wobble detection means for detecting undulation; and, in the photodetector region, the position shift amount between the light spot and the track center is divided into four by a track direction axis and an axis perpendicular to the axis. A push-pull tracking error detecting means for detecting by comparing the addition results of two parallel areas, a tracking control amount detecting means for obtaining a tracking control amount according to the positional deviation amount, and a tracking control amount based on the tracking control amount. Track for controlling the light spot in the direction of the track center Traverse control means for moving an optical pickup constituted by the laser light generating means, the light spot forming means, and the photodetector in an axis direction substantially perpendicular to the track direction axis; and reflection of the light spot. An optical disc drive having address detection means for extracting an address signal from a reproduction signal obtained from light; an address area passage signal detection means for detecting a state in which the light spot passes through an address area; Pulse number detecting means for measuring an address passing period pulse value by measuring with a reference pulse, and channel clock frequency calculating means for calculating a channel clock frequency from the address passing period pulse value; During detection by the wobble detection means Varying the frequency, the optical disk apparatus characterized by. 6. The optical disk device according to claim 5, wherein said wobble detecting means comprises at least one or more high-pass filter means or low-pass filter means, and sets a cut-off frequency of said high-pass filter means or said low-pass filter means. An optical disk device characterized by being changed independently.