JPH09251649A - Tracking error detecting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such a tracking error detecting circuit that an offset value to be generated is properly calculated by determining a parameter optimum to a tracking condition based on characteristics of an individual recording medium and a recorder and the offset value can be canceled. SOLUTION: In the wobble push-pull circuit 201 provided in an RF-IC (an integrated circuit in which circuits performing processings of RF signals are integrated), an offset value is made to be generated in a tracking error signal by moving an objective lens. A proper tracking servo is applied by canceling this offset value while inputting a forcive offset canceling signal KPPO to a subtractor 223. At this time, the offset cancel value CSL detected by offset value detecting circuits 211-218 is observed and the coefficient Kw of a coefficient multiplier 217 is adjusted so that this value becomes a proper value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a data recording / reproducing apparatus for recording / reproducing data on / from a disc-shaped recording medium such as a mini disc (MD), for tracking the disc-shaped recording medium. The present invention relates to a tracking error detection circuit that detects a tracking error.

[0002]

2. Description of the Related Art Recording / recording on so-called optical disks such as compact disks (CD) and mini disks (MD)
In a recording / reproducing apparatus for reproducing, as a tracking servo method for appropriately following a track, a three-spot method is mainly used in which the amounts of reflected light from two sub-beams sandwiching the main beam are compared. ing. But,
A push-pull method that can detect a tracking error with one spot is drawing attention from the viewpoints of simplification, downsizing of a device, and reliability. The push-pull method utilizes the fact that the intensity distribution of light that is diffracted and reflected by the pits and grooves and re-enters the objective lens changes depending on the relative position between the pits and grooves and the spot. This is a method in which light is received by a plurality of divided photodetectors, and a tracking error is obtained based on the difference in the amount of light received by each photodetector.

In the push-pull method, however, there is a problem that the spot moves on the photodetector when the objective lens fluctuates, and a DC offset occurs in the tracking error signal. This DC offset occurs when a pickup having a configuration in which only the objective lens moves is used, or when the disk surface is displaced from 90 ° with respect to the optical axis of the beam due to disk skew. Therefore, when using the push-pull method, it is necessary to cancel this DC offset.

When performing tracking on the MD,
As a method that can cancel such a DC offset and detect a tracking error appropriately,
The WPP (Wobble Push-Pull) method is often used.
The WPP method is an effective method when a tracking servo is applied to a disk-shaped recording medium in which wobbles (tracks meander) are formed on the tracks, and the wobbles included in the output signal of the photodetector. It utilizes that the amplitude of the frequency component changes depending on the position of the objective lens. That is, the amplitude of the wobble frequency component included in the light detection signal is detected, the position of the objective lens is obtained, and the offset value generated in the tracking error is canceled. The tracking error signal TE detected by the WPP method is represented by, for example, Expression 1.

[0005]

## EQU1 ## TE = (E−F) / (E + F) −K _W × (Ew−Fw) / (E−F) w (1) where E is the first-order diffracted light and F is − First-order diffracted light, Ew,
Fw and (EF) w are wobble amplitude components of E, F, and (EF), respectively.

In Expression 1, the first term on the right side corresponds to the push-pull signal, and the second term corresponds to the offset signal to be canceled. Further, the coefficient K _W for obtaining the offset signal to be canceled is based on the characteristics of the recording medium disk, the characteristics of the optical pickup, the characteristics of the circuit, and the like, and in consideration of their variations at the time of manufacture. It is set to a predetermined value.

[0007]

As described above, the coefficient K _W for obtaining the offset cancel value is set to a plurality of manufactured recording media or recording media so as to be able to cope with variations in the recording media or the recording / reproducing apparatus. It is determined based on the average characteristics of the playback device. However, this means that the optimum coefficient K _W for the tracking condition is not determined for each recording / reproducing apparatus and the recording medium mounted in the recording / reproducing apparatus. Therefore, there is a demand for obtaining the offset cancellation value with higher accuracy by using a more appropriate coefficient K _W. In addition, various characteristics of the recording / reproducing apparatus and the recording medium for determining the coefficient K _W are usually dependent on the use or the passage of time, such as the change of the characteristics of the circuit with time and the deterioration of the laser output of the optical pickup. It changes gradually. Therefore, there is also a problem that the coefficient K _W, which was an almost appropriate value when the recording / reproducing apparatus and the recording medium were manufactured, deviates with the passage of time, and an appropriate offset value cannot be obtained.

Further, such a tracking error signal detection circuit processes an RF signal for processing the RF signal from the head.
-In many cases, it is integrated and configured in the IC, and the coefficient K _W as described above cannot be easily changed. Further, due to recent increase in recording density and increase in access speed, more accurate tracking is required. Therefore, it is strongly desired to accurately obtain the offset value generated in the tracking error signal and appropriately cancel the offset value to obtain an accurate tracking error signal.

Therefore, an object of the present invention is to determine the optimum parameter for the tracking condition based on the characteristics of each recording medium and recording device, etc., and to appropriately find and cancel the offset value generated in the tracking error signal. Another object is to provide a tracking error detection circuit.

[0010]

In order to solve the above-mentioned problems, the parameter used for obtaining the offset cancel value can be adjusted to an arbitrary value from the outside. Also, a circuit for observing the detected offset component from the outside,
In addition, a circuit that forcibly cancels the offset component generated in the tracking error by a signal from the outside is provided, and the offset cancellation value detected for the intentionally generated offset component is observed to determine the optimum parameter. I was able to decide.

Therefore, in the tracking error detection circuit of the present invention, the MD in which the meandering groove (wobble) is formed.
A circuit for detecting the tracking error based on the light detection signal output from each sensor of the split sensor, by receiving the reflected light of the light beam of one spot irradiated on the disk-shaped recording medium such as , A push-pull signal detection circuit for detecting a push-pull signal which is an original tracking error signal based on the light detection signal, and a forced offset cancel circuit for forcibly canceling an offset component from the push-pull signal by an externally input signal And an offset component detection circuit that detects an offset component based on the amplitude of a wobble component included in the light detection signal, and a cancel signal detection that amplifies the detected offset component by a factor of K _W to obtain an offset cancel signal. The circuit and its offset based on the original tracking error signal. The offset cancel circuit that obtains the tracking error signal in which the offset component is canceled by excluding the offset cancel signal and the optical pickup are moved, and the offset component detected by the offset component detection circuit by the movement and the offset component are properly adjusted. And a parameter determining means for determining the coefficient K _W from the signal input to the forced offset cancel circuit for exclusion.

[0012] Preferably, the tracking error detection circuit of the present invention is the second tracking error detection circuit and the second embodiment for obtaining the tracking error signal when the track is off-track when the tracking is performed on the track on which the wobble is formed. Tracking error detection circuit, a third tracking error detection circuit that obtains a tracking error signal when tracking is performed on a track in which pits are formed, and tracking of the tracking target track and tracking servo based on the states thereof. The selection circuit that substantially enables any one of the error detection circuits is a circuit configured on the same integrated circuit.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the tracking error detection circuit of the present invention will be described with reference to FIGS.
In this embodiment, a compact disc (CD)
It is possible to process both a mini disc (MD) and a C
A tracking error detection circuit applied to an optical disk device that operates as a recording / reproducing device that is read-only for D and recordable / reproducible for MD will be described.
FIG. 1 is a block diagram showing a circuit related to detection of a tracking error in such an optical disk device. FIG.
As shown in, the detection of the tracking error is mainly performed by the photodetector PD, the signal combining unit 100, and the tracking error detecting unit 200.

In the present embodiment, the signal synthesizing section 100 and the tracking error detecting section 200 are RF
An integrated circuit (RF-I in which circuits for processing signals are integrated
C) It is integrally formed in 1 with other circuits.

Further, the user recording area of the MD to be recorded / reproduced in this embodiment is composed of a track having a meandering guide groove (wobble) as shown in FIG. In FIG. 4, a disc 500 is formed with a pre-groove 501 corresponding to a groove portion and a land 502 corresponding to a land portion, and an edge portion thereof meanders at a predetermined cycle. Then, the pre-groove 501 is spotted 503.
Tracks and plays back data. In the present embodiment, such a data track is hereinafter referred to as a wobbled track. On the inner peripheral side of the MD, there is a control information area in which control information is recorded, and data is recorded in this area by pits. Further, the CD used in the optical disk device of the present embodiment is a normally used optical disk in which data tracks are composed of pits. The track formed by the pit train applied to the control information area of the MD and the CD is hereinafter referred to as a pit track.

First, the configuration of each part related to detection of a tracking error of the optical disk device will be described. The photodetector PD is provided in the optical pickup (OP), detects the light diffracted / reflected by the recording medium, and outputs signals A to D corresponding to the amounts of light. The photodetector PD of the present embodiment has four photodetectors PD-A to P-P.
A 4-division PD in which D-D are arranged as shown is used. Of the four photo detectors PD-A to PD-D,
The two photo detectors PD-A and PD-B detect the first-order diffracted light reflected on the left side of the data track, and the remaining two photo detectors PD-C and PD-D are reflected on the right side of the data track.-1 Next time Detect breaking light.

The signal synthesizer 100 includes a photo detector P.
From the signal output from D, a desired signal suitable for input to the tracking error detection unit 200 described later is generated. The signal synthesizing unit 100 of this embodiment has three adders 101 to 103. First, the first adder 101
, The output signal A from the photo detector PD-A
And the output signal B from the photodetector PD-B are added, and the output signal L (= A +) corresponding to the light amount of all the first-order diffracted light is added.
B) is generated. The second adder 102 receives the output signal C from the photodetector PD-C and the photodetector PD-C.
The output signal D from -D is added, and the output signal R (= C + D) corresponding to the light amount of all the −1st order diffracted light is generated. The third adder 103 further adds the outputs of the first adder 101 and the second adder 102, and outputs an output signal I corresponding to the total amount of light detected by the photodetectors PD-A to PD-D.
g (= A + B + C + D) is output.

The tracking error detector 200 is a circuit for detecting a tracking error by the push-pull method. The tracking error detection unit 200 detects the tracking error TE based on the signal input via the signal synthesis unit 100. The configuration of the tracking error detection unit 200 will be described in detail with reference to FIG. The tracking error detection unit 200 has three tracking error detection circuits, a WPP unit 210, a track-on unit 230, a TPP unit 250, and switching circuits 271, 272 for them.

The WPP section 210 is a tracking error detection circuit of the present invention, which targets a wobbled track as shown in FIG. 4, and is particularly effective for tracking error detection in the on-track state. Circuit. The WPP unit 210 includes the first wobble amplitude detection unit 2
11 to holding means 218 offset value detection circuit, subtractor 219 to divider 220 push-pull signal detection circuit, switching device 221 and subtractor 2
The offset cancel circuit is composed of 22. The WPP section 210 includes an output signal A of the photodetector PD-A, an output signal D of the photodetector PD-D, an output signal L of the adder 101, an output signal R of the adder 102,
The output signal Ig, of the adder 103 is input. In particular, in the offset detection circuit adjustment mode, the forced offset cancellation signal k _ppo and the coefficient adjustment signal k _W in the coefficient multiplier 217 are input from the outside of the RF-IC 1.
The detected cancel value held in the holding unit 218 is output to the outside.

First, the structure of the offset value detection circuit will be described. The first wobble amplitude detector 211 detects the wobble amplitude signal Aw on the photodetector PD-A side (left side) from the output signal A of the photodetector PD-A. The configuration of the first wobble amplitude detection unit 211 is shown in FIG.
Shown in The first wobble amplitude detection unit 211 has a bandpass filter 225, a full-wave rectifier 226, and a lowpass filter 227. First wobble amplitude detector 21
1, the input signal A is band-limited by the bandpass filter 225 and shaped by the full-wave rectifier 226.
The amplitude of the signal A is detected by passing through the low pass filter 227.

The second wobble amplitude detector 212 has a first
The wobble amplitude signal Dw on the photodetector PD-D side (right side) is detected from the output signal D of the photodetector PD-D, similarly to the wobble amplitude detection unit 211 of FIG. The configuration and operation of the second wobble amplitude detection unit 212 are the same as the configuration of the first wobble amplitude detection unit 211 described above with reference to FIG. The subtractor 213 has a left wobble amplitude component Aw detected by the first wobble amplitude detector 211.
And a meandering difference Aw−Dw between the right wobble amplitude component Dw detected by the second wobble amplitude detection unit 212,
The difference is output to the divider 216.

In the subtractor 214, the difference between the output signal A from the photodetector PD-A and the output signal D from the photodetector PD-D is obtained, and the difference (A-
D) is output to the third wobble amplitude detector 215.
The third wobble amplitude detector 215 receives the wobble amplitude signal (A) in the input push-pull signal (A-D).
-D) Detect w and output it to the divider 216. The configuration and operation of the third wobble amplitude detection unit 215 are also the same as the configuration of the first wobble amplitude detection unit 211 described above. The divider 216 divides the signal Aw-Dw input from the subtractor 213 by the dividend, and the third wobble amplitude detector 2
The signal (A-D) w input from 15 is used as a divisor, the division shown in Expression 2 is performed, and the result is output to the coefficient multiplier 217.

[0023]

(2) (Aw-Dw) / (A-D) w (2)

Then, in the coefficient multiplier 217, equation 3
As shown in, the division result of the divider 216 is multiplied by a predetermined coefficient K _w to obtain the cancellation value of the tracking error signal. This coefficient K _W is determined by a control unit (not shown) during operation in an offset detection circuit adjustment mode, which will be described later, and is input from the outside.
Adjusted and determined by _W. The holding unit 218 holds the cancellation value obtained in the coefficient multiplier 217,
It is supplied to the subtractor 222 via the switch 221. Also,
The cancel value output from the holding unit 218 is externally referenced as the detection cancel signal CSL in the offset detection circuit adjustment mode. A control unit (not shown) detects the coefficient K _W at an optimum value based on the detection cancel signal CSL.

[0025]

[Number 3] _{K w × (Aw-Dw)} / (A-D) w ··· (3)

Next, the configuration of the push-pull signal detection circuit will be described. The subtractor 219 obtains the difference between the output signal L corresponding to the light amount of the total first-order diffracted light and the output signal R corresponding to the light amount of the all-first-order diffracted light, and subtracts the obtained result.
23. The subtractor 223 excludes the offset component from the push-pull signal by the signal input from the outside in the offset detection circuit adjustment mode. That is, from the signal of the subtraction result input from the subtractor 219,
Forced offset cancel signal k input from outside
_It subtracts _ppo and outputs the result to the divider 220. In the normal operation mode, since 0 is input as the signal k _ppo , the function of the subtractor 223 is substantially invalid. The divider 220 divides the subtraction result of the subtractor 223 as the dividend and the output signal Ig corresponding to the total input light quantity as the divisor, and obtains a push-pull signal normalized by the total light quantity.

Then, in the subtractor 222 which is an offset cancel circuit, the offset value held in the holding means 218 is subtracted from the push-pull signal obtained by the divider 220. As a result, it is a push-pull signal with offset canceled as shown in Equation 4,
A signal TE _W corresponding to the tracking error is obtained.

[0028]

[Equation 4] TE _W = (L−R) / Ig−K _w × (Aw−Dw) / (A−D) w (4)

The switch 221 is a switch for turning on / off the offset value cancellation in the WPP section 210. When the WPP unit 210 is effective and the offset value obtained by the first wobble amplitude detection unit 211 to the coefficient multiplier 217 and stored in the holding unit 218 is subtracted from the push-pull signal, the switching unit 221 has the terminal a. Select. In addition, in the offset detection circuit adjustment mode and when the track-on unit 230 described later is enabled, the switch 221 selects the terminal b and selects the subtractor 2
The subtraction value in 22 is set to 0, and the result of the divider 220 is output as it is. The output of the WPP section 210 is output to the track-on section 230 and the terminal a of the switching circuit 271.

The track-on unit 230 is the WPP unit 210.
This is a tracking error detection circuit for complementing the operation of. That is, as in the case of the WPP unit 210, when a recording medium having wobbles in the data track is the processing target, because the tracking servo is not applied, or when the WPP unit 210 is not effective immediately after being applied, the WPP It is a circuit for outputting a tracking error in place of the unit 210. Track-on section 230
Is a peak hold unit 231 and a bottom hold unit 23.
2, the intermediate value calculation unit 233, the holding unit 234, and the subtractor 235. A signal for controlling ON / OFF of a tracking servo (not shown) is input to the track-on unit 230, and the track-on unit 230 operates based on this signal.

The peak hold unit 231 and the bottom hold unit 232 hold the peak value and the bottom value immediately after the track jump, for example, at the moment when the tracking servo is turned on. Intermediate value calculation unit 233
Calculates an intermediate value between the peak value held in the peak hold unit 231 and the bottom value held in the bottom hold unit 232, and holds it in the holding unit 234 as an offset value of the tracking error signal. Then, the subtractor 235 subtracts the offset value held in the holding means 234 from the tracking error signal output from the WPP unit 210. As a result, a signal TE _R which is a push-pull signal with offset canceled and corresponds to a tracking error is obtained. The output of the track-on unit 230 is output to the terminal b of the switching circuit 271.

The TPP section 250 processes the pit track.
To output tracking error when targeting
Circuit. The TPP method will be explained with reference to FIG.
I do. FIG. 5 shows the signal L corresponding to the light amount of all first-order diffracted light.
It is an RF envelope waveform. In FIG. 5, the waveform P is the signal
The peak of signal L and signal S are tracked by push-pull method.
The RF envelope used when applying
Signal Q after passing through
It is a waveform showing a change in offset. Lens shift and
To cancel the offset due to the skew of the disk
May subtract the offset change q from the signal S. sand
This is q = K_tConstant K such that xp _t(K_t<1)
, The offset canceled signal is SK
_tIt is represented by xp. Therefore, the peak change p is calculated.
Then, the offset value can also be obtained. In addition. This implementation
In the form of_t= 0.8.

The TPP section 250 which performs such processing is
It has a first peak hold circuit 251, a second peak hold circuit 254, a first coefficient multiplier 252, a second coefficient multiplier 255 and subtractors 253, 256, 257. The first peak hold circuit 251 receives the peak value Lp of the output signal L corresponding to the total amount of input first-order diffracted light.
Hold. This peak value is added to the first coefficient multiplier 252
In step 3, the offset signal is multiplied by a predetermined constant K _t . Then, in the subtractor 253, this multiplication result K _t
By subtracting xLp from the output signal L corresponding to the light amount of all the first-order diffracted lights that are sequentially input, an output signal corresponding to the light amount of the first-order diffracted light with the offset canceled is obtained.

Similarly, the second peak hold circuit 254
Holds the peak value Rp of the output signal R corresponding to the light amount of the all-first-order diffracted light input. Second to this peak value
The coefficient multiplier 255 of (1) multiplies a predetermined constant K _t to obtain an offset signal. Then, in the subtractor 256, the multiplication result K _t × Rp is subtracted from the output signal R corresponding to the light amount of all the −first-order diffracted lights sequentially input, whereby the light amount of the offset-first-order diffracted light is canceled. An output signal corresponding to is obtained.

Then, in the subtractor 257, the subtracter 2
The difference between the output signal corresponding to the light amount of the offset canceled first-order diffracted light output from 53 and the output signal corresponding to the offset canceled-first-order diffracted light output from the subtractor 256 is obtained. The tracking error signal TE _T is output to the switching circuit 272.

The switching circuit 271 is switched based on the signal OFFTRK indicating whether or not the tracking servo is valid. When the tracking servo is valid, the terminal a is selected and detected by the WPP section 210. When the tracking error signal TE _W is output and the tracking servo is not effective, the terminal b is selected and the track-on unit 23 is selected.
The tracking error signal TE _R detected at 0 is output. It should be noted that the case where the tracking servo is effective is an on-track state, and conversely, a state where the WPP section 210 is operating correctly. In addition, when the tracking servo is not effective, the time during which the tracking servo is off due to a track jump or the like and the time during which the brake pulse is generated after the tracking servo is turned on and converges to the on-track state are matched. It is a period of time.

Further, in synchronization with the switching circuit 271, the switching unit 221 of the track-on section 230 is also switched.
Specifically, the switching circuit 271 selects the terminal a to select the WPP.
When the tracking error signal TE _W from the section 210 is selected, the switching device 221 also selects the terminal a and selects WPP.
Enable offset cancel circuit parts 210, switching circuit 271 selects the terminal b when selecting the tracking error signal TE _R from the track on section 230, switching unit 221 is WPP unit selects the terminal b From 210, a signal whose offset has not been canceled is input to the track-on unit 230.

The switching circuit 272 is switched according to the track to be processed based on the signal GR / PIT for identifying the track to be tracked. When the track to be processed is a wobbled track, the switching circuit 272
Selects the terminal a, and the tracking error signals TE _W and TE _R from the WPP section 210 or the track-on section 230 are selected.
To be output. When the track to be processed is a pit track, the terminal b is selected and the TPP
Tracking error signal TE _T from part 250 is to be outputted.

The configuration of each part relating to the detection of the tracking error of the optical disk device according to the present embodiment has been described above with reference to FIGS. 1 to 3. However, each of these parts is controlled by the control part (not shown). , Perform each function as described above. The control unit is composed of, for example, an arithmetic processing unit having a processor such as a one-chip microcomputer as a center, and performs setting / adjustment of parameters for each of the components and control of operation timing of each component.

Particularly with respect to the present invention, the control unit controls the operation in the offset detection circuit adjustment mode and the operation in the normal operation mode. The offset detection circuit adjustment mode can be set, for example, when the optical disk device is powered on or when M
This is an operation that is performed together with a series of initialization operations when D is exchanged, and the optical pickup is moved with respect to the MD to be recorded / reproduced to generate an offset value, which is detected by the offset value detection circuit at that time. Based on the offset cancellation value CSL, the coefficient K _{W of the} offset value detection circuit
Is an operation for determining. The normal operation mode is an operation for performing normal tracking error detection using the adjusted coefficient K _W.

Next, the operation of each part relating to the detection of the tracking error of the optical disk device of this embodiment will be described. First, the user of the optical disc device operates the switch to select the disc or set the disc to determine the type of the disc-shaped recording medium to be processed, and a control unit (not shown) controls the track to be tracked. The signal GR / PIT indicating the morphology is generated. When processing a wobbled track, the signal GR / PIT is L
ow. The generated track identification signal GR / PIT is applied to the switching circuit 272 of the tracking error detection unit 200, and when the signal GR / PIT is Low, the terminal a changes to the signal GR.
When / PIT is High, the terminal b is selected. That is, when the track to be processed is a wobbled track, the tracking error detected by the WPP section 210 and the track-on section 230 is output, and when the track is a pit track, the tracking error detected by the TPP section 250 is output. .

When the recording medium is set, the rotation of the disk is immediately started under the control of a control unit (not shown), and at the same time tracking servo is applied. First, the outputs of the photodetectors PD-A and PD-B on the left side and the photodetectors PD-C and PD-D on the right side are respectively output from the signal combining unit 10.
The output signal L on the left side and the detection signal R on the right side are generated by addition by the adder 101 and the adder 102 of 0, and are further added by the adder 103 to generate the signal Ig corresponding to the total light amount. It Photodetector PD-A,
The signals A, D output from the PD-D and the generated signals L, R, Ig are output to the tracking error detection unit 200.
And is used for processing of tracking error detection. Hereinafter, the operation of detecting the tracking error will be described separately for the case where the processing target is the wobbled track and the pit track.

When performing tracking on a wobbled track, the WPP is calculated based on the above-mentioned signal GR / PIT.
The section 210 and the track-on section 230 are substantially enabled, and further, the WPP section 210 and the track-on section 230 are based on the signal OFFTRK indicating the tracking state.
Is selected.

The signal OFFTRK indicating the tracking state is
As described above, a signal that is Low when the head is not following the track (when the track is off) and is High when the head is almost following the track (when the track is on track). Is. Specifically, during normal operation except when the device is started and stopped, a brake pulse is applied during the track jump and after the end of the track jump so that the head position is the desired track. Until it is almost settled to the above, it is in the off-track state, and the signal OFFTRK becomes Low.
This signal OFFTRK is applied to the switching device 221 and the switching circuit 271 of the tracking error detection unit 200 to generate the signal OF
When FTRK is Low, each terminal b, signal OFFTRK is Hi.
When it is gh, the terminal a is selected.

When MD is set, the difference between the signal L from the left photodetectors PD-A and PD-B and the signal R from the right photodetectors PD-C and PD-D is subtracted by the tracking error detector 200. 219 to generate a push-pull signal, and the result is the signal Ig.
Is divided by the divider 220 using as a divisor and normalized,
A tracking error signal before offset cancellation is obtained.

When the signal OFFTRK is High and is on-track, the first wobble amplitude detector 211 to holding means 21.
The offset value is obtained by the circuit of No. 8. First, from the signal A from the left outer photodetector PD-A and the signal D from the right outer photodetector PD-D, the wobble amplitude component is detected by the first wobble amplitude detection unit 211 and the second wobble amplitude detection unit 212. Aw and Dw are calculated,
Further, the subtractor 213 obtains the difference Aw−Dw between the amplitude components Aw and Dw. Further, the difference between the signal A and the signal D is obtained by the subtracter 214, and the wobble amplitude component (A−W) w is obtained by the third wobble amplitude detection unit 215 for the result which is the push-pull signal. . And
In the divider 216, (Aw-Dw) / (A-D) w
Is calculated and multiplied by K _w in the coefficient multiplier 217, the offset value based on the wobble is calculated. The calculated offset value is stored in the holding unit 218.

In the subtractor 222, the original tracking error signal obtained by the divider 220 is in the on-track state, so that the holding means 218 is input through the switch 221 whose terminal a is selected. The offset value stored in is canceled to generate the tracking error TE _W with the offset value canceled. The generated tracking error TE _W is output via the switching circuit 271 and the switching circuit 272.

Further, when the signal OFFTRK is Low and the track is off-track, the tracking error in which the offset value is canceled is obtained by the track-on unit 230. Since the terminal b is selected in the switch 221 during off-track, the subtractor 222 does not perform subtraction, and the divider 2
The tracking error signal in which the offset obtained in step 20 is not canceled is directly output to the tracking error detection unit 200.

When MD is set,
When the tracking state first becomes the on-track state, the offset detection circuit coefficient adjustment mode is entered, and the coefficient K _W is determined in order to obtain the optimum offset cancellation value. In the offset detection circuit coefficient adjustment mode, first, the objective lens of the optical pickup is moved to cause an offset in the tracking error. This offset is canceled by a forced offset cell signal k _ppo input from the outside to the subtractor 223 to ensure accurate tracking servo. Then, at this time, the cancel signal CSL detected by the offset value detection circuit and held in the holding means 218 is observed, and the coefficient K _W is determined so that the signal CSL has an accurate offset value. The determined coefficient K _W is immediately set in the coefficient multiplier 217, and the operation mode is returned to the normal operation mode. As a result, an accurate offset value can be obtained thereafter.

In the track-on section 230, the peak value and the bottom value at the moment when the tracking servo is turned on are set to the peak hold section 231 and the bottom hold section based on a signal for controlling ON / OFF of the tracking servo (not shown). 232, and the intermediate value calculation unit 233.
Then, the intermediate value is calculated and held in the holding means 234 as an offset value. Then, the subtractor 235 cancels the offset value stored in the holding unit 234 with respect to the tracking error signal whose offset has not been canceled, and generates the tracking error TE _R with the offset value canceled. Tracking error TE _R The generated switching circuit 271 is output via the switching circuit 272.

When performing tracking on the pit track, the TPP section 2 is based on the above-mentioned signal GR / PIT.
50 is substantially effective. In the TPP section 250, the peak values Lp and Rp of the signals L from the left photodetectors PD-A and PD-B and the signals R from the right photodetectors PD-C and PD-D are the first peak hold circuit 2.
51 and the second peak hold circuit 254 respectively detect the detected peak values Lp and Rp, and a predetermined constant K _t is multiplied by coefficient multipliers 252 and 255 to obtain each offset value. .

Next, in the subtractor 253, the offset values K _t × Lp and K _t × Rp are subtracted from the original signals L and R to obtain the first-order diffracted light and the −1st-order diffracted light whose offset values have been canceled. A corresponding output signal is obtained.
Then, in the subtracter 257, the difference between the output signal corresponding to the amount of the first order is canceled their offset order diffracted light and -1 order diffracted light is determined and is output to the switching circuit 272 as the tracking error signal TE _T. The output tracking error signal TE _T is the switching circuit 272
Is output via.

As described above, in the tracking error detection circuit of the present embodiment, the tracking error can be detected for both the wobbled track and the pit track by the push-pull method using the beam of one spot. . Further, for the wobbled track, the WPP circuit and the track-on circuit can be switched according to the tracking state to appropriately detect the tracking error.

In particular, in the WPP circuit for processing the wobbled track, the value of the coefficient K _W for obtaining the offset cancel value is determined by the operation in the offset detection circuit adjustment mode. It can be adjusted to an optimum value for the characteristics of the recording / reproducing device and the recording medium. As a result, the offset value is accurately calculated,
It is possible to cancel and detect an accurate tracking error.

Further, the signal synthesizing section 100 and the WPP section 21 for processing the signals from the photodetectors PD-A to PD-D.
0, the track-on unit 230, and the TPP unit 250 are integrally integrated in the RF-IC of the optical disc device, so that they can be easily mounted, the configuration can be greatly simplified, and the device can be downsized. It is possible to realize low power consumption. Further, since the circuit after this tracking error detection can use exactly the same circuit as before, only by replacing the optical pickup and the RF-IC of the present embodiment, the existing device can be improved in performance. It can be an optical disk device.

The present invention is not limited to this embodiment, but various modifications can be made. For example, the shape and arrangement of the split sensor of the optical pickup is not limited to the four-split PD shown in the present embodiment, and a split sensor of any configuration may be used. Also, for example, four-division P
When two sets of D are used, two corresponding PD outputs may be added to newly create A, B, C and D. Further, the configuration of the control unit and the coefficient K _W in the offset detection circuit adjustment mode, which are not shown in the present embodiment, are used.
The method for obtaining the above is not limited to the method shown in this embodiment, and any configuration and method may be used.

[0057]

As described above, according to the tracking error detection circuit of the present invention, the parameter used in the offset detection circuit is determined based on the characteristics of each recording medium and recording device, and this parameter is used. The offset value generated in the tracking error signal can be obtained. Therefore, even if the recording medium is changed or the characteristics of the circuit or the laser change due to changes over time, the tracking error can always be detected using the optimum parameter for the tracking condition, and appropriate tracking can be performed. A high performance optical disk device can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a circuit relating to detection of a tracking error of an optical disc device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a tracking error detection unit of the circuit shown in FIG.

3 is a WP of the tracking error detection unit shown in FIG.
It is a block diagram showing a configuration of a wobble amplitude detection unit of P section.

FIG. 4 is a diagram showing an example of a recording medium which is a processing target of the optical disc device of the present embodiment.

5 is a TP of the tracking error detection unit shown in FIG.
FIG. 9 is a waveform diagram for explaining a method of offset cancellation in the P section.

[Explanation of symbols]

PD ... Photo detector, 1 ... Integrated circuit, 100 ... Signal combiner 101-103 ... Adder, 200 ... Tracking error detector 210 ... WPP, 211, 212,
215 ... Wobble amplitude detector, 225 ... Band pass filter, 226 ... Full wave rectifier, 227 ... Low pass filter, 213, 214, 219, 222, 223 ... Subtractor, 216, 220 ... Divider, 217 ... Coefficient multiplier,
218 ... Holding means, 221 ... Switching device, 230 ... Track-on section, 231, ... Peak hold section, 232 ... Bottom hold section, 233 ... Intermediate value calculation section, 234 ... Holding means,
235 ... Subtractor, 250 ... TPP section, 251, 253 ...
Peak hold unit, 252, 255 ... Coefficient multiplier, 25
3, 256, 257 ... Subtraction unit, 271, 272 ... Switching circuit, 500 ... Optical disk substrate, 501 ... Pregroove,
502 ... Land, 503 ... Spot

Claims (2)

[Claims] 1. A split sensor receives reflected light of a light beam of one spot applied to a disc-shaped recording medium having a meandering groove, and the received light is output according to the amount of light received from each sensor of the split sensor. A tracking error detection circuit that detects a tracking error based on a light detection signal, the push-pull signal that detects a push-pull signal based on a light amount difference of reflected light received by each sensor based on the light detection signal. A signal detection circuit, from the detected push-pull signal, a forced offset cancellation circuit that excludes the input offset signal, based on the amplitude of the meandering component of the groove contained in the reflected light received by each sensor, An offset component detection circuit that detects an offset component generated in the push-pull signal, and based on the detected offset component, A cancel signal detection circuit that obtains an offset cancel signal for the push-pull signal by referring to a predetermined parameter, and an offset cancel circuit that obtains a tracking error signal by excluding the obtained offset cancel signal from the push-pull signal. And moving the optical pickup, based on the offset component detected by the offset component detection circuit by the movement, and the offset signal input to the forced offset cancellation circuit to appropriately exclude the offset component, A tracking error detection circuit having a parameter determination unit that determines the parameter referred to by the cancellation signal detection circuit. 2. A tracking error detection circuit for detecting a tracking error in order to perform tracking on a disk-shaped recording medium, which is on when tracking is performed on a track having a meandering groove. The tracking error detection circuit according to claim 1, wherein a tracking error signal is obtained in a track state, and a tracking servo obtained from the light detection signal is turned on when tracking is performed on the track and in an off-track state. A second tracking error detection circuit that obtains a tracking error signal in which the offset component is canceled based on the tracking error offset value at the instant when the tracking is performed on the track in which the pit is formed. Based on the amplitude of the peak value of A third tracking error detection circuit for obtaining a tracking error signal in which the offset component is canceled, and substantially any one of the three tracking error detection circuits based on the track to be tracked and the tracking state. The tracking error detection circuit according to claim 1, further comprising a selection circuit for enabling the circuits, the circuits being configured on the same integrated circuit.