JPH087300A - Focusing offset adjusting device - Google Patents

Abstract

PURPOSE:To enable recording/reproducing of high reliability, to unnecessitate the adjustment of a focusing offset at the time of shipment and to improve the productivity by optimally adjusting the focusing offset to an ambient temp. and a secular change at the time of using an optical disk device. CONSTITUTION:A wobbling signal is supplied to a focusing servo loop by means of a wobbling signal generating circuit 108. An offset adjusting circuit 110 detects the offset amount from the envelope voltages of a reproducing signal in the positive section and the negative section of the wobbling signal supplied from the wobbling signal generating circuit 108 and outputs an offset voltage for compensating the deviation of the focusing offset. The outputted offset voltage is added to a focusing error signal FE by means of an adder 106 and the adjustment of focusing offset is automatically and properly performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus offset adjusting device for adjusting an offset of a focus servo device for making an optical spot focus follow an optical disk recording surface in an optical disk device.

[0002]

2. Description of the Related Art Servo technology is a core technology in an optical disk device. Servo systems in an optical disk device include control (focus servo, tracking servo, and sled servo) that causes a light beam to accurately follow a recording portion of an optical disk, and rotation control (spindle servo) of an optical disk that is a recording medium.

In the optical disk device, the surface deflection of the optical disk is about 0.2 to 0.3 mm, and in some cases about 1 mm is generated, but the focal depth of the objective lens of the optical disk pickup is only about ± 1 μm. Therefore, a focus servo system for moving the objective lens up and down to keep the distance between the lens and the optical disc within the depth of focus of the lens is an important technique indispensable for recording and reproduction of the optical disc.

As a method for detecting a focus error signal for performing focus control, there is an astigmatism method for detecting a focus error by using astigmatism of an optical system. In the astigmatism method, a four-division detector is installed at a position where the beam cross section of the astigmatic optical system is circular when the information recording surface of the optical disc is on the focal plane of the objective lens, and the four output signals are shown in FIG. The focus error signal FE is obtained as the calculation result FE = (A + B)-(C + D) by performing the calculation in the circuit shown in FIG. FIG. 14 shows an example in which a cylindrical lens is used as an optical component that produces astigmatism. In FIG. 14, when the information recording surface of the disk is the focal plane of the objective lens, the beam cross section on the 4-division detector becomes circular and the calculation result of the focus error signal FE becomes FE = 0. When the disc approaches the lens, the image on the four-division detector becomes a vertically long ellipse and FE> 0. Further, since the image on the four-division detector becomes a horizontally long ellipse and FE <0 when the disc moves away from the disc, the focus error signal FE as shown in FIG.
Can be obtained.

[0005]

The above-mentioned astigmatism method is suitable for downsizing the optical system and has high detection sensitivity, but it is necessary to adjust the positions of the four-division detector and the incident beam. In this adjustment stage, if the center of the incident beam is not located at the center of the four-division detector, the focus error signal FE value is zero even if the information recording surface is the focal plane of the objective lens. However, an offset occurs in the focus error signal FE. Also, an offset occurs in the focus error signal FE due to the detection sensitivity of the four-division detector, variations in the arithmetic elements, and the like.

Therefore, in an optical disk device in which the offset is not properly adjusted, recording and reproduction are performed in a so-called defocused state, so that the amount of reflected light is reduced due to defocusing, the frequency characteristic is deteriorated, or the servo is easily lost. However, the reliability of information recording / reproducing decreases. Therefore, offset adjustment is essential. This offset adjustment is a major obstacle to improving production efficiency and reducing costs. Further, even when highly accurate and optimal focus offset adjustment is performed in the manufacturing process, it is difficult to always maintain the optimal adjustment state with respect to changes in ambient temperature and secular changes in component characteristics.

The object of the present invention is to eliminate such problems,
Reliable information in the optical disk device by always taking into account the state of the optical disk for recording and reproducing and the difference in the recording and reproducing environment and always performing the optimum focus offset adjustment even with changes in ambient temperature and changes in parts characteristics over time. It is an object of the present invention to provide a focus offset adjustment device that enables reproduction, eliminates the need for focus offset adjustment at the time of product shipment, and improves production efficiency.

[0008]

In order to achieve the above object, the present invention is for detecting an offset in addition to a system control means for controlling the entire optical disk device and a focus servo control means for the optical disk device. A wobbling signal generating means for generating a wobbling signal to be injected into the servo loop, a wobbling signal adding means for injecting the wobbling signal generated by the wobbling signal generating means into the focus servo loop, and a focus when the wobbling signal is injected. A specific signal extracting means for extracting only a specific signal from the sum signal or the pit reproduction signal, an envelope detecting means for detecting the envelope of the specific signal extracted by the specific signal extracting means, and a specific signal detected by the envelope detecting means. Envelope value Sample-hold means for pull-holding, summing means for summing the envelope values of the specific signals sample-held by the sample-hold means in the positive section and the negative section of the wobbling signal, and the wobbling signal positive section by the integrating section. Comparing means for comparing the integration results of the specific signal envelopes of the respective negative sections, offset calculating means for calculating and outputting an offset voltage added to the focus error signal from the result of the comparing means, and offset voltage output by the offset calculating means And an offset adding means for adding to the focus error signal.

[0009]

When the focus offset is adjusted in the present invention, the focus, tracking, sled, and spindle servo are operated. The wobbling signal generated by the wobbling signal generating means is injected into the focus servo loop by the wobbling signal adding means. When the focus offset is properly adjusted, the envelope value of the specific signal extracted by the specific signal extracting unit becomes equal in the positive section and the negative section of the wobbling signal injected into the focus servo loop. The envelope detection means performs envelope detection of the specific signal, and the detected envelope of the specific signal is sample-held by the sample-hold means. The integrating means obtains the sum of sample values of the specific signal in the positive section and the negative section of the wobbling signal injected into the focus servo loop, and the comparison means compares the sample values. The offset calculating means outputs an offset voltage such that the sum total of the sample values of the specific signal in the positive section and the negative section of the wobbling signal becomes equal based on the comparison result of the sum total of the sample values of the specific signal. Since the output offset voltage is added to the focus error signal by the offset adding means, the sum of the sample values of the specific signal in the positive section and the negative section of the wobbling signal becomes equal, and the focus offset is adjusted correctly.

Focus offset adjustment takes into consideration the state of the optical disk for recording / reproducing and the difference in recording / reproducing environment,
Further, in order to always adjust the focus offset optimally even when the ambient temperature changes or the component characteristics change over time, for example, when the power is turned on or the disc is replaced, the optical disc device is highly reliable. It becomes possible to reproduce information. In addition, there is no need to adjust the focus offset when shipping the product,
The production efficiency can be improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a focus offset adjusting device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit block diagram showing a first embodiment in which the focus offset adjusting device according to the present invention is applied to a CCS (Composit Continuous Servo) 3.5 "magneto-optical disk device. Reference numeral 101 is a 4-division detector for converting the reflected light from an unillustrated objective lens into an electric signal, 102 and 103 are adders for adding the outputs of the 4-division detector 101, and 104 is a focus error signal FE. A subtracter 105 is an adder for obtaining the focus sum signal FS, 106 is an adder for adding an offset voltage for focus offset adjustment to the focus error signal FE, and 107 is an objective by a focus actuator not shown by the focus error signal FE. Drive signal F-DR for controlling the lens
A focus servo circuit that outputs V, a wobbling signal generation circuit 108 that generates a wobbling signal W-DRV that is injected into the focus servo system, and a wobbling signal W- that is an F-DRV signal that is output from the focus servo circuit 107. An adder for adding DRV,
Reference numeral 110 is an offset adjustment circuit that generates an offset voltage for focus offset adjustment, and 111 is a drive microcomputer that controls the entire optical disk device.

When the power of the optical disk device is turned on or when the recording medium (optical disk) is replaced, the drive microcomputer 111 adjusts the focus offset. The focus offset is adjusted while the focus servo, tracking servo, and sled servo are operating. Reflected light from an optical disc, which is a recording medium (not shown), enters the four-division detector 101, and the adder 1
The focus error signal FE is calculated by 02 and 103 and the subtractor 104. The focus servo circuit 107 moves the objective lens up and down so that FE = 0 always due to the input focus error FE, which is a drive signal F-DR.
Output V.

The center of the incident beam is a four-divided detector 10.
1 is not properly adjusted to be the center of 1, or the detection sensitivity of the 4-division detector 101 varies due to aging or temperature change, or the adders 102, 1 for calculating the focus error signal FE
03 and the subtractor 104 have variations or errors in performance, as shown in FIG. 2, as an example, the focus error signal FE has a focus shift amount α in the case of FE = 0.
Focus error F when the focus shift amount is zero
E has an offset of β. In such a case, if the focus offset is not adjusted, the objective lens is controlled by the focus servo control so as to always have the focus shift α. Therefore, the reproduction signal from the optical disk decreases due to the focus shift, and the frequency characteristic deteriorates, so that accurate information reproduction may not be possible. Also,
Even when recording is performed, there is a possibility that the amount of heat required for recording cannot be obtained due to defocusing and correct recording cannot be performed.

Focusing on the focus sum signal FS, the focus sum signal FS is calculated from the total light amount of the four-division detector 101. Therefore, even when the focus error signal FE = 0 and the focus shift amount α are caused by the above-mentioned causes, the focus sum signal FS becomes maximum when the focus shift amount is zero, and thus the focus offset adjustment is performed. May be adjusted by the focus sum signal FS.

FIG. 3 shows the relationship between the wobbling signal W-DRV and the envelope of the focus sum signal FS in the focus offset adjustment. The focus sum signal FS becomes maximum when the amount of focus deviation is zero, and its magnitude decreases due to the focus deviation. When the focus offset is adjusted to zero, the focus of the objective lens is controlled to the position where the focus shift amount is zero by the servo control. In this state, as shown in FIG. 3A, when the wobbling signal W-DRV is injected into the focus servo loop and the objective lens is driven by the focus actuator so that the focus is forcibly deviated, the wobbling signal W-DRV
-DRV reduces the amplitude of the focus sum signal FS. However, since the focus actuator is driven around the point where the focus sum signal FS is maximum,
The changes in the focus sum signal FS in the positive and negative portions of the wobbling signal W-DRV become equal, and the focus sum signal FS in the positive and negative portions of the wobbling signal is equal.
Have the same envelope. On the contrary, when the focus offset is not adjusted to zero as shown in FIG.
The focus of the objective lens is controlled at the position of the focus shift amount α by the servo control. In this state, when the wobbling signal W-DRV is injected into the focus servo loop,
Since the objective lens is driven by the focus actuator around the position of the focus shift amount α, a negative wobbling signal W− that reduces the focus shift amount is obtained.
The amplitude of the focus sum signal FS increases when DRV is applied, and the amplitude of the focus sum signal FS decreases when a positive wobbling signal W-DRV that increases the focus shift amount is applied. , When comparing the envelopes of the focus sum signal FS in the positive part and the negative part of the wobbling signal W-DRV, the envelopes of the two focus sum signals FS are not equal.
From the above relationship, if the envelopes of the focus sum signal FS in the positive section and the negative section of the wobbling signal W-DRV when the wobbling signal W-DRV is injected into the focus servo loop are made equal, the focus sum signal The FS becomes maximum and the focus offset can be adjusted optimally.

When the focus offset is adjusted by the focus sum signal FS, the size of the focus sum signal FS varies depending on the pit length of the pits provided on the disc and the pit interval. In order to eliminate the influence of the difference in pit length and pit interval, it is necessary to specify the pit length used for adjustment. Since the reproduction spot diameter changes due to defocusing, this influence is remarkable in the reproduction frequency characteristic.
Therefore, the detection sensitivity can be increased by using the focus sum signal FS in the shortest recording pit of the code modulation method adopted by the optical disk device. For example, taking a CCS type 3.5 "magneto-optical disk device as an example, (2,7) RL
Focus offset adjustment is performed using the focus sum signal FS of 3T cycle (T: channel bit cycle) which is the shortest recording cycle of L modulation.

The CCS type magneto-optical disk device used in the present embodiment is compatible with three types of disks: ROM, RAM, and partial ROM. R for magneto-optical disk device
ROM when using OM or partial ROM disk
Considering that random data is recorded in advance in the area, it is considered that the shortest pits used for the focus error offset adjustment are evenly distributed over the entire ROM area.
Normally, when the recorded data in the ROM portion is reproduced, the reproduced data has an average signal of the shortest recording period. However, there is no pit in the data area of the RAM portion of the RAM disc or the partial ROM disc. Therefore, the focus offset cannot be adjusted using the shortest recording cycle of the data area reproduction signal. However, as shown in the disk format of the 3.5 "magneto-optical disk device of the CCS system of FIG. 4, there is a pre-formatted portion at the beginning of the sector regardless of ROM or RAM. Among them, the VFO portion (VFO1- The data of 3) is PL
It is a shortest recording period continuous data pattern for L (Phase Locked Loop) lock, and a repeating signal of the shortest recording period is written therein, and this can be used to perform focus offset adjustment. Preformatted VF
If the focus offset adjustment is performed by the focus sum signal FS in the O portion, the RAM disk, the partial R
Focus offset adjustment can be similarly performed regardless of whether an OM disc or a ROM disc is used.

The first embodiment for performing the focus offset adjustment by the focus sum signal FS in the pre-formatted VFO portion will be described below with reference to FIG. Since the drive microcomputer 111 adjusts the focus offset, first, the wobbling signal generation circuit 10
8 and the offset adjustment circuit 110, and sends the wobbling signal W-DRV to the wobbling signal generation circuit 108.
And the offset adjustment circuit 110 is operated.
The wobbling signal W-DRV generated by the wobbling signal generation circuit 108 is added by the adder 109 to the F-DRV signal output from the focus servo circuit 107.

The amplitude of the wobbling signal W-DRV generated by the wobbling signal generation circuit 108 is the amount by which the focus actuator is moved by several μm, and the focus servo does not deviate due to the injection of the wobbling signal W-DRV. Further, as shown in FIG. 3A, when the focus offset is proper, the cycle of the envelope of the focus sum signal FS is 1 of the wobbling signal W-DRV cycle.
Therefore, in order to observe the envelope change by sampling the focus sum signal FS once per sector according to the sampling theorem, the wobbling signal W-DR
The V cycle needs to be four times or more the sector cycle. Since the cycle of the wobbling signal W-DRV satisfies the above condition, the disk rotation cycle is set to the cycle of the wobbling signal W-DRV in this embodiment. Wobbling signal W-DRV
The waveform of may be a sine wave or a triangular wave.

The focus servo loop injected with the wobbling signal W-DRV is
A focus shift amount of several μm corresponding to the amplitude of V is added. Therefore, the focus actuator is forcibly driven within a range of several μm centering on the focus shift amount α before the focus offset adjustment. Focus sum signal FS modulated by wobbling signal W-DRV
Is output to the offset adjustment circuit 110.

FIG. 5 is a circuit block diagram showing a specific example of the offset adjusting circuit 110. In FIG. 5, 501 is a BPF (Ba) for extracting the repetitive signal of the shortest recording period.
ndPass Filter), 502 is an envelope detection circuit for performing envelope detection of the output of the BPF 501, 503
Is a sample and hold circuit for sampling and holding the output of the envelope detection circuit 502, 504 is a switch for switching the output destination of the sample and hold circuit 503, and 505 is a wobbling signal generation circuit 108 for generating a control signal for switching the switch 504. A comparator for comparing and generating the generated wobbling signal W-DRV, reference numerals 506, 507 for accumulating the sample hold values of the focus sum signal FS in the shortest recording period, and 508 for accumulators 506, 507. And a subtracter 509 for comparing the magnitudes of the integration results of
The offset output circuit outputs an offset voltage for focus offset adjustment according to the result of 08.

Next, the operation of the offset adjusting circuit 110 will be described with reference to FIGS. The BPF 501 receives the focus sum signal FS (5
From 10), the center frequency is set so that only the repetitive signal of the shortest recording period, which is the VFO portion of the pre-formatted data located at the head of the sector, is extracted.
The signal 511 of the shortest recording period which is the output of the BPF 501
Is envelope-detected by the envelope detection circuit 502 and becomes an envelope signal 512 depending on the amplitude value of the shortest recording period. The sample hold circuit 503 samples and holds the peak value of the envelope signal 512 up to the pre-formatted portion at the beginning of the next sector. The sample hold circuit 503 holds the value of the focus sum signal FS in the VFO section for one sector. The value of the focus sum signal FS held for one sector is determined by the switch 504.
Is output to the integrator 506 or the integrator 507. The signal for controlling the switch 504 is ON when the wobbling signal W-DRV is positive, and OFF when it is negative 2
Value signal, injected wobbling signal W-DRV
By the comparator 505.

The integrators 506 and 507 clear the integration result by the control signal from the drive microcomputer 111 at the start of the focus offset adjustment, and integrate the output of the sample hold circuit 503 for a predetermined time. In the integrated focus sum signal FS, not only the focus servo but also the tracking servo and the sled servo are operating, so that the signal does not decrease due to the tracking deviation. When the injected wobbling signal W-DRV is positive, the output of the sample hold circuit 503 is the switch 50.
It is input to the integrator 506 by 4 and is added to the integration result only once per sector. When the injected wobbling signal W-DRV is negative, the sample hold circuit 503
Is output to the integrator 507 by the switch 504 and added to the integration result only once per sector. Also, by integrating for a certain period of time, the influence of noise is averaged and removed. In this way, the integrators 506 and 507
However, the result obtained by integrating the output results of the focus sum signal FS of the VFO unit in the positive section and the negative section of the wobbling signal W-DRV for a certain period of time is compared by the subtractor 508. The subtractor 508 subtracts the integration result of the integrator 507 from the input integration result of the integrator 506, and outputs it as a comparison result to the offset output circuit 509.

The offset output circuit 509 outputs an offset voltage for adjusting the focus offset according to the input comparison result. When the input comparison result is negative, that is, as shown in FIG. 3B, the wobbling signal W
-DRV The wobbling signal W-DR is the integration result of the positive section.
If it is smaller than the integration result of the V negative section, it is set closer to the disc than the in-focus point, so the focus offset can be adjusted by adding an offset voltage in the direction of moving the objective lens away from the focus error FE. If the integration result of the wobbling signal W-DRV positive section is larger than the integration result of the wobbling signal W-DRV negative section, it is set farther from the focusing point than the disc, and the objective lens is moved closer to the disk. The focus offset can be adjusted by adding the offset voltage to the focus error FE.

The offset output circuit 509 has an offset output voltage of 0 according to a control signal from the drive microcomputer 111 when power is turned on, when focus offset adjustment is started, or when reset. Further, when the offset output circuit 509 starts the focus offset adjustment and the comparison result of the integration result is input from the subtractor 508, the offset output circuit 509 receives the comparison result and the appropriate offset output voltage as shown in FIG. The offset voltage determined by the comparison result is output. The output offset voltage is added to the adder 10
At 6, it is added to the focus error FE. As shown in FIG. 8, for a focus error FE having a focus shift α,
The focus offset is adjusted by adding the output offset voltage β of the offset output circuit 509.
When the offset output circuit 509 outputs the offset voltage, the offset output circuit 509 outputs to the drive microcomputer 111 a control signal indicating the end of the focus offset adjustment. The drive microcomputer 111 detects the end of the focus offset adjustment, ends the generation of the wobbling signal W-DRV by the wobbling signal generation circuit 108, and completes the focus offset adjustment processing.

As described above, according to the first embodiment of the present invention, since the focus offset is adjusted when the power is turned on and the disc is replaced, the state of the optical disc for recording / reproducing and the difference in the recording / reproducing environment, or Optimal focus offset adjustment is always performed even with changes in ambient temperature and aging of component characteristics, and highly reliable information reproduction can be performed. Also, since the focus offset is adjusted when the power is turned on and the disc is replaced,
It is not necessary to adjust the focus offset at the time of product shipment, and the production efficiency can be improved.

In the first embodiment of the present invention, the offset voltage for focus offset adjustment was uniquely obtained from the relationship between the comparison result and the proper offset voltage. However, the offset adjustment unit voltage Δ is set and wobbling is performed. The offset voltage may be increased or decreased by Δ until the envelopes in the positive section and the negative section of the signal become equal to each other to finally set an appropriate offset voltage.

Next, a second embodiment of the focus offset adjusting device according to the present invention will be described with reference to the drawings. FIG. 9 is a circuit block diagram showing a second embodiment in which the focus offset adjusting apparatus according to the present invention is applied to a CCS system 3.5 "magneto-optical disk apparatus when digital servo control is performed using a DSP (Digital Signal Processor). 9, 101 is a four-division detector for converting the reflected light from an objective lens (not shown) into an electric signal, 102 and 103 are adders for adding the outputs of the four-division detector, and 104 is a focus. Error F
A subtractor for obtaining E, 105 is a focus sum signal FS
901 is an adder for obtaining the focus error FE
A / D converter for D / A (Analog / Digital) conversion, 9
Reference numeral 02 denotes a DSP for performing focus servo control and focus offset adjustment operation, and 903 denotes a signal F-DRV for controlling a focus actuator (not shown) output from the DSP 902, which is D / A (Digital / Analog).
D / A converter for conversion, 904 is BPF 501,
Envelope detection circuit 502, sample hold circuit 5
A sample / hold circuit 905 for sampling and holding the envelope of the focus sum signal FS of the VFO section, and 905 A / D is the sample / hold value of the shortest pit signal of the VFO section detected by the envelope / sample / hold circuit 904. An A / D converter for conversion, and 111 is a drive microcomputer for controlling the entire optical disk device. It should be noted that the same numbers are added to the same parts as in FIG.

A focus offset adjusting device according to the second embodiment will be described below with reference to the drawings. When the power of the optical disk device is turned on or when the recording medium (optical disk) is replaced, the drive microcomputer 111 issues a focus offset adjustment command from the state in which the focus servo, tracking servo, and sled servo are operating.
Send to SP902. Upon receiving the command from the drive microcomputer 111, the DSP 902 sets the focus offset adjustment command reception flag and starts the focus offset adjustment. The DSP 902 is an A / D converter 9
The focus offset adjustment processing is performed while performing the focus servo processing that outputs the signal F-DRV for moving the objective lens up and down so that the value obtained by adding the offset to the focus error FE A / D converted by 01 is always zero. To do. Therefore, the DSP 902 requires at least a processing capacity for performing the focus offset adjustment processing during the focus servo control processing. Note that the focus error FE
Since the offset added to 0 becomes zero upon reset or start of focus offset adjustment, no offset is added to the focus error FE in the initial state.

At the time of adjusting the focus offset, in the first embodiment, the wobbling signal W-DRV by the wobbling signal generation circuit 108 is added to the F-DRV signal, but in the present embodiment, the wobbling is performed by the internal arithmetic processing of the DSP 902. The signal W-DRV is generated, added to the F-DRV signal and output while the focus offset adjustment command reception flag is set. Inside the DSP 902, the wobbling signal amplitude maximum value WBmax, the wobbling signal amplitude minimum value WBmin, the wobbling signal period Twb, and the F-DRV output period Tfd are calculated by the following (Equation 1).
A stepwise wobbling signal W-DRV that varies between x and WBmin is generated.

[0032]

## EQU1 ## WBstep = (WBmax−WBmin) × 2 × Tfd / Twb (Equation 1) F-DRV during focus offset adjustment is WBmax
The output of the wobbling signal W-DRV which changes from WBmin to WBmin by WBstep is added. The F-DRV of the digital signal added with the wobbling signal W-DRV and output from the DSP 902 is the D / A converter 90.
3 is converted into an analog signal and output to the focus actuator.
It is forcibly driven by DRV.

The focus sum signal FS modulated by the wobbling signal W-DRV is subjected to envelope detection by the envelope detection circuit 502 after extraction of the VFO signal by the BPF 501 in the envelope sample hold circuit 904. V at 503
The focus sum signal FS of the FO unit is sampled and held. The envelope of the focus sum signal FS of the VFO unit sample-held by the envelope sample-hold circuit 904 is A / D converted by the A / D converter 905,
It is output to the DSP 902. The DSP 902 integrates the input envelopes in the positive section and the negative section of the wobbling signal W-DRV, and obtains an offset for focus offset adjustment based on the comparison result of both.

A wobbling signal WD is generated in the DSP 902.
The distinction between the positive section and the negative section of RV can be known by the sign of the wobbling signal W-DRV added to F-DRV. Inside the DSP 902, the register for adding the envelope value is changed according to the sign of the wobbling signal W-DRV when the envelope value is input, and the sum of envelopes in the positive and negative sections of the wobbling signal W-DRV is obtained. After adding the wobbling signal W-DRV, refer to the internal timer or wobbling signal W
-Detecting the passage of a certain time by counting the sign change (zero cross) of DRV, comparing the wobbling signal W-DRV after the passage of a certain time with the envelope sum in the positive section and the negative section, and adding the offset to FE according to the comparison result. Add or subtract one bit to clear the register that holds the two envelope sums.

As described above, the wobbling signal W-DRV
When the absolute value of the comparison result of the envelope sums becomes smaller than a certain set value (focusing judgment value) γ, the focus offset adjustment error is regarded as the minimum and the focus offset adjustment is performed. To finish. D at focus offset end
SP902 notifies the drive microcomputer 111 of the end of focus offset adjustment, and clears the focus offset adjustment command reception flag. FIG. 10 shows a flowchart of the focus offset adjustment processing in the DSP 902 described above.

As described above, according to the second embodiment of the present invention, the focus offset is adjusted when the power is turned on and the disk is replaced in the same manner as in the first embodiment. It is possible to always perform highly reliable information reproduction regardless of differences in recording / reproduction environment, changes in ambient temperature, and secular changes in component characteristics, eliminating the need to adjust the focus offset at the time of product shipment. It is also possible to improve efficiency.

In the second embodiment of the present invention, the offset change for adjusting the focus offset is 1.
Although it is a bit unit, the offset change unit may be variable depending on the size of the comparison result of the total envelopes. Further, in the second embodiment of the present invention, the focus offset is gradually adjusted by the focus offset adjustment loop, but the optimum offset may be calculated by calculating the comparison result of the envelope sums. You may make it a ROM table and refer to it by the comparison result. When the DSP for performing the focus servo processing and the focus offset adjustment processing has a high processing capability, the servo processing such as tracking and sled servo can be performed by the same DSP, and the focus sum signal FS is A / D converted. It is also possible to input it to the DSP and perform the processing of the envelope sample hold circuit 904.

In the description of the first and second embodiments in which the present invention described above is applied to the CCS method 3.5 "magneto-optical disk apparatus, the focus sum signal FS of the preformatted VFO section is used for focusing. Although the offset is adjusted, the repeat signal of the shortest recording cycle is extracted from the reproduction signal of the control track portion in which the media information and the system information are recorded, and the focus offset adjustment is performed by the envelope change of the focus sum signal FS by the wobbling signal. You can do it.

Next, a third embodiment of the focus offset adjusting device according to the present invention will be described with reference to the drawings. FIG. 11 is a circuit block diagram showing a third embodiment in which the focus offset adjusting apparatus according to the present invention is applied to a sample servo type magneto-optical disk apparatus. In FIG. 11, 901 is an A / D converter for A / D converting the focus error signal FE, and 902 is a DS for performing focus servo control and focus offset adjustment operation.
P and 903 are signals F-D output from the DSP 902 for controlling a focus actuator (not shown).
A D / A converter for D / A converting RV, 1101 is a clock pit detection circuit for detecting a clock pit from a pit reproduction signal, and 1102 is a reproduction clock from the clock pit detected by the clock pit detection circuit 1101. A clock reproduction circuit for generation, 503 is a sample hold circuit for sample-holding the clock pit reproduction signal output from the clock pit detection circuit 1101, and 905 is A / D for the clock pit amplitude value sample-held by the sample-hold circuit 503. An A / D converter for conversion, and 111 is a drive microcomputer for controlling the entire optical disk device. It should be noted that the same parts as those in FIG. 9 are denoted by the same reference numerals.

In contrast to the CCS system optical disc apparatus in the first and second embodiments in which the PLL is synchronized with the reproduction signal of the VFO section recorded on the disc to generate the clock used for recording and reproduction, the sample servo system optical disc is used. The device is PLL from the clock pit recorded on the disc.
To generate a system clock for recording and reproduction. Therefore, the sample servo type optical disc does not have a VFO section, and the focus offset cannot be adjusted using the focus sum signal FS of the VFO section as in the first and second embodiments.

FIG. 12 shows a DBF (Discrete Block F) which is one of the formats of the sample servo system optical disk.
ormat) system disk format. In the sample servo system, a sector consists of a plurality of segments, and each segment has a servo mark. The servo mark includes an access mark used for access, a clock pit used for clock reproduction, and a wobble pit used for tracking control. The two wobble pits are arranged with offsets with respect to the center of the track, and in the sample servo system, tracking servo control is performed so that the reproduction signal amplitudes of these two wobble pits become equal.

Adjustment of the focus offset in the sample servo system may be performed so that the pit signal generated from the sum of the outputs of the four-divided photodetector is maximum, that is, the pit modulation degree is maximum.

In order to detect the point where the pit modulation degree is maximum, attention should be paid to the relationship between the pit modulation degree and the focus shift amount. When the focus error FE = 0 and the focus shift amount is zero, when the focus actuator drive signal is added so that the focus shift amount occurs in the positive direction and the negative direction around the zero focus shift amount, the pit modulation degree is reduced due to the focus shift. descend. In other words, if the focus actuator is forcibly vibrated by the drive signal to cause the focus shift, and the pit signal envelope indicating the change in the pit modulation degree is equal in positive and negative of the focus shift amount,
The pit modulation degree is maximum, which means that the focus offset adjustment is performed correctly.

When the focus offset is adjusted by the pit signal, since the size of the pit signal differs depending on the length of the pit to be reproduced and the pit interval, the focus offset is adjusted so as to maximize the modulation degree of the isolated pit. .

RO with sample servo type optical disk
Of the pits in the servo mark that can be used in both M and RAM disks, the clock pits and wobble pits are always isolated pits. However, since the wobble pits are used for tracking control as described above, it is impossible to determine whether the change in the wobble pit amplitude is due to the wobbling signal or the track shift. Therefore, in the sample servo system optical disk device, the focus offset adjustment is performed using the clock pits in the servo marks.

The focus offset adjusting device according to the third embodiment will be described below. When the power supply of the optical disk device is turned on or the recording medium (optical disk) is replaced, the drive microcomputer 111 is activated from the state in which the focus servo, tracking servo, and sled servo are operating.
Sends a focus offset adjustment command to the DSP 902. Upon receiving the command from the drive microcomputer 111, the DSP 902 sets the focus offset adjustment command reception flag and starts the focus offset adjustment. The DSP 902 performs focus offset adjustment processing while performing focus servo processing.

When the focus offset adjustment command reception flag is set, the DSP 902 generates a wobbling signal W-DRV by an internal calculation process, adds the wobbling signal W-DRV to F-DRV, and outputs it. A reproduction pit signal from an optical pickup (not shown) is input to the clock pit detection circuit 1101 and the clock pit is extracted. The clock reproduction circuit 1102 multiplies the clock pit frequency extracted by the clock pit detection circuit 1101 by a PLL to generate a reproduction clock.
Further, only the clock pit signal is extracted by the clock pit detection circuit 1101, and the clock reproduction circuit 1102 is extracted.
The sample-hold circuit 503 can sample and hold the clock pit amplitude value at the center of the clock pit by using the reproduction clock output by.

The amplitude of the clock pit signal modulated by the wobbling signal W-DRV is the sample hold circuit 50.
3 is sampled and held, and A / D converter 905
It is D-converted and output to the DSP 902. DSP902
Identifies whether the input clock pit signal amplitude is in the wobbling signal W-DRV positive section or in the negative section, integrates each section, and obtains an offset used for focus offset adjustment based on the comparison result of both sections.

Inside the DSP 902, the register for adding the clock pit signal amplitude value is changed according to the sign of the wobbling signal W-DRV when the clock pit signal amplitude value is input, and the clock in the positive section and the negative section of the wobbling signal W-DRV is changed. The sum of the pit signal amplitude values is calculated. After adding the wobbling signal W-DRV, the internal timer is referenced or the sign change (zero cross) of the wobbling signal W-DRV is counted to detect the elapse of a certain time, and after the elapse of the certain time, the wobbling signal W-D
The RV positive section and the negative section are compared with the clock pit signal amplitude value integration result, and the focus error FE is determined based on the comparison result.
Add or subtract 1 bit to the offset added to
Clear one clock pit signal amplitude value integration result register.

As described above, the wobbling signal W-DRV
When the absolute value of the comparison result of the clock pit signal amplitude value integration becomes smaller than a certain set value (focusing judgment value) γ, the clock pit modulation degree is maximum. Yes Focus offset adjustment is considered to be minimum, and focus offset adjustment is completed. Upon completion of the focus offset, the DSP 902 notifies the drive microcomputer 111 of the end of focus offset adjustment, and clears the focus offset adjustment command reception flag.

As described above, according to the third embodiment of the present invention, also in the sample servo type optical disk apparatus, the focus offset is adjusted when the power is turned on and the disk is replaced as in the first and second embodiments. Therefore, it is possible to always perform highly reliable information reproduction regardless of the state of the optical disk for recording / reproduction, the difference in recording / reproduction environment, the change in ambient temperature, or the secular change in component characteristics. It is also possible to improve the production efficiency by eliminating the need to adjust the focus offset at the time.

In the sample servo system, the offset of the focus servo is detected and adjusted from the degree of modulation of the clock pit. Separately from this, a wobbling signal is applied to the actuator so that the objective lens oscillates in the disk radial direction, and the clock pit is adjusted. It goes without saying that the off-track amount in the tracking direction can also be detected by detecting the modulation of. Therefore, this also enables the offset adjustment of the tracking servo as well.

In the third embodiment of the present invention, the focus offset adjustment is performed by the change of the clock pit modulation degree when the wobbling signal W-DRV is injected, but the SFP in which the media information and the system information are recorded. (Standed Formatted Part of the control t
The focus offset adjustment may be performed by extracting the reproduction signal of the maximum recording frequency from the reproduction signal of the (rack) section and changing the amplitude by the wobbling signal W-DRV.

In the description of the first, second and third embodiments described above, the signals used for adjusting the focus offset are all signals included in the disc format extracted from the reproduced signal. It was However, if a disc having a format in which a specific signal for performing the focus offset adjustment is recorded is used, the focus offset adjustment can be performed by reproducing the specific signal recording portion, and the same effect can be obtained.

When the focus offset device of the present invention is used in an optical disc device capable of recording / reproducing discs of a plurality of formats having different recording densities, the BPF of the BPF is detected by detecting the difference in the format with respect to the modulation code which is different depending on the format. Center frequency, envelope detection
An optical disk device capable of using a plurality of formats of disks by changing the time constant of sample hold according to the format, or by switching according to the format of the optical disk used, which has a BPF, an envelope detection circuit, and a sample hold circuit for each format. Also in, the optimum focus offset adjustment can always be performed.

[0056]

As described above, according to the present invention, the focus offset is adjusted when the power is turned on and the disc is replaced, so that the state of the optical disc for recording / reproducing and the difference in the recording / reproducing environment or the ambient temperature can be controlled. It is possible to perform highly reliable information reproduction by always adjusting the optimum focus offset even with changes and aging of component characteristics. Further, since the optimum focus offset is adjusted when the optical disc device is used, it is not necessary to adjust the focus offset at the time of shipping the product, and it is possible to improve the production efficiency of the optical disc device.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing a first embodiment of a focus offset adjusting device according to the present invention.

FIG. 2 is a diagram showing an example of a focus error signal when there is a focus offset deviation.

FIG. 3 is a diagram showing a relationship between a wobbling signal and a focus sum signal.

FIG. 4 is a diagram showing a sector format of a CCS system 3.5 ”magneto-optical disk.

FIG. 5 is a circuit block diagram showing a specific example of an offset adjustment circuit.

FIG. 6 is a signal waveform diagram in the offset adjustment circuit.

FIG. 7 is a diagram showing a relationship between a comparison result and an appropriate offset voltage.

FIG. 8 is a diagram showing a focus error signal in which focus deviation has been eliminated by focus offset adjustment.

FIG. 9 is a circuit block diagram showing a second embodiment of the focus offset adjusting device according to the present invention.

FIG. 10 is a flowchart of focus offset adjustment processing by the DSP.

FIG. 11 is a circuit block diagram showing a third embodiment of the focus offset adjusting device according to the present invention.

FIG. 12 is a diagram showing a format of a DBF type magneto-optical disk.

FIG. 13 is a diagram showing a 4-division detector and an arithmetic circuit for obtaining a focus error signal.

FIG. 14 is a diagram illustrating the principle of focus error detection by the astigmatism method.

FIG. 15 is a diagram showing a focus error signal by the astigmatism method.

[Explanation of symbols]

101 ... Quadrant detector, 106 ... Offset adder, 107 ... Focus servo circuit, 108 ... Wobbling signal generation circuit, 110 ... Offset adjustment circuit, 90
1, 905 ... A / D converter, 902 ... DSP, 903 ...
D / A converter.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshio Suzuki, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Ltd.

Claims (9)

[Claims] 1. A focus servo control device for an optical disc device, which detects a focus error and controls a focal position of a light beam, wobbling an objective lens in the vertical direction of the disc, and preformatted identification at this time. A focus offset adjusting device characterized by detecting a focus error offset based on a change in signal amplitude and adjusting the focus offset based on the result. 2. A focus offset adjusting apparatus according to claim 1, wherein a wobbling signal generating means for generating a wobble signal for focus wobbling and a wobbling signal generated by the wobbling signal generating means are injected into a focus servo loop. Wobbling signal adding means for extracting the specific signal from the pit reproduction signal or the focus sum signal when the wobbling signal is injected, and the envelope detection of the specific signal extracted by the specific signal extracting means. By means of an envelope detecting means for carrying out the above, a sample and hold means for sampling and holding the envelope value of the specific signal detected by the envelope detecting means, and a sample and hold means for each of the positive section and the negative section of the wobbling signal. An integrating means for integrating the envelope values of the sampled and held specific signals; a comparing means for comparing the integrated results of the envelopes of the specific signals in the positive section and the negative section of the wobbling signal by the integrating means; An offset calculation means for calculating and outputting an offset voltage to be added to the focus error signal from the result, and an offset addition means for adding the offset voltage output by the offset calculation means to the focus error signal are provided. A focus offset adjusting device characterized by adjusting. 3. The focus offset adjusting device according to claim 1, wherein the specific signal is a signal having a shortest recording period. 4. The focus offset adjusting device according to claim 1, wherein the specific signal is a signal of a VFO section of a composite continuous servo optical disk. 5. The focus offset adjusting device according to claim 1, wherein the specific signal is a signal of a clock pit of a sample servo type optical disk. 6. The characteristics of the specific signal extracting means, the envelope detecting means, and the sample and hold means in the focus offset adjusting apparatus according to claim 2, are changed according to the format of an optical disc for recording and reproducing.
A focus offset adjusting device capable of adjusting the focus offset even in a plurality of format discs. 7. When replacing an optical disk or turning on the power,
An optical disk device, wherein focus offset adjustment is performed using the focus offset adjustment device according to claim 1, 2, 3, 4, 5 or 6. 8. In a sample servo type optical disc apparatus, an optical pickup is wobbled in a disc radial direction, an offset of a tracking error signal is detected by a change in amplitude of a clock pit at this time, and a tracking offset is adjusted based on the result. A tracking offset adjusting device characterized by the above. 9. A recording medium characterized in that a specific signal for performing focus balance adjustment is recorded in advance by the focus balance device according to claim 1.