JP4060198B2 - Control device and optical disk device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical recording / reproducing apparatus that optically records information on an information carrier using a light source such as a laser, converts information recorded on the information carrier into a signal, and reproduces the signal. The present invention relates to an optical disc apparatus such as an optical reproducing apparatus that performs reproduction by converting information recorded on an information carrier into a signal. In particular, the present invention relates to a control apparatus and an optical disk apparatus for controlling a spot of a light beam to scan correctly on a track.
[0002]
[Prior art]
As an example of a tracking control device in a conventional optical disc device, a device that corrects a lens shift so that an offset of a phase difference tracking error signal becomes zero is known.
[0003]
FIG. 28 is a block diagram schematically showing the configuration of this conventional optical disc apparatus disclosed in Patent Document 1. In FIG. In the optical disc apparatus shown in FIG. 28, the optical pickup 20 has a laser light emitting element (not shown), a converging lens 22 and an actuator 23, and converges and irradiates the optical beam 21 on the optical disc 10. The optical pickup 20 further includes a photodetector 24 having detectors A to D divided into four, and the reflected beam 21 ′ reflected on the information recording surface of the optical disc 10 is detected by the photodetector 24. . Outputs of the detectors A to D of the photodetector 24 are input to the signal generation circuit 30.
[0004]
The signal generation circuit 30 includes phase difference adjustment circuits 31a and 31b, and the phase difference in the circumferential direction (tangential) of the disc with respect to the output signals of the detection units A and B input from the photodetector 24. (Referred to as tangential phase difference). Thereby, the offset accompanying the phase difference which arises between the outputs of each detection part AD can be removed. The addition circuits 32a and 32b generate an addition signal (A + D) and an addition signal (B + C) obtained by adding the outputs of the detection units located diagonally to the photodetector 24, and the phase difference detection circuit 33 causes these phase differences. Is detected. The output of the phase difference detection circuit 33 output through the LPF 34 is a phase difference tracking error signal (referred to as DPDTE).
[0005]
The digital signal processor (referred to as DSP) 50 includes an offset adjustment unit 52, a tracking control unit 53, an offset measurement unit 61, a lens shift correction unit 62, an A / D converter 51, and a D / A converter 54.
[0006]
The A / D converter 51 converts DPDTE into a digital signal. The offset in the tracking control is added to the digital signal of the offset adjustment unit 52DPDTE. In addition, the tracking control unit 53 generates a tracking drive value by performing a filter operation for performing phase compensation and low-frequency compensation on the digital signal of DPDTE. The generated tracking drive value is converted again to an analog signal by the D / A converter 54 and output to the drive circuit 91 as a tracking drive signal. The drive circuit 91 amplifies the tracking drive signal and drives the actuator 23 built in the optical pickup to perform tracking control.
[0007]
Next, a lens shift correction method in the prior art will be described. In the optical pickup 20, convergence is caused by an installation error of optical components such as the converging lens 22 and the photodetector 24, drooping of the converging lens by holding the apparatus vertically, or tilting of the optical axis of the beam emitted from the laser. The center of the lens 22 may deviate from the set position. In this case, the reflected beam may be shifted from the center of the photodetector 24 to form an image. In the following description, this state is referred to as lens shift. This lens shift is a shift between the position or optical axis of the convergent lens 22 and the center of the photodetector 24 that occurs in the optical pickup.
[0008]
FIGS. 29A to 29C show phase difference tracking error signals output from optical pickups in various lens shift states when tracking control is not performed. In the signals shown in FIGS. 29A and 29C, a tangential phase difference due to lens shift occurs. More specifically, the signals shown in FIGS. 29A and 29C are generated when the converging lens is shifted by about 300 μm to the inner and outer peripheral sides of the disc with respect to the track center, respectively. On the other hand, the signal shown in FIG. 29B is obtained when there is no deviation of the convergent lens.
[0009]
When there is a tangential phase difference due to lens shift as shown in FIGS. 29A and 29C, if the converging lens is shifted by tracking control, the symmetry of the phase difference tracking error signal deteriorates and an offset is generated. . The relationship between this DPDTE offset and lens shift is shown in FIG. In FIG. 30, the horizontal axis indicates the position of the converging lens, and the vertical axis indicates the DPDTE offset value.
[0010]
As shown in FIG. 30, the position of the converging lens and the DPDTE offset value show a linear relationship in the vicinity of the lens position where the lens position is optimal. By detecting this DPDTE offset and applying the offset to the tracking drive value so that the DPDTE offset becomes zero, the position of the converging lens 22 can be moved to correct the lens shift.
[0011]
Next, a procedure for correcting the lens shift will be described with reference to FIG. The adjustment of the phase difference adjustment circuits 31a and 31b of the signal generation circuit 30 is shifted so that a tangential phase difference is generated. When a lens shift has occurred, an offset of DPDTE occurs, so the offset measurement unit 61 measures the offset of DPDTE.
[0012]
The lens shift correction unit 62 applies this offset to the output value of the tracking control unit. The drive circuit 91 moves the converging lens 22 based on the output value of the tracking control unit to which this offset is applied. Here, if the converging lens 22 is moved so that the offset of the DPDTE detected by the offset measuring unit 61 is zero using the relationship of linearity shown in FIG. 30, the lens shift can be zero. .
[0013]
[Patent Document 1]
JP 2000-315327 A
[0014]
[Problems to be solved by the invention]
For example, when reproducing an address arranged with a shift of ½ track on the inner and outer circumferences of each track, such as a DVD-RAM disc, lens shift occurs due to eccentricity or optical axis tilt. And the balance of the RF signal in the address section is lost. For this reason, the gate signal for detecting and separating the address part cannot be generated, or the RF signal amplitude of the address part becomes small, so that the SN ratio is deteriorated and the address information cannot be reproduced correctly.
[0015]
In order to solve this problem by the lens shift correction method in the conventional optical disc apparatus described above, a tangential phase difference adjustment mechanism (detector) and an adjustment circuit as shown by the signal generation circuit in FIG. 28 are required. For this reason, there arises a problem that it is difficult to reduce the cost of the optical disk device or to downsize the optical pickup.
[0016]
The present invention has been made in view of the above problems, and is an apparatus that does not use a phase difference tracking error signal and does not have a phase difference adjustment circuit, or an optical pickup that has a simple divided photodetector. However, it is an object of the present invention to provide a tracking control device and an optical disk device that can make the lens shift zero.
[0017]
[Means for Solving the Problems]
The tracking control device according to the present invention includes a first address and a second address or a first address section and a second address which are shifted from the information track by about 1/2 track on the inner and outer peripheral sides. In order to perform optical recording and / or reproduction with respect to the information carrier having the address part, a converging means for converging and irradiating the light beam toward the information carrier, and reflection of the light beam obtained from the information carrier An optical head including light detecting means for detecting light and moving means for moving the converging means in a direction crossing the information track is controlled.
[0018]
The tracking control device of the present invention includes an address read unit that acquires an address recorded on the information carrier from an output of the light detection unit, and a first that determines that the address read unit has acquired a first address. The address read determining means, the second address read determining means for determining that the address read means has acquired the second address, and the moving means for moving the position of the convergence means at a predetermined distance interval. The number of times that the offset setting values are sequentially generated and the determination results of the first address read determination unit and the second address read determination unit both acquire an address at each position where the convergence unit has moved. Lens position characteristic measuring means that counts the maximum number of acquisition times, and the maximum number of acquisition times Based on the offset setting value when, and a lens shift adjustment means for moving the converging means by the moving means.
[0019]
Further, the tracking control device of the present invention compares the output of the difference signal generating means with a predetermined first level, a difference signal generating means for generating a difference signal of each detection signal divided and detected by the light detecting means. First gate generating means for generating a gate, second gate generating means for generating a gate by comparing the output of the difference signal generating means with a predetermined second level, and the convergence means at a predetermined distance interval The offset setting value for moving the position by the moving means is sequentially generated, and the number of gates generated by the first gate generating means and the second gate generating means at each position where the convergence means is moved A lens position characteristic measuring unit that obtains a number of measurements based on the number of gates generated by the sensor, and the number of measurements when the positional deviation of the convergence unit relative to the light detection unit is minimized. On the basis of the offset setting value corresponding to the number of measurements that includes a lens shift adjustment means for moving the converging means by the moving means.
[0020]
In a preferred embodiment, the measurement number is a sum of the number of gates generated by the first gate generation unit and the number of gates generated by the second gate generation unit, and the light of the convergence unit The number of measurements when the positional deviation with respect to the detection means is minimum is the maximum value.
[0021]
In a preferred embodiment, the measurement number is a difference between the number of gates generated by the first gate generation unit and the number of gates generated by the second gate generation unit, and the light of the convergence unit The number of measurements when the positional deviation with respect to the detection means is minimum is zero or a value closest to zero.
[0022]
In addition, the tracking control device of the present invention includes a difference signal generating unit that generates a difference signal between detection signals divided and detected by the light detecting unit, and a peak detecting unit that detects a maximum output of the difference signal generating unit. A bottom detection unit for detecting the minimum output of the difference signal generation unit, and an offset set value for moving the position of the convergence unit by the movement unit at predetermined distance intervals, and the convergence unit moves In each of the positions, the lens position characteristic measurement unit for obtaining a calculated value based on the detection value of the peak detection unit and the detection value of the bottom detection unit, and the positional deviation of the convergence unit with respect to the light detection unit is minimized. A lens shift that searches for a calculated value and moves the converging means by the moving means based on an offset setting value corresponding to the searched calculated value And a settling means.
[0023]
In a preferred embodiment, when the detection value of the peak detection means and the detection value of the bottom detection means are expressed as TEmax and TEmin, respectively, the calculated value is (TEmax + TEmin) / (TEmax−TEmin), and the convergence The calculated value when the positional deviation of the means relative to the light detecting means is minimum is zero or a value closest to zero.
[0024]
The tracking control apparatus of the present invention includes a difference signal generating unit that generates a difference signal between the detection signals divided and detected by the light detecting unit, and an output of the first address unit based on an output of the difference signal generating unit. A first address amplitude detecting means for detecting an amplitude; a second address amplitude detecting means for detecting the amplitude of the second address portion from the output of the difference signal generating means; and the convergence means at a predetermined distance interval. Are sequentially generated by the moving means, and the output of the first address amplitude detecting means and the second address amplitude detecting means at each position where the converging means is moved. Lens position characteristic measuring means for obtaining an output difference from the output, and searching for a value where the output difference is zero or closest to zero, and the output difference becomes zero or the maximum value closest to zero. Based on the offset setting value when, and a lens shift adjustment means for moving the converging means by the moving means.
[0025]
In addition, the tracking control device of the present invention performs the optical recording and / or reproduction with respect to the information carrier having the first and second regions having different reflection characteristics when irradiated with the light beam. A converging means for converging and irradiating the light beam toward the light source, a light detecting means for dividing and detecting the reflected light of the light beam obtained from the information carrier, and moving the converging means in a direction crossing the information track And an optical head having a moving means. The tracking control device includes: a difference signal generating unit that generates a difference signal between detection signals divided and detected by the light detecting unit; an offset measuring unit that measures an average value of the difference signal in a predetermined period; and a predetermined distance. The offset setting value for moving the position of the convergence means by the moving means is generated sequentially at intervals, and the average value at each position where the convergence means has moved is calculated as the first region and the second region of the information carrier. Lens position characteristic measuring means to be obtained for the area, the relationship between the offset setting value and the average value obtained in the first area of the information carrier, and the offset setting value and the average value obtained in the second area The average value when the positional deviation of the convergence means with respect to the light detection means is minimized is searched from the relationship with Based on the set setting values, and a lens shift adjustment means for moving the converging means by the moving means.
[0026]
In a preferred embodiment, the lens position characteristic measuring means acquires the number of acquisitions, the number of measurements, the calculated value, the output difference, or the average value while rotating the information carrier once or an integral multiple thereof. .
[0027]
In a preferred embodiment, the tracking control device further includes a tracking error signal generating unit that detects a track deviation from an output of the light detecting unit, and an offset adjusting unit that adjusts an offset of the tracking error signal generating unit, After the offset adjustment by the offset adjustment unit, the lens position characteristic measurement unit is operated.
[0028]
In a preferred embodiment, the tracking control apparatus further includes a tracking error signal generating unit that detects a track deviation from an output of the light detecting unit, and an offset adjusting unit that adjusts an offset of the tracking error signal generating unit, The lens position characteristic measuring means is operated before the offset adjustment by the offset adjusting means.
[0029]
In a preferred embodiment, the tracking control apparatus further includes a tracking error signal generating unit that detects a track deviation from an output of the light detecting unit, and an offset adjusting unit that adjusts an offset of the tracking error signal generating unit, The offset adjusting means is operated according to the amount of movement of the converging means by the moving means.
[0030]
In a preferred embodiment, the information carrier includes an information track formed by a convex portion and a concave portion, and the lens position characteristic measuring means performs measurement on each of the convex portion and the concave portion of the information track, and performs measurement. Based on the result, the lens shift adjusting means moves the converging means with respect to the convex portion and the concave portion, respectively.
[0031]
In a preferred embodiment, the lens position characteristic measuring means and the lens shift adjusting means are operated according to the position of the information carrier.
[0032]
In a preferred embodiment, the lens shift adjusting means is an approximate function determining means for determining an approximate function from the relationship between the number of acquisitions, the number of measurements, the calculated value, the output difference, or the average value and the offset setting value. The offset setting value when the positional deviation of the convergence means relative to the light detection means is minimized is obtained from the approximate function.
[0033]
In a preferred embodiment, the lens shift adjusting means obtains a range in which the number of acquisitions, the number of measurements, the calculated value, the output difference, or the average value is approximately constant, and corresponds to the center of the constant range. The offset setting value to be used is set as the offset setting value when the positional deviation with respect to the light detection means is minimized.
[0034]
In a preferred embodiment, the lens position characteristic measurement unit obtains the number of acquisitions, the number of measurements, the calculated value, the output difference, or the average value according to the rotation phase of the information carrier.
[0035]
In a preferred embodiment, the lens shift adjusting means determines the offset setting value according to a rotation phase of the information carrier.
[0036]
In a preferred embodiment, in the tracking control device, the first gate generation unit and the second gate generation unit detect an address using a level different from the first level and the second level.
[0037]
In a preferred embodiment, the first address amplitude detection means and the second address amplitude detection means are a predetermined portion whose amplitude is approximately constant in the first address portion and the second address portion of the information carrier. The amplitude is detected with.
[0038]
In a preferred embodiment, the lens shift adjusting means is obtained in a first function and a second region indicating a relationship between the offset setting value obtained in the first region of the information carrier and the average value. A second function indicating a relationship between the offset set value and the average value is obtained, and the convergence is performed by the moving unit based on the offset set value that can be obtained from an intersection of the first function and the second function. Move the means.
[0039]
An optical disc apparatus according to the present invention includes a converging unit for converging and irradiating a light beam toward an information carrier, a light detecting unit for detecting reflected light of the light beam obtained from the information carrier, and the converging unit as an information track. An optical head having a moving means for moving in a direction crossing the head, and a tracking control device defined in any of the above.
[0040]
According to the tracking control method of the present invention, the first address and the second address or the first address portion and the second address which are arranged to be shifted to the inner circumference side and the outer circumference side by about 1/2 track with respect to the information track. In order to perform optical recording and / or reproduction with respect to the information carrier having the address part, a converging means for converging and irradiating the light beam toward the information carrier, and reflection of the light beam obtained from the information carrier An optical head including light detecting means for detecting light and moving means for moving the converging means in a direction crossing the information track is controlled.
[0041]
The tracking control method sequentially generates an offset setting value for moving the position of the convergence means by the moving means at a predetermined distance interval, and at each position where the convergence means has moved, from the output of the light detection means A step of counting the number of times of obtaining the first address and the second address recorded on the information carrier, searching for a maximum value of the number of times of acquisition, and when the number of times of acquisition reaches a maximum value Moving the converging means by the moving means based on an offset set value.
[0042]
In the tracking control method of the present invention, the step of generating a difference signal between the detection signals divided and detected by the light detection means, comparing the difference signal with the first and second levels, When the difference signal is larger than the second level, the step of generating the first and second gates and the offset setting value for moving the position of the converging means by the moving means at predetermined distance intervals are sequentially performed. Generating and measuring the number of measurements based on the number of the first and second gates generated at each position where the converging means has moved, and when the positional deviation of the converging means relative to the light detecting means is minimized Searching for the number of measurements, and moving the convergence means by the moving means based on an offset setting value corresponding to the searched number of measurements.
[0043]
In a preferred embodiment, the number of measurements is the sum of the number of the first and second gates, and the number of measurements when the positional deviation of the convergence means relative to the light detection means in the moving step is minimum. It is the maximum value.
[0044]
In a preferred embodiment, the number of measurements is a difference between the number of the first and second gates, and the number of measurements when the positional deviation of the convergence means with respect to the light detection means is minimized is zero or zero. Is the closest value to.
[0045]
Further, the tracking control method of the present invention includes a step of generating a difference signal of each detection signal divided and detected by the light detection means, a step of detecting a maximum value and a minimum value of the difference signal, and a predetermined distance Sequentially generating an offset setting value for moving the position of the convergence means by the moving means at intervals, and obtaining a calculated value based on the maximum value and the minimum value at each position where the convergence means has moved; Searching for the calculated value when the positional deviation of the converging means relative to the light detecting means is minimized, and moving the converging means by the moving means based on the offset setting value corresponding to the searched calculated value. To do.
[0046]
In a preferred embodiment, when the maximum value and the minimum value are expressed as TEmax and TEmin, respectively, the calculated value is (TEmax + TEmin) / (TEmax−TEmin), and the positional deviation of the convergence means relative to the light detection means The calculated value when is minimum is zero or the value closest to zero.
[0047]
In the tracking control method of the present invention, the step of generating a difference signal between the detection signals divided and detected by the light detection means, and the amplitude of the difference signal in the first address part and the second address part Detecting an offset setting value for moving the position of the convergence means by the moving means at predetermined distance intervals, and at each position where the convergence means has moved, a first of the difference signal is detected. A step of obtaining an amplitude difference between the amplitude in the address portion and the amplitude in the second address portion, searching for a value where the amplitude difference is zero or closest to zero, and finding that the amplitude difference is zero or closest to zero. And the step of moving the convergence means by the movement means based on the offset setting value at the time.
[0048]
In addition, the tracking control method of the present invention provides the information carrier for optical recording and / or reproduction with respect to the information carrier having the first and second regions having different reflection characteristics when irradiated with the light beam. A converging means for converging and irradiating the light beam toward the light source, a light detecting means for dividing and detecting the reflected light of the light beam obtained from the information carrier, and moving the converging means in a direction crossing the information track And an optical head having a moving means. The tracking control device includes a step of generating a difference signal between the detection signals divided and detected by the light detection unit, a step of measuring an average value of the difference signal in a predetermined period, and the convergence at a predetermined distance interval. Sequentially generating offset setting values for moving the position of the means by the moving means, and obtaining the average value at each position to which the converging means has moved for the first region and the second region of the information carrier And the relationship between the offset setting value and the average value obtained in the first region of the information carrier, and the relationship between the offset setting value and the average value obtained in the second region. , Search for the average value when the positional deviation of the convergence means relative to the light detection means is minimum, and set the offset corresponding to the searched average value Based on, including the step of moving the converging means by the moving means.
[0049]
In a preferred embodiment, a first function indicating a relationship between the offset setting value obtained in the first area of the information carrier and the average value, and the offset setting value obtained in the second area, A second function indicating a relationship with the average value is obtained, and the convergence means is moved by the moving means based on an offset setting value that can be obtained from an intersection of the first function and the second function.
[0050]
A program to be executed by each step computer defined in the tracking control method described above is recorded on a computer-readable recording medium.
[0051]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 is a block diagram showing a configuration of a tracking control apparatus according to the present embodiment and an optical disk apparatus using the tracking control apparatus. In the optical disc apparatus 11, the optical pickup 120 includes a light emitting element (not shown) such as a laser, a converging lens 22 that is a converging unit, and an actuator 23 that is a moving unit. The converging lens 22 converts the light beam 21 into information. Irradiating while converging toward the optical disk 110 as a carrier. The optical disk 110 is disposed, for example, by shifting about 1/2 track with respect to the information track, and has an address portion including address information. The actuator 23 moves the converging lens 22 so as to cross the information track.
[0052]
The optical pickup 120 further includes a photodetector 124 including detectors A and B divided in the diameter direction of the optical disk, and the light beam 21 ′ reflected on the information recording surface of the optical disk 110 is a light that is a light detection means. Detection is performed by the detector 124. The outputs of the detection units A and B of the photodetector 124 are input to the subtraction circuit 130, and a signal obtained by subtracting the signal B corresponding to the light amount detected by the detection unit B from the signal A corresponding to the light amount detected by the detection unit A. That is, the RF difference signal of (A−B) is generated. The RF difference signal passes through a low-pass filter (LPF) 131 and is input to a digital signal processor (DSP) 150 serving as a tracking control device as a tracking error signal (hereinafter referred to as TE).
[0053]
The DSP 150 includes a signal processing unit 140, a lens position characteristic measurement unit 162, a memory 163, an optimum lens position search unit 164, a lens position setting unit 161, an A / D converter 51, an offset adjustment unit 52, a tracking control unit 53, and a D / D A converter 54 is included.
[0054]
The A / D converter 51 converts TE into a digital signal. The offset adjustment unit 52 adds a predetermined offset in tracking control to the TE converted into the digital signal, and outputs the result to the tracking control unit 53. The tracking control unit 53 generates a tracking drive value by performing a filter operation for performing phase compensation and low-frequency compensation on the TE converted into a digital signal. The generated tracking drive value is added to the output of the lens position setting unit 161 and is converted again into an analog signal by the D / A converter 54. The output of the D / A converter 54 becomes a tracking drive signal and is output to the drive circuit 91.
[0055]
The drive circuit 91 amplifies the tracking drive signal and drives the actuator 23 which is a moving means built in the optical pickup 120 to perform tracking control. At this time, the lens position setting unit 161 of the DSP 150 can add an offset to the tracking drive value that is the output of the tracking control unit 53 to shift the position of the convergent lens 22 relative to the photodetector 124.
[0056]
Further, the RF difference signal is input from the subtraction circuit 130 to the signal processing unit 140 of the DSP 150. This signal processing unit 140 can obtain address information. FIG. 2 is a block diagram showing a detailed configuration of the signal processing unit 140. In the signal processing unit 140, a high-pass filter (HPF) 141 removes a DC component of the RF difference signal. The RF difference signal from which the DC component has been removed is converted into data binarized at an appropriate slice level by the binarization circuit 142. The binarized data signal is input to the PLL circuit 143, and the frequency and phase of a synchronous clock signal for data extraction are controlled based on the binarized data signal. The output of the PLL circuit 143 is input to a decoder 144 which is an address reading means, and the decoder 144 outputs reproduction information, that is, code data of a track or sector address.
[0057]
The address read determination unit 145 serving as the first address read determination unit and the second address read determination unit determines whether the address has been read correctly based on the output result of the decoder 144. If it is determined that the address has been read, an address OK signal indicating that the address has been read is output to the lens position characteristic measuring unit 162 as shown in FIG.
[0058]
The lens position characteristic measuring unit 162 which is a lens position characteristic measuring unit offsets the lens position setting unit 161 so that the lens position setting unit 161 sequentially generates an offset for moving the position of the convergent lens 22 at a predetermined distance interval. A set value is output, and the number of address OK signals received at the offset set value is counted. The predetermined distance intervals are not necessarily equal. Then, the offset set value and the number of address OK signals at that time are output to the memory 163. The memory 163 sequentially stores the offset set value and the number of address OK signals. The lens position setting unit 161 sequentially generates an offset based on the offset setting value received from the lens position characteristic measurement unit 162, and adds the offset to the tracking drive value that is the output of the tracking control unit 53.
[0059]
As will be described in detail below, the optimum lens position searching unit 164 serving as a lens shift adjusting unit obtains the maximum value of the number of address OK signals, and uses the offset setting value at that time as an offset setting value that gives the optimum lens position. The data is output to the position setting unit 161. The lens position setting unit 161 generates an offset based on the offset setting value that gives the optimum lens position, and adds it to the tracking drive value. Thereby, the lens shift can be set to zero.
[0060]
FIG. 3 is a schematic diagram for explaining the physical structure of the optical disk 110 as an information carrier. In the optical disc 110, for example, tracks T1 formed by convex portions and tracks T2 formed by concave portions are alternately arranged with respect to the information recording surface. Information such as user data is recorded on the tracks T1 and T2 using dark and light marks or the like. The first address portion A1 is recorded at a position shifted by about ½ of the track on the inner circumference side of the disc with respect to the track T1, and the second address portion A2 is recorded on the disc with respect to the track T1. Is recorded at a position shifted by about ½ of the track.
[0061]
FIG. 4 is an example of an output waveform of the RF difference signal when the address portion of the optical disk 110 shown in FIG. 3 is reproduced. 4A shows a waveform when there is no lens shift, and FIG. 4B shows a waveform when the lens is shifted to the inner circumference side. When the lens is shifted to the inner periphery as shown in FIG. 4B, the waveforms of the two address parts become asymmetric, and the address part on the outer periphery side cannot obtain a sufficient RF signal amplitude, and the address is reproduced. become unable.
[0062]
The address read determination unit 145 shown in FIG. 2 determines that the address has been read when there is no error in reproduction of both the first address unit A1 and the second address unit A2, and generates an address OK signal. This is output to the lens position characteristic measuring unit 162. As is apparent from FIG. 4, when the lens shift occurs, the frequency at which the address OK signal is output decreases. Therefore, the lens shift can be detected by utilizing the fact that the number of address OK signals counted by the lens position characteristic measurement unit 162 is larger when the lens shift is smaller than when the lens shift is large.
[0063]
FIG. 5 shows the relationship between the offset setting value set by the lens position characteristic measuring unit 162 and the number of address OK signals. In FIG. 5, the horizontal axis represents the offset setting value, and the vertical axis represents the number of address OK signals. Since the lens position setting unit 161 generates an offset based on the offset setting value and adds the offset to the tracking drive value, the horizontal axis also indicates the relative lens position. In the characteristic shown in FIG. 5, the point A at which the address OK signal is maximum is an optimum lens position where there is no lens shift. The optimum lens position searching unit 164 obtains the maximum value of the number of address OK signals stored in the memory 163 and outputs the offset setting value at that time to the lens position setting unit 161 as the optimum lens position. The lens position setting unit 161 generates an offset based on the received offset setting value, and superimposes the offset on the tracking drive value. The tracking drive signal to which the offset is added is output from the drive circuit 91, whereby the lens shift is corrected, and the RF difference signal in the address portion always has a good waveform with good symmetry as shown in FIG. It becomes. That is, a good tracking signal and RF signal can be obtained, and a highly reliable optical disc apparatus can be provided.
[0064]
In the present embodiment, the photodetector 124 has a detection region divided into two. However, for example, using a four-part photodetector 24 as shown in FIG. 28 of the conventional example, the signal obtained by adding the outputs of the detectors A and C, and the outputs of the detectors B and D are added. The same effect can be obtained by performing processing using the processed signal.
[0065]
As described above, according to the present invention, the lens shift of the convergent lens with respect to the photodetector is corrected based on the signals obtained when the first address and the second address provided on the information carrier are reproduced. . In particular, in the present embodiment, the first address and the second address are shifted from the information track by approximately ½ track to the inner circumference side and the outer circumference side. Utilizing the fact that the lens shift becomes zero or small when playback is possible.
[0066]
Specifically, an offset setting value is sequentially generated to change the position of the convergent lens, and the position of the convergent lens with respect to the photodetector is changed. Then, the number of times that the first address and the second address can be correctly reproduced at each position is obtained. If the converging lens is moved using the offset setting value when the number of times is the largest, the lens shift can be corrected to be zero or minimum.
[0067]
As a result, in an apparatus that does not use a phase difference tracking error signal, does not have a phase difference adjustment circuit, and an optical pickup that has a simple divided photodetector, the initial error associated with optical component installation errors or vertical installation Even if the optical axis is tilted due to the movement of the objective lens, a good tracking signal and RF signal can be obtained.
[0068]
(Second Embodiment)
FIG. 6 is a block diagram showing a configuration of a tracking control device according to the present embodiment and an optical disk device using the tracking control device. In the optical disk device 12, the same components as those of the optical disk device 11 of the first embodiment are denoted by the same reference numerals.
[0069]
The optical pickup 120 includes a light emitting element (not shown) such as a laser, a converging lens 22 that is a converging unit, and an actuator 23 that is a moving unit. The converging lens 22 transmits the light beam 21 to the optical disc 110 that is an information carrier. Irradiate while converging toward.
[0070]
The optical pickup 120 further includes a photodetector 124 including detectors A and B divided in the diameter direction of the optical disk, and the light beam 21 ′ reflected on the information recording surface of the optical disk 110 is a light that is a light detection means. Detection is performed by the detector 124. The outputs of the detection units A and B of the photodetector 124 are input to the subtraction circuit 130, and a signal obtained by subtracting the signal B corresponding to the light amount detected by the detection unit B from the signal A corresponding to the light amount detected by the detection unit A. That is, the RF difference signal of (A−B) is generated. The RF difference signal passes through a low-pass filter (LPF) 131 and is input as a tracking error signal (hereinafter referred to as TE) to a digital signal processor (DSP) 250 which is a tracking control device.
[0071]
The DSP 250 includes an address gate unit 240, a lens position characteristic measurement unit 262, a memory 163, an optimum lens position search unit 264, a lens position setting unit 161, an A / D converter 51, an offset adjustment unit 52, a tracking control unit 53, and a D / D A converter 54 is included.
[0072]
The A / D converter 51 converts TE into a digital signal. The offset adjustment unit 52 adds a predetermined offset to the TE converted into the digital signal and outputs the result to the tracking control unit 53. The tracking control unit 53 generates a tracking drive value by, for example, performing a filter operation for performing phase compensation and low-frequency compensation on the TE converted into a digital signal. The generated tracking drive value is added to the output of the lens position setting unit 161 and is converted again into an analog signal by the D / A converter 54. The output of the D / A converter 54 becomes a tracking drive signal and is output to the drive circuit 91.
[0073]
The drive circuit 91 amplifies the tracking drive signal and drives the actuator 23 which is a moving means built in the optical pickup 120 to perform tracking control. At this time, the lens position setting unit 161 of the DSP 250 can add an offset to the tracking drive value that is the output of the tracking control unit 53 to shift the position of the convergent lens 22 relative to the photodetector 124.
[0074]
Also, TE that is an output from the LPF 131 is input to the address gate unit 240. The address gate unit 240 generates a gate signal based on TE and counts the number thereof.
[0075]
FIG. 7 is a block diagram showing a more specific configuration of the address gate unit 240. The address gate unit 240 includes a comparator 241a that is a first gate generation unit and a comparator 241b that is a second gate generation unit. The comparators 241a and 241b each output an output signal to the OR circuit 242 when TE exceeds a predetermined level. The OR circuit 242 generates an output signal when receiving a signal from the comparator 241a or the comparator 241b. The gate count unit 243 that is a counting unit counts the number of outputs of the OR circuit 242, and outputs the count number to the lens position characteristic measuring unit 262 that is a lens position characteristic measuring unit.
[0076]
The lens position characteristic measuring unit 262 sets an offset setting value to the lens position setting unit 161 so that the lens position setting unit 161 sequentially generates an offset for moving the position of the convergent lens 22 at a predetermined time interval and a predetermined distance interval. And the count number received from the address gate unit 240 at the offset setting value is counted. The predetermined distance intervals are not necessarily equal. Then, the offset set value and the count number at that time are output to the memory 163. The memory 163 sequentially stores the offset setting value and the count number. The lens position setting unit 261 sequentially generates an offset based on the offset setting value received from the lens position characteristic measurement unit 162, and adds the offset to the tracking drive value that is the output of the tracking control unit 53.
[0077]
As will be described in detail below, the optimum lens position searching unit 264 that is a lens shift adjusting unit obtains the maximum count value, and uses the offset setting value at that time as the offset setting value that gives the optimum lens position. 161 to output. The lens position setting unit 161 generates an offset based on the offset setting value that gives the optimum lens position, and adds it to the tracking drive value. Thereby, the lens shift can be set to zero.
[0078]
FIGS. 8A and 8B show the waveform of the signal of each part in the address gate part 240. FIG. As shown in FIG. 8A, when TE in the case where there is no lens shift is input to the address gate unit 240, the TE address part exceeds the comparator levels a and b set in the comparators 241a and 241b. The comparators 241a and 241b output an outer peripheral gate signal and an inner peripheral gate signal, respectively. In this case, the OR circuit 242 counts the outer peripheral gate signal and the inner peripheral gate signal and outputs a count number of 2.
[0079]
On the other hand, as shown in FIG. 8B, when TE is input when a lens shift occurs on the inner peripheral side, the address part of TE does not exceed a of comparator 241a. For this reason, the outer peripheral gate signal is not generated, and only the inner peripheral gate signal is generated from the comparator 241b. In this case, the OR circuit 242 outputs a count number of 1.
[0080]
Although only one address part is shown in FIG. 8, the lens position characteristic measurement part 262 sets a time interval for generating the offset setting value so as to receive a plurality of address parts at a certain offset setting value. Therefore, when the lens shift occurs, the count number of the generated gate signal is also reduced.
[0081]
FIG. 9 shows the relationship between the lens position based on the offset setting value set by the lens position characteristic measuring unit 262 and the generated gate count. In FIG. 9, the horizontal axis indicates the position of the converging lens, and the vertical axis indicates the gate count. Since the lens position setting unit 161 generates an offset based on the offset setting value and adds the offset to the tracking drive value, the horizontal axis also indicates the relative lens position. In the characteristic shown in FIG. 9, the point A at which the count number is maximum is an optimum lens position where there is no lens shift. The optimum lens position search unit 264 obtains the maximum value of the count number stored in the memory 163, and outputs the offset setting value at that time to the lens position setting unit 161 as the optimum lens position. The lens position setting unit 161 generates an offset based on the received offset setting value, and superimposes the offset on the tracking drive value. The tracking drive signal to which the offset is added is output from the drive circuit 91, whereby the lens shift is corrected, and the RF difference signal in the address portion always has a good waveform with good symmetry as shown in FIG. It becomes. That is, a good tracking signal and RF signal can be obtained, and a highly reliable optical disc apparatus can be provided.
[0082]
As described above, according to the present invention, the lens shift of the convergent lens with respect to the photodetector is corrected based on the signals obtained when the first address and the second address provided on the information carrier are reproduced. . In particular, in the present embodiment, the difference signal of each signal detected by dividing in the diameter direction of the optical disc is compared with the first and second levels, and the number of times the difference signal exceeds each level is counted. The first address and the second address are arranged so as to be shifted from the information track to the inner circumference side and the outer circumference side by about 1/2 track, so that the number of times exceeding the first level and the second address When the sum with the number of times when the level is exceeded becomes maximum, the fact that the lens shift becomes zero or a small value is used.
[0083]
Specifically, an offset setting value is sequentially generated to change the position of the convergent lens, and the position of the convergent lens with respect to the photodetector is changed. Then, at each position, the sum of the number of times of exceeding the first level and the number of times of exceeding the second level is obtained. If the converging lens is moved using the offset setting value when the number of times is the largest, the lens shift can be corrected to be zero or minimum.
[0084]
As a result, in an apparatus that does not use a phase difference tracking error signal, does not have a phase difference adjustment circuit, and an optical pickup that has a simple divided photodetector, the initial error associated with optical component installation errors or vertical installation Even if the optical axis is tilted due to the movement of the objective lens, a good tracking signal and RF signal can be obtained.
[0085]
(Third embodiment)
FIG. 10 is a block diagram showing a configuration of the tracking control apparatus according to the present embodiment and an optical disk apparatus using the tracking control apparatus. In the optical disk device 13, the same components as those of the optical disk device 11 of the first embodiment are denoted by the same reference numerals.
[0086]
The optical pickup 120 includes a light emitting element (not shown) such as a laser, a converging lens 22 that is a converging unit, and an actuator 23 that is a moving unit. The converging lens 22 transmits the light beam 21 to the optical disc 110 that is an information carrier. Irradiate while converging toward.
[0087]
The optical pickup 120 further includes a photodetector 124 including detectors A and B divided in the diameter direction of the optical disk, and the light beam 21 ′ reflected on the information recording surface of the optical disk 110 is a light that is a light detection means. Detection is performed by the detector 124. The outputs of the detection units A and B of the photodetector 124 are input to the subtraction circuit 130, and a signal obtained by subtracting the signal B corresponding to the light amount detected by the detection unit B from the signal A corresponding to the light amount detected by the detection unit A. That is, the RF difference signal of (A−B) is generated. The RF difference signal passes through a low-pass filter (LPF) 131 and is input as a tracking error signal (hereinafter referred to as TE) to a digital signal processor (DSP) 350 which is a tracking control device.
[0088]
The DSP 350 includes an address gate unit 340, a lens position characteristic measurement unit 362, a memory 163, an optimum lens position search unit 364, a lens position setting unit 161, an A / D converter 51, an offset adjustment unit 52, a tracking control unit 53, and a D / D A converter 54 is included.
[0089]
The A / D converter 51 converts TE into a digital signal. The offset adjustment unit 52 adds a predetermined offset to the TE converted into the digital signal and outputs the result to the tracking control unit 53. The tracking control unit 53 generates a tracking drive value by, for example, performing a filter operation for performing phase compensation and low-frequency compensation on the TE converted into a digital signal. The generated tracking drive value is added to the output of the lens position setting unit 161 and is converted again into an analog signal by the D / A converter 54. The output of the D / A converter 54 becomes a tracking drive signal and is output to the drive circuit 91.
[0090]
The drive circuit 91 amplifies the tracking drive signal and drives the actuator 23 which is a moving means built in the optical pickup 120 to perform tracking control. At this time, the lens position setting unit 161 of the DSP 350 can add an offset to the tracking drive value that is the output of the tracking control unit 53 to shift the position of the convergent lens 22 relative to the photodetector 124.
[0091]
Further, TE that is an output from the LPF 131 is input to the address gate unit 340. The address gate unit 340 generates a gate signal based on TE and counts the number thereof.
[0092]
FIG. 11 is a block diagram showing a more specific configuration of the address gate unit 340. The address gate unit 340 includes a comparator 341a as a first gate generation unit, a comparator 341b as a second gate generation unit, and gate count units 342a and 342b as count units.
[0093]
Each of the comparators 341a and 341b receives TE, and outputs a gate signal to the gate count units 342a and 342b when TE exceeds a predetermined comparator level. The gate count units 342a and 342b count the number of gate signals, and output the number to the lens position characteristic measurement unit 362, which is a lens position characteristic measurement unit.
[0094]
The lens position characteristic measuring unit 362 sets an offset setting value to the lens position setting unit 161 so that the lens position setting unit 161 sequentially generates an offset for moving the position of the convergent lens 22 at a predetermined time interval and a predetermined distance interval. And the difference between the counts received from the gate count units 342a and 342b of the address gate unit 340 at the offset setting value. The predetermined distance intervals are not necessarily equal. Then, the difference between the offset set value and the count number at that time is output to the memory 163. The memory 163 sequentially stores the difference between the offset set value and the count number. The lens position setting unit 161 sequentially generates an offset based on the offset setting value received from the lens position characteristic measurement unit 362 and adds the offset to the tracking drive value that is the output of the tracking control unit 53.
[0095]
As will be described in detail below, the optimum lens position searching unit 364 that is a lens shift adjusting unit uses the offset setting value when the difference in the count number is zero or a value closest to zero as the offset setting value that gives the optimum lens position. To the lens position setting unit 161. The lens position setting unit 161 generates an offset based on the offset setting value that gives the optimum lens position, and adds it to the tracking drive value. Thereby, the lens shift can be set to zero.
[0096]
As shown in FIG. 8A, when TE in the case where there is no lens shift is input to the address gate unit 340, the TE address unit exceeds the comparator levels a and b set in the comparators 341a and 341b. The comparators 341a and 341b respectively output an outer peripheral gate signal and an inner peripheral gate signal. In this case, the count numbers of the gate signals output from the gate count units 342a and 342b are each 1, and the difference between the count numbers is zero.
[0097]
On the other hand, as shown in FIG. 8B, when TE is input when a lens shift occurs on the inner peripheral side, the TE address part does not exceed the comparator level a of the comparator 341a. For this reason, the outer peripheral gate signal is not generated, and only the inner peripheral gate signal is generated from the comparator 341b. In this case, the count numbers of the gate signals output from the gate count units 342a and 342b are 1 and zero, and the difference between the count numbers is 1.
[0098]
Similarly to the second embodiment, a lens based on a more accurate difference between count numbers and an offset setting value is set by setting a time interval for generating an offset setting value so that the address gate unit 340 receives a plurality of address portions. The relationship with the position of is required.
[0099]
FIG. 12 shows the relationship between the position of the lens based on the offset setting value set by the lens position characteristic measuring unit 362 and the difference in the number of counts. In FIG. 12, the horizontal axis indicates the position of the converging lens, and the vertical axis indicates the difference in gate count. Since the lens position setting unit 161 generates an offset based on the offset setting value and adds the offset to the tracking drive value, the horizontal axis also indicates the relative lens position. In the characteristic shown in FIG. 12, the point A at which the difference in count number is zero is the optimum lens position without any lens shift. The optimum lens position searching unit 364 searches for a difference between the count numbers stored in the memory 163 or a value closest to zero, and outputs the offset setting value at that time to the lens position setting unit 161 as the optimum lens position. The lens position setting unit 161 generates an offset based on the received offset setting value, and superimposes the offset on the tracking drive value. The tracking drive signal to which the offset is added is output from the drive circuit 91, whereby the lens shift is corrected, and the RF difference signal in the address portion always has a good waveform with good symmetry as shown in FIG. It becomes. That is, a good tracking signal and RF signal can be obtained, and a highly reliable optical disc apparatus can be provided.
[0100]
As described above, according to the present invention, the lens shift of the convergent lens with respect to the photodetector is corrected based on the signals obtained when the first address and the second address provided on the information carrier are reproduced. . In particular, in the present embodiment, the first address portion and the second address portion of the difference signal of each signal detected by dividing in the diameter direction of the optical disc are compared with the first and second levels. Count the number of times the difference signal exceeded. The first address and the second address are arranged so as to be shifted from the information track to the inner circumference side and the outer circumference side by about 1/2 track, so that the number of times exceeding the first level and the second address When the difference from the number of times when the level is exceeded is zero or a value closest to zero, the fact that the lens shift becomes zero or a small value is used.
[0101]
Specifically, an offset setting value is sequentially generated to change the position of the convergent lens, and the position of the convergent lens with respect to the photodetector is changed. Then, the difference between the number of times exceeding the first level and the number of times exceeding the second level is obtained at each position. If the convergent lens is moved using the offset setting value when the number of times becomes zero or a value closest to zero, the lens shift can be corrected to be zero or minimum.
[0102]
As a result, in an apparatus that does not use a phase difference tracking error signal, does not have a phase difference adjustment circuit, and an optical pickup that has a simple divided photodetector, the initial error associated with optical component installation errors or vertical installation Even if the optical axis is tilted due to the movement of the objective lens, a good tracking signal and RF signal can be obtained.
[0103]
(Fourth embodiment)
FIG. 13 is a block diagram showing the configuration of the tracking control apparatus according to the present embodiment and the optical disk apparatus using the tracking control apparatus. In the optical disk device 14, the same reference numerals are assigned to the same components as those of the optical disk device 11 of the first embodiment.
[0104]
The optical pickup 120 includes a light emitting element (not shown) such as a laser, a converging lens 22 that is a converging unit, and an actuator 23 that is a moving unit. The converging lens 22 transmits the light beam 21 to the optical disc 110 that is an information carrier. Irradiate while converging toward.
[0105]
The optical pickup 120 further includes a photodetector 124 including detectors A and B divided in the diameter direction of the optical disk, and the light beam 21 ′ reflected on the information recording surface of the optical disk 110 is a light that is a light detection means. Detection is performed by the detector 124. The outputs of the detection units A and B of the photodetector 124 are input to the subtraction circuit 130, and a signal obtained by subtracting the signal B corresponding to the light amount detected by the detection unit B from the signal A corresponding to the light amount detected by the detection unit A. That is, the RF difference signal of (A−B) is generated. The RF difference signal passes through a low-pass filter (LPF) 131 and is input as a tracking error signal (hereinafter referred to as TE) to a digital signal processor (DSP) 450 which is a tracking control device.
[0106]
The DSP 450 includes a symmetry detection unit 440, a lens position characteristic measurement unit 462, a memory 163, an optimum lens position search unit 464, a lens position setting unit 161, an A / D converter 51, an offset adjustment unit 52, a tracking control unit 53, and a D. / A converter 54 is included.
[0107]
The A / D converter 51 converts TE into a digital signal. The offset adjustment unit 52 adds a predetermined offset to the TE converted into the digital signal and outputs the result to the tracking control unit 53. The tracking control unit 53 generates a tracking drive value by, for example, performing a filter operation for performing phase compensation and low-frequency compensation on the TE converted into a digital signal. The generated tracking drive value is added to the output of the lens position setting unit 161 and is converted again into an analog signal by the D / A converter 54. The output of the D / A converter 54 becomes a tracking drive signal and is output to the drive circuit 91.
[0108]
The drive circuit 91 amplifies the tracking drive signal and drives the actuator 23 which is a moving means built in the optical pickup 120 to perform tracking control. At this time, the lens position setting unit 161 of the DSP 450 can add an offset to the tracking drive value that is the output of the tracking control unit 53 to shift the position of the convergent lens 22 relative to the photodetector 124.
[0109]
Further, TE that is an output from the LPF 131 is input to the symmetry detection unit 440. The symmetry detector 440 detects the symmetry of the TE address part.
[0110]
FIG. 14 is a block diagram showing a more specific configuration of the symmetry detection unit 440. The symmetry detection unit 440 includes a peak detection circuit 441 that is a peak detection unit and a bottom detection circuit 442 that is a bottom detection unit. The peak detection circuit 441 holds the maximum TE value TEmax in the address portion. The bottom detection circuit 442 holds the minimum TE value TEmin in the address portion. The symmetry detection unit 440 outputs TEmax and TEmin to the lens position characteristic measurement unit 462 that is a lens position detection unit.
[0111]
The lens position characteristic measurement unit 462 outputs an offset setting value to the lens position setting unit 161 so that the lens position setting unit 161 sequentially generates an offset for moving the position of the convergent lens 22 at a predetermined distance interval. The predetermined distance intervals are not necessarily equal. In addition, TE symmetry (TEmax + TEmin) / (TEmax−TEmin) is calculated at the offset setting value. Then, the offset set value and the TE symmetry at that time are output to the memory 163. The memory 163 sequentially stores the offset setting value and the TE symmetry. The lens position setting unit 161 sequentially generates an offset based on the offset setting value received from the lens position characteristic measurement unit 462, and adds the offset to the tracking drive value that is the output of the tracking control unit 53.
[0112]
As will be described in detail below, the optimum lens position search unit 464 that is a lens shift adjustment means uses the offset setting value when the TE symmetry is zero or a value closest to zero as the offset setting value that gives the optimum lens position. The data is output to the lens position setting unit 161. The lens position setting unit 161 generates an offset based on the offset setting value that gives the optimum lens position, and adds it to the tracking drive value. Thereby, the lens shift can be set to zero.
[0113]
FIGS. 15A and 15B schematically show an enlarged waveform in the address portion of TE input to the address gate portion 440. FIG.
[0114]
As shown in FIG. 15A, the TE waveform in the address portion when there is no lens shift is symmetric with respect to zero. Therefore, the TE symmetry (TEmax + TEmin) / (TEmax−TEmin) calculated from the output TEmax of the peak detection circuit 441 and the output TEmin of the bottom detection circuit 442 becomes zero or a value close to zero.
[0115]
On the other hand, as shown in FIG. 15B, the TE waveform in the address portion when the lens shift occurs on the inner peripheral side is asymmetric with respect to zero. For this reason, TE symmetry (TEmax + TEmin) / (TEmax−TEmin) calculated from the output TEmax of the peak detection circuit 441 and the output TEmin of the bottom detection circuit 442 is a negative value.
[0116]
FIG. 16 shows the relationship between the lens position based on the offset setting value set by the lens position characteristic measuring unit 462 and the TE symmetry. In FIG. 16, the horizontal axis indicates the position of the converging lens, and the vertical axis indicates TE symmetry. Since the lens position setting unit 161 generates an offset based on the offset setting value and adds the offset to the tracking drive value, the horizontal axis also indicates the relative lens position. In the characteristics shown in FIG. 16, the point A at which the TE symmetry is zero is an optimum lens position with no lens shift. Optimal lens position search unit 464 sets TE symmetry stored in memory 163 to zero or a value closest to zero (for example, a value close to zero or a threshold value close to zero, and a value closer to zero than this threshold value) And the offset setting value at that time is output to the lens position setting unit 161 as the optimum lens position. The lens position setting unit 161 generates an offset based on the received offset setting value, and superimposes the offset on the tracking drive value. The tracking drive signal to which the offset is added is output from the drive circuit 91, whereby the lens shift is corrected, and the RF difference signal in the address portion always has a good waveform with good symmetry as shown in FIG. It becomes. That is, a good tracking signal and RF signal can be obtained, and a highly reliable optical disc apparatus can be provided.
[0117]
As described above, according to the present invention, the lens shift of the convergent lens with respect to the photodetector is corrected based on the signals obtained when the first address and the second address provided on the information carrier are reproduced. . In particular, in the present embodiment, the maximum value and the minimum value at the first address and the second address of the difference signal of each signal detected by being divided in the diameter direction of the optical disc are obtained. Since the first address and the second address are shifted from the information track by approximately ½ track to the inner circumference side and the outer circumference side, (maximum value + minimum value) / (maximum value− When the minimum value) is zero or a value closest to zero, the fact that the lens shift becomes zero or a small value is used.
[0118]
Specifically, offset setting values are sequentially generated to change the position of the convergent lens, and the position of the convergent lens relative to the photodetector is changed. Then, at each position, (maximum value + minimum value) / (maximum value-minimum value) is obtained. If the converging lens is moved using the offset setting value when the value becomes zero or a value closest to zero, the lens shift can be corrected to be zero or minimum.
[0119]
As a result, in an apparatus that does not use a phase difference tracking error signal, does not have a phase difference adjustment circuit, and an optical pickup that has a simple divided photodetector, the initial error associated with optical component installation errors or vertical installation Even if the optical axis is tilted due to the movement of the objective lens, a good tracking signal and RF signal can be obtained.
[0120]
(Fifth embodiment)
FIG. 17 is a block diagram showing a configuration of a tracking control device according to the present embodiment and an optical disk device using the tracking control device. In the optical disk device 15, the same components as those of the optical disk device 11 of the first embodiment are denoted by the same reference numerals.
[0121]
The optical pickup 120 includes a light emitting element (not shown) such as a laser, a converging lens 22 that is a converging unit, and an actuator 23 that is a moving unit. The converging lens 22 transmits the light beam 21 to the optical disc 110 that is an information carrier. Irradiate while converging toward.
[0122]
The optical pickup 120 further includes a photodetector 124 including detectors A and B divided in the diameter direction of the optical disk, and the light beam 21 ′ reflected on the information recording surface of the optical disk 110 is a light that is a light detection means. Detection is performed by the detector 124. The outputs of the detection units A and B of the photodetector 124 are input to the subtraction circuit 230, and a signal obtained by subtracting the signal B corresponding to the light amount detected by the detection unit B from the signal A corresponding to the light amount detected by the detection unit A. That is, the RF difference signal of (A−B) is generated. The RF difference signal passes through a low-pass filter (LPF) 131 and is input as a tracking error signal (hereinafter referred to as TE) to a digital signal processor (DSP) 550 which is a tracking control device.
[0123]
The DSP 550 includes an amplitude detection unit 540, a lens position characteristic measurement unit 562, a memory 163, an optimum lens position search unit 564, a lens position setting unit 161, an A / D converter 51, an offset adjustment unit 52, a tracking control unit 53, and a D / D. A converter 54 is included.
[0124]
The A / D converter 51 converts TE into a digital signal. The offset adjustment unit 52 adds a predetermined offset to the TE converted into the digital signal and outputs the result to the tracking control unit 53. The tracking control unit 53 generates a tracking drive value by, for example, performing a filter operation for performing phase compensation and low-frequency compensation on the TE converted into a digital signal. The generated tracking drive value is added to the output of the lens position setting unit 161 and is converted again into an analog signal by the D / A converter 54. The output of the D / A converter 54 becomes a tracking drive signal and is output to the drive circuit 91.
[0125]
The drive circuit 91 amplifies the tracking drive signal and drives the actuator 23 which is a moving means built in the optical pickup 120 to perform tracking control. At this time, the lens position setting unit 161 of the DSP 550 can add an offset to the tracking drive value that is the output of the tracking control unit 53 to shift the position of the convergent lens 22 relative to the photodetector 124.
[0126]
The RF difference signal output from the subtracting circuit 230 is input to the amplitude detector 540 serving as the first address amplitude detecting means and the second address amplitude detecting means. The amplitude detector 540 detects the amplitude in the address portion of the RF difference signal.
[0127]
FIG. 18 is a block diagram showing a more specific configuration of the amplitude detector 540. The amplitude detection unit 540 includes an HPF (High Pass Filter) 541, a peak detection circuit 542, a bottom detection circuit 543, and a subtraction circuit 544.
[0128]
The RF difference signal input to the amplitude detector 540 passes through the HPF 541 and its DC component is removed. The RF signal from which the DC component has been removed is input in parallel to the peak detection circuit 542 and the bottom detection circuit 543. The peak detection circuit 542 and the bottom detection circuit 543 each hold the maximum value and the minimum value of the RF signal from which the DC component is removed, and output the values to the subtraction circuit 544. The subtraction circuit 544 calculates the difference between the maximum value and the minimum value, and outputs the value as an RF signal amplitude to the lens position characteristic measuring unit 562 that is a lens position characteristic measuring unit.
[0129]
The lens position characteristic measurement unit 562 outputs an offset setting value to the lens position setting unit 161 so that the lens position setting unit 161 sequentially generates an offset for moving the position of the convergent lens 22 at a predetermined distance interval. The predetermined distance intervals are not necessarily equal. Further, a difference in RF signal amplitude between the first address portion A1 located on the inner peripheral side and the second address portion A2 (FIG. 3) located on the outer peripheral side with respect to the track is obtained. Then, the difference between the offset set value and the RF signal amplitude at that time is output to the memory 163. The memory 163 sequentially stores a difference between the offset setting value and the RF signal amplitude. The lens position setting unit 161 sequentially generates an offset based on the offset setting value received from the lens position characteristic measurement unit 562, and adds the offset to the tracking drive value that is the output of the tracking control unit 53.
[0130]
As will be described in detail below, an optimum lens position search unit 564 that is a lens shift adjustment means provides an optimum lens position as an offset setting value when the difference in RF signal amplitude is zero or a value closest to zero. Is output to the lens position setting unit 161. The lens position setting unit 161 generates an offset based on the offset setting value that gives the optimum lens position, and adds it to the tracking drive value. Thereby, the lens shift can be set to zero.
[0131]
When the address portion of the optical disk 110 having the structure shown in FIG. 3 is reproduced, the RF difference signal has a waveform as shown in FIGS. 19 (a) and 19 (b). As shown in FIG. 19A, when an RF difference signal is input to the amplitude detection unit 540 when there is no lens shift, the RF signal amplitude a1 in the first address unit A1 and the second address unit A2 The RF signal amplitude a2 is substantially equal. For this reason, the difference between the RF signal amplitudes of the two portions is almost zero.
[0132]
On the other hand, as shown in FIG. 19B, when TE is input when a lens shift occurs on the inner peripheral side, the RF signal amplitude a1 in the first address part A1 is higher than that in the second address part A2. The RF signal amplitude a2 is larger. For this reason, the difference (a1-a2) between the RF signal amplitudes of the two portions is a negative value.
[0133]
FIG. 20 shows the relationship between the lens position based on the offset setting value set by the lens position characteristic measuring unit 562 and the difference between the RF signal amplitudes. In FIG. 20, the horizontal axis indicates the position of the converging lens, and the vertical axis indicates the difference in RF signal amplitude. Since the lens position setting unit 161 generates an offset based on the offset setting value and adds the offset to the tracking drive value, the horizontal axis also indicates the relative lens position. In the characteristic shown in FIG. 20, a point A at which the difference in RF signal amplitude is zero is an optimum lens position with no lens shift. The optimum lens position searching unit 564 searches for a difference in RF signal amplitude stored in the memory 163 to zero or a value closest to zero, and outputs the offset setting value at that time to the lens position setting unit 161 as the optimum lens position. The lens position setting unit 161 generates an offset based on the received offset setting value, and superimposes the offset on the tracking drive value. The tracking drive signal to which the offset is added is output from the drive circuit 91, whereby the lens shift is corrected, and the RF difference signal in the address portion always has a good waveform with good symmetry as shown in FIG. It becomes. That is, a good tracking signal and RF signal can be obtained, and a highly reliable optical disc apparatus can be provided.
[0134]
As described above, according to the present invention, the lens shift of the convergent lens with respect to the photodetector is corrected based on the signals obtained when the first address and the second address provided on the information carrier are reproduced. . In particular, in the present embodiment, the amplitude values at the first address and the second address of the difference signal of each signal detected by being divided in the diameter direction of the optical disk are obtained. Since the first address and the second address are arranged so as to be shifted from the information track to the inner circumference side and the outer circumference side by about 1/2 track, the difference between the amplitude values is zero or a value closest to zero. Then, the fact that the lens shift becomes zero or small is used.
[0135]
Specifically, an offset setting value is sequentially generated to change the position of the convergent lens, and the position of the convergent lens with respect to the photodetector is changed. Then, the difference in amplitude value is obtained at each position. If the converging lens is moved using the offset setting value when the value becomes zero or a value closest to zero, the lens shift can be corrected to be zero or minimum.
[0136]
As a result, in an apparatus that does not use a phase difference tracking error signal, does not have a phase difference adjustment circuit, and an optical pickup that has a simple divided photodetector, the initial error associated with optical component installation errors or vertical installation Even if the optical axis is tilted due to the movement of the objective lens, a good tracking signal and RF signal can be obtained.
[0137]
(Sixth embodiment)
FIG. 21 is a block diagram showing a configuration of a tracking control device according to the present embodiment and an optical disk device using the tracking control device. In the optical disk device 16, the same components as those of the optical disk device 11 of the first embodiment are denoted by the same reference numerals.
[0138]
The optical pickup 120 includes a light emitting element (not shown) such as a laser, a converging lens 22 that is a converging unit, and an actuator 23 that is a moving unit. The converging lens 22 transmits the light beam 21 to the optical disc 110 that is an information carrier. Irradiate while converging toward.
[0139]
The optical pickup 120 further includes a photodetector 124 including detectors A and B divided in the diameter direction of the optical disk, and the light beam 21 ′ reflected on the information recording surface of the optical disk 110 is a light that is a light detection means. Detection is performed by the detector 124. The outputs of the detection units A and B of the photodetector 124 are input to the subtraction circuit 230, and a signal obtained by subtracting the signal B corresponding to the light amount detected by the detection unit B from the signal A corresponding to the light amount detected by the detection unit A. That is, the RF difference signal of (A−B) is generated. The RF difference signal passes through a low-pass filter (LPF) 131 and is input to a digital signal processor (DSP) 650 serving as a tracking control device as a tracking error signal (hereinafter referred to as TE).
[0140]
The DSP 650 includes an offset measurement unit 540, a lens position characteristic measurement unit 662, a memory 163, an optimum lens position search unit 664, a lens position setting unit 161, an A / D converter 51, an offset adjustment unit 52, a tracking control unit 53, and a D / D. A converter 54 is included.
[0141]
The A / D converter 51 converts TE into a digital signal. The offset adjustment unit 52 adds a predetermined offset to the TE converted into the digital signal and outputs the result to the tracking control unit 53. The tracking control unit 53 generates a tracking drive value by, for example, performing a filter operation for performing phase compensation and low-frequency compensation on the TE converted into a digital signal. The generated tracking drive value is added to the output of the lens position setting unit 161 and is converted again into an analog signal by the D / A converter 54. The output of the D / A converter 54 becomes a tracking drive signal and is output to the drive circuit 91.
[0142]
The drive circuit 91 amplifies the tracking drive signal and drives the actuator 23 which is a moving means built in the optical pickup 120 to perform tracking control. At this time, the lens position setting unit 161 of the DSP 650 can add an offset to the tracking drive value that is the output of the tracking control unit 53 to shift the position of the convergent lens 22 relative to the photodetector 124.
[0143]
The TE converted into a digital signal by the A / D converter 51 is input to the offset measuring unit 640. The offset measurement unit 640 obtains an average value (offset) of TE and outputs the value to the lens position characteristic measurement unit 662. The average value is reset based on information received from the lens position characteristic measurement unit 662. That is, the lens position characteristic measuring unit 662 commands a predetermined period during which the offset measuring unit 640 should obtain the average value. Alternatively, the offset measurement unit 640 itself may determine a predetermined period for obtaining the average value of TE.
[0144]
The lens position characteristic measurement unit 662 outputs an offset setting value to the lens position setting unit 161 so that the lens position setting unit 161 sequentially generates an offset for moving the position of the convergent lens 22 at a predetermined distance interval. The predetermined distance intervals are not necessarily equal. Further, a signal is output to the offset measurement unit 640 so as to obtain an average value of TE over a predetermined period in the offset setting value, and the average value of TE in the offset setting value is received from the offset measurement unit 640. When the offset measuring unit 640 itself determines a predetermined period for obtaining the average value of TE, each time the lens position characteristic measuring unit 662 receives the average value of TE, a new offset setting value is generated. Also good. The lens position characteristic measuring unit 662 outputs the offset set value and the average value of TE at that time to the memory 163. The memory 163 sequentially stores a difference between the offset setting value and the RF signal amplitude. The lens position setting unit 161 sequentially generates an offset based on the offset setting value received from the lens position characteristic measurement unit 662, and adds the offset to the tracking drive value that is the output of the tracking control unit 53.
[0145]
The optical disk device 16 performs this procedure for the areas A and B having different properties of the optical disk 610. Then, as will be described in detail below, the optimum lens position searching unit 664 serving as a lens shift adjusting unit, a curve indicating the relationship between the offset setting value in the region A and the average value of TE, the offset setting value in the region B, and TE An intersection point with a curve indicating the relationship with the average value of the average value is obtained, and the offset setting value at this intersection point is output to the lens position setting unit 161 as an offset setting value for giving an optimum lens position. The lens position setting unit 161 generates an offset based on the offset setting value that gives the optimum lens position, and adds it to the tracking drive value. Thereby, the lens shift can be set to zero.
[0146]
As shown in FIG. 22, the optical disc 610 includes a region A and a region B. Region A is composed of pit tracks, and region B is composed of concave and convex guide grooves. In these two regions, since the groove depth or the track pitch is different, the reflection characteristics with respect to the light beam 21 are different, and the TE modulation rate is also different. For this reason, the characteristics of the generated offset and the lens position, that is, the sensitivity of the TE offset to the lens position is different.
[0147]
In general, an offset on the circuit generated by the photodetector 124, the subtraction circuit 230, and the like is superimposed on the offset of the TE in addition to the offset due to the lens shift. Since it is difficult to separate these offsets, it is not possible to search for an optimum lens position without a lens shift from the TE offset. However, when the relationship between the offset setting value and the average value of TE is obtained in two regions A and B having different characteristics, the curves indicating the two relationships intersect at one point. In this regard, even if the sensitivity of the TE offset with respect to the lens positions in the regions A and B is different, no lens shift occurs, so the combination of the offset setting value and the TE offset matches.
[0148]
FIG. 23 shows the relationship between the lens position based on the offset setting value set by the lens position characteristic measurement unit 662 and the average value (offset) of TE in the region A and the region B. In FIG. 23, the horizontal axis indicates the position of the convergent lens, and the vertical axis indicates the average value of TE. Since the lens position setting unit 161 generates an offset based on the offset setting value and adds the offset to the tracking drive value, the horizontal axis also indicates the relative lens position.
[0149]
At the intersection A of the characteristic curves of the region A and the region B, for the reason described above, no lens shift occurs, and only the detection difference of the photodetector 124 and the circuit offset are included. Therefore, the lens position at the intersection A is an optimum lens position with no lens shift. The optimum lens position search unit 664 executes the above-described procedure. That is, from the data stored in the memory 163, the intersection of the curve indicating the relationship between the offset setting value in the region A and the average value of TE and the curve indicating the relationship between the offset setting value in the region B and the average value of TE. And the offset setting value at this intersection is output to the lens position setting unit 161 as an offset setting value that gives the optimum lens position. The lens position setting unit 161 generates an offset based on the received offset setting value, and superimposes the offset on the tracking drive value. The tracking drive signal to which the offset is added is output from the drive circuit 91, whereby the lens shift is corrected, and the RF difference signal in the address portion always has a good waveform with good symmetry as shown in FIG. It becomes. That is, a good tracking signal and RF signal can be obtained, and a highly reliable optical disc apparatus can be provided.
[0150]
As is clear from the above description, the TE average value at point A in FIG. 23 indicates an offset due to factors other than lens shift. Therefore, the TE average value at the point A can be input to the offset adjustment unit 52 as indicated by the arrow 660, and the TE offset due to factors other than the lens shift can be removed. This makes it possible to adjust the lens shift and the TE offset at the same time.
[0151]
As described above, according to the present invention, light detection is performed based on signals obtained when reproducing the first and second regions provided on the information carrier and having different reflection characteristics when irradiated with a light beam. Correct the lens shift of the converging lens relative to the instrument. In particular, in this embodiment, the average value of the difference signal of each signal detected by dividing in the diameter direction of the optical disc is obtained in the first region and the second region. Since the reflection characteristics of the first and second regions are different from each other, the degree of influence on the difference signal of the lens shift is different. However, when the lens shift is zero, the influence on the difference signal of the lens shift is eliminated. The fact that the average values of the difference signals in the first region and the second region match is used.
[0152]
Specifically, an offset setting value is sequentially generated to change the position of the convergent lens, and the position of the convergent lens with respect to the photodetector is changed. Then, at each position, an average value in the first area and the second area of the difference signal of each signal detected by being divided in the diameter direction of the optical disk is obtained. If the relationship between the offset setting value and the average value of the difference signal at that time is obtained for the first region and the second region, and the convergent lens is moved using the offset setting value that gives the intersection, the lens shift is performed. Correction can be made to be zero or minimum.
[0153]
As a result, in an apparatus that does not use a phase difference tracking error signal, does not have a phase difference adjustment circuit, and an optical pickup that has a simple divided photodetector, the initial error associated with optical component installation errors or vertical installation Even if the optical axis is tilted due to the movement of the objective lens, a good tracking signal and RF signal can be obtained.
[0154]
In each of the above embodiments, before the optimum lens position is searched and set, an offset occurs in TE due to lens shift, and tracking control may become unstable. For this reason, tracking control may be lost in the measurement of lens position characteristics for searching for the optimum lens position. In such a case, before the optimum lens position is searched, the offset adjustment unit 52 removes the TE offset, thereby realizing stable tracking control in the measurement of the lens position characteristics, and a highly reliable tracking device. Can be configured.
[0155]
Further, after searching for and setting the optimum lens position, the TE offset may change due to the adjustment of the lens position, and tracking control may become unstable. In such a case, stable tracking control is realized by searching for and setting the optimum lens position and removing it by the offset adjustment unit 52 after changing the lens position due to the optimum lens position setting. In addition, a highly reliable tracking device can be configured.
[0156]
Thus, if the tracking error signal offset is removed before the optimum lens position is searched and set, the lens shift can be corrected without being affected by the track position shift caused by the tracking error signal offset. In addition, if the tracking control offset is removed after searching for and setting the optimum lens position, the tracking error signal offset including the offset caused by the lens shift can be removed. As a result, it is possible to realize high-precision tracking control in which lens shift and track positional deviation are corrected. Whether the tracking error signal offset is removed before the optimum lens position is searched, the tracking error signal offset is removed after the optimum lens position is searched, or the tracking error signal is detected before and after the optimum lens position is searched. Whether to remove the offset may be determined according to the accuracy required of the tracking device.
[0157]
Note that when measuring the lens position characteristics, an offset occurs in TE as the lens position changes, and the tracking control target shifts. Therefore, the lens position characteristics affected by the track position shift are measured. Therefore, there is a possibility that a shift occurs in the search result of the optimum lens position. In this case, in order to eliminate the influence of the positional deviation of the track, the TE offset characteristic accompanying the change in the lens position is measured in advance. Then, the TE offset adjustment is performed based on the TE offset characteristics measured in advance according to the change in the lens position when the lens position characteristics are measured. This eliminates the influence of TE offset in the measurement of lens position characteristics, and can improve the search accuracy of the optimum lens position.
[0158]
Further, the lens position detection signals required by the lens position characteristic measurement unit such as the offset setting value stored in the memory 131 and the number of address OK signals at that time are x and y, respectively, and the relationship between these is the function y = f (x) The search accuracy for the optimum lens position can be improved. For example, the least square method is used to determine the coefficient of the approximate function. As described in the third, fourth, and fifth embodiments, when the offset setting value and the lens position detection signal obtained by the lens position characteristic measurement unit at that time are in a linear relationship, the offset setting value and its It is preferable to obtain two or more sets of lens position detection signals at the time and approximate these relationships with a linear function y = ax + b. FIG. 24 shows an example in which these relationships are approximated by a linear function. In FIG. 24, the horizontal axis represents the offset setting value x, and the vertical axis represents the lens position detection signal y. Since the lens position setting unit 161 generates an offset based on the offset setting value and adds the offset to the tracking drive value, the horizontal axis also indicates the relative lens position. An approximate linear function y = ax + b is obtained by determining the coefficient and b from the measurement points A to E in FIG. 24 by the least square method. Using this approximate function, x at which the lens position detection signal y is 0 is −b / a. Therefore, by setting this value as the offset setting value, it is possible to suppress the influence of the measurement error of the lens position detection signal and improve the search accuracy of the optimum lens position.
[0159]
Further, as in the first and second embodiments, when searching for the maximum or minimum in the lens position characteristics, the relationship between the offset setting value and the lens position detection signal at that time is expressed by a quadratic function y = ax. ² It is preferable to approximate by + bx + c. FIG. 25 shows an example in which the lens position characteristic is approximated by a quadratic function. In FIG. 25, the horizontal axis represents the offset setting value x, and the vertical axis represents the lens position detection signal y. Since the lens position setting unit 161 generates an offset based on the offset setting value and adds the offset to the tracking drive value, the horizontal axis also indicates the relative lens position. By determining the coefficients a, b and c from the measurement points A to E in FIG. 25 by the least square method, the approximate quadratic function y = ax ² + Bx + c is obtained. In this quadratic function, x that maximizes the lens position detection signal y is b / 2a. Therefore, by setting this value as the offset setting value, it is possible to suppress the influence of the measurement error of the lens position detection signal and improve the search accuracy of the optimum lens position.
[0160]
In particular, in the search for the optimum lens position using these approximation functions, the lens position detection signal y is obtained from the approximation function even if the offset setting value x at which the lens position detection signal y is zero or maximum is not actually obtained. The offset set value x that is zero or maximum can be estimated. Therefore, the lens position characteristic measurement unit can accurately set the optimum lens position even when the interval between the offset setting values to be set is not small. In addition, since the number of offset setting values x for searching can be reduced, the search time can be shortened.
[0161]
In the above embodiment, when the eccentricity of the optical disk is small and the influence of the lens shift due to the eccentricity is small, the lens position characteristic indicating the relationship between the offset setting value and the lens position detection signal as shown in FIG. , There may be a gradual change in the vicinity where the lens position detection signal is maximum (or minimum). In this case, an approximately maximum (or minimum) range is a range indicated by A in FIG. However, at the end of the range A, the lens position detection signal can greatly change with respect to a minute change in the offset value. That is, when the offset value of the end point A3 or the end point A4 of the range A is selected to give the optimum lens position, the margin due to the deviation of the lens position becomes narrow.
[0162]
Therefore, in such a case, the range A that is approximately the maximum is obtained from the measurement result, and the center of the range A is selected as an offset value that gives the optimum lens position, thereby widening the margin of the lens position deviation and stabilizing the range. Tracking control is possible.
[0163]
Further, when tracking control is performed, the lens shift state may change depending on the rotational phase of the disk because the disk is eccentric. At this time, the search result of the optimum lens position depends on the rotational phase of the disk in the measurement of the lens position characteristic. In order to prevent this, it is preferable to measure the lens position characteristics during one rotation of the disk or an integral multiple of the rotation and to average the influence of eccentricity. Alternatively, the lens position characteristic may be measured for each predetermined rotation phase range, and the optimum lens position corresponding to the rotation phase may be obtained and set. By such a method, stable tracking control can be performed even if there is a lens shift due to eccentricity of the disk.
[0164]
When recording or reproducing information on both the concave and convex portions of the track of the optical disc, in order to absorb the change in the lens position characteristic due to the concave and convex portions, the lens position characteristic in the convex portion and the lens position characteristic in the concave portion Can be measured separately, and an optimum lens position can be set separately for each uneven portion, whereby a tracking control device that is not affected by the uneven shape of the track can be configured.
[0165]
Further, the tilt state may change depending on the radial position due to warpage of the optical disk. When tilt occurs between the optical disk and the optical axis of the light beam, the reflected light of the light beam is shifted with respect to the photodetector, which affects the lens shift characteristics. In such a case, the result of adjusting the lens shift at the inner and outer peripheral positions of the optical disc is linearly interpolated, and the optimum lens position corresponding to the radial position is set, so that it is not affected by the tilt change. Tracking control is possible.
[0166]
In general, in an optical disk apparatus, the predetermined level of the comparator in the address gate unit is the lens position when the lens shift due to the eccentricity of the disk becomes maximum so that the address can be detected even if there is a lens shift due to the eccentricity of the disk. It is set low enough to generate a gate. However, in the second and third embodiments, when the predetermined level of the address gate unit is low, a subtle change in waveform due to a small lens position shift cannot be detected, and the address gate signal is not normal even though the waveform is not normal. Will be generated. For example, as shown in FIG. 27A, when the comparator levels a and b are low, the waveform exceeds the comparator levels a and b even though the waveform in the address portion of the RF difference signal is asymmetric. Two gate signals are generated.
[0167]
Therefore, in the second and third embodiments, it is preferable to measure the lens position characteristic by setting a comparator level different from the comparator level for detecting the address. For example, as shown in FIG. 27B, when measuring the lens position characteristics, the level a and b of the comparator are increased to such an extent that a gate can be generated in the waveform of the RF difference signal when there is no lens position deviation. To do. By doing so, it is possible to detect a subtle change in waveform due to any small lens position, thereby improving the detection accuracy of the optimum lens position and performing highly reliable tracking control.
[0168]
In the fifth embodiment, when the amplitude of the RF difference signal in the address portion is detected, the amplitude of the RF signal changes according to the address information recorded in the address portion, which causes the detection error of the optimum lens position. May be. Therefore, when the address portion of the optical disk is composed of address information and a predetermined pattern repetition signal for pulling in the PLL, it is preferable to measure the amplitude of the RF difference signal at the predetermined pattern repetition portion. As a result, the detection accuracy of the optimum lens position can be improved, and highly reliable tracking control can be performed.
[0169]
Although not particularly shown in the first to sixth embodiments, the tracking control procedure described in the first to sixth embodiments is realized by hardware using a circuit using electronic components. Alternatively, it may be executed by a microcomputer or a host computer of an optical disk device. When executed by a microcomputer or host, a computer-readable program (firmware) for executing the above procedure is stored in an information recording medium such as an EEPROM or a RAM.
[0170]
【The invention's effect】
According to the present invention, in an apparatus that does not use a phase difference tracking error signal and does not have a phase difference adjustment circuit, or an optical pickup that has a simple divided photodetector, it is possible to prevent errors in mounting optical components and vertical installation. Even if the optical axis is tilted due to the initial objective lens movement, a good tracking signal and RF signal can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a first embodiment of an optical disc apparatus of the present invention.
2 is a block diagram showing a configuration of a signal processing unit shown in FIG. 1. FIG.
FIG. 3 is a diagram showing the structure of an optical disc.
4A and 4B are examples of an output waveform of an RF difference signal when the address part of the optical disc shown in FIG. 3 is reproduced.
FIG. 5 is a diagram illustrating a relationship between the number of address OK signals and an offset setting value.
FIG. 6 is a block diagram showing a second embodiment of the optical disc apparatus of the present invention.
7 is a block diagram showing a configuration of an address gate section shown in FIG. 6. FIG.
FIGS. 8A and 8B are diagrams illustrating waveforms of RF difference signals input to an address gate unit. FIGS.
FIG. 9 is a diagram illustrating a relationship between a gate count number and an offset setting value.
FIG. 10 is a block diagram showing a third embodiment of the optical disc apparatus of the present invention.
11 is a block diagram showing a configuration of an address gate unit shown in FIG.
FIG. 12 is a diagram illustrating a relationship between a difference in gate count numbers and an offset setting value.
FIG. 13 is a block diagram showing a fourth embodiment of the optical disc apparatus of the present invention.
14 is a block diagram showing a configuration of a symmetry detection unit shown in FIG.
FIGS. 15A and 15B are diagrams showing the waveform of TE in the address portion input to the symmetry detection portion; FIGS.
FIG. 16 is a diagram showing the relationship between the symmetry of TE and the offset setting value.
FIG. 17 is a block diagram showing a fifth embodiment of the optical disc apparatus of the present invention.
18 is a block diagram showing a configuration of an amplitude detector shown in FIG.
FIGS. 19A and 19B are diagrams showing waveforms of an RF difference signal in an address portion input to an amplitude detection portion.
FIG. 20 is a diagram illustrating a relationship between an amplitude of an RF difference signal and an offset setting value.
FIG. 21 is a block diagram showing a sixth embodiment of the optical disc apparatus of the present invention.
FIG. 22 is a diagram schematically showing an optical disc having two regions having different characteristics.
FIG. 23 is a diagram illustrating a relationship between a TE offset and an offset setting value.
FIG. 24 is a diagram illustrating a relationship between a lens position detection signal and an offset setting value.
FIG. 25 is a diagram illustrating a relationship between a lens position detection signal and an offset setting value.
FIG. 26 is a diagram illustrating a relationship between a lens position detection signal and an offset setting value.
FIGS. 27A and 27B are diagrams showing waveforms of RF difference signals. FIGS.
FIG. 28 is a block diagram showing a configuration of a conventional optical disc apparatus.
FIGS. 29A to 29C are diagrams showing waveforms of phase difference tracking error signals. FIGS.
FIG. 30 is a diagram illustrating lens shift characteristics of a phase difference tracking error signal.
[Explanation of symbols]
21 Light beam
22 Converging lens
23 Actuator
51 A / D converter
52 Offset adjuster
53 Tracking controller
54 D / A converter
91 Tracking drive circuit
110 Optical disc
120 optical pickup
124 light receiving element
130 Subtraction circuit
131 Low-pass filter (LPF)
140 Signal processor
150 Digital Signal Processor (DSP)
161 Lens position setting section
162 Lens position characteristic measurement unit
163 memory
164 Optimal lens position search unit

Claims (12)

In order to perform optical recording and / or reproduction with respect to the information carrier having the first address and the second address, which are shifted from the inner track side and the outer track side by about 1/2 track with respect to the information track. A converging means for converging and irradiating a light beam toward the information carrier, a light detecting means for detecting reflected light of the light beam obtained from the information carrier, and moving the converging means in a direction crossing the information track A tracking control device for controlling an optical head provided with a moving means for
Address reading means for obtaining a first address and a second address recorded on the information carrier from an output of the light detection means;
Offset setting values for moving the position of the convergence means by the moving means are generated sequentially at predetermined distance intervals, and recorded on the information carrier from the output of the light detection means at each position where the convergence means has moved. Lens position characteristic measuring means for counting the number of times of acquisition of both the first address and the second address,
A lens shift adjustment unit that searches for a maximum value of the number of acquisition times and moves the convergence unit by the moving unit based on an offset setting value when the acquisition number of times is a maximum value;
A tracking control device comprising: In order to perform optical recording and / or reproduction with respect to the information carrier having the first address and the second address, which are shifted from the inner track side and the outer track side by about 1/2 track with respect to the information track. A convergence means for converging and irradiating a light beam toward the information carrier, a light detection means for dividing and detecting the reflected light of the light beam obtained from the information carrier, and the convergence means across the information track A tracking control device for controlling an optical head comprising a moving means for moving in a direction,
Difference signal generating means for generating a difference signal of each detection signal divided and detected by the light detecting means;
First gate generating means for comparing the output of the difference signal generating means with a predetermined first level to generate a gate;
A second gate generating means for generating a gate by comparing the output of the difference signal generating means with a predetermined second level;
The offset setting value for moving the position of the converging means by the moving means is sequentially generated at a predetermined distance interval, and the gate generated by the first gate generating means is generated at each position where the converging means is moved. Lens position characteristic measuring means for obtaining a measurement number based on the number and the number of gates generated by the second gate generating means;
A lens shift that searches for the number of measurements when the positional deviation of the convergence means relative to the light detection means is minimum, and moves the convergence means by the moving means based on an offset setting value corresponding to the searched number of measurements. Adjusting means;
A tracking control device comprising: The number of measurements is the sum of the number of gates generated by the first gate generation means and the number of gates generated by the second gate generation means, and the positional deviation of the convergence means relative to the light detection means. minimum and the measurement number of time made the tracking control apparatus according to claim 2 which is the maximum value. The measurement number is a difference between the number of gates generated by the first gate generation unit and the number of gates generated by the second gate generation unit, and the positional deviation of the convergence unit with respect to the light detection unit is the number of counts when the minimum tracking control apparatus according to claim 2 is a value closest to zero or zero. The information carrier includes an information track formed by a convex portion and a concave portion, and the lens position characteristic measuring unit measures each of the convex portion and the concave portion of the information track, and the lens based on a measurement result the tracking control apparatus according to any one of claims 1 to 4 for moving the converging means respectively shift adjustment means with respect to the protrusions and recesses. The lens position characteristic measuring means, the number of acquisitions in accordance with the rotation phase of the information medium, the measurement number, the calculated value, the tracking according to any one of claims 1 to 4 for determining the output difference or the mean value Control device. The lens shift adjusting means determines the offset setting value in accordance with the rotation phase of the information carrier, the tracking control apparatus according to any one of claims 1 to 4.   4. The tracking control according to claim 2, wherein the first gate generation unit and the second gate generation unit detect an address using a level different from the first level and the second level. 5. apparatus. In order to perform optical recording and / or reproduction with respect to the information carrier having the first address and the second address, which are shifted from the inner track side and the outer track side by about 1/2 track with respect to the information track. A converging means for converging and irradiating a light beam toward the information carrier, a light detecting means for detecting reflected light of the light beam obtained from the information carrier, and moving the converging means in a direction crossing the information track And a tracking control method for controlling an optical head including a moving means.
Offset setting values for moving the position of the convergence means by the moving means are generated sequentially at predetermined distance intervals, and recorded on the information carrier from the output of the light detection means at each position where the convergence means has moved. Counting the number of acquisitions of both the first address and the second address being acquired;
Searching for the maximum value of the number of acquisition times, and moving the convergence means by the moving means based on an offset setting value when the acquisition number of times is the maximum value;
Including a tracking control method. In order to perform optical recording and / or reproduction with respect to the information carrier having the first address and the second address, which are shifted from the inner track side and the outer track side by about 1/2 track with respect to the information track. A convergence means for converging and irradiating a light beam toward the information carrier, a light detection means for dividing and detecting the reflected light of the light beam obtained from the information carrier, and the convergence means across the information track A tracking control method for controlling an optical head comprising a moving means for moving in a direction,
Generating a difference signal of each detection signal detected by dividing by the light detection means;
Comparing the difference signal with first and second levels and generating first and second gates when the difference signal is greater than the first and second levels;
The position of the converging means at a predetermined distance interval sequentially generates the offset setting value for moving by the moving means, at respective positions where the converging means is moved, the number of the generated first and second gate Determining the number of measurements based on
Searching for the measurement number when the positional deviation of the convergence means relative to the light detection means is minimum, and moving the convergence means by the moving means based on an offset setting value corresponding to the searched measurement number; ,
Including a tracking control method. The measurement number is a sum of the number of the first and second gates, measuring the number of when the positional deviation with respect to the light detecting means is minimum of the converging means in the moving step is at its maximum value The tracking control method according to claim 10 . The measurement number is a difference in the number of the first and second gate, the number of counts when the positional deviation with respect to the light detecting means of said converging means is minimum in value closest to zero or zero The tracking control method according to claim 10 .

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