JP3646602B2 - Tracking error signal generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tracking error signal generating device of an optical information reproducing device that optically reads information from a recording medium.
[0002]
[Prior art]
Optical disc apparatuses are widely used as basic products of multimedia in recent years. In particular, CD-ROM drive devices are indispensable as data playback devices for personal computers. Furthermore, in recent years, DVD-ROMs having a recording capacity about eight times that of CD-ROMs have been developed with the increase in data scale, and DVD-ROM drive devices have begun to spread rapidly into the market.
[0003]
In an optical disc, information is generally recorded by a row of fine irregularities (hereinafter referred to as pits) on a recording medium, and a light beam from a light source such as a semiconductor laser is used as a minute light spot on the pit using a lens or the like. And information is read from the reflected light. When reading information, a pit string (hereinafter referred to as a track) in which information is recorded is displaced in the radial direction of the disk due to eccentricity accompanying rotation of the disk. For this reason, a tracking servo that generates a signal corresponding to the amount of displacement of the light spot with respect to the track (hereinafter referred to as a tracking error signal) and controls the position of the light spot using the signal is required. Various means for generating a tracking error signal using an optical method are considered. In a CD-ROM drive device, a sub beam is generated by providing a grating in the optical path, and tracking is performed by three beams. A three-spot method for generating an error signal is generally used. However, in DVD-ROM, the pit length and width are set to 1/2 each of CD-ROM in order to increase the recording capacity, so the spot area reduction cannot catch up with the pit area reduction, and the three-spot method can be used. It has become difficult. Therefore, in the DVD-ROM drive apparatus, a phase difference method for generating a tracking error signal only with a main beam is generally used.
[0004]
Hereinafter, the phase difference method will be described with reference to the drawings.
[0005]
FIG. 2 is a circuit block diagram showing the principle of tracking error signal generation by the phase difference method. In the figure, 101 is a photodetector comprising four light receiving cells a, b, c and d, 11 is an I / V conversion circuit, 12 is a waveform equalization circuit, 13 is a waveform shaping circuit, and 17 is a phase comparison. Circuit.
[0006]
A light beam emitted from a light source such as a semiconductor laser is condensed on a recording medium via an objective lens to form a light spot (not shown above). The light reflected on the information recording surface of the recording medium again enters the photodetector 101 via the objective lens, and forms a far-field image 201 on the light receiving cell of the photodetector.
[0007]
FIG. 3 is a diagram showing the positional relationship between pits and light spots and the received light intensity distribution on the lens surface. (A), (b), and (c) show changes in the received light intensity distribution on the lens surface of the disc reflected light when the light spot passes through the right side, the center, and the left side of the pit in the track direction, respectively. By performing ray tracing with this reflected light as an incident ray, the received light intensity distribution in the far-field image 201 formed on the photodetector 101 can be obtained. The sum signal of the light receiving cells a, c, b, and d at the diagonal positions of the photodetector 101 is taken out by the I / V conversion circuit 11 as two systems of voltage signals. The voltage signal is waveform-equalized by the waveform equalization circuit 12 and shaped into a rectangular wave by the waveform shaping circuit 13. The rectangular wave is input to the phase comparison circuit 17 and a voltage proportional to the phase difference between the two rectangular wave signals is output.
[0008]
FIG. 4 schematically shows a waveform at each point on the circuit in each positional relationship between the pit and the light spot shown in FIG. In the figure, a1, a2, a6, b1, b2, b6, and c correspond to the same symbols on the circuit diagram of FIG. 2 and FIG.
[0009]
FIG. 5 is a diagram showing an example of a detailed circuit of the phase comparison circuit 17. In the figure, 51 and 52 are D flip-flops, and 53 and 54 are inverters. 55 and 56 are analog switches, 57 and 58 are constant current sources, and 59 is a capacitor. These form a charge pump.
[0010]
The rectangular waves a2 and b2 binarized by the threshold Vsl in the waveform shaping circuit 13 are input to the clock terminals of the D flip-flops 51 and 52. In addition, the inverter outputs of the rectangular waves a2 and b2 are input to the preset terminals of the D flip-flops 52 and 51. In FIG. 4, when the spot is on the right side of the pit as shown in FIG. 4A, the waveform equalization circuit output signals a1 and b1 and the waveform shaping circuit output signals a2 and b2 have a phase difference as shown in the figure. Arise. At this time, in FIG. 5, since the signal a2 is input to the preset terminal of the D flip-flop 52 prior to the input of the signal b2, a pulse having a time width of the phase difference between the signals a2 and b2 as shown in FIG. Output to a6. The signal a6 (charge pulse) is input to the analog switch 55, and the switch is turned on when the signal is Hi. When the switch is turned on, current is supplied from the constant current source 57 to the capacitor 59, and the voltage at the terminal c rises to Va. Next, when the spot is on the left side of the pit as shown in (c), a pulse having the time width of the phase difference between the signals a1 and b1 is output as the signal b6. The signal b6 (discharge pulse) is input to the analog switch 56, and the switch is turned on when the signal is Hi. When the switch is turned on, current is drawn from the capacitor 59 from the constant current source 58, and the voltage at the terminal c drops to Vc. As shown in (b), when the spot is in the center of the pit, the signals a2 and b2 are simultaneously input to the D flip-flops 51 and 52. Not output. Therefore, the voltage at the terminal c does not change.
[0011]
With the above operation, a TE voltage signal proportional to the amount of displacement between the light spot and the pit can be obtained as shown in FIG.
[0012]
The apparatus and operation as described above are described in detail in JP-A-10-30277.
[0013]
[Problems to be solved by the invention]
The received light intensity distribution on the lens surface shown in FIG. 3 shows a symmetrical intensity distribution when the light spot is displaced by an equal amount left and right with respect to the track center. Therefore, assuming that the output voltage of the TE signal when the light spot is displaced by an equal amount X to the left and right with respect to the track center is Va and Vc, and the output voltage of the TE signal when the light spot is at the center of the pit is V0,
[0014]
[Expression 2]
｜ Va−V0 | = | Vc−V0 |
Thus, the absolute value of the track shift sensitivity of the TE signal is equal on the left and right. Hereinafter, the balance of the track shift sensitivity of the TE signal is assumed to be equal.
[0015]
Here, in an actual optical disc apparatus, the dividing line of the light receiving cells of the photodetector may be shifted with respect to the track direction and the disc radial direction as shown in FIG. Consider a case where the light spot is displaced by an amount equal to that in FIG. 3 with respect to the track center in the photodetector in which the dividing line of the light receiving cell is shifted as shown in FIG. 7 is a waveform diagram at each point on the circuit diagram of FIG. 2 in the case of FIG. When the light spot is on the right side with respect to the track center, the phase from light to dark on the light receiving cells a and c is earlier than in FIG. 3, and the time width of a6 is larger than that of a6 in FIG. A pulse is output. Therefore, the TE voltage Va2 obtained at the terminal c is larger than Va in FIG. Next, when the light spot is on the left side with respect to the track center, the phase from light to dark on the light receiving cells b and d is slower than that in FIG. 3, and b6 has a time width relative to b6 in FIG. A small pulse is output. Therefore, the TE voltage Vc2 obtained at the terminal c is smaller than Vc in FIG.
[0016]
When the above is expressed by a formula
[0017]
[Equation 3]
| Va2−V0 | ≠ | Vc2−V0 |
Thus, the left and right track shift sensitivity becomes unbalanced.
[0018]
As described above, when the balance of the track shift sensitivity of the TE signal is different, when the tracking servo is turned on and the track pull-in is performed, the lens is shaken in the left-right unbalance with respect to the track, which causes a slow pull-in. In addition, the tracking servo may be easily deviated due to disturbance due to imbalance in track shift sensitivity.
[0019]
The present invention solves the above-described conventional problem, and has a configuration capable of equalizing the track shift sensitivity of the TE signal at the left and right displacements of the light spot with respect to the pit, thereby providing a tracking error signal with high tracking pull-in performance. A generating device is provided.
[0020]
[Means for Solving the Problems]
The present invention proposes a tracking error signal generating apparatus described below for the above-mentioned problem.
[0021]
The first tracking error signal generator of the present invention forms a light spot by irradiating a light beam onto a recording medium having an optically reproducible information track, and at least two reflected lights of the spot are generated. A reproducing head that performs photoelectric conversion by a photodetector divided into two, a photoelectric conversion output signal of the reproducing head, or an output that detects a positive phase difference between at least two signals generated from the output and a negative position A gain comprising phase comparison means having an output for detecting a phase difference, and changing the gain of one or both of outputs converted by two conversion means for converting the detected phase difference into a voltage or a current value Has conversion means. In addition, for the method of adjusting the track shift sensitivity of the TE signal using the present invention, the output of the phase comparison means is stopped and the value of the tracking error signal (this is referred to as TE0) is stored in the storage means. Next, stop the output of the phase comparison means and reproduce the signal from the recording medium without applying the tracking servo. The maximum positive value for TE0 of the resulting tracking error signal (this is TEP) and negative Detect the maximum value (this is TEN)
[0022]
[Expression 4]
｜ TEP−TE0 ｜ ＝ ｜ TEN−TE0 ｜
The track shift sensitivity of the TE signal is adjusted so that Thereby, when the track shift sensitivity of the TE signal is unbalanced due to factors such as the mounting accuracy of the photodetector, the balance of the TE signal track shift sensitivity is adjusted by adjusting the gain of the gain converting means to equalize the balance. And the tracking pull-in performance can be improved.
[0023]
The second tracking error signal generation device of the present invention forms a light spot by irradiating a light beam onto a recording medium having an optically reproducible information track, and at least two reflected lights of the spot are generated. A read head that performs photoelectric conversion with a photodetector divided into two, and a positive phase difference and a negative phase difference between at least two signals of the photoelectric conversion output signal of the read head or a signal generated from the output are detected. Phase comparator means having two systems for outputting a pulse having a phase difference as a time width, and turning the current source ON / OFF during the period of either the Hi or Low pulse to determine the phase difference as a current signal. And a function of changing the current value of the current source. In the present apparatus, when the track shift sensitivity of the TE signal is unbalanced by adjusting the track shift sensitivity as in the first tracking error signal generating apparatus of the present invention, the current value of the current source is changed. Thus, the track shift sensitivity of the TE signal can be adjusted to equalize the balance, and the same effect as that of the first tracking error signal generation device of the present invention can be obtained.
[0024]
A third tracking error signal generation device of the present invention includes a circuit changeover switch in front of a balance adjustment circuit using gain conversion means generally used in a push-pull tracking error signal generation device, and balance adjustment is performed by a push-pull method. And switching between the two systems of signals converted by the two conversion means for converting the phase difference detected by the first tracking error signal generator of the present invention into a voltage or a current value. In this apparatus, by adjusting the track shift sensitivity similar to that of the first tracking error signal generation apparatus of the present invention, the gain conversion means for performing balance adjustment can be shared by the two tracking error signal generation apparatuses. The same effect as that of the first tracking error signal generator can be obtained, and the number of circuit elements can be reduced.
[0025]
A fourth tracking error signal generation device of the present invention includes a circuit changeover switch in front of a balance adjustment circuit using gain conversion means generally used in a three-spot tracking error signal generation device, and balance adjustment by a three-spot method. And switching between the two systems of signals converted by the two conversion means for converting the phase difference detected by the first tracking error signal generator of the present invention into a voltage or a current value. In this apparatus, by adjusting the track shift sensitivity similar to that of the first tracking error signal generation apparatus of the present invention, the gain conversion means for performing balance adjustment can be shared by the two tracking error signal generation apparatuses. The same effect as that of the first tracking error signal generator can be obtained, and the number of circuit elements can be reduced.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a circuit block diagram of a first embodiment of the present invention. In the figure, blocks having the same functions as those in FIG. 2 are given the same reference numerals as those in FIG. Reference numeral 15 denotes a balance adjustment circuit, and FIG. 9 shows an example of a detailed circuit thereof. A gain switching amplifier 84 can switch the gain stepwise by changing the value of the resistor 82 by the microcomputer 20. Reference numeral 85 denotes a fixed gain amplifier having the same configuration as 84, and the occurrence of an offset between the signals a3 and b3 is prevented by inputting the signal b3 to the fixed gain amplifier.
[0027]
Reference numeral 16 is a subtractor, and 20 is a microcomputer for controlling the operation of the tracking error generating circuit. Reference numeral 14 denotes a phase comparison circuit, which is different in circuit configuration from the phase comparison circuit shown in FIG. FIG. 8 shows an example of a detailed circuit of the circuit. In the figure, components having the same functions as those in the circuit diagram of FIG. 5 are denoted by the same reference numerals as those in FIG. A switch 62 is controlled by the microcomputer 20 to turn on and off the connection between the outputs of the D flip-flops 51 and 52 and the analog switches 55 and 56.
[0028]
FIG. 10 is a waveform diagram showing waveforms at each point of the circuit of FIG. 1 when the positional relationship between the light spot and the pit and the received light intensity distribution of the lens are shown in FIG.
[0029]
The operation of the first embodiment of the present invention will be described with reference to these drawings.
[0030]
Similar to the conventional example, signals a1 and b1 are obtained from the diagonal sum output of the photodetector 101 via an I / V conversion circuit and a waveform equalization circuit. The obtained signals a 1 and b 1 are input to the phase comparison circuit 14 as rectangular waves a 2 and b 2 by the waveform shaping circuit 13. In the phase comparison circuit, when the phase of the signal b2 is delayed with respect to the signal a2, the D flip-flop 51 outputs a charge pulse a6 having a time width equal to the phase difference between the signals a2 and b2. During the normal phase comparison operation, the switch 62 is in the ON state, the analog switch 55 is turned on only during the period when the charge pulse a6 is Hi, and the capacitor 60 is charged. As a result, a voltage output Va3 proportional to the time width of the charge pulse a6 is obtained as the signal a3. At this time, since no pulse is output to b6, no voltage is generated in signal b3.
[0031]
Similarly, when the phase of the signal b2 is advanced with respect to the signal a2, a charge pulse b6 having a time width equal to the phase difference between the signals a2 and b2 is output from the D flip-flop 52. Only when the charge pulse b6 is Hi, the analog switch 56 is turned on and the capacitor 61 is charged. As a result, a voltage output Vb3 proportional to the time width of the charge pulse b6 is obtained as the signal b3. At this time, since no pulse is output to a6, no voltage is generated in the signal a3.
[0032]
Next, the signals a3 and b3 are input to the balance adjustment circuit 15. Here, when the gain of the gain switching amplifier 84 is 0 dB, the signal a3 and the signal a4 are equal, and when the phase of the signal b2 is delayed with respect to the signal a2, the voltage Va3 is output to the signal a4. The signals a4 and b4 are subtracted by the subtracter 16, and the TE voltage Va3 is output to the terminal c. Similarly, when the phase of the signal b2 is advanced with respect to the signal a2, the voltage Vb3 is output to the signal b4 and the TE voltage −Vb3 is output to the terminal c. In this case, Va3 and -Vb3 are equal to Va2 and -Vb2 in FIG.
[0033]
[Equation 5]
| Va3−V0 | ≠ | Vb3−V0 |
The left and right track shift sensitivity is unbalanced.
[0034]
Here, when the gain of the gain switching amplifier 84 of the balance adjustment circuit 15 is reduced,
The voltage Va3 of the signal a4 when the phase of the signal b2 is delayed with respect to the signal a2 can be set to Va4. Therefore
[0035]
[Formula 6]
｜ Va4−V0 | = | Vb3−V0 |
By adjusting the gain of the gain switching amplifier 84 so as to be equal, the output voltage of the TE signal when the light spot is displaced by an equal amount to the left and right with respect to the track can be made equal, and the left and right track shift sensitivity Can be balanced.
[0036]
FIG. 11 shows a circuit block diagram of the second embodiment of the present invention. In the figure, blocks having the same functions as those in FIG. 1 are denoted by the same reference numerals as those in FIG. Reference numeral 22 denotes a phase comparison circuit, which is different in circuit configuration from the phase comparison circuit shown in FIGS. FIG. 12 shows an example of a detailed circuit diagram of the circuit. In this figure, blocks having the same functions as those of the circuit components in FIGS. 5 and 8 are given the same reference numerals as those in FIG. Reference numeral 571 denotes a variable current source, and the microcomputer 20 can change the current value stepwise.
[0037]
FIG. 13 is a waveform diagram showing waveforms at each point of the circuit of FIG. 11 when the positional relationship between the light spot and the pit and the received light intensity distribution of the lens are shown in FIG.
[0038]
The operation of the second embodiment will be described with reference to these drawings.
[0039]
When the light spot is displaced by an equal amount (a) on the right side and (c) on the left side with respect to the pit, output signals a6 and b6 of the D flip-flops 51 and 52 in FIG. 12 are as shown in FIG. At this time, since there is a difference between the pulse time width of the signal a6 at (a) and the pulse time width of b6 at (c), the TE voltage output to c in (a) and (c) Differences occur in absolute values. Therefore, by reducing the current value of the current source 571, the total current value (pulse area of (a7)) flowing from the current source 571 at (a) as shown in a7 and b7 in FIG. The total current value (pulse area of (b7)) flowing into the current source 58 at the time of c) can be made equal. As a result, the absolute values of the TE voltages output to c in (a) and (c) can be made equal, and the balance between the left and right track shift sensitivities can be made equal.
[0040]
FIG. 14 is a circuit block diagram showing a third embodiment of the present invention. In the figure, blocks having the same functions as those in FIG. 1 are denoted by the same reference numerals as those in FIG. In the upper part of the figure, two light receiving cells a, d, b, and c in the track direction of the photodetector 101 are added to form two voltage signals by the I / V conversion circuit 511, and the two systems are supplied to the subtracter 19. The push-pull tracking error signal is generated by inputting the voltage signal. In this circuit, a balance adjustment circuit 18 is provided in front of the subtracter 19 in consideration of a case where there is a difference in photoelectric conversion efficiency between the light receiving cells a, d and b, c. Further, the balance adjustment circuit 18 and the subtracter 19 can use a circuit having the same configuration as that of the first embodiment. Therefore, a circuit changeover switch 512 for switching between the two I / V converted push-pull signals a8 and b8 and the two outputs a3 and b3 of the phase comparison circuit described in the first embodiment is provided at the front stage of the balance adjustment circuit 18. By providing, the balance adjustment circuit 18 and the subtracter 19 can be shared by the push-pull tracking error signal generation circuit and the phase difference tracking error signal generation circuit, and the number of circuit elements can be reduced.
[0041]
FIG. 15 is a circuit block diagram showing a fourth embodiment of the present invention. In the figure, blocks having the same functions as those in FIG. 1 are denoted by the same reference numerals as those in FIG. The upper part of the figure is a circuit that generates a tracking error signal by the three-spot method using output signals from the light receiving cells e and f that detect the reflected light from the sub-spot.
[0042]
In this circuit, the balance adjustment circuit 18 is provided in the preceding stage of the subtracter 19 in consideration of the case where there is generally a difference in photoelectric conversion efficiency between the light receiving cells e and f. Further, the balance adjustment circuit 18 and the subtracter 19 can use a circuit having the same configuration as that of the first embodiment. Therefore, a circuit changeover switch 514 for switching the output signals a9 and b9 from the I / V converted sub-spot and the two outputs a3 and b3 of the phase comparison circuit described in the first embodiment is provided in the previous stage of the balance adjustment circuit 18. By providing, the balance adjustment circuit 18 and the subtracter 19 can be shared by the tracking error signal generation circuit by the three-spot method and the phase difference tracking error signal generation circuit, and the number of circuit elements can be reduced.
[0043]
In the first to fourth embodiments, as means for detecting the phase difference from the two signals a2 and b2 and generating the charge pulses a6 and b6, in addition to the method using the D flip-flop shown in FIG. However, various methods are conceivable, and the present invention is not limited to this method. Moreover, in the balance adjustment circuit, the method of adjusting the gain on one side of the two input signals by the gain switching amplifier has been shown. However, there are various other methods such as switching the gain on both sides of the two input signals by the gain switching amplifier. However, the present invention is not limited to this method.
[0044]
Next, an adjustment method for equalizing the balance of the left and right track shift sensitivities in the first to fourth embodiments will be described.
[0045]
FIG. 16 shows a sequence for performing the above adjustment in the optical disc apparatus. In the above adjustment, after first adjusting the offset of each servo signal, it is necessary to know the output voltage V0 of the TE signal when the light spot is at the track center (hereinafter referred to as the center voltage V0). . As shown in FIG. 3, when the light spot is at the track center, no pulse is output to the outputs a6 and b6 of the D flip-flops 51 and 52 in FIG. Therefore, by turning off the switch 62 in the phase comparison circuit of FIGS. 8 and 12, both the analog switches 55 and 56 are turned off and the center voltage V0 is output in a pseudo manner. This center voltage V0 has an offset when there is an offset in the voltages a3 and b3 due to circuit factors or the like, and this offset changes with the gain adjustment in the balance adjustment circuit 18. Therefore, a plurality of gains of the balance adjustment circuit are switched, and the fluctuation of the center voltage at that time is stored by a storage means such as a memory element in the microcomputer.
[0046]
Thereafter, the laser is turned on, the spindle motor is turned on, and the focus is pulled in. At this time, the tracking servo is kept off. FIG. 17 shows the TE signal when the tracking servo is OFF. In this state, the peak values VH and VL of the TE signal shown in the figure are detected using a microcomputer, DSP (digital signal processor), or the like. For these detected VH and VL
[0047]
[Expression 7]
| VH−V0 | − | VL−V0 | = VD = 0
The gain on one side of the balance adjustment circuit 15 is adjusted so that At this time, the center voltage V0 is also updated in accordance with the gain change of the balance adjustment circuit. As an adjustment method, the gain is initially set to 0 dB, VD is stored, VD is calculated by changing the gain by one step in the negative direction (this is referred to as VD1), and the magnitude of VD is compared. At this time
[0048]
[Equation 8]
VD1 <VD
Then, the gain is further changed in the minus direction by one step. Also,
[0049]
[Equation 9]
VD1> VD
Then, the gain is changed by one step in the plus direction.
[0050]
By repeating the above until VD falls below a certain threshold value VD0, the balance of the right track shift sensitivity can be made equal.
[0051]
Thereafter, in order to remove the offset generated by the balance adjustment, the TE offset adjustment is performed again from the offset fluctuation data of the center voltage by the balance adjustment stored in the initial stage, and the gain adjustment is performed so that the desired amplitude of the TE signal is obtained. Perform tracking pull-in.
[0052]
Although the center voltage is detected before the offset adjustment of each servo signal in the above, this may be performed at any timing as long as it is before the TE signal peak value is detected, and is limited to the above method. It is not a thing. In addition to the above-described method, various methods such as a method of increasing the gain step by step from the minimum value to reduce VD to a certain threshold value VD0 or less can be considered as the balance adjustment method, and the present invention is not limited to the above. Furthermore, although gain switching and current value switching for balance adjustment are step-like changes, the above-described gain and current for switching are also converted by converting the above VD value into voltage or current value, etc. A method of changing the value linearly is also conceivable and is not limited to the above.
[0053]
【The invention's effect】
The tracking error signal generation device of the present invention has a function capable of changing the track shift sensitivity of the TE signal independently of the positive and negative phase differences in the phase difference tracking error signal generation circuit. Thereby, when the track shift sensitivity of the TE signal in the left and right displacement from the pit of the light spot differs depending on the mounting accuracy of the photodetector, etc., this is corrected to equalize the track shift sensitivity of the TE signal in the left and right displacement. This makes it possible to improve the tracking pull-in performance, and at the same time reduce the tracking loss due to disturbance.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram of a tracking error signal generation circuit showing a first embodiment of the present invention.
FIG. 2 is a circuit block diagram of a conventional tracking error signal generation circuit.
[FIG. 3] (a) When the light spot is on the right side of the track, (b) When the light spot is at the center of the track, (c) The positional relationship between the light spot and the pit when the light spot is on the left side of the track FIG. 6 is a diagram showing a received light intensity distribution of the lens.
4 is a waveform diagram at each point in the circuit block diagram of FIG. 2 at each light spot position of FIG. 3;
FIG. 5 is a diagram showing an example of a detailed circuit diagram of the phase comparison circuit block 17 of FIG. 2;
6 is a diagram showing a case where the dividing line of the light receiving cell of the photodetector is shifted from the track direction and its vertical direction in FIG. 3;
7 is a waveform diagram at each point in the circuit block diagram of FIG. 2 at each light spot position of FIG. 6;
FIG. 8 is a diagram showing an example of a detailed circuit diagram of the phase comparison circuit block 14 of FIG. 1;
FIG. 9 is a diagram showing an example of a detailed circuit diagram of the phase comparison circuit block 15 of FIG. 1;
10 is a waveform diagram at each point in the circuit block diagram of FIG. 1 at each light spot position of FIG. 6;
FIG. 11 is a circuit block diagram of a tracking error signal generation circuit showing a second embodiment of the present invention.
12 is a diagram showing an example of a detailed circuit diagram of the phase comparison circuit block 22 of FIG. 11. FIG.
13 is a waveform diagram at each point in the circuit block diagram of FIG. 10 at each light spot position of FIG. 6;
FIG. 14 is a circuit block diagram of a tracking error signal generation circuit showing a third embodiment of the present invention.
FIG. 15 is a circuit block diagram of a tracking error signal generation circuit showing a fourth embodiment of the present invention.
FIG. 16 is a diagram showing an adjustment sequence of the present invention.
FIG. 17 is a TE signal waveform diagram during disk playback.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Photodetector 201 ... Far-field image, 11 ... I / V conversion circuit, 12 ... Waveform equalization circuit, 13 ... Waveform shaping circuit, 14, 17, 22 ... Phase comparison circuit, 15 ... Balance adjustment circuit, 16 ... subtractor, 20 ... microcomputer, 51, 52 ... D flip-flop, 53, 54 ... inverter, 55, 56 ... analog switch, 57, 58 ... constant current source, 571 ... variable current source, 59-61 ... capacitor, 81-82, 84 ... resistors, 83 ... variable resistors, 85, 86 ... operational amplifiers, 512, 514 ... circuit changeover switches.

Claims (11)

A reproducing head that irradiates a light beam onto a recording medium having an optically reproducible information track to form a light spot, and photoelectrically converts the reflected light of the spot by a photodetector divided into at least two parts. When,
Phase comparison means for detecting a phase difference between at least two signals of the photoelectric conversion output signal of the reproducing head or a signal generated from the output;
In the tracking error signal generating means comprising conversion means for converting the detected phase difference into a tracking error signal,
A tracking error signal generation apparatus characterized in that a coefficient of an output of a tracking error signal with respect to a phase difference having a negative polarity or a positive polarity can be changed. A reproducing head that irradiates a light beam onto a recording medium having an optically reproducible information track to form a light spot, and photoelectrically converts the reflected light of the spot by a photodetector divided into at least two parts. When,
Phase comparison means for detecting a phase difference between at least two signals of the photoelectric conversion output signal of the reproducing head or a signal generated from the output;
In the tracking error signal generating means comprising conversion means for converting the detected phase difference into a tracking error signal,
A tracking error signal generating apparatus characterized in that a coefficient of an output of a tracking error signal with respect to a phase difference with only negative or positive polarity can be changed. A reproducing head that irradiates a light beam onto a recording medium having an optically reproducible information track to form a light spot, and photoelectrically converts the reflected light of the spot by a photodetector divided into at least two parts. When,
Phase comparison means for detecting a phase difference between at least two signals of the photoelectric conversion output signal of the reproducing head or a signal generated from the output;
In the tracking error signal generating means comprising conversion means for converting the detected phase difference into a tracking error signal,
A tracking error signal generating apparatus, wherein a coefficient of an output of a tracking error signal with respect to a phase difference can be changed separately when the polarity of the phase difference is positive and negative, respectively. In Claims 1-3,
The phase comparison means has two systems of outputs that use the difference between the output voltage or current value as phase difference information,
A tracking error signal generating device comprising gain conversion means for changing the gain of one system or two systems on one side of the output. In Claims 1-3,
The phase comparison means comprises an output for detecting a positive phase difference and an output for detecting a negative phase difference,
Comprising two conversion means for converting the detected phase difference into a voltage or a current value;
A tracking error signal generating apparatus comprising gain converting means for changing the gain of one or both of the voltage or current output from the two converting means. In Claims 1-3,
The phase comparison means comprises an output for detecting a positive phase difference and an output for detecting a negative phase difference,
Comprising two conversion means for converting the detected phase difference into a voltage or a current value;
A tracking error signal generating apparatus comprising a function of changing a conversion coefficient from a phase difference to a voltage or a current value in one or both of the two conversion means. In Claims 1-3,
The phase comparison means comprises an output for detecting a positive phase difference and an output for detecting a negative phase difference,
It has two outputs that output a pulse with the detected phase difference as a time width,
A conversion circuit that converts a phase difference into a current signal by turning on and off the current source in a period in which the pulse is either Hi or Low;
A tracking error signal generating apparatus comprising a function of changing a current value of the current source. A reproducing head that irradiates a light beam onto a recording medium having an optically reproducible information track to form a light spot, and photoelectrically converts the reflected light of the spot by a photodetector divided into at least two parts. When,
In a push-pull tracking error signal generation circuit that detects a difference between at least two signals of a photoelectric conversion output signal of the reproducing head or a signal generated from the output,
Two signals for detecting a difference in the circuit, and two changeover switches for switching between the two signals according to claim 4 or 5,
A tracking error signal generating apparatus comprising gain conversion means for changing the gain of one system or both systems on one side of the outputs of the two changeover switches. A reproducing head that irradiates a plurality of light beams onto a recording medium having an optically reproducible information track to form a plurality of light spots, and photoelectrically converts the reflected light of the spots with a plurality of photodetectors; ,
In a tracking error signal generation circuit for detecting a difference between at least two signals output from a plurality of photodetectors of the reproducing head,
Two signals for detecting a difference in the circuit, and two changeover switches for switching between the two signals according to claim 4 or 5,
A tracking error signal generating apparatus comprising gain conversion means for changing the gain of one system or both systems on one side of the outputs of the two changeover switches. In Claim 1-9,
A tracking error signal generation device comprising a function of stopping output of a phase comparison means by external control. In claim 10,
Stop the output of the phase comparison means and store the value of the tracking error signal that is output (this is TE0) in the storage means,
Next, cancel the output of the phase comparison means,
A signal is reproduced from a recording medium having an optically reproducible information track without applying tracking servo,
Detects the maximum positive value (referred to as TEP) and negative maximum value (referred to as TEN) with respect to TE0 of the resulting tracking error signal,

A tracking error signal generating apparatus characterized by changing a coefficient of an output of a tracking error signal with respect to a phase difference of positive or negative polarity.

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