JPS63244327A - Tracking servo circuit - Google Patents

Abstract

PURPOSE:To exclude the trouble of balance adjustment, and to adjust the titled circuit even after manufacturing by comparing the mean value of the peak value and the bottom value of a tracking error signal, and adjusting the balance of two kinds of signals in a tracking error signal generating part through the aid of a balance adjusting part, according to the said comparison result. CONSTITUTION:The tracking error signal TE is inputted to an A/D converter 21, and converted into a digital data. Then, the mean value of the tracking error signal TE is calculated by a peak hold circuit 22, a bottom hold circuit 23, an adder 24, and an arithmetic operator 25. The mean value is compared with a reference value by a comparator 26, and an updown counter 27 controls the resistance value of an FET 31 as a variable resistor, through the A/D converter 30, according to the comparison result. This control is continued until the mean value, inputted to the comparator 26, comes to coincide with the reference value. Thus, the balance adjustment never takes time, and the adjustment can be performed even after manufacturing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a tracking servo circuit in an optical disc playback device.

(Prior Art) There are various types of tracking servo circuits in optical disc playback devices, among which the one shown in FIG. 5 is called a 3-beam system.

The circuit shown in the figure includes sub-beam detectors 11, 12,
Main beam detector 13, current-voltage converter 14.1
5, subtracter 16, phase compensation circuit 17, changeover switch 1
8, a driver 19, and a tracking actuator 20.

The sub-beam detectors 11.12 detect the sub-beams, the main beam detector 13 detects the main beam, and the current-voltage converters 14.15 convert the output currents of the sub-beam detectors 11.12 into corresponding voltages. The subtracter 16 detects the difference between the output voltages of the current-voltage converters 14 and 15.
Compensate the phase of the output of 6. The driver 19 controls the tracking actuator 2 according to the output value of the phase compensation circuit 17.
Drive 0. Tracking actuator 20 moves an optical head (not shown).

The changeover switch 18 is normally off, and the subtracter 16 detects the difference between the output values of the current-voltage converters 14 and 15 and outputs it as a tracking error signal ('T'E). One driver is a tracking error signal (T
Tracking actuator 2 so that E) becomes zero.
Drive 0. Therefore, tracking servo is performed.

However, for example, during manufacturing, the tracking error signal (TE) may deviate from the reference value. That is, FIG. 6 shows a case where the tracking error signal <TE) deviates, and shows a state in which the peak value is larger than the absolute value of the bottom value. In such a case, it is necessary to perform balance adjustment to correct the deviation as shown in FIG. 6(b).

For this reason, conventionally, when performing such balance adjustment, the user turns on the changeover switch 18, extracts the tracking error signal from the terminal Q, inputs it to an oscilloscope (not shown), etc., and then adjusts the manual variable resistor Rv. It was made variable to adjust the deviation of the tracking error signal (TE).

(Problems to be Solved by the Invention) The conventional balance adjustment described above was done manually, which required time and effort, and also caused problems such as imbalance due to differences in disc types and aging of parts. The problem was that it was impossible to deal with imbalances caused by changes.

The present invention has been made in view of the above problems, and an object thereof is to provide a tracking servo circuit that eliminates the trouble of balance adjustment and allows the adjustment to be made even after manufacturing.

[Structure of the Invention] (Means for Solving the Problems) To achieve the above object, the present invention provides a circuit for performing tracking servo of an optical head that reads data recorded on tracks of an optical disk. A tracking error signal generation unit that takes a difference between two types of signals that are output signals of the optical head and uses this as a tracking error signal, and compares the average value of the peak value and bottom value of the tracking error signal with a reference value. and a balance adjustment section that adjusts the balance between the two types of signals in the tracking error signal generation section according to the comparison result of the comparison section.

(Function) When the tracking error signal deviates from the reference value, the peak value of the tracking error signal and the average value of the volume values differ from the reference value, and this is detected by the comparison section. The balance adjustment section adjusts the balance between the two types of signals in the tracking error signal generation section according to the comparison result of the comparison section.
This adjustment is performed until the average value of the peak value and bottom value of the tracking error signal matches the reference value. When the average value matches the reference value, the balance adjustment is completed.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing the configuration of a tracking servo circuit according to a first embodiment of the present invention. Elements that perform the same functions as those of the conventional example shown in FIG. Avoid giving explanations.

That is, in the circuit shown in FIG. 1, an analog-digital converter (AD converter) 21 and a peak hold circuit 22 are newly added.
, Bottle hold time #I23. Adder 24, arithmetic unit 25
, comparator 26, up/down counter 27, flip-flop 28, changeover switch 29, digital-to-analog converter (DA converter) 30, field-effect transistor (
A variable resistor 31 consisting of a FET) is provided.

The AD converter 21 converts the output value of the subtracter 16 into digital data. The peak hold circuit 22 is the AD converter 2
The maximum value among the output values of 1 is detected and sent to the adder 24. The bottom bold circuit 23 detects the minimum value among the output values of the AD converter 21 and sends it to the adder 24. The adder 24 adds the output value of the peak hold circuit diagram 1N22 and the output value of the bottom hold circuit 23. Arithmetic unit 25 multiplies the output value of adder 24 by 172. Therefore, the peak value of the tracking error signal (TE) is detected by the peak hold circuit 22, the bottom value of the tracking error signal (TE) is detected by the bottom hold circuit 23, and the average value of these values is calculated by the adder 24 and the arithmetic unit 25. Calculated. The comparator 26 compares a preset reference value with the average value output from the calculator 25. The up/down counter 27 counts timing pulses in accordance with the output of the comparator 26. That is, when the average value is larger than the reference value, it counts down, and when the opposite is true, it counts up. The DA converter 30 operates as a variable resistor according to the output of the up/down counter 27.
Controls the resistance value of ET31.

The timing pulse is a timing pulse for capturing peak data and bottom data, and operates the up/down counter 27, as well as the peak hold circuit 22,
The bottom hold circuit 23 is reset.

Next, the operation of this circuit will be explained.

Normally, the changeover switch 18 and the changeover switch 29 are in the OFF state, and the changeover switch 29 is switched to the A side, and the tracking error signal (TE) is input to the driver 19.
9 drives the tracking actuator 20, and 1-racking servo is performed.

During balance adjustment, the changeover switch 18 is turned on and the two changeover switches are switched to the B side. Therefore, lens drive pulses input from a microcomputer (not shown) are input to the driver 19. This lens drive pulse is a signal that forcibly drives the lens (not shown) of the optical head in the tracking direction.
Stable and pseudo tracking error signal (TE) even if there is little lens kick or disk eccentricity during search
). This l racking error signal (TE) is input to the AD converter 21 and converted into digital data. Then, the average value of the tracking error signal (TE) is calculated by the peak hold circuit 22, the bottom hold circuit 23, the adder 24, and the arithmetic unit 25. This average value is compared with the reference value by the comparator 26, and the up/down counter 27 adjusts the AD according to the comparison result.
The resistance value of FET 31 as a variable resistor is controlled via converter 30. This control is performed until the average value input to the comparator 26 and the reference value match.

FIG. 2 is a waveform diagram of the tracking error signal (TE), timing pulse, and lens drive pulse. At the time the timing pulse P1 occurred, the tracking error signal (TE) was out of alignment, but the timing pulse P
3 is generated, the tracking error signal (TE
) has been resolved.

In this way, in this embodiment, balance adjustment can be performed by automatically varying the resistance value of the variable resistor 31.

FIG. 3 is a block diagram showing the configuration of a tracking servo circuit using a one-beam push-pull system according to a second embodiment of the present invention.

That is, in this circuit, the output signal of the main beam detector 13 is input to the current-voltage converter 14.15, and the subtracter 16 takes the difference between these signals to obtain the tracking error signal (TE). Tracking error signal (T
E) is input to the AD converter 21 in the same way as in FIG. And peak bold circuit 22, bottom hold circuit 23
, an adder 24, an arithmetic unit 25, a comparator 26, an up/down counter 27, and a DA converter 30 (note that these are omitted in FIG. 3) to control the resistance value of the variable resistor 31.

FIG. 4 shows a third embodiment of the present invention. This third embodiment is a DA converter 30 in the first embodiment.
The output value is input to a variable resistor 32 provided in the current-voltage converter 15. In this case as well, the first
Balance adjustment can be performed automatically as in the embodiment.

[Effects of the Invention] As described in detail above, according to the present invention, balance adjustment does not take much time and can be performed even after manufacturing.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of the first embodiment of the present invention, and FIG. 2 is a configuration diagram of the first embodiment of the present invention.
3 and 4 are block diagrams of the second and third embodiments of the present invention, FIG. 5 is a block diagram of the conventional example, and FIG. 6 is a tracking error signal. FIG. 11...Sub beam detector 13...
...Main beam detector 16...
...Subtractor 22 ...Peak hold circuit 23 ...
...Bottom hold circuit 24...
- Adder 25...... Arithmetic unit 26... Comparator 27... Up/down counter 31.3
2...Variable resistor applicant Toshiba Corporation Patent attorney Sa Suyama - Figure 5 Figure 6

Claims (1)

[Claims] (1) In a circuit that performs tracking servo for an optical head that reads data recorded on a track of an optical disk, the difference between two types of signals that are the output signals of the optical head is taken and this is used as a tracking error signal. a comparison section that compares the average value of the peak value and bottom value of the tracking error signal with a reference value; and a comparison section that compares the average value of the peak value and bottom value of the tracking error signal with a reference value, and a A tracking servo circuit comprising: a balance adjustment section that adjusts the balance of the signals.