JPH0467259B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a tracking servo circuit for an optical disc player that uses a light beam to reproduce information signals recorded on a disc.

BACKGROUND TECHNOLOGY AND PROBLEMS In an optical disc player that reproduces information signals such as audio signals and video signals recorded on a spiral or concentric track of a disc using a light beam from an optical pickup, the information signal is During playback, the light beam incident on the disk must scan the center of the track and be focused on the recording surface of the disk, and for this purpose tracking servo and focus servo are essential.

The tracking servo detects the deviation of the spot on the disk of the light beam incident on the disk from the track, so-called tracking error.
Based on the tracking error signal, which is the detection signal, the focusing lens of the pickup or the entire pickup is moved in the radial direction of the disk.
The focus servo is designed to reduce the tracking error to zero, and the focus servo detects the shift of the focus of the light beam incident on the disk with respect to the recording surface of the disk, so-called focus error, and detects the focus error, which is the detection signal. Following the error signal, the focusing lens of the pickup or the entire pickup is moved in the direction of the rotation axis of the disk so that the focus error becomes zero.

Incidentally, the gain of such a tracking servo has conventionally been set by adjusting a semi-fixed volume using a jig while reproducing a signal from a reference disk for gain setting during the manufacturing process of the player. I'm on my way. but,
This method not only requires an adjustment step for setting the tracking servo gain in the manufacturing process of the player, but also has the disadvantage that the tracking servo gain may be uneven due to variations in the adjustment. Moreover, a bigger problem is that commercially available discs have optical variations, so in a player where the tracking servo gain is set using this method, the tracking servo gain will be different from the disc being played. The disadvantage is that it is not always appropriate and it is difficult to expect stable playback regardless of the disc type.

Purpose of the Invention In view of the above, the present invention provides a system that automatically sets the tracking servo gain to an appropriate value depending on the disc to be played when the user attempts to play the disc. In addition, stable playback can be performed regardless of optical variations in the player, and an adjustment process for setting the tracking servo gain is not required in the manufacturing process of the player.

Summary of the invention When the tracking servo loop is turned off while the focus servo is applied and the optical beam of the optical pickup is moved across the track on the disk, the tracking error signal changes in the form of a sine wave. However, the level is proportional to the tracking servo gain. Therefore, the tracking servo gain can be adjusted by multiplying this tracking signal by a certain voltage using a multiplication circuit to change its level.
Moreover, since there are almost no variations in the player's electrical system, if the voltage applied to this multiplier circuit is set so that the level of the tracking error signal output from this multiplier circuit is a predetermined value, the disc optical A constant tracking servo gain can be obtained despite variations in the optical system of the player and variations in the player's optical system.

Focusing on this point, the present invention includes a voltage generating circuit that generates a voltage to be multiplied by the tracking error signal, and a multiplication circuit that multiplies the tracking error signal by the output voltage of this voltage generating circuit.
The voltage generation circuit described above calculates the above multiplication value based on the tracking error signal when the optical pickup's light beam is moved across the track on the disk with the tracking servo loop turned off. so that the level of the tracking error signal of the circuit output becomes a predetermined value.
The configuration is such that the value of the output voltage is set.

Embodiment FIG. 1 shows an example of a tracking servo circuit according to the present invention, in which an information signal such as a digitized audio signal is sent to a disk 10 to be reproduced in a spiral shape.
Information signals are recorded on a track so as to be reproducible by irradiation with a light beam, and information signals are read from the disk 10 by a pickup 21 sent in the radial direction of the disk 10 while irradiating the disk 10 with a light beam. It's summery. The pick-up 21 has a photodetector (not shown) consisting of a plurality of photodetecting elements for detecting tracking errors, and the output of each photodetecting element of this photodetector is supplied to an arithmetic circuit 22 to detect tracking errors. signal
TE is obtained. This tracking error signal TE
is applied to the focusing lens of the pick-up 21 or the pick-up 2 through the multiplication circuit 23, the switch 24, and the tracking servo amplifier circuit 25.
A tracking servo loop is formed by providing a tracking control means 26 such as a DC linear motor that moves the entire disk 10 in the radial direction of the disk 10.

When the disk 10 is attached to the player for playback as shown in the figure, the focus servo is activated and the light beam from the pickup 21 is directed to the disk 1.
0 recording surface, and then a start pulse SP as shown in FIG. 2 is obtained at the terminal 31. This start pulse SP
is supplied to the reset terminal R of the RS flip-flop 32, and at the trailing edge of the start pulse SP, the RS
Flip-flop 32 is reset, causing its output signal A to go low. The output signal A of this RS flip-flop 32 is supplied to the switch 24 as its on/off control signal, and the output signal A
When the signal goes low, switch 24 is turned off, turning off the tracking servo loop described above. Further, when a start pulse SP is obtained at the terminal 31 and the tracking servo loop is turned off, the pick-up 21 is sent in the radial direction of the disk 10, and the light beam of the pick-up 21 crosses the track on the disk 10. be moved by The light beam of pick-up 21 reaches disk 10.
By being moved in the direction across the track, the tracking error signal TE obtained from the arithmetic circuit 22 changes sinusoidally at a certain level as shown in FIG.

This tracking error signal TE is supplied to a peak hold circuit 41 to hold its peak value X, that is, its level, and the output voltage PH of this peak hold circuit 41 is supplied to an A/D conversion circuit 42. In addition, the start pulse SP obtained at the terminal 31 is connected to the monostable multivibrator 5 for delay.
1, the monostable multivibrator 51
A pulse E with a predetermined pulse width is obtained, this pulse E is further supplied to the monostable multivibrator 52, and the command pulse F for A/D conversion is obtained from the monostable multivibrator 52. and,
This command pulse F is supplied to the A/D conversion circuit 42, where the output voltage PH of the peak hold circuit 41 is A/D converted.
The A/D conversion circuit 42 converts the peak value
You can get decimal data.

The output data of this A/D conversion circuit 42 is supplied to an arithmetic circuit 44. Further, the command pulse F for A/D conversion obtained from the monostable multivibrator 52 is supplied to the monostable multivibrator 53 for delay, and a pulse G of a predetermined pulse width is obtained from the monostable multivibrator 53. Pulse G
is further supplied to the monostable multivibrator 54, and a command pulse H for calculation is obtained from the monostable multivibrator 54. This command pulse H is then supplied to the arithmetic circuit 44, where the binary data of the predetermined value Z is converted to the peak value X.
is divided by the output data of the A/D conversion circuit 42, which is binary data, and the binary data of Y=Z/X is obtained from the arithmetic circuit 44.

The output data of this arithmetic circuit 44 is stored in a memory 45.
is supplied to Further, the command pulse H for calculation obtained from the monostable multivibrator 54 is supplied to the monostable multivibrator 55, and the latch pulse I is obtained from the monostable multivibrator 55. Then, this latch pulse I is applied to the memory 45.
The output data of the arithmetic circuit 44, which is binary data of Y=Z/X, is latched into the memory 45. Furthermore, the output data of the memory 45 is supplied to the D/A conversion circuit 46 and subjected to D/A conversion, and a voltage having a value of Y=Z/X is continuously obtained from the D/A conversion circuit 46. is supplied to the multiplication circuit 23 and multiplied by the tracking error signal TE obtained from the arithmetic circuit 22. Therefore, the peak value, that is, the level, of the tracking error signal on the output side of the multiplication circuit 23 is equal to Y
= a predetermined value Z multiplied by the value of Z/X. Further, the latch pulse I obtained from the monostable multivibrator 55 is supplied to the set terminal S of the RS flip-flop 32, and at the time of the trailing edge of the latch pulse I,
RS flip-flop 32 is set and its output signal A changes from a low level to a high level, which turns on switch 24 and turns on the tracking servo loop described above. The tracking servo gain at this time is obtained by multiplying the tracking error signal TE obtained from the arithmetic circuit 22 by the voltage of the value Y=Z/X obtained from the D/A conversion circuit 46 in the multiplication circuit 23. remains constant regardless of optical variations. That is, the tracking servo gain is automatically set to an appropriate value depending on the disc 10 to be reproduced.

FIG. 3 shows another example of the tracking servo circuit of the present invention, in which a clock pulse of a constant frequency obtained from a clock pulse generation circuit 61 is sent to a binary counter 6.
The start pulse SP, which is supplied to the clock terminal CK of 2 and obtained at the terminal 31, is supplied to the control terminal of the counter 62, and the counter 62 receives the start pulse SP, which turns off the tracking servo loop.
From the time of the trailing edge of clock pulse generation circuit 61
The clock pulses supplied from the counter 62 are counted from a certain value, and the output data of this counter 62 is supplied to a D/A conversion circuit 63, where it is D/A converted, and the output data from the D/A conversion circuit 63 is shown in FIG. As shown, a voltage DA that changes stepwise from a certain value _Y0 for each cycle of the clock pulse is obtained, and this voltage DA is supplied to the multiplier circuit 23 and the arithmetic circuit 22.
The tracking error signal TE obtained from the above is multiplied by the tracking error signal TE, and the tracking error signal TE' whose peak value, that is, level changes stepwise every cycle of the clock pulse, is output to the output side of the multiplication circuit 23 as shown in FIG. is obtained.

The tracking error signal TE' output from the multiplication circuit 23 is supplied to the peak hold circuit 71, and its peak value, that is, the level, is held.
The output voltage PH' of this peak hold circuit 71 is supplied to a voltage comparison circuit 72 and compared with a reference voltage of a predetermined value Z, and the output voltage PH' of the peak hold circuit 71 is
When the value of PH' exceeds the predetermined value Z, the output signal B of the voltage comparison circuit 72 changes from low level to high level as shown in FIG. The output signal B of this voltage comparison circuit 72 is supplied to a monostable multivibrator 73, and the monostable multivibrator 73 is triggered at the time of the rise of the signal B from a low level to a high level.
A pulse C is obtained, and this pulse C is supplied as a latch pulse to the memory 64 to which the output data of the counter 62 is supplied. The counter 62 is stopped by being supplied to a control terminal other than the control terminal to which the aforementioned start pulse SP of 62 is supplied, and thereafter, the data latched in the memory 64 is supplied to the D/A conversion circuit 63. After D/A conversion, the value of the output voltage DA of the D/A conversion circuit 63 is the value Y=Z/
It is held at X. Monostable multivibrator 73
The resulting pulse C is also applied to the set terminal S of the RS flip-flop 32, and at the trailing edge of the pulse C, the RS flip-flop 32 is set, causing its output signal A to change from a low level to a high level. Switch 24 is turned on,
Tracking servo loop is turned on.

Furthermore, when removing the disc 10 from the player, a clear pulse CP is obtained at the terminal 33,
This is supplied to the memory 64, and the memory 64
The data latched to is cleared.

Effects of the Invention As is clear from the above, the present invention includes a voltage generation circuit that generates a voltage to be multiplied by a tracking error signal, and a multiplication circuit that multiplies the output voltage of the voltage generation circuit by the tracking error signal. The voltage generating circuit described above calculates the tracking error signal based on the tracking error signal when the light beam of the optical pickup is moved across the track on the disk with the tracking servo loop turned off. Since the above output voltage value is set so that the level of the tracking error signal output from the above multiplication circuit becomes a predetermined value, the tracking servo gain is adjusted according to the disc to be played. The tracking servo gain is automatically set to an appropriate value, allowing stable playback regardless of disc optical discrepancies, and eliminating the need for an adjustment process for tracking servo gain settings during the player manufacturing process. .

[Brief explanation of drawings]

FIG. 1 is a connection diagram of an example of the tracking servo circuit of the present invention, FIG. 2 is a waveform diagram for explaining its operation, and FIG. 3 is a connection diagram of another example of the tracking servo circuit of the present invention. FIG. 4 is a waveform diagram for explaining the operation. In the figure, 10 is a disk, 21 is a pick-up,
22 is an arithmetic circuit, 23 is a multiplication circuit, 25 is a tracking servo amplifier circuit, 26 is a tracking control means, 41 and 71 are peak hold circuits, 42
is an A/D conversion circuit, 44 is an arithmetic circuit, 45 and 6
4 is a memory, 46 and 63 are D/A conversion circuits,
61 is a clock pulse generation circuit, 62 is a binary counter, and 72 is a voltage comparison circuit.

Claims (1)

[Claims] 1. A voltage generating circuit that generates a voltage to be multiplied by a tracking error signal, and a multiplier circuit that multiplies the tracking error signal by the output voltage of this voltage generating circuit, and the voltage generating circuit has a tracking servo loop. Based on the tracking error signal when the light beam of the optical pickup is moved across the track on the disk in the off state, the level of the tracking error signal output from the multiplication circuit at this time is determined. A tracking servo circuit for an optical disc player, wherein the value of the output voltage is set to a predetermined value, and a tracking error signal output from the multiplication circuit is provided to a tracking control means.