JPS62264440A - Automatic offset adjusting device for radial servo system - Google Patents

Abstract

PURPOSE:To surely operate a radial servo, by providing a means to hold an offset part at a naught by a radial-on signal, and a means to perform the pull-in of the radial servo after setting an offset voltage at the naught. CONSTITUTION:An offset voltage RE1 that is the output of a low-pass filter 12 is supplied to an amplifier 11, and a radial error signal RE2 from which the voltage RE1 of the offset part is generated, and it is supplied to the driver 13 of the actuator of an objective lens in an optical system through a switch SW2, and the actuator 14 of the optical system is driven, then a requested radial servo is performed. Also, a radial servo system generates a signal RLC ON, that is a servo on signal, and operates a switch SW1, and also, through a delay circuit 15 of 0.1sec, operates the switch SW2. Therefore, the switch SW1 is opened by the signal RLO ON, and afterwards, the switch SW2 is closed by a delay signal RLC' after a time of 0.1sec, then the pull-in of the radial servo is performed. In such a way, the servo system can be surely operated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic offset adjustment device in a radial servo system that performs radial servo control of an optical pickup optical system of an optical information recording/reproducing apparatus with respect to an optical disk.

[Conventional technology]

A radial servo system detects the tracing state of a light beam relative to a track on an optical disk using a radial error signal, and moves the objective lens of an optical pickup in the radial direction to track a predetermined track on the optical disk as desired.

Conventionally, in this type of radial servo system, the optical pickup
After differentially amplifying the outputs of the two photodetectors using an amplifier, this differentially amplified radial error signal is directly supplied to the optical system of the optical pickup, for example, an actuator driver that drives the objective lens, and the actuator drives the objective lens. It was made to move in the desired radial direction.

[Problem that the invention seeks to solve]

If there is an offset in this radial error signal, this offset will also be applied to the lens actuator when the servo system is turned on, which may cause the objective lens to shift and the servo system to malfunction.

In order to solve this drawback, attempts have been made to provide a symmetry compensation circuit in the radial servo system. However, the provision of such a symmetry compensation circuit has the disadvantage that the configuration becomes complicated, the device becomes larger, and therefore becomes more expensive.

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic offset adjustment device for a radial servo system that is small and inexpensive and can operate the radial servo reliably by simply adding a simple circuit element.

Means, operation, and embodiments for solving problem C] The automatic offset adjustment device of the present invention includes means for extracting an offset included in a radial error signal in an optical information recording and reproducing device, and a means for extracting an offset included in a radial error signal, and a method for extracting this offset by a radial on signal. It is characterized by comprising means for holding the offset voltage at a zero value, and means for pulling in the radial servo after the offset voltage is set to the zero value.

The offset extracting means includes a low-pass filter.

The means for maintaining the offset at a zero value by the radial-on signal includes a differential amplifier provided after the low-pass filter, and a switch activated by the radial-on signal to activate the low-pass filter. .

The means for pulling in the radial servo after setting the offset voltage to zero value includes a delay circuit that delays the radial-on signal, and a switch activated by the output of the delay circuit to connect the output of the differential amplifier to the actuator driver. Make it.

The invention will be explained with reference to the drawings.

The structure and operation of the automatic offset adjustment device of the present invention are shown in FIGS. 1 and 2. In the automatic offset adjustment device for the radial servo system of the present invention shown in FIG. A certain radial error signal Rεθ (Fig. 2 (
a)) to the amplifier 11; This radial error signal REθ has an offset REI (Figure 2 (b))
is included.

In the present invention, the radial error signal REθ including this offset RBI is transferred to the switch St! 11 and is supplied to a low-pass filter 12. This low-pass filter has its cutoff frequency f. =Q, lHz, and thereby the offset voltage Rε1 of the radial error signal REθ
(Figure 2(b)) is generated.

Offset voltage RE, which is the output of the low-pass filter 12
1 is supplied to the amplifier 11, thereby performing differential amplification of the two human power signals to generate a radial error signal RB2 with the offset voltage RE1 removed, and this signal RE2 is sent to the objective of the optical system via a switch SW2. The signal is supplied to the lens actuator driver 13, and the driver 13 drives the optical system actuator 14 to perform desired radial servo.

Furthermore, when turning on the servo, the radial servo system generates a servo-on signal RLCON (Fig. 2(d)), which activates the switch S1ν1 and passes through the delay circuit 15 having a delay time of Q, 1 sec. The switch SW2 is activated. Therefore, the switch SWI is opened by this signal RLCON, and after 0.1 sec, the delayed RLC' signal (see Fig. 2 (e)
), the switch SW2 is closed and the radial servo is retracted. Because of this, the offset R8
After the value 1 becomes zero, the radial servo is pulled in.

〔Effect of the invention〕

As described above, according to the present invention, the offset of the radial error signal is zeroed during radial servo pull-in to perform servo pull-in, so that the servo system can be reliably operated.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of an automatic offset adjusting device in a radial servo system of the present invention, and FIG. 2 is a time chart showing signal waveforms at various points in the automatic offset adjusting device of FIG. 10.11... Differential amplifier 12... Low pass filter 13... Actiniator driver 14... Actuator 15... Delay circuit Patent applicant Olympus Optical Industry Co., Ltd. Representative patent attorney Takeshi Nara Procedure September 5, 1988 1, Display of the case 1986 Patent Application No. 108175 2, Title of invention Automatic offset adjustment device in radial servo system 3,
Patent applicant address: 2-43-2 Hatagaya, Shibuya-ku, Tokyo Name (037) Olympus Optical Industry Co., Ltd. Representative Satoshi Shimoyama Department 4, Agent 7, Amendment Contents (1) The specification attached to the present application is amended as per the attached amended specification. 8. List of attached documents (1) Corrected specification 1 Specification 1. Title of invention Automatic offset adjustment device 2 in radial servo system. Claim 1. Offset included in radial error signal in optical information recording and reproducing device. A radial servo system comprising means for extracting the offset amount, means for holding the offset amount slightly by a radial-on signal, and means for pulling in the radial servo after reducing the offset voltage to a zero value. Automatic offset adjustment device. 2. The automatic offset adjustment device in a radial servo system according to claim 1, wherein the offset extracting means includes a low-pass filter. 3. The means for maintaining the offset at a zero value by the radial-on signal includes a differential amplifier provided after the low-pass filter, and a switch activated by the radial-on signal to activate the low-pass filter. An automatic offset adjustment device in a radial servo system according to claim 2, characterized in that: 4. The means for pulling in the radial servo after the offset voltage is set to zero includes a delay circuit that delays the radial-on signal, and a switch that is activated by the output of the delay circuit and connects the output of the differential amplifier to the actuate driver. An automatic offset in a radial servo system according to claim 3, comprising: adjustment device. 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an automatic offset adjustment device in a radial servo system that performs radial servo control of the optical pink-up optical system of an optical information recording and reproducing device with respect to an optical disk. . [Prior Art] A radial servo system uses a radial error signal to detect the trace state of a light beam with respect to the trunk of an optical disk, and moves the objective lens of an optical pickup in the radial direction to track a predetermined track on the optical disk as desired. It is. Conventionally, in this type of radial servo system, two
After differentially amplifying the outputs of the two photodetectors using an amplifier, this differentially amplified radial error signal is directly supplied to the optical system of the optical pickup, for example, an actuator driver that drives the objective lens, and the actuator drives the objective lens. It was made to move in the desired radial direction. [Problem to be solved by the invention] If there is an offset in this radial error signal, this offset will also be applied to the lens actuator when the servo system is turned on, which may cause the objective lens to shift and the servo system to malfunction. . In order to solve this drawback, attempts have been made to provide a symmetry compensation circuit in the radial servo system. However, the provision of such a symmetry compensation circuit has the disadvantage that the configuration becomes complicated, the device becomes larger, and therefore becomes more expensive. SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic offset adjustment device for a radial servo system that is small and inexpensive and can operate the radial servo reliably by simply adding a simple circuit element. [Means and operations for solving the problem] The automatic offset adjustment device of the present invention includes means for extracting an offset included in a radial error signal in an optical information recording/reproducing device, and a means for extracting an offset included in a radial error signal, and a means for reducing this offset to a zero value by a radial on signal. The present invention is characterized by comprising means for holding the offset voltage and means for pulling in the radial servo after the offset voltage is set to a zero value. The offset extracting means is provided with a low-pass filter. The means for maintaining the offset at a zero value by the radial-on signal includes a differential amplifier provided after the low-pass filter, and a switch activated by the radial-on signal to activate the low-pass filter. . The means for pulling in the radial servo after setting the offset voltage to zero includes a delay circuit that delays the radial-on signal, and a switch 7 that is activated by the output of the delay circuit and connects the output of the differential amplifier to the actuator driver 8. and be prepared. [Function] With this configuration, the offset portion of the radial error signal is extracted by the low-pass filter and made into a zero value, so the objective lens does not need to be shifted, and therefore the radial servo can be operated reliably. [Example] The structure and operation of the automatic offset adjustment device of the present invention are shown in FIGS. 1 and 2. In the automatic offset Nl'fl adjusting device in the radial servo system of the present invention shown in FIG. , and supplies the output radial error signal REθ (FIG. 2(a)) to the amplifier 11. This radial error (J number REθ includes an offset REI (FIG. 2(b)). In the present invention, the radial error signal REθ including this offset REI is supplied to the low-pass filter 12 via the switch SWI. The cutoff frequency of this low-pass filter is set to fC・0.1 Hz, so that the voltage 1?E1 corresponding to the offset of the radial error signal REθ is
(Fig. 2(b)) is generated. Offset voltage RE, which is the output of the low-pass filter 12
1 to the amplifier 11, thereby generating a radial error signal RE2 in which the offset voltage l1E1 is removed by differentially amplifying the force signals.
2 is supplied to the driver 13 of the actuator of the objective lens of the optical system via the switch SW2, and this driver 13
The actuator 14 of the optical system is driven to perform desired radial servo. In addition, the radial servo system generates a servo-on signal RLCON (Fig. 2(d)) when turning on the servo, and this signal activates the switch SWI and also activates the delay circuit 15 having a delay time of 0.1 sec. After that, switch SW2 is made. Therefore, the switch SWl is opened by this signal RLCON, and after 0.1 sec, the delayed RLC' signal (Fig. 2 (e)
)) closes the switch SW2 to retract the radial servo. Because of this, the offset R
After EI reaches zero value, the radial servo is pulled in. [Effects of the Invention] As described above, according to the present invention, the servo system can be reliably operated because the servo pull-in is performed with the offset of the radial error signal made zero during the radial servo pull-in. 4. Brief description of the drawings Fig. 1 is a circuit diagram showing the configuration of the automatic offset adjustment device in the radial servo system of the present invention, and Fig. 2 shows signal waveforms at various points in the automatic offset 3Jl adjustment device shown in Fig. 1. It is a time chart figure.

Claims (1)

[Scope of Claims] 1. Means for extracting an offset included in a radial error signal in an optical information recording/reproducing device, and means for holding this offset at a zero value by a radial-on signal;
1. An automatic offset adjustment device for a radial servo system, comprising means for retracting the radial servo after reducing the offset voltage to a zero value. 2. The automatic offset adjustment device in a radial servo system according to claim 1, wherein the offset extracting means includes a low-pass filter. 3. The means for maintaining the offset at a zero value by the radial-on signal includes a differential amplifier provided after the low-pass filter, and a switch activated by the radial-on signal to activate the low-pass filter. An automatic offset adjustment device in a radial servo system according to claim 2, characterized in that: 4. The means for pulling in the radial servo after setting the offset voltage to zero includes a delay circuit that delays the radial-on signal, and a switch that is activated by the output of the delay circuit and connects the output of the differential amplifier to the actuator driver. An automatic offset adjustment device in a radial servo system according to claim 3, comprising: an automatic offset adjustment device for a radial servo system;