JPS6231039A - Optical axis controller for optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To detect the inclination of the surface of a disk even if the disk has recorded parts and unrecorded parts together and to irradiate the disk surface with a light beam by finding the height-directional displacement of the disk from the driving voltage of an actuator. CONSTITUTION:An optical block 19 is led toward the inner periphery of the disk in response to a retrieval signal (a) from a microcomputer 30 to reproduce a track having a specific address. At this time, a DC component Vo of the output (b) of a focus driving circuit 23 is read in the microcomputer 30. Then, the optical block 19 is moved to the outer periphery of the disk to reproduce a track having a specific address and a DC component V1 of the output (b) of the focus driving circuit 23 is read in the microcomputer. Consequently, when the microcomputer 30 outputs a digital signal (e) corresponding to the inclination theta of the disk to a D/A converter 31, a motor 34 turns until the output of a potentiometer 35 and the output of the D/A converter 31 coincide with each other and controls the optical axis so that the light beam is incident on the disk surface almost at right angles.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention provides information such as a video signal on a disc-shaped recording medium.
The present invention relates to an optical recording and reproducing apparatus that records or reproduces data in the form of optical characteristic changes in the medium, and particularly relates to a device that controls the optical axis of a light beam relative to a disk-shaped recording medium.

[Background of the invention]

Optical recording and reproducing devices generally use disk-shaped disk-shaped guide tracks with spiral or concentric guide tracks and address information to identify each guide track so that information can be recorded at high density as a recording medium. be done. The light beam from the laser light source is irradiated as a light spot on the guide track by well-known focusing and tracking control, and by modulating the light output intensity of the laser light source with a recording signal, optical characteristics such as reflectance of the light irradiated area can be adjusted. Record as characteristic changes. On the other hand, during reproduction, the optical characteristic change is detected by setting the optical output intensity of the laser light source to a constant output lower than that during recording, and the recorded information is reproduced in step 5.
0 In such information recording and reproducing devices, there is a trend toward higher density in the future due to the economical efficiency of recording media and miniaturization of devices. There is a growing demand for this.

One of the problems that arises with such narrowing of tracks is crosstalk from adjacent tracks. In particular, when the light beam is no longer incident perpendicularly to the disk surface due to disk warpage or the like, the shape of the light spot changes from a circle to an oval, making it easier to detect signals from adjacent tracks.

As a method to counter the above drawbacks, for example, Utility Model Application No. 59-1
There is a publication No. 6883. In this method, as shown in FIG. 3, the output from the light emitting element 36 is reflected by the optical disc 9,
This reflected light is received by two light receiving elements 37 and 38, and the tilt of the disk 9 is detected from the difference in the amount of reflected light.
The optical axis of the light beam is controlled so that this difference becomes zero, so that the optical axis and the disk surface are perpendicular. However, since this method uses light reflected from the disk surface, it is easily affected by the reflectance of the disk surface. In particular, in a recording/reproducing device that records and reproduces information by changing the reflectance of the recording material, there may be a mixture of recorded areas and unrecorded areas. Even if the angle is perpendicular, there is a difference in the light reflected from the unrecorded portion 9a and the recorded portion 9b of the disk. Therefore, the light receiving element 37.
The output of 38 should originally be 11j, but it becomes 1, j/
As a result, the position where '' becomes zero in the difference signal between the two shifts, causing a problem that the optical axis control of the light beam malfunctions.

[Purpose of the invention]

An object of the present invention is to prevent the inclination of the disk surface even on a disk having both recorded and unrecorded areas in an optical recording and reproducing apparatus that records as a change in reflectance of a recording medium and performs playback by detecting the change in reflectance. [Summary of the Invention] Therefore, in the present invention, the focus control circuit is configured to control the light beam in the height direction of the disc. Focusing on the fact that the actuator is driven to follow this displacement, the displacement in the disk height direction is calculated from the drive voltage or drive current of the actuator at the inner and outer peripheral positions of the disk We decided to detect the inclination of the disk from the displacement in the height direction and use this signal to control the light beam so that it is irradiated perpendicularly to the disk surface.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows the configuration of an optical axis control circuit and an optical recording/reproducing apparatus as an embodiment of the present invention.

The output light of the semiconductor laser 1 is first converted into parallel light by the condensing lens 2, and then converted into parallel light with an approximately circular cross section by the uneven cylindrical lens 3.4, and then sent to the beam splitter 5.
The light passes through the quarter-wave plate 6 and enters the objective lens 8 attached to the actuator 7, and is focused on the disk 9 as a light spot. The reflected light from the disk 9 passes through the objective lens 8 and the 1/4 wavelength plate 6, is guided by the beam splitter 5 toward the convex lens 10, is split by the mirror 11, and one side is incident on the two-split photodiode 12. The output of the photodiode 12 is differenced by a differential amplifier 13,
A tracking error signal corresponding to the deviation between the guide track on the disk and the optical spot is obtained. The tracking control circuit 14 drives the actuator 7 in the disk radial direction via the drive circuit 15, and performs control so that the deviation between the guide track and the light spot is 0.1 μm or less. On the other hand, the output of the tracking drive circuit 15 is also input to the slider control circuit 16 and drives the slider motor 18 via the slider drive circuit 17. 19 can be transferred in the radial direction of the disk. Further, the slider control circuit 16 is also capable of performing a well-known search operation by moving the optical block 19 in the disk radial direction at high speed in response to a search signal a from the microcomputer 30.

The other light split by the mirror 11 enters a two-split photodiode 20 placed at the focal point of the convex lens 10. The difference between the outputs of the photodiode 2o is taken by a differential amplifier circuit 21, and a seven-occasion error signal corresponding to the distance between the objective lens 8 and the disk 9 is obtained. The focus control circuit 22 controls the actuator 7 to move in the disk height direction [K via the drive circuit 23 so that the objective lens maintains the focal position with an accuracy of 1 μm or less. on the other hand,
The outputs of the two-split photodiode 20 for focus error detection are added together in an adder circuit 24 and input to an address circuit 26 via a low-pass filter 25. The address demodulation circuit 26 demodulates address information provided on the disk and inputs it to the microcomputer 30. The optical axis control circuit 27 includes a low-pass filter 28, an A/D converter 29,
It is composed of a microcomputer 30, a D/A converter 31, a differential amplifier circuit 32, a drive circuit 33, a motor 34, and a potentiometer 35. The operation of the optical axis control circuit 27 of the present invention will be explained below.

In focus control, an actuator (for example, one driven by a voice coil) to which the objective lens 8 is attached is driven in a direction perpendicular to the disk surface, so that the objective lens always maintains its focal position. Therefore, as shown in FIG. 2, a DC drive voltage is applied to the actuator to maintain the focal position of the objective lens in accordance with the displacement of the disk in the height direction. Therefore, the displacement in the height direction of the disk can be determined from the DC component of the actuator drive voltage.

When detecting the inclination of the disk in the optical axis control circuit of the present invention, first, the search signal a from the microcomputer 30 is used to detect the optical block 19 in accordance with a well-known search operation.
is moved toward the inner circumference of the disk, and the track at a predetermined address Ao is reproduced. From the output C of the LPF 28 at this time, the DC component VO of the output of the focus drive circuit 23 is calculated as A/
The digital signal d is read into the microcomputer 30 by the D converter 29.

Next, the search signal a from the microcomputer 30 is sent again.
to move the optical block 19 toward the outer circumference of the disk,
The track at the predetermined address A1 is reproduced. Similarly, the DC component v1 of the output from the focus drive circuit 23 is read into the microcomputer. The inclination θ of the disk is determined from the data Vo, V1 read into the microcomputer 30 and the address information Ao, Al using the following equation.

Here, the DC sensitivity ADcm/V] of the actuator 7 and the track pitch P(m) are known, and the inclination θ of the disk can be easily determined using the microcomputer 3°. Generally, the inclination θ of the disk is small, and the following approximation of equation (1) is sufficient.

Next, control of the optical axis will be explained. First, the microcomputer 3o outputs a digital signal e corresponding to the disk inclination θ to the D/A converter 31. A DC voltage f corresponding to the digital signal e is applied from the D/A converter 31 to the differential amplifier circuit 32, which drives the motor 34 via the drive circuit 33 to tilt the entire optical block 19 in the disk radial direction. Here, the potentiometer 35 interlocked with the motor 34 outputs a DC voltage g corresponding to the rotation angle of the motor 34. Therefore, the motor 34 rotates until the output of the potentiometer 35 and the output of the D/A converter 31 match, and the entire optical block is tilted by a predetermined angle so that the light beam is incident on the disk surface approximately perpendicularly. Control the axis.

〔Effect of the invention〕

As explained above, in the present invention, in order to detect the tilt of the disk from the focus drive voltage, the light beam is controlled so as to be irradiated perpendicularly to the disk surface even on a disk where recorded and unrecorded areas coexist. Is possible.

In the embodiment of the present invention, the displacement in the height direction of the disk is determined from the DC component of the focus drive voltage at two locations on the inner and outer circumferences,
Although the inclination is detected, the inclination may also be detected by determining the displacement in the height direction of the disk at several locations on the inner and outer circumferences of the disk.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an optical axis control circuit and an optical recording/reproducing apparatus as an embodiment of the present invention, and FIG. 2 shows detection of a disk tilt detection section of the optical axis control circuit according to the present invention. FIG. 3 is a diagram for explaining the operation, and is an explanatory diagram showing the principle of the conventional optical beam axis control method and its drawbacks. Explanation of symbols l... Semiconductor laser, 7... Actuator, 9... Disk, 19... Optical block, 23... Focus drive circuit, 27...・・・
・Optical axis control circuit, 28...Low pass filter, 2
9...A/Di converter, 30...Microcomputer, 31-...D/A converter, 32...
...Differential amplifier circuit, 33...Drive circuit, 34...
...Motor, 35...Potentiometer, 36...
...Light emitting element, 37.38... Light receiving element. l, Patent attorney Katsura Ogawa, ・. Figure 42 AD River
AFν person figure 5

Claims (1)

[Scope of Claims] 1. An objective lens for focusing a light beam emitted from a light source into a minute spot light, means for recording or reproducing information on a recording surface of a recording medium using the minute spot light, and said recording surface. a light detection means for detecting reflected light from the object lens and obtaining a reproduction signal and an error signal necessary for focus control, and using the error signal, the distance between the objective lens and the recording medium is kept constant at a desired value. In an optical recording/reproducing apparatus having means for driving the objective lens, an optical system tilting means for tilting the optical system with respect to the recording medium;
Optical recording characterized in that means is provided for generating a detection output according to the inclination of the light beam with respect to the recording medium from the error signal, and the optical system tilting means is driven in accordance with the detection output. Optical axis control device for playback equipment. 2. In the optical recording and reproducing apparatus according to claim 1, the means for generating a detection output according to the inclination of the light beam with respect to the recording medium obtains a DC component from the drive signal of the objective lens drive means. An A/D converter for converting the output of the low-pass filter into a digital signal, and an A/D converter that calculates the inclination of the light beam and the recording medium from the output of the A/D converter, A computing unit that outputs a signal, and a D/D converter that converts the digital signal output from the computing unit into an analog signal.
1. An optical axis control device for an optical recording/reproducing device, characterized in that it is comprised of an A converter.