JPS62217427A - Correcting system for inclination of optical disk - Google Patents

Abstract

PURPOSE:To correct an inclination of an optical disk by a simple constitution, by inputting an output of an inclination detector for detecting an inclination of the optical disk, to a differential amplifier, and applying an off-track based on the inclination of the optical disk, in the revere direction. CONSTITUTION:A reflected light from an optical disk 7 is inputted to a 4-split sensor 10-1 through a beam splitter 9 and an off-track signal is detected by a differential amplifier 12. This signal contains an offset caused by an inclination of the disk 7. On the other hand, from an output of the sensor 10-1, a focus error signal is obtained through a differential amplifier 16. This signal is amplified by a differential amplifier 13, a focus actuator 17 is driven and a recording and reproducing lens 6 is controlled so that a focus error becomes '0'. On the other hand, an inclination data of an inclination detector 30 of the optical disk is inputted to a differential amplifier 15 through a D/A converter 18. This amplifier 15 contains an offset caused by an inclination of the disk 7, and the amplifier 15 corrects the inclination, of the disk 7, and the amplifier 15 corrects the inclination, amplifies 13-1 this correcting signal and drives a track actuator 14.

Description

Detailed Description of the Invention [Summary] The present invention is a method for correcting the tilt of an optical disc in an optical disc device, which offsets a tracking signal containing an offset caused by the tilt of the optical disc with a signal proportional to the tilt of the recording medium. , and perform tracking control to improve access accuracy for recording and playback.

(Industrial Application Field) The present invention relates to an optical disc tilt correction method for correcting the tilt of an optical disc and accessing the optical disc when recording and reproducing data using an optical disc device.

Recently, optical disk devices using optical disks as information media have been widely used because of their high information recording density. Although optical disk devices are capable of high-density recording, they are also required to have high accuracy in accessing required locations on the optical disk. Therefore, the off-track is corrected by driving the track actuator with a trunk signal generated by the off-track.

However, if the optical disc is tilted for some reason, the above-described method is not sufficient to correct the tilt, resulting in poor access and making recording and reproduction impossible. Therefore, there is a need for an optical disc tilt correction method with a simple structure that can correct the tilt of an optical disc.

[Conventional technology]

Conventionally, an optical disk device is configured as shown in FIG. Parallel incident light 5 from a laser light source or the like is focused by a recording/reproducing lens 6 and formed into an image on an optical disk 7 . Reflected light 8 reflected by the optical disk 7 is incident on a two-split optical sensor 10 via a beam splitter 9. In addition,
A groove (pre-group) 11 is formed on the optical disk 7 with a depth of one-eighth of the wavelength λ of the laser beam used.

Therefore, in the on-track state where the image is formed exactly at the center of the groove 11, the two-split optical sensor IO detects light in a symmetrical state as shown in FIG. Detection is performed asymmetrically as shown in Figure 6 (al, tc+).

The difference in detected intensity of this two-split optical sensor 10 is detected by a differential amplifier 12.
The trunk actuator 4 is driven by the trunk error signal detected by the amplifier 13 and the optical system (recording lens 6) is corrected to the on-trunk state.

[Problem that the invention seeks to solve]

In the conventional optical disk device described above, when the optical disk 7 is deformed due to creep or aging and the optical disk 7 is tilted by θ as shown in FIG. This results in a shift of 2fθ (where f is the focal length of the recording/reproducing lens). Therefore, there is a problem in that an unnecessary offset signal is added to the off-track signal due to the inclination of the optical disc, which interferes with the original trunk flowing.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional situation, it is an object of the present invention to provide an optical disc tilt correction method in which the tilt of an optical disc can be corrected with a simple configuration.

[Means for solving problems]

As shown in FIG.
a differential amplifier 12 which receives the output of the optical disc and outputs an off-trunk signal including an offset node due to the tilt; and a differential amplifier 15 which receives the output of the differential amplifier 12 and the output of the optical disc tilt detector 30. , the output of the differential amplifier 15 is amplified by the current amplifier 13, and the output of the differential amplifier 15 is
It is configured to drive.

[Effect]

The output of the tilt detector 30 that detects the tilt of the optical disc 7, that is, a signal proportional to the tilt angle, is input to the differential amplifier 15, and off-trunk based on the tilt of the optical disc included in the trunk error signal is tracked in the opposite direction. It is added to the error signal to correct the tilt of the optical disc 7 and drive the trunk actuator 14.

Therefore, the tilt of the optical disc can be corrected with a simple configuration.

〔Example〕

FIG. 2 is a block diagram of one embodiment of the present invention.

The same parts as in the prior art are given the same reference numerals, and the explanation will be omitted.

The reflected light 8 is sent to a 4-split sensor 1 via a beam splitter 9.
0-1, and the differential amplifier 12 outputs (alb)-(
An off-trunk signal is detected as c+a). This off-track signal includes the unnecessary offset due to the above-mentioned tilt of the optical disc.

On the other hand, the output of the 4-split sensor is passed through the differential amplifier 16 (
A focus error signal of alc)-(b+d) is obtained. This signal is amplified by the current amplifier 13, drives the focus actuator 17, and controls the recording/reproducing lens 6 so that the focus error is always "0". Although the optical disk 7 has a warpage of several hundred micrometers, the focus actuator 17 follows this warpage with an error of several micrometers at most. Therefore, the displacement of the focus actuator 17 represents the warpage of the optical disc 7, and by calculating this displacement, the tilt of the optical disc can be obtained.

The slope detector 30 includes an equivalent circuit 1, an averaging circuit 1-1, and an A
It is composed of a /D converter 2, a memory circuit 3, and an arithmetic unit 4. The equivalent circuit 1 is an electrical equivalent circuit having the same transfer characteristics as the focus actuator 17, and the transfer characteristics of the spring-supported focus actuator 17 are approximated by a second-order low-pass filter, and it is possible to configure it with a CR equivalent circuit. It is publicly known.

Note that errors caused by proximal errors between the focus actuator 17 and the equivalent circuit 1 do not pose a problem since only the difference is handled, as will be described later.

Further, the averaging circuit 1-1 has a time constant corresponding to the time required for one rotation of the optical disk.

Of course, it is sufficient that the average value can be obtained without the averaging circuit 1-1. For example, the data may be stored moment by moment in the storage circuit 3 and the average value may be calculated by the calculator 4.

The output of the averaging circuit 1-1, that is, the average value, is converted into a digital value by the A/D converter 2, and is stored in the storage circuit 3. A track number is also input to the storage circuit 3 from a track access circuit (not shown), and the average value is also stored together with the corresponding trunk number.

Note that this track number is not for all tracks, for example,
All tracks are divided into 16 zones, and each zone is assigned a representative track number.

The calculator 4 refers to the storage circuit 3 and calculates the slope of track number A, for example, by calculating (a-b)/(A-8
) is calculated and stored in the slope column of the track number A column. Needless to say, there are calculation techniques to improve the accuracy of the slope value.

The tilt data of the optical disc tilt detector 30 described above is as follows:
The signal is input to the differential amplifier 15 via the D/A converter 18. On the other hand, as described above, a signal containing an unnecessary offset due to the tilt of the optical disk is inputted to the differential amplifier 15, and the differential amplifier 15 corrects the tilt and sends this corrected signal to the current amplifier 13-1. The signal is amplified to drive the track actuator 14.

FIG. 3 shows another embodiment of the present invention, and Shigenobu's embodiment shows an example of a dual servo system. Normally, in a dual servo system, track deviation is detected by an optical and electrical track detection section 40 in order to perform tracking. The actuator 41 is driven by this track deviation signal to move the recording/reproducing lens 6 so that the track deviation signal is minimized.

In order to move the recording/reproducing lens 6 of the first servo system, which moves in the minute range described above, at high speed, the laser light source and reflection information detection system (not shown) are connected to a second lens which can move over a wide range.
The displacement detector 43 detects the amount of displacement and moves the actuator 44 so that the incident light to the recording/reproducing lens 6 always passes through the optical axis of the recording/reproducing lens 6. is driven to move the trolley 42.

If the optical disk 7 is tilted by θ as shown in FIG. 4, the incident light 5 will be shifted by fθ (f is the focal length).

Therefore, if the incident light is moved by an amount of fθ caused by the tilt, it will coincide with the optical axis of the recording/reproducing lens 6. Therefore, in another embodiment, the arithmetic unit 45 calculates fθ from the inclination θ obtained by the above-mentioned inclination detector 30. This fθ is D/
The converter 46 inputs the analog value to the adder 47. The adder 47 adds the amount of displacement output from the displacement detector 43, drives the actuator 43 based on the added value, corrects the inclination, and moves the cart 42.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to easily and accurately correct the tilt of an optical disc in a stable manner without adding a complicated mechanism, and this invention provides an extremely useful effect when operating an optical disc device. play.

[Brief explanation of drawings]

Fig. 1 is a diagram of the principle of the present invention, Fig. 2 is a block diagram of an embodiment of the invention, Fig. 3 is a block diagram of another embodiment of the invention, and Fig. 4 is a media tilt in the case of double servo. FIG. 5 is a block diagram of off-track control of a conventional device, FIG. 6 is a state diagram of light detection by a two-split sensor, and FIG. 7 is a state explanatory diagram of reflected light. In the figure, 7 is an optical disk, 14 is a track actuator, 17 is a focus actuator, and 30 is a tilt detector. Figure 1 of the heather invention n Hei 1 Figure 1 / f4g month carrying school ψ3b IJ shift mouth, 97B 2nd
Figure 3. Figure 4. qB'AIE, /+77) Py7*j93pB°O.
y7g4fs5 figure pass J-2> uniform bar rainbow support mode m 6th figure dej sufushii-t! +:j3i)71c)6', ai
, 2CZ] Figure 7

Claims (2)

[Claims] (1) A tracking control circuit for an optical recording device, comprising means for detecting a tracking offset caused by the tilt of a recording medium, and a correction means for adding an output signal of the detection means in a direction to cancel the offset. Features a tilt correction method for optical discs. (2) Consisting of a first servo system that performs tracking in a minute range and a second servo system that performs tracking in a wide range,
The first servo system is displaced so that the tracking error is minimized, and the second servo system is a servo system that operates so that the displacement is minimized, and the amount of displacement obtained from the first servo system is An optical disk tilt correction method, characterized in that tracking control is performed on the second servo system by biasing the second servo system in proportion to 1/2 of a recording medium tilt signal.