JPH05174407A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To remove the influence of the tilt of a disk by detecting the tilting amount of the disk and removing the offsetting amount of a tracking error signal generated from the tilt of the disk by means of an electric signal processing means. CONSTITUTION:Laser beams emitted from a light source 1 are formed to be parallel beams through a collimator lens 2 and are converged on the disk 4 by means of an objective lens 3. The laser beam is reflected and diffracted at the guiding groove 4a of an information track on the disk 4, again passes through the objective lens 3, is deflected in an orthogonal direction by a beam splitter 5, is made incident on a bisecting photo-detector 6 symmetrically arranged to the center of the guiding groove on the information track and an output difference between two light receiving parts is detected by means of a differential amplifier 7 as the tracking error signal TS. Thus, by synthesizing the tracking error signal TS and the offsetting amount DTS, the offsetting amount generated by the tilt of the disk is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus for optically reproducing information or recording / reproducing information.

[0002]

2. Description of the Related Art An optical disk device requires a tracking servo in order to record or reproduce a signal on an information recording medium concentrically or spirally without contact. As for this tracking servo sensor method, there is a method called push-pull method as a method using diffracted light from a signal pit or a guide groove. FIG. 4 shows a conventional optical recording / reproducing apparatus using the push-pull method. In the figure, 1 is a light source for emitting a laser beam, 2 is a collimating lens, 3 is an objective lens, and 4 is a disc, and a guide groove 4a for an information track is formed on the disc 4. Reference numeral 5 is a beam splitter, and 6 is a two-split photodetector, which is connected to the differential amplifier 7. 8a and 8b are moving devices for the objective lens 3, 9 is a structure rigidly coupled to the objective lens 3 and has a hole, 10 is a light emitting element, 11 is a two-division photodetector, and a differential amplifier 12 is connected. The signals TS and LPS output from the differential amplifiers 7 and 12 are combined to obtain a signal C-TS. These configurations are the same in FIGS. 5 and 6.

Next, the operation will be described. The laser light emitted from the light source 1 becomes parallel light by the collimator lens 2,
It is focused on the disk 4 by the objective lens 3. Disk 4
The laser light reflected and diffracted by the guide groove 4a of the upper information track passes through the objective lens 3 again, is bent by the beam splitter 5 at a right angle, and is split into two light beams symmetrically arranged with respect to the center of the guide groove 4a of the information track. It is incident on the detector 6, and the output difference between the two light receiving portions is detected by the differential amplifier 7 as a tracking error signal TS. That is, when the condensed light spot and the center of the guide groove 4a of the information track coincide with each other, a reflected diffracted light distribution symmetrical to the guide groove 4a is obtained, and in other cases, the reflection diffraction is asymmetric. Next to
The light intensity distribution of the reflected light becomes asymmetric, and the tracking error signal T is obtained as the output difference between the two light receiving portions of the two-divided photodetector 6.
S is obtained.

By moving the objective lens 3 in a direction intersecting with the guide groove 4a on the disk 4 by the moving devices 8a and 8b of the objective lens 3 so that the tracking error signal TS becomes zero, the center of the light spot is set. Guide groove 4a
The center of can be matched. However, in the conventional optical recording / reproducing apparatus, when the information track follows the spiral guide groove due to the rotation of the disk 4 or jumps to the guide groove of the information track at a position away from the current position, Center of light spot and guide groove 4 of information track
Even if the center of a coincides with the center of a, the reflected light spot incident on the two-divided photodetector 6 deviates from the center of the two-divided photodetector 6, causing an offset in the tracking error signal TS. Therefore, in the conventional optical recording / reproducing apparatus, the amount of movement of the light spot is detected and signal processing for removing the offset corresponding to the amount of movement from the tracking error signal TS is performed.

FIG. 5 is a view showing a state in which the guide groove 4d has moved by d. Since the moving amount of the light spot is equal to the moving amount d of the objective lens 3, the moving amount of the objective lens 3 is detected. The light-emitting element 10 and the two-divided photodetector 11 that receives light passing through the hole are arranged at positions where the structure 9 having the hole is rigidly attached to the objective lens 3 and face each other across the hole. The amount of movement of the hole due to movement is divided into two photodetectors 11
The difference between the outputs of the two light-receiving units is detected by the differential amplifier 12 as the offset amount LPS of the tracking error signal TS corresponding to the movement amount of the objective lens 3, and the tracking error signal TS and the movement amount of the objective lens 3 are detected. A corrected signal tracking error signal C-TS can be obtained by performing signal processing on the offset amount LPS to be performed, and the objective lens 3 is moved by the moving devices 8a and 8b so that the signal C-TS becomes zero. As a result, the center of the light spot can be aligned with the center of the guide groove 4a of the information track without the influence of the offset accompanying the movement of the guide groove 4a of the information track of the disk 4.

[0006]

Since the conventional optical recording / reproducing apparatus is constructed as described above, when the disc 4 is tilted by θ as shown in FIG. 6, it is incident on the two-division photodetector 6. The tracking error signal T
Although an offset occurs in S, in order to correct this, a portion without a guide groove is provided in advance on the disc 4, and the inclination of the disc is detected from the reflected light when passing through this so that the light spot is perpendicular to the disc. The optical system itself was tilted so as to meet such requirements, and complicated means were added both mechanically and in signal processing. Further, there is a problem in that correction cannot be performed on a disc that does not have the above-mentioned reference portion on the disc for detecting the tilt of the disc.

The present invention has been made to solve the above problems, and by using a simple signal processing means, the position of the objective lens can be accurately detected without being affected by the tilt of the disk. The purpose is to obtain an optical recording / reproducing apparatus.

[0008]

An optical recording / reproducing apparatus according to the present invention detects a tilt amount of a disc and removes an offset amount of a tracking error signal corresponding to the disc tilt amount by using an electric signal processing means, The tracking error signal is not affected by the tilt of the disc.

[0009]

According to the present invention, an optical recording / reproducing apparatus which is not affected by the tilt of the disk is provided by a simple structure that does not require a complicated mechanism or electric signal processing means regardless of the type of the disk. can get.

[0010]

【Example】

Example 1. FIG. 1 is a diagram showing a connection of an optical system and an electric circuit of an optical recording / reproducing apparatus according to an embodiment of the present invention. In the figure, 1 is a light source for emitting a laser beam,
Reference numeral 2 is a collimator lens, 3 is an objective lens, 4 is a disc, information track guide grooves 4a are formed on the disc 4, 5 is a beam splitter, 6 is a two-division photodetector, and 7 is a differential lens. Connected to an amplifier. 8a and 8b are moving devices for the objective lens 3, 9 is a structure rigidly coupled to the objective lens 3 and has a hole, 10 is a light emitting element, 11 is a two-division photodetector, and a difference of 12 Connected to a dynamic amplifier. Reference numeral 13 is a light emitting element, and the light detectors 14a and 14b are arranged in the radial direction of the disk 4 with the light emitting element 13 interposed therebetween.
The tilt detector of the disk 4 composed of three and two light detectors 14a and 14b is an information track on the disk 4 on the side where the light spot is irradiated and on which the light spot is irradiated. It is arranged in the vicinity of the objective lens 3 on the same circle-centered circle as 4a. The two photodetectors are connected to 15 differential amplifiers. The outputs from the differential amplifiers 7, 12, 15 are combined together.

Next, the operation will be described. The laser light emitted from the light source 1 is collimated by the collimator lens 2 and focused on the disk 4 by the objective lens 3. The laser light reflected and diffracted by the guide groove 4a of the information track on the disk 4 passes through the objective lens 3 again and is bent at a right angle by the beam splitter 5, and is divided into two light beams symmetrically arranged with respect to the center of the guide groove of the information track. The differential amplifier 7 detects the output difference between the two light-receiving portions which is incident on the detector 6 as a tracking error signal TS. That is, when the condensed light spot and the center of the guide groove 4a of the information track coincide with each other, a reflection diffraction light distribution symmetrical to the guide groove 4a is obtained,
In other cases, the reflection diffraction becomes asymmetric, the light intensity distribution of the reflected light becomes asymmetric, and the tracking error signal TS is obtained as the output difference between the two light receiving portions of the two-divided photodetector 6. The center of the light spot and the guide groove 4a are moved by moving the objective lens 3 in a direction intersecting the guide groove 4a on the disk 4 by moving devices 8a and 8b of the lens 3 so that the tracking error signal TS becomes zero. The center of can be matched.

Further, in the case of following the information track of the spiral guide groove due to the rotation of the disk 4 or jumping to the guide groove of the information track distant from the current position, the two-divided light detection is performed by the movement of the light spot. The reflected light spot incident on the device 6 deviates from the center of the two-divided photodetector 6 and an offset occurs in the tracking error signal TS. A structure 9 having a hole is rigidly attached to the objective lens 3 against this offset, and a light-emitting element 10 and a two-divided photodetector 11 for receiving light passing through the hole are placed at positions facing each other across the hole. The displacement amount of the hole, which is equal to the displacement of the objective lens 3, is detected as the output difference between the outputs of the two light receiving portions of the two-divided photodetector 11, and the differential amplifier 12 performs tracking corresponding to the displacement amount of the objective lens 3. The offset amount LPS of the error signal TS is obtained.

By combining the tracking error signal TS and the offset amount LPS, the offset caused by the movement of the light spot can be removed. Further, when the disc 4 is tilted, the offset of the tracking error signal TS that occurs when the reflected light spot incident on the two-divided photodetector 6 deviates from the center of the two-divided photodetector 6 causes the disc 4 to move. Centering the light emitting element 13 and the light emitting element 13 in the vicinity of the objective lens 3 on the same concentric circle as the information track 4a on the side on which the light spot is illuminated and on the disk 4 on which the light spot is illuminated,
Two photodetectors 14 arranged in the radial direction of the disk 4.
a and 14b are provided, and light emitted from the light emitting element 13 is reflected by the disk 4 and received by the photodetectors 14a and 14b, and a device for detecting the disk tilt from the differential output thereof is provided.
Due to the tilting of the disc 4, the two photodetectors 14a,
A difference occurs in the amount of light incident on 14b, and this output difference is obtained by the differential amplifier 15 as the offset amount DTS of the tracking error signal TS caused by the inclination of the disk 4.

By synthesizing the tracking error signal TS and the offset amount DTS, the offset amount caused by the inclination of the disk 4 can be removed. That is, in order to obtain a tracking error signal when the center of the information track 4a of the disc 4 and the center of the light spot are controlled to coincide with each other, in the optical recording / reproducing apparatus of the present invention, the tracking error signal TS The offset amount LPS caused by the movement amount of the lens 3 and the offset amount DTS caused by the tilt of the disk 4 are combined so that the offset is removed, and the corrected tracking error signal C-TS is obtained and corrected. Tracking error signal C-TS
By moving the objective lens 3 by the moving devices 8a and 8b so as to make zero, the center of the light spot and the center of the guide groove 4a of the information track on the disk 4 can be aligned.

Example 2. In the first embodiment, the disk 4
On the other hand, an example in which a detector for disc tilt formed of the light emitting element 13 and the photodetectors 14a and 14b is provided on the incident side of the light spot is shown. However, as shown in FIG. The light emitting element 13 is provided at a position facing the light spot on the side opposite to the side on which the light spot enters.
A light detector 14a is inserted in the radial direction of the disc 4 with 3 in between.
The disc tilt may be detected by disposing 14b.

Embodiment 3. In addition, as shown in FIG. 3, a detector for disc tilt formed by the light receiving element 13 and the photodetectors 14a and 14b is arranged at a symmetrical position with respect to the rotation axis 16 of the disc 4, and the output signal of the differential amplifier 15 is output. The connection may be made in consideration of the DTS code.

Example 4. Although not shown in the figure, if the disc tilt angle changes rather than being constant at the radial position of the disc, the disc tilt detection is performed so that the disc tilt near the information track irradiated with the light spot can be detected. However, if the tilt angle of the disc is constant irrespective of the radial position of the disc, if it is near the line connecting the light spot and the rotation axis of the disc, It may be fixedly installed on either side.

[0018]

As described above, according to the present invention, the amount of tilt of the disc is detected, and the offset amount of the tracking error signal generated by the tilt of the disc is removed by using the electric signal processing means. It is designed to detect tracking error signals that are not affected by the signal, and a tracking error signal corrected using simple electric signal processing means can be obtained regardless of the type of disc and without adding a complicated mechanism. It is effective.

[Brief description of drawings]

FIG. 1 is a wiring diagram of an optical system and an electric circuit of an optical recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing wiring of an optical system and an electric circuit of an optical recording / reproducing apparatus according to another embodiment of the present invention.

FIG. 3 is a diagram showing wiring of an optical system and an electric circuit of an optical recording / reproducing apparatus according to another embodiment of the present invention.

FIG. 4 is a diagram showing connections of an optical system and an electric circuit of a conventional optical recording / reproducing apparatus.

FIG. 5 is a diagram showing a connection of an optical system and an electric circuit of an operation of a conventional optical recording / reproducing apparatus.

FIG. 6 is a diagram showing a connection of an optical system and an electric circuit as a problem of a conventional optical recording / reproducing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 light source 2 collimator lens 3 objective lens 4 disc 6, 11 two-division photodetector 7, 12, 15 differential amplifier 8a, 8b objective lens drive device 9 perforated structure 10, 13 light emitting element 14a, 14b photodetector

Claims (1)

[Claims] 1. A light source, an objective lens for condensing light emitted from the light source as a light spot, a disc used near the condensing point of the objective lens for recording or reproducing information, and this disc. 2-split photodetector for converting the reflected light from the optical signal into an electric signal, a differential amplifier for obtaining a differential output from the respective outputs of the 2-split photodetector, and an optical spot for a disc by an output signal of the differential amplifier. A light spot moving device for controlling in the direction crossing the upper information track, a detector for converting the amount of movement of the objective lens in the direction crossing the information track into an electric signal, and an optical axis of the objective lens of the disc. In an optical recording / reproducing apparatus equipped with a detector for converting the amount of tilt with respect to the electric signal, an electric signal obtained by converting the differential output signal of the two-division photodetector and the amount of movement of the objective lens. An optical signal, and a signal processing means for correcting a tracking error signal, which is an electric signal of the positional deviation amount between the information track and the light spot, by an electric signal and an electric signal obtained by converting the tilt amount of the disk. Recording / playback device.