JPS62243138A - Optical type information reproduction device - Google Patents

Abstract

PURPOSE:To decrease the generation amount of the crosstalk from an adjacent track, even in case an optical disk is bent due to deformation, dead weight, etc., by dividing a photodetector into plural photodetecting areas, and detecting an information signal from only the photodetecting area of a spot center part. CONSTITUTION:A reflected light from an optical disk 6 is converted to a parallel luminous flux again by an objective lens 5, and thereafter, reflected by a beam splitter 4, passes through a convex lens 7, and a cylindrical lens 8 and irradiated onto a photodetctor 9. Among luminous fluxes which are divided into three by a diffraction grating 3, + primary light and - primary light are irradiated to photodetecting areas of both sides of the photodetector 9, and '0' -order light is irradiated to the center of an 8-divided area of the center of the photodetector 9. An output signal of the photodetector 9 is recorded in the optical disk 6, and an information signal and a focusing error signal, and a tracking error signal are obtained. In such a way, even if a relative inclination is generated in the optical disk 6 and an optical pickup, the crosstalk contained in the information signal can be reduced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical information reproducing device for reproducing information signals recorded on an optical information recording carrier (hereinafter referred to as an optical disk), and in particular, relates to an optical information reproducing device for reproducing information signals recorded on an optical information recording carrier (hereinafter abbreviated as an optical disk). This invention relates to means for reducing crosstalk.

[Conventional technology]

Optical discs are transformed in optical information reproducing devices.

When it bends due to its own weight, crosstalk from adjacent tracks occurs, and the quality of the reproduced information signal deteriorates. For this reason, conventionally, as disclosed in Japanese Patent Application No. 59-168835, the relative inclination between the optical disc and the optical pickup is detected, and the original pickup is tilted so that the optical disc and the optical pickup are always parallel to each other. A method has been proposed.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology requires a detector for detecting the inclination of the optical disc and the optical pickup, a mechanism for tilting the optical pickup, a control circuit and a motor for controlling the optical disc and the optical pickup so that they are always parallel to each other, and so on. becomes complicated.

An object of the present invention is to provide an optical information reproducing device that does not require the above-mentioned mechanical circuits, and generates less crosstalk from adjacent tracks even when an optical disc is deformed or bent due to its own weight. Precautions to Solve the Problem] In order to achieve the above-mentioned object, in the present invention, crosstalk components from adjacent tracks are largely contained in the outer peripheral portion of the spot as reflected light from the optical disk. In this system, a photodetector for detecting reflected light (spot) is divided into a plurality of light-receiving areas, and information signals are detected only from the light-receiving area at the center of the spot.

[Effect]

Since the outer peripheral portion with many crosstalk components among the reflected light spots from the optical disc is not detected, it is possible to reduce the crosstalk included in the information No. 1g even if a relative tilt occurs between the optical disc and the optical pickup. .

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical information reproducing apparatus according to the present invention will be described in detail below with reference to embodiments shown in the drawings.

FIG. 1 is a perspective view showing an embodiment of an optical information reproducing apparatus according to the present invention, FIG. 2 is a plan view of a detection optical system for detecting reflected light from an optical disk, and FIG. The figure is a plan view of the photodetector in Figure 1, l! Figure 4 is a circuit diagram showing the signal detection circuit in Figure 1, and Figure 5 is an explanatory diagram showing the relationship between the tilt of the optical disc and the spot on the optical disc.
! FIG. 6 is an explanatory diagram showing the reflected light intensity distribution on the photodetector.

! In Fig. 1, a laser beam emitted from a semiconductor laser 1, which is a laser light source, is converted into a parallel beam by a collimator lens 2, and then converted into a 0th-order beam, +1st-order beam, and -1st-order beam by a diffraction grating 3.
After being split into three beams of secondary light, the beam splitter 4
The light is focused by the objective lens 5 onto the information track 6a of the optical disk 6 rotated by the motor 10. The reflected light from the optical disk 6 is converted into a parallel light beam again by the objective lens 5, and then reflected by the beam splitter 4, passes through the convex lens 7 and the cylindrical lens 8jE, and is irradiated onto the photodetector 9. Of the nine light beams divided into three by the diffraction grating 3, the +1st-order light and the -1st-order light are irradiated to the light receiving areas on both sides of the photodetector 9, and the 0th-order light is at the center of the 8-divided area in the center of the photodetector 9. is irradiated. As will be described later, the output signal of the photodetector 9 is recorded on the optical disk 6 to generate a striking signal and a focusing error signal.

A tracking error signal is obtained.

Here, in FIG. 1, the tracking error detection method is a multi-spot method, but since it is not relevant to the essence of the present invention, a description thereof will be omitted. The focusing error detection method is an astigmatism method.

In FIG. 2, the reflected light 11 from the nine optical disc 6 is separated by the beam splitter 4 and is reflected by the convex lens 7 and the cylindrical lens 8.
focused by. Here, the light beam 12 in the direction not subject to the focusing action of the cylindrical lens 8 and the light flux 15 in the direction subject to the focusing action of the cylindrical lens 8 intersect at a position indicated by a in FIG. 2.

At the position indicated by a, the light beam is approximately circular, and the diameter of the light beam is D. By arranging the photodetector 9 at the position indicated by a, the 7 spotting error signal can be detected from the change in the shape of the light beam on the photodetector 9.

Next, the intensity distribution of the spot on the disk 6 and the reflected light on the photodetector 9 when the objective lens 5 and the optical disk 6 are tilted will be described.

In FIG. 5, (a) shows the case where the objective lens 5 and the optical disc 6 are parallel, and (b) shows the case where the objective lens 5 and the optical disc 6 are tilted.

5(a) is a diagram showing the inclination of the objective lens 5 and the optical disc 6, (b) is a diagram showing the relationship between the spot 11 on the optical disc 6 and the signal bit 12 of the information signal, and (c) is a diagram showing the relationship between the spot 11 on the optical disc 6 and the signal bit 12 of the information signal. This is the intensity distribution of spot 11.

Spot 11 on information track 6a is located between signal bits 12 (spora indicated by a dotted line).If there is no signal bit 12 in the adjacent track, spot 11b is indicated by a solid line.
This is the case where the adjacent track has signal bit 12. If the objective lens 5 and the optical disk 6 are tilted here, comatic aberration occurs, and a crescent-shaped portion of high intensity is generated in the tilted direction. This crescent-shaped part is generated on the adjacent track when the optical disc 6 is deformed into a bowl shape due to its own weight, and the spot 11 is caused by the rotation of the optical disc 6 in the track direction (Y
direction), the crescent-shaped portion is diffracted by the signal pit 12 of the adjacent track, causing crosstalk. This situation will be explained with reference to FIG.

FIG. 6 shows the intensity distribution of the emitted light 11 on the detector 9, and the radius of the beam corresponds to the radius of the beam in FIG. Also, (a), (b), and (c) in Fig. 6 correspond to (a), (b), and (e) in Fig. 5, respectively.
The intensity distribution shown by the solid line in the figure and the intensity distribution shown by the dotted line correspond to the spot 11b shown by the solid line and the spot 11a shown by the dotted line in FIG. 5, respectively.

It can be seen from FIG. 6 that when a signal pit 12 exists in an adjacent track, the intensity of the reflected light on the detector 9 decreases in the periphery. The diagonally shaded portion corresponding to the difference between the solid line and the dotted line is the crosstalk component from the adjacent track. (b), (
As shown in e), when the optical disk 6 and the objective lens 5 are tilted, the crosstalk that occurs also increases, but most of the crosstalk occurs in the outer peripheral portion of the reflected light on the photodetector 9. From the above, it can be seen that if the information signal is detected only from the central portion of the reflected light, crosstalk can be reduced even when the optical disc 6 is tilted.

FIG. 3 shows the light receiving area of the photodetector 9. As shown in FIG. Also, the three circles indicated by dotted lines are 0th order light and +1st order light.

- This indicates the outer diameter of the luminous flux of the primary light, and its diameter corresponds to D in FIGS. 2 and 6.

FIG. 4 shows a signal detection circuit. 30 is a DC power supply.

31.32 is a differential amplifier, 33 is a high frequency amplifier, 20~
Reference numeral 29 indicates each light receiving area of the photodetector 9 shown in FIG.

Only the central portion of the reflected light spot enters the light receiving areas 20.21 and 22.25, and an information signal 34 is obtained from the sum of the output signals. Light receiving area 21, 23.25.27
A seven-tracking error signal 35 is obtained from the difference between the sum of and the sum of the light receiving areas 20, 22, 24, 26, and a tracking error signal 36 is obtained from the difference between the light receiving areas 28 and 29.

The 7 focusing error signal 35 is supplied to the 7 focusing actuator 14, and focusing control is performed by driving the objective lens 58 in the optical axis direction (two directions). The tracking error signal 36 is supplied to the tracking actuator 15 to move the objective lens 5 to the optical disk 6.
Tracking control is performed by driving in the radial direction (X direction). - Figures 7 and 1@8 are other specific examples of the photodetector used in the optical information reproducing device according to the present invention, and the reference numbers in the figures correspond to those in Figures 3 and 44.

The light receiving area for detecting the information signal may be rectangular as shown in FIG. Further, as shown in FIG. 8, a configuration may be used in which the reflected light is not received only on both sides of the optical disk 6 in the radial direction.

〔Effect of the invention〕

As explained above, according to the present invention, a photodetector is arranged in multiple light receiving areas by focusing on the fact that in reflected light from an optical disk, crosstalk components from adjacent tracks are mostly contained in the outer peripheral portion of the spot. By dividing the reflected light spot and detecting the information signal only from the central portion, crosstalk can be reduced, and focusing error No. 41 can also be detected using the same photodetector. As a result, it becomes unnecessary to control the relative tilt between the optical disc and the optical pickup, and the configuration of the optical information reproducing apparatus becomes simple.

[Brief explanation of drawings]

@Figure 1 is a perspective view of an optical information reproducing device that is an embodiment of the present invention, Figure Wc2 is a plan view of the detection optical system in Figure 1, @5
The figure is a plan view of the photodetector in Figure 1, Figure 4 is a circuit diagram showing the signal detection circuit used in Figure @1, Figure 5 is an explanatory diagram showing the relationship between the inclination of the optical disc and the spot on the optical disc, 6th
The figure is an explanatory diagram showing the reflected light intensity distribution on the photodetector, and FIGS. 7 and 8 are plan views showing other specific examples of the photodetector. 0 1...Semiconductor laser 5... Objective lens 6...
Optical disk 9... Photodetector 1st figure 2z Drop 3 figure η4 figure Otsu figure (good) (b) (
C)"l'17 Diagram 8

Claims (1)

[Claims] 1. A laser light source, an objective lens for condensing the laser light emitted from the laser light source onto an optical information recording carrier, and a laser light source that directs the reflected light from the optical information recording carrier from the laser light source. Separating means for separating from the optical path leading to the objective lens;
In an optical information reproducing apparatus, the optical information reproducing apparatus includes at least a photodetector for detecting reflected light from a separated optical information recording carrier as a spot. consisting of at least a first area for detecting the area and a second area for detecting the surrounding area,
An optical information reproducing device characterized in that an information signal is detected from a detection signal of a central portion of a spot detected from the first region. 2. In the optical information reproducing device according to claim 1, the first region further comprises a plurality of divided regions symmetrical when viewed from the spot center, and the detection signal from the divided regions is used to An optical information reproducing device characterized in that a focusing error signal is obtained.