JPS63263637A - Optical head device - Google Patents

Abstract

PURPOSE:To detect and correct a tracking offset factor by means of simple structure and to detect the position of an actuator part by dividing light beam and simultaneously detecting the relative deviation and inclination between the actuator part and an optical axis by means of a half mirror and a photodetector. CONSTITUTION:A light beam 35 radiated from a semiconductor laser 31 and polarized by a beam splitter 32 is made incident upon a two-dividing photodetector 37 through the half mirror 36, and if a relative deviation between the optical axis of the beam 35 and the actuator part 13 exists, the quantity of light made incident upon two photodetecting faces is different each other and an output from a differential amplifier 39 is a positive or negative. When the light beam 35 reflected by the mirror 36 is made incident upon a photodetector 38, a positive or negative output is generated from a differential amplifier 40 connected to the photodetector 38. Consequently, tracking offset can be removed by controlling the posture of the actuator part 13 so that the outputs from the amplifiers 39, 40 are zero.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] 7 The present invention relates to an optical head device for optically reproducing information or recording and reproducing information.

[Conventional technology]

Conventionally, optical head devices require tracking servo to reproduce or record signals concentrically or spirally on an information recording medium in a non-contact manner. Many methods have been proposed for this tracking servo sensor method, but there is a method called a push-pull method that uses diffracted light from a signal bit or a guide groove.

The principle of the conventional Bushgur method tracking servo sensor system will be explained using FIGS. 6 and 7.

Objective lens (4) is placed in the guide groove (2) of the information recording medium (1).
A focused spot (3) is formed by K. (5) is a convex lens. The two-split photodetector (6) has two light-receiving surfaces (
sa), (6b), and a two-split photodetector (6)
A differential amplifier (7) is connected to obtain a tracking error signal from the outputs from the two light receiving surfaces. Curves (8) and (9) are the diffracted light distributions diffracted by both classes of the guide groove (2), and the diffracted light distributions (10) and (11) are shown on the surface of the two-split photodetector (6). ) is projected.

When the objective lens (4) is located at the center of the guide groove (2), the intensities of the diffracted lights (8) and (9) become equal, and the output of the differential amplifier (7) becomes zero. However, due to eccentricity of the information recording medium (1), the objective lens (4) and the guide groove (
If the relative positional relationship with 2) deviates, the diffracted light distribution (
8) and (9) are no longer equal, the differential amplifier (
The output of 7) can be positive or negative. Therefore, a servo operation is performed to make this output zero, and the objective lens (4
) is translated in the direction of arrow CX').

In the conceptual diagram of the formula, in contrast to the fixed part (12) where the light source, sensor, etc. are arranged, the actuator part (13) is a driving means (not shown) that moves in the radial direction of the information recording medium (1), that is, in the arrow (X) direction. can be displaced to access the desired position. The reflecting mirror (14) bends the light beam emitted from the light source of the fixed part (12) toward the information recording medium (1).

(4) is an objective lens.

When the actuator section (13) moves, it may shift or tilt with respect to the optical axis. FIG. 9 shows a state in which the actuator section (13) is displaced in a direction perpendicular to the optical axis (focal direction) of the objective lens (4). The output optical axis (16) is at a position shifted by δ with respect to the input optical axis (ls) K. If the position of the fixed part (12) of the light source/sensor does not change, the projected diffracted light distribution will be distributed between the two light-receiving surfaces ( 6a).

(6b), and as a result, the output of the differential amplifier (7) does not become zero, resulting in a tracking offset. Figure 10 shows a state in which the actuator section (13) is tilted, and the incident optical axis (
15) and the output optical axis (16) are displaced by δ, causing a tracking offset. Also, in this case, aberrations occur because the optical axis is not perpendicularly incident on the information recording medium (K). Figure 11 shows that the incident optical axis (15) and the actuator IiS (13) f) movement axis (17) are This shows a state where the lens is tilted, and in this case as well, tracking offset aberration occurs for the same reason as before.

As a method for improving the above-mentioned drawbacks, there is a tilt detection method as disclosed in, for example, Japanese Patent Laid-Open No. 61-284840. This conventional tilt detection method will be explained using FIG. 12. Light source (18), photodetector (19), (20
) is attached to an actuator section (not shown). The light beam emitted from the light source (18) is transmitted to the information recording medium (1
) reflected from K.

At this time, the inclination of the actuator section and the information recording medium (1) is detected by utilizing the fact that the amount of light reflected by the photodetectors (19) and (20) changes depending on the relative inclination angle between the two. It is something to do. Another example is shown in FIG. 13. Light source (18), 2-split photodetector (21)
is attached to an actuator section (not shown), and a light beam is emitted from the light source (18) at an arbitrary angle that is not perpendicular to the information recording medium (1). This light beam is reflected by the information recording medium (1) and enters the light receiving surfaces (21a) and (21b) of the two-split photodetector (21), but the relative relationship between the actuator section and the information recording medium (1) The inclination is detected by utilizing the fact that the amount of light incident on both changes depending on the inclination angle.

[Problem to be Solved by the Invention 1] In the conventional optical head device as described above, the relative inclination between the actuator section and the information recording medium can be detected by the inclination detection device. It is impossible to simultaneously detect the relative positional deviation or inclination of the optical axis and the cutter part due to the deviation of the actuator part in the focal direction or the deviation of the actuator part movement axis and the optical axis, and due to these factors. It is said that tracking offset and aberration cannot be prevented from occurring.
There was a problem. Furthermore, a linear scale or the like is used to detect the position of the actuator section, but there are also problems in that adjustment is difficult and the device is complicated.

This invention was developed to solve the above-mentioned problems.It has a simple structure, and can simultaneously detect the relative positional deviation and inclination of the optical axis and the actuator part that occur in the actuator part separation method. The present invention aims to provide an optical head device that can also detect the position of an actuator section.

[Means for solving problems]

In the optical head device according to the present invention, a first photodetector that receives a reflected light beam from an information recording medium, a light source, and a first optical component that divides the light beam are installed in a fixed part. In addition, there is a second optical component that receives the divided luminous flux, partially transmits it and partially reflects it, and a second optical component that receives the transmitted luminous flux.
A photodetector is installed in the moving part that forms the actuator part.

Furthermore, a third photodetector is separately installed to receive the light beam reflected by the second optical component.

[Function] In the present invention, with a simple structure, it is possible to detect the tracking offset factor that occurs in the actuator part separation method, and at the same time, the position of the actuator part can also be detected.

〔Example〕

FIG. 1 and FIG. 2 show an embodiment of the present invention, and in the figures, symbols (1), (4), (6), (7)
, (12) to (14) indicate the same or corresponding parts as the same reference numerals in the conventional device described above. Fixed part (1
2), a semiconductor laser (31); Second beam splitter (32).

(33) is provided.

A light beam emitted from the semiconductor laser (31) is split into two beams by a first beam splitter (32).

The first light beam (34) is bent by the second beam splitter (33) and the reflecting mirror (14), passes through the objective lens (4), and is focused onto the information recording medium (1). . The condensed light beam (34) is reflected by the information recording medium (2-(14)), the optical path is bent by the reflection mirror (14), and passes through the second beam splitter (33) to the two-split photodetector (6). On the other hand, the second beam (35) split by the first beam splitter (32) enters the half mirror installed in the actuator section (13).
(36). A part of the incident light beam passes through the half mirror (36) and enters the two-split photodetector (37) placed behind it, and the remaining light beam is reflected and enters the two-split photodetector (38) K. do.

Next, the operation will be explained in more detail. For convenience, FIG.
36) is omitted. After passing through a half mirror (36) (not shown), the second light beam (35) enters the two-split photodetector (37)K, but as shown in Figure VC', the second light beam (35) is connected to the optical axis (35) and the actuator section (13). ) is relatively misaligned, the two light-receiving surfaces (37a) and (3
7b) is different, and the output of the differential amplifier (39) becomes positive or negative. Also, Figure 4 shows the second ray (
35) is partially reflected by the noof mirror (36), and the optical axis (35) and the actuator section (13
) are relatively tilted, the amount of light incident thereon differs, and the output of the differential amplifier (40) becomes positive or negative. Therefore, by correcting K using means not shown so that the outputs of both the differential amplifiers (39) and (40) become zero, the tracking offset can be eliminated.

FIG. 5 shows another embodiment in which a 4-split photodetector is used to receive the light beam reflected by a half mirror (36), and in the figure, (41) is a 4-split photodetector. The actuator section (13) moves in the direction of the arrow (X) to access the target position.

Accordingly, the optical axis of the light reflected from the half mirror (36)K moves from the optical axis (42) to the optical axis (43).

Therefore, the amount of light received by the 4-split detector (41) is (
(41a) + (4td) ) and ((41b) +
(41C) ), the actuator section (1
3) position detection can also be performed at the same time.

In the above embodiment, the first beam splitter (32) is used to split the light beam, but a half mirror may be used instead. In addition, although the actuator part photodetector (37) is arranged, a total reflection mirror is used, and a reflection mirror (14) is used.
) may be a half mirror, and a two-split photodetector may be placed behind it.

Further, in these embodiments, the light beam emitted from the semiconductor laser (31) is divided and used, but a plurality of light sources may be used.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to simultaneously detect the relative deviation and inclination between the actuator section and the optical axis by splitting the light beam and using a half mirror and a photodetector, so the structure is simple. The cause of tracking offset can be detected and corrected, and the position of the actuator section can be detected at the same time.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a main part of an embodiment of the present invention, FIG. 2 is a partial perspective view of the same, FIGS. 3 and 4 are explanatory diagrams of the operation of the one shown in FIG. 1, and FIG. FIG. 6 is a side view for explaining the principle of the push-pull tracking servo sensor system of the conventional optical head device;
FIG. 7 is a front view, FIG. 8 is a conceptual diagram for explaining the conventional actuator separation method, and FIGS. 9 to 11 are for explaining the causes of tracking offset in the conventional actuator separation method. Conceptual diagram, 1st
2 and 13 are perspective views of essential parts of a conventional tilt detection device, respectively. (1) Information recording medium, (4) Objective lens (condensing means), (6) 2-split photodetector (first photodetector)
, (12)...Fixed part of light source and sensor, (13)...Actuator part (moving part), (14)...Reflecting mirror (
optical means), (31)... semiconductor laser (light source), (3
2) , (33)...beam splitter (first optical component), (36)...-7 mirror (second optical component), (37), (38)...two-split photodetector (Second
．． third photodetector). In each figure, the same reference numerals indicate the same or corresponding parts. Figure 5 Figure 8 × Figure 9 Figure 11 Figure 12 Figure 13

Claims (3)

[Claims] (1) A light source, an optical means for converting the traveling direction of a light beam emitted from the light source, a light condensing means for condensing the light beam onto an information recording medium, and a first light source for receiving the reflected light beam reflected by the information recording medium. a photodetector, the light source and the first
In the optical head device, a photodetector is installed on a fixed part, the fixed part is installed with a first optical component that splits the light beam, and the fixed part is installed with a first optical component that splits the light beam, and a first optical component that receives at least one of the divided light beams and unites the light beam. a movable part in which a second optical component that partially transmits and partially reflects and a second photodetector that receives the transmitted light beam is installed; and a movable part that is installed separately and receives the light beam reflected by the second optical component. 1. An optical head device comprising: a third photodetector for detecting an image. (2) A second optical component that partially transmits and partially reflects the light beam is arranged at an angle that is not perpendicular to the light beam, and the third photodetector is a 4-split photodetector. The optical head device according to item 1. (3) The optical head device according to claim 1, comprising two or more light sources.