JPS62287437A - Light pickup - Google Patents

Abstract

PURPOSE:To contrive simplicity and light weight of a supporting part of an objective lens by making correction of slight deviation of beam optic axis of an optical disk to the track by rotation of a galvanomirror and integrally forming the aperture of a position detecting device in a body with the galvanomirror. CONSTITUTION:A position detecting device 20 consists of an aperture 21, light emission elements 22 and a light receiving element 23 arranged opposite to each other with the aperture 21 in-between. The aperture 21 is formed integrally in a body with a galvanomirror to form an aperture plate 24. Accordingly, the aperture plate 24 shakes with rotation of the galvanomirror, and the change of position of light incident on the light receiving element 23 through the aperture 21 on the light receiving face 23a is obtained as positional signals. Thus, a simple and lightweight optical pickup excellent in frequency characteristic and follow-up capacity can be obtained.

Description

[Detailed description of the invention] (Technical field) The present invention relates to an optical pickup.

(Prior Art) In a laser disk system, when writing and reading optical information on a predetermined track of an optical disk, generally a semiconductor laser beam is irradiated onto the optical disk through an objective lens, and the reflected light beam is sent to a polarizing beam splitter. A removable optical pickup is used.

In this optical pickup, in order to correct the deviation of the beam optical axis with respect to the track of the optical disk when the beam is irradiated onto the optical disk, the reflected light beam is focused on a detector through a condensing lens, and the spot light is focused on the detector. The above-mentioned tracking device is equipped with a tracking device that detects the amount of deviation of the beam optical axis from the position at and moves the optical pickup main body in a direction perpendicular to the track based on the detection result. Since the optical pickup main body is moved, there is a drawback that the response characteristics deteriorate to a slight deviation of the beam optical axis with respect to the track.

Conventionally, as a method to overcome this drawback, an optical pickup has been developed in which the position of the beam optical axis relative to the track is corrected by moving only the objective lens in response to a slight deviation of the beam optical axis relative to the track. It was proposed (Japanese Patent Application No. 60-216968).

However, the above conventional optical pickup.

The objective lens is movably arranged, and a drive unit for moving the objective lens in the bracket, and a position detection device for detecting the amount of deviation of the beam optical axis due to the movement of the objective lens are located around the objective lens. Since the objective lens is mounted, the support part for the objective lens becomes complicated and its weight increases, which has the disadvantage that the frequency characteristics and followability of the optical pickup deteriorate.

(Objective) An object of the present invention is to provide a simple and lightweight optical pickup with excellent frequency characteristics and followability.

(Structure) The present invention corrects a slight deviation of the beam optical axis with respect to the track of the optical disk using a galvanometer mirror that rotates a reflecting surface around the beam optical axis according to the amount of deviation, and The present invention is characterized in that an aperture of a position detection device for detecting the amount of rotation of the galvano mirror is formed integrally with the galvanometer mirror.

The present invention will be explained below based on an embodiment shown in the drawing.

In FIG. 1, an optical disc 1 is rotated in a predetermined direction by a turntable 2, and an optical pickup 3 writes and reads optical information on a track 1a of the optical disc.

The optical pickup 3 includes a semiconductor laser 4, a coupling lens 5, a polarizing beam splitter 6, a quarter wavelength plate 7, a galvanometer mirror 8, an objective lens 9, and a tracking device 10.
, and a position detection device 20.

In FIG. 1, a beam from a semiconductor laser 4 as a light source is converted into parallel light by a coupling lens 5, and is incident on an objective lens 9 via a polarizing beam splitter 6, a quarter wavelength plate 7, and a galvanometer mirror 8. The objective lens 9 focuses the light into a spot light having a diameter of about 1 μm, and the spot light is irradiated onto the track 1a of the optical disc l.

Tracking group [10 is track 1a of optical disc 1
This is a device for correcting the deviation of the beam optical axis 0 of the beam irradiated to the track 1a and the deviation of the beam focus.

This tracking device 10 includes a condensing lens 11. a detection unit consisting of a knife mirror 12, a tracking detector 13, and a focusing detector 14;
Based on the detection results of the tracking detector 13,
It includes a drive section (not shown) for moving the entire optical pickup 3 in the direction of the arrow X and for moving the entire optical pickup 3 in the direction of the arrow Y based on the detection result of the focusing detector 14.

``It should be noted that the operation of the tracking group [10]
Since it is detailed in the specification of No. 0-216968, the explanation here will be omitted.

On the other hand, the galvanometer mirror 8 is rotatably supported by a support shaft 8b so that its reflecting surface 8a rotates about the beam optical axis O. The support shaft 8b is arranged substantially parallel to the tangential direction of the track 1a of the optical disc 1. Moreover, this support shaft 8b.

It is configured to be rotated by a well-known servo control device (not shown). The servo control device rotates the support shaft 8b based on the detection result of the tracking detector 13, displaces the inclination angle of the reflective surface 8a of the galvanometer mirror 8, and adjusts the beam optical axis 0 of the beam irradiated onto the track 1a. , controls the rotation of the support shaft 8b so that it is correctly positioned with respect to the track 1a. As is clear here, the tracking of the beam optical axis 0 by the galvanometer mirror 8 is as follows.

If the correction range becomes too large, the track 1a
Since the angle of incidence of the beam optical axis 0 on the beam increases, it is necessary to monitor the above-mentioned correction range so that it does not become larger than the allowable limit.

The position detection device 20 performs the above-mentioned monitoring, that is, detects the rotation amount of the galvano mirror 8, and detects the tracking device 1 when the rotation amount of the galvano mirror 8 exceeds the above-mentioned allowable limit.
This is a device for operating the optical pickup 3 to move the entire optical pickup 3 in the direction of the arrow X in FIG. This position detection device i20 includes an aperture 21 and an aperture 2
It is composed of a light emitting element 22 and a light receiving element 23 which are arranged opposite to each other with 1 in between. Aperture 21 is
For example, as shown in FIG. 1, the aperture plate 24 is formed integrally with the galvanometer mirror 8.

The light emitting element 12 is made of, for example, an LED,
The optical axis 25 of the light beam is located at the aperture 2 when the galvanometer mirror 8 is located at the home position (the beam optical axis 0 is perpendicularly incident on the optical disc 1).
It is arranged so that it passes through the center of 1.

On the other hand, the light receiving element 23 is composed of, for example, a semiconductor device detection element (PSD) that senses the light of an LED and outputs a position signal according to the light receiving position, and the galvano mirror 8 is located at the home position. The position signal is placed at a position where the output of the position signal is zero when For example, as shown in FIG. 2, this light-receiving element 23 is connected to the electrode from the position on the light-receiving surface 23a of the incident light from the light-emitting element 22 irradiated through the aperture 21. Alternatively, a charge proportional to the distance to the position of the electrode H is generated. As a result, based on the difference between the amount of charge generated across the electrode I and the amount of charge generated across the electrode ■, using the optical axis 25 as a field,
A position signal corresponding to the incident position of the incident light can be detected.

Therefore, the aperture plate 24 swings as the galvanometer mirror 8 rotates, and the change in the position of the incident light that enters the light receiving element 23 through the aperture 21 on the light receiving surface 23a is obtained as the position signal. The amount of rotation of the galvanometer mirror 8 can be detected.

FIG. 6 shows an example of the relationship between the position signal and the amount of movement of the aperture 8. In FIG. Therefore, based on the position signal, it is possible to monitor whether the amount of rotation of the galvanometer mirror 8 exceeds its permissible limit. This position detection device 2
0, the span Q from the center of the aperture 21 to the rotation center of the galvano mirror 8 can be set arbitrarily, so by increasing the span Q, the aperture 21 The amount of movement of the galvano mirror 8 can be amplified, and a position signal with sufficient output can be obtained even with a slight change in rotation of the galvanometer mirror 8.

By the way, the aperture 21 in the above-mentioned position detection device 20 is formed in the aperture plate 24 integrated with the galvanometer mirror 8, but as shown in FIG. 4 or FIG. 5, for example, the aperture 21 is Even if it is formed directly on the galvanometer mirror 8 itself, it can perform exactly the same function as the above-mentioned one, and can be configured more simply than the above-mentioned position detection device i20.

Here, as in the former case (FIG. 4), when the aperture 21 is formed in the reflecting surface 8a which is out of the optical path of the beam of the galvanometer mirror 8, the aperture 21
1 is formed of a through hole or a transparent body.

On the other hand, as in the latter case (FIG. 5), the aperture 21 is connected to the reflecting surface 8a in the optical path of the beam of the galvanometer mirror 8.
If the aperture 2I is formed within the spectral reflection region of the aperture 2I, For example, as shown in FIG. 6, the If factor is formed to be high with respect to the wavelength of the beam and low with respect to the wavelength of the luminous flux from the light emitting element 22.

(Effects) As described above; the optical pickup according to the present invention corrects a slight deviation of the beam optical axis with respect to the track of the optical disk by rotating the galvanomirror, and also aligns the aperture of the position detection device with the galvanomirror. Since it is integrally formed, the supporting part of the objective lens can be simplified and lightened, and its frequency characteristics and followability can be improved.

[Brief explanation of drawings]

Fig. 1 is a perspective view of an optical pickup showing an embodiment of the present invention, Fig. 2 is an explanatory diagram of the operating principle of the position detecting device in the above embodiment, and Fig. 3 is an illustration of the aperture movement amount and position of the position detecting device. 4 is a side view showing another example of the position detecting device, FIG. 5 is a side view showing still another example of the position detecting device, and FIG. 6 is a side view showing another example of the position detecting device. 6 is a diagram showing the relationship between the wavelength and spectral reflectance of the aperture section of the position detection device shown in FIG. 5. FIG. 8... Galvano mirror 120... Position detection device, 21... Aperture, 24... Aperture plate.

Claims (1)

[Claims] 1. An optical system having a tracking device for correcting the position of the beam optical axis by detecting the amount of deviation of the beam optical axis with respect to the track of the optical disk when the beam is irradiated onto the optical disk through an objective lens. In the pickup, a galvanometer mirror is disposed in the optical path of the beam to displace the position of the beam optical axis with respect to the track according to the amount of deviation of the beam optical axis by rotating a reflecting surface about the beam optical axis, and The aperture of the position detection device including a light emitting element and a light receiving element arranged opposite to each other with an aperture in between is formed integrally with the galvano mirror, and the galvano mirror is rotated based on the detection result of the position detection device. An optical pickup characterized by detecting quantity. 2. The optical pickup according to claim 1, wherein the aperture is formed in a reflective surface of the galvanometer mirror that is out of the optical path of the beam. 3. The aperture is formed in the reflective surface of the galvanometer mirror in the optical path of the beam, and the spectral reflectance of the aperture-forming portion of the reflective surface is made high for the wavelength of the beam, so that the light emitted 2. The optical pickup according to claim 1, wherein the wavelength of the light beam from the element is set to be low.