JPH0697512B2 - Light head - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a separation type optical head having a fixed part composed of an optical system such as a light source and a movable part composed of a mechanical device such as a light beam drive. Is.

(Prior Art and Problems) An optical head, in an optical recording apparatus, forms a minute spot on a running recording medium to record and reproduce optical information. By driving the minute spot, focus tracking, track following, Track access. Representative of optical head 1
An example is shown in FIG. The optical disk 1 is rotated by the motor 2 and the optical head 3 is driven in the radial direction of the optical disk to select a track.

In the example of FIG. 5, the semiconductor laser 4, the coupling lens 5, the prism beam splitter 6, the 1/4 wavelength plate 7, the optical path conversion mirror 8, the condenser lens 9, and the photodetector 10 which are the components of the optical head are All are housed in a single case and move in the radial direction of the disk as a whole. In this case, even if heat fluctuation 11 or dust is generated outside the optical head, it does not affect the optical path 12. However, this structure has a drawback that the optical head becomes large and the track access cannot be speeded up. Therefore, to speed up track access,
It is effective to reduce the weight of the movable part.

In another example of the optical head shown in FIG. 6, in order to reduce the weight of the movable part, a fixed part 13 composed of an optical system such as a light source and a movable part 14 composed of a mechanical system such as a light beam drive are separated. Has been done. In this case, since the optical path 12 is exposed to the outside of the optical head, it is affected by thermal fluctuations 11, dust, etc., and the condensing performance of the minute spot condensed on the disk medium 1 by the objective lens 9 deteriorates. There is a drawback that.

(Means for Solving the Problems) In order to eliminate these drawbacks, the present invention provides a bellows at least on both side surfaces of the optical path along the optical path between the fixed part of the split type optical head and the movable part of the split type optical head. By disposing a plate-shaped or plate-shaped member, thermal fluctuations are suppressed and deterioration of the light condensing performance of minute spots of the optical head is prevented. Hereinafter, a detailed description will be given with reference to the drawings.

(Example) FIG. 1 shows an example of the present invention. In this separated type optical head, a thermal fluctuation suppressing member (a member for suppressing thermal fluctuation by arranging it in the optical path 12 between the fixed portion 13 and the movable portion 14,
I'll call it 15). This makes it possible to shield the optical path 12 from the outside of the optical head, and prevent deterioration of the laser condensing characteristics due to the effects of thermal fluctuation 11 and dust. Reference numeral 16 is a notch for allowing the light emitted from the objective lens 9 to reach the optical disc medium 1 when the movable portion 14 moves in the disc radial direction. 17 (a) is a laser emission window of the fixed part 13 and 17 (b) is a laser emission window of the movable part 14. 18 (a) is a guide, 18 (b) is a carriage, and 19 is a pedestal.

FIG. 2 shows another embodiment of the present invention. Heat fluctuation suppression member
Reference numeral 20 denotes a bellows-like flexible member, which has a higher degree of sealing and a smaller size than the pipe-type heat fluctuation suppressing member 15 shown in FIG.

FIG. 3 shows another embodiment of the present invention. The heat fluctuation suppressing member is a strip-shaped plate shown in 21 (a) and 21 (b), and has an optical path 12
Are located on both sides of. Although the optical path 12 is not covered on the upper surface, most of the thermal fluctuations can be prevented by the side plate, so such a configuration is simple and effective.

FIG. 4 is a waveform diagram showing the results of reproducing the data signal and the track signal of the optical disk in the case where the optical path 12 is subjected to thermal fluctuation and with or without the thermal fluctuation suppressing member in order to examine the action and effect of the present invention. is there. In FIG. 4 (a) showing the case where there is no heat fluctuation suppressing member, the temperature distribution in the optical path 12 produces a refractive index distribution in the air, which causes optical path distortion. For this reason, the light spot on the disk medium 1 causes distortion of the shape and enlargement of the spot system, and is inferior to the data signal 22 (a) and the track error signal 23 (a) as shown in FIG. 4 (a). Let On the other hand, when the heat fluctuation suppressing member is arranged, as shown in FIG.
(B), the track error signal 23 (b) is obtained.

The internal structure of each of the fixed part and the movable part of the optical head in the above embodiment is one example, and how to separate the fixed part and the movable part from each other as necessary. Can be changed freely.

(Effects of the Invention) As can be seen from the above description, the split type optical head of the present invention is provided with the thermal fluctuation suppressing member so as to cover at least both side surface portions of the optical path between the split portion and the fixed portion. The effects of heat fluctuation, dust, etc. are eliminated, and highly accurate error signal detection and stable recording / reproducing can be performed.

[Brief description of drawings]

1, 2 and 3 are views showing an embodiment of the separated type optical head of the present invention, FIG. 4 is a waveform diagram showing the effect of the present invention, and FIG. 5 is a conventional integrated type optical head. FIG. 6 is a diagram showing a configuration example, and FIG. 6 is a diagram showing a configuration example of a conventional separation type optical head. 1 ... Optical disc medium, 2 ... Motor, 3 ... Optical head, 4 ... Semiconductor laser, 5 ... Coupling lens,
6 ... Prism beam splitter, 7 ... 1/4 wave plate,
8 ... Optical path changing mirror, 9 ... Condensing lens, 10 ... Photodetector, 11 ... Thermal fluctuation, 12 ... Optical path, 13 ... Separation type optical head fixed part, 14 ... Separation type optical head movable Part, 15 ... Pipe-shaped heat fluctuation suppressing member, 16 ... Scraping, 17 (a),
(B) …… Laser emission window, 18 (a) …… Guide, 18
(B) ... Carriage, 19 ... Pedestal, 20 ... Flexible heat fluctuation suppressing member, 21 (a), (b) ... Strip plate, 22
(A), (b) ... Data signal, 23 (a), (b) ...
Track error signal

Claims (1)

[Claims] 1. A separation type optical head comprising a fixed part composed of an optical system such as a light source and a movable part composed of a light beam driving mechanism system, which are separated from each other by space propagation of a light beam. An optical head in which a bellows-shaped or plate-shaped member is arranged on at least both sides of an optical path of a propagating portion.