JPS62285240A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To continuously drive a prism for a minute angle and to stably keep the neutral position by providing a bimorph electrostriction element as a means driving a prism. CONSTITUTION:The bimorph has a structure where two piezoelectric elements whose electrodes are applied to the square surface expanded and contracted in the lengthwise direction are adhered, and when the one is expanded, the other is contacted to cause a benging motion in the direction of arrow B'. In such a case, a prism fixed part 32 fixed to the tip of the bimorph 33 is turned by an angle equal to the tip angle of the bimorph 33 and then the prism 31 is driven in the direction of arrow C'. Thus, the prism 31 in a direction A' is moved by a minute angle in this paper in the direction of arrow D'. Since the touch angle at the tip of the bimorph 33 is changed nearly proportional to the voltage applied to the bimorph 33, the position of the light spot is adjusted by changing properly the applied voltage based on a tracking signal by a detector 10'.

Description

[Detailed description of the invention] 3. Detailed description of the invention Industrial applications The present invention records signals using multiple optical spots.

The present invention relates to an optical recording and reproducing device that performs reproduction, erasing, etc., and particularly relates to an optical recording and reproducing device in which a plurality of light spots are stably arranged on the same track.

Conventional technology Conventionally, optical recording and reproducing devices with multiple optical spots have been used to detect dislocations between an amorphous state and a crystalline state in a recording thin film of an optical recording medium, or between one amorphous state and another stable state. There is an optical recording/reproducing device that repeatedly rewrites signals by causing dislocation between the amorphous material and the like.

In the above-mentioned apparatus, two laser beams with different wavelengths are focused into two minute optical spots using the same aperture lens, and these are placed close to each other on the track of an optical recording medium, one after the other. The structure is such that a signal is erased using one optical spot and at the same time a new signal is immediately recorded using a second optical spot.

In the apparatus having the above configuration, the following method has been considered as a tracking control method for the two light spots.

That is, for one of the two light spots (c below the first light spot) K, the reflected light from the optical recording medium is guided to a photodetector to obtain a tracking signal, and based on this, a known voice coil or the like is detected. Tracking control is performed by moving the diaphragm lens using a driving means according to the structure.

At this time, for another light spot (hereinafter referred to as the second light spot) that moves together with the first light spot, the reflected light from the optical recording medium is guided to another photodetector to generate a tracking signal. Based on this, an optical element such as a reflective mirror provided in the optical path of the beam that forms the second light spot is rotated, and the second light spot is moved independently of the first light spot. Tracking control is performed by this.

However, in the optical recording/reproducing device using two light spots as described above, the track pitch of the recording medium is 1.
．． Because it is very narrow, about 6 μm, the first and second light spots are perpendicular to the track.
When the track pitch deviates by more than the minimum, there is a possibility that tracking control is performed in which the two light spots track different tracks. In order to prevent this, even if the neutral position of the optical element such as a reflective mirror that moves the second light spot is mechanically maintained, and the movable range is made extremely small, the two light spots on the recording medium are If the allowable deviation is 0.1 μm, the allowable beam deflection angle is about 0.02 mrad, which is extremely small as the allowable angle deviation of the optical element, and it is mechanically highly accurate. Something complex is required.

As a means to solve this problem, Japanese Patent Laid-Open No. 60-2316
A device shown in Publication No. 13 has been proposed. 2nd below
An example of the configuration of this device will be described with reference to the drawings. In FIG. 2, a beam of wavelength λ1 emitted from a semiconductor laser 1 passes through a condenser lens 3 and a filter 7, is reflected by a polarizing beam splitter 5, passes through an A wavelength plate 6 and an aperture lens 8, and is optically recorded. The light is irradiated onto the track of the medium to form a light spot P1. The reflected light of this beam passes through the aperture lens 8, the A wavelength plate 6, the polarizing beam splitter 5, the A wavelength plate 6', and the filter 7', and is guided to the photodetector 10 via the lens 9, and is used for focusing and tracking. Obtain the control signal.

On the other hand, the beam of wavelength λ2 emitted by the other semiconductor laser 2 passes through the condenser lens 3' and the wedge prism 4, is reflected by the polarizing beam splitter 5, and passes through the A wavelength plate 6'. It is reflected by the filter 7' and passes through the wavelength plate 6'.
, polarizing beam splitter 5, wavelength plate 6, aperture lens 8
to form a light spot P2 on the track of the disk. The reflected light of this second beam is passed through the aperture lens 8, A
After passing through the wavelength plate 6, the light is reflected by the polarizing beam splitter 5 and filter 7 and enters the photodetector 1Q' to obtain a tracking control signal.

In this device, a beam of wavelength λ1 emitted from a semiconductor laser 1 is adjusted to the eccentricity and surface deflection of the disk by moving the aperture lens 8 based on the focus and tracking signals obtained by the photodetector 1o. It is designed to always follow the track. At this time,
A beam of wavelength λ2 emitted from the semiconductor laser 2 also moves at the same time, and there is a rotatable prism 4 in the optical path of this beam, and the prism 4 is rotated based on the signal obtained by the photodetector 10'. By adjusting the angle of incidence of the beam of wavelength λ2 on the aperture lens 8, tracking control of the optical spot P2 is performed. , will touch the rotation angle of the prism 4 by a very small angle, and by appropriately determining the apex angle of the prism 4 and the degree of precision with respect to the optical axis,
It is possible to achieve a beam deflection of about 1/100 of the prism rotation angle.

Therefore, the light spot formed by the beam passing through the prism 4 is maintained in a neutral position so that it is closely aligned with another light spot on the same track, and the range in which the light dropper is moved is Since it is easy to reduce the amount of light to a very small amount, it is possible to realize a tracking control mechanism in which the two light spots do not track separate tracks.

Conventionally, as a means for rotating the prism 4, an electromagnetic drive mechanism has generally been considered. An example of the mechanism of this electromagnetic drive system will be shown below with reference to FIG.

In FIG. 3, the prism 4 is supported by a prism fixing part 21, and a shaft 23 is passed through a hole 22 made in the prism fixing part 21. Rotate in such a direction that the prism 4
Based on known optical principles, the beam transmitted in the direction indicated by arrow B in the figure deflects in the direction C in the plane of the paper by a minute angle with respect to the deflection angle of the prism 4 in the direction of the arrow.

In this mechanism, the prism 4 is rotated by a magnet 24 and a coil 25.
By flowing a current in the direction, a force is generated in the direction shown by the arrow B or E in the figure according to Lemming's law, and the prism 4 is rotated. Further, the prism fixing portion 21 is connected to the fixing frame 27iC by a coil spring 26, and the neutral position is maintained by the action of the coil spring 26.

Problems to be Solved by the Invention Generally, in an optical recording/reproducing device using two light spots, the relative positional deviation between the two light spots is extremely small due to temperature, vibration, etc. The deviation occurs at a very slow rate. Therefore, as a prism rotation mechanism for correcting this deviation, it is desirable that the prism rotation mechanism be capable of continuously and smoothly rotating a small angle and stably maintaining a neutral position.

However, in the above-mentioned electromagnetic drive mechanism, there is friction and mechanical play between the rotating part and other components, and it is difficult to continuously and smoothly rotate minute angles or maintain a stable neutral position. It was inconvenient to maintain. Further, there were problems such as the structure being complicated and heat generation.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides an optical recording/reproducing device that includes a bimorph type electrostrictive element (hereinafter referred to as bimorph) as a means for rotating a prism. That is, the prism is fixed near the free end of the bimorph supported in the form of a cantilever by means of a fixing means.

Function The present invention has the above-described structure, and since the prism and bimorph rotate as one when a DC voltage of an appropriate magnitude is applied to the bimorph, there is no mechanical play and the prism can be rotated slightly. It can be continuously and smoothly rotated by the JS angle, and the neutral position can be stably maintained.

Furthermore, it has advantages such as a simple structure and little heat generation, and has great practical effects.

Embodiment FIG. 1 is a diagram showing a prism rotation mechanism of an optical recording/reproducing apparatus in a first embodiment of the present invention.

In FIG. 1, the prism 31 is fixed to a prism fixing part 32, and this prism fixing part 32 is connected to a support part 34.
It is glued near the free end of the bimorph 33 supported in a cantilever shape.

The support part 34 supports the bimorph 33 in a compressed and fixed manner by tightening the screw hole 36 formed in the fixed frame 35.

The bimorph has a structure in which two piezoelectric elements with electrodes attached to the rectangular plate-like surface that expands and contracts in the length direction are glued together. Causes a bending movement in the indicated direction. At this time, the prism fixing portion 32 fixed to the tip of the bimorph 33 rotates by an angle equal to the deflection angle of the tip of the bimorph 33, and thereby the prism 31 also rotates in the direction indicated by arrow C'. Therefore, the prism 31 moves by a small angle within the plane of the paper in the direction indicated by arrow D' in the direction indicated by M' in the figure.

Since the deflection angle of the tip of the bimorph 33 changes approximately in proportion to the magnitude of the voltage applied to the bimorph 33, the magnitude of this applied voltage is changed appropriately based on the tracking signal from the detector 10' in FIG. By this,
The position of the light spot can be adjusted. Also, by controlling the magnitude of the voltage applied to the bimorph 33,
Since the rotation range of the prism 31 can be limited, the two light spots will not track different tracks.

DETAILED DESCRIPTION OF THE INVENTION As described in detail, according to the present invention, the prism can be rotated continuously and smoothly, which is advantageous as an optical recording/reproducing device that stably arranges two light spots on the same track. It is.

In addition, the overall configuration is simpler compared to electromagnetic drive systems,
It has advantages such as no heat generation, and has great practical effects.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a prism rotation mechanism of an optical recording/reproducing device according to an embodiment of the present invention, Fig. 2 is a diagram showing an example of the overall configuration of the optical recording/reproducing device, and Fig. 3 is a diagram of a conventional electromagnetic drive. FIG. 3 is a configuration diagram of a prism rotation mechanism according to the method. 31... Prism, 32... Prism fixing part, 33... Bimorph, 34...
・Support part, 36...Fixed frame, 36...
screw hole. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (1)

[Claims] An optical system that uses a plurality of semiconductor lasers and focuses the beams emitted from the plurality of semiconductor lasers onto a track of an optical recording medium using the same aperture lens, and forms a plurality of close optical spots by arranging them one after the other on the track. a driving means for moving the plurality of light spots together in a direction perpendicular to the track; a prism disposed in at least one optical path of the plurality of beams; and a bimorph as a means for rotating the prism. Optical recording and reproducing device equipped with a type electrostrictive element.