JPS60157730A - Optical head - Google Patents

Abstract

PURPOSE:To secure an accurate position on a disk for each light spot, despite an assembling/control error, a change with time of an optical system by giving idependent focusing and tracking controls to each light spot. CONSTITUTION:The reflected light of a light spot 61 is turned into parallel luminous fluxes by a stop-down lens 7 and reflected again rectangularly by a polarizing prism after transmitted through a galvanomirror 6, a wavelength selecting prism 5 and a lambda/4 plate 4. Then the reflected luminous fluxes are led to a photodetector 12 by a cylindrical lens 11 for detection of a focal position and tracking signal. The focusing and tracking controls are carried out for a light spot 101 by a voice coil 8 and the mirror 6. While the relfected luminous fluxes of an optical spot 62 are led to a 4-split photodetector 30 by a lambda/4 plate 23, a polarizing prism 22, a convex lens 28 and a cylindrical lens 29 for detection of a focal position and tracking signal. Then a voice coil 25 and a galvanomirror 27 are driven to keep a prescribed relation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application] The present invention relates to an optical head, and particularly to an optical head suitable for an optical disc that performs recording/reproducing or erasing using multi-spots.

[Background of the invention]

Conventionally, in an optical head having two or more light spots using a single aperture focusing lens, automatic focusing and tracking have been performed by extracting a control signal from only one of the light spots. Therefore, for other light spots, it is necessary to mechanically adjust the narrowing position and track direction position according to the light spot from which the control signal is extracted, and high mechanical precision is required for the parts. Another disadvantage is that adjustment during assembly requires a great deal of effort. moreover,
It has not been possible to correct deviations in the position of the light spot due to changes over time in the optical system that guides two or more light beams to the focusing lens.

[Purpose of the invention]

An object of the present invention is to provide an optical head that generates at least two light spots using one aperture lens, so that the positions of the respective light spots can be accurately positioned on the disk surface even if there are assembly adjustment errors or changes in the optical system over time. The object of the present invention is to provide an optical head that can be positioned more accurately on a track.

[Summary of the invention]

Therefore, I believe that one aperture lens can achieve two
When generating more than one light spot, a suppression signal is extracted from the reflected light of the first of the light spots, and the aperture focusing lens, tracking galvanometer mirror, etc. are driven to perform automatic focusing and tracking control. . On the other hand, the other second light spot is adjusted to be at almost a predetermined position when assembling the optical head, that is, on the same plane as the first light spot and at a predetermined distance in a predetermined direction. . At this time, a movable lens and a movable mirror are provided between the light source and an optical component that combines the two light beams, and a control signal is obtained from the reflected light of the second light spot to drive the movable lens and movable mirror. . If you do this,
Normal automatic focusing and tracking control is performed on the first light spot. At this time, the second light spot is also controlled at the same time, so there is no problem as long as the second light spot is completely separated from the first light spot by a predetermined position. Due to adjustment errors or thermal deformation of the optical component holder, it may shift slightly from the specified position. In the optical head of the present invention, this shift is corrected by the movable lens and movable mirror, and as a result, automatic focusing and tracking control can be performed correctly for any light spot.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure shows an optical head that focuses the light beams emitted from two light sources 1 and 2o into two light spots 61 and 62 at slightly different positions on the disk surface by one focusing lens 7, and performs recording/reproduction. FIG. 2 is a configuration diagram of an optical system of FIG. Here, the light sources 1 and 20 are semiconductor lasers having different wavelengths. For example, the wavelength of light source 1 is 780nl'J
The wavelength of the light source 20 is LIi82Qn+B. In addition, the light source is not limited to a semiconductor laser, but also a semiconductor laser and He-1Ne.
There is no essential advantage in using a laser or a combination of a He-Ne laser and an Ar+ laser. The light beam emitted from the light source 1 is made into a parallel light beam by a coupling lens 2, passes through a polarizing prism 3, a λ/4 & 4, and a wavelength selection prism 5, and is reflected by a galvanometer mirror 6, and is then passed through an aperture lens 7 with a voice coil 8. The light spot 61 is narrowed down by
will occur.

The reflected light from the light spot 61 is turned into a parallel beam by the aperture lens 7, reflected by the galvanometer mirror 6, passes through the wavelength selection prism 5 and the λ/4 plate 4, and is reflected by the polarizing prism 3 in an approximately right angle direction. . Furthermore, this light flux is transmitted to the photodetector 1 by the lens 1o and the cylindrical lens 11.
2.

The photodetector 12 is divided into four parts, and focal position detection and tracking signals are detected by a well-known method, and these signals drive the voice coil 8 and galvanometer mirror 6, respectively, to focus and focus the light spot 101. Tracking control is performed. On the other hand, the light beam emitted from the light source 2o is made into a parallel light beam by the coupling lens 21, and is divided into a polarizing prism 22, a λ/4 plate 2, a metal plate 3, a movable lens 24 supported by a voice coil 25, and a fixed lens 26.
The light is reflected by the galvanometer mirror 27 and enters the wavelength selection prism 5. The wavelength selection prism 5 is the light source 1
0 wavelength, for example 780 nm, and reflects light at the wavelength of light source 2, for example 820 nm.Here, the light flux from light source 1 and the light flux from light source 2o are mixed, and the light source The light beam follows the same optical path as the light beam 1 and is focused as a light spot 62 to improve recording on the disk 9. At this time, the arrangement of the optical components is adjusted, and the light spot 61
and the light spot 62 are assembled in a predetermined relationship, for example, so that they are focused on the same track. however,
Errors are inherent in assembly and adjustment, and due to thermal deformation of the optical component holder and its mounting base, the predetermined relationship between the button and the button may be disrupted. For this reason, the reflected light beam of the light spot 62 is divided into four parts by the λ/4 plate, two metal plates, three optical prisms 22, a convex lens 28, and a cylindrical lens 29.
The cholera signal is guided to the split photodetector 3o, and the focal position and tracking signal are detected by a known method.The voice coil 25 and galvanometer mirror 27
are respectively driven to maintain the predetermined relationship. In this case, as is clear from FIG.
The lens 24 and the galvano mirror 6 are positioned almost in the predetermined position by focusing and tracking control, and only a small amount of correction is required by the movable lens 24 attached to the voice coil 25 and the galvano mirror 27. A movable lens and a movable mirror may also be used. In addition, the movable lens 24 and the fixed lens 26
The focal position correction system can be removed by attaching the light source 20 to a piezo element or the like and moving it.

Note that 50 and 53 shown in FIG. 1 are circuits for tracking signal detection and galvano mirror driving, and 51
and 52 are circuits for detecting a focal position signal and driving the whirlpool coil 1.

Another embodiment of the present invention will be described with reference to FIG.

FIG. 2 is a block diagram of an optical system for recording and reproducing information formed on four optical sporatra disk surfaces (91), and only the main parts of the optical system are shown.

The light sources 101, 111, 121, and 131 are lasers with different wavelengths. For example, each wavelength is 760
780 nm, 800 nm and 820 nm semiconductor lasers. Light sources 101, 111, 121 and 1
The light beams emitted from 31 pass through polarizing prisms or half prisms 102, 112, 122, and 132, respectively, and are combined into approximately one light beam by wavelength selection prisms 103, 104, and 123, and movable mirrors 115, 125, and 135. This light flux is transmitted to the disk 109 by a movable mirror 105 and a movable narrowing lens 106.
4 light slots) 108, 118, 128 and 138 are produced on the surface of the plane.

The reflected light flux of each light spot is transmitted through a prism 102.
112, 122 and 132 respectively have a photodetector 1
07, 117, 127 and 137. These photodetectors are, for example, quadrant photodetectors. Although not explicitly shown in FIG. 2, a focusing control signal and a tracking control signal are obtained from each detector by an optical system inserted in the reflection optical path, for example, by a combination of a convex lens and a cylinder force lens. A control signal from the photodetector 107 drives the movable aperture focusing lens 106 and the movable mirror 105, and the focusing and tracking of the light spot 108 are controlled.

Focusing and tracking control for light spots 118, 128, and 138 are provided by photodetectors 112.12, respectively.
The light source 111,
121, 131 and movable mirrors 115, 125, 13
This can be done by driving 5.

Here, we have described the case where four light spots are formed, but it is clear that even when more light spots are formed, the focusing and tracking control of each light spot can be performed accurately using the same method. be.

〔Effect of the invention〕

According to the present invention, when two or more light spots are formed by one aperture lens and recording/reproduction is performed, focusing and tracking control can be performed independently for each light spot, and assembly adjustment and optical It is possible to provide a stable optical head that is not affected by errors caused by deformation of component holders, etc.

Furthermore, since each light spot can be controlled independently, a greater degree of freedom is obtained in selecting tracks within the field of view of the aperture lens, making it possible to increase recording/reproducing efficiency.

As an example of an optical head that forms two light spots, there is a so-called D RAW (Direct l'jeadAft) function that checks the state immediately after recording.
According to the present invention, there is provided an optical head having a recording/reproducing/erasing optical head having a recording/reproducing optical spot and an oval erasing optical spot for use in a phase change type reversible optical disk. It becomes possible to ensure stable operation in each case.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the optical head of the present invention;
FIG. 2 is a configuration diagram showing the main parts of another embodiment of the optical head of the present invention. 1.20,101,111,121,131...Light source, 3,22,102,112,122,132...Polarizing prism, 5,103,104,123...Wavelength selection prism, 6,27 ,105,125°135...
Movable mirror, 7,106... Stop lens, 9,1
09... Disc, 24... Movable lens, 61.6
2,108,118,128,138... light spot, 12,30. 1o7. it7. x27゜fJ+ Totora? Reason

Claims (1)

[Claims] 1. An optical head in which at least two light spots are generated by one aperture narrowing lens, each of which has an automatic focusing function corresponding to each light spot. head. 2. The optical head according to claim 1, wherein each of the optical spots has a tracking function corresponding to each of the optical spots.