JPS62205546A - Optical head - Google Patents

Abstract

PURPOSE:To contrive miniaturization and light weight of a device and to shorten an access time by passing the laser light of a light transmission system guided to an information storing medium from a semiconductor laser and the laser light of a photodetecting system guide to a photodetector from the information storing medium through a similar optical path. CONSTITUTION:The laser light L emitted from a light source 21 passes through collimator lens 22 in common uses as a projection lens, converted to substantially parallel light and guided to a light guided member 23. Then, the laser light L guided to the member 23 is made incident on a prism 24 from a light refracting surface 24a, reflected on a polarization beam split surface 26 and converged to the information storing medium 29 through a 1/4 wavelength plate 27 and an objective lens 28. The converged light L is reflected on the medium 29, thereafter passes through the lens 28, the plate 27 again and is fed to the surface 26 from the prism 24. This laser light L transmits the surface 26, is totally reflected on the light separation surfaces 25a, 25b, 25c of a light separation member 25, and thereafter passes through the surface 26 again. The light L passes through the optical path of the photodetecting system substantially similar to the optical path of the light transmission system passing when directed to the medium from the light source 21 and advances to the photodetector 30 disposed near to the light source 21.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an information reproducing device, an information recording/reproducing device, etc. that can read at least information from an information storage medium using, for example, focused light. The present invention relates to an optical head that is passed through.

[Conventional technology]

As this type of optical head, one constructed as shown in FIG. 2 is conventionally known. That is, 1 is a semiconductor laser, and the laser beam emitted from this semiconductor laser 1 sequentially passes through a collimating lens 2, a polarizing beam splitter 3, a 1/4 wavelength plate 4, and is guided to an objective lens 5. The light is focused onto the information storage medium G by the objective lens 5. This focused laser light is reflected by the information storage medium 6, passes through the objective lens 5 and the quarter-wave plate 4 in order, is returned to the polarizing beam splitter 3, and is reflected by the sunlight beam splitter 3. . This reflected laser beam is divided into 2 minutes by half mirror 7,
One of them is projected by a lens 8 onto a photodetector 9 at I'11. As a result, information recorded on the information storage medium 6 is detected and track deviation detection is performed to detect the deviation of the laser beam focused on the tracking guide of the information storage medium 6 by the objective lens 5 from the tracking guide. It will be done. The other divided laser beam is extracted asymmetrically with respect to the optical axis by the light extraction member 10, and is projected onto the second photodetector 12 via the lens 11. As a result, defocus detection is performed using a so-called knife etch method.

[Problem that the invention seeks to solve]

In the above optical head, the laser light guided from the semiconductor laser 1 to the information storage medium 6 and the laser light guided from the information storage medium 6 to the photodetectors 9 and 12 are transmitted between the polarizing beam splitter 3 and the information recording medium 6. Since the optical paths pass through completely different optical paths except for A problem arises.

The present invention has been made based on the above circumstances, and an object thereof is to provide an optical head that can reduce the number of optical parts, thereby achieving reduction in size and weight and shortening of access time. It's about doing.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention provides a light source, an objective lens that focuses the light emitted from the light source onto an information storage medium, and A photodetector that detects the light that is focused by the objective lens and returned via the information storage medium, and the light of the light transmission system that is guided from the light source to the information storage medium and the light that is guided from the information storage medium to the photodetector. a light guiding member that guides both the light from the light receiving system, the light guiding member having a special reflecting surface and a light reflecting surface, and the light guiding member guiding both the light from the light transmitting system and the light from the light receiving system. The special feature is that one side is a special reflective surface and the light is reflected by the special reflective surface, and the other side is configured so that the light passes through the special reflective surface, is reflected by the reflective surface, and then passes through the special return port 1 surface again. .

[Function] The light from the light transmitting system guided from the light source to the information storage medium and the light from the light receiving system guided from the information storage medium to the photodetector can be made to pass through similar optical paths, so that common optical components can be used. The number of optical parts can be reduced.

[Embodiments of the invention]

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

Reference numeral 21 in FIG. 1 is, for example, a semiconductor laser (light source) which has a plurality of light emitting points and emits laser light (only the principal ray is shown) L from each light emitting point so as to travel at a slight angle to each other. The diverging laser light emitted from this semiconductor laser 21 is converted into a grid destination by passing through a collimating lens 22 which also serves as a projection lens, and then guided to a light guide member 23.

This light guiding member 23 includes a prism 24 and a light separating member 25.
A polarizing beam splitting surface (special reflecting surface) 26 is formed on the joining surface, and a light refracting surface 24a is formed on the portion of the prism 24 facing the polarizing beam splitting surface 26. Three light separating surfaces (light reflecting surfaces) 25a, 25b, 25c are adjacent to each other with inclinations in the portions facing the polarized beam sublits 1 to 26.
It has a configuration that forms.

The laser beam guided by the light guide member 23 is a light refracting surface 24
The light enters the prism 24 from a. This prism 24
The light refraction surface 24a is tilted with respect to the optical axis, so that refraction occurs when the laser beam is incident, and the spot size of the laser beam is changed in the refracted direction, thereby performing ellipse correction of the laser beam.

The laser beam incident on the prism 24 is reflected by the polarization beam splitting surface 26, passes through a quarter-wave plate 27 and an objective lens 28, and is then applied to an information storage medium 29.

This information storage medium 2 has a recording area provided with a recording layer on at least one surface that can be recorded or reproduced by laser light. In this recording area, a tracking guide by a pre-group is formed in a spiral shape or a concentric circle shape.

The laser beam focused on the information storage medium 29 is reflected by the two information storage media, and then passes through the objective lens 28.1/4 again.
After passing through the wavelength plate 27 , the light is incident on the prism 24 and then returned to the polarization beam splitting surface 26 . Here, by reciprocating through the 17'4 wavelength plate 27, the laser beam becomes a direct beam whose vibration direction is rotated by 90 degrees compared to when it is reflected at the polarizing beam splitting surface 26. The returned laser beam passes through the polarization beam splitting surface 26 and is guided to the light separation member 25, where it passes through the light separation surface 25a of the light separation member 25.

After being totally reflected by 25b and 25c, it passes through the polarizing beam splitter 26 again. Thereafter, the laser light passes through the optical path of the light receiving system that is almost similar to the optical path of the light transmitting system that it passed when going from the semiconductor laser 21 to the information storage medium 29, passes through the collimating lens 22 that also serves as a light emitting lens, and is directed to the semiconductor laser 21. It advances toward a photodetector 30 provided nearby. In this case, the light separating surfaces 25a, 25b, and 25c are provided non-parallel to the polarizing beam splitting surface 26, and therefore, between the polarizing beam splitting surface 26 and the photodetector 30 or the semiconductor laser 21, there is no transmission of light. The optical axis of the system's laser beam (at least one laser beam) L and the optical axis of the light-receiving system's laser beam (at least one laser beam) L are inclined to each other. Here, the light separation surfaces 25a, 25
The light separation surfaces 25a and 25b are arranged such that the laser light component reflected on at least one surface of the light separation surfaces 25a and 25c intersects the optical axis of the laser light of the light transmission system before reaching the photodetector 30.

The direction of 25C is set. In addition, the light separation surface 25b
The boundary line with the optical separation surface 25c is set to be approximately parallel to the direction in which the tracking guide of the information storage medium 29 extends or the direction in which the image of the tracking guide projected on the photodetector 30 extends. In addition, the light separation surface 25a
The laser beam component reflected at 01 is used for defocus detection using the principle of the so-called knife etching method, and
The light is focused between the upper defocus detection photodetection cells 31a and 31b. Further, the laser light components reflected by the light separation surfaces 25b and 25c are used for track deviation detection using the diffraction pattern of the reflected light from the tracking guide of the focused laser light. That is, the far field pattern for the focused spot of the information storage medium 29 is separated by the light separation surfaces 25b and 25c, and the light is focused on the light detection cells 32a and 32b for detecting track deviation of the photodetector 30, respectively.

Furthermore, the semiconductor laser 21 and the photodetector B30 are provided on the same mount 33. Here, the collimating lens 22 that also serves as a projection lens is a semiconductor laser 2.
The lens serves both as a lens for collimating the laser light emitted from the light transmitting system and as a lens for condensing the laser light from the light receiving system onto the photodetector 30. In other words, both the laser light from the light transmitting system and the light from the light receiving system pass through this collimating lens 22 which also serves as a light projection lens. Between the projecting lens and collimating lens 22 and the objective lens 28, the laser light is parallel light when in focus, so the laser light from the light receiving system is on the same plane as the light emitting point of the semiconductor laser 21 ( The light is focused on the focal plane of the collimator lens 22 which also serves as a projection lens. Therefore, the light emitting point of the semiconductor laser 210 and the light receiving section of the photodetector 30 are substantially arranged on the same plane.

The mount base 23 includes a semi-cylindrical portion 33a and a semi-circular ring frame portion 33b, and a photodetector 30 is provided on the end surface of the semi-cylindrical portion 33a, and a semiconductor laser 21 is provided on the side surface portion. ing.

When adjusting the detection system, the mounting base 33 and the collimating lens 22 which also serves as a light emitting lens are mounted on the top of the track deviation detection cell 328, 321) by changing the relative positional relationship with respect to the light separating member 25. The position of the laser beam for detecting track deviation is changed.

Further, the light emitting point of the semiconductor laser 21 is located at the rotation center of the mount base 33.
When the semiconductor laser 21 rotates, the optical axis of the laser beam emitted from the semiconductor laser 21 is prevented from shifting.

In addition, each cell 31a, 31b, 3 on the mount stand 33
2a and 32b, the defocus detection cell 31 is arranged along the rotational direction or string direction of the mounting base 33.
8.31b is arranged, and by rotating only this mount 33, the defocus detection system can be adjusted. In addition, in order to enable such FIJM, the defocus detection cell 31a is adjusted according to the direction along the circumferential direction of the mount base 33 and the defocus on the information storage medium 29.
.

The moving direction of the laser beam moving on 31b is substantially parallel to the moving direction. The light detection cells 32a and 3b for detecting track deviation are arranged along the radial (radial) direction of the mounting base 33, and as the mounting base 33 rotates, the laser beam for detecting track deviation is transmitted to the cells 32a and 32b for detecting track deviation. It is designed not to move on top.

According to the above configuration, the laser light of the light transmitting system guided from the semiconductor laser 21 to the information storage medium 29 and the laser light of the light receiving system guided from the information storage medium 29 to the photodetector 30 pass through similar optical paths. Therefore, it is possible to use common optical components such as the collimator lens 22 which also serves as a light projecting lens, and the number of optical components can be reduced. Therefore, it is possible to reduce the size and weight, and furthermore, the access VFG can be shortened due to the weight reduction.

In addition, a polarized beam splitter 26 and a semiconductor laser 2
1 or the photodetector 30, the optical axis of the laser beam of the light transmitting system and the optical axis of the laser beam of the light receiving system intersect with each other. The area through which light passes becomes narrower. Therefore, it is possible to use the collimator lens 22 that also serves as a projection lens and a small support frame (not shown) having a small external shape.

Note that the special reflecting surface is not limited to a polarizing beam splitting surface, but may also be a half mirror surface. Further, although the luminous intensity 01 surface is used as a light separation member, the luminous beam splitter 1- surface may be used as a light separation surface.

[Effects of the Invention] As explained above, according to the present invention, the light guided from the light source to the information storage medium and the light guided from the information storage medium to the photodetector can be caused to pass through similar optical paths. Therefore, it is possible to use common optical parts, thereby reducing the number of optical parts, thereby achieving excellent effects such as reduction in size and weight and shortening of access time.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of the present invention, and FIG. 2 is a perspective view showing a conventional example. 21... Light source (semiconductor laser), 25... Light guiding member, 25a, 25b, 25c... Light reflecting surface (light separating surface), 26... Special reflecting surface (Q light beam splitting surface), 28... Objective lens, 29... Information storage medium,
30... Photodetector.

Claims (6)

[Claims] (1) A light source, an objective lens that focuses the light emitted from the light source onto an information storage medium, and a photodetector that detects the light that is focused by the objective lens and returned via the information storage medium. , a light guide member that guides both the light of the light transmission system guided from the light source to the information storage medium and the light of the light reception system guided from the information storage medium to the photodetector, and this light guide member has a special reflective and a light reflecting surface, one of the light from the light transmitting system and the light from the light receiving system is reflected by the special reflecting surface, and the other is reflected by the light reflecting surface after passing through the special reflecting surface. An optical head characterized in that it is configured to pass through a special reflective surface again. (2) The light guiding member has at least a part of the special reflecting surface and at least a part of the light reflecting surface arranged non-parallel to each other, so that the optical axis of at least part of the light of the light transmitting system and at least part of the light receiving system The optical head according to claim 1, wherein the optical head is configured such that the optical axes of some of the lights are non-parallel. (3) The optical head according to claim 1, wherein the special reflecting surface of the light guide member is a polarizing beam splitting surface or a half mirror surface. (4) The optical head according to claim 1, wherein the light reflecting surface of the light guiding member utilizes total reflection. (5) The light guide member connects at least a portion of the special reflective surface and at least a portion of the light reflective surface to the optical axis of at least a portion of the light of the light transmitting system and the optical axis of at least a portion of the light of the light receiving system. 2. The optical head according to claim 1, wherein the optical head is configured to intersect between the light source and the special reflective surface. (6) The light guiding member has at least three light reflecting surfaces formed with either the special reflecting surface or the light reflecting surface having different inclinations from each other.
2. The optical head according to claim 1, wherein the optical head comprises two light separation surfaces.