JPS61289544A - Optical head device - Google Patents

Abstract

PURPOSE:To make the device small-sized, light and thin by being composed of a light dividing device to diffract the reflecting light from the recording media with the diffracting lattice and guide it to the light detecting device, and a prism to form into a single body with the light dividing device, deflect the luminous flux from the light source and guide it to the recording media. CONSTITUTION:After the luminous flux reflected from an information recording carrier 20 and including the information comes to be a parallel luminous flux through an objective lens 18 and is made incident on a parallel plate 16, the flux is diffracted by a diffracting lattice 15, while total reflection is executed in the parallel plate 16, comes to be luminous flux 22, is guided and through an analyzer 21, made incident on a light detecting device 23. The information is magnetically recorded in the information recording carrier 20, in accordance with the direction of the upward magnetization of the media and the downward magnetization, the force rotation in the different direction occurs at the incident light and the difference in the polarizing condition comes to be the strength difference of the light by the analyzer 21 and is detected. By the output from a light detecting device 23, the focus error and the tracking error can be detected. Thus, by the simple constitution, recording and reproducing can be made highly efficient or thin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical head device that writes or reads information by irradiating an information recording surface of an information medium with light.

[Prior art]

In an optical head device that records information on a disk-shaped information medium or reproduces recorded information, making the optical head smaller and lighter brings many advantages in achieving high-speed access.

The applicant has filed Japanese Patent Application No. 59-132293 and Patent Application No. 5
In No. 9-132294, a small and lightweight optical head was proposed.

FIG. 6 is a configuration diagram of the optical head device described in the above patent application.

In the figure, P-polarized light emitted from a semiconductor laser 11 is turned into a parallel beam by a collimator lens 12 and enters a light splitter 13. The light splitter 13 includes parallel plates 14 and 1
6 and a diffraction grating 15.

The P-polarized light transmitted through the light splitter 13 is condensed by an objective lens 18, and is focused onto a recording surface 20 formed on a substrate 19 with a diameter of 1 p.
A spot of around m is formed. Since information is magnetically recorded on the recording surface 20, the polarization plane of the reflected light 17 with respect to the polarization plane of the incident light rotates according to the recorded information (Kerr rotation due to the magnetic Kerr effect). ).

The reflected light 17 whose plane of polarization has been rotated enters the light splitter 13 again and is diffracted by the diffraction grating 15. This diffracted light 2
2 is guided through repeated total reflection on the upper surface of the parallel plate 14 or the lower surface of the parallel plate 16, and the 0 diffracted light 22 that enters the photodetector 23 via the analyzer 21 is the information recorded on the recording surface 20. Since the plane of polarization is rotated in accordance with the information recorded on the recording surface 20 by the analyzer 21, the change in light amount is converted into a change in light amount corresponding to the information recorded on the recording surface 20, and the change in light amount is converted into an electrical signal by the photodetector 23. .

As described above, the previously proposed optical head device is small and lightweight, but from the viewpoint of space saving, there has been a desire for a thinner structure including the light source and the like.

On the other hand, in the semiconductor laser used as the light source of the above-mentioned optical head device, as is well known, the divergence angle of the light beam emitted in the direction parallel to and perpendicular to the p-n junction surface is different, and the cross section of the light beam is different. The shape is usually oval. When such a light beam is focused onto a recording medium, the efficiency of recording and reproduction may be lowered due to a bias in the light amount distribution.

[Summary of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical head device that has a small and simple configuration and has a beam shaping function.

Another object of the present invention is to provide an optical head device that is small, lightweight, and suitable for fIj type.

The above-mentioned object of the present invention is to provide an optical head device including a light source, a condensing means for condensing a luminous flux emitted from the light source onto an optical recording medium, and a photodetector for detecting reflected light of the luminous flux from the recording medium. and a diffraction grating arranged along a plane substantially perpendicular to the optical axis of the incident light beam in the optical path of the light beam incident on the recording medium from the light source, and diffracting the light reflected from the recording medium. a light splitter that diffracts the light with a grating and guides the light to the photodetector;
This is achieved by comprising a prism that is formed integrally with the light splitter and deflects the light beam from the light source and guides it to the recording medium.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, the same members as those in the apparatus shown in FIG. 6 are given the same reference numerals.

FIG. 1 shows a first embodiment of the present invention. A light beam emitted from a semiconductor laser 11 is turned into a parallel light beam by a collimator lens 12, and enters a light splitter 33. light splitter 3
3 is composed of a parallel flat plate 16, a diffraction grating 15 formed on the parallel flat plate 16, and a beam shaping prism 34 which also serves as a cover glass for the diffraction grating 15. The light beam from the semiconductor laser 11 is deflected by the prism 34 so that its cross-sectional shape is rotationally symmetrical, and the zero diffraction grating 15, which is incident perpendicularly to the diffraction grating 15, is formed by mechanically processing a mold or by using a hologram. It is made by copying the relief of a mold with a graphic relief pattern. First, the mold is pressure-bonded to the parallel plate 16 through an ultraviolet curable resin layer.Next, a relief grating is formed on the parallel plate 16 by irradiation with ultraviolet rays, and appropriate characteristics are applied to the relief grating. After forming the polarizing film having the same or similar refractive index, the prism 34 is bonded using an adhesive having the same or similar refractive index to that used for copying.

As the adhesive used for this relief copy, in addition to an ultraviolet curing adhesive, a thermosetting adhesive such as an epoxy resin, or an X-ray curing adhesive can also be used. In addition, the hologram is not limited to such a relief type, and the volume type hologram described in the above-mentioned earlier application of the present applicant can also be used.

The light beam, which has become approximately rotationally symmetrical due to the beam shaping prism 34, passes through the diffraction grating 15 and the parallel plate 16, and passes through the objective lens 18 to the information recording carrier 20 formed on the substrate 19.
Causes spots on the top.

The light beam reflected from the information recording carrier 20 and containing information is
It passes through the objective lens 18 and becomes a parallel light beam, and the parallel plate 16
After being incident on the light beam, it is diffracted by the diffraction grating 15 and guided as a light beam 22 while being totally reflected in the parallel plate 16 , passes through the analyzer 21 and enters the photodetector 23 .

Information is magnetically recorded on the information recording carrier 20,
Media upwards! Depending on the direction of l magnetization and downward magnetization, the incident light undergoes Kerr rotation in different directions, and this difference in polarization state is detected by the analyzer 21 as a difference in light intensity.

Furthermore, it is also possible to detect focus errors and tracking errors from the output from the photodetector 23.

This example will be explained using FIG. 2.

FIG. 2 is a diagram of the light splitter 33 seen from the semiconductor laser 11 side, and the diffraction grating 15 has a piece grating 1t with centers at different positions.
It is divided into 2a, 112b, and 113. Lattice 113
The light beam diffracted by the beam enters the two-split photodetector 114.

Depending on whether the information recording carrier 20 is farther or closer to the reference position,
The reflected light beam is either divergent or convergent. Therefore, the position where the diffracted light beam enters the photodetector moves. Therefore, by taking the difference between the outputs from the photodetector 114, IA and IB, a focus error signal can be detected.

On the other hand, the light beams from the piece gratings 112a and 112b enter photodetectors 115 and 116, respectively. Now, if the grooves formed on the substrate 19 of the information recording carrier are arranged in the direction of AX in FIG.
The balance of the amount of light incident on 12b is lost. Therefore,
Tracking errors can be detected by taking the difference between the outputs IC and ID from the photodetectors 115 and 116.

FIG. 3 is a schematic configuration diagram showing a second embodiment of the present invention.6 The basic configuration of the light splitter 43 of this embodiment is the same as that of the device shown in FIG. 1, but the diffraction grating 45 The difference is that the bottom surface of the shaping prism 44 is formed by processing the bottom surface into an uneven shape using injection or compression technology. After a suitable reflective film is formed on this uneven surface, the parallel plate 16 is bonded to the prism 44 via an adhesive 46 having substantially the same refractive index.

By adopting such a configuration, it is possible to construct an optical head at a low cost with a smaller number of man-hours f1.

A third embodiment of the present invention is shown in FIG.
The light beam emitted from the light beam 1 becomes a parallel light beam by the collimator lens 12, enters the bending prism 47, is bent by the reflecting surface 48, and enters the light splitter 13. The prism 47 is the first parallel plate 1 constituting the light splitter 13.
It is glued to 4. The light beam passes through the parallel plate 14, the diffraction grating 15, and the parallel plate 16, and is focused by the objective lens 18 onto the information recording carrier 20 via the substrate 19. This reflected light beam is diffracted by the diffraction grating 15 to become a light beam 22, which passes through the analyzer 21 and enters the photodetector 23, where information signals, focus error signals, tracking error signals, etc. are detected.

FIG. 5 shows a fourth embodiment of the present invention.
The parallel plate 14 of the illustrated embodiment is omitted, and the light splitter 49 is constructed by using the prism 47 as a cover glass for the diffraction grating 15. The third and fourth embodiments have the advantage that the light beam is bent by 90'' at the reflecting surface 71, and the entire optical head can be made thin.

The optical head device of the present invention can be applied in various ways in addition to the embodiments described above. For example, the record carrier is not limited to the above-mentioned magneto-optical recording, but can also be applied to various carriers that utilize pit formation or change in reflectance. is available. In this case, the analyzer 21 of the embodiment
Hafu: W seven naru.

〔Effect of the invention〕

As explained above, in the optical head device of the present invention, the beam shaping prism or the prism for bending the optical path is formed integrally with the light splitter using the diffraction grating.
With a simple configuration, it has become possible to increase the efficiency of recording and playback or to make the device thinner.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of the present invention, and FIG.
FIG. 1 is a schematic plan view of the light splitter shown in FIG. 1 viewed from the semiconductor laser side, FIGS. 3, 4, and 5 are schematic diagrams showing the configuration of other embodiments of the present invention, and FIG. 1 is a schematic diagram showing the configuration of an optical head device using a diffraction grating to which the present invention can be applied. 11--m-semiconductor laser, 12--collimator lens, 15--single diffraction grating, 16--parallel plate,
18---one objective lens, 20---one information recording carrier,
23---One photodetector, 33---One light splitter, 34-
---Beam shaping prism.

Claims (3)

[Claims] (1) A light source, a condensing means for condensing the light beam emitted from the light source onto an optical recording medium, a photodetector for detecting reflected light of the light beam from the recording medium, and a light beam from the light source to the recording medium. A diffraction grating is arranged in the optical path of the incident light beam along a plane substantially perpendicular to the optical axis of the incident light beam, and the light reflected from the recording medium is diffracted by the diffraction grating to detect the photodetector. What is claimed is: 1. An optical head device comprising: a light splitter that guides a light beam to a recording medium; and a prism formed integrally with the light splitter that deflects a light beam from the light source and guides it to a recording medium. (2) The optical head device according to claim 1, wherein the prism is a beam shaping prism that changes the cross-sectional shape of the light beam from the light source. (3) The optical head device according to claim 1, wherein the diffraction grating is formed by processing one surface of the prism into an uneven shape.