JPH05203810A - Compound prism - Google Patents

Abstract

PURPOSE:To reduce the size of the optical system of an optical recording device by decreasing the number of the components which constitute the optical system, and to provide the compound prism which is easily assembled at the time of its manufacture. CONSTITUTION:The projection surface of a rotary polarizer 10 which rotates the plane of polarization of incident light by a specific angle and projects it is coupled with the incidence surface of a crystal body 11 which has a reflecting surface for reflecting the incident light toward the projection surface and the optical axis of the crystal body 11 is made almost perpendicular to the optical axis of the incident light and also almost parallel to the optical axis of the projection light. Then luminous flux which is made incident on this compound prism 9 has its optical axis changed in direction on the reflecting surface 12 of the crystal body 11 and is separated and projected as two pieces of luminous flux having a P-polarized light component and an S-polarized light component having mutually orthogonal planes of polarization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical component, and more particularly to an optical prism used in a device for recording and reading information on an optical disk or the like.

[0002]

2. Description of the Related Art In recent years, with the sophistication and mass production of information,
Optical recording media such as magneto-optical disks, which have a significantly larger storage capacity than magnetic recording media such as floppy disks, are becoming popular. FIG. 4 is a schematic diagram showing a configuration of an optical system of a magneto-optical disk device which has been conventionally used. A light flux emitted from a light source such as a semiconductor laser is shaped by a collimator lens or the like and passed through a beam splitter 1. By doing so, a linearly polarized light beam having one polarization component is formed, and the light beam is condensed by the objective lens 2 and applied to the magneto-optical disk 3 having a perpendicular magnetization film. The irradiated light flux is reflected in a state in which the polarization plane is rotated by a predetermined angle due to the so-called Kerr effect according to the magnetization direction of the magnetizing film. The reflected light again enters the beam splitter 1 via the objective lens 2, and the light flux reflected by the polarization separation film 4 provided on the joint surface of the beam splitter 1 is emitted to the Wollaston prism 5. The light flux incident on the Wollaston prism 5 is separated and emitted into two light fluxes each having a P-polarized component and an S-polarized component of two components whose polarization planes are orthogonal to each other.

Then, the two light beams are bent by the reflection mirror 6 arranged at the next stage of the Wollaston prism 5 and are made incident on the light receiving elements 7 and 7 ', respectively, to detect the light amount, and both outputs are output. The information on the magneto-optical disk 3 can be read by obtaining the difference between the two by the differential detector 8. As is well known, in recent years, in the field of electronic equipment, performance and miniaturization have always been demanded, and this requirement has been dealt with by providing a reflection mirror 6 and bending the optical axis of a light beam as shown in FIG.

However, in the optical system of the magneto-optical disk device having the above-mentioned structure, there is a contradiction that the number of components of the reflection mirror 6 is increased in order to achieve the purpose of downsizing. There is a defect that the miniaturization effect is small, the assembly is complicated, and the manufacturing cost is increased.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to eliminate the defects in the optical system of the conventional optical recording apparatus as described above, and the number of parts constituting the optical system of the optical recording apparatus is reduced. It is an object of the present invention to provide a composite prism which can be reduced in size and size, and can be easily assembled during manufacturing.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, a compound prism according to the present invention is provided with an exit surface of an optical rotator for rotating a polarization plane of incident light by a predetermined angle and outputting the same, and for reflecting the incident light in a direction of the exit surface. A structure in which an incident surface of a crystal body having a reflecting surface is combined, and the optical axis of the crystal body is substantially perpendicular to the optical axis of the incident light and is substantially parallel to the optical axis of the emitted light. As a result, the light flux incident on the compound prism is changed in the direction of the optical axis of the light flux on the reflection surface of the crystal body, and the polarization plane has a P polarization component and an S polarization component which are orthogonal to each other. It separates and emits into a light flux of a book. Further, the polarization plane of the light flux incident on the optical rotator is rotated by 45 ° and emitted, whereby the angle formed between the polarization plane of the light flux incident on the incidence plane of the crystal and the optical axis is 45 °. And separate and output 2
The light amount of the light flux of the book is the same.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings showing the embodiments. FIGS. 1 (a) and 1 (b) are a front view and an exploded perspective view showing the structure of an embodiment of a composite prism 9 according to the present invention. The crystal body 11 has an extremely simple structure in which the incident surface of the body 11 is coupled, and the crystal body 11 is configured to reflect the incident light flux on the reflection surface 12 and emit it to the emission surface. Thus, the compound prism 9 makes the optical axis of the crystal body 11 substantially perpendicular to the optical axis of the incident light beam and substantially parallel to the optical axis of the emitted light beam, and the optical rotator 10 causes the optical axis and the crystal body 11 to be parallel. By setting the angle formed by the plane of polarization of the light beam incident on the optical axis to be larger than 0 ° and smaller than 90 °, the reflecting surface 1 can be formed as in the case of the conventional Wollaston prism.
The light beam reflected at 2 has P whose polarization planes are orthogonal to each other.
It separates and emits as two light fluxes each having a polarization component and an S polarization component.

FIG. 2 shows a structure in which the composite prism 9 according to the present invention shown in FIG. 1 is used in an optical system of a magneto-optical disk device, and the same reference numerals as those in FIGS. 1 and 4 are the same. The explanation is omitted. Conventionally, as shown in FIG. 2, a portion which is composed of a Wollaston prism 5 having a light beam separating function and a reflection mirror 6 for bending the light beam emitted from the prism as shown in FIG. 4 is related to the present invention. It is possible to configure with only the composite prism 9, and it is possible to realize miniaturization and reduction in the number of parts at the same time.

When the angle between the optical axis of the crystal body 11 and the plane of polarization of the light beam incident on the crystal body 11 of the compound prism 9 is 45 °, the light amounts of the two light beams separated and emitted are separated. However, since the polarization plane of the emitted light of the beam splitter 1 is a light flux parallel or orthogonal to the optical axis, the rotator 10 has a polarization plane of 4 for the incident light.
Output by rotating 5 °, eg 45 ° optical rotating plate or 1
It is desirable to use a half wave plate. Further, when used in the optical system of the magneto-optical disk device, as shown in FIG.
The exit surface of the beam splitter 1 may be combined with and integrated with the entrance surface of the composite prism 9 according to the present invention shown in FIG. And the antireflection film, which had to be formed on the exit surface of the beam splitter 1 and the entrance surface of the optical rotator 10 in the related art, can be omitted. There are too many supplements. The invention of the present application is not limited to the configurations of the above-described embodiments. For example, if the crystal has a reflecting surface and has an optical axis satisfying the above-mentioned conditions, it may be a right-angle prism. It goes without saying that it is not necessary.

[0010]

Since the present invention is constructed as described above, it is possible to reduce the number of parts constituting the optical system of the optical recording apparatus to reduce the size and to facilitate the assembly at the time of manufacturing. In addition, it has a significant effect on cost reduction.

[0011]

[Brief description of drawings]

1A and 1B are a front view and an exploded perspective view showing a configuration of an embodiment of a composite prism according to the present invention.

FIG. 2 is a schematic diagram showing an optical system of a magneto-optical disk device using the compound prism of FIG.

FIG. 3 is a diagram showing a configuration of a modified example of the composite prism according to the present invention.

FIG. 4 is a schematic diagram showing an optical system of a magneto-optical disk device using a conventional composite prism.

[Explanation of symbols]

 1 ... Beam Splitter 9 ... Composite Prism 10 ... Optical Rotator 11 ... Crystal 12 ... Reflective Surface

Claims (3)

[Claims] 1. A composite in which at least an exit surface of an optical rotator that rotates a polarization plane of incident light by a predetermined angle to emit it and an entrance surface of a crystal body having a reflection surface for reflecting the incident light in the exit surface direction are combined. A composite prism, wherein the optical axis of the crystal is substantially perpendicular to the optical axis of incident light and substantially parallel to the optical axis of emitted light. 2. The compound prism according to claim 1, wherein the optical rotator rotates a polarization plane of a light beam incident on the optical rotator by 45 ° and outputs the light. 3. The composite prism according to claim 1, wherein an exit surface of the polarization beam splitter is coupled to an entrance surface of the optical rotator.