JPH03179301A - Polarizing prism - Google Patents

Abstract

PURPOSE:To obtain high-resolution polarization characteristics with small-sized constitution by forming the polarizing prism of anisotropic crystal so that its incidence surface of luminous flux is parallel to the optical axis, and its projection surface with a angle specific to the incidence surface. CONSTITUTION:The polarizing prism 1 consists of a triangular prism of artificial crystal of a compound material as anisotropic crystal. When the luminous flux is made incident, the luminous flux is parallel to the optical axis (Z axis) of the incidence surface 1a and the projection surface 1b intersection the incidence surface 1a on a ridge 5 is at the angle alpha to the optical axis (Z axis). Here, 0 deg. < alpha < 90 deg.. Consequently, light 2 which is made incident at right angles to the optical axis is polarized into projection light 3 and projection light 4 which have a mutual separation angle theta and 90 deg. different polarizing characteristics by the birefringence that the crystal has. Consequently, the high- resolution polarization characteristics are obtained and the prism can be made compact and lightweight.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a polarizing prism, and more particularly to a polarizing prism of an epsilon crystal having birefringence.

B3 Summary of the Invention The purpose of the present invention is to provide a small polarizing prism having high-resolution polarization characteristics, which is made of an anisotropic crystal, and which forms the incident surface of the light beam parallel to the optical axis. On the other hand, the polarizing prism has an exit surface with an angle of α (0° <α <90°), so compared to the Wallaston prism, which was conventionally constructed by a combination of multiple prisms, it can be used alone. We can provide high quality polarizers.

C0 As is well known in the art, a polarizing prism made of a birefringent material is a triangular crystal prism l0Ia as shown in FIG.

101b are connected such that their optical axes (Z-axes) are perpendicular to each other. (a) shows a side view, and (b) shows a front view. This polarizing prism 101 is a triangular prism 101a, 101 whose optical axis (Z axis) is in a certain direction.
The two pieces of b are optically glued together, and the incident light +03 is
It has a characteristic of separating the emitted light into two light beams 103a and 103b having polarization characteristics of .degree.

Conventionally, polarizing prisms have been widely used as optical heads for detecting information in magneto-optical disk drives. FIG. 3 shows the configuration of an optical head of a magneto-optical disk device, in which light source 1!
Lens I09. The light beam focused by the correction prism +08 is irradiated onto the disk 104.
The light reflected from the surface passes through the focusing lens IO5 and the quarter-wave plate 106, is polarized by the polarizing beam splitter 107, passes through the light receiving lens 111, and enters the polarizing prism 1.
03.

The incident light is transmitted through a polarizing prism 103 to a tracking photodiode 112 that detects the tracking state of the disk 104 and a force sensing photodiode 11.
The disc information detected by each photodiode is sequentially processed.

D1 Problems to be solved by the invention With the development of magneto-optical disk technology in recent years, the performance of the optical head, which is the center of information detection on the disk, has improved.

There is a demand for smaller size and lower cost.

However, conventional polarizing prisms consist of 2 to 3 triangular prisms.
Because of the configuration in which they are individually bonded, they are expensive, and because of the bonding process, there are variations in quality, so improvements were needed to meet the demands for stable high precision and high quality. Furthermore, the direction of light reception is subject to mechanical restrictions, making it difficult to miniaturize.

Furthermore, if a polarizing prism has foreign objects such as deposits on the surface that emits transmitted light and the surface that emits reflected light, the light will attenuate and cause detection errors to the photodiode in the light receiving section. was required.

The present invention was made in view of the above problems, and an object of the present invention is to provide a polarizing prism that is small and has high-resolution polarization characteristics.

E6 Means for Solving Problems The present invention is characterized by a single triangular prism made of an anisotropic crystal. It is a polarizing prism made of an anisotropic crystal, and the incident surface of the light beam is aligned with the optical axis (Z axis). ) and has an exit surface formed at an angle of α (however, Oo<α<90') with respect to the entrance surface.

F2 effect By using the above means, due to the birefringent property of the anisotropic crystal, the incident light incident at right angles to the optical axis (Z axis) has a separation angle of θ° from the exit surface. 90
° Two beams of light with different polarization characteristics are emitted.

G. Examples The present invention will be described in detail below. Figure 1 is a diagram explaining the configuration and functions of this embodiment, where (a) is a front view and (b) is a front view.
The figure is a side view.

The polarizing prism l of this embodiment is constituted by an artificial quartz triangular prism made of birefringent material as an anisotropic crystal. As shown in Figure (a), the polarizing prism l is formed parallel to the optical axis (Z-axis) of the entrance surface 1a on which the light flux enters, and the exit surface 1b, which intersects this entrance surface 1a at the ridge line 2, is parallel to the optical axis (Z-axis).
It is formed at an angle α with respect to the axis).

In this embodiment, the inclination angle α of the exit surface 1b with respect to the optical axis is set to 37°, and the ridge line 2 is formed at an angle of 45° with the optical axis.

A polarizing prism with the above configuration! (The light 2 incident perpendicularly to the incident surface 1a parallel to the optical axis, that is, perpendicularly to the optical axis, passes through the complex provided by the crystal at the exit surface 1b forming an angle of 37° with the incident surface 1a. Due to the refractive index, the light beams are polarized into the emitted light 3 and the emitted light 4, which have sharply different polarization characteristics by 90 degrees by FT at a separation angle of θ.

Furthermore, in this example, the relationship between the incident light 2 and the output light 3.4 was tested using polarizing prisms in which the inclination angle α formed by the incident surface 1a and the output surface 1b was configured at various angles. As a result, corresponding to the configuration in which the inclination angle α is changed in the range of 0° < α < 90°,
It was confirmed that the separation angle θ between the emitted light 3 and the emitted light 4 can be varied in various ways.

Although the polarizing prism of this embodiment has been described using artificial quartz crystal, it is of course applicable to other anisotropic crystals having birefringence characteristics.

H. Effects of the Invention As explained above, the polarizing prism of the present invention is made of an anisotropic crystal, and the incident surface of the light beam is formed parallel to the optical axis (Z axis), and α (however, 0 °〈α＜90'
), firstly, the conventional triangular prism, which uses two or three, can be constructed with one single prism, making it easier to create a lunar prism.

It has become possible to process and manufacture with a high yield, and it can now be provided at a low cost.

Second, it has become possible to uniformly manage high-resolution, high-precision quality, making it easier to improve product quality.

Thirdly, the separation angle (width) of the two light beams on the exit surface can be easily changed, and since the triangular prism is a single unit, the optical head can be made more compact and lightweight.

Fourthly, by changing the inclination angle α of the output surface, the separation angle θ of each beam can be changed, which facilitates the design of the optical system, and since each output beam has polarization characteristics that differ by 90°,
It can be widely applied not only to optical heads of magneto-optical disks but also to optical systems that require polarization characteristics.

Fifth, since the emitted light beams are on the same plane, there is no difference in the intensity change of each emitted light beam due to deposits on the surface.

[Brief explanation of drawings]

FIG. 2 is a diagram for explaining the configuration and functions of an embodiment of the present invention, and FIGS. 2 and 3 are diagrams for explaining an embodiment of the prior art. l...Polarizing prism, 1a...Incidence surface, ■b...
Output surface, 2...Incoming light, 3.4... Outgoing light, 5...
Edge line, α...Inclination angle (angle formed by the incident surface and the exit surface), θ...Separation angle between the emitted light 3 and the emitted light 4, Z axis...Optical axis. Figure 1 (Q) (b) Figure 2 (0) (b) Figure 3 104 degree isk

Claims (1)

[Claims] (1) A polarizing prism made of anisotropic crystal, in which the incident surface of the light flux is formed parallel to the optical axis (Z-axis) and at an angle of α (however, 0°<α<90°) with respect to the incident surface. A polarizing prism characterized by having an exit surface with.