JPH0687098B2 - Hologram disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] In a hologram disc, the light use efficiency decreases unless the polarization characteristics of the hologram disc and the polarization direction of the light source match. Therefore, by imparting different polarization characteristics to each facet, it is possible to form a hologram disc that always obtains high light use efficiency.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam scanning device used in a bar code reader or the like, and more particularly to a hologram disc having a plurality of facets having different polarization directions.

As a means for scanning a laser beam in a laser beam scanning device used for a bar code reader or the like, a mirror scanner using a reflecting mirror formed around a polyhedron has been conventionally used. In order to reduce the weight and reduce the price, a laser beam scanning device using a hologram disk has been recently developed.

The laser beam scanning device used for such a bar code reader or the like is required to be capable of multi-directional laser beam scanning, for example, horizontal scanning as well as diagonal scanning. Multi-directional scanning of laser light in a laser light scanning device using a hologram disk divides the hologram disk into a plurality of sections along the circumference (one section is called a facet), and each facet is divided into sections. This is achieved by giving different diffraction directions to each other.

However, since the output of the light source is determined according to the facet with the lowest light use efficiency, the loss of the light source increases as the difference in light use efficiency between the facets increases. Therefore, it is desired to develop a hologram disc that has different diffraction directions for each facet and can obtain the highest light use efficiency in each facet.

[Conventional technology]

FIG. 3 is a perspective view showing a conventional hologram disc.

In FIG. 3A, the conventional hologram disc 1 is
It is composed of a circular transparent substrate 11 and a medium 12 attached to the circular transparent substrate 11, and a hologram is formed by exposing the medium 12. The hologram has several types (two types in the figure) of facets 13 and 14, and the facets 13 and 14 have different diffraction directions.

In FIG. 3B, since the polarization direction of the light source 2 is S-polarized with respect to the facet 13, most of the light emitted from the light source 2 is diffracted by the facet 13 in the radial direction as shown in the figure and is focused on the point 15. . However, the hologram disc 1 is an arrow
Since it rotates in the direction of 16, the point diffracted and focused on the facet 13 moves and the locus becomes a curve 17.

When the hologram disc 1 further rotates and the light emitted from the light source 2 enters the facet 14 as shown in FIG. 3 (c), the polarization direction of the light source 2 becomes P-polarized with respect to the facet 14, so that the light source 2 emits light. A part of the emitted light is diffracted in the facet 14 in the direction parallel to the tangent line as shown in the drawing, and is focused on the point 18. However, since the hologram disk 1 is rotating in the direction of the arrow 16, the point diffracted and focused by the facet 14 moves and the locus becomes a curve 19.

[Problems to be solved by the invention]

FIG. 4 is a diagram showing an example of polarization characteristics in a conventional hologram disc, where the horizontal axis represents the polarization direction and the vertical axis represents the diffraction efficiency.

The polarization characteristic of the conventional hologram disk is uniform and, as shown in the figure, the diffraction efficiency for S-polarized waves is extremely high, but P
The diffraction efficiency decreases as it approaches the polarized wave, and the diffraction efficiency for the P polarized wave becomes extremely low. Therefore, in FIG. 3, the use efficiency of the light diffracted and focused by the facet 13 is high, but there is a problem that the use efficiency of the light diffracted and focused by the facet 14 is significantly reduced.

[Means for solving problems]

FIG. 1 is a perspective view showing a hologram disc according to the present invention.

The above problem is a hologram disk for a laser scanner, which is composed of a medium 32 containing a polymer having a carbazole ring as a main component and has several kinds of facets 33 and 34, and imparts different polarization characteristics to each of the facets 33 and 34. This is solved by the hologram disc of the present invention.

[Action]

In FIG. 1, for example, a facet 33 is formed with a hologram for increasing the diffraction efficiency for S-polarized waves,
Forming a hologram that increases the diffraction efficiency for P-polarized waves in 34, for example, by giving each facet 33, 34 different polarization characteristics, the use efficiency of the light that is diffracted and focused by facet 33 and facet 34 is increased. However, it is possible to form a hologram disc that has the highest quality.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. FIG. 2 is a diagram showing the exposure amount and polarization characteristics of a PVCz-based hologram. The horizontal axis shows the exposure amount, the vertical axis shows the diffraction efficiency, the solid line shows the polarization characteristics for S-polarized waves, and the broken line shows the polarization characteristics for P-polarized waves. .

The hologram disk 3 according to the present invention shown in FIG.
It is composed of a circular transparent substrate 11 and a medium 32 attached to the circular transparent substrate 11, and a hologram is formed by exposing the medium 32 to light. The hologram has several types (two types in the figure) of facets 33 and 34, and the facets 33 and 34 have different diffraction directions.

The medium 32 is a polymer having a carbazole ring, for example, a material having polyvinyl carbazole (PVCz) as a main component,
The hologram using this has different polarization characteristics depending on the exposure amount when forming the hologram as shown in FIG.

For example, the facet 33 that diffracts the S-polarized wave forms a hologram with the exposure amount shown in FIG. A, the facet 34 that diffracts the P-polarized wave forms a hologram with the exposure amount shown in FIG.
By imparting different polarization characteristics to the facets 33 and 34, it is possible to form a hologram disc that maximizes the use efficiency of the light diffracted and focused by the facets 33 and 34.

〔The invention's effect〕

As described above, according to the present invention, it is possible to provide a hologram disc in which the diffraction direction is different for each facet and the maximum light use efficiency is obtained in each facet.

[Brief description of drawings]

FIG. 1 is a perspective view showing a hologram disc according to the present invention, FIG. 2 is a diagram showing exposure amount and polarization characteristics of a PVCz hologram, FIG. 3 is a perspective view showing a conventional hologram disc, and FIG. FIG. 7 is a diagram showing an example of polarization characteristics of the hologram disc of FIG. In the figure, 3 is a hologram disk, 11 is a circular transparent substrate, 32 is a medium, and 33 and 34 are facets.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyuki Ikeda 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor, Yushi Inagaki 1015, Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited

Claims (1)

[Claims] 1. A medium (32) containing a polymer having a carbazole ring as a main component and comprising several kinds of facets (33, 34).
A hologram disc for a laser scanner, comprising: a facet (33, 34) having different polarization characteristics.