JPH03288881A - Optical device - Google Patents

Abstract

PURPOSE:To control a laser beam position by a simple means by providing the optical system with a lens group arranged before and after a liquid crystal light bulb and a pattern generator for recording a computer hologram in the light bulb. CONSTITUTION:Laser beams 109 projected from a laser light source 104 are converted into parallel light expanded by a collimeter lens 105 and made incident upon the liquid crystal light bulb 106. A liquid face is modulated by the action of the computer hologram recorded on the light bulb 106 and the beams pass through a lens to form a spot 110 on a prescribed output face 108. A video signal for recording the computer hologram on the light bulb 106 is formed by personal computer (PC) 101 and displayed by 16 gradations in each picture element and pattern data previously stored in a video memory 102 in the PC 101 are successively read out. Consequently, laser beam position control and the generation of an irregular spot array are executed by the simple means at real time.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an optical device using a hologram.

[Prior art 1] Conventional laser beam position control technology has mainly utilized mechanically movable parts such as polygon mirrors and galvano mirrors.

[Problems to be Solved by the Invention] However, with the conventional technology, in order to freely control the laser beam position in three-dimensional space, the scale of the equipment is very large6, and there are very few applications that can find industrial value. There weren't many.

The present invention aims to solve these problems6, and its purpose is to provide a laser beam position control technique using simple means.

[Means for Solving the Problems] A first optical device of the present invention includes a liquid crystal light valve, a lens group arranged before and after the liquid crystal light valve, and a computer-generated hologram for recording a computer-generated hologram on the liquid crystal light valve. A pattern generator.

A second optical device of the present invention is characterized in that, in the first optical device, the liquid crystal light valve is a TN mode liquid crystal panel;
It consists of two polarizing plates placed before and after the liquid crystal panel with their axes perpendicular to each other, and the transmission axis direction of the polarizing plate on the side where the laser beam is incident is set to the liquid crystal molecule director on the incident surface. It is characterized by being orthogonal.

A third optical device of the present invention is characterized in that, in the first or second optical device, the liquid crystal light valve is of a TFT active matrix type.

In a fourth optical device of the present invention, in the first to third optical devices, the computer generated hologram is a Fourier transform amplitude hologram, and one Fourier data is expressed by nine pixels of the light valve. It is characterized by

[Example] The content of the present invention will be described in detail below based on Example 6.

FIG. 1 shows the configuration of the optical device of the present invention. A laser beam 109 emitted from a laser light source 104 becomes parallel light that is expanded by a collimator lens 105 and enters a liquid crystal light valve 106. Then, the wavefront is modulated by the action of the computer-generated hologram recorded on the liquid crystal light valve 106, and after passing through the lens 107, a laser beam spot 110 is formed on a predetermined output surface 108.

A video signal for recording a computer-generated hologram on the liquid crystal light valve 106 is generated by a personal computer (PC) 1.
Created by 01. The signal is at the interface
18103 to the liquid crystal light valve, and is displayed in 16 gradations for each pixel. To rewrite the computer generated hologram displayed on the liquid crystal light valve 106 at high speed,
The pattern data stored in advance in the video memory 102 of the PCIOI may be read out one after another.

FIG. 2 shows another configuration of the optical device of the present invention. In FIG. 2(a), two mirrors 201.2'02 are used to bend the optical path. In FIG. 2(b), two light guide plates 21
1.212 was used to allow the laser beam to propagate between them.

By doing so, the optical device can be made smaller.

FIG. 3(a) is a schematic diagram showing the appearance of a liquid crystal light valve 301 which is a main component of the optical device of the present invention. This liquid crystal light valve has the following features.

(1) Crosstalk between pixels is eliminated by adding a Po1y-5i TFT to each pixel as an active element.

(2) It is a built-in driver type that takes advantage of the features of Po1y-5i TFT, and is small in size.

(3) 6 pixels of 320 pixels in the horizontal direction and 220 pixels in the vertical direction in the display area 302 of 19 x l 4 mm.

FIG. 3(b) is a schematic diagram showing the pixel structure of the liquid crystal light valve 106. The computer-generated hologram that functions in the optical device of the present invention is a Fourier transform amplitude hologram, and nine circuit elements, which are characterized by expressing one Fourier data with nine pixels 311, are arranged under the mask 3]2. ing.

By doing so, it is possible to write a computer-generated hologram to the liquid crystal light valve by effectively utilizing the limited number of pixels.

The liquid crystal light valve 301 shown in FIG.
In the present invention, which is composed of a twisted-nematic mode liquid crystal panel and two polarizing plates placed on both sides of the liquid crystal panel, the relationship between the axis directions of these elements is determined as follows.

(1) The axes of the two polarizing plates are orthogonal.

(2) The transmission axis direction of the polarizing plate on the side into which the laser beam is incident is made perpendicular to the liquid crystal molecule director on the incident surface.

The reason for this arrangement will be described below.

The liquid crystal light valve type computer generated hologram of the present invention is recorded using only the two-dimensional amplitude distribution of the laser beam. On the other hand, in TN mode liquid crystal light valves, generally
A phase change occurs along with an amplitude change (Opt, Le
tt, l 3.251-253+198811. Therefore, the relationship between the axis directions of the liquid crystal panel and the polarizing plate must be determined so that the phase change is as small as possible.

Figure 4 shows the relationship between the phase change and the voltage applied to the liquid crystal panel after four basic situations when using a TN mode liquid crystal panel. When the orientation of the polarizing plate is parallel and the orientation of the incident side polarizing plate is parallel to the liquid crystal molecule director on the incident plane, curve 2 is the polarizing plate on the incident side with the orientation of the polarizing plate parallel to the director on the incident plane. When the direction of the polarizing plate is orthogonal to the director, curve 3 is when the direction of the polarizing plate is orthogonal to the direction of the incident side polarizing plate and the direction of the incident side polarizing plate is parallel to the director. This is when it is orthogonal to .

From FIG. 4, it can be seen that the phase change is smaller by 6 when the orientations of the polarizing plates are made perpendicular to each other and the orientation of the incident side polarizing plate is made perpendicular to the director.

FIG. 5 shows the amplitude change with respect to the applied voltage when the liquid crystal panel and polarizing plate are arranged in this manner. A high contrast ratio and sufficient gradation are achieved.

By realizing these characteristics, we were able to record high-performance amplitude-type computer generated holograms on liquid crystal light valves.

As described above, according to the optical device of the present invention, highly accurate laser beam position control and irregular spot arrangement can be achieved by the optical wavefront conversion effect of the computer-generated hologram recorded on the liquid crystal light valve. can be done in real time.

The optical device of the present invention can be applied to laser beam scanning, laser beam steering, and optical interconnection.

[Effects of the Invention] According to the present invention, the laser beam position control and the generation of an irregular spot arrangement can be performed in real time by means simpler than conventional methods.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of an optical device of the present invention. FIGS. 2(a) and 2(b) are plan views showing another configuration of the optical device of the present invention. FIG. 3(a) is a plan view showing the appearance of the liquid crystal light valve. FIG. 3(b) is a plan view showing the pixel structure of the liquid crystal light valve. FIG. 4 is a diagram for explaining the phase modulation characteristics of a liquid crystal light valve. FIG. 5 is a diagram for explaining the amplitude modulation characteristics of a liquid crystal light valve. 01 02 103 ・ 04 105 ・ 106 ・ 107 ・ 108 ・ 109 ・ 10 01 202 ・ 211 ・ 212 ・ 01 ・ CPtJ ・Memory interface laser ・Frimeter lens ・Liquid crystal light valve ・Lens ・Output surface laser beam ・Spot ・Mirror ・Mirror, light guide plate, light guide plate, liquid crystal light valve 302 ・・Display area 1 ・Pixel・Mask or more

Claims (4)

[Claims] (1) Regarding the optical device that controls the position of the laser beam,
An optical device comprising a liquid crystal light valve, a group of lenses arranged before and after the liquid crystal light valve, and a pattern generator for recording a computer generated hologram on the liquid crystal light valve. (2) The liquid crystal light valve is composed of a TN mode liquid crystal panel and two polarizing plates arranged before and after the liquid crystal panel with their axes perpendicular to each other, and on the side where the laser beam is incident. 2. The optical device according to claim 1, wherein the transmission axis direction of the polarizing plate is perpendicular to the liquid crystal molecule director on the incident plane. (3) The optical device according to claim 1 or 2, wherein the liquid crystal light valve is of a TFT active matrix type. (4) The optical device according to any one of claims 1 to 3, wherein the computer generated hologram is a Fourier transform amplitude hologram, and one Fourier data is expressed by nine pixels of the liquid crystal light valve.