JPS61270731A - Reflection type light modulator - Google Patents

Abstract

PURPOSE:To improve the SN ratio of signal light by intersecting a perpendicular to the reflecting surface of a reflecting plate arranged on the back part of an optical modulator and a perpendicular to the front surface of the optical modulator at a certain angle. CONSTITUTION:The perpendicular direction 2 of the reflecting surface of the reflecting plate 1 obtained by cutting an Al base plate having a prescribed thickness by a numerically controlled lathe is intersected with the perpendicular direction 4 of the front surface of a twist nematic mode liquid crystal cell 3 at an angle theta deg. and the shape of the reflecting plate 1 is constituted by combining many fine reflecting surfaces to reduce the thickness. A light source 7 is arranged on the front and upper 45 deg. position and an optical path 6 reflected on the front of the cell 3 out of light rays projected from the light source 7 can be directed in a direction completely different from that of an optical path 5 reflected on the front of the cell 3 by setting up the angle to a proper value. Consequently, the SN ratio to be observed at the position 8 shows a high value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reflective light modulation device in which a liquid crystal and a light modulation element such as PI or ZT are applied to a reflective display or a signal conversion device.

[Summary of the invention]

The present invention relates to a reflective display that uses external light such as a desktop computer and a measuring instrument, a projection device that uses reflected light from a light modulation element, a memory that reads information using reflected light, and a system that converts information into light. In information conversion devices that use reflected light, the S/N ratio ( This is the ratio of signal light to noise light, hereinafter referred to as the S/N ratio in the text.

[Conventional technology]

Conventionally, for example, in reflective display devices that utilize the twisted nematic mode of liquid crystals, a diffuser plate made of a mirror surface of aluminum or the like that has been roughened with markings is attached to the back, and in projection display devices that use smectic thermal writing, the back surface is A mirror surface is obtained by vapor-depositing aluminum on the substrate.

[Problem that the invention seeks to solve]

However, the perpendicular to the front surface of these light modulation elements and the perpendicular to the reflective surface of the reflector plate almost coincided. Therefore, when light is projected onto a reflective light modulator, it passes through the light modulating pixel element, is reflected by the reflector, and then passes through the light modulating element again and is reflected by the front surface of the light modulating element. Because the rays are superimposed, s
/N ratio was inhibited.

SUMMARY OF THE INVENTION The present invention is intended to solve these conventional problems, and its purpose is to provide a reflection type light modulation device with a good 3/N ratio.

[Means to try to solve problems]

The light modulation device of the present invention is a light modulation device using a light modulation element such as a liquid crystal or PLZT, in which a reflection plate is provided at the rear of the light modulation element, and a line perpendicular to the reflective surface of the reflection plate and the light modulation element are provided. It is characterized by the perpendicular lines of the front surface intersect at a certain angle.

The reflecting plate may have a mirror surface or a light scattering surface depending on the purpose for which it is used.

[Effect]

Since the present invention has the above configuration, the direction of the light ray that passes through the light modulation element, is reflected by the reflection plate, and passes through the light modulation element again is different from the direction of the light ray reflected at the front surface of the light modulation element. Therefore, the light beams do not overlap at the measurement point (or light receiving point), and a good S/N ratio can be obtained.

〔Example〕

Hereinafter, the present invention will be described in detail based on an example using a liquid crystal cell to which a twisted nematic mode is applied as a light modulation element.

FIG. 1 is a sectional view of a reflective light conversion device of the present invention.

1 is a reflecting plate obtained by cutting an aluminum base plate with a thickness of 1 cIn using a No. lathe, and the perpendicular direction 2 of the reflecting surface intersects the perpendicular direction 4 of the front surface of the twisted nematic mode liquid crystal cell 5 at an angle θ0. Its shape is a combination of many tiny reflective surfaces to reduce its thickness. 7 is a light source located at a position 45° above the front surface of the cell, and 6 indicates the optical path of the light reflected from the front surface of the cell 3, which passes through the cell 5 and reaches the reflector plate 1. 5 indicates the optical path of the light that is reflected and passes through the cell 3 again.

Conventionally, as shown in FIG. 2, for example, light irradiated by a light source 7 located 45 degrees above the front surface is reflected from both optical paths 5 and 6 in a direction 45 degrees below the front surface, that is, toward an observation point 9. The light ends up being superimposed on the signal light on the optical path 5 as noise. If the reflection plate 10 is a scattering plate, a signal can be observed even in the front direction 8 of the cell, but the center of orientation is still facing the observation point 9, which is not preferable because only a very faint signal light can be observed. The S/N ratio at position 9 was 1B. On the other hand, as shown in FIG. 1, according to this embodiment, the reflected light 5 and the reflected light 6 can be directed in completely different directions by appropriately setting θ. That is, in this embodiment, by setting θ to 22.5', the reflected light 6 is distributed 45 degrees downward to the front surface, whereas the reflected light 5 is distributed perpendicularly to the front surface, and this effect is Accordingly, the S/N ratio observed at position 8 was 49, which was extremely good.The conventional example corresponds to θ=06.

When observing the display directly with the naked eye, it is desirable to set the size of θ in proportion to the magnitude of the parallax between the front end and the rear end (or left end and right end) of the display. It is desirable that θ is 3° or more.On the other hand,
In optical signal converters and projection display bodies in which the light source section or light receiving section is generally small, θ may be extremely small;
The smallest angle should be Q, 5° or more. Further, the direction of the angle θ formed by the perpendicular to the reflective surface opposite to the light source and the perpendicular to the front surface of the light conversion element may be directed toward the light source as in this embodiment, or may be opposite to the light source, or perpendicular to the light source. Or they may face oblique directions.

Further, the reflector may be cut out from a block of gold mfJ5, or may be made of plastic and a mirror or reflective surface obtained by vapor-depositing metal.

Further, as the light modulation element, in addition to one using liquid crystal such as twisted nematic mode or thermal writing smectic mode, one using the light modulation effect of a solid dielectric material such as PLZT can be used.

〔Effect of the invention〕

As described above, the present invention provides a reflective light modulation device in which the perpendicular to the reflective surface of the reflective plate provided at the rear of the light modulation element intersects the perpendicular to the light modulation element at a certain angle. As a result, we were able to separate the signal light that passed through the optical modulation element from the noise component light that was reflected in front of the optical modulation element.
This made it possible to improve the S/N ratio.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the optical modulation device of the present invention. FIG. 2 is a sectional view of a conventional reflective light modulator. FIG. 3 is a cross-sectional view of a liquid crystal cell using twisted nematic mode used in the example. 1...Reflector 2...Perpendicular to the reflective surface of the reflector 3.
......Liquid crystal cell 4...Perpendicular line 5 to the front of the liquid crystal cell
......Light ray 6 transmitted through the liquid crystal cell...
...Light ray 7 reflected from the front of the liquid crystal cell...
......Light source 8...Observation point (front direction)9...
... Observation point (45° below the front of the liquid crystal cell) 10...
... Conventional reflector 11 ... Polarizing plate 12 ... Cell substrate 13 ... Spacer 14 ... Transparent electrode 15 ... Alignment film 16...Liquid crystal molecules 17...Lead wire or more

Claims (1)

[Claims] (1) In a reflective light modulation element in which a reflection plate is provided at the rear of the light modulation element and the light transmitted through the light modulation element is guided through the light modulation element again to the front surface of the light modulation element, a line perpendicular to the reflective surface of the reflection plate is A reflective light modulator characterized in that perpendicular lines to the front surface of the light modulator intersect at a certain angle.