JPS6142613A - Optical modulating device - Google Patents

Abstract

PURPOSE:To obtain sufficiently a separation angle by a simple and small-sized constitution by providing an optical element for increasing a luminous flux separation angle of a modulating luminous flux and a non-modulating luminous flux, on the luminous flux emitting side of an optical modulating element in which the separation angle of the modulating luminous flux and the non-modulating luminous flux is small. CONSTITUTION:An irradiating luminous flux 28 by a light source 21 and an illuminating system 22 is made incident vertically on a deflecting element 24, and in case when the deflecting element 24 is not in a deflecting operation, a light source image 25 is formed on the optical axis of the illuminating system. On the other hand, in case the deflecting element is in a deflecting operation, said luminous flux is reflected as a deflected luminous flux 29 by the deflecting element 24. In this case, a volume type hologram 23 is constituted so as to satisfy a Bragg angle with respect to an incident angle to the hologram of the deflected luminous flux 29. In this way, only the deflected luminous flux can amplify an angle made by the optical axis of the illuminating system.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a light modulation device, and includes a planter,
This can be applied to displays, etc.

Conventionally, various optical modulation devices using elements that deflect an incident light beam according to an input signal are known.

As an example of a reflective light modulation element, for example, "Micr"
omechanial light modulat
error fabricated on
5ilicon” (Appl, Phys, Lett
, Vol. 31. There is a cantilever mirror element described in No. 8.1977).

The deflection principle of this element will be explained using FIG.

A light beam 2 incident on the thin film mirror 1 is reflected in the incident direction as a non-modulated light beam 3 when the mirror is in the state shown by the solid line in FIG. On the other hand, when a potential difference is applied between the base and the mirror, the mirror deforms as shown by the broken line due to electrostatic attraction.

As a result, the incident light beam 2 is reflected and deflected as a modulated light beam 4. Examples of transmissive light modulation elements include "Light is deflected by a change in refractive index due to heat" (Aperture Electronics, August 16, 1982) or JP-A-59-6872.
There is an element using the thermo-optic effect described in Publication No. 3. FIG. 2 shows this variable wR principle. A light beam 2 incident on a dielectric crystal 5 is emitted as an undeflected light beam 3.

However, when the heater 6 generates heat, the light is emitted as a deflected light beam 4 due to the refractive index distribution 7 generated in the crystal.

However, in the above-mentioned light modulation element, the separation angle between the modulated light flux and the non-modulated light flux is as small as a supersonic degree. When used as a light modulator by blocking either one of the two beams, in order to achieve a light modulator with a good S/N ratio, one of the two beams must be placed at a sufficient distance from the light modulator. It becomes necessary to shut it off. Furthermore, the light modulation elements shown in FIGS. 1 and 2 are arranged in a two-dimensional array or a two-dimensional array. When several light fluxes are arranged and used, the non-modulated light flux that is transmitted through the non-modulated area that does not contribute to modulation that occupies between the modulated areas that can modulate the incident light flux, or is reflected by the non-modulated area, is used as the modulated light flux. It is necessary to separate them sufficiently.

In view of the above-mentioned difficulties, it is an object of the present invention to have a simple and compact configuration that allows the angle of separation between the modulated light flux and the unmodulated light flux to be reduced even when a light modulation element with a small separation angle between the modulated light flux and the non-modulated light flux is used. The object of the present invention is to provide a light modulation device that can provide a sufficient amount of light.

In the light modulation element of the present invention, an optical element that increases the light beam separation angle between the modulated light beam and the non-modulated light beam is provided on the light beam output side of the light modulation element where the separation angle between the modulated light beam and the non-modulated light beam is small. The purpose is to achieve the above objective by providing the following. The type of element that constitutes this optical element can be appropriately selected based on the shape and function of the target light modulation element. The present invention will be explained in detail below.

Figure 7pIJ3 shows a volume hologram, which is an example of an optical element for increasing the separation angle between a modulated light beam and a non-modulated light beam used in the light modulation element of the present invention. , the inside of which can be regarded as a phase grating having an inclination of a predetermined angle ψ with respect to the plane normal of the hologram surface.
reaches the mirror 14 after passing through the hologram 10. If the surface of the mirror 14 is parallel to the surface of the hologram 10 as shown by the solid line, the incident light 11 will be
It is reflected at an angle of , and enters the hologram IO again. Here, by designing the inclination p of the grating to satisfy the Black condition with respect to the incident angle θ on the hologram surface, the light amount of the incident light can be changed to diffracted light of a specific order, for example, to the first-order diffracted light 12. It is possible to concentrate. At this time, the angle between the first-order diffracted light 12 and the normal to the hologram surface is 2p.
−θ. The above-mentioned diffraction efficiency is a function of the angle of incidence on the hologram surface, and the situation is shown in FIG.

The horizontal axis shows the incident angle, and the vertical axis shows the diffraction efficiency. The maximum diffraction efficiency is obtained when the incident angle θ satisfies the Brague condition. In the above explanation, when the incident light 11 enters the hologram at an incident angle of -0, it deviates greatly from the black condition, and as a result, most of the incident light goes straight through the hologram as zero-order light. , it is possible to maintain the same incident angle -0 with respect to the mirror 14. Let us assume that the mirror 14 is rotated by an angle of -0 as shown by the broken line as a zero-order state, which will be explained again with reference to FIG.

At this time, the incident light 11 is θ-2 with respect to the hologram 10.
It is incident at an angle of φ. However, as shown in FIG. 4, since the black condition is not met, most of the incident light passes through the hologram as zero-order light and becomes the output light 13. As can be understood from the explanation of 0 or more, the rotation of the mirror 14 Before and after the operation, the angle formed by the reflected light from each operation is 2φ immediately after reflection by the mirror, but when it passes through the hologram, it becomes 2(ψ−θ+φ).

Since ψ〉θ, the angle formed by the two rays is widened.

As a further configuration example, a flat glass plate or the like is bonded to the output side of the one-volume hologram 10, and only the first-order diffracted light 12 is totally reflected at the interface between the glass flat plate and the air, so that the light flux 13 and It is possible to make the angle formed even larger.

FIG. 5 shows an embodiment of the optical modulation device according to the present invention. In FIG. They are arranged perpendicular to the page. Light source 21. An illumination light beam 28 from the illumination system 22 is perpendicularly incident on the polarizing element 24, and forms a light source image 25 on the optical axis of the illumination system when the polarizing element 24 is not in a deflecting operation. - On the other hand, when the deflection element 24 is in a deflection (modulation) operation as shown by the broken line, the light is reflected by the deflection element 24 in the lower right direction in the drawing as a deflected light beam 29.

Here, the principle explained using FIGS. 3 and 4 can be applied by configuring the five-volume hologram 23 to satisfy the Black angle with respect to the angle of incidence of the deflected light beam 29 on the hologram. Accordingly, it is possible to widen the angle that only the deflected light beam forms with the optical axis of the illumination system. As a result, it is possible to place the imaging system 26 at a position optically separated from the light beam of the illumination system, and therefore only the polarized light beam is transmitted to the observation surface without picking up the illumination light beam (non-modulated light beam) that becomes a noise light component. It is possible to image on 27. In addition, although the example shows an arrangement of an illumination system similar to Koehler illumination in order to prevent unevenness in the amount of illumination light on the deflection element 24, it is not necessarily limited to this, and critical illumination It may be.

FIG. 6 shows a further embodiment of the light modulation element according to the invention. The feature of FIG. The result is 1. For example, it is possible to arrange the elements shown in FIG. 1 on the surface of the deflection element 24 in a two-dimensional matrix. The deflection element 24 is illuminated from below. The non-deflected (modulated) light beam specularly reflected on the surface of the deflection element 24 enters the volume hologram 23 from the lower left in the drawing, based on the principle explained using FIGS. 3 and 4. , by configuring the hologram 23 so that its volume satisfies the Black angle with respect to this incident angle, the angle formed with respect to the optical axis of the imaging system 26 can be increased.
It is possible to do tJ. On the other hand, the deflected (modulated) light beam shown by the broken line is imaged on the observation surface 27 by the imaging system 26 without being influenced by the one-body M1 base hologram 23.

FIG. 7 is a diagram showing a further embodiment of the light modulation device according to the present invention, in which the light modulation device 32 is deflected (modulated) using the light modulation device shown in FIG. 2 as the light modulation device. ) When not in the operating state, the illumination light beam 36 from the laser beam IX31 passes straight through the light modulation element 32 and enters the volume type gologram 33 described above. By configuring the hologram 33 to satisfy the black condition for the incident angle at this time, the undeflected (variant 2J!I) light beam 37 becomes
On the other hand, when the element is in the operating state, the deflected (modulated) light beam 38 shown by the broken line travels straight through the one-volume hologram and is focused onto the observation surface 35 by the imaging system 34. Even in this embodiment, the light modulation element 32 may be a one-dimensional array light modulation element having a plurality of variable wR elements in the direction perpendicular to the plane of the paper.

In the above embodiments, the light source is not necessarily limited to a monochromatic light source.

The above is the light modulation element according to the present invention.

By disposing means for increasing the angle formed by the modulated light beam and the non-modulated light beam on the light beam output side of the light modulation element, it is possible to provide a light modulation device with a good S/N ratio with a simple configuration.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 each show an example of a conventional light modulation element, and FIG. 3 and wIJ4 illustrate a volume hologram that is an example of an optical element used in the light modulation device of the present invention. FIG. 5, FIG. 6, and FIG. 7 are views each showing an embodiment of the light modulation element according to the present invention. 21------One light source 22---One illumination system 23---One volume hologram 24---One light modulation element 25---One light source image 26------ ---One imaging system 2-7--------Observation surface 28-----One illumination light beam 29--One deflection light beam one θ z-zp1 Hand Toe Nyū Orthographic (Method) Patent Agency Commissioner Manabu Shiga 1, Indication of the case Patent Application No. 164403 of 1982, 2 Name of the invention Light modulation device 3, Person making the amendment Relationship to the case Patent applicant address 3-30 Shimomaruko, Ota-ku, Tokyo 2 names (100
) Can Co., Ltd. Representative Noh Kaku 3 Department 4, Agent residence 3-30-25 Shimomaruko, Ota-ku, Tokyo 148 Date of amendment order (shipment date) November 27, 1980 6, Amendment Target specification M 7, content of amendment (1), 3rd line of page 2 of the specification, ““Micro’ma”
rll on the 5th line from canica11! ? ? ) J (Correct the existing description as follows. Note: Micro-mechanical light, modulator, array, fabricator, on, silicon (Micr
omachanical light modulat
or arra7fabricated an 5il
icon)"Applied,Physics,Letter,Volume,31,Number 8,' l 977 (AP
PL, PHYS, LETT, vol, 31. N
o, 8゜' 1fl? ? )J

Claims (2)

[Claims] (1) In a light modulation device equipped with a light modulation element that makes the output direction of an incident light beam variable in accordance with an input signal, a light beam modulated by the light modulation element and a light beam modulated by the light modulation element are placed on the light output side of the light modulation element. A light modulation device characterized by having an optical member arranged to increase the separation angle from a light beam that is not received. (2) The light modulation according to claim 1, wherein the optical member is a volume hologram that satisfies a black condition for either a modulated light flux or a non-modulated light flux emitted from a light modulation element. Device.