1984-07-06
1989-01-10
Arnold, Bruce Y.
350353, 350359, G02F 101
Patent
active
047969822
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an optical valve for switching on and off a light beam and, more particularly, to a basic arrangement of a high-speed optical valve for switching on and off a laser beam or a white light beam.
BACKGROUND ART
A conventional mechanical optical valve, such as a rotary chopper, rotary mirror or the like, has been able to provide only a low switching speed on the order of several tens of kHz. On the other hand, modern high quality image processing requires a high switching speed of several tens of MHz. Thus, the conventional mechanical optical valve cannot be used practically for such purposes.
SUMMARY OF THE INVENTION
Under these circumstances, the present invention aims at providing a novel high-speed optical valve which is capable of switching a light beam electrically.
To this end, the invention provides an optical valve comprising a transparent prism having a light input surface and a light output surface, is formed with a reflective control layer directly deposited on the bottom surface of the prism, wherein the switching of light is effected by applying an electric signal to the reflective control layer.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view showing a basic arrangement of an optical valve in accordance with the invention;
FIG. 2 is a sectional view showing an essential part of an embodiment of the optical valve in accordance with the invention;
FIG. 3 is a sectional view of an improved optical valve in accordance with the invention; and
FIG. 4 is a plan view of a heat generating member.
DESCRIPTION OF THE BEST MODE FOR CARRYING OUT THE INVENTION
Referring first to FIG. 1 showing the basic arrangement of an optical valve in accordance with the invention, the optical valve 10 including a transparent prism 13 having a light input surface 11 and a light output surface 12, is characterized by a reflective control layer 15 deposited on the bottom surface 14 of the prism 13. The refractive index of the prism 13 is selected to be greater than that of the reflective control layer 15. A light beam 16 is applied to the prism 13 at an incidence angle .theta., toward the central point O of the bottom surface through the light input surface 11. If the angle .theta. of incidence is greater than the total reflection critical angle which is determined by the prism 13 and the reflective control layer 15, the incident light is totally reflected at the central point O of the bottom surface of the prism 13 and is emitted through the output surface 12 as the reflected light 161. On the other hand by selecting an incident angle .theta. which is slightly smaller than the critical angle mentioned above the incident light 16 passes through the central point O of the bottom surface and is emitted through the bottom surface 14 of the prism as the transmitted light 162, because the condition for total reflection is not met in this case. If, however, the refractive index of the reflective control layer 15 is decreased by, for example, an externally supplied electric signal, the above-mentioned condition for total reflection is satisfied so that the incident light is totally reflected and emitted as the reflected light 161. Obviously, the same incident light can be emitted as the transmitted light 162 by increasing the refractive index of the reflective control layer 15 by the electric signal. Thus, the prism 13 serves as an optical switch for switching the incident light either to the reflected light 161 or the transmitted light 162.
The present inventors have found that, when using a thin deposited film of an electro-optical material having a film thickness not smaller than the wavelength of the incident light 16 and by applying an electric field as the electric signal around the central point O of the reflective control layer 15, it is possible to decrease the refractive index around the central point O thereby attaining a valve function for switching the light. Examples of such electrooptical material are materials of the ABO.sub.3 type, su
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"Total Reflection Liquid-Crystal Electrooptic Device", by R. A. Kashnov, Applied Optics, vol. 12, No. 10, Oct. 1973, pp. 2309-2311.
"Nematic Liquid Crystal Digital Light Deflector", by G. Labrunie, Applied Optics, vol. 13, No. 8, Aug. 1974, pp. 1802-1806.
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Kitabatake Makoto
Setsune Kentaro
Wasa Kiyotaka
Arnold Bruce Y.
Matsushita Electric - Industrial Co., Ltd.
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