Liquid crystal cells – elements and systems – Liquid crystal system
Patent
1993-09-28
1998-06-09
Sikes, William L.
Liquid crystal cells, elements and systems
Liquid crystal system
349 57, 349 58, 349 86, 349114, 349193, 362 18, G02F 11335, G02F 1137, G03B 1502
Patent
active
057643164
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a lighting system including a liquid crystal dimmer plate, and more particularly, it relates to a lighting system employable for TV film shooting illumination, movie film shooting illumination, photo-taking illumination, production illumination or display illumination. In such illuminations it is necessary to continuously adjust the brightness of the illuminating light over a wide range for illuminating an object to be photographed by a camera.
BACKGROUND INFORMATION
Referring to FIG. 1, an example of a conventional lighting system capable of controlling the brightness is schematically illustrated. In the known lighting system, an incandescent lamp or a discharge lamp is employed as a light source 2 comprising a reflector 1. The light source 2 is connected to a power supply 3 through a lead wire 6. When an incandescent lamp is employed as the light source 2, the brightness of the illuminating light 13 emitted from the light source 2 is adjusted by controlling a voltage which is supplied from the power supply 3 to the light source 2.
Namely, the power supply 3 provided in the lighting system of FIG. 1 includes an electronic circuit such as an SCR. Therefore, the known lighting system tends to have an increased size and weight, with the added disadvantage of a large heating value. Further, the lighting system shown in FIG. 1 also has yet another disadvantage that the time required for changing the brightness is relatively long, since the speed of response is low.
When a discharge lamp such as a xenon lamp is employed as the light source 2, on the other hand, the voltage which is supplied from the power supply 3 is adjustable only in a voltage range exceeding an ON-state voltage required for maintaining a discharge, whereby the brightness of the discharge lamp can be adjusted only in a narrow range. Moreover, when the discharge lamp is supplied with a voltage which is different from an optimum discharge maintaining voltage, the life of the discharge lamp is reduced. Once the discharge lamp is turned off, a time of several seconds is required for lighting the same again
FIG. 2 shows schematically another example of a conventional lighting system capable of adjusting the brightness. The lighting system shown in FIG. 2, which is similar to that shown in FIG. 1, includes a light damping plate 20. Light 12 which is emitted from the light source 2 passes through the light damping plate 20 to form illuminating light 13. In the lighting system shown in FIG. 2, a plurality of light damping plates 20 having different light absorption factors are selected to adjust the brightness of the illuminating light 13.
In the lighting system shown in FIG. 2, the brightness of the illuminating light 13 is adjusted through light absorption by the light damping plate 20, and hence the light damping plate 20 is readily deteriorated by heating. Therefore, no intense light source 2 can be employed and it is difficult to obtain a bright illuminating light 13. Further, the brightness of the illuminating light 13 cannot be continuously and quickly adjusted by selecting a plurality of light damping plates 20.
Referring to FIG. 3, sill another example of a conventional lighting system is schematically illustrated. The lighting system shown in FIG. 3, which is similar to that shown in FIG. 1, comprises a blind including a plurality of shading strips 21, whereby the brightness of the illuminating light 13 is adjusted by changing the inclinations of the shading strips 21.
In the lighting system shown in FIG. 3, the inclinations of the shading strips 21 are mechanically changed so that it is difficult to quickly change the brightness of the illuminating light 13. Further, the brightness on a region to be illuminated can easily become nonuniform due to influences exerted by shadows of the shading strips 21. In addition, noises are caused by the mechanical position changes of the strips 21.
SUMMARY OF THE INVENTION
In consideration of the aforementioned related art, it is an object of
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Fujikake Hideo
Kasahara Takamichi
Kashiwagi Tohru
Katsuda Morihiko
Kobayashi Osamu
Duong Tai V.
Fasse W. F.
Fasse W. G.
Nippon Hoso Kyokai
Sikes William L.
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