Liquid crystal dimmer plate and lighting system including the same

• US 5,764,316 A
• Filed: 09/28/1993
• Issued: 06/09/1998
• Est. Priority Date: 01/30/1992
• Status: Expired due to Term

• Current Assignee: Nippon Hoso Kyokai
• Original Assignee: Nippon Hoso Kyokai, Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Takata, Kensaku, Kasahara, Takamichi, Takizawa, Kuniharu, Katsuda, Morihiko, Kobayashi, Osamu, Nakamura, Masanori, Tanaka, Yoshiaki, Kashiwagi, Tohru, Tachikawa, Hiroshi, Fujikake, Hideo
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Duong, Tai V.
• Application Number:
  US08/122,576
• Time in Patent Office: 1,715 Days
• Field of Search: 359/48, 359/49, 359/51, 359/52, 359/66, 359/599, 362/16, 362/17, 362/18, 362/287, 362/307, 362/308, 362/318, 352/131, 352/244, 396/4, 396/164, 396/175, 396/205, 349/1, 349/113, 349/33, 349/114, 349/57, 349/58, 349/86, 349/193, 349/104, 349/105, 349/179
• US Class Current: 349/1
• CPC Class Codes: F21V 11/00 Screens not covered by groups F21V1/00, F21V3/00, F21V7/00 or F21V9/00 characterised by cooling arrangements F21V29/502
• CPC Class Codes: F21V 14/003 by interposition of elements with electrically controlled variable light transmissivity, e.g. liquid crystal elements or electrochromic devices
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 2203/05 wavelength dependent

Abstract

A lighting system has a light source (2), a liquid crystal dimmer plate (4) for scattering a desired quantity of light from the light source (2), and a control power supply (5) for controlling a light scattering rate or effect of the liquid crystal dimmer plate (4). A light component transmitted through the liquid crystal dimmer plate (4) can be controlled by controlling the scattering effect of the dimmer plate (4). The so controlled light can be used as an illuminating light for a camera for example.

Claims

1. A lighting system comprising:

a light source (2) emitting light for illuminating an object to be photographed by a camera having a frame frequency;

a liquid crystal dimmer plate (4) having control electrodes for scattering a desired quantity of said light from said light source (2); and

a control power supply (5) connected to said control electrodes of said dimmer plate (4) for generating an alternating control voltage for controlling a light scattering rate of said liquid crystal dimmer plate (4), said control voltage having a frequency corresponding to an integer times said frame frequency of said camera, and

wherein a part of said light from said light source (2), passes through said liquid crystal dimmer plate (4) without being scattered for illuminating said object, said system further comprising at least one optical lens (17) and an optical diaphragm (18) for selectively eliminating light scattered by said liquid crystal dimmer plate (4).

2. The lighting system in accordance with claim 1, wherein said control electrodes of said liquid crystal dimmer plate (4) include:

two transparent electrodes (11A, 11B),

a resin layer (7) held between said transparent electrodes (11A, 11B), and

a liquid crystal (8) dispersed in said resin layer (7), said liquid crystal including at least one of a nematic liquid crystal, a cholesteric liquid crystal and a smectic liquid crystal,

said resin layer (7) having a refractive index equivalent to an ordinary light refractive index of said liquid crystal (8).

3. The lighting system in accordance with claim 1, wherein said liquid crystal dimmer plate (4) comprises:

two transparent electrodes (11A, 11B),

a resin layer (7) held between said transparent electrodes (11A, 11B), and

a liquid crystal material (8) dispersed in said resin layer (7), said liquid crystal material (8) including a cholesteric phase,

wherein said liquid crystal material (8) having said cholesteric phase is a chiral nematic liquid crystal prepared by adding a chiral component to a nematic liquid crystal, and wherein a concentration of said chiral component is so adjusted that a transmittance for light in a shorter wavelength region is substantially identical to or larger than a transmittance for light in a longer wavelength region even if said control voltage applied across said transparent electrodes (11A, 11B) is changed.

4. The lighting system in accordance with claim 1, wherein a dielectric multilayer film (16) for transmitting visible light included in said light from said light source (2) and for reflecting at least one of infrared rays and ultraviolet rays, is positioned between said light source (2) and said liquid crystal dimmer plate (4).

5. The lighting system in accordance with claim 1, further comprising a dielectric multilayer film positioned for transmitting at least one of infrared rays and ultraviolet rays included in said light from said light source (2) and to reflect visible light toward said liquid crystal dimmer plate (4).

6. The lighting system in accordance with claim 1, further comprising a cylindrical casing (15) for mounting said light source (2) and said liquid crystal dimmer plate (4), said casing (15) having an opening for passing illuminating light (13) through said liquid crystal dimmer plate (4) and through said opening to the exterior.

7. The lighting system in accordance with claim 2, wherein said resin layer (7) held between said transparent electrodes (11A, 11B) is a transparent resin layer.

8. The lighting system in accordance with claim 2, further comprising a cylindrical casing (15) for mounting said light source (2) and said liquid crystal dimmer plate (4), said casing (15) having an opening for passing illuminating light (13) through said liquid crystal dimmer plate (4) and through said opening to the exterior.

9. The lighting system in accordance with claim 3, further comprising a cylindrical casing (15) for mounting said light source (2) and said liquid crystal dimmer plate (4), said casing (15) having an opening for passing illuminating light (13) through said liquid crystal dimmer plate (4) and through said opening to the exterior.

10. The lighting system in accordance with claim 4, further comprising a cylindrical casing (15) for mounting said light source (2) and said liquid crystal dimmer plate (4), said casing (15) having an opening for passing illuminating light (13) through said liquid crystal dimmer plate (4) and through said opening to the exterior.

11. The lighting system in accordance with claim 5, further comprising a cylindrical casing (15) for mounting said light source (2) and said liquid crystal dimmer plate (4), said casing (15) having an opening for passing illuminating light (13) through said liquid crystal dimmer plate (4) and through said opening to the exterior.