| 摘要 |
<p>1,120,093. Light modulators. WESTING- HOUSE ELECTRIC CORP. 8 June, 1966 [29 June, 1965], No. 25455/66. Heading H4F. [Also in Division H1] A light control element in a display system comprises a cholesteric phase liquid crystal film which exhibits a change in its optical properties in response to temperature changes. The optical properties of the cholesteric liquid crystal film utilized in the embodiments described are optical activity, circular dichroism and selective scattering, i.e. reflection. In a first embodiment, Fig. 1, the light control element 15 comprises a liquid crystal film 21 in good thermal contact with a layer 17 exhibiting the property of absorbing modulated ultra-violet radiation from a cathode-ray tube 27 and converting the radiation image into a heat image. The light control element is positioned between a polarizer 11 and an analyzer 13 and as the temperature of the liquid crystal film is changed it rotates the plane of polarization of input monochromatic light beam 35 varying amounts and thus an information image is formed on screen 41. Layer 17 may comprise tartrazine, anthracene or phenanthrene which do not absorb the radiation from source 35. Alternatively, layer 17 may comprise nickel which absorbs about half of the incident radiation from source 35 and tube 27 and transmits a quarter of the remaining. The circular dichroic properties, i.e. the selective scattering of right- or left-hand circularly polarized light, of the film may be used by removing polarizer 11 and analyzer 13 and positioning a circular polarizer between light source 35 and control element 15, the polarizer and the film being of the same polarization, i.e. right- or left-hand. Source 35 need not be monochromatic and depending on the temperature of the film 21 the transmission properties of the polarizer, analyzer and control element vary due to the circular dichroism effect within the optical activity range of the material of the film, Fig. 4, not shown. Three separate systems may be employed using red, green and blue radiation sources to produce a sequential or simultaneous high intensity colour television image. In a second embodiment, Fig. 2, not shown, the control element is formed within a cathoderay tube and the heat image is produced by bombarding the control element with a modulated electron beam. To increase the speed of response the inner surface of the tube is coated with a plastic film, the heat conductivity of which reduces the thermal time constant of the system. In a third embodiment, utilizing the reflection, i.e. selective scattering, properties of the cholesteric liquid crystal film, the control element is formed on the inner surface of the face plate of a cathode-ray tube, Fig. 5, not shown. The control element is provided with a light-absorbing black coating adjacent the liquid crystal film so that light from a white light source is reflected, the colour of the reflected light depending on the temperature of the liquid crystal film, i.e. on the intensity of the video signal which modulates the electron beam.</p> |
