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AssigneesNippon Hoso Kyokai, Sumitomo Electric Industries, Ltd.
InventorsKuniharu Takizawa, Hideo Fujikake, Tsunehiro Hirabayashi, Yoshiaki Tanaka, Kensaku Takata, Satoshi Takano, Tohru Kashiwagi
Estimating the term…
An illumination apparatus includes a liquid crystal device (L) disposed in the optical path of light projected from a light source (P) and a driving circuit (D) connected to the liquid crystal device for applying a special driving voltage to a composite film (1) of the device (L). The applied driving voltage alternately causes the composite film (1) to attain an opaque state and a transparent state. The time periods of the alternating voltage pulses are varied, thereby changing the ratio of the duration of the opaque state to the duration of the transparent state per unit time period, and thus controlling the power of light transmitted through the composite film (1) without undesirably altering the color spectrum of the transmitted light.
An illumination apparatus, comprising:
An apparatus for controlling the brightness of light transmitted therethrough to intermediate brightness levels between a maximum opaque state and a maximum transmissive state while substantially maintaining in the intermediate brightness levels a nominal color spectrum of the transmitted light in the transmissive state, wherein said apparatus comprises a liquid crystal device that is arranged in the path of the light and that includes a liquid crystal composite film sandwiched between two transparent conductive films, wherein said composite film includes a liquid crystal material non-uniformly dispersed within a transparent matrix film such that said composite film substantially maintains the nominal spectrum of the transmitted light also in the maximum opaque state, and said apparatus further comprises a driving circuit electrically connected to said conductive films and applying across said conductive films an alternating voltage waveform that alternates between a first voltage state for a time T.sub.off in which said liquid crystal material is in the maximum opaque state and a second voltage state for a time T.sub.on in which said liquid crystal material is in the maximum transmissive state, and that has the ratio of T.sub.on /(T.sub.on +T.sub.off) adjusted to achieve a desired intermediate time-averaged perceived brightness level of the light transmitted through said liquid crystal device without substantially altering the spectrum of the transmitted light from the nominal spectrum of the transmitted light in the transmissive state.
Dependencies are inferred from the claim text.