| 摘要 |
PROBLEM TO BE SOLVED: To miniaturize a device and to reduce the cost of the device by adopting holographic optical elements(HOEs) as a light separating means and a light synthesizing means. SOLUTION: HOEs becoming the light separating means and the light synthesizing means are made to be constitutions in which a transmission type hologram and a reflection type hologram respective have selectivities in diffracted wavelengths are laminatingly synthesized. In this case, only two sheets of HOEs of an HOE 20 as a light separating means and an HOE 28 as a light synthesizing means are needed. Moreover, four sheets of mirrors become necessary for mirrors 21-24 and the number of mirrors is increased as compared with that of a conventional device, however, an effect is small in the point of the rise of cost and the device becomes to have an advantage in the optical characteristic of the device more than the increasing of the number of mirrors. Then, since liquid crystal light valves 11∼13 are arranged just before the light synthesizing means HOE 28 and optical paths of respective video lights are nor complex and the distance between the liquid crystal light valves and a projection lens can be set shortly, it is made east toe cope with the miniaturizing of the device.
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