| 摘要 |
PURPOSE:To provide a projection type display device transmitting and receiving an image signal and a sound signal by a spatial light transmission device with high efficiency. CONSTITUTION:A photodetector part 21 is arranged near a projection lens 3, so that a large-diameter incident luminous flux made incident on a large-area screen is received with high efficiency by the condensing action of a Fresnel lens screen. The photodetector part 21 has a light guide in front of a photodetector, and efficiently receives the condensed luminous flux from all the surface of the screen. As a result, a spatial transmitting distance is easily made longer and further an angle in the allowable range of an optical signal incident angle on the screen is made wider, especially, in a horizontal direction by the diffusing effect of a lenticular screen. |
