| 摘要 |
PURPOSE:To reduce the effect of indoor illumination light and to utilize a projection screen in a bright room by providing a control means turning a diffusion plate into a diffusing state when illuminance is low and a transparent state when the illuminance is high. CONSTITUTION:An observer can use projection screens 5a and 5b as a simple diffusion plate in such a manner that repetition is attained at a frequency so as to hardly feel a flicker by the control means 9 based on information detected by an illuminance detecting means 7. In the (a), when detecting that the illuminance by the indoor illumination light is comparatively low, the projection screen 5a is turned into a diffusion plate state and at this time, projected light L1 from a projector 1 is diffused/transmitted by the projection screen and becomes transmitted light t1D. Then, part of the transmitted light L1D is made incident on the eye of the observer 13 and the observer 13 can observe picture information by the projected light L1. In the (b), when detecting that the illuminance by the indoor illumination light, is high the projection screen 5b is turned into a transparent plate state. |
