PROJECTION TYPE PICTURE DISPLAY DEVICE

• Main Author: EHATA YASUO
• Format: Patent
• Language: English
• Published: 18.10.1994
• Edition: 5
• Subjects: ACCESSORIES THEREFOR; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USINGWAVES OTHER THAN OPTICAL WAVES; APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FORPROJECTING OR VIEWING THEM; CINEMATOGRAPHY; ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; ELECTROGRAPHY; HOLOGRAPHY; PHOTOGRAPHY; PHYSICS; PICTORIAL COMMUNICATION, e.g. TELEVISION

PURPOSE:To prevent the contrast ratio of a projected picture from being lowered even in a bright room by making the device have a selective screen having such reflection spectral characteristics that reflectance on plural wavelength areas is high and reflectance on the other areas is low. CONSTITUTION:The projection type picture display device is constituted of a projection optical system 1 and the selective reflection screen 2 which has the reflection spectral characteristics that the reflectance is high on at least three wavelength areas and the reflectance is low on the other wavelength areas. The projection optical system 1 is constituted of a light source 3, a liquid crystal panel 5 which parallel beams from a collimator lens 4 are made incident, a dichroic mirror 6 synthesizing light beams transmitted through the panel 5 to each color, and a projection lens system 7 projecting the synthesized light beams on the selective reflection screen 2. The light source 3 has emission spectrum where the wavelength corresponding to three color components R, G and B is set as the central wavelength and whose band width is narrow; and the reflection characteristic of the screen 2 is set to obtain the high reflectance only on the wavelength which nearly coincides with the spectrum of the light source, and to obtain the low reflectance on the other wavelength band.