| 摘要 |
PROBLEM TO BE SOLVED: To obtain a transmission type screen which prevents the formation of double images and decrease in the resolution by providing the light-outgoing face of the sheet with a Fresnel lens sheet having light absorptivity. SOLUTION: A Fresnel lens sheet 11 disposed in the face where light outgoes of the transmission type screen has absorptivity for light, and practically, the sheet base material is colored so that the absorptivity of light is controlled to about 50%. The Fresnel lens sheet 11 is colored by using dyes or pigments by mixing or dispersing in the molding resin. Double images are produced when part of light entering the Fresnel lens sheet 11 is reflected from the face of a Fresnel lens 11a and further reflected from the back face of a Fresnel lens 11b and then the light outgoes. Therefore, the optical path length (shown as a double dotted chain line) L2 of the double image is three times or more as long as the optical length L1 in the Fresnel lens sheet 11 for a normal image. Thus, by controlling the absorptivity of the sheet to 50%, the light of the double image is decreased by (0.5)3=0.125, namely, about 1/10, and the double image is hardly seen.
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