Patent ID: 7057809

Claim:
A projection screen for projecting thereupon narrow-band tricolor wavelength band light to display an image; comprising a film which has high reflection properties regarding said narrow-band tricolor wavelength band light, and has high transmission properties regarding at least visible wavelength band light other than said wavelength band light; wherein said film is comprised of a dielectric multi-layer film wherein high-refractive-index layers and low-refractive-index layers are alternately layered, and wherein, with the refractive index of each layer in the dielectric multi-layer film as n and the film thickness of each layer as d, the optical thickness nd of each layer of the dielectric multi-layer film satisfies the following Expression (1) with regard to each wavelength λ of said narrow-band tricolor wavelength band light nd =λ( a ±¼) (where a is a natural number).