| 摘要 |
PURPOSE:To make the color rendering property and density of a copy uniform by forming a thin film on a flat plate-like transparent substrate of a filter in such a way that the thickness of the thin film is specifically disposed with respect to the incident angle of the ray incident thereto. CONSTITUTION:A filter 5 is so constituted that a thin film 7 consisting of, for example, mangnesium fluoride, having no light absorptivity is formed in a single layer on a flat plate-shaped transparent substrate 6 of glass, etc. The thickness (d) of the thin film is formed to such a film thickness distribution as to satisfy the equation with respect to the incident angle theta1 of the ray incident thereto. Only the light of a prescribed wavelength region out of the light incident to the filter 5 is thereby transmitted always at a specified transmittivity through the filter irrespectively of the incident angle thereof, by which the quality and quantity of the light after transmission through the filter are made uniform. The uniformity of the color rendering property and density of the copy is thus improved. |
