PROBLEM TO BE SOLVED: To restrain aliasing artifact at low cost over a wide spectral range by providing material for forming a transparent substrate and plural transparent spots and satisfying a specified condition. SOLUTION: The spots are irregularly arranged on the substrate for making a phase difference between a light wave front transmitted through the spot and a part other than the spot of the substrate, and the phase difference satisfies the condition ϕO=π. In such a case, ϕO is the phase difference caused by the spot in specified wavelength λO satisfying λB<=λO<=λR, and it is given by an expression I and has feature shown by an expression II. In the expression, nO means a refractive index in the specified wavelength λO of the material forming the spot, nO' means the refractive index in the specified wavelength λO of a medium surrounding the spot, and (t) means the physical thickness of the spot. Thus, the filter is suitable for the use in a solid-state camera performing discrete image sampling.
PHASE NOISE TYPE WIDE SPECTRAL BAND WIDTH OPTICAL LOW-PASS ANTI-ALIASING FILTER