Patent ID: 8736960

Claim:
A structure with an observation port, comprising: an observation port comprising a substrate, a first anti-reflection film disposed on an outside surface of the substrate, and a second anti-reflection film disposed on a backside surface of the substrate; and an internal structure placed on a backside of the observation port and comprising a third anti-reflection film, the first anti-reflection film being a film that reduces reflected light owing to light interference, the second anti-reflection film and the third anti-reflection film each having a surface formed by multiple protruding portions, a width between apexes of adjacent protruding portions being not greater than a visible light wavelength, light reflected from a surface of the first anti-reflection film, light reflected from a surface of the second anti-reflection film, and light reflected from a surface of the third anti-reflection film, each having wavelength dispersion including an arbitrary reflectance value outside the range of ±1.0% from the reflectance at a wavelength of 550 nm within the visible light range, and light obtainable by combining light reflected from the surface of the first anti-reflection film, light reflected from the surface of the second anti-reflection film, and light reflected from the surface of the third anti-reflection film having wavelength dispersion in which any reflectance value within the visible light range is within the range including ±1.0% from the reflectance at a wavelength of 550 nm.