Patent ID: 6624956
Filing Date: 2003-09-23
Classification: G01J

Abstract:
A numerical aperture limiter for an optical thermal imaging system, comprising:at least two pairs of wedge-like prisms, each prism being defined by surfaces and a vertex angle and made of a transparent material having a known index of refraction, the second pair of said prisms being of a mirror-symmnetrical orientation and optically coupled to the first pair of said prisms, said prisms of the pair of prisms being immovably disposed in close mutual proximity and in opposite orientation with the narrow end of one prism adjacent to the wide end of the other prism, the prism surfaces facing one another of said pair of prisms being spaced apart from one another by a distance at least equal to a wavelength of the light rays used by said imaging system, with the vertex angle of said prisms being a function of a desired numerical aperture and said index of refraction upon said light rays with directions exceeding said desired numerical aperture being reflected from the prism surfaces due to total internal reflection principle.