Patent ID: 7428102

Claim:
An optical element with a wavelength selecting function for reflecting or transmitting light by selecting wavelength of said light, comprising: an optical block having a cavity part with an opening formed on an optical path and an inclined face formed in an internal face of said cavity part at a prescribed inclining angle with respect to a traveling direction of light, wherein multilayer films of same structure are formed at least on said internal face of said cavity part and on an interface between light incident end and/or emission end of said optical block and outside, said multilayer film formed on said inclined face in said internal face of said cavity part has said wavelength selecting function for light to be used, said multilayer film formed on other face than said inclined face has an antireflective function for light to be used; and said internal face of said cavity part is formed with a first face and a second face, which are orthogonal to each other in an adjacent state, and a third face adjacent to both the first and second faces and making an acute angle between the first and second faces.