Patent ID: 7864325

Claim:
An interferometer comprising a splitting element including: a first splitting portion which splits incident light into a first split beam and a second split beam; and a second splitting portion which causes interference between the first split beam and the second split beam propagated over different optical paths, while compensating a phase difference between the first split beam and the second split beam occurring upon splitting of the incident light by said first splitting portion, wherein: said splitting element includes a first transparent medium having a triangular pole shape, a cross-sectional shape of said first transparent medium being a right isosceles triangle, and a first splitting film being partially formed on a first side face which forms a hypotenuse of said right isosceles triangle, and a second transparent medium having a triangular pole shape, a cross-sectional shape of said second transparent medium being a right isosceles triangle, and a second splitting film being partially formed on a second side face which forms a hypotenuse of said right isosceles triangle; said first side face is laminated to said second side face such that said first splitting film and said second splitting film do not overlap with each other; said first splitting portion is a portion on which said first splitting film is formed, and said second splitting portion is a portion on which said second splitting film is formed; and said splitting element is positioned such that a positional relationship between said second transparent medium and said second splitting film in said second splitting portion with respect to a direction of incidence on said second splitting portion of the first split beam that is the incident light reflected by said first splitting portion, is opposite to a positional relationship between said first transparent medium and said first splitting film in said first splitting portion with respect to a direction of incidence on said first splitting portion of the incident light.