Patent ID: 6925227

Claim:
An optical device comprising: a first refractive index distribution type lens having a first end face and second end face, said first end face being ground diagonally; first and second ports connected to the first end face of said first refractive index distribution type lens; an optical functional element connected to the second end face of said first refractive index distribution type lens; a second refractive index distribution type lens having a third end face and a fourth end face, the fourth end face being ground diagonally and the third end face being placed so as to face the second end face of said first refractive index distribution type lens via said optical functional element, and a third port connected to the fourth end face of said second refractive index distribution type lens, wherein an optical path length from said first port to said second port after reflection by said optical functional element for an optical path length of reflected light through the first refractive index distribution type lens is equal to an optical path length from said first port to said third port through said optical functional element for an optical path of a transmitted light through the second refractive index distribution type lens.