Patent ID: 8687254

Claim:
An optical filter comprising: a first substrate; a first mirror formed on the first substrate; a second substrate coupled to the first substrate, the second substrate including a concave portion; and a second mirror formed on the concave portion and facing the first mirror; the first substrate including: a first portion located on the first mirror, a second portion located surrounding an outer periphery of the first portion and located outwardly of the outer periphery of the first portion as viewed along a first direction normal to a reflective surface of the first mirror facing a reflective surface of the second mirror, a third portion located surrounding an outer periphery of the second portion and located outwardly of the outer periphery of the second portion as viewed along the first direction normal to the reflective surface of the first mirror facing the reflective surface of the second mirror, and a fourth portion located surrounding an outer periphery of the third portion and located outwardly of the outer periphery of the third portion as viewed along the first direction normal to the reflective surface of the first mirror facing the reflective surface of the second mirror, both a thickness of the second portion and a thickness of the fourth portion being smaller than a thickness of the first portion.