Patent ID: 8570510

Claim:
An optical unit comprising: a filter member that separates transmitted light; and a photodetector having a plurality of light receiving elements, wherein the filter member includes: a light transmissive substrate; a plurality of protrusions formed with a first metallic material on one surface of the substrate; and a metal film formed by a second metallic material having a higher refractive index than the first metallic material, so as to cover the one surface of the substrate along with the plurality of protrusions, the plurality of protrusions are disposed such that the metal film located between adjacent protrusions serves as a diffraction grating and incident light that is incident the filter member from an other side of the photodetector propagates inside the protrusions as an evanescent wave, at least one of a grating pitch of the diffraction grating, a height of the protrusions and a thickness of the metal film is set, such that a wavelength of light transmitted through the filter member changes for each portion, to a different value for each of the portions, and the photodetector is disposed such that each of the plurality of light-receiving elements receives light transmitted through the filter member.