Patent ID: 8786861

Claim:
An optical device comprising: a variable wavelength interference filter that include an effective measurement area and that transmits a first light reinforced by multiple interference out of an incident light; a telecentric optical system that guides the incident light to the variable wavelength interference filter; and a detection section that detects a second light transmitted through the variable wavelength interference filter, wherein the variable wavelength interference filter includes a first substrate, a second substrate opposed to the first substrate and provided with a movable section, and a holding section that holds a periphery of the movable section and that holds the movable section so as to allow a back and forth movement of the movable section with respect to the first substrate, a first reflecting film provided to the first substrate, a second reflecting film provided to the movable section, and opposed to the first reflecting film via a gap having a center gap and a peripheral gap, and a gap varying section that displaces the movable section to thereby vary a dimension of the gap, the telecentric optical system guides a principal ray of the incident light perpendicularly to one of a plane of the first reflecting film and a plane of the second reflecting film, and collects the incident light in the effective measurement area of the variable wavelength interference filter, a center, which has the center gap when the movable section is displaced with a maximum amount by the gap varying section, of the effective measurement area is in a central axis of the movable section, and a periphery, which has the peripheral gap when the movable section is displaced with the maximum amount by the gap varying section, of the effective measurement area is in a peripheral area of the first and second reflecting films, and a gap difference between the center gap and the peripheral gap is within a predetermined nanometric range.