Optical device with variable wavelength interference filter

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.