OPTICAL FILTER ELEMENT, WAVELENGTH VARIABLE OPTICAL BANDPASS FILTER MODULE, WAVELENGTH VARIABLE LIGHT SOURCE APPARATUS, AND SPECTROSCOPIC ENDOSCOPE APPARATUS

摘要

PROBLEM TO BE SOLVED: To enable more efficient separation of light with less optical filter elements.SOLUTION: An optical filter element according to an embodiment of the present invention comprises a pair of reflection surfaces disposed in parallel at a predetermined interval to constitute a Fabry-Perot resonator. At least one of the pair of the reflection surfaces is a wavelength selective reflection surface containing a dielectric multilayer film, which has a vacuum layer or a gas layer disposed between a pair of reflection films such that narrowband light having a center wavelength within an absorption band of a prescribed biological substance is allowed to selectively transmit and the center wavelength varies according to the incident angle.