Patent ID: 8665435

Claim:
A wavelength detector comprising: a parallel lens group configured to convert light beams having partial wavelength ranges, which are extracted from three or more reflection light beams produced by irradiating with three or more illumination light beams having a spectrum in a prescribed wavelength range to three or more reflection surfaces of an illumination subject portion, into light beams that are parallel with each other using three or more lenses; a spectroscope element configured to receive the light beams coming from the parallel lens group, and to output the light beams in exit directions corresponding to their partial wavelength ranges, respectively; a detection lens group configured to condense the output light beams of the spectroscope element using three or more lenses, respectively; and a photodetecting element group configured to detect focusing positions of three or more light beams condensed by the detection lens group, respectively, the photodetecting element group comprising a plurality of photodetecting elements which are arranged in a single plane and cover variation ranges of the focusing positions, depending on the exit directions from the spectroscope element, of the three or more light beams condensed by the detection lens group, wherein the wavelength detector calculates wavelengths of the three or more light beams on the basis of the respective detected focusing positions.