OPTICAL ELEMENT HAVING WAVELENGTH SELECTIVITY

摘要

An optical element easy to produce, reduced in production costs and having a wavelength selectivity, comprising an optical wave-guide sheet (22) having t wo facing end surfaces (22a, 22b), and a multi-layer film filter (23) formed on at least one of the two facing end surfaces. The multi-layer film filter includes high-refractive-index dielectric layers and low-refractive-index dielectric layers alternately laminated one upon another with its thickness changing continuously according to the positions of the facing end surfaces of the optical wave-guide sheet. Center wavelength of light transmitting the multi-layer film filter differs according to the positions of end surfaces o f the optical wave-guide sheet. When a mixed ray of light is shone onto the multi-layer film filter from each lens via the optical wave-guide sheet, the mixed ray of light is separated into rays of light having different center wavelengths by the multi-layer film filter having different thicknesses.