VISIBLE LIGHT SHIELDING AND INFRARED RAY TRANSMITTING FILTER

摘要

PROBLEM TO BE SOLVED: To obtain a filter that can be utilized as an IR radiating light source (black light), has a high IR transmittance and a very low visible light transmittance and makes a light source invisible when the light source is seen through the filter. SOLUTION: High refractive index layers comprising a semiconductor material and low refractive index layers comprising a transparent dielectric are alternately laminated in 17-45 layers on at least one face of an appropriate substrate 21 to obtain the objective filter which shields visible light from a light source and transmits IR by multilayer film interference. The filter has >=80% average IR transmittance in the range of 900-1,500 nm and <=0.1% visible light transmittance in the range of 400-800 nm.