Feature

Silicon Photodiodes Matched to the CIE Photometric Curve Using Color Filter Glass

James P. Ritzel and Spike Sojourner

Color filter glasses are integrated with silicon photodiodes for spectral matching that correlates to the same visual sensitivity of a normal human observer. The actual response curve is defined by CIE (Commission Internationale de Eclairage), and is referred to as the Standard Photometric Observer. The response curve is based on several different studies from the 1910s and '20s using a statistical sample of individuals representative of the population at large. To match the relative response of the human eye to radiation at a given wavelength, unique subtractive color glass filters are prescribed to a thickness and installed in front of the detector. The filters mold the spectral response of the detector/filter combination to simulate the relative response of the human eye. The sensors may be manufactured on a production basis; however, careful attention must be paid to both detector and color glass filter variations.