Photometer having asymmetrical aperture and with compensation for direction of incidence

摘要

A photometer having asymmetrical apertures and with compensation for direction of incidence includes a photodetector, a mask having asymmetrical apertures and arranged before the photodetector and a compensation prism arranged either before or after the mask. The photometer is adapted to compensate for the difference in quantity of light incident on the photodetector caused by the mask depending on the difference in the direction of incidence of the light.