BACK VERTEX ANNULAR APERTURE FOR A SPHERO-CYLINDRICAL LENS SYSTEM

摘要

Apparatus for measuring the refractive properties of an optical system of the type utilizing a light beam scanned in a circle or predetermined radius about the central axis of the optical system to provide a refracted beam. A generally opaque mask having specially configured annular transparent portions positioned in the path of the refracted beam to eliminate errors caused by deviations in radial height from the scanning radius of the refracted beam as it exits the optical system due to refraction within the interior of the optical system. A position-sensitive photodetector generates a signal indicative of the instantaneous position in a given plane due to refraction of the portion of the light beam passing through the mask. The photodetector output signal is then processed to provide an indication of the refractive properties.