Optical beam splitter system for automatic focus device in measuring instrument

摘要

The system has a pair of light receiving elements (15) which receive respective light beams divided by a splitting surface (11). The light beams are incident on the splitting surface at different angles. An optical element (17,18) is arranged between the splitter surface and the light receiving elements, for attenuating the light beam having the greater light quantity so that the difference between the light quantities received by the receiving elements is reduced.