OPPOSITION TYPE LIGHT BEAM GUARD

摘要

PURPOSE:To remove an inspection error by providing polarizing filters with different polarization angles for every pair of the filters in front of projectors and light receivers and constructing such that the filter does not receive the light from the opposite filter for every pair of the polarizing filters. CONSTITUTION:Polarizing filters 5 with the same polarization angle are provided in front of a projector 1a and a light receiver 2a for receiving the light from he projector 1a. Polarizing filters 6 with the same polarization angle but different from that of the polarizing filters 5 are provided in front of another projector 1b and another light receiver 2b for receiving the light from the projector 1b. Thus, even through shielded by a reflector 4, the light projected from the projector 1a and polarized is not incident upon the light receiver 2a because the light has the polarization angle different from that of the polarizing filter 5 provided in front of the light receiver 2a. Thus, the light projected from the projector 1b is not received by the light receiver 2b and therefore an inspection error can be removed.