PHOTOELECTRIC DISPLACEMENT DETECTOR

摘要

PURPOSE:To detect the relative rotational displacement between the 1st and the 2nd plate bodies by placing two polarizing plates of the 2nd plate body opposite nonoverlap parts of two polarizing plates of the 1st plate body, and calculating variation in the quantity of transmitted light between them and the quantity of transmitted light of the 1st plate body and correcting the quantity of light for a set value. CONSTITUTION:A plate body 10 having a large-diameter polarizing disk 11 and a small-diamete polarizing disk 12 overlapping with each other concentrically while axes of transmission have a 45 deg. shift is fixed integrally on a shaft 1 which is supported rotatably. A plate body 40 is arranged facing nonoverlap parts composed of only a disk 11 and polarizing plates 41 and 42 are fixed to the plate body 40 so that axes of transmission shift by 45 deg. from ach other. Light sources 21 and 23 and photodetection parts 31 and 32 are arranged across the polarizing plates 41 and 42 and nonoverlap parts of the plate body 10, and a light source 23 and a photodetection part 33 are arranged across the overlap part of the disks 11 and 12. The light sources 21-23 are connected in series and turned on by a turn-on control part 50. An arithmetic part 60 processes photodetection outputs of the photodetection parts 31-33 to detect the relative rotational displacement between both plate bodies.