| 摘要 |
PURPOSE:To permit easy working without spoiling accuracy by making constant the angle of photodetectors of a photosensor disposed to face the slits of a slit plate and supporting the photosensor and the slit plate in such a way that either one thereof can move in parallel. CONSTITUTION:A slit plate 12 with slits 12A, B is disposed between a light source 1 and a photosensor 11 which receives the parallel rays 2 thereof. Plural photodetectors 11A-C, etc. are arranged like a grating to constitue the sensor 11. The photodetectors 11A-C, etc. are disposed at the angle theta which is neither parallel nor rectangular with or to the slits 12A, B. Either of the sensor or the plate, for example, the plate 12 is made movable in a way as not to change the angle theta and the bright parts 13A, B by the slits 12A, B of the rays 2 are measured with the photodetectors 11A-C, etc., by which the moving distance of the plate 12 is determined. The need for working fine slits is thus eliminated. |
