| 摘要 |
877,925. Photo-electric devices. LEITZ G.m.b.H., ERNST. April 11, 1960 [April 9, 1959], No. 12774/60. Class 40(3) [Also in Group XX] An optical sensing arrangement for sensing a movable raster by the derivation of two electric signals in quadrature comprises a fixed raster similar to the movable raster, an optical imaging system interposed between the rasters and forming in the plane of the fixed raster two partial images of the movable raster displaced relatively to each other and photoelectric receivers responsive to each partial image. In one embodiment the imaging system comprises a microscope objective 3, Wollaston prism 4 and telescope objective 5. Beyond fixed raster 2 is arranged a beam divider 7 transmitting perpendicularly polarized light and reflecting parallel polarized light to respective photo-cells 8, 9. The movable raster images separation is adjustable by displacing the prism along the optical axis. The corresponding photo-cell outputs may be used in known manner for counting the raster elements or measuring scale graduations. The prism may be replaced by a Savart plate. In another embodiment coloured partial images are used and are produced by a direct-vision prism or a diffraction grating, Fig. 2 (not shown). |
