| 摘要 |
PURPOSE:To obtain the high resolving power at detection of displacement by providing a code plate arranged with plural data elements subjected to optical binary coding so as to correspond to displacement quantity and an optical pickup means which generates the electric signal corresponding to the relative displacement quantity with the code plate. CONSTITUTION:The data elements 8 subjected to the optical binary coding are arranged on the plural tracks on the code plate 7 in such a manner that the combination thereof changes successively according to rotating angles. The plural beams split by a diffraction grating 1 transmit a beam splitter 12 and are focused by a focusing lens 13. The focused beam focuses the spot B3 of the very samall diameter on each track 20 of the code plate 7. The quantity of the reflected light changes according to the presence or absence of the data elements (bits) 8 in the stage of reflection. The reflected beams focused at the lens 13 are reflected by the beam splitter 12, are stopped down by a photodetecting lens 14 and are transmitted through a cylindrical lens 15, from which the beams are made incident respectively to the corresponding photodiodes of a photodetecting element 16 consisting of the plural photodiodes. These beams are converted to electric signals. |
