| 摘要 |
PURPOSE:To enable scanning at a low cost and a high speed, by disposing many holograms which are overlapped in positions on a hologram rotating body, and providing photodetectors of the number equal to the overlapped number on the scanning plane. CONSTITUTION:Two photodetectors S1, S2 are fixedly disposed on the main scanning direction (x) of a scanning plane 6, and holograms H1 and H2, H2 and H3- are overlapped and recorded doubly on a disc 2, whereby holograms HG1, HG2- are arranged on a concentrical circle. The holograms are so constituted that the reflected light by the one luminous flux L1 from an optional hologram HG1 is detected through the photodetector S1, that the reflected light by the luminous flux L2 is detected through the photodetector S2 and that the flux L1 and the flux L2 scan on different scanning lines on the plane 6. In other words, there are two kinds of the space frequencies of the holograms so that the space frequencies of the holograms adjacent to each other differ from each other |
