| 摘要 |
PURPOSE:To facilitate reproduction of signals by using an off-axis grating lens to produce a difference between the optical axis of the light incident on said grating lens from a light source and the optical axis of the light which is reflected from an information recording surface and transmitted through the grating lens. CONSTITUTION:The light beams 21 delivered from a light source 20 are turned into parallel luminous fluxes 24 through a collimating off-axis grating lens 23 and then made incident to a focusing off-axis grating lens 26. The primary diffracted light 27 forms a focal point 30 on an information recording surface 29, and the reflected light including information is sent again to the lens 26. While the zero-order transmitted light 31 goes back just as the transmitted light with an optical axis different from that of the flux 24. Then a focusing error, signal, a tracking error signal and a record information signal are detected out of the reflected light including the light 31 through a grating lens 32 for astigmatic optic and a photodetecting part including a 4-split photodiode 33. In such simple constitution, the signal can be easily reproduced. |
