| 摘要 |
PURPOSE:To make a device small in size and light in weight and to enhance the utilization factor of light by constituting an optical head as a uniaxial system by using one hologram element. CONSTITUTION:The crystal optical axis of the hologram element 5 and the crystal optical axis of a diffraction grating 11 are set to be vertical to and parallel with the plane of polarization of radiated light 2 from a semiconductor laser 1 respectively. The light 2 is made incident on the element 5 as normal light and on the grating 11 as abnormal light respectively, and it is diffracted only by the grating 11. The phase difference of the abnormal light at the grating 11 is diffracted for a sub beam which is used to detect a track error signal. The light 2 accompanied with the sub beam is changed to collimated light 10, changed to circularly polarized light by a lambda/4 plate 6, and converged on an optical disk 8 through a converging lens 4. The returning light reflected on the optical disk 8 is diffracted only by the element 5. +1st order diffracted light, out of diffracted light, is made incident on a six-division photodetector 7 and used to detect the error signal and a recording signal, and -1st order diffracted light is made incident on a photodetector 12 and used to detect the recording signal. |
