| 摘要 |
PURPOSE:To reduce the number of parts by transmission diffracting and light shielding a central part of an outgoing beam by using a transmission type first diffraction grating and transmitting the peripheral part of the outgoing beam by using a second diffraction grating. CONSTITUTION:The outgoing beam (a) outgoing from a semiconductor laser 12 becomes parallel rays of light by a collimate lens 13 to be incident on a polarization dependency diffraction grating 14. The grating 14 is constituted of the transmission type first diffraction grating 14a formed on the central part and second diffraction gratings 14b, 14c formed on both sides peripheral parts of the grating 14a. Then, the beam B1 of the central part of the beam (a) is transmitted and diffracted, and is light shielded by changing an advancing direction by using the grating 14a. Further, by making the beams B2, B3 of the peripheral part of the beam (a) go ahead by using the grating 14b, only the beams B2, B3 are converged, and are irradiated on an optical disk surface, and a super resolution phenomenon occurs. Thus, a function by the super resolution phenomenon and a polarizing beam splitter function are compounded to one piece of element. |
