| 摘要 |
PURPOSE:To make a device light in weight and high in speed by providing a luminous flux transmission member with first and second diffraction gratings and setting the angle of diffraction by which a luminous flux is made incident at such prescribed angle that it is totally reflected and the reflected light from a medium is returned. CONSTITUTION:The divergent luminous flux from a light source is converted to a luminous flux of parallel rays by a collimator lens and is made incident on a first diffraction grating 11 of a luminous flux transmission member 12 through a mirror 8. A luminous flux 13 diffracted by the grating 11 is totally reflected in the member 12 and is advanced and is diffracted by a second diffraction grating 14 provided on the other end upper face and is made incident on an objective lens 15. The member 12 is set to the angle of diffraction by which the luminous flux is made incident on the grating 11 at such angle that it is totally reflected and the reflected light from a recording medium 17 can be returned through the member 12. Since the member to transmit the totally reflected luminous flux is used in this manner, the member is made thin to make the device light-weight and high-speed. |
