| 摘要 |
PROBLEM TO BE SOLVED: To prevent a read miss of information due to relative positional relation between a sensor unit and a diffraction grating body by providing a light transmission element (convex lens, etc.,) at a suitable position in an optical path until diffracted light by a diffraction grating arrives at an optical head. SOLUTION: The optical head 2 is constituted integrally with a light source 1, and receives diffracted light occurring from the light-irradiated position of the diffraction grating of the diffraction grating body (e.g. hologram) 3 by irradiation with reproducing light from the light source 1 to transduce it into an electric signal. A convex lens 4 is inserted and arranged at the suitable position in the optical path until the diffracted light by the diffraction grating arrives at the optical head 2, and corrects the direction of the diffracted light occurring from the light-irradiated position of the diffraction grating to lead it to the optical head 2. Thus, though the sensor unit housing the light source 1 and the optical head 2 is rotated relatively with diffraction grating body 3, the diffracted light is led onto the optical head 2 precisely within the range of the aperture of the convex lens 4, and the read miss of the information due to the relative positional relation between the sensor unit and the diffraction grating 3 is prevented. |
