| 摘要 |
PURPOSE:To always secure the stable servo control of an optical pickup by adding an optical modulation part to a photodetecting optical system forming an optical system of an optical pickup. CONSTITUTION:A photodetecting optical system 20 consists of a light receiving element 21 which converts the state of the beams formed an image into electric signals, a condenser lens 22 which focuses the beams reflected by an optical disk D and then by a polarized beam splitter 14 to the element 21, an optical modulation part 30 which changes the transmitted light quantity in response to the output of a driving circuit 11a, and a cylindrical lens 23. The part 30 includes an optical modulation element 31 like a Pockels cell, etc., a polarized beam splitter 12, and a control circuit 13 which impresses an electric field to the element 31 in response to the output of the circuit 11a. The element 21 is connected to a servo circuit 21a which gives the servo control to the optical pickup based on the electric signal received from the element 21. |
