| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical pickup device adopting an optical module which is high in optical coupling efficiency, small in optical disk condensing spot, can be easily produced and can be easily assembled and adjusted. SOLUTION: The light which is emitted from a semiconductor laser 1 of the optical module M and has an elliptic shape in sectional light intensity is separated to zero order light and ±1st order light by a first diffraction element 2. The light is then transmitted through a second diffraction element 3 of, for example, an elliptic shape in a plane shape and a beam splitter 4, is converted into parallel light beams by a collimating lens 5, is shaped to an approximately circular shape in the section by a regulating prism 6 and is made incident on an objective lens 7 to form three spots on the optical disk 8. The reflected light from the optical disk 8 is transmitted through the objective lens 7, is reduced and shaped by the regulating prism 6, is transmitted through the beam splitter 4 and is diffracted by the second diffraction element 3 of the optical module M. The first order diffracted light is received by a photodetector 12, and a servo signal (focus error signal or tracking signal) is detected. |
