| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive multi-track read type optical pickup by providing two photodetectors photodetecting prescribed plural pieces of beams and constituting so that the light quantity made incident on one of n-di-vided light receiving areas of a first light receiving means is nearly equal to the light quantity made incident on one photodetector of a second light receiving means. SOLUTION: This photodetector 32 forms the photodetectors 51, 52, 53 respectively light receiving return light from a reading spot, a common photodetector 54 light receiving the return light from a tracking spot and the common photodetector 55 light receiving the return light from the tracking spot on the same semiconductor substrate. Then, three return light placed on one side edge of a track are light received by the common photodetector 54, and the other side return light are light received by the common photodetector 55. Thus, since I/V converter and computing unit with relatively narrow dynamic range are used, the optical pickup is constituted inexpensively. |
