| 摘要 |
PROBLEM TO BE SOLVED: To improve the reliability of an optical head without extending the size of a photodetector and making a light beam of a main spot interfere with a light receiving part for a sub-spot. SOLUTION: The emitted light beam from a light source is divided into a main beam for detecting an information signal and a sub-beam for tracking, a mini-disk is irradiated with the beams and the respective reflected beams from the mini-disk are converged on divided photodetectors H (light receiving part A.B), J (light receiving part C.D) and a second photodetector 13 composed of photodetectors E1.E2.F1.F2, respectively. This head is provided with a concave cylindrical mirror for forming the reflected beams so that the respective spot shapes of the reflected beams become elliptical shapes flattened in the arranging direction of S component S1 S (P component S1 P) of main beam for detecting information signal and the S component S2 S (P component S2 P) of sub-beam for tracking or S3 S (P component S3 P). |
