| 摘要 |
PROBLEM TO BE SOLVED: To reduce the adverse effect of external disturbances on focus control caused by noncoincidence between one dividing line for dividing a light receiving area for focus error detection of a photodetector because of the limitation of optical arrangement and the different direction of the intensity distribution of a light beam generated by the effect of external disturbances by a signal track. SOLUTION: One dividing line 18 for dividing a light receiving area is set in a direction shifted in the tangential direction PT-PT' of a signal track by π/4(rad) from an astigmatism generating direction PB-PB' on a light receiving area 17. Thus, without narrowing the width of a disk in a diameter direction in the outer dimension of an optical head device, the effect of external disturbances caused by a signal track generated in a focus error signal is reduced. |
