| 摘要 |
PROBLEM TO BE SOLVED: To obtain accurate focusing error signals or the like by setting a ratio between the area of the light receiving surface of a multiple photocletector for detecting focusing errors and the area of a spot on a light receiving surface by a reflected light from an optical disk within a particular range. SOLUTION: If the area of the light receiving surface of the multiple photodetector 31 of a photodetector 30 is denoted as DS and the area of a spot on the light receiving surface of the multiple photodetector 31 by a reflected light from a digital video disk(DVD) is BS, by setting l.2<=DS<=2.5, accurate information signals or focusing error signals are obtained without any flaring influence. If this upper limit is exceeded, focus detection is not performed accurately during DVD reproduction because of flaring influence and the jitters of information signals are increased. If a lower limit is exceeded, a focus detection range is narrowed during CD reproduction. |
