| 摘要 |
<p>PROBLEM TO BE SOLVED: To execute the tracking servo mechanism of an optical recording medium having a pit depth ofλ/4 without splitting the principal ray, by providing a photodetector having eight divided photodetecting sections by quartering the photodetecting section of the element into four parts and further dividing each quarter section into two parts by drawing a line crossing the quartering lines. SOLUTION: A photodiode PD1 in the fore stage is quartered into strip-like parts symmetrically with respect to a central dividing line, so that the quantity of light received by the two outside parts may become equal to that received by the two inside parts in a state where focusing and tracking are matched. The photodiode PD1 is further divided into eight parts by diving each quartered part into two parts by drawing a line nearly perpendicularly to the quartering lines. On the other hand, a photodiode PD2 in the post stage is quartered into strip-like parts, so that the quantity of light received by the two outside parts may become equal to that received by the two inside parts in an adjusted focus and matched tracking state.</p> |
