| 摘要 |
PURPOSE:To reproduce recording information accurately by changing a target set value according to optical information read by a photoelectric conversion element to correct tracking controlling correction signals. CONSTITUTION:The information output detected by a photoelectric conversion element is latched in latch part 17 through A/D converter 16 and is compared with the one-cycle preceding detection information output of a prescribed timing cycle by comparator 18. By the comparison output corresponding to modulation degree change of the detection information output of comparator 18, up and down count of up/down counter 21 is controlled by change direction designation part 20, and a target value set in counter 21 is changed. Consequently, a focusing tracking correction signal formed on a basis of difference between the target value and the detection information output is always so corrected that the set target value may correspond to the focusing position by change of the light source light quantity, change of the optical system dependent upon temperature change, etc. As the result, recording information can be accurately read and reproduced optically. |
