| 摘要 |
PURPOSE:To obtain a tracking error signal which is free from any deflection and a wobbling signal including no noise caused by a recording pit when they are recorded on a recordable optical disk. CONSTITUTION:The light beam radiated from a semiconductor laser 1 is diffracted by a 1st diffraction grating 2a and focused by a lens 10. A 2nd diffraction grating 2b placed on a surface where a light source image is formed by the lens 10 diffracts the + or - 1st-order diffracted light of the grating 2a and transmits the 0-order diffracted light at is. A main spot is formed by the 0-order diffracted light of the grating 2a to record or read the information. The pairs of subspots are formed before and after the main spot by two pairs of + or - 1st- order diffracted light of the grating 2b with displacement secured by 1/4 track pitch in both directions opposite to each other from the center of an information recording track. Then, a tracking error signal is obtained from the signals sent from four subspots (2 pairs) formed in such a way. |
