| 摘要 |
PROBLEM TO BE SOLVED: To always discriminate correctly a kind of a loaded optical disk, e.g. whether the optical disk is a CD or a DVD. SOLUTION: In the case of loading, e.g. a DVD 100, a time difference Ths between a pulse 107 resulting from a peak 103 caused by surface reflection and a pulse 108 resulting from a peak 104 caused by reflection on a signal side in a signal binarizing a sum signal based on a reflected light is measured. Furthermore, a time difference Tfs between pulses 111, 112 based on S-shaped signals resulting from reflection on the signal side in a signal binarizing a focus error signal is measured. A ratio Ths /Tfs is calculated from the measured values. Similarly to the case above, a ratio Ths /Tfs of a CD 200 is calculated. Since the ratio Ths /Tfs denotes it that the effect of dispersion in the sensitivity in a focus direction of an actuator moving an objective lens 24 is eliminated based on the time Ths reflecting a thickness of a substrate of the optical disk, a type of the optical disk is correctly discriminated based on the ratio Ths /Tfs . |
