| 摘要 |
PROBLEM TO BE SOLVED: To respectively optimumly reproduce various kinds of optical disks having different formats. SOLUTION: In this optical disk device, light beams 122 emitted from a semiconductor laser 120 irradiates the track 130 on an optical disk 100 as an optical spot via a collimating lens 124, a beam splitter 126 and an objective lens 128 and a reflected light is read via the objective lens 128, the beam splitter 126, a detection lens 136, an optical beam detecting means 138, a first demodulator 140a and a second demodulator 140b. Then, the shape of the optical spot 110 on the optical disk 100 is arbitrarily controlled by arranging an offset adding means 150 in between the automatic focusing control mechanism 134 controlling the focal position of the objective lens 128 and a control system 132 and by intentionally changing the target focal position of the objective lens 128 in accordance with the class of the format of the optical disk 100 and by utilizing the astigmatism of the light beam 122. |
