| 摘要 |
PURPOSE:To surely read a high density recorded information. CONSTITUTION:A second objective lens 20, which image forms high region signals, is placed adjacent to a first objective lens 13 which detects low region signals. The opening of the beam which passes the lens 20 is controlled by an aperture control diaphragm 21 at the image forming position of the lens 20. A signal demodulator 23 demodulates the information that indicates pit lengths contained in the formed image by the lens 20 and the information by the lens 13. Thus, the reproduced spatial frequency of an optical pickup is equivalently made wider, a short pit is identified without using a larger NA objective lens and light spot form variation caused by the aberration such as the tilt of an optical disk 14 is made small. Therefore, a disk information recorded at a high density is surely read. |
