DIFFRACTION TYPE LENS AND OPTICAL PICKUP DEVICE USING THE SAME

摘要

PROBLEM TO BE SOLVED: To focus light at two wavelengths onto the recording faces of the respective optical recording media having different disk thickness while satisfying the requirement for a compact and low-cost optical pickup device without making the structure of the device complicated by separately applying zone plates having different wavelength selectivity and focusing effects from each other on the top and back faces of a lens. SOLUTION: When a CD-R 26 is mounted on a turntable to carry out recording and reproducing, the laser beam at 780 nm wavelength (λ2) in almost parallel beams incident to a diffraction lens 8 is focused by the zone plate on the face in the light source side of the lens 8 onto the recording face 26A of the CD-R 26. When a DVD 36 is mounted on the turntable to carry out recording and reproducing, the laser beam at 634 nm wavelength (λ1) in almost parallel beams incident to the diffraction lens 8 is focused by the zone plate formed on the face in the disk side of the lens 8 onto the recording face 36A of the DVD 36.