Diffraction lens for optical recording on DVD and CD-RW disks has number of annular areas of different diffraction effects

摘要

The optical pickup system has a pair of light sources and detectors co-operating with a lens system to access either a DVD or CD-RW disk. A wavelength selective element combines the source beams and separates the reflections of each wavelength. Both beams pass through a flat plate lens (35). This has a central area (351) that passes both wavelengths. Outer rings (352,353) include diffraction staircase style gratings that pass one wavelength and focuses the other wavelength.