An optical pickup apparatus compatible with at least two types of optical recording media, using light beams having respective different wavelengths for recording and reading information, the optical pickup apparatus including two laser light sources to emit light beams having the different wavelengths,...http://www.google.fr/patents/US6304540?utm_source=gb-gplus-shareBrevet US6304540 - Optical pickup compatible with a digital versatile disk and a recordable compact disk using a holographic ring lens
Optical pickup compatible with a digital versatile disk and a recordable ...
