Holographic Laser Module with Dual Wavelength for Digital Versatile Disc Optical Heads

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Backward compatibility with CD-R necessitates having two laser sources in the digital versatile disc (DVD) pickup head. The dual-wavelength optical head complicates pickup design and enlarges the volume of the head. Moreover, it increases the number of components and assembly cost. In this paper, we present a new design for a dual-wavelength holographic pickup-head module. Packaged together in the module are two laser diodes, photodiodes and a holographic optical element (HOE) for diffracting reflected light from the disk onto the corresponding photodetectors. This module can be used as the core of an optical head capable of reading DVD, CD and CD-R.