Abstract
ABSTRACT We proposed a combo design of pick-up head used prism to shorten the geometrical size and reduce the optical components. We apply a rhomboid beam splitter to separate two diodes in the design for the optical pick-up head of DVD and HD-DVD. Keywords: HD-DVD, DVD, Optical Pick-up Head, Rhomboid Prism, Penta prism 1. INTRODUCTION !!! According to diffraction limit, the spot size of light focused on the disk is proportional to O /NA, where O is the laser diode wavelength and NA is the numerical aperture of the objective lens. To realize the high-density optical storage, it is important to reduce the light source wavelength and increase the numerical aperture (NA) of the optical pick-up head. Table 1 shows the specifications of DVD (Digital Video Disk) and HD-DVD (High-dens ity Digital Video Disk). The specification of DVD, a laser diode of 650nm, a NA (number aperture) of 0.6, a storage capacity of 4.7GB, and a thick substrate of 0.6mm are specified in one of the design. The specification of HD-DVD, a laser diode of 405nm, a NA of 0.85, a storage capacity of 15GB, and a thick substrate of 0.1mm are used
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