An ordinary half-height size optical pickup with high light-use efficiency for Blu-ray Discs (BDs) has been realized. It has two objective lenses arranged tangentially. Although one of the objective lenses, BD objective lens, does not follow the line that passes thorough the center of the spindle motor, stable tracking-error detection has been achieved by enhancing a one-beam method. This pickup has a beam shaper which changes a divergent angle of light with high magnification. Although beam shapers are sensitive to a positional error, our pickup accomplished stable positioning by introducing a new structure.
We propose a dual focus optical head with a holographic optical element (HOE) which compensates for spherical aberration, allowing it to read both 0.6 mm disks and 1.2 mm disks. The thin disk is read using transmitted light and the thick disk is read using +1st order diffracted light of the blazed HOE. The characteristics of the focused spot, the servo signal detection and the signal of the Compact Disc indicate that both disks can be read by the dual focus optical head.
Recent advances in optical pickup heads using holographic optical elements (HOEs) are reviewed, with emphasis on a practical servo-signal detection system that can realize compact integration of HOE, laser diode, photodetectors, and objective lens. This paper presents a new type of holographic servo method that employs a blazed HOE placed in close proximity to the objective lens so that wide allowance range of the optical system is maintained, thus allowing the lens and HOE to move simultaneously. The blazed HOE and the integrated optical system are analyzed and discussed in detail.
Conference Committee Involvement (1)
Optical Data Storage Topical Meeting 2004
18 April 2004 | Monterey, California, United States
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