Akihiro Arai

Novel one-beam tracking detection method for dual-layer blu-ray discs

In this paper, we propose a new advanced push–pull (APP) method as a new one-beam tracking detection method suitable for a dual-layer Blu-ray disc (BD) system. This method overcomes two issues. One of them is tracking error signal (TES) offset at the boundary between recorded tracks and unrecorded tracks, and the other is TES offset caused by the stray lights from the other layer of dual-layer discs. The new APP-TES is stable at the boundary in the dual-layer BD system, because the dividing area of a far-field pattern is optimized and the detecting areas are allocated to avoid stray lights from the other layer. Its stable characteristics are confirmed experimentally.

Radial Tilt Detection Using Push–Pull Signals

A high-density optical disk system uses an objective lens with a high numerical aperture (NA) and a light source with a short wavelength (λ). However, the coma aberration caused by a relative radial tilt between the objective lens and an optical disk increases in proportion to NA3/λ. Therefore, the reliability of the optical disk system can be improved by detecting and compensating the radial tilt because the coma aberration deteriorates the read and write performance. This paper describes a radial tilt detection method that is based on analysis of the intensity distribution of reflected light from the optical disk. This method can be performed with high accuracy even at the boundary area of recorded and unrecorded tracks, and with an objective lens displacement. Furthermore, a tracking error signal detection method that can be used with the tilt detection method simultaneously is described. Its performance was confirmed experimentally using the optical pickup for a Blu-ray Disc (BD).

Radial Tilt Detection Using Push-Pull Signals

A radial tilt detection method that performs with high accuracy even at the boundary area between recorded tracks and unrecorded tracks was developed, and its performance was confirmed experimentally.