Tomo KISHIGAMI, Yusuke KANATAKE, and Nobuo TAKESHITA

Advanced Technology R&D Center, Mitsubishi Electric Corporation, Nagaokakyo, Kyoto 617-8550, Japan

(Received November 28, 2013; Accepted May 15, 2014)

We developed an optimization method for spherical aberration and focus offset for an optical disc drive using an elliptical approximation. This method measures the small number of points that are located at specific positions. Furthermore, it approximates a characteristic distribution to an ellipse and calculates the center of the ellipse as the optimal point. The effectiveness of this method is experimentally confirmed using Blu-ray discs with three types of protective layer of various thicknesses.

Key words: focus offset, beam expander, spherical aberration