[OPTICAL REVIEW Vol. 19, No. 3 (2012) 131-141]
© 2012 The Japan Society of Applied Physics

Enhancement of the Lohmann-Type Computer-Generated Hologram Encoded by Direct Multilevel Search Algorithm

Hitoshi TAMURA* and Yasuhiro TORII

Department of Electronics, University of Industrial Technology, Sagamihara 252-5196, Japan

(Received November 22, 2010; Accepted December 13, 2010)

An optimization-coding algorithm is required to produce high-quality computer-generated holograms (CGHs). For such a purpose, we have developed the direct multilevel search (DMS) algorithm using the rigorous reconstructed-image representation for encoding Lohmann-type CGHs. However, it required much time owing to the one-by-one search process: the optimal amplitude and phase must be selected from many multilevel amplitudes and phases. To solve this problem, we have established the ± 1-trial search method, which can greatly reduce the trial search number: searches are limited only to the minimum shifts in amplitude and phase instead of all the possible shifts. Moreover, the DMS algorithm that incorporates the oversampled encoding method has been verified to be effective for reducing the optical reconstructed-image error by preparing the CGHs using electron-beam lithography.

Key words: computer-generated hologram, cell-oriented hologram, Lohmann-type hologram, iterative Fourier transformation algorithm, direct search algorithm

*E-mail address: tamura@uitec.ac.jp