二次元記録符号におけるエラーブロック分析と デコード法の検討

抄録

This study reports on error-block analyses and decoding method in the 4/9 two-dimensional recording code for holographic memories. The algorithm for zero-value determination of pixel levels was changed for improving bit error rate (BER) characteristics. In the algorithm, a block was determined to be the (0000) code block when all the four pixels,at which bright spots could be reproduced, exhibited lower levels than the threshold. In the numerical aperture (NA) of 0.14, a W-shaped deterioration in BER at threshold of ∼20% was disappeared. However, this method was not useful for reproduction in NA = 0.07, where errors occurred because of displacements of reproduced bright spots by optical interference between the spots.