1. Advanced Devices Development Center, Matsushita Electric Industrial Company, Ltd., 3-1-1 Yagumo-Nakamachi, Moriguchi, Osaka 570-8501, Japan, Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe 657-8501, Japan, and Image Devices Development Center, Matsushita Electric Industrial Company, Ltd., 3-1-1 Yagumo-Nakamachi, Moriguchi, Osaka 570-8501, Japan