oa Foreword

In this issue of the journal of Recent Patents on Signal Processing we present another set of interesting research and overview papers giving the readers a glance on the multidisciplinary nature of applied aspects involved in the field of signal processing. Specifically this issue presents seven papers. One of the papers deals with vision and image processing. The authors show that the non-linear nature of the human visual response to achromatic contrast is a key element to improve the performance in achromatic image coding. In their paper they describe a general procedure to define color contrast for any spatial basis functions with any chromatic modulation. Another paper deals with optical devices. The article focuses on the realization of all-optical signal processing functions based on the nonlinearities of a semiconductor optical amplifier by reviewing the recent and significant patents and publications related to these new developments and applications. Then, additional three papers deal with communication while the first of them presents novel selection method based on the low granularity block to reduce the complexity for a MUDiv/OFDMA. The second gives an overview of the broadcasters' requirements and the solutions with IP networks with focus on video file transfer. The third paper presents optical information processing systems for optical image encryption and watermarking. The last two papers on this issue deal with Tera Hertz (THz) radiation in sense of presenting the progress in compact room temperature THz radiation sources and then in discussing the recent advances of THz imaging technologies.