Recent Patents on Signal Processing (Discontinued) - Volume 2, Issue 1, 2012

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.

INTRODUCTION Optical signal processing is a quite wide area with the combination of optoelectronic technologies and signal processing technologies. It deals with the various optical signal operations including optical logical operation [1], imaging [2, 3], encoding and decoding [4], data transmission and exchange [5], encryption [6], etc. Owing to the advantages of high-speed and high-capacity signal processing ability, wide spatial imaging scales, and unique terahertz (THz) interactions with biological systems etc, optical signal processing has been widely used in a range of applications, in particular, optical fiber communications [7-9], biomedicical imaging [10-12], sensing [13], security screening [14, 15], vision chips [16, 17], information security [18] etc. Photonic computer might be one of the most potential applications of this field in the future. Lately, far infrared (IR), or THz wave imaging technologies have grown up due to the ever-increasing demand for the security screening as well as medical diagnosis. THz wave imaging technologies have many excellent advantages over those imaging technologies using other electromagnetic spectrum. The THz wave can penetrate a wide range of materials which are opaque to visible or near IR light or produce only low quality images in X-ray region. It has advantages of low damage to the biological tissues and high image resolution. Currently high-power, pulsed THz radiation sources are already commercialized and used in research and industry, however, the need for more efficient and compact THz signal emission still leads to the continuous development of novel quantum-dot based THz devices, which will be introduced in this issue. Although optical holograms have been used in authentication and security applications for several decades, the impact of optical systems on the information security systems becomes much more impressive nowadays, e.g., in the area of optical data transmission. Benefits of optical systems over other traditional electronic systems emphasize that optical processing provides the maximum number of degrees of freedom and that optical encryption is ideal for information storing in holographic media. Various novel schemes have been proposed in the last decade. In this issue, we review and discuss the recent progress on the patents and research articles on the frontiers of optical signal processing. We mainly focus on the latest development of far IR THz imaging technologies, quantum-dot based THz radiation sources and optical information security systems. This special issue aims to bring the researchers insight and prospect of the relevant issues concerning optical engineering, mathematics, imaging as well as optoelectronic devices....

Terahertz radiation (0.1-10 THz) sits in the electromagnetic spectrum between microwave and mid infrared region. Imaging technologies utilizing this frequency range have recently attracted interests of many scientists considering their potential applications in various areas, such as non-invasive security screening, chemical identification, pharmaceutical and biological sensing. In this paper, we review recent advances and patents in Terahertz imaging technologies, especially, the progress of Terahertz imaging system integration and applications.

There is currently a great deal of interest in the development of efficient compact sources of terahertz (THz) radiation. There are many factors of device and materials design which are still under ongoing improvement with the aim of producing an efficient, high power, room-temperature THz signal emission device which is tunable over a practical THz frequency range. The recent advances in production of various room-temperature THz radiation sources are reviewed with particular emphasis on photomixer antenna devices, and recent patents on technology and methods relating to: pulsed and continuous wave (CW) THz generation via nonlinear crystals; quantum cascade lasers (QCLs); ultrafast diodes and photodiodes; and heterodyne sources are discussed.

Optical systems as information processing systems have become quite impressive recently in optical image encryption and watermarking. Benefits of optical systems over the electronic counterparts are that optical processing provides the maximum number of degrees of freedom, and that optical encryption is ideal for information stored in holographic media. Various schemes have been proposed in the last decade. In this article, we review the recent progress and patents in this field, and point out some challenges that might lead to practical optical information security systems

The non-linear nature of the human visual response to achromatic contrast is a key element to improve the performance in achromatic image coding. Expressing transform coefficients in the appropriate contrast units is relevant when some particular non-linear processing hasto be applied. In the achromatic case, the use of non-linear psychophysical models is straightforward since achromatic contrast computation from image transform coefficients is quite simple. However, using equivalent color masking models in transform coding is not easy since psychophysical results are expressed in color contrast units which are non-trivially related to the transform coefficients in opponent color spaces. In this patent we describe a general procedure to define color contrast for any spatial basis functions (such as block-DCT or wavelets) with any chromatic modulation. The proposed definition is based on (1) simple psychophysics to define purely chromatic basis functions, and (2) statistical analysis of the chromatic content of natural images to define the maximum chromatic modulation. The proposed color contrast definition allows for a straightforward extension of the well known non-linear achromatic masking models to the chromatic case for color image coding. In this work, the use of the proposed color contrast definition is illustrated by a particular non-linear color image coding scheme based on block- DCT, non-linear perceptual response transforms in YUV color channels, and non-linear machine learning response selection. This non-linear scheme is compared to the equivalent linear (JPEG-like) scheme, where color contrast definition is not relevant due to its linear nature.

ATM, SDH or satellite have been used in the last century as the contribution network of Broadcasters. However the attractive price of IP networks is changing the infrastructure of these networks in the last decade. Nowadays, IP networks are widely used, but their characteristics do not offer the level of performance required to carry high quality video under certain circumstances. Data transmission is always subject to errors on line. In the case of streaming, correction is attempted at destination, while on transfer of files, retransmissions of information are conducted and a reliable copy of the file is obtained. In the latter case, reception time is penalized because of the low priority this type of traffic on the networks usually has. While in streaming, image quality is adapted to line speed, and line errors result in a decrease of quality at destination, in the file copy the difference between coding speed vs line speed and errors in transmission are reflected in an increase of transmission time. The way news or audiovisual programs are transferred from a remote office to the production centre depends on the time window and the type of line available; in many cases, it must be done in real time (streaming), with the resulting image degradation. The main purpose of this work is the workflow optimization and the image quality maximization, for that reason a transmission model for multimedia files adapted to JPEG2000, is described based on the combination of advantages of file transmission and those of streaming transmission, putting aside the disadvantages that these models have. The method is based on two patents and consists of the safe transfer of the headers and data considered to be vital for reproduction. Aside, the rest of the data is sent by streaming, being able to carry out recuperation operations and error concealment. Using this model, image quality is maximized according to the time window. In this paper, we will first give a briefest overview of the broadcasters' requirements and the solutions with IP networks. We will then focus on a different solution for video file transfer. We will take the example of a broadcast center with mobile units (unidirectional video link) and regional headends (bidirectional link), and we will also present a video file transfer file method that satisfies the broadcaster' requirements.

Recently, orthogonal frequency division multiplexing (OFDM) has been adopted as the standard of the next generation mobile networks. We proposed the several transmission techniques in the patents. OFDM allows only one user on the channel at any given time. To accommodate multiple users, orthogonal frequency division multiple access (OFDMA) has been proposed. In the conventional OFDM systems, large pilot symbols are required to obtain an accurate channel state information (CSI). To reduce this problem, a time frequency interferometry (TFI) for OFDM has been proposed. In a wireless network, the transmitted signal of each user has independent channel fluctuation characteristics. By using such characteristic, a multiuser diversity (MUDiv) for OFDMA has been proposed. The conventional MUDiv/OFDMA is considered the block selection. The block selection is based on the estimation of the SNR for the subcarrier block and chooses the strong subcarrier block. For the block of small number of subcarriers, the system achieves a diversity gain, but a complexity is large. In this paper, we propose the novel selection method based on the low granularity block to reduce the complexity for a MUDiv/OFDMA.

This article focuses on the realization of all-optical signal processing functions based on the nonlinearities of a semiconductor optical amplifier (SOA) by reviewing the recent and significant patents and publications related to these new developments and applications. One of the main contributions of this paper is to highlight the feasibility of experimental implementation of three logic gates: NAND, OR, and NOR optical gates by exploiting the nonlinear polarization rotation in a SOA structure without changing the setup configuration. Switching between each optical function is done by only adjusting the input optical power level. The experimental investigation is done in free space, allowing optimum control and preservation of the polarization state of the injected and collected signals.

The patents annotated in this section have been selected from various patent databases. These recent patents are relevant to the articles published in this journal issue, categorized by the processes and technologies related to various disciplines of signal processing sciences.