A novel array configuration composed of multiple concentric circles is proposed for sparse aperture imaging systems. To get better image quality, one property of the modulation transfer function, called the practical resolution limit, is chosen as the optimization criterion. The optimized novel array configurations with aperture numbers of 6, 7, 9, 10, and 12 are given by using the simulated annealing algorithm. The comparisons of modulation transfer function with Golay and circle arrays with an equivalent sub-aperture number are implemented. Results show that the optimized arrays have smaller practical resolution limit than other array configurations with relative continuous and uniform coverage in the frequency plane.
Passive millimeter-wave imaging is attractive due to the ability to obtain images in low-visibility conditions. In this
paper, a passive millimeter-wave imaging method using photonic processing is presented. The principle of the
millimeter-wave photonic signal processing method is described. The relationship between the signal conversion gain
and the component parameters is discussed. The noise characteristic of this detection method is analyzed. A millimeterwave
radiometer using photonic processing is presented in this paper. A passive millimeter-wave scanning imaging
system using this processing method was implemented. The imaging experiment results show that this imaging method
Proc. SPIE. 6622, International Symposium on Photoelectronic Detection and Imaging 2007: Laser, Ultraviolet, and Terahertz Technology
KEYWORDS: Digital signal processing, Image processing, Imaging systems, Detection and tracking algorithms, Night vision systems, Semiconductor lasers, Signal processing, Infrared imaging, Image quality, Digital filtering
According to characteristics of infrared imaging in darkness, a night vision system with laser illumination based on
embedded structure was developed. The system detected remote target at night with a high-power infrared
semiconductor laser diode as illuminating source, overcoming the defect of weak energy in passive imaging system.
A reliable driver was designed to stabilize output power of the laser. Technologies were adopted to improve
performance of the source greatly, such as slow start-up circuit, current interruption protection and over-current
limit circuit. The illuminating source met the needs of detection in various distances and achieved satisfying
transmission effect. The imaging part, where TMS320C6713 served as the center processor, realized functions of
image capture, processing and export. As is known, infrared image has defects of small dynamic range and low
contrast. Otherwise, the source, environment and electronic devices brought various noises that reduced image
quality. Algorithms of image enhancing and noise inversion were designed correspondingly, which filtered noises
and restrained background influences to gain high contrast of the target. Compared with traditional image
processing based on computer, the adoption of DSP not only greatly improved image quality, but also made this
system miniature and portable. The system could capture real-time image of remote target in 3~5km accurately in
starless nights or under poor weather conditions.