Proc. SPIE. 11048, 17th International Conference on Optical Communications and Networks (ICOCN2018)
KEYWORDS: Signal to noise ratio, Energy efficiency, Modulation, Telecommunications, Turbulence, Free space optics, Wireless communications, Fiber optic communications, Binary data, Free space optical communications
A 4×8 overlapping amplitude and pulse position modulation scheme under non-Kolmogorov turbulent Gamma-Gamma Channel Free-Space Optical Communication system is proposed and simulated. Then the bit-error-rate performance is simulated for further research and application.
The performance of small and dim IR target detection is mostly affected by the signal to noise ratio(SNR) and signal to clutter ratio(SCR), for the MWIR especially LWIR array detector, because of the background radiation and the optical system radiation, the SCR cannot be unlimited increased by using a longer integral time, so the frame rate of the detector was mainly limited by the data readout time especially in a large-scale infrared detector, in this paper a new MWIR array detector with windowing technique was used to do the experiment, which can get a faster frame rate around the target by using the windowing mode, so the redundant information could be ignore, and the background subtraction was used to remove the fixed pattern noise and adjust the dynamic range of the target, then a local NUC(non uniformity correction) technique was proposed to improve the SCR of the target, the advantage between local NUC and global NUC was analyzed in detail, finally the multi local window frame accumulation was adopted to enhance the target further, and the SNR of the target was improved. The experiment showed the SCR of the target can improved from 1.3 to 36 at 30 frames accumulation, which make the target detection and tracking become very easily by using the new method.
A high dynamic range imaging method of GEO staring imaging is proposed based on radiance simulation
of GEO remote sensing targets and analysis of foreign and domestic remote sensing payload characteristics. Due
to the high temporal resolution of GEO staring imaging, multiple exposure method is used and image sequences
are captured with different integration times; Then a high dynamic range image is obtained after fusion with the
contrast of neighborhood pixel values being the weighting factor. Finally experiments are done in lab with
visible plane array 2048*2048 imaging system for verifying multiple exposure test. It can be proved that using
multiple exposure capture fusion method can obtain an 11 bit high dynamic range image. The essence of the
method is that it sacrifices time resolution in exchange for high dynamic range, which overcomes the defect of
small dynamic range of single exposure and is of practical significance in terms of GEO high dynamic range
Proc. SPIE. 8923, Micro/Nano Materials, Devices, and Systems
KEYWORDS: Signal to noise ratio, CMOS sensors, Aerospace engineering, Imaging systems, Sensors, Linear filtering, Spectral resolution, Integrating spheres, Modulation transfer functions, Analog electronics
With the requirements of high time resolution, high spatial and high spectral resolution development in geostationary orbit, photodetector pixel size has gradually become the bottleneck of the space exploration technology. Shanghai Institute of Technical Physics of Chinese Academy of Science has made a new breakthrough in CMOS image sensor area. The scale of its new CMOS image sensor achieves 2.5K×2.5K, and then use 24 detectors to achieve a detector whose scale is 150 million. The detector has been successfully imaging on the ground. In the application process, presents a systematic test and measurement methods to deal with the time noise, dark current, fixed pattern noise, MTF and other parameters of the detector. The test results are below. The MTF of the detector is 0.565 which is measured at 57.21/mm Nyquist frequency. The number of saturated electrons reaches 8.9×10<sup>4</sup>. The total number of transient noise electrons is smaller than 16. The signal to noise ratio is 58.02dB. Through comprehensive analysis and measurement, it shows that the overall performance of the 2.5K×2.5K detector among the same types of products is in the leading position currently.
With limited dynamic range, images acquired by ordinary image sensors can not cover all information of the given scenario. In order to acquire a high dynamic range picture which contains both light parts and dark parts, this article presents one method improving dynamic range of images from given scenes by using double exposure. The principle of this algorithm goes as follows: one scene is confronted with two exposures by the same sensor, then image data got from exposure will be used for image fusion to enlarge the dynamic range. As to over-exposure and under-exposure in images, the algorithm enhances the contrast between them and displays both of them. This algorithm can work in a fast speed within 23 ms to fuse two 512*512 images, and can work in high dynamic range circumstances, which means it can adjust essential values according to different scenes to achieve a better fusion.
Currently, the number, size, fill factor, response rate and other aspects of photoelectric detector have made great
progress. However, the expansion of its dynamic range is always lagging behind. This paper will present the latest
international ways. From the pixel electronic structure and the optical structure, these two aspects to explain the
expansion ways. Focus on analyzing the advantages and disadvantages of them.