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
information capture.
AS infrared CMOS Digital TDI (Time Delay and integrate) has a simple structure, excellent performance and flexible operation, it has been used in more and more applications. Because of the limitation of the Production process level, the plane array of the infrared detector has a large NU (non-uniformity) and a certain blind pixel rate. Both of the two will raise the noise and lead to the TDI works not very well. In this paper, for the impact of the system performance, the most important elements are analyzed, which are the NU of the optical system, the NU of the Plane array and the blind pixel in the Plane array. Here a reasonable algorithm which considers the background removal and the linear response model of the infrared detector is used to do the NUC (Non-uniformity correction) process, when the infrared detector array is used as a Digital TDI. In order to eliminate the impact of the blind pixel, the concept of surplus pixel method is introduced in, through the method, the SNR (signal to noise ratio) can be improved and the spatial and temporal resolution will not be changed. Finally we use a MWIR (Medium Ware Infrared) detector to do the experiment and the result proves the effectiveness of the method.
KEYWORDS: Sensors, Modulation transfer functions, Imaging systems, Analog electronics, CMOS sensors, Signal to noise ratio, Integrating spheres, Linear filtering, Spectral resolution, Aerospace engineering
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 8.9×104. 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.
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