KEYWORDS: Night vision systems, Reflectivity, Target detection, Transmittance, Night vision, Contrast transfer function, Visual process modeling, Objectives, Environmental sensing, Visibility
With the progress of technology and the development of society, night vision technology is widely used in various fields such as aerial reconnaissance, man-portable combat, civilian outdoor scene perception and security monitoring. For direct view night vision system, the adult is usually regarded as the identification target in the assessment of detection distance. However, for the night vision system which used in fixed-wing aircraft, the targets which include airport runway, building and so on are treated as identification target in the assessment of detection distance. Due to the verification demand of long-distance detection of night vision system, this paper analysis the equivalent assessment method of detection performance, deduces the relationship of the detection distance, target size and the target characteristics parameters, proposes the principles and steps which determine the equivalent assessment parameters. Through analyzing examples, this paper calculates and verifies the feasibility of the detection performance equivalent assessment method, which can provide theoretical support for the verification of the equivalent evaluation of the detection performance of the night vision system.
Star sensor provides high precision coordinate and spatial orientation through taking stars as the frame of reference, which is a kind of high-precision attitude sensitive measuring instrument. It has the advantages of high precision, strong anti-interference capacity, autonomous working and so on. In this paper, it analyzed the advantages and disadvantages between CMOS and CCD, and then, it introduced the working principle of the star sensor. After that, it deduced the correlation between the non-uniformity index and the other key technical indexes of star sensor, such as SNR, field of view, focal length, detection capability and photoelectric conversion efficiency. Finally, it has made a simulation of the relationship between PRNU and SNR according to the certain CMOS detector and theoretical design parameters, which can provide the theoretical basis for the CMOS detector selection of star sensor.
In the electro-optical pod, the dynamic range is an important performance index of photo detector. The low dynamic range (LDR) can cause saturation at high end or compression at low end, which directly leads to the loss of information. In order to improve the dynamic range of photo detector, it introduces the dual channel scientific complementary metal oxide semiconductor (sCMOS) in this article, which adjusts the gain level of two imaging channels according to the scene and illumination, and then performs the procedure of image synthesis in each pixel. After making a further research of the imaging principle of dual channel monochrome sCMOS, it mainly studies the relationship between the dynamic range and the gain level. Through calibrating radiation response curve by adapting different gain level, the paper has verified the dynamic range of this dual channel monochrome sCMOS and provides a theoretical basis for the application of it in different scenarios.
KEYWORDS: Image fusion, Sensors, High dynamic range imaging, Image processing, Cameras, Image sensors, Field programmable gate arrays, Data conversion, High dynamic range image sensors
Due to the impact of urban lighting in low illumination environment, the images that collected by the low illumination sensor may appear “local saturation” phenomenon. When the traditional image sensor captures high dynamic range (HDR) of the sense, either the brighter part of the generated image is over exposure that may lost many details, or the dark part of the generated image is underexposure which cannot be resolved. In order to overcome this problem, it makes a research on the dual channel monochrome scientific complementary metal oxide semiconductor (sCMOS) sensor, which can generate both a high gain (HG) channel image and a low gain (LG) channel image in a same frame exposure. Take the way of image fusion by using these two images; it can get the HDR image in low illumination environment. Comparing with the traditional image sensor, the dynamic range of dual channel monochrome sCMOS sensor is obviously extended. The scheme based on dual channel sCMOS can effectively conquer the defects of low dynamic range bring by traditional image sensor, and it can overcome the problem of insufficient real time performance due to multiframe exposure. For dual channel sCMOS has the features of HDR, it can operate at a lower illuminative condition and will have a wide application area.
The dual channel complementary metal-oxide semiconductor (CMOS) can get high dynamic range (HDR) image through extending the gray level of the image by using image fusion with high gain channel image and low gain channel image in a same frame. In the process of image fusion with dual channel, it adopts the coefficients of radiation response of a pixel from dual channel in a same frame, and then calculates the gray level of the pixel in the HDR image. For the coefficients of radiation response play a crucial role in image fusion, it has to find an effective method to acquire these parameters. In this article, it makes a research on radiation calibration of high dynamic range based on the dual channel CMOS, and designs an experiment to calibrate the coefficients of radiation response for the sensor it used. In the end, it applies these response parameters in the dual channel CMOS which calibrates, and verifies the correctness and feasibility of the method mentioned in this paper.
Light spot centroid detection is one of the key technologies in optical measurement. In order to overcome the poor stability caused by small scale spot, we proposed an extract method by using saturated light spot in this paper. By increasing the input voltage of LED and adjusting the exposure time of CCD, the image of LED which projected in the image plane become larger, it can help enhancing the stability of light spot centroid extracting. The experiment results showed that the extract stability of saturated light spot has improved obviously compared with small scale spot. This method can be adopted in close range measurement; it reflected the sub-pixel coordinate of spot in image plane coordinate more accurately after calibrating the distorted image.
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