Assessment Of Laser-dazzling Effects On Electro-optical System

The photoelectric imaging system fulfils various functions such as high-resolution imaging, detection, tracking and recognition by means of photodetector. Laser is widely used in radiation jamming and damage because of its monochromaticity, coherence, directivity and high intensity. The imaging device forms are saturated and damaged with increasing of irradiance. This leads to quality reduction of the image and errors of the recognition. Therefore, it is necessary to understand the cause of distortion and analyze the human visual system characteristics, laser spot features, image statistical characteristics and the loss of location information quantitatively. The evaluation algorithm designed gives the guidance to the laser-dazzling equipment development and photoelectric imaging system defense.For the imaging reconnaissance system based on artificial cognition, the algorithms, combining with human visual system characteristics, by means of wavelet decomposition, losses of image features and varieties of laser spot are proposed. For the image processing system to fulfill target detection, tracking and recognition, the algorithms based on feature-point change are proposed. In order to evaluate the dazzling effects in the period of time, the algorithm based on the dynamic features of multi-frame images is proposed. In terms of experiment results,these algorithms give accurate and quantitative evaluation results for laser-dazzling images. The results are suitable for the subjective visual feeling.The mainly work studied in the thesis is arranged as follows:(1) Theoretical results and analysisFor the imaging reconnaissance system, whose end user is observers, the subjective feeling reflects the variation of image quality. A wavelet-weighted multi-scale structural similarity(WWMS-SSIM) algorithm is proposed. This algorithm, based on the human visual system, simulates the image processing and sensitivity to different frequency bands. The results are consistent with the subjective feeling. Considering the masking effect and information loss of the laser-dazzling image, a full-reference weighted feature-similarity(WFSIM) algorithm and a no-reference feature variation metric(FVM) are proposed. These algorithms analyze the human visual system characteristics and consider the size, intensity, position of the laser spot. The algorithms combine laser spot feature change with image information loss. The evaluation results can reflect more reasonable dazzling effects.For the image processing system, the image feature extraction accuracy reflects the variation of image quality. A full-reference feature-point similarity(FPSIM) algorithm and a no-reference feature-point complexity metric(NRFPCM) are proposed. These algorithms analyze the position, amount of the feature points, local luminance and contrast distortion. The algorithms combine target recognition with evaluation methods. The evaluation results can reflect the image distortion impact on target recognition.Laser jamming is a continuous, variable and cumulative process, so the assessment of single frame cannot reflect dazzling effects. It is necessary to evaluate multi-frame image quality. A no-reference image quality assessment algorithm based on the dynamic features of multi-frame images is proposed, which is called feature-point dynamic(FPD). This algorithm can evaluate the laser-dazzling image quality of a single image and it gives a more reasonable evaluation result for multi-frame laser-dazzling effects in the period of time.(2) Experiment and analysisIn the way of availability, we evaluate the image quality of the LIVE database. In order to get quantitative measures on the performance of these algorithms, we followed the performance evaluation procedures employed in the video quality experts group(VQEG). The correlation coefficients, root mean square error, mean absolute error and outlier ratio are calculated to verify the accuracy and consistency. In the way of adaptability, NMSE, PSNR, SSIM and algorithms proposed are used to evaluate different laser-dazzling images,containing different interference power, different background intensity and different spot position. The quality scores are compared and the subjective consistency, objective reasonableness are verified. In the way of expansivity, we analyze the time overhead of some algorithms. The applied prospect of dealing with incremental datas is verified.