CMOS Imaging Design Of Coordinated Multichannel Based On Drift Angle Adjusting Mechanism

With the deepening of space exploration,high-resolution imaging tasks put forward higher requirements for the image motion compensation accuracy and image collinearity.In order to obtain a larger imaging range,space camera is developing towards a wide field of view.The larger the focal plane size of the wide-range space camera,the larger the residual drift angle between the image point farther away from the center point and the center point on the focal plane.However,the traditional drift angle compensation method of the focal plane rotation is hard to effectively reduce the residual drift angle,so it is difficult to meet the actual needs of high-resolution imaging.Although the new drift angle compensation method of rotation of each sensor can effectively improve the accuracy of image motion compensation,it is difficult to make the space camera output linear and continuous image strips.In order to facilitate on orbit real-time target recognition and tracking,electronic racemization can be used to deal with the image discontinuity problem in hardware,but it has the defects of too large amount of calculation and hard to realize in hardware.In view of the above problems,from the perspective of hardware implementation,an electronic imaging system based on CMOS image sensor and FPGA is designed.The effectiveness and applicability of the imaging system are verified by numerical simulation and experimental examples.The main research contents include the following aspects :(1)The reason of the drift angle in the imaging process of space camera is studied.The influence of traditional and new methods on the image is analyzed and compared.The structure and working principle of CMOS image sensor and CCD image sensor are explained.Aiming at the image discontinuity problem of the new drift angle compensation method,a method is proposed to output part of the image data by using the windowing function of CMOS sensor to realize the clipping function of noncollinear part of image in adjacent detectors,and provide the basis for space camera to form continuous image strips.(2)The hardware framework of space camera imaging system is built,with FPGA and CMOS image sensor as the core electronic system.On the basis,FPGA peripheral circuit,CMOS image sensor peripheral circuit,camera link interface,motor interface and encoder interface are designed.Among them,the motor is used to simulate the slice rotation of CMOS image sensor,and the encoder is used to obtain the rotation angle of sensor,which provides input source for subsequent cutting algorithm.(3)On the basis of FPGA hardware circuit,the overall logic design and function simulation of the imaging system are completed,including CMOS driver module,clock module,SPI interface,camera link interface and UART interface.Aiming at the problem that the algorithm is hard to implement in hardware,based on CORDIC principle,a noncollinear partial clipping algorithm is designed,which is convenient for hardware operation,to realize the output function of continuous image strip of space camera.(4)The hardware of the electronic imaging system is debugged,the actual imaging test is completed,and the error analysis is carried out according to the test results.The experimental results show that when the rotation angle difference between adjacent detectors is 0.4 ’,the number of error pixels is 981,and the ratio of error pixels to total pixels is 0.007796%.In the case of low less loss of image details,continuous images can be obtained,which verifies the effectiveness of the proposed algorithm.