Research On An Optical Imaging System For High Precision Measurement Of Rotation Angle

The collimator imaging technology based on the principle of Fourier transform has attracted the attention of experts at home and abroad due to its advantages of high sensitivity and high reliability,and has gradually become the first choice for space detection of solar hard X-ray loads.The solar hard X-ray imager?HXI?adopts this kind of collimator imaging technology.The collimator system consists of several groups of grating pairs which are respectively assembled on the front and back grating substrates.The front and rear grating substrates are at a certain distance and parallel to each other.The source image can be obtained by photoelectric conversion and inverse Fourier transform of the hard X-ray source modulated by multiple gratings.In order to obtain high quality source images,it is necessary to monitor the relative position changes of the front and rear substrates with multiple grating pairs,and provide data support for subsequent correction.This paper mainly studies the system for measuring the relative rotation angle of the front and rear substrates,analyzes the scheme for measuring the relative rotation angle of the front and rear substrates,uses Zemax software to simulate and design the optical system of the deformation monitoring mirror,studies the inversion algorithm of the rotation angle,and realizes the high-precision measurement of the rotation angle.The main research contents are as follows:1.Based on the structural characteristics and measurement indexes of the collimator system,two kinds of rotation angle measurement schemes are analyzed and compared,which are grating direct imaging method and ground glass+deformation monitoring mirror imaging method,and the measurement scheme is determined,which provides the basis for the following optical system design and inversion algorithm research.2.According to the imaging characteristics and design principles of deformation monitoring mirror,the optical system parameters such as working band,field of view,focal length and F number are determined.The deformation monitoring mirror is designed and simulated with Zemax software and the aberration is analyzed.The effect of the ghost image of the optical system on the imaging is analyzed,and the conclusion is drawn that the ghost image has little effect and can be ignored.According to the black body radiation law,the energy of the system is calculated and the transmittance of the ground glass is 0.3788.3.The correctness of rotation angle inversion algorithm is studied and verified.Firstly,the transformation relationship between the coordinate system in the process of three-dimensional space coordinate to the image coordinate based on pixel is analyzed,which provides theoretical guidance for the subsequent simulation;Secondly,the coordinate relationship before and after the change of the facula is deduced under the condition of different rotation centers.The inversion algorithm of the relative rotation angle is studied.The theoretical measurement accuracy of the rotation angle is in the range of 10^-10?through simulation calculation.The influence of the rotation center position and distortion on the measurement accuracy is analyzed.The results show that the measurement accuracy of the rotation angle has nothing to do with the rotation center position.The distortion causes the center positions of the three spots to shift by0.12pixel,0.12pixel,and 0.08pixel;Finally,the stability of the deformation monitoring mirror is analyzed,and the repeatability measurement standard deviation of the spot coordinates is calculated to be less than 0.02 pixels,which provides a strong basis for the subsequent measurement accuracy verification;The experimental data verifying the measurement accuracy of the rotation angle of the deformation monitoring mirror is analyzed and processed,and the error analysis is performed.The results show that the average value of the rotation angle measurement accuracy of the deformation monitoring mirror is 1.8?,which meets the index requirement that the rotation angle measurement accuracy is better than 5?.