Design Of Polarization Imaging System Based On DMD

The resolution of wide-band polarized infrared imaging is severely limited by the technical level of wide-band infrared detectors.At present,the highest resolution infrared detector is Polar^[1]of Raytheon in the United States,with a resolution of640×512,which is still relatively small compared with the resolution of visible light detectors,and it is difficult to meet the requirements of people who want high-resolution infrared imaging.In addition to the low resolution of the detector itself,polarization imaging further reduces the imaging resolution.Usually polarization imaging needs to obtain scene information with four different polarization states for one observation,in view of this problem,the use of traditional spectroscopic path structure requires four optical paths and four detectors,which is not conducive to the system’s requirements for light miniaturization;The use of spectro-pupil or focal plane structure will double the resolution of the detector,which will make it worse for the medium and long wave infrared band with low resolution,and seriously lose scene details.Aiming at the needs of simultaneous polarization and high-resolution imaging in wide band,a split-aperture simultaneous polarization super-resolution imaging system based on reflective free-form optical system and Digital Micro-mirror Device（DMD）is proposed,which has the advantages of being used for simultaneous imaging of any optical band,multiple polarization states,single detector,high resolution,and easy weighting.The aberration correction principle and design optimization method of the optical structure of this imaging system are given,and the Wassermann-Wolf（W-W）theory is further developed,and the reflective Wassermann-Wolf differential equation that can eliminate various aberrations is derived.At the same time,combined with Seidel aberration theory,the boundary condition of distort is added to the solution of the Wassermann-Wolf equation,and the optical initial structure that simultaneously eliminates spherical aberration,coma,astigmatism and distortion is obtained through iterative methods.The initial structure is processed off-axis and further optimized,and a custom optimization evaluation function is written to strictly control the position of the main light landing point of each sub-aperture and each field of view on the middle image plane and the final image surface,so as to effectively suppress the distortion in the final system,avoid the mismatch error of mirror elements and cells in the process of super-resolution reconstruction,and improve the reconstruction quality.Finally,the design of the four-sub-aperture free-form off-axis reflection super-resolution imaging optical system was completed,with a large relative aperture（F#=2.5）,compact structure,and the imaging quality of each polarization channel was close to the diffraction limit.The above aberration correction principle and image quality optimization method can effectively guide the design of ultra-wide band simultaneous polarization super-resolution imaging optical system.Based on this four-sub-aperture free-form off-axis reflection super-resolution imaging optical system,a super-resolution imaging simulation experiment based on compressed sensing is carried out,and the effect of compressed sensing on image resolution improvement is verified.