Optical System Design And Imaging Quality Evaluation Of Multi-band Short-Wave Infrared Camera

Short-wave infrared(SWIR)is between near-infrared band and thermal infrared band,one of the atmospheric windows.SWIR is similar to visible light,results from the ambient light reflected by ground objects.This similarity makes the SWIR images have more details and high-resolution comparable to those in visible images.Excellent optical characteristics of SWIR make it possible to image all-weather and all-time.With the rapid progress of remote sensing technology and uncooled SWIR focal plane arrays since 1960 s,SWIR remote sensing technology has attracted more attention and developed rapidly,which is playing an increasingly important role in science,economy and military affairs of contemporary world.The research and development capability of SWIR arrays and SWIR satellite has become the symbol of comprehensive national strength.The development of SWIR remote sensing technology and related detectors in our country started late,although we have made considerable progress,the related technology is still relatively backward.SWIR remote sensing imaging has broad application prospects and huge economic benefits.With the rise of commercial satellites,it is of great significance to study optical system of SWIR camera.A small-size and light-weight SWIR camera using In Ga As detector was researched in this paper with the purpose of verifying SWIR imaging technology and providing support for following cameras and imagery application.By tracing the transmitting procedure of light radiation between satellite platform and ground objects,the imaging model and atmospheric radiative transfer model are established firstly.The theoretical signal-to-noise ratio(SNR)model and modulation transfer function(MTF)model are then established based on above models,which plays an important role in the following analysis.Consideration the dependence of conventional glass selection methods on discrete Fraunhofer lines and edge bands,the instantaneous dispersion parameters and Buchdahl model are introduced into SWIR.The glass is then represented as a vector in 3D space.In response,the selection of glass material is converted into the form of vector operation,provides a new method for apochromatic lens design.Based on the above theoretical analysis and method,another selection method of glass and mechanical materials suitable for achromatism and athermalization lens design is derived by combining the heating effect of glass materials and mechanical materials.According to the overall design requirements of remote sensing camera,a lightweight spaceborne SWIR optical system is finally designed by combining ray tracing and computer-aided optimization algorithm.The design result and optical performance of SWIR camera is evaluated using a series of ground experiments and in-orbit tests.Ground experiments including spectral calibration and radiometric calibration,while in-orbit tests including dynamic MTF test and SNR test.Meanwhile,the repeatability and time linearity of the detector’s response are analyzed experimentally.In order to reduce the influence of the ground objects’ discretization on the conventional spacesequence based SNR test method,a new method based on time-sequence imaginary is discussed for low-resolution remote sensing cameras.