| Spectral imaging technology has gradually played an important role in various fields.Since its emergence,it can not only achieve the detection of targets in a single map,but also achieve the screening and discrimination of material properties,showing a strong superiority over traditional optical means,and has been widely used in military reconnaissance,ecological environment,disaster monitoring,mineral exploration,agricultural assessment and other fields.With the rapid development of spectral imaging technology and the increasing demand of frontier in multidisciplinary fields,there is an increasing demand for the performance of spectral imaging systems.On the one hand,the spectral imager with higher optical performance index is obtained through optical optimisation design,on the other hand,the superior performance of the spectral imager is achieved by finding and controlling the optical link error source,which can be seen from both aspects,further promoting the Rapid development.In this thesis,the optical link transfer function model of the spectral imaging system is constructed from the perspective of the imaging link,the coupling relationship between typical error sources and the modulation transfer function is clarified,the error sources of the acousto-optic tunable spectral imaging system are explored,an improved acousto-optic tunable hyperspectral imaging system is designed,which combines the advantages of large aperture and compact structure while ensuring excellent image quality and imaging surface energy,using The sensitivity index analysis and Monte Carlo stochastic simulation were used to verify the accuracy of the error traceability and the reliability of the error assignment,and the tolerance term was optimally assigned to ensure the imaging performance with good results.This thesis focuses on the following research based on the above scientific questions and engineering needs:Firstly,this thesis investigate the current status of research on optical link modelling for remote sensing detection and spectral imagers at home and abroad,and the analysis is usually carried out on the optical system,mounting stress,detector impact and other aspects.In this thesis,we focus on the analysis of optical systems with aberrations,and investigate the design deviations of optical systems,optical material manufacturing defects,optical component manufacturing process defects and errors in the assembly and commissioning process and their traceability.Secondly,from the perspective of the imaging chain of an optical system,an optical link transfer function model of a conventional spectral imaging system is constructed,specifically including the influence of the optical system link and the sampling influence of the detector components,and the role of these layers on the modulation transfer function of the system is a cascade multiplication relationship.On the basis of this model,the contribution of typical error sources to system performance is analysed in depth,wavefront aberration is used as a link in the coupling relationship,off-axis error is introduced into wavefront aberration,and then the coupling relationship between typical error sources and the optical transfer function for optical systems with aberration is established using the physical relationship between wavefront aberration and the optical transfer function,and the influence of typical error sources on wavefront aberration.At the same time,the accuracy of the current manufacturing and mounting processes is combined with the degree of influence of each error on the evaluation index,and the quantitative influence of 10 error terms on the wavefront aberration is analysed in depth.Thirdly,the working mechanism of the Acousto-Optic Tunable Filter(AOTF)spectral imaging system is analysed as an example.A improved AOTF spectral imaging system consisting of an objective lens,a collimator lens,an acousto-optic tunable filter and an imaging lens is designed as an evaluation vehicle to verify the accuracy of the optical link error traceability model.The AOTF hyperspectral imaging system uses two glass materials,introduces an improved Cassegrain system and aspherical mirror structure,allocates optical parameters to subsystems and designs independent optical systems,and then integrates into a complete acousto-optical tunable spectral imager under the requirements of ensuring the subsystem’s optical pupil matching and excellent image quality,and completes a large-aperture and compact optical The design of the structure is completed with a large aperture and compact optics,while meeting the requirements of image quality stability.Finally,wavefront error(WFE)and modulation transfer function(MTF)are used as evaluation indexes to find the important driving tolerance term by optical full system error sensitivity analysis,and the important driving tolerance term of the AOTF spectral imaging system is explored to be the eccentricity error,i.e.the eccentricity and tilt errors,which are consistent with the error traceability results of the AOTF spectral imager optical link transfer function model.A deeper sensitivity analysis was performed for the typical error sources of eccentricity and tilt,and the effect of eccentricity and tilt errors on wavefront aberration and MTF for each lens in the AOTF spectral imaging system was investigated.The weighting factors for eccentricity and tilt errors are given by mathematical analysis to limit the range of eccentricity and tilt errors for certain driver lenses and to guide the error allocation in the mounting process.A Monte Carlo stochastic model is also used to simulate and verify the accuracy of the error sources and the reliability of the error assignment of the AOTF spectral link transfer function model.In the ’inverse increment’ mode,the main error sources obtained overlap with those analysed in the optical link error traceability model by 83%.In the "sensitivity" mode,the typical error sources were compared to the degradation of the evaluation metrics before and after the error assignment,confirming the driving contribution of the typical error sources to the degradation of the imaging performance,and the results based on the error assignment showed that the probability of the AOTF spectral imaging system reaching an MTF of 0.41@42lp/mm was greater than 80%. |
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