Research Of Acoustic And Optical-electronic Collaborative Modulation Detection Technology Based On Moving Platform

AOTF(Acousto-optic tunable filter)based staring imaging spectrometer has the advantages of flexible spectral selection,controllable sampling interval,and fast wavelength tuning ability,which has a wide range of potential applications in deep space remote sensing and other aerospace exploration.While in actual application,the optical design and instability of platform leads to the mis-registration of bands,which means that one object will appear at different locations in images of different bands.However,compared to the grating type,Fourier transform type splitting mechanisms,the AOTF’s time-series spectral scanning characterisic leads to the mis-registration of bands due to the motion platform attitude and position instability and other factors.Misregistration of bands means that the detection targets do not overlap in different spectral bands,more specifically,it will lead to the mismatch between spatial and spectral information,which affecting the spectral purity of the acquired target and the accuracy of quantitative inversion.At the same time,the dispersion shift of AOTF caused by the acousto-optic nonlinear effects which means that the diffraction exit angle at different bands varies with the change of the crystal driving frequency,resulting in lateral drift of the acquired target spectral image.It also affects the reconstruction of the target spectral data cube.On this background,this paper analyzes the spectral mis-registration of AOTF imaging spectrometer caused by motion platform and the crystal itself,explores and implements the registration of AOTF imaging spectrometer based on the motion platform.Firstly,this paper analyzes the problem of band mismatch of AOTF imaging spectrometer,evaluates the acousto-optic interaction splitting mechanism of AOTF crystal using momentum matching law,summarizes the main optical performance parameters affecting the imaging quality of AOTF,and establishes the mathematical physics model of AOTF.Then,the dispersion drift characteristics of AOTF is analysed in detail.The numerical analysis shows that it is theoretically feasible to compensate for the spectral image shift using the AOTF dispersion drift characteristics.While in practical airborne and spaceborne application,the influences of parameters such as integration time,platform attitude,position stability,and pointing accuracy on the shift of the spectral bands and the image shift uniformity within the entire field of view are analyzed.The analysis results show that the image mismatch between the spectral bands mainly refers to horizontal shift valued about tens of pixels in the case of attitude and position stability as well as shorter integration time,which provides favorable conditions for the compensation of the horizontal shifts caused by motion platform making use of the AOTF’s dispersion drift.According to the dispersion drift characteristics of AOTF,a high-precision AOTF diffraction exit angle measuring system based on image processing is designed.Firstly,the basic principle of the image processing algorithm used in this paper is introduced.the SIFT(Scale-invariant feature transform)matching algorithm and the Hough transform based geometric shape detection algorithm are respectively adopted to acquire the horizontal drifts at different bands,the diffracted angle curve of ±1st-order diffracted beam with opical wavelength ranged 450 nm to 800 nm is obtained through the contrast of the horizontal drifts results getting from the two algorithms.On the basis of AOTF’s diffraction angle data,the spectral registration scheme of the AOTF imaging spectrometer based on the motion platform is introduced.Firstly,the AOTF imaging spectrometer system is designed according to the index parameters.Secondly,the spectral registration schemes with different target positions and the spectral registration scheme with fixed platform motion velocity are also designed.The specific implementation method of imaging acquisition drive control is described.In addition,the principle verification system of registration scheme is established and the target position,diffraction wavelength,diffraction angle correspondence relationship is built according to the processing of experiment data.The acquisition of the target spectral data cube based on the motion platform is finally achieved,and the registration accuracy of the acquired spectral data is also evaluated.Error evaluation shows that this method satisfies the requirements of the registration accuracy within 0.3 pixels for AOTF imaging spectrometer.