Research On Demodulation Method Of Spatially Modulation Full Polarization Imaging System Based On Wide Bandwidth Incident Light

The three primary features of light—polarization,frequency and intensity—are particularly significant.Since polarization information can provide additional information from a unique perspective.the extraction of polarization information has become an increasingly popular research area.Researchers choose the spatially modulated full polarization imaging method since it can simultaneously capture all Stokes polarization information,high spatial imaging resolution and capture moving objects.However,the applicability of this scheme is restricted to monochromatic polarization imaging due to the blurring of interference fringes and the mixing of polarization information in broadband polarization imaging.It is necessary to evaluate the broadband spatially modulated full polarization imaging method in order to improve the demodulation scheme and increase the efficiency and accuracy of demodulation.The main focus of this paper is the demodulation scheme for a spatially modulated full polarization imaging system in the broadband situation.After beam split with a birefringent crystal,polarizated imaging system will modify the target’s polarization information into the interferogram.How to more effectively demodulate the polarization information from the interferogram is the next tricky part.In this paper,we first analyze the polarization information distribution in the frequency domain for the broadband situation,and then propose method for determining the limiting bandwidth of the incident light.Then,in contrast to the existing demodulation schemes,a Gaussian high-pass filtering demodulation scheme is developed that can effectively withstand the influence of interference information and provide a superior demodulation result.And after that,in order to decrease the required demodulation time,the issue of low demodulation efficiency of existing frequency domain demodulation schemes is investigated.Local domain filtering and frequency domain centrality removal are proposed as optimization methods.Finally,broadband polarization imaging and demodulation experiments were carried out,and experimental research was used to determine the efficiency of the Gaussian high-pass filtering demodulation scheme.Which was then employed in the polarization imaging project.The specific research work includes:(1)The first research focuses on the characteristics and functions of each optical component in the spatially modulated full polarization imaging system as well as the pertinent theories of the polarization imaging process.The distribution of polarization information in the frequency domain is then investigated by comparing the contrasts between the interferograms produced for different frequency of incident light.Then a theoretical analysis of polarization imaging in the broadband situation is performed,accompanied by an investigation into the issue of interference fringe blurring and polarization information mixing caused by the beam split of Savart prisms.Finally,an approach to estimate the limiting bandwidth of incident light in the frequency domain based on the pixel size is proposed.This method is based on the investigation of theoretical models and simulated experiments.By discrete pixel parallelism with the incident light’s wavelength range,the limiting bandwidth of the incident light is determined in the frequency domain.A graphic analysis of the limiting bandwidth determination scheme serves as the basis for further research into broadband polarization imaging.(2)To expand the application of spatially modulated full polarization imaging system,issues with the current Gaussian low-pass filtering demodulation methods are analyzed.Existing demodulation methods have issues with broadband demodulation,loss of high frequency polarization information,and interference from other polarization information.A frequency domain demodulation method based on Gaussian high-pass filtering is presented in considering of the investigation of these issues.The influence of interference polarization information is reduced and the target’s high frequency polarization information is retained by accurate interference polarization information filtering using a Gaussian high-pass filter.In the case of broadband polarization imaging,it also has a good demodulation performance,which is confirmed by theoretical analysis and polarization imaging experiments.(3)In order to discover a solution for the low demodulation efficiency of the frequency domain demodulation scheme,every part of the frequency domain demodulation method is analyzed.The frequency domain demodulation method is modified by removing frequency domain centrality and local domain filtering.Demodulation experiments on simulated interferograms with various pixel counts are frequently used to confirm the viability of the optimization strategies.As an illustration,the Gaussian low-pass filtering demodulation method is investigated.After using the two modified method,the demodulation time of interferogram demodulation experiment with 1024×1024 pixels was reduced from 3.027 seconds to 0.134 seconds,and the demodulation speed was increased by 97.72%.The demodulation time is decreased in the experiment for the pixel 6144×6144 interferogram from 444.329 seconds to 4.637 seconds,and the demodulation speed was increased by98.75%,which is a more notable improvement.After comparing and analyzing the demodulation results through simulation experiments,it was shown that optimization scheme could still maintain a good demodulation performance.Finally,the optimized frequency domain demodulation scheme is applied to the aerial polarization camera project,and better results are obtained after adjusting to the actual requirements.