Research On Displacement Measurement Technology Based On Polarized Contrast-enhanced Optical Flow Method

The relatively stable polarization distribution of sunlight in the sky is formed by the scattering of atmospheric particles.Many insects can identify the orientation according to this fixed polarization distribution.After a long-term research,scientists have established a model to describe the dispersion mode of polarized light in the sky,and extracted the feature information from the image of polarized light in the sky for navigation.More and more researchers are involved in the development of polarimetric navigation sensor because of its small accumulated error and no electromagnetic interference.However,at present,polarization navigation can only calculate the navigation angle information of the carrier according to the polarization angle of the sky light,and cannot measure the distance in the navigation application.The main research content of this paper is to propose the polarized contrast-enhanced optical flow technology to achieve the function of polarization navigation distance measurement,and build a three channel imaging displacement measurement system based on the polarized contrast-enhanced optical flow method.Optical flow can calculate the navigation speed through the collected image of adjacent frames,but it is easy to be affected by external light,especially in low illumination environment.Polarized contrast-enhanced optical flow method is aimed at this situation,using polarization imaging to enhance image contrast to overcome the influence of ambient brightness on optical flow calculation.The main work of this paper is as follows:Firstly,in order to solve the problem that the displacement cannot be measured by polarization navigation,a polarized contrast-enhanced optical flow method is proposed.The principle of displacement measurement is introduced in detail,the principle of polarization contrast enhancement is studied,and the improvement effect of polarization imaging on traditional optical flow algorithm is analyzed.Secondly,in order to highlight the advantages of polarized contrast-enhanced optical flow method that is less affected by the ambient brightness when measuring displacement,a 5-level contrast experiment of ambient light intensity is set up,and the contrast of polarization image and polarized optical flow value are used as verification standards.The experimental results show that the error of polarized contrast-enhanced optical flow method is less than 8 mm even in the environment of low illumination of 0.7198 lx,and the accuracy of displacement measurement is twice that of the control group.Then,a three channel imaging displacement detection system is built based on polarized contrast-enhanced optical flow algorithm.The HI3520DV300 processor of embedded Linux system is selected as the core of the system.According to the system requirements,an optical acquisition part consisting of 8mm C-Port lens,CMOS image sensor and linear polarizer is built.According to the hardware condition of the device,the software scheme of the device is designed,and the functions of lens focusing,image registration and polarization image calculation,and displacement calculation of polarized contrast-enhanced optical flow method are completed.Finally,the indoor calibration experiment and outdoor test experiment of the displacement detection system are carried out to verify the feasibility of the polarization contrast-enhanced optical flow algorithm in measuring displacement on the system platform.The indoor calibration results show that the accuracy of the system after compensation is ±0.02mm(5mm),which has a certain robustness.At the same time,the system has been tested in the daytime and night,the error is ±0.02m(2m)and ±0.038m(0.1m)respectively.The research of this paper improves the problem that the polarized light navigation can not measure the distance to achieve the positioning function.