Research On Imaging Heading Measurement System Based On Skylight Polarization Field

The skylight polarization field is a vector field with the natural properties of the earth.Combined with the insect polarization visual navigation mechanism,the bionic polarization navigation technology using the polarized skylight as the information source has the characteristics of error-free accumulation,anti-interference and good concealment,and it`s the hot research direction of the new concept bionic navigation technology.The polarized light sensor currently developed from the bionic insect single compound eye structure,which uses the polarization sensitive mechanism of POL neurons to detect the point the single direction polarized skylight,which is a source measurement system,and related to the full sky range detection of the insect array compound eye.There are differences in characteristics and lack of robustness and information integrity.The imaging polarization navigation technology facing the skylight polarization field is closer to the visual polarization characteristics of insects,especially in low light,cloudy and other environments,this method has better robustness and anti-interference ability.In this thesis,the research status of the heading measurement technology method about imaging skylight polarization field was studied.The factors affecting the extraction of the solar meridian of the polarization field image and the optimization of the polarization data screening mechanism of the digital signal were studied.The specific research contents are as follows:Comparing the current heading measurement method based on imaging polarization field,firstly,the long-distance imaging polarization test of skylight polarization field over the ocean was analyzed,and the Libradtran software package by Linux was used to simulate the test process.The feasibility of using the solar meridian to provide the heading reference from the figures of polarization field under long-distance navigation conditions was analyzed.Through the analysis for angle of polarization(AOP)and degree of polarization(DOP)images of polarization field imaging,the factors affecting the two-dimensional imaging effect of daytime and nighttime skylight polarization field under sunny and cloudy weather were studied,and a solar meridian extraction algorithm based on binning-data filtering under the premise of threshold segmentation was proposed.Combined with Stokes vector polarization imaging technology,a three-channel imaging heading measurement system for skylight polarization field was built.The system consists of fisheye lens,linear polarizer,CCD image sensor and DSP digital signal processor.The selection of each device and the design of three-channel image decoding module was completed.The embedded software system of the measuring device was designed,and the program framework of complete image acquisition,polarization angle information calculation,solar meridian extraction and heading reference angle output were built.The acquisition of sky polarization image and the serial port real-time output of the device direction reference angle was realized in DSP embedded system.The feasibility of the device and algorithm for extracting the direction of the solar meridian was verified by the initial calibration of the imaging heading measurement system for polarized light.The experimental results showed that the sensor has the compensated absolute indoor error with ±1° in artificial polarized light source.The actual outdoor experiment results showed that this system has certain robustness under low light and low polarization conditions with the ±2.5° compensated error.To a certain extent,the algorithm research and system construction in this thesis enrich the existing research of polarization navigation sensor based on feature extraction of skylight polarization field.