Measurements Of Polarization And Phase Based On Pixelated Micro-Polarizer Array

Pixelated micro-polarizer array has became an advanced research hotspot, and the polarization direction of each adjacent2×2units are0°,45°,90°and135°. To achieve the integration of the array and the imaging chip, the pitch of the micro-polarizer unit must be the same as the pixel size of the imaging chip. Micro-polarizer array can be used in real-time measurements of the polarization and phase, and has significant potential applications in defense, security, interference measurement, three-dimensional imaging, etc. However, the related products are manufactured mainly by the United States and Japan, and the price is expensive. To break their monopoly, our group first carried out the the fabrication and application researches of micro-polarizer array based on metal nano-grating in the country, and this dissertation mainly includes the following aspects:1. The advantages and disadcantages of three major kinds of micro-polarizer array (based on iodide-containing film, based on the liquid crystal material and based on metal nano-gratings) are comprehensively analyzed, and the micro-polarizer array based on metal nano-grating is choosen to be fabricated and researched, which is of better polarization performance, thinner, and wider application range.320x240micro-polarizer arrays are firstly fabricated by electron beam lithography technique instead of the conventional interference exposure technique. The pitch of the units is7.4μm, and there is no pollution or defective pixel in the array. The period, duty cycle and thickness of the nano-grating are140nm,0.5and70nm, respectively.In order to evaluate the performance of the micro-polarizer array, the light maximum polarization transmittance and extinction ratio are measured. For red, green, blue green bands, the maximum polarization transmittance are75.74%,78.84%and78.01%, respectively; and the extinction ratio are75.0,51.8and30.2, respectively.2. Micro-polarizer array is applied to real-time polarization measurements. In The traditional measurement techniques, four images of different polarization direction filtering are captured and processed, thus it is difficult to achieve real-time measurements. The polarization directions of each adjacent2×2micro-polarizer units are0°,45°,90°and135°, thus four polarization filtered images of different directions can be obtained from a single image by interpolation method, and it is possible to achieve real-time polarization measurements. The polarizer plates and outdoor objects are measured by a camera which is integrated with a micro-polarizer array, and not only the ordinary image but also the degree of linear polarization (DoLP) image and the angle of linear polarization (AoLP) image are obtained in real time. The object of high polarization degree is highlighted from the object of low polarization degree, and the contour information of the smooth surface can be acquired.3. Micro-polarizer array is applied to real-time phase measurements. The camera which is integrated with a micro-polarizer array is applied to the conventional polarization phase-shifting method to achieve real-time phase measurement, and the phase of dynamic plane wave, spherical wave and a special vortex wave are obtained, which is significant for the promotion of the phase-shifting interferometry and vortex beam research. In addition, the author proposed the wave plate phase-shifting method and wave plate array structure, based on the micro-polarizers array and phase-shifting technology, and gives the feasible fabrication technique of wave plate array. The feasibility of wave plate array to achieve real-time phase measurement is theoretically proved, which gives a low-cost substitution to replace the micro-polarizer array.Furthermore, the author also engaged in other areas during graduate studies, including the following:1. Bionic research of pit vipers on infared imaging. The pit membrane and biological tissue are separated by an air cavity, thus the pit membrane is a substrate-free structure. Finite element analysis simulations show that the temperature rise of this substrate-free structure can reach several times of the substrate structure at the cost of sacrificing contrast reproduction capability. Inspired by the pit organ, our group intruduces this unique structure to the infrared focal plane array (FPA). The substrate-free FPA is fabricated by the microfabrication technology, and an optical readout infrared imaging platform based on edge filter is built. Body infrared image are obtained when the substrate-free FPA is placed under air and vacuum conditions, thus the bionic of pit organ on infared imaging is achieved.Based on optical readout uncooled infrared imaging technology, this paper proposed polarized optical readout system to eliminating the stray light received by the CCD. Theoretical analysis shows that the stray light can not reach the CCD target surface, thus the average gray of FPA image can increase50%, and NETD value can decreased to67%. Experimental results show that NETD value decrease to65%, which is consistent with the theoretical analysis value, and infrared imaging performance is optimized.2. Trapping of absorbing aerosol particles. Spherically aberrated lens or frosted glass is used to form light bottle to achieve trapping of a large number of absorbing aerosol particles. In addition, infrared microscope is used to record infrared image of the trapped particles, and the temperature rise phenomenon of the trapped particles is confirmed, which provides the experimental basis for photopheresis force theory.