Design Of High-Light-Efficiency Microstructure Film For Vehicle Head Up Display

As an emerging technology,the vehicle head up display(HUD)directly projects the displayed information as a virtual image in the direction of the driver’s line of sight.It not only enriches the fun of car driving;increases the convenience of operation,but also greatly improves the safety of driving.However,most of the current HUD products have the problem that the scattering angle of the image source does not match with the system structure,which cause a part of the bright display image can still be viewed outside the fixed viewing area.As a result,part of the image light energy is not utilized,which is an important factor for the low light efficiency of HUD systemThis paper has made a series of researches on the above-mentioned problems of the vehicle HUD system.The main works include the following aspects:1.Draw the equivalent light path of the imaging system according to the basic structure of the vehicle HUD system,analyze the source of the image light of the system outside the fixed viewing area-Eyebox.Then derive the general formula that the angle of the light outside the Eyebox on the source image based on the geometric relationship of the equivalent light path.2.The paper adopts the method of designing the optical microstructure profile to adjust the image light outside the Eyebox as much as possible into the Eyebox,and use a single column of pixels as the design unit.By measuring and analyzing the divergence angle of the image source and the energy distribution within the angle,the designed input conditions are obtained;and the boundary conditions of each column the pixels just entering the Eyebox area are calculated as the designed output conditions.According to the characteristics of the input and output conditions,the theoretical knowledge of photometry and the law of conservation of energy,a method of designing the profile of the optical microstructure unit is proposed.3.According to the content of the design method,use MATLAB to program to calculate the microstructure profile of each column pixels.The calculated profile number of each microstructure unit is processed to obtain the profile data of the microstructure film,which is imported into the optical simulation software Light Tools to establish an optical model.According to the design parameters,the optical model of the HUD system is established for simulation,and the simulation results are analyzed to feedback and optimize the profile to obtain a suitable microstructure morphology.4.The mask less lithography machine in the laboratory was used to process the microstructure surface,After many times of processing,testing and optimization compensation,the appropriate surface was obtained and the microstructure template was made,and then the microstructure template was sent out to emboss form the microstructure film sample.Build the HUD experiment system according to the design parameters,test the relevant parameters of the system,and analyze the test results.The results show that the designed microstructure film has a good effect on improving the energy utilization of HUD system,the maximum brightness of the display image is increased by 29.5%,the average brightness is increased by 31.8%,and the light efficiency of HUD system is significantly improved.