Research On HUD Holographic Display Technology

Head-up display(HUD)allows drivers to see important driving information without lowering their heads.It is an important driving assistance device to assist drivers in driving safely and reduce the incidence of accidents,especially AR-HUD combined with augmented reality technology.Important information such as road condition information and navigation guidance can be directly combined with the real road,which further improves the perception efficiency of drivers.However,several mainstream HUD projection technologies currently perform poorly in AR-HUD’s most desirable 3D imaging effect,while holographic display technology,as the most ideal true 3D reconstruction technology,provides a new image generation unit for AR-HUD.Solutions.With the rapid development of computer technology,computational hologram(CGH)has gradually replaced the traditional recording holography due to its advantages of easy acquisition and storage,and plays an important role in the current holographic display technology.However,there are still various problems in the 3D reconstruction of computational holography based on the phase-based spatial light modulator,including speckle noise,poor depth of field and other problems,which restrict the application of holographic display in AR-HUD.In this paper,the holographic display is used as the image generation unit of AR-HUD,and the focus is on improving the three-dimensional reconstruction quality of pure phase holograms.Based on this,a multi-plane imaging algorithm based on double-phase encoding and a gradient based on complex amplitude error function are proposed.The method of descent is used,and the feasibility of the algorithm is verified by simulation and optical experiments.The main research contents of this paper are as follows:1.This paper first reviews the development of HUD and holographic display.This paper analyzes and compares several existing HUD technical routes,and focuses on the advantages and disadvantages of several projection technologies currently used in HUD,as well as the advantages of holographic display compared to these projection technologies.In the theoretical aspect of computational holography,including scalar diffraction theory,holographic threedimensional display and several phase hologram calculation methods are discussed,which leads to two improved hologram calculation methods studied in this paper.2.A multi-plane double-phase coding algorithm is proposed.Compared with the traditional double-phase coding algorithm,the distance parameter is introduced,so that the image information that is not on the holographic surface propagates through the Fresnel or angular spectrum to the holographic surface,and then passes through the spectrum.The lowpass filtering of the high-order noise filters out high-order noise,thereby extending the doublephase encoding algorithm to multi-plane.3.A complex amplitude error gradient descent method is proposed.The error function in the traditional gradient descent method only considers the error between the amplitude of the target image and the reconstructed image.In this paper,the target image amplitude and uniform phase are used as the target complex amplitude,and the The complex amplitude obtained by simulating the propagation is used as the mode difference and used as the error function.When calculating the multi-plane hologram,a mask is used to avoid calculation irrelevant errors.At the same time,in the iterative process,low-pass filtering is introduced to converge the algorithm.4.The above two algorithms are verified from both simulation and optical experiments.Both algorithms have achieved good results at the simulation level.In optical experiments,the results of the multi-plane dual-phase encoding algorithm are not ideal,and the The amplitude error gradient descent method achieves desirable results.In the end,the feasibility of waveguide pupil dilation in holographic display is verified by simulation and experiment.The research of this paper provides theoretical and experimental reference for the application of holographic display in HUD,and is of great significance to the further research of holographic display in HUD.