Holographic 3D Display And Its Application In Augmented Reality

Holography technology is the most perfect 3D display technology,which records and reconstructs the phase and amplitude of an object optical field,thus producing a vivid 3D vision as if it comes from a natural 3D scene.However,it is still challenging how to realize dynamic and real-time holographic 3D display and make it meet the demands of practical applications including large size and filed of view,high image-quality,high resolution,and high refresh-rate.Meanwhile,recently,the near-eye dislay with augmented reality(AR)as the representative is rising,which bring a new application scenario for holographic display.The near-eye display has lower demand for the light modulation device of holographic display,compared to the eyenaked display.However,the near-eye display is usually head-mounted,which proposes new request of being small and lightweight for holographic display.Our work foucuses on those chanllenges.We have made efforts on some key techniques of eye-naked and near-eye holographic display,including algorithm,light modulator and optical system.The main work is shown as follows:1.We conduct studuy on algorithms of computer-gnerated hologram,especially iterative algorithms for phase-type hologram.To improve the image-quality of holographic reconstruction,two improved iterative algorithms are proposed,namely the symmetrical Gerchberg-Saxton(GS)algorithm and the dynamic compensatory GS algorithm,respectively.(1)The symmetrical GS algorithm introduces weighting factor in the process of amplitude constraint among algorithm iteration,which is able to eliminate the image distortion in holographic reconstruction for binary image.(2)The dynamic compensatory algorithm is designed for multi-plane object.This method makes further modulation on the basis of the symmetrical GS algorithm,which dynamically adjusts each weighting factor according to the image-quality of each image-plane.With the dynamic compensator algorithm,image-quality unbalance among multiple planes is eliminated and the average image-quality is increased.2.Holographic 3D display based on doped-liquid-crystal optical-addressed light modulator is studied.Current electrical-addressed light modulators have the problems of small size and low resolution,due to the limitation of fabrication techniques for pixel electrode.However,optical-addressed light modulators could get agroud these problems.(1)Inverstigation is carried out on the mechanism of holographic grating in doped liquid crystals.With the optimization of recording conditions for holographic grating,a fast response time of 8.46 ms is achieved.(2)A dynamic holographic 3D display is conducted based on the dopedliquid-crystal optical-addressed light modulator,which realizes high refresh-rate.(3)The optical nonlinearity of doped liquid crystal is investigated.The third order optical nonlinearity is measured using a method of nonlinear interferometry.3.Inverstigation about near-eye holographic 3D display is implemented,which is focused on holographic display in AR systems.To decrease the volume and weight of holographic display system and make it more suitable for head-mounted AR systems,it is proposed to use holographic optical elements(HOEs)to replace the traditional optical elements and subsystems,aiming at small and compact holographic AR display.(1)A holographic AR waveguide display with zero-order elimination is designed.This design adds a lens function and a separating hole in two HOEs of diffracted waveguide AR constructure,which realizes zero-order elimination without bulky 4-f system and simplificates the holographic AR system.(2).A holographic AR system with beam-expander is proposed with two HOEs,which achieves functions of beam expanding,AR combiner and ocular lens,simultaneously.