Research On Amplitude-only Holographic Display Based On Digital Micromirror Device By Point Source Method

Computer-generated three-dimensional(3D)display technology based on spatial light modulator is considered to be one of the most promising solutions to achieve true 3D display.Because it can provide all the information of 3D objects and quickly realize dynamic display.As an amplitude-only spatial light modulator,DMD has been widely concerned because of its high refresh rate,which can realize better color dynamic display.However,most of the current computer-generated holographic 3D display solutions are based on viewpoint,and other technologies are needed to observe the complete information of 3D reconstructed images within a certain range,while most of the current solutions are based on the sacrifice of frame frequency to improve the reconstruction image quality of computer-generated holographic display based on DMD,which is difficult to realize color dynamic computer-generated holographic display.Therefore,this paper proposes a point source method amplitude-only hologram optimization algorithm based on holographic viewing windows to improve the reconstruction image quality without sacrificing or reducing the sacrifice of DMD frame rate,and builds a color computer-generated holographic display system based on DMD.The main research contents are as follows:Firstly,this paper introduces the mainstream technology of 3D display and the research status of relevant technology of 3D color computer-generated holographic display based on spatial light modulator.The specific characteristics and analysis of DMD for computergenerated holographic display applications are discussed.Based on the diffraction characteristics of DMD in flat state,the diffraction characteristic formulas analogous to a blazed grating in open state are derived.The simulation compares different display schemes of DMD,and proposes a display scheme based on the bitwise grading of the original object and the calculation of the loaded binary hologram.Secondly,an optimization algorithm for amplitude-only holograms based on point source method is proposed.The original image is converted from grayscale to binary format,and the effective bits of each pixel are extracted in turn to generate eight frames of binary original,and the constant phase to be optimized is introduced on the wavefront phase of the point source to superimpose the wavefront and generate a grayscale hologram with binary encoding.The effectiveness of the optimization algorithm in improving the image quality is verified by simulation and optical experiments.Thirdly,a technical solution is proposed for stitching objects in time sequence to improve the image quality of holographic display.The relationship between the ratio of hologram sampling points to object sampling points and the quality of reconstructed images is analyzed and calculated.By segmenting the object and introducing carrier frequencies,the computer-generated hologram is optimized.The high refresh rate of DMD is utilized for time-multiplexed display stitching to achieve the goal of improved image quality.The effectiveness of the image quality enhancement scheme is verified through simulation and optical experiments.Lastly,a time-division multiplexed color computer-generated holographic display system is designed and built.The synchronization controller’s role in timing calibration between DMD and lasers is analyzed.A scheme is developed to eliminate color aberration in reconstructed images and holographic viewing windows based on the principle of chromaticity formation.The feasibility of achieving high-quality color holographic displays using the optimization algorithm is validated through simulation and optical experiments.