蒋晓瑜 Jiang Xiaoyu’s scientific contributions

The basic principle of one-step holographic stereogram printing method based on effective perspective images' segmentation and mosaicking (EPISM) is briefly introduced. The influence of EPISM method on the reconstructed quality change of different scene depths is analyzed. The causes of visual hopping in holographic stereogram based on EPISM are studied. The curvature distortion of holographic stereogram is also analyzed. The effect of curvature distortion on the reconstructed quality of holographic stereogram is verified. The reconstructed quality of the three dimensional scene with short depth is effectively improved when we reduce the size of holographic hogel.

Holographic stereogram printing technology is a widely used holographic technology. In recent years, our project team has proposed a new method to preprocess the perspective images and print the holographic stereograms, called as the effective perspective image segmentation and mosaicking (EPISM) method, in which the holographic printing effect can be achieved via one-step recording beyond the traditional two-step recording, and thus it possesses high research value. In order to predict the printing results of holographic stereograms based on the EPISM method before optical experiments, a numerical algorithm for the reconstruction of holographic stereograms after EPISM is proposed. This algorithm performs a numerical reconstruction of synthetic perspective images processed by the EPISM method and the reproduced images seen at different viewing angles and viewing positions prior to optical printing can be pre-obtained. Through the comparison among the original sampling images, the numerically reconstructed images and the experimentally reproduced images, it is found that the proposed algorithm can be used to simulate the optical experimental results of holographic stereogram printing with the EPISM method.

To solve the problem that the memory space is large and the calculation speed is slow in the novel look up table (N-LUT) method when calculating the color hologram three-dimensional scene. The depth and wavelength compensating N-LUT method (DWC-N-LUT) is proposed to generating color hologram three-dimensional scene fast. The point cloud, which compose three-dimensional scene, are sliced as a series of two-dimensional images with defined depth. The principle fringe pattern (PFP)for red (R) channel corresponding to one depth is obtained according to the pre-stored depth compensating factors. The complex amplitude of object point for R channel is acquired by shifting the PFP. The complex amplitude of object point for G and B channel is directly generated through multiplying that for R channel by wavelength compensating factors. Numerical simulation experiments with an airplane model and a car model indicate that the color and depth of three-dimensional scene can be precisely provided with DWC-N-LUT method. The coherent noise in the reconstruction images can be obviously eliminated by adding random phase to the complex amplitude of object point. The memory space of DWC-N-LUT method is 10 times less than that of N-LUT method, and the computational speed of the proposed method is approximately improved 22% comparing with N-LUT method.

Because of the low imaging resolution of holographic stereogram, a method using wavefront plane is proposed to improve imaging quality. The resolution limit of holographic stereogram is mainly affected by spatial sampling, angular sampling and diffraction. The influences due to these factors are analyzed with mathematical equations. Supposing that the distance between hologram and human eyes is about 600 mm, the relationship between imaging resolution limit and depth of three-dimensional scene or Hogel size is provided according to acuity of human eyes. The depth limit of three-dimensional scene and optimal Hogel size are 12.80 mm and 90 μm, respectively, if the wavelength is 632.8 nm. A wavefront plane which is decided by depth limit is set. The experiments are performed with two three-dimensional scenes to evaluate the proposed method. With numerical simulation method, the tank model which has complicate structures is reproduced. The elaborate features of tank model at every depth are accurately obtained. A teapot model is optically reconstructed with holographic three-dimensional display system based on spatial light modulator. The three-dimensional cues such as depth and gloss are well provided in the reconstructed images.