KEYWORDS: Lenticular lenses, 3D displays, Cameras, 3D image processing, MATLAB, 3D acquisition, Displays, Stereo holograms, Stereoscopic displays, Binary data
Stereoscopic display technology has a high sense of presence and can bring unparalleled stereoscopic enjoyment to the audience, which requires stereoscopic glasses, helmet display and other auxiliary visual tools in that greatly limits its application. Auto-stereoscopic display technology (especially based on lenticular lens ) enables the audience to feel the visual impact brought by stereoscopic images freely and clearly with the naked eye in multiple positions within the larger perspective, thus greatly promoting the development and application of stereoscopic display technology. In this paper, an integrated imaging technique based on lenticular lens (88 inches) and projection equipment is introduced. The parameters of lenticular lens grating are calculated firstly, then, we use the 3Ds Max software to acquire the parallax images of the object, integrating all the parallax image pixels together to obtain an image with parallax by using Matlab program. The integrated parallax image is matched by the optical transmission characteristics of the lenticular lens. Experiment show that, the integrated imaging technique based on lenticular lens (88 inches) and projection equipment can display a good stereo image and realize super large-size, true color, dynamic and smooth parallax display. A 3D display by using a large lenticular lens and a projector is achieved in this paper.
Phase-only hologram is the way to generate holograms generated by computers. Although the imaging quality is generally acceptable, the edge and line patterns of the reconstructed images are fuzzy. In this paper, we propose two methods which are the image preprocessing of the original images based on edge-preserve to improve the imaging quality. One is to use the Smallest Univalue Segment Assimilating Nucleus (SUSAN) for the extraction of original image edge, and the other one is to employee the Gaussian filter in frequency domain to separate high frequency and low frequency. Numerical reconstructions and optical reconstructions with a phase-only spatial light modulator (SLM) show that these methods can enhance the edge and line patterns of the reconstructed images, and the merits and drawbacks of the imaging quality using two methods are analyzed.
KEYWORDS: Holography, Holograms, Computer generated holography, Near field diffraction, Speckle, 3D image reconstruction, 3D displays, Optical engineering
Computer holography has made a notably progress in recent years. The point-based method and slice-based method are chief calculation algorithms for generating holograms in holographic display. Although both two methods are validated numerically and optically, the differences of the imaging quality of these methods have not been specifically analyzed. In this paper, we analyze the imaging quality of computer-generated phase holograms generated by point-based Fresnel zone plates (PB-FZP), point-based Fresnel diffraction algorithm (PB-FDA) and slice-based Fresnel diffraction algorithm (SB-FDA). The calculation formula and hologram generation with three methods are demonstrated. In order to suppress the speckle noise, sequential phase-only holograms are generated in our work. The results of reconstructed images numerically and experimentally are also exhibited. By comparing the imaging quality, the merits and drawbacks with three methods are analyzed. Conclusions are given by us finally.
The speckle noise will seriously influence the quality of reconstructed images in holographic displays based on spatial light modulators (SLMs). In order to suppress the speckle noise quickly, we propose a method which combines temporal averaging effect by superposing multi sub-frame images and adding a rotating symmetric diffuser in optical path. The sub-frame images are reconstructed from sequential sub-frame kinoforms. The sequential kinoforms are calculated using Fresnel diffraction based algorithm by adding dynamic pseudorandom initial phase factors. A rapidly rotating symmetric diffuser is replaced the pinhole in optical path to produce illumination light sources with various speckle patterns over a short periods of time. Hence, various holographic images with different speckle patterns can be reconstructed and superposed to reduce the speckle noise. Optical reconstructions with a phase-only SLM show that, with the proposed method, the speckle noises are well suppressed by superposing fewer sub-frame images compared to use temporal averaging method only. The proposed method is useful for improving the quality of reconstructions in holographic displays with pixelated SLMs.
Hologram calculation of 3D object with look-up-table (LUT) method using Fresnel zone plate (FZP) is a typical and commonly used approach. However, the types of Fresnel zone plate (FZP) significantly affect the holographic imaging quality of 3D objects. This paper mainly analyzes the relationships between imaging quality and the modulation types of FZP. Simulation reconstruction and optoelectronic reconstruction results with amplitude-modulation type and phase-only modulation type of FZP show that, conjugate image exists in the imaging plane using amplitude-type FZP in LUT method. However, no conjugate image exists in the imaging plane using phase-type FZP in LUT method. The experimental results show that, compared to the amplitude-type FZP, the phase-type FZP is more suitable for improving the imaging quality of holographic 3D display.
Doped liquid crystals, as super-fast refresh holographic media, are very useful in holographic 3D video display because of their extraordinarily high optical nonlinearity arising from laser-induced director axis reorientation. We obtained real-time dynamic holographic display with holographic response time under an order of a microsecond using the super-fast-response liquid crystal films. The hologram formation time and self-erasable time can both reach ~ 1 ms in this film. Holographic video display was realized using them without any cross talk between the holograms. In this paper, the mechanism of real-time hologram recording and self-erasure will be presented based on light-induced liquid crystal molecular reorientation in the films.
We have achieved real-time dynamic holographic display with holographic response time under an order of a microsecond using super-fast-response liquid crystal films. The hologram formation time and self-erasable time can both reach ~ 1 ms in this film. Holographic video display was realized using it without any cross talk between the holograms. However, the holographic display videos we obtained before need to be improved in image quality. This paper presents improvement of holographic video display of the films, and our achievement may be useful for its potential applications in a large-size, high-definition, and color holographic three-dimensional video display.
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