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.
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.
In the optoelectronic reconstruction of full-color hologram, transverse and longitudinal chromatisms are introduced due
to the hologram is sensitive to wavelength, which makes the colorful image fuzzy. The image quality is also affected by
the characteristic of the spatial light modulator used in optoelectronic projection system. Multi-order diffraction images
occurred due to the ratio of active area and dead area (fill rate). In the colorful holographic projection system, three lasers
with red, green, and blue color are applied as the light sources, color crosstalk due to the switching of the different lasers
also impairs the image quality. In order to improving the image quality of full color holographic projection system, this
paper analyzes the effect of the fill rate and the color crosstalk on the reconstruction image quality. Transverse and
longitudinal chromatisms are removed by resampling the object information and loading a specially designed virtual
phase distribution in the computer hologram respectively. We proposed time sequence updating chart of RGB laser to
solve the problem of color crosstalk. Experimental results are also provided to verify the improvement of the image
quality.
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