The fully analytical method has been widely studied for its higher accuracy and efficiency, and the addition of shading rendering can effectively improve the three-dimensional perception of reconstructed images. However, existing fully analytical polygon-based shading rendering methods suffer from high computational complexity and complexity due to the need for additional calculation of the highlight spectrum. Based on previous research, we employ a continuous light and shadow algorithm that uses linear interpolation to decouple the reflection term from the spectrum, meaning that we incorporate the specular component into the calculation of vertex modulus, and separately compute the vertex modulus and the corresponding spectrum values, simplifying the calculation process of existing Blinn Phong lighting models. The algorithm can effectively generate highly realistic holographically reconstructed images with high gloss effects under continuous illumination. It achieves computational efficiency than existing algorithms, without increasing the number of polygons. Simulations and experimental results have verified the effectiveness of our proposed method.
KEYWORDS: Holograms, Computer generated holography, Algorithm development, Reconstruction algorithms, Light sources and illumination, Interpolation, Fluctuations and noise, 3D displays, 3D acquisition, Testing and analysis
Polygon-based computer-generated holography algorithms can achieve high realism at low computational cost. Many recent contributions improve the hologram generation efficiency and solve many issues of 3D realistic rendering. This manuscript provides a comprehensive evaluation of their performance and potential through a detailed classification and comparison. Although the numerical-based algorithms using spectral interpolation offer greater flexibility in achieving realistic 3D displays, further phase-optimization algorithms are needed to render 3D reconstructions with higher definition, reduced noise, and faster updates.
We investigate Irgacure 784/PMMA photopolymers doped with single-walled carbon nanotubes (SWCNTs) of various concentrations. Doping the photopolymer samples with SWCNTs results in an increase in the peak diffraction efficiency from 63% to 88%, as opposed to the undoped state. Holographic imaging of real objects using the SWCNT-doped photopolymer has also been performed.
The introduction of nanoparticles into photopolymers has been proven as an effective approach to enhance the holographic performance of photopolymers. Among these nanoparticles, nano-diamonds (NDs) with high hardness, stability, and refractive index represent an ideal doping component. In this study, we investigate the impact of doping different concentrations of ND nanoparticles on the holographic performance of Irgacure 784/PMMA photopolymers. The doping of ND nanoparticles leads to significant enhancements in diffraction efficiency for the photopolymer samples. Notably, photopolymers doped with 0.5×10-3 wt% ND nanoparticles achieve a maximum diffraction efficiency of approximately 87%, nearly doubled when compared to undoped photopolymers. Subsequently, holographic imaging of real objects is conducted on ND-doped photopolymers. Experimental results show that our investigated polymers have high peak diffraction efficiency and is capable of reconstructing high-quality and stable holographic reconstructed images. This investigation shows enhancement of holographic performance by doping ND nanoparticles into the photopolymer, providing a new pathway for the further advancement of holographic technology and significant guidance for designing high-performance holographic recording materials.
Optical scanning approach to image processing has advantages over frequency-plane architecture in terms of accuracy and flexibility. We will review an optical scanning approach to image processing that includes the capability of holographic recording.
In the analytical method of polygon-based computer-generated holography, the spectrum of the surface function of an arbitrary polygon (triangle) is expressed in terms of the spectrum of a unit right triangle, which is known analytically. We perform texture mapping by dividing the triangle into many unit right sub-triangles which contain the texture information. The method has been verified by computer simulations and optical experiments.
Off-axis optical scanning holography (OSH) has been recently proposed to perform scanning holography without the use of heterodyning. In the present work, we combine the principle of off-axis scanning holography operating in the coherent mode with the idea of a layer-based method to achieve a new computational imaging technique for optical tomography. The point cloud data of a complex three-dimensional (3D) scene is layered along the depth direction as the 3D object is divided into a series of planar layers parallel to the hologram along the optical axis direction. The data of each layer generates a single-layer hologram under coherent off-axis scanning holography. Finally, the hologram of a complex three-dimensional object is obtained by superimposing all the single-layer holograms. We use a single-sideband filter to extract the hologram spectrum to obtain a positive first-order reconstruction and demonstrate numerical reconstruction with different diffraction distances. Also, optically reconstructed images are displayed by a spatial light modulator. The results indicate that the proposed method can realize the holographic recording and reconstruction of a complex three-dimensional object without the zeroth-order beam and the twin image, providing a new computational method for the generation of holograms of large-scale and long-depth 3D objects.
Edge extraction is an important pre-processing operation in image processing and pattern recognition in machine vision. For example, coherent optical image processing for edge detection can be performed in a standard 4-f system with proper pupil designs. The possibility of pre-processing using digital holography for 3D image edge extraction is intriguing. In this talk, we will review some of the edge detection techniques used in single-pixel digital holography called optical scanning holography (OSH). OSH is a two-pupil system and different edge detection schemes through the different combinations of pupils are discussed.
Graphene oxide (GO) is a precursor material for producing graphene. The electrical and optical properties of GO can be modified by reduction of the oxygen-containing groups. In this report, we have prepared graphene oxide polymers (GO-polymer) with different vol. % of GO and reduced the polymer by direct laser writing. We have found the refractive index modulation of the GO-polymer up to 10^(-1) for 15 vol.%.
Optical scanning holography (OSH) is a single-pixel holographic recording technique. We will first briefly review OSH. We then show some recent results in pre-processing (such as edge extraction) of holographic information.
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