KEYWORDS: Printing, Holography, RGB color model, Digital holography, 3D printing, 3D modeling, Holographic materials, 3D image processing, Computer generated holography, Holograms
In this paper, simplified digital content generation using single-shot depth estimation for full-color holographic printing system is proposed. Firstly, digital content generation is analyzed completely before the hardware system of holographic printing is run to provide a high-quality three-dimensional (3D) scene without degrading information of the original 3D object. Here, the single-shot depth estimation method is applied, and 3D information is acquired from the estimated highquality depth data and a given single 2D image. Then the array of sub-holograms (hogels) is generated directly by implementing fully analyzed computation considering chromatic aberration for full-color printing. Finally, the generated hogels are recorded into holographic material sequentially via effectual time-controlled exposure under synchronized control with three electrical shutters for RGB laser beam illuminations to obtain full-color 3D reconstruction. Numerical simulation and optical reconstructions are implemented successfully.
In this paper, color optimization of a full-color holographic stereogram printing system using a single SLM based on iterative exposure is proposed. First, an array of sub-holograms (hogels) is generated effectively within fast computergenerated integral imaging, and fully analyzed phase-modulation for red, green, and blue (RGB) channels of hogel. Then, the generated hogels are recorded into holographic material sequentially where SLM displays the R, G, and B channels of a single hogel via effectual exposure under synchronized control with three electrical shutters for RGB laser illumination to obtain verified color optimization. Numerical simulation and optical reconstructions are implemented.
his report proposes a three-dimensional/two-dimensional switchable augmented-reality display system using a liquid crystalline lens array and an electrical polarizer. A depth camera that is connected to the proposed augmented-reality display system acquires the three-dimensional or two-dimensional information of the real objects. Here, the dual function liquid-crystalline lens array is switched its function according to the polarizing directions of an electrical polarizer. The proposed system's overall procedure is as follows: the depth camera captures the depth/color, or only color image according to the switcher of a polarizer, and the three-dimensional or two-dimensional images are displayed separately on the augmented-reality display system. It gives an opportunity that three-dimensional and two-dimensional modes can be switched automatically. In the two-dimensional mode, the captured color image of a real object is displayed directly. In the three-dimensional mode, the elemental image array is generated from the depth and color images and reconstructed as a three-dimensional image by the liquid-crystalline microlens array of a proposed augmented-reality display system. Even the proposed system cannot be implemented the real-time display in the three dimensional mode, the direction-inversed computation method generates the elemental image arrays of the real object within a possible short time.
In this paper, a full-color holographic stereogram (HS) printing system based on effective digital content generation using the inverse-directed propagation (IDP) algorithm is proposed. The digital content is generated effectively within the fast computation based on the IDP algorithm, and an optimized phase-modulation of hogel for red, green, and blue (RGB) channels of computer-generated hologram (CGH). Parallel computing is applied to provide high-resolution hologram data based on the independent hogel property. Finally, the generated hogels are recorded into holographic material sequentially as a volume hologram via fully-automated hogel printing setup using a single spatial-light modulator (SLM) to obtain a full-color HS. Numerical simulation and optical reconstructions demonstrate the simple and effective computation operated in content generation using the proposed IDP-based full-color HS printing system without degrading the image quality of the holograms.
A holographic stereogram printing system is a valuable method to output the natural-view holographic three-dimensional images. Here, the 3D information of the object such as parallax and depth information, are encoded into the elemental holograms, i.e. hogels, and recorded onto the holographic material via the laser illumination of the holographic printing process. However, according to the low resolution of the hogels, the quality of the printed image is reduced. Therefore, in this paper, we propose the real object-based fully automatic high-resolution light field image acquisition system using the one-directional moving camera array and smart motor-driven stage. The proposed high-resolution light field image acquisition system includes interconnected multiple cameras with one-dimensional configuration, the multi-functional smart motor and controller, and the computer-based integration between the cameras and smart motor. After the user inputs the main parameters such as the number of perspectives and distance/rotation between each neighboring perspectives, the multiple cameras capture the high-resolution perspectives of the real object automatically, by shifting and rotating on the smart motor-driven stage, and the captured images are utilized for the hogel generation of the holographic stereogram printing system. Finally, the natural-view holographic three-dimensional visualization of the real-object is outputted on the holographic material through the holographic stereogram printing system. The proposed method verified through the optical experiment, and the experimental results confirmed that the proposed onedimensional moving camera array-based light field image system can be an effective way to acquire the light field images for holographic stereogram printing.
We proposed an effective method of digital content generation for the holographic printer using the integral imaging technique. In order to print the three-dimensional (3D) holographic visualizations of the given object, a printed hologram consists of an array of sub-hologram (hogels) should be generated, before the hardware system of the holographic printer is run. There are mainly three parts related to the digital content generation. In the first part, the acquisition of the 3D point cloud object is applied and the second part provided an encoding of directional information extracted from the 3D object. The array of hogel is generated by implementing direction inversed computer-generated integral imaging plus phasemodulation for improvement of the content generation, and displayed on the reflective phase-only spatial light modulator (SLM) then recorded onto holographic material one-by-one in sequence, while motorized X-Y translation stage shifts the holographic material; so, the full-parallax holographic stereogram (HS) is printed on the holographic material and 3D visualization of the object is successfully observed. Numerical simulation and optical reconstructions are verified effective computation and image quality respectively.
KEYWORDS: Holograms, 3D image reconstruction, Image quality, Wavefronts, Computer generated holography, Digital holography, Holography, 3D modeling, Image enhancement, RGB color model
In this paper, a uniform multiple wavefront recording planes (UM-WRPs) method for enhancing the image quality of the RGB-depth (RGB-D) image hologram is proposed. The conventional multiple wavefront recording planes (M-WRPs) based full-color computer-generated hologram (CGH) have color uniformity problem caused by intensity distribution. In order to solve the problem, the proposed method generates depth-related wavefront recording planes (WRPs) to enhance the color uniformity and accelerate hologram generation using a fixed active area. Compared with conventional MWRPs methods, the quality of reconstructed images of this method is improved significantly. The image improvement of the proposed method is confirmed by numerical reconstruction
In this paper, we have implemented a 3D content generation simulator based on integration of phase-only spatial light modulator (SLM) and LabVIEW software to develop a holographic stereogram printer that consists of a coherent laser, a spatial light modulator and X-Y translation stage with stepper motors. This content generation platform provides encoding of directional information extracted from rendered perspective images of real or virtual 3D object. There are mainly three parts related to the implementation for holographic stereogram printer. In the first part, “Digital content generation” phaseonly SLM will be applied to the holographic printer system by loading series of perspective 2D images for each holographic elements (hogel). Regarding this part, phase-only SLM can be converted into an amplitude modulator by adjusting the angles of the polarizer. The second part is “Control system” made in LabVIEW based platform for automatic recording of the holographic stereograms which is synthesized from previous part. The third implementation part is “Optical system” for printing of parallax-related hogels on the holographic plate. To check the performance of the developed approach, numerical simulations and optical experiments are implemented. The hogel images are sequentially exposed using the perspective images to form the whole holographic stereogram on the holographic light sensitive material.
A design and implementation of full-parallax holographic stereogram printer is presented. The holographic stereogram is synthesized using 2D perspective images of the 3D object that are rendered from multiple directions. The perspective images of the 3D scene are firstly captured by a virtual camera and transformed to two-dimensional holographic elements called hogels. The hogels are exposed using the perspective images to form the whole holographic stereogram. After all the hogels are exposed successively, a holographic stereogram can be achieved. Numerical simulation and optical reconstructions are implemented.
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