Hologram synthesis of three-dimensional real objects using portable integral imaging camera

Comprehensive High-Quality Three-Dimensional Display System Based on a Simplified Light-Field Image Acquisition Method and a Full-Connected Deep Neural Network

We propose a high-quality, three-dimensional display system based on a simplified light field image acquisition method, and a custom-trained full-connected deep neural network is proposed. The ultimate goal of the proposed system is to acquire and reconstruct the light field images with possibly the most elevated quality from the real-world objects in a general environment. A simplified light field image acquisition method acquires the three-dimensional information of natural objects in a simple way, with high-resolution/high-quality like multicamera-based methods. We trained a full-connected deep neural network model to output desired viewpoints of the object with the same quality. The custom-trained instant neural graphics primitives model with hash encoding output the overall desired viewpoints of the object within the acquired viewing angle in the same quality, based on the input perspectives, according to the pixel density of a display device and lens array specifications within the significantly short processing time. Finally, the elemental image array was rendered through the pixel re-arrangement from the entire viewpoints to visualize the entire field-of-view and re-constructed as a high-quality three-dimensional visualization on the integral imaging display. The system was implemented successfully, and the displayed visualizations and corresponding evaluated results confirmed that the proposed system offers a simple and effective way to acquire light field images from real objects with high-resolution and present high-quality three-dimensional visualization on the integral imaging display system.

Three-dimensional computer holography enabled from a single 2D image

To compute a high-quality computer-generated hologram (CGH) for true 3D real scenes, a huge amount of 3D data must be physically acquired and provided depending on specific devices or 3D rendering techniques. Here, we propose a computational framework for generating a CGH from a single image based on the idea of 2D-to-3D wavefront conversion. We devise a deep view synthesis neural network to synthesize light-field contents from a single image and convert the light-field data to the diffractive wavefront of the hologram using a ray-wave algorithm. The method is able to achieve extremely straightforward 3D CGH generation from hand-accessible 2D image content and outperforms existing real-world-based CGH computation, which inevitably relies on a high-cost depth camera and cumbersome 3D data rendering. We experimentally demonstrate 3D reconstructions of indoor and outdoor scenes from a single image enabled phase-only CGH.

Efficient calculation scheme for high pixel resolution non-hogel-based computer generated hologram from light field

We propose a method that reduces the computation time and memory requirement in non-hogel-based hologram synthesis from light field data. The non-hogel-based technique synthesizes coherent complex field for a three-dimensional scene from its light field. Unlike conventional holographic stereogram, the non-hogel-based technique reconstructs continuous parabolic wavefront for individual three-dimensional object point by globally processing the light field. However, the global processing increases the computational load significantly, making it hard to synthesize holograms with high pixel resolution. The proposed technique reduces the computational burden by processing each two-dimensional angular frequency slice of the four-dimensional light field independently. Hologram tiling technique is also proposed to make the hologram synthesis process scalable. Using the hologram tiling and the angular-frequency-slice-based processing, 25K×25 K pixel resolution hologram was synthesized successfully.

Non-hogel-based computer generated hologram from light field using complex field recovery technique from Wigner distribution function

We propose a novel method that synthesizes computer-generated holograms from light field data. Light field, or ray space, is the spatio-angular distribution of light rays coming from three-dimensional scene, and it can also be represented using a large number of views from different observation directions. The proposed method synthesizes a hologram by applying the complex field recovery technique from its Wigner distribution function to the light field data. Unlike conventional approaches, the proposed method synthesizes holograms without hogel configuration, generating a converging parabolic wave for each object point with continuous wavefront. The proposed method does not trade the spatial resolution with angular resolution like conventional hogel-based approaches. Moreover, the proposed method works not only for random phase light field like conventional approaches, but also for arbitrary phase distribution with corresponding carrier waves. Therefore, the proposed method is useful in synthesizing holographic contents for a wide range of applications. The proposed method is verified by simulations and optical experiments, showing successful reconstruction of three-dimensional objects.

Simple and fast calculation algorithm for computer-generated hologram based on integral imaging using look-up table

We proposed a simple and fast algorithm for computer-generated hologram (CGH) based on pinhole-type II using a look-up table. The method consists of two steps: in the first step, the unity amplitude diffraction pattern of the center pinhole on hologram plane is pre-calculated and stored as many sub-regions. Secondly, diffraction patterns for other pinholes are obtained by simply shifting and tiling the pre-calculated sub-regions, and the final CGH is obtained by adding them all together. The calculation time is short because only addition and multiplication of the stored diffraction pattern are required. In addition, the required memory space is small since only one diffraction pattern is stored. Numerical simulation and reconstruction are performed on both plane object and object with continuous depth profile to verify the proposed method. Result shows that the proposed method can easily achieve real-time hologram generation with several CPU threads running simultaneously.

Full-color digitized holography for large-scale holographic 3D imaging of physical and nonphysical objects

Digitized holography techniques are used to reconstruct three-dimensional (3D) images of physical objects using large-scale computer-generated holograms (CGHs). The object field is captured at three wavelengths over a wide area at high densities. Synthetic aperture techniques using single sensors are used for image capture in phase-shifting digital holography. The captured object field is incorporated into a virtual 3D scene that includes nonphysical objects, e.g., polygon-meshed CG models. The synthetic object field is optically reconstructed as a large-scale full-color CGH using red-green-blue color filters. The CGH has a wide full-parallax viewing zone and reconstructs a deep 3D scene with natural motion parallax.

Real-time depth controllable integral imaging pickup and reconstruction method with a light field camera

In this paper, we develop a real-time depth controllable integral imaging system. With a high-frame-rate camera and a focus controllable lens, light fields from various depth ranges can be captured. According to the image plane of the light field camera, the objects in virtual and real space are recorded simultaneously. The captured light field information is converted to the elemental image in real time without pseudoscopic problems. In addition, we derive characteristics and limitations of the light field camera as a 3D broadcasting capturing device with precise geometry optics. With further analysis, the implemented system provides more accurate light fields than existing devices without depth distortion. We adapt an f-number matching method at the capture and display stage to record a more exact light field and solve depth distortion, respectively. The algorithm allows the users to adjust the pixel mapping structure of the reconstructed 3D image in real time. The proposed method presents a possibility of a handheld real-time 3D broadcasting system in a cheaper and more applicable way as compared to the previous methods.

High resolution integral holography using Fourier ptychographic approach

An innovative approach is proposed for calculating high resolution computer generated integral holograms by using the Fourier Ptychographic (FP) algorithm. The approach initializes a high resolution complex hologram with a random guess, and then stitches together low resolution multi-view images, synthesized from the elemental images captured by integral imaging (II), to recover the high resolution hologram through an iterative retrieval with FP constrains. This paper begins with an analysis of the principle of hologram synthesis from multi-projections, followed by an accurate determination of the constrains required in the Fourier ptychographic integral-holography (FPIH). Next, the procedure of the approach is described in detail. Finally, optical reconstructions are performed and the results are demonstrated. Theoretical analysis and experiments show that our proposed approach can reconstruct 3D scenes with high resolution.

Light ray field capture using focal plane sweeping and its optical reconstruction using 3D displays

We propose a method to capture light ray field of three-dimensional scene using focal plane sweeping. Multiple images are captured using a usual camera at different focal distances, spanning the three-dimensional scene. The captured images are then back-projected to four-dimensional spatio-angular space to obtain the light ray field. The obtained light ray field can be visualized either using digital processing or optical reconstruction using various three-dimensional display techniques including integral imaging, layered display, and holography.