Real-time layer-based computer-generated hologram calculation for the Fourier transform optical system

Adaptive layer-based computer-generated holograms

We propose a novel, to the best of our knowledge, and fast adaptive layer-based (ALB) method for generating a computer-generated hologram (CGH) with accurate depth information. A complex three-dimensional (3D) object is adaptively divided into layers along the depth direction according to its own non-uniformly distributed depth coordinates, which reduces the depth error caused by the conventional layer-based method. Each adaptive layer generates a single-layer hologram using the angular spectrum method for diffraction, and the final hologram of a complex three-dimensional object is obtained by superimposing all the adaptive layer holograms. A hologram derived with the proposed method is referred to as an adaptive layer-based hologram (ALBH). Our demonstration shows that the desired reconstruction can be achieved with 52 adaptive layers in 8.7 s, whereas the conventional method requires 397 layers in 74.9 s.

Fast 3D Analytical Affine Transformation for Polygon-Based Computer-Generated Holograms

We present a fast 3D analytical affine transformation (F3DAAT) method to obtain polygon-based computer-generated holograms (CGHs). CGHs consisting of tens of thousands of triangles from 3D objects are obtained by this method. We have attempted a revised method based on previous 3D affine transformation methods. In order to improve computational efficiency, we have derived and analyzed our proposed affine transformation matrix. We show that we have further increased the computational efficiency compared with previous affine methods. We also have added flat shading to improve the reconstructed image quality. A 3D object from a 3D camera is reconstructed holographically by numerical and optical experiments.

Automotive Holographic Head-Up Displays

Driver's access to information about navigation and vehicle data through in-car displays and personal devices distract the driver from safe vehicle management. The discrepancy between road safety and infotainment must be addressed to develop safely operated modern vehicles. Head-up displays (HUDs) aim to introduce a seamless uptake of visual information for the driver while securely operating a vehicle. HUDs projected on the windshield provide the driver with visual navigation and vehicle data within the comfort of the driver's personal eye box through a customizable extended display space. Windshield HUDs do not require the driver to shift the gaze away from the road to attain road information. This article presents a review of technological advances and future perspectives in holographic HUDs by analyzing the optoelectronics devices and the user experience of the driver. The review elucidates holographic displays and full augmented reality in 3D with depth perception when projecting the visual information on the road within the driver's gaze. Design factors, functionality, and the integration of personalized machine learning technologies into holographic HUDs are discussed. Application examples of the display technologies regarding road safety and security are presented. An outlook is provided to reflect on display trends and autonomous driving.

Polygon-based computer-generated holography: a review of fundamentals and recent progress [Invited]

In this review paper, we first provide comprehensive tutorials on two classical methods of polygon-based computer-generated holography: the traditional method (also called the fast-Fourier-transform-based method) and the analytical method. Indeed, other modern polygon-based methods build on the idea of the two methods. We will then present some selective methods with recent developments and progress and compare their computational reconstructions in terms of calculation speed and image quality, among other things. Finally, we discuss and propose a fast analytical method called the fast 3D affine transformation method, and based on the method, we present a numerical reconstruction of a computer-generated hologram (CGH) of a 3D surface consisting of 49,272 processed polygons of the face of a real person without the use of graphic processing units; to the best of our knowledge, this represents a state-of-the-art numerical result in polygon-based computed-generated holography. Finally, we also show optical reconstructions of such a CGH and another CGH of the Stanford bunny of 59,996 polygons with 31,724 processed polygons after back-face culling. We hope that this paper will bring out some of the essence of polygon-based computer-generated holography and provide some insights for future research.

Real-Time Computation of 3D Wireframes in Computer-Generated Holography

Computer-Generated Holography (CGH) algorithms simulate numerical diffraction, being applied in particular for holographic display technology. Due to the wave-based nature of diffraction, CGH is highly computationally intensive, making it especially challenging for driving high-resolution displays in real-time. To this end, we propose a technique for efficiently calculating holograms of 3D line segments. We express the solutions analytically and devise an efficiently computable approximation suitable for massively parallel computing architectures. The algorithms are implemented on a GPU (with CUDA), and we obtain a 70-fold speedup over the reference point-wise algorithm with almost imperceptible quality loss. We report real-time frame rates for CGH of complex 3D line-drawn objects, and validate the algorithm in both a simulation environment as well as on a holographic display setup.

Acceleration of polygon-based computer-generated holograms using look-up tables and reduction of the table size via principal component analysis

In this study, we first analyze the fully analytical frequency spectrum solving method based on three-dimensional affine transform. Thus, we establish a new method for combining look-up tables (LUTs) with polygon holography. The proposed method was implemented and proved to be accelerated about twice compared to the existing methods. In addition, principal component analysis was used to compress the LUTs, effectively reducing the required memory without artifacts. Finally, we calculated very complex objects on a graphics processing unit using the proposed method, and the calculation speed was higher than that of existing polygon-based methods.

Photorealistic computer generated holography with global illumination and path tracing

Computer generated holography (CGH) algorithms come in many forms, with different trade-offs in terms of visual quality and calculation speed. However, no CGH algorithm to date can accurately account for all 3D visual cues simultaneously, such as occlusion, shadows, continuous parallax, and precise focal cues, without view discretization. The aim is to create photorealistic CGH content, not only for display purposes but also to create reference data for comparing and testing CGH and compression algorithms. We propose a novel algorithm combining the precision of point-based CGH with the accurate shading and flexibility of ray-tracing algorithms. We demonstrate this by creating a scene with global illumination, soft shadows, and precise occlusion cues, implemented with OptiX and CUDA.

Mixed constraint in global and sequential hologram generation

In this paper, we implement a mixed constraint scheme with a global Gerchberg-Saxton algorithm for the improved generation of phase holograms from multiplane intensity distributions. We evaluate the performance of the proposed method compared to the mixed constraint sequential Gerchberg-Saxton algorithm, as well as the implementation of both schemes in several scenarios involving intensity distributions of up to nine independent planes. We also show that a careful selection of the parameters involved in the mixed constraint hologram generation technique can lead to even greater improvements in reconstruction quality. We present numerical results validating the effectiveness of our proposal.

Three-dimensional deeply generated holography [Invited]

In this paper, we present a noniterative method for 3D computer-generated holography based on deep learning. A convolutional neural network is adapted for directly generating a hologram to reproduce a 3D intensity pattern in a given class. We experimentally demonstrated the proposed method with optical reproductions of multiple layers based on phase-only Fourier holography. Our method is noniterative, but it achieves a reproduction quality comparable with that of iterative methods for a given class.

Toward the next-generation VR/AR optics: a review of holographic near-eye displays from a human-centric perspective

Wearable near-eye displays for virtual and augmented reality (VR/AR) have seen enormous growth in recent years. While researchers are exploiting a plethora of techniques to create life-like three-dimensional (3D) objects, there is a lack of awareness of the role of human perception in guiding the hardware development. An ultimate VR/AR headset must integrate the display, sensors, and processors in a compact enclosure that people can comfortably wear for a long time while allowing a superior immersion experience and user-friendly human-computer interaction. Compared with other 3D displays, the holographic display has unique advantages in providing natural depth cues and correcting eye aberrations. Therefore, it holds great promise to be the enabling technology for next-generation VR/AR devices. In this review, we survey the recent progress in holographic near-eye displays from the human-centric perspective.

Analytic computation of line-drawn objects in computer generated holography

Digital holography is a promising display technology that can account for all human visual cues, with many potential applications i.a. in AR and VR. However, one of the main challenges in computer generated holography (CGH) needed for driving these displays are the high computational requirements. In this work, we propose a new CGH technique for the efficient analytical computation of lines and arc primitives. We express the solutions analytically by means of incomplete cylindrical functions, and devise an efficiently computable approximation suitable for massively parallel computing architectures. We implement the algorithm on a GPU (with CUDA), provide an error analysis and report real-time frame rates for CGH of complex 3D scenes of line-drawn objects, and validate the algorithm in an optical setup.

Phase added sub-stereograms for accelerating computer generated holography

Phase-added stereograms are a form of sparse computer generated holograms, subdividing the hologram in small Fourier transformed blocks and updating a single coefficient per block and per point-spread function. Unfortunately, these algorithms' computational performance is often bottlenecked by the relatively high memory requirements. We propose a technique to partition the 3D point cloud into cells using time-frequency analysis, grouping the affected coefficients into subsets that improve caching and minimize memory requirements. This results in significant acceleration of phase added stereogram algorithms without affecting render quality, enabling real-time CGH for driving holographic displays for more complex and detailed scenes than previously possible. We report a 30-fold speedup over the base implementation, achieving real-time speeds of 80ms per million points per megapixel on a single GPU.

Fast calculation method for viewpoint movements in computer-generated holograms using a Fourier transform optical system

Augmented reality (AR) using a holographic head-mounted display has been attracting a great deal of attention. In the AR system, computer-generated holograms (CGHs) are calculated and displayed on an electronic display. However, the time required for making CGHs is very long. Here, we propose a fast calculation method for arbitrary viewpoint movements in holographic AR systems. The calculation uses a Fourier transform optical system to enlarge the visual field of electroholography. In experiments, the generation time of the proposed method was approximately twice as fast as that of the conventional method. Furthermore, the quality of the CGHs generated by our method was sufficiently high.

Wide visual field angle holographic display using compact electro-holographic projectors

Electro-holography has the problem of having a narrow visual field angle, because the resolution of a spatial light modulator is insufficient for displaying a fringe pattern. To solve this problem, this paper proposes a projector-type electro-holographic compact display that achieves a wide visual field angle by using the combination of an optical system and calculation algorithms. The results of experiments show that the visual field angle is three times larger than that of a normal electro-holographic display. In addition, it is demonstrated that the system has the ability to display 3D reconstructed images with binocular, full-color, high-resolution, and accurate depth presentation.

Efficient algorithms for the accurate propagation of extreme-resolution holograms

Display-sized full-parallax holograms with large viewing angles require resolutions surpassing tens of Gigapixels. Unfortunately, computer-generated holography is computationally intensive, particularly for these huge display resolutions. Existing algorithms designed for diffraction of typical Megapixel-sized holograms do not scale well for these large resolutions. Furthermore, since the holograms will not fit in the RAM of most of today's computers, the algorithms should be modified to minimize disk access. We propose two novel algorithms respectively for short-distance and long-distance propagation, and accurately compute the diffraction of a 17.2 Gigapixel hologram on a standard desktop machine. We report a 500-fold speedup over the reference rectangular tiling algorithm for the short-distance version, and a 50-fold speedup for the long-distance version.

Direct calculation of computer-generated holograms in sparse bases

Computer-generated holography is computationally intensive, making it especially challenging for holographic displays where high-resolutions and video rates are needed. To this end, we propose a technique for directly calculating short-time Fourier transform coefficients without the need for a look-up table. Because point spread functions are sparse in this transform domain, only a small fraction of the coefficients need to be updated, enabling significant speed gains. Twenty-fold accelerations are reported over the reference implementation. This approach generalizes the notion of the phase-added stereogram, allowing for the calculatiion of an arbitrary number of Fourier coefficients per block, enabling high calculation speed with holograms of good visual quality, targeting minimal memory requirements.