Ray-sampling Plane Research Articles

Interactive Operation of Projection-type Holographic Display Based on HOE Screen when Using Ray-sampling Plane

Interactive Operation of Projection-type Holographic Display Based on HOE Screen when Using Ray-sampling Plane

Interactive Operation of Projection-type Holographic Display Based on HOE Screen when Using Ray-sampling Plane

Interactive Operation of Projection-type Holographic Display Based on HOE Screen when Using Ray-sampling Plane

Real-time colour hologram generation based on ray-sampling plane with multi-GPU acceleration

Although electro-holography can reconstruct three-dimensional (3D) motion pictures, its computational cost is too heavy to allow for real-time reconstruction of 3D motion pictures. This study explores accelerating colour hologram generation using light-ray information on a ray-sampling (RS) plane with a graphics processing unit (GPU) to realise a real-time holographic display system. We refer to an image corresponding to light-ray information as an RS image. Colour holograms were generated from three RS images with resolutions of 2,048 × 2,048; 3,072 × 3,072 and 4,096 × 4,096 pixels. The computational results indicate that the generation of the colour holograms using multiple GPUs (NVIDIA Geforce GTX 1080) was approximately 300–500 times faster than those generated using a central processing unit. In addition, the results demonstrate that 3D motion pictures were successfully reconstructed from RS images of 3,072 × 3,072 pixels at approximately 15 frames per second using an electro-holographic reconstruction system in which colour holograms were generated from RS images in real time.

Analysis of computational complexity in holographic lens-less projection

In lens-less projection the illuminating wavefront must be modified, so that after propagation on a certain distance it would form an image on the screen. Formed images will be displayed with frame rate minimum 20 fps in case of animated movie. Thus, the speed of computing is extremely important. Computing might be performed by central processing unit (CPU) or graphics processing unit (GPU). Reaching a compromise between computational complexity (as well as the time of computing) and quality of obtained image is needed. This leads to a need to a proper iteration number of the algorithm, its parameters and size of computing matrices. Full Text: PDF References S. W. Keckler, W. J. Dally, B. Khailany, M. Garland and D. Glasco, GPUs and the future of parallel computing, IEEE Micro, 31(5), 7-17 (2011). CrossRef T. Shimobaba, T. Ito, N. Masuda, Y. Ichihashi, and N. Takada, Fast calculation of computer-generated-hologram on AMD HD5000 series GPU and OpenCL, Opt. Express 18, 9955-9960 (2010). CrossRef A. Kowalczyk, M. Bieda, M. Makowski, M. Sypek, and A. Kolodziejczyk, Fiber-based real-time color digital in-line Appl. Opt. 52, 4743-4748 (2013). CrossRef C.-J. Cheng, W.-J. Hwang, C.-T. Chen, and X.-J. Lai, Efficient FPGA-Based Fresnel Transform Architecture for Digital Holography, J. Display Technol. 10, 272-281 (2014). CrossRef Y.-H. Seo, H.-J. Choi, J.-S. Yoo, and D.-W. Kim, An architecture of a high-speed digital hologram generator based on FPGA, Journal of Systems Architecture, Vol. 56. pp. 27-37 (2009). CrossRef M. Makowski, Minimized speckle noise in lens-less holographic projection by pixel separation, Opt. Express 21, 29205-29216 (2013). CrossRef T. Utsugi and M. Yamaguchi, Speckle-suppression in hologram calculation using ray-sampling plane, Opt. Express 22, 17193-17206 (2014). CrossRef F. Wyrowski and O. Bryngdahl, Iterative Fourier-transform algorithm applied to computer holography, J. Opt. Soc. Am. A 5, 1058-1065 (1988). CrossRef M. Makowski, I. Ducin, K. Kakarenko, J. Suszek, M. Sypek, and A. Kolodziejczyk, Simple holographic projection in color, Opt. Express 20, 25130-25136 (2012). CrossRef

Speckle-suppression in hologram calculation using ray-sampling plane.

Speckle noise is an important issue in electro-holographic displays. We propose a new method for suppressing speckle noise in a computer-generated hologram (CGH) for 3D display. In our previous research, we proposed a method for CGH calculation using ray-sampling plane (RS-plane), which enables the application of advanced ray-based rendering techniques to the calculation of hologram that can reconstruct a deep 3D scene in high resolution. Conventional techniques for effective speckle suppression, which utilizes the time-multiplexing of sparse object points, can suppress the speckle noise with high resolution, but it cannot be applied to the CGH calculation using RS-plane because the CGH calculated using RS-plane does not utilize point sources on an object surface. Then, we propose the method to define the point sources from light-ray information and apply the speckle suppression technique using sparse point sources to CGH calculation using RS-plane. The validity of the proposed method was verified by numerical simulations.

Computer generated hologram from full-parallax 3D image data captured by scanning vertical camera array (Invited Paper)

Full-parallax light-field is captured by a small-scale 3D image scanning system and applied to holographic display. A vertical camera array is scanned horizontally to capture full-parallax imagery, and the vertical views between cameras are interpolated by depth image-based rendering technique. An improved technique for depth estimation reduces the estimation error and high-density light-field is obtained. The captured data is employed for the calculation of computer hologram using ray-sampling plane. This technique enables high-resolution display even in deep 3D scene although a hologram is calculated from ray information, and thus it makes use of the important advantage of holographic 3D display.

Occlusion processing for computer generated hologram by conversion between the wavefront and light-ray information

In the field of computational holography for three-dimensional (3D) display, the mutual occlusion of objects is one of the crucial issues. We propose a new mutual occlusion processing that is achieved by the conversion between the light-ray and wavefront on a virtual plane called ray-sampling (RS) plane located at near the interrupting object. The wavefront coming from background scene is converted into light-ray information at the RS plane by using Fourier transform based on the angular spectrum theory, then the converted light-rays are overwritten with those from interrupting object in the light-ray domain as an occlusion culling process. The ray information after the occlusion process is reconverted into wavefront by inverse Fourier transform at each RS point, then wave propagation from RS plane to hologram is computed by general light diffraction computation techniques. Since the light-ray information is used for the occlusion processing, our approach can realize a correct occlusion effect by a simple algorithm. In addition, high resolution 3D image can be reconstructed with wavefront-based technique. In the numerical simulation, we demonstrate that our approach for deep 3D scene with plural objects can realize a correct occlusion culling for varying observation angle and focusing distance.

High-resolution three-dimensional holographic display using dense ray sampling from integral imaging

We present a high-resolution three-dimensional (3D) holographic display using a set of elemental images obtained by passive sensing integral imaging (II). Hologram calculations using a high-density ray-sampling plane are achieved from the elemental images captured by II. In II display, ray sampling by lenslet array and light diffraction limits the achievable resolution. Our approach can improve the resolution since target objects are captured in focus and then light-ray information is interpolated and resampled with higher density on ray-sampling plane located near the object to be converted into the wavefront. Numerical experimental results show that the 3D scene, composed of plural objects at different depths from the display, can be reconstructed with order of magnitude higher resolution by the proposed technique.

Calculation for computer generated hologram using ray-sampling plane

We introduce a new algorithm for calculating computer generated hologram (CGH) using ray-sampling (RS) plane. RS plane is set at near the object and the light-rays emitted by the object are sampled at the plane. Then the light-rays are transformed into the wavefront with using the Fourier transforms. The wavefront on the CGH plane is calculated by wavefront propagation simulation from RS plane to CGH plane. The proposed method enables to reproduce high resolution image for deep 3D scene with angular reflection properties such as gloss appearance.