Wavefront Recording Plane Research Articles

Review of Fast Calculation Techniques for Computer-Generated Holograms With the Point-Light-Source-Based Model

Computer-generated holograms (CGHs) are a key technology in electroholography systems; however, heavy calculations are required to calculate CGHs. We review fast calculation techniques for CGH calculation of a point-light-source-based model, which is a simple and general model of a three-dimensional object in an electroholography system. To reduce the calculation time, many methods that reduce the temporal and spatial redundancy of the CGH calculation have been developed (e.g., look-up table method, the wavefront recording plane method, and other approximation techniques). The implementation of such methods on parallel computers (e.g., graphic processing unit and field programmable gate arrays) has also been reported.

54‐3: Lensless Holographic 3D Display based on Fast Calculated Computer‐Generated hologram

A method of lensless holographic 3D display is proposed based on the fast calculated computer‐generated hologram (CGH). The CGH is calculated by using a virtual nonuniform sampled wavefront recording plane (NS‐WRP) which is close to the 3D object. The calculation process consists of two steps: first, the 3D object is calculated to the NS‐WRP using nonuniform fast Fourier transform (NUFFT) based algorithm. Second, the NS‐WRP is propagated to the CGH using Fresnel diffraction algorithm. This method can provide fast and simple calculation of CGH which can reconstruct high quality 3D object with perceptual depth cue in space. Both of simulation and experiment demonstrate the proposed method.

An accelerated hologram calculation using the wavefront recording plane method and wavelet transform

Fast hologram calculation methods are critical in real-time holography applications such as three-dimensional (3D) displays. We recently proposed a wavelet transform-based hologram calculation called WASABI. Even though WASABI can decrease the calculation time of a hologram from a point cloud, it increases the calculation time with increasing propagation distance. We also proposed a wavefront recoding plane (WRP) method. This is a two-step fast hologram calculation in which the first step calculates the superposition of light waves emitted from a point cloud in a virtual plane, and the second step performs a diffraction calculation from the virtual plane to the hologram plane. A drawback of the WRP method is in the first step when the point cloud has a large number of object points and/or a long distribution in the depth direction. In this paper, we propose a method combining WASABI and the WRP method in which the drawbacks of each can be complementarily solved. Using a consumer CPU, the proposed method succeeded in performing a hologram calculation with 2048×2048 pixels from a 3D object with one million points in approximately 0.4s.

High efficient generation of holographic stereograms based on wavefront recording plane

A computer generated holographic stereogram based on the wavefront recording plane (WRP) is presented. A WRP closed to the parallax image plane is introduced to record the complex amplitude in a small region for each point in the parallax image. By using three times of fast Fourier transform (FFT) to execute the Fresnel diffraction calculation between the WRP and the holographic stereogram plane, the object wave contributing to the hologram pattern can be achieved. The computation complexity of the proposed approach is dramatically reduced. The results show that the calculation time can be decreased by more than one order of magnitude.

Numerical study for the calculation of computer-generated hologram in color holographic 3D projection enabled by modified wavefront recording plane method

A method of calculating computer-generated hologram (CGH) for color holographic 3D projection is proposed. A color 3D object is decomposed into red, green and blue components. For each color component, a virtual wavefront recording plane (WRP) is established which is nonuniformly sampled according to the depth map of the 3D object. The hologram of each color component is calculated from the nonuniform sampled WRP using the shifted Fresnel diffraction algorithm. Finally three holograms of RGB components are encoded into one single CGH based on the multiplexing encoding method. The computational cost of CGH generation is reduced by converting diffraction calculation from huge 3D voxels to three 2D planar images. Numerical experimental results show that the CGH generated by our method is capable to project zoomable color 3D object with clear quality.

Simple calculation of a computer-generated hologram for lensless holographic 3D projection using a nonuniform sampled wavefront recording plane.

In this paper, we present a method for calculation of a computer-generated hologram (CGH) from a 3D object. A virtual wavefront recording plane (WRP) which is close to the 3D object is established. This WRP is nonuniformly sampled according to the depth map of the 3D object. The generation of CGH only involves two nonuniform fast Fourier transform (NUFFT) and two fast Fourier transform (FFT) operations, the whole computational procedure is greatly simplified by diffraction calculation from a 2D planar image instead of 3D object voxels. Numerical simulations and optical experiments are carried out to confirm the feasibility of our proposed method. The CGH calculated with our method is capable to project zoomable 3D objects without lens.

Computer-generated holograms by multiple wavefront recording plane method with occlusion culling.

We propose a novel fast method for full parallax computer-generated holograms with occlusion processing, suitable for volumetric data such as point clouds. A novel light wave propagation strategy relying on the sequential use of the wavefront recording plane method is proposed, which employs look-up tables in order to reduce the computational complexity in the calculation of the fields. Also, a novel technique for occlusion culling with little additional computation cost is introduced. Additionally, the method adheres a Gaussian distribution to the individual points in order to improve visual quality. Performance tests show that for a full-parallax high-definition CGH a speedup factor of more than 2,500 compared to the ray-tracing method can be achieved without hardware acceleration.

Fast generation of digital holograms based on warping of the wavefront recording plane.

This paper reports a fast method for generating a 2048x2048 digital Fresnel hologram at a rate of over 100 frames per second. Briefly, the object wave of an image is nonuniformally sampled and generated on a wavefront recording plane (WPR) that is close to the object scene. The sampling interval at each point on the WRP image is then modulated according to the depth map. Subsequently, the WRP image is converted into a hologram. The hologram generated with our proposed method, which is referred to as the warped WRP (WWRP) hologram, is capable of presenting a 3-D object with faster speed as compared with existing methods.

Acceleration of computer-generated holograms using tilted wavefront recording plane method.

Computer Generated Holograms (CGH) are generated on computers; however, a great deal of computational power is required because the quality of the image is proportional to the number of point light sources of a 3D object. The Wavefront Recording Plane (WRP) method is an algorithm that enables reduction of the amount of calculations required. However, the WRP method also has a defect; it is not effective in the case of a 3D object with a deep structure. In this study, we propose two improved WRP methods: "Least Square Tilted WRP method" and "RANSAC Multi-Tilted WRP method."

Fast calculation of computer-generated hologram for RGB and depth images using wavefront recording plane method

In a three-dimensional display by a computer-generated hologram?(CGH), fast computation of CGH is required. In this paper, in order to accelerate CGH generation, the following two methods are used; the first method is band-limited double-step Fresnel diffraction. Compared with the convolution-based diffraction, such as angular spectral the proposed method requires less computational time and memory. The second method is a wavefront recording plane (WRP) method which reduces the calculation amount by placing WRPs in the vicinity of the object. We succeeded in speeding up CGH calculation by combining the two methods. Full Text: PDF References T. C. Poon (Ed.), holography and three-dimensional display: Principles and Applications, Springer (2006). CrossRef S. C. Kim and E. S. Kim, Effective generation of digital holograms of three-dimensional objects using a novel look-up table method, Appl. Opt. 47, D55–D62 (2008) . CrossRef K. Matsushima, H. Shimmel, and F. Wyrowski, Fast calculation method for optical diffraction on tilted planes by use of the angular spectrum of plane waves, J. Opt. Soc. Am. A. 20, 1755-1762 (2003). CrossRef M. Yamaguchi, H. Hoshino, T. Honda, and N. Ohyama, Phase-added stereogram: calculation of hologram using computer graphics technique, Proc. SPIE 1914, 25-31 (1993). CrossRef N. Okada, T. Shimobaba, Y. Ichihashi, R. Oi, K. Yamamoto, M. Oikawa, T. Kakue, N. Masuda, and T. Ito, Band-limited double-step Fresnel diffraction and its application to computer-generated holograms, Opt. Express 21, 9192-9197 (2013). CrossRef F. Zhang, I. Yamaguchi, and L. P. Yaroslavsky, Algorithm for reconstruction of digital holograms with adjustable magnification, Opt. Lett. 29, 1668-1670 (2004). CrossRef T. Shimobaba, N. Masuda and T. Ito, Simple and fast calclulation algorithm for computer-generated hologram with wavefront recording plane, Opt. Lett. 34, 3133-3135 (2009). CrossRef T. Shimobaba, H. Nakayama, N. Masuda and T. Ito, Rapid calculation of Fresnel computer-generated-hologram using look-up table and wavefront-recording plane methods for three-dimensional display, Opt Express 18 19504-19509 (2010). CrossRef J. Weng, T. Shimobaba, N. Okada, H. Nakayama, M. Oikawa, N. Masuda and T. Ito, Generation of real-time large computer generated hologram using wavefront recording method, Opt. Express 20, 4018-4023 (2012). CrossRef T. Shimobaba, T. Kakue, N. Masuda, Y. Ichihashi, K. Yamamoto and T. Ito, Computer holography using wavefront recording method, Digital Holography and Three-Dimensional Imaging(DH) DH2013, DTu1A. 2 (2013). CrossRef A. -H. Phan, M. -l. Piao, S. -K. Gil, and N. Kim, Generation speed and reconstructed image quality enhancement of a long-depth object using double wavefront recording planes and a GPU, Appl. Opt. 53, 4817-4824 (2014). CrossRef P. Tsang, W. -K. Cheung, T. -C. Poon, and C. Zhou, Holographic video at 40 frames per second for 4-million object points, Opt. Express 19, 15205-15211 (2011). CrossRef

Review on theory and applications of wavefront recording plane framework in generation and processing of digital holograms

The wavefront recording plane (WRP), subsequently generalized to be known as the virtual diffraction plane (VDP), is a recent concept that has been successfully deployed in fast generation and processing of digital holograms. In brief, the WRP and its extension, the VDP, is a hypothetical plane that is located between the hologram and the object scene, and which is at close proximity to the latter. As such, the fringe patterns on the hypothetical plane are carrying the holistic information of the hologram, as well as the local optical properties of the object scene. This important property enables a hologram to be processed with classical image processing techniques that are normally unsuitable for handling holographic information. In this paper we shall review a number of works, that have been developed based on the framework of the WRP and the VDP.

A review on several methods for fast generation of digital Fresnel holograms

Computer generated holography (CGH) is technology for generating holograms of synthetic, three dimensional (3D) objects which may not exist in the physical world. The process, however, requires heavy amount of computation as the resolution of a hologram is significantly higher than that of a typical optical image. This paper reviews four modern techniques for fast generation of digital Fresnel holograms which are important in the development of holographic video systems. The methods that will be described include the virtual window, sub-line, wavefront recording plane (WRP), and the interpolative WRP schemes. These works share the common objective to generate digital Fresnel hologram at a speed that is close to the video frame rate, and with complexity which is realizable with affordable computing and reconfigurable hardware devices. The author will present the principles and realization of these works, as well as some potential area of research in digital holography.

Real-time relighting of digital holograms based on wavefront recording plane method

Relighting is an important technique in photography which enables the optical properties of a picture to be modified without retaking it again. However, different from an optical image, a digital hologram cannot be relit by simply varying the value of individual pixel, as each of them is representing holistic information of the entire object scene. In this paper, we propose a fast method for the relighting of a digital hologram. First, the latter is projected to a virtual wavefront recording plane (WRP) that is located close to the object scene. Next, the WRP is relit, and subsequently expanded into a full hologram. Experiment results have demonstrated that our proposed method is capable of relighting a 2048x2048 hologram at a rate of over 50 frames per second. To the best of our knowledge, this is the first time relighting is considered in the context of holography.

Generation of real-time large computer generated hologram using wavefront recording method

We report the generation of a real-time large computer generated hologram (CGH) using the wavefront recording plane (WRP) method with the aid of a graphics processing unit (GPU). The WRP method consists of two steps: the first step calculates a complex amplitude on a WRP that is placed between a 3D object and a CGH, from a three-dimensional (3D) object. The second step obtains a CGH by calculating diffraction from the WRP to the CGH. The disadvantages of the previous WRP method include the inability to record a large three-dimensional object that exceeds the size of the CGH, and the difficulty in implementing to all the steps on a GPU. We improved the WRP method using Shifted-Fresnel diffraction to solve the former problem, and all the steps could be implemented on a GPU. We show optical reconstructions from a 1,980 × 1,080 phase only CGH generated by about 3 × 10(4) object points over 90 frames per second. In other words, the improved method obtained a large CGH with about 6 mega pixels (1,980 × 1,080 × 3) from the object points at the video rate.

Holographic video at 40 frames per second for 4-million object points

We propose a fast method for generating digital Fresnel holograms based on an interpolated wavefront-recording plane (IWRP) approach. Our method can be divided into two stages. First, a small, virtual IWRP is derived in a computational-free manner. Second, the IWRP is expanded into a Fresnel hologram with a pair of fast Fourier transform processes, which are realized with the graphic processing unit (GPU). We demonstrate state-of-the-art experimental results, capable of generating a 2048 x 2048 Fresnel hologram of around 4 × 10(6) object points at a rate of over 40 frames per second.

Rapid calculation algorithm of Fresnel computer-generated-hologram using look-up table and wavefront-recording plane methods for three-dimensional display

A rapid calculation method of Fresnel computer-generated-hologram (CGH) using look-up table and wavefront-recording plane (WRP) methods toward three-dimensional (3D) display is presented. The method consists of two steps: the first step is the calculation of a WRP that is placed between a 3D object and a CGH. In the second step, we obtain an amplitude-type or phase-type CGH to execute diffraction calculation from the WRP to the CGH. The first step of the previous WRP method was difficult to calculate in real-time due to the calculation cost. In this paper, in order to obtain greater acceleration, we apply a look-up table method to the first step. In addition, we use a graphics processing unit in the second step. The total computational complexity is dramatically reduced in comparison with conventional CGH calculations. We show optical reconstructions from a 2,048×2,048 phase-type CGH generated by about 3×10(4) object points over 10 frames per second.

Simple and fast calculation algorithm for computer-generated hologram with wavefront recording plane

We present a simple and fast calculation algorithm for a computer-generated hologram (CGH) by use of wavefront recording plane. The wavefront recording plane is placed between the object data and a CGH. When the wavefront recording plane is placed close to the object, the object light passes through a small region on the wave recording plane. The computational complexity for the object light is very small. We can obtain a CGH to execute diffraction calculation from the wavefront recording plane to the CGH. The computational complexity is constant. The total computational complexity is dramatically reduced in comparison with conventional CGH calculations.