Spatial Imaging Based on extremely High-Definition Computational Holography : Wave-Field Oriented 3D imaging

Extremely high-definition displays beyond Super Hi-Vision give us a new horizon in the field of 3D imaging. This paper introduces spatial 3D imaging brought by computational holographly and techniques for numerical propagation of wave-fields that make it possible to create the spatial 3D images

Shifted angular spectrum method for off-axis numerical propagation

A novel method is proposed for simulating free-space propagation from an input source field to a destination sampling window laterally shifted from that in the source field. This off-axis type numerical propagation is realized using the shifted-Fresnel method (Shift-FR) and is very useful for calculating non-paraxial and large-scale fields. However, the Shift-FR is prone to a serious problem, in that it causes strong aliasing errors in short distance propagation. The proposed method, based on the angular spectrum method, resolves this problem. Numerical examples as well as the formulation are presented

Wave Optical Algorithm for Creating Digitally Synthetic Holograms of Three-Dimensional Surface Objects

Progress in a novel wave-optical algorithm for synthesizing object waves of three-dimensional surface objects is reported. The algorithm has been proposed last year and has a feature of wave-optical calculation in diffraction by object surfaces. Numerical simulation of diffraction is implemented by a method based on coordinates rotation in Fourier spectrum. Source fields on a surface of objects are given as complex property functions defined on each object surface. These property functions provide information on each surface, such as the shape and diffusiveness. General formulation of the algorithm has been presented, but its numerical implementation was limited only to the cases of single axis rotation of plane surfaces. In this investigation the limitation is removed, i.e. two-axes rotation of plane surfaces is presented and reconstruction of holograms of 3-D objects composed of rotated planes are demonstrated. Furthermore, compensation of surface brightness is discussed for accurate shading objects

Exact hidden-surface removal in digitally synthetic full-parallax holograms

A new algorithm for removing hidden surfaces from reconstruction of computer-generated holograms is presented. The object used in the algorithm is defined by surface model and each polygon composing the object provides a mask for blocking the incident field into the backside of the polygon. The computational cost of the proposed algorithm is 2 FFT/polygon by handling field transmission in Fourier space and integrating the surface diffraction method for generating fields. Reconstruction of a hologram synthesized by using the presented algorithm is demonstrated

Formulation of the rotational transformation of wave fields and their application to digital holography

Rotational transformation based on coordinate rotation in Fourier space is a useful technique for simulating wave field propagation between nonparallel planes. This technique is characterized by fast computation because the transformation only requires executing a fast Fourier transform twice and a single interpolation. It is proved that the formula of the rotational transformation mathematically satisfies the Helmholtz equation. Moreover, to verify the formulation and its usefulness in wave optics, it is also demonstrated that the transformation makes it possible to reconstruct an image on arbitrarily tilted planes from a wave field captured experimentally by using digital holography

Band-Limited Angular Spectrum Method for Numerical Simulation of Free-Space Propagation in Far and Near Fields

A novel method is proposed for simulating free-space propagation. This method is an improvement of the angular spectrum method (AS). The AS does not include any approximation of the propagation distance, because the formula thereof is derived directly from the Rayleigh-Sommerfeld equation. However, the AS is not an all-round method, because it produces severe numerical errors due to a sampling problem of the transfer function even in Fresnel regions. The proposed method resolves this problem by limiting the bandwidth of the propagation field and also expands the region in which exact fields can be calculated by the AS. A discussion on the validity of limiting the bandwidth is also presented

Smooth shading of specular surfaces in polygon-based high-definition CGH

High-definition computer-generated holograms (CGH) created by the polygon-based method feature reconstruction of very fine 3D image accompanied with strong sensation of depth. However, rendering technique for specular surfaces has not been established. We propose a novel technique for smooth shading of specular surfaces in the polygon-based method. This technique divides the surface function of polygons into some segments and controls the spectral envelopes.2011 3DTV-Conference: The True Vision - Capture, Transmission and Display of 3D Video (3DTV-CON 2011), 16-18 May 2011, Antalya, Turke

Fast calculation method for optical diffraction on tilted planes by use of the angular spectrum of plane waves

A novel method for simulating field propagation is presented. The method, based on the angular spectrum of plane waves and coordinate rotation in the Fourier domain, removes geometric limitations posed by conventional propagation calculation and enables us to calculate complex amplitudes of diffracted waves on a plane not parallel to the aperture. This method can be implemented by using the fast Fourier transformation twice and a spectrum interpolation. It features computation time that is comparable with that of standard calculation methods for diffraction or propagation between parallel planes. To demonstrate the method, numerical results as well as a general formulation are reported for a single-axis rotation

A high-resolution fringe printer for studying synthetic holograms

A high resolution fringe printer developed for driving the research in computer-generated holograms is presented. This fringe printer consists of a rotation drum and a laser diode and is capable of printing elliptical dots of 1.5 times 3.0 microns in diameter on photosensitive films. These dot sizes are approximately converted into resolutions of 17,000dpi × 8,500dpi. The horizontal and vertical angles of viewing-zone of holograms printed by the printer reach 24 and 12 degrees, respectively. The designed maximum scan speed is more than 200mm/s, and at current stage of development, a hologram of approximately 50 mm square can be printed in approximately 2 hours