4K-DMDNet:diffraction model-driven network for 4K computer-generated holography

Deep learning offers a novel opportunity to achieve both high-quality and high-speed computer-generated holography(CGH).Current data-driven deep learning algorithms face the challenge that the labeled training datasets limit the training performance and generalization.The model-driven deep learning introduces the diffraction model into the neural network.It eliminates the need for the labeled training dataset and has been extensively applied to hologram generation.However,the existing model-driven deep learning algorithms face the problem of insufficient constraints.In this study,we propose a model-driven neural network capable of high-fidelity 4K computer-generated hologram generation,called 4K Diffraction Model-driven Network(4K-DMDNet).The constraint of the reconstructed images in the frequency domain is strengthened.And a network structure that combines the residual method and sub-pixel convolution method is built,which effectively enhances the fitting ability of the network for inverse problems.The generalization of the 4K-DMDNet is demonstrated with binary,grayscale and 3D images.High-quality full-color optical reconstructions of the 4K holograms have been achieved at the wavelengths of 450 nm,520 nm,and 638 nm.

Grid-based computer-generated holograms synthesizing for holographic three-dimensional display

To reduce the computing time of composite computer-generated holograms （CGHs） gen- eration based upon the angular projection algorithm for holographic three-dimensional （3D） display, a grid-based holographic display （ GHD ） scheme was designed. The grid computing technology was applied to numerically process the different angular projections of an object in distributed-parallel manner to create the corresponding CGHs. The whole treatment of a projection was regarded as a job executed on the grid node machine. The number of jobs which were submitted to grid nodes, therefore, was equal to that of the projections of the object. A Condor-based grid testbed was constructed to verify the feasibility of the GHD scheme, and a graphical user interface （GUI） program and several service modules were developed for it. A 3D terrain model as an example was processed on the testbed. The result showed that the scheme was feasible and able to improve the execution elficiency greatly.

Discovering Crustal Deformation Bands by Processing Regional Gravity Field

Objectives： This article presents a new computational procedure to discover scratches buried in the earth＇s crust. We also validate this new interdisciplinary analysis method with regional gravity data located in a well-known Dabie orogenic zone for test. Methods： Based on the scratch analysis method evolved with mathematical morphology of surfaces, we present a procedure that extracts information of the crustal scratches from regional gravity data. Because the crustal scratches are positively and highly correlated to crustal deformation bands, it can be used for delineation of the crustal deformation belts. The scratches can be quantitatively characterized by calculation of the ridge coefficient function, whose high value traces delineate the deformation bands hidden in the regional gravity field. In addition, because the degree of crustal deformation is an important indicator of tectonic unit divisions, so the crust can be further divided according to the degree of crustal deformation into some tectonic units by using the ridge coefficient data, providing an objective base map for earth scientists to build tectonic models with quantitative evidence. Results： After the ridge coefficients are calculated, we can further enhance the boundary of high ridge-coefficient blocks, resulting in the so-called ridge-edge coefficient function. The high-value ridge-edge coefficients are well correlated with the edge faults of tectonic units underlay, providing accurate positioning of the base map for compilation of regional tectonic maps. In order to validate this new interdisciplinary analysis method, we select the Dabie orogenic zone as a pilot area for test, where rock outcrops are well exposed on the surface and detailed geological and geophysical surveys have been carried out. Tests show that the deformation bands and the tectonic units, which are conformed by tectonic scientists based on surface observations, are clearly displayed on the ridge and ridge-edge coefficient images obtained in this article. Moreover, these computer-generated images provide more accurate locations and geometric details. Conclusions： This work demonstrates that application of modern mathematical tools can promote the quantitative degree in research of modern geosciences, helping to open a door to develop a new branch of mathematical tectonics.

Computer-generated holograms for 3D display(Invited Paper)

We have been studying various types of computer-generated holograms for three-dimensional （3D） displays both for a real-time holographic video display and a hard copy, or a printed hologram. For the hard copy output, we have developed a direct fringe printer, which is achieved to print over 100 gigapixels computer-generated hologram with 0.44μm pitch. In this paper, we introduce our recent progresses on the rainbow hologram, the cylindrical holograms, and the disk hologram for 3D display.

Computer-generated image hologram

We investigate the computer-generated hologram with full parallax and which can be reconstructed with white light. The object of the hologram is processed from three-dimensional computer graphics polygon data and has shaded surface for hidden surface removal. The optically reconstructed image from the printed hologram is evaluated.

Real-time gradation-expressible amplitude-modulationtype electroholography based on binary-weighted computer-generated hologram

In amplitude-modulation-type electroholography, the binary-weighted computer-generated hologram(BW-CGH) facilitates the gradation-expressible reconstruction of three-dimensional(3 D) objects. To realize real-time gradation-expressible electroholography, we propose an efficient and high-speed method for calculating bit planes consisting of BW-CGHs. The proposed method is implemented on a multiple graphics processing unit(GPU) cluster system comprising 13 GPUs. The proposed BW-CGH method realizes eight-gradation-expressible electroholography at approximately the same calculation speed as that of conventional electroholography based on binary computer-generated holograms. Consequently, we were able to successfully reconstruct a real-time electroholographic 3 D video comprising approximately 180,000 points expressed in eight gradations at 30 frames per second.

Distinguishing Computer-Generated Images from Natural Images Using Channel and Pixel Correlation

With the recent tremendous advances of computer graphics rendering and image editing technologies,computergenerated fake images,which in general do not reflect what happens in the reality,can now easily deceive the inspection of human visual system.In this work,we propose a convolutional neural network(CNN)-based model to distinguish computergenerated(CG)images from natural images(NIs)with channel and pixel correlation.The key component of the proposed CNN architecture is a self-coding module that takes the color images as input to extract the correlation between color channels explicitly.Unlike previous approaches that directly apply CNN to solve this problem,we consider the generality of the network(or subnetwork),i.e.,the newly introduced hybrid correlation module can be directly combined with existing CNN models for enhancing the discrimination capacity of original networks.Experimental results demonstrate that the proposed network outperforms state-of-the-art methods in terms of classification performance.We also show that the newly introduced hybrid correlation module can improve the classification accuracy of different CNN architectures.

Full-color and less-speckled modified Gerchberg–Saxton algorithm computer-generated hologram floating in a dual-parabolic projection system

This Letter proposes to apply full-color computer-generated holograms to the virtual image projection system so that the viewers can comfortably view floating images. Regarding the spatial division and distribution operation,a modified Gerchberg–Saxton algorithm is used for acquiring the phase infographics, which are input into the spatial light modulator for the reconstructed projection. Such a virtual image projection system could reach the vertical angle of view of 15°–75° and the horizontal angle of view 360°, and the mixed-light modulating proportion contains a 3 m W red light laser, a 2 m W green light laser, and a 2.6 m W blue light laser to achieve the full-color mixed-light proportion with a speckle contrast of 6.65%. The relative diffraction efficiency and root mean square error of the reconstructed image are 95.3% and 0.0524, respectively.

Holographic imaging of full-color real-existing three-dimensional objects with computer-generated sequential kinoforms

We propose a computational method for generating sequential kinoforms of real-existing full-color three- dimensional （3D） objects and realizing high-quality 3D imaging. The depth map and color information are obtained using non-contact full-color 3D measurement system based on binocular vision. The obtained full-color 3D data are decomposed into multiple slices with RGB channels. Sequential kinoforms of each channel are calculated and reconstructed using a Fresnel-diffraction-based algorithm called the dynamic- pseudorandom-phase tomographic computer holography （DPP-TCH）. Color dispersion introduced by different wavelengths is well compensated by zero-padding operation in the red and green channels of object slices. Numerical reconstruction results show that the speckle noise and color-dispersion are well suppressed and that high-quality full-color holographic 3D imaging is feasible. The method is useful for improving the 3D image quality in holographic displays with pixelated phase-type spatial light modulators （SLMs）.

Use of Virtual Medium in Designing of the CGH Wave Front Generator for Aspheric Testing

Design method and procedures of computer-generated hologram （CGH） used for aspheric test are in- troduced in detail. For CGH phase calculation, virtual medium which has zero refractive index at given wavelength is used to model ideal aspheric wavefront. Reflective Fresnel zones located in a ring area concentric to the CGH structure is designed to reduce or eliminate alignment errors. Substrate figure error, pattern distortion, etching and duty cycle variations that influence the reconstructed wavefront are quantitatively analyzed in theory and corresponding error equations are obtained to guide the tolerance distribution during CGH fabricating. A design example is given and the uncertainty of t achieves λ20.

Color representation method using RGB color binary-weighted computer-generated holograms

We propose a method for color electroholography using a simple red-green-blue （RGB） gradation representa- tion method without controlling the respective brightness of tile reference RGB-colored lights. The proposed method uses RGB multiple bit planes comprising RGB binary-weighted computer-generated holograms with various light transmittanees. The object points of a given three-dimensional （3D） object are assigned to RGB nmltiple bit planes according to their RGB gradation levels. The RGB multiple bit planes are sequentially displayed in a tim-division-multiplexe- manner. Consequently, the proposed method yields a color gradation representation of a reconstructed 3D object.

Phase-only stereoscopic hologram calculation based on Gerchberg–Saxton iterative algorithm

A phase-only computer-generated holography（CGH） calculation method for stereoscopic holography is proposed in this paper.The two-dimensional（2D） perspective projection views of the three-dimensional（3D） object are generated by the computer graphics rendering techniques.Based on these views,a phase-only hologram is calculated by using the Gerchberg–Saxton（GS） iterative algorithm.Comparing with the non-iterative algorithm in the conventional stereoscopic holography,the proposed method improves the holographic image quality,especially for the phase-only hologram encoded from the complex distribution.Both simulation and optical experiment results demonstrate that our proposed method can give higher quality reconstruction comparing with the traditional method.

2-D Binary Conjugation Holographic Grating Multiplexers for Laser Coherent Imaging Systems

This Paper studies a reflection-type 2-D computer-generated holographic phase grating used in laser coherent imaging Systems as beam shaping elements. In the applications the diffractive gratings must have high diffractionefficiency and produce uniform intensities in the diffracted other desired. In this paper we discuss in some detail theuse of conjugation gratings applied mainly to laser coherent imaging systems with detector arrays to create 2-D gratingstructures that produce multi-fold diffracted beams.

Computer-Generated Holograms for Recording Multiple-Phase-Shifte Fiber Bragg Grating Corrugations

A new method of fabricating multiple-phase-shifts fiber Bragg grating by CGHsis proposed . The authors present an example of such CGH by which a section multiple-phase-shiftefiber Bragg grating with twoπ/2 phase shifts and grating length L = 21.2 μm was produced. Theauthors describe the production process and finally give an example of a reconstructed fiber gratingwith two phase-shifts.

(3+1)-dimensional localized self-accelerating Airy elegant Ince-Gaussian wave packets and their radiation forces in free space

We construct analytically linear self-accelerating Airy elegant Ince-Gaussian wave packet solutions from （3＋1）-dimensional potential-free Schr？dinger equation. These wave packets have elliptical geometry and show different characteristics when the parameters （p, m） and ellipticity ε are adjusted. We investigate these characteristics both analytically and numerically and give the 3-dimensional intensity and phase distribution of these wave packets. Lastly, we analyze the radiation forces on a Rayleigh dielectric particle. In addition, we also find an interesting phenomenon that if the energy distribution between every part of wave packets is uneven at the input plane, the energy will be transferred between every part in the process of transmission.

Chinese Optics Letters(《中国光学快报》)2009年“Nanophotonics”和“Digital and Computer-Generated Holography”专题征稿启事

(Chinese Optics Letters(《中国光学快报》)计划于2009年10月在正刊上推出'Nanophotonics'('纳米光子学')专题,特向国内外广大读者以及作者征集该方面原创性的研究论文。征稿范围包括:·Metamaterials:negative index,cloaking and nonlinear

Fast compression of computer-generated holographic images based on a GPU-accelerated skip-dimension vector quantization method

A method for fast and low bit-rate compression of digital holograms based on a new vector quantization （VQ） method known as the skip-dimension VQ （SDVQ） is proposed. Briefly, a complex hologram is converted into a real off-axis hologram, and partitioned into a set of image vectors. The image vectors are passed into a graphic processing unit （GPU）, and compressed through SDVQ into a set of code indices considerably smaller in data size than the source hologram. Experimental evaluation reveals that our scheme is capable of compressing a digital hologram to a compression ratio of over 500 times, in approximately 20-22 ms.

Machine-learning-based high-speed lensless large-field holographic projection using double-sampling Fresnel diffraction method

Machine learning can effectively accelerate the runtime of a computer-generated hologram.However,the angular spectrum method and single fast Fresnel transform-based machine learning acceleration algorithms are still limited in the field-of-view angle of projection.In this paper,we propose an efficient method for the fast generation of large field-of-view holograms combining stochastic gradient descent(SGD),neural networks,and double-sampling Fresnel diffraction(DSFD).Compared with the traditional Gerchberg-Saxton(GS)algorithm,the DSFD-SGD algorithm has better reconstruction quality.Our neural network can be automatically trained in an unsupervised manner with a training set of target images without labels,and its combination with the DSFD can improve the optimization speed significantly.The proposed DSFD-Net method can generate 2000-resolution holograms in 0.05 s.The feasibility of the proposed method is demonstrated with simulations and experiments.

Dynamically taming focal fields of femtosecond lasers for fabricating microstructures

Micromachining based on femtosecond lasers usually requires accurate control of the sample movement,which may be very complex and costly.Therefore,the exploration of micromachining without sample movement is valuable.Herein,we have illustrated the manipulation of optical fields by controlling the polarization or phase to vary periodically and then realized certain focal traces by real-time loading of the computer-generated holograms(CGHs) on the spatial light modulator.The focal trace is composed of many discrete focal spots,which are generated experimentally by using the real-time dynamically controlled CGHs.With the designed focal traces,various microstructures such as an ellipse,a Chinese character "Nan",and an irregular quadrilateral grid structure are fabricated in the z-cut LiNbO_(3) wafers,showing good qualities in terms of continuity and homogeneity.Our method proposes a movement free solution for micromachining samples and completely abandons the high precision stage and complex movement control,making microstructure fabrication more flexible,stable,and cheaper.

Deep holography

With the explosive growth of mathematical optimization and computing hardware,deep neural networks(DNN)have become tremendously powerful tools to solve many challenging problems in various fields,ranging from decision making to computational imaging and holography.In this manuscript,I focus on the prosperous interactions between DNN and holography.On the one hand,DNN has been demonstrated to be in particular proficient for holographic reconstruction and computer-generated holography almost in every aspect.On the other hand,holography is an enabling tool for the optical implementation of DNN the other way around owing to the capability of interconnection and light speed processing in parallel.The purpose of this article is to give a comprehensive literature review on the recent progress of deep holography,an emerging interdisciplinary research field that is mutually inspired by holography and DNN.I first give a brief overview of the basic theory and architectures of DNN,and then discuss some of the most important progresses of deep holography.I hope that the present unified exposition will stimulate further development in this promising and exciting field of research.