Accurate reconstruction of horizontal parallax-only holograms by angular spectrum and efficient zero-padding

2020 ◽  
Vol 59 (27) ◽  
pp. 8450
Author(s):  
Tomasz Kozacki ◽  
Juan Martinez-Carranza ◽  
Rafał Kukolowicz ◽  
Weronika Finke
Keyword(s):  
Angular Spectrum ◽  
Zero Padding ◽  
Accurate Reconstruction

Accurate reconstruction of digital holography using frequency domain zero padding

2017 ◽  
Author(s):  
Jun Geun Shin ◽  
Ju Wan Kim ◽  
Jae Hwi Lee ◽  
Byeong Ha Lee
Keyword(s):  
Frequency Domain ◽  
Digital Holography ◽  
Zero Padding ◽  
Accurate Reconstruction

scholarly journals An Accurate Reconstruction of CMB E Mode Signal over Large Angular Scales using Prior Information of CMB Covariance Matrix in ILC Algorithm

2020 ◽  
Author(s):  
Ujjal Purkayastha ◽  
Vipin Sudevan ◽  
Rajib Saha
Keyword(s):  
Power Spectrum ◽  
Linear Combination ◽  
Covariance Matrix ◽  
Large Scale ◽  
Prior Information ◽  
Future Generation ◽  
Temperature Anisotropy ◽  
Satellite Mission ◽  
Angular Power Spectrum ◽  
Accurate Reconstruction

Abstract Recently, the internal-linear-combination (ILC) method was investigated extensively in the context of reconstruction of Cosmic Microwave Background (CMB) temperature anisotropy signal using observations obtained by WMAP and Planck satellite missions. In this article, we, for the first time, apply the ILC method to reconstruct the large scale CMB E mode polarization signal, which could probe the ionization history, using simulated observations of 15 frequency CMB polarization maps of future generation Cosmic Origin Explorer (COrE) satellite mission. We find that the clean power spectra, from the usual ILC, are strongly biased due to non zero CMB-foregrounds chance correlations. In order to address the issues of bias and errors we extend and improve the usual ILC method for CMB E mode reconstruction by incorporating prior information of theoretical E mode angular power spectrum while estimating the weights for linear combination of input maps (Sudevan & Saha 2018b). Using the E mode covariance matrix effectively suppresses the CMB-foreground chance correlation power leading to an accurate reconstruction of cleaned CMB E mode map and its angular power spectrum. We compare the performance of the usual ILC and the new method over large angular scales and show that the later produces significantly statistically improved results than the former. The new E mode CMB angular power spectrum contains neither any significant negative bias at the low multipoles nor any positive foreground bias at relatively higher mutlipoles. The error estimates of the cleaned spectrum agree very well with the cosmic variance induced error.

scholarly journals Computing 3D Phase-Type Holograms Based on Deep Learning Method

Photonics ◽  
2021 ◽  
Vol 8 (7) ◽  
pp. 280
Author(s):  
Huadong Zheng ◽  
Jianbin Hu ◽  
Chaojun Zhou ◽  
Xiaoxi Wang
Keyword(s):  
Deep Learning ◽  
Signal To Noise Ratio ◽  
Contrast Ratio ◽  
Angular Spectrum ◽  
Structural Similarity ◽  
Computational Time ◽  
Experimental Investigations ◽  
Training Strategy ◽  
Holographic Display ◽  
Phase Type

Computer holography is a technology that use a mathematical model of optical holography to generate digital holograms. It has wide and promising applications in various areas, especially holographic display. However, traditional computational algorithms for generation of phase-type holograms based on iterative optimization have a built-in tradeoff between the calculating speed and accuracy, which severely limits the performance of computational holograms in advanced applications. Recently, several deep learning based computational methods for generating holograms have gained more and more attention. In this paper, a convolutional neural network for generation of multi-plane holograms and its training strategy is proposed using a multi-plane iterative angular spectrum algorithm (ASM). The well-trained network indicates an excellent ability to generate phase-only holograms for multi-plane input images and to reconstruct correct images in the corresponding depth plane. Numerical simulations and optical reconstructions show that the accuracy of this method is almost the same with traditional iterative methods but the computational time decreases dramatically. The result images show a high quality through analysis of the image performance indicators, e.g., peak signal-to-noise ratio (PSNR), structural similarity (SSIM) and contrast ratio. Finally, the effectiveness of the proposed method is verified through experimental investigations.

scholarly journals Optical Encryption Based on Computer Generated Holograms in Photopolymer

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1358
Author(s):  
Taihui Wu ◽  
Jianshe Ma ◽  
Chengchen Wang ◽  
Haibei Wang ◽  
Liangcai Cao ◽  
...  
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Angular Spectrum ◽  
Quick Response ◽  
Response Code ◽  
Optical Encryption ◽  
Large Size ◽  
Quick Response Code ◽  
Computer Generated Holograms ◽  
Encryption Method

An optical encryption method based on computer generated holograms printing of photopolymer is presented. Fraunhofer diffraction is performed based on the Gerchberg-Saxton algorithm, and a hologram of the Advanced Encryption Standard encrypted Quick Response code is generated to record the ciphertext. The holograms of the key and the three-dimensional image are generated by the angular spectrum diffraction algorithm. The experimental results show that large-size encrypted Quick Response (QR) code and miniature keys can be printed in photopolymers, which has good application prospects in optical encryption. This method has the advantages of high-density storage, high speed, large fault tolerance, and anti-peeping.

Time-resolved Passive Cavitation Mapping using the Transient Angular Spectrum Approach

2021 ◽  
pp. 1-1
Author(s):  
Mucong Li ◽  
Juanjuan Gu ◽  
Tri Vu ◽  
Georgy Sankin ◽  
Pei Zhong ◽  
...  
Keyword(s):  
Angular Spectrum ◽  
Time Resolved

Accurate reconstruction for the measurement of tilt surfaces with digital holography

2021 ◽  
pp. 127135
Author(s):  
He Yuan ◽  
Xiangchao Zhang ◽  
Feili Wang ◽  
Rui Xiong ◽  
Wei Wang ◽  
...  
Keyword(s):  
Digital Holography ◽  
Accurate Reconstruction

Angular spectrum measurements of atmospheric turbulence

1977 ◽  
Vol 67 (2) ◽  
pp. 178 ◽  
Author(s):  
A. R. Lewis ◽  
V. H. Rumsey
Keyword(s):  
Atmospheric Turbulence ◽  
Angular Spectrum ◽  
Spectrum Measurements
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