<title>Wideband Angular Spectrum Aberrations-Free Holoconcentrators</title>

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.

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Optical Encryption Based on Computer Generated Holograms in Photopolymer

Polymers ◽

10.3390/polym13091358 ◽

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.

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