Optical image encryption based on two beams’ interference

We proposed a method for optical image encryption on the basis of interference theory. An optical image can be produced by the interference of two beams passed two different masks. One of the masks can only modulate the phase of the beam and another can only modulate the amplitude of the beam. The encryption method is quite simple and does not need iterative algorithm. The results of simulation coincide with our method and demonstrate the feasibility of this method.     

基于级联相位恢复算法的光学图像加密

在虚拟光学数据加密理论模型的基础上,提出了一种光学图像加密的可视化密码构造算法。该加密算法基于自由空间传播的光学系统,利用级联迭代角谱相位恢复算法把待加密图像分别编码到两块相位模板之中,从而实现图像的加密。该加密技术不但可通过同时调整两块相位模板的相位分布的搜索策略来扩大搜索空间,提高安全强度,而且扩大了系统密钥空间,使系统获得更高的安全性,且能通过简单的数值运算或光学实验装置得到质量非常高的解密图像,还从理论上分析了该算法的时间复杂度。计算机模拟结果表明,该加密算法的收敛速度快,能迅速找到非常好的近似解,解密图像质量高且系统安全性良好。     

Securing color image by using phase-only encoding in Fresnel domains

We propose a novel color image hiding scheme with three channels of cascaded Fresnel domain phase-only filtering. The original color image is encoded into three phase masks by using the Gerchberg–Saxton iterative phase retrieval algorithm with another predefined phase key. The individual phase masks are placed in the inputs of the Fresnel domains of the red–green–blue channels and the phase key in the public channel, during the optical retrieval. The physical parameters in the optical system will be regarded as the additional keys for security enhancement. Numerical simulation is performed to test the validity of our scheme.     

用振幅-相位型全息透镜实现光学变换的一般理论

本文将文献[1]和[2]中所讨论的纯相位型的全息透镜系统实现光学变换的理论推广到更普遍情形,提出了用振幅-相位型全息透镜组所构成的光学系统实现给定线性变换的一般理论,推导出诸全息透镜的振幅和相位分布所满足的方程组,应用计算机迭代求解法,不难得到它们的解。     

Low-cross-talk polarization-insensitive 10-GHz-spaced 128-channel arrayed-waveguide grating multiplexer-demultiplexer achieved with photosensitive phase adjustment

We successfully fabricated a polarization-insensitive 10-GHz-spaced 128-channel arrayed-waveguide grating whose cross talk ranged from -39 to -36 dB . The optical phases of all arrayed waveguides were adjusted simultaneously by means of a photoinduced refractive-index change under ArF excimer laser irradiation through metal masks.     

Characteristics of photopolymer holographic matched filters in a van der Lugt correlator

Parameters of van der Lugt holographic matched filters for phase and amplitude transparencies, including random phase masks, are studied. Conditions for recording such filters in a phase self-developing photopolymer are determined. A significant difference in the recording conditions for the holographic filters for amplitude transparencies and phase masks is demonstrated. The holographic filters for phase masks with a signal-to-noise ratio of 20–40 dB and η from 6 to 70% that are recorded in the photopolymerizable composition seem to be promising for optical pattern recognition.     

Pixelated phase masks and their synthesis

An approach to the design of holograms and masks for optical lithography is proposed on the basis of digitizing an image and dividing the sample into three phase components defined on a special bitmap. The equivalence conditions of the continuous and discrete methods of specifying a transmission function are studied. Computer modeling is used to reconstruct the images generated by means of the discrete phase masks synthesized. The locality principle has proven to hold: the transmission function at a given mask point is determined by the position of the nearest aperture.     

Features of the manufacture of deep X-ray lithography masks in the siberian synchrotron and terahertz radiation center

The development of a low-cost technology to manufacture high-contrast X-ray LIGA masks is topical because this technology is important for various applied research on microstructured products with minimum element sizes of 10–50 μm, such as microfluid analytical systems, selective waveguide mesh-based elements to control terahertz (THz) radiation, microshaped optical elements for the visible range, etc. Technological particularities of mask manufacture are considered. A method to check the quality of masks is presented. Test microproducts manufactured using the produced deep X-ray lithography masks are demonstrated.     

Electron beam duplication of integrated optical circuits and masks

An electron beam duplication technique has been developed that permits the rapid (2–15 min) fabrication of masks suitable for integrated optical elements (2000 A precision over a 5 × 5 cm area). The technique is based on the use of a master mask, which, when exposed to UV light emits electrons in the desired pattern. The electrons are then accelarated and focused onto the substrate. We have used this technique to duplicate complex optical waveguide structures in electron resist (polyphenylsiloxane) and to prepare masks for the fabrication of waveguides in inorganic materials (SiO₂).     

利用双全息透镜实现光学普遍变换

在一般情形下(傍轴近似或非傍轴情形)和离散取样情形下,应用逐次反馈迭代算法,导出实现任意给定变换的双全息透镜的振幅-相位分布所满足的方程组.以四维自然序的Walsh变换为例子,给出了双全息透镜的振幅-相位分布和相应的逼近“距离”值,结果令人满意,表明本方案是切实可行的。 关键词：     

Gyrator transform-based optical image encryption,using chaos

We propose a new method for image encryption, using gyrator transform and chaos theory. Random phase masks are generated using chaos functions and are called as chaotic random phase masks. In the proposed technique, the image is encrypted using gyrator transform and two chaotic random phase masks. Three types of chaos functions have been used to generate the chaotic random phase masks. These chaos functions are the logistic map, the tent map and the Kaplan-Yorke map. The computer simulations are presented to verify the validity of the proposed technique. The mean square errors have been calculated. The robustness of the proposed technique to blind decryption in terms of rotation angle and the seed values of the chaotic random phase mask have been evaluated. The optical implementation of the encryption and the decryption technique has been proposed.     

Double images hiding based on optical interference

A double images hiding technology based on optical interference is proposed. The images are hiding into two computer generated phase only masks which are located at the determined positions. Two beams propagate through the masks and interfere at the preset positions. The desired images will appear at the preset positions. The positions coordinates and wavelength can also be used as encoding parameters. Computer simulations show the validity of this new method.     

基于数字微镜技术的阿达玛变换近红外光谱仪

构建了一个基于数字微镜技术的新型阿达玛变换近红外光谱仪.光学信号采用光纤引入,以光栅作为分光元件,利用数字微镜代替传统的机械式阿达玛模板进行光学编码调制,使用单点InGaAs红外探测器检测调制后的光信号,通过快速阿达玛解码还原出原始光谱.通过实验检验了光谱仪的分辨率、信噪比、稳定性以及谱图获取速度等指标.实验结果表明,...     

前向迭代多随机相位光学图像加密方法的研究

基于光学4f级联系统,采用前向迭代算法和通过产生多个随机相位板对图像进行了加密和解密。给出了该方法的原理和迭代实现的过程。对该方法在收敛速度、解密图像质量、相位板数目和相位量化阶数对解密图像质量的影响以及保密和安全性能等方面进行了分析和研究。模拟结果表明,该方法收敛速度快,解密图像质量好,可以降低相位板相位量化阶数有限所引起的误差对解密图像质量的影响,图像的安全和保密性能也得到了很大的提高。     

Nonlinear image self-filtering with liquid crystal spatial light modulator

Nonlinear spatial filtering is realized due to the electro-optical effect in spatial light modulators (SLMs). Optical methods with nonlinear filtering are suggested for various optical applications such as optical inspection of photolithography masks, wavefront sensor, etc. A fast optical response of the SLM allows optical inspection with a video (or faster) rate. The optical system proposed is tolerant to the vibrations and temperature variations because of the dynamic properties of the SLM.     

Cascaded Fresnel holographic image encryption scheme based on a constrained optimization algorithm and Henon map

We propose an image encryption scheme using chaotic phase masks and cascaded Fresnel transform holography based on a constrained optimization algorithm. In the proposed encryption scheme, the chaotic phase masks are generated by Henon map, and the initial conditions and parameters of Henon map serve as the main secret keys during the encryption and decryption process. With the help of multiple chaotic phase masks, the original image can be encrypted into the form of a hologram. The constrained optimization algorithm makes it possible to retrieve the original image from only single frame hologram. The use of chaotic phase masks makes the key management and transmission become very convenient. In addition, the geometric parameters of optical system serve as the additional keys, which can improve the security level of the proposed scheme. Comprehensive security analysis performed on the proposed encryption scheme demonstrates that the scheme has high resistance against various potential attacks. Moreover, the proposed encryption scheme can be used to encrypt video information. And simulations performed on a video in AVI format have also verified the feasibility of the scheme for video encryption.     

Nanostructuring with spatially localized femtosecond laser pulses

Spatially localized femtosecond pulses have been produced by a combination of scanning near-field optical microscopy with ultrashort pulse lasers. With these pulses direct ablative writing on metal surfaces is demonstrated. Possible applications of this technique for nanostructuring, repair, and production of lithographic masks are discussed.     

Single-pixel camera with hole-array disk

Optical Review - A single-pixel camera is composed of optical coding masks, a photo detector, and a computational decoder as the important feature that it requires no image sensor for imaging, and...     

Cryptanalysis for double-image encryption using the DTLM in frequency plane with QR decomposition and gyrator transform

Optical Review - To enhance the security in optical image encryption scheme and to safeguard it from the invaders, this paper proposes a new scheme using devil’s toroidal lens masks (DTLMs)...     

Optical image encryption based on diffractive imaging

In this Letter, we propose a method for optical image encryption based on diffractive imaging. An optical multiple random phase mask encoding system is applied, and one of the phase-only masks is selected and laterally translated along a preset direction during the encryption process. For image decryption, a phase retrieval algorithm is proposed to extract a high-quality plaintext. The feasibility and effectiveness of the proposed method are demonstrated by numerical results. The proposed method can provide a new strategy instead of conventional interference methods, and it may open up a new research perspective for optical image encryption.