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Image encryption based on extended fractional Fourier transform and digital holography technique 总被引:1,自引:0,他引:1
We present a new optical image encryption algorithm that is based on extended fractional Fourier transform (FRT) and digital holography technique. We can perform the encryption and decryption with more parameters compared with earlier similar methods in FRT domain. In the extended FRT encryption system, the input data to be encrypted is extended fractional Fourier transformed two times and random phase mask is placed at the output plane of the first extended FRT. By use of an interference with a wave from another random phase mask, the encrypted data is stored as a digital hologram. The data retrieval is operated by all-digital means. Computer simulations are presented to verify its validity and efficiency. 相似文献
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An encryption scheme based on phase-shifting digital holography and amplitude-phase disturbance 下载免费PDF全文
In this paper, we propose an encryption scheme based on phase-shifting digital interferometry. According to the original system framework, we add a random amplitude mask and replace the Fourier transform by the Fresnel transform.We develop a mathematical model and give a discrete formula based on the scheme, which makes it easy to implement the scheme in computer programming. The experimental results show that the improved system has a better performance in security than the original encryption method. Moreover, it demonstrates a good capability of anti-noise and anti-shear robustness. 相似文献
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In this paper we propose an encryption/decryption technique of gray-level image information using an on-axis 2-f digital holographic
optical encrypting system with two-step phase-shifting method. This technique reduces the number of holograms in phase-shifting
digital holography and minimizes the setup of the encryption system more than multistep phase-shifting technique. We are able
to get the complete decrypted image by controlling the K-ratio which is defined as the reference beam intensity versus the object beam intensity. We remove the DC-term of the phase-shifting
digital hologram to reconstruct and decrypt the original image information. Simulation results show that the proposed method
can be used for encryption and decryption of a 256 gray-level image. Also, the result shows some errors of the decrypted image
according to K-ratio. 相似文献
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We propose an image encryption scheme based on double random amplitude coding technique by using random Hartley transform, which is defined according to the random Fourier transform. The significant feature of this algorithm is that the encrypted image is real and convenient for storage as well as transfer of the encrypted information. Moreover, the algorithm has enhanced security and the correct information of original image can be well protected under bare decryption, blind decryption and brute force attacks. Numerical simulation results are also presented in support of the proposed scheme. 相似文献
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Potential of digital holography in particle measurement 总被引:14,自引:0,他引:14
This paper describes the potential power of digital holography in particle measurement and its expected development in the near future. In digital holography, image reconstruction is carried out numerically on a computer using observed hologram patterns and some quantitative information can be derived from the reconstructed images. In this paper, the basic concept and procedure of digital in-line holography are shown mainly for particle depth measurement and the performance test results obtained in numerical simulations and experiments are demonstrated to examine the potential of the present method. 相似文献
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We present a basic optical encryption architecture that admits several cryptography applications based on multiplexing. Users can decrypt different private images from the same encrypted image, a superuser can have a key that decrypts all encrypted images, and multiplexed images can be encrypted with different levels of security. This system is presented in the context of a general framework of optical encryption application development. We illustrate with a real-world three-dimensional scene, captured with digital holography, and encrypted using the fractional Fourier transform, where different users have access to different three-dimensional objects in the scene. 相似文献
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In this paper, the root mean square (rms) technique is applied in order to reduce the non-coherent noise in phase-contrast image. The proposed technique is applied to a sample of 200 μm step height nominally. The recorded off-axis interferograms generated from two different wavelengths are processed to obtain an object wave (amplitude and phase) for each wavelength separately. The independent phase maps are subtracted and a phase map for the beat-wavelength is obtained and converted to height map. The rms values of 10 pixels profiles from the obtained height map are calculated automatically to show the three-dimensional (3D) profile. The experimental results show that the non-coherent noise is reduced by the order of 90% when the rms technique is applied and the uncertainty in measurement has been found to be of the order of 1.5 μm. The proposed technique can provide a simple and real solution for measuring 3D objects having high abrupt height difference. 相似文献
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We present a new method for variable tomographic scanning based on the wavelength scanning digital interference holography (WSDIH). A series of holograms are generated with a range of scanned wavelengths. The object field is reconstructed in a number of selected tilted planes from each hologram, and the numerical superposition of all the tilted object fields results in a variable tomographic scanning. The scanning direction can be arbitrary angles in 3D space but not limited in a 2D plane, thus the proposed algorithm offers more flexibility for acquiring and observing randomly orientated features of a specimen in a WSDIH system. Experiments are performed to demonstrate the effectiveness of the method. 相似文献
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A multi-image encryption scheme based on interference of computer generated holograms (CGH) is proposed. The encrypted information can be divided into several parts and recorded by corresponding CGHs that distribute randomly. With interference of all CGHs, the original information can be reconstructed. So the multi-image encryption is achieved, and every hologram can be regarded as the key to the corresponding image. Multi-user authentication and storage of information is implemented by applying unique CGH to interfere the common CGH. Furthermore, the CGHs can be cascaded to implement classification of images. When images of different level are assigned to corresponding user, hierarchical encryption is completed successfully. Numerical simulation verifies the feasibility of the method, and demonstrates the security of the algorithm and the decryption characteristics. Flexibility and variability of scheme can be higher than the existing methods. There are a lot of scheme's details still to consider and fulfill in the future. 相似文献
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本文提出了一种基于光学全息的“指纹锁”,将其放置在智能卡的IC芯片前面,用于对用户的个人识别号(PIN码)进行预先加密和认证,和智能卡原有的数字加密算法相结合,可进一步提高信息存储和提取的安全性.该指纹锁是以指纹图像和随机相位板为密钥,记录在光折变晶体材料内的一组角度复用加密全息图.这种光学加密全息图与传统的角度复用全息图不同,其参考光兼有指纹密钥的振幅调制和随机相位调制,具有私密性好、携带方便、安全性高等优点. 相似文献
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High resolution digital holography 总被引:11,自引:0,他引:11
In digital Fresnel holography, present specifications of charge-coupled device cameras require the incident beams to be quasi-parallel. That implies large speckle grain size and low lateral resolution in reconstructed images. Better lateral resolutions are demonstrated in our work, down to 8 μm, allowing the observation of sub-millimetre objects by digital holography. The experimental set-up built samples the incident light distribution with a definition of 500 pixels mm−1. The maximum acceptable angle is then widened and the hologram recording and reconstruction distances are drastically reduced, as well as the speckle size. Interferometric holography was implemented for the measurement of the deformation of a sub-millimetre silicon cantilever and results in phase-contrasts imaging are also reported. The design of dedicated complementary metal-oxide-semiconductor active pixel sensor cameras is also discussed. 相似文献
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M. Gustafsson M. Sebesta B. Bengtsson S. G. Pettersson P. Egelberg T. Lenart 《Optics and Lasers in Engineering》2004,41(3):1251
A spherical reference field is used to construct a digital holographic system with a demonstrated resolution up to 228 line pairs per mm. The reference field originates from a GRIN lens placed 1 mm from the illuminated object. This allows the use of a standard sensor to record the hologram with the required numerical aperture. The image is determined by evaluation of the Rayleigh–Sommerfeld diffraction integral that relates the object field in the image plane to the object field in the sensor plane. Experimental results are given for two charge coupled device sensors and one complementary metal-oxide-semiconductor active pixel sensor. 相似文献
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Aperture synthesis can improve image resolution in digital holography by increasing the numerical aperture of the system. In this paper, we show that both the lateral resolution and image field of view can be enhanced at the same time using a more general Fresnel holography setup and hologram stitching. The impact of aperture synthesis on the lateral resolution is investigated both theoretically and experimentally. In the experiment, the synthesis is executed by moving the compact digital holographic system in two directions. Nine holograms are recorded and stitched into one hologram. The reconstruction results show that expanding aperture improves the lateral resolution. The lensless Fresnel holography used in this paper is demonstrated to have the ability to provide a larger numerical aperture and can compress the object spectrum in recording process. 相似文献
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A novel image encryption method based on the random sequence generated from the generalized information domain and permutation–diffusion architecture is proposed. The random sequence is generated by reconstruction from the generalized information file and discrete trajectory extraction from the data stream. The trajectory address sequence is used to generate a P-box to shuffle the plain image while random sequences are treated as keystreams. A new factor called drift factor is employed to accelerate and enhance the performance of the random sequence generator. An initial value is introduced to make the encryption method an approximately one-time pad. Experimental results show that the random sequences pass the NIST statistical test with a high ratio and extensive analysis demonstrates that the new encryption scheme has superior security. 相似文献
20.
Md. Mosarraf Hossain Dalip Singh Mehta Chandra Shakher 《Optics & Laser Technology》2008,40(1):120-128
An optical hologram contains substantially more information than necessary for some specific applications. Practical methodology of handling huge information contents in these holograms for such applications is cumbersome. In this paper, a method of information reduction, which aims at efficient storage and transmission of holograms, is investigated using digital composite holography in lensless Fourier transform configuration. The maximum information reduction factor obtained in our experiment is 105. The advantages/disadvantages of this method over an earlier method used in optical holography [Lin LH. A method of hologram information reduction by spatial frequency sampling. Appl Opt 1968;7:545] are also discussed. 相似文献