2020, Cheremkhin, P. A., Evtikhiev, N. N., Krasnov, V. V., Rodin, V. G., Shifrina, A. V., Starikov, R. S., Черёмхин, Павел Аркадьевич, Евтихиев, Николай Николаевич, Родин, Владислав Геннадьевич, Шифрина, Анна Владимировна, Стариков, Ростислав Сергеевич

In this paper new method of asymmetric optical encryption is presented. It is based on the double encryption using spatially incoherent illumination: to obtain a ciphertext a plaintext is encoded twice, first time by sender, second time-by recipient. This way no exchange of encryption keys is required. Two variants of this method were analyzed: one in which both encryption procedures are implemented optically and another one in which the first operation is done optically and the second one-numerically. Both variants were numerically simulated and the latter one was implemented optically. Results of numerical and optical experiments demonstrate high quality of decrypted images (decoding error 0.19), thus confirming usability of proposed method.

2020, Evtikhiev, N. N., Krasnov, V. V., Molodtsov, D. Y., Rodin, V. G., Starikov, R. S., Cheremkhin, P. A., Евтихиев, Николай Николаевич, Родин, Владислав Геннадьевич, Стариков, Ростислав Сергеевич, Черёмхин, Павел Аркадьевич

© 2020, Allerton Press, Inc.Abstract: The possibility of using a digital micromirror device (DMD) for implementing the optical encryption with time integration in quasimonochromatic spatially incoherent light is considered. An experimental setup for optical registration of image to be encrypted on a digital camera is presented. Images containing text and graphic information are encrypted and successfully decrypted using inverse filtering. The use of time integration in optical encryption makes it possible to reduce the noise caused by binarization of holograms display on DMD that contains encryption keys and to increase the diffraction efficiency of the encryption process.

2019, Cheremkhin, P. A., Kurbatova, E. A., Черёмхин, Павел Аркадьевич

© 2018 Elsevier Ltd Binary digital and computer-generated holograms are used in a number of digital micromirror device (DMD) applications, including holographic displays, media characterisation, optical encryption, and others. Binarisation is one of the most simple and efficient methods of hologram compression. In this paper, 12 local and 18 global thresholding techniques of different groups were analysed and compared based on attribute similarity, clustering, entropy, histogram shape, and local adaptive factors. Optically recorded off-axis digital holograms of different objects were binarised using these methods. The amplitude quality of the obtained reconstructed images was compared using PSNR and SSIM values. The clustering-based methods achieved the highest quality. The results of binarisation by global and local methods were comparable on average.

2021, Evtikhiev, N. N., Krasnov, V. V., Ryabcev, I. P., Rodin, V. G., Starikov, R. S., Cheremkhin, P. A., Евтихиев, Николай Николаевич, Родин, Владислав Геннадьевич, Стариков, Ростислав Сергеевич, Черёмхин, Павел Аркадьевич

© 2021, Springer Science+Business Media, LLC, part of Springer Nature.We consider the problem of achieving high stability and linearity of phase liquid-crystal space-time light modulators, which are widely used for optical reconstruction of diffractive optical elements, including holograms. Modern high-resolution space-time light modulators one uses a digital signal addressing circuit, which leads to phase shift fluctuations during the frame. For the modern high-resolution phase liquid crystal space-time light modulator Santec SLM-200, the dependences of the phase shift on the level of the addressed signal and time from the beginning of the frame have been measured. Using the Santec SLM-200 light modulator, optical reconstruction of images from diffractive elements of different types was performed, their diffraction efficiency and the quality of the reconstructed images were evaluated. The values of the diffraction efficiency were obtained in the range of 3–10%; a sharp drop in the brightness of the reconstructed images is observed with distance from the optical axis in the plane of reconstruction.

2020, Evtikhiev, N. N., Krasnov, V. V., Kuzmin, I. D., Molodtsov, D. Y., Rodin, V. G., Starikov, R. S., Cheremkhin, P. A., Евтихиев, Николай Николаевич, Родин, Владислав Геннадьевич, Стариков, Ростислав Сергеевич, Черёмхин, Павел Аркадьевич

An optical encryption scheme with spatially incoherent illumination based on two micromirror light modulators has been experimentally implemented for the first time. Currently, such modulators arc the fastest tools for spatio-temporal light modulation; their high frame rates provide possibilities for developing optical encryption systems with a bandwidth of several gigabites per second.

2020, Kurbatova, E. A., Rodin, V. G., Cheremkhin, P. A., Родин, Владислав Геннадьевич, Черёмхин, Павел Аркадьевич

© 2020, Allerton Press, Inc.Abstract: Binarization of digital holograms is used for storage and on-line transfer of registered information and for optical reconstruction of images using binary digital micromirror devices. The capabilities of binarization of optically registered holograms by iterative methods with application of the error diffusion method either at each step of varied binarization threshold or only at the final iteration are considered. The variation of method parameters is analyzed and the quality of reconstructed images is compared with the quality of the binarized holograms. It is determined that the method with application of the error diffusion operation only at the final stage increases the quality of image reconstruction by 12% compared to the one-step methods.

2019, Molodtsov, D. Yu., Cheremkhin, P. A., Krasnov, V. V., Rodin, V. G., Черёмхин, Павел Аркадьевич, Родин, Владислав Геннадьевич

© OSA 2019 © 2019 The Author(s)Scheme of real time optical encryption using DMD modulator is described. Experimental results of optical encryption of images in spatially incoherent light are demonstrated.

2020, Cheremkhin, P. A., Evtikhiev, N. N., Krasnov, V. V., Rodin, V. G., Черёмхин, Павел Аркадьевич, Евтихиев, Николай Николаевич, Родин, Владислав Геннадьевич

© COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.Digital holography is technique for registering of 2D- and 3D-scenes characteristics: amplitude or phase images of object, roughness, and etc. Numerical reconstruction allows fast images recovery. However high quality optical reconstruction is not so fast due to the hologram transferring to the spatial light modulator (SLM), hologram digital preprocessing, SLM calibration, and etc. In this work we analyzed possibilities of fast processing of the holograms for increasing of quality of optically reconstructed images. Amplitude type holograms were registered and images were optically reconstructed using phase liquid crystal SLM. Various techniques of improvement of reconstruction quality were used.

2020, Evtikhiev, N. N., Zlokazov, E. Y., Krasnov, V. V., Rodin, V. G., Starikov, R. S., Cheremkhin, P. A., Евтихиев, Николай Николаевич, Злоказов, Евгений Юрьевич, Родин, Владислав Геннадьевич, Стариков, Ростислав Сергеевич, Черёмхин, Павел Аркадьевич

© 2020 Kvantovaya Elektronika and Turpion Ltd.We report the results of simulations and experiments on the formation of light distributions by holograms and diffraction elements displayed by digital micromirror devices. Examples of successful experiments on the implementation of optical-digital systems based on them are demonstrated.

2021, Kulakov, M. N., Rodin, V. G., Starikov, R. S., Cheryomkhin, P. A., Родин, Владислав Геннадьевич, Стариков, Ростислав Сергеевич, Черёмхин, Павел Аркадьевич

© 2021, Springer Science+Business Media, LLC, part of Springer Nature.The reconstruction methods, which are based on compressed sensing (CS), make it possible to record and reconstruct information basing on its sparse or compressed representation. In this work, we study resistance of CS-based single-pixel imaging to partial loss of the intensity of the recorded radiation from an object with a limited area of the detector. The problem was solved experimentally by implementing the so-called single-pixel camera, as well as detecting optical radiation from the object and reconstructing its image with the use of CS methods. The method resistance to spatial radiation losses is estimated as a function of the size and shape of the detector aperture. The quality of image reconstruction depending on the two following factors is assessed: the fraction of the intensity of the detected radiation and the quantity of single-pixel detections. The results can ensure significantly wider application of the method to reconstruct data, both detected in dynamic and scattering media (including the introduction of various apertures and Fourier filtering) and in the case of significant spatial radiation losses.