Images can convey information and needs to be protected, which is usually done by encryption. Traditional image encryption methods usually use software or hardware encryption, which has improvement approach in terms of better safety and robustness. And the study arouses sympathy to researchers based on both software and hardware encryption. This paper proposes an encryption method that combines software algorithm encryption and hardware encryption using a spatial light modulation (SLM) and 4f optical system. Firstly, the image is chaotically encrypted using the chaos encryption algorithm. Secondly, the discrete cosine transform (DCT) is adopted for further encryption based on chaos encryption picture. Thirdly, the cipher text image is transformed into the 4f system using SLM, which performs a random amplitude on the image to achieve hardware encryption. Finally, the simulation and experiment are performed to verify that the scheme, which shows that the method can realize the encryption and unencryption under the combination of software and hardware encryption. The proposed method has application value to guarantee the higher security of information.
In the traditional microfield speckle pattern interference measurement system, due to the use of high-magnification objective lens, the working distance is small and the shearing device cannot be introduced to implement shearography measurement. Thus the distribution of the deformation gradient on a microstructure surface cannot be measured. A system for the synchronous measurement of the surface deformation and gradient distribution of a microstructure was designed. Through the combination of focusing lens, convex lens, and low-magnification objective lens, the microstructure surface was clearly magnified and the internal distance of the system was enlarged. Thus the shearing device can be introduced to realize the shearography measurement under the microfield view. The synchronous full-field measurement of the structural surface deformation and its gradient distribution was further realized by the introduction of a reference light and designing of an optical path switch. In addition, the designed system had a zoom feature, which can facilitate the measurement in variable field of view in a certain range. The feasibility of the system was verified by theoretical analysis and experiment, and the practicability was validated by testing the chip and circuit board.
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