In view of whether the optical system of a focal length 14~360mm continuous zoom TV can obtain high quality and high reliability images in high and low temperature environment, especially in extreme low temperature environment. The thermal design of zoom TV optical-mechanical system using passive thermal control and active thermal control is proposed. The passive thermal control uses polyimide as insulation material to increase the thermal resistance between the camera interior and the outside. Active thermal control uses electric heating film to dynamically heat the key parts of the camera lens. Under the condition of low temperature, the finite element method is used to establish the heat transfer model of the whole lens assembly in the workbench finite element software, and analyze the heat load composition, including the heating power load, the heat convection load and the heat radiation load, and carry on the steady state thermal analysis. Through thermodynamic analysis and experimental verification, the consistency of focal plane of zoom camera optical system is good after taking active thermal control measures at the extreme low temperature of -45°C. The optical transfer function (OTF) of zoom lens at cut-off frequency (100lp/mm) is 0.25 higher than that before thermal design, which can meet the requirements of thermal control design with better transfer function distribution and higher imaging quality. The correctness of the simulation results and the rationality of the optical-mechanical design are verified.
In the light of optical-electronic imaging system ,designed a continuous zoom lens with a optical aperture of 60mm and a zoom range of 18-246mm. Summarized the disadvantages of the former zoom lens and a low temperature resistant and high precision structure ,named the special-shaped slide and cam zoom structure is proposed, and carrying out the theoretical analysis and the detailed structural design. Theoretical analysis shows that this kind of structure can make the sliding friction between the cam and the main mirror tube turned into rolling friction ,thus reducing the torque demand.it also helps to eliminate the stuck phenomenon of the cam in low temperature environment .The special-shaped slide frame structure can help eliminate the tilt Angle of the moving mirror group in the zoom process ,thus reducing the variation of optic axis .In the he final test, the zoom time is not longer than 8s in the environment which temperature is only -45°C,and the variation of optic axis is smaller than 0.3milliradian,both meet the target requirement.
Thermal control and temperature uniformity are important factors for space remote sensing cameras. This paper describes the problems with existing systems and introduces the thermal design of a space optical remote sensing camera. Firstly, based on the theory of wave-front aberration distribution, the thermal control index of a space remote sensing camera is proposed. Then on the basis of the analysis of the heat flux environment outside the camera space, the thermal optical analysis of the camera is performed by using the finite element analysis method at high and low temperature conditions. The results show that the transfer function of the optical system with the resolution of 50 lp in the full field of view is more than 0.4. The optical design index can be satisfied, and the rationality of the thermal design is verified. The simulation result meets the requirements of optical design very well. Therefore the study in this paper can be used as an important reference for other space optical systems, which has certain engineering significance.
In combination of the advantages of the optical encryption technology and optical hiding technology, this paper is going
to reveal the way of hiding the encrypted result obtained from scrambling technology in the low-frequency coefficients
of secondary discrete wavelet transform domain of another public image. Meanwhile, the information in different pixels
is hidden by different coefficient matrixes generated by chaos technology in the hiding process. It makes the encrypted
result more difficult to decipher. The proposed method is proved to be a valid approach for hiding the confidential
information as secret image in another non-confidential image via computer simulation and validation. The quality
decline of the carrier image is unapparent, which is unlikely to cause the attackers' attention. This method can effectively
resist the influence of noise, cutting, compression and other attacks. What’s more, the broad key space and good
robustness are of high practical value.
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