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17 November 2010 A new method of calculating the diffraction efficiency for diffraction/refraction infrared hybrid system
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In this paper, a new method of calculating the diffraction efficiency for diffraction / refraction infrared hybrid system is given. By using this method, an automatic measurement system is designed. This system covers the wavelength range of 1~3 μm, 3~5μm and 8~12μm. We use a blackbody as the energy source, put the lens which is to be measured above a computer controlled turntable in order to gain different results in different filed of view. We also have several relay lenses to cope with long or negative focal length. We use two types of detectors to deal with wavelength range of 1~3μm and 3~12μm .Both the detector and preamplifier are assembled together so we can easily change them for different wavelength ranges. To improve the accuracy of the measurements, a new theory of measuring the main energy is developed to minimize the negative impacts of other diffraction orders and the environment. We use an adjustable slit cooperating with a two-axis stage to scan the focal point and by adjusting the width of the slit we can reduce the energy of other diffraction orders and the environment that may come into our detector. During the experiment process we can manually control the slit and two-axis stage to improve the efficiency and use our computer program to improve the accuracy. The energy modulator and lock-in amplifier also help to improve the accuracy of our system. We designed two standard lenses for the 3~5μm wavelength range. Both of them are made of the same material, have the same focal length of 200mm and their shape is almost the same. The only difference between them is that one of them is pure refraction piece which acts as a reference and the other one has a diffraction surface to achromatic aberration. The result fits our theory well and the possible causes of the differences are discussed. This system has a practical meaning in the quality evaluating of infrared hybrid system.
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Tao Wang, Jian Bai, Yiyong Liang, and Xiyun Hou "A new method of calculating the diffraction efficiency for diffraction/refraction infrared hybrid system", Proc. SPIE 7848, Holography, Diffractive Optics, and Applications IV, 78482G (17 November 2010);

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