Design of Flat Field Holographic Concave Grating for Near-Infrared Spectrophotometer
XIANG Xian-yi,WEN Zhi-yu
Key Laboratory of Optoelectronic Technology and System of the Education Ministry of China, Chongqing 400044,China Micro-system Research Center of Chongqing University, Chongqing 400044,China
Abstract：Near-infrared spectrum analysis can be used to determine the nature or test quantitatively some chemical compositions by detecting molecular double frequency and multiple frequency absorption. It has been used in agriculture，biology, petrifaction, foodstuff, medicament, spinning and other fields. Near-infrared spectrophotometer is the main apparatus for near-infrared spectrum analysis, and the grating is the most important part of the apparatus. Based on holographic concave grating theory and optic design software CODE V, a flat field holographic concave grating for near-infrared spectrophotometer was designed from primary structure, which relied on global optimization of the software. The contradiction between wide spectrum bound and limited spectrum extension was resolved, aberrations were reduced successfully, spectrum information was utilized fully, and the optic structure of spectrometer was highly efficient. Using CODE V software, complex high-order aberration equations need not be solved, the result can be evaluated quickly, flat field and resolving power can be kept in balance, and the work efficiency is also enhanced. A paradigm of flat field holographic concave grating is given, it works between 900 nm to 1 700 nm, the diameter of the concave grating is 25 mm, and F/# is 1.5. The design result was analyzed and evaluated. It was showed that if the slit source, whose width is 50 μm, is used to reconstruction, the theoretic resolution capacity is better than 6.3 nm.
Key words：Flat Field Concave Holographic Grating;Near-Infrared;Spectrophotometer;CODE V
