A spectrophotometer is a combination of a spectroscopic instrument and a photometer. It is a photoelectric analysis instrument that uses the selective absorption of light by substances to perform qualitative and quantitative analysis of substances. Spectrophotometers can be divided into ultraviolet spectrophotometers, ultraviolet-visible spectrophotometers and ultraviolet-visible near-infrared spectrophotometers according to the measured wavelength range.
 
NIR spectrophotometer is an analytical instrument used in the field of physics，and near-infrared light (NIR) is an electromagnetic wave between visible light (VIS) and mid-infrared light (MIR). The near-infrared spectrophotometer can perform qualitative and quantitative analysis on the correlation between the molecular structure of organic compounds and the near-infrared spectrum, hot issues in chemical reactions, and structural analysis of unknown compounds. It is used for the testing of solid and liquid samples in food and agricultural products, chemistry and chemical engineering, polymer, biology, petroleum industry and other sub-disciplines and chemistry-related disciplines.
 
The near-infrared spectrophotometers can be divided into five types according to the spectroscopic system, namely fixed wavelength filter, grating dispersion, fast Fourier transform, acousto-optical tunable filter and array detection. Since near-infrared light has good transmission characteristics in conventional optical fibers, and it is relatively simple, fast in analysis speed, non-destructive and small in sample preparation, almost suitable for various sample analysis and simultaneous determination of multi-components  and multi-channels, It has become an important role in online analytical instrumentation.
 
Near-infrared spectroscopy (NIR) is one of the fastest-growing and most eye-catching analysis techniques since the 1990s. With the development of chemometrics, optical fiber and computer technology, online near-infrared spectroscopy analysis technology is being applied at an astonishing speed in many fields such as agriculture and animal husbandry, food, chemical industry, petrochemical, pharmaceutical, tobacco, etc., which provides a very broad use space for scientific research, teaching and production process control.