What is the Imaging Spectroradiometer?
The structure of the imaging spectrometer consists of an entrance slit, a dispersion system, an imaging system and one or more exit slits. The electromagnetic radiation of the radiation source is separated into the required wavelength or wavelength region by the dispersive element, and the intensity is measured at the selected wavelength. The radiant energy of the ground target passes through the pointing lens, is collected by the objective lens and irradiated on the dispersive element through the slit enhanced collimation, the dispersive element is spectrally dispersed in the straight strip direction, and the condenser lens is used to converge and image the two-dimensional CCD used in the sensor. The area array exploration elements are scattered on the focal plane of the spectrometer.
The imaging spectrometer provides fast, simple, repeatable, and more importantly, non-invasive qualitative and quantitative analysis. It does not require sample preparation, and the sample can be measured directly through a fiber optic probe or through glass, quartz, and fiber optics. When investigating in a straight direction, in addition to the Rayleigh scattering with the same frequency as the original incident light, there are also a series of symmetrically scattered Raman lines that are weakly displaced with the incident light frequency.
A transmissive volumetric holographic diffraction grating is used, which has the characteristics of low stray light and low absorption in the visible light to near-infrared waveband. Since the core part is sealed in glass or other transparent materials, it has a long life, is easy to clean, and is resistant to scratches. It is very suitable for various harsh outdoor application environments. The previous working method was mainly push-broom type. In order to realize the scanning process, an external scanning platform is generally used to drive the operation of the spectrometer. Because the scanning platform is relatively heavy and increases power consumption, it brings a lot of inconvenience to field work. Therefore, the new imaging spectrometer cancels the scanning platform and changes to a built-in scanning design, which reduces the weight and energy consumption of the whole machine, and can directly measure vertically downwards, which is more conducive to field use.
On the basis of hyperspectral measurement, it has the advantage of unifying the spectrum. It can be accurate to a single point on the leaf to detect the characteristics of different stress symptoms of the crop, and can also obtain the spectral information of the surface of the stressed crop, and the combination of point and surface can comprehensively reflect the degree of stress on the crop. Therefore, imaging spectrometers have become a research hotspot at the world. Scholars use hyperspectral imaging technology to quantitatively extract the characteristics of various stresses suffered by crops, analyze the leaves and local areas of the leaves based on high-resolution images, so as to carry out mechanism detection and research on a more microscopic scale.
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