The hyperspectral camera can combine imaging technology with spectral detection technology. While imaging the spatial features of the target, it can form multiple narrow bands for each spatial pixel to achieve continuous spectral coverage, and different spectral information can fully reflect the interior of objects. differences in physical structure and chemical composition. Compared with traditional spatial two-dimensional imaging, hyperspectral cameras can simultaneously acquire the spatial and spectral information of the target. Under a certain spatial resolution, it can acquire the unique continuous characteristic spectrum of objects in a wide spectral range, which can greatly improve the accuracy of objects. Accurate identification and detection have significant advantages and have now become an important cutting-edge technology for remote sensing of the ground.
With the rapid development of filter coating technology, the development of filter spectroscopic hyperspectral cameras has been greatly promoted. The advantages of light and small size have become an important part of hyperspectral remote sensing payloads, and have been widely used in the networking of micro-nano satellite hyperspectral constellations.
According to Memes Consulting, recently, the research group of Liu Chunyu from the Changchun Institute of Optics, Fine Mechanics and Physics of the Chinese Academy of Sciences published a report on "The Development Status and Trends of Filter Spectroscopic Hyperspectral Cameras" in the journal "Infrared and Laser Engineering". article on the subject. Researcher Liu Chunyu is mainly engaged in the research of optical system design and overall design of optoelectronic system.
Schematic diagram of the principle of hyperspectral imaging
This research mainly reviews the filter-split hyperspectral cameras, and introduces the typical filter-split spaceborne hyperspectral imaging payloads at home and abroad, as well as the filter-split hyperspectral imaging systems under development on the ground. The technical solutions, performance indicators and application prospects of these systems are analyzed, and the technical characteristics, advantages and disadvantages of hyperspectral cameras based on the principle of filter spectroscopy are expounded. Finally, the development trend of filter spectroscopy hyperspectral cameras is prospected.
The filter wheel hyperspectral camera uses the filter wheel as the light-splitting element, and obtains spectral images of different wavelength bands by rotating the filter wheel, thereby completing the splitting of polychromatic light to monochromatic light. The key component of the filter wheel hyperspectral camera is the filter wheel, which can replace the filter wheel of the corresponding spectral range according to the different observation bands. The optical path structure is simple and the spectral band can be replaced flexibly. With the development of spectral imaging technology, the number of detection bands is increasing, and the filter wheel can no longer meet the observation of wide spectrum and high resolution, so it is more and more used in multi-spectral detection.
Tunable filter hyperspectral cameras use tunable filters as spectroscopic components. According to different tuning methods, they are mainly divided into liquid crystal tunable filters (LCTF) hyperspectral cameras, acousto-optic tunable filters Acousto-Optic Tunable Filter (AOTF) hyperspectral camera, MEMS tunable FP cavity filter (MEMS Tunable Fabry-Perot Cavity Filters) hyperspectral camera.
The wedge-shaped filter hyperspectral camera, also known as the gradient filter type hyperspectral camera, can achieve continuous sampling in the spectral region and the spatial region. Its design concept is to use a wedge-shaped multi-layer thin film medium as a filter, And it is installed in the position close to the two-dimensional array detector, so that several pixels of the detector correspond to a certain spectral band of the gradient filter. According to the corresponding relationship between each wavelength band of the gradient filter and the detector pixel, the hyperspectral camera with gradient filter can be divided into linear gradient type and filter array type.
Linear Gradient Filter Structure and Spectral Diagram
Quantum dots, also known as "nanocrystals", are inorganic materials with high intrinsic stability and a radius smaller than that of the bulk exciton Bohr radius. By integrating different types of quantum dots, simultaneous detection of different wavelengths can be achieved. The quantum dot spectrometer (CQD) is developed based on this principle. Spectrometers in the traditional concept are equipped with high-precision optical and mechanical components, which are bulky, expensive, and complex in structure, and their application fields are severely limited.
Schematic diagram of near-infrared quantum dot spectrometer
In general, the filter spectroscopic hyperspectral camera is in its infancy, and its spectral resolution cannot be compared with the high-precision grating dispersion spectroscopic method. The general development direction of hyperspectral cameras, especially with the development of coating technology and new materials such as quantum dots, the spectral resolution and energy utilization rate of hyperspectral cameras based on coating have been greatly improved, and the research and development costs are expected to further increase. In addition, the combination of the filter and the detector will further improve the spectral resolution of the system, which can even be comparable to the high-precision grating dispersion spectroscopy. Therefore, the combination of the filter and the detector element is also a coating type. A major development trend in spectral cameras. It is not difficult to see that the development of filter-type hyperspectral cameras will promote the subversive development in the field of hyperspectral imaging, and thus drive the development of hyperspectral remote sensing technology for micro-nano satellites, which will be in orbit for the future constellation of micro-nano hyperspectral satellites. Business operation, better serve the national economy and lay a technical foundation.
This project was supported by the National Natural Science Foundation of China (41504143), the Scientific Research Equipment Development Project of the Chinese Academy of Sciences (YJKYYQ20190044), the Natural Science Foundation of Anhui Province (1908085 ME135), and the Youth Innovation Promotion Association of the Chinese Academy of Sciences (2016203).
