Spectral imaging technology can obtain a three-dimensional data cube of the target, which has the advantage of "unification of maps". Analyzing the "fingerprint" spectral information of space targets is a powerful method for space target identification. In response to the needs of space target material identification and key part identification, this paper proposes a new method of computational spectral imaging with high Light utilization for space target detection. A high-resolution spatial spectral image is obtained through the combination of panchromatic channel and calculated spectral channel. Introduce the calibration technology of the system, including the target's spectrum calibration and the system's coding calibration technology. The multi-spectral image of the satellite model taken by the new spectral imaging system is used to expand the sample, and the training set data is used for training, and the entire data set is tested. The average recognition rate of the five categories of satellite main body, windsurfing board, pot body, antenna and space background is 74.86%. If only the identification of the target and the background is considered, and the non-critical part of the satellite antenna is not considered, the probability of correct recognition as a target is 98.92%, and the probability of correct recognition as a background is 99.11%.
The conventional diffractive optical imaging spectrometer uses the single-channel scheme, it is mainly aimed at simple targets, or gas targets with known spectral characteristics. The main disadvantage of conventional system is: if the target is a complex scene such as a natural scene, it's very difficult to demodulate spectral images accurately. Because, the focused and defocused spectral information are superimposed on each other. And, the real system has noise, manufacturing error, testing error and calibration error. So, it is difficult to correctly describe the dispersion parameters of the diffractive spectrometer, which will cause large errors of spectral demodulation accuracy. To solve this problem, an efficient system of diffractive spectral imaging is discussed, which includes a reference channel. Based on the conventional single-channel system, a grayscale camera or a color camera is added for imaging. It can provide a priori knowledge of complex scenes for the diffraction imaging channel. The data of the two channels are jointly processed to improve the final demodulation accuracy of the spectral data. The system composition and basic principles are introduced, the performance of the system is analyzed. The virtual simulation experiment of diffractive optic imaging is established. The simulation of diffractive imaging and spectral demodulation of complex scene have been finished. The demodulation output images are almost the same as the original input image. The experiment system of diffractive optic imaging in visible band is also established in the laboratory. Theoretical analysis, imaging simulation and imaging experiment have verified the validity and feasibility of the diffraction imaging system with reference channel. Compared with the single channel system, the spectral demodulation effect is obviously improved, which greatly improves the application potential and application value.
The simultaneous acquisition of spatial information, spectral information and polarimetric information can obtain more characteristic information to distinguish targets. The conventional spectral polarization imaging system mainly includes the filter/polarization wheel rotation system, the crystal modulation system and multi-path beam splitting system. The disadvantages of these systems are: unsynchronized spectral polarization detection, requiring dynamic modulation, complex system, etc. To solve these problems, a spectral polarization detection technology based on optical fiber image bundle is proposed, which combines optical fiber imaging spectral technology with pixel level polarization detection technology. The input shape of the optical fiber image bundle is plane, and the output shape is linear. Optical fiber image bundle can transform the information of array target into that of linear array. The linear array information is the input of spectral imaging system. The polarization detection uses a micron level polarization array to match the pixel size of the detector. The technology can synchronously acquire the two-dimensional spatial information, the spectral information and linear polarization information of the target. The technology can be used to image the area target in snapshot mode. The experimental device is set up to obtain the spectral image in the visible light range, as well as the polarization degree image and polarization angle image of each spectral segment. The data acquisition ability of the system is verified. With the improvement of optical fiber manufacturing technology, the integration of optical fiber is getting better, and the scale of optical fiber is getting larger. The technology will have a high application value in astronomical observation, atmospheric detection, target recognition and other fields.
The spectral polarization imager can detect the spectral polarization information of the target reflection or radiated light that cannot be obtained by ordinary optical instruments. The obtained spectral polarization image can provide richer target information than the intensity image and the spectral image. At the same time, being able to achieve snapshot imaging and improve the spectral resolution is the research and development direction of polarization spectrum imaging technology. In this paper, we present a dual channel snapshot compressive spectral polarization imaging technique for simultaneous acquisition of two-dimensional intensity information, one-dimensional spectral information, and four-dimensional polarization information of a target in visible range. One channel is based on a coded mask and micro-polarizer array, and one channel is based on a pixel-level polarizer array detector. The main optical path replaces the ordinary detector with a micro-polarizer array based on CASSI. The micro-polarizer array consists of 0°, 45°, 90°, and 135° linear micro-polarizers regularly distributed, and each pixel matches the pixel of the detector. The three Stokes parameters of the scene are compressed and sensed, and a four-dimensional (4D) data cube is projected onto a two-dimensional (2D) focal plane. Through nonlinear optimization with sparsity constraints, a 4D spectral polarization data cube is reconstructed from 2D measurements. The addition of a pixel-level polarizer array detector helps to improve the measurement accuracy of spectral information and polarization information. Optical experimental results confirm that the architecture reduces the total number of measurements required to obtain a spectrally polarized image compared to traditional acquisition methods. The dual channel combination enables simultaneous acquisition of spectral and polarization information, and improves the quality of reconstructed image based on compressed sensing algorithm. A dual-channel experimental device with coded aperture spectral polarization imaging channel and polarization imaging channel was set up to obtain spectral data cubes with 4 polarization states in 25 bands in the range of 450nm-650nm, and the polarization degree and polarization angle of each band. The spectral resolution was better than 10nm, and the spectral restoration accuracy was about 86.3%. Compared with the single-channel imaging method, the spectral reconstruction accuracy was improved by 10.5%.This has guiding significance for the design and research of light and miniaturized hyperspectral polarization imagers in the future. It is expected to be widely used in astronomical observation, atmospheric detection, biomedical diagnosis, earth environment monitoring, target detection and identification and other fields.
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