Effects of Orientation and Quality on Spatial Spectrum Characteristics of Fruits in Southern Xinjiang
XU Jia-yi1, 3, HUANG Xue2, 3, LUO Hua-ping1, 3*, LIU Jin-xiu1, 3, SUO Yu-ting1, 3, WANG Chang-xu1, 3
1. College of Mechanical and Electrical Engineering, Tarim University, Alar 843300, China
2. College of Plant Science，Tarim University, Alar 843300, China
3. The Key Laboratory of Colleges and Universities under the Department of Education of Xinjiang Uygur Autonomous Region，Alar 843300, China
Abstract：Hyperspectral nondestructive testing technology is widely used in quantitative nondestructive testing of fruit. In this paper, the spatial characteristic spectra of jujube, grape and pear are taken as the research objectives, and the influencing factors and inversion methods of spatial characteristic spectra are explored, which provides a new idea for improving the accuracy of outdoor fruit nondestructive testing. The spectral library of three kinds of fruits was extracted, and the spatial characteristic spectra were calculated. The characteristic wavelengths were selected by Mahalanobis distance, concentration residual and competitive adaptive weight sampling algorithm. Model characteristic spectra of three kinds of fruits after pretreatment with quality parameters and positional parameters respectively.The modeling results are as follows: In the sugar model, the R of jujube, grape and pear were 0.853 3, 0.822 7 and 0.913 3 respectively; In the water model, the R were 0.741 3, 0.784 7 and 0.891 3 respectively; In the detection angle model, the R were 0.985 6, 0.992 7 and 0.974 7 respectively; In the azimuth angle model, the R were 0.941 8, 0.910 5 and 0.936 9 respectively; In the phase angle model, the R were 0.960 9, 0.957 0 and 0.956 3 respectively. In summary, the correlation of different fruit positional models was significantly higher than quality models. Therefore, the positional factor is the main reason affecting the characteristic spectrum. Therefore, the roujean model and waltall model are used to invert the characteristic spatial spectrum of different directions. The inversion results are as follows: roujean model is used when retrieving the spatial characteristic spectra of three kinds of fruits (in the order of jujube, grape and pear), R2 is 0.934 4, 0.928 1 and 0.830 6 respectively; R is 0.990 2, 0.983 9 and 0.969 1 respectively; RMSEP is 0.030 9, 0.048 7 and 0.062 7 respectively; the average model error is 7.27%, 11.02% and 8.61% respectively. The results showed that R2 was 0.943 3, 0.859 7, 0.839 0; R was 0.991 8, 0.971 8, 0.970 2; RMSEP was 0.036 6, 0.066 1, 0.068 7; the average model error was 6.19%, 15.40%, 7.84%. It can be seen that roujean model can well describe the characteristic spatial spectrum of jujube and grape, and also can better describe the characteristic spatial spectrum of pear; waltall model can well describe the characteristic spatial spectrum of jujube, and also can better describe the characteristic spatial spectrum of grape and pear. In conclusion, roujean model can be used to invert the characteristic spatial spectrum of grape and pear, and waltall model can be used to invert the characteristic spatial spectrum of jujube to improve the accuracy of outdoor fruit nondestructive testing.
Key words：Bidirectional reflectivity distribution function; Background spectrum; Roujean model; Walthall model
徐嘉翊，黄 雪，罗华平，刘金秀，索玉婷，王长旭. 方位和品质对南疆果品空间特性光谱影响及反演方法研究[J]. 光谱学与光谱分析, 2022, 42(03): 910-918.
XU Jia-yi, HUANG Xue, LUO Hua-ping, LIU Jin-xiu, SUO Yu-ting, WANG Chang-xu. Effects of Orientation and Quality on Spatial Spectrum Characteristics of Fruits in Southern Xinjiang. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2022, 42(03): 910-918.
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