## 3 Results
### Crop Phenotype Parameter Acquisition Performance  
#### 3.2.1 System Stability  
The independently developed crop phenotype acquisition device was used to continuously and synchronously acquire the crop phenotypes of Guofu 909 peppers, and the obtained visible light images, thermal images, and laser point cloud images (as shown in Figure 7) were stored in the system in categories. The equipment continuously acquired data for one hour. On the basis of no missed acquisitions, 133 successful acquisitions were achieved, and 133 sets of data were obtained. All images in this article were taken under natural light conditions without additional lighting.  
(1) Stability of Visible and Thermal Image Acquisition  
During the data acquisition process, due to the shift in sunlight, the brightness changes in the visible light images and thermal infrared images were relatively obvious in the early and late stages of shooting. As shown in Figure 8, the brightness value of the visible light image was 113.52 nits in the early stage of shooting and 139.37 nits in the late stage; the brightness value of the thermal infrared image was 101.94 nits in the early stage of shooting and 113.70 nits in the late stage. For the 133 sets of visible light images and thermal infrared images, the two indicators of SSIM and DSSIM were calculated to characterize the similarity between the images, and the maximum error and mean absolute error of the acquired data were calculated to measure the stability of the system acquisition. The results are shown in Table 3.  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Data Type** & \begin{tabular}{c} **Maximum** \\ **Pixel Error (\%)** \\ \end{tabular} & \begin{tabular}{c} **Pixel Mean** \\ **Absolute Error (\%)** \\ \end{tabular} & \
\begin{tabular}{c} **Pixel Mean Square** \\ **Deviation** \\ \end{tabular} &
\begin{tabular}{c} **SSIM** \\ **DSSIM** \\ \end{tabular} \\ \hline Visible light image & 3.52 & 2.8926 & 11.2633 & 0.8266 & 0.9688 \\ Thermal infrared images & 3.36 & 3.2549 & 23.5559 & 0.8887 & 0.9555 \\ \hline \end{tabular}
\end{table}
Table 3: Similarity analysis of visible and thermal maps.  
Figure 7: Ten groups of capsicum crop phenotypic data., Visible light image (top), thermal infrared image (middle), point cloud (bottom).  
(2) Stability of Point Cloud Acquisition  
To verify the stability of the system in point cloud data acquisition, statistical indicators, distribution characteristic indicators (Charm distance), and structural characteristic indicators (Hausdorff distance) were used for quantitative characterization. For 133 point cloud images (each image contains 3600 point cloud data), two statistical indicators (average point number difference and average coordinate error) were calculated. The average point number error of the point cloud files was about 2%, the average coordinate error was within 5%, the Charm distance was only 1.1448 mm, and the Hausdorff distance was only 5.54516 mm.  
The Charm and Hausdorff distances between more than 130 point cloud images were small, with errors at the millimeter level, indicating that the point cloud data acquired by the crop phenotype acquisition system designed in this paper showed no obvious differences in distribution characteristics and structural characteristics. It showed that the point cloud files in this study were statistically very similar, further indicating that the system had good stability.