## 5 Conclusions  
Aiming at addressing the problems of low measuring accuracy, discontinuous measuring region and narrow infrared response waveband for surface-scattering-rate measurement in laser-protective-materials diagnostics, a high-precision material-surface-scattering-rate measurement system based on three-hole integrating sphere was proposed in this paper that could achieve high-precision quantitative measurement in any region on a coating surface, with a wide response waveband from near-infrared to far-infrared band. Firstly, in terms of theoretical research, the current integrating-sphere scattering model was improved, and the quantitative expression between the luminous flux received by the detector and the scattering rate on the coating surface was obtained, which was closer to the actual situation. Based on theoretical result, the simulation of the new integrating-sphere measuring system and the analysis of relative uncertainty sources were carried out. A high-precision scattering-characteristic measurement system based on a three-hole integrating sphere was designed and established. The influence of the main design parameters on the expected measuring accuracy of the system was studied by TracePro simulation, and the optimal design parameters of the system were obtained. Combined with the experimental results, the main measuring relative uncertainty sources for the scattering rate of the system were investigated. The measurement accuracy evaluation for the five main relative uncertainty factors, namely laser-power stability, laser incident angle, sample gap distance, ambient-light interference and off-center position of incident beam, was also carried out. The results showed that the laser incident angle had the greatest influence on the relative measurement uncertainty in the system, followed by the sample gap distance. The stability of the laser power depended on the selected laser performance, while the influence of the ambient light angle and the off-center position of incident beam could be ignored in the laboratory environment. Finally, according to the error propagation theory, the total experimental relative measurement uncertainty of the system was found to be \(\pm\)2.22%, which was 26-56% higher than the existing measurement accuracy. The new scattering-rate measuring system proposed in this paper provides an effective experimental method for high-precision quantitative measurement and performance evaluation in the field of laser-protective-materials diagnostics.  
Conceptualization, Z.Y. and J.Z.; methodology, Z.Y. and Y.Y.; software, Y.Y. and Z.Y.; validation, Y.Z. and Y.Y.; formal analysis, Z.Y. and Y.Y.; investigation, Z.Y., Y.Y., J.Z. and X.G.; data curation, Y.Y. and Z.Y.; writing--original draft preparation, Z.Y. and Y.Y.; writing--review and editing, J.Z., Z.Y. and Y.Y.; supervision, Y.Z. and K.L.; project administration, J.Z. and Z.Y. All authors have read and agreed to the published version of the manuscript. This research was funded by the National Natural Science Foundation of China (No. 61905053) and a Postdoctoral Fellowship in Heilongjiang Province (No. LBH-Z17092). The author would like to thank [PERSON], Y.Y., X.G. and K.L. for providing many valuable insights and substantial help. The authors declare no conflict of interest.