Fig. 1. Schematic of target scattering spectrum measurement

Fig. 2. Experimental device diagram

Fig. 3. Spectral lines of BRDF value of ice wire sample in purple sample group calculated when the incident angle is 45° and the observation angle is 30°, 45°, and 60° as function of wavelength. (a) Spectral lines; (b) normalized spectral lines

Fig. 4. Spectral lines of each sample in purple sample group calculated when the incident angle is 45° and observation angle is 60°. (a) Spectral line of BRDF value changing with wavelength; (b) spectral line of the difference value between X-fiber and each sample in purple sample group as a function of wavelength; (c) spectral line of the first-order differential of BRDF value varying with the wavelength; (d) spectral line of the first-order differential difference of BRDF value between X-fiber and each sample in purple sample group as a function of wavelength

Fig. 5. Spectral lines of each sample in purple sample group calculated when the incident angle is 45° and observation angle is 45°. (a) Spectral line of BRDF value changing with wavelength; (b) spectral line of the difference value between X-fiber and each sample in purple sample group as a function of wavelength; (c) spectral line of the first-order differential of BRDF value varying with the wavelength; (d) spectral line of the first-order differential difference of BRDF value between X-fiber and each sample in purple sample group as a function of wavelength

Fig. 6. Spectral lines of each sample in purple sample group calculated when the incident angle is 45° and observation angle is 30°. (a) Spectral line of BRDF value changing with wavelength; (b) spectral line of the difference value between X-fiber and each sample in purple sample group as a function of wavelength; (c) spectral line of the first-order differential of BRDF value varying with the wavelength; (d) spectral line of the first-order differential difference of BRDF value between X-fiber and each sample in purple sample group as a function of wavelength

Fig. 7. BRDF value and least square fitting curve of each sample in gray sample group calculated when incidence angle is 45° and observation angle is 30°

Fig. 8. Simulation results of three samples in red sample group by Davis model.(a) Silk sample; (b) cotton sample; (c) woolen sample 1

Fig. 9. Simulation results of three samples in red sample group in wavelength of 500-950 nm by Davis model. (a) Silk sample; (b) cotton sample; (c) woolen sample 1

Table 1. Classification table of fiber samples

Table 2. Least square fitting parameters of BRDF value of each sample in gray sample group calculated when incident angle is 45°and observation angle is 30°

Table 3. Relationship between surface roughness of each sample in red sample group and autocorrelation length