Fig. 1. Spatial correlation function of triangular range-intensity for three-dimensional reconstruction

Fig. 2. Original two-dimensional gate images and gray distribution curves. (a)(b) Two-dimensional gate images; (c) gray distribution curves

Fig. 3. Comparison of gray value distribution curves of two two-dimensional gate images before and after bilateral filtering

Fig. 4. Results of guided filtering of image including four-layer detail information. (a)(b) Results after guided filtering; (c)(d) images of four detail layers

Fig. 5. Effect of pre-processing on original image. (a) Comparison of gray value distribution curves before and after guided filtering; (b)(c) comparison of SSIM values of time-slicing images

Fig. 6. Three-dimensional reconstruction images. (a) Reconstruction of original image; (b) reconstruction of images after bilateral filtering; (c) reconstruction of images after guided filtering with four detail layers combined with bilateral filtering; (d) reconstruction of images after guided filtering with two detail layers; (e) reconstruction of images after guided filtering with three detail layers; (f) reconstruction of images after guided filtering with four detail layers

Fig. 7. Sampling of pixel information in three-dimensional reconstruction. (a) 260 columns; (b) 300 rows

Fig. 8. Local structure extraction from Figs. 6(a) and 6(c). (a)(b) Edge area in 70 pixel×70 pixel; (c)(d) internal structure area in 120 pixel×120 pixel