Fig. 1. Orbital robot with a laser transmitter and a camera

Fig. 2. Influence of stitching position on imaging perspective. (a) Pixels in the rightmost column of each frame are stitching; (b) pixels in the middle column of each frame are stitching

Fig. 3. RGB long image generated by a video

Fig. 4. Ranging principle. (a) Principle of structured light ranging; (b) optical imaging path

Fig. 5. Depth map

Fig. 6. Extraction for the laser center line by the adaptive threshold method after pre-segmenting the laser domain. (a) Original image; (b) laser domain pre-segmenting; (c) adaptive threshold method extraction

Fig. 7. Adaptive threshold method

Fig. 8. Extraction results of laser center line. (a) Original image; (b) thresholding method; (c) extreme method; (d) proposed method

Fig. 9. Improved YOLOv5 network structure

Fig. 10. RGB-D map generated from a video

Fig. 11. Contrast images at low brightness

Fig. 12. Examples of damages on thermal insulation layer. (a) Hole; (b) crack; (c) rockfall

Fig. 13. Damage detection result