Author Affiliations
1School of Mechatronic Engineering and Automation, Shanghai University, Shanghai 200444, China2The Palace Museum, Beijing 100009, China3China-Greece ‘Belt and Road’ Joint Laboratory on Cultural Heritage Conservation Technology, Beijing 100009, Chinashow less
Fig. 1. Schematic diagram of digital holographic diffuse imaging system
Fig. 2. Flow chart of digital holographic deformation detection
Fig. 3. Digital holographic deformation detection system and experimental samples. (a) Photo of the experimental system; (b) aluminum plate sample; (c) spiral micrometer
Fig. 4. Holograms collected before and after excitation and spectrum distribution. (a) Hologram collected before excitation; (b) hologram collected after excitation; (c) spectrum distribution of holograms
Fig. 5. Deformation fringes and three-dimensional distribution of aluminum plate sample surface. (a) Deformation fringes produced by 5 μm displacement; (b) three-dimensional distribution of deformation fringes produced on force-excited aluminum plate surface by 5 μm displacement; (c) central cross-section diagram of three-dimensional deformation distribution shown in Fig. 5(b); (d) deformation fringes produced by 10 μm displacement; (e) three-dimensional distribution of deformation fringes produced on force-excited aluminum plate surface by 10 μm displacement; (f) central cross-section diagram of three-dimensional deformation distribution shown in Fig. 5(e)
Fig. 6. Optical system and integration. (a) Photo of digital holographic deformation detection system; (b) interface of software about data collection and processing
Fig. 7. Schematic diagram of defects on wood-based mural sample. (a) Front side of the sample; (b) reverse side of the sample; (c) photo of mural sample defect detection
Fig. 8. A group of deformation fringes produced from defects on wood-based mural sample by acoustic scanning excitation
Fig. 9. Deformation fringes produced from defects on wood-based mural sample by acoustic scanning excitation. (a) Deformation fringes produced from layer edges (acoustic excitation with 250 Hz); (b) deformation fringes produced from bonding parts (acoustic excitation with 224 Hz); (c) deformation fringes produced from back holes (acoustic excitation with 280 Hz)
Fig. 10. Building walls defect detection. (a) Subsurface of building walls; (b) photo of building walls defect detection
Fig. 11. Subsurface defects on building walls. (a) Photo of subsurface crack defect; (b) schematic diagram of subsurface crack defect cross-section; (c) photo of subsurface void defect; (d) schematic diagram of subsurface void defect cross-section
Fig. 12. A group of deformation fringes produced from subsurface cracks by acoustic scanning excitation
Fig. 13. Deformation fringes produced from subsurface defects by acoustic excitation. (a) Deformation fringes produced from subsurface crack (acoustic excitation with 224 Hz); (b) deformation fringes produced from subsurface void (acoustic excitation with 620 Hz)
Fig. 14. Photo of in-situ detecting of the mural and the detected zones. (a) Photo of in-situ detecting; (b) detection zones on the south wall; (c) detection zones on the western wall
Fig. 15. Schematic diagram of the structural section of the tested mural
Fig. 16. In-situ detection results of micro-defects on the south wall. (a) Deformation fringes of sampling zones A‒F; (b) three-dimensional distributions of abnormal structures in sampling zones A‒F
Fig. 17. In-situ detection results of micro-defects on the western wall. (a) Deformation fringes of sampling zones A‒F; (b) three-dimensional distributions of abnormal structures in sampling zones A‒F