Fig. 1. Optical path diagram of capsule surface defect measurement system based on optical path matching and spherical compensation

Fig. 2. Schematic diagram of measurement system.（a）Spherical compensation schematic diagram of interference imaging module；（b）optical path matching module schematic diagram

Fig. 3. Simulation results of different topography restoration algorithms.（a）Complicated surface；（b）seven-step phase shift algorithm；（c）centroid method；（d）HDVSI algorithm

Fig. 4. Component characteristic diagram.（a）Spectral curve of light source；（b）transmission characteristic curve of PBS

Fig. 5. System experimental device diagram.（a）System integral assembly；（b）system accuracy verification step plane

Fig. 6. Standard step measurement and shape restoration results.（a）Step plane white light interference fringe；（b）step shape measurement results；（c）transverse profile of step surface topography

Fig. 7. Commercial white light interferometer measurement results.（a）Step plate interference fringe；（b）step shape measurement results；（c）transverse profile of step surface topography

Fig. 8. Interference images of each surface of capsule and corresponding restored morphologies.（a）Front outer surface interferogram；（b）front inner surface interferogram；（c）back inner surface interferogram；（d）front exterior surface topography；（e）front inner surface topography；（f）rear inner surface topography