Investigation of hidden diffuse surfaces using phase-shifting endoscopic digital speckle pattern interferometry

Digital speckle pattern interferometry (DSPI) is an important optical tool which is widely used in many sophisticated applications. However, a traditional DSPI system can only be used to investigate the outer surfaces which can be easily observed. Therefore, an endoscopic DSPI was proposed to detect the internal and hidden surfaces. It has a rigid or flexible endoscopic tube to allow a hidden surface being clearly imaged. A fiber-optics-based setup makes the proposed DSPI system compact and robust. The temporal phase-shifting technique is used to help precise extraction of phase distributions from speckle patterns.