Endoscopic displacement sensor based on laser speckle imaging

This study proposes a displacement measurement technique using optical fiber bundles and laser speckle images. The two-dimensional displacement of the speckle pattern was quantitatively measured by applying a two-dimensional cross-correlation analysis method to the laser speckle pattern images according to the specimen movement on the precision micro stage. By comparing and analyzing the actual displacement of the precision micro-stage, a high correlation of 0.99 was obtained. This endoscopic based sensor, which can be miniaturized less than 1mm of a diameter, can be employed to a detection probe accessible to very confined areas, such as cracks in the specimen. Furthermore, it has the potential to be applied as a contactless strain sensor in environments where human or complex optics are not accessible