Three-dimensional mapping and ranging of objects using speckle pattern analysis

In this chapter, we present two novel approaches for 3-D object shape measurement and range estimation based on digital image processing of speckle patterns. In the first one, 3-D mapping and range measurement are retrieved by projecting, through a ground glass diffuser, random speckle patterns on the object or on the camera for a transmissive and reflective configuration, respectively. Thus, the camera sensor records in time sequence different speckle patterns at different distances, and by using correlation operation between them, it is possible to achieve 3-D mapping and range finding. In the second one, the 3-D mapping and ranging are performed by sensing the visibility associated with the coherence function of a laser source used to illuminate the object. In this case, the object depth is encoded into the amplitude of the interference pattern when assembling a typical electronic speckle pattern interferometric (ESPI) layout. Thus, the 3-D object shape is reconstructed by means of a range image from the visibility of the image set of interferograms without the need for depth scanning. In both cases, we present experimental implementation validating the proposed methods.