Three-dimensional data acquisition by digital correlation of projected speckle patterns

Reliable methods for the optical acquisition of three-dimensional (3D) coordinates like the fringe projection technique or 3D laser scanning are sensible to object movements because they require the recording of a sequence of images. In contrast, techniques using the projection of a random pattern reduce the measurement time to a single exposure time. A method is presented which allows the 3D acquisition of a surface from a single stereo image pair by projecting a laser speckle pattern. The use of a laser enables a simple design of the projection device as well as a suppression of ambient light by narrow band-pass filtering. Corresponding image points are determined by a digital image correlation algorithm. In order to optimize the introduced method, the influence of various parameters on the number and accuracy of the determined 3D coordinates is analyzed on the basis of comparative measurements with the fringe projection technique. It is demonstrated that the introduced approach allows the acquisition of 3D data of skin surfaces.