Repeatable speckle projector for single-camera three-dimensional measurement

Triangulation-based three-dimensional (3-D) optical metrology utilizing structured illumination requires the projector and camera to be geometrically calibrated. The projection of laser speckle structures in temporal correlation-based methods has been found to be useful for high-speed 3-D measurement. However, it requires the use of a stereo-camera configuration as speckle projection does not utilize conventional projection optics. Previously, we have shown a model-less method to calibrate these unconventional projection systems. This re-enabled single-camera setups where stereo systems used to be required. Due to the random nature of speckle production, speckle structures were not suitable as a set of repeatable illumination structures is needed for the model-less calibration method to succeed. A projection apparatus is proposed, which enables the production of a repeatable set of speckle structures. This device is then utilized in a single-camera optical metrology 3-D measurement system.