The working of phase-shift 3D scanners is based on the phase measurement principle. The laser diode emits light pulses with a defined wavelength and pulse repetition frequency. Due to the runtime difference between the internal reference path and the external measurement path, the light pulses, reflected on a target and received from the scanner, have experienced a phase shift in relation to the light pulses received through the internal reference path. That phase difference between those two signals is proportional to the distance between instrument and target.
They are mainly used in industry and tunnels for generating as built plans of industrial plants and checking tunnels. This type of scanner are much faster in data acquisition, but have limitations on the working distance, between 120 and 300 meters in the best of cases nd depending on the conditions of reflectivity of the surface where incident. They can create “noise points” that requires further postprocessing, making necessary to filter and clean the three-dimensional point cloud model.
Its application in the cultural heritage field has been introduced in recent years due to its speed, supplying the color value with calibrated metric cameras and then mapping the point cloud.