DESCRIZIONE
A markerless tracking device (100) has a source, a sensor and a processor. The source is configured to direct a beam on a plurality of beam paths (124), where each beam path (124) illuminates a distinct region (142) of an object (170). The sensor is configured to receive beam (126) reflected from each region (142) in order to generate an image of each region (142). A processor is configured to generate a metric which indicates suitability of a beam trajectory (132), where the beam trajectory (132) is a path over which the beam is to be directed by the source during markerless tracking of the object (170). The metric is generated by comparing images of selected regions (142). [Image Omitted]