COORDINATE MEASURING DEVICE

A six-DOF probe includes a retroreflector, a collection of target lights, and a stylus having a probe tip. A laser tracker measures a distance, a first angle, and a second angle to the retroreflector and captures an image of the illuminated target lights. A processor determines the three-dimensional coordinates of the probe tip based at least in part on the measured distance, measured first angle, measured second angle and on a central portion of the captured image, the size of the central portion based at least in part on the measured distance.