Metrology system

A metrology system comprising:

• a laser tracker having:
• an opto-electronic distance meter configured to emit a distance measurement beam towards a cooperative target of a moveable accessory device in the direction of an aiming axis, and to provide distance measurement data based on at least a part of the distance measurement beam returning from the cooperative target, wherein the cooperative target is configured to cooperate with a tracking unit of the laser tracker to generate a tracking signal,
• an angle determining unit configured to provide angle determination data for determining the pointing direction of the aiming axis, and
• the tracking unit configured
• to receive over a tracking channel the tracking signal which is indicative of a change in angular location of the cooperative target,
• to determine the change in angular location of the cooperative target based on the tracking signal, and
• to generate control data for adjusting an alignment of the aiming axis based on the determined change in angular location,
• the movable accessory device, configured for scanning or probing of an object, and
• a computing unit configured to generate coordinate measuring data for the object by using the distance measuring data and the angle determination data to determine a position of the movable accessory device, and by using the determined position of the movable accessory device for referencing the scanning and/or probing by means of the movable accessory device to a coordinate system relative to the laser tracker, and
• a referencing unit configured to determine a positional change between the referencing unit and a reference point on the object to detect a movement of the object in at least one degree of freedom, wherein:
• the referencing unit is provided by the laser tracker or by a separate device which is different from the movable accessory device, wherein the separate device and the laser tracker are configured such that the referencing data are referenceable to the coordinate measuring data,
• the positional change is determined by referencing data generated by the referencing unit independently from the opto-electronic distance meter, the reference point is embodied by a cooperative target mounted on the object or defined by a reference surface of the object, and
• the computing unit is configured to take into account the referencing data to generate the coordinate measuring data.