Laser tracker system (LTS) is one of the latest portable three dimensional large size coordinate measuring machines (CMMs). It can measure moving object coordinates with the advantages of broad range

high speed and high accuracy. However

its measuring accuracy is highly dominated by the geometric errors of the tracking mirror mechanism. Proper modeling and error analysis of LTS is essential prior to use it for metrology. The kinematics model and tracking mirror center offset model of LTS have been developed

based on the research on the structure and working principle of LTS

These models can describe not only the motion but also the geometric variations of LTS. The error of LTS base point position

tracking mirror tracking target retro-reflector and tracking mirror reflective surface out of vertical to laser beam is deeply analyzed. Theoretical analyses have demonstrated that the gimbals axis misalignment

tracking mirror center offset

base point position variation and laser beam reflected point non-coincidence with base point are the key contributors to measuring errors of LTS. In order to ensure the laser beam reflected point position coinciding with base point and the position unchanged in the course of LTS tracking the target retro-reflector

the distance between the tracking mirror surface and rotation point should be minimized in the structure design of tracking mirror.