Proposal of “open-loop” tracking interferometer for machine tool volumetric error measurement

The tracking interferometer, or the laser tracker, is a laser interferometer with a mechanism to control the laser beam direction to follow a retroreflector (“target”). Applying the multilateration principle, the targetʹs three-dimensional position is measured. This paper proposes a novel concept of “open-loop” tracking interferometer, where the laser beam is controlled towards the command target position. Its advantage is in the elimination of the automated tracking mechanism, which may significantly reduce its manufacturing cost. The paperʹs emphasis is on analytical evaluation of its measurement uncertainty, introduced by the elimination of automated tracking mechanism. A prototype “open-loop” tracking interferometer is developed, and its measuring performance is experimentally investigated.