Patent ID: 7920273

Claim:
A method for estimating a distance between a tracking type laser interferometer and a target, the tracking type laser interferometer including: a laser interferometer, an optical axis deviation detection sensor for detecting a deviation of an optical axis of the laser interferometer, a two-axis turning mechanism for turning the laser interferometer to any optional direction, an angle sensor for detecting a turning angle of the two-axis turning mechanism, a retroreflector for reflecting its reflected light to a direction parallel to the incident light, and a controller for driving the two-axis turning mechanism so as to track the retroreflector based on signals of the optical axis deviation detection sensor and the angle sensor, comprising the steps of: detecting stop of the retroreflector, and calculating a target distance from the turning center of the laser interferometer to the center of the retroreflector based on the total sum of deviation of an optical axis during movement, which is obtained by the optical axis deviation detection sensor, and a turning angle during movement, which is obtained by the angle sensor, when detecting the stop of the retroreflector.