Measurement method and measurement apparatus using tracking type laser interferometer

摘要

A tracking type laser interferometer including: a retro-reflector 20 for reflecting incident measurement light and returning the same in the incident direction and a main body 10 having means for emitting measurement light, means 30 for receiving return light reflected by the recursive reflector and returned therefrom, and means 40 for controlling the emission direction of measurement light so that the distance between both optical axes of measurement light and return light becomes constant at all times, and the tracking type laser interferometer outputs a measurement value in response to an increase or a decrease in distance between the reference point in the main body and the recursive reflector, wherein at least one light reflecting means 80 is disposed in an optical path between the main body 10 and the retro-reflector 20, and the directions of the optical axes of the measurement light and return light are changed, whereby without moving the tracking type laser interferometer, the measurement range can be expanded, and the measurement accuracy at a specific point can be improved.