Laser interferometer type length measuring apparatus and positioning method using the same

摘要

In a laser interferometer type length measuring apparatus, a measurement laser beam will be influenced by disturbance such as air fluctuation and a change in air pressure distribution due to movement of an object so that a displacement of the object cannot be accurately measured. In order to obviate such an inconvenience, air controlled at a predetermined temperature is uniformly blown at a fixed speed on the entire optical path of the measurement laser beam.