Precision ranger for measuring large mechanical components.

We present a precision laser ranger system for the measurement of large manufactured components and structures. The system was developed based on a beat-wave interferometry principle. The light source of this system is a frequency-stabilized laser with a frequency stability of 1 × 10-7 (in open air) or 10-8 (in the laboratory). The laser operates in two longitudinal modes, and the two modes are generated in common resonator; therefore the two beams are naturally coaxial. The precision ranger system does not need a long guide or any heavy machinery. In this system an adaptive filter and a wavelet-transform program are used to improve the measurement accuracy. The system described here has a measuring range of 0–20 m and a measuring uncertainty of 30 μm/10 m.