Detection and correction of line indexing ambiguities in Flying Triangulation

Precise and fast non-contact distance measurements are important in many industrial applications. One key requirement is the insensitivity of the measurement to environmental influences such as temperature fluctuations. Measurement schemes using two frequency combs offer potentially fast and precise measurements [1,2], but rely on femtosecond lasers for comb generation, which require considerable technical effort for stable operation in an industrial environment. In this work, we generate frequency combs from continuous-wave (cw) lasers by using electro-optic Mach-Zehnder modulators (MZM) [3]. This leads to a tunable and stable line spacing defined precisely by the modulation frequency and the possibility to choose one or more center wavelengths by choice of the wavelengths of the cw lasers. Dual-color frequency combs are generated and exploited for distance measurements with simultaneous calibration measurements to cancel environmental influences. We demonstrate distance measurements with acquisition times of 9 μs and a standard deviation of 2 μm. Reliable measurement results with micrometer precision are maintained while the optical fiber leading to the sensor is heated by over 25 K. Technical objects are digitized by mounting the sensor on a coordinate measurement machine (CMM)