High-precision laser ranging for industrial metrology with dual-color electro-optic frequency combs

Non-contact three-dimensional surface profiling with micrometer precision is of great importance in industrial metrology. For technical surfaces, highly sensitive measurement schemes are required which provide precise absolute distance measurements for a large range of received signal power levels. In this context, optical frequency combs (FC) based on femtosecond lasers have emerged as a valuable tool. However, an industrial environment with temperature fluctuations and vibrations poses significant challenges. Here we use continuous-wave lasers and electro-optic modulators to generate FC. We generate dual-color FC by coupling lasers with wavelengths of 1550 nm and 1300 nm to the same modulator, generating two FC with different center wavelengths and a line spacing defined by the modulator driving frequency. A dichroic beam splitter in a fibercoupled sensor head splits both FC, thereby enabling a reference measurement at another wavelength for compensating temperature effects. The sensor head is mounted to a coordinate measurement machine. Three-dimensional surface profiles of technical parts are measured with micrometer precision, agreeing well with tactile reference measurements.