A high-performance ranging method with a long distance range and high accuracy

Distance measurement technology can greatly aid scientific research and engineering applications. The optical frequency-domain interferometry ranging method (OFDI-RM) has attracted a great deal of attention as it can achieve accuracy down to the micron and nanometer resolution. However, the main drawback of OFDI-RM is its short measuring range, which hinders its widespread use. In this paper, we present a high-performance OFDI-RM with a long distance range, high accuracy and high resolution. A high return-loss focus ranging probe is used to match the light intensity of reference and signal beams for acquiring high visibility interference fringes in the frequency domain at a distance of more than 100 mm. A novel signal processing method, which takes advantage of high-degree polynomial fitting and Hilbert transform (HT) to perfectly extract the harmonic component of the frequency-domain interference fringes, has also been demonstrated. The performance of OFDI-RM is verified by a linear motion measurement experiment. The measured range of OFDI-RM increased up to 170 mm, with an accuracy and resolution of up to 0.0040 mm–0.0005 mm/step, respectively.