Analysis of frequency excursion in high-precision measurement of machine tool's roll angle

In order to decrease the phase-different fluctuation and increase the roll angle measuring accuracy in extrapolation interference method, a new mathematical model of measurement optical path and reference optical path was established through Jones matrix method. The model takes the frequency unsteadiness of two-frequency laser and the difference of photo-detector's response time into consideration based on the existing model and deduces that the frequency difference between the reference signal and measuring signal (frequency excursion) is the main cause of phase-different fluctuation. So it can be concluded that the frequency excursion is caused by the frequency unsteadiness of two-frequency laser and the difference of photo-detector's response time. The effect of frequency excursion on the roll angle measuring accuracy is also calculated. Based on the model, this paper presents a method of increasing two-frequency laser frequency stabilization and decreasing the difference of photo-detector's response time to eliminate phase-different fluctuation. Experimental results indicated that after decreasing the difference of photo-detector's response time, the range of phase fluctuation was decreased from 7°to 1° and the roll angle measuring error decreased by 85.7%, which proves that the new model is feasible. © 2016, Xi'an Jiaotong University. All right reserved.