Research Of Measurement Technology Of The Nonlinearity Error Of Dual-frequency Laser Interferometer

Laser interferometer measurement techniques are widely used in ultra-precisionmeasurement such as gauge test, calibration lathe and Nano sensor calibration due to theadvantages of non-contact, high precision, traceable. But further improve of themeasurement resolution and accuracy is severely constrained because of the inherentoptical nonlinearity error of heterodyne interferometer measurement system. The opticalnonlinearity error detection technique is the key premise of the optical non-linear errorcompensation and elimination. It has important practical significance for themeasurement accuracy of the Nano scale. It is also one of hot and difficult of the laserinterferometer measurement technology.The paper depth analyzed the domestic and foreign research status of the dual-frequency laser interferometer optical nonlinearity error detection technology, describedthe measurement principle and technical characteristics of the existing research methodsand summarized the existing advantages and disadvantages. For the shortcomings of theexisting methods such as the measuring device is huge, the cost is too high, and appliesonly to the static or quasi-static conditions, we have found an optical nonlinearity errormeasurement methods based on the dual photoelectric detection and IQ demodulationphase detection. And we established the corresponding experimental measurementplatform, and finished the experimental verification. This topic mainly completed thework as follows:Established the mathematical model and the formula of optical nonlinearity error inheterodyne laser interferometer measurement. From the frequency mixing phenomenonof the measured path and the reference path of the heterodyne laser interferometer, wededuced the functional relationship of the measured signal and frequency aliasingparameters of the heterodyne laser interferometer in the case of optical frequency mixing.And then compared with the standard measurement signals, derived optical nonlinearityerror formula. All the things we have done reveals the variation of the opticalnonlinearity error, laid a theoretical foundation for this article optical nonlinearity errordetection method;Developed a heterodyne interferometer optical nonlinearity error detection modelbased on dual photoelectric detection. We use polarizing beam splitter to separate thelaser interferometer output optical signal into two parts. And we used two symmetricalphoto detectors to have signal detection and get two measurement signals with the samefrequency. We analyzed the measurement signals of the two-way according to opticalnonlinearity error model and the formula established under this article. The two nonlinearphases have equal sizes and opposite signs. So we can obtain the optical nonlinearity error of the measurement system by detecting the difference of the two phases. And thenestablished the heterodyne interferometer optical nonlinearity error detection modelbased on dual photoelectric detection. We also build the optical system of the opticalnonlinearity error detection experiment platform according to the theoretical model.Developed data processing technology of optical nonlinear error based on the IQdemodulation phase detection principle. The technology guides us to make the outputsignals of two photo detectors input to IQ modulator circuit and change the measuringsignal of each path into two orthogonal low frequency sinusoidal signals. The quadraturesignal is sampled by the high-speed AD acquisition circuit, and then we got differentphase value between two measured signal and the IQ modulator circuit local oscillatorsignal by arctangent operations. The difference between the two is the phase differenceof the two measurement signals-nonlinear optical phase error of the heterodyneinterferometry system. In this paper the development of the electrical system of theoptical nonlinearity error detection experiment platform and the user of the hostcomputer software program according to this technology.We designed and developed detection experiment platform of the opticalnonlinearity error measurement of the heterodyne laser interferometer on the basis of theabove theoretical analysis and technical studies in this paper and made experimentaltesting and validation. Tests showed that: The system’s bandwidth is50MHZ, uncertaintyof the nonlinear error measurement is0.13°, uncertainty of the phase difference of thephase detection unit measurement is0.05°.