Dual-frequency heterodyne interferometer has been widely applied in many fields. It is also an important part for measuring position error in the system that laser simultaneously measure six degree of freedom geometric motion errors of a linear guide. To segregate the heat source, simplify the optical path and obtain a convenient delivery, a polarization maintain fiber (PMF) is used in the system for linking the laser source and the measurement section. However, the nonlinear error caused by PMF will reduce the measurement accuracy, and cannot be ignored in ultra-precision measurement. In this paper, a measurement model for analyzing the nonlinear error caused by the axis misalignment between the laser source and PMF was established with the Jones Matrix. Experiments were performed for verifying and calculating. The results show that the measuring error caused by nonlinear error is less than 2 nm with the axis misalignment being up to 10 degrees.
We present a small-amplitude, high-frequency vibration measurement system. This system is based on the reflective holographic grating in a crystal of bismuth silicon oxide without applying an external electric field. A quarter-wave plate is applied in the reference beam path, with a polarizer after the crystal, to fulfill the quadrature condition when no electric field is applied to the crystal. A reflection configuration is used to obtain a good overlapping of the interference beams, which increases the beam coupling. The factors that affect the diffraction efficiency, including the signal-to-reference-beam intensity ratio and the recording angle, has been investigated. The experimental results coincide with the theoretical results, and the optimal conditions are obtained. The results of comparisons of our system with the vibrometer TEMPO show that the nanometer vibrations of a piezoelectric transducer can be reliably detected.
A novel method to measure the roll angle using a quarter wave plate and a Wollaston prism is presented in this paper. The setup and principle of the measurement system are introduced. According to the optical structure, the mathematical model was established by Jones matrix method. The output voltage from an optical detector located after the Wollaston prism can be used to determine the roll angle. Theoretical analysis and experimental results show that the sensitivity of roll measurement can reach arc-second. The chief advantages of the sensor are simply, stable and compact. This system can be applied to dynamic roll angle measurement. Experimental results have shown that the angular resolution is 0.04 arc-minute in a ±40 are-minute range.