Highly linear sub-nanoradian tilt measurement based on dual-beam interferometry

Area of Science:

• Optics and Photonics
• Metrology
• Instrumentation

Background:

• Nonlinearity in tilt measurement systems can limit accuracy and dynamic range.
• Dual-beam interferometry offers potential for enhanced measurement precision.

Purpose of the Study:

• To introduce a novel tilt measurement method using dual-beam interferometry.
• To mitigate nonlinear errors for improved performance over a large dynamic range.

Main Methods:

• Utilized dual-beam interferometry for displacement measurement.
• Leveraged the symmetric properties of nonlinear errors in measurement arms.
• Employed a Gaussian beam model for theoretical analysis of nonlinear errors.

Main Results:

• Achieved a measurement noise floor of 0.4 nrad/√Hz at 1 Hz.
• Demonstrated a nonlinearity of less than 60 nrad across a ±500 µrad measurement range.
• Identified second-order nonlinear error as the dominant factor.

Conclusions:

• The proposed dual-beam interferometry method effectively counterbalances nonlinear errors.
• This technique enables high-precision tilt measurements with a wide dynamic range.
• The results validate the theoretical analysis and experimental performance.