Frequency-scanning nonlinearity suppression for FSI ranging based on a phenomenological modeling approach

Area of Science:

• Optical Metrology
• Laser Interferometry
• Nonlinear System Modeling

Background:

• Frequency-scanning interferometry (FSI) systems utilize external cavity diode lasers (ECDLs) for precise measurements.
• Frequency scanning nonlinearity in ECDLs fundamentally limits ranging precision in FSI systems.
• Existing methods struggle to accurately characterize and compensate for the complex nonlinear optical frequency response.

Purpose of the Study:

• To propose and validate a novel method for suppressing frequency scanning nonlinearity in FSI systems.
• To improve the ranging and velocity measurement precision of FSI systems.
• To introduce a rate-dependent asymmetric Prandtl-Ishlinskii (RA-PI) model for characterizing ECDL nonlinear optical frequency response.

Main Methods:

• Development of a rate-dependent asymmetric Prandtl-Ishlinskii (RA-PI) model to characterize ECDL nonlinear optical frequency response.
• Implementation of an inverse RA-PI model as a feedforward compensator to linearize frequency scanning.
• Experimental validation of the proposed compensation method using an FSI system.

Main Results:

• Frequency scanning linearity was improved by approximately one order of magnitude.
• Maximum standard deviation of absolute distance measurements reduced from 58.25 μm to 9.79 μm.
• Velocity measurement precision for dynamic targets improved by a factor of 2.61 to 5.75.

Conclusions:

• The proposed RA-PI modeling approach effectively characterizes and compensates for frequency scanning nonlinearity in ECDL-based FSI systems.
• The method significantly enhances ranging precision and velocity measurement accuracy.
• This work provides a robust solution for overcoming a fundamental limitation in FSI technology.