Real-Time and Meter-Scale Absolute Distance Measurement by Frequency-Comb-Referenced Multi-Wavelength Interferometry

Area of Science:

• Metrology
• Optical Engineering
• Precision Measurement

Background:

• Accurate long-distance measurement is critical for advanced manufacturing and space missions.
• Traditional interferometry faces limitations in range and ambiguity for absolute distance determination.

Purpose of the Study:

• To develop a frequency-comb-referenced absolute interferometer for instant, long-distance, and unambiguous measurements.
• To integrate multi-wavelength interferometry with direct synthetic wavelength interferometry for enhanced performance.

Main Methods:

• Utilizing a femtosecond laser frequency comb for simultaneous calibration of four wavelengths.
• Implementing direct synthetic wavelength interferometry with a fifth wavelength to extend the unambiguous measurement range.
• Performing linearity tests against a He-Ne laser interferometer over a 3 m distance.

Main Results:

• Achieved subwavelength distance measurement accuracy.
• Extended the non-ambiguous measurement range to meter-scale using synthetic wavelengths.
• Demonstrated a residual error of less than 70.8 nm (peak-to-valley) over 3 m.
• Obtained fractional deviations of approximately 3 × 10⁻⁸ over 10 hours for a 3 m distance.

Conclusions:

• The developed absolute interferometer provides precise, stable, and long-term distance measurements.
• The system is suitable for absolute positioning in large-scale manufacturing and space missions.
• This technology advances the capabilities of optical metrology for demanding applications.