Calculating the Effective Center Wavelength for Heterodyne Interferometry of an Optical Frequency Comb

Two-dimensional angle measurement with sub-arcsecond precision and MHz update rate using heterodyne interferometry with optical frequency comb

Heterodyne interferometry is a powerful tool for achieving high precision and fast measurement. We developed an angle measurement system based on heterodyne interferometry by combining discrete equal-spacing longitudinal modes of optical frequency comb with an acousto-optic modulator. Using a self-designed grating-corner-cube sensor, this method can achieve a two-dimensional angle measurement with sub-arcsecond accuracy and megahertz (MHz) update rate. We experimentally demonstrate a precision of 0.073 arcsec under a 3 MHz update rate, and comparison residuals are kept within 0.063 arcsec over 300 arcsec when compared to a piezo stage. In the dynamic measurement of a 40 Hz frequency, the continuous sinusoidal motion of 0.05 arcsec can be clearly distinguished and reconstructed.

Compression-coding-based surface measurement using a digital micromirror device and heterodyne interferometry of an optical frequency comb

We propose a compression-coding-based surface measurement method that combines single-pixel imaging and heterodyne interference using an optical frequency comb. The real and imaginary parts of the heterodyne interference signals are used to obtain the depth information rapidly. By optimizing the ordering of the Hadamard measurement basis, we reconstruct a three-step sample with heights of approximately 10, 20, and 30 µm without an iterative operation in 6 ms, with a precision of 5 nm. Compared with the uncompressed measurement, the sampling times reduced to 20%, and the measurement time reduced by five times without measurement accuracy loss. The proposed method is effective for rapid measurements, particularly for objects with a simple surface topography.