Swept-Angle Synthetic Wavelength Interferometry

TL;DR

This paper introduces a robust full-field 3D imaging technique using swept-angle synthetic wavelength interferometry, combining high resolution, speed, and insensitivity to aberrations and scattering for practical inspection applications.

Contribution

The paper presents a novel swept-angle synthetic wavelength interferometry method that improves robustness to aberrations and scattering while maintaining high resolution and speed.

Findings

Achieves 5 micron lateral and axial resolution

Captures full-frame depth at 5 Hz frame rate

Effective under strong ambient light and scattering conditions

Abstract

We present a new imaging technique, swept-angle synthetic wavelength interferometry, for full-field micron-scale 3D sensing. As in conventional synthetic wavelength interferometry, our technique uses light consisting of two narrowly-separated optical wavelengths, resulting in per-pixel interferometric measurements whose phase encodes scene depth. Our technique additionally uses a new type of light source that, by emulating spatially-incoherent illumination, makes interferometric measurements insensitive to aberrations and (sub)surface scattering, effects that corrupt phase measurements. The resulting technique combines the robustness to such corruptions of scanning interferometric setups, with the speed of full-field interferometric setups. Overall, our technique can recover full-frame depth at a lateral and axial resolution of 5 microns, at frame rates of 5 Hz, even under strong ambient light. We build an experimental prototype, and use it to demonstrate these capabilities by scanning a variety of objects, including objects representative of applications in inspection and fabrication, and objects that contain challenging light scattering effects.