Swept-angle synthetic wavelength interferometry

Alankar Kotwal, Anat Levin, Ioannis Gkioulekas

CVPR 2023

Reconstructing the eagle embossed on a $20 bill at 5 Hz. The features on the eagle are raised 10 μm off the surface of the bill. The recovered depth shows fine details such as the gaps between the wings reconstructed with high lateral and axial resolution.


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 μm, 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.

Synthetic wavelength interferometry

(a-b) Collimated illumination from a point source emitting at two narrowly separated wavelengths is injected into a Michelson interferometer. (c) As the reference mirror position l is scanned, each wavelength contributes to the interference a sinusoid with period equal to its wavelength. (d) The sinusoid sum has an envelope that is another sinusoid at a synthetic wavelength peaked at l = d.

Interferometric setups

(a) A full-field interferometer efficiently acquires full-frame depth, but is susceptible to phase corruptions due to aberrations and indirect illumination. (b) A scanning interferometer is robust to such corruptions, but requires slow lateral scanning. (c) A swept-angle full-field interferometer achieves both efficiency and robustness.



A visualization of all our 3D reconstruction results is available at the interactive supplemental website.

scene no swept-angle ours (Gaussian) ours (bilateral)


Paper: Our paper and supplement are available on CVF open access, on arXiv, and locally (paper, supplement).

Poster: Our poster is available here.

Presentation: Our presentation slides are available here.

Code: Our code is available on Github.

Data: The data to reproduce our experiments is available here.


	author    = {Kotwal, Alankar and Levin, Anat and Gkioulekas, Ioannis},
	title     = {Swept-Angle Synthetic Wavelength Interferometry},
	booktitle = {Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR)},
	month     = {June},
	year      = {2023},
	pages     = {8233-8243}


We thank Sudershan Boovaraghavan, Yuvraj Agrawal, Arpit Agarwal, Wenzhen Yuan from CMU, and Veniamin V. Stryzheus, Brian T. Miller from The Boeing Company, who provided the samples for the experiments in Figure 1 of the paper. This work was supported by NSF awards 1730147, 2047341, 2008123 (NSF-BSF 2019758), and a Sloan Research Fellowship for Ioannis Gkioulekas.