WASHINGTON — Researchers have developed a new LiDAR approach that makes it possible to image small objects with much greater precision and accuracy than is possible with conventional LiDAR. The method could be useful for acquiring non-contact measurements of critical parts or features during manufacturing.
"LiDAR systems like the ones used in autonomous cars typically measure large objects like roads, cars and trees at large distances with an accuracy of a few centimeters," said research team leader Derryck T. Reid from Heriot-Watt University in the U.K. "Our LiDAR imaging technique makes it possible to acquire measurements with much greater accuracy while maintaining fully electronic detection, which avoids the complexity and scalability challenges of some high-precision systems."
In the Optica Publishing Group journal Optics Letters , the researchers describe their new imaging technique, which is based on two-photon dual-comb ranging. They show that the approach can be used to create detailed 3D representations of small aluminum objects with micron-scale precision from 40 cm away.
"Our optical dual-comb LiDAR imaging technique could be useful in manufacturing, where measuring critical features on an object traditionally requires a mechanical tool that must be in contact with the object," said Reid. "For example, it could be used to verify that a hard-to-reach component inside an engine has been manufactured correctly."
Boosting accuracy with shorter pulses
The new research stemmed from an industrial collaboration between Heriot-Watt University and Renishaw PLC, which makes precision measurement tools for the aerospace and automotive industries.
"The two-photon dual-comb LiDAR imaging technique is an extension of previous work that provided very accurate measurements at a single point but was not able to measure many points across a surface," said Reid. "In that research, we showed how to measure distances to surfaces like brass, copper and aluminum, so it was natural to try to extend this capability to accomplish full imaging of small metal objects."
The new approach combines ultra-precise laser timing with a nonlinear detection method to measure distance with very high accuracy. While conventional LiDAR systems use nanosecond-scale light pulses, the new system uses pulses lasting only a few hundred femtoseconds. These shorter pulses make it possible to achieve measurements with much greater accuracy.
Although many investigators have been researching dual-comb laser technology, Reid's research team developed the first fully electronic method of achieving detection for dual-comb imaging. The approach uses a phenomenon called two-photon absorption to convert returning light pulses directly into an electrical signal. This makes the system less sensitive to fluctuations, allowing simpler lasers to be used.
Imaging small metal objects
To demonstrate the new method, the researchers worked with the University of Huddersfield's Centre for Precision Technologies , which provided aluminum objects for testing. The objects were CNC-milled and contained a variety of specially designed features. For example, one object had a volume of 50 × 50 × 30 mm3 with a surface containing a circle, diamond, square, ledges and counterbored holes.
Using these test objects, they showed that two-photon dual-comb LiDAR could render
3D point-cloud datasets with micron precision and make measurements with accuracies between 9 and 38 microns for three surfaces.
Now that they have completed a proof-of-concept demonstration, the researchers are working to speed up the technique by scanning the light across the object rather than physically moving the test object underneath the laser beam. They are also experimenting with lasers that have higher pulse repetition rates, which would improve performance.
This work was funded in part by the Royal Academy of Engineering.
Paper: A. J. M. Nelmes, S. Fletcher, A. Longstaff, J. M. Charsley, H. Wright, D. T. Reid, "Two-photon dual-comb LiDAR imaging," Opt. Lett., 51, (2026).
