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FireLiDAR
Light Detection and Ranging (LiDAR) is a powerful tool to precisely measure and track the surface geometry of solid objects. However, in fire environments, no method has excelled at measuring three-dimensional shapes with millimeter precision while offering resistance to the extreme conditions posed by flames. This research initially explored the use of single-point displacement measurements through flames using a blue lasers. It then evolved to leverage coherent Frequency Modulated Continuous Wave (FMCW) LiDAR to capture three-dimensional measurements of objects within a fire at stand-off distances of several meters. This approach has achieved millimeter-precision measurements even in the presence of natural gas flames up to 1.5 meters in depth, which obscure the target.
FMCW LiDAR offers several advantages for imaging through flames. The heterodyne detection technique utilized in FMCW LiDAR is highly resistant to background radiation from the fire. It is also extremely sensitive (photon efficient), allowing it to measure distances to diffusely scattering surfaces in or behind flames with low to moderate soot yields. Furthermore, FMCW LiDAR can operate over large stand-off distances, providing the flexibility to position the measurement equipment safely away from the fire hazard.
The laser ranging and detection system is a commercial, fiber-based unit emitting light at an optical wavelength of 1550 nm. After exiting the polarization-maintaining fiber, the light passes through a collimator and is expanded by a free-space beam expander designed to focus the light on targets located between 2 meters and 8 meters away. During measurement, photons diffusely reflected from the target are collected by the beam expander and coupled into the fiber for range calculations performed by the ranging unit.
This system represents a significant leap in the capabilities of fire measurement technology, offering valuable insights into the dynamic interactions between fire and solid objects in a range of research settings.
News & Blog
- NIST Shows Laser Ranging Can ‘See’ 3D Objects Melting in Fires
- A Laser Could Offer a Peek Into the Insides of Our Muscles or Look Through Fire
Related Publications
- Hoehler, M. , Chernovsky, A. , Bundy, M. and Baumann, E. (2023), Coherent Laser Ranging of Deforming Objects in Fires at Sub-Millimeter Precision, Fire Safety Journal, [online], https://doi.org/10.1016/j.firesaf.2023.103864, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=936329 (Accessed March 18, 2025)
- Baumann, E. , Chernovsky, A. and Hoehler, M. (2023), Application of Coherent Laser Ranging to Characterize Object Geometry Changes in Large Fires, CLEO, San Jose, CA, US, [online], https://doi.org/10.1364/CLEO_AT.2023.ATu4K.2, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=935991 (Accessed March 18, 2025)
- Mitchell, E. , Hoehler, M. , Giorgetta, F. , Hayden, T. , Rieker, G. , Newbury, N. and Baumann, E. (2018), Coherent laser ranging for precision imaging through flames, Optica, [online], https://doi.org/10.1364/OPTICA.5.000988 (Accessed March 18, 2025)
- Hoehler, M. and Smith, C. (2016), Application of Blue Laser Triangulation Sensors for Displacement Measurement Through Fire, Measurement Science & Technology, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=920007 (Accessed March 18, 2025)