Remote sensing can detect human heartbeats in buildings through various non-invasive methods, including Doppler radar-based sensors, laser vibrometry, and continuous-wave Doppler radar. These technologies enable the detection of physiological motions and vital signs, providing accurate occupancy detection, estimation of heart and respiratory rates, and proactive environmental adjustments in response to occupants’ well-being. The following methods have been proposed and developed for remote heartbeat detection in building environments:
1. Doppler Radar-Based Sensors: Doppler radar-based sensors can sense small physiological motions, providing accurate occupancy detection and estimation of vital signs in challenging, realistic circumstances. They work by transmitting an electromagnetic signal and detecting the reflected signal’s phase shift, which is proportional to the object’s motion. This method has been shown to accurately differentiate occupancy from an empty room and detect heart and respiratory rates in various seating positions within a room[1].
2. Laser Vibrometry: Laser vibrometry, such as the Remote, Noninvasive, Cardiac Activity Tracer (RENCAT) instrumentation developed by NASA, uses a pulsed laser-based highly sensitive vibrometer to measure minute vibrations caused by cardiac activities. This non-invasive method provides precise magnitude and timing information about heart functions, such as valve/chamber opening and closing cycles, away from the heart region and without interference from patient garments[2].
3. Continuous-Wave Doppler Radar: Continuous-wave Doppler radar has been used to develop a method for fast and reliable contactless heartbeat detection using artificial neural networks. This approach is based on detecting small signal ripples resulting from individual heartbeats and has been shown to achieve good heart rate estimation accuracy with low latency operation[3].
4. Infrared Laser-Based Detection: The Pentagon has developed a device called Jetson, which uses an infrared laser to detect the unique cardiac signature of individuals from a distance by measuring the surface movement caused by the heartbeat. This method has been shown to achieve over 95% accuracy under good conditions and can work through typical clothing like shirts and jackets[4].
5. Face Video-Based Methods: Remote heart rate detection from frontal face videos has also been explored using methods such as photoplethysmography (PPG) under ambient light, automatic heart rate detection using face color recordings, and estimation of heart rate based on subtle head motions. These methods are based on recovering the heartbeat signal from changes in face color or subtle head motions caused by cardiovascular activities[5].
In summary, remote sensing technologies such as Doppler radar-based sensors, laser vibrometry, continuous-wave Doppler radar, and infrared laser-based detection offer non-invasive and contactless methods for detecting human heartbeats in building environments, enabling various applications in occupancy detection, vital signs monitoring, and environmental optimization.
Citations:
[1] https://www.nature.com/articles/s41598-023-27425-6
[2] https://technology.nasa.gov/patent/LAR-TOPS-315
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7219229/
[4] https://www.technologyreview.com/2019/06/27/238884/the-pentagon-has-a-laser-that-can-identify-people-from-a-distanceby-their-heartbeat/
[5] https://www.frontiersin.org/articles/10.3389/fbioe.2018.00033/full
