The Electromagnetic Spectrum and Thermal Imaging
Everything above absolute zero (-273.15°C) emits infrared radiation. Thermal cameras detect this invisible heat radiation and convert it into visible images. Unlike regular cameras that see reflected light, thermal cameras see emitted heat — they work in total darkness.
How Thermal Cameras Work
A thermal camera contains a microbolometer — an array of tiny temperature-sensitive resistors. Each pixel measures incoming IR radiation and converts it to a temperature reading.
Thermal Camera Specifications
| Spec | Entry Level | Mid-Range | Professional |
|---|---|---|---|
| Resolution | 80×60 | 160×120 | 640×480 |
| NETD | <150mK | <60mK | <30mK |
| Frame Rate | 9Hz | 30Hz | 60Hz |
| Lens | 25° FOV | 25–50° FOV | Interchangeable |
| Examples | FLIR Lepton 3.5 | DJI Zenmuse H20T | FLIR A65 |
Hands-On Project: Thermal anomaly detector
Build a system to automatically detect hot spots in thermal images from drone surveys:
Key Takeaways
- Thermal cameras detect infrared radiation (heat), not visible light
- LWIR (8-14μm) is most common for drone applications (uncooled sensors)
- Emissivity affects accuracy — different materials radiate heat differently
- Common palettes: Ironbow (color), White Hot/Black Hot (grayscale)
- Applications: building inspection, search & rescue, agriculture, industrial monitoring
- NETD (Noise Equivalent Temperature Difference) indicates sensitivity