Infrared Technology - Seeing the Invisible (Part One: Physics)
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Transcript of Infrared Technology - Seeing the Invisible (Part One: Physics)
Infrared Imaging: Seeing the Invisible
Part One:
Physics
What Can You See in These Images?
NIR / SWIR LWIR Visible
Electromagnetic Spectrum:
A Helpful Taxonomy
IR Radiation - Characteristics
• Invisible to the human eye … but not to certain sensors
• Caused by the vibration and rotation of atoms and molecules
• Emitted from all objects with a temperature above 0 K (-273 °C)
• Interacts like other electromagnetic radiation, including:
Reference temps: White hot steel ~1200 °C Melting point of aluminum 660 °C Water boils at 100 °C Uncooled camera at 38 °C Human body at 37 °C, radiates at ~ 10 μm Water freezes at 0 °C
IR Energy vs. Object Temperature
Measuring Temperatures
• Emissivity: ratio of actually emitted energy to energy radiated by a black body at same temperature
– Black body by definition ɛ = 1
– In general the duller and blacker, the closer to ɛ = 1
– The more reflective, the less emissive
• Knowing emissivity permits absolute temperature measurement
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