How Thermal IR Cameras Work Without Cryogenic Cooling

• 0:00 Introduction: The video explains how modern thermal infrared (IR) cameras work without cryogenic cooling, unlike older models.

• 0:20 Older Thermal Cameras: Thermal cameras from the 1980s needed liquid nitrogen cooling because the infrared light emitted from the inside the camera would ruin the image.

• 0:50 Everything Emits Infrared: All objects at room temperature emit infrared radiation. The only exceptions are materials that reflect or transmit infrared light. The camera irradiates itself, and the objects in the view will also irradiate the sensor.

• 1:53 Sensor Sensitivity and Noise: Modern thermal cameras use highly sensitive and low-noise sensors.

• 2:05 Consistent Internal Radiation: The key is that the camera's internal components emit a relatively constant level of infrared radiation because the camera is at a mostly-consistent temperature.

• 2:35 Baseline Subtraction: The camera software identifies the darkest spot in the image (least infrared) and sets that as the baseline. All other brightness levels are relative to this baseline.

• 3:07 No Absolute Temperature (in some models): Cameras that use this method alone can't determine the absolute temperature of objects. They only show relative temperature differences. This is because the darkest spot is now a baseline.

• 3:45 Internal Shutter for Calibration: Cameras that can measure absolute temperature have an internal shutter. The shutter periodically closes to block incoming infrared.

• 3:56 Baseline Measurement: With the shutter closed, the sensor measures only the internal infrared radiation of the camera.

• 4:05 Temperature Calculation: By subtracting the internal radiation baseline from the total radiation when the shutter is open, the camera calculates the amount of infrared coming from the scene and thus the object's temperature.

• 4:23 Emissivity: Most surfaces are good at radiating infrared. Things that don't radiate well include metals, infrared lenses, and some plastics.

• 5:31 CO2 Detection: Carbon dioxide blocks and radiates infrared, making warm CO2 (like in flames or smoke) visible.

• 6:05 Observing the Shutter: The presenter uses a second thermal camera (a monocular) and a germanium lens to observe the internal shutter mechanism of the camera being discussed, since the lens cover of the observed camera is opaque to visible light.

• 7:14 Sensor Temperature: Observing the shutter closing suggests the internal sensor is warmer than the lens, as the lens appears darker when the shutter is closed.

• 7:53 Topdon Sponsorship: The video is sponsored by Topdon, a maker of thermal cameras, and mentions an ongoing Amazon promotion.