1. Every object with a temperature above absolute zero (-273°C) emits invisible infrared (IR) energy as a result of the motion of its molecules.
2. Focusing Optics: A lens inside the thermometer gathers and concentrates the infrared radiation onto a tiny internal receiver.
3. Detection & Conversion: The receiver—usually a thermopile (a cluster of thermocouples)—absorbs the IR energy, turns it into heat, and converts that heat into a proportional electrical voltage.
4. Signal Processing: Internal electronics calculate the voltage, adjust for ambient temperature compensation, and translate the data into a temperature value.