Lesson 14 – Optical Detectors

Optical radiation is commonly detected by one of two means, using a thermal detector or a photon detector. Thermal detectors are heated when illuminated, and this absorbed energy is detected as a change in an electrical parameter, such as the detector’s resistance. Thermistors, thermopiles, and calorimeters are thermal detectors. In photon detectors, the photon is converted into an electrical charge carrier such as an electron, which flows through circuitry to create a current or generate a voltage. Photodiodes, photomultipliers, and photovoltaic (PV) cells operate as photon detectors. Detectors may be arrayed into a grid to make a camera sensor’s focal plane array (FPA).