Photodetectors

Photodetectors are sensors of light and other electromagnetic energy. They work by converting light signals into voltage or current. They use an illuminated window with anti-reflective coating to absorb light photons. They are calibrated to detect light and radiation in a specific spectrum. They are essential components in fibre optic communications and industrial systems. Photodetectors are usually categorised according to their detection method. These include photoemission, photoelectric, photovoltaic, thermal, polarisation, photochemical and weak interaction effects. Photodetectors can have different configurations too. Single sensors check overall light levels while a 1-D array in a line scanner measures the distribution of light along a line. A 2-D array of photodetectors can be used as an image sensor to form images from patterns of light. Photodetectors have a wide range of applications. Devices like active-pixel sensors are installed in mobile phone or web cameras while in factories they are used in safety equipment like electrical arc detection. Position sensors in collision detection systems in cars contain a photodetector. In construction they are found in surveying instruments. Charge-coupled devices use a photodetector to record images in astronomy and for digital photography. Other applications include particle detection, infrared scanning and for bar code scanners in supermarkets.