lichtdetector

Lichtdetektor, or photodetector, is a sensor that converts incoming light into an electrical signal. Detectors are designed to sense electromagnetic radiation across various spectral ranges, from ultraviolet through visible to near infrared, depending on the semiconductor material or device design. The underlying operating principles include the photovoltaic effect in diodes and solar cells, photoconductivity in materials whose electrical conductivity increases with light, and photoemission in devices such as photomultiplier tubes.

Common types include photodiodes (including silicon and germanium junctions, and PIN diodes), avalanche photodiodes for enhanced sensitivity, and phototransistors, which combine a photodetector with current amplification. For imaging, charge-coupled devices (CCD) and complementary metal-oxide-semiconductor (CMOS) sensor arrays are used. Light-dependent resistors (LDRs), typically cadmium sulfide or cadmium sulfide/cadmium sulfide variants, provide high resistance in darkness and lower resistance in light. Photomultiplier tubes offer very high gain for extremely low light levels but require high voltage.

Key characteristics are spectral response, responsivity (current or voltage output per unit radiant flux), dynamic range, linearity, dark current, noise, and response time. Detectors are typically paired with electronics such as transimpedance amplifiers to convert current into a usable voltage signal and to set gain and bandwidth.

Applications span optical communication, spectroscopy, astronomy, environmental monitoring, industrial automation, barcode scanning, camera imaging, and safety sensors. The term lichtdetektor emphasizes the German usage of the concept, while photodetector is common in English-language contexts.