![]() This can be represented in the form of a noise spectral density. Noise spectrum: The intrinsic noise voltage or current as a function of frequency.Response time: The time needed for a photodetector to go from 10% to 90% of final output.Dark current: The current flowing through a photodetector even in the absence of light.Gain: The output current of a photodetector divided by the current directly produced by the photons incident on the detectors, i.e., the built-in current gain.Detectivity: The square root of the detector area divided by the noise equivalent power.Noise-equivalent power: The amount of light power needed to generate a signal comparable in size to the noise of the device.Responsivity: The output current divided by total light power falling upon the photodetector.Quantum efficiency: The number of carriers (electrons or holes) generated per photon.Spectral response: The response of a photodetector as a function of photon frequency.There are a number of performance metrics, also called figures of merit, by which photodetectors are characterized and compared A 2-D array of photodetectors may be used as an image sensor to form images from the pattern of light before it.Ī photodetector or array is typically covered by an illumination window, sometimes having an anti-reflective coating. A 1-D array of photodetectors, as in a spectrophotometer or a Line scanner, may be used to measure the distribution of light along a line. Single sensors may detect overall light levels. Photodetectors may be used in different configurations. Weak interaction effects: photons induce secondary effects such as in photon drag detectors or gas pressure changes in Golay cells.Photochemical: Photons induce a chemical change in a material.Polarization: Photons induce changes in polarization states of suitable materials, which may lead to change in index of refraction or other polarization effects.Thermal: Photons cause electrons to transition to mid-gap states then decay back to lower bands, inducing phonon generation and thus heat. #Ambient light sensors freePhotoemission or photoelectric effect: Photons cause electrons to transition from the conduction band of a material to free electrons in a vacuum or gas.Photodetectors may be classified by their mechanism for detection: A commercial amplified photodetector for use in optics research ![]()
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