What is "dark current"

n. (context physics English) The temperature-dependant current that flows in a photodetector when no light is shining on it

Dark current is the constant response exhibited by a receptor of radiation during periods when it is not actively being irradiated. It may refer to:

• Dark current (biochemistry) : The depolarizing current, carried by Na ions, that flows into a photoreceptor cell when unstimulated
• Dark current (physics): The relatively small electric current that flows through a photosensitive device when no photons are entering the device
• Dark current (chemistry) : The constant response produced by a spectrochemical receptor, in the absence of radiation

In physics and in electronic engineering, dark current is the relatively small electric current that flows through photosensitive devices such as a photomultiplier tube, photodiode, or charge-coupled device even when no photons are entering the device. It is referred to as reverse bias leakage current in non-optical devices and is present in all diodes. Physically, dark current is due to the random generation of electrons and holes within the depletion region of the device.

The charge generation rate is related to specific crystallographic defects within the depletion region. Dark-current spectroscopy can be used to determine the defects present by monitoring the peaks in the dark current histogram's evolution with temperature.

Dark current is one of the main sources for noise in image sensors such as charge-coupled devices. The pattern of different dark currents can result in a fixed-pattern noise; dark frame subtraction can remove an estimate of the mean fixed pattern, but there still remains a temporal noise, because the dark current itself has a shot noise.

Category:Electronic engineering

In analytical chemistry, dark current refers to the constant response produced by a spectrochemical receptor, even in the absence of radiation. This response adds to the signal produced when the receptor is used to measure light and so must be dealt with to determine how much of the detector response is actually due to the radiation. To compensate for this extra signal, the dark current may be measured in the absence of radiation and then subtracted from the final signal or reduced to zero by a compensating circuit. Dealing with dark current is a form of blank correction.