![]() Scientific cameras can use thermoelectric (TE) or Peltier cooling in combination with forced air or liquid cooling in order to reduce the temperature of the sensor during operation, as seen in Fig.2. However, as dark current is dependent on the temperature its effects can be reduced using cooling. The higher the dark current, the less able a camera is to perform long-exposure imaging. This indicates how many electrons build up on each pixel for every second of exposure, typically shown as e –/p/s. This is known as the dark current.Įvery model of scientific camera, whether using a CCD, EMCCD, or CMOS sensor, will have a dark current specification. ![]() Unfortunately, the camera sensor doesn’t know the difference between these types of electrons, and so any thermal electrons that accumulated in the sensor pixel wells (along with the photoelectrons) are counted as signal upon readout, despite not being part of the signal from the sample. These thermal electrons are independent of the photoelectrons generated proportional to the photons (light intensity) falling on the sensor. As a camera sensor is exposing an image, the electronics in the camera will heat the sensor, and this accumulation of thermal energy causes thermal electrons to build up on the sensor. Dark Currentĭark current arises from thermal energy within the camera sensor. This noise will spread across the camera as the heat increases over long exposures and will impact image quality. Figure 1: Thermal build-up and dark current noise at the edges of a camera sensor.
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