Low light imaging (LLI), or low-light imaging, occurs in conditions where the luminous flux is less than 1 lux (a unit of illuminance), which is roughly comparable to the illumination of the earth's surface under a "full" moon. Low light imaging is often referred to in connection with night vision devices or night vision cameras. The first application of LLI was for the purpose of improving human night vision capability. However, over the last decades, low-light imaging has been applied in many areas of science, such as astronomy, fluorescence or luminescence imaging, etc.
An ideal detector for low light imaging has a high numerical aperture (NA) value, a high quantum efficiency (QE ) value, and the ability to amplify the signal to detect as many photons emitted by the object as possible. These features and low read noise ensure a high signal-to-noise ratio(SNR). High demands are also placed on high resolution, high dynamic range, high repetition rate and good camera usability, among other things. Two types of cameras based on different signal amplification techniques in particular meet these requirements. The first type is the EMCCD cameras (Electron Multiplying CCD), which provide high quantum efficiency values (up to 92 %), but due to the signal amplification directly on the CCD chip, the camera needs to be cooled continuously (to achieve a high SNR). The second type is the ICCD cameras (Intensified CCD), where the signal is amplified in the image intensifier upstream of the CCD chip. ICCDs achieve high SNRs at low illumination intensities even without active cooling.