Signal-to-noise ratio performance comparison of Electron Multiplying CCD and Intensified CCD detectors

Basic principles of current Electron Multiplying CCD (EMCCD) and Intensified CCD (ICCD) detectors are reviewed. Based on their noise characteristics, complete signal-to-noise ratio (SNR) theoretical models are constructed for both devices. At high gain levels, we derive that an ICCD is mainly affected by photocathode noise and micro-channel plate (MCP) noise and the effective readout noise of an EMCCD is less than one electron. Therefore, we propose simplified SNR models of ICCD and EMCCD cameras. SNR performances are compared through simulations and experiments to identify the most influencing parameters. The results show that the SNR performance provided by the ICCD is constricted by photocathode quantum efficiency and noise factor of the MCP. The EMCCD is strongly influenced by thermal dark current noise which will be multiplied up along with the signal by the gain register. Thus, EMCCDs must be strongly cooled in order to get the optimum image quality. Cooled EMCCDs always outperform ICCDs.