Image sensors
Biomedical fluorescence microscopy

In fluorescence, light levels are low, and sensor efficiency and noise play a significant role in the final image. Depending on the technology used, the image will be acquired point by point, line by line, or, more often, by direct filling of a CCD-type matrix sensor.

Sensors are characterized by their quantum efficiency and noise level. Efficiency is measured in % of electrons per photon. It depends on wavelength, and can approach 95%.

Thermal noise is the stochastic production of electrons in the absence of a light source. This noise is roughly doubled every 8°C. Sensors are cooled either to a temperature slightly above 0°C, or to a lower one, down to – 90 ^°C, taking into account the risk of icing and condensation (dry air blower, for example).

On cameras, read noise is the uncertainty at the moment of measurement. It is measured in electron numbers, ranging from...