A CCD sensor manufacturing technology in which the incident photons must first cross the electrodes(Gate Electrode Structure) and then hit the light-sensitive layer(Depletion) where an adequate charge is generated. On the electrode layer, light radiation of different wavelengths is absorbed or reflected, which has a negative effect on the quantum efficiency of the sensor. Compared to back-illuminated sensors, front-illuminated sensors exhibit lower quantum efficiency but have the advantage of lower cost.
