A color sensitive pixel with tunable spectral responsivities

A recently proposed pixel device relies on the wavelength dependence of the Silicon absorption
coefficient for color sensing without color filters. A suitable transverse electric field configuration, in the depleted region beneath the pixel surface of this device (TFD), makes it possible to collect at different superficial contacts the carriers generated at different depth from the surface. With three or more junctions the color information can be reconstructed. With respect to a conventional color sensitive pixel sensor based on Color Filter Arrays (CFA), in a TFD pixel sensor each single pixel is by itself color sensitive and therefore no subsequent demosaicking algorithms are needed to interpolate the colors.

A unique characteristic of this new device is the capability of fine spectral responses tunability,
which can be obtained by simply changing the voltage configuration of the superficial junctions (and thus the carriers collection paths), without affecting the overall quantum efficiency. This feature allows to change the sensor native color space and to adjusting it to the scene. In the presentation it will be shown how the spectral responses tunability can be exploited to perform a White Balance operation, to compensate for the illuminant spectrum prior to image acquisition. Further applications may include filter tuning to reduce color error, filter optimization and adaptation of the camera to the scene.