Fill factor (image sensor)

The fill factor of an image sensor array is the ratio of a pixel's light sensitive area to its total area. For pixels without microlenses, the fill factor is the ratio of photodiode area to total pixel area,^[1] but the use of microlenses increases the effective fill factor, often to nearly 100%, by converging light from the whole pixel area into the photodiode.^[2]

Another case that reduces the fill factor of an image is to add additional memory beside each pixel, so as to achieve a global shutter on CMOS sensors.^[3]

Additional memory to achieve global shutter effect for CMOS sensor^[3].

References

1. Sebastiano Battiato; Arcangelo Ranieri Bruna; Giuseppe Messina; Giovanni Puglisi, eds. (2010). Image Processing for Embedded Devices: From CFA Data to Image/video Coding. Bentham Science Publishers. p. 12. ISBN 9781608051700.
2. Sebastiano Battiato; Arcangelo Ranieri Bruna; Giuseppe Messina; Giovanni Puglisi, eds. (2010). Image Processing for Embedded Devices: From CFA Data to Image/video Coding. Bentham Science Publishers. p. 29. ISBN 9781608051700.
3. "Sensors: Global shutter - Personal View Talks". www.personal-view.com. Retrieved 2017-07-29.