Microlenses

Vincent Bockaert, 123di.com

To overcome the limitations of a low fill factor, on certain sensors an array of microlenses is placed on top of the color filter array in order to funnel the photons of a larger area into the smaller area of the light sensitive photodiode.

Microlens funnels the light of a larger area into the photodiode (indicated in red) of the pixel Electron microscope image of real microlenses
This article is written by Vincent Bockaert,
author of The 123 of digital imaging Interactive Learning Suite
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