How does backside illumination work

You can see what this new sensor technology means to you by attending one of our roadshows or arranging a private demo evaluation. Remember me Log in. Lost your password? Down the Well. How a typical, non-BSI sensor sees the world. Patrick McDonough. It typically includes transistors and wiring for amplifying the charge, transferring it to the signal processing portion of the chip, and resetting itself between frames.

Those electronics get placed on top of the silicon layer, partially obscuring it from the light and resulting in a well-like appearance for a typical pixel. Microlenses are used to reduce this problem the human eye uses waveguides known as Muller cells , but a meaningful amount of light is still lost before it gets to the photodiode to be captured.

Light bouncing around inside the electronics can also cause other problems such as vignetting and crosstalk. Thus a design which puts the photodiodes on top is clearly desirable. Having the photosensitive area on the side of the chip facing the light also dramatically improves the angular response of the sensor.

Next page: The devilishly hard process of putting photo receptors on top. But in use, they're like night and day -- almost literally. The always fascinating Preston Scott over at Camera Technica has the in-depth explanation, but the quick version is surprisingly interesting.

Frontside and backside refer to where the circuitry sits on the chip. Delicate silicon is made thick to stop it from breaking, and then the pixels are added.

On top of this goes the circuitry.