Today Apple announced the new iPhone and a number of the hardware changes were targeted at the camera. We expected the 5 mega-pixel camera and flash but it also gained backside illumination.

What is backside illumination?

First stop giggling... ok... I’ll admit I think they could have found a better name. Backside illumination is a trick of getting better digital photos in limited lighting.

First an overview on digital cameras

The key part of all digital cameras is a chip called the CCD which senses the light falling on to the surface of its silicon. The light affects the charge a grid of millions of tiny capacitors created on the silicon when the chip is etched, implanted and deposited during what is known as the fabrication process. The chip has additional circuitry that measures the charge of all of the capacitors which is basically how the light levels of the image are read.

To be able to read all of t

these capacitors there are minutely thin wires running over the top. They’re not actually wires but a thin layer of aluminum or copper that is effectively sprayed on to the chip and then carefully eaten away using acids to leave connecting traces, which are pretty much metal wires bonded to the chip.

The image to the left shows the grid of wires running over the chip and a zoom in on the capacitors underneath

Why backside illumination?

All those wires and other parts of the capacitors sit on top of  a square silicon tile with the capacitors at the bottom. The circuitry and wires don’t obstruct it too much as it works but it does block some light and scatter some in to surrounding capacitors which reduces the quality of image captured especially with limited lighting.

Back to that square silicon tile. Silicon is the main ingredient of regular glass (silicon dioxide) but the stuff used in making chips is a super pure silicon crystal and transparent. With backside illumination  the issues with traditional CCD’s of the capacitors being on the bottom is quite literally turned upside down and now you shine the image on what was the bottom of the silicon tile and let the light shine through the silicon to the capacitors. This way you avoid all the wires and get more light to the capacitors.

It’s kinda reassuring to us here at Sparkplug Industries to see Apple take such measures to improve the quality of photos taken in dim lighting. We knew the camera let the iPhone down too often and its nice to be have Apple agree. We look to help existing iPhone owners while Apple is offering a whole new phone.

If you have an existing iPhone, be it the original, 3G or 3GS, the Spark Plug Flash gives you a high brightness LED flash that plugs into your iPhone to light scenes for photos and video. See more about Spark Plug Flash here.