Thin is in. But what sets the limit for the thickness (or thinness) your smart phone? Is it the powerful processor that renders 3D games? Or is it the battery that runs for days on end between charges? Nope. Those components could fit comfortably into much thinner housings than even the 7.6 mm iPhone 5.
Apple marketing photo
The thickness is actually limited by the main camera. Back in the day, most cell phones had no means of taking pictures. Today’s leading smartphones have two cameras. There is a main camera unit in the back for taking high quality stills and video. A secondary camera generally faces the user for video conferencing or convenient self-portraits.
Camera modules determine the minimum thickness of the smart phone because the image sensor chip (invariably CMOS today) must sit a certain distance away from the lens.
Higher quality cameras incorporate more lens elements and autofocus which also add to the depth (or z-height) of the module. Good old physics sets these limits since the area of the CMOS image sensor will determine how far away the lens must be to focus light over the full imaging array. Higher pixel count (notice I avoided the term “higher quality”) devices generally require larger area chips, and tend to expand the module height.
Camera Module
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http://www.intomobile.com/2013/03/28/toshiba-creates-worlds-thinnest-13-megapixel-camera-module
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The secondary cameras are smaller and thinner than the main imaging units. Pixel counts are smaller, and the corresponding area of the CMOS image sensor chip is smaller than the main camera. This allows the sensor module with fixed focus lens to fit into a shallower depth.
Taking my own primary camera (and primary computer), the iPhone 5, the front-facing camera is 1.2 megapixels while the main camera is an 8 megapixel autofocus unit. These were unconceivable just a few years ago – in any size device let alone something less than a third of an inch thick.
My first digital camera was a Canon G1. It was sophisticated and amazing for its time. It’s hard to imagine, but that G1 was a 3.1 megapixel camera – somewhere between my front and back iPhone cameras. And I never could remember to take it with me.
Recent articles about major components inside today’s smartphones:
Applications Processors – The Heart of the Smartphone
Power Choices for Smartphone Designers