Module Or Discrete?

Beyond the basic image sensor, manufacturers of imaging chips often provide value-added solutions in the form of complete camera modules (see the figure). These modules contain the imaging chip, a fixed- or adjustable-focus lens, and sometimes additional image processing, flash control, and auto-focus circuitry. Camera modules also come from independent companies that specialize in the low-cost assembly and manufacturing of products for the mass market.

These modules present a challenge because the most critical specification after price tends to be size. All three dimensions must be as small as possible so placing the module inside the cell phone doesn't cause an increase in the cell phone's size.

Fixed-focus lenses offer the lowest cost and most compact solution, but they don't deliver the sharpest image. Other focus schemes include the use of a voice-coil-based electromagnetic system or a piezoelectric scheme, since the focus adjustment distance is a small fraction of a millimeter. A more novel approach emerging from research labs uses a liquid-based lens that can be focused using a form of electrostatic deflection, eliminating all moving parts. Such liquid lenses promise better reliability while further shrinking the height of the lens assembly.