The CMOS image sensor has the last few years evolved in to a competitor to the Charged Coupled Device. There are two basic designs of CMOS sensors, passive and active array.

The passive CMOS image sensor is basically just an array of photodiodes with a common amplifier for all diodes in a column. But since the photodiodes have a relatively low sensitivity to light, this system is sensitive to noise. This problem rises the further away the diode is from the amplifier.

In the active sensor a transistor is added to each diode, thus the signal is stronger and less susceptible to noise. But the addition of a transistor means that each sensor in the array becoms bigger and this causes the arrays resolution to fall. The CCD uses only one component and can be made with a higher density. But one big advantage with the CMOS is that it uses less power. This means a lower power drain on a portable device's power source. The technology to produce CMOS sensors has also fallen in price the last years. This has made the active CMOS image sensor a good choice in cheaper, low resolution, digital cameras.

As the technology behind this type of sensor advances, it will probably have a future in mobile devices.

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