Windows Mobile is considering capacity screen support

The iPhone, Palm Pre, Android have capacitive screen support, while Windows Mobile only supports resistive screen. Even Steve Ballmer mentioned in recent interview the reason why. Microsoft certainly will consider to implement this feature in future Windows Mobile OS releases.

Taken from a recent Microsoft development blog, which gives a nice summary of the touchscreen technologies

Resistive

Touch enabled Windows Mobile devices traditionally sport a plastic tipped stylus and have a touch screen based on resistive technology.

In brief resistive screen technology is based on two layers of transparent conducting material (Indium Tin Oxide or ITO) separated by an air gap held apart with tiny insulating plastic beads. Pressing the screen deforms the two sheets and makes contact between them and from the change in resistance the screen firmware can identify where the stylus has been placed. There are lots of variations on this technology.

Resistive screens have several killer properties: they are cheap, very accurate for a stylus, and they can continue to work in quite hostile environments i.e. dirty screens.

However they do suffer in other areas: they require an amount of force to deform the screen and make contact between the conducting layers; because of the multi plastic layers placed on top of the display and the air gap, some brightness is always lost; cheap & readily available traditional resistive screens really only support a single touch point – more advanced digital resistive sensors have been demonstrated which do support multiple touch points, but this is a future development; it’s quite tough to get more information beyond just the point location i.e. size of the touch area; and durability can be an issue due to the use of moving parts – i.e. deformation of the screen.

Capacitive

Another touch technology that has rapidly gained in popularity is capacitive (as found in the iPhone, Palm Pre and Android G1). This technology works by continually measuring the capacitive property of different areas of the screen. When conducting material such as a finger is placed on the screen, its capacitive properties change and the screen driver can determine where the finger is based upon the changes.

Capacitive technology has several advantages: zero pressure is required to make an input because nothing needs to be deformed and this leads to a much more natural interface experience; although additional material is laid onto the screen, there is no air gap so optical clarity is much improved reducing the need for backlighting making power draw lower; multiple touch points can be supported; things like touch size and pressure can be extrapolated from the capacitive data.

However they do suffer in other areas: in general the cost is currently higher than the equivalent resistive screen; supporting a stylus is hard because it must be made of conducting material and must make sufficient contact to change the capacitive property of the screen; in several areas the accuracy tends to be lower than resistive e.g. around the edges of the screen, combined with the lack of a stylus and lower sample rates makes things like handwriting input very hard.

There are other input technologies developing all the time, but at the moment these two represent nearly all the market for mobile devices.

Windows Mobile 6.5 has primarily been designed for resistive screens because some input areas still rely on small controls and require a high level of input accuracy that can’t be easily achieved with a finger and require a stylus; however some device manufacturers are considering options to ship capacitive screens.

Looking forward the mobile team is considering how to address these issues and support many more screen types including capacitive.

Rumor: HTC Leo, first capacitive display Windows phone Patch Providing SDHC Support on Windows Mobile 5 & 6 - Electraspan High Capacity Battery

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