Sony explains how floating touch works on Xperia Sola

The latest touch screen technology on Sony Ericsson Xperia Sola would allow users to use the screen just by waving the fingers above the screen. So now you don’t even have to touch it (Should the screen still be referred as touchscreen?). Xperia Sola is the first device to incorporate this floating touch feature. To use it the finger needs to be in a 20mm range. The phone can also detect the distance of the finger from the screen. This could be used as an added gesture for controls.

Sony Ericsson Xperia Sola

The technology sounds very fascinating and everyone wants to know how it works. We know that most of the good touch screens are based on capacitive sensing. Xperia Sola uses the same capacitive technology for the purpose. Under the screen there is an electrode grid aligned along X and Y axis. A small voltage is applied to the electrodes and when finger comes in close proximity of the screen, electric field changes and the changed field is used to calculate the touch co-ordinates.

There are two types of devices working on this technology. The first ones working on mutual capacitance offers multi touch gesture detection and the second ones work on self-capacitance. Self Capacitance does not allow multi touch due to an effect called Ghosting. However self Capacitance offers better accuracy since the signals generated in this are stronger. Mutual capacitance produces smaller changes hence provides a lower accuracy.

In case of mutual capacitance each X-Y junction is a separate sensor and hence distance between two fingers touching the screen can be calculated. Hence it can detect two sets of co-ordinates for two fingers. But in self capacitance the whole grid is one big capacitor. A bigger capacitor results in a higher change in electric field when touched. The changes are big hence when the finger comes near the screen it still creates detectable changes. Also the accuracy of these devices is higher. Ghosting effect occurs when self capacitive screens experience multi touch. It creates for probable positions of two fingers and the real position can’t be detected.

The floating touch technology has been developed in collaboration with Cypress Technologies. They have combined both technologies (mutual capacitance and self capacitance) to create the floating touch. Mutual capacitance helps in multi touch and self capacitance helps is calculating the touch event details. Multi touch can work just like we have been using it.

All the existing apps would work fine with this technology ; however, the hover events can be used to create apps like never before. The hover event works like a mouse gesture in case of PC. Hence the existing webpages would work just like before. There is no need to change anything since it is working through standard HTML hover events. App developers would have the great opportunity to create innovative apps using open APL for floating screen.

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