LIGHT-BASED TOUCH SCREEN
A touch screen arrangement ( 1 ) fitted to a mobile telephone apparatus (T) and built-on or resting on a substrate ( 2 ). The touch screen includes a display unit ( 3 ) and a number of light pulse emitting units ( 4 L) and a number of light pulse receiving units ( 5 P), said units being edge-related to said display unit ( 3 ). The light pulse emitting units ( 4 L) and the light pulse receiving units ( 5 P) are orientated adjacent said display unit ( 3 ), with the directions of said emitted and received light pulses ( 40 a, 40 b ) being at right angles, or at least generally at right angles, to a planar surface ( 3 a ) on the display unit ( 3 ). The touch screen also includes four light pulse deflecting devices ( 7, 8; 7′, 8′ ) positioned close to the display surface ( 3 ).
1 - 17 . (canceled)
18 . A controller for an optical touch sensor, comprising:
interfaces to (i) an application processor, (ii) light emitters that, when activated, emit parallel light beams across a display, wherein the display renders buttons for use as input to the application processor, and (iii) light receivers that, when activated, detect the emitted beams, wherein detections of the emitted beams change when an object impinges the beams;
an activating unit activating the light emitters and light receivers via said interfaces, in accordance with an activation sequence;
a first calculating unit configured to identify a touch position on the display when detection by the light receivers of only one of the parallel beams changes, based on the beam for which the detection changes;
a second calculating unit configured to identify a touch position on the display when detections by the light receivers of at least two neighboring ones of the parallel beams change, based on other ones of the parallel beams the detections of which do not change; and
a mapping unit configured to determine an intended button on the display based on the touch position identified by said first or second calculating units, wherein the controller transmits an indicator of the intended button to the application processor via said interfaces.
19 . The controller of claim 18 , wherein said first and second calculating units are maintained in an inactive state as long as detections of the parallel beams by the light receivers do not change.
20 . The controller of claim 18 , further comprising a signal strength adapter that receives outputs from the detectors and adapts an intensity of the emitted light beams to ambient light conditions indicated by the detector outputs.
21 . The controller of claim 20 , wherein said signal strength adapter minimizes the intensity of the emitted light beams under dark ambient light conditions.
22 . The controller of claim 18 , further comprising a timing circuit that receives outputs from the detectors and switches the activation sequence for the emitters and detectors from a high-power sequence to a low-power sequence after a period of time during which detections of the parallel light beams by the light receivers do not change.
23 . The controller of claim 22 , wherein said activating unit activates fewer light emitters in the low-power sequence than in the high-power sequence.
24 . The controller of claim 23 , wherein said activating unit activates only one emitter in the low-power sequence.