Light-based touch screen
First Claim
1. A touch screen comprising:
- a display screen;
a plurality of light pulse emitters emitting light across said display screen;
a plurality of light pulse detectors detecting the emitted light;
an emitter driver selectively activating said emitters;
a detector driver selectively activating said detectors;
a signal processor generating detection signals representing amounts of light detected by said detectors;
a scan controller controlling said emitter and detector drivers to activate an automated sequence of a plurality of emitter-detector pairs, the scan controller comprising registers for storing, prior to executing the automated sequence, parameters designating a scan sequence of emitter-detector pairs that are to be activated during the automated sequence, and for storing the detection signals generated by said signal processor for the emitter-detector pair activations; and
a host processor displaying derived touch locations on said display screen, comprising a temporal filter, the host processor configured to (i) receive the stored detection signals, (ii) derive, from the stored detection signals, location coordinates of a moving object touching said display screen at a sequence of times, (iii) calculate a contact area between the object and said display screen, and (iv) apply said temporal filter to the sequence of location coordinates to balance the trade-off between (a) apparent jitter, and (b) perceptible lag between actual touch locations and touch locations displayed by the host processor on said display screen, based on the object'"'"'s speed of movement,wherein said temporal filter is designed to apply more weight to removal of apparent jitter than to removal of perceptible lag when the calculated contact area is larger than a threshold area, and to apply more weight to removal of perceptible lag than to removal of apparent jitter when the calculated contact area is less than the threshold area.
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Abstract
A state machine for controlling a sensor including a chip package coupled with photo-emitters and photo-detectors mounted in a device, and with a host processor, including an emitter driver, a detector driver, a signal processor for generating signals representing amounts of light detected by the detectors, and a scan controller for controlling the emitter and detector drivers to activate an automated sequence of emitter-detector pairs, the scan controller including registers for storing parameters designating emitter-detector pairs that are to be activated during the automated sequence, and for storing the signals generated by the signal processor for the emitter-detector pair activations, and at least one input/output pin for receiving parameters from the host processor to be loaded into the registers, and for outputting the stored signals in the registers to the host processor, for the host processor to identify therefrom location coordinates of an object near or touching the device.
288 Citations
20 Claims
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1. A touch screen comprising:
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a display screen; a plurality of light pulse emitters emitting light across said display screen; a plurality of light pulse detectors detecting the emitted light; an emitter driver selectively activating said emitters; a detector driver selectively activating said detectors; a signal processor generating detection signals representing amounts of light detected by said detectors; a scan controller controlling said emitter and detector drivers to activate an automated sequence of a plurality of emitter-detector pairs, the scan controller comprising registers for storing, prior to executing the automated sequence, parameters designating a scan sequence of emitter-detector pairs that are to be activated during the automated sequence, and for storing the detection signals generated by said signal processor for the emitter-detector pair activations; and a host processor displaying derived touch locations on said display screen, comprising a temporal filter, the host processor configured to (i) receive the stored detection signals, (ii) derive, from the stored detection signals, location coordinates of a moving object touching said display screen at a sequence of times, (iii) calculate a contact area between the object and said display screen, and (iv) apply said temporal filter to the sequence of location coordinates to balance the trade-off between (a) apparent jitter, and (b) perceptible lag between actual touch locations and touch locations displayed by the host processor on said display screen, based on the object'"'"'s speed of movement, wherein said temporal filter is designed to apply more weight to removal of apparent jitter than to removal of perceptible lag when the calculated contact area is larger than a threshold area, and to apply more weight to removal of perceptible lag than to removal of apparent jitter when the calculated contact area is less than the threshold area. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification