Optical control system with modulated emitters

摘要

An optical control system is described, which employs a series of optical emitters and detectors arranged about a touch area. The emitters are driven by a series of orthogonal functions, and the system is operable to correlate the signals received at the detectors with the modulation functions to determine the amount of energy received by the detectors from each of the emitters. This system means that all or many emitters can be modulated simultaneously, so the scanning process is accelerated. Also, the energy estimates arrived at by correlation with the modulating functions are largely unaffected by external interference signals as well by each other. An additional benefit of the present invention is that the correlation processing makes use of many detector samples and tends to yield results which have higher resolution than the sample values themselves, due to the averaging of noise over the sample set.

主权项

1. An optical touch detection system comprising:
a touch sensitive area within which touch events are to be detected; emitters and detectors arranged around a periphery of the touch sensitive area, the emitters producing optical beams received by the detectors, wherein touch events disturb the optical beams; and an optical control system coupled to the emitters and detectors, the optical control system configured to:
control activation of a plurality of the emitters and detectors simultaneously according to a modulation scheme that modulates each optical beam with a different function, each function having a code length when the function is applied to the corresponding emitter and having at least one activation period for the corresponding emitter, wherein the optical control system is further configured to control activation of the detector corresponding to the beam to:
sample a first detector output during the code length before the activation period;sample a second detector output during the activation period;sample a third detector output during the code length after the activation period; andcorrelate output from the detectors regarding which optical beams have been disturbed by a touch event with the different functions to determine a location within the touch sensitive area where the touch event occurred.