Abstract: An acoustic touchscreen (1a) has transmitting transducers (23a, 23b) for generating acoustic signals which are deflected across a touch-sensitive area (2) by an array 13 of partially acoustically reflective elements 14. A touch on the touch-sensitive area causes a perturbation in the acoustic signals. After traversing the touch-sensitive area, the acoustic signals are redirected by another array 13 of partially acoustically reflective elements 14, towards receiving transducers (26a, 26b), where the signals (and any perturbations) are sensed. To accommodate touchscreens having narrow border regions (15a), the acoustic signals are propagated across the border regions using acoustic waveguides (18). The waveguide confines the acoustic signals to traveling along a narrow path width, but yet permit them to be deflected across the touch-sensitive area. In this manner, the transducers and reflective elements can in turn be of narrower construction and can fit within narrow border regions.

Abstract: A method and apparatus for adapting an acoustic touchscreen controller to the operating frequency requirements of a specific touchscreen are provided. The adaptive controller can either utilize look-up tables to achieve the desired output frequency or the it can use a multi-step process in which it first determines the frequency requirements of the touchscreen, and then adjusts the burst frequency characteristics, the receiver circuit center frequency, or both in accordance with the touchscreen requirements. In one embodiment, the adaptive controller compensates for global frequency mismatch errors. In this embodiment a digital multiplier is used to modify the output of a crystal reference oscillator. The reference oscillator output is used to control the frequency of the signal from the receiving transducers and/or to generate the desired frequency of the tone burst sent to the transmitting transducers.

Abstract: A position touch sensor having a substrate and a resistive layer disposed on the substrate. At least one pair of electrodes is positioned on the resistive layer. A portion of one electrode is spaced from a portion of another electrode to produce an overlapped resistive region between the spaced portions of the electrodes. An insulating region extends into and terminates in the overlapped resistive region from a resistive region of the resistive layer outside the overlapped resistive region. A method for controlling the flow of current through a resistive layer for converting physical position information on the resistive layer into electrical signals. The method includes determining a dimension of a length of a generally continuous resistive section which is to be located in the resistive layer. The dimension of the length is determined through the use of electrical excitation in the resistive layer.

Abstract: An acoustic wave touch sensor comprising an acoustic wave transducer, for transducing an acoustic wave; a substrate, having a front surface. A surface bound acoustic wave interface, having at one least bevel edge, is provided, having an transmitted acoustic wave signal attenuation of less than about 3 dB. The acoustic wave transducer is mounted to transmit the acoustic wave through the interface into the substrate, so that the energy of the acoustic wave appears at the surface. The acoustic wave transducer is mounted on a beveled region of the substrate, inclined to the front surface. The beveled edge has an effective radius which is small as compared to the wavelength and a bevel angle such that the acoustic wave is attenuated by less than about 3 dB on transmission across the edge. In this manner, means are provided to recess transducers for improved product robustness and compactness of design.