Abstract: A system for providing input to a computer comprises a touchscreen apparatus for generating a grid of horizontal and vertical light beams and producing a set of output signals, each indicating whether a corresponding one of the light beams strikes an object. A scanning device repeatedly scans the states of the output signals, stores data representing the last scanned state of each output signal, and transmits a first interrupt signal to the computer whenever the state of any one of the output signals changes. In response to the interrupt signal, the computer reads the stored scan data, determines whether the data indicates that a horizontal and a vertical light beam is striking an object, and if so, sets parameter values to identify the horizontal and vertical light beams.

Abstract: For an oscilloscope capable of simultaneously displaying a plurality of waveforms on a screen and capable of performing operations with respect to a selected one of the displayed waveforms, a method and apparatus for permitting an operator to select a waveform. A touchscreen mechanism provides input signals to the oscilloscope indicating when and where an operator touches the surface of the screen and a microcomputer within the oscilloscope determines from data controlling the display of each waveform and from the data provided by the touchscreen whether the operator is touching any portion of a displayed waveform. If so, the microcomputer assumes that the operator has selected the waveform touched and reconfigures oscilloscope operation such that operations are performed with respect to the waveform touched by the operator.

Abstract: A touch panel input apparatus including two arrays of light detectors placed on the opposite sides of the display device screen and four light sources, each of which is placed at a corner and at angle to illuminate at least the entire array of the light detectors on the opposite side. The light detectors are scanned in synchronization with the selection of the light beam sources. A controlling microprocessor has stored in its memory four sets of data, one for each light source, regarding ambient light condition and beam interrupt thresholds for the light detectors. By software, two equations representing a line are determined and solved to obtain a cross point which corresponds to X-Y position of the finger on the screen.