Tektronix, Inc.

R David Meadows

Roger J McCoy

Joseph H Hubert

David H Price

The invention is a method for accumulating and displaying digital waveform data, representing the behavior over time of an electrical signal that includes the steps of: repeatedly acquiring and digitizing (10) waveform data during a first set of time intervals, repeatedly acquiring and digitizing (10) waveform data during a second set of time intervals, the second set of time intervals alternating with the first set of time intervals, during each one of the time intervals in the first set of time intervals, ORing (83) each acquired and digitized waveform together to produce first composite waveforms, during each one of the time intervals in the second set of time intervals, ORing (86) each acquired and digitized waveform together to produce second composite waveforms, displaying (81,84) each first composite waveform during a next occurring time interval in the second set of time intervals, and displaying (81,84) each second composite waveform during a next occurring time interval in the first set of time intervals. In a preferred embodiment, the ORing process is qualified on a pixel-by-pixel basis dependent on the results of a comparison between a randomly generated number and a predetermined threshold. In an alternative embodiment, only a single set of composite waveforms is produced and the display exhibits persistence to maintain the display during the next acquisition cycle.

Slow display method for digital oscilloscope with fast acquisition system

A detection circuit (30, 32) for carrying out a rapid search technique for locating the position of a stylus (12) relative to a display screen (10). A microprocessor (34) and related components select a group of light detectors (20, 28) that are positioned near the display screen (10). The summed output current of the selected group of detectors (20, 28) is monitored to determine whether the output of any detector in the selected group is reduced because of the presence of a stylus (12). Whenever the selected group shows such reduction in output current, that selected groups is divided into two subgroups. The subgroup having reduced current output due to the presence of the stylus (12) is further divided until the particular detector(s) having reduced output current is found, the position of the detector is correlated to the location of the stylus (12) relative to the screen (10).

Stylus position detection system for optical touch panel

A capacitive touch panel system (10) having a faceplate (14) with an electrically conductive layer (20) of a consistent resistivity employs a position measurement apparatus (12) to generate an address signal indicative of a position (46) on the faceplate in contact with a stylus (48). The position measurement apparatus includes a position measurement signal source (56) that generates a square-wave measurement signal of a frequency that varies in a substantially random manner. The position measurement signal is applied to a first pair of opposed electrodes (36) and (40) and a second pair of opposed electrodes (38) and (42) positioned along respective side margins (26, 30, 28, and 32) of the faceplate. The resistivity of the conductive layer establishes effective resistances of R.sub.x and R.sub.y between the respective first and second pairs of electrodes. Position measurement subcircuits (54a-54d) are locked-in with the random measurement signal frequencies to measure currents drawn through the electrodes whenever the stylus contacts the conductive layer, thereby to form an address signal indicative of the location at which the stylus contacts the faceplate. The random measurement signal frequencies reduce the susceptibility of the position measurement apparatus to electromagnetic noise and distributes over a relatively broad bandwidth the electromagnetic noise generated by the position measurement apparatus.

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Portland, OR, United States of America

R David Meadows