Touch sensitive screen signal detection arrangement

Claim 1

An arrangement for detecting the exact time of a non-cyclic signal change within a portion of an otherwise cyclically repeating time varying signal having constantly changing signal levels within each cycle, said arrangement comprising. means for establishing a data base of cyclic signal values, means for dividing each cycle of said time varying signal into incremental parts, each said part representative of a specific time of said varying signal, means for sampling said varying signal at each said specific time to obtain a signal value representative of said cyclic signal at each said incremental part, means for averaging like incremental value samples from several cycles of said cyclic signal to provide reference values, one said reference value for each said established incremental time, means for comparing sample values from subsequent cycles for each incremental part against said like averaged reference value; and means for providing a unique output only when there is a detected difference between said compared values.

Claim 5

A system for determining the position of a touch with respect to a touch sensitive screen where a periodically repeating illumination source sweeps across said screen and where an output signal, generated as a result of said illumination source, is modified during the instant of time the source generates light under a touched portion of said screen, said system comprises means for dividing said output signal into parts, each part corresponding to the time when said source illuminates certain portions of said screen, means for obtaining samples of said output signal at certain selected parts, means for averaging said obtained samples with subsequently obtained samples at like selected parts, means for storing said averaged samples, means for comparing subsequently obtained sample values at said certain selected parts with like stored averaged values to determine which of said stored values is one corresponding to a part where said output signal has been modified, and means controlled by said comparing means for providing a positional determination corresponding to the position of said touch.

Claim 6

A system for determining the position of a touch with respect to a touch sensitive screen where a periodically repeating illumination source sweeps across said screen and where an output signal, generated as a result of said illumination source, is modified during the instant of time the source generates light under a touched portion of said screen, said system comprises means for dividing said output signal into parts, each part corresponding to the time when said source illuminates certain portions of said screen, means for obtaining samples of said output signal at certain selected parts, means for averaging said obtained samples with subsequently obtained samples at like selected parts, means for storing said averaged samples, means for comparing subsequently obtained sample values at said certain selected parts with like stored averaged values to determine which of said stored values is one corresponding to a part where said output signal has been modified, and means controlled by said comparing means for providing a positional determination corresponding to the position of said touch.

Claim 10

A system for use in combination with the screen of a CRT, said CRT operable for generating light images on the screen thereof, said light images occurring as a result of a horizontal and vertical scan of an electron beam directed against said screen, said system arranged to determine the position of a touch of an image generated on said screen, said system including a sheet of material having inner and outer parallel surfaces through which light generated at said CRT screen will pass with a refraction angle θ1 at said inner surface next to said CRT screen and with a refraction angle θ2 at said outer surface, light utilization means communicating with at least one edge of said device and operable for providing an output representative of the magnitude of light which impinges on said light utilization means, means for positioning said light utilization means such that said impinging light comes substantially from between said surfaces of said device and such that when said refraction angle θ2 is changed to refraction angle θ3 said light utilization means output reflects said angle change, said refraction angle θ3 being below the critical angle for total internal reflection to occur, means for dividing said light utilization output into parts, each part corresponding to the time when said beam passes certain portions of said screen, means for obtaining samples of said light utilization output at certain selected parts, means for averaging said obtained samples with subsequently obtained samples at like selected parts, means for storing said averaged samples, and means for comparing subsequently obtained sample values at said certain selected parts with like stored averaged values to determine which of said stored values is one corresponding to a part where said corresponding light utilization output reflects said angle change.

Claim 11

A system for use in combination with the screen of a CRT, said CRT operable for generating light images on the screen thereof, said light images occurring as a result of a horizontal and vertical scan of an electron beam directed against said screen, said system arranged to determine the position of a touch of an image generated on said screen, said system including a sheet of material having inner and outer parallel surfaces through which light generated at said CRT screen will pass with a refraction angle θ1 at said inner surface next to said CRT screen and with a refraction angle θ2 at said outer surface, light utilization means communicating with at least one edge of said device and operable for providing an output representative of the magnitude of light which impinges on said light utilization means, means for positioning said light utilization means such that said impinging light comes substantially from between said surfaces of said device and such that when said refraction angle θ2 is changed to refraction angle θ3 said light utilization means output reflects said angle change, said refraction angle θ3 being below the critical angle for total internal reflection to occur, means for dividing said light utilization output into parts, each part corresponding to the time when said beam passes certain portions of said screen, means for obtaining samples of said light utilization output at certain selected parts, means for averaging said obtained samples with subsequently obtained samples at like selected parts, means for storing said averaged samples, and means for comparing subsequently obtained sample values at said certain selected parts with like stored averaged values to determine which of said stored values is one corresponding to a part where said corresponding light utilization output reflects said angle change.