Light pen detection for plasma display system using specially-timed erase pulse

Claim 2

In a display system comprising a plurality of display cells, each cell being capable of remaining in a first state for a period of at least T0 seconds, absent any external factors, means for applying erase signals selectively to said plurality of display cells to restore selected ones of said cells in said first state to a second state before the expiration of said T0second period of time has elapsed, the effect of said erase signals being operative over a period of duration T1<T0 seconds to effect said restoration to said second state, said restoration being accompanied by a characteristic lighT signal, means for applying sustain signals to sustain those of said plurality of cells which are in said first state for an additional T0-second interval, the improvement comprising: means for generating delayed replicas of said erase signals, means for sequentially applying said delayed erase signals to those of said plurality of display cells which are in said first state, thereby to give rise to respective characteristic light signals at a time associated with the application of said delayed erase signals, and means for detecting said characteristic light signals resulting from the application of said delayed erase signals.

Claim 3

Apparatus according to claim 1 wherein said first state is an ''''on'''' state and said means for applying sustain signals comprises means for applying signals sufficient in magnitude to cause those of said display cells which are in said first state to emit light signals during each T0-second interval.

Claim 4

Apparatus according to claim 2 wherein said means for delaying comprises means for delaying an erase signal by an amount such that said T1-second period overlaps the application of a subsequent sustain signal, thereby to prevent the effect of said erase signal from becoming complete.

Claim 5

Apparatus according to claim 3 wherein said means for sequentially applying said erase signals comprises means for generating sequences of addresses for selecting particular ones of said cells.

Claim 6

Apparatus according to claim 4 wherein said system further comprises a light sensitive device responsive to said characteristic light signal for generating an output signal, and means responsive to said output signal and said delayed erase signal for indicating that said light pen is directed at a cell currently having said delayed erase signal applied to it.

Claim 7

Apparatus comprising an array of light-emitting devices, each having a stable ''''off'''' state and at least one stable ''''on'''' state, said devices being maintainable in one of said ''''on'''' states by the periodic application of sustain signals, first means for periodically applying sustain signals to said array, second means for generating an erase signal which erase signal, when applied to one or more selected devices in said array, is operative to cause those of said selected devices which were in an ''''on'''' state to generate a characteristic light signal, said erase signal also being operative over a finite interval of time, T1in the absence of any other factors, to restore those of said selected devices which were in an ''''on'''' state to said ''''off'''' state, third means for causing said erase signal to occur in such time relation with said sustain signals that said T1 period does not occur without the application of said sustain signals, fourth means for selectively applying said erase signal occurring in said time relation with respect to said sustain signals to one or more devices in said array which are in said ''''on'''' state, whereby, said devices to which said fourth means applies said erase signal give rise to a characteristic light signal associated with the application of said erase signal but are nevertheless sustained in their pre-existing ''''on'''' state.

Claim 8

Apparatus comprising an array of light-emitting devices, each having a stable ''''off'''' state and at least one stable ''''on'''' state, said devices being maintainable in one of said ''''on'''' states by the periodic application of sustain signals, first means for periodically applying sustain signals to said array, second means for generating an erase signal which erase signal, when applied to one or more selected devices in said array, is operative to cause those of said selected devices which were in an ''''on'''' state to generate a characteristic light signal, said erase signal also being operative over a finite interval of time, T1in the absence of any other factors, to restore those of said selected devices which were in an ''''on'''' state to said ''''off'''' state, third means for causing said erase signal to occur in such time relation with said sustain signals that said T1 period does not occur without the application of said sustain signals, fourth means for selectively applying said erase signal occurring in said time relation with respect to said sustain signals to one or more devices in said array which are in said ''''on'''' state, whereby, said devices to which said fourth means applies said erase signal give rise to a characteristic light signal associated with the application of said erase signal but are nevertheless sustained in their pre-existing ''''on'''' state.

Claim 9

Apparatus according to claim 6 wherein said light-emitting devices each comprise one or more plasma discharge cells.

Claim 10

Apparatus according to claim 6 wherein said second means comprises means for generating an erase signal at a time sufficiently removed in time from operative portions of said sustain signals to effectively restore said selected devices to said ''''off'''' state, and wherein said third means comprises means for selectively delaying said erase signal.

Claim 11

Apparatus according to claim 6 further comprising means for detecting said light signal associated with the application of said erase signal to said one or more selected devices.

Claim 12

Apparatus according to claim 6 wherein said fourth Means comprises means for sequentially generating signals identifying each of a covering plurality of subsets of devices in said array and means responsive to said identifying signals for sequentially directing said erase signal having said time relation with respect to said sustain signals to respective ones of said subsets of devices.

Claim 13

Apparatus according to claim 10 further comprising means for detecting said light signal associated with the application of said erase signal having said time relation with respect to said sustain signals to one or more of said subsets of said devices.

Claim 14

Apparatus according to claim 11 further comprising means for associating the detection by said means for detecting of a light signal from a given selected subset of said devices with the signals identifying said given selected subset.

Claim 15

Apparatus according to claim 12 wherein said given selected subset comprises a single plasma discharge device and said means for detecting comprises an operator-held light pen, and wherein said means for sequentially generating signals comprises a programmed data processor, whereby said operator is able to indicate a position on said array to said data processor.

Claim 16

The machine method of identifying an area on a two dimensional array of plasma discharge display elements comprising A. generating a sequence of address signals corresponding to each of a covering plurality of subsets of said display elements, B. applying periodic sustain signals to said array, C. applying in sequence to at least some of said subsets a pseudo-erase signal which precedes said sustain signals in such close time relation that the restoration of display elements in an ''''on'''' condition to an ''''off'''' condition cannot proceed to completion before said sustain signals reestablish said ''''on'''' condition, and D. detecting the presence a light signal generated by the application of said pseudo-erase signal at a time associated with said application of said pseudo-erase signal to a particular subset of said display elements corresponding to said area.

Claim 17

The machine method of identifying an area on a two dimensional array of plasma discharge display elements comprising A. generating a sequence of address signals corresponding to each of a covering plurality of subsets of said display elements, B. applying periodic sustain signals to said array, C. applying in sequence to at least some of said subsets a pseudo-erase signal which precedes said sustain signals in such close time relation that the restoration of display elements in an ''''on'''' condition to an ''''off'''' condition cannot proceed to completion before said sustain signals reestablish said ''''on'''' condition, and D. detecting the presence a light signal generated by the application of said pseudo-erase signal at a time associated with said application of said pseudo-erase signal to a particular subset of said display elements corresponding to said area.

Claim 18

The method according to claim 14 further comprising the step of sending the address signal corresponding to said particular subset to a utilization device upon said detecting of said light signal.