Identification of coordinates of a region of a display device and the discharge state of that region is accomplished by means of a randomly positionable light detector and appropriate controls for selectively and non-destructively altering the discharge state of discharge sites in the device. A device offering spatial discharge transfer between discharge sites of individual cells such that if any site of a cell is in the "on state" of discharge the remaining sites of that cell will be transferred to an "on state" has its cell coordinates scanned by transferring a portion of the "on" sites of a cell to an off state to emit a localized light pulse while the cells of the device are otherwise in a non-light-emitting state. The light detector is gated only during that non-light-emitting state for successive cycles of operation in which the cell matrix is scanned with partial "turn off" signals and marks the scan area at the moment the detector responds to the light emitted by the turn off discharge. Since only a portion of a cell is erased, the remainder thereof retains its original state and that memory retaining remainder restores the erased portion to an on state of discharge, the readout by this light detector is non-destructive of the cell memory. Off state cells can be detected by inverting the discharge state of the panel and scanning cells by partial turn off signals. Increased speed of scan is achieved by actuating blocks of the cell matrix and localizing the region to be scanned in detail.
A method and an apparatus for determining coordinates in a self-shift type gas discharge panel by means of a light pen, the panel comprising a group of X electrodes connected in common at periodic intervals and a group of Y electrodes crossing said X electrodes. The Y electrodes comprise display Y electrodes and scanning Y electrodes, and detection with the light pen is performed by shifting discharge spots along the scanning Y electrodes by shift pulses applied to the X electrodes.
An improved light pen is provided for a gas display panel of the type in which an alternating polarity sustain voltage produces a succession of brief light flashes in a matrix of light emitting cells. The timing for the sustain voltage is disturbed along a selected coordinate of the matrix. The coordinate of a light pen is identified when light with this disturbed timing is detected by the pen. Circuits for disturbing the sustain voltage of an individual cell of the matrix are also disclosed.
An interactive display having an array of independently labelled display elements such as LEDs. The output of a recirculating shift register is supplied as long or short pulses which are scanned across the array. Each element in response emits either long flashes and appears lit or short flashes and appears unlit. A light-pen, when pointed at an element, detects the flash from that element, and causes a bit of the opposite sense to be introduced into the shift register in place of the recirculated bit. The display state of each element can thus be changed, both from lit to unlit or vice versa. The contents of the shift register can also be transferred to exterior equipment or supplied by it, allowing the display to act as an input/out device.
A gas discharge panel includes several pairs of column (X) electrodes arranged on a first substrate and several pairs of row (Y) electrodes arranged on a second substrate, the column and row electrodes being orthogonally oriented and in spaced, opposed relation to define therebetween a gap filled with an ionizable gas. In a first driving configuration, a corresponding electrode of each pair of (X) electrodes is selectively driven by an (X) address driver and similarly a corresponding one of each of the (Y) electrode pairs is selectively driven by a (Y) address driver. The other electrode of each of the (X) and (Y) electrode pairs then is connected in common to respective (X) and (Y) sustain voltage driver terminals. In a further embodiment, each of the (X) and (Y) electrode pairs is arranged in corresponding groups of electrode pairs, each group including a common number of such pairs. First electrodes of each pair of each group are connected to a common output terminal of an address and sustain voltage driver; thus, plural address and sustain voltage driver outputs corresponding to the plural groups are employed for each of the (X) and (Y) electrode pairs. The second electrodes of corresponding pairs of the plural groups are connected to respectively corresponding, further common output terminals of address and sustain voltage drivers; thus, a plurality of further common terminals corresponding to the number of electrode pairs in each group are provided, as to each of the (X) and (Y) electrodes. The panel as thus configured affords decoding of addressing signals applied to the common terminals by means of plasma coupling within the panel whereby the discharge point or cell defined by a desired electrode of each of the column and the row electrode pairs can be addressed selectively. A further embodiment provides shifting of the display to successive positions in either the (X) or (Y) directions.
An enhanced light pen capability is provided in plasma display panels by applying specially timed write and erase pulses in a scanning manner over the panel, the pulses being shaped and positioned relative to the normal sustain pulse sequence in such manner that a light pulse is emitted upon the resulting momentary write or erase which is detected by a light pen of standard design while avoiding any but transient modification to the state of the cell wall capacitance. The scanned write pulses advantageously assume the form of modified write pulses with shortened duration and less abrupt terminations than is usual. Dynamic keep-alive circuitry for applying location-dependent priming enhances the operating margins to permit reliable, constant-voltage write and erase signals for all cell locations.
