US 3601532 A
Abstract available in
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Description (OCR text may contain errors)
United States Patent Donald L. Bitzer;
Hiram Gene Slottow, both of Urbana, Ill. 765,950
Oct. 8, 1968 Aug. 24, 1971 University of Illinois Foundation Urbana, Ill.
 Inventors [21 Appl. No. ['22] Filed  Patented  Assignee  PLASMA DISPLAY PANEL APPARATUS HAVING VARIABLE-INTENSITY DISPLAY 8 Claims, 5 Drawing Figs.
 US. Cl l78/7.3 D, 178/75 D  Int. Cl H04n 5/66  Field of Search l78/7.3 D, 7.3 E, 7.5 D, 7.5 E; 315/169 TV, 169; 313/108 D, 108 B  References Cited UNITED STATES PATENTS 2,015,885 10/1935 Dallenbach 2,933,648 4/1960 Bentley 315/169 3,048,824 8/1962 Thompson 315/169 3,300,581 1/1967 Steinmeyer..... 178/75 D 3,311,781 3/1967 Duinker et a1. 315/169 TV Primary Examiner-Richard Murray Arsismn! Examiner-Alfred l-l. Eddleman Attorney-Merriam, Marshall, Shapiro & Klose ABSTRACT: Plasma display panel apparatus having a variable-intensity display for displaying periodically changing information, such as television video signals, the display panel apparatus including means for decoding the information signal of varying intensity levels into respective voltage levels corresponding to the respective cells in a display of the plasma displ y panel, means for entering'the respective voltage levels into corresponding cells such that the initial wall voltage of each cell corresponds to the incoming information signal intensity level to be displayed at the respective cells forming the plasma display panel; and means for discharging the cells in accordance with the initial wall voltage, such that a variableintensity display is obtained.
w CYCLING VIDEO SIGN- IP- AZNCOFND IOUNDMIOO) PLASMA DISPLAY PANEL APPARATUS HAVING VARIABLE-INTENSITY DISPLAY This invention relates to display devices, and in particular to gaseous discharge display panel apparatus having variable intensity, such apparatus being particularly adaptable for displaying periodically changing information, such as television video signals.
The present invention is directed to display apparatus utilizing a gaseous discharge panel of the type commonly known as a plasma display panel previously described in a copending application of Donald L. Bitzer, H. Gene Slottow and R. H. Willson,- entitled: Gaseous Display and Memory Apparatus, U.S. Ser. No. 613,693, filed Dec. 22, 1966, which disclosure is incorporated herein in its entirety. The display panel described in this copending application comprises a plurality of discharge cells having associated electrodes so as to form discharges of the gaseous medium within the cells and forming cell wall charges in each cell, the presence or absence of wall charges conveying the desired display information. Such a gaseous discharge panel has become known in the art as the plasma panel, and when utilized for display purposes is commonly referred to as the plasma display panel. Reference may also be had to the following publications disclosing the type of plasma panel related to the present invention, such publications being incorporated herein in their entirety:
l. Bitzer, D. L. and Slottow,'H. G. The Plasma Display PanelA Digitally Addressable Display with Inherent Memory, Proceedings of the Full Joint Computer Conference, San Francisco, California, Nov. 1966.
2. Atom, B. M., Bitzer, D. L., Slottow, H. G., and Willson,
R. H., The Plasma Display Panel-A New Device for Information Display and Storage," Proceedings of the Eighth National Symposium of the Society for Information Display, May 1967.
3. Bitzer, D. L. and Slottow, H. G. The Plasma Display Panel-A New Device for Direct View of Graphics, Conference on Emerging Concepts in Computer Graphics;
University of Illinois Nov. 1967, to be published by tioned copending application and the above-listed publica-' trons.
In accordance with the principles of the present invention, there is provided display apparatus including means for decoding an incoming signal containing varying intensity information which is to be displayed into respective voltage levels corresponding to the respective cells in a display line of the plasma display panel; means for entering the respective voltage levels into corresponding cells, such that the wall charge of each cell corresponds to the incoming signal intensity information; and means for discharging the cells in response to the wall charges thereby obtaining a variable intensity display. In one embodiment of the invention the discharging of the cells in response to the entered level of wall charge occurs with the highest intensity cells discharging first and the lowest intensity cells last during the display time, with the cells continuing to discharge in a pulsing manner after their respective initial discharges, so that the highest intensity cells will be discharged many more times than the lower intensity cells within the same display time. There is therefore provided a variable intensity display on the panel in response to the information signal. Alternatively, the means for discharging the cells in response to the entered levels of wall charge can be accomplished by using a rippled sustaining signal having mul tilevel stable states, such as described in a copending application of Donald L. Bitzer, H. Gene Slottow and William D. Petty, entitled Plasma Display Panel Apparatus Having Multi- Level Stable States for Variable Intensity," said application being filed concurrently with the present application and incorporated herein in its entirety. Since the present application is directed to the display of information which is periodically changing, the plasma display panel apparatus herein need not incorporate specific stable states. Therefore, in still another embodiment,'a modified form of the rippled sustainer can be utilized in the display apparatus of this invention.
As will be described in more detail hereinafter, the means for entering the respective voltage levels of the corresponding cells so that the wall charges of each cell correspond to the incoming information signal intensity is provided by means for sampling the incoming information signal to detect the actual intensity level at the sampling time, means for holding or clamping the corresponding signals to the voltage level corresponding to the sampled intensity, means for providing a corresponding signal whose slope represents the sampled intensity or input voltage level, and means for discharging the respective cell in response to the sloped signal, with the amount of initial wall charge and thus initial wall voltage set into the cell being a function of the slope of the exciting signal. As an alternative embodiment, there will also be described in more detail herein apparatus using a pulse strobe signal having very fast rise and decay times for setting in the respective wall charges in each cell corresponding tensity.
One type of display system to which the present invention is especially adaptable is the display of received television electrical video signals, since the normal television system displays two separate fields of one-sixtieth of a second each during a frame time of one-thirtieth of a second. New video information is thus received periodically and displayed. While the principles of this invention will be illustrated in connection with the display of television video information, it is to be understood that this is merely for purposes of setting forth an example, whereas the principles of the invention can be applied to any situation where the new information to be displayed is periodically changing at a rate sufficiently high that the time interval between the arrival of the old and the new information is less than the decay time of the old information which has been entered into the cells and displayed.
The invention will be better understood from the following detailed description thereof taken in conjunction with the accompanying drawings in which:
FIG. 1 is a chematic diagram illustrating display apparatus constructed in accordance with the principles of the present invention and including a plasma display panel, means for decoding the incoming television electrical video signal for setting in the proper wall charges in the panel cells, and sustaining signal means for discharging the bright cells many more times than the dim cells within the same respective display time;
FlG. 2 is an illustration of the wall voltages of a bright cell and of a dim cell and showing the relative numbers of discharges between the two cells during the same display time;
FIG. 3 is a. schematic diagram illustrating alternative apparatus providing a fast strobe pulse for setting in of the initial wall charges in the display panel in accordance with the intensity level of the video information to be displayed;
-FlG. 4 is a diagram illustrating the alternative manner in which the wall charges are set in by the strobe pulse so the respective wall-charges correspond to the intensity of the sampled video signal; and
FIG. 5 is a schematic diagram illustrating an alternative embodiment of the sustainer providing a sustaining signal with a waveform of changing slope, and illustrating the higher initial wall voltage and corresponding firing of a bright cell at a point of high slope, and the relatively lower initial wall voltage and corresponding firing of a ,dim cell at a point of relatively lower slope on the sustaining signal.
to the incoming signal in- Referring now to FIG. 1 there is illustrated a plasma display listed publications, and incorporating a first group of cells 12,
column electrodes 14, and row electrodes 16, the column and row electrodes intersecting at the respective cells 12; and a second set of cells 18, column electrodes 20 and row electrodes 22, with the column and row electrodes 22 intersecting at the respective cells 18. Thus, it is to be noted that the rows of cells 12 along row electrodes 16 form lines from the top of the display to the bottom of the display panel interleaved by lines formed by cells 18 along the row electrodes 22 of the second grid set. As will be described in more detail hereinafter, the cells 12 are activated line by line from the top of the display panel towards the bottom in a first display time of one-sixtieth of a second corresponding to one display field, and the display of the cells 18 is accomplished line by line in the next one-sixtieth of a second to complete the normal television frame in the standard television frame time of one-thirtieth of a second. For convenience, the complete field displayed by the cells 12 will be hereinafter termed field A, and the field displayed by the cells 18 will be termed field B. It is to be understood that the complete display panel has not been shown in FIG. 1 for convenience, however, there are 512 row electrodes and 512 column electrodes, with the field A having 256 electrodes in each of the row electrodes 16 and column electrodes 14, and field B having 256 electrodes in each of the column electrodes 20 and row electrodes 22. It is also to be noted that in accordance with the principles of the invention of the previously mentioned Bitzer, Slottow and Willson copending application, either one or both electrodes associated with a cell can be electrically insulated from the shown in FIG. 1 includes means for setting into respective cells of the plasma display panel an initial wall voltage corresponding to the intensity of the video signal, and selective firing of the cells by a sustaining signal to obtain a variable intensity in the display, the sustaining signal not being sufficient to discharge a cell not having wall charges, but being of sufficient amplitude to discharge a cell with wall charges. More specifically, in the preferred embodiment of the invention as illustrated in FIG. 1. means are provided connected to the column electrodes 14 of field A for sampling the input video signal and setting the respective wall charges in corresponding cells along the lines formed by row electrodes 16in a line-byline manner from the top of the display toward the bottom thereof in response to sequential addressing of the row electrodes in a manner similar to that in which the first field is written into a cathode-ray tube as in standard television practice. During this writing interval, the sustaining signal is applied to the field B row electrodes 22 and column electrodes 20 so as to display the information entered into field B during the previous writing time. In the next sequence, the information which has been entered into field A is displayed by means of the sustaining signal, and the video signal is sampled and the wall charges are set into the cells of field B in a line-by-line manner. Thus, a complete frame comprises two fields A and B of one-sixtieth of a second each and interlaced in the standard one-thirtieth of a second frame time.
Specifically, in FIG. 1 the received television electrical video signals containing the information to be displayed on panel 10 is applied to a series of sample and hold means 30, each of the sample and hold means comprises well known apparatus in the art for sampling input data at a preset rate for detecting the instantaneous amplitude of the input signal at the sampling time, with the output on the sampling and hold means 30 being clamped at a voltage level which represents the intensity level of the input video signal at the particular sampling time. Any number of standard circuits can be utilized for this purpose, and as an example reference may be had to Pulse Digital and Switching Waveforms" by Jacob Millman and Herbert Taub, 1965, the teachings of which are incorporated hereina A cycling clock 32'controls the sampling rate of the sample and hold means 30 and also synchronizes the sequencing of the sequential addresser 34 so that the sampled information is set into the corresponding cells line by line starting from the top line corresponding to the top row electrode 16 down to the bottom row electrode 16, which corresponds to the bottom line of the field A of the plasma display panel 10. Wallcharge-setting means 36 convert the amplitude or voltage level information at the output of the sample and hold means 30 into corresponding information which reflects the desired level of wall voltage to be set into each particular cell in the line. Various apparatus can be utilized for performing this function, one particular type of apparatus being an integrator foideveloping a sloped waveform wherein the slope of the w ve form'is a function of the voltage level input, the higher the voltage level (the greater the intensity) the higher the slope of the output signal from the integrator, and correspondingly the lower the voltage level from sample and hold means 30 (the dimmer this particular point is to be on the display) the'lower the slope of the output waveform from the in-' tegrator. This is illustrated in FIG. 1, wherein the extreme lefthand top comer cell 12 of field A is displaying information at a low level of intensity, and the extreme right-hand bottom corner cell 12 of field A is displaying information at a relatively brighter intensity. Theindicated sloped waveform output of the wall-charge-setting means 36 assumes of course that the previously described integrator circuit is provided for this function. It is to be understood that for convenience the sample and hold means 30 and the wall-charge-setting means 36 have only been illustratedfor the first and last lines, whereas each of the other electrodes 14 therebetween will be similarly connected to such apparatus. 1
The function of the wall-charge-setting means 36 is to set in a level of wall (wall voltage) which corresponds to the respective value of intensity of the information to be displayed at eachparticular cell point in the display. The slope technique which can' be utilized for this purpose is based on the fact that the amount of charge transferred to the cell walls in a discharge is a function of the slope of the exciting voltage at the time of discharge, and reference may be had to the previously mentioned copending application of Donald L. Bitzer, H. Gene Slottow and William D. Petty entitled Plasma Display Panel Having Multi-Level Stable States for Variable lntensity."
Another technique which may be utilized to obtain the initial setting of the wall charges is illustrated in F IG. 3, and uses a fast strobe pulse, the principles of which will be described in more detail hereinafter. With reference'again to FIG. 1, as the cycling clock 32 controls the sequence of events,and the input video signal containing the information which is to be displayed along the top line of the plasma display panel 10 has been sampled and the wall-charge-setting means has the corresponding information ready for entering into the cells along the first line, the sequential addresser 34 provides a suitable drive signal to the top line (top row electrode 16) so that the desired wall voltage is set in at each of the cells 12 of field A along this line. This sampling and setting procedure continues in a line-by-line manner from the top row electrode 16 to the bottomrow electrode 16, until all of the respective video information corresponding to field A has been set in on the plasma display panel 10. The actual setting in of the information is accomplished by a sum or combination of the addresser signal and the voltage level of the wall-charge-setting means combining to discharge the corresponding cell 12 with the wall voltage of the cell 12 being set at the respective level of sampled intensity from the video signal. Each cell will discharge in sequence at least once during this wall charge setting inprocedure, however, the individual discharges only occur once in the frame time of one-thirtieth of a second, and
since they last only for about 50 nanoseconds, .the visual effect During the line-by-line wall charge setting in time for field A which corresponds to a field time of about one-sixtieth of a second, field B, corresponding to the cells 18 connected with respective column electrodes 20 and row electrodes 22, is being displayed on the panel 10. The display of the wall charge information entered into the cells can be accomplished by various techniques. In the sustainer 40 shown in FIG. 1, the variable intensity for the panel is provided by a varying amplitude-sustaining signal which is supplied selectively to each of the row and column electrodes in field A and field B, during their respective times. The purpose of the sustainer apparatus 40 is to discharge the cells which are to be the brightest in the display panel more times within a corresponding period of time than the dim cells in the panel. Thus, as an example, a bright cell might discharge ten times within a reference period which would have the effect of a relatively brighter display or higher intensity than a cell which discharges only once during the same period. To develop the increasing amplitude trapezoidal-shaped waveform for the sustaining signal shown in FIG. I, a ramp generator 42 providing a slowly increasing voltage waveform varies the gain of a gain control amplifier 44, so as to increase the amplitude of a square wave input from square wave generator 46. The amplitude level of the resulting increasing amplitude sustaining signal is adjusted so that the lowest level of the sustaining signal will fire a cell having a relatively high initial wall voltage (corresponding to a high value of charge and a bright intensity) previously set into the cell; whereas the highest level of the sustaining signal has a sufficient level so as to discharge a dim cell having a very low wall voltage (corresponding to a low level of charge and a low intensity).
In order to illustrate the manner in which the variable intensity display is attained in the plasma display panel 10,
reference can be made to FIG. 2, wherein there is shown in schematic form the wall voltage for a bright cell in the upper diagram, and the wall voltage for a relatively dim cell in the lower diagram. In the upper diagram, there is illustrated the conditions for a bright cell in which an initial wall voltage has been entered corresponding to the initial wall voltage C This initial wall voltage has of course been set in for instance on field A during the time in which field B is being displayed. The wall voltage remains at the initial voltage level until the sum of the initial wall voltage and the voltage clue to the sustaining signal is greater than the firing voltage, V this occurring at reference point 50 on the wall voltage waveform. For convenience, the sustaining signal waveform is not illustrated in FIG. 2, but it is of the form shown in FIG. 1. The cell then discharges and the wall voltage rises rapidly due to the charge transfer within the cell until an opposite polarity equilibrium wall voltage of C is obtained, the cell firing each time the wall voltage and the sustaining signal combination is greater than the firing voltage. It is to be understood that for convenience, FIG. 2 illustrates only the initial discharge and the equilibrium condition, whereas in practice the equilibrium wall voltage C can be reached in several cycles.
It is so adjusted that the ramp generator 42 increases the square wave amplitude in gain control amplifier 44 from a relatively low amplitude and rising to a substantially higher amplitude during the display time. Thus, the reference point 50 on the wall voltage waveform in FIG. 2 represents the cell discharging with an input corresponding to the low amplitude of the sustaining signal. The cell continues to discharge during each half cycle of the sustaining signal throughout the display time, In the lower diagram of FIG. 2, it can be schematically seen that the wall voltage of the dim cells continues at the initial lower wall voltage level, C until such time as the sum of the increasing amplitude sustaining signal and the initial wall voltage, C, is greater than the firing voltage, such as at reference point 52 on the diagram. Once the cell fires, it will continue to periodically fire until the end of the display time. However, it must be noted that for the reference display period shown in FIG. 2, the bright cell has discharged nine times, whereas the relatively dimmer cell is only discharged three times, the effect being that a viewer of the display panel 10 would view the firing of the bright cell as a relatively brighter spot on the display panel as compared to the spot on the display panel corresponding to the dim cell.
As explained previously, the rising amplitude trapezoidal sustaining signal is applied simultaneously to all of the cells connected to either field A or field B so that the respective field is displayed at one time during the display period of approximately one-sixtieth of a second.
Referring now to FIG. 3, there is illustrated an alternative embodiment of the present invention incorporating alternative apparatus for setting in of the wall voltages or wall charges in the respective fields corresponding to the sampled amplitude of the video signal. In the illustration of FIG. 3 it is to be understood that the panel 10 is constructed in a similar manner as the panel 10 of FIG. 1, that is, having the two sets of electrode grids, one associated with field A, and the other associated with field B. Each of the column electrodes 14 is connected to a resistor-capacitor element 60, the input of which is connected to the sampled voltage level corresponding to the video intensity at the sampled time. Thus, each of the capacitors 62 is charged to a level corresponding to the required video intensity for display on the panel 10.
A fast strobe pulse generator 64 or a plurality thereof is connected to the row electrodes 16. The pulse generator 64 provides a fast rise time and fast decay time strobe signal for setting in the wall charges into each line in a line-byline manner from the top of panel 10 toward the bottom. lfa fastpulse-exciting waveform is used to supply the discharge for the cells, that is, a pulse ofthe type which rises quickly beyond the firing potential, but which also decays quickly, this enables the cell wall voltage to very quickly rise to the voltage level connected to the column electrodes 14 and remain at that voltage level. It is believed that the fast strobe pulse can provide this result since it insures only a slow transfer of charge to the cell walls so that the cell wall voltage only rises to the voltage level of the sampled video.
As a schematic illustration, reference may be had to FIG. 4, wherein there is illustrated a first waveform labeled V, which represents the intensity of the sampled video for RC circuit 60. With the objective in mind of transferring this voltage level into a corresponding wall voltage for the associated cell in the display, a strobe pulse 66 from pulse generator 64 is applied to the first line of row electrodes 16 for entering the proper wall voltage into each cell associated with the first row electrode 16 and each of the intersecting column electrodes 14. The wall voltage, V due to the wall charge remains at a reference zero level until the sum of the strobe pulse and the sampled voltage, V, is greater than the firing voltage V,, at which time the wall voltage rises rapidly due to the transfer of charge to a value equal to the amplitude of the sampled video voltage V,. Because of the rapid decay of strobe pulse 66, the wall voltage remains at the amplitude of the sampled video so that the sampled video signal can thereafter be decayed to the zero reference level. Assuming that the strobe pulse 66 has been applied to the top row electrode 16, all of the cells 12 along this first line would have a wall voltage corresponding to the intensity of the sampled video associated with the respective column electrodes 14. Under control of the cycling clock 32, which controls the sampling rate, the respective strobe pulses are supplied line by line in sequence to each of the row electrodes 16 from the top to the bottom of display 10 as the sampled voltage corresponding to the video intensity is coupled to the RC elements 60 for each cell position in the panel. All of this above-described procedure is taking place of course, during the setting in of the proper wall charges into one of the fields, such as field A, while the cells associated with field B are being coupled to the sustaining signal for display. Thus, during the next one-sixtieth of a second field time, a suitable sustaining signal is applied between column electrodes 14 and the row electrodes 16 for simultaneouslydisplaying the information entered into the field A, while the information connected with the next field B which is to be displayed is set into the B field cells. Displaying of the cells which have the wall voltages set in by the fast strobe technique of FIG. 3 can be displayed in a manner similar to that previously described and as shown in FIG. 1, by utilizing similar apparatus for providing a rising amplitude sustaining signal. It is to be understood, of
course, that similar-shaped sustaining signals can be utilized, such as an increasing amplitude sawtooth or an increasing amplitude sinusoidal waveform, or truncated versions of these waveforms; or a constant amplitude sinusoidal square wave shaped or sawtooth superimposed on a ramp.
Referring now to FIG. 5, there is illustrated another altemative embodiment for providing the sustaining signal which will drive the cells having the suitable wall charges previously set in to provide a variable intensity display on the panel 10. In this connection, the sustainer apparatus 70 provides a waveform output having a variable slope as shown in FIG. 5. As indicated in a copending application of D. L. Bitzer, H. G. Slottow and W. D. Petty, which has been previously referred to as being filed concurrently with this application and the disclosure of which is incorporated herein, there is described a multilevel intensity technique wherein the variation in intensity is a function of charge and slope. For instance, in referring to FIG. 5, a cell having an initial charge C and firing at a reference point 72 on the sustaining waveform would exhibit a higher intensity than a cell having an initial wall charge corresponding to a voltage level C and firing at a time represented by the reference point 74 on the sustaining signal waveform. It is believed that this is due to the fact that because the initial wall charge (voltage) C is larger than the initial wall charge (voltage) C the reference point 72 is at a higher slope point than the reference point 74, and therefore the discharge is more intense.
The previously mentioned application of Bitzer, Slottow and Petty discloses a rippled sustaining signal which contains alternate stable and unstable regions so that the firing of cells in the described panel will be in accordance with several discrete stable states. Such a waveform can be used with the present apparatus, however, if desired, a modified form of the stable sustainer can be utilized. Thus, the nonrippled sustaining signal and apparatus shown in FIG. 5 is sufficient for the present application since the television display on panel is not of a permanent type, but rather is replaced after each frame time, namely after each one-thirtieth ofa second. Thus, while the nonrippled sustaining waveform of FIG. 5 would not discharge the cells 12 and 18 in panel 10 of FIG. 1 to form a permanent display, such cells would be suitably discharged by such a sustaining signal and the information properly displayed for the length of time required in connection with the television example of the present invention and any similar display system where the information is periodically changed at relatively fast rates. The nonrippled sustaining signal waveform can be provided by a suitably wave-shaping network 76 which receives a square wave input from a convenient square wave generator and transforms such a square wave into the desired nonrippled waveform. In operation, the nonrippled sustaining signal is applied to the row and column electrodes associated with one of the fields during the time in which such field is to be displayed, the wall voltages ofa bright and a dim cell being shown in FIG. 5 for illustration.
The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom as modifications will be obvious to those skilled in the art.
What is claimed is:
1. In gaseous pulsing discharge display panel apparatus, including a gaseous medium in said panel, and display points defined by associated paired electrodes arranged in a grid of crossing paired row and column electrodes, said display points including gaseous discharge cells having cell walls for forming and out of said panel by manipulating wall charges associated with the selective pulsing discharge of the gaseous medium at the display points by cou ling suitable exciting signals to the associate paired electro es, the combination further including means for sequentially displaying video signal information line by line, each line associated with a respective row, from one row end to the other row end of the panel, said means comprising:
decoding means for decoding said video signal information into respective voltage levels corresponding to associated display points in a line; wall-charge-setting means for entering said respective voltage levels into said corresponding display points such that the respective wall charges at each display point corresponds to said incoming video signal level; and
sequential discharge means for sequentially discharging said gaseous medium at the display points line by line in response to the associated wall charges entered at each display point to obtain a variable-intensity display of said video information. 2. Display panel apparatus as claimed in claim 1, wherein said sequential discharge means includes means for discharging the display points as a function of the respective amount of wall charge entered at each display point.
3. Display panel apparatus as claimed in claim 2, wherein the gaseous medium at the display points having the highest amount of wall charge are discharged first and repetitively discharged more times than the gaseous medium at display points having the lowest amount of wall charge which are discharged last within a prescribed display period, the relative amount of repetitive discharging of said gaseous medium at the display points within the display period providing a variable-intensity display.
4. Display panel apparatus as claimed in claim 3, wherein said sequential discharging means includes an increasing amplitude sustaining signal.
5. Display panel apparatus as claimed in claim 1, wherein said decoding means comprises sample and hold means for sampling the video information at a rate commensurate with the entering of said information line by line into said panel, and providing a discrete voltage level corresponding to the sampled level of video information.
6. Display panel apparatus as claimed in claim 5, wherein said wall-charge-setting means comprises means for transforming said sampled voltage level from said decoding means into corresponding sloped signals, the amount of said slope of each signal being proportional to the sampled voltage level.
7. Display panel apparatus as claimed in claim 1, including: a second grid ofcrossing row and column electrodes; said first grid associated with display field (A), and said second grid associated with display field (B);
the combination of said display fields (A) and (B) forming a complete display frame;
said wall-charge-setting means entering the respective voltage levels associated with the video information of display field (A) into one of said grids; and
said sequential discharge means sequentially discharging the gaseous medium at the display points associated with display field (B) in the other ofsaid grids.
8; Display panel apparatus as claimed in claim 7, wherein the video information is entered into display field (A) simultaneously with the displaying of display field (B), and thereafter the video information is entered into field (B) while the previously entered video information in display field (A) is displayed.