|Publication number||US3781600 A|
|Publication date||Dec 25, 1973|
|Filing date||May 22, 1972|
|Priority date||May 22, 1972|
|Also published as||CA975072A, CA975072A1|
|Publication number||US 3781600 A, US 3781600A, US-A-3781600, US3781600 A, US3781600A|
|Inventors||W Coleman, W Kessler|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (22), Classifications (12)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent 11 1 Coleman et al.
[111 emos) 5] Dec. 25, 1973 PLASMA CHARGE TRANSFER DEVICE  Inventors: William Earl Coleman; Clarence William Kessler, both of Dayton, Ohio  Assignee: The National Cash Register Company, Dayton, Ohio  Filed: May 22, 1972 ] Appl. No.: 255,547
 US. Cl. 315/169 TV, 313/188, 313/220,
340/336  Int. Cl. H05b 37/00  Field of Search 315/169 R, 169 TV;
235/92 SH; 340/173 PL, 324 M, 336, 339; 313/188, 201, 220
 References Cited UNITED STATES PATENTS 2,869,036 1/1959 Engelbart 313/201 X 3,407,341 10/l968 Franks 317/234 571 I 1 ABSTRACT A plasma charge transfer device utilizable as a shift register memory and/or display utilizing ionizable gas contained in an enclosure with a plurality of individual transfer electrodes covered with a dielectric material aligned parallel on opposite internal walls of the enclosure, but offset one another, throughout its length. This plasma charge transfer device utilizes: an ionizable gas; an input electrode which can be either directly or capacitively coupled to the gas; capacitively coupling to the gas of oppositely offset transfer electrodes; and the wall voltage which results when charge is transferred as the result of a gaseous discharge occurring between two oppositely offset transfer electrodes the additive effect of this wall voltage to an applied voltage such that a gaseous discharge occurs between two transfer electrodes if charge was transferred to one of the electrodes during a previous discharge whereas a gaseous discharge will not occur with this same applied voltage between any two oppositely offset electrodes which do not have the proper charge trapped on the wall of at least one of the electrode pairs. Upon the proper application of command signals, a gaseous discharge can be successively transferred between subsequent oppositely offset transfer electrode pair, one electrode position at a time, or continuously shifted throughout the entire length of the plasma charge transfer device, or may be held stationary at any oppositely offset transfer electrode pair position within the device. When the plasma charge transfer device is used as a shift register memory, information to be retrieved at the register output may be optically or electronically recognized and erased.
20 Claims, 22 Drawing Figures [Riff 2 PATENTEUUECZSJIGYS 3.781.600
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SHEET 09 HF 13 PATENTED UEEZ 5 [975 MA A 1 r 41 /1 1 1 1 1 1 1 1 1 J v u as E A 1 PLASMA CHARGE TRANSFER DEVICE BACKGROUND OF THE INVENTION 1. Field of Invention This invention utilizes the plasma charge transfer phenomena to form a shift register memory and/or display.
2. Description of the Prior Art The possibility of using gaseous discharge glow transfer devices has long been recognized and there has been many attempts to develop practical versions thereof. At the present time one such typical prior art device is a DC counting tube wherein a single glow discharge is stepped from one discrete position to another in response to applied direct current input potential. This device does not sustain or simultaneously shift a plurality of glow discharges as would be required for the operation of such devices as shift register memory or a display device with inherent memory.
Another typical prior art device developed for special utilization such as a shifting register in a computer, applied a high frequency burst pulse to a pair of capacitively coupled electrodes which caused a glow in the gas there-between and which partially ionized the gas between a second pair of electrodes due to its proximity to the glow discharge. Thus when the burst pulse is removed from the first pair of electrodes, and applied to the second pair in a time shorter than that time for the partial ionization of the gas between the second pair of electrodes to die out, the glow is transferred to the second pair of electrodes. Thus when a so-called sustaining potential, i.e., burst of AC, is applied to the primed cell formed by the second electrodes, a glow is caused in this localized area whereas if the priming did not take place, the application of the same potential would not cause the localized glow. Therefor, utilizing the priming principle, upon the proper application of a burst potential to successive cells, the glow discharge is successively stepped or advanced from input to output. This device is limited in its utility because it depends on the principle of priming and upon necessary use of high frequency burst potentials; Another limitation, not apparent from this brief description, is the fact that the electrodes, being external of the gaseous envelope, poorly couple the electrodes and the gas, severely limiting the light output if the device is to be used as a display.
A third typical prior art device, operating principally as a display device utilizes still a third electrode and what could be termed a continous cell adjacent the shifting cells and which utilized the priming principle through apertures in the one set of electrodes adjacent the second cell to initiate a glow discharge in this second cell. This device is simply a combination of the counting technique plus the priming technique and, as such, when utilized as a display device, has no inherent memory.
It should be noted that the first two described devices representing typical prior art are more fully disclosed and described in the four US. Pat. Nos. 2,847,615; 2,923,853; 2,937,317 and 2,984,765 which issued to DC. Engelbart and the third device is described in Brittween adjacent cells and, as such, has many advantages as will become apparent from the detailed description hereinafter. It will also become clear from the following description that the device has a different mode of operation.
SUMMARY OF THE INVENTION In the physical construction of the plasma charge transfer device, an ionizable gas is contained in an enclosure having a plurality of transfer electrodes aligned parallel on opposite inside walls of the enclosure; the transfer electrodes being covered with a dielectric material and being offset from one another throughout its length. The input is serially addressed by applying electrical pulses to an input electrode which can be either directly (uncoated) or capacitively (coated with a dielectric material) coupled to the gas and forming, with the first or nearest of the offset transfer electrodes, the first gaseous cell within the device. When the potential of the electrodes is such that the potential difference between it and the input electrode is above the threshold, V, V, (where V, is the potential difference between the input and first electrode and V, is the firing voltage) a gaseous discharge occurs. This discharge between the input and the first electrode is quickly extinguished because the trapped charge on the first elec- I trode gives rise to a voltage opposing the initially applied voltage. Next a voltage V, is applied between the first and second electrodes. The presence of the trapped charge on the first electrode which resulted when the discharge was initiated between the input and the first electrode gives rise to a voltage V between the first and second electrodes. When V, is applied to the first and second electrodes, V adds algebraically such that the total voltage between the two is greater than the firing voltage V, thus a gaseous discharge oc curs. Stated mathematically: V, V V On the other hand, if no discharge add occurred between the input electrode and the first electrode, no trapped charge would be present on the first electrode. Then, when V, is applied between the first and second electrode, no gaseous discharge wil occur. Stated mathematically: V, V,. Utilizing the trapped charge on the electrode wall of a previously discharged cell, the trapped charge initiated by the input pulse can be transferred along the length of the plasma charged transfer device.
Any input serially addressed into the plasma charged transfer device can be held at any time before there is a serial transfer to the ouput by applying an alternating potential between any two oppositely adjacent electrode pairs.
The present invention may be utilized either as a shift register or a display device. When used as a shift register, the input pulse represents a bit of information which is transferred along the device by the above described charge transfer mechanism. An absence of an input pulse will be recognized as a digital 0 an the presence of a input pulse will be recognized as a digital l as the information is clocked into the register and transferred out. When used as a shift register as such the information transfer occurs throughout the length of the shift register until it is coupled to an output electrode where the information may be optically or electronically recognized. Once recognized, the information is erased by an erase electrode which is DC coupled to the ionizable gas.
Since light is a by-product of this plasma charge transfer device, this device can be used as a display where the input pulse is transferred serially as described above. The capability of holding information for any length of time by applying alternating potential between any two oppositely adjacent electrode pairs gives the display a memory, and in a manner identical with the shift register technique, the absence of an input pulse forms a space on the dis- ,play whereas an input pulse will represent a lighted From the foregoing, it can be seen that one major advantage of this invention is its flexibility. It is operable as a memory register, a recirculating register or a display device and either as a static or a dynamic device. When operated in parallel with similar devices, a typical display can be ade up so that one character line comprises seven parallel devices with each human readable character being five cells wide thereby forming a 7 X matrix. The number of characters in a line can be expanded indefinitely without increasing the address electronic cost.
Another major advantage of this invention is that by placing the electrodes on the inner walls of the enclosure and coating them with a dielectric material, the capacitance formed by the walls of the dielectric material between the electrode and the gas is many times greater than the capacitance formed by the gas itself with the walls of the dielectric material. Mathematically stated as: C C, where C represents the capacitance of the dielectric as a dielectric and the gas as a dielectric. This ratio of C to C provides more efficient coupling thus reducing the input potential required and increasing the amount of charge transferred during one gas discharge. Since light output is proportional to the amount of charge transferred during one discharge, light output efficiency is increased by increasing C Another advantage is the use of a selected dielectric material having high secondary electron emission due to photons formed by the discharged gas in the cell. This reduces the charging time in the time required for the coupling capacitors to be charged when a gas discharge occurs between two electrodes thereby increasing the charge transfer rate.
Since light output is directly proportional to excitation frequency, a short charging time of the coupling capacitor C allows higher operating frequency and therefore higher light output.
Other advantages of this invention over the'prior art will become obvious to those skilled in the art from a reading of the following description.
A BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view of the plasma charge transfer device with amplifier drivers;
FIG. 1a is a partial schematic cross-sectional drawing of the device showing an AC input;
FIG. 2 is a schematic cross-sectional drawing of the device showing the direction of transfer of gaseous discharge of each next opposite electrode, the electrode drive lines and a photodetector and an electronic detector in the output;
FIG. 3 is a schematic cross-sectional drawing of the device during a hold mode of operation;
FIG. 4 is a simplified equivalent circuit of device showing a DC connected input, the gas capacity designated as C and the dielectric electrode coating capacity designated as C liresle r s;
FIG. 4a is a partial circuit similar to FIG. 4 but showing an AC input;
FIG. 5 is a timing diagram of the waveform representations for a load and hold sequence using a DC input and with an alternative AC input in dashed lines since if an AC input is employed, the input voltage must be higher;
FIGS. 6a, b, c & d are detailed reference charts showing the charge transfer through the device in relation to the electrodes and to time;
FIG. 7 is an exploded perspective view showing the device in its practical version illustrating to advantage the manner in which the electrodes and cells are formed by sandwiching the various elements together;
FIG. 8 is a cross-sectional view of a portion of FIG. 7 looking in the direction of the arrows;
FIG. 9 is a cross-sectional view of a portion of the device shown in FIG. 7 looking in the direction of the arrows;
FIG. 10 is a cross-sectional view of a portion of the device shown in FIG. 7 looking in the direction of the arrows;
FIG. 11 is an exploded view of to that shown in FIG. 7 but further showing the keep- FIGS. 12 and 12.. are rat. Vanni. device is which one portion of the enclosure is laid open in an 99, sanda slitya shw ns FIG. 13 is a fragmented plan to advantage the keep-alive input electrodes and the transfer channel;
In connection witlithe foregoing drawins and before describing the embodiments of the invention in detail, a brief explanation is in order. FIGS. 1 through 6 are a schematic illustration of a preferred embodiment of a plasma charge transfer device as a plasma shift register memory and in the following description will be referred to as such solely for the purpose of explaining the invention and its operation whereas FIGS. 7 through 16 are more nearly illustrative of the practical version for a commerical light display and as such will be described. Nonetheless, as a practical matter the shift register memory shown and described in FIGS. 1 through 6 could operate equally as well as a display device and conversely the display device shown in FIGS. 7 through 16 could be operated as a shift register. It being significant to note that where such terminology as bits of information" as used in connection with the description of the shift register could be easily replaced and thought of as lighted cells or dark areas in the light display. The only difference in the described devices is the manner in which the information is read.
from or utilized in the device; the bits of information being sensed in the region of the erase electrode as the shift register memory is unloaded or read whereas from the display device it is not necessary to sense bits of information at the erase. Conversely, it is not necessary to visually observe bits of information being held in a shift register whereas in the display that is a prerequisite.
DESCRIPTION OF-A PREFERREDv EMBODIMENT OF THE PLASMA CHARGETRANSFER DEVICE AS A SHIFT REGISTER -MEMORY Referring now to'FIGS. l and .2, the gaseous .discharge plasma shift register memory 10, utilizingthe teachings of the present invention, is shown schematically as a six bit shiftrregister.Shift-register comprises enclosure or substrate 12 of any suitabledielectric'material, such as clearglass, defining a channel 13 containing an ionizable gas, such as neon and nitrogen, at a predetermined pressure. A- plurality of electrodes '"14 (which may transparent, if .desired) are located on the wall of the. enclosure or substrate opposite one another in parallel alignment but laterally offset in a relationship to subject .theeionizablegas to an electric field when a suitable potential is applied to any two opposing electrodes. In the embodiment shown, all transfer electrodes are located on the inside wall 16 and coated with a dielectric layer 18 (except the inputelectrode i and the erase electrode e). The ionizable gas between any two opposing external'electrodes effectively form a gas cell dischargeable when subject to a suitable potential, and byalternating the applied'potential V, step by step along the length of the register, thegaseous'discharge is transferred successively in cells through the length of the register.
The shift register utilizes an ionizablegas, an input electrode i which can be either directly or capacitively coupled to the gas, .capacitively coupling to the gas of oppositely ofiset electrodes, the wallvoltage which'results when charge istransferredas the result of a gaseous discharge occurring between two oppositely offset electrodes, the additive effect of this wall voltage to an applied voltage suchthata gaseous discharge occurs between two oppositely offset electrodes if charge was transferred to one of. the electrodes duringaprevious discharge whereas a gaseous discharge will not occur with this same applied voltage between any two oppositely offset electrodes which do not have charge trapped on the wall of at least one of the electrode pairs.
As schematically shown in FIG. 3, the electrodes utilize the immediate area-of thedielectric and the immediately adjacent internal wallsurface of the dielectric as a first capacitivecoupling C of each electrode with the gas. In turn, the gas itself forms a dielectric for. each of the oppositely adjacent internal glass wall surfaces forming capacitance C Utilizing these capacitive properties C and C, andwith the application of a suitable applied voltage, a gaseous discharge is located between the two adjacently opposite electrodes causing a charge to be formedon the positive electrode and on the negative electrode, respectively, to produce the wall charge or, as it is sometimes called, a trapped charge. The voltage attributed to the wall charge has a polarity opposite to the applied voltage which initiated the discharge andupon reversal of the applied voltage after discharge,the applied voltage and wall charge are additive thereby causing another gaseous discharge.
The charging time, defined as'the e'lapsedtime after initiation of a gaseous discharge in a plasma cell until the electrode walls are charged to 90 percent of their final value, is primarily a function of the secondary electron emission coefficient y. When secondary electrons are emitted from the cathode due to bombardment of the cathode by positive ions the chargingtime is of the order of several microseconds. Howeer, when secondary electrons are emitted from the cathode due to bombardment of the cathode by photons, the charging time is usually less than 1 microsecond and can be as small as 0.1 microsecond depending on the physical conditions. Therefore, to achieve submicrosecond charging times the surface of the cell walls must efficiently emit electrons when bombarded by photons. This could be achieved by adding a small portion of molecular gas to the ionizable gas or by using a dielectric material (which covers the electrodes) that has a high photo-emissive efficiency.
'The maximum speed of operation of the plasma shift register will depend on charging time. The smaller the charging time the faster the operational (shifting) speed of the plasma shift register.
The use of this phenomena to form the present shift register will become apparent in the more detailed explanation hereinafter.
In this embodiment of the invention every other electrode on each side of the enclosure is connected in common through four electrode line groups identified as 1, 2, 3, and 4 through a suitable switch (not shown); said line corresponding in number to the position of the electrode in sequence along the register.
As hereinabove mentioned, the shift register 10 is provided with an input electrode i in direct coupled relationship with the encapsulated ionizable gas, i.e., not coated with the dielectric material 18. However,- this input electrode i may be capacitatively coupled to the gas in the same manner as the other electrodes 1, 2, 3, and 4, although a different input voltage is required. This is shown in FIG. 1a.
FIGS. 1 and 2 also show a keep-alive cell formed by a pair of electrodes 6 and 7 capacitively coupled to the gas and connected to a source 20 of alternating pulse voltage of sufficient magnitude to ionize the gas within the cell to insure sufficient ionized particles always available at the first cell formed by input electrode i and first electrode.
At the end of the register is also provided an erase electrode e, also directly coupled to the encapsulated gas to clear and transfer any bit information at the last load position in the register, and means are provided in the form of aphotodetector 22 for detecting the discharge of the last gas cell as a means of reading the information out in the register. The alternative electronic read out means 24 is also shown in FIG. 2 in theform of an induction coil 26 for sensing the current on the line of erase electrode e as an indication of the information at the end of the shift register.
Reference is now made to FIGS. 5 and 6a-d for an explanation of the shifting of bit information along the shift register 10 when the register is in the shifting mode and for an explanation of the holding ability when the register is in a hold mode and is performing as a static register.
FIG. 5 is a timing diagram showing the voltage pulse sequence applied to the common electrode lines 1, 2, 3, and 4 and the input electrode to load and hold bits of information onto the shift register memory shown in FIGS. 1 and 2. Increments of time T,T and T, correspond to the load operation and each is divided into 9 sub-increments in order to depict the exact timing of the voltage pulses. Increments of time T T and Ty correspond to the hold operation and each is divided into 4 sub-increments in order to depict the exact timing of the voltage pulse for this sequence. In a typical case, T, would be 40 microseconds with the time between and l of 2.5 microseconds; between 1 and 2 of 2.5 microseconds; between 2 and 3 of microseconds; 3 and 4 of 5 microseconds; 4 and 5 of 5 microseconds; 5 and 6 of 5 microseconds; 6 and 7 of 5 microseconds; 7 and 8 of 5 microseconds; 8 and 9 of 5 micro seconds; and T would be microseconds with the time between 0 and 1 of 5 microseconds, etc.
In FIGS. 6a-d times T, with its 9 increments, represented along the left hand side of the figures, with the electrodes again represented simply by the numerals l, 2, 3, and 4. The solid segmented horizontal lines represent the internal glass wall but identified by its corresponding electrode wall number of the cell with the wall charge being represented by the conventional positive and negative symbols. In these figures, V,- represents the input voltage pulse; V, represents the voltage sufficient to cause discharge of the gas in the cells; V, is the clocking voltage applied to the four common groups of electrodes; V represents a potential due to the trapped wall charge; and, for the sake of clarity, the actual trapped charge on each internal wall representing the portion of charge trapped on that coupling capactior will be referred to as 0, which charge, as stated aforesaid, does not appear until after the gaseous discharge in any particular cell.
Again, input voltage V, is always greater than the discharge voltage, V,, and the sustaining voltage, V,, is always less than V, and will not be sufficient to cause discharge unless combined with V,,.. The voltage, gas compositions, and pressure utilized to operate this shift register according to the teachings of this invention using the DC input, by way of example only, are V, 200v, V; z 180v, and V, 16011. The enclosure contains a gas mixture of 9 3.7 neon a rid the" ifiareamai "ga additive may be a combination of 0.02 nitrogen and 0.01 argon and a 200 millimeters of mercury.
Turning now to FIG. 5, the timing diagram, at time T, the input electrode i is switched from zero volts to V, but no discharge takes place in cell 1 since the potential difference between input electrode i and the first electrode 1 is not sufficiently high (V, V, V,); electrode 1 being at V,. At time T all electrodes 1 are driven to zero voltage while the input electrode is held at V, so that V,, the discharge voltage, is exceeded (V, V,) causing a gaseous discharge between be input electrode and the electrode of the first cell of electrode 1. This discharge, however, is extinguished in a very short period of time (0.2 microseconds to 0.5 microseconds) and the wall charge Qtc is trapped on the wall of the dielectric covering the first electrode 1. Since the input electrode is directly coupled to the gas discharge, no charge is trapped on the input electrode. This is shown in FIG. 6a at T,., and at T,.,, where the large arrow represents the discharge direction and these positive and. negative symbols represent the wall charges 0, respectively.
No charge is deposited on the walls adjacent any of the other electrodes since there has been no gaseous discharge between them even though all other electrodes l were switched from V, to zero.
At time 'I,..,, all electrodes 1 are returned to V, while the input electrode is maintained at V,-so there will be no backfiring of cell 1 to input electrode 1.
At time T, all electrodes 2 are driven to zero volts while all electrodes 1, 3 and 4 are held at V, which creates a potential difference between all electrodes 1 and 2 and all electrodes 2 and 3. The additive effect of the -Q, on the wall adjacent electrode 1 as explained in connection with time T, gives rise to a voltage V which adds to the applied voltage between the first electrodes 1 and 2. Since V,,. V, V,, the gas discharge between the electrodes 1 and 2 of cell 2 causing a reversal in polarity of the wall charge adjacent the electrode 1 and a positive charge on the wall adjacent the electrode 2. Note no discharge occurs at any other cell because of the lack of sufficient potential difference therebetween without any Q, thereat and that input electrode i is no longer held at V,.
At time T, all electrodes 2 are driven to V, leaving the trapped charge in cell 2 as it was immediately after discharge at time T, Although QM is not exactly the same, it is almost the same to a first order approximation since C, C,,.
At time T all electrodes 3 are driven to zero while all electrodes 1, 2 and 4 are held at V, creating a potential difference between the electrodes 2 and 3 which together with the potential difference caused by the trapped charge cause cell 3 to fire reversing the polarity of the trapped charge on wall adjacent the electrode 2 of cell 2 and creating a positive charge on the wall adjacent the electrode 3 of cell 2.
At time T, all electrodes 3 are again driven to V, leaving the trapped charge in cell 3 as it was immediately after discharge in T,
At time T,' the electrode 4 are driven to zero which together with the trapped charge cause a discharge in cell 4 between the electrodes 3 and 4 and it again causes a reversal in polarity of the charges adjacent the electrode 3 and a positive charge adjacent electrode 4 of cell 3.
At time T, again all electrodes are driven to V, leaving the trapped charge as it was at the end of the discharge which occurred at T,
At time T in FIG. 5 it is to be noted that the input electrode i is not driven to V, and as a consequence at times T,, and T,, even though all electrodes 1 are driven to zero, there is no discharge in cell 1 and as a consequence there is no trapped charge to be transferred through the initial four cells. However, since all four electrodes are coupled together, the first bit is transferred through the second bit position of the register in the same manner and using the wall charge to cause the transfer as it was explained in connection with the original transfer of the bit through the load position.
The foregoing operation can continue until the initial bit reaches the end of the register as shown in FIGS. 5 and 6b at times T,,, through T,,,
However, at any time during the sequential operation when a bit has arrived in a load position, the register can be placed in a hold mode so that the bits are not transferred but held at the load position thus forming a static register. This is accomplished as shown between timing diagrams, FIG. 5 and FIG. 6d, typically in the T sequence and schematically shown in FIG. 3. In this sequence at T, all electrodes 3 are driven to zero while all electrodes 1, 2 and 4 are held in V,. This causes a gaseous discharge between the cells having a 1's bit which is shown in FIG. 6c in the first and third load position of the 3 bit register. Again, because of the discharge, the wall cell charge is reversed, and, at time T, when all electrodes 3 are driven to V,, there is no discharge and thecapacitive charge of the cell wall remains the same.
At time T all electrodes 4 are driven to zero while all electrodes 1, 2 and 3 are held at V, creating a potential difference which together with the wall cell charges 0,, adding to the applied voltage causes a firing and hence a reversal of the wall charge. At time T,,, all electrodes 4 are returned to V, while all electrodes 3 are held at V, so that nothing takes place at any cell. This sequence can be repeated as often as desired and is shown by the sequence of discharges T through T,, in FIG. 5d and so on T,,, through T until such time as the electrodes 1, 2, 3, and 4 are operated in sequence as explainedin T,, T T,,,, etc.
When the register is again put in its shifting mode, when a bit of information, a digital 1 or a digital 0, reaches the last load position, the discharge of this last cell may be read either optically by a conventional photo-detector 22 (FIG. 2) which produces a signal output to be read by any suitable device, or can be read directly electronically by sensing the charge transferred from the last electrode position to the erase electrode by induction coil 26. The voltage pulse sequence applied to the erase electrode e will be identical to that appliced to electrodes 1.
The voltage pulse sequence and a pictorial representation of the charge transfer condition is shown for a portion of the load mode when the input electrode is capacitively coupled is shown in FIG. 6d. At T, a discharge occurs between the input and the first electrode 1'. V, in this case is higher than the DC case therefore. the charge deposited on the wall of the dielectric covering the input and 1 is depicted as larger than the DC case. At T the charge on the input remains trapped there since the input is capacitively coupled. At time T the input electrode goes back to 0 and all electrodes 2 are driven to 0. A voltage greater than V, exists between the input and the first electrode 1 and the first electrode 1 and the first electrode 2 and a gaseous discharge occurs between both of these pairs resulting in the charge condition shown. At T all electrodes 1 are driven back to V, leaving the charge condition shdwn in T, .;At this point, the input is in a condition where it can properly fire (gaseous discharge) at the next T,, time if the input is at V, at that timeor not fire if the input is at 0 at that time.
While the foregoing has been described in connection with a six bit register, the register can be of any bit length desired, can be made recirculting, and while only one register is shown, obviously a number of registers can be operated parallel utilizing the same pulse amplifiers and, it is foreseeable, depending upon the gas used, that information may be transferred through the length of the register at frequencies of typically 25 KHz. Practical limits on the transfer rate are approximately 125 KHz on the high end to 0 Hz on the low end.
DESCRIPTION OF A PREFERRED EMBODIMENT OF THE PLASMA CHARGE TRANSFER DEVICE AS A PLASMA DISCHARGE DISPLAY DEVICE Referring now to FIGS. 7through 16 the items having the same function as an item in FIGS. 1-6, will be given the same reference numeral except with an exponent. Thus, for example, the plasma discharge display device is indicated generally at 10 corresponds to the gaseous discharge shift register memory 10 of FIGS. 1-4.
In FIGS. 7-10 the display device 10' comprises an enclosure formed of two flat substrates 12'. For conductor 14' are located on the inside wall 16 of each of the flat substrates along the outer edges of the sub-- strates forming a continuous conductor with a plurality of interstices or electrodes 1-4' extending laterally. Two sheets of dielectric material 18' for coating the electrodes overlay the instices. In FIG. 7 the top sheet of dielectric material is shown separately for the purposes of clarity. Sandwiched between the two layers of dielectric material 18' are 2 flat sheets of opaque glass cavity forming material 12" together with the substrate 12 and the dielectric coating material 18' form seven channels 12. As shown in FIG. 7 and more clearly in FIGS. 8 and 9, the two parts of the display formed by the glass substrate 12 with the electrodes thereon the dielectric material 18 and one sheet of the opaque glass cavity material 12" are offset lengthwise one to another to conveniently expose the ends of the conductors 1'4. In addition, this offset also exposes conveniently the seven input electrodes i i, and erase electrode e, 2'
As clearly depicted in FIGS. 8-10, the channels each operate in a manner identical to that described in connection with the operation of the device shown in FIGS. 1 and 2 but in this instance a discharging cell forms a light emitting dot as a bit of information and the timing for the load mode and the hold mode is exactly as shown in FIG. 5.
FIG. 11 shows one-half of a seven channel display device similar to that described in FIGS. 7-10, and FIGS. 12a and 12b show both pairs forming the seven channels laid in and open sandwich configuration to clearly show the additional seven keep-alive electrodes, 6' and 7' which function in this display identically as described in connection with the device shown in FIGS. 1 and 2. These keep-alive electrodes like the other electrodes capacitively coupled to the gas in each of the channels by a coating of dielectric material 18' formed by two sheets of such material when the two sections are sandwiched together such as described in connection with FIGS. 7-10.
For the sake of clarity only, FIG. 13 is an enlarged fragmentary portion showing some of the channels and electrodes formed in the display device.
Turning now to FIG. 14 where there is shown a schematic illustration of a plasma charge transfer device as a one character line display with two characters. In this illustration a character would comprise a 5 X 7 matrix but for the sake of clarity to describe the operation of the device only seven input i and 4 transfer electrodes 1 through 4 with conductors 14' are shown without showing the other details such as the channels. The erase electrodes e' through e' are connected to the same driver as conductor electrodes 1. It should be noted also that, although the plasma charge transfer device in its plasma display configuration shown in FIGS; 7 through 13 had seven inputs and seven channels, it is obvious that the plasma display device could have many more inputs and charge transfer channels. For example, a large plasma page display could have 512 channels and 512 sets of electrodes 1' through 4' for each channel. This could give the display 262,244
dots, any dot of which could be lit via the plasma dischargeat that position.
Of practical value in the area of visual displays is the alphanumeric dot matrix display where the alphanumeric character A, B-Z; 0, 1-9 is formed by an array of 35 dots seven high and five wide.
The alphanumeric array X 7 is shown in FIG. while the electrode configuration for a two character display is shown in FIG. 14. Each display dot is formed by the interaction of a channel and a set of transfer electrode pairs 3' and 4.
The load and hold modes of operation are exactly as described in connection with FIGS. 5 and 6a-d. For purposes of illustration, however, loading for one alphanumeric character will be described.
Six bits of digital information are entered at the input of the character generator 30 (shown in the lower right hand comer of FIG. 14). One such character generator being Texas Instrument SN 5103 andits operation be described hereiiii After the first clock 4 time (see T of FIG. 5) after the character generator has been addressed, column 1 on the character generator is strobed giving a set of outputs corresponding to the first column of seven dots in a character dot matrix. The output from character generator 30 addresses the seven input drivers, illustrated schematically in the block diagram 32, driving these ouputs high whenever a dot is desired. The plasma charge transfer then proceeds on those addressed channels shifting the charge from the input electrodes to transfer electrodes 1' through 4 as the sequence progresses. At the second clock 4 time column two of the character generators 30 are strobed given a set of outputs corresponding to the second column of dots in the character dot matrix. This proceeds until the seventh column of the character generator has been scanned and entered into the display. At this time the entire character has been loaded into the plasma charge transfer display. This character can be displayed indefinitely by going to the hold mode of operation described previously. Likewise, to enter a second character new digital information corresponding to this character is entered on the load mode of operation for the charge transfer device is activated, at which time the character presently in the display,;entered in accordance with the procedure above described, is shifted to the next character position as the present character is shifted into the first character position.
It is'obvious that the character line need not be limited to the two characters as illustrated in FIG. 14 but could have as many characters as desired. As a matter of fact, one of the principle advantages of the present invention as previously mentioned in that the number of characters in a line can be increased without any additional address electrodes.
Turning now to FIG. 16 which shows a plurality of character lines 10", each character line similar to that shown in FIG. 14, preferably all connected on a common substrate although shown separately in FIG. 16
. with separate drivers 32' and AND gate 36 each having a common enable as shown in blocks 36 all of which blocks are connected to a character generator 30. Information can be loaded into any character line from the character generator 30' by selecting the line, for example line I, with the enable switch E, and applying the load mode voltage sequence to the charge transfer electrodes 1',, 2' 3',, 4' common to character line 1 similar to that described in FIG. 14. The other character lines do not have their enable'switches E E and E selected and the voltage sequence applied to their charge transfer electrodes 1' through 4' 1' through 4' and 1' through 4'., is the hold mode sequence previously described. Displayed information that was previously loaded into these character lines remains unchanged, still being displayed as it was before.
What is claimed is:
l. A plasma charge transfer device comprising:
means including at least one envelope defining an elongated channel containing an ionizable medium;
input electrode means within said channel;
a plurality of transfer electrode means arranged in alternating sequence and offset one from another on opposite sides of the inside walls of said channel and capacitively coupled to said medium;
means for applying at controlled times a potential of sufficient magnitude to said input electrode means to cause an ionization of said ionizable medium in proximity of said input electrode means; and
means for applying sequentially to said transfer electrode means a sustaining potential of-a magnitude no greater than that required to maintain ionization if ionization of the ionizable medium were taking place in proximity to said transfer electrode means, said sustaining potential being applied after the ionization of said ionizable medium has ceased but before the charge stored at the transfer electrodes by the capacitor coupling to said medium, when added to said sustaining potential, reduces to a level below the level required to cause ionization such that the sequential application of said sustaining potential will cause an ionization of the ionizable medium between certain of said transfer electrode means and a shifting of the occurrence of plasma discharges along the length of said channel.
2. The plasma charge transfer device as claimed in claim 1 further including output means for identifying the plasma discharges transferred along said channel.
3. The plasma charge transfer device is claimed in claim 2 wherein said output means is a light sensitive means responsive to the light emitted by a plasma discharge in the last pair of transfer electrode means.
4. The plasma discharge transfer device as claimed in claim 2 wherein said output means comprises an electrode means within said channel and coupled to inductive means for measuring the transfer of energy from the last of said transfer electrode means as said plasma discharges at the end of said channel.
5. The plasma charge transfer device as claimed in claim 1 wherein said input electrode means is capacitively coupled to said ionizable medium.
6. The plasma charge transfer device as claimed in claim 1 wherein said transfer electrode means are coated with a dielectric material which material forms the dielectric for the capacitive coupling of the electrode means to the medium.
7. The plasma charge transfer device as claimed in claim 6 wherein said dielectric material has a high gamma so as to efiiciently emit secondary electrons upon bombardment of photons during plasma discharge.
8. The plasma charge transfer device as claimed in claim 1 further including keep-alive electrodes within said channel energizable by electrical energy to maintain ionized particles in said ionizable medium and located'in close proximity to said input electrode means.
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|U.S. Classification||345/60, 313/582|
|International Classification||H01J17/49, G09G3/285, G11C19/20, G09G3/29|
|Cooperative Classification||G11C19/205, G09G3/29, H01J11/00|
|European Classification||H01J11/00, G09G3/29, G11C19/20C|