US3198977A - Interline read-out system for storage tube - Google Patents

Interline read-out system for storage tube Download PDF

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US3198977A
US3198977A US220315A US22031562A US3198977A US 3198977 A US3198977 A US 3198977A US 220315 A US220315 A US 220315A US 22031562 A US22031562 A US 22031562A US 3198977 A US3198977 A US 3198977A
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target
scan
path
potential
read
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Manley Brian William
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US Philips Corp
North American Philips Co Inc
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/58—Tubes for storage of image or information pattern or for conversion of definition of television or like images, i.e. having electrical input and electrical output
    • H01J31/60—Tubes for storage of image or information pattern or for conversion of definition of television or like images, i.e. having electrical input and electrical output having means for deflecting, either selectively or sequentially, an electron ray on to separate surface elements of the screen

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  • This invention relates to circuit arrangements employing charge storage tubes, and more particularly to arrangements capable of providing non-destructive readout of the information stored.
  • non-destructive reading in storage tubes is achieved by the use of a beam modulation process effected with the aid of a grid electrode interposed between the gun and the target.
  • the insulating storage layer is supported on this metallic mesh.
  • Potential variations on the surface of the insulator, established in the writing process, control the passage of an electron beam through the mesh, but the potentials are such that no electrons from the beam can land on the insulator.
  • the beam strikes a fluorescent screen after passing through the mesh.
  • an information storage tube such as the Raytheon CK 7702
  • the focused beam scans over the mesh area, and the transmitted electrons reach a final electrode to constitute the output signal.
  • Grid modulation reading of this type preserves the stored charge and, in the case of a tube like the Hughes Memotron operated in a bistable mode, augments it, so that reading may proceed for long periods.
  • secondary-ernissive is intended to cover substances having a secondary-emission coefficient 6 which is less than unity when bombarded with electrons of energy less than a certain critical value known as the first cross-over potential V and a secondary-emission coefficient greater than unity for a range of bombarding energies above this critical energy.
  • the materials used may have a second cross-over potential V where the coefficient is unity again before becoming Smaller, but materials can also be used in which said second cross-over does not exist for practical purposes or cannot be determined.
  • the invention provides a circuit arrangement comprising a charge storage tube having an electron gun for producing an electron beam which gun includes a cathode, a control grid and an anode, and having a target having an uninterrupted secondary-emissive insulating storage surface which target is provided with a backing of elec trically conductive material and a collector for collecting electrons obtained by secondary emission from said target, the circuit arrangement also comprising means for causing the beam to eiiect a writing scan in a focused condition over a first path on the storage surface, means for applying input signals between grid and cathode during said scan so as to modulate the intensity of the beam current and cause a charge pattern to be set up on the storage surface in accordance with the input signals, means for causing the beam to effect a reading scan over grates atent a second path spaced from but adjacent to said first path while maintaining the beam in a constant-current focused condition and ensuring that the potential difference between each part of the target scanned and the cathode is greater than the first cross-over potential
  • the term insulating includes target materials which can, in known manner, be rendered conductive by bombardment with high-energy electrons but remain non-conductive under bombardment by low-energy electrons such as are used in the reading process. If the latter type of material is used, then the writing can be done by bombardment-induced conductivity obtained by scanning with high energy (erg. 6 K.V.) electrons; then the target backing may be maintained at a positive potential with respect to the bombarded surface so that, when the writing process renders the target conductive, the potential gradient through the thickness of the target will transfer positive charge to the target surface (alternatively a negative backing can cause transier of negative charge).
  • target materials which can, in known manner, be rendered conductive by bombardment with high-energy electrons but remain non-conductive under bombardment by low-energy electrons such as are used in the reading process. If the latter type of material is used, then the writing can be done by bombardment-induced conductivity obtained by scanning with high energy (erg. 6 K.V.) electrons; then the target backing may be
  • the writing can be done by secondary emission in which case a positive charge pattern is set up and it is necessary to ensure that the potential difference between each part of the target scanned and the cathode is at all points greater than the first cross-over potential of the material of the target but less than any second cross-over potential.
  • the reading operation employs secondary-emission and is based on the principle that the grid action of the target for each reading scan is controlled by the electrostatic fields of the written charge pattern in a manner which will be described more fully, and this control effect Will, for convenience, be referred to as co-planar grid action from the analogy of a control grid lying in the same plane as the target surface (but this term does not imply that the target surface must in all cases be a plane surface). Said charge pattern is not destroyed by a reading scan because the latter takes place on different parts of the target.
  • the output information obtained during the scan of any element of the second path corresponds to the positive charge which can be deposited on that element despite the presence of written charge on the adjacent element of the first path and this in turn :will depend on the amplitude of the input signal and the magnitude of the negative charge (if any) already deposited on that path.
  • the term element refers to an arbitrary elemental area occupied by one bit of information in a binary system or one picture element in a television or like systom, and should not be taken as implying any physical subdivision or discontinuity in the target surface.
  • the areas unscanned during the reading operation take the place of the interposed storage grid of the aforesaid RCA and Raythcontubes and act so as to control the action of the beam during its reading scan.
  • This control action "is quite different since it is no longer a question of controlling the passage of the beam (through grid apertures) to a more distant, and separate, target.
  • What is controlled is the ability of secondary electrons to escape to the collector electrode from the target areas scanned in the reading process, and it is this latter process (which can be repeated) that provides the read-out signal.
  • a charge storage grid is no longer required, and this is one of the reasons why a cheaper and simpler tube can be used for nondestructive reading.
  • One such tube is the Mullard Tenicon tube (type ME 1260) which is a low voltage, single gun information storage tube employing a capacitive discharge read-out process, and the feature of low voltage operation is a further advantage.
  • This tube has a collector mesh parallel to the target, but this meshis made entirely of metal and is not a storage mesh; in principle, even this mesh can be dispensed with for the purposes of the present invention provided that it is replaced by some other form of collector electrode (e.g. a peripheral ring) which is suitable in the sense of being able to provide a substantially uniform collecting field all over the target.
  • the information to be stored may be written on a line or on a raster of parallel lines as half-tone or as bipotential modulation.
  • the reading scan is performed between the written lines on an interlaced raster; if the lines of the reading raster are substantially equally spaced between lines of the written raster (as will be the case in the first embodiment described below), then the output signal for any given element will correspond to a mean of the information stored in the adjacent elements of the two neighbouring written lines; alternatively, it is possible to place each reading line much nearer to one of the two neighbouring lines of the written raster so that the influence of that line is predominant and controls substantially entirely the read-out of information.
  • each reading scan is followed by a re-stabilizing scan which destroys the pattern generated by the reading process and leads to a half-tone type of operation.
  • a re-stabilizing scan it is ensured that the potential difference between each target element scanned and the cathode is less than the first cross-over potential of the material of the target; although described as a raster scan with a defocused beam, re-stabilization could, with an appropriate tube, be performed by flooding the whole target since this would not destroy the stored pattern (the reason for this is the same as that given later for the defocused beam scan described).
  • the re-stabilizing process is omitted and this leads to a bipotential type of operation.
  • the first reading scan or scans establish the read path at equilibrium potentials determined by the co-p lanar grid action of the adjacent written elements.
  • Successive reading scans (which may be several thousands) provide signals of substantially constant amplitude generated (as far as can be ascertained by redistribution eifects in the areas of the reading lines.
  • FIGURES 1 to 4 illustrate the co-planar grid action
  • FIGURES 5A and 5B are charge writing and reading diagrams relating to the first embodiment
  • FIGURE 6 is a circuit diagram related to the first embodiment
  • FIGURES 7A and 7B are charge writing and reading diagrams relating to the second embodiment.
  • the two embodiments will be described as applied to the Tenicon or to a similar storage tube having a collector mesh parallel to the target surface and magnetic focusing.
  • the co-planar grid action and the operation of the embodiments will be described, for convenience, with the aid of specific voltage values; although these are realistic, they should not be taken as being limitative in any way.
  • FIGURES 1 to 3 it should be assumed that an element 61 of an insulating target is being read by bombardment with an electron beam 62 of finite crosssection, while the adjacent element 63 of the target 60 on either side of the element 61 have a charge which has been written into them in the writing scan.
  • Each of these figures is, in effect,'the cross-section of two written lines 63 and an interleaved read line 61.
  • FIGURE 1 represents the case when all elements of the target 60 are at the same potential, in which case all secondary electrons produced at the bombarded element 61 are drawn to the collector mesh 64, the trajectories of these secondary electrons being indicated by 65.
  • the negative potential regions 63 surrounding the bombarded element 61 influence the potentials in front of the target 60 in the way indicated by the lines representing equipotential surfaces. In this condition only a portion of the secondary electrons liberated at the bombarded element and indicated by 65 escape to the collector 64, some of the secondary electrons being returned to adjoining regions of the target as indicated by trajectories 66.
  • the potential of the surrounding negative target areas 63 with respect to the potential of element 61 is reduced to a value (e.g. 10 volts) at which value the number of secondary electrons escaping to the collector (trajectories 65) is assumed to be equal to the number of primary electrons (beam 62) striking the target area.
  • a value e.g. 10 volts
  • the actual potential difference at which the effective secondary-emission coeificient is reduced to unity will be determined by the width of the space between the written lines and the magnitude of the electric field normal to the bombarded element, resulting from the potential of the collector mesh 64.
  • the potential of the element does not change. What this equilibrium potential is will depend upon the spacing between the Written lines. For the line spacings used in the following embodiments the equilibrium potential is about l0 v.
  • This signal circuit may be incorporated either in the connection to a conductive backing plate of the target 60 or in the connection to the collector mesh 64.
  • FIG. 4 represents the changes in the aforesaid effective secondary emission coefiicient 5 of an element 61 in dependence upon changes in the negative potential of the adjacent written elements 63 of FIGURES 1 to 3.
  • a coefficient of unity corresponds to an adjacent potential of 10 v. (FIGURE 3) while the maximum coefficient (which may be about 4) corresponds to an adjacent potential of zero volts (FIGfl).
  • FIGURE 5A like the FIGURES 53, 7A and 7B schematically representing the charge distribution on a given part of the surface of the target W (i) and W(i+l) represent two adjacent written charge lines of a writing scanof rectangular raster form while RU, i+1) represents a line of a similar reading scan and the potential pattern left thereby.
  • R(i, i-l-l) represents the uniform charge set up by a re-stabilizing scan on read line R(i, i-l-l).
  • the scan lines are divided arbitrarily into discrete elements difiering by one or more volts, but in practice the Writing is efiected in a continuous half-tone manner corresponding e.g. to a video signal (the presence of intermediate 5- volt elements represents the half-tone nature of the operation).
  • the target in the operation of writing, the target is scanned so as to produce a series of separated parallel lines, such as W(i) and W(i, i+1), of modulated charge in which the target potential varies from an initial value of about 10 volts, positively to a maximum of zero volts representing peak stored signal amplitude.
  • the operation of reading comprises a readin scan and also (in this example) a sub sequent restabilizing scan.
  • the focused beam is scanned along the spaces between the written lines. This is like the interlaced field of a television scan.
  • the beam strikes the target surface, secondary electrons will be emitted. Whether or not these secondary electrons escaped to the collector mesh, which is held at about +200 v. and is spaced e.g. a few millimetres from the target, will depend upon the target potential in the surrounding target areas, in particular the adjoining elements in the Written lines W on either side of the read line R.
  • the re-stabilizing scan now restores to zero the potentials of the elements scanned during reading. lrVith the cathode at zero potential the beam is scanned over the same track R as that followed during reading. Areas which had been shifted positively during reading Will be cathodepotential stabilized to zero (FIGURE 53) and, at the completion of this scan, the target is ready for a further reading scan.
  • the landing current during this scan is substantially equal in amplitude and of reverse polarity to that obtaining during the reading scan, and this signal could be used as an output in addition to that obtained in the reading scan.
  • the difficulty of scan registration arises as a result of the different potentials applied to the tube in the reading and re-stabilizing scans This results in a slight rotation of one scan with respect to the other (When magnetic focusing is used) so that the re-stabilizing scan paths do not coincide with the reading paths.
  • the output signal amplitude decays in time, with successive read-outs, in a Way similar to that observed in half-tone display storage tubes.
  • the decay is the result of positive ions, generated by the reading beam, falling on the storage insulator and charging it positively.
  • written areas of the target are similarly shifted positively, in this case by the release of secondary electrons generated by the arrival of primary electrons in the skirts of the electron beam used in the reading process, which skirts overlap the written paths.
  • this positive shift of the target surface potential results in the DC. level of the signal from all parts of the target increasing in time towards the value corresponding to the collection of all secondaries generated by the reading beam in the reading paths at the collector electrode. Finally a uniform white signal is obtained from all parts of the target.
  • the useful storage time depends upon the spacing of the write and read scan lines but, with 200 read scan lines in a target diameter of 25 mm. as is available in the Tenicon, about 1000 read-outs may be obtained before the amplitude of the output signals has dropped by a factor of 2.
  • the resolution in the line scan direction under these conditions corresponds to about 400 picture elements for a target diameter of 25 mm.
  • Erasing consists of restoring all the target areas which are to be used for Writing to the most negative value representing zero stored signal (-10 v.). This is accomplished by scanni g the target with the cathode at a potential of l() v. and the collector at a potential such that'the potential difference between collector and cathode during this scan is less than the first cross-over potential. All scanned areas of the targe W'll then be stabilized at -l() v.
  • a defocused beam may be used to avoid scan registration problems since it is of no consequence that the areas of the target which are to be used for reading are also stabilized at -l0 v. by this operation: in fact, the read elements will be driven positively in the first few reading scans and will thus adopt their equilibrium values.
  • a notable feature of the erasing process is that it leaves no residual image.
  • the problem of a residual image after erasing is common to many non-destructive readout tubes and is probably a function or" the high voltage at which the target is bombarded.
  • FIGURE 6 One possible circuit arrangement suitable for the first embodiment is shown schematically in FIGURE 6.
  • the tube of which the envelope is not shown, is a Mullard Tenicon tube W h anodes A2 and A3 connected together.
  • the output circuit employs a conductive backing "iii of the insulating target 6% as a si nal plate connected to an output load "ill and coupled to an amplifier.
  • the first anode Al has applied to it over a capacitor 79 negativegoing tlyback suppression pulses 78, which, of course, have to be related to the particular scans used for a ing and reading (the means for ensuring this correlation are omitted for simplicity).
  • the voltage values given are, again, realistic (for the Tenicon) but not limitative. Magnetic deflection and focusing by means of coils 72 and 73 respectively are employed in the conventional manner.
  • TB1, TBZ Separate time-base systems (TB1, TBZ) for feeding the coil 72 are shown for writing and reading: for simplicity, the line and field circuits and the line and field deflection coils are shown and treated together.
  • the write and read scans may be effected (by TB1 and T132) at different speeds so long as the requirement of correct raster interlacing is maintained.
  • switch 74 either TB1 or T32 is operatively connected With coil 72
  • the input signal 75 is applied to the beam-intensity control electrode of grid G, and the grid-cathode (G-K) conditions for the various operations are determined by a twin ganged switch system Sa-Sb having four positions (1 to 4).
  • the beam is infocus when the focus coil is energized, 200 volts are applied to anodes A2A3, and the cathode K is at l v. (This means that the beam is defocused for switch positions S1 and S4 where the cathode is held at v. and earth respectively.)
  • the system provides for the following operations:
  • Reading-Switches Sa-Sb are in position 3 and by means of switch 74 now time-base TB2 is switched into circuit so as to displace the scans to an interlaced position between the written lines.
  • the grid is at -50 v. with reference to cathode and this determines the amplitude of the output signal across load 71.
  • Re-stabilization.Switches Sa$b are in position 4 p and time-base T32 is kept in circuit.
  • the grid voltage is zero with reference to the cathode and this permits large beam currents, but the target will only accept the amounts of current needed for re-stabilization.
  • FIGURES 7A, 7B Two successive written lines are shown at W(i) and W(z'+1).
  • the information is of a binary character and is stored in a bipotential manner so that each element assumes one of two voltages. The information is the same on both of the written lines and this will be dis cussed later.
  • a circuit generally similar to that of FIGURE 6 can be used as far as writing and reading are concerned, with switches in positions 2 and 3 respectively.
  • R(i, i+1) represents the charges set up by a reading scan on read line (i, i+1) immediately after the beam has passed.
  • R(i, i+1) represents the same charges as modified after a lapse of time corresponding to about one field scan of the read raster but before the beam has again scanned the elements shown. This modified pattern is ready for a further read scan during which it will be restored to the values of FIGURE 7A as will be explained.
  • the written information (that is in the tracks W(i) and W(i+1) is shown as a square Wave potential modulation 8 having an amplitude of 10 v. (FIGURE 7A).
  • the cathode potential is set to about v., and the beam tracks between the written lines W as in the first method. In this case, however, the reading operation can be repeated without an intermediate re-stabilization process.
  • the read elements at +10 v. their potential does not drift negatively during the progress of a read scan and therefore substantially no signal output occurs when they are re-scanned (this is quite in order in the case of binary information) a If the elements which had reached the highest positive potential (+20 v.) were to remain at that potential during the course of each reading scan, they would always be found (at the next scan) in the equilibrium condition where the effective'secondary emission coefficient is unity. If this were so, they could not be shifted in potential by the passage of the beam during the new reading scan and they could therefore not give an output in any reading scans other than the first, or first few, reading scans. It is only because of the re-distribution effect just described (whereby an element at +20 v. drifts down to, say, +19 v. during the remainder of each reading scan) that more than one read-out is possible without the need for a re-stablilizing scan such as that used in the first embodiment.
  • the storage time depends upon line density but, with 200 read lines in a target diameter of 25 mm., about 9000 read-outs may be obtained before the amplitude of the output signal drops by a factor of 2. It is worth noting that the output signal in fact remains sensibly constant during about the first 8000 read operations and falls rapidly in the last 1000 scans.
  • the second embodiment may, as aforesaid, employ a circuit similar to that of FIGURE 6 with the switch positions 2 and 3 employed for the writing and reading scans respectively as before.
  • the main change in the use of the circuit is that switch position 4 is used instead of switch position 1 for the erasing process while the collector is switched from +200 v. to a potential (e.g. +20 v.) lower than the first cross-over (the latter may be about 50 v.).
  • This can be done by a switch ganged to Salb.
  • the entire target surface is stabilized at 0 v. instead of 10 v. in this case the circuitry for position 1 becomes redundant.
  • FIGURES 5A-5B the output signal is effectively an average value of the adjacent input signals in the two written scan lines lying on either side of the reading line.
  • Such processes may be permissible for television pictures, and indeed offer a convenient way of performing linear interpolation for purposes of bandwidth compression; what makes this possible is the statistical likelihood of adjoining lines of a television picture being very similar (for patterns in which the information varies rapidly in a direction at right angles to the line scan this method may not be suitable).
  • Such interpolation is possible because, when there is a difference between two adjacent written lines, the output is, as aforesaid, a mean (not necessarily the arithmetical mean) between the two written signals.
  • the output would also be a mean between the two adjacent written lines W but this does not have much significance in the case of binary information, particularly when (as shown) the two 21 jacent lines contain identical information. In practice, this may be achieved by effecting the Writing operation with a spot-wobbled beam so that the written information is concentrated on two spaced parallel lines between which the reading will take place.
  • each reading line R is kept much closer to one Written line than to the other.
  • This modification can be applied to FIGURES 5A, 5B and also to FIGURES 7A, 7B.
  • the output is still influenced by two written lines but the effect of one written line is greatly preponderant.
  • storage may be limited to a single line in cases where a raster is not required.
  • the collector mesh may conveniently have a transparency of about 60 to 70% with 750 meshes per inch, and it may be disposed at a distance from the target within the range of 2 to mm., preferably a distance of 3 mm.
  • the material of the target may be mica.
  • the bi-potential embodiment described has the advantage of being adapted to maintain the same conditions, both for reading and for writing, at all the circuit elements affecting the focus of the beam.
  • the arrangement illustrated may be adapted to operate with bombardment-induced conductivity (8.1.0) writing.
  • the target material must be changed from mica to a material having BJLC. properties (eg. ZnS or magnesium fluoride) and the DC. voltage applied to the end of the output load 71 remote from backing plate '70 may be changed from earth to a positive value of about 20 volts.
  • the charge pattern is written as positive charge but it may be changed to a negative charge pattern by a suitable change of target material and changing the +20 v. (applied to the load), to, say, -20 v.
  • the invention may be modified so that a two-dimensional char e pattern or picture is set up independently of the location of the intended reading scan, said pattern or picture being then, in effect, cut into separate strips by the initial action of the line scans of a reading scan of raster form; after this initial action the reading scan will have formed for itself target areas which can then act as the second paths along which subsequent read scans can effect read-out by co-planar grid action.
  • the operation is such that the initial reading scans establish on the target a reading path or paths within the area of the originally established charge pattern. The reading process then taking place along these paths will sense the content of the stored charge pattern in the areas adjacent to the paths, in the manner previously described.
  • the first of these modifications provides an arrangement wherein the means for causing the writing scan are adapted to give said scan the form of a raster of lines and wherein the means for causing the reading scan are adapted to give the latter scan the form of a raster of lines which intersect the written lines at a two-dimensional array of intersection points.
  • A. typical application of this arrangement is the conversion of a display from a radial (P.P.l.) radar-type raster to a rectangular raster of parallel lines.
  • a second modification provides an arrangement wherein the charge storage tube is 1-1 camera tube having a secondary-emissive insulating storage surface, and wherein the means for causing a writing scan and for applying input signals are replaced by means for effecting optical projection of the information to be stored to produce a two-dimensional pattern or picture on said storage surface while the means for causing a reading scan are adapted to give said scan the form of a raster of parallel lines.
  • the target must have 6 l at a convenient primary electron energy.
  • the camera tube is of the vidicon type and the arrangement is adapted to set up a charge pattern on the target in response to said optical projection by the action of photoconduction in the target material.
  • the reading operation is very similar to that described for a Tenicon or like tube.
  • vidicon tubes typically do not have suitable secondaryemissive targets, it is a simple modification to the manufacturing process to rectify this.
  • the target material e.g. Sb S can be evaporated in vacuum rather than (as is usual) in an inert gas atmosphere held at a few Hg pressure.
  • the camera tube is of the image- Orthicon type and the arrangement is adapted to set up a charge pattern on the target in response to said optical projection by the action of photo-emission from the target.
  • the tube would be modified to use an insulating target (eg. MgO) rather than the more usual semi-insulating glass target.
  • Vhat is claimed is:
  • An electrical signal stora e system comprising a charge storage tube having a target for storing electric charges, said target comprising a secondary-emissive storage surface composed of an insulating material and an electrically conductive backplate, means for projecting a beam of electrons onto said target surface, a collector electrode positioned near said target for collecting secondary emission electrons from said target, beam intensity control means in said tube, means for applying an input signal to said intensity control means thereby to modulate the beam current, means for focusing and scanning said modulated beam over a first path on said target storage surface thereby to write a charge pattern on said surface determined by said input signal, means for reading out.
  • the charge pattern of information stored in said first path comprising means for maintaining said beam in a constant current focused condition and means for scanning said beam over a second path on said surface in close proximity to said first path, said read-out means further comprising means for controlling said beam during a read scan so that an effective velocity of said beam is produced which is greater than the first secondary emission cross-over point of said target material and in which the secondary emission coefiicient is maintained greater than unity, and an output circuit responsive to signals produced by said read scan for deriving an output signal determined by the charge pattern stored in said first path.
  • An electrical signal storage system comprising a charge storage tube having an electron gun for producing an electron beam and a target located in the path of said beam, said gun comprising a cathode, control grid and anode, said target comprising a secondary-emissive storage surface composed of an insulating material and an electrically conductive backplate, a collector electrode positioned near said target for collecting secondary emission electrons'from said target, means for focusing said electron beam, means for scanning said beam over a first path on said target storage surface, means for applying an input signal to said tube grid during said scan thereby to intensity modulate said beam current so as to write a charge pattern on said storage surface, read-out means for the charge pattern of information stored in said first path comprising means for maintaining said beam in a constant current focused condition and means for scanning said beam over a second path on said surface which is spaced from but adjacent to said first path, means for applying an operating voltage between said cathode and target during said read scan which is greater than the first cross-over potential of said target material and in which the secondary emission coefficient is
  • An electrical signal storage system comprising a charge storage tube having an electron gun for producing an electron beam and a target located in the path of said beam, said gun comprising a cathode, control grid and anode, said target comprising a secondary emissive storage surface composed of an insulating material and an electrically conductive backplate, a collector electrode positioned near said target for collecting secondary emis sion electrons from said target, means for focusing said electron beam, means for scanning said beam over said storage surface in a first raster of substantially parallel spaced lines, means for applying an input signal to said tube grid during said scan thereby to intensity modulate said beam current so as to Write a charge pattern on said storage surface, read-out means for the charge pattern cathode and target during said read scan which is greater than the first cross-over potential of said target material and in which the secondary emission coefiicient is maintained greater than unity, and an output circuit responsive to signals produced by said read scan for deriving an output signal determined by the charge pattern stored in said first raster of lines.
  • each read line of said second raster of lines is located substantially equidistant between two Write lines of said first raster of lines and wherein the lines of said first raster are parallel to the lines of said second raster.
  • An electrical signal storage system comprising a charge storage tube having an electron gun for producing an electron beam and a target located in the path of said beam, said gun comprising a cathode, control grid and anode, said target comprising a continuous secondaryemissive storage surface composed of an insulating material and an electrically conductive backplate, a collector electrode positioned near said target'for collecting secondary emission electrons from said target, means for focusing said electron, beam, means for scanning said beam over a first path on said target storage surface, means for applying an input signal to said tube grid during said scan thereby to intensity modulate said beam current so as to write a charge pattern on said storage surface, means for applying an operating voltage between said cathode and target during said Write scan which is greater than the first cross-over potential of said target material and less than any second cross-over potential thereby producing, a charge pattern on said target by secondary emission of said target electrons, read-out means for the charge pattern of information stored in said first pathcomprising means for maintaining said beam in a constant current focused condition and means
  • An electrical signal storage system comprising a charge storage tube having an electron gun for producing an electron beam and a target located in the path of said beam, said gun comprising a cathode, control grid and anode, said target comprising a continuous secondaryemissive storage surface composed of an insulating material and an electricallyconductive backplate, a collector electrode positioned near'said target for collecting'see ondary emission electrons from said target, means for writing information signals on said target surface comprising means for scanning said beam over'a first path on said target storage surface, means including said electron gun for focusing said electron beam during the write scan and means responsive toan input signal for modulating said beam current so as to write a charge pattern'on said storage surface path, means for reading-out the charge a pattern stored in said first path comprising means for maintaining a constant current focused beam and means for scanning said beam over a second path on said surface spaced from said first path, means for providing a potential difference betwen said cathode and target which is greater than the first cross-over potential and less than a
  • Apparatus as described in claim 7 further compris- 13 ing means for restabilizing the elements comprising said second path to a reference potential of said cathode, said restabilizing means comprising means for scanning said electron beam over said second path subsequent to a read scan, means for defocusing said electron beam during said restabilizing scan and means for providing a potential difference between said cathode and target which is less than the first cross-over potential of the target material,
  • Apparatus as described in claim '7 comprising means for erasing said stored charge pattern from the target, said erasing means comprising means for scanning the electron beam over the target surface, means for defocusing said electron beam, and means for stabilizing said target surface at a potential value representative of zero stored signal, said stabilizing means comprising means for providing a potential difference between said cathode and target which is less than the first cross-over potential of the target material.
  • said scanning means comprises deflection means located outside of said electron beam, first and second deflection circuits and switch means for selectively coupling said first and second deflection circuits to said deflection means.
  • Apparatus as described in claim it) further com prising an output circuit which comprises an impedance element connected to said target backplate, means connecting said target to ground, means for supplying a positive voltage to said collector thereby to attract secondary emission electrons of said target, and second switch means for supplying operating voltages to said cathode and control grid, said second switch means having a first and second position for supplying negative voltages to said cathode and grid, said grid being biased more negative than said cathode into the region of beam cut-oil, and said second switch means having a third position connecting said cathode and grid to ground.
  • said collector comprises a grid-like structure interposed be tween the cathode and target and uniformly spaced from the target surface.
  • said write scanning means further comprises means for defiecting said beam to produce a first raster of lines and said read scanning means further comprises means for deflecting said beam to produce a second raster of lines in directions different than said first raster whereby the lines of said second raster intersect the lines of said first raster in a two-dimensional array of intersection points.
  • a television storage tube system comprising a charge storage tube having an electron gun for producing an electron beam and a target located in the path of said beam, said gun comprising a cathode, control grid and anode, said target comprising a secondary-emissive storage surface composed of an insulating material and an electrically conductive backplate, a collector electrode positioned near said target for collecting secondary emission electrons from said target, means for focusing said electron beam, said target material being responsive to an input light pattern for storing an information charge pattern thereon determined by said light pattern, means for reading said stored charge pattern comprising means for maintaining a constant current focused beam and means for scanning said beam over said target to form a raster of spaced parallel lines, said charge pattern being stored in the interstices between the lines of said read scan, means for providing a potential difference between said cathode and target which is greater than the first cros over potential and less than a second cross-over potential of said target material, and an output circuit responsive to signals derived from said target during said read scan.
  • Apparatus as described in claim 14 wherein said camera tube is of the vidicon-type and said target storage surface comprises a photo-conductive material which stores a charge pattern in response to a light pattern by the action of photo-conduction in said target material.
  • the method of retrieving information stored as a charge pattern in a first path on the surface of a signal storage screen composed of a secondary-emissive insulating material which comprises applying an operating potential to said storage screen which is greater than the first cross-over potential of said screen material, scanning an electron beam over a second path on said screen surface which is adjacent to said first path while maintaining said operating potential thereby to liberate secondary electrons from said screen, and deriving an electric signal in response to said liberated electrons and determined by the charge pattern stored in said first path.
  • the method of retrieving information stored as a charge pattern along a first path on the surface of a signal storage screen composed of a secondary-emissive insulating material which comprises applying an operating potential to said storage screen which is greater than the first crossover potential of said screen material and of sufficient value to maintain the secondary emission coefiicient of said material greater than unity, scanning a constant current focused electron beam over a second path on said screen surface which is adjacent to said first path while maintaining said operating potential thereby to liberate secondary electrons from said screen, and subsequently scanning the electron beam over said second path while maintaining said operating potential at a value less than the first cross-over potential of said screen material.

Landscapes

  • Luminescent Compositions (AREA)
  • Manufacture Or Reproduction Of Printing Formes (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
US220315A 1961-09-07 1962-08-29 Interline read-out system for storage tube Expired - Lifetime US3198977A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB32247/61A GB994065A (en) 1961-09-07 1961-09-07 Improvements in or relating to circuit arrangaments employing charge storage tubes

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US3198977A true US3198977A (en) 1965-08-03

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US220315A Expired - Lifetime US3198977A (en) 1961-09-07 1962-08-29 Interline read-out system for storage tube

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BE (1) BE622271A (id)
DE (1) DE1464292A1 (id)
GB (1) GB994065A (id)
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NL282857A (id)
GB994065A (en) 1965-06-02
DE1464292A1 (de) 1970-04-16

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