US2962623A - Color shift direct-view half-tone storage tube - Google Patents

Description

Nov. 29, 1960 2,962,623

COLOR-SHIFT DIRECT-VIEW HALF-TONE STORAGE TUBE Filed Sept. 15, 1959 C. D. BEINTEMA 3 Sheets-Sheet 1 Nov. 29, 1960 c. D. BEINTEMA 2,962,523

COLOR-SHIFT DIRECT-VIEW HALF-TONE STORAGE TUBE Filed Sept. 15, 1959 3 Sheets-Sheet 2 wals/mex: @Aurox/; :Para/Muff! 4PM v4 im Nov. 29

C. D. BEINTEMA COLOR-SHIFT DIRECT-VIEW HALF-TONE STORAGE TUBE Filed Sept. 15, 1959 3 Sheets-Sheet 5 IMM# MM United States Patent COLOR-SHIFT .DIRECT-VIEW HALF-TONE STORAGE TUBE Chester D. Beintema, Santa Monica, Calif., assigner to Hughes Aircraft Company, Culver City, Calif., a corporation of Delaware Filed Sept. 15, 1959, Ser. No. 840,113

7 Claims. (Cl. 315-12) This invention relates to a direct-view half-tone type color storage tube and, more particularly, to a direct viewing storage tube for presenting a display wherein signals of varying intensity appear in different colors.

In the tube of the present invention, a shift from one color to another is employed to indicate a change in the intensity level of the signal. The tube is not of the type generally employed to reproduce a scene in color in a conventional manner.

In conventional color storage tubes capable of producing a presentation in color, the resolution is limited to the extent that three dots of phosphor are required for each element of the presentation. Also, because of the mask which is used to control the charging of the storage surface about the apertures in the storage screen which correspond to different colored phosphor dots, the brightness of the presentation is somewhat limited. Further, because it is requisite that different colored phosphor dots be printed opposite apertures in the storage screen which are in all respects similar, it is necessary to use an additional mask over the storage screen to elect the printing of the dots. This use of an additional mask makes it necessary to limit the diameter of the viewing area and to employ an absolutely flat faceplate on the tube to maintain color purity.

It is an object of this invention to produce a half-tone type direct-view storage tube wherein variations in signal intensity level are reproduced in different colors.

Another object of the invention is to provide a directview type storage tube particularly adapted to produce a radar presentation wherein target echo signals normally appear in a different color from those resulting from nolse.

A further object of the invention is to provide a color storage tube capable of producing a presentation in color which has increased resolution and brightness over that available in conventional color storage tubes.

A still further object of the invention is to provide a color shift storage tube having a curved faceplate thus enabling a presentation of increased area and brightness to be produced.

The color-shift storage tube of the present invention includes an evacuated envelope for housing the various elements of the tube having either a at or curved faceplate on the inner surface of which is disposed the phosphor configuration which constitutes the viewing screen. In particular, the viewing screen is made up of phosphor dots of one color. Each of the phosphor dots is surrounded by one or more concentric rings of dilferent colored phosphor. The outer ring about each of the dots may overlap with adjacent rings without detrimental effect on the operation of the device and thus form a continuous single-colored background for the dots and, if more than two colors are used, the inner rings. In addition, a conventional type storage screen is employed having circular apertures of approximately one-half the diameter of the phosphor dots disposed in alignment with the center portion of each dot. A collector grid, an

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electron writing gun and an electron Hood gun with a suitable llood electron collimation system are also employed in a conventional manner.

In operation, the electron writing gun produces a charge pattern on the storage surface which, in turn, controls the ow of flood electrons through the apertures of the storage screen to the viewing screen. It has been found that when the charge surrounding an aperture first becomes sufliciently positive to allow llood electrons to penetrate through the aperture to the viewing screen, the electrons are focused on the center of the corresponding phosphor dot. As the charge surrounding the aperture -becomes progressively more positive, the ood electrons are focused over the entire dot. A still more positive charge causes the flood electrons penetrating through the aperture to be focused in the form of a spot which expands in diameter with increasing positive charge on the storage surface surrounding the aperture. In the event that each dot of the viewing screen is surrounded by only one ring of a different color, the flood electrons will first excite only the dot and then the dot and the ring as the charge on the storage surface surrounding the corresponding aperture in the storage screen is progressively increased in a positive direction. A more distinct transition may be achieved by spacing the rings from the respective dots or inner rings, if any.

The above-mentione-d and other features and objects 0f this invention and the manner of obtaining them will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, wherein:

Fig. l shows a cross-sectional schematic view of one embodiment of the present invention;

Fig. 2 shows an enlarged portion of a phosphor dot viewing screen wherein each dot is surrounded by only one ring which overlaps with adjacent rings together with a cut-away portion of the storage screen;

Fig. 3 shows an enlarged portion of an alternative embodiment of the viewing screen wherein each dot is surrounded by two concentric rings of two dilerent colors, the outer rings overlapping with adjacent rings together with a cut-away portion of the storage screen;

Fig. 4 shows a cross-sectional view of enlarged portions of the collector grid, storage screen and viewing screen of the embodiment of Fig. 1; and

Fig. 5 is a characteristic of the relative degrees of brightness of the different colored phosphors for various potentials on the storage surface.

Referring now to the drawings, Fig. 1 shows a directviewing color-shift storage tube in accordance with the present invention. This tube comprises an evacuated envelope 10 which includes a comparatively large bellshaped section 11 which has an axially aligned neck portion 12 at the left eXtermity, as viewed in the drawing, for housing an electron gun 14 for producing an electron beam of elemental cross-sectional area and horizontal and vertical deecting plates 15, 16, respectively, for controlling the deflection of the electron beam. The right extremity of the bell-shaped portion 11 of evacuated envelope 10, as viewed in the drawing, has an extension which constitutes an annular metallic flange 17 and a face-seal liange 18. The face-seal ange 18 is, in turn, sealed olf by a faceplate 20.

A viewing screen 22, a more detailed description which will be hereinafter presented, is disposed on the inner surface ofthe faceplate 26,. Adjacent to and co-extensive with this viewing screen 22, there is disposed in the order named, a storage screen 24 supported about its periphery by a ring 25 and a collector grid 26 supported about its periphery by a ring 27. The ring 27 includes an annular portion which is of sufficiently small diameter as to be accommodated by the ring 25.

The storage screen 24 comprises a thin sheet of metal 28 composed, for example, of cupronickel. The metallic sheet 28 is of the order of from 1 to 6 mils thick. As shown in Figs. 2 and 3, the cupronickel sheet 28 is provided with circular apertures 29 which may, for example, have a uniform diameter of 1.0 mil. A storage surface is provided by a layer 30 of dielectric material disposed over the remaining areas of metallic sheet 28 on the side thereof opposite the viewing screen 22. This layer 30 of dielectric material may constitute, for example, a layer of magnesium fluoride of the order of 3 microns thick evaporated on one side of the cupronickel sheet 28. Alternatively, the layer 30 may be constituted of zinc sulfide which is made and operated in accordance with the teachings of applications for patent, Serial No. 795,727, entitled Cathode Ray Tube, filed February 26, 1959, by Norman Lehrer, and Serial No. 800,180, entitled Storage Tube, filed March 18, 1959, by Norman H. Lehrer, both of which have been assigned to the same assignee as is the present case.

Disposed adjacent to and co-extensive with the storage surface side of storage screen 24 is collector grid 26. The collector grid may be provided by either a woven or electro-formed mesh having a pitch of approximately 250 meshes per inch. In operation, the metallic sheet 28 of storage screen 24 and the collector grid 26 are maintained at potentials of |10 volts and +120 volts, respectively, by means of connections therefrom to intermediate'terminals of a battery 32, the negative terminal of which is connected to ground. In particular, a lead 33 from ring 25 and metallic sheet 28 of storage screen 24 is connected to the battery 32 through a load resistor 34. This enables the output from a pulse generator 35 to be connected directly to the cupronickel sheet 28. Pulse generator 35 provides pulses having positive excursions, which pulses raise the potential of the storage surface, thus enabling it to be erased by the flood electrons as will be hereinafter explained in more detail.

As previously specified, neck portion 12 of evacuated envelope houses electron writing gun 14 together with the horizontal and vertical deflecting plates 15, 16, respectively. The gun may, of course, be magnetically deflected equally well in cases where magnetic, rotating deflection yokcs would be used, i.e., for a P.P.I. display. The electron writing gun 14 includes a cathode 37 and an intensity grid 38. The cathode 37 of gun 14 is maintained at a potential of the order of -3000 volts with respect to ground by means of a connection therefrom to the negative terminal of a battery 40, the positive terminal of which is connected to ground. Further, the intensity grid 38 of gun 14 is maintained at a quiescent potential of the order of 75 volts negative with respect to cathode 37. This is accomplished by means of a connection from the grid 38 through a load resistor 41 to the negative terminal of a source of biasing potential 42, the positive terminal of which is referenced to the cathode 37. Means for modulating the intensity of the electron writing beam is provided by a connection from an input terminal 43 through a capacitor 44 across the load resistor 41 to the intensity grid 38 of gun 14.

The electron beam produced by electron writing gun 14 is scanned over the storage screen 24 in the desired manner by means of horizontal and vertical deflection voltages generated by horizontal and vertical deflection voltage generators 46 and 4S, respectively. The horizontal deflection signal is applied to the horizontal dellecting plates 15 through capacitors S0, 51 across isolating resistors 52, 53. Similarly, the vertical deflection signal is applied to the vertical deflecting plates 16 through capacitors 54, 55 across isolating resistors 56, 57. The horizontal and vertical deflecting plates 15, 16 are maintained at a quiescent potential of the order of 100 volts positive with respect to ground by means of connections from the common junctions between resistors 52, 53 and 56, 57 to a tap 58 of a potentiometer 59 4 which, in turn, is connected across the terminals of the battery 32. In addition to the above, an equipotential region is maintained intermediate the deflecting plates 15, 16 and the annular flange 17 by means of a conductive coating 61 disposed over the inner surface of the bellshaped portion 11 of evacuated envelope 10 throughout this region. This conductive coating 61 may, for example, be composed of Aquadag and is maintained at a potential which may be equal to that of the quiescent potential applied to deflecting plates 15, 16 by means of a connection therefrom to the tap 58 of potentiometer 59.

A ring source of flood electrons is provided by a flood gun 63 disposed concentrically about the longitudinal axis of the cylindrical portion 12 of evacuated envelope 10 at the left extremity of bell-shaped portion 11, as viewed in the drawing. Flood gun 63 includes a directly-heated circular lament 64, which has a plurality of uniformly spaced connections, alternate ones of which are connected across the secondary winding 65 of a filament transformer 66 which provides an alternating-current voltage of approximately l volt. The mean potential of cathode 64 of flood gun 65 is operated at ground potential by means of a connection from the mid-point of secondary winding 65 to ground. Further, the flood electrons are diffused and collimated over the area of the storage screen 24 by means of a channel-shaped electrode 67 disposed about the circular filament 64 with the open side facing the storage screen 24. In addition, an annular funnels'haped electrode 68 is disposed about the periphery of the collector grid 26 and extends towards the flood gun 63 by a distance which is a function of the diameter of the tube. In any event, it does not overlap the bell-shaped portion 11 of envelope 10. The channel-shaped electrode 67 of flood gun 63 and the annular funnel-shaped electrode 68 are maintained at a potential that is slightly positive relative to the potential of collector grid 26. This potential may, for example, be of the order of volts positive with respect to ground and is effected by means of connections from the electrodes 67, 68 to the positive terminal of the battery 32.

Referring now to Fig. 2, there is shown a plan view of an enlarged portion of the viewing screen 22 which is partially covered by a correspondingly enlarged portion of the storage screen 24. As previously specified, the storage screen 24 comprises a metallic sheet 28 which is provided with spaced apertures 29 and covered with a layer 30 of secondary electron emissive dielectric material which provides storage surface. The viewing screen 22 includes phosphor dots 70 which are disposed in alignment with each of the circular apertures 29 in the storage screen 24. The phosphor dots 70 are all constituted of a single colored phosphor which may, for example, be of a red light emitting type. These phosphor dots 70 have a diameter which is from 50% to 100% greater than the diameter of the circular apertures 29. Thus. in the case where the circular apertures 29 are l mil in diameter, the diameter of the phosphor dots will be from 1% to 2 mils in diameter. Surrounding each of the phosphor dots 70 there is disposed a concentric ring of different colored phosphor. In the event that the apertures 29 are sufficiently close together to allow the concentric rings to overlap, there will be a continuous layer 72 or background of different colored phosphor which surrounds all of the phosphor dots 70. This continuous layer 72 may, for example, be provided by a green light emitting phosphor. Also, if it is desired to have an abrupt transfer from the color of the dots 70 to the color of the background layer 72 in the operation of the tube, the background layer 72 is spaced from the phosphor dots 70. On the other hand, if it is desired to have a gradual transition from the one color to the other in the operation of the tube, the background layer 72 is juxtaposed to each of the phosphor dots 70. Lastly, a thin film 74 of aluminum is evaporated over the entire area of the viewing screen 22.

In fabricating the viewing screen 22, there are several nethods which can be `used to print the phosphor dots 70 and the layer 72. First, after positioning the storage screen 24 in front of treated surface where the viewing screen 22 is to be produced, a point source of light is moved in a circle. The image thus exposed on the photographically treated phosphor plate will be a ring, the size of which depends on the geometry of the printing lighthouse setup. The dots may be exposed by moving the point source of light along its axis and thus expose the center of the rings.

Secondly, an annular light source may be used to print the rings by imaging the annular light source through the storage screen 24. As before, a` point source of light can be used lto print the dots 70.

Also, reverse printing may be used. That is, the dots 70 are printed first and then the second phosphor is exposed from the faceplate side. The first set of dots 70 will mask the phosphor behind them and the light from the faceplate side thus cannot fix the phosphor in these .areas and it will be washed away in the developing process. The phosphors used and the order of deposition will depend on the ultimate use of the device.

Referring again to Fig. 1, the aluminum film 74 of viewing screen 22 is maintained at a potential of the order of 5000 volts positive with respect to ground. This is accomplished by a metal pin 75 which is inserted through a glass bead 76 which is, in turn, sealed to the periphery of an aperture through the side wall of the face-seal flange 18. The inner surface of the face-seal flange 18 intermediate the viewing screen 22 and the pin75 is insulated by means of a layer 77 of frit which is subsequently fused. A mixture of gold flake and frit is then painted over layer 77 between the pin 75 and the aluminum film 24 of viewing screen 22 and fused thereby to provide an electrical connection 78 from the pin 75 to the viewing screen 22. The pin 75 is then connected to the positive `terminal of a battery 79, the negative terminal of which is connected to ground.

According to the present invention, the operation of the disclosed direct-viewing half-tone storage tube may be similar to that of the half-tone storage tube disclosed in Patent No. 2,790,929, entitled Direct-Viewing Half-Tone Storage Device, issued to Elvin E. Herman, et al., on April 30, 1957, which patent is assigned to the same assignee as the present application. In general, the fiood gun 63 is operated to provide a uniform collimated flow of low velocity electrons over the entire storage area of storage screen 24. The storage surface of storage screen 24 is prepared for writing by applying a 5 4to 10 volt positive pulse generated by the pulse generator 35 .to the cupronickel sheet 28 of the storage screen "224. Initially the ood electrons will have charged the storage surface to the potential of the flood gun cathode 64, which potential is substantially at ground. yBecause of the-,capacitance between the storage surface and the cupron'ickel sheet 28, the application of the pulse to the cupronrickel sheet 28 raises the potential of the storage surface by lan amount which corresponds to the amplitude of the pulse. The flood electrons can then commence charging the storage surface towards ground potential. Upon completion of the pulse, the potentials of the storage surface follow the negative excursion of the trailing edge of the"` pulse whereby thestorage surface ultimately assumes aquiescent potential of fromy 5 to 10 volts negative with respect to ground.

Writing is accomplished by applying a signal to input terminal 43 thereby to current modulate the high-energy high-current density electron beam produced by the electron writing gun 14. This high-energy current-modulated electron beam is caused to scan the storage surface of the storage screen 24 by the application of suitable defiection voltages generated by horizontal and vertical voltage generators 46, 48 to the deflecting plates 15, 16, respectively. As the storage screen 24 is scanned by the high-energy electrn beam, the storag' surface is charged towards the mean potential of ood cathode 64 by an amount which is a function of the input signal impressed on terminal 43. The potential of the area of storage surface surrounding a given aperture controls the flow of flood electrons through that aperture and thus controls the brightness of illumination of the corresponding phosphor dot in the manner hereinafter explained.

Referring to Fig. 4, there is shown a cross-sectional view of enlarged portions of the collector grid 26, the storage screen 24 and the viewing screen 22 of the ernbodiment of Fig. 1 for the purpose of illustrating the manner in which the device of the present invention operates. In particular, the storage surface about a specific aperture 29a of storage screen 24 is charged to a potential which is in the range of from 5 to -3.5 volts negative with respect to the potential of cathode 64 of flood gun 63. This particular range will, of course, vary with the size of the aperture and the spacing between the storage screen 24 and the viewing screen 22. At potential levels within this range for the present device, however, the iiood electrons represented by dashed-lines are just able to penetrate through the aperture 29a. The effect of the charge surrounding the aperture 29a produces an electron lens, in effect, which focuses the flood electrons directly on the phosphor dot 70 which lies in alignment with the aperture 29a. Under these circumstances, only the red of dot 70 will be excited; hence, no green will be visible. V

In the next case, the storage surface surrounding the specific aperture 29b of storage screen 24 is charged positively to a potential within the range of from 3.5 to 1.5 volts relative to the potential flood gun cathode 64. Under these circumstances, it has been found that the aperture 29b produces a lens which directs the flood electrons in a manner such that they impinge on the viewing screen 22 in the form of a spot which is slightly larger than the dotv 70. Thus, the dot 70 is energized to produce red light and the inner peripheral regions of phosphor layer 72 immediately adjacent the dot 70 are energized to produce green light. The combination of red and green in this manner produces light which appears yellow to the eye.

Lastly, if the storage surface surrounding a specific circular aperture 29e of storage screen 24 is charged positively to a potential which is from 1.5 to 0 volts negative with respect to the potential of flood gun cathode 64, and the green phosphor of layer 72 is more efficient than the red phosphor of dots 70, the green light will override the red light, whereby only green light will be observed. It is thus apparent that as the storage surface surrounding Ithe apertures 29 of storage screen 24yis charged in the positive direction from -5 to 0 volts relative to the potential of flood gun cathode 64, the colors produced by the flood electrons on the viewing screen 22 are first red, then yellow and, lastly, green. This change in color with charge on the storage surface is illustrated by the characteristic 82 shown in Fig.` 5. It is to be noted that as the charge on the storage surface becomes more positive, the brightness also increases in addition to the colorshift. This is because increasing numbers of electrons penetrate through apertures which open up sufficiently to shift colors. Referring now to Fig. 3, there is illustrated an alternative embodiment of the viewing screen 22 within additional different colored concentric rings 84 are interposed between the phosphor dots 70 and the background layer 72. These additional concentric rings 84 may, for example, be composed of a phosphor which emits blue light. The operation is the same as previously described.

What is claimed is:

1. A direct-view storage tube comprising a viewing screen having a plurality of fluorescent dots of a single predetermined light emitting color disposed in spaced relationship over the entire area thereof and fluorescent material of a light emitting color different from said predetermined light emitting color disposed concentrically about each of said dots; a storage screen disposed adjacent to and coextensive with said viewing screen and having apertures in substantial alignment with each of said dots; means for producing a charge pattern on said storage screen; and means for directing flood electrons uniformly over said storage screen whereby the charge on the storage surface surrounding each aperture controls the characteristics of the flow of said flood electrons therethrough to said viewing screen to produce a presentation wherein different potential levels of said charge pattern correspond to different colors.

2. A direct-view storage tube comprising a viewing screen having a plurality of fluorescent dots of substantially uniform diameter and of a first light emitting color disposed in spaced relationship over the entire area thereof and fluorescent material of a second light emitting color different from said first light emitting color disposed concentrically about each of said dots; a storage screen disposed adjacent to and co-extensive with said viewing screen having circular apertures in substantial alignment with each of said dots, the diameter of said circular apertures being no less than the diameter of said dots; means for producing a charge pattern on said storage screen; and means for directing flood electrons uniformly over said storage screen whereby the charge on the storage surface surrounding each aperture controls the characteristics of the flow of said ood electrons therethrough to said viewing screen to prod-ucc a presentation wherein different potential levels of said charge pattern correspond to different colors.

3. The directview storage tube as defined in claim 2 wherein said circular apertures are all of an equal diameter that is from 50% to 100% greater than the diameter of; said tluorescent dots of substantially urlifnrnv diameter.

4. The direct-view storage tube as defined in claim 2 wherein said first light emitting color is red and said second light emitting color is green.

5. The direct-view storage tube as defined in claim 2 wherein said fluorescent material of a second light emitting color is disposed immediately adjacent to said fluorescent dots.

6. The direct-view storage tube as defined in claim 2 wherein said fluorescent material of a second light emitting color is spaced concentrically about said fluorescent dots.

7. A direct-view storage tube comprising a viewing screen having a plurality of fluorescent dots of substantially uniform diameter and of a first light emitting color disposed in spaced relationship over the entire area thereof, a fluorescent material of a second light emitting color different from said first light emitting color disposed concentrically about each of said dots, and fluorescent material of a third light emitting color different from said first and second light emitting colors disposed over the remaining area of said viewing screen; a storage screen disposed adjacent to and co-extensive with said viewing screen and having circular apertures in substantial alignment with each of said dots, the diameter of said circular apertures being no less than the diameter of said dots; means for producing a charge pattern on said storage screen; and means for directing flood electrons uniformly over said storage screen whereby the charge on the storage surface surrounding each aperture controls the characteristics of the flow'of said flood electrons therethrough to said viewing screen -to produce a presentation wherein different potential levels of said charge pattern correspond to different colors.

No references cited.

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