US2918601A - Signal storage tube - Google Patents

Description

Dec. 22, 1959 w. BERTHOLD 1 2,918,601

SIGNAL STORAGE TUBE Filed July 7, 1954 WRITING GUN 2 7 POTENTIAL /7 SOURCE INVENTOR W. BERTHOLD AT TORNE Y ness variation of the optical picture. ment bears the great advantage of not having to operate SIGNAL STORAGE TUBE Wolfgang Berthold, Stuttgart-Wei] im Dorf, Germany,

assignor to International Standard Electric Corporation, New York, N.Y., a corporation of Delaware Application July 7, 1954, Serial No. 441,841

Claims priority, application Germany July 8, 1953 4 Claims. (Cl. 315-12 This invention relates to a signal storage tube.

Signal storage tubes are generally employed for storage of short electric impulses, solitary short oscillating processes, or electrically transmitted pictures for a longer time.

Especially adapted to this purpose are electrostatically charged controlled signal storage tubes, because with the aid of such tubes it is possible to produce and to erase pictures in almost inertialess manner. With such types of signal storage tubes an electron beam scans a raster on an electrode which is provided with a thin layer of insulation. By emitting secondary electrons said layer of insulation is charged. The loading or charging of each individual point depends on the strength and velocity of the impacting beam, or else on the field absorbing the secondary electrons. The electrostatic charge signal or picture produced in such a manner will then be either converted into brightness values of an optical picture or into a time succession of current values. Various arrangements are known for this purpose. For example there are known photo or secondary emission cathodes covered with insulating particles, and which said insulating particles are charged by the scanning electron beam and serve to block a certain range or area of the cathode, which again dependson the magnitude of the charge imposed upon the insulating particles. In a modified version of such an arrangement the insulator is coated on a grid which controls with its charge the electrons of a special flood cathode, or else the cathode which previously caused the charging of the insulating particles.

In order to obtain a black-and-white control of a picture, the potential of the grid must lie near volt, because only in such a case will the beam be completely blocked; this, however, is necessary with the black parts of the picture. Owing to this fact the greatest portion of the electrons produced by the flood cathode cannot contribute towards the brightness of the picture, and will be reflected from the grid to the collector. The abovementioned photo or secondary emission cathode respectively, bears the disadvantage that it is technically very diflicult to manufacture it with the necessary uniformity. With the conventional arrangements for converting the electrostatic signal (charge picture) into an optical picture, there is involved the intensity control of an electron beam. In accordance with the present invention it is suggested to replace the intensity control by a direction control, in that the stored charge changes the direction of the electron beam according to the respective charge or load. The thus performed change in direction will then be converted with the aid of suitable diaphragms into a bright- This arrangewith grid voltages of 0 volt, so that all flood electrons will pass through the control electrode.

1 By way of example, the idea of invention may be realized in the following way: Instead of the grid there will be employed a system of.v parallel wires, tapes or United States Patent 2,918,601 Patented Dec. 22,1959

stripes. This system will be flooded by electrons proceeding from one point and forming a homocentrical bundle. By suitably selecting the voltage at the wires etc. there will be formed a cylindrical lens system, splitting up the homogeneous bundle of electron beams into sharp lines.

The arrangement, for example, is made in such a way that every second wire, for example, iscovered either completely or partially with insulating material. By the bombardment with electrons from any source of electrons the wires covered with the insulating material will be charged in relation to the uncovered wires, to a different potential. By suitably selecting this potential the electron bundles will be arranged in pairs of lines. By means of an electron beam scanning a raster, which beam is controlled according to the contents of the information concerned, the insulated wires will be charged in correspondence with the signal. The flood electrons will be affected by this charging and will be deflected out of their usual direction according to the local charging. In case the electron beams which are arranged in pairs of lines, for example, hit a stripe of luminescent substance having the approximate width of the electron beam bundle, then the whole stripe will be illuminated. By deflection owing to the local charge of the insulated wires the flood electrons will be deflected according to the. content of the information, and on the luminescent stripe there will be produced corresponding luminous and dark spots. In case the luminescent stripes are arranged aside from the electron bundles assembled in pairs of lines, then the said stripes are normally dark and will only be lighted up by the deflectionof the flood electrons owing to the local charging corresponding to the content of the information.

It is also possible to cover all wires partially with insulating material. In the present invention it is preferred that the insulating material be applied to the side of the wires not facing the source of flood electrons, because thereby a discharge of the electrostatic charge thereon by the flood electrons is nearly completely ex- .cluded. Accordingly, there will be obtained a substantially longer storing time. The local charging is attained with this arrangement by means of an electron beam controlled according to the content of the information and striking the wires from the side opposite the electron gun. I

Instead of having the luminescent material arranged I in stripes and having the lines of the electron bundles deflected with respect thereto, it is possible to use a uniform luminescent layer and provide a masking means such as for example a plurality of stripes in front of the luminescent layer, different areas of said stripes being struck by the electrons depending upon the deflection of the beam thereof. For thepurpose of avoiding interferences it may be appropriate to scan the picture vertically in relation to the direction of the grid wires. At places where an impacting of flood electrons is unavoidable, it may be of advantage to adjust the velocity of the electrons to such an extent that the secondary emission coeflicient equals 1, i.e. when the electrons produced by theflood gun impinge on the insulation then, for each electron of the flood gun, there is supposed to be tripped one secondary electron, this being achieved by the velocity of the electrons produced by said flood gun. By employing this arrangement no changes of the picture contents will be caused by the electrons of the electrodes there may be used, for example,'t-he coveringup stripes referred to herein above and described in connection with Fig. 2 hereinafter.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood, by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is a schematic diagram of a portion of a cathode ray storage tube and Fig. 2 is a similar view of a modification thereof.

In Fig. 1 reference numeral 6 denotes the glass envelope of an electric discharge tube which is partially shown; the constitutent parts which do not contribute towards enabling a better understanding of the invention, such as the electron gun systems (beam generating systems), deflecting and focusing systems, etc., have been omitted.

5 denotes the point from which the fan-shaped electron beam (flood electrons) proceeds. On the face plate of the discharge tube envelope 6 there are arranged strips of fluorescent substance 4. In front of these strips there are provided parallel-tensioned wires 1. Every second one of these wires is coated with a layer ofinsulating material 3. The non-insulated and the insulated wires are charged to a suitable potential with the aid of a source of voltage 7. A separate writing gun 8 for writing an electrostatic charge on the insulating material 3 is provided and is arranged at any suitable point. (The writing gun 8, which is denoted by dashlines in Fig. l, is supposed to indicate that it may also be arranged at any other suitable point.)

The system of parallel wires serves to split up the beam of electrons, which proceeds from 5, into individual sharp lines proceeding between an insulated and a noninsulated Wire. The flood electrons impinging on the insulated wires change, on account of the secondary emission, the potential of these wires with respect to the non-insulated ones. By suitably selecting the voltages at the wires or on the surface of the isolation coating, the electron beams, which are produced between an insulated and a non-insulated wire and are focused to sharp lines, are assembled in groups of two each impinging on the strips of fluorescent material arranged behind the wire system.

By means of the focused electron beam of the writing gun 8, which is led in a raster-shape over the system of the parallel wires, and the intensity or speed of which i can be controlled according to the contents ofthe in formation, the charge applied to the insulated wires will be locally changed. At that particular point, wherethe charge has been changed, the flood electrons will be deflected from the strip of fluorescent material and there will be produced, according to the recorded picture of charge, either bright or dark spots on the strips of fluorescent material 4.

The focused scanning beam and the deflecting and focusing systemsare not shown in Fig. 1 for reasons of clarity. The recording of the picture of charge by the inscribing beam and the reproduction of the'recorded picture of charge by the flood electrons mayzbe effected successively. However, it is also possible to perform both processes simultaneously, whereby the flood electrons (with properly selected insulating material. and the employed voltages) can be used to maintain the recorded contents of the information. For this process. there is utilized the well-known fact of. the unstable equilibrium at the lower point where the voltage of the secondary emission equals 1 (one). (This process is particularly described in the book by M. Knoll and B. Kazan Storage Tubes and Their Basic Principles on page 24 in the chapter entitled Bistable Writing with the Aid of a Holding Beam) The flood electrons or the secondary electrons which are emitted thereby cause a displacement of. the. charge. distribution, the. mean. potential value. of

which lies at the upper point where the voltage of the secondary emission equals 1 (one), towards different sides to more positive or more negative potential respectively, quite depending on the charge caused by the inscribing beam, and thereby serve to maintain a certain black-white distribution of the picture. If these processes are performed successively then one system can be employed instead of the two beam generating systems, said one system generating first the inscribing beam and thereafter the flood beam. I

A somewhatmodified embodiment relating to a change of the strips of fluorescent material will be seen from Fig. 2 of the drawings. The same components are also given the'same reference numerals as in Fig. 1. Instead of the strips of fluorescent material, which are shown in Fig. 1, there is now employed a continuous layer of fluorescent substance 9 and a diaphragm system 10, which is arranged in a suitable position with respect to the layer of fluorescent substance 9 and to the paralleltensioned wires 1. According to the picture of charge on the insulated wires, which has been caused by the inscribing beam, the flood electrons are emitted either onto the diaphragm system or through the spaces between the diaphragms onto the layer of fluorescent substance. The diaphragm system 8 consists, for instance, of metal electrodes to which a potential has been applied and which serve as a collector for all electrons impinging thereon.

By employing this method there will be obtained on the layer of fluorescent substance a luminescent picture which corresponds to the picture of charge.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention asset forth in the objects thereof and in the accompanying claims.

What is claimed is:

1. In a cathode ray storage'tube of the type in which an electrostatic charge is stored on the storage electrode, a substantially planar storage electrode comprising a plurality of parallel, linear storage elements each including insulating material and a conductive portion on which said insulating material is arranged, and a plurality of parallel, linear non-storage elements in the form of bare conductors arranged between said storage elements and spaced therefrom.

2. A cathode ray image reproducing tube system comprising a storage means for storing potentials corresponding to an image, a writing electron gun for impressing image charges on said storage means, and a reading source of electrons controlled by said storage means for reproducing said image on a target, said system having in combination a first group of conductors, a second group of conductors, the conductors of said first and second groups positioned substantially in a plane and. arranged alternately parallel with each other, said first groupof conductors having storage insulating coatings thereon to provide said storage means, said sec- .ond group of conductors being bare, whereby passage of said electrons from said reading source between said conductors of said first and second groups will be in sheet-like formed beams producing lines on said target, means for applying a predetermined potential to said conductors, whereby a control potential difference will be produced between said second group of conductors and said first group of conductors upon storage of charges from said writing gun to produce lateral deflection of said sheet-like formed electron beams and then deflection of said lines in accordance with the variations in the stored charges, said target having strips of material parallel with said conductors responsive to energy of said. sheet-like beams and positioned to receive a predeterminedproportion of said energy when no charge is References Cited in the file of this patent UNITED STATES PATENTS Farnsworth Oct. 1, 1940 Wertz Sept. 6, 1949 Schlesinger Dec. 5, 1950 Sziklai Nov. 6, 1951 Michaels Aug. 21, 1956 Haeff Aug. 28, 1956 Hansen Apr. 9, 1957 Pensak Sept. 10, 1957

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