DE1111744B - Circuit of a storage tube - Google Patents

Description

INTERNAT.KL. H 01 j

GERMAN

PATENT OFFICE

C 17317 Vmc / 21g

REGISTRATION DATE: AUGUST 7, 1958

NOTICE
THE REGISTRATION
AND ISSUE OF THE
EDITORIAL: JULY 27, 1961

The invention relates to a circuit for a storage tube with which a signal is written one after the other, is read and erased and in which the storage tube from a storage screen with a Metal counter electrode, an insulating layer attached to the counter electrode with a fine mesh Metal grid, an electron gun with a cathode, a control electrode, acceleration and lens electrodes for forming a concentrated one directed toward the storage screen grid Electron beam and deflection devices for deflecting the beam over the surface of the Storage screen consists and in which the electrodes of the electron gun on fixed Potentials with respect to the cathode, the storage screen grid at a low positive Potential to earth and at which the control electrode or the counter electrode are the input signals and the output signals are taken from the storage screen grid.

There are storage tubes known in which the electron beam during the reading process when Hitting the storage layer makes more secondary electrons free than the primary electrons Strike layer, in other words, where the secondary electron emission ratio is greater than One is.

The aim of the invention is to create a storage tube circuit in which the stored signals without distortion of the course of their time function and without phase shift compared to the initial instant of the respective period in one or more reading periods between the times nT and (n + 1) T, where η is a integer can be reproduced when the signals have been stored between time zero and T of a writing period.

This condition is for an accurate reproduction of a single signal that corresponds to the recorded Signal is read, just as necessary as for an accurate comparison between several signals read successively with or without time intervals between periods. Therefore the previous reading may be the one written on the storage screen during the write period Do not influence the charge values. The reading process is based on the stored charges controlled without deleting them themselves, unless deletion is intended.

Furthermore, the transfer function must be at a writing speed, the sampling period of the Circuit of a storage tube

Applicant:

Compagnie Generale de Telegraphie sans FiI, Paris

Representative: Dr. W. Muller-Bore

and Dipl.-Ing. H. Gralfs, patent attorneys,

Braunschweig, Am Bürgerpark 8

Claimed priority:
France 8 August 1957

Francis Boulet and Jacques Toulemonde, Paris,
have been named as inventors

It is on the order of a fiftieth of a second to allow the correct reproduction of intermediate tones.

This goal is achieved according to the invention in that the lens electrodes for the purpose of decelerating the electrons are on decreasing potentials with respect to the cathode and that the cathode for the Write and read process on earth potential and for the erase process on a high negative potential is to be brought to earth and that the counter electrode of the storage screen for the write process on a to bring a higher potential against the potential of the storage screen grid when the input signals the control electrode are fed, and that the counter electrode for the reading and erasing operations is essentially brought to ground potential when the input signals are fed to the control electrode or to be brought to earth potential for all work processes if the input signals of the Counter electrode are fed.

The invention is explained below with reference to FIGS. 1 and 2 of the drawings show an embodiment of the invention, described.

Fig. 1 is a longitudinal section through an inventive Tube, the circuit of the tube being indicated schematically;

FIG. 2 is a cross section taken along line 2-2 of FIG. 1.

109 649/319

The tube according to Fig. 1 consists of a ventilated cylindrical glass envelope 1 with an electron gun, Means for guiding the electron beam and a storage screen.

The electron gun contains a cathode 2, a filament 3, a Wehhelt electrode 4, a first acceleration anode 5 and a second acceleration anode 6, which is connected to the metallic Covering 7 is connected - which covers part of the wall of the shell 1 on the inside.

In order to guide the electrons hitting the storage screen in parallel paths, the Tube on several cylindrical or conical guide electrodes 8, 9 and 10. The electrode 10 has a Cross grid 11, which runs parallel to the screen and is of the same extent as this.

The screen consists of a very thin grid 12 on an electrically insulating layer 13. Die Layer 13 is deposited on a metal layer 14 and the grid 12 faces the grid 11, i.e. H., it faces the electron gun.

To connect the electrodes 2, 3, 4, 5, 6, 8, 9, 10, 11, 12 and 14 to the external circuit are provided in the envelope 1 vacuum-tight bushings.

A DC voltage source 15 supplies the potentials for the elements of the electron gun. For example If there is a negative potential of 70 volts at the Wehnelt electrode 4, at the anode 5 positive potential of approximately 400 volts and at the anode 6 a positive potential of approximately 1000 volts, if one regards the cathode potential as a reference potential. The filament 3 is removed from the power source 16 fed.

At a DC voltage source 17 is the voltage divider 18, the lead electrodes 8, 9 and 10 progressively decreasing and adjustable positive potentials. These potentials can, for example have the following values:

500 volts at electrode 8,

300 volts at electrode 9 and
30 volts at electrode 10,

where the cathode potential is regarded as the reference potential will. Cathode 2 is at the negative pole of voltage source 17 and therefore at its potential.

The terminal of the current source 15, which is at cathode potential, is connected to the switch 19. This places the cathode in the position indicated by a solid line in the drawing to a potential that is equal to or close to ground potential. In the other position, shown in dashed lines in the drawing is indicated, it connects the cathode with a high negative potential compared to ground, for example a potential of -400VoIt, the is removed from the DC voltage source 20.

The representation of the switch 19 is only symbolic in the drawings. This switch corresponds to in practice any suitable switching means, such as e.g. B. electronic or electromagnetic Switching devices.

The grid 12 of the screen is connected to a terminal of a DC voltage source via a resistor 21 connected, which has a positive potential of a few volts, e.g. B. 5 volts to ground.

The metallic layer 14 of the screen is connected to the switch 23. The above apply to this comments made with respect to the switch 19 also. In the one undressed In the position indicated in the line, the switch 23 connects the layer 14 to ground or to a ground potential very close potential. In the position indicated by dashed lines, the layer 14 is connected to the DC voltage source 24 connected, of which you have a positive potential of, for example, 20 volts Mass is supplied.

Two pairs of deflection coils 25 fed by suitable deflection voltage sources (not shown) are for the horizontal and vertical magnetic deflection of the electron gun generated electron beam 26 is arranged around the neck of the shell 1.

An output circuit 27 for the signal read is via capacitor 28 to the grid 12 on a Point connected between this grid 12 and the resistor 21.

The input circuit 29 of the signal to be stored is in the example shown via a capacitor 30 connected to the Wehnelt electrode 4. Instead, it can also be connected to the line be that connects the metal layer 14 to the switch 23, as indicated by dashed lines at 29 'and 30' is. The Wehnelt electrode 4 must have a suitable DC potential, as below is still being discussed.

Mode of action

First of all, the screen has no charge; i.e., all points on the surface opposite the grid 12 the insulating layer 13 have the same potential that is given to the grid 12 by the voltage source 22, namely 5 volts in the present case Example.

At the beginning of the write period, the switch 19 is so that the cathode is grounded and the switch 23 is in such a position that the layer 14 gives a positive potential of 20 volts will. The write signal source is connected at 29 to the Wehnelt electrode 4, which is so biased is that the electron beam disappears in the absence of a signal. The said signal is modulated the beam 26, which the surface of the grating 12 and the insulating layer 13 under the influence of the deflection coils 25 scans.

The paths of the beam 26 initially run during their passage through the electron gun apart, however, are curved by the action of the lead electrodes 8, 9 and 10 and finally brought in its last piece in paths parallel to the axis of the tube.

The electron optical system is designed so that the beam parallelism over the entire scanning period remains evenly maintained. As a result, the electrons pass through the grid 11 perpendicular through and hit the grid 12 regardless of the point of impact in one to the screen perpendicular direction.

The electrons of the beam 26 are emitted from the cathode, which is at zero potential and partly collected by grid 12, which is at a potential of 4-5 volts, and the resistor 21 supplied. As a result of this small potential difference, the electrons are slow. The remaining Beam electrons pass through the mesh of the grid 12 and are from the surface of the Insulating layer 13 added on higher

Potential than the grid 12 is because the supporting metal layer 14 is supplied with a potential of 20 volts will.

The bombardment with slow electrons causes secondary electron emission on the insulating layer with an emission coefficient less than one. Consequently, at a point of impact is the number of emitted electrons smaller than the number absorbed, so that this point is negatively charged, where its potential is proportional to the number of electrons it has absorbed, d. H. so proportional to the modulating signal applied at 29, decreases (becomes less positive). The potential of the Circuitry are preferably chosen so that the maximum amplitude of the modulating input signal brings the potential of the point under fire to zero.

The scanning of the surface of the coating 13 by the beam 26 is produced during the writing period thus on this surface a potential image that reflects the changes in the input signal during the writing period is equivalent to.

At the end of the writing period, the switch 21 is placed in the position in which it removes the metal layer 14 connects with mass. The potentials of all points of the surface 13 then decrease by an amount that of the Reduction of the potential of the metal plate 14 by the 20 volts of the power source 24 corresponds. The points, at which the potential did not change during the write process because the signal was zero then turn to zero potential while the points which are under the action of the maximum Signal were brought to the potential zero, now lie on a negative potential, the same the uniform potential reduction on the plate 14 is.

The potential differences between the individual charged points on the surface 13 are relative to one another is not changed by this process, and the signal is thus retained until there is a reading period comes. This can immediately follow the writing period, but does not need to be. For reading the screen is scanned with a constant intensity beam which z. B. is obtained by that a fixed amplitude signal is applied at 29 during the scan. The potentials of all electrodes are kept at the same values as they had at the end of the writing period.

At each point in time of the reading period, the path of the electron beam is exactly the same as in the corresponding one Time of the write period, provided that the power supply voltages of the Tube are sufficiently stable. As before, the reading beam arriving at grating 12 consists of slow ones Electrons. Again, regardless of where it hits, it hits the screen vertically on.

In contrast to the situation during the writing period, however, the electrons now find their way behind the grid an insulating surface with points that are either at zero potential lie - in areas that correspond to the signal zero - or on a negative potential opposite Ground, the potential value of each negatively charged point of the amplitude of a given Signal instantaneous value. In the areas where the potential is zero, all electrons are collected from the grid 12. In areas with negative charges, the points act as insulating Surface that carry these negative charges, like Wehnelt electrodes, and throw the electrons return. The so thrown back or reflected electrons are distributed in such a way that one Part of the grid 12 is picked up and the other part moves backwards, namely initially under the influence of the grid 11 and then by virtue of the electrodes 10, 9 and 8. The ratio,

ίο in which the reflected electrons are on this Distribute wisely depends on the potential value of the negative charge of the respective point, i.e. H. ultimately from the amplitude of the signal value stored at the point under consideration. In The electrons are never picked up by the insulating surface. Hence changes the reading process does not record the potential values stored on the surface. Such a reading process can theoretically be repeated an infinite number of times; it is only practical because it gradually drains away of the stored charges due to the not infinitely large specific resistance of the insulating Layer limited. The specific resistance will of course be kept as high as possible.

The electrons collected by the grid 12 flow through the resistor 21. After that the current in this resistor is at its maximum and that derived from electrodes 11, 10, 9 and 8 Current at the minimum when the stored signal is zero. With increasing signal amplitude the current through the resistor gradually decreases during that through said electrodes current carried away increases. For a given value of the signal amplitude, the current is in the Resistance 21 zero; the system will be designed so that this amplitude value is the highest at Tube input corresponds to the expected signal amplitude. This way the peak amplitude of the signal is matched with an absolute current level in the load resistor. Assuming that the current in resistor 21 is zero, then the voltage is between the connection point of the capacitor 28 and ground equal to the bias voltage of the grid 12, and since this voltage gradually decreases as the current in resistor 21 increases, it can be seen that the through the Capacitor 28 to the output circuit voltage accurately reproduces the signal that during the Write period had been brought to the input, the peak value of the voltage being replaced by the the current source 22 is given a certain bias voltage of the grid 12.

If after any desired number of readings it is desired to close the screen delete to make it ready for a new memory image, the control arm of the switch 19 is after brought into the position indicated by dashed lines on the right. The control arm of the switch 23, however, remains in its left position (solid line), in which it was before. All potentials of the electron gun belonging electrodes as well as the lead electrodes are then by the same amount reduced, which corresponds to the voltage of the battery 20, which in the example under consideration Cathode to a potential of -400 volts with respect to ground. The Wehnelt electrode receives from Input 29 here is a constant signal that allows a beam to pass through. The electrons that do that

Grid 12 reach the + 5VoIt potential fast electrons. They pass through the grid and hit the insulating layer 13, which they scan under the action of deflection coils 25. Then an emanating from the layer 13 occurs Secondary electron emission with a secondary emission coefficient that is greater than one. Therefore, at a certain point of impact, the amount of electrons emitted is greater than that of the received, and the point is positively charged. This process eventually destroys the at this point stored negative charge, and the potential will be at a value close to the potential of the still brought to + 5VoIt grid 12. In the end all points of the insulating layer reach the same potential as the grid, and the extinction process is finished.

If after a single scan the cancellation is not sufficient, it can be multiple times be repeated; then a new write period follows and the cycle described above begins all over again.

If, according to the modified embodiment of the invention, the signal to be stored, instead of being sent to the Wehnelt electrode 4, modulates the potential of the plate 14 via the circle indicated at 29'-30 ' , nothing changes in the operation of reading and erasing compared to what was said above. Only the writing process is influenced by the modification mentioned. However, the result remains the same. In this variant, the control arm of the switch 23 is left in the left position and the potential of the plate 14 is thus left at zero, while the Wehnelt electrode is given such a bias that an electron beam can emerge from the electron gun. The constant intensity of this beam scanning the screen is suitably set at the Wehnelt electrode so that the secondary emission does not change the charge storage on the insulating layer 13, i.e. the potential of each surface point is brought to the value zero when it is driven by the beam of constant intensity is hit. If the signal applied at 29 'varies the potential of the plate 14, this potential fluctuation is communicated to all points of the layer 13; however, at the point under fire, the potential is kept at zero by the beam. As a result, a potential is stored on the surface 13. If then at the end of the writing period the disk 14 is again at the potential zero, the points which were exposed to the bombardment when the disk received the signal will assume negative potentials corresponding to the respective instantaneous amplitude which the input signal had at the moment of the bombardment . The result is the same as when the beam is modulated by the Wehnelt electrode.

From the above, it can be seen that the electrodes of the electron gun and the lead electrodes are removed during the writing and reading periods were operated with the same power supply voltages. Therefore, the playback will be the saved Information not affected by errors in the geometry of the tube and errors in the scanning. Only the more or less great perfection of the diversion of time and the Stability of the power supply voltages in the playback.

The charge image stored during the writing process is not disturbed by the reading process.

Since it is finally possible for the maximum signal to coincide with that threshold value too let, in which the current through the resistor 21 disappears, one is also able to produce a uniformly valid relationship between every mean value of the amplitude and a certain im Resistance to produce flowing current, i.e. to reproduce the intermediate tones correctly.

The requirements for the storage tube circuit mentioned in the objective are therefore met by the circuit according to the invention met. The invention is not limited to the illustrated embodiments limited, but changes and modifications within the concept of the invention are accessible.

Claims (3)

PATENT CLAIMS: 1.Circuit of a storage tube, with which a signal is written, read and erased one after the other and in which the storage tube consists of a storage screen with a metal counter-electrode, an insulating layer attached to the counter-electrode with a fine-meshed metal grid, an electron gun with a cathode, a control electrode, acceleration - and lens electrodes for forming a concentrated electron beam directed in the direction of the storage screen grid and deflection devices for beam deflection over the surface of the storage screen and in which the electrodes of the electron gun are at fixed potentials with respect to the cathode, the storage screen grid at a low positive potential with respect to earth and in which the input signals are to be fed to the control electrode or the counter electrode and the output signals are to be removed from the storage screen grid, characterized in that for the purpose of Fig Remsung the electrons the lens electrodes (8, 9, 10) are at decreasing potentials with respect to the cathode (2) and that the cathode is to be brought to earth potential for the writing and reading process and to a high negative potential to earth for the erasing process and that the counter electrode (14) of the storage screen for the writing process is to be brought to a higher potential than the potential of the storage screen grid (12) when the input signals are fed to the control electrode (4), and that the counter electrode (14) for the reading and erase operations are to be brought to essentially earth potential when the input signals are fed to the control electrode (4), or to be brought to earth potential for all operations when the input signals are fed to the counter electrode (14). 2. A circuit of a storage tube according to claim 1, characterized in that the potentials of the various electrodes are chosen so that during the writing and reading process the electrons hitting the storage screen are slow and the secondary emission ratio is less than one, whereas during the erasing process those on the storage screen impinging electrons are fast and the secondary emission ratio is greater than one. 3. Storage tubes in the arrangement of the circuit according to claim 1 or 2, characterized in that the lens electrodes (8, 9, 10) between the deflection devices (25) and the storage screen (12, 13, 14) are arranged so that between the Electrodes such electrostatic lens fields are created that the 10 Deflectors cause deflected electron beam, essentially perpendicular to to hit the storage screen. Considered publications:
German Auslegescnrift W18069 VHIc / 21g (published on November 22, 1956). 1 sheet of drawings