US3302054A

US3302054A - Direct viewing storage tube having inclined flood gun and virtual cathode

Info

Publication number: US3302054A
Application number: US273068A
Authority: US
Inventors: Courtan Bernard
Original assignee: CSF Compagnie Generale de Telegraphie sans Fil SA
Current assignee: Thales SA
Priority date: 1962-05-03
Filing date: 1963-04-15
Publication date: 1967-01-31
Anticipated expiration: 1984-01-31
Also published as: DE1200959B; NL292012A; GB1004949A; FR1329685A

Description

1967 B. COURTAN DIRECT VIEWING STORAGE TUBE HAVING INCLINED FLOOD GUN AND VIRTUAL CATHODE Filed April 15, 1963 I I g1 I I mvemon: col/R74 BY pmkl ATTORNEY United States Patent T The present invention relates to direct View storage tubes, that is to tubes comprising two guns and a so-called storage grid covered with an insulation on the face thereof turned toward the guns, one of these guns, provided with usual intensity control devices and electron beam deflection devices, being the writing gun that emits electrons of which the speed is sufficient so that a deposit of positive charges is possible on the insulation of the grid, and the other gun being a flood gun which sends a slow and uniform beam over the entire grid. Behind this grid is disposed a fluorescent screen; at the places at which the positive charges have been deposited on the insulation by the writing beam, the electrons of the flood. gun, which traverse the grid without erasing these charges and which are accelerated thereupon, come to impinge on this screen thus rendering visible the trace inscribed by the writing gun. several minutes of very brief and very rapid phenomena.

The known tubes of this type comprise generally the flooding gun in the axis of the tube and the writing gun disposed laterally in such a manner as to emit an oblique beam with respect to this axis. It may, nevertheless, be useful, for reasons of bulkiness and interchangeability with conventional cathode ray tubes, to dispose the guns in an inverse fashion, that is to place the writing gun in the axis of the tube and to reduce very significantly the length of the tube with the same dimensions of the image. Nevertheless, one encounters then the difiiculty in that the flooding gun, which ione is obligated to dispose laterally, is not capable of uniformly flooding the storage grid. This is principally by reason of the different electron density of the beam between the edges and the center due to the fact of its large angle of aperture. Furthermore, the angle of incidence of the flooding electrons on the grid which is very different from zero degrees due to the fact, on the one hand, of the large angle of aperture mentioned hereinabove and, on the other, to the dissymmetry of the collimation electrodes with respect to the flood beam. This defect cannot be corrected even by disposing a plurality of flooding guns in the manner of a ring about the axis, for experience indicates that there are then formed a plurality of overlapping areas on the storage gird of which each correspond to the flooding of a portion of the grid, and not a single uniform flooding zone covering the entire grid. From this follow non-uniformities of brilliance in the trace viewed on the screen, and even complete holes in the observed image.

The present invention relates to direct viewing tubes of reduced length .with an axial writing gun, and has for its purpose to remedy the difliculty exposed hereinabove, so as to assure a uniform flooding of the storage grid by the flooding gun.

According to the present invention, there is disposed between the Writing gun and the storage grid, and parallelly to the latter, a grid carried at a potential near that of the cathode of the flooding gun. This grid decelerates the electrons of this gun which arrive at its level with a substantially zero velocity. These electrons are accelerated anew by the relatively strong and uniform field which exists between this deceleration grid 'and the socalled collector grid, usually disposed in front of the stor- This arrangement permits the observation during 3,362,054 Patented Jan. 31, 1967 age grid and carried at a relatively high positive potential. This field straightens the electron trajectories which arrive at the collector grid substantially perpendicularly to the surface thereof, to traverse this grid, attain the storage grid and eventually traverse the same to reach the screen as in the known direct viewing storage tubes. This deceleration grid therefore constitutes in fact a virtual cathode of large surface, emitting at slow speed the flooding electrons uniformly and perpendicularly to the storage grid, notwithstanding the lateral position of the flooding gun.

Accordingly, it is an object of the present invention to provide a direct view storage tube which eliminates the shortcomings mentioned hereinabove that have been encountered heretofore in the known storage tubes of this type.

Another object of the present invention resides in the provision of a direct view storage tube in which the writing gun is arranged axially to the tube while the flooding gun is arranged laterally of this axis without, however, producing any non-uniformities in the viewed picture.

Still another object of the present invention resides in the provision of a direct view storage tube in which, for reasons of bulkiness and interchangeability with ordinary cathode ray tubes, the writing gun is arranged in the axis of the tube while the flooding gun is arranged laterally thereof thereby considerably reducing the length of the tube with sameness in the dimensions of the viewed image.

A still further object of the present invention resides in the provision of a direct viewing storage tube provided with an asymmetrically disposed flooding gun in which simple means are provided to assure satisfactory uniformity of the viewed picture on the screen.

These and other objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, in longitudinal cross sectional view one embodiment in accordance with the present invention.

Referring now to the single figure of the drawing, there is disposed within the axis of the evacuated glass envelope 1 the writing gun 2 composed of a cathode 3 carried, for example, at a potential of 2 kv., of a Wehnelt electrode 4 carried at a suitable potential taking into consideration the desired intensity of the beam, and of a series of anodes 6, 7 and 8, wherein the anodes 6 and 8 are carried, for example, at zero potential, and the intermediate anode 7 is carried at a potential sufiicient to concentrate the electrons into a fine beam, for example, 'at +1.3 kv.

The beam 5 is subjected to the action of deflection means, for example, of magnetic deflection means, it being understood that the mention of magnetic deflection means is not limitative of the present invention, of which a portion is represented in cross section by two windings 9 and 10 disposed along the periphery of the neck of the tube. Reference numeral 11 designates the interior metallization of the tube, carried, for example, at +10 v., while reference numeral 12 designates the collimation electrode, carried, for example, at +20 v. and reference numeral 13 the fluorescent screen, carried, for example, at +10 kv. The connections which permit excitation of all of the electrodes at the different potentials indicated hereinabove have not been shown in the drawing to simplify the same.

In front of the screen 13 are disposed successively, starting from the screen:

a first, so-called storage grid 14, covered with an insulation on the side opposite the screen and carried, for example, at a potential of +6 v.;

a second, so-called collector grid 15, carried, for example, at a potential of the order of +250 v.;

a third grid 16 according to the present invention disposed at some millimeters from the grid 15 and parallelly to the latter and to the grid 14, and carried at a potential of the order of +5 to v.

Laterally of the axis of the tube and obliquely with respect thereto is disposed the flooding gun 17, composed of a cathode 18, carried, for example, at zero potential, of an accelerating anode 19 carried at a potential of the order of +100 to +150 v., and of a Wehnelt electrode 20 carried at a suitable potential whereby the flooding beam 21 leaves the gun with a large angle of aperture to enable the beam to flood the entire surface of the grid 16.

In operation the electrons of the beam 21 arrive at all points of the grid 16 with a substantially Zero velocity, thereupon, after having traversed this grid 16, restart under the influence of the accelerating potential of grid along parallel trajectories or paths perpendicular to the grids 14, 15 and 16 and with a substantially identical velocity at all points of the cross section of the beam. Having traversed the grid 15, the electrons uniformly flood the entire surface of the grid 14 of which the potential with respect to the cathode 18 is such that they are relatively slow, that is that they produce at the impact of the grid 14 less secondary electrons leaving the dielectric covering this grid than the quantity of primary electrons arriving thereat. The insulating face of the grid 14 is thereby charged negatively and repels the beam 21 in such a manner that at the state of equilibrium this beam just barely reaches the grid without traversing the same.

If now a beam of relatively rapid electrons 5, modulated by the signal, is emitted by the writing gun 2 and is deflected by the COils 9 and 10, the insulating face of the grid 14 finds itself swept with creation of positive charges since, at the speed of these electrons, there are less primary electrons than secondary electrons due to the impact thereof. The positive charges form a relief conforming to the variations of the signal and compensate more or less the negative charges deposited by the slow beam 21. The electrons of the latter may then pass in more or less large quantity through the grid 14, are accelerated by the high voltage of the screen 13, and bombard the latter While exciting the observed image as in the known direct viewing tubes.

There has thus been realized a relatively short direct viewing storage tube with respect to the dimension of the image and with an axial writing gun, in which nevertheless the storage grid is flooded uniformly which assures the correct operation of the tube with a uniformly brilliant image.

While I have shown and described one embodiment in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications within the scope of a person skilled in the art and I, therefore, do not wish to be limited to the details shown and described herein but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

I claim:

1. A direct viewing storage tube, comprising:

viewing screen means,

storage grid means disposed ahead of said screen means,

writing electron gun means located along an axis substantially perpendicular to said screen means and including means for emitting a beam of relatively rapid electrons in the direction toward said storage grid means,

flood gun means located laterally to and inclined with respect to said axis including means for emitting a beam of relatively slow electrons in the direction toward said storage grid means,

and means located between and in the path of said flood gun means and said storage grid means and forming effectively virtual cathode means providing a substantially uniform flooding of said storage grid means by the electrons emitted from said flood gun means. 2. A direct viewing storage tube, comprising: a fluorescent screen,

5 storage grid means extending substantially parallelly to said screen,

writing electron gun means located along an axis substantially perpendicular to said screen and including means for emitting a beam of relatively rapid electrons in the direction toward said storage grid means, means for impressing a signal upon said first-mentioned beam and means for deflecting said firstmentioned beam to thereby sweep said storage grid means and therewith store said signal therein,

flood gun means located laterally and tilted with respect to said axis and operable to emit a beam of electrons, said flood gun means including means for emitting a widely diverging beam of relatively slow electrons in a direction toward said storage grid means,

deceleration grid means extending between said flood flood gun means and said storage grid means and disposed substantially parallely to the latter, said deceleration grid means being carried at a potential to decelerate said slow electrons substantially to zero velocity upon arrival in the plane of said decelerating grid means, and means for re-accelerating the electrons from said flood gun means after passing said deceleration grid means for flooding said storage grid means along substantially parallel paths substantially perpendicular to said storage grid means.

3. A direct viewing storage tube, comprising:

a fluorescent screen,

storage grid means extending substantially parallelly to said screen,

writing electron gun means located along an axis substantially perpendicular to said screen including means for emitting a beam of relatively rapid electrons in the direction toward said storage grid means, means for impressing a signal upon said first-mentioned beam and means for deflecting said firstmentioned beam to thereby sweep said storage grid means and therewith store said signal therein,

flood gun means located laterally and tilted with respect to said axis and operable to emit a beam of elecrons, said flood gun means including means for emitting a widely diverging beam of relatively slow electrons in a direction toward said storage grid means,

deceleration grid means extending between said flood gun means and said storage grid means and disposed substantially parallelly to the latter, said deceleration grid means being carried at a potential to decelerate said slow electrons substantially to zero velocity upon arrival in the plane of said decelerating grid means,

and collecting grid means extending between said storage and decelerating grid means and substantially parallelly thereto, said collecting grid means being carried at a potential to re-accelerate the electrons emitted by said flood gun means for flooding said storage grid means along substantially parallel paths substantially perpendicular to said storage grid means.

References Cited by the Examiner UNITED STATES PATENTS 2/1958 Smith 3l5l2 3/1960 Hunter 315-l3

Claims

1. A DIRECT VIEWING STORAGE TUBE, COMPRISING: VIEWING SCREEN MEANS, STORAGE GRID MEANS DISPOSED AHEAD OF SAID SCREEN MEANS, WRITING ELECTRON GUN MEANS LOCATED ALONG AN AXIS SUBSTANTIALLY PERPENDICULAR TO SAID SCREEN MEANS AND INCLUDING MEANS FOR EMITTING A BEAM OF RELATIVELY RAPID ELECTRONS IN THE DIRECTION TOWARD SAID STORAGE GRID MEANS, FLOOD GUN MEANS LOCATED LATERALLY TO AND INCLINED WITH RESPECT TO SAID AXIS INCLUDING MEANS FOR EMITTING A BEAM OF RELATIVELY SLOW ELECTRONS IN THE DIRECTION TOWARD SAID STORAGE GRID MEANS, AND MEANS LOCATED BETWEEN AND IN THE PATH OF SAID FLOOD GUN MEANS AND SAID STORAGE GRID MEANS AND FORMING EFFECTIVELY VIRTUAL CATHODE MEANS PROVIDING A SUBSTANTIALLY UNIFORM FLOODING OF SAID STORAGE GRID MEANS BY THE ELECTRONS EMITTED FROM SAID FLOOD GUN MEANS.