US2230134A - Image analyzing tube - Google Patents

Description

Jan. 28, 1941. R. COLBERG EI'AL IMAGE ANALYZING TUBE Filed Jan. '12, 1938 II III 3&4 1 04W Patented Jan. 28, 1941 UNITED STATES 2,230,134 Y IMAGE ANALYZINGTUBE Rolf Colberg, Berlin Dahlem, and Heinrich Striibig, Teltow, Germany, assignors to the firm Fernseh Aktiengesellschaft,- Zehlendorf, near Berlin, Germany Application January 12, 1938 Serial No. 184,684 In Germany January 13, 1937 4 Claims.

An image analyzing tube is described in the copending application, Ser. No. 138,235, filed Apr. 21, 1937, now United States Patent No. 2,161,643 issued June 9,- 1939, in which the electrons liberated from the mosaic by the scanning beam are guided to an electron multiplier and are multiplied therein. In this device, the electron multiplier is disposed in a protrusion of the tube.

This invention relates to such an arrangement which allows especially efficient utilization of space, and which also has advantages in electrical respects. According to the invention, the electron multiplier is disposed in a portion of the tube symmetrical about an axis, preferably a cylindrical or spherical portion, in such a manner that it lies in the space between that scanned by the scanning beam and the wall of the tube. Such an arrangement also simplifies the making of the tube because the electron multiplier can be combined into one mechanical unit with the mosaic electrode, and no large protrusions of the vacuum receptacle are required.

The drawing shows several embodiments of the invention. Figs. 1 and 2 show a cylindrical arrangement, while Fig. 3 shows a spherical arrangement. In Fig. 1 an electron gun I 4 is placed in the elongation 2 of the cylindrical portion l of the vacuum receptacle, in the other end of whichis the mosaic electrode 3. In this case a double-sided mosaic is provided which is illuminated from the right side and scanned on the left side. It consists of a multitude of elements permeating the plate which form small condensers together with a common counter-electrode, the lead from which is brought out of the vacuum receptacle at 4. The photoelectrons are drawn towards the ring-shaped wall coating l3. A rectangular or square portion of any cross section of the tube, perpendicular to its axis, is traversed by the deflected electron beam during the scanning action, while the space between this rectangular or square portion and the wall of the tube is so far not utilized. According to the invention, the electron multiplier is now disposed in this space. In this case it consists of a silver plate 8, which serves as the first secondary emitting electrode, and of several electron-permeable electrodes l2 placed in back of each other and held at increasing potentials. The anode is also electron-permeable and its lead is brought out at 6. The emitting electrodes derive their potential from a potentiometer, which may be placed inside or outside of the vacuum tube. The first grid 5 has a curvature towards the mosaic.

A screen I separates the electron multiplier from the space .traversed by the scanning beam and simultaneously fulfills the function of the anode wall coating generally used. The potential of the electrode 8 is held preferably slightly higher than the potential of the screen 1, while the grid 5 is held at a still higher potential. This secures guidance towards the electron multiplier of all secondary electrons produced during scansion. The deflection occurs by means of two schematically indicated magnetic deflecting coils 9 and I0. It may be necessary to provide a further screen II in order to avoid the influence of the magnetic fields upon the electron multiplier.

Fig. 2 shows two possibilities for the construction of the screen and multiplier. In both cases the figure shows a cross section through Fig. 1 in the plane AA. The left half of the figure shows a conical screen, whereas the right half shows a screen of rectangular section which is accurately matched to the extreme positions of the electron beam. In the first case (left half) the grid I2 of the electron multiplier has the shape of a ring. In the second case the emitting electrode consists of four interconnected partial electrodes. The ring-shaped arrangement has the advantage over the arrangement of rectangular cross section that the screen need not be accurately dimensioned and aligned to clear the extreme positions of the scanning beam. However, the area of the emitting electrodes then becomes smaller. The screen I has a negative potential in respect to all emitting electrodes. A wall coating on the inside of the wall of the tube surrounding the electrodes can be provided and is then held at the same potential as the screen 1. This wall coating, as well as the screen 1, then causes concentration of the electrons in the space between the emitting electrodes.

It is not absolutely necessary that the electron multiplier completely surroundsthe space traversed by the scanning beam. In many cases, however, it will be to advantage to have the electrodes 8 and 5 completely surround said area. By doing this, nonuniform space charge in front of the mosaic is surely avoided. Therefore, no further measures are necessary to compensate for non-uniformity of the sensitivity of the mosaic, which often exists.

In Fig. 3, the spherical portion of the tube is indicated by 2|. The electron gun I 4 and two deflecting systems are disposed in a protrusion 2. The sphere possesses a ring-shaped protrusion 22, which carries two stems supporting the electrodes, and is the mosaic 3. In place of the wall coating I3 of Fig. 1, a grid 23 of very open mesh is provided. The optical system is shown at 24. The electron multiplier may consist of a series of grids, sieves, foils or plates, which are surround- 5 ed by a screen 25. The arrangement may be ring-shaped or consist of two or four symmetrically arranged, separate systems. The first grid 5 has a curvature in a direction towards the arriving primary electrons. v In the embodiments shown in the drawing,

double-sided mosaics are used. This invention can also be applied to tubes in which the mosaic is illuminated and scanned on the same side. In case of the cylindrical tube of this type, the axis 5 of the electron gun can be oblique to the axis of the tube, as in known arrangements, whereby the cathode is illuminated through a plane window in the tube, and whereby the electron gun can be placed in or out of the light paths. Obviously, the electron multiplier must then be placed in such a position that it is neither in the path of the light nor in the path of the electron beam.

t will be understood that it is also possible to incorporate other types of electron multipliers in the tube. The arrangement shown in the drawing has the advantage, for the cylindrical type of tube, that there is no difiiculty in increasing the size of the emitting electrodes from stage to stage, because the cross section traversed by the scanning beam decreases in the direction of the electron gun. This is favorable inasmuch as the current density and space charge density in front of the various emitting electrodes thereby do not increase so rapidly as for electrodes of constant areas.

In making a tube as shown in Fig. 1, it is preferable to assemble the screen I, the electron multiplier and the mosaic plate into one unit before placing them into a portion of the vacuum 401 receptacle, consisting of the cylindrical part I and the window 16, which is then fused together at 'l-5with. a portion possessing the elongation 2.

In a tube according to Fig. 3, the electron multiplier system is preferably built together with the system 3 and 23 upon a common glass support, which is then introduced into the sphere through an opening at 22.

j Theemitting electrodes of the electron multiplier may consist of alloys which contain, for 5Q instance, bariumor caesium. Such electrodes can be made in such a manner that no special forming is required. Thereby, difiiculties are eliminated which arise from-the necessity of a separate formation of the photocathode and the 5 secondary emitting electrodes.

We claim:

1. A television picture signal generating device comprising an envelope having an enlarged portion, a source of electrons at one end of said envelope and a screen at the other end in said enlarged portion, means for establishing a cathode ray beam between said source of electrons and said screen and deflecting said ray through a region within said enlarged portion defining a pyramid with its ase facing said screen and its opposite end pointed in the direction of said source of electrons, and an electron multiplier in the space defined by the enlargedv portion of said envelope and said pyramidical re gion, said electron multiplier comprising a plurality of parallel spaced electrodes surrounding said pyramidical region and of increasing areas in the direction of said source of electrons.

2. A television picture signal generating device comprising an envelope having a substantially cylindrical portion, a source of electrons at one end of said envelope and a screen at the other end in said cylindrical portion, means for establishing a cathode ray beam between said source of electrons and said screen and deflecting said ray through a region within said cylindrical portion defining a pyramid with its base in said screen and its opposite end toward said source of electrons, and an electron multiplier in the space defined by the substantially cylindrical portion of said envelope and said pyramidical region, said electron multiplier comprising a plurality of parallel spaced electrodessurroimding said pyramidical region and of increasing areas in the direction of said source of electrons.

3. A television picture signal generating device comprising an envelope having substantially cylindrical portion a source of electrons atone end of said envelope and a screen at the other end, in said cylindrical portion, means for establishing a cathode ray beam between said source of electrons and said screen and defiecting saidraythrough a region within said cylindrical portion defining apyramid wvith its base toward said screenv and its opposite end toward said' source of electrons, screen means disposed about said pyramidical region, and an electron multiplier inv the space defined by the cylindrical per. tion of said envelope and. said screen means, said electron multiplier comprising a plurality of para allel spaced electrodes surrounding said screen means and of increasingareas in the directionof said source of electrons.

4. A television picture signal generating device comprising an envelope having a substantially rcylindrical portion a source: of electrons atone end of said envelope and a screen at the other end, in said, substantially cylindrical portion,

means for establishing a cathode ray beam between said sourceof electrons and said screenv and deflecting said ray through a region within said cylindrical portion defining a pyramid with its base in said screen and its opposite end toward said source of electrons, and an electron multiplier inthe space defined by the substantial-.

ly cylindrical portion of said envelope and. said pyramidical region, electron multiplier comprising a plurality of parallel spaced electrodes surrounding said pyramidical region and of increas-' ing areas in the direction of said source of elec-. trons, and means shielding said electron multi.-

plier from said deflecting means. f l j ROLF corneas.

CERTIFICATE OF C ORRECTION Patent No. 2,250,15Lp January 2 19in.

ROLF COLBERG, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, sec- 0nd column, line 55, strike out the word "is"; and that the said Letters Patent should be reed with this correction therein. that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 25th day of March, A. D. l9l|,l.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents.

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