US2213179A - Television transmitting device - Google Patents

Description

Aug. 27; 1940. H. A. lAMs TELEVISION TRANSMITTING DEVICE Filed July 29, 1959 2 Sheets-Shea?i Z INVENTOR. HARLEY ,4. [AMS ATTORNEY.

Patented ug. 27, 1940 TELEVISHON TRANSMITTHJG DEVICE Delaware Application July 29, 1939, Serial No. 287,260

9 Claims.

My invention relates to television transmitting tubes and is more particularly directed to tubes of the low velocity electron scanning beam type.

Television transmitting tubes of the low velocity electron beam scanning type have been made in which a combination magnetic-electrostatic deflection system including electrostatic plates wholly immersed in a uniform axial magnetic field shifts the beam in a plane parallel to the 10 plates to scan a mosaic electrode to generate picture signals. An electrostatic image representative of an optical image is formed on the mosaic electrode and scanned by an electron beam having a velocity approaching zero in the vicinity of 35 the mosaic electrode. Since the electrons of the beam approach the mosaic electrode at low Velocity, they are modulated in accordance withthe electrostatic image, a portion of the electrons of the low velocity beam returning to an electron 2@ collecting electrode to generate picture signals. In the operation of such tubes it is desirable to have the electron beam of such intensity that the mosaic electrode is completely discharged during one sweep of the beam, irrespective of the light intensity on the mosaic electrode. As a consequence, the quantity oi electrons returning to the electron collecting electrode is relatively large so that some noise may be generated by the relatively large electron iiow. A further disadvantage possessed by the tubes of the prior art has been the diiiioulty experienced in the proper adaptation of electron multiplying arrangements Within television transmitting tubes of the low velocity electron beam scanning type, since by the use of such arrangements the noise signal is greatly increased.

It is an object of my invention to provide a television transmitting tube of the low velocity electron beam scanning type wherein only the picture modulated electrons are collected for utilization purposes. It is another object of my invention to provide such a tube wherein the electrons which are not modulated in accordance with the picture may be separated from the picture modulated electrons. It is a further object to provide a tube wherein electron multiplication may be utilized to its fullest advantage and wherein the signals may be amplied by electron multiplier arrangements while keeping the noise distortion at a minimum value.

In accordance with my invention an electrostatic image corresponding in electrostatic energy distribution to the light distribution of an optical image is formed on a target of the picture grid mosaic type which is scanned with a low velocity (Cl. FX8-7.2)

electron beam from an electron source such als an electron gun, the electrons not reaching lthe target and not modulated by the electrostatic image being returned from the target and coly lected, while the electrons of the beam whichare '5 modulated in accordance with the electrostatic image pass through the target and are directed to an electron multiplier Where the energy representative of these modulated electrons may be l multiplied and utilized to provide television siglo' nais. More particularly in accordance with my invention, I provide a structure which separates the electrons representative of signal energy from other electrons generated during the normal U operation of the tube, thereby maintaining avery 5 low noise level and consequent high signal to noise ratio in the output circuit of the device.

A better understanding of my invention will be obtained and further objects, features and advantages will appear from the following descrip- 20 tion taken in connection with the accompanying drawings in which:

Fig. 1 is a cross-sectional view of a television transmitting tube and circuit embodying my; in- 4, vention, Fig. 2 is an elevation perspective View of 25 the tube shown in Fig. l, Fig. 3 is a plan view showing in enlarged detail a portion of the electrode structure shown in Figs. l and 2, and Fig. 4 is a plan perspective View of a tube incorporating a modication of my invention. 30

In general, the apparatus of my invention comprises an elongated evacuated envelope having a target of the picture grid mosaic type wherein the apertures of the picture grid are surrounded with a great number of mutually insulated photo- 35 sensitive particles. The picture grid is positioned so that one side oi it may be scanned by an electron beam and that it may also have focused upon it an optical image of the object of which a picture is to be transmitted. The electron beam o preferably has a velocity approaching zero in the vicinity of the picture grid so that the grid may have maximum control of the electrons of the beam and to prevent the emission of secondary electrons from the surface of the grid. On the 45 .opposite side of the picture ygrid from that side whicli is scanned by the low velocity electron beam I provide means to collect the electrons passing through the grid and to neutralize the deiiection received by the electrons during the 50 scanning operation so that the electrons passing through the grid may be collected over a relative-` ly small area. In operation elemental areas of the mosaic electrode acquire electrostatic potentials proportional to the intensity of the light 5g incident thereon,thus particles of the picture grid which are more highly illuminated acquire the more positive electrostatic charges with respect to the unilluminated particles, and these charges which represent an electrostatic image of a picture to be transmitted are used to control the flow of electrons through the picture grid. The electrons passing through the picture grid are directed to a point or a small area preferably out of the range of the light rays forming the optical image on the picture grid, at which point or area they are collected by an electron collecting electrode. The collecting electrode may be surrounded by an electron multiplier to obtain increased output. Intermediate and extending wholly between the electron gun and the electron collecting electrode I provide a uniformY magnetic eld having lines of force extending in the direction of the undeflected electron iiow and means within the iield to generateA electrostatic elds which scan the electron beam over the picture grid and cause the electrons passing through the picture grid to be dedefiected so that they may be collected over the relatively small area occupied by the electron collecting electrode.

Referring particularly to my tube structure shown in Figs. 1 and 2, the tube includes an elongated evacuated envelope I enclosing at one end an electron gun assembly 2 adapted to project electrons toward a picture grid mosaic electrode 3 located near the midsection of the tube and so positioned that an optical image such as represented by the arrow 4 may be focused thereon through the lens system 5 and the window 6 of the envelope. Adjacent the window 6 and preferably displaced from the optical path between the lens 5 and the picture grid mosaic electrode 3 I provide an electron collector and multiplier 'structure 1 to collect electrons from the electron gun 2 which pass through the apertures of the picture grid mosaic electrode. The picture grid may be made of a porous insulating structure, with or without a base metal. One form of picture grid may be made as follows: The picture grid mosaic electrode 3, as best shown in Fig. 3, is formed from an apertured foundation 8 such as an apertured metal sheet or a closely woven wire mesh screen having a number of interstices or apertures 9 which are provided in sufficient quantity to satisfy the requirements of the device such as the requirements for picture definition. More specifically, the foundation 8 comprises a perforated metal sheet which may to advantage have 150-200 or more apertures 9 per linear 4inch if the tube is to be suitable for reproducing a television image in good detail. 'Ihe apertures are preferably square or rectangular in shape, and the foundation 8 may to advantage be rolled and treated with acid to increase the area of the interstices or apertures 9 as described by W. H. Hickok in U. S. Patent 2,047,369. The foundation is provided on one side with a coating of insulation I0 such as enamel on which the photosensitive mosaic of mutually separated and insulated particles Il is deposited. 'I'he choice of insulating material depends on whether the tube is to be used in applications wherein the scene or image to be transmitted varies slowly or rapidly in degrees of brilliance or whether the scene to be transmitted is in motion or not. In astronomical work, for instance, in which a minute or longer might be allowed for generating the electrostatic image on the picture grid or mosaic, the resistance of the insulation I0 may be very high. For television work, however, the resistance may be made lower to assist in the dissipation of the charges acquired in response to a focused optical image so that most of this charge can be dissipated within the time of scanning one picture frame which in conventional systems is approximately /o second.

Prior to insulating the foundation I find it advantageous to clean it thoroughly and, if made of oxidizable material such as nickel, to then oxidize it slightly by heating it in air and, if made of nickel, until it assumes a greenish color probably due to a iilm of nickel monoxide. The foundation is then coated on one side only with the coating of insulation I0 having the desired electrical resistance. In spraying the foundation, care should be taken that the enamel does not flow through the interstices or apertures 9"'to the opposite' side 4of the foundation. I therefore prefer to perform the spraying operation with the perforated foundation held horizontally and with the spraying -gun below the foundation so that the enamel is prevented by gravitation from overflowing the upper surface of the foundation. The uncoated side of the foundation should be cleaned such as yby wiping with a vdry cloth to remove any of the particles which may have fallen on this surface. The sprayed foundation is then fired in air at about 900 C. to fuse the enamel into a smooth glassy coating. The enamel may berbuilt up on the foundation to the desired thickness by applying the enamel in several thin coats and firing the foundation after each coat is applied; Instead of spraying the insulation on the foundation member, insulating materials such as cryolite or calcium fluoride may be vaporized on the clean foundation. Following the formation of the coating of insulation l0 on one side and on the walls of the apertures of the foundation, I provide the insulated surface with a mosaic of a great number of mutually separated and insulated metal particles Il. These particles may be deposited by a number of methods such as by dusting an easily reducible metal compound which, if silver, may be silver oxide on the insulated surface and reducing the compound to a metal. Another method which I have found -equally advantageous for providing the metal particles Il is to deposit, for example by vaporization, a thin film of metal and to break this metal lm up into the particles Il by a suitable heat treatment. These and other methods for forming small metal particles are disclosed in U. S. Patent 2,065,570. Following the formation of the mosaic of metal particles on the insulated side of the foundation and referring again to Figs. 1 and 2, the foundation is suitably supported near the midsection of the envelope l so that the insulated surface of the foundation provided with the particles Il faces the window 6 preferably in a plane normal to the axis of the tube and normal to the axes of the electron gun 2 and the electron multiplier 1. As a last step in the preparation of the mosaic and following the introduction of the other electrodes yet to be described Within the tube, the tube is evacuated and the metal particles Il of the picture grid mosaic are photosensitized in a manner well known in the art such as by oxidizing the particles and subjecting them to caesium vapor followed by suitable heat treatment.

Surrounding the envelope I and extending over the space separating the electron gun 2 from the electron multiplier 1 I provide a magnetic coil l2 to generate a magnetic field having lines of force extending substantially from one end of the envelope to the other, the lines of force being sub- .stantially perpendicular to the picture grid mosaic electrode 3.

The electron gun 2 is of a conventional type and comprises a cathode I3 from which electrons may be drawn, a control electrode I4 connected to the usual biasing battery, and a rst anode I5 maintained positive with respect to the cathode I3. The electron stream leaving the first anode I5 is concentrated into an electron scanning beam focused on the uninsulated surface of the picture grid mosaic electrode by the axial magnetic field generated by the coil I2 and by the electrostatic eld from a second anode I6 which is preferably an apertured tubular member partially surrounding the first anode- I5. The first anode I5 and second anode I6 are maintained at the desired positive potentials with respect to the cathode by a battery II, and the cathode is preferably connected directly to the foundation 8 of the picture grid mosaic electrode so that this foundation member may be maintained at cathode potential, although it may be maintained slightly positive or negative if so desired.

The electron multiplier 'I may be of well-known design such as a structure comprising a number of perforated electrodes such as the wire mesh screens i8, I9, 20 and 2| interposed in the order named between the picture grid mosaic electrode 3 and an electron collecting electrode or anode 22. These wire mesh screens are constructed of material having good secondary electron emitting properties, for example, of bright nickel. The wire mesh screens I8--2I may, for ease in assembly, be supported by concentric metallic cylinders 23, 243, 25 and 26 which are in good electrical contact with the respective wire mesh screens and connected to a potential source such as a battery 2l through a bleeder resistance 28, the wire mesh screen I8 and its associated supporting cylinder being connected to ground and consequently to the anode I6. The electron collecting electrode 22 is connected through an output impedance 29 to the input electrode of a translating device and to the positive terminal of the battery 2I so that signals generated in the tube may be amplified and applied to a transmission network as well known in the art.

In accordance with my invention, I provide means between the electron gun 2 and the picture grid mosaic electrode 3 to scan the beam of electrons generated by the gun 2 over the picture grid mosaic electrode, and on the opposite side of the picture grid mosaic electrode and between this electrode and the electron multiplier 'I I provide means to counterbalance or neutralize either all or a portion of thedefiection produced by the rst-named deflection means so that the electrons passing through the picture grid mosaic electrode are directed to the relatively small area occupied by the electron multiplier 1.

More specifically in accordance with my invention, I provide between the picture grid mosaic electrode 3 and the electron gun means to deflect the beam over the mosaic comprising a pair of plates 35i-3! wholly immersed in the magnetic field generated by the coil l 2 to deflect the beam in one direction and a pair of magnetic coils 32--33 to deflect the beam in a direction substantially normal to the direction of deection produced between the plates ISB- 3L The plates Sil- 3l are preferably supplied with the horizontal deflection potentials from a suitable source, the plates being connected to such a source and to ground through a center-tapped resistor 34. Further in accordance with my invention, I provide, on the opposite side of the picture grid mosaic electrode from the electron gun 2, similar means for deecting electrons of the beam which pass through the interstices or apertures of the picture grid mosaic, this deflection being in the opposite direction to the deflection produced between the plates 3Il-3I and by the coils 32-33. This means may cornprise a further set of deflection plates 35-36 and a similar set of deflection coils 31-38. The decction produced by the coils 31-38 is preferably equal and opposite to that produced by the coils 32-33, while with respect to that produced by the plates 3-3I, is determined by the positioning of the multiplier 1.

As mentioned above, I prefer to locate the elec tron multiplier I out of the optical path between the lens system 5 and the picture grid mosaic so that light from any desired source may be focused without interference upon the picture grid mosaic electrode. Thus, while the electron multiplier 7 might for certain applications be provided within the tube in line with the electron gun 2 and along the axis of the tube, such applications being for use with short focal length wide aperture lens arrangements, I prefer to locate the multiplier as indicated above and displace the electrons passing through the interstices or apertures of the photo grid mosaic electrode by coupling the deflection neutralizing plates 35--36 to a source 39 of direct current potential through the resistors l0-4I. The deflection plates 35-36 are cross-connected to the horizontal deflection supply and to the plates -3I through the coupling capacitors I2-43 in such a manner that for a given dcilection in one direction by the plates i-3 l, the deflection between the plates 35-36 will be sufficient to direct the electrons to the multiplier l. The coils 31--38 are similarly cross-connected to the coils 32-33 to provide equal and opposite deflection of the electrons of the beam from the gun 2 which pass through the interstices or apertures of the picture grid mosaic electrode 3. It will be apparent that for symmetrical location of the electron multiplier 'I, that is, where the multiplier is located along the longitudinal axis of the electron gun and envelope, that the reversed deliection potentials supplied to the plates 35-733 with respect to the plates SII-3l are sufcient to neutralize the deflection and deflect the beam to the electron multiplier, provided the length of the two pairs of plates 3D3I and 35-38 are equal. It is therefore desirable tomake these sets of plates of equal length, although if of unequal length, the plates 35-36 may be supplied with opposite but unequal deflection voltage impulses. Where the desired construction is used, that is, where the multiplier is offset from the axis of the gun, the direct current potential supplied by the potential source 39 should be made just sufficient to add a deflection component to the eld between the plates to additionally deflect the beam over a distance equal to the distance the multiplier is offset from the axis.

During the operation of the tube shown in Figs. 1 and 2 and referring particularly to Fig. 2, the electron beam generated by the electron gun 2 is under the control of the longitudinal magnetic field generated by the coil I2. For purposes of explanation, I have assumed two conditions of operation showing the deflected beam between the plates Bil- 3l as following either the path A-B or the path A-B While it is between the plates 30-3 I, these paths being representative of` two conditions of horizontal deflection of the beam. The two paths, A-B and A-B', are in the same plane and in a plane parallel with the plates 30-3I, this plane being referred to as the plane of deflection between the plates SII- 3L After the beam leaves the field between the plates, it is constrained by the magnetic field generated by the coil I2 and follows a path such as represented for the two conditions'of deflection as the paths B-C and B'C' which are parallel to the magnetic field generated by the coil I2. The beam is then deflected in directions perpendicular to the said plane of deflection between the plates 30-3I along the paths C-D and C'-D' by the magnetic coils 32-33. After the beam has been deflected by the coils 32--33, the beam is again acted upon only by the longitudinal magnetic field and follows paths parallel to the magnetic field of the coil I 2 to the picture grid mosaic electrode along D-O and D'-O. It will be noted that the point O is directly above the point O, this being a condition when the magnetic field produced by the defiection coils 32-33 is of the same intensity for both degrees of horizontal deflection along the paths C-D and C'-D.

An optical image such as represented by the arrow 4 is, during operation, focused on the picture grid mosaic electrode to cause various areas thereof to develop an electrostatic image or picture replica of the-optcal image. Depending upon the average intensity of the charges surrounding the apertures of the picture grid mosaic at points O and O', the Velectrons flowing along the paths D-O and D'-O will be repelled or attracted in direct proportion to the intensity of this charge, and the intensity of the beam from the electron gun and the potential difference between the foundation 8 and cathode I3 may be so adjusted that for zero illumination no electrons pass through the picture grid mosaic electrode, under which conditions any increase in illumination will cause a proportionate increase ef electrons to pass through the mosaic electrode. rI'he electrons which pass through are therefore picture modulated in accordance with the charge surrounding the aperture through which they passed. The electrons then follow the paths O-E and O-E, being under the influence of the magnetic field generated by the coil I2 and are dedeiiected by the field produced by the coils 37-38 by an amount equal to and in a direction opposite to that deflection produced by the coils 32--33. The coils 32-33 and 31-38 are positioned as shown in Fig. 1, the showing in Fig. 2 being displaced from their actual position for the sake of clarity in the figure. The paths F-G and F'-G are likewise parallel, since at the points F and F' the beam passes out of the influence of the dedefiection coils 31-38 and is under the influence of the axial magnetic field produced by the coil I2. The beam then passes into the dedefiection electrostatic field produced between the plates 35-36 at the points G-G'. As pointed out above, the plates 35-36 are cross-connected with the plates 3U-3I and are supplied with a direct current potential so that the beam while passing along the path GH and G-H is not only subjected to a dedeflection field but to a constant electrostatic field which directs the electrons toward the electron multiplier l. It is obvious that should the multiplier be aligned with the electron gun and tube axis the only field necessary to generate between the plates would be the dedefiection field. However, with the construction shown, the deflection field is substantially overcome bythe D. C. field along the path from G to H, whereas from point G to H the dedefiection field and D. C. field is cumulative. It will therefore be appreciated that for any beam deflection produced by the plates 30-3I and the coils 32-33 the electrons which pass through the picture grid mosaic electrode will not only be dedefiected but will be directed toward the elec-tron multiplier 'I over a relatively small area directly in front of the electron multiplier. These electrons at this point are still under the influence of the field produced by the coil I2, and they therefore follow parallel paths into the electron multiplier where the energy representative of these electrons may be multiplied, collected and applied to the input electrode of the amplifying device connected across the impedance 29. While I have referred to certain paths as being parallel, such as the paths B-C, B-C', D-E, etc., the fields produced by the deflection plates and the deflection coils may actually overlap, which would cause the horizontal and vertical deflection to merge over a portion of the beam paths.

I have mentioned above that I prefer to position the electron multiplier I out of the optical path between the lens system and the picture grid mosaic electrode 3. It will, of course, be obvious that for some applications utilizing my device only a small amount of the light used to form the optical image will be intercepted by the electron multiplier 'I even if it is in the optical path between the lens system and picture grid mosaic electrode. For such applications I may therefore desire to have the multiplier axially aligned with the electron gun, in which case it is not necessary to apply any direct current potential to the plates 35-36, since for suc-h an arrangement, the electrons need not be displaced guring the defiection produced by the plates Referring to Fig. 4 which shows another modication of my invention and in which the corresponding structure shown in Figs. '1 and 2 is ksimilarly referenced, the tube comprises an electron gun structure 2, deflection plates 30-3I and deflection coils 32-33 similarly positioned with respect to the picture grid mosaic electrode 3 so that this electron gun and deflection plate structure is not shown. The plates SI1-5I are similar to the plates 35-36 and occupy similar positions, that is, the plates Sli-5I are in planes parallel with the plates 3Il-3I and are connected to a source of D. C. potential such as the battery 52. Between the plates 50--5I and the picture grid mosaic electrode 3 I provide a second pair of deflection-neutralizing plates 53-5 in planes perpendicular to the planes of the plates 50-5I and offset from the picture grid mosaic electrode so that an optical image may be focused thereon through the space-z separating the plates 5ft-5I. Near one edge of the plates 53-54 I provide the electron multiplier 'I similarly' connected to a potential source and output circuit as shown in Fig. 1. The electron multiplier in this modification is preferably slightly below the deflection plates 53-54 so that the electrons flowing between the plates may be directed outside of the electrostatic field between the plates to the multiplier.

In the operation of my device as shown in Fig. 4, an electrostatic image formed on the picture grid mosaic controls the flow of electrons through the apertures or interstices of the mosaic electrode in a manner similar to that previously deasiento scribed. The constant potential applied between the plates ii-i deiiects the beam along the path J-K or J'K', whereupon the electrons pass out of the field between the plates and follow paths toward the .window 6. The window, however, due to previous scansions of the beam, has acquired a potential substantially equivalent to the potential applied to the cathode I3 and directs the electrons baci: toward the plates Ell-5|. As the electrons approach the space separating the plates Fail-5i they are again subjected to the constant electrostatic field between the plates bil- 5i and are deflected such as along the paths K-L or K'L', leaving the field 'between the plates sil- 5i at the points L and L. Since the magnetic coil l2 extends over the tube shown in Fig. l in the same manner and for the same purpose as shown in connection with Figs. 1 and 2, the electrons, after reaching the points L and. L out of the electrostatic field between theI plates til-5i, follow paths controlled solely by the axial magnetic field which directs them toward and between the plates tl- 5d along the paths L M and L M. The plates 553-5@ are connected across a source of direct current potential, such as a battery 55, to produce a uniform electrostatic eld between the plates, and the plates are also wholly immersed in the axial magnetic held produced by the coil l2. Under this combined iield the motion of the electrons between these plates is in a plane parallel with the plates, and the beam follows paths to points outside of the eld between the plates 53-52 to the points N and N From the points N and N the beam goes directly to the electron multiplier a, since it is under the sole inuence of the axial magnetic eld.

It will be appreciated that the plates iil are utilized to absorb the deflection component such as the horizontal deflectionproduced by the plates S-ti and that the plates tit- 5c are utilized to absorb the other deflection component such as the vertical deflection produced by the coils :i2-33. it is therefore obvious that the dedeiiection coils S'l--ii shown in connection with Figs. l and 2 are not needed in the construction of Fig. e, since their` function is performed by the plates 53-5l While I have mentioned that the window t after a few scansions of the electron beam acquires a potential substantially equivalent to the potential applied to the cathode i3 and tubes have been operated without any special precautions being taken to maintain the window t at cathode potential, it may be desirable to provide a light transparent conductive coating which is connected to a potential at or near that of the cathode i3 on the inner surface of this window, although have found such a coating to be unnecessary and furthermore undesirable, since it absorbs a small proportion of the light projected through the window and upon the picture grid mosaic electrode. Furthermore, while I have not shown any conductive wall coating on the cylindrical portion of the envelope i between the electron gun 2 and the window 6, such a conductive coating is preferably used to prevent the accumulation of an electrostatic charge on this portion of the interior of the envelope.

While I have indicated the preferred embodiments of my invention and have indicated the specific application as directed to cathode ray television transmitting tubes, it will be apparent that my invention is by no means limited to the purpose of television transmission and that many variations may be made in the particular strucn ture disclosed without departing from the scope of the invention as vset forth in the appended claims.

I claim:

1. A television transmitting tube comprising a mosaic electrode having mutually separated apartures of elemental picture area for the passage of an electron beam and mutually separated and Ainsulated photo-sensitive particles surrounding said apertures to generate an electrostatic image of an optical image projected on said electrode along an optical axis normal to thev surface of said electrode, means to generate an electron beam of elementary picture area cross section and to direct said beam in a direction toward and normal to the surface of said electrode, means to scan said beam over said apertures in hor zontal and vertical direction components, an electron collecting electrode to collect electrons of said beam passing through said apertures, means to generate a magnetic iield having lines of force extending between said electron gun and said collecting electrode a pair of oppositely disposed electrostatic deflection plates along a porN tion of the path of the electrons passing through said mosaic electrode to generate a field opposn ing one direction of scanning imparted to said beam to remove the said one direction component of scanning frornsaid electrons, and addi tional deflection means along a portion of the path of the electrons passing through said mosaic electrode to generate a eld opposing the other direction of scanning imparted to said beam to remove the other direction component of scanL1 ning and to direct said electrons to said collecting electrode.

2. A television transmitting having an electron gun to generate a beam of electrons, a perforated light sensitive mosaic electrode in a plane normal to the undeflected path of said beam to control the ow of the electron beam in accordance with electrostatic charges formed thereon in response to an optical image focused on the said electrode along an optical axis normal to the surface of said electrode, an electron collecting electrode on the opposite side of said mosaic electrode from said electron gun to colm lect electrons controlled byand passing through said mosaic electrode, means to generate a mags netic held having lines of force extending loetween said electron gun and collecting electrode, a first pair of electrostatic deflection plates wholly immersed in said magnetic field between said electron gun and said mosaic electrode to deflect the beam over said mosaic electrode in a direction parallel with said plates and a second pair of dellection plates on the opposite side of said mosaic electrode from said electron gun to neutralize the deflection imparted by said irst deflection plates to the electrons of said beam passing through said mosaicelectrode and to .direct the electrons passing through. said mosaic electrode to said electron collecting means.

`3. A television transmitting tube comprising an elongated envelope, a picture grid mosaic electrode adapted to have an optical image fo-n cused thereon alongan optical axis which is normal to the surface of said mosaic electrode, said electrode being positioned intermediate the ends of said envelope, means including an elecm tron source to generate a beam of electrons and direct said beam toward one side of said mosaic electrode in a direction normal to the surface of said mosaic electrode, a rst system of electro- Elli liti

static field generating plates between said electron source and said mosaic electrode to deiiect and scan the beam over said mosaic electrode, a second system of electrostatic iield generating 5 plates on the opposite side of said mosaic electrode from said electron source, the plates of said second system being positioned parallel with the plates of said rst system and adapted to be electrically cross connected with the plates of said first system to deflect the beam in a direction opposite to the deflection produced by said first system, a magnetic electron beam focusing coil extending axially over said envelope and enclosing the said systems of deiiection plates and means to collect the electrons deected by said second system of plates to develop signals representative of an optical image focused on said mosaic electrode.

4. A television transmitting device having an electron gun to develop an electron beam, an electron collecting electrode to collect electrons from said electron gun, a magnetic electron beam focusing coil extending over the space separating said electron gun from said collecting electrode to generate a magnetic field parallel with the undeflected path of said electron beam a perforated light-responsive mosaic electrode having an extended surface, said mosaic electrode being positioned in a plane normal to the undeflected path of said beam and between said electron gun and said collecting electrode, deflection eld generating means between the gun and mosaic electrode to deflect the beam in two mutually perpendicular directions, additional field generating means including a pair of oppositely disposed deflection plates surrounded by said focusing coil along the path of the beam between said mosaic electrode and said collecting electrode to deiiect the beam in two mutually perpendicular direc- Lo tions and means to energize both of said deflection means to generate substantially equal and opposite fields so that the directions of deiiection in each of said mutually perpendicular directions issubstantially equal and opposite to direct said ,5 beam to said collecting electrode.

5. A television transmitting device having two sets of deflection plates, each set comprising a pair of oppositely disposed plates, a light sensitive perforated mosaic electrode intermediate the 0 sets of deflection plates in a plane normal to a longitudinal axis extending between said sets of deection plates, an electron gun to generate and direct an electron beam through the space separating one set 'of plates through the mosaic 5 electrode and through the other` set of plates,

means to apply equal and opposite deiiecting potentials to the plates of said two sets of plates so that the deiection imparted by the said one set of plates to the electrons passing through the L) mosaic electrode is neutralized by the deection between the said other set of plates, and means to collect electrons from said electron gun passing through said mosaic electrode after the electrons have been deflected by said other set of i plates.

p and project a beam oi electrons normal to the plane of, toward and through said mosaic electrode, deection means between said electron gun and said mosaic electrode to deflect the electron beam from said gun over said mosaic electrode, an electron collecting electrode on the opposite side of said mosaic electrode from said electron gun to collect electrons of said electron beam passing through said mosaic electrode, and further deflection means eiective over the path of the electrons passing through said mosaic electrode electrically cross connected with said first mentioned deflection means to neutralize the deilection of the beam received prior to passing through said mosaic electrode, said further deiiection means being positioned to direct the electrons passing through said mosaic electrode to the said electron collecting electrode.

7. A device for generating television signals comprising an elongated envelope including a window, an apertured mosaic electrode foundation opposite. said window positioned in a plane normal to the longitudinal axis of said envelope, a mosaic of mutually separated and insulated photo-sensitive particles supported by the side of said foundation facing said Window to develop an electrostatic image in response to an optical image focused thereon, an electron gun axially aligned with the longitudinal axis of said envelope and adjacent the end of the tube opposite said window to generate and direct a beam of electrons perpendicularly incident upon the opposite side of said foundation, an electron focusing coil to generate a magnetic field having lines of force extending in a direction normal to the plane of said mosaic electrode over substantially the entire length of said envelope, means including a pair of oppositely disposed deflection plates wholly immersed in said magnetic field one on either side oi a portion of the path of the electron beam between saidy gun and mosaic electrode, means to energize said plates with beam l deflecting potentials to scan said beam over said mosaic electrode, an electron multiplying structure to multiply the electrons from said gun passing through said mosaic electrode foundation located between said window and said foundation and a second pair of deiiection plates wholly immersed in said magnetic field electrically cross connected with said first mentioned plates to direct the electrons passing through said mosaic electrode foundation to said electron multiplying structure.

8. A television transmitting device comprising an elongated envelope, a light sensitive picture grid mosaic electrode intermediate the ends of said envelope and extending in a plane normal to the longitudinal axis of said envelope, a magnetic coil surrounding said envelope to generate a magnetic field having lines of force extending through said envelope for substantially the entire length thereof, an electron gun axially aligned with the longitudinal axis of said envelope and on one side of said mosaic electrode to generate and direct an electron beam through said mosaic electrode, an electron multiplying structure on the other side of said mosaic electrode to receive electrons passing through said mosaic electrode, a pair of electrostatic deflection plates and a pair of' magnetic coils in the order named between said gun and said mosaic electrode to generate beam deflection elds, a second pair of electrostatic deection plates and a second pair of magnetic coils positioned in the order named between said electron multiplying structure and said mosaic electrode, a source of beam deection potential connected to the rst mentioned pairs vof plates and cross connected to said second pair directing said beam to said electronmultiplying i Y structure.

the said one pair of plates, through said mosaic electrode and between the other pair of plates, means to generate a magnetic field having lines of force extending between the plates of said pairs of plates in directions parallel with said plates, means to energize the said one pair of deection plates with deflection potentials to deect the beam over said mosaic electrode, a third pair of deection plates mutually perpendicular to said pairs of plates in the space separating said mosaic electrode and the said other pair of plates and out of a direct line between said mosaic electrode and said last mentioned plates, a source of direct current potential connected across said other pair of plates to direct the electron beam between said third pair of plates, an electron collecting electrode `petween said third pair of plates and said mosaic electrode, and a source of direct current potential connected across said third pair of plates to direct the electrons from said gun passing between said pairs of plates and through said mosaic electrode to said collecting electrode.

HARLEY A. IAMS.

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