US2286280A - Electronic device - Google Patents

Description

June 16, 1942.

H. A. IAMS ELECTRONIC DEVICE Filed Dec. 14, 1937 2 sheets-sheet 2 35 +/000 l( +/300 +2100 V. +102 +/foau Hegau T0 AMPL/F/ER +1300 +2/0o u +/01/. +1/00u +/090u To AMPL/F/ER *Xi .XS l INVENTOR.

HARLEY A. MN5

MVM/- I ATTORNEY.

Patented June 16, 1942 a ELECTRONIC DEVICE Harley A. Iams, Berkeley Heights, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application December 14, 1937, Serial No. 179,679

`1 Claim. (Cl. 178-7.2)

The present invention relates to image amplifying tubes and is concerned primarily with electronic devices for scanning and transmitting image signals.

In the past it has been customary in electronic types of scanning devices to provide electronic image transmitting tubes of either the storage or non-storage type and to use either the resultant electrostatic charges produced from storage or to use the current image signals from the non-storage type of device to develop signalling impulses for transmission. Whilethe 'storage type tube of the aforesaid character offers some considerable increase in the magnitude of the output signal energy obtained under scansion from that of the current type tube, nevertheless, it has been found in many instances that the signal to noise ratio is not as high as would be desirable for transmission purposes. Accordingly, the present invention provides Ways and means for obtaining, without introducing distortion, extremely high ratios of output signal energy compared to any possible noise developed in the system as due, for example, to thermal agitation in coupling resistors and'the like.

In the prior art, where a storage type of tube has been used as the light translating element, such tube has usually been construed as a device formed with a mosaic electrode comprising a signal plate, an insulating sheet member mounted upon the signal plate and a photosensitive coating of isolated minute size particles of photoelectric material'separated from the ysignal plate by the dielectric. An optical image projected upon the mosaic electrode causes charges E.

to be developed betvveeny the photosensitive particles and the signal plate and these charges are released during scansion by a cathode ray beam which is directed to traverse the photosensitive surface of the mosaic in a two dimensional path. In order to utilize the stored charges which are which is apertured andl behindwhich is a collecting pin or target. The complete electron image in the form of a current image is caused to sweep the aperture in the target in tWo directions and by virtue of the voltage drop across the resistor connected with the target electrode signals are transmitted to the input circuit Iof the amplifier whose input connects across the resistor.

The present invention makes use to some eX- tent of a combination of each of the aforesaid types of devices in that there is initially produced an electron current image which is converted into a charage` image and this charge image is then magnified in intensity to produce the magnified charge image and is scanned by a scanning beam. This invention relates, insofar as it uses for the purpose of producing the initial charge image'an insulated grid structure which is flooded by an uncontrolled stream of electrons, to the structure which has been described for a receiving type tube by my cepending application, Serial No. 116,689 lecl December 19, 1936 (now U. S. Patent No. 2,259,507).

When the charge image has been produced upon the insulated grid the uncontrolled flooding stream of electrons then carries over to form on I a two-sided mosaic electrode structure an addireleased by the cathode ray beam scanning action, it is possible to produce the signal .output directly from the secondary emission which is released from the impact side photosensitive surface of the mosaic by the impact of the scanning beam thereon or to utilize a potential drop oc* curring across an output resistor connected to the signal plate of the mosaic electrode and across the input circuit of the associated signal amplifier.

With a tube of the non-storage type a light image is projected upon a photosensitive surface to release electronsk which are caused to flow in the direction of a target electrode, the center of tional magnified charge image and this charge image is then scanned point by point by means of a scanning electron beam in a manner already explained in connection with the scanning of the so-called two-sided mosaic structures in the patent granted to W. Hickok 2,047,369 of July 14, 1936. In an alternative form of the device the optical image is focussed upon a' semi-transparent photosensitive cathode and the released photoelectrons are projected upon an insulated grid structure of the general character shown and described in my aforesaid application. The insulated grid structure is also subjected to the flooding effect of an uncontrolled intensity but high density field of flooding electrons and the resultant magnified current image determined in accordance with the' charges -accumulated upon the insulated grid structurels then projected as a magnied intensity current image through deflecting fields. Further, the magnified current image is suitably focussed so that when deflection in two mutually perpendicular directions takes place, the electron current image representing the elemental section or area of the optical image may fall through an aperture in an accelerating electrode to impinge up'on a collecting target.

In each of the above mentioned forms of image amplifying devices suitable for translating an joptical image into a train of electric signal impulses magnification of the resultant electric signal impulse takes place within the scanning tube. As a result, the signal intensityproduced Yin the first stage of the external amplifier is considerably increased and a more satisfactory ratio of signal to noise level is obtained.

From the above it will be appreciated that included among the objects of this invention or those of obtaining directly within a scanning tube a magniiication of the effects of electrical signals resulting from the translation of the light values of an optical image into either electrostaticcharges, which are to be released to an external circuit, or an increase in the electronic current iiow which it is tocause the resultant electric signal impulses.

A further object of th'e invention is to provide a purely electronic type of conversion device for converting optical images into electrical images of either the current, voltage or static type, which images are to be translated into electric signalling impulses.

Still a further object of the invention is to obtain a light translating and-scanning device which will simplify translation of optical effects into signalling impulses and simultaneously amplify the resultant signalling impulses directly within the scanning device.

Still a further object of the invention is to provide within a scanning tube a multiplication of the normal signal output resulting from scanning an optical image by a purely electronic device of. thje character now known.

Still other objects and advantages of the present invention will become apparent and at once suggest themselves to those skilled in the art to which -the invention is directed by reading the following speciiication in connection with the accompanying drawings; wherein.

Figure 1 represents conventionally a light image conversion scanning device wherein the signals result from the scansion of an electrostatic image;

Figure 2 represents a modification of Fig. 1

providing for scanning from the opposite side to that used with the device of Fig. 1;

Figure 3 represents a modification wherein the electric signalling impulses result from the scansion of an electronic current image;

Figure 4 represents a modification of Fig. 3: and

Figure 5 illustrates conventionally the struc- 'ture of the insulated grid electrode lby which the magnification of the signal effects produced within the scanning device results.

Referring now to the drawings, and iirst to Fig, 1 thereof, for a further understanding of this invention, light representing any subject I,

which may be some person, object, lm, a transtions such as tholse known, for example,` as pincushioning.

About midway between the end 'I of the scanning tube Shaving the photosexsitized coating 5 and the opposite end II of the tube whereat an electron seam is developed by means of a suitable electron gun I3 comprising the usual electron emitting cathode, a control grid and an anode arranged in a cooperative relationship with a second anode I4 to provide more accurate beam focussing, there is positioned an insulated grid electrode I5 of the general character shown and described by my copending application Serial No. 116,689 filed December 19, 1936. Suitable potentials are applied to the. electrodes forming the electron gun structure and to the second anode for causing the development of an electron scanning beam I6 which is deflected in each of two mutually perpendicular directions by means of suitable electromagnetic defiecting coils pairs positioned in two mutually perpendicular directions which are connected in the, usual and well known manner to suitable sources of deflecting current.

The electrons released from the photosensitive surface 5 at the end of the tube which is illuminatedby the light of the` subject to be scanned are directed toward the insulated grid electrode through a plurality of electrode members 2li and 2| preferably formed in the nature of conducting bands around the inner surface of the tube wall intermediate the photoelectric surface 5 ,and the insulated grid I5. These bands are maintained at progressively'higher potentials (of which suitable examples are indicated by the drawings) relative to the photoelectric surface so as to accelerate electrons released by the light and toA focus these electrons upon the insulated grid I5. Intermediate the insulated grid I5 and second anode II-of the scanning tube but closely adjacent the insulated grid is positioned a two-sided mosaic electrode 23, which, for instance, may be of the general nature described by Flory orl Hickok in U. S. Patents Nos. 2,045,986 and 2,047,369. This double mosaic electrode 23 may be of any general form and shape but preferably is made in accordance with the structure described by the above mentioned Hickok patent. So constituted, the two-'sided mosaic electrode is formed from a mesh-like surface in which the wires constituting the mesh are suitably enameled and have supported in the interstices of the mesh suitable conducting packings which extend through the mesh and on the surface thereof toward the insulated grid electrode there is a photoelectric coating. The photoelectric coating covering the metallic packing of the mesh intervstices constitutes a series of actual photoelectric areas which are insulated from each other by the enameled coating' upon the wires forming a mesh.

Within the portion of the scanning tube between the semi-transparent photosensitive cathode member 5 and the insulated grid I5, there is positioned an electron emitting cathode 25 in'co- .operative relationship with respect to a control electrode element or grid 21 so that electrons released therefrom will ood the insulated grid electrode structure I5.

, As was explained in my copending application Serial No. 116,689 with respect to the charges produced upon the insulated grid structure by a scanning electron beam, the photoelectrons moving from the photosensitive cathode 5 toward the insulated grid I5 and accelerated thereto and focussed thereupon by means of the electrodes 20 and 2l also cause charges to be accumulated upon the insulated grid structure simultaneously with the emission oi a di'spersing stream of electrons from the electron emitting thermionic cathode 25, which releases an velectron stream of high density arranged to `flood the'insulated grid I5. The ooding electron stream from the emitv to photoelectric emission caused by light impinging upon the photosensitive cathode 5. Since the photoelectrons moving toward the insulated grid I from the photo-emitting-cathode 5' are accelerated toward the insulated grid I5`and focussed thereon by electrodes 20 and 2| .so as to strike thereupon at relatively high impact velocity secondary electrons are caused to be emitted on.

the surface of impact. The lnumber of secondary electrons which are released by the impact ofthe arriving photoelectrons being greater than `one secondary electron per arriving primary electron causes the surface of the insulated grid to acquire at different elemental areas thereof different positive potentials relative to the wires on which the enamel or insulated coating is supported so that there is thus developed between the insulator and the supporting mesh an electrostatic charge image of the light image, although this charge image While tending to be dissipated within a short time period due to leakage within the tube during predetermined time intervals is preserved by the continued arrival of the photoelectrons upon the insulated grid. Naturally, the magnitude of the electrostatic charge image developed on the insulated grid I5 is a function of the electron density of the photoelectric current due to the light image and consequently in view of the fact that the release of secondary electrons takes place from the insulated grid when it is subjected to impact of photoelectrons, the flooding electrons are drawn rapidly toward the insulated grid structure by reason of the positive charge acquired thereon. In view of the fact that the flooding electron stream is of substantial magnitude some of the electrons of the flooding stream will be lost in neutralizing or replacing the secondary electrons, lost to produce the charge, but still other'flooding electrons will be passed through herein by way of rample this may be of the order of 2100 volts positive). While it has not been shown herein' it isl also contemplated by this invention that there may be located between the insulated grid member I5 and the mosaic electrode. 23 (or the equivalent electrode of Fig.- 2) a coarse mesh conducting electrode in 4order to collect the secondary electrons which are emitted from the mosaic electrode 23 `when the'magnified electron flow passing from the insulated grid I5 strikes or impinges upon the mosaic electrode. Such a grid electrode would normally be operated at a potential of the order of 20 to 100 volts positive relative to the potential ofthe mosaic electrode 23 (or the anode I4).

In order to release from the double mosaic 23 a signal to an external circuit which is representative of the charges acquired by the insulated grid I5 and then transferred to the double mosaic, the latter electrode is scanned by the scanning beam or cathode ray I6 developed within the tube and impingingupon the double vmosaic 23 from the opposite sidefrom that which is initially subjected to electron impact representative of the light image. In accordance with the arrangement of Fig. 1 this scanning takes place by virtue of the application of suitable, de-

iecting currents passed through the deflecting coils I1 and I8 so that the beam I6 traverses the double mosaic in a bi-directional path in well known manner to release the stored charge signal to an external circuit 24.

However, it should also be appreciated that after the manner disclosed by-Fig. 2 and following the broad principles set forth by Bedford in application Serial No. '746,094 led Sept. 29, 1934, or in the British Lubszynski Patent #442,666 the scanned electrode element 23 need not necessarily be a double mosaic electrode but may be one of the type known as the single sided mosaic 23 in order that the electron stream representative of the light image impact from the same side which is to be subjected to the impinging electrons of the scanning electron beam. In such an event as disclosed by either Bedford or Lubszynski, the surface of the electrode element 23' will then be merely one which embodies a single signal plate 26 and a suitable dielectric element the interstices of the insulated grid. Electrons of the flooding beamA or stream which pass through the electrode i5 are thus of a magnitude which is -governed in accordance with the charges acquired by elemental sections of the insulated grid structure. This results in an electron ow toward the double mosaic electrode of the character above described which is of greater magntudethan would be any stream of electrons due to the light image alone. The action of the stream of electrons which passes through the insulated grid structure I5 whether this stream of electrons be due to the photoelectrons emitted from the .surface 5 or to the flooding stream from the source 25 or to both, causes charges to be acquired upon the impact side of the double' scanning portion of the tube (as illustrated 28', such as a mica sheet upon which the charges may be directly accumulated or upon the surface it is initially activated by the mpinging electron stream and the scanning by the cathode ray I6 in this event will then serve merely to remove the accumulated charges from the single sided mosaic as is the case with the arrangement of Fig. 1 wherein the charges from the double m'osaic are removed by scanning the double mosaic lelectrode from the rear side. Itshouldbe understood, however, that suitable correction for the keystoning effect, as setV forth by Ogloblinsky Patents 2,040,813 or 2,069,460, for example, should herein be used.

With the arrangement of Fig.' 2, since` the insulated grid I5 is separated from the mosaic the tube) it ls usually desirable, in order to obtain high definition images resulting from scanning, to employ a focussing eld, such as that developed by the coil 63 to focus the magnified electron flow passing to the right of the insulated grid electrode I5 (as shown) upon the mosaic 'electrode 23. Also, ln order that the stray magnetic field from the focussing coil 63 may be shielded from the gun section I3 of the tube section wherein the scanning beam I6 is developed, as well as the deflecting coils I1 and I8, a magnetic shield member 65, such as a soft iron member, is located in the manner conventionally represented by Fig. 2. This then prevents any substantial distortion of the normal scanning pattern of the mosaic electrode 23 which would be traced by the beam I6 when deflected by the currents owing through the deflecting coils I1 and I8.

In Fig. 3 a slightly modified form of the invention has been illustratedlwherein instead of providing a double mosaic electrode 23 for the purpose of translating a dense electron current image into a charge image which is to be scanned, the magnied electron current image is directed through the accelerating field provided by the conductive coating 28 extending from a portion of the tube beyond and away from the insulated grid electrode I5 so that such electron stream constitutes a dense current image which then may be scanned by deflecting the complete magnifled current image in bi-directional paths across an aperture 29 behind which is 'positioned an electron current target 3l. In the form which the arrangement has been shown by Fig. 3 the portions of the tube which are located to the left of the insulating grid structure are substantially like that of Fig. 1. However, instead of providing in Fig. 3 the scanning cathode ray beam I6 and the double mosaic electrode 23 of Fig. 1 the inner surface of the tube wall to the right of the insulated grid electrode is a conducting coating 28 and maintained at a relatively high positive potential with respect to the insulated grid member I5 itself. Suitable operating potentials have been indicated by the drawings, although these suggested voltages are not in any sense to be considered as limiting but rather as illustrative. The end of this coating 28 terminates in an inner coating on the end inner surface of the tube wall which is apertured at its central portion 29 or the coating may terminate in a disc-like electrode member 30 which extends transversely of the tube for substantially its complete width. Under such circumstances the electrode 30 is apertured at its centralmost portion 2S. Behind the aperture 29 is positioned a collecting target 3I in accordance with the teachings of Roberts, Farnsworth or Deickman. In order to focus the magnified current image passing through the conducting coating 28 in order that elemental sections may be passed through the aperture 29 for scansion as the magnified current image is deflected any suitable focussingcoil such as that which has been conventionally illustrated at 33 may be used. In addition, there is positioned to surround the focussing coil (or internally of the focussing coil where desired) suitable deflecting coils 35 which are of substantially similar characteristics to the coils I1 and I8 shovm with respect to Fig. 1 and which may be, for example,'of the general nature described and shown by U. S. patents to Tolson #2,074,764 and Urtel #2,100,618.

electrode 23 (due primarily to the geometry of- In still another modification of the invention as it has been shown by Fig. 4, the arrangement is closely analogous to that of Fig. 3 with the exception that photosensitive mesh-like electrode 5', which may be of substantially the same character as shown by copending application of V. K. Zworykin, Serial- No. 468,610 filed July 17, 1930, is positioned and supported within the end 1 of the tube 9 to replace the semi-transparent photosensitive coating 5 suggested by the ar rangements of each of Figs. 1 and 2.

The construction of the double mosaic elecv trode 23 suggested for the arrangement of Fig. 1

is too well known and too universally adopted and so fully disclosed in the above mentioned Flory and Hickok patents that anymore than conventional illustration herein is believed to be necessary. However, the insulated grid structure I5 while having been disclosed in several of its preferred forms by my copending application Serial No. 116,689, above referred to, has been schematically illustrated in one of those forms by Fig. 5 of these drawings. Referring to Fig. 5 it will be seen that this electrode comprises preferably a ring-like outersupporting element 44 which preferably rests against the inner surface 50 of the tube wall I2. The ring-like member 44 has one edge 52 bent or flanged inwardly So that it can be secured or welded to the wires 41 of the mesh to support the mesh, and strung from its outer ring-like member are a greater number of fine mesh wires 41. The wires forming the mesh 41 for the insulated grid electrode 45, after the mesh has been suitably rolled and flattened so that the wires thereof are substantially flat, are preferably coated with a suitable insulating material 48. The insulating material will then also coat the flange 52 of ring 50, as shown. The enameling process may be carried forward to a predetermined degree by dipping the mesh-like grid into enamel to provide a coating of enamel thereon of desired and suitable thickness. This insulator in the case of the enamel coating is then baked in suitable manner prior to assembling the tube. When the tube is assembled the mesh and support ring are positioned within the tube and fit tightly therein. In the glass blowing process the tube Wall may be heated to cause the glass of the tube wall II to fit tightly about the ring 44 to hold it and position it.

It should further be appreciated that while the general arrangements described by each of Figs. 1 through 4, for example, set forth onlya single magnification of electronic vimage resulting from subjecting a photosensitive cathode to a light image, it is of course within the scope of this invention to utilize several magniflcations of the resultant electronic image and, accordingly, reference is herein made also to my c0- pending application filed concurrently herewith (Docket 13206) wherein, as applied particularly to an image amplifier tube provision has been made for magnifying the resultant electronic image to a still further degree bythe incorporation within the tube of a plurality of insulated grid electrodes and a plurality of sources of flooding electrons. In this way it is possible to obtain a first magnification of the current flow resulting from subjecting a photosensitive cathode t a light image and then magnifying the previously magnified light effect to a still further degree, whereby the magnification is such that for two stages, for example, the magnificationwould be substantially a square function obtained with the arrangements illustrated by Figs. 1 through 4, etc.

Further than this, as set forth by my copending application (D-l3206) filed concurrently herewith, it is also contemplated that the insulated grid structures conventionally illustrated at I5 in each of Figs. 1 through 4 and described more particularly with respect to Fig. 5 may be either photoelectric or non-photoelectric. In addition, it is also contemplated as being fully within the scope of this disclosure to curve the end of the tube and provide suitable curvature of the field distribution therein so that the end of the tube upon which the light image is directed relative to the final positioning of the insulated grid member is not in direct line with the portion of the tube wherein scanning takes place so that where the insulated grid member is photoelectrically responsive such grid member will not be-exposed directly to the light of the image in order that improved operation may result and further this prevents any re-generation within the tube which would be due to light from the uorescent screen reacting back upon the photoelectron surface producing the initial current ow.

Many other and further modincations in this invention are naturally possible and accordingly I believe myself to be entitled to make and use all of such inventions and especially which follow from my copending applications hereinabove referred to to which reference is made for the purpose of completing this disclosure, provided, of course, such inventions and changes fall fairly within the scope and spirit of the hereinafter appended claim. l

What I claim is:

In an electronic light image translating and scanning system, means for producing a con` trolled intensity electron ow corresponding to the light densities of an optical image,4 an in. sulated grid structure positioned to receive the controlled intensity electron flow whereby electrostatic charges of a magnitude proportional to the intensity of the electron ow are produced over elemental areas of the insulated grid, an electron source for flooding the insulated grid structure with a substantially constant density electron flow to produce in accordance with the charges acquired an intensified electron flow substantially like the originally produced electron current flow, a mosaic electrode means to receive the intensiiied electron flow and to produce an intensied substantial duplicate of the initially developed electrostatic charges and means for translating the intensied electrostatic charges into electrical signals for transmission.

HARLEYAIAMS.

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