Патент USA US2404046код для вставки
July 16, 1946. |_. E. FLORY ET AL 2,404,046 TELEVISION TRANSMITTING APPARATUS Filed June 21, 1941 2 Sheets-Sheet 1 ?|.b_>L“ -. a INVENTO RS LESLIE E. FLO/Z)’, ERNEST A. MASSA AND GEORGE A. M0}? zfoN WI ‘ ATTORNEY July 16, 1946. 2,404,046 L- E- FLORY ET AL TELEVIS ION TRANSMITTING APPARATUS 2 Sheets-Sheet‘ 2 Filed June 21, 1941 Q1%. m’ INVENTOR-S LESLIE E. FLORY, ERA/ESTA. MA 55A AND GEORGEALMORTON BYv I W”W I ATT_O RN'EY ' 2,404,046 Patented July 16, 1946 UNITED STATES OFFICE; v2,404,046 TELEVISION TRANSMITTING-APPARATUS Leslie E. Flory, Oaklyn, N. .J., Ernest A. 'Massa, Osborn, Ohio, and George A. Morton, Haddon Heights, N. J ., assignors _to Radio Corporation of America, a corporation of Delaware Application June 21, 1941, \SerialiNo..399’,110 8 Claims. (01. 178-123 1 Our invention relates to television apparatus, tubes and systems and is concerned primarily with apparatus incorporating a tube in which an electron beam having substantially zero veloc ity is scanned over a target to generate signals representative of an optical image for television transmission. It has been customary 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 to develop signalling impulses for transmission of an optical image replica. The storage type of tube offers considerable increase 15 in the magnitude of the output signal energy ob tained when a mosaic of photoemissive elements Tubes which we :have designed .for'usev ‘without ’ a longitudinal magnetic ?eld and wherein the electron; beam ' approaches the target ¢orl mosaic electrode with substantially"zero'velocity have’ - exhibited considerable distortional elTects which we have termed “crawling” or f‘cree'ping” inas much as the recreated image replica continuously shifts or moves especially over vareas remote from the center of the image; A fullycomprehensive theory of why this crawling or creeping occurs has not ‘been formulatedrbut. whenever, tubes utilizing low velocity beam scanning have been operated without a longitudinal magnetic-?eld these crawling effects have been most objectione ab-le.“ ' .1 ‘ .It. is an object of our’ invention to" provide highly sensitive television apparatus and syse tems capable of developing picture replicas with is scanned with a high velocity electron beam, out "distortion wherein a (low velocity electron however, the non-uniformity of secondary elec tron collection and emission saturation results 20 bea'mri’s ‘directed upon a target by purely ~elec' in a signal-to-noise ratio which is not as high as might be desired. trostati-c *means. It is :another object to provide a lighttranslating and scanning system which Local variations in the potential distribution will simplify the translation of optical effects into_ on the mosaic generate spurious signals which are usually referred to as dark spot signals in that they produce a non-uniform gradation of shading corresponding, not to the desired dis tribution of light and shade of the optical image television‘signalling impulses with a; minimum of dlstortionale?'ects. It is a further object vto pro vide a television transmitting tube wherein .elec formed on the mosaic, but to random areas of light and shade which do not correspond to those of the desired image. Since the ?eld utilized for collecting secondary electrons emitted by a mo- ‘ saic electrode under scansion is modi?ed by the electron scanning beam and consequently is of unequal intensity or e?ect over the scanned area of the electrode, it has been found di?icult to .trostatic charges ‘representative of the light and shade areas of an'optical image may be neutral ized over a relatively'large extended _area,‘and it is ‘a still ‘further object to minimize orjsube stantially ‘eliminate distortional effects occa sioned by grazing incidence of an ‘electron beam on a target. 7 r - t In accordance with our invention we provide television apparatus incorporating a tube wherein the electron beam is directed along paths oblique collect uniformly the secondary electron emis with respect‘ to the surface of a target and then sion from the surface of the mosaic electrode directthe electrons of the beam along paths sub-y whereby it might be ampli?ed such as by second stantially normal to the elemental surface areas ary emission ampli?cation. 4.0 of the target‘by correlating theobliquity of the original paths, the position and contour of the The above di?iculties may be obviated by pro viding a tube and system wherein the tube gen target, and the effects of an electrostatic ?eld immediately adjacent the target. These and ” erates an electron beam which is directed’ upon the target or mosaic electrode with a velocity ap other objects, features and advantages of our in vention will become apparent upon consideration proaching zero so that no secondary electrons of the following description and the accompany: are liberated which would inherently be distrib uted non-uniformly over the surface of the mo ing drawings vin which’: ‘ ‘ ~ Figure 1 is a longitudinal view of television saic electrode and cause what has been referred transmitting apparatus incorporating our inven to above as dark spot signals. A low velocity beam scanning tube and system is described by 50 tion; ‘g g j Figure 2 is a graph showing electron beam Albert Rose in his U. S. Patent 2,213,174 which utilizes a magnetic ?eld to direct the beam along trajectories in a conventional’ television trans paths normal to the target. The use of magnetic mitting tube; and _> . , q ‘ ?eld generating means is often disadvantageous Figure 3 is a graph similar to that; of Figure} for use in compact television camera units and 55 showing trajectories of- the electron beam‘ in a especially in application where it is desired to tube In of the'illustrative the type of Figure embodiment 1. of our invention .' . combine the Rose tube with reflection type opti cal systems, inasmuch as the magnetic means as shown in ‘Figure 1, the apparatus includes a discharge device or tube comprising ‘a highly which surrounds the Rose tube occupies consid 60 evacuated glass envelope or bulb l with a tubular erable space and intercepts considerable light. 3 arm or neck section enclosing _a conventional type electron‘ gun to form and direct’ an electron beam upon a target or mosaic electrode 2 which, in accordance with our invention, is of a prede: ‘ termined contour. The target is symmetrically positioned in the enlarged portion of the en velope so that its projected surface is substan- _ tially perpendicular to the longitudinal axis of 4, the drawings ‘of Figure 1, this meansmay com prise one or more conductors (t'wo'being shown) adjacent the target, such as the electrodes l5 and I5 maintained at the desired positive poten tials with respect to the cathode by the battery 9. These electrodes may comprise electrically con ductive coatings on the inner wall of the bulb l adjacent the mosaic electrode, although it is within the spirit of our invention to provide these the bulb I and so that it may be scanned by a beam of electrons from the electron gun and may 10 electrodes in the form of wire mesh screens lon gitudinally displaced along and transverse to the also have projected thereon an optical image of longitudinal axis of the tube. The function of which a signal replica is to be transmitted. As the electrodes !5 and I6 will be considered in shown, the mosaic electrode 2 is preferably de considerable detail in connection with Figures 2 posited or formed on the inner surface of the and 3. end ‘wall of the envelope'which may in this case Referring more particularly to the con?gura determine the predetermined contour of the mo saic electrode. ' tion and construction‘ of the mosaic electrode 2. this electrode is preferably of spherical form with The electron gun is of a conventional type and its center of curvature intermediate the center comprises a cathode 5 from which an electron stream may be drawn,‘ a control electrode 6 con 20 of deflection and the‘ target surface, and while this electrode may be‘ supported within the bulb nected to the usual biasing battery, and a ?rst l, we have shown the structure as being formed anode 1 maintained positive with respect to the directly on the inner wall of the bulb I which in cathode 5. The electron stream leaving the ?rst this case has a curvature corresponding to the anode ‘I is accelerated and concentrated into an electron scanning beam and directed toward the 25 desired curvature of the ‘electrode. While any form of light responsive electrode capable of re surface of_ the target or mosaic electrode 2 facing solving individual elemental'areas of light and the electron gun by a second anode 8 which is shade into elemental 'chargeareas may be used, preferably a conductive coating on‘ a portion of we prefer to pro'vide‘an electrode of the semi the inner surface of the envelope I. The ?rst anode ‘I and the second anode 8 are maintained 30 transparent type including alight permeable elec at the desired positive potentials‘by a potential source represented as the battery 9. Although we have shown one form of a suitable electron gun other forms may serve to equal advantage. Intermediate the ?rst anode ‘I and ‘mosaic elec trode ‘2 and at a predetermined distance from thermosaic electrode as measured along the'elec ‘tron gun axis We provide conventional electron beam de?ection means such as the coils l0 and trically conducting} ?lm, such as the metal ?lm 20 deposited directly on the inner end wall of the bulb l. The electrically conducting ?lm 20 serves as a signal plate in capacitive relation with the photosensitized particles of the mosaic 22 and is connected to a translating device such as the am pli?er 25 and to a potential at or near that of the cathode l5 through an output impedance 26. This connection, as indicated above, causes the II to de?ect the beam from its axial path and 40 mosaic 22 to assume an average potential which is equal to or near the cathode potential, thereby sweep the beam in horizontal and vertical planes decelerating the electron ‘beam adjacent the tar from a center point of de?ection such as the point get. The metal'?lm 20 may be provided with a l2.v It will ‘be noted that as the electron beam non-‘conducting coating 2|, such as of aluminum leaves the electron gun 2, its path is coaxial with oxide, china‘ clay, glass or'othe'r dielectric ma the ‘?rst anode, but upon reaching the center of terial. The ‘coating 2| ‘is likewise substantially de?ection I2 the beam is deviated or de?ected transparent and bears on its exposed surface a from this path and approaches the target from mosaic 22 of phot'osensitized metallic particles so this point as a de?ection center. It will likewise that an optical image such as represented by the be appreciated that in the absence of further de?ection means or electrostatic lenses between 50 arrow 23 may be focused thereon through a lens system 24. Inasmuch ‘as the‘ mosaic electrode is the center of de?ection l2 and the mosaic elec of spherical con?guration, the lens system may trode, the electron beam trajectories would be be designed to provide a spherical image ?eld, or straight lines. As the electrons comprising the re?ection optical systems inherently producing electron beam leave the junction of the ?rst and second anodes they are directed along converg 55 a spherical image fleld‘may be substituted for the particular lens system 24, as shown in the 'ing paths, only the central or average path of ‘drawings. '_ ’ which is shown in Figure 1. Furthermore, the For a better understanding of the principles average potential of the mosaic electrode is main underlying our invention, reference may be had tained substantially equal to the potential of the to Figure 2 which shows a graph of electron beam cathode 5, as explained in greater detail here trajectories in a tube incorporating a, plane tar after, so that the electrons are decelerated in the get and an electron lens immediately adjacent vicinity of the mosaic electrode to a velocity of the target. As shown in Figure 2, the target rep substantially zero. resented at 30 is of planar form, only a portion In accordance with our invention we so modify the electron beam trajectories intermediate the 65 of the target being shown to‘ one side of the axis 31 on which the center of deflection I2 is located center of ‘de?ection and the target and likewise at a predetermined distance from the target. The provide the target of predetermined con?gura positions of the ‘second anode 8 and the electron tion preferably of spherical form with its center lens forming electrodes ‘l5 and I6 are shown, it of curvature located on‘the electron gun axis and preferably between the center of de?ection and 70 being assumed that potentials of 1000, 600 and 450 volts with respect to cathode are applied to these electrodes respectively} Assuming a, unit charge on the surface of the target 30 such as comprise one or more electrodes surrounding the might be occasioned by light representative of a electron beam between the second anode 8 and the target or mosaic electrode 2. Referring to 75 uniform illumination over the surface of the tar the target surface. More particularly, the means to modify the electron beam trajectories may 2,404,046 5 6 get, an electron beam approaching the target along the axis 3| of unit intensity is collectedl'by the target to neutralize the unit charge. If, how ever, the beam is de?ected at the center of de ?ection l2 through an angle of approximately 3° with the axis, the electron beam trajectory will be as shown at 32. The electrostatic ?eld devel oped by the electrodes l5 and I6 for the poten face area :along paths substantially normal there to. Figure'3 is .a'graph similar to thatshown in Figure 2 wherein the radius of curvature of the target has been correlated with and chosen with respect to the voltages applied to the electrodes l5 and I6 and with respect to the initial center of de?ection. In accordance with our invention and as shown by Figure 3 the electron beam ap proaches the mosaic along paths which are sub-' stantially normal to elemental surface areas. It tials referred to above is a ?eld of such intensity as to form equi-potential ?eld gradients sub stantially corresponding to the normal decelera tion ?eld gradients through which the electron beam approaches the target. Thus the potentials will be noted that the trajectories 32’, 34’, 36’ and 38' have points of nearest approach 33’, 35’, 31' and 39' which are substantially coincident of the electrodes I5 and is are here chosen such with thesurface of the target. It is likewise noted that they have little if any effect on the electron 15 that the radius of curvature of the equi-potential beam trajectories. The axial velocity of the line marked 25 along the axis of the tube is sub stantially equal to the radius of curvature of the proach the target, but the radial velocity, that is, target over the principal portion of its length. a velocity transverse to the axis, remains sub Thus, while the graph of Figure 3 applies to' a stantially constant so that the electron beam, in 20 tube having a potential of 200 volts applied to the stead of approaching at the original 3° angle of electrode It, a slight increase in this‘ potential will produce an even closer symmetry between de?ection, increases its effective de?ection adja cent the target so that the beam is shifted from the'target curvature and that of the adjacent equi-potential ?eld. the intended point of contact with the target and As a particular example of a tube made in ac fails to reach the target because when the elec trons reach their nearest point 33 of approach to cordance with our invention and of which the the target, the electrons are re?ected and return graph of Figure 3 is representative, the axial dis in the general direction of the electron gun. tance between the center of de?ection and the This effect is even more pronounced with larger target was made equal to 9. inches with aradius angles of de?ection. For a de?ection of approx- ' of curvature of the target of '7 inches, the po imately 5%“ the trajectory as shown at 34 ap tential of the electrodes 8, l5 and I6 beingequal, proaches the target at its nearest point 35 which to approximately 1000, 500 and 200 volts respec tively, the target being rectangular and measur is even farther removed from the target than point 33. Similarly, for larger angles of de?ec ing 11/2 x 2 inches. This tube, made in accord tion, such as approximately 7° and 8°, the elec ance with our invention, exhibited a ‘minimum of distortion due to non-normal approach of the tron beam follows the trajectories 3t and 38, the nearest points of approach to the target being electron beam and resultant crawling effects, as well as a minimum of spherical aberration ef the points 31 and 39. It will be noted that as the angle of de?ection increases, the distance be fects occasioned by the electron lens between the tween the target and the nearest point of ap 40 second anode and target. While we have described our invention with re- ‘ proach for the various trajectories increases cor spect to the provision of a tube and system where respondingly, and it will be evident that while a unit picture charge may be neutralized by the in more uniform approach of the electron beam to the target is obtained, it should be understood beam having an axial trajectory, the beam will have progressively less effect upon a unit charge that the principal criterion for satisfactory oper ation is the path along which the electron beam as the angle of de?ection is increased. Actual approaches the target surface, this path being measurements have shown that a unit charge ca pable of being neutralized by an axial trajectory normal to the elemental surface areas of the target. We have observed that the rate of the. beam must be increased to 12, 20, 46 and 70 units for the four trajectories respectively, as shown 50 crawling or creeping effect in both horizontal and in Figure 2. vertical directions is the same which seems to in While it is possible to partially compensate the dicate that this effect is associated with the in stability of accumulations of charges over the effects produced by non-uniform distances of mosaic‘surfacepthis instability resulting in the approach of the beam to the target by increas ing the strength of the electron lens formed be 55 moving charge excesses and de?ciencies causing the effect. Therefore, while we have not sought tween the electrodes 8, l5 and I6, we have found to set forth a positive explanation of the e?'ect that lens strengths sufficient to overcome even a it will be appreciated that we have overcome the major portion of the difficulties introduce severe spherical aberration elfects so that the resulting di?iculty by so correlating the target contour and ' picture replica, while of more uniform response, 60 the desired beam trajectories that‘ the beam ap becomes distorted with respect to the original proaches along a path normal to the elemental target surface and thereby eliminating the crawl picture content. However, in accordance with ing or creeping distortion. Furthermore while we our invention, these di?iculties may be overcome have indicated the preferred embodiments of our by providing only a small lens action immedi electron beam decreases as the electrons ap ately adjacent the target by forming the target 65 in such a manner that its surface is substantial ly coincident with the electrostatic ?eld gradient _ adjacent the surface. In this manner the radius of curvature of the target is made substantially equivalent to the radius of curvature of adjacent equi-potential ?eld gradients and preferably less than the radius of de?ection which may be de ?ned as the axial distance between the center of de?ection and the target. This results in the electron beam approaching the elemental sur invention of which we are now aware, and have ' provided ‘a tube and system for avoiding the for mation of certain distortional effects it will be apparent that many variations maybe made therein without departing from the scope of our 70 invention as set forth in the appended claims, We claim: " 1. Apparatus for television transmission com prising an evacuated envelope having an ‘end portion which is spherically concave to the in 75 terior thereof, a. substantially transparent "elec 2,404,046 8 7 trically conducting electrode on one surface of said end portion, a mosaic of light sensitive photo trajectories substantially radially incident on said emissive particles adjacent said electrode and in capacitive relation therewith the exposed surface 5. Apparatus for television transmission com prising a tube having an electron gun to develop target. " ' _ an electron beam, an oppositely disposed light of said mosaic conforming to the spherical con cavity of said end portion, an electron gun op sensitive target positioned transversely to the axial path of said beam to receive electrons of positely disposed from said mosaic to develop an electron beam, scanning means to direct said said beam, said target being spherically concave with respect to said gun and having its center beam along paths oblique with respect to the radii of said curved end portion and centered at 10 of curvature lying on said axial path, means more remote from said target than said center of curva a point more remote from said mosaic than the ture to deflect said beam over said spherically center of spherical concavity thereof, and means concave target whereby said beam follows trajec to divert said beam from the oblique paths imme tories oblique to the radii of said target, and diately adjacent said mosaic to paths radially in means adjacent said target to de?ect said beam cident thereon to develop signals in response to 15 to follow trajectories substantially radially inci light projected upon said mosaic. dent on said target said last-mentioned means 2. Television signal generating apparatus com including said target and a plurality of electrodes prising an evacuated envelope, an electron gun adjacent said target. ‘ within said envelope to develop a high velocity 6. Apparatus for developing signals for tele electron beam, a target having a great multiplic 20 vision transmission comprising a tube having an ity of electrostatic charge retaining mosaic ele electron source, an anode to accelerate electrons ments arranged on a spherical surface which is concave with respect to said electron gun, the said from said source, a target having a ?nite radius of curvature, the ,center of curvature lying on the target being symmetrically disposed and trans axis between said source, anode and target, means 25 verse to the axis of said beam, means to de?ect surrounding the said axis at a region more re said beam at a predetermined rate through a mote from said target than the center of con vertical angle and means to de?ect said beam cavity thereof to scan said electrons over paths at a predetermined higher rate through a hori obliquely incident on said target, means includ zontal angle said last two mentioned means be ing said target to decelerate said electrons to a ing positioned about the beam axis at a region 30 substantially zero velocity in the vicinity of said more remote from said target than the center target, said means including an electrode adja of concavity thereof, means to develop an electro cent said target to direct electrons from said static image of varying electrostatic charge in tensity over the surface of said target, a plurality of electrodes between said de?ection means and target, and means to decelerate and direct said beam following said de?ection along paths radial to the surface of said target to develop signals substantially proportional to said charges and in a time sequence determined by the uniform paths to paths radially incident on said target. 7. Apparatus for developing signals for tele vision transmission comprising a tube having an electron source, an anode to accelerate electrons from said source, a target having a ?nite radius of spherical curvature, the center of curvature 40 lying on the axis between said source, anode and rates of de?ection. 3. Apparatus for television transmission com prising a tube having an electron gun to develop an electron beam, an oppositely disposed light sensitive target positioned transversely to the target, means surrounding the said axis at‘ a re gion more remote from said target than the cen ter of concavity thereof to scan said electrons over paths normally oblique to the surface of said target, means including said target to develop an electrostatic equipotential ?eld directly adjacent said target which is of spherical curvature con forming substantially to the curvature of said target to direct electrons from said paths to paths axial path of said beam to receive electrons of said beam, said target being concave with re spect to said gun, means to de?ect said beam from a center of de?ection further removed from ' 50 radially incident on said target. the said concave target than the center of curva 8. Apparatus for developing signals for televi ture thereof whereby said beam follows trajec sion transmission comprising a tube having an tories oblique to said target, and a plurality of evacuated envelope a portion of which‘ is adapted electrodes adjacent said concave target to de?ect to bear a light sensitive target, an electron source, said beam to follow trajectories substantially 55 an anode to accelerate electrons from said source, radially incident on said concave target. a target having a ?nite radius of spherical curva 4. Apparatus for television transmission com ture between said envelope portion and said elec prising a tube having an evacuated envelope one tron source, the center of curvature of said target portion of which is spherically concave with re lying on the axis between said source, anode and spect to its interior, an electron gun oppositely 60 target, means surrounding a portion of said axis disposed from said concave portion to develop an and between said source and said center of curva electron beam, a light sensitive target adapted ture to scan said electrons over portionsof paths to develop elemental charges representative of the light and shade areas of an optical image deposit normally oblique with respect to said target, means including said target to decelerate said ed on and conforming to the concavity of said 65 electrons to a substantially zero velocityin the portion to receive electrons ?owing along a path vicinity of said target, said means including an from said electron gun, beam de?ection means electrode adjacent said target to develop a spher surrounding a portion of said beam path at a ical equipotential ?eld which substantially congreater distance from said target than the center forms ‘to the curvature of said target immediately of curvature of said concave portion to de?ect said 70 adjacent the surface thereof whereby electrons beam from a center of de?ection removed from are de?ected from said paths to paths radially the center of curvature of said concave portion incident on said target. whereby said beam follows non-.radial trajectories toward said target, and means adjacent said target to modify the trajectories of said beam to 75 LESLIE E. FLORY. , ERNEST A. MASSA. . GEORGE A. MORTON.