US2481839A - Color television - Google Patents

Description

Sept. 13, 1949,

. A. N. GOLDSMITH COLOR TELEVIS ION 'T Sheets-Sheet 1 Filed Aug. 5, 1944 INVENTOP.

147'7'019/VEK l A. N. GOLDSMITH 2,481,839

COLOR TELEVISION Filed'hug. 5, 1944 I 7 Sheets-Sheet 2 Sept. 13, 1949. A. N. GOLDSMITH 2,481,839

COLOR TELEVISION Filed Aug. 5, 1944 7 Sheets-Sheet 4 as a2 I 1E HoP/zoA/mz. Z: 7

Dex-250110 1 log GENERATOR 5: r

lM E/vrog fi'owwwliz ATTOPNE X Sept. 13, 1949. A. N. GOLDSMITH 2,481,839

COLOR TELEVISION Filed Aug. 5, 1944 I 7 Shee'ts-Sheet 6 INVENTPP Sept. 13, 1949. A. N, GOLDSMITH COLOR TELEVISION 7 Sheets-Sheet 7 Filed ,Aug. 5, 1944 lVE/VTOP ATTORNEY WWW Patented Sept. 13,, 1 949 2,481,839 COLOR TELEVISION Alfred N. Goldsmith, New York, N. Y., assignor to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application August 5, 1944, Serial No. 548,238

' 29 Claims.

This invention relates to television, and particularly to forms of electronic television systems using cathode ray image scanning or reproducing tubes for such images, where the images are scanned and/or reproduced in colors closely approximating those of the scanned image at the transmission scanning points.

Broadly speaking, the invention is directed primarily to television systems wherein the image reproduction is accomplished by the superpositioning, in registry, of a group of color component images by multicolor, tricolor or bicolor reproduction in selected primary, supplementary, or key colors which, together, add to produce resultant images in substantially their natural colors and with a reasonably acceptable approach to the natural luminous gradations. the reference above to the so-called key colors it is to be understood that such terminology is intended essentially to constitute the neutral shades, such, for example, as gray, since images in key colors have been found to contribute quite materially, in many cases, to the accuracy of gradationrather than only to the actual color value.

In a more specificapplication, the present invention is directed to a form of television system wherein the image producing tube is provided with a target or screen area based upon a focal or quasi-focal plane upon which one or more electron beams are substantially focused and upon which the images, as produced, are made to appear directly in substantially their natural colors. Such a system incorporates, as

well, an appropriate color selective scanning system for the several component colors of the composite image. Under such circumstances, provision is made for geometrically and otherwise re.- lating the separate scannings to the multicolor fluorescent, luminescent or phosphorescent target or screen area.

In one form of the invention the color images result from the impact of a plurality of separately controlled electron scanning beams upon a target or screen area from somewhat different directions of scanning. The invention provides ways and means for correcting any boundary distortions in the component color images which result from such forms of scanning and which would otherwise militate against accurate registry oi the component colors.

In another form of the invention, provision has been made for an image scanning or camera type tube for translating the light values of the scene or object into electrical currents or voltages, where such tube comprises substantially or equivalently the counterparts of the image reproducing device or tube hereinabove referred to. Essentially, therefore, the image scanning or camera tube comprises a focal or quasi-focal plane upon which are positionedgroups of multiplicities of light responsive materials with suitable light filtering means for segregating the different component colorsof light from difierent coreiated multiplicities of light sensitive elements. The light sensitive elements are supported upon the so-called quasi-focal (or focal) plane which, in this instance, may constitute a dielectric surface which separates the light sensitive elements from the so-called signal plate. Accordingly, electrostatic charges may be built up across the dielectric element with the magnitude of the charges proportional or related to both the intensity of the light and the color of the light to which the related element is subjected.

In one of its broadest senses the invention furthermore may be considered as involving a systern wherein provision is made for simultaneously or, under some circumstances, sequentially reproducing television images in color upon a focal or quasi-focal plane of a target or luminescent screen of a cathode ray image reproducing tube. The impacted areas upon which the produced cathode ray beams impinge are formed in different sections or areas, later to be described in more detail, which, generally speaking, comprise groups of multiplicities of rudimentary or elementary surfaces comprising contiguous elements systematically located relative to the focal or quasi-focal plane of the tube, with each of the multiplicities of elements being sensitized to luminesce, fluoresce' or phosphoresce when activated by the scanning cathode ray beam, for instance, to radiiate light in one of the colors corresponding to the selected primary colors. In this way, the produced light values when visually added together will produce the picture in substantially its natural coloration. Where the elements or rudimentary surfaces all lay in one plane, it may be regarded as a focal plane."

If the elements extend outwardly to a slight ex-' tent from a plane, it may be considered to be a quasi-focal plane.

To this end the system comprises, for colorreproduction purposes, a supporting surface or target, hereinafter termed, for convenience, the quasi-focal plane (in the light of the above statement) on which is positioned a group of multiplicities. of rudimentary or elementary size surfaces which are systematically located and where the multiplicities of elementary surfaces are, at least in part, covered by material which becomes fluorescent, luminescent or phosphorescent under electronic impact in approximately one of the component colors for production of additive color images. For activating or energizing the elements, a plurality of electron scanning beams, corresponding in number to the component colors selected, are provided. The operation is so arranged that each of the scanning beams is restricted to scanning substantially only one of the multiplicities of elementary surfaces and, at the same time, provision is made for correcting the boundary distortion of the images thus scanned so as to enable accurate dimensioning and registering of the composite scanned areas.

Still further, the present invention comprises, as one of its component parts, suitable means for providing, in many cases, for the alteration of the focus of the beam in proportion to the deflection thereof from a normal or datum position, e. g., the approximate center of the image, since it is apparent that the greater the angle of deflection and obliquity of scanning (e. g., near the edges or corners of the image) the greater the possible defocusing, which can be overcome to a substantial extent by a suitable control of the focus which will be a measure, at least to some extent, of the actual change in position from the normal position of the beam. The energy for providing such correction of focus which will tend tocompensate for defocusing may be derived from one or both of the deflecting energy waves which develop the electrical field actually to cause the deflection of the cathode ray beam across the target areas.

Regarding correction systems and means for such correction of focus and distortion, it will be appreciated that the focusing correction is 50 suitable electron beam deflecting arrangementsv or components to bring the image areas back to rectangular dimensions of the desired aspect ratio. I

It is known, in television systems, that to produce a tricolor additive process image (which will herein be mentioned as one example) requires, at the transmitting station, the resolving of the image or field scanned into preferably three component fields or images which will usually be the red, the green, and the blue versions of each separate image. These separate color versions may be scanned either simultaneously, cyclically or sequentially, and the process may be either continuous or intermittent to produce a composite resultant image. The scanned fields or color versions or color component images are then resolved into electrical signal energy which is transmitted to receiving points to produce the desired color component image signals which are suitably separated one from the other and caused to control the energization or activation of the impacted surface or target areas.

In simultaneous three-color systems to which this invention is particularly thought not exclusively directed, it is desirable to provide three angles, as well as from, or in place of, paths substantially normal to the surface.

While the three-color additive process has been particularly referred to hereinabove, it will be apparent from' what has been above stated that 'the invention is equally applicable to use with multicolor systems or bicolor systems, or with various numbers of component colors functioning together, either alone or in conjunction with supplementary or key colors. In case the system is applied, however, to a two-color system, it is apparent that co-planar scanning beams, which are oppositely inclined and with which conventional keystoning correction for each is substantially oppositely applied, may be resorted to. Under such circumstances, in the case of the image reproduction, one of the two component colors will be a reddish-orange and the other component color will be a greenish-blue, in contrast to the selected red, green, and blue which constitute the primary colors for the'selected additive tricolor process.

Accordingly, the present invention makes pro- .vision for taking care of the various obliquities of impact of the resultant scanning beams upon the target area so as to compensate for any boundary distortion or foreshortening of the im age in one or two dimensions, as would normally result in the absence of the introduction of suitable corrective components into the deflection cycle. Such corrective components are arranged primarily to care forand correct any nonrectangularity of the scanning pattern from each separate electron beam, as well as to provide for an exact matchingv of the amplitude of the deflections in order that correct and proper registration of the difierent component elements shall at all times occur.

Still further, the present invention is directed to a system whereby the target area of the re- 'ceiver image reproducing tube, which is impacted by the electron beams operating simultaneously or in sequence, where desired, shall have certain elements excited by electron impact to produce one color of light, approaching, for instance, as closely as possible to the red component; a second group of elements reacting to the electron beam from another gun, for instance,

to produce the same conditions of light as would approximate, as nearly as possible, the green color component of the scanned image of the transmitter; and, a third group of elements acting to produce light approximating, as closely as possible, to produce at the receiver the blue color component of the image which was scanned at the transmitter. It is, of course, apparent that the close approximation of the light radiation emitted by each of the respective multiplicities of elements forming a single color group of the desired primary color component may be increased, to some extent, by surrounding or supporting the impacted material which luminesces, fiuoresces or phosphoresces in a medium or underlay having color filtering capabilities of the desired sort, but nevertheless resistive to or shielded from electron impact and capable of maintaining color under impact without the release of gas which would reduce unduly the vacuum within the tube. Such color filtering medium, when needed and used, 'must lie at least in part in the path of. the light, which, after emission from the fluorescent material, passes directly or indirectly to the eyes of the observers.

In one of the systems herein to be described wherein multiplicities of inclined component color fluorescent or luminescent ele'mentsare systematfrom the corresponding electron gun of the same color component in order that the general effect of substantial shielding or absence of impact from the scanning beams of the other two guns, corresponding to the other color components, shall result. In this connection-it may be mentioned that unless precautions are taken, the angle of impact of the beam on the target varies over the entire image area, although, broadly speaking, the angle of change is not excessive so that this disclosure, for simplification, will not discuss specificallyvarious compensating schemes. This is particularly true of the systems herein to be described which will be identified further in their more specific aspects by the monoplane and biplane type of construction or scanning as contrasted with the multicolor scanning with the triply divided scanning type of planar screen such, particularly, as that of the general type and character shown more particularly, as to the specific screen construction, by Leverenz Patent No. 2,310,863, granted on February 9, 1943 which is one example of such a screen structure.

In the last-named form of system including a target of the general type disclosed by Leverenz, the luminescent screen or target consists essentially of long narrow strips of fluorescent material adjacent each other, with one set of such strips having the property of luminescing under electron impact in one primary color, the next set of strips luminescing in a second primary color, and the third luminescing in the third selected primary color, so that when each of the strips is caused to become luminescent the result will be a tri-color additive reproduction of some desired image. Each color strip may be regarded as a series of substantially or actually contiguous colored scanning elements arranged along its length and collectively forming thestrip. In this connection it is important to note that strips of like color response are separated one from the other by spacings equal to twice the strip width.

In connection with all of the types of scanning hereinabove referred to, it is apparent that the -scanning spot, that is, the cross sectional area of the scanning beam as it impacts any given surface, should preferably be inscribable within one of the substantially contiguous elemental areas and still provide a reasonably practical marginal tolerance in the way of a border area external to the actual beam in'order to provide reasonable freedom in alignment of the impacted areas, regardless of minor or incidental variations or errors in the electron gun operation, defects in the deflection system, and the like.

The present invention is also concerned to some extent with the specific construction of screen or target areas of the various types hereinabove mentioned, but with regard to the last named general type of tube screen reference to the aforesaid Leverenz patent is made by way of example to c te one suitable form of such screen or target structure. In connection with the present dis-. closure, it will be understood that the invention known and used particularly in connection with sequential three-color television.

Another'object of the invention is that of producing color television images without mechanically moving parts in either the transmitting or the receiving system.

Another object of the invention is that of producing color television images on cathode ray image producing tubes or Kinescopes which can be made responsive either to color television signals transmitted simultaneously, or to systems where the separate color component images are transmitted cyclically or sequentially.

A further object of this invention is to produce colored television pictures or images upon a single cathode ray tube screen by an additive color process so that the images resulting may be viewed directly or by various projection methods known in the art in order to provide enlarged television images. Any suitable enlarging system may be used, .but among the systems of the prior art which are generally best adapted to-this use are those heretofore suggested by Landis, Rama berg, this applicant and others and fully disclosed in the patented art and elsewhere.

A further object of the invention is that of producing color television images in any desired number of color combinations, and in any desired number of repetitions of the separate colors in the production of one complete television image, so that it is not essential, in one of the forms of the invention, that the rates of scanning be identical for the several colored images, although, with identical rates of scanning and detail for each selected component color, exact registry of the image elements is particularly readily achieved.

A further object of the invention is that of pro-- ducing multicolor television images upon the target area of a cathode ray image producing tube for either direct viewing or for projection.

A further object is that of producing on a target area of an image producing tube, difierent component color images in accordance with the angle or angular positioning from the screen at which the particular controlling electron scanning beam emanates, and, at the same time, to provide for the arrangement of a plurality of component electron guns to produce scanning beams each of which will excite the luminescent or fluorescent target in substantially only one of its color components in accordance with the direction or range of directions from which the electron scanning beam emanates.

A further object of the invention is that of 7 correcting boundary distortion of foreshortenin of the scanned images which would normally be produced because of obliquity of scanning, at least to some extent, by the provision of a plurality of electron guns angularly disposed relative to the impacted target area.

A further object of the invention is that of providing means for accurate dimensioning and registration of the color component images produced by the independent obliquely located scanning beams.

A further object of the invention is that of correcting for beam defocusing which tends to occur in some portions of the image due to the different distances between the electron gun and the scanned surface during certain portions of the scanning process.

All of the foregoing objects likewise apply with equal force to a transmitter type of tube where the light of the image is caused to influence different elemental sections of the tube, as above indicated, to produce electrostatic charges which are a measure of one only of the selected component colors or, also, a key color where such key colors are combined in the transmission.

Still other objects of the invention are those of providing a three-color television system which functions to produce either sequential three-color or multicolor images, or simultaneous of threecolor or multicolor images, which will be, considering the general complexities of any form of color scanning system, of relative simplicity and yet high efficiency.

Other objects of the invention are those of providing a system for producing multicolor images, either sequentially, cyclically or simultaneously, which will overcome heretofore known defects in the art and which will provide television images in multicolor which shall accurately portray, in all regards, the image scanned at the point of transmission.

.Still further objects of this invention are those of providing a television scanner or camera tube of the electrical variety whereupon optical images may be cast and which, when projected upon a target or mosaic area through appropriate filters, may be caused to produce video or image signals upon scanning of the target which will represent diiferent color visions of the optical image.

Still another object of the invention is that of providing a television scanning or camera tube for separating an optical image into selected image or video signal trains, which signals shall represent the selected primary colors and used to control suitable image reproduction at receiver points so that the optical image may be recreated in substantially its natural colors.

A still further object of the invention is that of providing a multicolor television system in which the principles disclosed are directly applicable either to transmitter or receiver, especially, but not exclusively, in so far as the disclosed systems for correcting for boundary distortion or foreshortening, normally tending to prevent bringing the component images into accurate registration, are concerned.

Other objects and advantages of the invention will become apparent and at once suggest them selves to those skilled in the art to which the invention is directed by reading the following specification and claims in connection with the accompanying drawings, wherein;

. 8 Fig, 2 is an elevational view in schematic form of a scanning tube of one suitable form for multicolor television uses;

Fig. 3 is a view of the tube in Fig. 2 in plan or square pyramid replacing the triangular pyramid or tetrahedron of Fig. 1;

of a tetrahedron or pyramid forming a portion of the target area;

Fig. 7 is a schematic representation of a section of a target area formed from a multiplicity of the square pyramids of the type shown by Fig. 6;

Fig. 8 is a schematic representation of a scanned area of the general form shown by Fig. 4;

Fig, 9 illustrates schematically the scanning angle of the electron beam issuing from one of the several electron guns;

Fig. 10 is a schematic showing for illustrating one method of forming the target;

Fig. 11 is to illustrate another step in the process of target formation;

Fig. 12 schematically illustrates one form of distorting pattern traced with a keystone effect resulting in the absence of correction systems;

Fig. 13 shows a modification of the deflecting wave for controlling the traced area of the target;

Fig. 14 represents one pattern which would normally be traced by seaming beams in the absence of deflection correction and also the pattern area which is desired and which results with appropriate correction systems in use;

Fig. 15 shows one form of a compensating circuit particularly adapted for compensation of distortion in one of two dimensions where, for

example, the horizontal dimensions is symmetrically shortened;

Fig. 6 illustrates another form of pattern which by correction may be transformed into a rectangular area of desired aspect ratio by virtue of the correction systems shown in connection with Fig. 15, for instance;

Fig. 1'7 is a further correcting circuit for pattern correction; 1

Fig. 18 illustrates the distorted pattern normally traced and the transformed rectangular pattern provided by the'correction system of Fig. 17; 7

Figs. 19 and 20 represent two forms of deflection wave patterns to provide image pattern corrections;

Figs. 21 and 22 schematically represent scanning arrangements within a multicolor scanning tube for use with one of the component scanning tracers;

Fig 23 represents a scanned pattern substantially like that of Fig. 12 but with the scanning" distortion recurring in reversed direction:

Fig. 24 represents one manner by which the signal plates of light sensitive elements of a scan ning or camera tube may be connected; and,

Fig. 25 is a sectional view taken on the line 25-25 of Fig. 24.

When reference is. made particularly to the drawings. for a color reproducing system, the term color element will be used to some extent light' which will be of 'acolor approximating as closelyas possibleone'of the primary or color components for additive color image production sions of such color elements should be of a preand operated as a three-colorsystem wherein the assumed primary colorsshallbe red, green, and

blue, it will be appreciated thatthe various color elements on the fluorescent or luminescent screen 'or target for any one color component are to be 7 impacted by onlyone of three selected and separately cont'rolledscanning beams., As a result of such conditions, itnatura-lly follows that in the practical construction and form of the multi- I ,color image producing tube hereIn to be described in more detail by what is to follow, in

connection with the system by whichit is oper ated and controlled, all of the separate color elements of the given color should be arranged at a like angle (preferably, but not necessarily, normal on the average) to the corresponding scanningbeam. Therefore, the separate color elemerits should be positioned at substantially constant angles relative to the, supporting surface, at least as far as the central portion thereof is concerned, in order to avoid distortion or color or brightness changes in the produced image.

When any such surface is scanned, it will be apparent that toward theboundaries of the scanned surface'the scanning beam isincr'easingly oblique in its impact and, consequently, the angle between the color elements of any one color and a' with or without color f llteri ng' therein or adjacent thereto. In such applications, the dimen color elements of a will iluoresce ingreen, while the rear I, 2, l to be coated with of the pyramid willbe assumed material which shall fluoresce blue.

, The particular luminescent which arcchosen to provide the red, the green, and the blue fluorescent efiects' may vary widely but, for purposes of illustration, suitable materials may. i 1 be those which have been disclosed in the aforedetermined size relativeto the cross-sectional mentioned Leverenz Patent No. 2,310,863, granted February 9, 1943. For instance, toprovide the red luminescent effects, use may be made'o! chromium activated aluminum berylliate or zinc cadmium sulphide activated by, silver; the blue effects may result from silver activated zinc sulphide, zinc silicate and zirconium silicate; while the green luminescent efiects may be providedby alpha-willemite activated with manganese and zinc cadmium sulphide activated with silver, all

as explained in theaforesaid Leveren'z patent.

To represent in a conventional manner the several scanning beams which are intended to 1m: pinge upon the various pyramid faces, the scanning beams 5, 8, I are illustrated for the purpose of indicating the control by which the red, the

reen and the blue lights or fluorescing areas are produced.

I 3, the viewed target area will be formedfrom a v supporting surface may be graduallyincreased.

However, as afirst approximation and forthe purposes of this description, it is considered that the angle between the color elements of one color,

' x and the supporting'surface may be regarded for all practical purposes asbeing constant. If the distance between the screen and the limited region wherein beam deflection takes place is large compared to the screen dimensions, this condition will be closely approximated. It thereiorefollows that each group of the color elements, of

which the three assumed primary color images are tobe formed, will be on the surface or surfaces of a pyramid which will be a substantially right pyramid with its apex tumed, generally speaking, in a direction substantially toward the mean position of the sources from which the forth, is depicted, and, in the specific illustration given, theapex l of the pyramid is intendedto be turned in a general direction toward the elec-,

tron guns or sources from which the scanning beams originate. The base 2, 3, 4 of the pyramid is intended to rest upon'some suitable support area such, for example, as theviewed target plane (not shown specifically. by Fig. l) The pyramid face i,:3, 4, is intendedto be coated with amaterial which will iluoresce red, for instance. The face L2, 3 of the pyramid maybe assumed to be coated with some suitable material which In the fabrication of a tube element for viewing a tricolor additive picture of the type hereinabove described, and which'tube is schematically illustrated by the exempliflcations of Figs. 2 and multiplicity of the general form ofpyramidal elements, which were described by, Fig. 1. A screen or target of this general character is illustrated by the arrangement of Fig. 4 which is intended to show, in plan, a small portion of the composite surface formed from a multiplicity of pyramidal elements, such asthose shown by Fi 1. r

In the arrangement of the composite screen or.

targetof Fig. 4, the apex! of each of the pyramids is intended to be pointed in the direction opposite that from which a viewer views the screen ,(this, however, is not a necessary condition). As

the surface is positioned in Fig. .4, it would be assumed that the viewer would look at the composite screen fromapositionbeneath the surface of the sheet of paper, and, in Fig. 4, as in Fig. 1, the various pyramid faces are similarly numbered and, when activated, are to provide radiation of light in the three chosen primary colors. Underconditions when the pyramids are mounted and positioned as in Fig. 4, it will be seen that there are a numberof small spaces or areas I! in the space between the several pyramids. These areas, generally speaking, will be triangular, or substantially so, when the pyramids are set up and formed from such elements as those disclosed in Fig. 1. A

These areas ll may be either clear, gray, or black, but in any casexshould-besubstantially freeirom any fluorescent or iuminescent coatinc so, that any impingement of any of the scanning beams on the areas I! will be without sig- "nificant efiect as far as producing light, which will be visible to an observer, isconcerned. This condition comes about, generally speaking, because in the composite arrangementof a series of pyramids, such as thoseshown by, Fig. 1, the severalscanning beam. 5, ,6, l, mayimpinge to a very slight extent, at least on theoverlap areas II, and thus with the severalscanning beams being signal controlled in one onlyof the several selected component colors, it can be appreciated that sensitization or activation of any of the areas II by fluorescent material could preclude the possibility of obtaining high fidelity color picture representation for the observer.

'A slight modification of the arrangement of Figs. 1 and 4' will be found in the structural rep-'- resentations of Figs. 6 and 7. ,In this connec-.

tion, Fig. 6 shows a quadrangular pyramidal element which is provided with approximately a square base 22, 23, 24, 25 and from the apex 2i of the pyramid to the various sides of the base, the triangles which are formed are coated with different fluorescent materials so as to produce, when activated, the light in the several different' colors. For instance, the triangular face 2!, 22, 24 will be assumed to be coated with red fluorescent material; the triangular face 2|, 22, 22 may be assumed to be covered with material which fluoresces to'radiate green light; the pyramid face 2|. 2'4, 25 will be assumed to be coated with material to fluoresce' in blue, while the fourth surface of the pyramid 2!, 22, 25 may be either clear, gray, or black or, alternatively, it may becoated with a material which fluoresces to give back and white or so-called key images, in which event, the image producing tube would be provided with a fourth electron gun;

Generally speaking, an impingement of a scanning beam upon the several areas or pyramid faces 2i, 22, 25 would produce black and white key pictures or image representations, which L the various faces or surfaces so that the individual scanning beams excite fluorescence in one only of the several component colors.

Generally speakingfsome of the advantages from the use of the four-sided pyramids, disclosed by Figs. 6 and 7, result in that no gaps or inactive spaces are generally produced between the pyramids, and also, as will be apparent from what is to follow, a double. obliquity of scanning may be avoided so that each of the scanned areas in the absence .of suitable corrective means is distorted either vertically or horizontally, but not both vertically and horizontally, as is the general case with the threesided pyramid. The result; is that four-sided pyramids simplify the corrective means which willbe hereinafter further explained.

It will be explained also, from what is to follow, how the surface covered with the various pyramids may beproduced in various ways as well'as the method of sensitization of the various pyramid faces with luminescent or fluores cent material which will give ofl the desired light color when activated. a

Under some circumstanceathe fluorescent material with which the pyramid faces are activated may not produce light of exactly the color component value desired, so that filtering is required to obtain the correct color. Togthisend, a suitable filter may be arranged as an underlay on the corresponding pyramid face or surface and the luminescent material deposited thereupon or, alternatively, the fluorescent material maybe applied-by means of abonding or binding agent which contains an inorganic coloring material having the desired filtering characteristics, or the pyramid material which supports the individual fluoresent layer may itself be colored. Except in. the last mentioned case' the pyramid units themselves shall bev substantially transparent to all colors of light so that an observer viewing a composite target or screen structure, forexample those ofthe type shown.

by Figs. 4 and "I, from thebase of the pyramid, shall be able to see readily light in the different primary colors as initiatedin the activation'of; the surfaces by the scanning electron beams i, 1

illustrative case, the apex of each pyramid faces away from the observer I 6, as was before mentioned. The arrangements of Figs. 2 and 3 are,

showings of the same. tube 30 with the tube positioned at twd 90, viewing. 3 points. In this arrangement, it will beseen that as above noted, two

the tube proper contains separate neck portions 26, 21 and 28, which include, as conventionally illustrated, several electron gun structures ii, 32, 33 from which the scanning beams 5, 6 and I emanate. These scanning beams 5, 6 and l are directed toward the, target I5 along the paths schematicallyshown. e

If Fig. 3 particularly be considered, it will be noted that the so-called red sca'nning takes place from below and centrally upward to the target or screen IS. The green scanning may be considered as being from the left above and obliquely downward, while the blue scanning, for, illustration,

purposes, is considered as being from the right above and obliquely downward, with the expres- F sions right" and left" being representative of directions from the viewpoint of the person facing the target or screen surface.

While specific detailed illustration has not been made of the various systems by which the deflection of the electronbeams emanating from the electron guns contained within the several neck portions of the tubeis accomplished, it will be appreciated that electrostatic or electromagnetic systems, or combinations of these,lmay be utilized. Further, it will be appreciated that while specific illustration of such forms of deflection systems a have not been shown, except rather generally herein, the invention contemplates .the provision of any necessary and desired types of shielding between the several deflectingsystems so. as to provide full and complete freedoinfrom the interaction of one deflection system upon another.,

With these forms of scanning it will be seen that the angle from which-theseveral scanning beams 5, 6 and I strike the target or screen 15:

are, generally speaking, greatest at one boundary, at anintermediate value at thecenter, and least at another boundary. The differences in the angle of incidence of the scanning beam across the target surface I5 is relatively small in the normal type of tube, although to insure accurate image a registry compensation may be provided in various ways in order tomaintain substantially normal of the tricolor component, scannings over the entire screen area.

Both theory and experiment indicate that the leeway in permissible angle of scanning beam impact relative to the target or screen area l in- 5 creases as the altitude or elevation of the elementaryscreen t'etrahedra or the pyramidal height increases. It thus becomes evident that the higher the tetrahedra or pyramids the shorter are the permissible side tubulatures of the multicolor scanning tube within which the electron gun is mounted and through which the scanning beam passes. With pyramidal elements or tetrahedra, which are relatively high, the angle A, whiclmi's represented particularly in connection I with the showing of Fig. 9 (later to be described) may be even twice that which itnwould be if the height of the tetrahedra were reduced substantially.

Reverting to the theoretical desirability of maintaining equi-angular impact of the scanning beams on the tetrahedral faces throughout their motion over the image area, it is frequently desirable to vary the tetrahedral angles or altitudes systematically over the image or view area;

Usually this is not necessary, although it will be appreciated that certain refinements may be obtained from the modification. In cases where there is a variability in the pyramids or tetrahedra, this slight variability in pyramid angles may be taken care of in the manufacture of the screen in order that substantially normal impact may always result. It should, however, be here noted that entirely acceptable operation may be secured with constant pyramid angles over the entire screen surface, provided reasonable beam deflection angles and adequate pyramid heights are used.

In making reference to Fig. 5, the area thereof may be regarded as a rectangular area of normal image aspect ratio which results from a normal electron scanning of a target area by an electron beam scanning the surface or area 35 where the scanning beam is generated in an electron gun positioned normal to the surface and at approximately on a line drawn through the center of v the area 35. Neglecting, in the pattern shown, a very slight pin cushioning effect, which is extremly small unless the gun is very closely adjacent the target, the scanned area 35 is a of the vertical and horizontal scannings taking 6;

place respectively from left to right for the horizontal scanning and from the top to the bottom for the vertical scanning. 7

If now, a condition be assumed where the axis of the electron gun is located in a plane per- 05 pendicular to the image surface and passing through its vertical central line, and if the gun points toward the center ofthe image area in this plane and is inclined downward from the normal to this plane, the resulting image, in

the absence of correctionmeans, would be foreshortened, as indicated generally by the area 36. To correct this conditiomas is well known, a voltage or current of appropriate polarity and magnitude, determined in accordance with the vertical deflection, may be introduced into the horizontal deflection current or voltage which is producing the lateral deflection or motion in the direction H. In this way, the foreshortening shown by the area 36 is neutralized and, by the usual image dimension controls, the size of the image, as well as its rectangularity, is maintained and brought back to an area such as that shown at 35.

If the axis of the electron gun is in a plane perpendicular to the image area 35, this plane in this instance passing through the center of the image and horizontally (that is parallel to the scanning lines) and if the electron gun points to the center of the image area and is inclined to the right relative to the normal to this plane,

the resulting image in the absence of any corrective means will be foreshortened, as indicated by the area 31 of Fig. 5. If a certain amount of the horizontal deflection current or voltage is added in an appropriate polarity to the vertical deflection current or voltage, .the foreshortening effect shown in the area 31 may be eliminated and, as before, the rectangular shape of the pattern restored so that the pattern assumes its original dimensions.

The circuits for accomplishing such effects will be hereinafter mentioned in more detail. However, generally speaking, circuits for avoiding the keystoning efiects in one direction, such as that shown in one direction for the area 36 of Fig. 5, but not for those in another direction, such as that shown by the area 31 of Fig. 5, are known and disclosed'both in the literature and in the patented art. That is, keystoning" resulting from shortening of the horizontal deflection lines can be corrected by known methods, but keystoning resulting from shortening of the vertical deflection on one side of the image has not, as far as applicant is aware, been corrected by any previously known means.

If now, a further condition be assumed where the electron gun points toward the center of the image area but does not lie in either of the perpendicular planes above mentioned, the incidence of the electron beam as it is projected toward the area may be said to be doubly oblique." The result is that the image or scanned area 35 will be found to be distorted both vertically and horizontally, as indicated by the pattern represented as the area 38. In this showingit will be seen that two sides of the pattern 38'slope so as to be similar to those along paths coinciding with the sloping sides of the area 36, while the other two sides of the area 38 slope in a manner resembling the sloping sides of the area 31, and both of these conditions occur simultaneously.

'Circuits to provide correction of distortions of this composite or doubly oblique nature, generally speaking, involve at least a combination of the circuits for caring for distortion in the individual patterns or scanned areas represented at 36 and 31 and will be discussed more fully in what is to follow. As far as applicant is aware, such circuits have also been previously absent from the art. It will, of course, be appreciated further that each of the color scannings will have in this way different foreshortening and will each require different correction circuits, although functioning with corresponding constants of operation (vertical and horizontal deflection frequencies and return times). To this end, it will be appreciated that under some circumstances of operation elements of the types shown by Figs. 6 and '7 are to be preferred for some conditions over those 0f the types shown by Figs. 1 and 4 in order that the so-called doubly oblique conditions represented by the area 38 may not have to be dealt with as would be the case when the three-sided elements of Fig. 4, for instance, are considered. Nevertheless, the doubly oblique foreshortening can be corrected by the practical methods herein to be described and set forth.

Considering, however, further, the type of operation wherein the tetrahedra (pyramids) of the type shown by Fig. 4 are utilized as the screen or target upon which the scanning beams impinge, these tetrahedra may be of the so-called equilateral type, or, in anothertype, they may have an altitude (that distance measured from the apex I to the base 2, 3, 4) which is of the order of two-thirds that of an equilateral tetrahedron, or, in still another type, the altitude may be about 50% greater than that of an equilateral tetrahedron. For present consideration and as illustrative, it will be assumed, however, thatthe tetrahedra of Fig. 4, used as the target area, are of the equilateral type.

Referring now to Fig. 8, which is a tetrahedral array viewed along-the direction of an oblique scanning beam impinging approximately normally on the surfaces 3, 4, and the like, it will be assumed that a scanning beam 5 (see Fig. 2) scans the tetrahedra in such a manner as to impinge upon the red responsive areas or triangles I, 3, t. The scanning spot of the beam 5 should preferably cover an area of the impacted triangular tetrahedral face I, 3, 4, which is represented by that area 40 which is confined within the circular area of impact designated. This, as it. will be seen, leaves a small margin on each side of the tetrahedral face when the scanning spot is most centrally located. When the scanning spot, however, moves to the next tetrahedron of the sequence, it tends to occupy a position, which has been indicated within the circular area marked 4 l, and tends to fall upon the area H (see also Fig. 4) which was assumed to constitute a dead area between the two tetrahedral faces and is almost exactly inscribed in the forward angle portion of that area, although it can be seen that a very slight and harmless overlap into adjacent like-color tetrahedral faces may occur. It should be understood that in the scanning of the tetrahedral faces of the tetrahedra, the scanning electron beam is directed so that it strikes almost exactly normal at the centermost portion of the combination. While adjacent tetrahedral faces are impacted, to some extent, by the edge portions of the scanning beam, as indicated at M, so that luminescent eifects of like-color result, the brilliance of such luminescent effects is very substantiallyreduced over that of the scanning electron beam, in a position such as 40, due to the fact that only minute areas of the tetrahedral faces in line between. the electron gun and the dead areas ll come within the range of the scanning electron beam. Thus, effectively unique primary color scanning appropriately occurs for each beam.

It will be appreciated, in considering what has herein been stated, that actually all three of the assumed component color scanning spots or beams will fall upon the dead areas H at certain times during the scanning sequence, although the scanning beams or spots which are to produce the assumed green and blue luminescent efiects will strike the dead or fiuorescently inactive areas H from paths substantially. 120 spaced from that path along which the assumed scanning spot 40 is directed upon the tetrahedral faces I, 3, 4, which faces are assumed,.foril1ustrative purposes, to be red responsive. The direction of impact of the scanning spot .40. as determined by the altitude o-f-the beam (that is, the angle of inclination of the scanning beam to the plane ofthe target, such as the target plane |.5 see Fig. 2 for example) is such that viewed alon the scanning beam,the apices of the tetrahedra project slightly, but noticeably, into the next dead or fiuorescently inactive area II. It is, of course, apparent that, the tetrahedra may be formed as frustra of tetrahedra so as to have substantially flat top portions which could also serve as fiuorescently inactive .or dead areas.

The frustra effect could readily be achieved, for

instance, by slightly grinding or polishing the points of the apices of the tetrahedra by any appropriate'means. 1

- In-the arrangement of Fig.8, the assumed direction of scanning is, as indicated by the arrow, adjacent the scanning spot whereby the sequence will be from one tetrahedral face to another, with the scanning of a dead area or a fluorescently inactive area, shown by H onFig. 4, for instance, intervening between-each successive tetrahedral face impacted;

In connection with the showing, it is desirable to point out that with a multicolor target area of the type herein disclosed, black and white images may be produced as readily as color images in that it will be appreciated that the separate control electrodes of the image reproducing tubes of the general type shown, for instance, by Figs. 2 and 3, and formed from target sections such as shown by Fig. 4, for instance, can allbe controlled from the same signal which represents, under these circumstances, a black and White image sequence. Accordingly, if the sam control signal is applied to all of the component color gun or electron beam controls, for example, upon the scanning beams 5, 6 and 1 of Figs. 2 and 3, a black and white image sequence will result from the screen or target area I 5, irrespec tive of whether or not the signals are applied to all of the control electrodes or guns simultaneously or sequentially.

To this end, it will be appreciated that a system of the type herein disclosed thus is not, in any way, limited to color image production, but rather is adaptable for use also for black and white image production. In case the black and white image production is relied upon, then it becomes evident that the brilliance of the resulting pattern of viewed image will be enhanced, to some degree, due to the additive effects of light to all of the component color areas.

Furthermore, in connection with scanning of the target area, such-as thatformed, for instance, according to the showing of Fig. 4,-where the areas Il may be the so-called dead areas which represent the triangular spaces between the tetrahedral or pyramidal surfaces, these surface areas may be coated with a suitable luminescent material which luminesces under electronic activation to produce black and white light effects.

Under these conditions, if the scanning beams which would normally strike or impinge upon the red, the green, and the blue responsive fluorescent areas should overlap these respective areas so as to strike the so-called black and white responsive areas or the dead areas, the result will be the formation of a further black and white image in addition to, and in registration with, the separate component color images which normally rerun to an increase of the order approaching 200% or more.

No illustration of this form of' seaming has been applied, but it will be appreciated that the black and white or overlap key image may readily result where the cross sectional area of the scanhing beam is slightly enlarged, for instance over what is shown in Fig. 8, so that the spot or beam more readily impinges upon the black and white responsive areas ll intermediate the tetrahedral or pyramidal surfaces of the target.

In order to avoid possibly false color production, as would result for instance if the scanning beam 5, assumed to impinge upon the red responsive areas or tetrahedral faces I, 3, 4, were to impact a blue responsive area, such as the area I, 2, 4, or a green responsive area such as the area I, 2, 3, it can be appreciated that the obliquity of the scanning direction becomes a material consideration. To this end, Fig. 9 is intended to show the permissible angle of the beam for scanning, in that it indicates the range of angles to the central normal surface 35 within which the scanning beam may impact with reference to the scanned tetrahedral surface without causing false color effects to begin to be observed. This angle is indicated as the angle A; and d indicates the distance from the electron gun to the target area so that at the target area the distance traversed on either side of the normal may be represented as D. Thus, the actual angle within which the scanning beam must lie for correct color impact has a value of twice that of the angle A indicated, in that the beam was assumed to originate from a central location which is essentially the region wherein beam deflection occurs. Likewise, the distance D, shown by Fig. 9. is for approximate grazing incidence of the beam on the desired shielded side of the tetrahedron. Theory and measurement show that the leeway in permissible angle of beam impact will be found to increase as the altitude of the ele-- mentary' screen tetrahedra increases, or in other words, tetrahedra of the lowest altitudes are more subject to color distortion by grazing incidence of the scanning beam in the outer portions of considerable beam deflection angles on inappropriate color responsive faces which are other than those upon which-the beam is intended to impact from more nearly a normal path in order to produce one of the chosen primary color images.

It might be noted, in connection with what has been stated above, that in cases where the distance between the electron gun 3|, for instance, and the plane of the target (see Fig. 2) is relatively short so that the target area subtends a considerable solid angle at the location of the electron gun, tetrahedra or pyramids of different altitudes may be used at the center of the target area than are used at the outer edges of the target area with, of course, the-greatest height or altitude being used at the outer edges of the target area and the lowest at the centermost portion. Such tetrahedra naturally may be varied in height in steps from the center of thetarget area outwardly to itscorners, or they may continuously vary in height where so desired. Generally speaking, however, the height of various tetrahedra may be appropriately selected at a single value for use in a tube with reasonable length of electron paths between the electron gun and the target area so that uniformity of the tetrahedra may be retained and yet little or no color distortion from the edge areas will be introduced.

With regard to the manner by which the various target areas may be produced it is, of course, apparent that recourse may be had to various manufacturing methods so long as the resulting product generally conforms with the configuration hereinabove mentioned. Accordingly, it is to be understood that the specific manner of manufacturing the target areas may be varied within wide limits without departing either from the spirit or the scope of this invention or its disclosure. However, for the sake of illustrating one of a number of suitable methods by which the screen or target area may be formed, reference may be had especially to the disclosure of Figs. 10 and 11 of this application.

Referring now to Fig. 10, there is shown, in plan, the top of a block of material which should be transparent and as free as possible from gas emission in vacuo and under electronic bombardment (that is, through the interstices, such as I l, in the fluorescent, luminescentor any other type of coating). The block 50, illustrated by Fig. 10, may initially be of solid nature and then it will be sliced, so to speak, by a slicing machine of microtomic nature by cuts taken at angles at relative to each other in the formation of a target (of the general form shown by Fig. 4, for instance) which slices or cuts are indicated, for instance, by the paths 5|, 52, and 53, 54, and 55, 56 respectively, for each of the 120 angles.

After these cuts have been made; the block is reassembled, and Fig. 10 then illustrates the top view thereof. As shown by-Fig. 10, the resulting cuts produce triangular elements or areas at the tops of the prismatic elements or splints and it will be noted that two placements of the triangular tops of the splints, of which the block 50 is composed, are possible. One of these ar rangements places the units in such a way that one of the splints 60, 6|, 62 has its apex turned backward, while another of the type indicated by 63, 6|, 62 has its apex turned forward. In the arrangement to be described, half of these units, namely those corresponding to the type shown in plan at 60, 6|, 62, will be usable in the procedure to be described further. The other half will require further modification or a different mode of use which need not be here described.

The block shown in Fig. 10 is made up of a SEdL by-side assembly of a substantial number of splints or prisms of triangular cross sections, which will each be relatively long in comparison with the dimension of the top face. Accordingly.

each will have a cross section which correspond to an equilateral triangle and thus fit together into a sort of tessellated structure which is indicated by Fig. 10. To obtain this formation it of course, apparent that small amounts of thinned adhesive material may be used, if desired, to hold the assembly or parts of it together temporarily or permanently, and water glass or a suitable resin may form one of the usable adhesives.

When the tessellated assembly has been made, as above stated. or otherwise, it is caused to have its top surface inclined to the length of the splints at an angle selected appropriately for the particular desired height of tetrahedra (which angle is of course less than 90 and is determined by the desired altitudinal height of the tetrahedra or pyramids which are ultimately to be produced from the prismatic splints), the inclined top surface of the tetrahedra may be appropriately produced by merely sliding the splints produced, as shown in Fig. 10, so that they rest against a suitably inclined surface, or it may result from obliquely grinding or cutting the desired inclined surface from the clamped tessellated assembly of splints. In either case, however, the resulting production will be of the general formation shown by Fig. 11, where the area indicated as 55, 66, 61, 68 is the tilted surface which corresponds substantially to the surface shown in the plan of Fig. 10. The tops of the triangular prismatic splints are indicated by like reference numerals to those used in Fig. 10. As is indicated, from Fig. 11, the angle designated 61, 66, 69 determines the height of the various tetrahedra, which are to be produced by the assembly in sets of three of the splints in Fig. 11 after they have sen appropriately and separately coated with fluorescent or luminescent materials of the desired component color fluorescence (with or without underlying coloredfiltering media). way of example, typical splints might be indicated by the formation BI, 63, 10, 1| and 65.

' and 66, in which case the tetrahedra of greatest Now, assuming that the surface 65, 66, 61 and I 68 has been made flat by grinding and polishing, or otherwise, it is to be coated with the desired component color fluorescent material which, under activation of one of the electron beams, will emit one of the desired primary colors of the tricolor additive group. To this end, the fluorescent coating in question may be directly coated on the tessellated surface, or, if it is desired to correct in any measure the color of the emitted light produced by electronic impact as the light is viewed from the underside of the tri-color tetrahedra which are later to be formed and assembled from the splints, the fluorescent material is coated over a filter layer which has been sprayed or brushed or otherwise deposited on the tessellated surface. Alternatively, the filter material may be appropriately contained within the luminescent compound itself so that when the electronically activated compound is viewed through the proper thicknesses of the splint material from its under or concave side, as will be customary, the desired amount of filtering action will take place.

In the process of fabrication, the next step is to level the complete bundle of splints, as shown by Fig. 11, so that the bases of the coated surfaces all lie in the same plane normal to the length of the splints. After this has been done, the cut indicated by the dotted line 15, 16, 11 is made, thus producing the assembly of coated splints 15, 15, 11, 69, 66, 65. The bottom of this surface is flat, but the top consists of coated triangularly inclined surfaces of which half will be usable in the next step. To this end the three groups of tessellated component color (that is, the red, green, and blue) splints are formed into a multicolor tetrahedral screen between the tetrahedra of which will be blank .or dead areas" which will be filled with triangular cross section splints having their free ends cut off normal to their lengths and either uncoated or coated with a black and opaque substance oi. minimum secaltitude will result from the splint-shear the back of the area (that is, nearest the edge 61, 68), while the tetrahedra of the least altitude will result from the splints near the front edge 65, 66.

Referring back to the pattern areas 35, 36, 31 and 38 of Fig. 5, various forms of distortion patterns relative to the rectangular pattern 35 were illustrated. These are also more particularly shown again by Figs. 14, 16 and 18.

In the pattern area of Fig. 14, one form of foreshortening is shown which is more or less well known in view of the somewhat extensive use in the art of the "Iconoscope" type image scanning or camera tube, wherein the electron gun is at an angle to the impacted target upon which an optical image is projected. In this way. When the electron beam from the electron gun scans the target or mosaic area, it tends totrace a pattern wherein one of the horizontal dimensions, such as the dimension 80, 8|, is symmetrically shortened and the area of the pattern 88, 8|, 82, 83, is to be transformed or converted, as indicated by the arrow, into the usual rectangular area 8 1, 85. 86, 81, which has a generally accepted or standard aspect ratio of 4 :3.

To obtain this result and transformation of the pattern from the area 80, BI, 82, 83 into the area 84, 85. 82, 83,- a more or less conventional method has been represented by the circuit diagrammatically shown by Fig. 15. To this end,

energy for deflecting the cathode ray beam along I a horizontal path is shown, for instance, conven tionally as being developed from a horizontal deflection generator I00, while the energy to effect vertical deflcetion may be assumed to be gener-' cally by the vertical deflection through the aid of the tubes I02 and I03.

The circuit herein illustrated by Fig. 15 is largely schematic in order to aid in understanding the invention, and for further reference to the general type of circuit utilized, reference may be had to the book entitled Television published by Drs. Zworykin and Morton (publication by John Wiley 8: Son, New York) where a. circuit of the general nature of 15 is set forth and described by Pa es 4'72. et seq. Accordingly, the

70 description in detail will not herein be repeated,

except to state that the disclosed arrangement,

' by which the pattern at the left hand of Fig. 14

is transformed into the symmetrical rectangular pattern of the right hand portion of Fig. 14, corresponds to a scanning beam in the plane passing vertically through the centers of the long dimensions 82, 83 and 84. 85 of the area 33 and with its 7 axis inclined to the plane of the picture.

22 of the image (where n equals N/2) is zero since the pattern is symmetrically Ioreshortened.

If, however, the electron gun is centered in a plane which passes normally through the center of the short or the vertical sides 01 the picture (83, 84' and 82, 85) and with its usual axis also inclined to the plane of the picture, a difierent form of distortion results, as is shown by Fig. I6

or the right hand upper half of Fig. 5. It is be-, lieved that no correction means for this type of distortion have been previously disclosed in the art. Such distortion may occur singly or in combination with the type of distortion above ex'- plained in connection with Fig. 14. The result is that the area generally represented as 31 in Fig. 16 must be changed into the so-called normal aspect ratio area such as 35.

The result is that the requirement for making the pattern rectangular results in a peculiar form of vertical deflection wave which is schematically represented in Fig. 13 by the wave form I20, I2I, I22-I24, I25, I26, I21, I29, I30, I3I, I32, which is illustrated by way of example. From this wave it will be seen that the first half of the rising portion of the vertical deflection wave up to its center point, intermediate points I25 and I26,

- is such that there must be added to the normal deflection wave a further component which inwill be seen that the area 35, which is desired,

is represented in part by the rectangular dotted outline, while the area 31 is represented within the solid outline so that the rectangle corresponding to the area 35 is included within the area 84, 85, 82, 83, while the area 31 would be represented within the area limited by the points 84, 86, 81 and 83.

Under these circumstances, the vertical side of normal length H, represented by the line '83, 84, is the same for each of the areas 35 and 31. The symmetrically foreshortened vertical side of length It is represented as the side 86, 81 in each of Figs. 12 and 16. Accordingly, in order that the area may be scanned, typical scanning lines, which might be designated 95, 96. etc., to 31 are shown, with the return trace formed during the blanking period between these scanning lines being such as that represented by way of example by the single dotted return line II5 (actually the scanning beam is suppressed for this portion of the cycle). When an area such as that indicated at 31 is scanned, it is apparent that the first scanning terminates on the right hand edge of the area at a distance represented by a space 82. 81, or at a distance which is indicated as where H represents the length of the undistorted edge, h represents the length of the distorted edge, 12 represents the identifying number of the particular scanning lines in the field scanning sequence, and N represents the total number of lines per image field. It will accordingly be seen from this expression, that the shift at the center eludes the horizontal or line deflection wave, al-

though this component is not added with constant amplitude but rather with an amplitude which diminishes linearly from the value atthe beginning of the deflection wave (at point I20) to a value of zero at the center of the deflection wave.

Then, for the second half of the rising portion of the vertical deflection wave starting at its mid-point and ending at point I32, there must be subtracted from the normal linear deflection wave a. component which also is based on or a function of the horizontal or line deflection wave. As in connection with the added component, the subtracted component must not be of constant amplitude, but rather must increase linearly from zero value at the beginning of this portion of the deflection wave, that is, between the mid-point and point I 32, until a maximum value of I discussed in detail. To achieve the results and the wave formation last above mentioned, reference may be had to the circuit shown by Fig. 17.

In its analysis, the elements of the system as herein to be utilized might be considered as embodying a receiving instrumentality, wherein there are suitable circuits for separating output energy signals representative of the different selected component color signal modulations or video energy waves.

In the mascot a tri-color system therewould, of course, be three signals, but in connection with cases where the so-called key images are utilized, there could readily be four separate signals, with the "key image signal being in addition to the signals representative of the red, green and blue color components.

Similarly, in systems based on primary colors of red, yellow, green and blue, there would be four signals.

In connection with each of these signals, as separated, there is a scanning means for producing a scanning beam arranged to scan a target area and to be controlled in its scanning path to provide compensation 'for distortion due to obliquity of impact and to provide for electron beam modulation of any character, which shall be in accordance with the segregated component color To provide the compensation hereinabove mentioned, there must be associated with the controlled scanning beams suitable means to compensate for any obliquity introduced, whereby rectangularity of pattern trace results and superpositioning of the produced light radiations in the several component colors for predetermined points of the traced pattern always results.

The result of this arrangement is naturally that the pattern traces representative of the several component color areas, with or without the addition of key images or fourth primary-color images, must be a geometric trace assembly in which there is substantially exact registry for like points of the various individualtracings or pattern which, when viewed collectively, add up to produce thepicture in substantially its natural colors as-desired.

In the light of what has been stated above, the pattern at the left of Fig. 16 may be transformed into the rectangular area 35 (at the right of Fig. 16) by taking recourse to the schematically illustrated form of the deflection wave generator combination shown by Fig. 17. In this arrangement, the deflection wave generators I and.IOI, for developing the horizontal and the vertical wave deflection energy respectively, are

again provided, as with the arrangement of Fig.

15. The horizontal wave deflection energy is supplied by way of conductors I50 and II to provide the horizontal wave deflection energy which is made available at the terminals I03 to energize and control the horizontal electron beam deflection. With the system of Fig. 1'1, the vertical wave deflection generator IOI will be seen to deliver a portion of its output energy by way of conductors I52 and I 53 directly to a mixer circuit I55, later to be described in more detail. The output energy from the mixer circuit is supplied at the terminals I56 to energize the means, such as the deflection plates or coils (not shown), which controls the electron beam deflection in a vertical path in the scanning or camera. tube or in the image reproducing tube of the type of tube 30, for instance.

To compensate for the distortion of the pattern 31 (Fig. 16), however, another portion of the output of the vertical deflection generator I 0| is tapped at points I51 and I58 which are connected to the conductors I52 and I53 respectively, to establish a further control through control tubes I 60 and I6I.

By virtue of the connection made at points I51 and I 58, suitably controlled and oppositely phased energy waves may be fed or supplied by way of the potentiometer I62 to the inner control grids or electrodes I63 and I64 of the tubes I60 and I6I. These control voltages are applied by way of conductors I65 and I66 which are connected at appropriately chosen tapping points I61 and I68 on the potentiometer I62. and, by virtue of a thirdconnection made to an intermediate point I 69 on the potentiometer I62 by way of conductor I which connects to the oathode elements of each of the tubes I60 and IN, oppositely phased and correctly adjusted vertical wave deflection energy is fed or supplied to the control electrodes I63 and I64 of the control tubes I60 and I6I. It will be seen that point I61 is negative and point I68 is positive relative to point In contrast to the arrangement of the circuit conventionally suggested in Fig. 15, where vertical deflection wave energy was introduced into fiection. Accordingly, connections are made at points I12 and I13 on the conductors I and I5I to derive horizontal deflection control energy and supply this energy by way of the conductors I14 and I 15 to the secondary or outer control electrmies or grids I16 and I11 of the tubes I60 and I5I. w r

This auxiliary control energy is derived by connecting the cathodes of the tubes I60 and I6l directly to one of the connection points from which the horizontal deflection control energy is derived, such as the point I12, and then connecting a. potentiometer I80 between the connection points I12 and I13 and deriving a voltage to be supplied to the control electrodes I16 and I11 by virtue of a connection made for the conductor I15 at an intermediate tapping point IBI on the said potentiometer I80.

The control tubes I60 and I 6|, respectively. have their anode or plate electrodes I82 and I83 connected to receive energizing voltages from a common source I 64 fed through the load resistors I85 and I86, respectively, for these two tubes.

' Depending upon the current flowing the respec- I53, while the tube I6I is to provide horizontally v controlled deflection wave energy In the same mixer circuit I by way of the voltagesupplied through conductor I88 in such a manner that the horizontal deflection wave energy due to the tube I6I, which combined with the vertical deflection wave energy. shall be subtractive from the linear deflection wave energy output of the generator IOI.

The manner in which the tube I is arranged to be inactive only during the first half of the vertical deflection wave in accordance with the above description of Fig. 13, and the manner by which the tube IBI is caused to be active only during the second half of the vertical deflection wave, are brought about by the use of appropriate bias controls on each of these tubes. By virtue of the bias source conventionally shown at I90, negative bias is applied to the control electrode I63 of the tube I 60 in such a way that when the vertical deflection wave energy reaches its central value. that is, a value represented by g the point intermediate points I25 and I26 on Fig. 13, and this voltage is combined with that derived from the horizontal deflection generator, the tube I60 reaches a cutoff value and becomes inactive during the second half of the rising portion of the Vertical deflection wave.

It may be observed-in this connection, that the vertical deflection wave applied to the control electrode I63 of the tube I60 appears as a progressively increasing negative bias on this tube. On the other hand, by virtue of the connection of the control electrode element I64 through the bias source I! and conductor I66 to the tapping point I68 on the potentiometer I62, it will be apparent that the vertical deflection wave is applied to the control electrode or grid I64 as a progressively increasing positive 25 bias which is opposed to the negative bias I9I normally serving to control'tube I 68.

In other words, it might be remarked that the bias provided on tube I60 through the bias source I90, and by virtue of the connection of the control electrode I63 through the bias source and conductor I65 to the potentiometer IE2 at point I 61, the bias is so set that tube I68 cuts off at the central point of th vertical deflection wave (for instance, half way between points I28 and I32 on Fig. 13), while the bias provided by the bias source I9I and the connection of the control electrode I64 through the bias source of th conductor I66 to the point I68 on the potentiometcr I62 is such that tube I6I is supplied with a negative cutofl bias which becomes ineffective at the point in the vertical deflection cycle where tube I60 ceases to draw current (or is cut off) and, at this point in the vertical deflection wave, the tube I6I takes over, so to speak,

and the wave formation of Fig. 13, indicated between points I26 and I32, for instance, is obtained as a voltage applied to the mixer I55 through conductor I88.

It thus can be seen that the combination of the two biases applied, as above described, on the tubes I60 and I6I control the operative periods of those tubes and, by virtue of the introduction of some of the horizontal deflection controlled energy upon the tubes through conductor I15, proper combination of the horizontal and vertical deflection controlled energy results. If, of course, some undesired vertical deflection control energy wave component appears in the conductors I81 and I88 supplying energy to the mixer circuit I55,'this component of energy can readily be eliminated by well known filter means or potentiometric arrangements which are well known in the art and are therefore neither illustrated nor described in detail. I

The mixer circuit I55 comprises a tube of the usual mixer type in which there is a plurality of control electrodes which, in this instance, may be energized in accordance with the output of all of the deflection controlled generator IIII and the tubes I68 and I6I. Thus, the current output of the mixer I55, as it appears at the output terminals I56 to be supplied to the vertical deflection coils, is of the general wave formation exemplified b Fig. 13. This is then indicative of the form of wave energ which is supplied to the deflection plates or coils (not shown) to control the deflection of the electron beam (which would normally tend to trace the pattern 31 across the target I in the absence of separate deflection control) so that the scanned pattern is transformed into a rectangular pattern area 35.

In this connection it should be pointed out I that the vertical deflection control system must be so designed as to be capable of controlling vertical deflection at frequencies as high as the horizontal deflection frequency (or a suitable multiple thereof in accordance with the usual practice) in order that the corrective deviations in the vertical deflection wave from its linear normal form shall be effective. In the absence of providing main deflection coils for the Vertical deflections which shall respond at frequencies as high as the horizontal deflection frequency, it is, of course, evident that the scanning beam normally tending to trace the pattern 31, in the absence of correction, may be controlled both by the usual type of deflection coil and by an auxiliary deflection coil whichwill be responsive at the relatively high line frequency and which an arrangement, where desired.

26 would then preferably derive its energy from the output of the tubes I68 and I6I with or without the inclusion of the mixer element I in the circuit.

Conditions can readily arise where the area represented at 31 in Fig. 16, for instance, is reversed from left to right so that its shortened edge is at th left rather than the right and, under these circumstances, the correction of the distortion may be carried forward by the same circuit arrangement as is schematically illustrated by Fig. 17 except, for instance, that an appropriate phase delay, corresponding to the time represented between points I20 and IN of Fig. 13, must be introduced into the circuit included in the conductors I50 and I5I which supply energy to th horizontal deflection coils so that when the horizontal deflection of the first lin starts, points III of the deflection wave will already have been reached. It might be pointed out also that, for best operation under these con-- ditions, the energy appearing in the conductors I14 and I15 may be supplied from a second modified horizontal deflection wave generator (not shown) which is arranged to operate synchronously with the horizontal deflection wav'e generator I88 but which produces a wave output with a relatively rapid rise and a relatively slow drop, or, in other words, a wave which is substantially the left to right mirror image of the wave produced by the horizontal deflection generator I88.

It is possible to avoid some of the aforesaiddifliculties, for example, by designing and arranging the horizontal scanning direction of some of the component color images in reverse order to present conventional scanning in order that the horizontal and vertical deflection waves may always start in the same direction or instantaneous phase so to speak. Recourse may be had to such In Fig. 12, reference was made to one form of image distortion, and that form of distortion was further particularly exemplified in the showing of Fig. 16 and the compensating circuit of Fig. 15 to correct such distortion. It is, of course, apparent however, that conditions might occur where the distortion, such as that shown by Fig.

12, is completely in the reverse order. In other words, if the scanning pattern is assumed to be from left to right and from top to bottom of the area of Fig. 12 or the left half of Fig. 16, then it can be appreciated that the left hand edge of the pattern might, in some conditions, be represented by the line dimension h and the right hand of the area represented by the line or edge dimension H.

Under these circumstances, the vertical deflection wave, that is, a normal deflection of sawtooth configuration, would have added to it another component to correct for such distortion.

A wave of this general character is particularly represented by the showing in Figs. 19 and 20, respectively. The diagram showing of Fig. 19 is. in many respects, very close to that reprcsrntcd by Fig. 13, except, of course, that the distortion of the deflection wave is different in that the showingof Fig. 13 had to provide adequate horizontal compensation distortion in contrast to the vertical compensation distortion represented by Figs. 19 and 20.

To this end, the vertical deflection wave with a scanning pattern shown by Fig. 12, for instance,

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