US2669672A - Color image target structure - Google Patents

Description

Feb. 16, 1954 s. H. KAPLAN COLOR IMAGE TARGET STRUCTURE 3 Sheeis-Sheet 1 Filed March 10, 1953 FIG. 1

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HIS ATTORNEY.

Feb. 16, 1954 s. H. KAPLAN COLOR IMAGE TARGET STRUCTURE 3 Sheets-Sheet 2 Filed March 10, 1953 SAM H: KAPLAN INVENTOR.

HIS ATTORNEY.

1954 s. H. KAPLAN COLOR IMAGE TARGET STRUCTURE 3 Sheets-Sheet 3 Filed March 10, 1955 SAM H. KAPLAN INVENTOR.

HIS ATTORNEY.

Patented Feb. 16, 1954 UNITED STATES PATENT OFFICE COLOR IMAGE TARGET STRUCTURE Sam-H.- Kaplan, Chicago, Ill.

Application March 10, 1953, Serial No. 341,444

4 Claims.

I This invention pertains toa new and improved target structure for a color-image device of the cathode-ray type and is particularly directed to atarget in which moirpatterns are substantially eliminated.

One of the better known typesof color-image device, which has beenextensively used for experimental color television work, comprises a single cathode ray tube includinga tri-color reproducing screen and' three electron guns. A parallax mask or gridstructure is interposed between the electron'guns and the screen'of the cathode-ray tube and serves to restrict the area bombarded by each of the guns to-a group of elemental target areas having a consistent colorradiation characteristic inresponse toelectron bombardment. The grid structure usually comprises-a metallic sheet-or mesh including a multiplicity of apertures which'are aligned with clusters or triads of the elemental target areas. Insofar as moir'orbeat patterns are concerned, this type of image-reproducing device is generally acceptable when scanning is carried out in but one direction, since the :grid structure and screen may be so oriented as to effectively eliminate beat patterns. However, if this technique is applied to an image-reproducing device using a radial rotating scanning pattern, usually known as a- P. PVI. scan, moir patterns aredeveloped in varying degrees at different-anglesas the screen is scanned. The beat? patterns produced at certain scanning anglesare quite prominent and can often mask the desired information, particularly when the device is. used in conjunction with radar search apparatus.

It is an object of this invention, therefore, to

provide a newand improved target structure for use in a color-image device employing a radial rotating scanning pattern, the" structure of the target being such asto minimize moire or beat patterns.

It is a further object. ofthe invention to provide an improved target adapted for use'with any type of color-image device comprising an aligned "mask-screen arrangement.

It is a corollary object of the invention to provides. new and improved target structure which to electronbombardment. The elemental-target areas are interspersed 'throughout apredetermined scanning area to constitutea multiplicity of clusters individually including one: elemental target area oieach of the groups. The scanning area comprises a plurality of portions individually having a different inter-cluster angular orientation, with respect to a referenceaxis, from that of adjacent ones of the portions -whereas the angular orientation of the elementalzareas within each of the clusters is substantiallyidentical, with respect to the reference axia through out the scanning area.

The features of the invention which arebelieved to be novel are set forthwithparticularity in the appended claims. 'I'he 'organization and manner of operation of the invention itself,:to gether with further object'and advantages thereof, may best be understood by TBfEIBIICBWO thB following description taken in conjunction *With the accompanying drawingsfin which:

Figure 1 -is--a schematic representation of a receiver including a color-image deviceincorporating a direction-sensitive target structure;

Figure 2 illustrates a portion-of-the-target structure of the color-image device of Figure- 1, constructed in accordance with known techniques, taken along line- 2-2;

Figure 3 is aschematic representationofithe scanning pattern employedin'the colon-image device of Figure 1;

Figure l is an explanatory diagram showing the eiTect of moir or beat. patterns on-thecolorimage device of Figure l;

Figure-5 illustrates a portion of athetarget structure of the color-image device of Figured constructed inaccordancewith one embodiment of the invention;

Figure 6 illustrates a preferred embodiment oi the target structure of the invention; while Figures 7a-and 7b are enlarged-views-of-portions. of the target structures shown in Figures 5 and 6.

The receiver of. Figure 1, which may be considered asa color radar receiver or-any other type of color-imageapparatus employing a radialrotating scan, includes a color-image device will comprising an envelope Hand three electron guns I2, l3 and I 4 mounted within envelope. Three control electrodes [5, l6, .and ll are-indi-P vidually included in guns l2, I3 and 14 respectively; each of the control electrodes is-coupled to the receiver control circuits, shown as unit 18.

Unit it, which may include detectors, amplifiers, heterodyning stages, and other types of circuits,v .depending upon the requirements of the particular "receiver; is also coupled to anantenna l9 and to a sweep signal generator 20. Generator is connected to a deflection system comprising deflection coils 2i; any suitable type of deflection elements or coils may be used and, if preferred, an electrostatic deflection system may be substituted for the magnetic system illustrated. A convergence control source 2'. is included in the receiver and is coupled to a convergence lens 23 mounted within envelope II. Color-image device In also includes a direction-sensitive target structure comprising a luminescible target 24 and a parallax mask or grid structure 25; target 24 and grid 25 are mounted in parallel spaced relation to each other within envelope I I and form the image screen of device II].

As seen in the enlarged view of Figure 2, target 24 comprises a plurality of distinct groups of elemental target areas 26, the groups being designated R, G, and B to correspond to the usual tri-color primaries, red, green and blue. Groups R, G and B, of course, each have a different colorradiation characteristic in response to electron bombardment; it will be understood that a three color system using these primary colors is chosen purely for illustration and that any other multicolor system employing suitable colors may be used without departing from the teaching of the invention. Elemental areas 23 are interspersed throughout a predetermined scanning area, usually substantially all of the face area of device I0, and form a multiplicity of clusters individually -including one elemental target area from each of the color groups; one of these clusters is indicated by dash line 21. Grid structure 25 includes a multiplicity of electron-permeable areas or apertures 28 which are individually aligned with target clusters 21, as will be more completely described hereinafter.

The apparatus of Figures 1 and 2, as thus far described, is virtually identical in all material respects with apparatus well known in the colortelevision field and currently being extensively used for experimental color television work; accordingly, a detailed description of the operation thereof is deemed unnecessary. Briefly, antenna I 9 receives a signal representative of an image to be developed by the receiver of Figure 1 and supplies that signal to the receiver control circuits of unit I8. It will be understood that the signal received at antenna I9 may assume any one of a multiplicity of forms, depending upon whether the receiver is considered as a radar or search device or is used to reproduce a telecast radiated from distant points. The received signal is utilized, in unit I8, to derive suitable control signals which are applied to control electrodes I5, I6 and IT to modulate the intensity of the electron beams 29, 30 and 3| developed by electron guns I2, I3 and I4 respectively. In the usual system,

each of the beams is modulated in accordance with information respresentative of one of the primary colors in the image to be reproduced. Beams 293I are projected toward target 2425 and, as they pass through convergence lens 23, are directed toward a predetermined center of deflection 32. In the usual system, guns I2I4, and individual beams 29-3 I, are equally radially spaced about a reference axis 33 and deflection center 32 is located on axis 33 approximately in the plane of grid 25. Convergence of beams 29-3I is carried out in accordance with suitable signals supplied by source 22, which may be coupled to control circuit unit I8. After converging at deflection center 32, the electron beams pass through one of the apertures 28 in grid 25 and diverge slightly, impinging upon individual ones of the elemental target areas 26 comprising screen 24. Grid structure 25 restricts each of the beams in well-known fashion so that it impinges upon only those areas 26 comprising one of the color groups R, G and B. In order to reproduce the complete image, the electron beams are simultaneously deflected by means of sweep signals generated by unit 20 and applied to the deflection system comprising coils 2|; the scanning deflection is controlled by signals applied to sweep generator 20 from control unit I8.

For some specialized applications, such as radar presentations, it is desirable to traverse beams 29-3I across the target structure of device In in a radial rotating scanning pattern; this type of scanning pattern is generally illustrated in Figure 3. As seen therein, the beams, as a unit, scan target 24 radially with respect to deflection axis 33 as indicated by arrows A. At the same time, the scanning pattern rotates about deflection axis 33, as shown by arrows C.

Returning to Figure 2, it is seen that the aperture pattern of mask 25, which corresponds to the cluster pattern of target 24, presents a consistent angular orientation with respect to any reference axis taken parallel to target 24 and mask 25 and intersecting deflection axis 33. For purposes or" convenience, axis X1 will be employed as a reference axis throughout the remainder of this specification. It is also apparent that it is possible to locate three separate axes intersecting deflection axis 33 (which, at one point, includes deflection center 32) along which apertures 28 are closest together. These three axes are designated Y1, Y2, and Y3 respectively. Furthermore, axes X1, X2, and X3 generally define directions along which apertures 28 are regularly spaced, as along the Y axes, but are more widely separated. Theory indicates and experience verifies that f scanning along the X axes of Figure 2 results in a minimum of moir or beat patterns in the resulting image, whereas scanning along the Y directions produces maximum moire. Accordingly, where a single direction of scanning is employed, as in the usual television reproduction, it is possible to orient the target structure com prising mask 25 and target 24 so that scanning is carried out along one of the X axes; when this is done, the moir patterns are not noticeable and therefore present no real problem. However, it is not possible to so orient the target structure when a scanning pattern such as that of Figure 3 is employed.

In Figure 4, the screen or scanning area of image device I I) is divided into a plurality of portions or sectors centered about the X and Y axes illustrated in Figure 2. The shaded sectors 34, centered about the Y axes, represent those portions of the target in which moir patterns are most noticeable and most disadvantageous with respect to the reproduced image when a radial rotating scanning pattern is employed, whereas the unshaded portions 35, centered about the X axes, are relatively unaflected by beat patterns. It should be noted that each of the sectors 34 and 3 comprises a 30 sector of the screen. In order to minimize and substantially eliminate the moir patterns in sectors 34, the relationship between the aperture or cluster pattern and the direction of scanning is altered by rotating the aperture pattern.

Figure 5 shows a portion of a target structure comprising a mask or grid 25' generally correspondingto mask 25 of Figures 1 and 2 and including a plurality of sectors 34 and 35 correspending to the areasof maximum and-minimum moire for radial scanning as illustrated in Fi ure 4. The'location andarrangement ofapertures 28 included in sectors 35 is identical'with the pattern usually used for linear unidirectional scanning and shown in Figure'Z. In' sectors 34, however, the apertures have a different" angular orientation, with respect to axis X1, fromthe apertures in'sect0rs 35. This difierence in orientation is indicated in mask portion 34a, in which the location ofsome of the apertures as they would appear if located in accordance with usual techniques .is indicated by dash outlines 36a,'35b and-36ccorresponding to adjacent apertures 28a, 28b 2 and 280 respectively. In effect, the positionsof apertures 28 in sector 34w are rotated in'groups of threethrough anangle of thirty degreesfrom'. the positions they would occupy ifthe orientation of sectors 35 were used throughout the'mask. Those apertures 28 formed in the reina'ining ones of maximum moir sectors 340i screen 25 are formed in a pattern corresponding to the alignment of the apertures in portion 34a so that each of these sectors has an intercluster angular orientation, with respect to any referenceaxis drawn through deflection center 32, different from the adjacent sectors-35. Accordingly, those mask openings 28 occurring in sectors as are oriented along lines parallel to and at angles of sixty and one hundred twenty degrees with respect to axis X1 (for example, dash lines 31a, 31b, and 310), whereas the apertures in sectors 35 are oriented along lines perpendicular to and at angles of thirty and one so that the pattern of apertures'orclusters within the sector remains consistent in internal spacing. This consistent internal spacing is of considerable advantage with respect to the efficiency of the image device, as will be more clearly explained hereinafter. The net effect, in the embodiments of both Figure 5 and Figure 6, is to alter the orientation of the aperture or cluster pattern so that the Y axes also comprise directions of minimum of moire; as a result, the beat patterns are minimized for 12 directions with respect to deflection center 32 instead of the six directions represented by the X axes of Figures 9 and 4.

Mere rotation or re-orientation of the aperture pattern in grid structure 25, as described in connection with Figures 5 and 6 is not always sulficient to provide for a minimum of best patterns while still maintaining an operable color-image device. This will be obvious from the fact that electron guns lZ-i (Figure 1) normally must have a fixed orientation with respect to the aperture pattern of mask 25 and the corresponding dot or target area cluster pattern of screen 24. The same consideration holds true if the three separate electron guns are supplanted by a single electron gun and means to shift the beam developed thereby to individual virtual color sources or if the three guns are replaced with a device in which a single beam is deflected as it traverses the space between mask 25 and screen 24 to im tors.

ipmge iupon appropriate color areas. "IIhe fixed "natureci the 'eleotron sources in any or these'systems limp'lies that -the screen pattern must be made to correspond to boththe aperture pattern of theimask and to the fixed electron source alignment.

:Figures UmandVb-illustrate screen or cluster patterns which may be employed in conjunction with the grid structures illustrated in Figures 5 and 6. ln liligure 7a," the orientation used in the unmodified or standard orientation portions :of the :screen,icorresponding to sectors '35 on mask .2'5,rris. il'lustrated. 'Zlihreeclusters, designated 27d, :25le,rsand-21?; are shown, the positions of the associatediapertures on mask 25' or mask 25" being indicatedlin dotteii outline as 28d, 28c, and-2'8) respectively. oe comparison of Figurela with the mask :and target structure shown in Figure 2 indicateslthat' thebasic relationship of the mask and. screen'elem'ents remain unchanged, the only significantldifierence being the separation or disassociation ofthe'elem'ental target areas 26 so thatthey'no longerv form a closelynested pattern butane. segregated into discrete clusters.

In Eigurellb, thearrangement of the elemental target areas of screen .24 corresponding to sectors as of mask25forrnask'25" is shown. In this figure, as Figure 7a., three clusters are illustrated, being designated 21a, 21b and 210 to correspond to apcrtures 28a,:.28b and-28c respectively, which are shown in'da'sh outline. The angular orientation of the clusters .inthese sectors corresponds to the orientation of "the apertures in sectors 34a and-3460f Figures 5- and 6. However, the internalangular orientation of each of the clusters, as-represented'by-one target area from each of the areaigroups'R, Gand B within each cluster, remainsthesamewith respect to axis Xmas in the sectors represented in Figure 7a. Accordingly; it :becomes *possibleto use a fixed'set of electronsourcestor guns'for image device it in conjunction with :a variable screen and aperture pattern.

In an image device. inwhich the gun pattern :or-:orientation'- withrrespect to the screen is not fixed, it :not necessary to alter the screen pa."- tern in "accordance with Figures 7a and 72); rather, iormationofthe aperture pattern in accordancewith'thattofmask 25" in Figure 6 is sufiicient' and the elemental areas of the screen may be retained in a closely nested pattern. However, with this type of structure it becomes necessary to shift the effective gun positions as each sector is scanned. In a single gun tube in which color variations are introduced by rotational deflection and gating of a single electron beam, this may be eiiectively carried out by changing the gating cycle as the scanning pattern moves through the difierent sectors. Furthermore, if an additional reduction in moire or beat patterns is found desirable, screen 24 may be divided into a greater number of sectors; for example, 18 separate sectors of 20 may be designated instead of the 12 shown in Figure 4, using the original axes as boundary lines between sec- In this case, as before, six of the sectors remain unchanged, whereas modified to shift the aperture or cluster pattern 20 in one direction and six are rotated 20 in the opposite direction. As a result, there are nine axes or 18 directions of minimum moire in the target structure and the maximum angular deviation from the minimum-moire directions corresponds to 10, which is in most instances virtually unnoticeable.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from the invention in its broader aspects. The aim of the appended claims, therefore, is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

Iclaim:

1. In a color-image device, a target comprising: a plurality of distinct groups of elemental target areas, each of said groups having a different color-radiation characteristic in response to electron bombardment, said elemental areas being interspersed throughout a predetermined scanning area to constitute a multiplicity of clusters individually including one elemental target area from each of said groups, said scanning area comprising a plurality of portions individually having a different inter-cluster angular orientation, with respect to a reference axis,

from that of adjacent ones of said portions, the angular orientation of said elemental target areas within each of said clusters being substantially identical, with respect to saidreference axis, throughout said scanning area.

2. In a color-image device, a target structure comprising: a plurality of distinct groups of elemental target areas, each of said groups-having a different color-radiation characteristic in response to electron bombardment, said elemental areas being interspersed throughout a predetermined scanning area to constitute a multiplicity of clusters individually including one elemental target area from each of said groups; said scanning area comprising a plurality of portions individually having a difierent inter-cluster angular orientation, with respect to a reference axis, from that of adjacent ones of said portions, the angular orientation of said elemental target areas within each of said clusters being substantially identical, with respect to said reference axis, throughout said scanning area, and a grid structure mounted in spaced parallel relation to said scanning area, said grid structure including a multiplicity of electron-permeable areas individually aligned with said target clusters.

3. In a color-image device including means for developing a plurality of electron beams spaced about a deflection axis, directing said beams toward a predetermined center of deflection located on said axis, and deflecting said beams angularly and radially with respect to said center of deflection, a target structure comprising: a corresponding plurality of distinct groups of elemental target areas, each of said groups having a different color-radiation characteristic in response to electron bombardment, said elemental areas being interspersed throughout a predetermined scanning area normal to said deflection axis to constitute a multiplicity of clusters individually including one elemental target area from each of said groups, said scanning area comprising a plurality of portions angularly disposed about said deflection axis and individually having a different inter-cluster angular orientation, with respect to a reference axis located in the plane of said scanning area and intersecting said deflection axis, from that of adjacent ones of said portions, the angular orientation of the elemental target areas Within each of said clusters being substantially identical, with respect to said reference axis, throughout said scanning area.

4. In a color-image device, a target structure comprising: a plurality of distinct groups of elemental target areas, each of said groups having a different color-radiation characteristic in response to electron bombardment, said elemental areas being interspersed throughout a predetermined scanning area to constitute a multiplicity of clusters individually including one elemental target area from each of said groups, said scanning area comprising a plurality of portions individually having a different inter-cluster angular orientation, with respect to a reference axis, from that of adjacent ones of said portions; and a grid structure mounted in spaced parallel relation to said scanning area, said grid structure including a multiplicity of electron-permeable areas individually aligned with said target clusters.

SAM H. KAPLAN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,590,764 Forgue Mar. 25, 1952 2,611,100 Faulkner et al Sept. 16, 1952 2,625,734 Law Jan. 20, 1953

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