US2985784A - Optical image-forming devices - Google Patents

Description

May 23j 1961 t s, M. MacNgILLrz-z 2,985,784

' OPTICAL mcfr'oaumc Dsvrcgg .L I i 4Irma Aug. 1a, y195s [NVE-'Mme STEPHEN M. MAcNE/LLE BY" @Lm ttl .Jammu-m... m www...

2,985,184 OPTICAL rMAGnFonMiNG DEVICES Stephen M. MacNeille,' Thompson, Coun., ass-ignot- 'to American Optical Company, Southbridge, Mm.

Filed Aug. 18, 1958, No. 755,769 f lo be receptive to lightand a cellularstructure in optical t contact with one side of said assembly of a precoutrolled thickness, the individual cells of said structure eachhavf ingllight-reective side walls and each being substantially iilled with phosphorescent material whereby lightpro` l l duced by said material, when electronically bombardetlr*` will be prevented-from spreading laterally beyond the 3 Claims. 313-92) This invention relates to improvements in optical imageforming andtransferring devices of the type embodying a multiplicity of elongated relatively slender light-conducting elements orfibers in group formation and has particular-reference to improved means andmcthod for forming optical images of increased brilliance at a first. object plane and transporting said images to a second or image plane without appreciable loss of light or deteriora tion'of the resolution or contrast of said images duringl v transit.

In devices employing the use of cathode ray tubes, there has long been a need for tubes which are capable of producing optical images of increased brilliance without deterioration of image yresolution or contrast.

lt isiwell known that one can observe increased brightness from a 'phosphor layer excited by an electron beam by increasing the thickness of the phosphor layer and simultaneously increasing the voltage ofthe electron beam. The optimum situation is that in which the phosphor thickness and beam voltage are such that the electrons are just stopped by the phosphor. lln this way, light is generated throughout the entire thickness of the phosphor during the slowing down oi' the electrons by said phosphor. During this slowing down stage, light produced per-electron is at its maximum.

Since the size of the light spot increases rapidly with the thickness of the phosphor layer, the thickness of the layer must not be allowed to exceed an amount of the Y 2,985,784 Patented May 23,' 1961 Another object is tov provide novel means on -face plates of the abovecharacter for producing spots of image-forminglig'ht when bombarded electronically and for controllably'rcstricting the lateral scatteringof light from said spots'.

Another object is to provide a face plate of the above character which is formed ofan assembly of a great uuml 1` ber of coated or clad light-conduetiug filaments or ber! bundled together in connected side-by-side relationwith each other with their opposite ends optically tinished tov limits of the cell walls and will be directed-only into the Another object is to provide a face plate of the above character wherein the brilliance of the light produced by said phosphor maybe controlled as desired inaccordance with the thickness of the abovementioned cellularstructure and the lateral spreading of the light produced by the phosphorescent material within the individual cells thereof Ymay also be controlled as desired in accordance with'the I individual cell size of said structure.

A further object is to provide a relatively simple, yet highly efficient, image-producing and'transferring face plate which when used in conjunction with cathode'r'ay tubes or the like is adaptedto improve the image-producing capabilities of suchtubes by providing mcansfor producing images of a high degree of resolution which elevational view of a cathode ray type of electronic tube order of magnitude of the desired spot diameter. Therefore, in' conventional cathode ray tubes, a limitation is imposed upon the increasing of the thickness of the phosphor layer and electron beam voltage by the degree of phosphor which spreading, when excessive, causes an overlapping of the light from adjacent light spots.

The present invention .overcomes thev problems previy ously encountered in increasing the brilliance ofimages formed by cathode ray tubes by providing novel means for permitting the thickness o f phosphor and the voltage of the electron beam of such'tubes to be increased as desired without detriment to image resolution or contrast.

' It is, therefore, a primary object of this invention t0 provide an opncal image-transporting device and method of making the same for transferring image-forming light from one location to another, said device having meansfor providing images of high quality resolution and brilliance. A

Another object is to provide improved fiber optical face plates for cathode ray tubes..

are considerably more brilliant than has heretofore been possible.

l Other objects and advantages of the invention will be- .come apparent from the following description when taken in conjunction with the accompanying drawings in which: Fig. 1 is a partially cross-sectioned diagrammatic'side embodying this invention;

Fig. 2 is a greatly enlarged fragmentary cross-sectional view of the imageforming face part of the cathodcray tube illustratedin Pig. l; v

Fig. 3 is a fragmentary exploded view illustrating in' greater detail .the structure of the face part of said cathode ray tube;

Fig. 4 isa still further enlarged fragmentary crosssectional view of the f ace part ofligs. l, 2 and 3 wherein L, there is diagrammatically illustrated the light-gatherin and transmitting characteristics of said face part; and

Fig. 5 isagreatly enlarged cross-sectional view of t" modified form of the device of the invention.

Referring more particularly to the drawings,thcrc i'x Villustrated in Fig..l a cathode-ray type 'of electronic tube 10 having an image-forming face plate 11 ,embodying a forwardly directed light-conducting section 11a 'formed of a great number of individually light-insulated or cladlight-conducting' bers 12 arranged in connected side-byside relation with each other and a rearward image-form; v ing section 11b disposed within the vacuumized body of thetube'ltl' and in optical conactwith the fibers-'12 (see Figs. 2 and it).v `The section I11b of the faceplate 11 is in :he form ora cellular `tructure 13, the individual cehs of which are filled with a phosphorescent'matei'ial 14 of the well known type commonly used'to produce image-forming light inconventional cathode ray tubes. When bombarded by electrons, the phosphores'cent ma.-

terial become luminous 4and being in optical contact with fibers 12, the light produced by the material 14 will pass into the fibers 12 and be` transferred thereby Y to the outer. surface of the' face plate 11.

lt is pointed out that other than theface plate 11,v

AAnother method of fabricating the cellular structure 13 consists of forming the structure of metal tubeswhich are welded or soldered together. A cellular structure 13 of thin-walled metal tubes may be fabricated by cladding the cathode ray' tube 10 is strictly conventional in nature and may be of any shape, size or design to fulfill the requirements of the particular apparatus with which it isto be used and the face plate 111 of this invention is formed to an outer contour shape and size---in accordance with that required fer the particular tube to' which itis to be applied.

nie fibers 12 are initially formed individually with fcore parts of light-conducting material having a relatively high indexof refraction such as, for enample, a flint glass and outer coatings or claddings of material having i arelatively low index of refraction such as,'for example,

acrotvn glass. The fabrication of the fibers `l2 may be accomplished by placing a rodlike member of the high index material withina relatively thin walled tubular member of the low index material and heating the assembly to a fiber-drawing viscosity whereupon it is drawn to a desired size. It is particularly pointed out lthat the fibers 12 may be formed by any of the known techniques or of any of the known materials common to the manutween each of the fibers. Reference may be made to an application for patent bearing Serial Number 715,406,

-lited'February 14, 1958, `in the name of Wilfred P.

wires formed of copper or other similarly characterized metals with a plating metal such as gold 'or the like which is highly resistant to attack by etching materials such as I nitric acid or other suitable acid. The clad wires may be formed by the well known method of forming gold filled wire wherein a rod of coppcr'is. placed within a7 tube-of' gold and the assembly is olled to a desired wire V plated or clad wires byplacing them in side-by-side paral.

clad wires may be rolled to a reduced size prior to theA Bazirlet, lr., for more detailed information regarding one method by which such assemblies of .fibers may be made.

Having nlade anrassembly of fibers 12, the assembly'is cut Orotherwise formed to a desired thickness and the opposite sides thereof are optically ground and polished to render` the ends of the fibers 12 readily receptive to light.

lt should be understood that although the fibers 12 have been illustrated as being generally square in crosssectional shape, they may alternatively be hexagonal, octagonal or of any other desired crosssectional shape, it being only important that 'upon being fused or otherwise bonded together, they be in intimate connected relation with each other to form a completely airtight structure which when assembled with the enlarged envelope of the cathode ray tube 10, as shown in Figs. l and 2, the-assembly will folm an airtight seal for the end of said envelope thereby permitting the usual necessary vacuum to-be provided within the interior of the tube 10.

`lel relation with each o'therwhereupon the wires are se-` cured togethc'r. v The assembly is then cut transversely Ainto sections of the thickness desired of the cellular structure 13 'and the wiresare etched out of'the sections to* leave a cellular structure 13 consisting of vonly the clad-` l dings.' The wires, if made lof copper', may be etched v' out of the structure 13 by placing the same in asolntion consisting of equal parts 'of nitric acid and water. Other 'combinations of metals and etching solutions may beV readily 'substituted'for the examples given above, andit should be understood that said examples have been Vgiven by way of illustration only.

If'it is required that the cell sizeof Vthe structureV 13 be extremely small, the l*secured assembly of plated or the assembly is reducedin 'size by the rolling or othersimilar operation. Y

The cellular structure 13 is so formed that it may be placedin direct contact with the side of the light-conduct ing section 411a which is to be disposed inwardly of the tube- 10. If formed of glass tubing, the structure 13.1': fused or cemented to the light-conducting section 11a and if formed of metal, it is cemented in place with a glassto-metal bond of any well known type, a great variety of which are readily available commercially.

The cells of the structure 1 3 are filled, preferably level full, of the phosphorescent material 14 either before or after the structure 1 3 is anse'mbledwith the, light-conducting section 11a. The filling of the cells of the structure 13 is accomplished by forming a liquid or 'paste-like mixture of phosphor powder and .water glass I'in the conventional manner well known and commonly practiced in cathode ray tube manufacture whereupon the mixture Various methods suggest themselves for the fabrication of the cellular structure 13 which forms the inner poi'tlon of the face plate 1l, one of which would be to assemble a'bundle of thin-walled glass tubes in a manner smilarto the assembling ofthe fibers 12 discussed above. v

Upon assembly, the tubes are fused or otherwise securely bonded together and the assembly cut transversely to a desired thickness in accordance with the thickness desired of the phosphorescent' material 14 which will be Y discussed in greater detail hereinafter. vIf it is required that the tubes be of extremely small cross-sectional size,

wherein some difiicultymight be encountered in precisely aligning the same during assembly, thin-walled tubes'of a relatively large cross-sectional size may be assembled in sideby-side relation with each other and the assembly thereafter drawn and fused simultaneously to reduce the crosssectiona size of the tubes as desired.' Structures snch as 13 would then be cut from the drawn assembly to the thickness desired thereof.

i attempt is made to register each of-,the cells ofv the'- so that any loss of'resolution due to lack of registra- In either of the above-mentioned cases, the resultant thin-walled tubular or cellular assembly is provided with opaque and' reflective side walls by gas plating, evaporation, chemical silvering, or the like.

is forced intoI the cells of the structure l3..v In filling said cells, care must be taken to avoid the trapping of air in the cells. By `fillingthe structure lbefore is is attached to the section 11a of the face-plate, there will be little danger of trapping air within the cells since the cellsof the structure 13 are open' at each end. It shouldj" be understood-that vapor deposition techniques or other known methods "of filling the cells with phosphor may be used if desired.

When assemblingfthefcellular structure 13 with the' light-conductingsection'lla'of theface plate 11, no

structure 13 with a corresponding fiber since n-constructing both the light-conducting section 11a and the cellil lar structure 13, the -'cross-sectional size of the respective ,Q fibers and cells thereof are'formed of a size small enough i I" to each, in themselves, have `a high enough resolution.

tion would be negligible and the overall imageresolving power of the face plate 11 will be such as to produce4 clear and distinct images.v However, in order to improvethe image resolution, it has been found to lb'e'of advantage to consti-act the section 11a and structure 13" with bers and cells respectively which' differ in cross- .n assembly is' then made of aof the with said cell. terial 14 were not deposited in a cellular structure such Vsectional sizes. For example, thecross-sectional size of the bers 12, may be somewhat smaller than the crosssectional size of, the cells in the structure 13, as illustrated, or, alternatively.. the cells may be smaller than the bers, it being immaterial as to which choice is made. In this manner, a continuity in the relative positions of the cladding parts of the bers and the sidewall parts of the cells is avoided when the section 11a and structure 13 are in assembled relation with each other and no distinct line pattern is produced by rsaid claddings 'and side wall parts. It is pointed out that the crosssectional r mediately adjacent thereto.

shapes of the bers and cells needv not be similar, as v shown in the drawings, that. is, square bersmay'be used with circular, hexagonal, octagonal or other differently shaped cells or square cells may be used -with hexagonal, octagonal or other differently shaped bers.

It should be understood that it islwell within the scope of this invention to form structures suchas `13 and to assemble the parts of the face plate 11 in such a manner as to cause 'each of said cells to be in registry with a respective adjacentfber. However, sucha/cor.-v struction would notmaterially improve'the resolution of 'images produced and transmitted by the face plate over ,ting portion of'the tube. Therefore, the voltage must be controlled in accordance with the thickness of the phosphorcsccnt material or vice-versa so as to cause the electrons to be just stoppedby the phosphoreszent material for the .reasons discussed hereinabove Heretofore, a

f s" cause said iight to emerge only into the bers 12 im# Upon receiving light from the cells of 13, the bers 12, being individually light-insulated, function to conduct said light to the viewing face 17 of the face plate 11 and in so doing, prevent a further scattering of the light from the structure 13 thereby overcoming the effects of parallax or halation common to' conventional v face plates which are formed of solid glass plates. Y Y

From the above; it 'can be seen'that the bright ness of the image-forming light canbe increased as desired by increasing the thickness of the cellular structure 13 and increasing the voltage of the electronA beam accordingly,

" the optimum situation beingv that in which the thickness and ight-conducting sections such as 11a with cellsand fibers respectively which are of identical sizes and shapesv limitation'has been placed upon the thickness to which the phosphor'may be made, as was also discussed hereinabove, with thc result that the brightness of the imageforming. light cannot be increased beyond certain limits without detriment to the image resolution.

With the face plate 11 of this invention, light which is produced at a point 15, fr example', or at any other point within one of the cellsof the "structure 13, will inherentlj,- be scattered in all'directions surrounding said point and the laterally scattered light such as illustrated by the arrows 16 and "16', for example, will be reected by the side walls of the respective cell and directe thereby only into the fibers 12 which are in end contact AssumingI that the phosphorescent maas 13 but was in the form. of a conventional'continuous layer, it can be seen that the light 16 or 16 would follow' generally the path indicated'by the respective dashed arrows 16a or l6b and be directed into other bers 12 not disposed forwardly of the point 15 whereas some of the forwardly directed light from the point 15 would simultaneously be directed into said forwardly disposed bers. This effect would take place throughout the phosphorescent layer and cause an overlapping of light from varrous point sources to inte'trnix the image-forming elements of the, overall picture image vbeing produced" and thus cause 4a dilution or washing out of said elements with the result of poor image resolution.

Rather than reduce the thickness of the phosphorcsccnt material so asV to reduce the lateral scattering as has been the practice heretofore, the present invention provides the cellular structure 13 to confine the lateral spreading of the light to an area determined by the size of the cells whereby the light-reecting side walls of said cells will of the phosphorescent material 14 and the electron beam voltage are such that the :electrons are iust stopped by ,the material 17 upon reaching the interfacial surface between the material 14 and the'bers 12. "Furthermore,

itshould be apparent that for a given thickness ofphosphorescent material 14 and voltage of the electron beam, Itlieresolution of the pictureiimage formed by the face plate 11 is improved as the cell sizes and ber sizes are reduced to within practical limits. The cell and fiber sizes should not be so smallias to approach the wavelength of light.

- A face plate 11 which is. approximately two inches in diameter and of an overall center thickness of approximately one-fourth of an inch with bers 12 which are .O02 inch in diameter and embodying a cellular structure 13 of approximately .O10 inch thick with cells of approximately .O03 inch in diameter will produ high quality images in accordance with this invention. It should be vclearly understood that the above dimensions have beengiven by'way of example only and should not, in any way, limit this invention since the ber and cell sizes and other dimensions of the face plates are selected to` ulll the particular requirements of the apparatus in which the cathode ray tube 10 is used.

In Fig. 5, there is shown a modified face plate 18 which is similar in character to the face plate 1l just described. The face plate 18 is fused or otherwise secured to the forward end of a cathode ray tube 10 to form the image-forming face of the tube 10. The face plate 1 8 embodies a multiplicity of clad light-conducting fibers 19 which are fused, cemented or otherwise connected in side-by-side intimately grouped relation with each other so as to form an airtight-seal for the forward end of the tube 10. -The ace 20 of the assembly' of bers 19 is opv tically finished and the core parts 2'1 of each of the ben 19 are recessed at the opposite side of the assembly to a depth in accordance with the thickness desired vof the phosphoresce'nt material 23 which lls said recesses. The inner side surfaces 24 of the portion of the claddings 21 which form the side walls of the recesses are rendered opaque and retiective and light formed in said recesses by the phosphorescent material'23 therein is rcstrictedf from lateral spreading beyond the connes of the surfaces 24 and directed into the core parts 21 of the bers 19 in the manner disclosed with regardto the face plate 11. In short, the face plate 18 i's equivalent to the face plate 11 'in that the phosphorescent material $2.3 is deposited in a cellular structure within the interior of the tube 10, which cellular structure, in this case, embodies the recessed core parts 21 of the bers 19.A

in fabricating the face plate 18, the bers 19 are initially formed with 'core parts 21 of a relatively high index glass or similar material such as, for example, a flint glass which may be readily etched with a solution of one part 5%hydrouoric acid and onepart 5% hydroy chloric acid or other suitable solutions. The cladding parts 22 of the bers 19`are formed. of a relatively lowindex glass or similar material such as for example, an aluminum metaphosphate glass cr the like which is substantially impervious to attack by the above-mentioned etching solution. Following the forming of the bers 19, they are assembled in fused or otherwise connected sidebyside relation with each other inthe manner disclosed 11a of' the face plate 11.l The side of the assembly of abovefor the' fabrication of. the ligbeconducting section fibers 19 which isV to be disposed inwardly of the tube 10 is then placed in the etching solution for a period of time ods of making mirrored surfaces and thegrecesses are thereafter filled with-:the phosphorescent material 23.

It is pointed out that in place of the reflective surface 24; the fibers 19 may be initially constructed with double claddings wherein a first cladding of transparent lowindexv glass or similar material would be surrounded with an opaque coating of metal or other suitable material Awhich would not be attacked by the solution employed for the etching.l In such a case, the first cladding would "act to reflect the light through the core parts of the fibers 19 in the usual manner and the opaque outer coating would act to prevent lateral light-scattering which takes place in the phosphor 23 from passing through the side4 walls of the recesses in the face plate.

. It is vpointed out .that various combinations of highand low index glassor similar light-conducting material may be used to fabricate the face pilates of this invention as-will be appreciated by anyone skilled in the art and this invention is not inl-any way limited to the examples o materials given hereinabove as ail matters shown and described have kbeen given by way of illustration.

From the foregoing, it will be seen that simple, efficient and economical meansand method have been provided for accomplishingall the objects and advantages of the invention. Nevertheless, it should be apparent that many changes in the details of construction, arrangement of parts or steps in the process may be made without departing from the spirit of the invention as expressed in the accompanying claims.

Having described my invention, I claim:

1. A face plate for use with a cathode ray tube or the like embodying an electron gun and a fluorescent screen adapted to receive electrons emitted by said gun,

said face plate comprising a plurality of very fine r'ilamentlike lightconducting fibers bundled and secured together in adjacent side-by-sidc airtight relation with each other by a transparent material having a lower index of refraction than said fibers, said fibers-being of pre-controlled length in accordance with the thickness desired of said face plate and having their respective adjacent end surfacesV aligned to form a continuous surface part on at least one side of said face plate, astructure ernplate and having their respective adjacent end surfaces 'A aligned to form a continuous surface part on at least one bodying a plurality of open-ended cells of relatively small L diameter having relatively thin opaque walls secured in close side-by-side relation with each other to the opposite t "side of said t'ace plate and being of a le agth'substantially equal to the thickness desired of a phosphorscent matrrialE to be supported on said opposite -side of said face plate, said cells opening outwardly away from and being in substantially parallel relation with said fibers, and phosplzcrescent material in each of'said cells, said cells `being of a length 'controlled in accordance with the increased thickness desired of saidwphosphorescent matev rial over that which has been practical for use in conventional tubcs of. the type embodying a continuous layer of such material and being such as toenable the voltage of the electron gun to be accordinglyincreased over the voltages which were practical for use in such conventional tubes whereby a brighter image having increased resolution and definition may be obtained' as the result of the 8 substantial elimination of scattering of the light by said thin opaque walls of said' cells and the elimination ofl parallax and halation as results from said very fine lightconducting bers. t

2. A face plate for use with a cathoderay tube orfthe like embodying an electron gun and auorescent screen in accordance with the thickness desired of said face side of said face plate, a structure embodying a plurality of open-ended cells of relatively small diameter havngf thiclmess desired of a phosphorescent material to be sup#- 'ported on said opposite side of said face plate, said cells opening outwardly away from and being in substantially parallel relation with said fibers, and phosphorescent material in each of said cells, said cells being of a length controlled in accordance with the increased thickness desired of said phosphorescent material over that which was practical for use in conventional tubes of the type embodying a continuous layer of such material and be. ing such as to enable the voltage of the electron gun to be accordingly increased over the voltages which were practical for use in such conventional tubesA whereby a brighter image having increased resolution and definition may be obtained as the result of the substantial elimination of scattering of the light by said thin opaque Walls 1 of said cells and the elimination of parallax andhalation as results from said very fine light-conducting fibers.

3. A face plate for use with a cathode ray tube or the like embodying an electron gun and a fiuorescent screen adapted to receive electrons emitted by said gun,

said face plate comprising a plurality of very ne tilament- Y like light-conducting fibers each embodying a -core of transparent giass of a relatively high indexvof refraction having a thin cladding of transparent glass of a relatively low index of refraction thereon and having highly reecf tive interfaces, said fibers being bundled and secured together in adjacent sidebyside airtight relation with each other, said iibers being of pre-controlled length in accordance with the thickness desired of said face plate and having their respective adjacent end surfaces aligned to form a continuous surface pari on at least one side, of said face plate, a structure embodying a plurality of openended cells of relatively small diameter having relatively thin opaque walis secured in close side-.byaside relation' with each-other to the opposite side of said face plate and being of a length substantially equal to the thick-V ness desired of a phosphorescent material to be supported on said opposite side of said face vplatasaid cells opening outwardly away from and being in substantially paral lel relation with said bers, and phosphorescent material in each of said cells, said cells being of a length controlled in accordance with the increased thickness desired' of said phosphorescent material over that which has been practical for use in conventional tubes'. of the type embodying a continuous layer of such material and being such as to enable the voltage of the electron gun to be accordingly increased over the voltages which wercpractieal for use insuch conventional tubes whereby n 2,091,152 2,354,591 Goldsmith..4 .v u.July 25, 1944 'Y of said cells and the elimination f paallax md halation as results from sad very ne 1ightconncnng fibers.

References Cited inthe le of this paten't UNITED STATES PATENTS Malpica `Aug. 24. 1937 Henroteau June 6, 1950 Schultz Dec. 4, 1951 Jacobs et al. June 19, 1956 Shoberl -1.--- Mar. 25, 1957 McNaney Sept. 3, 1951 Bingley July 8, 1958

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