Method for obtaining in projection images in color

  • Inventors:
  • Assignees:
  • Publication Date: February 13, 1940
  • Publication Number: US-2189751-A



Feb. 13, 1940. c. BoccA ET AL 2,189,751 METHQD FOR OBTAINING IN PROJECTION IMAGES IN COLOR Filed F9b 93 6 Sheets-Sheet 1 yNVENTQR CARLO 500094 and JJOMEN/co RUB/1 77.5 na New: Feb. 13, 1940. c. BOCCA ET AL METHOD FOR OBTAINING IN PROJECTION IMAGES IN COLOR 6 Sheets-Sheet 2. Filed Feb. 4, 1938 I N V E N TO R S CAHL 03006;: a (1 ZOMEN/do R0174 775 ATTORN 5Y5 Feb. 13, 1940. c. BOCCA ET AL 2,189,751, METHOD FOR'OBTAINING IN PROJECTION IMAGES IN COLOR Filed 1938 e Shee'ts-Sheet s IHVENTO R5 ammo B0067 ahdflo/vilv/c'o Hap/i775 32/: 1444... A 4 TORN gva Feb. 13, 1940. c, BQCCA AL 2,189,751 METHOD FOR OBTAINING IN PROJECTION IMAGES IN COLOR Filed Feb. 4, 1938 6 Sheets-Sheet 4 INVENTORS B24 k c ATTQRNEY Feb. 13, 1940. c. BOCCA ETAL 2,189,751 METHOD FOR OBTAINING IN PROJECTION IMAGES'IN COLOR Filed Feb. 4, 1938 6 sh t t 5 Feb. 13, 1940. c BQCCA Er AL 2,189,751 METHOD FOHOBTAINING IN PROJECTION IMAGES IN 001.011 6 Sheets-Sheet 6 Filed Feb. 4. 1938 INVNTOR5 ammo 30cm n-(Z flame/wee Raj/m5 5 4%,QA .4 a, ATTORHE.Y S Patented Feb. 13, 1940 PATENT OFFICE METHOD roa onmmmo m raomcrros unions m oomas Carlo Becca and Domenico Rudatis, Venice, Italy Application mm, 4', 1m, 881181 No. ream m rm, December 15, 19:1 13 Claims. The present invention relates to a process making possible the projection of still or motion images in colors, and avoiding many usual losses of light. It is characterised by the fact that at those points of thesubject, for whose reproduction in colors it. is-necessary to employ a determined primary color, there are corresponding points in the projection image at which there are refracting elements capable of retracting the light in determined directions, distinct from he directions in which 'the light is retracted by analogous retracting elements corresponding to the other primary colors, and furthermore all of the retracting elements are given directions which cause the refraction plane, of each of the primary colors of the polychromatic selection employed, to have a diiierent orientation. In practice this purpose is served by using either prismatic elements or cylindrical lenticular elements. Upon the projection image these elements must be so placed that, when an optical device for the projection collects the light reiracted by elements having the same direction, one will obtain images of the luminous source 2 completely distinct from those formed by the light refracted by elements having a diflerent direction. The main object of our invention is to provide a method and means for projecting images 80 in colors which will have an even and uniform degree of good illumination upon the entire field projected. Another object is to have such an invention in which the unrefracted or normal light can be ll utilized in useful manner. A'further object is to have such an invention which is highly emcient in passing light to the projected image and in directing the greatest amount possible of the light used directly toward 4. said image. Other objects and the various advantages of our invention will appear more fully as this specification proceeds. In the accompanying drawings, Fig. 1 is a perspective partly in section of a gofiered prismatic image plate or the like for use in projection according to the invention.- Fig. 2 is aside view in section of such a a goifered plate in operative relation with respect to a projecting lens. Fig. 3 illustrates how image points in three directions are obtained when using plates with prismatic goilerings arranged in three directions upon said plates. - and blue) Fig. 4 shows a modification of Fig. 1, the goflering being lenticular instead of prismatic. Fig. 5 is similar to Fig. 2, but shows a lenticular gciiered plate cooperating with a projecting lens. Fig. 6 shows the improvement over Fig. 3 when using the plate of Figs. 4 and 5 instead of that of Figs. 1 and 2. Fig. '7 illustrates diagrammatically a complete projection system utilizing a. transparent lenticular or prismatic plate with a color filter having an opaque portion. Fig. 8 similarly shows a system wherein the plate is partly opaque and the color filter free 1 from any opaque portion. Throughout the views the some references in.- dicate the same or corresponding parts. It. may be mentioned that the present invention is an improvement over Patent No. 2,050,417 of August 11, 1936. For carrying out the present invention it is possible toemploy projection images which are totally transparent. Further it is possible to select the inclination of the prismatic faces and, respectively, the curvature of the lenses, in such manner that all of the light refracted will remain comprised within the angular opening which can be embraced by the optical device for projection; it is obvious however that in the case of prismatic elements there is scant loss of light because prisms retract and deviate all of the light which falls upon them (excepting of course that part of the, light which is absorbed by the prisms and which can, however, be reduced to very small quantities by suitable selection 01 the substance constituting the prisms) and consequently this light is entirely utilized. We shall now describe a form of executing of the present invention. In so doing we shall refer, merely asan example, to the case 01 a 4 trichromatic selection, although our invention is not intended as confined to a trichromatic selection since it can be employed also with other selections than trichromatic. a The subject to be reproduced is photographed I through three filters, each one colored in one of the three primary colors (for example, red, green Three partial negatives are thus obtained, from the printing of which are obtained three corresponding partial diapositives (hereinafter referred to as the diapositive of red, of green and of blue). Each diapositive is printed upon a goflfered layer constituted by a colloid, or a mixture of sensitized colloids spread upon a support. The-goi'lering of the sensitized layer II v regards the projection the convex gofierings are methods; it must be such as to form upon the sensitized layer on which is copied, for example, .the disapositive of red, a series of retracting elements of the type already mentioned diversely directed in respect of'the analogous elements of the sensitized layers upon which are respectively the diapositives of green and of blue. In the end one thus obtains three copies, each one upon a sensitized layer on which is goflered a series of retracting elements all having a same direction which is diiferent from the direction of the analogous series gofiered upon the other two copies. These three copies are then washed so as to remove all, or part, of the non-impressed colloid or colloids. Thus after washing there will remain at various points of each of the three copies a quantity of colloid that will be greater the greater will have been the intensity'of the luminous impression. The three copies, hardened by any one of the known methods, constitute three matrixes on which the retracting elements are impressed only in those parts which correspond to the parts of the subject whose reproduction in colorsrequires the primary color relating to that matrix. Further, saidelements will be more or less impressed according to whether that particular primary color is present in greater or lesser extent. The image for projection is obtained by impressing the three copies in succession and in such a manner that corresponding points will be superposed (the copies in this case serving as partial matrixes) upon any plastic material r which will be hardened after it-has received the aforesaid impressions. It is of course possible to employ materials which are momentarily rendered superficially plastic (for example by heating) and then resume their original consistency. One obtains the same result by printing the three partial diapositives upon non-gofiered sensitized layers, then washing said layers and goffering the washed layers, which after hardening, also serve as matrixes. What one obtains by the superposition of these three mechanical impressions is a layer which can serve directly as projection image or as matrix for the preparation of any number whatsoever of projection images. When the said layer is destined to serve as projection image it is necessary of course that both the goffered layer and its support be transparent. When on the contrary it has to serve as matrix for preparation of projection images, care must be taken that the support shall have the mechanical resistance necessary (this same consideration applies to supports of partial matrixes). In practice it has been observed that it is .well' to employ metal bands as supports. As regards the the refracting elements which are in the manner described, to be impressed on the projection image, it should be noted that when impressing prismatic elements one obtains identical prismatic elements, whereas when one impresses lenticular elements from convex elements one obtains concave elements, and vice versa; this shall be taken into account in establishing the goifering of lenticular elements in partial matrixes; however as equivalent to the concave ones. The gofferings can also be made by optical means in various ways, some of which are already known (for example impressing the surface to be gofiered through a transparent stratum having a surface on which is the goffe'ring to be reproduced). The optical goffering can be employed can be accomplished by any one of the known in the preparation of partial matrixes as well as in the preparation of the general matrix, or of the image for projection, by printing the three partial diapositives successively, or simultaneously upon a single stratum of sensitized colloids. each partial diapositive being printed together with its respective goffering, and then proceeding to washing and hardening the impressed layer. The projection image obtained by any one of the methods described is projected using an optical device capable of collecting all the light, refracted and non-refracted, which issues from the projection image, and to form with said light real images of the luminous source. It is sufflcient to intercept the non-refracted light, and to color the light refracted in each direction with the primary color corresponding to said direction, in order to obtain upon the screen an image in colors of the subject reproduced. These colorations are imparted by means of' colored filters placed in the, plane in which form real images of the luminous source, or in proximity of the plane itself. To understand why, in this manner, one obtains upon the screen an image in colors, let us consider what occurs when a parallel light beam falls upon a transparent stratum with a prismatic g'offering like the one shown in Fig. 1. Referring to Fig. 2, in which A is the stratum on which is a prismatic goffering and O is an objective: the parallel rays falling uponv A are refracted by the faces of the prisms, to that from A there issue two beams of parallel light, both inclined at a certain angle a in respect of the optical axis. Each of these two beams creates- It is obvious that the same thing is repeated for each of the goffering, so that with a stratum having three prismatic goiferings diversely orientated, three pairs of images (L1,L'1, Li, L'z, La, L's) of the luminous source will be obtained, disposed in the manner indicated in Fig. 3, the shape and dimensions of which depend upon the luminous source. On the, basis of Fig. 2 it is easy to establish what must be the angle a and consequently the form of the goffering so as to permit that all of the light will be collected by the objective. In the case represented in Fig. 4, that is to say of a transparent stratum having a goffering of cylindrical lenticular elements, the parallel light falling upon each lenticular element issues in the form of abeam having an angle opening 23 as shown in Fig. 5, in which B is the gofiered layer, 0 the objective, F the focal plane of the objective. The extreme rays r1, 1"1, 12,1"2, n, r';;, n, r'4 , etc. of'each beam are the rays refracted by the borders of each lenticular element, whilst the central raysm, R2, R3, R4 etc. of each beam are those which have not been deviated and conse-' quently preserve their direction parallel to the optical axis. They go to form the central image L1.v On the contrary the rays reaching the ob-' jective in parallel position but in phase-opposition interfere with one another and are annulled. With three direction gofferings one obtain three series of images in star formation as shown in Fig. 6,'in which L is the central image iormed by 7 2,100,751 rays issuing parallel to the optical axisrwhilst the others are images formed'by rays which have been deviated by the lenticular elements and were in phase-coincidence. The images corresponding to a determined direction of goii'ering are those which in Fig. 6 are placed along a same dotted line; their numbenwhich depends upon the curvature of the lenticular elements, can also be very large. Also in the case of lenticular goilering it is easy to establish what must be the opening of angle 9 to allow all the light tobe collected by the objective. Figure '7 represents schematically one of the most simple devices which can be used for projecting a projection image prepared in the man,-' ner which we have described and to obtain an image in colors. The light issuing from luminous source S is collected by condenser C whence it Merely for purposes of demonstration we have shown in the figure a projection image consisting of three parts, of which the upper part has a com-- plete prismatic gofiering, the intermediate one a reduced goiierin'g, and the lower one no goii'ering, which corresponds in practice to saying that in the upper part one musthave the maximum coloration, in the intermediate a lighter coloration and in the lower one complete shadow. The rays issuing from the upper part which is perfectly goifered are refracted in the manner shown in Fig. 2, andso, for example, the rays issuing from points P1 and P: which, after having contributed to form images L1 and L1 of the luminous source, 'tute a color filter are also pass through color filter D and give on screen T the images ,Pi and P: of said points. In the zone with reduced gofl'ering not all of the light is deviated andtherei'ore for example, from points Q1 and Q2 there issue non-deviated rays which contribute to form the'central image of the luminous source, and also deviated rays which, after contributing to form images L1 and U1 of the lumi'ff nous source, give in (2'1 and Q: the image of said points. Lastly the non-deviated rays which issue from the non-goil'ered zone contribute solely to forming central image L of the. luminous source. In the plane in which form the images'of the luminous source is placed an opaque disc E which intercepts all of the light of the central image; colored filters assembled together so as to constiplaced in said plane in such manner that'the light refracted by thegoffering of the image of the red color will be colored in red, and similarly the light retracted by the goil'ering of the green and of the blue will be respectively colored in green and blue. In this manner we obtain on the screen an image in natural colors with all the color graduations and shadows. Operating in this manner in carrying out the present invention, and using the prismatic goileringdescribed we eliminate principally the iollowing three losses of light: (1) Loss of light due to opaqueness of theimage projected because inthis case the image is completely transparent; (2) Iossot light due to incomplete refraction of lightzbecausaas stated above, the prisms re fract almost all thelight'which tails upon them; I (3) Loss of light due'to the fact that part of the refracted ht cannotreach the projection screen because the light intercepted by the central opaque discJii of color filter D in Fig. '1 is solely the light which it is necessary to intercept to reproduce on the screen in the mat faithful manner the ratio of luminosity of the diiierent parts of the subject, that is to say to modulate the chiaroscuro. In quite the same manner the matters proceed when projecting images with lenticular gotferings, although with these the result in luminosity; even working under most favorable conditions, is somewhat lower because, even in zones completely goilered part of the issuing light is not deviated, as can be seen in Fig. 5, and contributes to forming the central image intercepted by opaque disc E. This loss can however be reduced to the point of being negligible, owing to the fact that the light subdivides in practically uniform manner in the various images which it forms in the focal plane of the objectives; it is suflicient, therefor, to arrange that these images will be in adequate number to correspondingly reduce the loss in question. Thus it can be said that even with lenticular gofi'erings the third loss is also avoided. 1 Another way to carry out the present invention consists of employing a projection image upon which, in addition to the goil'erings already described is reproduced an image in black and white of the subject. This projection image can be projected in the manner described and illustrated in Fig. 7, or else by removing opaque disc E which intercepts the light forming central image L of the luminous source; in this case the projection takes place as shown in Fig. 8. By the general arrangement shown in this figure, in which the various reference letters have thesame value as in Fig. 7, it is easy to see how the projection occurs. It will be observed that in. the center of color filter D of Fig. 8, in the place of opaque disc E of Fig. 7, there is a transparent zone. Naturally the image in black and white intercepts light to a greater or lesser extent according to the blackening which it presents. However the quantity of light thus intercepted is only'the quantity which it is indispensable to intercept to permit the image on the screen to possess its necessary chiaroscuro, for which reason this light interception cannot be regarded as a loss. In any case it is evident that when a projection image which is provided with an image in black and white is projected in the manner indicated in Fig. 8, that is to say without opaque disc E of Fig. '1, the three mentioned losses are entirely avoided both in the case of prismatic goflering and of lenticular goflering. The projection carried out without the aforesaid opaque disc affords the advantage of a greater general luminosity if the aforesaid image in black and white is suitably printed; a certain quantity of white light goes to add itself to. the individual colors on the screen, but this quantity can be contained within such proportions as to not disturb even to a minimum degree the rendering of the colors themselves. The projection can also be accomplished substituting to opaque disc E 01' Fig. 'l a partly first of all the advantage of preventing that possible lines or scratches produced on the surface of the projection image by any cause whatsoever (for example lines on the surface of films due to wear from usage), as well as deposits of dust, should appear in the form of luminous lines or spots on the dark portions of the image obtained on the screen as a result of diffraction and refraction phenomena and thus disturb the projection. Another highly important advantage deriving from the addition of the image in black and white, and it can only be achieved by means of this system, appears from the following considerations. A projection image gofiered in the manner described and projected without using the image in black and white, and without intercepting the light which forms the central image of the luminous source, whilst it gives on the screen a special image colored in all the colors of the subject, it does not render the true chiaroscuro of the I complete a lesser quantity of light will be deviimage; in fact all of the shadows are replaced by a white which is all the more intense the more intense is the corresponding true shadow, and which image could be defined as a"chromatic image with negative chiaroscuro. Evidently one can attain from this image a chromatic image having the desired chiaroscuro if for each point of the image a certain quantity of white light will be prevented from reaching the screen. To accomplish this it is sufiicient to add, as stated, the image in black and white, and since by suitably varying the printing of said image it is possible also tovary its chiaroscuro ratio, and as a result to correspondingly vary also the chiaroscuro ratio of the image obtained in projection, it is easy to see that in the process which forms the object of the present invention the addition of an image in black and white offers the advantage of making it possible to obtain in projection colored images possessing any desired ratio of chiaroscuro. Decidedly by the present process one has available various means, each practically independent 02 the other, which permit regulating at will the characteristics of the image obtained in projection. That is to say we can regulate independently both the characteristics of the coloring 'and thecharacteristics of the chiaroscuro. Regulation of chiaroscuro is obtained by intercepting a greater .or lesser quantity of colored light. This interception can be accomplished with the image in black and white, in which case the percentage of incident light which is intercepted may vary from one zone to another; it can also be accomplished by intercepting a greater or lesser quantity of the light forming the central image of the luminous source, in which case of the non-deviated light issuing from each point of the projectionhmage there will be intercepted a same percentage which can be regulated at'will. The regulation of coloration is two-fold; the tints are regulated by means of the filters in the projectionand by means ofthe direction of the gofiering in printing, whilst the tones are regulated by means of a greateror' lesser completeness of the gofierings..- As regards the regulation of tints it is in fact obvious that it is sufiicient to change the filters in order to obtain corresponding variations in the colors on the screen. The choice of colors in the filters can of course be quite arbitrary if, for example, in the case of films having a fantastic character; one desires to obtain unreal coloring. Furthermore in certain cases it may be advan tageous to place the filters in such manner that of the light refracted by each gofiering, part will take a given color and the remainder a different color; this effect can also be obtained by not changing the filter and simply varying the direction of the goflzerings, when the printing is carried out. It is obvious therefore that in printing we can vary at will all of the tints, singly or jointly. It may also happen to be useful to insert, between the filters colored in primary colors, other filters having a color intermediate between the two adjacent primary colors. Lastly by moving all of the filters or some of these it is possible to pass from any one coloration to another. As regards the regulation of tones it is obvious that the tones will be all the more saturated, that is to say the tints will be all the more intense, the more complete is the goffering in the corresponding zone; whereas when the goffering is inthrough the colored the preparation ated and caused to pass filters. Now it is easy to regulate of the partial diapositives in such manner that i; ' to print the sound column in the'goifered image, although-the gofiering is complete in the zones corresponding to saturated colors, the goifering corresponding to another tone will be incomplete. The four mentioned regulations can of course be operated singly or jointlyl A fifth regulation which can also be used in combination with the others and which permits imparting at will any one to the entire image,withouthowever altering the primary colors of the polychromatic selection employed, is obtained by coloring all or part oi. the central image of the'luminous source, and this can be done either for corrective purposes or for purely artistic reasons. Also in films prepared according to the present process, the sound column can be added by any of the known processes; it may-be advantageous together with the image in black and white. I Decidedly the present process, in addition to predominant coloring I giving in projection exceptionally brilliant images, affords the possibility of regulating within very vast limits, and independently one from the other, the characteristics of the image obtained in projection, so that said characteristics may be varied and combined with one another with a freedom far greater than that afforded by any other process, meeting the most varied requirements and artistic purposes. 7 Having now particularly described and ascertained the nature of our said invention and in what manner the same is to. be performed, we declare that what we claim is: 1. Method of producing'projected pictures in natural colors which comprises, after preparing by images of polychromatic selection of the subject. the steps of obtaining of each partial positive image a copy on a separate gofiered layer of sensitized colloids, the gofiering of each layer consisting of elements refracting the light in determined directions distinct from the directions in which the light is refracted by the gofferings of the other layers, the refraction plane ofthe gofiering of each layer also having an orientation different from the orientation of the refraction plane of the gofferings of the other layers, washing out the layers to remove unaffected colloids, hardening the colloids remaining in known methods a series .of partial positive the washed layers, 75 I the corresponding points in register upon a plastic, transparent layer of material, hardening the impressed layer, illuminating the impressed hardened layer with a beam of parallel light emanating from a luminous source, forming on a given plane by means of unrefracted light a central real image of the luminous source and by means of refracted light as many distinct series of real images of the luminous source as there are partial positive copies, each series being formed of images aligned along a common direction passing through the center of the central image, obturating the unrefracted light forming the central image, coloring the refracted light forming the images aligned along the common direction with the same color as that of the color filter employed for preparing the partial positive image printed on the layer whose goffering .refracts the light forming said images, and projecting the colored diffracted light on the projection screen. 2. A method according to claim 1, wherein the gofierings of all layers have a repeated cylindrical lenticular form. 3. A method according to claim 1, wherein the gofierings ofall layers have repeated prismatic form. 4. A method according to claim 1, wherein the goflfering of some layers has a repeated cylindrical lenticular form and the gofiering of the others a repeated prismatic form. 5. A method according to claim '1, wherein the layers of sensitised colloids are goffered before the partial'positive images are copied on them. 6. A method according to claim 1, wherein the layers of sensitised colloids are goffered after the partial images are copied on them. 7. A modification of the method according to claim 1, wherein the layers of sensitized colloids are goifered after the washing out of the unaffected colloids has been performed. 8. A modification of the method according to claim 1, wherein the goflering of each layer of sensitised colloids is performed by copying upon it together with a partial positive image a transparent stratum of material having a surface provided with the gofiering to be reproduced. 9. A modification of the method according to claim 1, wherein the partial positive images are copied successively upon a common layer of sensitised colloids, each partial positive image being copied together with a transparent layer of material having a surface provided with a goffering, the sensitised layer washed out being employed for obtaining the projected image in natural colors. 10. A method according to claim 1, wherein the layer of material on which all goflerings are impressed is used as matrix, said layer being impressed on layers of plastic transparent material which are hardened after impression, the impressed hardened layers being employed for obtaining in projections the image in natural colors of the subject as well as for obtaining other similar impressed hardened layers of material to be used for obtaining in projection the image in colors. 11. A method according to claim 1, wherein an image in black and white of the subject is projected together with the layer on which all the gofferings are impressed on the screen. 12. A method according to claim 1, wherein an image in black and white of the subject is projected together with the layer on which all the gofierings are impressed on the screen and only a part of the unrefracted light forming the central image of the luminous source is obturated. 13. A method according to claim 1, wherein an image inrblack and white is projected on the screen together with the layer on which all the gofferings are impressed and the unrefracted light forming the central image of the luminous source is not obturated. CARLO BOCCA. DOMENICO RUDATIS.



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