US2177247A

US2177247A - Electrical transmission of color pictures

Info

Publication number: US2177247A
Application number: US138683A
Authority: US
Inventors: William G H Finch
Original assignee: Individual
Current assignee: Individual
Priority date: 1937-04-24
Filing date: 1937-04-24
Publication date: 1939-10-24
Anticipated expiration: 1956-10-24
Also published as: FR857550A; GB526585A; BE433812A; US2290228A; CH215530A

Description

w. G. H. FINCH TRANSMISSION OF COLOR PICTURES Filed April 24, '19s! i AMPLIFIER AMPLIFIER Patented Oct. 24,1939

I ELECTRICAL TRANSMISSION OF COLOR PICTURES William G. n. Finch, Spuyten Duyvil, N. Y.

Application April 24,

4 Claims.

This invention relates to the electrical transmission of colored pictures to remote points.

Telepicture systems have come into rather extensive use for rapid transmission of pictures between widely separated oflices of a newspaper chain. The electrical transmission of pictures has been commercially restricted to the black and white types due to the extreme precautions heretofore necessary in the transmission of. coll0 ored photographs. A colored picture may be resolved into three primary color separation prints such as blue, red and yellow which may be superimposed to faithfully reconstruct the colored picture. However, any misalignment or other inaccuracy occurring among the three prints during their electrical translation will cause color streaks and distortions when they are superimposed to form the final picture.

I have discovered that by transmitting the color separation prints simultaneously with similar portions ofeach print scanned at the same time, variations which occur in practical facsimile transmission will not operate to distort the final superposed colored facsimile. In accordance with my present invention, the three prints are arranged parallel to each other'upon a single record sheet and the prints are scanned transverse to their parallel arrangement so that similar portions of the picture are simultaneously scanned.

Any variations in the speed or alignment of the receiver with respect to the transmitter, or any phase displacement or distortion which might occur therebetween, is practically simultaneously induced in the three prints to an equal degree. Thus, when the prints are superposed, they will bear the similar distortion characteristics. Such distortions being symmetrical in the three superposed prints will practically v be unnoticeable. These inaccuracies which might occur in facsimile transmission and reception are not serious when a black and white picture is required. However, the principle of my present invention serves to cancel or minimize the effects of these inaccuracies to permit accurate superposition of the three primary color prints, irrespective ofv any practical variations in their transmission, as will be hereinafter described in more detail.

The colored reproductions produced by my present invention bear very fine detail, and substantially all traces of streaksand the scanning lines which make up the picture are toned out so as to be unnoticeable. A small three-dimensional effect occurs in the final colored picture due in some extent, to the superposition of. the

1937, Serial No. 138,683

(01. lie-5.2)

three translucent colored prints to form a substantial thickness. The fine detail of the colored facsimile permits enlargement thereof to a much greater extent as compared to ordinary blackwhite facsimiles, since scanning lines and extraneous marks are rendered unnoticeable.

Newspaper services are enabled by my present invention to economically transmit to remotely scattered plants of their organization comic strips, colored advertisements and colored fea- 10 ture supplements for newspapers, colored copy for magazines, and for other purposes. The transmission of such pictures may be readily carried out over a telephone line without physical interconnection thereto, and using conventional 15 black-white facsimile systems. The three colored prints composing the colored picture may be received directly upon the sensitive film or may be directly engraved upon printing plates for the presses as will be hereinafter fully described.

It is accordingly an object of my present invention to provide a novel method of. transmitting colored photographs.

Another object of my present invention is to providea novel method for electrically transmitting the primary color separation prints of a colored picture to a remote point.

A further object of my present invention is to provide a novel method of producing a colored facsimile with relatively great detail, and free 80' from streaks and distortions inherent in commercial facsimile transmission systems.

These and other objects of my present invention will become apparent in the following description taken in connection with the drawing, 85 in which:

Figure 1 illustrates my preferred arrangement of the three primary color prints upon a record sheet for transmission.

Figure 2 is a plan view of a preferred telepicture transmitter for transmitting the colored picture over a telephone system.

Figure 3 is a plan view of the picture receiver corresponding to Figure 2.

Figures 4 and 5 are illustrations of portions of the received prints used for describing my present invention.

Figure 6 illustrates the superposition of the three color separation prints to form the final colored picture.

Figure '7 illustrates how my present invention overcomes misphasing distortion in the electrical transmission of colored photographs.

A colored photograph may be resolved into three individual monochrome prints correspond- 55 ing to the three primary colors, red, blue and yellow. The prints corresponding to the primary colors may be prepared by conventional color photography methods. A photograph of still-life may be made by taking three successive photographs of the scene using correspondingly colored light filters to produce the primary colored prints. For action scenes, a single-exposure camera employing reflecting mirrors is used to. simultaneously snap the three primary colored prints. The color filter used for each individual primary color print absorbs all the color comgraphic film, resulting in a black-white negative in each instance. The light which reaches the film during exposure is the filtered light which affects the emulsion on the film to a degree proportional to the intensity of the particular color passing through the filter. A colored scene or photograph is composed of varying amounts of the primary colors. The original brilliant color of the photograph is reproduced by suitably preparing and arranging the primary color prints. It is to be understood that the individual primary color prints are merely black-white counterparts of the respective colors and bearing the relative intensities of these colors.

In accordance with my present invention, the

original black-white counterparts of the primary color prints are transmitted by telepicture apparatus for reproduction at a remote point. The black-white pictures are then resolved to their original color and shading, in a manner to be described, to reproduce the colored picture. It is necessary to obtain accurate superposition of the three primary prints in order to produce a quality reproduction, otherwise colored streaks and color distortions will be evident. -My present invention is directed to the elimination of inaccuracies which might occur during electrical transmission of the associated primary or color separation prints.

An important feature of my present invention resides in the positioning of the three colorseparation prints for transmission and reception in a particular manner so as to eliminate variations in picture transmission. The transmission variations do not materially affect the appearance of ordinary black-white pictures but are serious for colored facsimile reproduction due to the superposition of three individual prints. In accordance with my present invention, I arrange the three primary or color-separation prints to be transmitted, B, R and Y, corresponding to the preferred primary colors, blue, red and yellow respectively, upon the sheet ID as shown in Figure l. The prints B, R and Y are arranged so that their axes ll, l2 and iii are all substantially parallel for reasons to be hereinafter set forth.

The color separation prints B, R and Y are prepared from the monochrome or black-white negatives resulting from the original color separation photography procedure. The B, R and Y prints of my preferred embodiment are positives of the original negatives. Although the B, R and Y positive prints may be individually prepared and secured to a common backing sheet, I prefer to print them directly on sheet ill in the parallel arrangement referred to. -Sheet Iii accordingly contains the three prints B. R and Y, arranged in parallel one beneath the other. The prints are the black-white counterparts of the respective tones or intensity values of the primary colors blue, red and yellow making up the original picture colors. The illustrated scene shows three adjacent mountain peaks with the sun ll in the background. The general outline of the picture usually appears in all three prints, but the relative shading in the different portions of the prints varies in accordance with the elemental coloring in the original print.

In practising my invention the B, R and Y prints are not arranged in perfect vertical alignment as the illustration in Figure 1 shows. The sun ll, for example, is not vertically aligned in the three prints. Any point of the picture is preferably not horizontally displaced more than one-half inch or an inch with respect to the corresponding point in the other of the. B, R

and Y prints for reasons to be hereinafter set forth. However, it is important to maintain the horizontal axes of the prints more or less accurately parallel. By the horizontal axis I mean an axis such as H, l2 or l3 which may be drawn through corresponding portions of the B, R and Y prints arranged one abovethe other. The axis referred to, corresponds to some imaginary line drawn through the same portions of each of the B, R and Y prints,'which line is parallel with respect to the other when the prints are placed one above the other on sheet I 0.

Sheet i0 containing the color separation prints B, R and Y is mounted upon the drum I 5 of the telepicture transmitter l6 shown in Figure 2.

a I prefer to electrically transmit a facsimile of sheet ill by a system such as disclosed in my co-pending application. Ser. No. 128,920, filed March 4, 1937. However, it will be evident that other facsimile transmission and reception mechanisms can be used to, in effect, relay the B, R and Y black-white color separation prints to the receiver station. Details of the transmitter l6 and the preferred method of signalling across a telephone network is disclosed in my Patent No. 2,047,863 of July 14, 1936, entitled Telecommunication systems.

The transmitter I6 is powered by a synchronous motor I'I energized from an alternating current line at leads l8. Drum I5 is rotated, preferably at 100 revolutions a minute, through reduction gearing I20. Drum I5 is removably mounted on the transmitter mechanism and contains sheet mounting clamps 2i at a predetermined portion thereof for fastening the record sheet Hi. All electrooptical scanner 22 is moved along tracks 2323 arranged parallel to the axis of the-drum by means of a feed screw 24 geared to reduction gearing 20. Electrooptical scanning carriage 22 is preferably moved at the rate of one inch per minute so as to scanthe record sheet l0 one hundred lines per inch. The scanning lines schematically shown at 25 form a continuous helix about the cylindrically arranged sheet I0. Scanning lines 25 are shown.

with exaggerated width for illustration purposes. The transverse angle of the scanning lines 25 corresponds to the helical lead angle of preferably .01 inch in the present example.

The electrooptical scanner at 22 contains a photoelectric cell which generates electrical ourthe transmitter.

rents varying in intensity in accordance with the shading of the elemental print areas upon the record sheet iii. The signals are conducted along cable 26 to an electronic amplifier 21. A carrier wave or audio frequency tone generated at the amplifier unit 21 is modulated in accordance with the picture currents generated at the scanner 22 in a manner described in my Patent No. 2,047,863 hereinabove referred to. The amplified picture modulated carrier current is passed through a coupling solenoid 28 which is placed coaxially with the induction coil Iii within the phone box II of the telephone station at the transmitter. A telephone connection is established between the telephone station 32 at the transmitter and the corresponding telephone station 33 at the receiver across necting telephone wires 34.

When the telephones 32 and 33 are in operative connection, the picture signals are electromagnetically induced into the telephone line 34 across the induction coil. These currents flow through the induction coil 35 at the receiving station shown in Figure 3, and are picked-up by the pick-up solenoid 38 of the facsimile receiver unit 31. The picture signals picked-up by solenoid 38 are introduced to the receiver amplifier 38 for amplification and connection to the electrooptical system within receiver carriage 4.. The electrical current variations corresponding to-the picture variations at the transmitter scanner 22 are detected and translated into correspondingly varying light intensities and projected upon the light sensitive record sheet 4i mounted upon the receiver drum 42 rotated in synchronism with the transmitter drum ii.

The design of the telepicture receiver 31 corresponds to that of the transmitter unit i6, and is driven by motor 43 at the predetermined speed of motor l1. As'disclosed in my application Serial No. 128,920 referred to above, the receiver drum 42 is continuously rotated by the motor 43 which is maintained substantially close to the predetermined synchronous speed by a governing mechanism such as a mechanical governor'44 attached to it. The receiver scanner is driven parallel to the axis of drum 4! and records on sheet 4| along a helical scanning line 45 similar to the scanning line 2! generated at The scanning line 45 will be inclined at a small angle to the axis of the recordsheet 4! equal to the helical advance of the scanner 40 upon the rotating drum 42 as will be evident to those skilled in the art. The facsimile reproduction of the record sheet i0 upon sheet 4i may be performed with varying line width, varying line density, half-tone spots.-

or dot-dash methods, dependent upon the option of the user and the particular facsimile system used.

Figure 4 diagrammatically illustrates the porthe interconduction. The scanning lines 48 are parallel and form an angle with the vertical axis of sheet 4| equal to the helical lead angle of scanning already referred to. With perfect synchronous reception of the triple-print facsimile, the orientation of the respective portions of the prints at the transmitter. Accordingly, it will be noted that the sun I 4 is not in vertical alignment but corresponds to itsalignment in Figure 1.

The colored picture reproduction is prepared by using a gelatin or other conventional transparent sensitive film 4i and creating the corresponding light and dark areas on the film corresponding to the transmitting shade variations of the original positives (or negatives) B, R and Y. The received prints B, R and Y are in the form of positives" upon translucent or transparent film 4|. After the film 4| is developed, it is bleached in a conventional manner. The B, R and Y portions of the film are severed and represent the blue, red. and yellow portions of the picture. In order to compose the final colored facsimile, it is now necessary to dye or tone the individual prints to their proper color. The blue, red and yellow prints are idenwill be identical to their orientation on sheet ill tified in some predetermined manner such as by their location on the sheet 4| or by an obvious mark upon each individual print.

The tinting or coloring of the individual prints to blue, red or yellow may be performed by dyeing the bleached films with an aniline dye or by toning them with metallic salt solutions which combine with the silver retained in the print in a manner well known in the photographic art. Toning the film brings out the high lights of the final picture in a better manner than the dyeing process does. The monochrome colored B, R and Y. prints are then superimposed to tically to indicate the manner in which they are to be superimposed. The sun l4 for example is seen to lie along a straight line as are the other portions of the prints. The scanning lines 45, of exaggerated width for illustration, is seen to be parallel in the three prints. However, it is important to note, that the scanning lines 45, of B. R and Y prints are not aligned but intersect so'that superposition will cause overlapping between the edges and central portions of the scanning regions or lines 45. This factor causes the effective elimination of possible streaks in the final picture. 1

In Figure 6 I illustrate a preferred manner for preparing the final colored photograph by the three color prints. The tinted or toned blue, red and yellow films B, R, and Y are accurately superimposed one above the other and upon a white backing sheet 46 with transparent adhesive material. The superposition of the films is such as to match the outline of the picture with corresponding portions falling in line. The scanning lines 45 on the. respective prints have been' drawn in to illustrate the advantages of my present invention. The scanning region lines 45 on the Y print correspond to the lines already described in connection with Figures 4 and 5. The illustration shows the R. print positioned above the Y print. The scanning lines "eat the overlapping region of R and Y appearmore dense since the borders of the scan-.

ning lines overlap. Similarly, the scanning line region 45b illustrating the superposition of the three prints B, R and Y is more densesince the outline of the scanning lines 45 overlap as will now be evident.

It will be noted thatdue to the original horizontal disposition of the three color prints on overlapping of the scanning lines at 45b evensout or tones the final image so as to effectively dissolve or cause any possible outline of the individual scanning lines which may be apparent in an individual print to disappear in the final color print.

In the transmission of pictures over a telephone line, there sometimes occurs a bright or dark streak across the picture, which streak is referred to as a line-noise mark. This may be due to contact clicking or to some extraneous signal impressed upon the line for a short interval. Such a'mark occurring upon an ordinary black-white picture reproduction would appear as a definitely visible streak on the picture and interfere with its quality. The final color picture of my present invention is, however, produced by the superpositioning of three individual prints, no common line of which normally bears an identical streak in the three prints due to the horizontal displacement referred to above in Figure 1. The efiect of a streak in any one scanning line along the film 4| as viewed in Figure 4 will be minimized by the superposition of the two other prints which are not streaked at the identical region. In-a similar manner, any line marks due to irregularities in the apparatus such as gear noise and the like will be toned out in the final color pictures. The parallel alignment of the scanning lines 45 in the final print accordingly produces a homogeneous and smooth color reproduction which tones-out or effectively dissolves possible streakiness or latticed scanning line appearance of the picture to produce a facsimile of fine detail and pleasant appearance.

An important advantage of the relatively high detail colored reproduction having its scanning lines, streaks, marks and other minor faults which creep in in practical picture transmission toned out, is that the color reproduction may be enlarged as much as threeor four-to-one and still retain the pleasing appearance of a quality picture. The enlargement of the colored'picture is performed by photographically enlarging in a conventional manner each of the B, R and Y prints as they are produced upon the film 4| in Figure 4. The enlarged black-white prints are bleached and then dyed or tinted in the manner already described. a a

The receiving apparatus 37 is maintained in substantial synchronism with the transmitter l6 by the governor 44. However, a slight difference in synchronism between the transmitter and receiver will cause a progressive phase shift in the reproduction and produce the result illustrated in Figure 'l. The axes ll, I2 and 13' of the prints are no longer parallel to the recordsheet 4| but are at an angle thereto. The dotted line 41 near the edge of the sheet 4| illustrates the progressive phase shift of each line of scanning from the left to the right side of the sheet due to the difierence in scanning speed at the receiver from that at the transmitter. This phenomenon is described in detail in my co-pending application Ser. No. 128,920 referred to hereinabove.

An important result is that the axes H, I!

and I3 and corresponding portions of the prints B", R" and Y" remain parallel to each other.

The prints of sheet 4| are accordingly progressively displaced in correspondence with the phase shifting operation. The shifting of the axes andphasing line 41 is slightly exaggerated for illustrative purposes but in a practical arrangement is not more than about seven degrees. The practical advantage of maintaining the prints aligned in parallel arrangement is that similar portions of the prints are correspondingly displaced.

Accordingly, distortions due to progressive fore an alignment within the order of an inch will still permit accurate superposition of the prints for the final picture result. The parallel arrangement of the prints as described in connection with Figure 1 accordingly serves the purpose of keeping similar portions of the picture in exact correspondence with any vagaries of synchronism, hunting, phase shifting and the like since the similar portions of the picture are affected in like manner. In most practical systems, any such change is more or less gradual so that it is not necessary to perfectly align the prints vertically but practical variation in this respect is permissible.

In accordance with my present invention, colored photographs of any character and particularly colored pictures for newspaper work where economical transmission to difierent units of a newspaper chain is important, may be car'- rled out with ordinary black-white picture apparatus. Colored pictures for comic sections of newspapers, for special feature sections, for advertisem'ents, for magazines and the like, can all be economically transmitted with such apparatus without requiring special precautions to avoid inherent commercial distortions. I The received triple print facsimile may be used for the photolithographic process accompanying printing operation. It is also feasible to directly engrave the triple print records upon a zinc or other metallic plate for printing. Variations and modifications of my present invention will be evident to those skilled in the art, and accordingly I do not intend to be limited except as set forth in the following claims.

I claim:

1,. The method of transmitting a colored picture which comprises preparing a set of primary color separation prints from the picture, arranging the prints substantially parallel to each other and horizontally displaced with respect to each other not more than one-half inch, successively scanning said prints line byline transverse to the parallel axes thereof, transmitting said prints to a distant station by electrical signals varying in accordance with the elemental shading of the prints, producing a transparent record of the prints by a scanning line of finite width, and superimposing the transparent records whereby the scanning lines composing each print are substantially parallel and overlap to tone out the irregularities in the electrical production of the prints to produce a colored picture with sharp deta l.

2. The method of transmitting a colored picture which comprises preparing a set of primary color separation prints from the picture, arranging the prints substantially parallel to each other and horizontally displaced with respect to each other not more than one-half inch, successively scanning said prints line by line transverse to the parallel axes thereof, transmitting said prints to a distant station by electrical signals varying in accordance with the elemental shading of the prints, producing a transparent record of the prints by a' scanning line of ilnite width,- successively composing the prints by scanning in substantial synchronism with the transmitter scanning operation whereby phase displacements simultaneously occur in all prints to maintain the records thereof symmetrical, and

superimposing the transparent records whereby the scanning lines composing each print are substantially parallel and overlap to tone out the prints to produce a colored picture with sharp detail.

irregularities in the electrical production of the 3. Themethod of transmitting a colored picture which comprises arranging individual primary color separation prints of the picture substantially parallel to each other and staggered not more than one-half inch with respect to the direction transverse to the parallel direction, successively scanning the prints line by line transverse to the parallel axes thereof, transmitting electrical signals to a distant station corresponding to the scanning ,of the prints, and producing monochrome facsimiles of the prints by successive line by line reproduction whereby irregularities in the print due to distorted reception are blended out upon superposition of the facsimiles in producing the colored reproduction of the picture.

4. The method of transmitting a colored picture which comprises arranging individual primary color separation prints of the picture substantially parallel to each other and staggered not more than one-half inch with respect to the direction transverse to the parallel direction, successively scanning the prints line by line transverse to the parallel axes thereof, transmitting electrical signals to a distant station corresponding to the scanning of the prints, and producing monochrome facsimiles of the prints by successive line by line reproduction at a rate near the transmitting scanning rate whereby irregularities in the print due to distorted reception are blended out upon superposition of the facsimiles in producing the colored reproduction of the picture and whereby distortions in the outline of the facsimiles due to loss in synchronism of reception correspondingly affect the individual facsimiles in a manner to permit accurate superposition of the prints for the colored reproduction.

WILLIAM G. H. FINCH.