US2799722A - Reproduction with localized corrections - Google Patents

Description

H. E. J. NEUGEBAUER 2,799,722 REPRODUCTION WITH LOCALIZEO CORRECTIONS July 16, 1957 Filed April 26, 1954 6 Sheets-Sheet l ,I Hl E. J :o: HA IJ 1: O b Mn. Im: u: 1 s Mw A. o: 19| 9 LUII. im; ,CE m; li-.. Il l 4.7 li.- Lf Lf n1 :i ,Ii

July 16, 1957 H. E. J. NEUGEBAUER. I 2,799,722

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` REPRoDUcTxoN 'WITH LOCALIZED CORRECTIONS Filed April 26, 1954 6 Sheets-Sheet 4 From 9 From 6) 6u lll To lll-,14214 14 July 16, 1957 H. E. J. NEUGEBAUER 2,799,722

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REPRODUCTION WITH lI .OCLIZED CORRECTIONS 6 Sheets-Sheet 6 Filed April 26, 1954 lrwzntor 2%, /7/ Attorneys United States Patent C signor to Adalia Limited, Montreal, Quebec, Canada, a corporation of Canada Application April 26,` 1954, Serial No. 425,567

Claims. (Cl. 17H-5.2)

Thisinvention relates to. a method and apparatus for making,'reproductionsy with. corrections to sectional areas ofv the picture which may be inaddition to but dierent from overall corrections to the picture.

It. is .necessary that corrected color separations be made Where a colored original is to be reproduced as the color mixture.l laws governing the preparation of uncorrected separations are not the same as'the color mixture. laws of the reproducing system. A number of method-s and apparatuses for making these corrected color separations have been developed, based on scanning the originalpicturea-nd: separating its spectral components to provide what may be called tristimulus signals which are some function of the tristimulus values of the portion ofthev original being scanned. These tristimulusl signals are directed. toy a computer which generates corrected signalsfor use in controlling the recording means. One suitable method and apparatus for this purpose is that' described in my copending application Serial'N-o. 420,434, filed the lst day of April 1954.

A disadvantage of electrical methods andY apparatuses for making corrected color separations hitherto' developed isthatthey lack the iieXibil-ity of manual' methods in that there isV no convenient way of making localized corrections to sectional' areas of the picture. Thisdefect gives riseto problemswhere for example the initial trial prints are satisfactory except for the reproduction of the color in4 one area, say the skin area of a person pictured. in. theV original. Itwill be dit-heult and time consuming. to` attempt to remedy this by overallcorrections,` as when.y the. particu-lar area in questionf has. been` corrected the' colors in other areas may then become distortedv and unsatisfactory. Localized corrections may also be de'- sirable to effect deliberate deviations from the colors of the original. Thusit may bedesirable.. to make localized colorcorrections where Ythe color in a` particular area has fadedror is unsatisfactory for artistic reasons. For eroV ample, color corrections to localized areas may be de-v sirable to harmonize the reproductions of several differenti pictures to be printed on' the samev page;

The object of this invention is to provideV a method andl apparatus which can. conveniently be used asv part of an electrical method or apparatus for producing corrected coljor separations with localized corrections to sectional areas. Although the main object ofthe invention is the' provision of localized corrections forl the reproduction of colored originalsit iscontemplated that the. method and apparatus of this invention will also be suitable for making'y localized density corrections to monochrome pictures.

The general principle of this invention isV that a mask is provided having areas of a dilerential transmission, ratio in comparison to the. remainder of the mask. These areas of diilerential transmission ratio, correspondto the. areas of the original which are to receive localized corrections. The mask is scanned synchronously with the o ri'gnalandy control signals are generatedcorresponding to the transmission ratio of the portion of the mask "2,799,722 Patented July 16, 1957 ice scanned. These control means are used to control a switching means which brings a precomputing means into the electrical circuit to give the desired` corrections for localized areas when the areas of the mask of diierential transmissiony are being scanned.y The switching means causes the' precomputing means to be by-passed when areas other than the localized areas of themask are being scanned. Where colored pictures are being scanned there will be a computing means to which the tristimulus signals are normally fed to give overall color corrections for the signalssupplied tothey recording means. For the special corrections to localized areas the precomputing means can conveniently be included` in the` circuit which feeds the tristimulus signals to the computing means so that the precomputing means will changel the input signalsfto the computer forthe localized areas. Alternatively,- the precom-putingmeans can be loca-ted` so that it acts on the output signals from the computer. As a further alternative a separate circuit can be used for the localized areas so that the precomputer imparts both the overall corrections and the special corrections. Where density corrections are being made to a monochrome it may be possible toomit the computer and use only the precomputer. Where different corrections are to be applied to different localized areas the mask can have a diierent transmission ratio and a separate'. precomputer can be providedfor each localized area.

In accordancewith a preferredl embodiment of this in vention` provision is made for the use of approximate masks in'- whichthe areas of differential transmission ratio are larger than are approximately contoured totV the shapeof the localized areas of the original. The usev of approximate masks' greatly reduces the time requiredA to make the masks and also eliminates the effectV of minor maladjustments in the positioning of the mask and. origi-r nal or in the synchronism of the means for scanning` the mask` andithe means forscanning the original. Accurate` corrections are obtained with these approximate masks by including means within the switching means for including the precomputer in the circuit only when. not only is. an area of the mask of differential transmission ratioV beingscannedbut also. when the. tristimulus signals each fall within afpredetermined range of values; in almost every case this will give` a satisfactory resultas usually the tristimulus values of the areas of the` original immediately adjacent to the area being corrected will have4 diierent. tristimulus values fromv the area being cor` rected. Approximatemasks can, in many cases, be usedA for making density corrections toaV monochrome, but. there4 is a greater likelihood that the surrounding areas will have a similar density to the area being correctedV than that these surroundingare'as will have similar tristimulus values to the area beingcorrected; In some: cases where colored reproductions are being made satis-A factory results" may be obtainable byl controlling.` the switching` means enti-rely by the tristimulus signals but it ispreferredk that a combination of approximatel masks' and the'tristimulus signals be used to control the switching; means.

In the drawings which illustrate the embodimentsof this invention:

Figure'l l is aI circuit diagram in block form illustratingv the. preferred embodiment of this invention;

Figure-22 shows an original picture to', be. reproduced;

Figure 2a showsfoneform of mask. for use in making: localized corrections to Figure y2;

Figure 2bshowsa-second form of mask for use" in making localizedv corrections to Figure 2; A

liigurev 3 is a detailed view of'v the switch. bornand` switches;`

Figure, 4 is a detailed'. view; off4 a m'odied circuitr for: the;` switch`v box. shown in-ligurey 3;"

Figure 5 shows a modified circuit as an alternative to part of the circuit shown in Figure l;

Figure 6 shows a further alternative to part of the circuit shown in Figure 1;

Figure 7 shows an alternative to the switching device shown in Figure 3 Figure 8 is a detailed elevation view of diaphragm 53;

Figure 9 is a detail elevation View of diaphragm 66;

Figure l() shows a modification of part of Figure 7.

In the drawings which illustrate the preferred embodiment of this invention and in which similar numerals designate similar parts, Figure l shows a circuit diagram illustrating the method and apparatus in accordance with the preferred embodiment of the invention; Figure 2 shows an original to be reproduced; Figure 2a shows one form of mask for use in association with the apparatus in Figure 1; Figure 2b shows another form of mask. it may be assumed, for example, that in the original picture 1 shown in Figure 2 that the skin of the Woman is too pale, the arms and hands 1a needing more yellow and magenta, the face 1b needing more yellow and slightly more magenta. In addition the blue 1c of the Flowers may be too dull, a purer and brighter blue would be desirable. The rest of the picture may be assumed to be satisfactory.

An electronic scanner for obtaining such corrected separations that the desired changes of the colors of arms, face and flowers are produced automatically is represented in Figure 1. Original 1 is scanned by means of light source 4 and three photo electric cells 5, 5', 5 picking up light reflected from the illuminated point of the original. Other scanning methods may be used. The spec tral response curves of the photo cells'S, 5 and 5 multiplied by the spectral transmission curves of color filters 5a, 5a and 5a which may be arranged between the original and the photo cells are such that the signals b, g, r generated by the cells are trichromatic coordinates of the color of the original. Their relation to the tristimulus values of the original has been explained in my copending patent application Serial No. 420,434. Sig nals b, g, r which will be referred to for brevityl as tristimulus signals are preamplified by amplifiers 6, 6', 6" respectively.

Signals m, j, c, n generated by the computing means subsequently to be described and having a predetermined relationship to signals b, g, r are fed into recorders 14, 14', 14, 14 which produce by known methods four corrected color separations on sheet material 15, 15, 15"' or three corrected separations where no black printer is included. The designation corrected color separation means that these separations, when processed by a standardized method, yield printed multicolor pictures which are faithful reproductions of the original except for such color distortions as are an unavoidable consequence of the limited color gamut of the printing inks, and. except for those areas (skin and flowers in the example of Figure 2) where deviations from the original color are dcsired.

When signals b, g, r are fed into the four computers 13, 13', 13", 13"', these computers yield signals m, j, c, n,

which are used for controlling recorders 14, 14', 14, 14l` respectively, such that the separations 15 lead to faithful reproductions of original 1 within the limits of the color gamut of printing inks. When neither a point of the skin nor of the flowers is being scanned, preamplifiers 6, 6', 6 are directly connected to computers 13, 13', 13, 13".

A mask Figure 2a is scanned synchronously with original 1. The scanning is synchronized by synchronizing means 3 controlling light sources 4 and 7. The transmission ratio of the mask is different from the remainder of the mask at areas corresponding to such areas of the original in which localized color changes are desired. For instance, the mask 2' Figure 2a can have an overall transmission ratio substantially equal to unity. Its transmission ratio can be substantially zero at the areas 2c corresponding to the flowers...it-canibe about atthe areas 2a corresponding to the arms, and be about 70% at the areas Zb corresponding to the face.

Mask 2 lis scanned by means of light source 7 and photo electric cell S. Signals generated by the photo cell are preamplified by amplifier 9 and fed into a switch box 10.

Switches 12a, 12a', 12d" are controlled by switch box 10 in such a way that switches 12a, 12a', 12a", 12b, 12C, 12C are open and switches 12d, 12d', 12d are closed when photo cell 8 receives maximum light. In this state of the switches preamplifiers 6, 6', 6 are connected to computers 13, .`13". The preampliers are also connected to precomputers 11a, 11a', 11's". However, as long as switches 12a, 12C" are open the precomputers are disconnected from Ycomputers 13, 131i?.

When the intensity of light falling on photo cell 8 is reduced to about 70% of its maximum value, switch box 1t) transmits signals to the switches so that only switches 12a, 12a', 12a" are closed while the other switches 12b 12C" remain open and switches 12d, 12d', 12d" are opened. Preampliers 6, 6', 6" and precomputers 11b, 11b', 11b", 11C, 11e', 11C" are thus disconnected from computers 13, 13".

Precomputers 11a, 11a', 11a produce signals b', g', r'

which are fed into computers 13, 13" instead ofk b, g, r respectively. Signals b', g', r are the trichromatic coordinates of such colors as the face should have to give a pleasant picture. Precomputers 11a, 11a', 11a" are adjusted to give the desired effect on the basis of experience or trial experimentation.

If photo cell 8 receives only 30% of the maximum light switch box 10 sends out signals which close switches 12b, 12b', 12b While all the other switches remain open or are opened. In this case signals b, g", r" generated by precomputers 11b, 11b', 11b" are fed into computer 13, 13" instead of b, g, r. They are the trichromatic coordinates of the colors of hands and arms which Will theV owers.

give a pleasant picture.

If, photo cell S receives no light, precomputers 11e,l

11C', 11C" are similarly connected by switches 12C, 12', 12 to computers 13, 13". Precomputers 11C, 11C', 11e" provide signals b", g", r" which are the trichromatic coordinates of the desired blue of the flowers.

A photographic method can be used to facilitate making the mask. A photographic negative of original 1 is made and all the sections of the picture which are to be clear on the mask, are covered with a protective layer which is impermeable to light. The uncovered areas are bleached in a silver solvent and the areas corresponding to the hands and the face covered by pieces of thin material of the appropriate transmission ratios. A photographic print of this negative constitutes the mask.

Since, quite often, the contours of the areas which need special corrections, are difficult to follow with the brush, the method can be altered so that the simplified mask of Figure 2b can be used. To accomplish this, the action of switch box 10 is controlled not only by signals from photo cell 8 but also by signals b, g, r.

Under the assumption that the trichrornatic coordinates of the `blue flowers, as they are represented on the original, lie between the limits Bf and Bf', Gf and Gr', Rf and Rf' the switch box is adjusted in such a way that switches 12C, 12e', 12C" are closed when Since it could happen that a color with trichromatic coordinates between the same limits occurs also in other sections of the picture, for instance in the womans frock, the switches 12e, 12e', 12C are closed only when, at the same time, photo cell 8 receives no light. Therefore, a mask is still usually needed, but its contours can be very inaccurate as can be seen from Figure 2b, in which 2"a represent the areas of the mask for correcting the hands, 2b the areas for the face and 2c the areas for v A suitable construction for` switch box and switches 12d, 12b, 12e, 12a? is shown in` Figure-3. In Figure 3 voltage supplied` by preamplifier 6' and proportional to signal b isn applied t'o potentiometers 21a, 21h', 21e. In the same way voltages proportional'to g and r are applied to six poteutiometers 22a, Y. 23e. Potentiometers 21a, 22a, 23a will lirst be considered; Two relays 2411 and 24a are arranged in parallel toparts of the resistor 21a,rand theA variable contacts of the potentiometer are adjusted so that tlie contact of relay 24a is actuated when voltage b rises over, or drops under the value Bs, while the contact of relay 24a is actuated when voltage b rises over, or dropsunder, the-value' Bs. By' an initial measurement the. values Br andl VBt' have been determined as lower and upper limits of bk when tlie trichromatic coordinates ofthe color of skin as represented on originall 1 are measured.4 Thev corresponding limits for g and r may be' Gs, Gs', RsuRs'. The variable contacts of potentiometers 22a" and 23a are adjusted in' such a way that the contacts' of relays 25a, 25a', 26a, 26a are actuated` when signal g passes the values Gs or Gs' or signal r the" values Rs or Rs respectively.

The contacts et said six relays are arranged@ in series. The contacts of Figure 3 are drawn under the assumptionthat signals b, g, r`l lie between the limiting values Bg, Bs; Gs, Gs'; Rs, Rs ev., that all area. ot the picture representing skin is being scanned. Contacts 24a, 25a, 26a are open, contacts 24a', 25a', 26a' are closed when no current is tiowing, Therefore, when skin is being scanned, all the six contacts areiclosed.

Since, on original 1, the womans Atace' and arms are represented by the same color, but different corrections are desired, potentiometers'` 211:', 225, 23b are" adjusted in suchv a way thatrelays- 2'4b, 26h' are actuated at theY same values of b, g, r as relays 24a-,1. 26a. By means of mask 2 relays 24a to 26a will be used in the correction of the color of the face, relays. 24h to 26h will be used in correcting the color of the arms.

Contacts' 24e toA26c are used in correcting- Vthe color of the flowers; Consequently thecontacts of potentiometers` 21e, 22e, 23e are adjusted such that the contacts of relays, 24C to 26c'are actuated at the values Bf and Br for b, Gf and Gr for g, Rf and Rr for 1'.

The manner in which the mask is used to control the operations will now be described. A` resistor 2 7 is connected to preamplifier 9. Relays 28.42, 29a, 28b,y 29b, 29e are connected in parallelto sections of resistor 27 inY such a way that 29a is operated when the transmission ratio of the mask drops below, for example, 85%; 28a and 29h are operated when it drops below 50%, and 285' and 29C are operated when it drops below 15%. Contacts 28a and 29a are arranged in series with contcts 24a to 26u. Contact-s 28b and 29b are. in series with contacts 24b to` 2Gb'. Contact 29e is inv series with contacts 24e to 26o'.

At the moment when the womans face is being scanned, the voltage applied to resistor 27 will be 70% of its maximum value. Therefore contactsy 28a` and 29a are closed, but contacts 29b and 29C are open. Constant D. C'. voltages are applied to the terminals 30a, 30b, 30C, therefore a' current is flowing in the circuit with the terminals 30a, but no current is owing in the two other cCit'S'.

If the womans arms are being scanned all twelve conta'cts 24a to 26a and 24'b to 26h' are' closed as shown in Figure 3. But the voltage' applied to resistor 27 is `only 30% of its maximum. Therefore contacts 28a and 29C are open, while contacts Zeb and 29b closed. Only the circuit with the `terminals 3017' is carrying current. lf finally the ilo'wers areV being scanned the contacts 24e to'ic and contact 29e areclosed while 28h and 28a are op'e'. In this case only the circuit with terminals 30e carries current.A v

Switches 12a, 12b and 12C containing relays are cond nected so that' their relays are actuatedr by the circuits containing` contacts- 29a, 29h and 29e respectively and switch 12d also containingv relays is connected so that its-relays: will be actuated by all three circuits. It should be mentioned that none' ofthe three circuits carries cur-` rent when a clear part of the mask is being scanned-` be cause then thel three contacts 29a, 291;, 29's` arel open. Consequently the six contacts of switch 12d' are closed, whereas those of switches 12a, 12b, 12o are open'. When either the face, or the arms, or the owers are being scanned, either the contacts of switch 1221 or of switch 12b or of switch 12b, respectively are closed while one pair of the contacts of switch 12d is open.

Switches 12a' 12d are similarly connected in parallel to the four switches'l 12av to 12d asV shownV i-n Figure l.

In Figure 3' all the relayshave been illustrated as being of the electro-mechanical type. It will be apparent that they can be replaced by tubes for fast working scanners. Each relay can for instance be replaced by the nip-nop shown in Figure 7 which will'` be explained below.

If a picture contains only two areas needing special corrections diterent from the rest of the picture, then two transmission ratios of the mask, for instance 30% and 70% but not zero, are used and the potentiometers 21a, 22a, 23a,.21b, 2`2b, 23h are adjustedto their cor,- responding limiting. values as explained before.

If apict'ure contains more than three areas. needing special corrections the same principle as shown in Figure 3 can be extended to four, five, or six special corrections.

Another possibility where two or more areas require ditterent corrections is t use the same transmission ratio for the portions of the mask corresponding to these areas and to rely on thev tristimulus signals to differentiate between the areas.

Where accurate masks as shown in Figure 2a are used the circuit shown in Figure 3 can be simplified to omit the provision for controlli-ng the switches by means of the tristimulus signals. The simplified circuit is shown in Figure 4 the elements of which bear the same designations and operate in a similar manner to the corre-v spending elements in Figure 3.

Computers 13 and precomputers 11 may conveniently be of the type described in my copending application Serial No. 420,434 but other computers can be used as substitutes.

Figure 5 shows a different arrangement where alter native computers are used instead of precomputers. Four computers 31, 31, 31", 31 are adjusted so that each of them supplies a different quadruplet of signals m, j, c, n when the same triplet of signals b, g, r is fed into them. Switches- 12ml, 12n" are operated by signals from switch box 10 so that only one of the computers 31 to 31 is connected to the lines designated m, j, c, n, and leading to the recorders 14 to 14 of Figure l. Switch box 10 may be controlled by signals from the mask or by signals from mask and original or uncorrected separations. In the latter two cases the connections shown by dotted lines 3419', 34g, 34r in Figure 5' are completed.

In many cases the special corrections desired in restricted areas of the picture can be effected at asuicient accuracy by such simple transformations as where P', Q', U are properly chosen constants. In this case the computer arrangement can be simplied considera'bly' as shown in Figure 6. i

Three variable gain ampliiers 32, 32', 32" are inserted in the paths from preampliiers 6, 6', 6" to computers 13 to 13". If the gain of the amplifiers is adjusted to one specified value,y for instance 100, then the signals m, j, c, n supplied by computers 13 to 13" may be those'leading to a faithful reproduction within the gamut of printing inks. The gainv can be varied by changing the grid voltage ofthe amplifier tubes 32, 32', 32". For this purpose potentiometers, 33a, 33d,- fed by a constant D. C. voltage can be adjusted so that diiferent gains are obtained according to the state of switches 12a, 12d.

If, for instance, switches 12a, 12a', 12a" are closed and the other switches 12b to 12d are open then the gain of amplifiers 32, 32', 32" is controlled by potentiometers 33a, 33a', 33a". It may be assumed as a matter of example that these potentiometers are adjusted such that the gain is 100.

If switches 12b, 12b', 12b" are closed and the other switches are open then the potentiometers 33h, 3311', 33h" are controlling the gain. They may be adjusted so that the gains of the amplifiers 32, 32', 32" are respectively lOOP', lOOQ', lOOU' In a similar manner potentiometers 33e, 33C' 33d" are adjusted and used to produce different corrections. Switches 12a to 12d" and switch box 10 may be of the same type as shown in Figure 3 or Figure 4.

Figure 7 shows an example of an electronic switching device. Cr tubes with magnetic detiection are preferable as switching means because ditferent sections of the switching device and of the computers can be kept separate without conducting connections between them.

The beam of Cr tube 51 is deviated by currents which are proportional to signals g and r. The screen of the tube is imaged by lens 52 onto diaphragm 53 which has a rectangular aperture which can be adjusted in such a way that light passes through the aperture when Gs g Gs' and RS 1' RS'. Lens 54 images lens 52 onto photo cell 55. The voltage drop along resistor 56, when the photo cell receives light, is used to control the beam intensity of Cr tube 57. Voltage is applied between grid and cathode of tube 57 such that no beam leaves the gun when both terminals of resistor 56 are at the same voltage. When photo cell S receives light the potential of the grid is shifted towards positive values so that an electron beam is produced. This beam is deviated by currents proportional to signals b and by signals from the mask. The screen is imaged by lens 58 onto diaphragm 59, lens 58 is imaged by lens 60 onto photo cell 61. The rectangular aperture of diaphragm S9 is adjusted so that photo cell 61 receives light when BS b Bs and, at the same time, the transmission ratio of the mask is about 70%.

Triode 64 is connected in parallel to resistor 62. The grid voltage is such that an anode current is owing when there is no voltage drop between the terminals of resistor 62. When photo cell 62 receives light the grid voltage is shifted towards negative values so that the anode current is interrupted. The switching voltage is produced between the points A+ and A- of resistor 63. When the womans face on the picture is being scanned the voltage drop between A+ and A- is Zero. When any other part of the picture is being scanned A- is negative with respect to A+. Y

In a corresponding manner two switching voltages are produced between the terminals of resistors 63' and 63". Diaphragme 53', 59', 53", 59" are adjusted in such a way that points B+ and B- as well as C+ and C- are at the same potential except when either the womans arms (B3 b Bs', Gs g Gs', Rs r Rs, and transmission ratio of mask about or the flowers and transmission ratio of mask zero) are being scanned. When the arms are being scanned B- is negative with respect to` B+ and when the flowers are being scanned C- is negative with respect to C+. l

A fourth switching voltage is generated between terminals D+ and D- of resistor 70. Grid and cathode of Cr tube 65 are connected to resistor 63' in such a way that an electron beam leaves the gun when B+ is positive with respect to B-, but that the electron beam is interrupted when B+ and B- are at the same voltage. The two deviation coils are connected to resistors 63 and 63" respectively and a diaphragm 66 is arranged in front of the screen in such a way that light from the screen reaches photo cell 67 when A+ is positive with respect to A- and C+ is positive with respect to C-. lt however, either A+ and A- or C+ and C- are at the same potential the electron beam changes its direction so that the luminous spot of the screen is covered by diaphragm 66. Triode 69 is connected to resistor 68 in such a way that resistor 70 is free from current while a current tiows through 68 and vice versa.

The lower half of Figure 7 shows the manner in which the switching voltages can be used to control four different computers to produce four different signals m, m', m, m" The computers may be of the memory type described in my copending application Serial No. 429,434. Intelligence recorded on lenticulated memory screen 71 is read by means of Cr tube 72 and orthicon 73. Resistor 7i) is connected to grid and cathode of the orthicon in such a way that the latter works when D+ and D- are at the same voltage, but is interrupted when D- is negative with respect to D+. In a similar way orthicons 73', 73" and '73" are connected to resistors 63, 63', 63 respectively. The intelligence recorded on lenticulated memory screens 73', 73", '73" is different according to the desired corrections.

As is obvious from above descriptions and from Figure 7 only one of the four orthicons is working at any moment and not the three other orthicons. Ordinarily signals m are produced by orthicon 73. When the tace is being scanned orthicon 73' produces signals m', when the arms are being scanned orthicon 73" produces signals m, and when the flowers are being scanned orthicon 73" produces signals m Either signals m, m', m" or m" are transmitted to recorder 14 of Figure l.

lt may be noted that any one of the switching voltages is zero when the corresponding orthicon is working. For example, A+ and A- are at the same potential when orthicon 73 is working. Therefore, the intensity of the electron beam emitted by the gun of the orthicon is independent of the switching means. Special feed back systems can be used to keep the intensity of the electron beam constant while the orthicon is working.

The triodes 64, V64', 64" and 69 serve to secure this independence of the orthicons from the switching means. Such an independence could not be obtained when the voltages at the terminals of resistors 62, 62', 62" and 68 were used for switching purposs because then a current would be owing through one of the resistors while the corresponding orthicon is working. Current variations would cause intensity variations of the orthicon.

Additional sets of computers can be used to produce signals c, j, n, and these can be connected in parallel to those shown in Figure 7, or the'four corrected separations can be made in succession. In the latter case no change to the lelectrical circuits are required, but the memory screens are replaced in turn by screens representing the corrected values of ic, j, n respectively.

In Figure 8 diaphragm 53 is shown in elevation view. The circle indicates the image of the screen of tube 51. Four angular holders have grooves in which thin metal plates 81 and 81a are slidably mounted. The small rectangle almost at the centre is the aperture of the diaphragm. Plate 81 is brought in such a position that its lower edge goes through the image of the luminous spot on tube 51 when g=Gs. The upper edge of plate 81' is adjusted so that its upper edge passes through the image of the luminous spot when g=G's.

Correspondiugly plates 81a and 81a' `are adjusted so that their edges pass through the images of the luminous spot when either r=RS or r=Rs, leaving open between them the spaceR's-l-r-l-Rs.

Diaphragms 53', 53, 59, 59', 59 are alll ofthe same design. In the case of diaphragm 59, for instance, plates 81 and 81 are adjusted so that the edges correspond to the values b=Bs and b=Bs respectively, and' plates 81a and 81a are adjusted so that their edges leave'a space free between them which corresponds to transmission coefficients of mask 2'" or 2" between the limiting values 50% and 85%. The pla-tes are similarly adjusted' in the cases of the other diaphragms with obvious modifications,

Figure 9 is an elevation view` of diaphragm 66.` The hatched area is impermeable-to light.

Thatpart of Figure 7 within the dashed line can be used as switch box 10 of Figure l or Figure 5. In this caseit is advisable to replace themechanical relays 12a, 12b; 12e, 12d, 12a', a. s. o'. by electronic tubes as, for instance, shown in Figure llO.

Pentode 85d serves to transmit or out off signals from preamplifier 6 whoseI exit is connected to cathode and lirst grid of the pentode; Cathode and second grid are connected to points D+ and D- of'Figure 7'. TheV grid bias is adjusted in such. a way' that the tube transmits an anode current when- D+ and D- are at the same potential, and that the anode current is interrupted when D- is negative with respect to D+. A voltage proportionalE to thev signals from preamplifier 6 is supplied at points D+ and D"- when D+ and D- are at the same potential. This sectionY of: Figure- 10 can be used `as switch 12d. The pentodes 85a, 857:, 85o are connected Vsimilarly to pentod'e 85d with obvious modiiications as shown` in Figure l0, so that they will serve as switches 12a, 12b, 12o.

From the foregoing explanations it is apparent that all: the mechanical relaysshown: in the figures and mentioned i'n this specification can be replaced by electronic tubes'- toi ensure higher operational speed.

l claim:

li'. Arr` apparatus for making corrected color separations for use in making reproductions of'a colored kpicture with color corrections for at least one sectional area of the picture differing from the overall color corrections, comprising means for scanning the picture and generating electric tristimulus signals-corresponding to the tristimulus values of thev picture, means for scanning a mask having areas: with a transmission ratio differing from the transmissi'onratio of theremainder of the mask in synchronism with the scanning of the picture, said areas of the mask corresponding to the portions of the picture which are to have color corrections differingv from the. overall color corrections, meansfor generating' sign nals corresponding to the transmission ratio` of the portion. of the mask being scanned, recording means for recording; corrected. color separations computing means for generating inputy signals for the. recording meanshaving overall corrections,..precomputing meansr for generating additionallycorrected signals for said sectional'area, switching-means; controlled by said signals corresponding tofthetransmission: ratio ofthe. portion of the mask being scannedl for: luy-passing. said precomputing means and directing the. tristimulus signals to the recording means through ther computing means: when` areas, of the picture other than said at least one sectional area are being scannedI andfor directing the tristimulus signals to the recording meansft-hrou'gh the. precomputing means and the computing means when said at least one sectional area is; being scanned: i

2. An apparatus for making corrected color separations for use in makingV reproductions of a colored pic-l ture with color corrections for sectional areas of the picture differing from the overall color corrections and from each other, comprising means for scanning the picture and generating electric tristimulus signals corresponding to the tristimulus values of the picture, means for scanning a mask having areas with a transmission radiodiifering fromfthe' transmission lratio o f the remainder of the mask, the transmission ratio differing between` each' area` in which a different color correction is to be made, the scanning of the mask' being in syn'- chronisrrr withthe'scanni'ng ofthe picture, said*A areas of the mask corresponding to the portions of the picture which are to havev color corrections, means for generating signalsl corresponding to the transmission' ratio of the portion of the mask being scanned, recordingy means for recording corrected color separations computing means for generating input signals for the recording means having overally corrections, a precomputing means for each area in which a separate correction isl toI be made for generating' additionally corrected signals for the last mentioned area, switching means controlled by said signals corresponding to the transmission ratio of the portion of the mask being scanned for by-passingsaid precomputingy means and directing the tri'stimulussignals to the recordingd means' through the computing means when' areas of thel picture other thanV saidl sectional areas are being scanned and for directing the tristimulus signals to the recording meansl through the precomputing means for one-of the sectional areas and the computingmeans whenI said" one ofthe sectional areasis being scannedi.

3. An apparatus for making reproductions ofr al picture with density corrections to at least one sectional area of the picture comprising means for scanning the picture and generating' signals corresponding toy at least one spectral component of: the picture, means` for scanning a mask havingareas with a transmission ratio' difiering from the transmission ratio of" the remainderl of the mask in synchronism with the scanning of the picture, saidy areas of the mask corresponding to they portions of the picturev which are to have said density corrections and being largerthan said portions soasv to have approximately similar outlinesl to said portions, means for generatingl signals' corresponding tothe transmission ratio of the portion of the mask being scanned, recording means for're'cording said reproductions means for generating corrected signals" for saidl sectional area, switching means controlledl by said signals corresponding to at least one spectral component of the original and by said signals corresponding to the transmissiony ratio of' the portion of the mask being' scanned forv directing signals to the recording means without said' corrections when areas offl theA picture'- other thanl saidV areasv of' the mask are being scanned? ory when said signals corresponding to at least one spectral component of" the picture are Out*- side ay predetermined range off values and forv directing signals' to the recording means; including said density correctionsj when said=y areas of the mask are being scannedandwhenalso*- saidsignal's corresponding tov at least' one spectral? component or' the picture arey within 'said predetermined: range of values.

4;. An apparatus for makingV corrected" color separations foruse in making reproductions of a coloredy picture with' color corrections forV sectional areas of the picture differing from the overall color corrections and from eachother, comprisingmeans for scanning the picture and generatingY electric trist-imulus signals cor-responding tothe tristimulus values of the picture; means for scanning a-- mask having areas with a transmission ratioy diitering from"` the transmission ratio of th'e'l remainder of the mask'- ini` synchronismv with the scanning of the picture, saidr areas of the mask corresponding to the portions off the picture which are-to have saidl density corrections.- andbeing larger thanA said portions so as'r4 to have` approximately similar outlines to said" portions; means forf generating-1 signalsl corresponding to the' transmission ratio of the portion of the mask being scanned, recording means for recording corrected color separations, computing means for generating input signals for the recording means having overall corrections, a precomputing means for each area in which a separate correction is to be made for generating additionally corrected' signals for the last mentioned area, switching means controlled by said tristimulus signals and by said signals corresponding to the transmission ratio of the portion of the mask being scanned for by-passing said precomputing means and directing the tristimulus signals to the recording means through the computing means vwhen areas of the mask are being scanned or when said tristimulus signals are outside a predetermined range of values and for directing the tristimulus signals to the recording means through the precomputing means for one of the sectional areas and the computing means when said areas of the mask are being scanned and when also said tristimulus signals are within said predetermined rangeof values.

5. An apparatus for making reproductions of a picture -with density corrections to at least one sectional area of the vpicture comprising means for scanning the picture land generating uncorrectedr signals corresponding to at least one spectral component of the picture, means for scanning la mask having areas with a transmission ratio differing from the transmission ratio of the remainder of the mask in synchronism with the scanning of the picture, said areas of the mask corresponding to the portions of the picture which are to have said density corrections, means for generating signals corresponding to the transmission ratio of the portion of the mask being scanned, recording means for recording said reproductions, means controlled by said means for scanning the .picture for generating corrected signals for said sectional area, switching means having means acting when in one lposition to direct only uncorrected signals corresponding to said at least one spectral component of the picture to the recording means and acting when in a second position todirect only said corrected signals to the recording means and said switching means including control means actuated by said signals corresponding to the transmission ratio of the portion of the mask being scanned for adjusting said switching means to said one position when areas of the picture other than said at least one sectional area are being scanned and for adjusting said switching means to said second position when said at least one sectional area of the picture is being scanned,

6. An apparatus for making reproductions of a picture with density corrections for at least one sectional area o f the picture differing from the overall density corrections, comprising means for scanning a picture and generating signals corresponding to at least one spectral component of the picture, means for scanning a mask having areas with `a transmission ratio differing from the transmission ratio of the remainder of the mask in synchronism with the scanning of the picture, said areas of the mask corresponding to the portions of the picture which are to have density corrections differing from the overall density corrections, means for generating signals corresponding to the transmission ratio of the portion of the mask being scanned, recording means for recording said reproductions, computing means for generating input signals for the recording means having overall corrections, means additional to said computing means for generating differently corrected signals for said sectional area, said input signals and differently corrected signals being derived from the means for scanning a picture and generating signals corresponding to at least one spectral component of the picture, means for directing signals corresponding to said one spectral component of the picture'and corrected only by said computing means to the recording means, means for directing signals corresponding to said one spectral component of the picture and corrected both by said computing means and by said means additional to the computing means to the recording means, switching means having means acting when in one position to direct only said signals corrected only by the computing means to the recording means and acting when in a second position to direct only said sigynals corrected both by said computing means and by said means additional to the computing means to the recording means, and said switching means including control means actuated by said signals corresponding to the transmission ratio of the portion of the mask being scanned for adjusting said switching means to said one position when areas of the picture other than said at least one sectional area are being scanned and for adjusting said switching means to said second position when said at least one sectional area of the picture is being scanned.

7. An apparatus for making corrected'color separations for use in making reproductions of a colored picture with color corrections for at least one sectional area of the picture differing from the overall color corrections, comprising means for scanning the picture and generating electric tristimulus signals corresponding to the tristimulus values of the picture, means for scanning a mask having areas with a transmission ratio differing from the transmission ratio of the remainder of the maskv in synchronism with the scanning of the picture, said areas of the mask corresponding to the portions of the picture which are to have color corrections differing from the overall color corrections, means for generating signals corresponding to the transmission ratio offthe portion of the mask being scanned, recording means for recording corrected color separations, coniputing means for generating input signals for the recordingmeans having overall corrections, means additional to said computing means for generating differently corrected signals for said sectional area, said input signals and differently corrected signals being derived from the means for scanning a picture and generating electric tristimulus signals corresponding tothe tristimulus values of the picture, means `for directing said electric tristimulus signals corrected only by said computing means to the recording' means, means for directing said tristimulus signals corrected both by`said computing means and by said means additional `to the computing means to the recording means, switching means having means acting when in one position to direct only said tristimulus signals corrected only by said computing means to the recording means and acting when in a second position to direct only said signals corrected both by said cornputing means and by said means additional to the computing means to the recording means, and said switching means including control means actuated by said signals corresponding to the transmission ratio of the portion ofthe mask being scanned for adjusting said switching means to said one position when areas of the picture other than said areas of the picture which are to have color corrections differing from the overall color corrections are being scanned and for adjusting said switching means to said second position when the areas of the picture which are to have color'corrections differingV from the overall color correctionspare being scanned.

References Cited in the le of this patent UNTTED sTATEs PATENTS 2,413,706 Gunderson Jan. 7, 1947 2,434,561 Hardy Jan. 13, 1948 2,571,322 Yelland Oct. 16, 1951

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