US3155001A - Apparatus for making corrected color separations - Google Patents

Description

B. SITES 3,

APPARATUS FOR MAKING CORRECTED COLOR SEPARATIONS Nov. 3, 1964 Filed Jun'e 13, 1961 2 Sheets-Sheet 1 INVENTOR.

BENJLQMIN L. SWES ATTDRNEYS Nov. 3, 1964 B. SITES 3,155,001

APPARATUS FOR MAKING CORRECTED COLOR SEPARATIONS Filed June 15, 1961 2 Sheets-Sheet 2 INVENTOR.

BENJAMIN L. SITES.

$WMM*%Z ATTORNEYS.

United States Patent 3,155,0tl1 APPARATUS IFGR MAKING CURRECTED CULGR SEPARA'HGNS Benjamin L. Sites, Eimhurst, Ill, assignor to Miehle-Gcss- Dexter, incorporated, Chicago, Ill, a corporation of Delaware Filed tune 13, 19611, Ser. No. 116,776 8 (Ilairns. (Cl. 8t52d) The invention relates in general to the art of making process color printing plates for the printing industry. It is directed more specifically to apparatus for making corrected, color separation transparencies directly from multicolored subjects in accordance with the principle disclosed in the Sites Patent 2,567,240.

According to the present disclosure the light energy reflected from or transmitted by the subject or copy to be reproduced, is separated into a plurality of selected spectral color bands covering the gamut of the spectrum. As a matter of fact the invention contemplates the use of all the spectral components of the light emitted or reflected from the colored subject in the form of bands each having a width which is substantially one Nth of the spectrum wherein N is the total number of bands. Each oand will be less than a major portion of the spectrum, and the same will have an exact composition with respect to its spectral components. More particularly it should be understood that N will equal one plus the number of primary, secondary and tertiary colors required to reproduce the original.

A suitable optical assembly in each color band creates a corresponding light image of the original, and the intensities of the respective light images are modulated in accordance with predetermined factors, having positive and negative signs, which are based on the reflectance,

absorbance characteristics of printed samples of the pig ments and paper to be used in making the reproductions. All of the images thus formed are then combined in a manner whereby the overall intensity of those images having negative sign factors is subtracted from the overall intensity of those images having positive sign factors to produce a resultant light image whose overall light intensity represents a corrected, primary color separation which is used to expose a photosensitive element.

Accordingly it will be evident that by a suitable combination of optical means alone, a composite light image representing a corrected primary color separation can be obtained from which a high fidelity, corrected color separation transparency can be made direct.

It is a primary object of the present invention to provide a relatively simple and economical device for making corrected, primary color separation transparencies.

Another object is to provide a device employing optical means alone for making corrected, color separation transand particularly pointed out in the specification, drawings and claims appended thereto.

In the drawings which illustrate an embodiment of the device and wherein like reference characters are used to designate like parts- FIGURE 1 is a schematic perspective view illustrating the arrangement of the various components of the invention;

FIGURE 2 is a side elevational view taken along the axis of FIGURE 1;

FIGURE 3 is a fragmentary sectional view of a modification including a lens board incorporating the various components of the invention;

FIGURE 4 is a view similar to FIGURE 3 but additionally showing the production of an image by the components of the lens board;

FIGURE 5 is a View illustrating the manner of incorporating the lens board in a camera; and

FIGURE 6 is an elevational view showing the circular arrangement of the apertures in the lens board of FIG- URE 3.

This application is a continuation-in-part of my Patent No. 3,099,557, granted July 30, 1963, and entitled Optical System and Method for Making Corrected Color Separations.

As illustrated in the drawings FIGURES 1 and 2, this invention is adapted to be incorporated in a substantially conventional process color camera such as is commonly used for making three and four color process printing plates. In place of the customary lens board, however, I provide a panel 10 which is equipped with a multiple number of optical assemblies, indicated at 11, which are arranged in circular fashion about the normal optical axis 12.

Each one of the respective optical assemblies essentially comprises a lens 13, a spectral color filter 14, a

diaphragm or aperture control member 16, a shutter 17 and a reflecting system represented by mirror 18.

The lenses 13 are accurately matched and they are arranged and located so as to have common conjugate focal planes. Thus, the images of the copy 19 created by the respective lenses 13 will be precisely superimposed in the focal plane 21. Because the lenses are offset with respect to the normal optical axis 12, the mirrors 18 are provided to reflect the respective images to a common focal point in the plane 21. Only one such mirror is shown in the drawings to simplify the illustrations, but it will be understood that a similar mirror is included in each optical assembly.

As stated above each optical assembly also includes a spectral color filter. These filters are selected so as to embrace the gamut of the spectrum and each one will transmit light waves in a predetermined band thereof. Thus when the subject to be reproduced is viewed by the respective optical assemblies, a corresponding number of complete images, each in a diiferent selected wave band of the spectrum, will be created or projected in superimposed relation in the focal plane 21 of the camera.

In the drawings I have illustrated eight optical assemblies, with their respective filters, which number I have determined is adequate to produce high quality commercial reproductions. This is not to be taken as a limitation, however, because the number of optical. assemblies and filters used, and thus the number of selected the same pigments are used to make the reproductions.

1 others will have negative signs.

7 spectral color bands in which the subject is sensed or analyzed depends upon the number of primary, secondary and tertiary colors in the subject and/or the quality desired in the reproductions.

From the description thus far it will be apparent that when the subject to be reproduced is viewed by the respective optical assemblies, eight continuous tone images thereof are created, each in its respective wave band. However, because of the inability of commercial pigments to absorb and reflect light waves in the respective spectral 10 bands in their true values, it is necessary to modulate the intensity of the respective light images in order to compensate for this condition.

For example, a spot of solid red in the subject should reflect 100% of the light waves in the red band of the spectrum and, therefore, should be represented by a maximum light intensity at the corresponding area of the light image formed through the redfilter. Conversely, the same red spot should absorb 100% of the light waves in the green band of the spectrum and should be represented by a complete absence of light intensity at the corresponding area of the light image formed through the green filter. Such conditions are impossible to achieve, however, due to the inherent deficiencies of commercial pigments and in actual practice it Will be found that the red spot will be represented by somewhat less than the maximum intensity in the light image formed through the red filter. Moreover, instead of absorbing all of the light waves in the green band of the spectrum, a certain amount will be reflected and will be represented by a proportionate light intensity in the light image formed through the green filter.

Thus it will be evident that in order to obtain a true reproduction of the subject in its original colors, the

light intensity of the respective images must be modified control the light intensity of the respective images in accordance with predetermined intensity factors which are based on the reflectance absorbance characteristics of the actual pigments and paper to be used in making the reproductions. The method whereby these factors are determined is clearly described in the Patent 2,567,240 and,

therefore, reference may be had thereto for a more complete explanation. It will be understood, however, that the required information is derived directly from a color chart made from the actual pigments to be used in making the reproduction and which chart comprises the solid primary and secondary colors, as Well as black and white.

Once the factors have been determined for a given set i of pigments the respective diaphragms 16 can be set accordingly and these settings will remain fixed as long as for some reason-it becomes necessary to utilize different pigments, having different reflectivity characteristics, new intensity factors can readily be determined and the diaphragms or apertures modified accordingly.

Having thus described the various elements involved 13 in the present invention, the method whereby they are utilized to make corrected color separation transparencies will now be explained. It is first necessary to determine the intensity factors for the respective spectral color bands for each particular primary color separation to be made. It will be appreciated that these factors will be different for each particular primary color separation. For example, the red or magenta separation will require one group of settings, the yellow separation, another group of settings, etc.

This is done in the manner described in Patent 2,5 67,240 from a color chart made from the actual pigments to be used in making the reproductions and as evident there from some of the factors will have positive signs whereas Once these factors have been determined the respective apertures are set for the particular primary color separation to be made, which, for the sake of example, we will consider as the red separation.

At this point, the shutters 17 for those spectral color bands which have been determined to have negative sign intensity factors are opened, whereas the shutters for those spectral color bands which have positive sign intensity factors are closed. A panchromatic film 22 is placed in the camera with its emulsion side facing away from the lens board 10 and in the focal plane 21. The copy 19 is then illuminated by a suitable light source 23 and the film 22 exposed to the combined overall intensities of the light images formed in the spectral color bands having negative sign factors. The length of the exposure will depend upon the film speed and will be relatively standardized.

After exposure, the film 22 is removed from the camera and developed to provide a mask, the overall density of which is equivalent to the combined intensities of the negative sign images. This mask is then replaced in the camera in its original position.

At the stage of the process the shutters for the negative sign images are closed and those for the positive sign images are opened and a panchromatic photosensitive transparency or film 24 is placed in the camera with its emulsion side facing the lens board lit and preferably in close contact with the adjacent surface of the mask 22.

Thereupon the copy T19 is again illuminated whereby to expose the film 24 to the combined intensities of the positive sign images, through the mask 22. The latter has the effect of reducing the overall intensity of'the combined positive sign light images by an amount equivalent to the combined intensities of the negative sign images so that, upon development, the overall density of the film 24 represents a fully corrected primary color separation, red in this instance.

The same procedure will be followed in making the other primary color separations, i.e., yellow, blue and also black, requiring only that the aperture settings be readjusted accordingly for each color separation.

Having thus described my invention in its simplest form it will be evident that various modifications may readily be made and therefore I do not Wish to be limited to the specific disclosure.

For example any onerof several means may be utilized to control the aperture settings such as adjustable iris type diphragms or plates having fixed apertures which would be interchangeable depending upon specific requirements. Moreover, the particular type of filters used is not critical, the only requirement being that they be capable of maximum light transmission within relatively narrow spectral bands.

The optical systems also may be as shown or it may comprise a single objective lens in combination with suitable refiecting prisms and mirrors whereby the original beam is split into its selected spectral components then recombined in one composite image. g

It will also be evident that the masking operations may be accomplished in a manner other than that described herein. As an example, the silver emulsion mask may be replaced by a special type of light sensitive emulsion having a much slower speed than silver, such as can be reproduced with certain azo dyes, and which would become opaque in relation to exposure. In such case the special emulsion would be exposed to the combined light intensities of the negative sign light images and would produce a mask without special development. Then a silver emulsion could be exposed to the combined intensities of the positive sign images, through said mask and because of the relatively high speed of the silver emulsion, this second exposure would not change the characteristics of the mask. The silver emulsion, upon development, would constitute the corrected primary color separation transparency.

' In the modification shown in FIGURES 3. to 6, inclusive, the lens board is indicated inits entirety by the numeral and said lens board is provided with a single lens 31. The said lens 31 is employed in a manner to produce the several light images of the object 32 in the same focal plane 33, each image being superimposed on the others as previously described. A pair of diaphragmfilter discs 34 and 35 are fitted into openings 36 in the lens board and on respective sides of the lens 31. Each disc is properly aligned with the lens and oriented by the pins 37.

Each disc 34 and 35 is formed with a plurality of apertures 38 angularly spaced an equal distance and located around the periphery of the disc. For illustration purposes, eight of such apertures 38 are shown, FIG- URE 6, for producing eight continuous tone images in selected spectral color bands as determined by one plus the number of primary, secondary and tertiary colors used to reproduce the original. For the disc 34 a diaphragm type shutter 40 is located in each of the apertures 38. For the other disc 35 a filter such as 41 is located in each of the apertures and as described the filters are selected so as to embrace the gamut of the spectrum, and each one will transmit light waves in a predetermined band thereof.

Accordingly when the lens board 30 is employed in a camera such as 42 in FIGURE 5, the object 32 will be viewed by the respective spectral assemblies and a corresponding number of complete images, each in a different selected wave band of the spectrum, will be created and projected in superimposed relation in the focal plane of the camera containing the film 43.

In operation, the lens board functions substantially the same as described for the apparatus of FIGURES l and 2. The diaphragm shutters 40 are set for an aperture opening so as to control the light intensity of the respective images in accordance with the intensity factors as determined by the method disclosed in Patent 2,567,240. Some of these intensity factors will have a positive sign and others will have a negative sign. For producing the mask, the shutters for the spectral color bands having positive sign intensity factors will be closed, and an exposure is made of the superimposed images of the negative sign spectral color bands. For the next operation the shutters for the spectral color bands having negative sign factors are closed and those for the positive sign factors are Opened. A second exposure is now made of the combined intensity of the positive sign images through the mask and upon development of the exposed film a fully corrected, primary color separation is obtained.

After the diaphragm-type shutters 40 have been set for their particular intensity factor, it is not desirable to close and then reopen them to their setting. Accordingly an additional diaphragm shutter or control member may be located in advance of each of the devices 4d and which would be fully closed or fully opened during operation. Thus the shutters 40 could be respectively set for the various intensity factors and it would not be necessary to change the same except when different pigments are used requiring different intensity factors.

The invention is not to be limited to or by details of construction of the particular embodiment thereof illustrated by the drawings, as various other forms of the device will, of course, be apparent to those skilled in the art without departing from the spirit of the invention or the scope of the claims.

What is claimed is:

1. Apparatus for producing corrected, primary color separation transparencies or the like directly from a multicolor subject comprising, a multiple number of optical assemblies, each including a color separating element, for creating a corresponding number of light images of the subject in selected spectral color bands, said optical assemblies having common conjugate focal planes wherein the respective light images are superimposed, means associated with each optical assembly for controlling the overall intensity of the respective light images in accordance with predetermined intensity factors, and selectively operable means for controlling the projection of the respective images in predetermined selected groups.

2. Apparatus for producing corrected, primary color separation transparencies or the like directly from a multicolor subject comprising, a multiple number of radially disposed optical assemblies each having a spectral color filter associated therewith for creating a corresponding number of light images of the subject in selected spectral color bands, said optical assemblies having common conjugate focal planes wherein the respective light images are superimposed, a diaphragm associated with each opti cal assembly for controlling the overall intensity of the respective images in accordance with predetermined intensity factors, and a selectively operable shutter for each optical assembly for restricting the projection of said images at any given time to selected groups thereof in accordance with the requirements of the particular color separations to be made.

3. Apparatus for producing primary color separation transparencies or the like comprising, a light source for illuminating the subject to be reproduced, light dispersion means for separating the light emitted from said subject into a plurality of selected spectral color bands, an optical system for creating a light image of the subject in each one of said selected spectral color bands, said optical systems having common conjugate focal planes wherein the multiple images of the subject are superimposed, and means for controlling the overall intensities of the respec tive images.

4. Apparatus for producing primary color separation transparencies or the like comprising, a light source for illuminating the subject to be reproduced, light dispersion means for separating the light emitted from said subject into a plurality of selected spectral color bands, an optical system for creating a light image of the subject in each one of said selected spectral color bands, said optical systems having common conjugate focal planes wherein the multiple images of the subject are superimposed, means for controlling the overall intensities of the respec tive images in accordance with predetermined intensity factors having negative and positive signs, and means for successively exposing photosensitive elements to the combined intensities of selected positive and negative sign groups of said light images.

5. Apparatus for producing primary color separation transparencies from an original subject, comprising a light source for illuminating the subject to be reproduced, light dispersion means for separating the light emitted from said subject into N number of selected spectral color bands where N is equal to one plus the number of primary, secondary and tertiary colors used to reproduce the original subject, an optical system in associated relation with said light dispersion means for creating a light image of the subject in each one of said selected spectral color bands, said optical systems having common conjugate focal planes wherein the multiple images of the subject are superimposed, means for controlling the overall intensities of the respective images in accordance with predetermined intensity factors having negative and positive signs, and other means for successively exposing photosensitive elements to the combined intensities of selected positive and negative sign groups of said light images.

6. Apparatus for producing primary color separation transparencies from an original subject as defined by claim 5, wherein the optical system for creating a light image of the subject in each one of the N number of spectral color bands comprises a single lens disposed within a lens board and wherein said board is provided with N number of apertures angularly spaced and located around the periphery of the lens.

7. Apparatus for producing primary color separation transparencies from an original subject as defined by claim 5, wherein the optical system for creating a light image of the subject in each one of the N number of spectral color bands includes a single lens disposed within a lens board, wherein said board is provided with N number of apertures angularly spaced and located around the periphery of the lens, and wherein the means for controlling the overall intensities of the respective images comprises diaphragm mechanism associated with each aperture and which is adjustable from a fully closed to a fully open position.

8. Apparatus for producing primary color separation transparencies from an original subject, comprising a light source for illuminating the subject to be reproduced, a lens board, a single lens retained by the board, said board References Cited in the file of this patent UNITED STATES PATENTS 2,474,958 Richards July 5, 1949 2,605,181 Alexander et al July 29, 1952 2,736,229 Huebner Feb. 28, 1956

Claims (1)

1. APPARATUS FOR PRODUCING CORRECTED, PRIMARY COLOR SEPARATION TRANSPARENCIES OR THE LIKE DIRECTLY FROM A MULTICOLOR SUBJECT COMPRISING, A MULTIPLE NUMBER OF OPTICAL ASSEMBLIES, EACH INCLUDING A COLOR SEPARATING ELEMENT, FOR CREATING A CORRESPONDING NUMBER OF LIGHT IMAGES OF THE SUBJECT IN SELECTED SPECTRAL COLOR BANDS, SAID OPTICAL ASSEMBLIES HAVING COMMON CONJUGATE FOCAL PLANES WHEREIN THE RESPECTIVE LIGHT IMAGES ARE SUPERIMPOSED, MEANS ASSOCIATED WITH EACH OPTICAL ASSEMBLY FOR CONTROLLING THE OVERALL INTENSITY OF THE RESPECTIVE LIGHT IMAGES IN ACCORDANCE WITH PREDETERMINED INTENSITY FACTORS, AND SELECTIVELY OPERABLE MEANS FOR CONTROLLING THE PROJECTION OF THE RESPECTIVE IMAGES IN PREDETERMINED SELECTED GROUPS.

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