US3292486A - Apparatus for reversing colour images - Google Patents

Apparatus for reversing colour images Download PDF

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Publication number
US3292486A
US3292486A US327939A US32793963A US3292486A US 3292486 A US3292486 A US 3292486A US 327939 A US327939 A US 327939A US 32793963 A US32793963 A US 32793963A US 3292486 A US3292486 A US 3292486A
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United States
Prior art keywords
colour
image
images
powder
photographic
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Expired - Lifetime
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US327939A
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English (en)
Inventor
Mey Hansjuerg
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Gretag AG
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Gretag AG
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G13/00—Electrographic processes using a charge pattern
    • G03G13/01—Electrographic processes using a charge pattern for multicoloured copies
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/01—Apparatus for electrographic processes using a charge pattern for producing multicoloured copies
    • G03G15/0142—Structure of complete machines
    • G03G15/0147—Structure of complete machines using a single reusable electrographic recording member
    • G03G15/0152—Structure of complete machines using a single reusable electrographic recording member onto which the monocolour toner images are superposed before common transfer from the recording member
    • G03G15/0163—Structure of complete machines using a single reusable electrographic recording member onto which the monocolour toner images are superposed before common transfer from the recording member primary transfer to the final recording medium
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
    • G03G5/12—Recording members for multicolour processes

Definitions

  • Methods of and apparatus for reversing colour images are used particularly for judging colour negatives or for printing and enlarging colour diapositives on normal colour negative material.
  • Proposed methods of image reversal are for example infrared extinction or a television type of splitting and reproduction of the image in fine lots by means of electric signal reversal. While the first-mentioned method is not suitable for the reversal of coloured images, the second-mentioned method is extremely expensive. Instruments working on theelectric signal reversal principle have already been built. These instruments have a colour television screen (monitor) on which an image can be produced which corresponds to the picture to be expected subsequently on paper. The extremely great expenditure for electronic equipment however prevents wider application of such instruments.
  • the present invention proposes to use xerographic means for the reversal of colour images.
  • Xerography is in itself known generally.
  • This method of reproduction consist essentially in that the image to be copied is projected onto an electrostatically charged photographic semiconductor layer and the latter then has a likewise electrostatically charged coloured powder strewn over it. Since the individual parts of the photographic semiconductor layer are charged to a greater or lesser extent in accordance with their exposure (lighttime integral) more or less powder remains adhering to the various parts of the surface.
  • a reversed powder image of the original to be printed can be obtained on the plate.
  • this powder image is then transferred to a sheet of paper.
  • the sheet of paper is placed on the plate and electrically charged to constitute an image-former.
  • the powder attracted by the charged paper is then fixed by a heating process.
  • a method of reversing colour images comprising the steps of producing optical colour separations of a colour image, producing xerographic reversed images from said colour separations, and reproducing these xerographic partial images superimposed on one another and in correct register.
  • colour images as employed in this specification is to be understood to include both negatives and positives.
  • the present method therefore starts with reversed images which can be produced on a photographic semiconductor layer.
  • the semiconductor layer may be sensitised for a determined spectral range, or in the case of panchromatism may be restricted by means of filters to a determined spectral range.
  • the effect may be achieved that the photographic semiconductor layer will be influenced practically only by a single colour layer in the negative film; the positive obtained by powder development is then a colour separation positive of the colour negative original.
  • the powder image is a colour separation negative of the colour positive original.
  • the xerographic partial images could be projected with colourless light.
  • blackand-white positives of the coloured negative original would be obtained.
  • the colour of the projection light is so selected that this colour coincides at least approximately with the primary colour of the light which was used to obtain this partial image.
  • the xerographic partial image corresponding to the yellow separation of the negative will be projected with blue light
  • the partial image corresponding to the magenta separation will be projected with green light
  • the partial image corresponding to the blue-green separation will be projected with red light. This will produce a positive colour image of the negative original capable, for example, of being made visible on a ground glass screen and used for judging the picture.
  • a modification of the present method consists in that in the reversal of colour positives the xerographic partial images are projected with correct register onto colour negative material. Negative material exposed in this manner can then be developed into a positive of a positive original.
  • the powder image is transferred to a paper carrier and fixed on the latter by fusing or the like. Resolution losses naturally occur when this is done.
  • this disadvantage may be avoided by carrying out the reversal process on powder lying loose on the photographic semi-conducting layer.
  • the powder images to be projected therefore need neither be transferred to a paper carrier or the like, nor fixed.
  • the powder can easily be removed from the semiconductor layer, so that not only the same semiconductor layer but also the same powder can be repeatedly re-used.
  • apparatus for reversing a colour image comprising a light source for illuminating the colour image, an optical system comprising a plurality of light splitters for separately projecting a respective colour separation of the colour image, an electrostatically chargeable photographic semiconductor layer constituting an image plane for each of said colour separations, means for electi'ostatically charging said layer, means for developing a reversed xerographic partial image on said layer, and means for projecting into a second image plane said partial images of the individual colour separations superimposed on one another and in correct register.
  • Dichroic mirrors are preferably used as light splitters. However, semi-transparent mirrors followed by colour separation filters may also be used.
  • the apparatus includes a white light source 1 arranged to illuminate through a condenser system 2 a colour picture 3a (colour negative or colour positive) which is disposed in a plane 3, and which in the present case is transparent, so as to reproduce the picture through an objective 5.
  • the path of the image-forming rays runs through a first dichroic mirror 6, which for example reflects the blue light fraction up to a wavelength of 500 m but on the other hand allows the green and red light fractions to pass.
  • the light rays passing through the mirror 6 pass on to a second dichroic mirror 7, which reflects for example the green light fractions up to a wavelength of 600 m so-that finally only the red light fractions above 600 mu impinge on an ordinary surface-coated mirror 9.
  • a deviating mirror 12 reflects the blue light fractions onto the plane of the image, whereby a sharp delineation of the picture original 3a disposed in the plane 3 is produced in region 16.
  • an image is formed in region 14 with the green light fractions through a deviating mirror 8 and in region 15 with the red light fraction through a deviating mirror 10.
  • the arrangement, particularly the adjustment of the mirror systems 67912-810 is so disposed that the three partial images of the single picture original 3a disposed in the plane 3 lie in the same image plane.
  • the two dichroic mirrors 6 and 7 together form a light splitter, which divides roughly into three spectral ranges the light from the lamp 1 after it has been coloured by the picture original.
  • Finer adaptation of the three light fractions to the spectral absorption of the picture original 3a is achieved with three colour filters, each of which is inserted into one image ray path: a green filter 28, a red filter 29, and a blue filter 30. These three filters are grouped together in a common filterplate 11.
  • the three images produced in the regions 14, 15 and 16 are therefore the colour separations of the colour picture original disposed in the plane 3, which are to be reversed with the aid of xerographic means.
  • the image plane consists of a photographic semi-conducting layer 13 provided on a conducting carrier, for example a zinc oxide layer on an aluminium foil.
  • the photographic semiconducting layer 13 is sensitised for the entire spectrum utilised, that is to say the spectrum determined by all three negative or positive absorptions of the picture original.
  • the carrier is an endless flexible band 17 of conducting material, which is guided around at least two guide rollers 19 and 20 and on the outer side of which the photographic semiconducting layer 13 is provided, at least one of the guide rollers 19, 20 being adapted to be driven mechanically.
  • the band 17 or the photographic semiconducting layer 13 provided on said band passes beneath a charging device before entering the projection zone.
  • This charging device consists of a corona discharge device 21, which is fed by a high tension source 22, while the carrier band 17 is earthed through the guide roller 19.
  • a developer slide 23 slidable on rails 27 is provided, and is equipped with a magnetic brush of known type, formed by a magnetised roller 24.
  • the slide 23 can be moved over the semiconductor layer 13 from the right-hand position shown in the drawing, in which it is situated above a container 25 holding developer powder and open at the top.
  • the roller 24 can be rotated. In the position shown in the drawing the rotating roller 24 withdraws developer powder from the container 25, said powder accumulating on the periphery of the roller or on iron powder particles situated there, thus being charged by triboelectrical effect. If the slide 23 is now guided above the photographic semiconductor layer 13, with the periphery of the roller 24 almost in contact with said layer, the individual parts of the surface of the photographic semiconductor layer attract more or less developer powder in accordance with their condition of charge.
  • the arrangement is such that the image forming system for the xerographic images lies in the reciprocal ray path of the image forming systems 5, 6, 7, 9, 12, 8 and 10 of the colour original.
  • the light source can also be used, after removal of the picture original 3a, for projecting the xerographic partial images.
  • the necessary beam splitting can be achieved by disposing a semi-transparent deviating mirror 4 between the image forming optical system 5 and the light source 1. Consequently a part of the light from the light source 1 which is remitted from the xerographic images passes into the image plane 31.
  • the mirror 4 is preferably removed from the ray path.
  • Increased remission of the powder images into the solid angle utilisable for their projection is achieved by forming the photographic semiconductor layer 13 of transparent, preferably optically clear material, while the carrier surface facing the photographic semiconductor layer 13 either has a surface reflecting at the restricted solid angle, or this surface of the carrier is formed by a retroflective material which reflects. in itself the impinging light rays.
  • the carrier used may be a film which is coated at least on the side carrying the photographic semiconductor layer with a conductive transparent coating.
  • Another possible way of projecting the powder images with a separate source of light consists of a dark field arrangement, in which the projection light source is disposed laterally and .only slightly above the powder images.
  • the projection light source is disposed laterally and .only slightly above the powder images.
  • the projection light rays are reflected away out of the angular range of the image forming optical system, While the image parts coated with powder produce stray light which falls intothe angular range used and iscollected by the objective 5.
  • the reversal of a colour negative takes place for example in the following mannerz'
  • the band, 17 coated on its outer side with ithe photographic semiconductor layer 13 is moved in the direction of the arrow 18 such a distance that the portions of the band which at the beginning of the movement are. situated above the roller 19 located on the left in the drawing come to lie over the right-hand roller 20.
  • the photographic semiconductor layer is moved past under the corona discharge device 21 which is switched on at the commencement of the movement, so that at the end of themovement of the band the entire region of the photographic semiconductor layer 13 coming to lie in the image plane of the picture original is charged.
  • the separation negatives are now exposed onto the photographic semiconductor layer 13.
  • the developer slide 23 is then moved over the photographic semiconductor layer 13 (fromright to left in the drawing).
  • the latent electrostatic charge image is thereby developed into a powder image.
  • three positive powder images are left on the photographic semiconductor layer 13 in the regions 14, 15, and 16.
  • the negative (3a) is now pushed out of the path of the rays, so that the powder images are each homogeneously illuminated by the white light source 1 in their corresponding primary colours through the exposure optical system.
  • the light remitted by the powder images passes back through the same exposure optical system with reciprocal ray paths.
  • the plane 31 which is the same distance from the objective 5 as the negative plane 3, an additive mixing of the three positive powder images, each in its primary colour, is effected through the semi-transparent mirror 4, that is to say a coloured diapositive is formed.
  • the image plane 31, which is for example provided with a ground glass screen, is the viewing plane. Geometric distortions of the image-forming optical system are eliminated, since the path of the rays runs through the optical system in both directions if only the semiftransparent mirror 4 is optically fiat.
  • the visible positive is therefore a colorimetrically purely additive mixed product of the three colour separation positives.
  • the filter plate 11 with the filters 28, 29, and 30 should be replaced by a different filter disc with a new filter triplet for the projection of the positive, because the exposure filters 28, 29 and 30 are adjusted to the negative colorants and do not correspond to the additive primary colour conditions.
  • the filters 28, 29, 30 could be simply omitted in the positive projection, since the dichroic mirrors 6 and 7, which are passed through twice during the projection, in any case already produce primary colours similar to optimum colours, with the limits 500 and 600 m indicated as an example.
  • a correcting projection filter set for example ideal colour filters
  • the saturation of the colours may be increased, but only at the expense of their brightness.
  • the band carrying the photographic semiconductor layer is moved once again, as described above.
  • a photographic semiconductor layer homogeneously acted on by the corona discharge device is thereby brought into the image plane once again.
  • the powder which produced the previous xerographic images is swept off by a stationary brush 26 and drops into the storage container 25, where it restores to the normal value the remaining developer powder mixture.
  • a mixing device (not illustrated) ensures the homogeneity of the powder mixture, which is thus ready for the next development.
  • the effect is achieved that a fresh semiconductor layer is always available for exposure. This is important inasmuch as a layer one exposed will return to its state of rest only after a certain time, this being known as dark adaptation.
  • the endless band may also be guided over more than two guide rollers. The mean utilisation time of the same part of the layer is thereby reduced and the rest time increased.
  • the image can be exposed through a mosaic screen, in which case the gradation can be varied within wide limits by means of control diaphragms in the case of optical mosaic screening.
  • An improvement in the half-tone properties can also be achieved by projecting not merely three images, but for example three images for each primary colour, that is to say a total of nine images, the partial images of each primary colour being exposed with an increasing light-time integral.
  • the additive superimposition of these individual images gives a variable gradation with better half-tone properties.
  • the present image reversal process may be carried out both by using black powder and white photographic semiconductor material, and by using white powder and black photographic semiconductor material.
  • the polarity of powder and plate should be the same in the first case, and opposite to one another in the second case.
  • Zinc oxide which has previously been mentioned, amorphous selenium, or the like may be used as photo graphic semiconductor materials.
  • Apparatus for reversing a colour image comprising a light source for illuminating the colour image, an optical system comprising a plurality of light splitters for sep arately projecting a respective colour separation of the colour image, an electrostatically chargeable photographic semiconductor layer constituting an image plane for each of said colour separations, means for electrostatically charging said layer, means for developing a reversed Xerographic partial image on said layer and means for projecting into a second image plane said partial images of the individual colour separations superimposed on one another and in correct register.
  • Apparatus for reversing a colour image comprising a light source for illuminating the colour image, an optical system comprising a plurality of light splitters for separately projecting a respective colour separation of the colour image, filter means insertable into the light paths of said colour separations, an endless flexible band of conducting carrier material, at least two guide rollers over which said band is guided, an electrostatically chargeable photographic semiconductor layer disposed on the outside of said band and arranged to constitute a common image plane for all said colour separations, means for driving at least one of said guide rollers mechanically, an electrostatic charging device for charging said layer as the latter passes under the device, a developer slide movable over said layer to develop a reversed xerographic partial image thereon, and means for projecting into a second image plane said partial images of the individual colour separations superimposed on one another and in correct register.
  • the surface of the carrier is formed by a retroflective material which at least substantially reflects in itself impinging light rays.
  • Apparatus for reversing a colour image comprising a light source for illuminating the colour image, an optical system comprising a plurality of light splitters for separately projecting a respective colour separation of the colour image, an electrostatically chargeable optically transparent photographic semiconductor layer constituting an image plane for each of said colour separations, means for electrostatically charging said layer, means for developing a reversed xerographic partial image on said layer, a semi-transparent deviating mirror interposable between the image-forming optical system for the colour image and said light source, at least one projection light source disposed beneath the layer and an imageforming optical system for the xerographic partial images lying in the reciprocal path of the image forming optical system for the colour image, whereby said partial images can be reproduced superimposed on one another and in correct register.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Color Electrophotography (AREA)
  • Overhead Projectors And Projection Screens (AREA)
US327939A 1962-12-07 1963-12-04 Apparatus for reversing colour images Expired - Lifetime US3292486A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH1441962A CH453891A (de) 1962-12-07 1962-12-07 Verfahren und Einrichtung zur Umkehr von Farbbildern

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US3292486A true US3292486A (en) 1966-12-20

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US327939A Expired - Lifetime US3292486A (en) 1962-12-07 1963-12-04 Apparatus for reversing colour images

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US (1) US3292486A (ja)
BE (1) BE640915A (ja)
CH (1) CH453891A (ja)
GB (1) GB1029078A (ja)
NL (1) NL301478A (ja)
SE (1) SE309535B (ja)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3601484A (en) * 1970-06-19 1971-08-24 Minnesota Mining & Mfg Color copying apparatus
US3690756A (en) * 1971-03-22 1972-09-12 Xerox Corp Color xerography
US3756718A (en) * 1972-03-29 1973-09-04 Eastman Kodak Co Color printer
US3769884A (en) * 1972-04-24 1973-11-06 T Sigman Photolettering apparatus
US3795917A (en) * 1969-05-22 1974-03-05 Canon Kk Electronic photocopying apparatus
US3801198A (en) * 1968-12-23 1974-04-02 Logabax Apparatus for automatic half-tone (direct-screen) or continuous tone colour separation work in photomechanical reproduction
US4027962A (en) * 1975-01-13 1977-06-07 Xerox Corporation Color transparency reproducing machine
US5303003A (en) * 1992-02-06 1994-04-12 Eastman Kodak Company Color transparency having toner images transferred to both sides and method of making

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4669811A (en) * 1983-11-17 1987-06-02 Pilkington P.E. Limited Optical filtering apparatus
JPS60181710A (ja) * 1984-02-29 1985-09-17 Fujikura Ltd 光信号の合・分波器
JPH07234501A (ja) * 1994-02-22 1995-09-05 Matsushita Electric Ind Co Ltd 色分解装置およびカラー画像読取装置

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2986466A (en) * 1955-12-06 1961-05-30 Edward K Kaprelian Color electrophotography
US3121375A (en) * 1962-03-16 1964-02-18 Horizons Inc Method and apparatus for copying
US3215030A (en) * 1961-11-30 1965-11-02 Time Inc Color print simulator

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2986466A (en) * 1955-12-06 1961-05-30 Edward K Kaprelian Color electrophotography
US3215030A (en) * 1961-11-30 1965-11-02 Time Inc Color print simulator
US3121375A (en) * 1962-03-16 1964-02-18 Horizons Inc Method and apparatus for copying

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3801198A (en) * 1968-12-23 1974-04-02 Logabax Apparatus for automatic half-tone (direct-screen) or continuous tone colour separation work in photomechanical reproduction
US3795917A (en) * 1969-05-22 1974-03-05 Canon Kk Electronic photocopying apparatus
US3601484A (en) * 1970-06-19 1971-08-24 Minnesota Mining & Mfg Color copying apparatus
US3690756A (en) * 1971-03-22 1972-09-12 Xerox Corp Color xerography
US3756718A (en) * 1972-03-29 1973-09-04 Eastman Kodak Co Color printer
US3769884A (en) * 1972-04-24 1973-11-06 T Sigman Photolettering apparatus
US4027962A (en) * 1975-01-13 1977-06-07 Xerox Corporation Color transparency reproducing machine
US4068939A (en) * 1975-01-13 1978-01-17 Xerox Corporation Color transparency reproducing machine
US5303003A (en) * 1992-02-06 1994-04-12 Eastman Kodak Company Color transparency having toner images transferred to both sides and method of making

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NL301478A (ja)
CH453891A (de) 1968-03-31
GB1029078A (en) 1966-05-11
SE309535B (ja) 1969-03-24
BE640915A (ja)

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