US3197558A - Process for the reproduction of continuous tone pictures - Google Patents

Process for the reproduction of continuous tone pictures Download PDF

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Publication number
US3197558A
US3197558A US110598A US11059861A US3197558A US 3197558 A US3197558 A US 3197558A US 110598 A US110598 A US 110598A US 11059861 A US11059861 A US 11059861A US 3197558 A US3197558 A US 3197558A
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dots
picture
reproduced
tone
block
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US110598A
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Ernst Marc Henri Marie
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/46—Colour picture communication systems
    • H04N1/56—Processing of colour picture signals
    • H04N1/60—Colour correction or control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/024—Details of scanning heads ; Means for illuminating the original
    • H04N1/032—Details of scanning heads ; Means for illuminating the original for picture information reproduction
    • H04N1/036—Details of scanning heads ; Means for illuminating the original for picture information reproduction for optical reproduction
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/40—Picture signal circuits
    • H04N1/405—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels
    • H04N1/4051—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels producing a dispersed dots halftone pattern, the dots having substantially the same size
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/40—Picture signal circuits
    • H04N1/405—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels
    • H04N1/4055—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels producing a clustered dots or a size modulated halftone pattern

Definitions

  • This invention relates to a process for the reproduction of continuous tone pictures by means of juxtaposed dots forming a half-tone screen.
  • Process-engraving is a known process for the reproduction by printing of the type indicated above. it utilises process blocks in which the image is formed by a pattern or screen of equidistant dots, the blocks being generally obtained by photo-engraving. in tln's known process local variations of tone of the picture to be reproduced are represented by corresponding variations in the dimensions of equidistant dots of the screen. It presents numerous disadvantages.
  • the process according to the present invention is liliewise of the above-mentioned type but it has none of the disadvantages of process-engraving. it is characterized by the fact that local variations ⁇ of tone of the picture to be reproduced are represented by variations in the mutual distances between the dots forming the screen.
  • the dots can also vary in size.
  • the process according to the invention has a wider application than process-engraving. ln fact it not only allows the reproduction of continuous tone pictures in the form of a screened block of the same kind as, but of diierent structure from those obtained by photo-engraving, but it also makes it possible to reproduce a continuous tone picture in the form of a luminous screened picture, for example a fluorescent screened picture of the same kind as pictures formed of iuorescent screens used in cathode tubes, in radioscopy etc., but having a screened structure.
  • Luminous pictures for example fluorescent pictures
  • the process is thus applicable in particular to television, and especially to the additive process of colour teievision.
  • the invention likewise extends to apparatus for carrying out the reproduction process according to the present invention and includes apparatus for obtaining screened printing blocks, apparatus for the distant transmission of photographs, and finally apparatus for the production of luminous, screened pictures, for example television pictures.
  • FIG. l shows the various continuous tones which can be reproduced by process-engraving and bythe process according to the invention
  • FIG. 2 is a diagram intended t-o facilitate the setting out of the general principle of the invention
  • FIG. 3 is a block diagram of one embodiment of an apparatus according to the invention for the reproduction of a continuous tone picture in the form of a screened block;
  • FIG. 4 is a block diagram of one embodiment of a television installation according to the invention.
  • FIG. 5 shows diagrammatically one embodiment of the main electrical circuits of the apparatus of FIG. 3.
  • a represents the range of continuous tones which can be theoretically reproduced by the known process or" process-engraving.
  • This process utilises dots and spots which stand out against a lighter background. All the tones to be reproduced are represented by dots which are equidistant from one another but of different dimensions.
  • Dark grey (zone 3) can be reproduced by dots which are so close to one another as to be almost touching.
  • Black (zone 4) can be reproduced by dots which are of still larger dimensions and whichpartially overlap.
  • Medium grey (zone 2) and light grey (zone il) can be reproduced by dots which are of smalier dimensions but still the same distance apart.
  • Strip b of FIG. l shows the tonal range effectively reproduced by printing by means or a block on which the continuous tones ot the picture have been represented in accordance with the range a of FiG. l.
  • the dots of zone 2 of FIG. l are the only ones that retain their correct dimensions when printed (zone 2'). The dots ofthe other zones do not retain their proper size when printed.
  • Printing has the eliect of reducing the size of those dots which are smaller than the dots of the preferential zone 2, as shown for example by a comparison of the sizes of the dots of zones l and l of a and b, FIG. l, which corresponds to light grey. Conversely, those dots which are larger than the dots of the preferential zone Z are enlarged.
  • This etiect tends to reduce the transverse dimensions of the deposited spot of ink.
  • the other effect which is of mechanical origin, results from the squashing of the spot of ink, due both to the pressure of the block on the printing support and the relative speed between the said printing support and the block, for example when the latter is carried on the cylinder of an offset printing press.
  • This squashing effect naturally tends to increase the transverse dimensions of the spot of ink.
  • the worst effect in the print of the change in the dimensions of the dots of the block is that a certain number of dark grey zones, such as 3, in the range of reproagar/,ess
  • Retouching is of course very fine work and is consequently time-consuming and costly, since it can only be carried out by hand by highly skilled Workmen. This disadvantage is especially serious in the case of the reproduction of pictures in colours by colour photography.
  • the three-colour process utilises four screened blocks obtained by photographing the picture through complementary colour iilters. Each of the four blocks requires special retouching, but the retouching work carried out on each block must take into account the retouching work carried out on the other three, and this particularly complicates the work.
  • the corresponding printed dots ⁇ will also be all of the same size, although the printed dots may differ in size from the dots of the block, in consequence of the inaccurate tone rendering of the printing process, as explained above.
  • the dots of the block may be given the preferential dimensions corresponding to the zones 2 and 2 of the strips a and b of FlG. l, so that the printed dots are exactly the same size as the corresponding dots of the block.
  • the dots which are to reproduce the dark grey areas of the picture can be so spaced that the corresponding printed dots do not overlap, and the corresponding Zone of the reproduced picture is then a true dark grey (zone 3) and not black (zone 3') as in the case of ordinary process-engraving.
  • This possibility results from the fact that the dots of the screen are all the same size, and consequently the tone rendering obtained in the print is uniform for the whole block.
  • the continuous tones of the picture can be reproduced with great fidelity and moreover, reproductions obtained by the process can have a great richness of tonal range, for example up to 15 or 20 shades of grey ranging between pure White and dark grey or black.
  • Another advantage of the process of reproduction according to the invention lies in the fact that the iineness of the reproduction is independent of the depth of tone of the reproduced areas, since the said neness depends only on the dimensions of the dots of the screen, and since the latter are identical for all the reproduced tones. Thus by choosing dots of sufficiently small dimensions, all the details included in the medium grey areas and the dark grey areas of the continuous tone picture can always be reproduced.
  • the essential advantage of the process according to the invention lies in the fact that owing to the uniformity of the tone rendering obtainable in the print retouching of the blocks which is essential in the case of process-engraving is no longer necessary, since the risk of reproducing a dark grey area of the picture by a black of darker area is removed.
  • Another advantage lies in the fact that complementary screened blocks obtained by the process according to the invention do not possess a repeating structure since the dots of their screens are not equidistant. Watering defects are thus avoided without having to take into account the relative orientations of the screens of the different blocks.
  • local tone variations of the picture to be reproduced are made to correspond to the corresponding variations not only in the mutual distances between the dots of each line of the screen, but also the mutual distances between the lines of the screen.
  • the abscissas of the diagram represent the different values of the ratio of the dimension D of the dots of a zone of the block screen (for example their diameter if the dots are round) to the mutual distances d between the dots.
  • the ordinates of the diagram represent the diierent values of the density I of a zone of the reproduction. ln other words, every point on this diagram has an Ordinate which represents the density or" the resulting tone of a zone of the reproduced image formed by juxtaposed dots, the dimensions D of which bear a ratio to their mutual distances d equal to the abscissa or" the point in question.
  • the full line curve C corresponds to the range of tones represented by strip a of FIG. 1. lf the constant mutual distance between all the dots of an ordinary process-engraving screen is designated by do, the curve C extends from the point il having an abscissa Dm/do which corresponds to the lightest strip l of the strip a of FG. 1 (Dm being the diameter of the smallest technically obtainable dots of the block) to the point 4 having an abscissa 1 which corresponds to the black zone 4 of strip a formed by dots, the dimension D of which is substantially equal to the constant distance do, that is to say dots which touch or even slightly overlap.
  • the broken line curve C corresponds to the range of tones effectively obtained by printing, which is shown in strip b of FIG. 1.
  • this retouching operation which is intended to counteract the lack of uniformity of tone rendering of the print, is effected systematically. ln the preferred embodiment described above, the retouching operation is effected systematically, not by reducing the dimensions D of the dots of the screen, as in the case of retouching by hand in process-engraving, but on the contrary by maintaining constant the dimension D of the said dots and increasing the distance d between the dots so as to reduce the abscissa of the point M of the curve C sufficiently to bring it to the position N.
  • the process according to the invention consists in varying simultaneously the dimension D of the dots of the block scr en and their distance apart d in a co-ordinated manner so as to reduce the abscissa of the point M to the value of that of thc point N.
  • Process-engraving can thus be regarded as a particular case of the general process according to the invention in which the distance d between the dots of the screen is maintained at a constant value do.
  • the preferred embodiment of the invention shown in strip c of FIG. l corresponds to the symmetrical case of process-engraving in which the dimension D of the dots of the screen is maintained constant but the distance d between the dots, at least in each line of the screen, is caused to vary.
  • the process according to the present invention only utilises the simultaneous and co-ordinated variations of the dimensions of the dots of the screen and the distance between them, in the case of relatively dark tones, that is to say tones corresponding to densities I of a value relatively near to 1, so as to facilitate the reproduction of very dark tones and ilat tones.
  • relatively dark tones that is to say tones corresponding to densities I of a value relatively near to 1, so as to facilitate the reproduction of very dark tones and ilat tones.
  • the dimensions of the dots of the screen will be maintained constant and preferably equal to the preferential dimensions for which the dots of the block are reproducedin the print Without change of dimensions.
  • the apparatus according to the invention for the reproduction of a continuous tone picture in the form of a screened block consists essentially of a light source 5 from which by means of a suitable optical system 6 a parallel light beam is directed on to a point of Ithe continuous tone picture 7 which is to be reproduced, it being assumed that the picture is transparent.
  • the assembly 5 and 6 is stationary and the picture 7 is given a movement of translation in its place in such a way that every point is caused to pass successively through the light beam from the optical system 6.
  • the scanning of the surface of the picture 7 which is to be lreproduced can be effected in accordance with any law (rectilinear scanning, spiral scanning, etc).
  • the light beam transmitted through the transparent picture 7 is focussed by an optical system 6 on to a light-energy detector S, for example a photo-electric cell.
  • a light-energy detector S for example a photo-electric cell.
  • the picture 7 to be reproduced can be mainta-ined fixed, the assembly 5, 6, 6' and S being then displaced as a whole so as to scan every point on the surface of the picture.
  • the continuous electrical signal from the photoelectric cell 8 passes through adjustable corrector circuits 9, 9 and 9 each of which has the efrect of modiying t-he instantaneous amplitude of the signal in accordance with a predetermined law, but is capable of being P7 e adjusted and the precise functions of the said circuits will be described in detail below.
  • the continuous signal thus corrected actuates an electrical pulse generator l@ so as to modulate the recurrence frequency and amplitude of the pulses which it produces, in accordance with its own variations -o-f amplitude, through connections liti and lll respectively.
  • the said generator itl procures a series of electrical pulses, of which on the one hand the recurlrence periods, that is to say the time intervals between successive pulses of the series, vary for example in accordance with the law of variation of the amplitude of the continuous signal supplied by the cell 8, that is to sa, precisely in accordance with the law of variation of the tone along the line scanned during the time interval in question.
  • the amplitudes of the electrical pulses of the said lseries are likewise modulated, but in accordance with a law which is inverse to the law of the variations of tone along the corresponding line of the picture to be reproduced.
  • the light areas of the picture will be represented by series of pulses which are widely spaced from one another and the amplitudes of which will be relatively small.
  • Dark areas of the picture on the other hand will be represented by series of fairly closely spaced pulses of relatively great amplitudes.
  • the electrical pulses from the generator it?, thus modulated, are used to energise a flashing lamp f2 through the intermediary of a control circuit lll.
  • the durations of the successive light flashes produced by the flashing lamp i2 are exactly equal to the durations of the successive electrical pulses produced by the generator on one hand, .and on the other hand the intensities of the light pulses are exactly proportional to the amplitudes of the said electrical pulses.
  • the light flashes emitted by the flashing lamp l2 are concentrated by an optical system i3 on to a sensitised surface 7 which is given a tmovement of translation in its plane in sync-hronism with the picture 7 to be reproduced, :as indicated diagrammatically by the broken line )ld which connects 7 to 7.
  • the modulation of the in-tensity of the successive flashes of the lamp l2 can be converted into variations of dimension of the spots produced on the sensitised surface, for example by inserting a filter ftd having a bellshaped absorption curve between the sensitised surface :and the lamp l2.
  • the filter which has not been shown, can consist for example of a substance having a uniform absorption coefficient, but the thickness of which increases from the centre towards the edges.
  • a screened block having uniformly spaced dots similar to that obtained by photo-engraving can be obtained.
  • a block 7 can be obtained, the screen of which is formed by non-equidistant dots which are all of the same dimensions, using ⁇ a preferred embodiment of the 1process according to the invention, which is shown in strip c of FIG. l.
  • the apparatus is arranged so that 4the continuous analysing signal which actuates the electrical pulse generator il@ through the connection itl can modulate the amplitude of the electrical pulses which it emits, only when its own ampli-tude is at least equal to a predetermined minimum value, having a threshold function, in
  • Orne of the circuits, for example circuit 9 makes it possible to improve the contrasts of the picture to be reproduced, if there is insufficient contrast, by modifying the law connecting the variations of continuous tone of the picture to be reproduced and the variations in the recurrence frequency, and possibly in the amplitude, of the electrical pulses emitted by lid.
  • Another circuit, for example circuit 9 compensates for variations in the dimensions of the dots of the screen which are produced during printing in such a way as to reduce the abscissa D/d of the point M on curve C of FlG.
  • an additional corrector circuit 9 makes it possible to correct the tones effectively recorded on the block 7 with a view to obtaining a better colour rendering of the pictures to be reproduced.
  • @ther corrector circuits could correct for cer-taindefects of the document to he reproduced, such as for example the presence of fogging, or a prevailing colour in the case of a coloured picture.
  • the apparatus shown diagrammatically in FlG. 3 is provided with an improvement consisting in a second light detector d', for example a photo-electric cell, to which a part of the light beam from the optical system o is deflected by a suitable device, for example a semi-reflecting mirror le.
  • the selection filter f7 corresponding to the fundamental tone of the block to be reproduced is inserted between lid and d.
  • a complementary colour selection filter i7 is inserted between le and d.
  • the continuous analysing signals from the photo-electric cells 8 and d respectively actuate the pulse generator l@ in opposite phase and with relative amplitudes controlled by means of the corrector circuits such as 9 and 9".
  • This device thus makes it possible to subtract from the intensity of the fundamental tone selected by the filter f7, the whole or at least part of the intensi-ty of the complementary tone which is generally superimposed on the said fundamental tone in the colour of the area of the picture which is analysed.
  • This correction has the same effect as the retouching operation known as masking which is currently carried out on screened colour blocks, and consequently renders such retouching operations unnecessary.
  • the electrical pulse generator l@ can be an asynchronous multi-vibrator, the recurrence frequency and possibly the amplitude of the pulses of which can be modulated by the continuous analysing signal owing to conventional arrangements.
  • the corrector circuits 9, 9 and 9" are capable of very varied embodiments, the most simple of which utilise potentiometric lay-outs.
  • the electrical pulse generator (itl in FIG. 3) is of the blocking oscillator type, ⁇ and is adapted to produce very short pulses of high recurrence frequency. It comprises essentially a multielectrode electronic tube 22, between the anode circuit and grid circuit of which a strongly reactive coupling is provided by a transformer 23. A condenser 2d is connected between the grid circuit of the tube 22 and its cathode (earthed in the example shown),
  • the tube 22 is linitially locked by the potential of the condenser 24 which is strongly negative in relation to earth, but it becomes conductive as soon as the condenser 24 has discharged suiciently through the cell 8 (which is made conduct-ive by the exploring light beam) for the control grid of the tube 22 to exceed its cut-oli potential.
  • a single pulse then appears in the anode circuit of the tube 22, the condenser 24 being immediately negatively recharged so as to again lock the tube 22.
  • the said pulses are fed to a third winding of the transformer 23, which transmits them t the cont-rol circuit 11 of the flashing lamp 12.
  • the purpose of the circuit 2S is to allow adjustment of the minimum value of light intensity to which the apparatus is sensitive (threshold of sensitivity). As it is merely a question of limiting the positive range of the grid potential of the tube 22, it is capable of numerous known embodiments which do not need to be described.
  • the circuit Z6 connected between the control grid of the tube 22 .and another grid of the said tube is intended to stabilise the cut-ofi potential of the tube so as t0 improve the linearity and the stability of its operation.
  • the reproduction apparatus shown in FIG. 3 is capable of numerous modifications.
  • the light source 5 can be replaced by a source of other radiant energy, for example an X-ray generating tube, 7 being in that case a body analysed by transparency by the beam of X- rays emitted by 5.
  • the apparatus has the valuable possibility of modifying the contrast of the picture 7 and has a function similar to .the known contrast intensifiers, the reproduced picture 7 however having a screened structure.
  • the dashing lamp 12 can emit flashes of radiant energy of any other kind, for eX- ample infra-red, ultra-violet or X-rays.
  • the device for analysing the picture 7, w-hich consists of the members 5, 6, 6 and S, can be replaced entirely by .a television camera.
  • the camera feeds a continuous electrical analysing signal directly to the corrector circuits and to the pulse generator and furnishes synchronising signals which can be used either for controlling the synchronous displacement of the sensitised surface 7 or for controlling the scanning of the electronic beam of a reproducing cathode ray tube which replaces the flashing lamp 12.
  • the block 7 can be obtained simply by photographing the fluorescent screen of the reproducing cathode ray tube.
  • FIG. 4 is a block diagram of a television installation according to the invention which comprises essentially a television camera 18 which produces a continuous signal for analysing the picture as well as synchronising signals. These signals are used .for modulating the carrier wave of suitable frequency emitted by a television transmitter 19.
  • the said carrier wave can be demodu-lated by a conventional television receiver 2.0, which could be placed a great distance from the transmitter 19.
  • the demod-ulated aualysing continuous signal energises the electrical pulse generator 10 as in the case of the apparatus of FIG. 3.
  • the electrical pulses emitted by 10 are used in the control circuit 11 to release the electronic beam of the cathode ray tube 21.
  • the spot width of the electronic beam can be modulated by the amplitudes of successive electrical pulses.
  • the cathode ray tube 21 receives directly from the television receiver 2t) signals which deflect its electronic beam.
  • the luminous picture which is formed on the fluorescent screen of the tube 21 has a screened structure according tothe invention.
  • the continuous analysing signal could directly energise the electrical pulse generator 1h accommodated in the transmitting station, the carrier wave being in this case modulated by the pulses produced by the generator lil.
  • the present invention also allows the production of television pictures in colour having a screened structure in accordance with the additive process. In this application the present invention has the advantage that watering defects are appreciably suppressed.
  • the reproduction of continuous tone pictures or documents by slow analysis as carried out by the apparatus of FIG. 3, can be effected at a distant station, without departing from the scope of the invention.
  • it is ⁇ only necessary to transmit, preferably by means of a carrier current or carrier waves of suitable frequency propagated through conductors or through an insulating medium, either the continuous signal for analysing the picture to be reproduced, or the electrical pulses emitted by the generator 10.
  • An apparatus for the reproduction of a continuous tone picture including a television camera, adapted to generate an electric video signal, the picture to be reproduced being placed before said television camera so as to ⁇ be scanned thereby, a generator of electric pulses, means to modulate the recurrence frequency of said electric pulses according to the modulation of the video signal generated by said television camera, a cathode-ray tube with an electron beam releasing electrode, on which said frequency modulated electric pulses are applied, and means to synchronize the electron beam sweeping of said cathode-ray tube with the scanning of said television camera.
  • An apparatus including further means to modulate also the amplitude of the electric pulses, according to the modulation of the video signal generated by the television camera, the cathode-ray tube being further provided with a control electrode for adjusting the size of the electron beam spot, on which the frequency and amplitude modulated pulses are also applied.
  • An apparatus including further means to photograph the screen of the cathode-ray tube, so as to obtain a screened block for the reproduction of the continuous tone picture by a printing process.
  • A11 apparatus for obtaining a monochromatic screened block from a continuous tone colour picture including means to sweep the picture to be reproduced with a light beam, whereby said beam is modulated by the Variations in tone of the picture along each sweeping strip, means to divide the modulated light beam into two partial beams, two complementary colour filters disposed so as to be respectively passed through by said partial beams, twophotoelectric cells arranged to collect respectively the liltered partial beams, whereby said photoelectric cells respectively deliver continuous electric signals, with mod-ulation following the respective modulations of said partial beams, a differential circuit adapted to subtract from one of said continuous signals, an adjustable part of the other continuous signal, a generator of electric pulses, means to modulate the recurrence frequency and the amplitude of said electric pulses according to the differential electric 1 1 signal, a flashing lamp adapted to be energized by the fre- 2,032,541 l3/ 36 Losier 101--40l-1 queney and amplitude modulated electric pulses, a screen, 2,041,882

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  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Facsimile Image Signal Circuits (AREA)
US110598A 1960-04-01 1961-03-31 Process for the reproduction of continuous tone pictures Expired - Lifetime US3197558A (en)

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FR823140A FR1300718A (fr) 1960-04-01 1960-04-01 Procédé et appareil pour la reproduction des images à teintes continues

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FR2596226A1 (fr) * 1986-03-19 1987-09-25 Vignon Bernard Procede de reproduction d'une image a partir de la numerisation de cette image
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US4713746A (en) * 1982-05-14 1987-12-15 Canon Kabushiki Kaisha Method for forming pictures
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US4758886A (en) * 1986-07-24 1988-07-19 Minnesota Mining And Manufacturing Company Optimal color half-tone patterns for raster-scan images
US4772911A (en) * 1984-01-19 1988-09-20 Canon Kabushiki Kaisha Image formation apparatus
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US4800442A (en) * 1985-08-15 1989-01-24 Canon Kabushiki Kaisha Apparatus for generating an image from a digital video signal
EP0260020A3 (en) * 1986-08-25 1989-09-27 Hewlett Packard Company A method of generating a gray scale image
EP0371544A1 (en) * 1988-11-24 1990-06-06 Océ-Nederland B.V. Method of and apparatus for processing and reproducing image information
US5055943A (en) * 1988-04-14 1991-10-08 Dainippon Screen Mfg. Co. Ltd. Method of and apparatus for recording halftone image
USH996H (en) 1987-01-20 1991-11-05 Recognition Equipment Incorporated High resolution page image display system
EP0487084A3 (en) * 1990-11-22 1993-03-03 Canon Kabushiki Kaisha Image forming method and apparatus
EP0457229A3 (en) * 1990-05-18 1993-03-03 Hitachi, Ltd. Printing apparatus and information processing apparatus using the same
EP0587187A1 (en) * 1992-09-10 1994-03-16 Kabushiki Kaisha Toshiba Image data recording apparatus and method and facsimile apparatus comprising such recording apparatus
US5299020A (en) * 1991-03-08 1994-03-29 Scitex Corporation Ltd. Method and apparatus for generating a screened reproduction of an image using stored dot portions
EP0603167A1 (en) * 1988-05-11 1994-06-22 Canon Kabushiki Kaisha Image processing method and apparatus
EP0734147A1 (en) * 1995-03-22 1996-09-25 Agfa-Gevaert N.V. Intensity modulated stochastic screening for preparing a lithographic printing plate
EP0734151A1 (en) * 1995-03-22 1996-09-25 Agfa-Gevaert N.V. Size modulated stochastic screening
EP0740457A1 (en) * 1995-04-28 1996-10-30 Agfa-Gevaert N.V. Improved halftone screen and method for making same
US5625397A (en) * 1994-11-23 1997-04-29 Iris Graphics, Inc. Dot on dot ink jet printing using inks of differing densities
EP0758180A4 (en) * 1995-02-27 1997-10-01 Toray Industries ELECTROPHOTOGRAPHIC DEVICE, ELECTROPHOTOGRAPHY AND METHOD FOR PREPARING SHEETS CARRYING IMAGES OBTAINED BY TONER
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US3646262A (en) * 1968-03-25 1972-02-29 Printing Dev Inc Electronic reproduction of continuous image with controlled modification of image reproduction
US3580995A (en) * 1968-04-29 1971-05-25 Rca Corp Constant sized halftone dot image generator
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US3819854A (en) * 1970-02-20 1974-06-25 Harris Intertype Corp Composing apparatus
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US3920951A (en) * 1974-06-03 1975-11-18 Gen Electric Laser etching apparatus for forming photographic images on metallic surfaces
US4106061A (en) * 1977-03-03 1978-08-08 The Mead Corporation Density control for ink jet copier
US4219850A (en) * 1978-02-16 1980-08-26 The Mead Corporation Optical encoder
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FR2497043A1 (fr) * 1980-12-19 1982-06-25 Cit Alcatel Dispositif d'impression d'une image
US4713746A (en) * 1982-05-14 1987-12-15 Canon Kabushiki Kaisha Method for forming pictures
US4604654A (en) * 1982-07-23 1986-08-05 Canon Kabushiki Kaisha Image forming method and apparatus
US4692773A (en) * 1982-07-23 1987-09-08 Canon Kabushiki Kaisha Image forming method using image forming elements having different concentrations and pitches
US4727436A (en) * 1982-09-01 1988-02-23 Canon Kabushiki Kaisha Method and apparatus for producing a picture
US4772911A (en) * 1984-01-19 1988-09-20 Canon Kabushiki Kaisha Image formation apparatus
US4714964A (en) * 1984-07-13 1987-12-22 Canon Kabushiki Kaisha Intermediate gradient image forming method
US4686538A (en) * 1984-10-31 1987-08-11 Canon Kabushiki Kaisha Tone recording method
FR2587572A1 (fr) * 1985-03-20 1987-03-20 Canon Kk Appareil et procede de traitement d'images
US4800442A (en) * 1985-08-15 1989-01-24 Canon Kabushiki Kaisha Apparatus for generating an image from a digital video signal
USRE38942E1 (en) * 1985-08-15 2006-01-24 Canon Inc. Apparatus for generating an image from a digital video signal
US4782398A (en) * 1986-02-14 1988-11-01 Canon Kabushiki Kaisha Image processing apparatus
EP0239480A1 (fr) * 1986-03-19 1987-09-30 Bernard Vignon Procédé de reproduction d'une image à partir de la numérisation de cette image
FR2596226A1 (fr) * 1986-03-19 1987-09-25 Vignon Bernard Procede de reproduction d'une image a partir de la numerisation de cette image
EP0241569A1 (de) * 1986-04-15 1987-10-21 Maurer Electronics Gmbh Bildwiedergabesystem zur Erzeugung eines digitalen Bildes
US4758886A (en) * 1986-07-24 1988-07-19 Minnesota Mining And Manufacturing Company Optimal color half-tone patterns for raster-scan images
EP0260020A3 (en) * 1986-08-25 1989-09-27 Hewlett Packard Company A method of generating a gray scale image
USH996H (en) 1987-01-20 1991-11-05 Recognition Equipment Incorporated High resolution page image display system
US5055943A (en) * 1988-04-14 1991-10-08 Dainippon Screen Mfg. Co. Ltd. Method of and apparatus for recording halftone image
EP0603167A1 (en) * 1988-05-11 1994-06-22 Canon Kabushiki Kaisha Image processing method and apparatus
EP0371544A1 (en) * 1988-11-24 1990-06-06 Océ-Nederland B.V. Method of and apparatus for processing and reproducing image information
EP0457229A3 (en) * 1990-05-18 1993-03-03 Hitachi, Ltd. Printing apparatus and information processing apparatus using the same
US5864406A (en) * 1990-11-22 1999-01-26 Canon Kabushiki Kaisha Method and apparatus for forming halftone images on organic-silver-salt-based printing plates
EP0487084A3 (en) * 1990-11-22 1993-03-03 Canon Kabushiki Kaisha Image forming method and apparatus
US5299020A (en) * 1991-03-08 1994-03-29 Scitex Corporation Ltd. Method and apparatus for generating a screened reproduction of an image using stored dot portions
EP0587187A1 (en) * 1992-09-10 1994-03-16 Kabushiki Kaisha Toshiba Image data recording apparatus and method and facsimile apparatus comprising such recording apparatus
US5625397A (en) * 1994-11-23 1997-04-29 Iris Graphics, Inc. Dot on dot ink jet printing using inks of differing densities
EP0758180A4 (en) * 1995-02-27 1997-10-01 Toray Industries ELECTROPHOTOGRAPHIC DEVICE, ELECTROPHOTOGRAPHY AND METHOD FOR PREPARING SHEETS CARRYING IMAGES OBTAINED BY TONER
US6256051B1 (en) 1995-02-27 2001-07-03 Toray Industries, Inc. Electrophotographic device, electrophotography, and process for preparing sheet bearing toner images
EP0734147A1 (en) * 1995-03-22 1996-09-25 Agfa-Gevaert N.V. Intensity modulated stochastic screening for preparing a lithographic printing plate
EP0734151A1 (en) * 1995-03-22 1996-09-25 Agfa-Gevaert N.V. Size modulated stochastic screening
EP0740457A1 (en) * 1995-04-28 1996-10-30 Agfa-Gevaert N.V. Improved halftone screen and method for making same
EP0910206A1 (en) * 1995-04-28 1999-04-21 Agfa-Gevaert N.V. Improved halftone screen and method for making same
CN1062079C (zh) * 1995-06-21 2001-02-14 时代集团公司 调幅调频挂网方法

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CH391467A (fr) 1965-04-30
BE602105A (fr) 1961-10-02
LU39915A1 (en(2012))
FR1300718A (fr) 1962-08-10

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