Classifications

• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
  • G06K15/00—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers
  • G06K15/02—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers using printers
  • G06K15/10—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers using printers by matrix printers
  • G06K15/102—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers using printers by matrix printers using ink jet print heads
  • G06K15/105—Multipass or interlaced printing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J19/00—Character- or line-spacing mechanisms
  • B41J19/14—Character- or line-spacing mechanisms with means for effecting line or character spacing in either direction
  • B41J19/142—Character- or line-spacing mechanisms with means for effecting line or character spacing in either direction with a reciprocating print head printing in both directions across the paper width
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/21—Ink jet for multi-colour printing
  • B41J2/2132—Print quality control characterised by dot disposition, e.g. for reducing white stripes or banding
• • 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
  • H04N1/04—Scanning arrangements, i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing medium, or vice versa
  • H04N1/19—Scanning arrangements, i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing medium, or vice versa using multi-element arrays
  • H04N1/191—Scanning arrangements, i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing medium, or vice versa using multi-element arrays the array comprising a one-dimensional array, or a combination of one-dimensional arrays, or a substantially one-dimensional array, e.g. an array of staggered elements
  • H04N1/1911—Simultaneously or substantially simultaneously scanning picture elements on more than one main scanning line, e.g. scanning in swaths
  • H04N1/1912—Scanning main scanning lines which are spaced apart from one another in the sub-scanning direction

Definitions

• This invention relates to bidirectional ink jet printing systems and, more particularly, to a new and improved bidirectional ink jet printing system which exhibits a reduced banding effect.
• a reciprocating ink jet head having an array of ink jet orifices projects corresponding arrays of ink drops onto a record medium during successive passes in its reciprocating motion adjacent to the record medium.
• the record medium is normally advanced a distance corresponding to the effective length of the array of ink jet ori ⁇ fices between successive passes of the ink jet head. Because the placement of the ink drops on the record medium varies depending on the direction of motion of the ink jet head, however, the image portions produced by successive passes of the ink jet head in opposite directions are often slightly different and therefore tend to produce detectable bands in the composite image.
• the ink jet head has several arrays of orifices arranged to project drops of different colors toward the same locations on the record medium so that an additive color such as green is produced by overprinting drops of one color such as yellow on drops of another color such as cyan
• the drops of the second color to be printed generally spread less than the drops of the first color, causing portions of the drops of the first color to be visible, which shifts the hue of the combined colors toward that of the first color.
• the hue of a green produced by printing cyan over yellow tends to be shifted toward yellow, while the hue of a green produced by printing yellow over cyan will be shifted towards cyan. Consequently, in bi ⁇ directional color printing, the bands produced by combinations of colored drops projected from orifice arrays during adjacent passes of the ink jet head in opposite directions will have a difference in hue which produces a detectable color banding in the com ⁇ posite image.
• Another object of the invention is to provide a bidirectional ink jet printing system in which ink drop placement errors and color variations resulting from printing during motion of the ink jet head in opposite directions are not detectable in the compos ⁇ ite image.
• a bidirectional ink jet printing system in which an ink jet head has a plurality of orifices which print a corresponding plurality of lines on an adjacent record medium during each pass of the ink jet head with respect to the medium and wherein at least some lines printed during one pass of the ink jet head are interlaced with lines printed during the succeeding pass of the ink jet head so that the spacing between adjacent lines printed by motion of the ink jet head in opposite directions is less than the minimum required for visual detectability of differences in printing.
• an ink jet head having an array of orifices which are spaced at twice the spac- ing of adjacent lines in the ink jet image is advanced a distance equal to an odd number of lines after one pass and a distance equal to a different odd number of lines after the next pass, the total number of lines corresponding to the distance advanced after the suc ⁇ cessive passes being equal to twice the number of orifices used in printing during each pass.
• Fig. 1 is a schematic diagram showing the lines produced by successive passes of an ink jet head in a conventional system, exaggerated to illustrate the banding effect;
• Fig. 2 is a graphical representation showing the limit of visual detectability of edge raggedness in an ink jet image as a function of error size and spatial period;
• Fig. 3 is a graphical representation illustrating the threshold for visual detectability of image-band ⁇ ing as a function of contrast and spatial period;
• Fig. 4 is a schematic diagrammatic view illus- trating the operation of one form of ink jet system for eliminating the effects of banding in accordance with the invention.
• Fig. 5 is a schematic diagrammatic view illus ⁇ trating the operation of another form of ink jet sys- tem arranged to eliminate the effects of banding in accordance with the invention.
• an ink jet head 10 has an array of orifices 11 from which ink is ejected drop by drop onto a substrate 12 during successive transverse motions of the head 10 with respect to the substrate 12 to produce a pattern 13 o the substrate.
• the head 10 is driven in a re ⁇ ciprocating path adjacent to the substrate as indi- cated by the arrow 14 and, for bidirectional printing, i..e. printing in both directions, the substrate 12 is advanced in the direction of the arrow 15 after each pass of the head 10 a distance 16 which is equal to the effective length of the array of orifices 11 plus the spacing between orifices.
• the location of the head 10 with respect to the substrate 12 prior to each pass subsequent to the first pass is illus ⁇ trated in phantom.
• the spacing between the orifices 11 in the ink jet head 10 is as small as possible and, to reduce the spacing between adjacent lines 17 produced by the drops from adjacent orifices 11, the array of orifices in the head 10 may be tilted at an angle to the direction of reciprocating motion 14 of the head rather than being perpendicular thereto as shown in Fig. 1.
• the head may include two or more adjacent arrays of orifices with the orifices of one array located at positions between those of the orifices of another array.
• an ink jet orifice array may include adjacent groups of orifices projecting inks having different subtractive colors.
• the arrays of cyan and magenta ink orifices must be arranged and controlled so that one of those inks is printed over the other one on a subsequent pass of the ink jet head.
• Fig. 1 illustrates on a logarithmic scale the effect of the spatial period of the bands, i.e..
• edge raggedness when the edge raggedness is more than about 0.002 inch (0.05mm), it is visually detectable regardless of the spatial period of the bands and, when the edge ragged ⁇ ness is about 0.001 inch (0.025mm), it is detectable if the spatial period is between about 0.007 and 1.0 inches (0.175mm and 25mm) whereas, if the edge ragged- ness is about 0.0002 inch (0.0005mm), it is visually detectable only if the spatial period is between about 0.015 and 0.10 inch (0.375 and 2.5mm). Even if the edges of adjacent bands are in per ⁇ fect alignment, bidirectional ink jet printing may cause variations in density or hue which produce visu ⁇ ally detectable color banding.
• Fig. 3 illustrates on a logarithmic scale the effect of variations in contrast between adjacent bands, with percent contrast represented on the ordinate scale, and variations in the spatial period represented in inches on the abscissa scale, on the visual detectability of such bands in an ink jet image.
• the line 21 in Fig. 3 represents the limit of visual detectability when the banding is a square wave function of intensity and the line 22 in Fig. 3 repre ⁇ sents the limit when the banding is a sinusoidal func ⁇ tion of intensity.
• banding is detectable for all spatial periods greater than about 0.01 inch (0.25mm), whereas for 1% contrast between adjacent bands, banding is detectable for sinusoidal variations in density only if the spatial period is between about 0.02 and about 0.5 inch (0.5mm and 1.25mm) and for square wave variations of density at all spatial periods above 0.02 inch (0.5mm).
• the spatial period of any bands produced as a result of bidirectional printing should be kept below the threshold for detectability not only with respect to edge raggedness but also with respect to contrast.
• bidirectional printing in accordance with the invention is arranged to produce bands having a spatial period of no more than about 0.01 inch (0.25mm) and, desirably, the spatial period of any bands produced by bidirectional printing are less than 0.005 inch (0.13mm).
• the ink jet system of the pres ⁇ ent invention is arranged to interlace the lines pro- **d by successive passes of the ink jet head so that the width of adjacent image portions produced by mo ⁇ tion of the head in opposite directions is no more than the spacing between adjacent lines of the image.
• adjacent line spacing of about 0.003 inch (0.075mm)
• any bands resulting from bidirectional printing, whether resulting from edge raggedness or color variations have a spatial cycle which is below the visual threshold of an observer.
• the ink jet head may, for example, have an array of orifices spaced at twice the intended line spacing in the image and the substrate may be moved by a distance equal to the adjacent line spacing in the image at one end of the bidirectional motion of the head and by a distance equal to the total length of the array minus the spac ⁇ ing between adjacent image lines at the opposite end of the array.
• the substrate may be advanced by a distance corresponding to three or five lines, for example, at one end of the head motion and by a distance equal to the total array length minus three or five lines at the opposite end of the head motion.
• Fig. 4 illustrates schematically the arrangement of a typical ink jet system arranged in accordance with the invention.
• an ink jet head 23 has eight orifices 24 spaced by a distance 25 of 0.006 inch (0.15mm) which is twice the intended spac ⁇ ing between adjacent lines 26 and 27 in the image 28 to be generated by operation of the ink jet head.
• the adja ⁇ cent ends of the lines 26 and 27 are displaced by a distance 32, producing an edge raggedness in the image. Because the spatial period of the edge ragged ⁇ ness is equal to the orifice spacing 25, which in this case is 0.006 inch (0.15mm), the raggedness lies in the region below the line 20 in Fig. 2, so that it cannot be visually detected.
• the number of ori ⁇ fices supplied with black ink may be larger than the number supplied with ink of each of the primary colors.
• the orifices supplying black ink may be alternated with color ink orifices in the ink jet head so that, when black images are being printed, the printing speed can be twice that obtained when color images are being printed.
• Fig. 5 illustrates a typical ink jet head ar ⁇ ranged to produce both black and multicolor printing in accordance with the invention.
• a head 33 has an array 34 consisting of 16 orifices arranged to project black ink and three adjacent ar ⁇ rays 35, 36 and 37 of eight orifices each arranged to project yellow, magenta and cyan inks, respectively, these orifices being aligned with the alternate ori ⁇ fices in the array 34.
• any differences in intensity or hue resulting from the reversal of the order of laying down of colored ink drops has a spatial period which is less than the lower limit for visual detection of the banding effect as shown in Fig. 3.
• the entire array of black orifices 34 may be utilized if edge raggedness is not a problem.
• the substrate is advanced by a distance equal to the length of the array 34 plus the distance between adja ⁇ cent orifices in that array between successive passes of the head, thereby producing images at twice the speed of color printing. If banding is produced as a result of edge raggedness, only alternate orifices in the array 34 are used, and the lines produced by suc ⁇ cessive passes of the ink jet head are interlaced in the manner described with respect to Fig. 4.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Quality & Reliability (AREA)
• Mathematical Physics (AREA)
• General Engineering & Computer Science (AREA)
• General Physics & Mathematics (AREA)
• Theoretical Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Ink Jet (AREA)
• Particle Formation And Scattering Control In Inkjet Printers (AREA)

Applications Claiming Priority (2)

Publications (2)

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• 1990
  • 1990-05-03 KR KR1019900702603A patent/KR920700110A/ko not_active IP Right Cessation
  • 1990-05-03 EP EP19900907716 patent/EP0428658A4/en not_active Withdrawn
  • 1990-05-03 JP JP2507813A patent/JPH03503146A/ja active Pending
  • 1990-05-03 WO PCT/US1990/002457 patent/WO1990014957A1/en not_active Application Discontinuation

Non-Patent Citations (2)

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