EP1245398A1 - Méthode d'alignement pour appareil d'impression et dispositif associé - Google Patents

Méthode d'alignement pour appareil d'impression et dispositif associé Download PDF

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Publication number
EP1245398A1
EP1245398A1 EP01108128A EP01108128A EP1245398A1 EP 1245398 A1 EP1245398 A1 EP 1245398A1 EP 01108128 A EP01108128 A EP 01108128A EP 01108128 A EP01108128 A EP 01108128A EP 1245398 A1 EP1245398 A1 EP 1245398A1
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EP
European Patent Office
Prior art keywords
pattern
offset
sensor
printhead
media
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP01108128A
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German (de)
English (en)
Inventor
Jorge Castano
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
HP Inc
Original Assignee
Hewlett Packard Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hewlett Packard Co filed Critical Hewlett Packard Co
Priority to EP01108128A priority Critical patent/EP1245398A1/fr
Priority to DE60141451T priority patent/DE60141451D1/de
Priority to EP01121159A priority patent/EP1245399B1/fr
Priority to AT01121159T priority patent/ATE459483T1/de
Priority to JP2002085749A priority patent/JP2002361965A/ja
Priority to US10/113,856 priority patent/US6755499B2/en
Publication of EP1245398A1 publication Critical patent/EP1245398A1/fr
Priority to US10/831,607 priority patent/US20040196325A1/en
Withdrawn legal-status Critical Current

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    • 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
    • B41J29/00—Details of, or accessories for, typewriters or selective printing mechanisms not otherwise provided for
    • B41J29/38—Drives, motors, controls or automatic cut-off devices for the entire printing mechanism
    • B41J29/393—Devices for controlling or analysing the entire machine ; Controlling or analysing mechanical parameters involving printing of test patterns
    • 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
    • B41J2/2135—Alignment of dots

Definitions

  • the present invention relates to printer devices, and particularly, although not exclusively, to a method and apparatus for determining and correcting misalignments between printheads in ink jet devices.
  • paper copies also known as "hard” copies of files stored on a host device, e.g. a computer using a printer device.
  • the print media onto which files may be printed includes paper and clear acetates for use in lectures, seminars and the like.
  • a conventional host device in this case a personal computer, linked to a printer device 2 via a cable 3.
  • a printer device 2 linked to a printer device 2 via a cable 3.
  • FIG. 2 there is illustrated schematically part of a prior art printer device comprising an array of printer nozzles 4 arranged into parallel rows.
  • the unit comprising the arrangement of printer nozzles is known herein as a printhead.
  • the printhead 5 is constrained to move in a direction 6 with respect to the print media 7 e.g. a sheet of A4 paper.
  • the print media 7 is also constrained to move in a further direction 8.
  • direction 6 is orthogonal to direction 8.
  • printhead 5 is moved into a first position with respect to the print media 7 and a plurality of ink drops 9a, 9b are sprayed from a number of printer nozzles 4 contained within printhead 5.
  • This process is also known as a print operation.
  • the printhead 5 is moved in a direction 6 to a second position and another print operation is performed.
  • the printhead 5 is repeatedly moved in a direction 6 across the print media 7 and a print operation performed after each such movement of the printhead 5.
  • modern printers of this type are arranged to carry out such print operations while the printhead is in motion, thus obviating the need to move the printhead discrete distances between print operations.
  • the print media When the printhead 5 reaches an edge of the print media 7, the print media is moved a short distance in a direction 8, parallel to a main length of the print media 7, and further print operations are performed. By repetition of this process, a complete printed page may be produced in an incremental manner.
  • printers with more than one printhead are typically used.
  • four printheads are used, each storing and printing a different colour; for example: cyan; magenta; yellow; and black.
  • the inks from the four printheads are mixed on the print media to obtain any other particular colour.
  • the mechanical misalignment of a printhead may result in an offset in the positioning of ink drops on the print media. Such offsets may occur in the X direction (in the media advance/media axis) or the Y direction (in the carriage/scan axis). Additionally, angular offsets may also arise. If each printhead in a printer is not sufficiently accurately aligned with the remaining printheads of the printer, a misregistration between the images formed by the different coloured ink drops on the print media may result. This may cause too much ink to be deposited in some areas and too little ink to be deposited in others. This often gives rise "grainy" appearance in the printed image. This type of print error is often particularly noticeable to the viewer. Consequently, such misregistrations are generally unacceptable, with colour printing typically requiring image registration accuracy from each of the printheads of 1/2400 inch.
  • each alignment patch consists of a series of parallel lines. However, the spacing of the lines of the two alignment patches is slightly different, thus giving rise to an interference pattern.
  • the operator manually inspects them to determine the position in the overlying alignment patches of the maximum or minimum ink density. From this information, the relative offset between the two printheads in the media feed direction may be determined.
  • the processor of the printer compensates for any offset in the media feed direction between printheads by avoiding using those nozzles in each printhead that extend in the media feed direction beyond the nozzles of the other printhead.
  • the processor of the printer also resets the "logical zero" in terms of the nozzles' numbering in each printhead. That is to say that the nozzles which are to be used in each printhead are re-numbered, where necessary, such that the nozzles in each printhead which correspond in terms of their position along the media feed direction are allocated the same number, in order to ensure correct registration between the images printed by the different printheads. In this manner, the print output of the two printheads may be aligned at the expense of a slightly reduced number of usable nozzles.
  • This technique suffers from the disadvantage that it is relatively slow, being non-automated and reliant upon an operator. Furthermore, the process is less suitable for use in printers having more than two printheads, due to the increased difficulty of determining the relative offsets for a greater number of printheads.
  • a second type of known system is generally used on large format ink jet printers, which employ separate printheads for each ink colour. In order to ensure that no misregistration occurs between the images formed by the different coloured ink drops on the print medium, an alignment routine is performed.
  • alignment patches are printed across the sheet of print media with each printhead so that they are approximately aligned along the scan axis; i.e. in a direction perpendicular to the media feed direction.
  • the positions of the alignment patches in the media feed direction are then measured using an optical scanner, often referred to as a line scanner, which is mounted on the printer carriage. This is achieved for each alignment patch by positioning the line scanner at the appropriate point along the scan axis so as to be able to detect the alignment patch and then feeding the print media backwards (i.e. in a reverse feed direction) so that the position of the patch on the media in the media feed direction may be determined.
  • the line scanner is then positioned at the appropriate point along the scan axis to detect the next alignment patch and the print media is fed forwards once again in readiness for determining the position of the next patch in the media feed direction. Once the position of each alignment patch in the media feed direction has be determined in this manner, the relative offsets in the media feed direction between the individual printheads are calculated.
  • the print output of the different printheads are then aligned in the media feed direction in the same manner as described above with respect to the first type of prior art system; i.e. by avoiding using those nozzles in each printhead that extend in the media feed direction beyond the nozzles of the other printheads and by resetting the "logical zero" in terms of the nozzles' numbering.
  • a method of determining a registration offset in a hard copy apparatus comprising the steps of: marking a alignment pattern on a print medium with a first pen; traversing the pattern in a first direction with a sensor and measuring the position of a portion of the pattern in the first direction; and, determining the offset of the pattern in a second direction, the pattern being configured such that the measured position in the first direction is indicative of a registration offset in a second direction.
  • an alignment pattern that is configured such that a measurable distance associated with the pattern in a first direction, for example along the scan axis of a printer device, allows the placement of the pattern in a second direction, for example along the media feed direction of the printer device, to be determined several advantages are realised.
  • the alignment pattern may be printed and then scanned in the same direction, for example, along the scan axis direction of a printer.
  • the two processes may be implemented without having to feed the print media, or having to scan the alignment pattern in a direction different from that in which the alignment pattern was printed.
  • complex scanning arrangements may be avoided.
  • the present embodiment does not suffer from the disadvantage known in some prior art methods of requiring the alignment patterns, once printed, to be moved backwards and forwards under an optical scanner in order to establish their position along the media feed axis.
  • the process by which the printheads offsets in the media feed direction may be achieved according to the present invention is comparatively rapid. This is because one pass of an optical scanner across the print medium may be sufficient to measure offsets of even a large number of printheads in the media feed direction.
  • the alignment pattern of the present invention comprises two lines, one arranged parallel to the media feed axis and a second arranged at 45 degrees to the first.
  • the distance between the two points in the scan path intersected by the two lines may be measured. Due to the fact that the two lines of the alignment pattern are arranged at 45 degrees to each other, the measured distance will be equal to the perpendicular distance from the scan path to the point at which the two lines intersect.
  • a change in the offset of a printhead in the media feed axis will cause the position of the alignment pattern, including both lines, to be offset relative to the scan path.
  • the distance between the two points in the scan path intersected by the two lines will change in proportion to the offset.
  • the offset of the printhead in the in the media feed axis may be determined.
  • the present invention also extends to the corresponding apparatus for implementing the above method. Furthermore, the present invention also extends to a computer program, arranged to implement the method of the present invention.
  • FIG. 3 shows a perspective view of an inkjet printer 10 having a housing 12 mounted on a stand 14.
  • the housing has left and right drive mechanism enclosures 16 and 18.
  • a control panel 20 is mounted on the right enclosure 18.
  • a print medium 33 such as paper is positioned along a vertical or media axis by a media axis drive mechanism (shown in Figure 5).
  • the media axis is called the X-axis denoted as 13
  • the scan axis is called the Y-axis denoted as 15.
  • a carriage assembly 30, illustrated in phantom under a cover 22, is adapted for reciprocal motion along a carriage bar 24 (i.e. along the scan axis), which is also shown in phantom and is arranged to support and position the four inkjet print cartridges 38, 40, 42, and 44 (shown more clearly in Figure 4) that store ink of different colours, e.g., black, magenta, cyan and yellow ink, respectively.
  • the carriage assembly also holds the circuitry required for interface to the ink firing circuits in the print cartridges.
  • selected nozzles in the inkjet print cartridges are activated and ink is applied to the medium 33.
  • the colours from the three colour cartridges are mixed to obtain any other particular colour.
  • FIG. 4 is a perspective view of the carriage positioning mechanism 31 and the encoder strip 32 together with the carriage assembly 30, which is shown supporting the four print cartridges 38, 40, 42, and 44, and positioned above the media roller 35b, of which a partial view is shown.
  • an optical sensor 50 which is described below with respect to Figures 6 and 7, is connected to the carriage assembly 30.
  • the carriage positioning mechanism 31 includes a carriage position motor 31a which has a drive shaft and a drive roller 31b and 31c, respectively, and which drives a belt 31d.
  • the belt is secured by idler 31e and is attached to the carriage 30. In this manner, the position of the carriage assembly 30 may be moved in the Y-axis 15 along the carriage bar 24.
  • the carriage assembly 30 may be moved in either a positive or a negative direction, as is indicated by the arrow 15 in the figure, in dependence upon the direction of rotation of the motor 31a.
  • the position of the carriage assembly 30 in the scan axis is determined precisely using the encoder strip 32.
  • the encoder strip 32 is secured by a first stanchion 34a at one end and a second stanchion 34b at the other end.
  • An optical encoder strip reader (not shown) is disposed on the carriage assembly 30 and provides carriage position signals that are utilized to determine the position of the carriage assembly 30 in the Y-axis 15.
  • FIG. 5 is a perspective view of a simplified representation of the media positioning system 35 of the printer 10, in relation to the printer carriage assembly 30.
  • the media positioning system 35 includes a motor 35a, which is normal to and drives the media roller 35b.
  • the position of the media roller 35b is determined by a media position encoder 35c on the motor.
  • An optical reader 35d senses the position of the encoder 35c and provides a plurality of output pulses, which indirectly determine the position of the roller 35b and, therefore, the position of the media 33 in the X-axis.
  • the media and carriage position information is provided to a processor on a circuit board 36 disposed on the carriage assembly 30 for use in connection with printhead alignment techniques of the present invention.
  • Figure 6 illustrates the optical sensor unit 50 of the printer 10.
  • the optical sensor 50 is arranged to sense marks or ink on the print media 33, which have been ejected by the printheads 38, 40, 42, 44.
  • the optical sensor 50 is mounted on the carriage assembly 30 and thus is free to sense marks on any portion of the print media 33 by moving the printer carriage 30 and/or the media 33 to selected locations along the X and Y-axes, respectively.
  • FIG 6 shows a more detailed view of the optical sensor unit 50 shown in Figure 4.
  • the optical sensor unit 50 includes: a photocell, or optical detector 50a; a holder 50b; a cover 50c; an optical element or lens 50d; and, a light source such as two LEDs 50e, 5Of.
  • the optical sensor unit 50 in this exemplary embodiment includes two LEDs, one green and one blue; the green LED being used to scan all of the patterns or marks except the patterns or marks used to obtain information from the yellow ink printhead.
  • a protective casing (shown in Figure 4) that also acts as an ESD shield for sensor components is provided for attachment to the carriage. Also shown in the figure are the relative positions of the object plane and the image plane that are offset from the plane of the lens by distances S1 and S2, respectively.
  • the light from the light sources 50e, 50f illuminates the object, such as a printhead alignment pattern printed on print media 33.
  • the image of the object is focussed by the optical element 50d on the image plane and is detected by the optical detector 50a in a conventional manner.
  • the optical sensor unit 50 is arranged to scan a "line" across the print medium 33 in the scan or Y-axis direction as the printer carriage assembly 30, to which the optical sensor unit 50 is mounted, is moved across the scan axis.
  • the signal output by the optical detector 50a will vary in dependence upon the local changes in the detected levels of reflectivity.
  • Such areas include marks or portions of alignment patterns printed on the print medium 33 by one of the four inkjet print cartridges 38, 40, 42, and 44. In this manner, changes in the output signal of the optical detector 50a can be used to determine the position of a mark on the print medium 30.
  • Figure 7a This is illustrated in Figure 7a.
  • the optical sensor unit 50 is illustrated at the point that it passes over a mark 52a as it traverses the scan axis (as indicated by the arrow in the figure).
  • the optical detector 50a has a photosensitive area or areas which produce electrical sensor signals 56a that follow the optical transfer function (OTF) of the optical system.
  • OTF optical transfer function
  • This OTF is the response of the optical sensor to the light reflected from the media.
  • the spatial response of the sensor is the mapping of the signal from the sensor in response to a point light source scanning along the viewing area of the optical system.
  • the optical response can be defined mathematically as the "point spread function" (PSF), i.e. the response of the detector system to light from a point in space.
  • PSF point spread function
  • Figure 7c illustrates the spatial response of the sensor, determined by mapping the PSF along all the points of the space to be analysed, here the space along the media plane.
  • the values of the coordinates in Figure 7c for this example are in space coordinates of I/1200 inch.
  • the sensor signal 56a output by the optical detector when the sensor is scanning across the mark 52a on the media is the mathematical convolution of the reflectivity of the mark 52a and the spatial response of the optical sensor.
  • the optical sensor signal is dominated by the shape of the mark.
  • the resulting sensor signal 56a has a plateau in the maximum of the signal.
  • the plateau adds inaccuracies in determining the position of the centre of the mark.
  • nonuniformities in the marks on the medium can produce lack of consistency of the plateau, introducing erroneous centre position signals.
  • the sensor signal is dominated by the response curve of the optical sensor. This is illustrated in Figure 7b, where the size of the mark 52b is smaller than the size of the viewing area 54b of the sensor. This produces a corresponding sensor signal 56b, with a clear and relatively sharp peak. Therefore, in the present embodiment, it is desirable that the marks or lines to be detected are sized smaller than the sensor viewing area dimension in the direction in which the measurement is to be made. In this example, the application need only know the position along the scan axis at which the centres of the marks are detected. Thus, the dimension of the marks or lines can be made larger than the viewing area in the media axis direction, but preferably are smaller than the viewing area dimension in the scan axis direction.
  • the optical sensor can be modelled like a first order OTF (corresponding to a normal curve), and the size of the mark is smaller than the sensor viewing area, the position of the mark on the media can be calculated with the precision of the mechanical scanning system of the optical sensor.
  • This system provides an effective technique to find the centre of the mark because the signal has a clear and sharp peak corresponding to the centre.
  • each printhead has two columns of nozzles with a column offset 41c. Furthermore, each printhead is separated from adjacent printheads in the Y-axis or scan axis direction by a Y-axis offset 41a. Due to inaccuracies in the location of each printhead in the printer carriage 30, each printhead is located slightly differently along the X-axis or in the media feed direction, giving rise to vertical printhead misalignments. By comparing the relative positions along the X-axis of corresponding nozzles between two printheads, while they remain on the carriage, it is possible to determine an actual offset 41b between those printheads along the media axis 13.
  • the printhead alignment method of the present embodiment is generally performed when a printhead is replaced, when the relative offsets of one or more of the printheads in the media axis (X-axis) are likely to change. This may be done either immediately on replacing a printhead, or, when the printer is powered up and the new printhead is detected.
  • the method of the present embodiment may also be manually triggered by a user using the user interface 20 of the printer, at such a time as is determined by the user. This may be done, for example, after a printhead crash has occurred; i.e. when one or more printheads have come into contact with the print medium and possible been moved relative to the printer carriage assembly 30.
  • the printer may be programmed to implement the method of the present embodiment at periodic intervals; for example, after a predetermined period of time or after a predetermined amount of use.
  • the printer carriage assembly When the method is implemented, the printer carriage assembly is brought to the right hand end of the scan axis, as is shown in Figures 3 and 4; i.e. adjacent the right hand drive mechanism enclosure 18.
  • the media positioning system 35 of the printer 10 then feeds the media 33 currently in the printer forwards, if required, so that the method may be carried out using clean print media.
  • the printer carriage assembly 30 is then controlled by the printer control unit of the printer (not shown) to traverse the print media 33 along the scan axis 15 as in a normal printing mode.
  • each of the four printheads in sequence, prints an alignment pattern on the print media 33 under the control of the printer control unit.
  • Each alignment pattern is printed using all of the nozzles in the printhead.
  • each alignment pattern has substantially the same alignment characteristics as the printhead that printed it, whilst it is mounted in the carriage assembly 30.
  • the height of each alignment pattern is therefore the same as the height of the columns of nozzles of the printhead in the media movement direction (X-axis); otherwise known as the "swath height" of the printhead.
  • any offset in the media axis of a given printhead will be reflected in the position of the alignment pattern in the media axis on the print medium.
  • Figure 9a illustrates the four alignment patterns 61-64, which respectively represent the black, cyan, magenta and yellow alignment patterns printed by the printheads 61-64, respectively.
  • each alignment pattern consists of three straight lines 60a, 60b and 60c (labeled only on alignment pattern 61 in the figure). Two of the lines 60a and 60c are parallel to the media axis (X-axis) and are positioned level with each other along the media axis.
  • the third line 60b joins one end of the line 60a and the opposing end of the line 60c so as to form a line at 45 degrees to both the media axis (X-axis) 13 and the scan axis (Y-axis) 15.
  • the direction of the slope of the line 60c may be varied. Thus, instead of sloping upwards from left to right as is shown in the figure, the line 60b could instead slope downwards from left to right in the figure.
  • Each of the alignment patterns is printed at a predetermined location along the scan axis 15, as measured by the carriage positioning mechanism 31 in conjunction with the processor on the circuit board 36 of the carriage assembly 30. In this manner, it is ensured that no two alignment patterns overlap. This means that it is easier to distinguish one alignment pattern from another when determining their positions on the print medium.
  • at least partially overlapping alignment patterns may additionally or instead be used.
  • Figure 9a also schematically illustrates that each of the alignment patterns is positioned slightly differently along the media or X-axis, due to the vertical misalignments of the printheads 38, 40, 42 and 44, as is illustrated in Figure 8. As is the case in Figure 8, these misalignments have been exaggerated in Figure 9 for the sake of clarity.
  • the optical sensor unit 50 passes over the alignment patterns 61-64 shortly after they are printed; i.e. in the same pass of the printer carriage assembly 30 over the print media 33 in which the alignment patterns are printed.
  • the print media 33 remains stationary between the step of printing the alignment patterns and subsequently sensing the positions of the alignment patterns with the optical sensor unit 50.
  • Figure 9b illustrates the path 65 of the optical sensor unit 50 superimposed over the alignment patterns 61-64.
  • the direction of movement of the optical sensor unit 50 is shown by the arrows in the figure.
  • the signal output by the optical detector 50a decreases in response to the reduced levels of reflectivity of the printed marks relative to the surrounding print medium 33.
  • Figure 9c illustrates the signal 66 output by the optical detector 50a as it detects those portions of the alignment patterns 61-64 lying beneath the optical sensor unit path 65 shown in Figure 9b.
  • the optical detector 50a outputs a narrow pulse as it passes over each line 60a-c of each of the alignment patterns 61-64.
  • the peak value of each pulse corresponds to the detection of the centre of each corresponding line.
  • the optical detector 50a outputs three detection pulses; A, B and C that correspond to the detection of lines 60a, 60b and 60c, respectively.
  • these detection pulses are labelled: A k , B k and C k in respect of the black (k) alignment pattern 61; A c , B c and C c in respect of the cyan (c) alignment pattern 62; A m , B m and C m in respect of the magenta (m) alignment pattern 63; and, A y , B y and C y in respect of the yellow (y) alignment pattern 64.
  • the printer control unit records the instantaneous positions of the optical sensor unit 50 when the peak value of each of the detection pulses A-C is output. These positions correspond to the positions along the scan axis at which the three lines 60a-c are intersected by the path 65 of the optical sensor unit 50.
  • the separation "d 1 " is also equal to the distance "d 2 " (also shown in Figure 9d) between the point at which the optical sensor unit path 65 crosses the line 60a and furthest point of the line 60a in the direction of the negative media feed direction (X-axis) as shown in the figure. Therefore, the distance “d 1 " indicates the length of the line 60a, and indeed the alignment pattern 61 as a whole, which extends beyond the optical sensor unit path 65 in the negative media feed direction (negative X-axis).
  • the length of the line 60a is known. In this embodiment, it is equal to the swath height of the printhead that printed the alignment pattern 61. Therefore, the length of the line 60a, and thus the alignment pattern 61 as a whole, which extends beyond the optical sensor unit path 65 in the positive media feed direction (positive X-axis) is given by: swath height - d 1
  • a positive value offset indicates that the offset is in the positive media direction (X-axis) and a negative value offset indicates that the offset in the negative media direction (X-axis).
  • the relative offset of the alignment pattern may also be calculated, in the same manner as described above, using the distance "d 3 ", shown in the figure, which separates the points at which the optical sensor unit path 65 crosses the second and third lines 60b and 60c.
  • the separation "d 3 " is also equal to the distance "d 4 " (also shown in Figure 9d) between the point at which the optical sensor unit path 65 crosses the line 60c and furthest point of the line 60c in the direction of the positive media feed direction (X-axis) as shown in the figure.
  • the offset in the media feed direction (X-axis) for each alignment pattern may be measured using either or both of the values "d 1 " and "d 3 ".
  • a check may be introduced into the procedure, in that if the calculated offsets are not equal using both measurements, then it may be concluded that an error has occurred and that the routine should be performed again.
  • the offsets O c , O m and O y in the media feed direction (X-axis) are then calculated in the same manner for the cyan, magenta and yellow patterns 62-64, respectively.
  • each of the printheads relative to one another is calculated. In the present embodiment, this is achieved in the following manner.
  • the offset of each printhead O b , O c , O m and O y is subtracted from the offset O b of the black ink printhead 38.
  • Relative offset cyan O b - O c
  • Relative offset magenta O b - O m
  • Relative offset yellow O b - O y
  • the relative offsets for the cyan, magenta and yellow patterns are determined relative to the black pattern, which is deemed to have a zero relative offset.
  • this information is used by the printer control unit in order to correct for any misalignment that there might be between the printheads in the media feed direction. If there is a misalignment, the print output of the different printheads are then aligned in the media feed direction in the same manner as described above with respect to the prior systems; i.e. by excluding from use nozzles in each printhead that extend in the media feed direction beyond the nozzles of the other printheads and by resetting the "logical zero" in terms of the nozzles' numbering.
  • FIG. 8b This is schematically illustrated in Figure 8b, in which the minimum value O min and the maximum value O max of the calculated relative offsets are marked relative to the logical zero nozzle Z 1b of the black printhead 38.
  • logical zero it is meant the nozzle of the black printhead in the most advanced point in the X axis (positive direction as shown in the figure), which is referenced by the number 0 in printing commands sent to the printhead).
  • the values O min and O max define between them a band "A" across which not all of the printheads 38, 40, 42 and 44 have nozzles, as a result of their relative offsets in the X-axis.
  • the nozzles in each printhead that fall in this band are accordingly not used in printing operations in order to ensure that the print output of each printhead is correctly registered with that of the remaining printheads in the X-axis.
  • the black, cyan and yellow printheads 38, 40 and 44 have nozzles that fall into this band, including their original logical zero nozzles: Z 1b , Z 1c and Z 1y , respectively.
  • Z 1b , Z 1c and Z 1y respectively.
  • Z 2b , Z 2c and Z 2y respectively.
  • the remaining nozzles are then sequentially renumbered in a manner known in the art.
  • the original logical zero nozzle Z 1y lies on the line O min .
  • this nozzles of the printhead 42 are not renumbered.
  • the present invention may be applied to devices other that ink jet printer such as, for example traditional plotters which utilise felt-tipped pens and the like.
  • ink jet printer such as, for example traditional plotters which utilise felt-tipped pens and the like.
  • present invention is also applicable to monochrome printers.
  • printers that employ two, three or more than four printheads.
  • the invention may also be used to advantage with printers having only one printhead, should the exact placement in the direction of the media axis of the printed output need to be measured or controlled.
  • the printhead alignment patterns may be varied in a variety of ways.
  • the present invention may be implemented using a reduced number of lines parallel to the media axis (X-axis).
  • the invention may be implemented using printhead alignment patterns which have only one of lines 60a and 60c; in the case shown in the figure, only line 60a.
  • both of the lines 60a and 60c may be dispensed with in the printhead alignment pattern. This is shown in Figure 10b.
  • the position measurement normally made by measuring the position of the line 60a along the scan axis may be replaced by the recorded position along the scan axis of a nozzle that printed a particular known point in the alignment pattern at the time that it was printed; for example one or other of the ends a or b of the line 60b, as shown in Figure 10b.
  • each alignment pattern was printed using all of the nozzles in the printhead, the skilled person will appreciate that this need not be the case.
  • each alignment pattern may instead by printed using just selected nozzles of the printhead.
  • half of the nozzles in one column could be used, as is shown in Figure 10c.
  • the nozzles located about the center of one column are used in order to allow the patterns to be centrally located with respect to the path of the optical sensor unit 50.
  • the alignment patterns may each be arranged to overlap the path of the optical scanner unit.
  • the optical scanner may determine the position of each of the alignment patterns in one pass of the print media, without it being necessary to feed the print media in order to individually position each alignment pattern in order that it might be detected by the optical scanner.
  • the angle of 45 degrees of the line 60b joining the two lines 60a and 60c parallel to the media movement direction (X-axis) may be varied to a different known angle.
  • the printhead offset in the media direction may in this case be determined by finding the measurement made in the scan axis direction in a look up table relating measurements made in the scan axis direction with printhead offset in the media direction.
  • a simple trigonometric calculation may be preformed in order to determine the offset in the media movement direction (X-axis) direction from the measurement made in carriage movement direction (Y-axis).
  • a further example of a different alignment pattern which may be used in conjunction with the present invention may include a curved line or curved edge of a graphic instead of a straight line, such as 60b of the above embodiment, for determining the printhead offset in the media axis.
  • the offset of the pattern in the media direction may be determined from the measurement of the position of the pattern in scan axis.
  • the printhead offset in the media direction may be determined by finding the measurement made in the scan axis direction in a look up table relating measurements made in the scan axis direction with printhead offset in the media direction.
  • the present invention may be implemented using a detector other that an optical detector in order to determine the position of aspects of the alignment patterns.
  • Any suitable property of the mark which differentiates it from the medium upon which it is located may be used in order to determine its position.
  • the invention may be implemented using a sensor that detects the magnetic or conductive properties, instead of the optical properties of the marks.
  • the scanning step to detect the position of the alignment patterns need not be performed on the same pass of the carriage over the print media as that in which the alignment patterns are printed. In practice this could be implemented on any subsequent pass of the printer carriage over the print medium. However, if the scanning step is implemented on the return pass of the printer carriage or in any subsequent pass in the reverse direction, the order in which the pulses output by the optical detector as it passes over each line of each alignment pattern will be reversed.
  • the process of reducing the offset in the media feed direction between printheads relies upon excluding certain nozzles from use and resetting the "logical zero" in terms of the nozzles' numbering
  • the skilled person will realise that the other methods may be used to implement the present invention.
  • an electro-mechanical system to physically move the printheads into alignment along the media movement axis. This may be achieved for each printhead, for example, by using a piezo-electric actuator to move the printhead and a position sensor to detect the resultant change in position of the printhead.

Landscapes

  • Engineering & Computer Science (AREA)
  • Quality & Reliability (AREA)
  • Length Measuring Devices By Optical Means (AREA)
  • Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
  • Inking, Control Or Cleaning Of Printing Machines (AREA)
  • Moulding By Coating Moulds (AREA)
  • Encapsulation Of And Coatings For Semiconductor Or Solid State Devices (AREA)
  • Steering Control In Accordance With Driving Conditions (AREA)
  • Ink Jet (AREA)
EP01108128A 2001-03-30 2001-03-30 Méthode d'alignement pour appareil d'impression et dispositif associé Withdrawn EP1245398A1 (fr)

Priority Applications (7)

Application Number Priority Date Filing Date Title
EP01108128A EP1245398A1 (fr) 2001-03-30 2001-03-30 Méthode d'alignement pour appareil d'impression et dispositif associé
DE60141451T DE60141451D1 (de) 2001-03-30 2001-09-04 Verbessertes Druckgerätausrichtungsverfahren und -apparat
EP01121159A EP1245399B1 (fr) 2001-03-30 2001-09-04 Méthode d'alignement améliorée pour dispositif d'impression et appareil correspondant
AT01121159T ATE459483T1 (de) 2001-03-30 2001-09-04 Verbessertes druckgerätausrichtungsverfahren und -apparat
JP2002085749A JP2002361965A (ja) 2001-03-30 2002-03-26 プリンタ装置の位置合わせ方法及び装置
US10/113,856 US6755499B2 (en) 2001-03-30 2002-03-28 Printer device alignment method and apparatus
US10/831,607 US20040196325A1 (en) 2001-03-30 2004-04-23 Printer device alignment method and apparatus

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP01108128A EP1245398A1 (fr) 2001-03-30 2001-03-30 Méthode d'alignement pour appareil d'impression et dispositif associé

Publications (1)

Publication Number Publication Date
EP1245398A1 true EP1245398A1 (fr) 2002-10-02

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ID=8177003

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Application Number Title Priority Date Filing Date
EP01108128A Withdrawn EP1245398A1 (fr) 2001-03-30 2001-03-30 Méthode d'alignement pour appareil d'impression et dispositif associé

Country Status (3)

Country Link
EP (1) EP1245398A1 (fr)
AT (1) ATE459483T1 (fr)
DE (1) DE60141451D1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016128068A1 (fr) * 2015-02-13 2016-08-18 Hewlett-Packard Development Company, L.P. Imprimante et procédé exécuté par ordinateur pour commander une imprimante
EP3377328A4 (fr) * 2016-02-05 2019-06-26 Hewlett-Packard Development Company, L.P. Capteurs de barre d'impression

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5796414A (en) * 1996-03-25 1998-08-18 Hewlett-Packard Company Systems and method for establishing positional accuracy in two dimensions based on a sensor scan in one dimension
EP0867298A2 (fr) * 1997-03-28 1998-09-30 Canon Kabushiki Kaisha Dispositif d'impression et procédé d'impression de motifs de contrÔle
US5835108A (en) 1996-09-25 1998-11-10 Hewlett-Packard Company Calibration technique for mis-directed inkjet printhead nozzles
EP0895869A2 (fr) * 1997-07-31 1999-02-10 Seiko Epson Corporation Procédé d'impression d'un motif d'essai et dispositif correspondant

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5796414A (en) * 1996-03-25 1998-08-18 Hewlett-Packard Company Systems and method for establishing positional accuracy in two dimensions based on a sensor scan in one dimension
US5835108A (en) 1996-09-25 1998-11-10 Hewlett-Packard Company Calibration technique for mis-directed inkjet printhead nozzles
EP0867298A2 (fr) * 1997-03-28 1998-09-30 Canon Kabushiki Kaisha Dispositif d'impression et procédé d'impression de motifs de contrÔle
EP0895869A2 (fr) * 1997-07-31 1999-02-10 Seiko Epson Corporation Procédé d'impression d'un motif d'essai et dispositif correspondant

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016128068A1 (fr) * 2015-02-13 2016-08-18 Hewlett-Packard Development Company, L.P. Imprimante et procédé exécuté par ordinateur pour commander une imprimante
CN107206784A (zh) * 2015-02-13 2017-09-26 惠普发展公司，有限责任合伙企业 打印机和用于控制打印机的计算机实施的过程
US10011108B2 (en) 2015-02-13 2018-07-03 Hewlett-Packard Development Company, L.P. Printer and computer-implemented process for controlling a printer
US10532559B2 (en) 2015-02-13 2020-01-14 Hewlett-Packard Development Company, L.P. Printer and computer-implemented process for controlling a printer
EP3377328A4 (fr) * 2016-02-05 2019-06-26 Hewlett-Packard Development Company, L.P. Capteurs de barre d'impression
US10427406B2 (en) 2016-02-05 2019-10-01 Hewlett-Packard Development Company, L.P. Print bar sensors

Also Published As

Publication number Publication date
ATE459483T1 (de) 2010-03-15
DE60141451D1 (de) 2010-04-15

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