Patent Grant
9296229
This application claims priority to Japanese Patent Application No. 2014-185525 filed Sep. 11, 2014 the subject matter of which is incorporated herein by reference in entirety.
The present invention relates to a printing apparatus and a printing method for printing images onto a web.
Examples of such currently-used apparatus include an inkjet printing apparatus (also referred to as an image recorder). The printing apparatus includes a transport mechanism transporting web paper (web), and inkjet heads each discharge ink (ink droplets) onto the web paper to be transported for printing images. For instance, four inkjet heads are provided in a transportation direction of the web paper, and discharge ink in four colors individually for color printing.
The web paper sometimes serpentines when the transport mechanism transports the web paper. Such serpentine web paper causes misregister that an actual printing position is shifted from a target printing position. This causes a color shift that printing positions for different colors shift relative to one another. There has been disclosed a method of performing registration by moving the inkjet heads (printing heads) in accordance with detection values by edge sensors or a method of conform the color shift by shifting printing data for adjusting the misregister or the color shift generated in the above manner. See, for example, Japanese Unexamined Patent Publication No. 2002-099178A. In Japanese Unexamined Patent Publication No. 2002-099178A, a position of forming a latent image by an electro photographic printing apparatus is corrected.
A precise positioning mechanism is required for moving the heads for registering. This leads to an expensive apparatus. Accordingly, another method has been disclosed to perform registration while shifting the print data. On the other hand, when the print data is shifted in a page of the web, a discontinuous part DC in an image (see
The present invention has been made regarding the state of the art noted above, and its one object is to provide a printing apparatus and a printing method that allow suppression of misregister or a color shift upon printing of an image onto a web transported in a serpentine manner.
The present invention is constituted as stated below to achieve the above object. One embodiment of the present invention discloses a printing apparatus printing an image onto a web. The printing apparatus includes a transport mechanism transporting the web; a printing head printing an image onto the web to be transported; a serpentine amount sensor detecting a serpentine amount caused by transportation of the web at a position in which the printing head is disposed or a position therearound; a predicted waveform data generating unit generating predicted waveform data of the serpentine amount to be produced in the following web in accordance with actually measured waveform data on the detected serpentine amount; a shift amount determining unit determining a shift amount of the printing position of the image to be shifted in a width direction of the web, orthogonal to a transportation direction of the web, in a direction in which the predicted serpentine amount is decreased in accordance with the predicted waveform data; and a correcting unit correcting the printing position of the image in accordance with the shift amount and applying a corrected printing position to the printing heads.
With the printing apparatus according to the embodiment of the present invention, the serpentine amount sensor detects the serpentine amount caused by the transportation of the web. The predicted waveform data generating unit generates the predicted waveform data on the serpentine amount to be produced in the following web in accordance with the actually measured waveform data on the detected serpentine amount. The correcting unit corrects the printing positions of the image in accordance with the shift amount, and applies the corrected printing position to the printing head. Here, the shift amount is determined with the shift amount determining unit in accordance with the predicted waveform data. Accordingly, the shift amount is determinable in accordance with the actually measured waveform data on the serpentine amount detected with the serpentine amount sensor more accurately than that with a method using a shift amount directly. This allows suppressed misregister.
Moreover, it is preferable that a plurality of printing heads of the printing apparatus according to the embodiment of the present invention is disposed in the transportation direction of the web, and a plurality of serpentine amount sensors is provided for the printing heads individually. The serpentine amount sensors are provided for the printing heads individually. This allows suppression of the misregister and the color shift in the image printed with the printing heads.
Moreover, it is preferable in the printing apparatus according to the embodiment of the present invention that the actually measured waveform data is composed of differential serpentine amounts obtained by calculating a difference between the serpentine amount detected by one of the serpentine amount sensors and a reference serpentine amount detected with another one of the serpentine amount sensors on either an upstream or downstream side of the one of the serpentine amount sensors in the transportation direction. Specifically, the predicted waveform data generating unit generates the predicted waveform data on the serpentine amounts to be produced in the following web in accordance with the actually measured waveform data composed of the differential serpentine amounts obtained by calculating the difference between the given serpentine amount and the reference serpentine amount. Here, the differential serpentine amount corresponds to a relative amount of the given serpentine amount and the reference serpentine amount. Consequently, the color shift can be suppressed more easily than that when the shift amount is determined only from the given serpentine amount.
Moreover, in the embodiment of the present invention, the predicted waveform data generating unit of the printing apparatus generates the predicted waveform data per page onto which the printing is performed. This allows suppression of the misregister and the color shift per page onto which the printing is performed.
Moreover, in the embodiment of the printing apparatus according to the present invention, the correcting unit corrects the printing position of the image by shifting the printing position with the printing head. Specifically, with an inkjet printing apparatus, the correcting unit performs correction such that ink to be discharged from inkjet nozzles in given positions is discharged from inkjet nozzles shifted in accordance with the shift amount. This achieves correction of the printing position of the image while no image data is changed.
Moreover, in the embodiment of the present invention, the correcting unit of the printing apparatus corrects the printing position of the image by changing a positional relationship in the image data. Specifically, the correcting unit changes the positional relationship in the image data without shifting the printing position with the printing head. This achieves correction of the printing position of the image.
Another embodiment of the present invention discloses a printing method of printing an image onto a web. The printing method includes a serpentine amount detecting step of detecting a serpentine amount caused by transportation of the web by a serpentine amount sensor at a position of a printing head or a position therearound; a predicted wave form data generating step of generating predicted waveform data on the serpentine amount to be produced in the following web by a predicted waveform data generating unit in accordance with actually measured waveform data on the detected serpentine amount; a shift amount determining step of determining a shift amount of the printing position of the image by a shift amount determining unit in a width direction of the web, orthogonal to a transportation direction of the web, in a direction in which the predicted serpentine amount is decreased, in accordance with the predicted waveform data; and a correcting step of correcting the printing position of the image by a correcting unit in accordance with the shift amount and applying a corrected printing position to the printing head.
With the printing method according to the other embodiment of the present invention, the serpentine amount sensor detects the serpentine amount caused by the transportation of the web. The predicted waveform data generating unit generates the predicted waveform data on the serpentine amount to be produced in the following web in accordance with the actually measured waveform data on the detected serpentine amount. The correcting unit corrects the printing position of the image in accordance with the shift amount, and applies the corrected printing position to the printing head. Here, the shift amount is determined by the shift amount determining unit in accordance with the predicted waveform data. Accordingly, the shift amount is obtainable in accordance with the actually measured waveform data on the serpentine amount detected with the serpentine amount sensor more accurately than a shift amount obtained directly. This allows suppressed misregister.
With the printing apparatus and the printing method according to the embodiments of the present invention, the serpentine amount sensor detects the serpentine amount caused by the transportation of the web. The predicted waveform data generating unit generates the predicted waveform data on the serpentine amount to be produced in the following web in accordance with the actually measured waveform data on the detected serpentine amount. The correcting unit corrects the printing position of the image in accordance with the shift amount, and applies the corrected printing position to the printing head. Here, the shift amount is determined with the shift amount determining unit in accordance with the predicted waveform data. Accordingly, the shift amount is determinable in accordance with the actually measured waveform data on the serpentine amount detected with the serpentine amount sensors more accurately than that through a method in which a shift amount directly determined. This allows suppressed misregister.
For the purpose of illustrating the invention, there are shown in the drawings several forms which are presently preferred, it being understood, however, that the invention is not limited to the precise arrangement and instrumentalities shown.
The following describes one embodiment of the present invention with reference to drawings.
<Entire Configuration of Printing Apparatus>
Reference is made to
The paper feeder 2 holds web paper WP in a roll form to be rotatable about a horizontal axis, and unwinds the web paper WP to feed it to the inkjet printer 3. The take-up roller 5 winds up the web paper WP printed by the inkjet printer 3 about the horizontal axis. Regarding the side from which the web paper WP is fed as upstream and the side to which the web paper WP is taken up as downstream, the paper feeder 2 is disposed upstream of the inkjet printer 3 whereas the take-up roller 5 is disposed downstream of the inkjet printer 3.
The inkjet printer 3 includes a drive roller 7 upstream thereof for taking in the web paper WP from the paper feeder 2. The web paper WP unwound from the paper feeder 2 by the drive roller 7 is transported downstream toward the take-up roller 5 along transport rollers 9. A drive roller 11 is disposed between the most downstream transport roller 9 and the take-up roller 5. The drive roller 11 feeds the web paper WP transported on the transport rollers 9 toward the take-up roller 5. Here, the transport rollers 9 are rotatable rollers with no drive mechanism.
The inkjet printer 3 includes a print unit 13, a drier 15, and an inspecting unit 17 in this order from upstream thereof between the drive rollers 7 and 11. The drier 15 dries portions printed by the print unit 13. The drier 15 includes a heat drum (not shown) with a heater embedded therein. The inspecting unit 17 inspects the printed portions for any stains or omissions. Here, the drive rollers 7 and 11 and the transport roller 9 correspond to the transport mechanism in the present invention.
The print unit 13 includes a plurality of printing heads 19 discharging ink individually. The print unit 13 also includes a plurality of (e.g. four) printing heads 19 (19a to 19d) along a transportation direction 201 of the web paper WP. In the present embodiment, the printing heads 19 are formed by a first printing head 19a, a second printing head 19b, a third printing head 19c, and a fourth printing head 19d in this order from upstream thereof. The printing heads 19 are individually spaced away from each other at a given interval in the transportation direction 201.
The printing heads 19a to 19d discharge ink in at least two colors, and allow color printing onto the web paper WP. For instance, the first printing head 19a discharges ink in black (K), and the second printing head 19b discharges ink in cyan (C). The third printing head 19c discharges ink in magenta (M), and the fourth printing head 19d discharges ink in yellow (Y).
As illustrated in
The printing apparatus 1 also includes edge sensors 23 (23a to 23d), and a positional shift corrector 25. The edge sensors 23 each detect a serpentine amount (actually measured serpentine amount) MJ caused by transportation of the web paper WP. The positional shift corrector 25 corrects a positional shift of the image to be printed in accordance with the serpentine amount MJ detected by each of the edge sensors 23. The edge sensors 23 and the positional shift corrector 25 are to be described later in detail. Here, the edge sensors 23 correspond to the serpentine amount sensors in the present invention.
Hereinunder, the printing heads 19a to 19d are simply referred to as the printing heads 19 if the heads are not particularly distinguished from one another. In addition, the edge sensors 23a to 23d are simply referred to as the edge sensors 23 if the sensors are not particularly distinguished from one another. The same is applicable to the other components.
The printing apparatus 1 further includes a main controller 27 controlling en bloc the components of the apparatus 1, a storing unit 29 storing image data G to be printed, an input unit 31 used for operator's input setting, and a display unit 33 displaying an operation screen and the like. The main controller 27 is formed by a central processing unit (CPU). The storing unit 29 is formed by a ROM (Read-only Memory), a RAM (Random-Access Memory), or a storage medium such as a hard disk. The input unit 31 is formed by a keyboard, a mouse, a touch panel, and the like. The display unit 33 is formed by a liquid crystal monitor and the like.
<Edge Sensor and Positional Shift Correcting Unit>
The following describes the edge sensors 23 and the positional shift corrector 25 formed by at least either a hardware or a software as characteristic features of the present invention with reference to
The printing apparatus 1 includes the edge sensors 23, a collecting unit 41, and a predicted waveform data generating unit 43. The edge sensors each detect the serpentine amount MJ caused by the transportation of the web paper WP. The collecting unit 41 collects the detected serpentine amount MJ. The predicted waveform data generating unit 43 generates the predicted waveform data HY on the serpentine amount MY to be produced in the following web paper WP in accordance with actually measured waveform data HJ on the detected and collected serpentine amount MJ. The printing apparatus 1 further includes a shift amount determining unit 45 (see
The serpentine varies sequentially in its period and its amplitude. Accordingly, it is difficult to print the image to the serpentine web paper WP accurately. For instance, the actually measured waveform data HJ detected with the edge sensors 23a and 23b in
The edge sensors 23 each detect the serpentine amount MJ caused by the transportation of the web paper WP. Specifically, as illustrated in
The following describes determining positions (i.e., setting positions) of the edge sensors 23 in the transportation direction 201. The edge sensor 23a detects the serpentine amount MJ at a setting position of the printing head 19a or around the position. Specifically, the setting position of the printing head 19a is, for example, a setting position of the inkjet nozzles 20. Moreover, the edge sensor 23a is disposed at the setting position.
It is preferable that the edge sensor 23a detects the serpentine amount MJ at the setting position of the inkjet nozzles 20 of the printing head 19a in the transportation direction 201 or around the setting position. That is for determining the shift amount SF1 with the serpentine amount MJ1 detected with the edge sensor 23a. However, because of a gap between the printing head 19a and the web paper WP, the edge sensor 23a is disposed upstream of and spaced away from the printing head 19a over the transport path of the web paper WP, as illustrated in
Determining positions of the other edge sensors 23b to 23d are each the same as the determining position of the edge sensor 23a. Moreover, it is preferable that the edge sensors 23 are formed by the edge sensor 23a, the edge sensor 23b, the edge sensor 23c, and the edge sensor 23d in this order from the upstream of the web paper WP in the transportation direction 201. In other words, it is not preferable that the edge sensor 23a for the first printing head 19a is disposed downstream of the edge sensor 23b for the second printing head 19b.
The collecting unit 41 in
The predicted waveform data generating unit 43 generates the predicted waveform data HY on the predicted serpentine amount MY to be produced in the following web paper WP in accordance with the actually measured waveform data HJ on the serpentine amount MJ detected with the edge sensors 23 and collected with the collecting unit 41. See
The predicted waveform data HY is generated through a linear predicting method such as a Yule Walker equation.
Here, the predicted waveform data generating unit 43 updates the predicted coefficient for the linear predicting method used upon generation of the predicted waveform data HY every determination of the preset number of serpentine amounts MJ. This allows accurate generation of the predicted waveform data HY. Moreover, the predicted waveform data HY may be generated at a previous timing, such as a timing denoted by the numeral S in
The shift amount determining unit 45 determines the shift amount SF by which the printing position of the image is shifted in the width direction 202 of the web paper WP, substantially orthogonal to (intersecting) the transportation direction 201 of the web paper WP, in a direction in which the predicted serpentine amount MY is decreased in accordance with the predicted waveform data HY generated with the predicted waveform data generating unit 43. It is assumed that one page corresponds to an area where one printing object (contents) is included. Under this assumption, the shift amount determining unit 45 determines the shift amount SF in accordance with the predicted waveform data HY, at the shift amount SF a misregister amount being minimized in a page R (see
The correcting unit 47 corrects the printing position of the image in accordance with the shift amount SF determined with the shift amount determining unit 45, and applies the corrected position to the printing head 19. The printing head 19 print the image whose printing position is corrected by the correcting unit 47.
The correcting unit 47 corrects the position by two ways, both of which are adoptable. The following describes the first way. That is, the correcting unit 47 corrects the printing position of the image by shifting the printing position (printing formation position) with the printing head 19 in accordance with the shift amount SF. In other words, as illustrated in
The following describes the second way. The correcting unit 47 corrects the printing position of the image by changing the positional relationship in the image data G in accordance with the shift amount SF. That is, the correcting unit 47 does not shift the printing position with the printing head 19, but changes the positional relationship in the image data G by editing the image data G to be printed. This achieves correction of the printing position of the image. Here, the correcting unit 47 does not only correct the printing position of the image but also controls a discharging position by fine movement of the printing head 19. Such may be adopted.
<Operation of Printing Apparatus>
The following describes operation of the printing apparatus 1. Firstly, a method of correcting the misregister for the first printing head 19a is described, and then a method of correcting the misregister (color shifts) for each of the second to fourth printing heads 19b to 19d is described.
<Method of Correcting Misregister for First Printing Head 19a>
The following describes a method of correcting misregister for the first printing head 19a disposed the most upstream side. Reference is made to
The predicted waveform data generating unit 43 generates predicted waveform data HY1 after the actually measured waveform data HJ1, i.e., the predicted waveform data HY1 on the predicted serpentine amount MY1 to be produced in the following web paper WP, in accordance with the actually measured waveform data HJ1 on the obtained serpentine amount MJ1 as illustrated in
The shift amount determining unit 45 determines the shift amount SF1 by which the printing position of the image is shifted in the width direction 202 of the web paper WP, orthogonal to the transportation direction 201 of the web paper WP, in a direction in which the predicted serpentine amount MY1 is decreased in accordance with the predicted waveform data HY1, as illustrated in
When the pages R are printed, the correcting unit 47 corrects the printing position of the image to be printed with the printing head 19a in accordance with the shift amount SF1, and applies the corrected position to the printing head 19a. Here, the shift amount SF1 is constant from start to completion of one-page printing. The same is applicable to the shift amounts SF2 to SF4. The printing head 19a discharges ink in black (K) to print the image whose printing position is corrected. This allows suppression of the misregister of the image printed in black (K) with respect to the given position of the web paper WP.
<Method of Correcting Misregister (Color Shift) for Second to Fourth Printing Head 19b to 19d>
The following describes a method of correcting misregister (color shifts) for second to fourth printing heads 19b to 19d. The edge sensor 23b detects a serpentine amount MJ2 caused by transportation of the web paper WP.
Moreover, the edge sensor 23c for the third printing head 19c detects a serpentine amount MJ3. The edge sensor 23d for the fourth printing head 19d detects a serpentine amount MJ4.
The collecting unit 41 collects actually measured waveform data HJ2, mentioned later, so as to suppress a color shift between the image printed with the printing head 19a and that printed with the printing head 19b. That is, the actually measured waveform data HJ2 is composed of a differential serpentine amount MJ2-MJ1 obtained by calculating a difference between the upstream serpentine amount MJ1 detected with the edge sensor 23a upstream in the transportation direction 201 and the downstream serpentine amount MJ2 detected with the edge sensor 23b downstream in the transportation direction 201. In other words, the actually measured waveform data HJ2 is composed of the differential serpentine amount MJ2-MJ1 obtained by calculating a difference between the serpentine amount MJ2 detected with the edge sensor 23b and the serpentine amount MJ1 detected with the edge sensor 23a, other than the edge sensor 23b, upstream in the transportation direction.
Moreover, the actually measured waveform data HJ3 used for suppressing the color shift of the image printed with the third printing head 19c is composed of a differential serpentine amount MJ3-MJ1. The actually measured waveform data HJ4 used for suppressing the color shift of the image to be printed with the fourth printing head 19d is composed of a differential serpentine amount MJ4-MJ1.
The predicted waveform data generating unit 43 generates predicted waveform data HY2 on the predicted serpentine amount MY2 to be produced in the following web paper WP in accordance with the actually measured waveform data HJ2 on the differential serpentine amount MJ2-MJ1. For instance, the predicted waveform data generating unit 43 generates the predicted waveform data HY2 per page. The predicted waveform data HY2 is generated through the linear predicting method. This obtains the entire or partial predicted waveform data HY2 for pages R to be printed.
Similar to the actually measured waveform data HJ2, the predicted waveform data generating unit 43 generates predicted waveform data HY3 on the predicted serpentine amount MY3 to be produced in the following web paper WP in accordance with the actually measured waveform data HJ3 on the differential serpentine amount MJ3-MJ1. Moreover, the predicted waveform data generating unit 43 generates predicted waveform data HY4 on the predicted serpentine amount MY4 to be produced in the following web paper WP in accordance with the actually measured waveform data HJ4 on the differential serpentine amount MJ4-MJ1.
The shift amount determining unit 45 determines a shift amount SF2 in a direction in which the predicted serpentine amount MY2 is decreased in accordance with the predicted waveform data HY2. By the shift amount SF2, the printing position of the image is shifted in the width direction 202 of the web paper WP orthogonal to the transportation direction 201 of the web paper WP. That is, the shift amount determining unit 45 determines the shift amount SF2 at which the misregister amount is minimized. The misregister amount is, for example, obtained by determining an average value of the entire or partial predicted waveform data HY2 in one of the pages R to be printed.
Moreover, similar to the predicted waveform data HY2, the shift amount determining unit 45 determines a shift amount SF3 in accordance with the predicted waveform data HY3, and determines a shift amount SF4 in accordance with the predicted waveform data HY4.
The correcting unit 47 corrects the printing position of the image printed with the printing head 19b in accordance with the shift amount SF2, and applies the corrected position to the printing head 19b. The printing head 19b discharges ink in cyan (C) to print the image whose printing position is corrected. This allows suppression of the misregister of the image printed in cyan (C) with respect to the image printed with the printing head 19a.
Moreover, the correcting unit 47 corrects the printing positions of the images printed with the printing heads 19c and 19d in accordance with the shift amounts SF3 and SF4, respectively. The printing heads 19c and 19d discharge ink in magenta (M) or yellow (Y), respectively, to print the images whose printing positions are corrected. This allows suppression of the misregister of the images printed in magenta (M) and yellow (Y) with respect to the image printed with the printing head 19a.
The predicted waveform data generating unit 43 generates predicted waveform data HY2 on the predicted serpentine amount MY2 to be produced in the following web paper WP in accordance with the actually measured waveform data HJ2 on the differential serpentine amount MJ2-MJ1 obtained by calculating a difference between the serpentine amount MJ2 and the serpentine amount MJ1 as a reference. Here, the differential serpentine amount MJ2-MJ1 is a relative amount of the serpentine amount MJ2 and the serpentine amount MJ1 as a reference. Accordingly, the color shift can be suppressed more easily than with the shift amount SF2 determined only from the serpentine amount MJ2. The same is applicable to the serpentine amounts MJ3 and MJ4.
The following describes an effect through the linear predicting method (Yule Walker equation).
With the present embodiment, the edge sensors 23 detect the serpentine amounts MJ caused by transportation of the web paper. The predicted waveform data generating unit 43 generates the predicted waveform data HY on the serpentine amounts MY to be produced in the following web paper in accordance with the actually measured waveform data HJ on the obtained serpentine amounts MJ. The correcting unit 45 corrects the printing positions of the images in accordance with the shift amounts SF, and applies the corrected positions to the printing heads 19. The shift amounts SF are determined by the shift amount determining unit 45 in accordance with the predicted waveform data HY. This allows determination of the shift amounts SF in accordance with the actually measured waveform data HJ on the serpentine amounts MJ detected with the edge sensors 23 more accurately than those by a method of directly determining the shift amounts. Accordingly, the misregister can be suppressed.
A plurality of printing heads 19 is provided in the transportation direction of the web paper WP, and the edge sensors 23 are provided for the printing heads 19 individually. Since the edge sensors 23 are provided for the printing heads 19 individually, the misregister of the image printed with the printing heads 19 can be suppressed. In addition, a color shift can be suppressed.
Moreover, the predicted waveform data generating unit 43 generates the predicted waveform data HY per page to be printed. Accordingly, the misregister or the color shift can be suppressed per page to be printed.
The present invention is not limited to the foregoing examples, but may be modified as follows.
(1) In the embodiment mentioned above, the four printing heads 19 are disposed. However, another number of printing heads 19 may be adopted. For instance, six printing heads 19 may be disposed. In this case, six edge sensors 23 are provided for the printing heads 19 individually in the transportation direction 201 of the web paper WP. Alternatively, one printing head 19 may be adopted.
(2) In the embodiment and the modification (1) mentioned above, the edge sensors 23a to 23d detect the serpentine amounts MJ1 to MJ4, respectively. The actually measured waveform data HJ2 is composed of the differential serpentine amount MJ2-MJ1. Moreover, the actually measured waveform data HJ3 is composed of the differential serpentine amount MJ3-MJ1. The actually measured waveform data HJ4 is composed of the differential serpentine amount MJ4-MJ1. Then, the shift amounts SF2 to SF4 are determined in accordance with the actually measured waveform data HJ2 to HJ4, respectively, for correcting the color shifts. However, the actually measured waveform data HJ2 to HJ4 is not limited to the above.
For instance, the actually measured waveform data HJ2 may be composed of the serpentine amount MJ2, the actually measured waveform data HJ3 may be composed of the serpentine amount MJ3, and the actually measured waveform data HJ4 may be composed of the serpentine amount MJ4. In this case, the misregister for each of the serpentine amounts can be suppressed. In addition, when the given positions of the web paper WP each as a reference agree with each other, the misregister can be suppressed to the same degree as the effect of the color shift in the present embodiment.
Moreover, the actually measured waveform data HJ2 may be composed of the differential serpentine amount MJ2-MJ1, the actually measured waveform data HJ3 may be composed of the differential serpentine amount MJ3-MJ2, and the actually measured waveform data HJ4 may be composed of the differential serpentine amount MJ4-MJ3. In this case, the misregister for each of the serpentine amounts can be suppressed. In addition, when the given positions of the web paper WP each as a reference of the serpentine amount MJ1 and the serpentine amount MJ3 agree with each other, the misregister can be suppressed to the same degree as the effect of the color shift in the present embodiment.
(3) In the embodiment and the modifications mentioned above, the actually measured waveform data HJ2 to HJ4 is each formed in accordance with the serpentine amount MJ1. Alternatively, the actually measured waveform data may be formed in accordance with the serpentine amount MJ2. In this case, the actually measured waveform data HJ1 is composed of the differential serpentine amount MJ1-MJ2, and the actually measured waveform data HJ2 is composed of the serpentine amount MJ2. Moreover, the actually measured waveform data HJ3 is composed of the differential serpentine amount MJ3-MJ2, and the actually measured waveform data HJ4 is composed of the differential serpentine amount MJ4-MJ2.
(4) In the embodiment and the modifications mentioned above, the serpentine amount sensor is the edge sensor 23. However, this is not limitative. For instance, the web paper WP contains a line printed in the transportation direction 201, and a serpentine amount is obtained by determining a positional variation of the line in the width direction 202 using a photoelectric sensor. Such is adoptable.
(5) In the embodiment and the modifications mentioned above, the web paper WP is web as a long print medium to be transported. Alternatively, the web paper WP may be a resin (plastic) sheet.
(6) In the embodiment and the modifications mentioned above, the inkjet printing apparatus 1 has been described. Alternatively, other types of printing apparatus printing images onto the web paper WP may be adopted. For instance, an electro photographic printing apparatus may be adopted. In this case, the printing heads in the present invention correspond to a latent image formation unit (not shown). The latent image formation unit forms a latent image by irradiating an electrically charged photoreceptor with laser beams or the like. The latent image formation unit corrects the printing position of the image by changing a timing of writing the latent image with the laser in accordance with the shift amount SF.
The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.
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| 2014-185525 | Sep 2014 | JP | national |
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