Printing apparatus

A color inkjet printing apparatus in which an image capturing part captures an image of a page identifier printed on each page of a printing medium, and an inspection part compares a page identification result acquired from an output of the image capturing part with page identification information included in print data. The page identifier includes single-color parts that are each printed with only one of a plurality of colors used in the printing apparatus. Thus, a printing defect can be quickly detected during inspection of the first page in which the printing defect has occurred, irrespective of the ink color in which the printing defect has occurred.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a 35 U.S.C. §371 national phase conversion of PCT/JP2010/060839 filed Jun. 25, 2010 and claims priority of JP2009-223671 filed Sep. 29, 2009, both incorporated herein in their entirety.

TECHNICAL FIELD

The present invention relates to a printing apparatus.

BACKGROUND ART

Conventionally, there have been used inkjet printing apparatuses that perform printing on a printing medium by scanning, relative to the printing medium, an ejection mechanism in which a plurality of outlets for ejecting minute ink droplets are arranged. In recent years, inkjet printing apparatuses have also been used for printing where the content to be printed varies for each page (so-called variable data printing) such as in credit card bills or the like, in which case, for example, printing is continuously performed on both the front and back surfaces of a plurality of pages set for a long-length printing medium.

Along with such printing apparatuses, various techniques for inspecting a printing defect where the content printed on the front surface of a page does not correspond to the content printed on the back surface of that page (i.e., the content to be printed on the back surface of one page is printed on the back surface of a different page) have been proposed. For example, Japanese Patent Application Laid-Open Gazette No. 2001-58446 discloses a technique for use in an inkjet printer that performs color printing on both the front and back surfaces of a long-length printing medium, in which an identifier such as a number, a symbol, or a bar code is printed on the front and back surfaces of each page, and a printing defect where the contents printed on the front and back do not correspond to each other is inspected by capturing and comparing images of the identifiers on both the front and back surfaces on the downstream side of the conveyance direction of the printing medium.

Meanwhile, like Japanese Patent Application Laid-Open Gazette No. 2001-58446, Japanese Patent Application Laid-Open Gazette No. 2004-314610 discloses a technique for use in an electrophotographic printing apparatus, in which a printing defect where the contents printed on the front and back do not correspond to each other is detected by printing a bar code or the like on both the front and back surfaces of a printing medium and capturing and comparing images of the bar code or the like on the downstream side. The printing apparatus disclosed in Japanese Patent Application Laid-Open Gazette No. 2004-314610 also enables detection of a printing defect where the front and back surfaces of a certain page are both missing, by comparing the bar codes on the front surfaces of adjacent pages and also comparing the bar codes on the back surfaces of these pages.

Incidentally, with the printing apparatuses as disclosed in Japanese Patent Application Laid-Open Gazettes Nos. 2001-58446 and 2004-314610, the bar codes on the front and back of each page are printed with a black (K) ink that can be read by an ordinary bar code reader. Therefore, a printing apparatus that performs color printing cannot detect printing defects due to inks of colors other than black even if such printing defects have occurred.

SUMMARY OF INVENTION

The present invention is intended for a printing apparatus, and it is an object of the present invention to detect printing defects due to inks of all colors in inkjet color printing.

The printing apparatus includes a printing mechanism by which printing is performed on a printing medium with inks of a plurality of colors using an inkjet system, a print control part that, when each page of the printing medium is printed, prints a page identifier on the printing medium based on page identification information included in print data of the page, by controlling the printing mechanism, an image pickup part that captures an image of the page identifier, and an inspection part that detects a printing defect by acquiring a page identification result from an output of the image pickup part and comparing the page identification result with the page identification information, wherein the page identifier includes at least one single-color part that is printed with only any one of the plurality of colors, and under control of the print control part, printing of single-color parts with all of the plurality of colors is performed during a period in which printing is being performed on only a predetermined number of pages. According to the present invention, it is possible to detect printing defects due to inks of all colors in inkjet color printing.

In a preferred embodiment of the present invention, the page identifier on each of the pages includes single-color parts printed with all of the plurality of colors. This enables quick detection of a printing defect. More preferably, the inspection part acquires a page identification result from each of the single-color parts printed with the plurality of colors and compares each of the page identification results with the page identification information. As a result, the color of an ink with which a printing defect has occurred can be easily specified.

In another preferred embodiment of the present invention, the page identifier on each of the pages is printed with only any one of the plurality of colors. Accordingly, the color of an ink with which a printing defect has occurred can be easily specified. More preferably, a color of the page identifier is sequentially changed for each page. This enables quick detection of a printing defect.

In still another embodiment of the present invention, the page identifier on each of the pages is a bar code. Accordingly, the page identification result can be easily acquired.

In still another embodiment of the present invention, the printing mechanism performs printing on both sides of the printing medium, in which case the page identifier is printed on both of the sides, the image pickup part captures images of the page identifiers on both of the sides, and the inspection part inspects consistency in printing between both of the sides by acquiring page identification results for both of the sides from an output of the image pickup part.

In still another embodiment of the present invention, the printing mechanism includes a supply part that holds a roll of unprinted printing medium and lets the printing medium out from the roll, and a taking-up part that takes up a portion of the printing medium that has undergone printing.

MODE FOR CARRYING OUT THE INVENTION

FIG. 1is a perspective view showing an external appearance of a printing apparatus1according to a first embodiment of the present invention. The printing apparatus1is an apparatus that performs inkjet color printing on a printing medium9, which is printing paper of long length. The printing apparatus1includes a printing mechanism11for performing printing on a main surface91(hereinafter referred to as a “front surface91”) of the printing medium9on the (+Z) side with inks of a plurality of colors, an image capturing part6that captures an image of a portion of the printing medium9that has undergone printing, and a control unit that controls these mechanisms.

The printing mechanism11includes a scanning mechanism27for moving the printing medium9in the Y direction (hereinafter also referred to as the “scanning direction”) inFIG. 1, and an ejection unit3that ejects minute ink droplets toward the printing medium9that is being conveyed by the scanning mechanism27. The ejection unit3and the image capturing part6are disposed above the scanning mechanism27(on the (+Z) side) and fixed to a frame25that is provided on a base20so as to span over the scanning mechanism27.

In the scanning mechanism27, a plurality of rollers271that are each long in the X direction (i.e., the direction that is horizontal and is perpendicular to the Y direction) inFIG. 1are arranged in the Y direction, a supply part272that holds a roll (supply roll) of unprinted printing medium9is provided on the (+Y) side of the plurality of rollers271, and a taking-up part273that holds a roll (taking-up roll) of printing medium9is provided on the (−Y) side of the plurality of rollers271. In the following description, it is assumed that the printing medium9as simply referred to means the printing medium9that is being conveyed (that is, the printing medium9on the plurality of rollers271).

An encoder29that detects the moving speed of the printing medium9in the scanning direction is provided in one roller271aof the scanning mechanism27. By a later-described scanning controller412(seeFIG. 3) controlling motor rotation of the taking-up part273based on the output of the encoder29, a portion of the printing medium9that has undergone printing is taken up by the taking-up part273, and at the same time, the printing medium9is let out from the supply roll in the supply part272and moves at a constant speed in the (−Y) direction. At this time, the printing medium9smoothly moves on the plurality of rollers271without waving, by a load (tension) being applied to the printing medium9in the direction ((+Y) direction) opposite to the movement direction by a motor of the supply part272.

FIG. 2is a bottom view showing the ejection unit3. The ejection unit3includes inkjet heads31that are a plurality of (in the present embodiment, four) heads each ejecting an ink of a different color, and these inkjet heads31have the same configuration. The plurality of inkjet heads31are arranged in the Y direction (i.e., the scanning direction) and attached to an attachment part30of the ejection unit3.

InFIG. 2, the inkjet head31located closest to the (+Y) side ejects an ink of black (K) color, the inkjet head31located on the (−Y) side of the black inkjet head31ejects an ink of cyan (C) color, the inkjet head31located on the (−Y) side of the cyan inkjet head31ejects an ink of magenta (M) color, and the inkjet head31located closest to the (−Y) side ejects an ink of yellow (Y) color. Note that the ejection unit3may also be provided with inkjet heads or the like for other colors such as light cyan, light magenta, or white.

As shown inFIG. 1, the image capturing part6is provided with a two-dimensional charge coupled device (CCD) camera61including a plurality of CCD elements. The two-dimensional CCD camera61is disposed on the (−Y) side of the ejection unit3, which is the downstream side in the conveyance direction of the printing medium9, and captures an image of a part of the front surface91of the printing medium9that has undergone printing and is passing through under the camera.

In the printing apparatus1, each inkjet head31(seeFIG. 2) is provided extending over the entire printing area of the printing medium9in the X direction (here, extending across the entire width of the printing medium9in the X direction), and printing of an image on the printing medium9is completed through a single operation of the scanning mechanism27moving the printing medium9relative to the ejection unit3in the scanning direction (i.e., by a single pass of the printing medium9, which is moving in the (−Y) direction, under the ejection unit3) (so-called single-pass printing is performed).

FIG. 3is a block diagram showing the functions of a control unit4. InFIG. 3, a part of the configuration of the printing apparatus1connected to the control unit4is shown together. The control unit4includes a print control part41that controls the printing mechanism11, an inspection part42that detects a printing defect on the printing medium9, and a storage part43that stores various types of information. The print control part41includes an ejection controller411that controls ejection of inks from the four inkjet heads3of the ejection unit3, and the scanning controller412that performs control of the scanning mechanism27.

As shown inFIG. 4, a plurality of pages93that are arranged in the scanning direction and on which images are to be printed are set for the printing medium9. The printing apparatus1performs variable data printing in which a different image is to be printed on the front surface91of the printing medium9for each page93. InFIG. 4, the border between each pair of adjacent pages93is indicated by the chain double-dashed line. The storage part43shown inFIG. 3stores a plurality of print data pieces431that correspond respectively to images to be printed on the plurality of pages93of the printing medium9. The print data431of each page includes page identification information432for identifying the page from other pages (e.g., information indicating the page number of the current page).

In the printing apparatus1shown inFIG. 1, printing onto the printing medium9is performed by the print control part41controlling the scanning mechanism27and the ejection unit3based on the plurality of print data pieces431(seeFIG. 3) so that inks are ejected from the ejection unit3toward the printing medium9in synchronization with the movement of the printing medium9relative to the ejection unit3in the scanning direction. When printing is performed on each page93of the printing medium9shown inFIG. 4, a page identifier95is printed in an identifier printing area950set in one edge portion of the page93in the width direction (in the present embodiment, the edge portion on the (−X) side), based on the page identification information432included in the print data431of the page. Although the identifier printing area950is indicated by the chain double-dashed line inFIG. 4in order to facilitate understanding of the figure, the rectangle indicated by the chain double-dashed line is in actuality not printed (the same applies toFIGS. 5,7, and8).

The identifier printing area950is set, for example, outside punching holes that are formed in opposite sides of the printing medium9in the X direction for use in conveyance of the printing medium9or the like. Also, marks or the like indicating, for example, a page break and a print start position are printed upstream and downstream of the identifier printing area950(on the (−Y) and (+Y) sides). The aforementioned punching holes or other marks or the like are not shown inFIG. 4.

FIG. 5is an enlarged plan view of a page identifier95. InFIG. 5, the Y direction drawn parallel to the longitudinal direction inFIG. 4has been drawn parallel to the lateral direction. The page identifier95includes a single-color part (unicolor part)951aprinted with only an ink of K color, a single-color part951bprinted with only an ink of C color, a single-color part951cprinted with only an ink of M color, and a single-color part951dprinted with only an ink of Y color. In other words, the page identifier95includes the single-color parts951ato951dprinted with all of the plurality of (in the present embodiment, four) colors used for printing in the printing apparatus1.

The single-color parts951ato951dare printed respectively in four single-color-part printing areas955ato955dthat are arranged in the Y direction within the identifier printing area950, and a blank area955e(i.e., an area on which printing is not performed) is provided between each pair of adjacent single-color-part printing areas. The single-color parts951ato951deach represent one of single-digit integers from “0” to “9” depending on the shape. Although the single-color-part printing areas955ato955dare each encircled by the chain double-dashed line inFIG. 5in order to facilitate understanding of the figure, these rectangles indicated by the chain double-dashed lines are in actuality not printed (the same applies toFIG. 8).

FIG. 6is a diagram showing the relationship between the shapes of the single-color parts and the numerical values represented by the single-color parts. As shown inFIG. 6, if only the leftmost area (which corresponds to the (−Y) side on the printing medium9) is colored out of four areas obtained by dividing one single-color-part printing area into four in the Y direction, the single-color part represents “0”. If the two leftmost areas are colored, the single-color part951represents “1”, and if only the second area from the left is colored, the single-color part951represents “2”.

The single-color part951represents “3” if the second and third areas from the left are colored, and represents “4” if only the third area from the left is colored. If the two rightmost areas of the single-color-part printing area955are colored, the single-color part951represents “5”, and if only the rightmost area is colored, the single-color part951represents “6”. Furthermore, the single-color part represents “7” if the second area from the left and the rightmost area are colored, represents “8” if the leftmost area and the rightmost area are colored, and represents “9” if the leftmost area and the third area from the left are colored.

In the printing apparatus1shown inFIG. 1, in parallel with the printing performed on the printing medium9, the image capturing part6captures an image of the page identifier95(seeFIG. 5) printed in the identifier printing area950on each page. An output from the image capturing part6is transmitted to the inspection part42of the control unit4(seeFIG. 3), and the inspection part42acquires a page identification result from the output of the image capturing part6. At this time, the inspection part42acquires the page identification result from each of the single-color parts951ato951dof the page identifier95whose image has been captured by the image capturing part6. In the present embodiment, values of “4”, “3”, “2” and “1” are acquired as the numerical values represented respectively by the single-color parts951ato951d, and it can thereby be seen that the imaged page is the 1234th page. Then, each of the identification results is compared with the page identification information432included in the print data431(seeFIG. 3), and a printing defect is detected if the page identification result and the page identification information432are different.

The following describes a specific embodiment of detecting a printing defect, taking an ink of K color as an example. Note that the following description also applies to inks of the other colors. If data to be printed on a different page with an ink of K color has been printed on the current page due to a missing page or the like, a printing defect due to the ink of K color is detected because the page identification result acquired from the black single-color part951aof the page identifier95differs from the page identification information432.

Furthermore, with the print data431corresponding to a single page of the printing medium9, if the result of printing with the ink of K color has shifted in the Y direction due to, for example, a loss of part of data to be printed on that page with the ink of K color, the black single-color part951ais printed at a position shifted in the Y direction from the identifier printing area950. As a result, a printing defect due to the ink of K color is detected because the image of the single-color part951acannot be appropriately captured by the image capturing part6and accordingly the page identification result acquired from the single-color part951adiffers from the page identification information432.

If all the data to be printed with the ink of K color has been lost or if printing using the ink of K color has not been performed due to, for example, the occurrence of an ejection failure in the inkjet head31for ejecting the ink of K color, a printing defect due to the ink of K color is detected because the black single-color part951ais not printed and accordingly the page identification result corresponding to the single-color part951acannot be acquired.

As described above, in the printing apparatus1, the image of the page identifier95printed on each page of the printing medium9is captured by the image capturing part6, and the page identification results obtained from the output of the image capturing part6and the page identification information432included in the print data431are compared in the inspection part42. Since the page identifier95includes the single-color parts951ato951dprinted with inks of all of the plurality of colors used in the printing apparatus1, a printing defect can be quickly detected during inspection of the first page in which the printing defect has occurred, irrespective of with which ink color out of the plurality of colors the printing defect has occurred. Furthermore, the color of an ink with which a printing defect has occurred can be easily specified by the inspection part42acquiring the page identification result from each of the single-color parts951ato951dof the page identifier95and comparing each of the page identification results with the page identification information432.

With the printing apparatus1, it is also possible, by changing the control performed by the print control part41, to print the entire page identifier on each page of the printing medium9with only an ink of one of the plurality of colors used in the printing apparatus1and to perform printing of page identifiers with inks of all of the plurality of colors during the period in which printing is being performed for a predetermined number of pages (which is the number of pages greater than or equal to the number of ink colors (in the present embodiment, four) used in the printing apparatus1, and is hereinafter referred to as a “unit page number”). In other words, the page identifier forms one single-color part, and under the control of the print control part41, printing of single-color parts with all of the above plurality of colors is performed during the period in which printing is being performed for the unit page number.

For example, in the case where the unit page number is four, a page identifier is printed with the ink of K color in the identifier printing area950(seeFIG. 4) on the first page, a page identifier is printed with the ink of C color in the identifier printing area950on the second page, a page identifier is printed with the ink of M color in the identifier printing area950on the third page, and a page identifier is printed with the ink of Y color in the identifier printing area950on the fourth page. As for the fifth and subsequent pages, the color of the page identifier is changed for each page in order starting with K, then to C, to M, and to Y.

FIG. 7is a view showing another page identifier95ahaving a different relationship between the shape and the numerical value from that of the page identifier95shown inFIG. 5. In the example shown inFIG. 7, an identifier printing area950in which the page identifier95ais to be printed includes a plurality of color areas953aand a plurality of blank areas953bthat are alternately arranged in the Y direction, and the plurality of color areas953aarranged in the (+Y) direction from the (−Y) side correspond respectively to a plurality of binary digits from the lowest to the highest. A colored color area953arepresents a corresponding binary-digit value of “1”, and a non-colored color area953arepresents a corresponding binary-digit value of “0”. Accordingly, the page identifier95ashown inFIG. 7indicates the fifth page.

In the printing apparatus1shown inFIG. 1, as described above, the image capturing part6captures the image of the page identifier95a(seeFIG. 7) on each page, and the inspection part42acquires a page identification result from the output of the image capturing part6and compares the page identification result with the page identification information432(seeFIG. 3) in the print data431. Then, if a mismatch between the page identification result and the page identification information432has been detected on a certain page, a printing defect on that page is detected, and at the same time, the printing defect is determined to have occurred with the ink color used to print the page identifier95aon that page. In this way, the color of an ink with which a printing defect has occurred can be easily specified by printing the page identifier95aon each page with an ink of any one of the plurality of colors used in the printing apparatus1.

Incidentally, with the method for printing the page identifier95aon each page with only an ink of a single color, for example, if the color of the page identifier95ais assumed to be changed for each page in order starting with K from the first page, then to C, then to M, and then to Y and a printing defect due to the ink of K color has occurred on the second page, that printing defect cannot be detected until the end of inspection of the fifth page on which the page identifier95ais next printed with the ink of K color. Accordingly, from the viewpoint of reducing the time from the occurrence of a printing defect to the detection of the printing defect as short as possible, the interval between pages on which the page identifier95ais printed with an ink of the same color is preferably as short as possible.

As described above, the printing apparatus1can relatively quickly detect a printing defect by sequentially changing the color of the page identifier95afor each page on condition that the unit page number is made equal to the number of ink colors (in the present embodiment, four) used in the printing apparatus1.

Next is a description of a printing apparatus according to a second embodiment of the present invention. The printing apparatus according to the second embodiment has the same configuration as that of the printing apparatus1shown inFIG. 1, with the exceptions that a bar code96shown inFIG. 8is printed, instead of the page identifier95shown inFIG. 5, as the page identifier in the identifier printing area950on each page of the printing medium9, and that a bar code reader is provided, instead of the two-dimensional CCD camera61, in the image capturing part6shown inFIG. 1. In the following description, the same reference numerals have been given to constituent elements of the printing apparatus according to the second embodiment that correspond to those of the printing apparatus1shown inFIG. 1.

In the printing apparatus according to the second embodiment, the bar code reader of the image capturing part6captures an image of the bar code96printed on each page of the printing medium9, and the inspection part42(seeFIG. 3) compares the page identification result acquired from the output of the image capturing part6(i.e., the result of readout by the bar code reader) with the page identification information432included in the print data431(seeFIG. 3). Since the bar code96includes single-color parts951ato951dprinted with all of the plurality of colors (in the present embodiment, four) used in the printing apparatus1as shown inFIG. 8, a printing defect can be quickly detected during inspection of the first page in which the printing defect has occurred, irrespective of with which ink color out of the plurality of colors the printing defect has occurred, as in the first embodiment. Although the single-color parts951ato951dare encircled by the chain double-dashed lines inFIG. 8in order to facilitate understanding of the figure, these rectangles indicated by the chain double-dashed lines are in actuality not printed.

Also, as in the first embodiment, the color of an ink with which a printing defect has occurred can be easily specified by the inspection part42acquiring a page identification result from each of the single-color parts951ato951dof the bar code96and comparing each of the page identification results with the page identification information432. Furthermore, using the bar code96as the page identifier facilitates acquisition of the page identification results from the page identifier, using an existing bar code reader.

With the printing apparatus according to the second embodiment, as in the first embodiment, it is also possible, by changing the control performed by the print control part41, to print the entire bar code96on each page of the printing medium9with only an ink of any one of K, C, M, and Y colors and to perform printing of bar codes96with inks of all K, C, M, and Y colors during the period in which printing is being performed for the unit page number. In other words, the bar code96forms one single-color part, and under the control of the print control part41, printing of the single-color parts with all of the above plurality of colors is performed during the period in which printing is being performed for the unit page number.

With the printing apparatus according to the second embodiment, as in the first embodiment, the color of an ink with which a printing defect has occurred can be easily specified even if the bar code96on each page is printed with only an ink of a single color out of inks of the plurality of colors used in the printing apparatus. Furthermore, as in the first embodiment, a printing defect can be relatively quickly detected by sequentially changing the color of the bar code96for each page on condition that the unit page number is made equal to the number of ink colors (in the present embodiment, four) used in the printing apparatus.

Next is a description of a printing apparatus according to a third embodiment of the present invention.FIG. 9is a front view showing the configuration of a printing apparatus1aaccording to the third embodiment. In the printing apparatus1a, an inversion mechanism5for inverting the front surface91and a back surface92of the printing medium9is provided on a conveyance path of the printing medium9. Also, the printing mechanism11further includes another ejection unit3adisposed on the (−Y) side of the inversion mechanism5, facing the back surface92of the printing medium9, and the image capturing part6includes another two-dimensional CCD camera61adisposed on the (−Y) side of the ejection unit3a. The other constituent elements are the same as those of the printing apparatus1shown inFIG. 1, and in the following description, the same reference numerals have been given to constituent elements of the printing apparatus1athat correspond to those of the printing apparatus1.

In the printing apparatus1a, the ejection unit3ejects minute ink droplets toward the front surface91of the printing medium9, and the two-dimensional CCD camera61of the image capturing part6sequentially captures images of the identifier printing areas950(seeFIG. 4) of a plurality of pages set for the front surface91of the printing medium9. Then, the inversion mechanism5inverts the front surface91and the back surface92of the printing medium9such that the back surface92is on the (+Z) side, and the ejection unit3aejects minute ink droplets toward the back surface92of the printing medium9in synchronization with the movement of the printing medium9in the scanning direction. In the printing apparatus1a, the printing mechanism11(i.e., the ejection unit3, the ejection unit3a, and the scanning mechanism27) performs printing on the front surface91and the back surface92of each page of the printing medium9, and the page identifier95(seeFIG. 5) including the single-color parts951ato951dprinted with inks of all of the plurality of colors used in the printing apparatus1a(in the present embodiment, inks of four colors including K, C, M, and Y) is also printed on both sides of each page of the printing medium9.

The two-dimensional CCD camera61aof the image capturing part6sequentially captures images of the identifier printing areas950(seeFIG. 4) of a plurality of pages set for the back surface92of the printing medium9that is passing through under the camera. In the printing apparatus1a, the two-dimensional CCD cameras61and61aof the image capturing part6capture images of the page identifiers95on both sides (i.e., the front surface91and the back surface92) of the printing medium9, and the inspection part42of the control unit4(seeFIG. 3) acquires the page identification results for both sides from the output of the image capturing part6.

Then, for each of the front surface91and the back surface92of the printing medium9, as in the first embodiment, the page identification result for each page is compared with the page identification information432(seeFIG. 3) included in the print data431of the page stored in the storage part43of the control unit4, and a printing defect is detected if the page identification result and the page identification information432are different.

With the printing apparatus1a, as in the first embodiment, a printing defect can be quickly detected during inspection of the first page in which the printing defect has occurred, irrespective of with which ink color out of the plurality of colors used in the printing apparatus1athe printing defect has occurred. It is also possible to easily specify the color of an ink with which a printing defect has occurred.

With the printing apparatus1aaccording to the third embodiment, it is in particular possible to easily inspect consistency in printing between the front surface91and the back surface92of each page (i.e., whether or not the content printed on the front surface91of a single page of the printing medium9corresponds to the content printed on the back surface92of that page), by comparing a combination of the page identification result acquired from the image capturing result of the front surface91of each page and the page identification result acquired from the image capturing result of the back surface92of that page with a combination of the page identification information432included in the print data431of the front surface91of the page and the page identification information432included in the print data431of the back surface92of the page.

While the above has been a description of embodiments of the present invention, the present invention is not intended to be limited to the above-described embodiments, and various modifications are possible.

The page identifiers described above and shown inFIGS. 5 through 8are preferable examples, and the relationship between the shape of the page identifier and the numerical value indicated by the page identifier may be appropriately changed in accordance with the content to be printed on the printing medium9or the like. Furthermore, various types of information (e.g., character information) other than numerical values may be indicated by a page identifier or single-color parts included in a page identifier.

The page identifier95or the bar code96does not necessarily have to be printed with either inks of all of the plurality of colors used in the printing apparatus or only an ink of any one of these colors, and it may be printed with, for example, inks of an arbitrary number of colors, which is at least two, out of the above plurality of colors, so as to include single-color parts, the number of which is equal to the arbitrary number of colors. In other words, the page identifier95or the bar code96includes at least one single-color part printed with any one of the plurality of colors used in the printing apparatus. Then, by printing single-color parts with all of the plurality of colors during the period in which printing is being performed for the unit page number, it is possible to detect printing defects due to inks of all of the colors in inkjet color printing.

In the printing apparatuses according to the above-described embodiments, for example, instead of moving the printing medium9with the scanning mechanism27, the printing medium9may be fixed and the ejection unit3and the image capturing part6(and also the ejection unit3a) may be moved in the scanning direction. In other words, it is sufficient that the scanning mechanism27causes the printing medium9to move in the scanning direction relative to the ejection unit3and the image capturing part6(and also the ejection unit3a).

The configuration of the printing apparatus1may be applied to a printing apparatus in which an ejection unit moves back and forth in a direction perpendicular to a scanning direction and a printing medium9is moved by a predetermined distance in the scanning direction for each single unidirectional movement of the ejection unit (so-called shuttle printing is performed). Furthermore, the printing apparatus1may perform, for example, sheet-fed printing in which printing is sequentially performed on a plurality of printing media that do not have a long length.

DESCRIPTION OF REFERENCE SIGNS