JP2002328097A - Method and device for inspecting printing mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for inspecting a printed paper capable of easily absorbing variation in the amount of reflected light from an inspection light source, with no special correction. SOLUTION: A printing mechanism 1 which prints on a paper is inspected by selectively turning ON/OFF a plurality of print pixels which are arrayed in the direction Y substantially perpendicular to the transportation direction X of a paper 8. A CCD line sensor 4 comprising a plurality of image acquiring pixels arrayed in the Y direction substantially perpendicular to the transportation direction X of the paper is used to acquire a reflected light quantity data Di of inspection regions C1 and C2 provided on the paper 8. The printing mechanism 1 is inspected based on the acquired reflected light quantity data Di of image acquiring pixels and reflected light quantity data Di-1 and Di+1 of adjoining image acquiring pixels.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inspecting printed matter for inspecting printing defects such as de-marking and smearing of printed matter, and more particularly to a method and an apparatus for inspecting printed matter which can very easily absorb variations in the inspection light source. It relates to an inspection device.

[0002]

2. Description of the Related Art In order to improve print quality, image data of a predetermined area of a printed matter is captured by a CCD camera, and the printed image is compared with reference image data to inspect the printed matter for de-marking and dirt. (See, for example, JP-A-11-348241). For example, a printed matter printed by a printing machine is measured by a CCD camera for the amount of reflected light for each pixel divided by n lines × m columns,
By comparing the measured amount of reflected light with a reference amount of reflected light stored in advance for each pixel, the printed matter is inspected for de-inking, smearing, and the like.

However, when a printed image of a printed matter is captured by a CCD camera, the amount of light from the light source for the CCD camera varies depending on the position of a pixel, and thus the measured amount of reflected light needs to be corrected.

For this reason, in Japanese Patent Application Laid-Open No. 7-323527, the maximum value of the measured reflected light amount is obtained, the reflected light amount is corrected for each pixel using this maximum value, and the corrected reflected light amount and the reference reflected light amount are corrected. It has been proposed to verify the presence / absence of stamping and smearing of the printed matter by comparing the above.

[0005]

However, the inspection method disclosed in Japanese Unexamined Patent Publication No. 7-323527 involves a process of obtaining the maximum value of the amount of reflected light and using this to correct the amount of reflected light for each pixel. Therefore, a processing circuit and a processing program for the processing are separately required, and there is a possibility that the apparatus becomes complicated and the cost increases.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and a method of inspecting a printed material capable of extremely easily absorbing variations in the amount of light of an inspection light source without any special correction processing. And an inspection device.

[0007]

(1) In order to achieve the above object, according to the present invention, a plurality of printing pixels arranged in a direction substantially perpendicular to the transport direction of a printing medium are selectively provided. A method for inspecting a printing mechanism for performing printing on the print medium by turning ON or OFF a sensor having a plurality of image acquisition pixels arranged in a direction substantially perpendicular to a conveyance direction of the print medium. Using, to obtain the light amount data of the inspection area provided on the print medium, based on the obtained light amount data of each image acquisition pixel and the light amount data of image acquisition pixels adjacent thereto, the printing mechanism An inspection method of a printing mechanism to be inspected is provided.

In the inspection method of the printing mechanism of the present invention, the light quantity data of the inspection area is acquired by using a plurality of image acquisition pixels arranged in the width direction of the print medium. In evaluating a defect of the printing mechanism based on the data, light amount data of adjacent image acquisition pixels is compared. That is, the light amount varies depending on the inspection position due to a difference in the distance from the inspection light source or the characteristics of the light source itself, but such variation can be almost ignored between adjacent image acquisition pixels. Therefore, it is not necessary to perform a complicated correction process, and a print defect can be detected with high accuracy only by comparing light amount data of adjacent image acquisition pixels.

Note that the light quantity data in the present invention is defined as data of reflected light quantity when light emitted from a light source is reflected on a print medium and transmitted light quantity data when light emitted from the light source is transmitted through a print medium. The purpose is to include both.

(2) In the above invention, the specific method of comparing the light amount data of one image acquisition pixel with the light amount data of an adjacent image acquisition pixel is not particularly limited. Then, a difference between the light quantity data of the image acquisition pixel and the light quantity data of the adjacent image acquisition pixel is obtained. If the difference is larger than the reference difference, it is determined that the printing mechanism has a defect. Alternatively, the difference between the light quantity data by the image acquisition pixel and the light quantity data by two adjacent image acquisition pixels is calculated, and the sum of the two differences is calculated as described in claim 3. If the sum is larger than the reference difference sum, it is determined that the printing mechanism has a defect. Further, as described in claim 4, this operation is called the Nth order difference sum (N is an integer of 2 or more)
If the calculated Nth order difference sum is larger than the reference difference sum, it is determined that the printing mechanism has a defect.

According to the printing mechanism inspection method according to the second aspect, a printing defect can be detected by a very simple operation, whereas according to the printing mechanism inspection method according to the third and fourth aspects, the detection accuracy is improved. Higher erroneous detection can be prevented.

(3) In the above invention, the inspection pattern printed in the inspection area can be selected according to the type of defect to be inspected. For example, when inspecting a stain defect due to ink leakage of a print pixel, it is sufficient to set a non-print area (a print area on which no print data is printed, a ground color area of a print medium) or a blank area as an inspection area.
On the other hand, when inspecting a mark removal failure due to ink clogging of the print pixels, at least all the print pixels should be at least substantially perpendicular to the transport direction of the print medium in the inspection area of the print medium. It is preferable to use a plurality of inspection marks that are turned on and off once. In particular, in this case, as described in claim 5, it is more preferable to print a plurality of test mark modules including a plurality of test marks for turning on and off all the print pixels at least once according to the arrangement pattern of the image acquisition pixels. preferable.

When the light quantity data of the inspection mark module printed in the same pattern is acquired by using the image acquisition pixels, the light quantity data of the adjacent modules have the same value. Therefore, the presence / absence of a defect can be evaluated only by comparing (for example, a difference) the obtained light amount data for each adjacent image acquisition pixel. That is, the reference light amount data does not have to be stored in advance for each image acquisition pixel.

Incidentally, it is also possible to detect a stain defect due to ink leakage of a printing pixel in an inspection area where the inspection mark module is printed.

(4) In the above invention, the inspection area provided on the printing medium may be provided over the entire printing area of the printing mechanism in the width direction of the printing medium, but may be provided continuously or divided depending on the printing specifications. (See claim 6).

By providing the inspection area continuously in the width direction of the print medium, one position setting of the inspection area is sufficient.
Further, by providing the inspection area in a divided manner, the empty space of the print medium can be effectively utilized.

(5) In the above invention, it is more preferable that a mark for identifying whether or not the page is the page for setting the inspection area is printed for each page of the print medium (see claim 7). Based on the detection signal of this mark,
The start and end of the inspection work can be determined.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. Hereinafter, the present invention will be described by taking an example of an inspection apparatus that inspects for a problem such as nozzle clogging or ink dripping of a so-called continuous ink jet printing machine. However, the inspection device and the inspection method for a printing mechanism of the present invention selectively turn on or off a plurality of printing pixels arranged in a direction substantially perpendicular to the conveying direction of the printing medium.
The printing mechanism is not particularly limited to a specific printing method of a printing machine as long as the printing mechanism performs printing on a print medium by performing the printing.

Further, since the present invention is to prevent the occurrence of printing defects in a printed matter by detecting a failure of a printing mechanism, from another viewpoint, the present invention is also applicable to a method and an apparatus for inspecting a printed matter. is there.

First, as shown in FIG.
Has a paper feed roll 11, a plurality of print heads 12, and a paper discharge roll 13.
Supplied to

As shown in FIGS. 2 and 3, each print head 12 has an ink tank 121 containing ink.
And an ink pressurizing device 12 which pressurizes and supplies this ink.
2, a piezo element 123 for turning the ink supplied by the ink pressurizing device 122 into particles, a plurality of nozzles 124 for discharging the particleized ink, and a nozzle 1
A charge electrode 125 for applying a charge voltage corresponding to image data (bitmap data of print data) to ink ejected from the charge electrode 24;
5, a deflection electrode 126 for electrically sucking the ink charged by the charge electrode 125, and a catcher 127 for collecting the ink deflected by the deflection electrode 126 are provided.

Then, a voltage is applied / not applied to each charge electrode 125 according to the image data sent from the print control means 2, and the ink charged by this is
The ink that is deflected by the deflecting electrode 126 and collected by the catcher 127 while not being charged by the charging electrode 125 falls onto the paper 8 to form one dot.

In the print head 12 of this embodiment, a number of such print head chips shown in FIG. 2 are arranged side by side in the Y-axis direction by a print width (indicated by L in FIG. 6) and provided in a paper feed mechanism. Image data to be printed is sent from the print control unit 2 to each print head 12 together with the encoder data. Hereinafter, the original image data stored or generated in the print control unit 2 or a unit substantially equivalent thereto is referred to as print image data A. This print image data A is printed on the print area PA of the paper 8 indicated by the dotted line in FIG.

On the other hand, the print area PA
A first inspection area C1 for printing an inspection mark CM, which will be described later, by using an area other than the inside or the printing area PA;
A second inspection area C2 using a blank area where the printing area PA is not printed, and a determination area where an identification mark DM (see FIG. 7) for identifying whether or not to perform an inspection on a page of the paper is printed. C3 are provided. FIG. 6 shows a setting example of the first inspection area C1, the second inspection area C2, and the determination area C3.

The first inspection area C1 is a region in which the nozzle 124 of the printing mechanism is clogged with foreign matter or the ink pressurizing device 12
This is an area for inspecting a so-called white spot defect in which ink is not ejected due to a failure of No. 2 and the paper 8 is not printed. In this example, a dedicated inspection page is provided for every n pages.
The first inspection area C1 is set somewhere in the area corresponding to the print area PA of the inspection page. On the other hand, the second inspection area C2 is the charge electrode 125 of the printing mechanism.
In this example, the second inspection area is set for all pages using the margin area of the print area PA in the present embodiment. The determination area C3 is provided on each page as shown in FIG. 7. For example, a page for inspecting a blank defect is two line marks, and a page for inspecting a streaker defect is one line mark. Pages without any inspection are unmarked.

In the example of the front side of the sheet 8 shown in FIG.
The first inspection area C1 for the white spot defect inspection is a sheet 8
The second inspection area C2 for streaker inspection is provided continuously in a row at the lower end of the sheet along the width direction of the paper,
Utilizing the margin of the paper, the paper is divided into two in the width direction. In this case, the second inspection area C2 is set so that the two areas have a slight wrap margin in the width direction of the sheet 8 and, when combined, cover the entire area in the width direction of the sheet 8.

On the other hand, in the example of the back surface of the sheet 8 shown on the right side of FIG.
2 is provided continuously in a line along the width direction of the paper 8, and the first inspection area C1 for white spot defect inspection is divided into three in the width direction by using a margin of the paper. It is provided. In this case, the first inspection area C1 is set so that the three areas cover the entire area of the sheet 8 in the width direction of the sheet 8 when the three areas are combined with a slight wrap margin in the width direction of the sheet 8. Note that the first or second inspection area C1,
In the case where C2 is divided, erroneous detection on the division plane can be further prevented by giving a slight wrap margin. However, the present invention is not particularly limited, and the lap margin may be omitted.

Although the specific mode of the inspection mark CM printed on the first inspection area C1 will be described later, a print command of the inspection mark CM is issued in advance by, for example, an inspection page (the first inspection area C1 is changed every 500 pages). (A page to be created) is set to be printed and stored in the print control unit 2 shown in FIG. When the inspection page is reached, the print control means 2 prints an inspection mark C on each print head 12.
The print data for M is transmitted, and the inspection mark CM is printed, and at the same time, the identification mark DM is printed in the determination area C3. The inspection mark data serving as a reference for this inspection evaluation is referred to as inspection mark print data B.

In FIG. 1, the inspection mark print data B is stored in the print control means 2. However, depending on the specific configuration of hardware and software,
The inspection mark print data B may be embodied by storing it in another memory or the like.

Downstream of the print head 12 of the printing machine 1, there is provided an image acquisition means 4 composed of a CCD camera, a CCD line sensor, a laser scanner, or the like. Then, the image data of the inspection mark CM actually printed on the paper 8 is obtained by the image obtaining means 4. Actually, the amount of reflected light from the light source 3 is detected by the image acquisition unit 4. For the print image data A and the inspection mark print data B,
This image data is referred to as reflected light amount data D of the inspection mark CM.

The CCD line sensor serving as the image acquisition means 4 has a plurality of CCD pixels (corresponding to the image acquisition pixels of the present invention) arranged in parallel in the Y-axis direction of the paper 8. It has a resolution capable of analyzing the acquired reflected light amount data D in dot units.

The inspection apparatus for a printing mechanism of this embodiment uses the reflected light amount data D of the inspection mark CM captured by the image acquisition means 4.
After calculating and analyzing the data, it is determined whether the analysis result is within the reference value.If the analysis result is within the reference value, “no printing defect” is obtained. It has operation evaluation means 5 for outputting the result to an external device such as a display or an alarm. This operation evaluation means 5
For example, it can be constituted by a personal computer or a microcomputer having a CPU, a ROM and a RAM.

In this embodiment, the analysis and evaluation of the reflected light amount data D are executed by a personal computer. However, the analysis and evaluation of the data may be constituted by separate hardware. Is within.

Next, an example of the inspection mark CM of the present invention will be described. FIG. 4 shows the first inspection area C of the sheet 8 shown in FIG.
1 is an enlarged view, and it is assumed that a portion having gradation represents “printing (ink ON)” and a portion having no gradation represents “non-printing (ink OFF)”.

One print cell 9 shown in FIG. 1 has a width of 1 dot and a length of 6 dots in terms of the number of dots of the printing mechanism 1.
It is a dot. This size depends on the resolution of the CCD line sensor used as the image acquisition means 4,
When the resolution is high, the size of the print cell 9 can be reduced. Conversely, when the resolution is low, the size of the print cell 9 needs to be increased. That is, the size of the print cell 9 is such that when the print of one print cell 9 is missing, the difference from the size of the print cell 9 that is not missing can be clearly identified.
Although details will be described later, in this example, the print cells 9 of 6 frames × 6 columns are regarded as one module (corresponding to the inspection mark module of the present invention), and the amount of reflected light from the light source 3 is evaluated for each module. Any size may be used as long as the difference in the light amount between the case where the printing of one print cell 9 in one module is missing and the case where the printing is not missing is mechanically and electrically identifiable.

As described above, in this example, the inspection mark CM printed in the first inspection area C1 is constituted by a plurality of modules having the same pattern. That is, as shown in the figure, all the modules from the first module at the left end to the last module at the right end are each 6 frames ×
Print cells 9 in one module, composed of 6 rows of cells
Is turned on at least once from the nozzle 124 of the printing mechanism. In the example shown in the drawing, one cell corresponds to one dot of printing in the width direction of the paper 8, so that one printing cell 9 exists in one module, and In the direction X, one print cell 9 exists in each frame. Among the combinations satisfying these requirements, the combination shown in FIG. 1 is one in which six print cells 9 are regularly printed obliquely from upper left to lower right. The reason why a small space S is provided between the frames is that if the spaces are brought close to each other, even if a blank defect is actually occurring, there is a risk that the printing may be erroneously detected as normal printing due to ink bleeding. .

The inspection mark of this example has a print width L of 6
Printing is performed to the maximum width that can be divided by dots, and inspection is performed within this range.

The inspection mark CM configured as described above is denoted by C
When the image is captured by the CD line sensor 4 and the reflected light amount data D from the light source 3 is acquired, adjustment is made so that one inspection mark module can be detected by one or an integral multiple of CCD pixels. For example, in this example, one inspection mark module corresponds to four CCD pixels in the Y-axis direction. FIG.
FIG. 5 is a conceptual diagram showing the reflected light amount data acquired by the CCD line sensor 4 in the longitudinal direction of the line sensor.
Up to

The respective reflected light amount data D1 to Dn are
It is sent as a digital signal to the operation evaluation means 5 shown in FIG. 1, where the difference between adjacent reflected light amount data, that is, the difference between Di and Di-1, Di + 1 is obtained. That is, Di-Di-
1 and Di−Di + 1 are obtained. Further, in this example, the two differences thus obtained are added. That is, 2D
Find i-Di-1-Di + 1.

In the example shown in FIG. 5, the reflected light amount data D
Assuming that there is a blank defect in 6 and D12, 2D6-D5-
The value of D7 and the value of 2D12-D11-D13 are reflected light amount data without white spot defect, for example, 2D3-D2 for D3.
Since it becomes larger (brighter) than the value of -D4, it is possible to immediately detect a white spot defect. In this example,
Since the reflected light amount data of adjacent CCD pixels are compared,
Even if there is some variation in the light amount from the light source 3, this can be absorbed, and the white spot defect can be detected with high accuracy without performing complicated correction processing.

Since the first module and the last module have different amounts of reflected light, they are evaluated according to the procedures shown in FIGS. That is, FIGS. 8 and 9 are diagrams showing image data captured by the CCD line sensor 4. As shown in FIG. 8, for the head module, first, in the first inspection area C1 and the inspection mark CM A reference pattern 50 having a size of 1 pixel in width and 5 pixels in length is set on the left outer side of the print area, and the amount of reflected light is obtained. Here, since the position of the print area of the inspection mark CM is detected in the pre-processing, 1
The amount of reflected light in the pixel × 5 pixel area and the reference pattern 50
And the amount of reflected light. In the case of the example shown in the figure, first, the amount of reflected light of the reference pattern 50 and one pixel ×
The reflected light amount in the area 51 of five pixels is compared, and if the difference is large, it is determined that there is an edge of the print pattern there.
In this example, since the print pattern exists in the seventh area counted from the first area 51, the edge of the print pattern can be detected.

Next, the reference pattern 50 is shifted by three pixels in the transport direction X of the sheet 8, and the edge of the print pattern is detected in the same manner. This is sequentially repeated, and the positional relationship of the detected edge coordinates of each column is two times greater than the edge coordinates of the upper column.
If it is more than a pixel away, if no edge is detected,
If the inspection pattern width is different from the reference width by 3 pixels or more, it is determined that there is a printing failure.

For the last module, edge detection is performed in the same manner as in the above-mentioned first module to detect the presence or absence of a printing failure. In this case, as shown in FIG.
The reference pattern 50 is set within 1 and on the right outside of the print area of the inspection mark CM, and scanning is performed from right to left. Other steps are the same as those for the first module.

As described above, by detecting the printing failure in the first module and the last module by the edge detection, it is necessary to previously store the reference reflected light amounts of the first module and the last module as compared with other embodiments described later. Excellent in that there is no.

Incidentally, the second inspection area C2 shown in FIG.
When the streaker defect is detected by acquiring the reflected light amount data D, the reflected light amount data D1 to Dn acquired by the CCD
Is evaluated by calculating the difference between the adjacent reflected light amount data as shown in FIG. Further, in this example, the evaluation of the streaker was performed using the non-printing area, but the first inspection area C
1 can also be used for detection. In other words, when a streaker failure occurs, the non-printing cells in the inspection mark module are in a printing state, so the reflected light amount of that module is different from the reflected light amount of the normal module, and it is possible to detect the streaker. it can.

It is also possible to calculate the reflected light amount data adjacent to each other, that is, the difference between Di, Di-1, and Di + 1, and evaluate the difference.

Further, the operation evaluation means 5 determines whether or not the sum of the two differences obtained earlier is within a predetermined threshold value. If the value exceeds the value of the reference difference sum, the result of "print defect" is output to an external device such as a display or an alarm.

The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

For example, the inspection mark CM shown in FIG.
It can be modified as shown in FIG. In the example shown in FIG. 10, the inspection mark CM printed on the first inspection area C1 is configured by a plurality of modules having the same pattern. That is, as shown in the figure, the final module will be described later, but the intermediate modules are each 6 frames ×
The printing cell 9 in one module is constituted by six rows of cells, and is turned on at least once from the nozzle 124 of the printing mechanism.
It is configured to be. In the example shown in the drawing, one cell corresponds to one dot of printing in the width direction of the paper 8, so that one printing cell 9 exists in one module, and In the direction X, one print cell 9 exists in each frame. In addition, among the combinations satisfying these requirements, the combination shown in FIG. 6 is one in which the six print cells 9 are printed at positions as far apart as possible.

It is to be noted that the leftmost column of the first module is constituted by all cells to be printed (ON), so that the left end of the inspection mark can be detected. However, if there is a cell to be printed within two dots adjacent to the leftmost column, the cell in the leftmost column is a non-printing cell. In the example shown in the figure, frames 3 and 5 are non-printing cells. This is because, if adjacent patterns are used, even if a white spot defect occurs, it may be erroneously detected as normal due to ink bleeding. As for this head module, the amount of reflected light is different from that of the general module,
The reference amount of reflected light is known in advance.

In the last module, the width of the print area may not be divisible by 6 dots of the printing mechanism. In this case, the same pattern as that of the intermediate module is printed from the left, but is not printed to the right end of the pattern. The size of the final module will be different from the size of the general module. In addition, in the same meaning as the leftmost column of the first module, all rightmost columns of the last module are printed (ON).
And the right end of the inspection mark can be detected. However, if there is a cell to be printed within two dots adjacent to the rightmost column, the cell in the rightmost column is set as a non-printing cell for the same purpose as the above-described first module. In the example of FIG.
Are non-printing cells. Also for this final module, since the amount of reflected light differs from that of the general module, the amount of reflected light serving as a reference is known in advance.

In this example, the evaluation of the intermediate module is performed in the same manner as in the above-described embodiment. However, for the first module and the last module, a printing failure is determined by comparing with the reference reflected light amount data stored in advance. . In this example, the inspection can be performed up to the right end even if the width of the inspection area does not become an integral multiple of the module width.

[0053]

As described above, according to the present invention, the variation in the light amount of the inspection light source is absorbed only by the process of comparing the reflected light amount data of the adjacent image acquisition pixels without performing a complicated correction process. And printing defects can be detected with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a printing mechanism inspection apparatus according to the present invention.

FIG. 2 is a perspective view illustrating an example of a print head of the printing press.

FIG. 3 is a block diagram illustrating the printing mechanism of FIG. 2;

FIG. 4 is a front view of a printed material showing an example of an inspection mark according to the present invention.

FIG. 5 is a diagram for explaining a process of analyzing reflected light amount data according to the present invention.

FIG. 6 is a front view of a printed material showing an example of an inspection area according to the present invention.

FIG. 7 is a front view of a printed material showing an example of an identification mark according to the present invention.

FIG. 8 is a diagram for explaining a processing procedure of image data of a leading module according to the present invention.

FIG. 9 is a diagram for explaining a processing procedure of image data of a final module according to the present invention.

FIG. 10 is a front view of a printed material showing another example of the inspection mark according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Printing machine 2 ... Printing control means 3 ... Light source 4 ... CCD line sensor (image acquisition means) 5 ... Operation evaluation means

Claims (7)

[Claims] 1. A method for inspecting a printing mechanism for printing on a print medium by selectively turning on or off a plurality of print pixels arranged in a direction substantially perpendicular to a transport direction of the print medium. By using a sensor having a plurality of image acquisition pixels arranged in a direction substantially perpendicular to the transport direction of the print medium,
Printing for inspecting the printing mechanism based on light intensity data of each acquired image acquisition pixel and light intensity data of an image acquisition pixel adjacent to the acquired light intensity data of an inspection area provided on the print medium. Inspection method of mechanism. 2. The method according to claim 1, wherein a difference between the light quantity data of the image acquisition pixel and the light quantity data of an adjacent image acquisition pixel is obtained, and if the difference is larger than a reference difference, it is determined that the printing mechanism is defective. Item 2. The inspection method for a printing mechanism according to Item 1. 3. A difference between light amount data obtained by the image acquisition pixel and light amount data obtained by two image acquisition pixels adjacent thereto is obtained. If the sum of these two differences is larger than the reference difference sum, a printing mechanism is used. The inspection method for a printing mechanism according to claim 1, wherein it is determined that the printing mechanism has a defect. 4. A difference between the light quantity data of the image acquisition pixel and the light quantity data of two adjacent image acquisition pixels is obtained, a first-order difference sum of these two differences is obtained, and The second-order difference sum of the first-order difference sum is obtained, and this is repeated until the N-th order difference sum (N is an integer of 2 or more). If the N-th order difference sum is larger than the reference difference sum, the printing mechanism is defective. The method according to claim 1, wherein it is determined that there is a printing mechanism. 5. An inspection mark comprising a plurality of inspection marks for turning on and off all of the print pixels at least once in a direction substantially perpendicular to a direction in which the print medium is conveyed, in an inspection area of the print medium. 2. A plurality of modules are printed according to an array pattern of the image acquisition pixels.
5. The method for inspecting a printing mechanism according to any one of claims 1 to 4. 6. The inspection area is divided into a plurality of areas substantially perpendicular to the transport direction of the print medium, and is printed at different positions along the transport direction of the print medium. Item 6. The inspection method for a printing mechanism according to any one of Items 1 to 5. 7. The inspection method according to claim 1, wherein a mark for identifying whether or not the page is a page for setting the inspection area is printed for each page of the print medium.