JP4631384B2 - Printing state inspection method, character inspection method, and inspection apparatus using these methods - Google Patents

Description

The present invention performs an inspection to determine whether or not the printed body has a printing defect by imaging a printed body such as a character string or a mark including at least one character and processing the obtained image with a computer. Belongs to the technical field. In particular, the present invention uses a print body printed using a print head in which a plurality of nozzles are arranged in one direction as a test target, and whether or not a print defect has occurred in the print line of each nozzle. The present invention relates to a method and an apparatus for inspecting the above.

  Character strings such as date of manufacture, expiration date, and product code written on a package such as processed food are generally printed by an inkjet printer. An industrial ink jet printer used for this type of purpose has a print head in which a predetermined number of nozzles are arranged in a vertical row, and selects a nozzle that ejects ink according to the character to be printed. However, the printing operation is set to be performed (hereinafter, a band-like region where dots are printed by one nozzle is referred to as a “print line”).

  In the conventional inspection for the character string printed with dots as described above, the inspection using a pattern matching method is generally performed (see Patent Document 1).

JP 2003-187187 A

  When printing is performed by an ink jet printer, if any one of the nozzles is defective, a dot is always printed on the print line corresponding to the nozzle (hereinafter referred to as “dot filling”) or the above. There may be a defect in which no dot is hit on the print line corresponding to the nozzle (hereinafter referred to as “missing dot”).

FIG. 17 shows an example of the printing failure described above.
In the figure, the left side shows an example in which dot filling has occurred, and the right side shows an example in which dot dropout has occurred, and shows an example in which defects have occurred at the upper end, the center, and the lower end of the character string, respectively. In any example, the portion surrounded by the thin line frame is a defective portion. It should be noted that since dot embedding and omission occur when ink is ejected, printing defects do not occur in blank portions between characters.

  By the way, as described in Patent Document 1, a food package or the like has a printed surface that is not completely flat, and thus a printed character string is often distorted. It is possible. In view of such circumstances, there is a tendency that the determination reference value in pattern matching is set sweetly in the field. However, if the judgment reference value is made loose, there is a problem that a good judgment is made even for a character string in which a defect occurs over one print line as shown in FIG.

  The present invention has been made paying attention to the above-mentioned problems, and an object thereof is to make it possible to carry out an inspection specialized for printing defects occurring in units of one printing line.

In the printing state inspection method according to the present invention, a print head having a plurality of nozzles arranged in the vertical direction or the horizontal direction is moved relative to a print object along a direction orthogonal to the nozzle arrangement direction. The printing body formed on the printing object is imaged by controlling the printing operation of the dots of the nozzles while the nozzle is moved along the direction of movement of each nozzle relative to the printing object using the obtained image. It is inspected whether or not a printing defect has occurred in each printing line.
In the first print state inspection method according to the present invention, assuming that the print lines of the respective nozzles are orthogonal to the nozzle arrangement direction , dots are assumed in the direction of the assumed print line of the image of the print body. A range including the whole or a part of the distribution range is set as a processing range, while a range including all the assumed print lines corresponding to a plurality of nozzles in the direction orthogonal to the assumed print line of the image is set as the processing range. A first step of setting; projecting an image in the processing target area specified by the processing range set in the first step along the direction of a hypothetical print line, and assuming printing based on the projection result identify distribution range of dots in the direction orthogonal to the line, the processing target area, aligned along the direction of the assumptions of the printing line and in the direction perpendicular to the hypothetical print line Contact That ranges second step of setting a plurality of regions corresponding to a range that is the identified; projecting along said second respective hypothetical print line image in each area set in step, the projection the distribution range of dots in a direction perpendicular to the hypothetical print line based on the results as well as specific to each region, to identify the maximum length in the length of these distribution range, perpendicular to the assumption of the printing lines in each area Assuming that the range in each direction includes the distribution range of dots specified for each region, and the length of each region in the direction perpendicular to the assumed print line is unified to the maximum length. third step of correcting the position and length of each region in the direction perpendicular to the print line; in between the regions after executing the third step, the print line assumptions within each region Of each line along the direction, the combination for each one relative position corresponding in a direction perpendicular to the hypothetical print line, for each combination, the fourth to accumulate the number of pixels representing the dots in each the combined lines of Step: extracting a maximum value from the cumulative value obtained for each combination of the respective lines, comparing the extracted maximum value with a predetermined threshold value, and comparing the result that the maximum value is larger than the threshold value. When it is obtained, the fifth step of determining that dot filling has occurred along the direction of the actual print line is executed.

In the above, it is desirable that the nozzles of the print head be arranged in a line, but there may be some variation in the arrangement of the nozzles as long as the print lines do not overlap. This also applies to the following method and apparatus.
The “print line direction” refers to the length direction of the print line described above, and can be considered as a direction orthogonal to the arrangement direction of the nozzles. Further, it can be considered that the “direction perpendicular to the printing line” corresponds to a direction along the arrangement direction of the nozzles. When the object to be printed is a character string, printing is generally performed so that the characters constituting the character string are arranged along a print line. However, the relationship between the character string and the print line is not limited to this, and it is also possible to print such that each character is arranged along a direction orthogonal to the print line.

The actual print line may be distorted due to the shape of the workpiece, but it is assumed that the print line on the image processing is linear.
In the following description, it is assumed that the nozzles are arranged vertically, and the direction of the print line on the image is the horizontal direction (x-axis direction) and the direction orthogonal to the print line is the vertical direction (y-axis direction). When the nozzles are arranged side by side, the direction of the print line may be replaced with the y-axis direction, and the direction orthogonal to the print line may be replaced with the x-axis direction.

In the first step, a processing range having a predetermined width can be set for each of the x and y axes. The processing range in the x-axis direction can be set to a length that includes the entire dot printing range, but is not limited thereto, and can be set to a length that includes a part of the printing range.
When the print is a character string, the length of the processing range corresponding to the direction along the character string can be set to a length including an arbitrary number of one or more characters. Further, the starting end position of the processing range in the x-axis direction is not limited to the beginning of the character string, and can be set to the position of any second or subsequent character. On the other hand, the processing range in the orthogonal direction of the character string (corresponding to the height direction or width direction of the character) is large so that the entire range including all the print lines corresponding to the plurality of nozzles is surely included. Set to
The printing range can be considered as a range in which dots constituting the printed body are distributed.

In the second step , for example, the highest print position and the lowest print position of the dots are extracted by projecting the image data in the processing target area along the x axis, and these positions are set as the upper end and the lower end. Set the area to be used.

In the print object to be inspected according to the present invention, there is a possibility that dots corresponding to the same nozzle may not be printed in a line depending on the shape of the work to be printed. For this reason, there is a possibility that a shift occurs in the print range for each line along the y-axis direction in the processing target area.
The third step is to adjust the position and length of each area in accordance with such a shift in the print range. Each area is positioned at a height position corresponding to the fluctuation of the print range in the area. At the same time, the length of each region in the y-axis direction can be unified according to the maximum print width in the processing target region. As a result, the relative positional relationship between the print lines in the region can be made uniform among the regions.
When aligning the areas, for example, a process of aligning the upper end of the area with the upper end of the print range or a process of aligning the lower end of the area with the lower end of the print range can be executed.

When the print line direction is the x direction, in the fourth step, the horizontal line in each region that has undergone the adjustment in the third step is the first set of the first line, the second set of the second line,. Thus, the relative height position in the region can be combined for each line. Then, for each combination, the number of pixels representing dots on each combined line can be obtained and accumulated .

When dot filling occurs in a predetermined printing line, it is considered that the number of dots in the line corresponding to the defect occurrence position is larger than usual. Therefore, in the fifth step , it is possible to accurately determine whether or not dot filling has occurred by comparing the maximum value in the cumulative value for each combination of lines with a threshold value.

In the second printing state inspection method of the present invention, after executing the first same first to fourth steps and methods, the process target range of the width corresponding to the distance between the print lines due to adjacent nozzles A plurality of totals corresponding to the processing target range among the total values obtained for each combination of lines in the third step while adjusting the width direction in a direction orthogonal to the assumed print line and sequentially moving along the direction. The process of adding values is repeatedly executed, and the minimum value of the addition values obtained by each addition process is compared with a predetermined threshold value to obtain a comparison result that the minimum value of the addition value is smaller than the threshold value. In this case, it is determined that missing dots have occurred along the direction of the actual print line.

When missing dots occur in a predetermined print line, the number of dots in the range corresponding to the print line is considered to be extremely small. According to the second method, for each processing target range having a width corresponding to the distance between print lines, the degree of pixels representing dots in a plurality of lines included in the range is added, and Since the minimum value is compared with a predetermined threshold value, it is possible to accurately determine whether or not a dot is missing.
Is desirable.

In the first and second printing state inspection methods , when the inspection target is a character string, processing range setting information in a direction orthogonal to the character string (y-axis direction) is determined in advance. Also good. Alternatively, after setting a processing range in the x-axis direction, an image in the y-axis direction in this range may be searched to extract a dot printing range, and the processing range may be set based on the upper and lower ends of the range. .

Next, in the character inspection method according to the present invention , a horizontally written character string is imaged using a print head that prints vertically arranged dots by a plurality of nozzles, and the obtained character image is used for the character string. Along with this, it is inspected whether a printing defect has occurred. In the first method, an image of a character string to be inspected is projected along a direction orthogonal to the character string, and for each character constituting the character string in the image based on the projection result, the character is Extracting the range in which the dots to be distributed are distributed in the width direction of the character, projecting the image of the character string to be inspected along the direction of the character string, and representing the entire character string based on the projection result Extract the range distributed in the height direction of the character string, and for each character, the distribution range of dots extracted in the width direction for each character, and the dots in the height direction of the character string extracted for the entire character string said first image in the processing region of each character set in step projected along the direction of the respective string, the projection result; step of first setting the determined processing area by the distribution range The distribution range of the dot strings in the height direction as well as specific for each character based, to identify the maximum length in the length of these distribution range, in the height direction of the character string of each character in the processing region The height direction of the character string so that the range includes the distribution range of dots specified for each character and the length of each processing area in the height direction of the character string is unified to the maximum length. direction between the processing region after performing the second step, the line along the width direction of the processing region, perpendicular to the string; second step of correcting the position and length of each processing region in the the combination for each one relative positions corresponding in, for each combination, a third step of accumulated number of pixels representing the dots in each the combined line; union of the third at step each line When the local maximum value is extracted from the cumulative value obtained every time, the extracted local maximum value is compared with a predetermined threshold value, and the comparison result that the local maximum value is larger than the threshold value is obtained, the character The fourth step of determining that dot filling has occurred along the row direction is executed.

In the above, the “direction of the character string” is the arrangement direction of the characters constituting the character string, and can be considered to correspond to the printing direction of the nozzles. In the following description, the direction of the character string is described as the horizontal direction (x-axis direction), and the direction orthogonal to the character string is defined as the vertical direction (y-axis direction) . In this case, the length of the character in the x-axis direction corresponds to “character width”, and the length of the character in the y-axis direction corresponds to “character height” .

  In the first step, each character included in the character string can be cut out by projecting the image to be processed along the x-axis and y-axis directions. In this specification, in the projection process, it is assumed that the density value of each pixel along one horizontal line or one vertical line on the image is added, and the addition value of the density indicating the projection result is “projection value”. Call it. The projection process when the image to be processed is a binary image can be performed by a process of counting the number of black pixels or white pixels on one line. Therefore, the count value of the number of pixels can be considered as the projection value. On the other hand, when processing a grayscale image, it is desirable to process an image in which a character image is set to have a higher gradation than the background portion.

According to the correction processing of the processing area in the second step , if there is a variation in the position of the character in the character string in the y-axis direction, the same variation occurs in the position of the processing area. On the other hand, even if the height of each character varies due to distortion of the character string, etc., the height of each processing area is unified based on the maximum height, so the number of horizontal lines in each processing area is the same. Can be. Therefore, each horizontal line can be associated between the processing regions based on the relative position of the horizontal line within the processing region.

In the third step, horizontal lines that are relatively at the same height position are combined between the areas corresponding to the respective characters, and the number of pixels representing the dots in each line can be accumulated .
In the second step, since the lengths of the respective regions are unified, in the third step, all the horizontal lines in the respective regions can be associated with each other and the above-described accumulation process can be performed.

According to the processing in the second and third steps, the same height region is set for the characters having a variation in height. Therefore, the line correspondence between the corrected regions is the actual one. The print misalignment may not be accurately reflected. However, basically, printing is performed by a predetermined number of nozzles arranged in a vertical row, and therefore, the height variation between characters is considered to be slight. Therefore, if one dot is represented by a plurality of pixels, even if the horizontal line correspondence is slightly shifted, the horizontal line set associated with the region includes a horizontal line associated with the same print line. It can be considered that many are included. Accordingly, by accumulating the projection values for each set of corresponding horizontal lines, data reflecting the state of each print line with high accuracy can be obtained.

When dot filling occurs at a predetermined height position, it is considered that the number of pixels representing dots is larger than usual in the horizontal line of each character corresponding to the defect occurrence position. According to the above-described character inspection method, since a cumulative value for a horizontal line with a large number of pixels representing dots is extracted as a maximum value, it is accurately determined whether or not dot filling has occurred based on this cumulative value. be able to.

In the second character inspection method of the present invention, after executing the first to third steps similar to the first character inspection method, the processing target range having a width corresponding to the distance between the print lines by the adjacent nozzles is obtained. , the combined width direction of the string in the height direction, while moving sequentially along the direction, a plurality of cumulative corresponding to the processing target range of the cumulative value obtained for each combination of each line in the third step The process of adding values is repeatedly executed, and the minimum value of the addition values obtained by each addition process is compared with a predetermined threshold value to obtain a comparison result that the minimum value of the addition value is smaller than the threshold value. A fourth step is executed to determine that missing dots have occurred along the direction of the character string.

The predetermined threshold value used in the second character inspection method can be extracted from the image data of the print line where the missing dot has occurred. Alternatively, a cumulative value of the number of pixels representing dots when about one to two dots exist on one horizontal line may be obtained by calculation, and the obtained value may be used as a threshold value.

It should be noted that the cumulative value of the number of pixels representing dots is added to the blank portion between the print lines when the missing dot is determined by the second print state inspection method or the second character inspection method. This is in consideration of the possibility that the projection value on the horizontal line is close to zero. For example, if the size of the target range of the addition process is set to a value corresponding to the distance between adjacent print lines, the cumulative value for only the blank portion will not be compared with the threshold value, and It is possible to prevent a portion from being erroneously determined as a missing dot. In addition, in the addition process, if the range of the addition process is shifted pixel by pixel, the accuracy of determination can be further increased.

In certain printing line, if the missing dot has occurred, the number of pixels representing dots definitive horizontal line ranges corresponding to the print line is considered to be smaller than usual. In this case, the added value of the number of pixels for each horizontal line becomes the minimum value, and a comparison result is obtained that the minimum value is smaller than the threshold value. Therefore, it is possible to accurately determine that there is a missing dot. it can.

When inspecting a character string or other printed material according to the present invention, it is desirable to execute both a process for determining the presence or absence of dot filling and a process for determining the presence or absence of missing dots.
Further, in these determination processes, the numerical value to be compared (maximum value or minimum value of the addition value) is normalized based on the projection value of the line when the maximum number of dots are hit on one horizontal line, and similarly You may make it compare the normalized threshold value. In this case, if the maximum value after normalization and the minimum value of the addition value are displayed, the user can sensuously determine the degree of dot filling and omission.

Further, in a preferred aspect common to the first and second character inspection methods, in addition to the first to fourth steps, the length of each processing region in the height direction of the character string is specified in the second step . When the maximum length is compared with a predetermined threshold value and the comparison result that the maximum length is smaller than the threshold value is obtained, it is determined that a dot dropout has occurred at the edge of the character string. Step 5 is executed.

When the upper end of the dots or the lower end of the dot string is missing is a character of the cut-out process of the first step, it can not be accurately extracted height of characters. The predetermined threshold value for the fifth step can be set based on the character height when one dot print line is missing. Since the height of the area after the correction in the second step is based on the maximum value of the height of each character, the upper end or the lower end can be determined by comparing this height with the above threshold value. It is possible to accurately determine whether or not there is any missing dot. Judgment based on the maximum value of character length, rather than judgment based on the length of a specific character, may be caused by a misjudgment due to a symbol having a short character length such as “.” (Period). This is to prevent the occurrence.

Next, the printing state inspection apparatus according to the present invention is configured to make a print head having a plurality of nozzles arranged in the vertical direction or the horizontal direction relatively to a print object in a direction orthogonal to the nozzle arrangement direction. Direction of movement of each nozzle relative to the printing object using an image obtained by imaging a printing body formed on the printing object by controlling the printing operation of dots of each nozzle while moving Is an apparatus for inspecting whether or not a printing defect has occurred in a printing line for each nozzle along the line. The first printing state inspection apparatus according to the present invention assumes that the image input means for inputting the image of the printed body as an inspection target image and that the print lines of the nozzles are orthogonal to the nozzle arrangement direction. In the direction of the assumed print line of the inspection target image input by the image input means, a range including the whole or part of the dot distribution range is set as a processing range, while the assumption of the inspection target image is set . In a direction orthogonal to the print line, a processing range setting unit that sets a range including all assumed print lines corresponding to the plurality of nozzles as a processing range, and an area specified by the processing range in each direction is set as a processing target area after setting, by projecting along an image of this processing target area in the direction of the assumptions of the printing line, in a direction perpendicular to the hypothetical print line based on the projected result Kicking Identify distribution range of dots, in the processing target area, aligned along the direction of the assumptions of the printing line, and a plurality of regions range in the direction perpendicular to correspond to a range that is the specific assumptions print line an area setting means for setting, said projecting along an image of each area set in each hypothetical print line by the area setting means, the distribution of dots in the direction perpendicular to the hypothetical print line based on the projected result range as well as specific to each region, these distributions to identify the length maximum length in the range, distribution of dots each identified per the area in a range in a direction perpendicular to the assumption of print lines in each area range contains, and as the length of each region in the direction perpendicular to the assumption of the printing lines are unified to the length of the maximum, the direction perpendicular to the hypothetical print line Definitive and region adjusting means for correcting the position and length of each region, in between the regions corrected by the region adjusting means, each line along the direction of the assumptions of the printing lines in each area, the assumption of a printing line Combining for each corresponding relative position in the orthogonal direction, and for each combination, the total processing means for accumulating the number of pixels representing the dots in each combined line, and the total processing means for each line combination The maximum value extraction means for extracting the maximum value from the cumulative value and the maximum value extracted by the maximum value extraction means were compared with a predetermined threshold value, and a comparison result that the maximum value was larger than the threshold value was obtained. A determination unit that determines that dot filling has occurred along the direction of the actual print line, and an output unit that outputs a determination result by the determination unit.
In the second printing state inspection device according to the present invention, instead of the above-mentioned maximum value extracting means, the processing target range having a width corresponding to the distance between the printing lines by the adjacent nozzles is changed to the assumed printing line in the width direction. A process of adding a plurality of cumulative values corresponding to the processing target range among the cumulative values obtained for each combination of lines by the cumulative processing means while repeatedly moving along the direction according to the orthogonal direction is repeatedly executed. And a minimum value specifying means for specifying the minimum value among the added values obtained by the addition processing each time. Further, the determining means compares the minimum value specified by the minimum value specifying means with a predetermined threshold value, and when the comparison result that the minimum value is smaller than the threshold value is obtained, it follows the direction of the actual print line. It is determined that missing dots have occurred.

In the above, the image input means may include an input interface for taking in image data of the printed material, an A / D conversion circuit, and the like. According to the first inspection apparatus, it is possible to accurately inspect the dot filling along the direction of the printing line based on the first printing state inspection method. According to the second inspection apparatus, the second printing can be performed. Based on the state inspection method, it is possible to accurately inspect for missing dots along the direction of the printing line .

  Note that the above-described print state inspection apparatus can be provided with a binarization processing unit that binarizes an image to be processed. This binarization processing means can be a dedicated circuit, but can also be constituted by a computer in which a binarization threshold and a binarization processing procedure are set.

The printing state inspection apparatus according to a preferred aspect includes input means for inputting processing range setting information in the assumed print line direction, and the processing range setting means receives the setting information input from the input means. And configured to set a processing range in the direction of the assumed print line .

Next, the character inspection apparatus according to the present invention uses the image obtained by capturing an image of a horizontally written character string printed using a print head that prints vertically arranged dots by a plurality of nozzles. The first character inspection apparatus is an image input means for inputting an image of the character string as an inspection object image; input by the image input means. The inspection target image is projected along a direction orthogonal to the character string, and dots representing the character are distributed in the width direction of the character for each character constituting the character string in the inspection target image based on the projection result. A range is extracted, and the inspection target image is projected along the direction of the character string, and a range in which dots representing the entire character string are distributed in the height direction of the character string is extracted based on the projection result. Area setting means for setting a processing area determined for each character by the dot distribution range in the width direction extracted for each character and the dot distribution range in the height direction of the character string extracted for the entire character string The image in the processing area for each character set by the area setting means is projected along the direction of the character string, and the distribution range of dots in the height direction of the character string is projected for each character based on the projection result. In addition to specifying, the maximum length among the lengths of these distribution ranges is specified, and the distribution range of the dots specified for each character is included in the range in the height direction of the character string in the processing area of each character. And the position and length of each processing region in the height direction of the character string so that the length of each processing region in the height direction of the character string is unified to the maximum length. Correction region adjusting means; between region adjusting means processing area after correction by combining the respective lines along the width direction of the processing region, for each that relative positions corresponding in the direction perpendicular to the string, each combination Cumulative processing means for accumulating the number of pixels representing dots in each combined line for each time; Maximum value extracting means for extracting the maximum value from the cumulative values obtained by the cumulative processing means for each combination of lines; When the local maximum value extracted by the value extracting means is compared with a predetermined threshold value and a comparison result is obtained that the local maximum value is larger than the threshold value, dot filling is occurring along the direction of the character string. Discriminating means for discriminating; and output means for outputting a discrimination result by the discriminating means.
In the second character inspection device according to the present invention, instead of the above-described maximum value detecting means, a processing target range having a width corresponding to the distance between print lines by adjacent nozzles is set, and the width direction is set to the height of the character string . Repeatedly execute a process of adding a plurality of cumulative values corresponding to the processing target range among the cumulative values obtained by the total processing means for each combination of lines while sequentially moving along the direction according to the direction. The minimum value among the addition values obtained by the addition process is specified. The determining means determines that a missing dot has occurred along the direction of the character string when the comparison result that the minimum value is smaller than the threshold value is obtained.

According to the first character inspection device, it is possible to accurately determine the missing dot along the direction of the character string in the inspection of the horizontally written character string formed by the vertically aligned dots. Further, according to the second character inspection device, it is possible to accurately determine the filling of dots along the direction of the character string in the inspection of the horizontally written character string having the same configuration as described above.

  In this character inspection apparatus, when the output means displays the determination result, the data in which the parameters such as the maximum value, the minimum value, and the height of the region are compared with the threshold value to be compared. May be output.

Further, the character inspection apparatus can be provided with binarization processing means for binarizing the image to be processed. In this case, the projection processing for the image can be performed as processing for counting the number of black pixels or the number of white pixels on one line.
The binarization processing means can also be a dedicated circuit as in the printing state inspection apparatus, but is constituted by a computer in which a binarization threshold value and a binarization processing procedure are set. You can also

In a preferred aspect of the character inspection apparatus, the determination unit compares the maximum length specified by the region setting unit with a predetermined threshold for the length of each processing region in the height direction of the character string. When the comparison result that the maximum length is smaller than the threshold value is obtained, it is determined that a dot is missing at the edge of the character string.

  The printing state inspection apparatus and the character inspection apparatus can be connected to an imaging unit (camera) for imaging an inspection target and a display unit (monitor) for displaying an inspection result. Each time a trigger signal is received from a workpiece detection sensor or the like, the imaging means is activated, the generated image data is taken in, and the above-described inspection methods are executed, so that dot filling or dot missing is performed for each workpiece. It is possible to determine whether or not such a defect over one print line has occurred. In addition, if the output from the output means is given to a device that performs processing for removing defective products or its control device, it is possible to quickly remove a work that has been determined to have a printing failure. In addition, defects due to deficiencies in the inkjet printer, such as dot filling and missing, are likely to occur continuously, but if the output from the output means is given to the inkjet printer side, a printing operation is performed according to the defect detection. Can be stopped.

  Note that peripheral devices such as the above-described imaging means and display means can be integrated into the inspection apparatus. In the character inspection device, means for performing character inspection by conventional pattern matching can be set separately. In this case, it is possible to make a pass / fail judgment by integrating the result of the inspection related to dot filling or dot missing and the result of the inspection by pattern matching, and to output the determination result.

  According to the present invention, since it is possible to accurately perform inspection specialized for printing defects that occur along one printing line, such as dot filling or dot missing, a character string by dot printing is an unprecedented viewpoint. Can be inspected from. Therefore, it is possible to accurately detect printing defects that may be overlooked in the inspection by the conventional pattern matching method.

FIG. 1 shows an installation example of a character inspection apparatus 1 (hereinafter simply referred to as “inspection apparatus 1”) to which the present invention is applied.
The inspection apparatus 1 uses a character string A dot-printed on a predetermined workpiece 10 at a factory as an inspection target, and checks whether a predetermined print line of the character string A is filled with dots or missing dots. It is for inspection. A CCD camera 3 (hereinafter simply referred to as “camera 3”) for imaging the character string and a sensor 4 for detecting a workpiece (for example, a photoelectric switch) are provided in the vicinity of the conveyance line 7 of the workpiece 10. The inspection apparatus 1 is installed at a predetermined position while being connected to peripheral devices such as a monitor 5 and a console 6 in addition to the camera 3 and the sensor 4. An ink jet printer 2 for printing the character string is installed upstream of the camera 3 in a state of being connected to the workpiece detection sensor 9. Reference numeral 2a in the figure denotes a print head of the ink jet printer 2.

  Downstream of the camera 3, a defective product discharge device 11 (including a discharge conveyor, a defective work collection box, etc.) for discharging the workpiece 10 determined to be defective by the inspection device 1 is provided. . The inspection device 1 is connected to a programmable logic controller (PLC) 12 that controls the operation of the defective product discharge device 11, and outputs a determination signal indicating good or bad for the character string A to be inspected. When the determination signal indicating “defective” is input, the PLC 12 operates the defective product discharge device 11 to discharge the target workpiece 10 out of the conveyance line 7.

  FIG. 2 shows an electrical configuration of the inspection apparatus 1. The inspection apparatus 1 is mainly controlled by a CPU 13 and includes an image memory 16 for storing grayscale image data and binary image data to be processed in addition to a ROM 14 and a RAM 15. The ROM 14 stores a program for executing an inspection procedure described later, a program for binarization processing, and the like.

  In addition to the above, the inspection apparatus 1 is provided with an A / D conversion unit 17, a D / A conversion unit 18, an input unit 19, an output unit 20, and the like. The A / D converter 17 takes in the image signal from the camera 3 and digitally converts it. The D / A converter 18 converts the digitally converted grayscale image into an analog display signal and outputs it to the monitor 5. The input unit 19 includes an interface circuit for the console 6 and the workpiece detection sensor 4, and the output unit 20 includes an interface circuit for the PLC 12.

  FIG. 3 shows an example of the character string image 100 to be inspected. This character string is printed in a state in which the characters are not aligned in a horizontal line due to the influence of the surface state of the workpiece 10 and the positions thereof vary. In the following specific examples of processing, this image 100 is the processing target.

  FIG. 4 shows an inspection procedure for one character string. Hereinafter, with respect to each step shown in FIG. 4 (hereinafter, “ST”, which is an abbreviation of “STEP” may be used), detailed processing contents will be described with reference to other drawings as necessary. This will be explained in order.

(1) Image input and binarization (Step 1)
The procedure of FIG. 4 is started in response to the input of a workpiece detection signal from the sensor 4. In step 1, the camera 3 is operated to image the workpiece 10, and the input image data is binarized. Subsequent processing is performed on the binary image.

(2) Cutting out characters (Step 2)
In this step, as shown in FIG. 5A, a predetermined processing target area is set on the binary image. This setting is based on predetermined setting data, and the processing target area 101 having a size sufficiently including the entire character string on the image is set. Next, for each of the x-axis and the y-axis, each character included in the character string is cut out by projecting the image data in the processing target area 101 along the axial direction. This projection process is performed as a process of counting the number of black pixels on one line. As for the x axis and the y axis, as shown in the upper left of FIG. 5, the direction along the print line is set as the x axis, and the direction orthogonal thereto is set as the y axis. The same applies to the following examples.

Further, in step 2, based on the cut-out process, an individual processing area Rn (n = 0, 1, 2,... CN-1; hereinafter, these areas are referred to as “character areas”) for each character. Set temporarily. Note that CN corresponds to the number of extracted characters. FIG. 5 (2) shows the result of this area setting. In the x-axis direction, as a result of projecting the image data in the processing target area 101 along the y-axis direction, a range corresponding to the character width can be cut out for each character. In contrast, in the y-axis direction, since the range of up to the highest position of the upper end of the printed characters at the position Y _S lower end position of the printed characters at the lowest position from the Y _E is extracted, any character area Rn also coordinates of the upper end in the _{Y S,} the coordinates of the lower end in the _{Y E,} are aligned respectively. The setting range of each character area Rn is represented by the coordinates of the upper left vertex (X _S (n), Y _S ) and the coordinates of the lower right vertex (X _E (n), Y _E ).

(3) Extraction of the total number P _max of vertical lines including black pixels (step 3)
FIG. 6 shows an outline of the processing in step 6. In this step 3, for each of the character regions Rn, a black pixel is focused while sequentially paying attention to a vertical line Ln (a line along the y-axis and the length is equal to the height of the character region Rn) included in the region. Extract lines containing. A line including even one black pixel is an extraction target. Further, in step 3, the sum total of the vertical lines extracted for each character region Rn is obtained and set as _Pmax . This P _max is used in the normalization process in step 9 described later.

FIG. 7 shows a detailed procedure of Step 3.
First, in the first ST301, the P _max and the counter n indicating the target character area are set to 0, respectively. Next, in ST302, X _S (n) corresponding to the x coordinate of the first line of the character region Rn is set as a target of interest, and in ST303, the number of black pixels on the vertical line corresponding to the coordinate X _S (n). Count. Here, when this count value is larger than 0, it progresses to ST305 from ST304, The said _Pmax is updated to the value which added 1 to the present value.

Thereafter, the number of black pixels in each vertical line is counted while updating the value of x until the value of x reaches X _E (n) at the right end of the region. Increment _max . When the processes for all the vertical lines in the area are completed, the process proceeds from ST307 to ST308, and the value of n is updated. Thereafter, in ST309, the process returns to ST302 until it is determined that the updated n is greater than or equal to CN-1 indicating the final character area, and is included in each character area Rn by executing the procedures of ST302 to 307. Only lines including black pixels are extracted from the vertical lines to be calculated, and the total number P _max of the lines is calculated.

(4) Correction of character area (step 4)
FIG. 8 shows an outline of the processing in step 4. In step 4, the upper end position of the character area Rn temporarily set in step 2 is set to the corresponding character, and the height of each character area Rn (referred to as the length of the area in the y-axis direction). The set position and height of each character region Rn are corrected so as to be the maximum value Ysize in the height of each character. The set position and size of the corrected character area are represented by the coordinates of the upper left vertex (X _S (n), YT (n)), Ysize, and the x coordinate X _E (n) of the lower right vertex. Is done.

  9 and 10 show the detailed procedure of Step 4. FIG. FIG. 9 mainly shows processing for extracting the Ysize and the margin for each region, and FIG. 10 shows processing for setting the coordinates YT (n) indicating the upper end position of each character region Rn based on these setting values. Show.

First, in ST401, a counter n indicating a target character area is set to an initial value of 0. Thereafter, in ST402 to 407, while updating the value of n, coordinates y (Y _S ≦ for each character area Rn). A process of counting black pixels on the horizontal line at the position of y ≦ Y _E ) is executed (that is, image data in the region is projected along the x-axis direction). This count value is stored in the RAM 15 as the two-dimensional array data S (n, y) based on the counter n and the coordinate y indicating the position of the horizontal line to be processed.

  Next, in ST408, the value of n is reset to zero and the initial value 0 is set in Ysize. Thereafter, the processing of ST409 to 422 is executed for each character region Rn while updating the value of n.

Details of the processing for each character area Rn will be described below.
First, in ST409 to 411, the target character area Rn is searched downward from the upper end, and the y coordinate of the first horizontal line in which the number of black pixels S (n, y) is greater than 0 is extracted. When the y coordinate is extracted, in the next ST412, the difference between the extracted coordinate value y and the coordinate Y _S indicating the upper end of the current character region Rn is obtained, and this is obtained as the upper margin YZT ( Set as n).

Next, in ST413 to 415, the character region Rn is searched upward from the lower end, and the y coordinate of the first horizontal line in which the number of black pixels S (n, y) is greater than 0 is extracted. When the y-coordinate is extracted, in the next ST 416, obtains the difference between the coordinate y, which is the extracted coordinate Y _E showing the lower end of the character area Rn, which, bottom margin in the character area Rn YZB (n ).

  In the next ST417, the upper margin YZT (n) and the lower margin YZB (n) set by the above processing are added, and this is set as a margin addition value tmp. The margin addition value tmp is a variable shared between the character areas Rn, and the value is rewritten every time ST417 is executed.

In ST418, the character height H (n) is obtained by subtracting the margin addition value tmp from the current length (Y _E −Y _S +1) of the character region Rn. In ST419, the height H (n) of the character is compared with the Ysize. If H (n) is larger than Ysize, Ysize is rewritten with the value of H (n) in ST420.

When the processing for the last character region R _CN-1 is completed and the loop of ST409 to 422 is completed, the maximum value of the height of each character is set as Ysize. The Ysize, the upper margin YZT (n), the lower margin YZB (n), and the character height H (n) for each character area Rn are stored in the RAM 15 for the next processing.

Next, in ST423 of FIG. 10, the value of n is reset again, and the y-coordinate value YT (n) indicating the upper end position of the corrected character area Rn is determined for each character area Rn by the following procedure. .
First, in ST424, the upper margin YZT (n) of the character area Rn under consideration is checked. If YZT (n) = 0, that is, if there is no upper margin, the process proceeds to ST426. This ST426, sets the coordinate _{Y S} of the current upper end position in the YT (n).

  If YZT (n)> 0, the process proceeds from ST424 to ST425, and the bottom margin YZB (n) is checked. If YZB (n) = 0, that is, if there is no bottom margin, the process proceeds to ST427. In ST427, the difference between the Ysize and the height H (n) of the character to be processed is added to the upper end position Ys of the current character area Rn, and the value is set as YT (n).

  On the other hand, if YZB (n)> 0, that is, if there are margins in the upper and lower portions of the character region Rn, the process proceeds from ST425 to ST428. In ST428, YT (n) is calculated by applying each value of Ys, Ysize, H (n), YZT (n), and YZB (n) to the following equation (A).

  With the above procedure, the coordinates of the upper end position of the character region Rn are updated to the value YT (n) adjusted according to the height of the character and the state of the margin. Since the height of any character region Rn is unified to Ysize, a space of (Ysize−H (n)) is provided below the character in the character region Rn in which ST426 is executed. Will be set. In the character region Rn for which ST427 has been executed, a margin with a size of (Ysize−H (n)) is set above the character. Furthermore, in the character region Rn in which ST428 is executed, margins are set both above and below the character, and the total value of these margins is equal to (Ysize−H (n)). In the character area Rn where H (n) = Ysize, the upper and lower margins are all zero.

(5) Cumulative processing of the number of black pixels P (y) on the corresponding horizontal line (step 5)
The process of step 5 is executed for the corrected character area Rn, and FIG. 11 shows an outline of the process. In this step 5, the horizontal line H _ny (the horizontal line at the same distance from the upper end of the area; the range of y is 0 ≦ y ≦ Ysize−1) corresponding to the character area Rn. Paying attention in order, the number of black pixels S _0y , S _1y ,... S _{(CN−1) y} on the line is obtained by the projection processing for each line. Further, the number of black pixels for each line is accumulated, and the accumulated value is stored in the RAM 15 as P (y).

(6) Extraction of local maximum values PT _max , PM _max , PB _max (step 6)
The cumulative value P (y) obtained in step 5 can be represented as a histogram along the y-axis, as shown in FIG. In Step 6, three local maximum values PT _max , PM _max , and PB _max are extracted by scanning such an array of P (y). The maximum value PT _max is a maximum value extracted first when the histogram is scanned from above. On the other hand, the maximum value PB _max is the maximum value extracted first when the histogram is scanned from below. Further, the maximum value PM _max is a maximum value existing between the maximum values PT _max and PB _max . In the histogram of FIG. 12, the cumulative value P (y) value close to zero can be considered to reflect a blank portion between print lines.

FIGS. 13 and 14 show detailed procedures for extracting the local maximum values PT _max , PM _max , and PB _max . In this procedure, first, the value of y is set to 0 in order to find the maximum value PT _max (ST601). In ST602 to 604, P (y) and P (y + 1) are compared while increasing the value of y by one. Here, when P (y)> P (y + 1), the value P (y) at the current position of interest y becomes larger than the value P (y + 1) at the next lower position, and at the same time one higher. It also increases with respect to the value P (y−1) at the position. This is because y-1 corresponds to y when this loop is executed last time, and at this time, the current y is y + 1, and ST602 is “NO” by comparing both (ST612 described later). Also at ˜614, the maximum value PB _max is extracted based on the same idea. Therefore, when ST602 becomes “YES”, the process exits the loop and proceeds to ST605, where the current value of P (y) is set as the maximum value PT _max .

When the maximum value PT _max is set, in the next ST606 to 608, the comparison between P (y) and P (y + 1) is continued while scanning below the position where the maximum value PT _max is obtained. If P (y + 1)> P (y), the process proceeds to ST609, and P (y + 1) at that time is set as the maximum value PM _max . However, the maximum value PM _max at this time is provisional. In the next ST610, a position (y + 2) one level lower than the maximum value PM _max is stored in the variable ys for the process of determining the maximum value PM _max later.

Next, in ST611, the value of y is set to the maximum (Ysize-1). In the subsequent ST612 to 614, P (y) and P (y-1) are compared while decreasing the value of y one by one. In this loop, if it is determined that P (y)> P (y -1), the process proceeds from ST612 to ST 615, set the value of P (y) at that time as the local maximum value _{PB max.}

When the maximum value PB _max is set, in the next ST616 to 618, P (y) and P (y−1) are continuously compared above the maximum value PB _max . If P (y-1)> P (y), the process exits the loop and proceeds to ST619, where the value of (y-1) at that time is set in the variable ye. Hereinafter, the ST620～624, while moving the value of y in the range up ye from said ys, extracts the maximum value of P (y) in this range, the value a maximum value _{PM max.}

  In the loops of ST602 to 604, ST606 to 608, ST612 to 614, and ST616 to 618, if a local maximum value is not found within a focusable range, the process proceeds to error processing (not shown).

(7) P (y) addition process (step 7)
Also in step 7, the cumulative value P (y) is set as a processing target. The process of step 7 corresponds to a process of adding the cumulative values P (y) included in the range of the predetermined width w on the y axis of the histogram. This addition processing is executed while moving the y values one by one in order from 0, and the addition value obtained for each y value is stored in the array AP (y).

(8) Extraction of minimum value AP _min (step 8)
FIG. 15 shows the added value AP (y) obtained in step 7 as a histogram along the y-axis similar to FIG. 12 (however, the scale in the x-axis direction is reduced). ). In step 8, the addition value AP (y) is compared in order to determine the minimum value AP _min .

(9) Normalization processing (step 9)
In step 9, the local maximum values PT _max , PM _max , PB _max , and the minimum value AP _min obtained by the above processing are normalized using P _max obtained in ST3. In normalization of the maximum values PT _max , PM _max , and PB _max , the current value is divided by the P _max . Further, in normalization of the minimum value AP _min of the addition value, the current value is divided by (P _max × w). w is used to indicate the range of calculation of the added value AP (y).

The P _max is the total number of vertical lines in which at least one black pixel corresponding to a dot appears in each character region Rn. Therefore, each value after the normalization can be considered to indicate how much the actual black pixels appear with respect to the maximum value of the black pixels that can appear on one horizontal line. The degree of dot printing can be shown in an easy-to-understand manner.

(10) Determination process (step 10)
In this step 10, the normalized values for the local maximum values PT _max , PM _max , PB _max and the minimum value AP _min of the addition values are respectively compared with predetermined threshold values. The threshold value corresponding to each local maximum value reflects the number of black pixels applied to the print line in which dot filling has occurred. If any local maximum value is larger than the threshold value, it corresponds to the local maximum value. It is determined that dot filling is occurring at the position.

The threshold value corresponding to the minimum value AP _min of the addition value reflects the number of black pixels of the horizontal line applied to one print line on which about 1 to 2 dots are applied. If the value of AP _min after normalization falls below this threshold value, it is determined that dot missing has occurred at a position corresponding to AP _min .

The AP _min is used to extract dot missing in a print line other than the upper and lower end lines among a plurality of dot print lines. In ST10, in order to discriminate dot missing in the upper and lower end lines, a discrimination process using the height Ysize of the corrected character region Rn is separately performed.

As described above, since Ysize is the maximum value of the height of each character in the character string, if dot missing occurs on either the top or bottom print line, this Ysize is the height of the original character. It will be lower than this.
Therefore, in this embodiment, a threshold value is set based on the character height when one print line is missing, and this threshold value is compared with Ysize. If Ysize is smaller than the threshold value, it is determined that dot missing has occurred in the upper or lower print line.

(11) Determination result output (step 11)
If it is determined in step 10 that dot filling or dot missing has occurred at any position, in step 11, a determination signal indicating “defective” is output to the PLC 12. In addition to this, in step 11, a determination result display screen as shown in FIG.

In FIG. 16, an upper filling determination upper limit value, a middle filling determination upper limit value, and a lower filling determination upper limit value correspond to the maximum values PT _max , PM _max , and PB _max , respectively. Further, the lower omission determination lower limit value corresponds to the minimum value AP _min of the addition value AP (y), and the lowermost upper / lower omission determination lower limit value corresponds to the Ysize.

In the illustrated example, for these five types of parameters, the measured values obtained by the above-described procedure and the threshold values used for the discrimination processing are displayed in association with each other. Each numerical value relating to PT _max , PM _max , PB _max , AP _min represents the normalized numerical value in percentage units, and the numerical value relating to Ysize is the number of pixels.

As described above, according to the processing described above, the character region Rn for each character in the character string is adjusted according to the position of the character on the y-axis, and the height of each character region Rn is the maximum character height. since fit ysize, the correspondence between the horizontal line H _ny between the region Rn can be performed without any problem, it is possible to obtain a ysize number of accumulated value P (y).

  Of course, there are variations in the height between characters, and margins are set for characters with a small height. Therefore, it can be said that the horizontal lines combined between the character regions Rn faithfully show the actual correspondence. Absent. However, since one dot on the image has a size of several pixels, a combination including a large number of horizontal lines on the same print line is set for the print line, and a blank portion between the print lines is also the same. It can be considered that a combination including a large number of horizontal lines covering the blank portion is set. Therefore, according to the cumulative value P (y), sufficiently reliable data can be obtained for the printing state of each printing line. Based on the maximum value and the minimum value, dot filling and dot The presence or absence of omission can be determined with high accuracy.

Further, regarding the missing dots, the discrimination process is performed using the minimum value AP _min obtained by adding the cumulative value P (y) corresponding to the range of the predetermined width w. Can be prevented from being erroneously extracted. In addition, in this embodiment, since the discrimination process using Ysize extracted for correcting each character area is performed, it is possible to accurately discriminate the missing dots at the upper and lower ends.

The width w can be obtained in advance using an image obtained by capturing an image of a character string of a model having no printing defect. In this case, for each character, the same process as in steps 1 to 4 in FIG. 4 is executed to obtain the value of Ysize, and w can be set based on the value obtained by dividing this Ysize by the number of print lines. In this case, it is desirable that the inspection procedure of FIG. 4 is executed once based on the set value, and the value of w is adjusted by the value of the minimum value AP _min . For example, when the blank portion between the print lines is small, the value of the minimum value AP _min is considered to be large. In this case, it can be dealt with by adjusting the value of w so as to decrease. In addition, when the blank portion between the print lines is large, the value of the minimum value AP _min is considered to be small, but in this case, it can be dealt with by adjusting the value of w in the direction of increasing.

  Further, as shown in FIG. 16, when the dot filling state or the missing dot state is indicated by the ratio to the maximum number of black pixels in one horizontal line, the relationship between the printing state and the numerical value can be easily grasped. Therefore, it is possible to cause the user to input a numerical value for the threshold value for the determination process of ST10.

In the inspection apparatus 1 of this embodiment, a binary image is processed. However, the present invention is not limited to this, and a grayscale image after digital conversion may be processed. In this case, the process of counting the number of black pixels in ST2, ST303, ST403, etc. is replaced with the process of adding the density value of each pixel on the line. In ST3, a vertical line including pixels having a density corresponding to the character image is extracted.
For grayscale images, if the method of counting the number of pixels having density values corresponding to the character image is used instead of the density value addition, data similar to the projection value in the binary image can be obtained. Can do.

  In addition, in the inspection apparatus 1 of this embodiment, it is possible to separately perform character inspection by conventional pattern matching. If inspection is performed by a plurality of methods as described above, printing defects due to various factors can be detected, and the accuracy of inspection can be greatly improved.

By the way, in the above-described embodiment, the description has not been made until individual characters in the character string are distorted. However, depending on the inclination of the print surface, the print line may be distorted even in the width range of one character. . In such a case, the region along the character string may be subdivided into units smaller than the width of one character, and the same processing may be performed. In this case, it is desirable to set the width of each region in accordance with the degree of distortion of the character to be processed.
In the above-described embodiment, the character string is the inspection target. However, when a print body other than a character such as a mark is the inspection target, the inspection can be performed by the same method.

It is a figure which shows the example of application of the character inspection apparatus concerning this invention. It is a figure which shows the electric constitution of a character inspection apparatus. It is a figure which shows the example of the image of the character string of a test object. It is a flowchart which shows a series of test | inspection procedures. It is a figure which shows the outline | summary of the cut-out process of a character, and the process which temporarily sets a character area. It is a figure which shows the outline | summary of the process which extracts the total number of the vertical line containing a black pixel. It is a flowchart which shows the detailed procedure of the process of FIG. It is a figure which shows the outline | summary of the correction process of a character area. It is a flowchart which shows the detailed procedure of the process of FIG. 10 is a flowchart continued from FIG. 9. It is a figure which shows the outline | summary of the process which accumulates the number of black pixels on a corresponding horizontal line. It is a histogram which shows the cumulative result of the number of black pixels together with the maximum value. It is a flowchart which shows the procedure concerning extraction of local maximum. 14 is a flowchart continued from FIG. 13. It is a histogram which shows the addition value of a cumulative value with the minimum value. It is a figure which shows the display screen of a determination result. It is a figure which shows the example of the filling of a dot and the defect of a missing dot.

A Character string Rn Character area 1 Character inspection device 2 Inkjet printer 3 Camera 13 CPU
14 ROM
15 RAM
16 Image memory 20 Output section

Claims (11)

A printing head having a plurality of nozzles arranged in the vertical direction or the horizontal direction is moved relative to a print object in a direction orthogonal to the nozzle arrangement direction, and the dot printing operation of each nozzle is performed. The printing body formed on the printing object is imaged by controlling, and using the obtained image, a printing defect occurs in the printing line for each nozzle along the direction of movement of each nozzle with respect to the printing object. A method for checking whether or not
Assuming that the print line of each nozzle is orthogonal to the direction in which the nozzles are arranged, in the assumed print line direction of the image of the print body, a range including all or part of the dot distribution range is processed. A first step of setting a range including all hypothetical print lines corresponding to the plurality of nozzles as a processing range in a direction orthogonal to the hypothetical print lines of the image,
Dots in the direction orthogonal to the assumed print line are projected based on the projection result by projecting the image in the processing target area specified by the processing range set in the first step along the direction of the assumed print line. The distribution range is specified, and a plurality of regions in the processing target region are arranged along the direction of the assumed print line and the range in the direction orthogonal to the assumed print line corresponds to the specified range. A second step of:
By projecting the image of each region set by the second step along each hypothetical print line, specifying the distribution range of dots in a direction perpendicular to the hypothetical print line based on the projected result for each area In addition , the maximum length among the lengths of these distribution ranges is specified, and the range in the direction orthogonal to the assumed print line of each region includes the distribution range of dots specified for each region, and A third step of correcting the position and length of each region in the direction orthogonal to the assumed print line so that the length of each region in the direction orthogonal to the print line is unified to the maximum length ; ,
Between each region after performing the third step, each line along the direction of the assumed print line in each region is combined for each corresponding relative position in the direction orthogonal to the assumed print line, For each combination, a fourth step of accumulating the number of pixels representing the dots in each combined line;
The maximum value is extracted from the cumulative value obtained for each combination of the lines, the extracted maximum value is compared with a predetermined threshold value, and a comparison result that the maximum value is larger than the threshold value is obtained. A fifth step of determining that dot filling has occurred along the direction of the actual print line,
A printing state inspection method characterized by being executed. A printing head having a plurality of nozzles arranged in the vertical direction or the horizontal direction is moved relative to a print object in a direction orthogonal to the nozzle arrangement direction, and the dot printing operation of each nozzle is performed. The printing body formed on the printing object is imaged by controlling, and using the obtained image, a printing defect occurs in the printing line for each nozzle along the direction of movement of each nozzle with respect to the printing object. A method for checking whether or not
Assuming that the print line of each nozzle is orthogonal to the direction in which the nozzles are arranged, in the assumed print line direction of the image of the print body, a range including all or part of the dot distribution range is processed. A first step of setting a range including all hypothetical print lines corresponding to the plurality of nozzles as a processing range in a direction orthogonal to the hypothetical print lines of the image,
Dots in the direction orthogonal to the assumed print line are projected based on the projection result by projecting the image in the processing target area specified by the processing range set in the first step along the direction of the assumed print line. The distribution range is specified, and a plurality of regions in the processing target region are arranged along the direction of the assumed print line and the range in the direction orthogonal to the assumed print line corresponds to the specified range. A second step of:
By projecting the image of each region set by the second step along each hypothetical print line, specifying the distribution range of dots in a direction perpendicular to the hypothetical print line based on the projected result for each area In addition , the maximum length among the lengths of these distribution ranges is specified, and the range in the direction orthogonal to the assumed print line of each region includes the distribution range of dots specified for each region, and A third step of correcting the position and length of each region in the direction orthogonal to the assumed print line so that the length of each region in the direction orthogonal to the print line is unified to the maximum length ; ,
Between each region after performing the third step, each line along the direction of the assumed print line in each region is combined for each corresponding relative position in the direction orthogonal to the assumed print line, For each combination, a fourth step of accumulating the number of pixels representing the dots in each combined line;
The process target range of a width corresponding to the distance between by the adjacent nozzles print line, in accordance with the direction perpendicular to the width direction on the assumption of the print line, while moving sequentially along the direction, the third step The process of adding a plurality of cumulative values corresponding to the processing target range among the cumulative values obtained for each combination of lines is repeatedly executed, and the minimum value among the added values obtained by each addition process is set to a predetermined threshold value. When the comparison result that the minimum value of the addition value is smaller than the threshold value is obtained, a fifth step of determining that a missing dot has occurred along the actual print line direction is executed. And a printing state inspection method. Image a horizontally written character string printed using a print head that prints vertically arranged dots by a plurality of nozzles, and use the obtained image to determine whether a print defect has occurred along the character string. A method of inspecting,
An image of the character string to be inspected is projected along a direction orthogonal to the character string, and for each character constituting the character string in the image based on the projection result, a dot representing the character is the width direction of the character And extracting an image of the character string to be inspected along the direction of the character string, and distributing the dots representing the entire character string in the height direction of the character string based on the projection result A processing area that is determined by the distribution range of dots in the width direction extracted for each character and the distribution range of dots in the height direction of the character string extracted for the entire character string. A first step of setting
The image in the processing area for each character set in the first step is projected along the direction of the character string, and the distribution range of dots in the height direction of the character string is calculated for each character based on the projection result. In addition to specifying the maximum length among the lengths of these distribution ranges, the range in the height direction of the character string in the processing area of each character includes the distribution range of dots specified for each character. And a second step of correcting the position and length of each processing region in the height direction of the character string so that the length of each processing region in the height direction of the character string is unified to the maximum length. When,
Between each processing area after executing the second step, each line along the width direction in each processing area is combined for each corresponding relative position in the height direction of the character string , and for each combination A third step of accumulating the number of pixels representing dots in each combined line;
The maximum value is extracted from the cumulative value obtained for each combination of lines in the third step, the extracted maximum value is compared with a predetermined threshold value, and the maximum value is greater than the threshold value. When a comparison result is obtained, a fourth step of determining that dot embedding has occurred along the direction of the character string,
A character inspection method characterized by being executed. Image a horizontally written character string printed using a print head that prints vertically arranged dots by a plurality of nozzles, and use the obtained image to determine whether a print defect has occurred along the character string. A method of inspecting,
An image of the character string to be inspected is projected along a direction orthogonal to the character string, and for each character constituting the character string in the image based on the projection result, a dot representing the character is the width direction of the character And extracting an image of the character string to be inspected along the direction of the character string, and distributing the dots representing the entire character string in the height direction of the character string based on the projection result A processing area that is determined by the distribution range of dots in the width direction extracted for each character and the distribution range of dots in the height direction of the character string extracted for the entire character string. A first step of setting
The image in the processing area for each character set in the first step is projected along the direction of the character string, and the distribution range of dots in the height direction of the character string is calculated for each character based on the projection result. In addition to specifying the maximum length among the lengths of these distribution ranges, the range in the height direction of the character string in the processing area of each character includes the distribution range of dots specified for each character. And a second step of correcting the position and length of each processing region in the height direction of the character string so that the length of each processing region in the height direction of the character string is unified to the maximum length. When,
Between each processing area after executing the second step, each line along the width direction in each processing area is combined for each corresponding relative position in the height direction of the character string , and for each combination A third step of accumulating the number of pixels representing dots in each combined line;
The processing range of the width corresponding to the distance between the print lines by the adjacent nozzles is adjusted in the third step while moving the width direction to the height direction of the character string and sequentially moving along the direction. The process of adding multiple cumulative values corresponding to the processing target range among the cumulative values obtained for each combination is repeatedly executed, and the minimum value among the added values obtained by the addition processing is compared with a predetermined threshold value. A fourth step of determining that a missing dot has occurred along the direction of the character string when the comparison result that the minimum value of the addition value is smaller than the threshold value is obtained;
A character inspection method characterized by being executed. The character inspection method according to claim 3 or 4,
The maximum length specified in the second step per the length of each processing region in the height direction of the character string is compared with a predetermined threshold value, that the maximum length is less than the threshold value A character inspection method, comprising: performing a fifth step of determining that a missing dot has occurred at an edge of the character string when a comparison result is obtained. A printing head having a plurality of nozzles arranged in the vertical direction or the horizontal direction is moved relative to a print object in a direction orthogonal to the nozzle arrangement direction, and the dot printing operation of each nozzle is performed. Using an image obtained by imaging a printed body formed on the print object by controlling, a print defect occurs in a print line for each nozzle along the direction of movement of each nozzle relative to the print object. A device for checking whether or not
Image input means for inputting an image of the printed body as an inspection target image ;
Assuming that the print line of each nozzle is orthogonal to the direction in which the nozzles are arranged, in the assumed print line direction of the inspection target image input by the image input means, the entire distribution range of the dots or A process of setting a range including all of the assumed print lines corresponding to the plurality of nozzles in the direction orthogonal to the assumed print line of the inspection target image while setting a range including a part as the process range. Range setting means;
After the area specified by the processing range in each direction is set as the processing target area , the image in the processing target area is projected along the direction of the assumed print line, and based on the projection result, the assumed print line is formed. A distribution range of dots in an orthogonal direction is specified, and the range in the direction orthogonal to the assumed print line corresponds to the specified range in the processing target area along the direction of the assumed print line. Area setting means for setting a plurality of areas;
By projecting the image of each area set by said area setting means along each assumption printing line, the distribution range of dots in a direction perpendicular to the hypothetical print line based on the projection result with identifying for each region these distributions to identify the length maximum length in the range, includes the distribution range of dots each identified per the area in a range in a direction perpendicular to the assumption of a printing line in each region, and assumptions as the length of each region is unified to the length of the maximum in the direction perpendicular to the print line, a region adjusting means for correcting the position and length of each region in the direction perpendicular to the assumption of a printing line,
In each area after correction by the area adjusting means, each line along the direction of the assumed print line in each area is combined for each corresponding relative position in the direction orthogonal to the assumed print line. A cumulative processing means for accumulating the number of pixels representing the dots in each combined line for each;
A maximum value extracting means for extracting a maximum value from the total value obtained for each combination of lines by the total processing means;
When the local maximum value extracted by the local maximum value extracting means is compared with a predetermined threshold value, and the comparison result that the local maximum value is larger than the threshold value is obtained, dot filling is performed along the direction of the actual print line. A discriminating means for discriminating that it has occurred;
A printing state inspection apparatus comprising: output means for outputting a discrimination result by the discrimination means. A printing head having a plurality of nozzles arranged in the vertical direction or the horizontal direction is moved relative to a print object in a direction orthogonal to the nozzle arrangement direction, and the dot printing operation of each nozzle is performed. Using an image obtained by imaging a printed body formed on the print object by controlling, a print defect occurs in a print line for each nozzle along the direction of movement of each nozzle relative to the print object. A device for checking whether or not
Image input means for inputting an image of the printed body as an inspection target image ;
Assuming that the print line of each nozzle is orthogonal to the direction in which the nozzles are arranged, in the assumed print line direction of the inspection target image input by the image input means, the entire distribution range of the dots or A process of setting a range including all of the assumed print lines corresponding to the plurality of nozzles in the direction orthogonal to the assumed print line of the inspection target image while setting a range including a part as the process range. Range setting means;
After the area specified by the processing range in each direction is set as the processing target area , the image in the processing target area is projected along the direction of the assumed print line, and based on the projection result, the assumed print line is formed. A distribution range of dots in an orthogonal direction is specified, and the range in the direction orthogonal to the assumed print line corresponds to the specified range in the processing target area along the direction of the assumed print line. Area setting means for setting a plurality of areas;
By projecting the image of each area set by said area setting means along each assumption printing line, the distribution range of dots in a direction perpendicular to the hypothetical print line based on the projection result with identifying for each region The maximum length among the lengths of these distribution ranges is specified, and the range in the direction orthogonal to the assumed print line of each region includes the distribution range of dots specified for each region, and printing A region adjusting means for correcting the position and length of each region in the direction orthogonal to the assumed print line so that the length of each region in the direction orthogonal to the line is unified to the maximum length;
In each area after correction by the area adjusting means, each line along the direction of the assumed print line in each area is combined for each corresponding relative position in the direction orthogonal to the assumed print line. A cumulative processing means for accumulating the number of pixels representing the dots in each combined line for each;
The total processing means moves each line along the processing target range having a width corresponding to the distance between the printing lines by the adjacent nozzles, with the width direction aligned with the direction orthogonal to the assumed printing line, and sequentially moving along the direction. Minimum value specifying means for repeatedly executing a process of adding a plurality of cumulative values corresponding to the processing target range among the cumulative values obtained for each combination of the values, and specifying a minimum value among the added values obtained by each addition process When,
When the minimum value specified by the minimum value specifying means is compared with a predetermined threshold value and a comparison result that the minimum value is smaller than the threshold value is obtained, missing dots are detected along the actual print line direction. A discriminating means for discriminating that it has occurred;
A printing state inspection apparatus comprising: output means for outputting a discrimination result by the discrimination means. In the printing state inspection device according to claim 6 or 7,
An input means for inputting processing range setting information in the direction of the assumed print line;
The processing range setting unit is a printing state inspection apparatus that sets a processing range in the direction of a hypothetical print line using setting information input from the input unit. Whether or not a print defect has occurred along the character string using an image obtained by imaging a horizontally written character string printed using a print head that prints vertically arranged dots by a plurality of nozzles A device for inspecting
Image input means for inputting an image of the character string as an image to be inspected;
The inspection target image input by the image input means is projected along a direction orthogonal to the character string, and for each character constituting the character string in the inspection target image based on the projection result, a dot representing the character is displayed. A range distributed in the width direction of the character is extracted, the inspection target image is projected along the direction of the character string, and a dot representing the entire character string is projected in the height direction of the character string based on the projection result Processing to extract the distribution range, and for each character, the dot distribution range in the width direction extracted for each character and the dot distribution range in the height direction of the character string extracted for the entire character string Area setting means for setting an area ;
The image in the processing area for each character set by the area setting means is projected along the direction of the character string, and the distribution range of dots in the height direction of the character string is specified for each character based on the projection result. In addition, the maximum length among the lengths of these distribution ranges is specified, and the distribution range of the dots specified for each character is included in the range in the height direction of the character string in the processing region of each character , And the area adjustment means which corrects the position and length of each processing area in the height direction of the character string so that the length of each processing area in the height direction of the character string is unified to the maximum length ,
Between the processing areas after correction by the area adjusting means, the lines along the width direction in each processing area are combined for each corresponding relative position in the height direction of the character string, and combined for each combination. A cumulative processing means for accumulating the number of pixels representing dots in each line obtained ;
A maximum value extracting means for extracting a maximum value from the total value obtained for each combination of lines by the total processing means;
When the maximum value extracted by the maximum value extracting means is compared with a predetermined threshold value and a comparison result that the maximum value is larger than the threshold value is obtained, dot filling occurs along the direction of the character string. A discriminating means for discriminating that
A character inspection apparatus comprising output means for outputting a discrimination result by the discrimination means. Whether or not a print defect has occurred along the character string using an image obtained by imaging a horizontally written character string printed using a print head that prints vertically arranged dots by a plurality of nozzles A device for inspecting
Image input means for inputting an image of the character string as an image to be inspected;
The inspection target image input by the image input means is projected along a direction orthogonal to the character string, and for each character constituting the character string in the inspection target image based on the projection result, a dot representing the character is displayed. A range distributed in the width direction of the character is extracted, the inspection target image is projected along the direction of the character string, and a dot representing the entire character string is projected in the height direction of the character string based on the projection result Processing to extract the distribution range, and for each character, the dot distribution range in the width direction extracted for each character and the dot distribution range in the height direction of the character string extracted for the entire character string Area setting means for setting an area ;
The image in the processing area for each character set by the area setting means is projected along the direction of the character string, and the distribution range of dots in the height direction of the character string is specified for each character based on the projection result. In addition, the maximum length among the lengths of these distribution ranges is specified, and the distribution range of the dots specified for each character is included in the range in the height direction of the character string in the processing region of each character , And the area adjustment means which corrects the position and length of each processing area in the height direction of the character string so that the length of each processing area in the height direction of the character string is unified to the maximum length ,
Between the processing areas after correction by the area adjusting means, the lines along the width direction in each processing area are combined for each corresponding relative position in the height direction of the character string, and combined for each combination. A cumulative processing means for accumulating the number of pixels representing dots in each line obtained ;
The process target range of a width corresponding to the distance between by the adjacent nozzles print lines, the combined width direction of the string in the height direction, while moving sequentially along the direction, the cumulative processing means of each line combination A minimum value specifying means for repeatedly executing a process of adding a plurality of cumulative values corresponding to the processing target range among the cumulative values obtained every time, and specifying a minimum value among the added values obtained by the addition process each time;
When the minimum value specified by the minimum value specifying means is compared with a predetermined threshold value and a comparison result is obtained that the minimum value is smaller than the threshold value, missing dots are missing along the direction of the character string. A discriminating means for discriminating that it has occurred;
A character inspection apparatus comprising output means for outputting a discrimination result by the discrimination means. In the character inspection device according to claim 9 or 10,
The discriminating means compares the maximum length specified by the area setting means with respect to the length of each processing area in the height direction of the character string with a predetermined threshold, and the maximum length is a threshold. A character inspection apparatus that determines that a missing dot has occurred at an edge of the character string when a comparison result indicating that the value is smaller than the value is obtained.

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