JP7193416B2 - Printing system and printing method - Google Patents

Description

The present invention relates to a printing system and printing method.

2. Description of the Related Art In recent years, inkjet printers, which are printing apparatuses that perform printing using an inkjet method, have been widely used. Further, conventionally, a method is known in which a test pattern drawn by an inkjet head is photographed with a camera, and defective nozzles (ejection failure nozzles) are detected using the photographed image (see, for example, Patent Document 1). . In such a method, for example, by printing a test pattern while the inkjet printer is in operation and detecting defective nozzles, it is possible to minimize the continuation of the operation in a state where ejection failure due to defective nozzles exists. be able to.

JP 2018-134833 A

When detecting a defective nozzle by photographing a test pattern, it is necessary to analyze an image obtained by photographing the test pattern. In order to properly perform such analysis, it is necessary to acquire a high-resolution image that can be recognized with sufficiently high accuracy to reliably detect defective nozzles for patterns corresponding to individual nozzles included in the test pattern. is required. Also, in this case, it is not enough just to be able to recognize the patterns, and it is important to be able to accurately grasp which pattern corresponds to which nozzle. In this case, it is usually necessary to capture the entire test pattern in one image by one shot. The entire test pattern is, for example, the entire pattern necessary for checking the state of each nozzle in one inkjet head.

Therefore, conventionally, in order to detect a defective nozzle by photographing a test pattern, it has been necessary to use a camera with a high resolution and a wide field of view. However, since such a camera is expensive, adding a defective nozzle detection function to the inkjet printer greatly increases the manufacturing cost. Therefore, conventionally, it has been desired to more appropriately detect defective nozzles. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a printing system and a printing method that can solve the above problems.

The inventor of the present application has studied a method of more appropriately detecting a defective nozzle when detecting a defective nozzle in parallel with a printing operation. Then, first, instead of photographing the entire test pattern in one photographing, it was considered to photograph a part of the test pattern a plurality of times. With this configuration, for example, even when using an inexpensive camera such as a camera with a low resolution and a narrow field of view, the patterns corresponding to the respective nozzles can be photographed with an accuracy sufficient to appropriately detect defective nozzles. be able to.

However, in this case, it may be difficult to recognize the corresponding relationship between each part of the test pattern and the nozzles in a part of the test pattern shown in each image. More specifically, for example, the control of photographing the test pattern may be performed independently of the control of the printing operation. Further, for example, depending on the configuration of the printing apparatus (hardware or software configuration, etc.), there are cases where the timing of the printing operation (for example, timing to start printing the test pattern, etc.) cannot be transmitted to the camera. In these cases, it becomes impossible to perform photographing in accordance with the operation of printing the test pattern, and it becomes difficult to specify which nozzles used to draw part of the test pattern in each image (specification of the nozzle number). It is conceivable that it will become difficult. Moreover, as a result, for example, even if a portion corresponding to a defective nozzle is found in the test pattern, it may not be possible to determine which nozzle is the defective nozzle. In addition, when only a part of the test pattern is photographed in one photographing operation, for example, even if the test pattern photographing control is performed in synchronization with the printing operation, it is possible to correctly identify the defective nozzle due to a slight timing deviation or the like. It is possible that it will not be possible.

On the other hand, the inventors of the present application, through extensive research, have found that, rather than simply photographing a portion of the test pattern, the test pattern includes a position mark indicating a predetermined reference position, and a position shown in the image. I thought of using the mark to identify the nozzle. With this configuration, it is possible to appropriately detect a defective nozzle even when using an inexpensive camera such as a camera with a low resolution and a narrow field of view.

Further, the inventors of the present application have conducted further intensive research and found the characteristics necessary to obtain such effects, and have completed the present invention. In order to solve the above-described problems, the present invention provides a printing system for printing on a medium by an inkjet method, comprising an inkjet head having a plurality of nozzles for ejecting ink onto the medium; a main scanning drive unit that causes the inkjet head to perform a main scanning operation of ejecting ink while moving relative to the medium in a scanning direction; a sub-scanning driving unit that causes the inkjet head to perform a sub-scanning operation that moves relatively; a camera that acquires a partial area image that is an image obtained by photographing a partial area of the medium; and an imaging operation of the camera. and a print control that causes the inkjet head to draw a print image, which is an image to be printed, by controlling the operations of the inkjet head, the main scanning driving unit, and the sub-scanning driving unit. and a defective nozzle detection unit that detects defective nozzles having defective ejection characteristics among the plurality of nozzles based on the partial area image captured by the camera, and rendering the print image. In some cases, the print control unit further causes the inkjet head to draw a test pattern used for detecting the defective nozzle, and the imaging control unit generates a plurality of the test patterns, each of which has a different range. causing the camera to acquire a partial area image, wherein the camera acquires the partial area image in which only a partial area of the test pattern in the sub-scanning direction is photographed in one shot; The test pattern includes a nozzle corresponding pattern, which is a pattern drawn by each of the plurality of nozzles, and a position mark, which is a pattern indicating a preset reference position in the test pattern, and the defective nozzle detection unit includes: Based on the nozzle corresponding pattern, by identifying which of the nozzles drew the nozzle corresponding pattern reflected in the partial area image based on the position mark reflected in the partial area image, The defective nozzle is detected.

In such a configuration, the range captured by the camera in one shot is limited to only a part of the test pattern in the sub-scanning direction, so that an inexpensive camera such as a camera with a low resolution and a narrow field of view can be used. , it is possible to appropriately capture an image with accuracy that allows determination of a defective nozzle. Also, in this case, by using a test pattern including position marks, it is possible to appropriately identify which nozzles drew the nozzle corresponding pattern shown in the image (partial area image). Therefore, with this configuration, it is possible to appropriately detect a defective nozzle, for example.

Here, in this configuration, a defective nozzle is, for example, a nozzle whose ejection characteristics are out of a predetermined normal range (ejection failure nozzle). Further, the defective nozzle detection unit detects defective nozzles, for example, based on one partial area image, with respect to the nozzles that draw the nozzle correspondence pattern included in the partial area image. In this case, the defective nozzle detection unit selects, for example, a partial range in the partial area image based on the position mark, and detects defective nozzles with respect to the nozzles that draw the nozzle correspondence pattern within that range. good too.

Also, the position mark can be considered, for example, as a mark indicating the nozzle number of any nozzle in the inkjet head. In this case, the nozzle number is, for example, a number set for each nozzle to distinguish each of the plurality of nozzles of the inkjet head. Further, the position mark can also be considered as a mark indicating a predetermined nozzle in an inkjet head, for example.

Further, in this configuration, the print control unit causes the inkjet head to draw a test pattern on a region outside the range in which the print image is drawn, for example. With this configuration, for example, the test pattern can be drawn appropriately while avoiding the influence on the printed image. In addition, the imaging control unit causes the camera to perform imaging a plurality of times at different timings such that at least one sub-scanning operation is performed in between, thereby capturing a plurality of images of mutually different parts of the test pattern. Let the camera acquire a partial area image.

The printing system may also include, for example, a plurality of inkjet heads that each eject ink of a different color. In this case, the test pattern can be considered as, for example, a pattern used for checking ejection characteristics of a plurality of nozzles in one inkjet head. Also, part of the test pattern can be considered as a range including, for example, a nozzle correspondence pattern corresponding to only some nozzles in one inkjet head.

Moreover, in this configuration, the test pattern preferably includes a plurality of position marks drawn on the medium with their positions shifted in the sub-scanning direction. In this case, the imaging control unit, for example, determines that two or more position marks appear in each of the partial area images, and that two or more position marks appear in the two consecutively shot partial area images. A camera acquires a plurality of partial area images so that any of the marks are commonly captured. Then, the defective nozzle detection unit detects a position mark commonly appearing in the two partial area images captured in succession and a nozzle corresponding pattern appearing in one of the two partial area images. Based on this, the nozzles corresponding to the nozzle corresponding pattern appearing in the other of the two partial area images are identified. With this configuration, for example, it is possible to appropriately identify the nozzles corresponding to the nozzle correspondence pattern appearing in the plurality of partial region images that are successively and sequentially acquired.

Further, in this case, it is preferable that adjacent position marks of a plurality of position marks drawn with their positions shifted in the sub-scanning direction have mutually different patterns. With this configuration, for example, among a plurality of position marks appearing in one partial area image, it is possible to more easily and appropriately identify the position mark appearing in common with other partial area images. can. Further, in this case, it is more preferable to draw the position marks so that all of the plurality of position marks appearing in one partial area image have different patterns.

Further, in this configuration, it is conceivable to use, for example, a line-shaped pattern drawn by one nozzle in one main scanning operation as the nozzle corresponding pattern corresponding to each nozzle. With this configuration, it is possible to appropriately detect a defective nozzle, for example.

Further, in this configuration, the operation of drawing the test pattern may be executed by performing correction to add the test pattern to the data representing the print image, for example. Further, in this case, it is conceivable to execute such a correction operation according to a program such as firmware, for example. In this case, the configuration of the printing system can be considered to be, for example, a configuration in which test patterns are created by firmware. As such firmware, for example, firmware of a printing device that executes printing operations in a printing system may be used.

More specifically, in this case, the print control unit draws a test pattern for ejection position designation data, which is data indicating a print image, by designating ejection positions at which ink is ejected by an inkjet head, for example. Correction is performed by adding an ejection position for ejecting ink to . Then, the inkjet head is caused to draw a print image and a test pattern by causing the inkjet head to eject ink based on the corrected ejection position designation data. With this configuration, for example, the print image and the test pattern can be printed appropriately.

Also, in this configuration, the printing system may print on the medium, for example, in a multi-pass manner. In this case, the multi-pass method is, for example, a method in which main scanning operations are performed a plurality of times for each position of an area in which a print image is printed on a medium. In this case, as the data representing the print image, data that completes each portion of the print image by a plurality of main scanning operations to the same position is prepared. Further, in this case, it is conceivable that the correction for adding the ink ejection positions for drawing the test pattern is performed on the data corresponding to each main scanning operation. More specifically, for example, when main scanning data is defined as data specifying the ejection positions at which ink is ejected by an inkjet head in one main scanning operation, the ejection position specification data may be data for drawing a print image. It is conceivable to use data including main scanning data corresponding to each main scanning operation to be performed. In this case, the print control unit corrects, for example, the main scanning data corresponding to at least one of the main scanning operations by adding ejection positions at which ink is ejected to draw the test pattern. With this configuration, for example, even when the print image is printed by the multi-pass method, it is possible to appropriately draw the test pattern including the nozzle corresponding pattern.

Further, in this configuration, by using the position marks, it is possible to appropriately identify the nozzles corresponding to the nozzle corresponding patterns shown in the respective partial area images, as described above. Therefore, the operation of photographing the partial area image can be performed at a timing independent from the timing of the operation of drawing a print image or the like. More specifically, in this case, the photographing control unit causes the camera to photograph a plurality of partial area images at timings independent of timings at which the operation of drawing a print image is started, for example. With this configuration, it is not necessary to notify the start timing of the operation of drawing a print image, for example, so it is possible to detect defective nozzles with a simpler configuration.

In this case, it is conceivable to use, as the test pattern, a pattern that further includes a start mark, which is a pattern indicating the position at which drawing of the test pattern is to be started. With this configuration, for example, the start position of the test pattern can be detected more reliably in the plurality of partial area images. Also, this makes it possible, for example, to more appropriately identify the nozzles corresponding to the nozzle correspondence pattern.

Moreover, in this configuration, the inkjet head has, for example, a plurality of nozzles that are arranged with their positions in the sub-scanning direction mutually shifted. In this case, the shooting range of the partial area image in the sub-scanning direction can be narrower than the nozzle row length, which is the width of the range (range in the sub-scanning direction) in which the plurality of nozzles are arranged in the inkjet head. Conceivable. With this configuration, for example, a camera with a narrow field of view can be used more appropriately.

Further, when the area on the medium where drawing is performed by the inkjet head is defined as the image printing area, the position mark can be considered, for example, as a mark indicating a preset reference position in the image printing area. Further, in this case, the operation of the print control unit during drawing of the print image can be considered, for example, as an operation of causing the inkjet head to further draw a position mark in the image printing area. Further, the operation of the photographing control unit can be considered, for example, as an operation of causing the camera to acquire a plurality of partial area images each of which is a different range in the image printing area. In this case, the camera obtains, for example, a partial area image in which only a partial range in the sub-scanning direction of the image print area is captured by one shot. Further, the defective nozzle detection unit identifies, for example, which range in the image printing region the range appearing in the partial area image is based on the position mark appearing in the partial area image. Defective nozzles are detected by identifying nozzles that have drawn at least a portion of the partial area image.

Considering this, depending on the configuration of the printing system, for example, it is conceivable to detect a defective nozzle without using the nozzle corresponding pattern. Further, in this case, for example, it is conceivable to detect defective nozzles using a printed image. Even when configured in this way, by using the position mark, it is possible to appropriately detect a defective nozzle, for example, using a camera with a narrow field of view.

Further, as a configuration of the present invention, it is conceivable to use a printing method or the like having the same characteristics as those described above. Also in this case, for example, the same effect as described above can be obtained.

According to the present invention, for example, defective nozzles can be detected appropriately.

1 is a diagram illustrating a printing system 10 according to an embodiment of the invention; FIG. FIG. 1A shows an example of the configuration of the printing system 10. As shown in FIG. FIG. 1B shows an example of the configuration of the printing device 12. As shown in FIG. FIG. 1C shows an example of the configuration of the head section 102 in the printing device 12. As shown in FIG. 4 is a diagram for explaining in more detail the control unit 120 and the camera unit 110 in the printing apparatus 12; FIG. FIG. 2A shows an example of a detailed configuration of the control unit 120. FIG. FIG. 2B shows an example of the configuration of the camera unit 110. As shown in FIG. It is a figure which demonstrates in more detail about the test pattern used in this example. FIG. 3A shows an example of an area where printing is performed on the medium 50. FIG. FIG. 3B shows an example configuration of the test pattern 504 . FIG. 7 is a diagram for explaining in more detail the operation of detecting a defective nozzle in the defective nozzle detection unit 306, how to use the position mark 608, and the like. 5 is a diagram showing an example of a detailed configuration of a test pattern 504; FIG. FIG. 11 is a diagram for explaining a modified example of the test pattern 504; FIG. 6A and 6B show modified examples of the test pattern 504. FIG. FIG. 5 is a diagram showing a modification of the configuration of the control unit 120; FIG. 5 is a diagram showing a modification of the configuration of the control unit 120;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments according to the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a printing system 10 according to one embodiment of the invention. FIG. 1A shows an example of the configuration of the printing system 10. As shown in FIG. It should be noted that, except as noted below, the exemplary printing system 10 may have features that are the same as or similar to known printing systems.

In this example, the printing system 10 is a system that performs printing on a medium to be printed using an inkjet method, and includes a printing device 12 and a host PC. The printing device 12 is an inkjet printer that prints on a medium using an inkjet method, and executes a printing operation based on print input data received from the host PC 14 . In this case, print input data is, for example, input data indicating a print image that is an image to be printed. Also, in this example, the print input data is an example of ejection position designation data. In this case, the ejection position designation data is, for example, data indicating a print image by designating ejection positions at which ink is ejected by an inkjet head in the printing device 12 .

The host PC 14 is a computer that controls the operation of the printing device 12, generates print input data outside the printing device 12, and supplies the generated print input data to the printing device 12, thereby controlling the operation of the printing device 12. to control. More specifically, in this example, the host PC 14 generates print input data by performing RIP (Raster Image Processor) processing. In this case, the RIP process is, for example, a process of generating a raster format image that matches the number of colors of ink used in the printing apparatus 12, the printing resolution, and the like. As print input data supplied from the host PC 14 to the printer 12, data generated by performing a known RIP process or the like can be preferably used. In this case, the process of generating print input data in the host PC 14 can be performed, for example, in the same or similar manner as known processes.

As described above, in this example, the printing system 10 is composed of two devices, the printing device 12 and the host PC 14 . However, in a modification of the printing system 10, the printing system 10 may be configured with only one device. In this case, for example, it is conceivable to use a printing device 12 that also functions as the host PC 14 . Also, the printing system 10 may be configured with three or more devices. In this case, for example, the configuration corresponding to part of the printing device 12 (eg, the configuration corresponding to the camera unit 110 described below) can be considered as a separate device from the printing device 12 .

Next, the printing device 12 in the printing system 10 will be explained in more detail. FIG. 1B shows an example of the configuration of the printing device 12. As shown in FIG. FIG. 1C shows an example of the configuration of the head section 102 in the printing device 12. As shown in FIG. In this example, the printing device 12 has a head section 102 , a platen 104 , a main scanning drive section 106 , a sub-scanning drive section 108 , a camera unit 110 and a control unit 120 .

It should be noted that, except as noted above and below, the printing device 12 may have the same or similar features as known inkjet printers. In addition to the illustrated configuration, the printing apparatus 12 may further have various configurations necessary for printing operations and the like. For example, the printing device 12 may further include fixing means for fixing the ink to the medium 50 according to the type of ink used.

The head section 102 is a section that ejects ink onto the medium 50, and has a carriage 200 and a plurality of inkjet heads. A carriage 200 is a holding member that holds a plurality of inkjet heads. Further, in this example, the head unit 102 includes a plurality of inkjet heads, as shown in FIG. k). Each of the inkjet heads 202y to 202k is an inkjet head that ejects inks of different colors onto the medium 50 by an inkjet method. It has a plurality of nozzles arranged in a staggered manner, and ejects ink toward the medium 50 from each nozzle. Further, in this example, the inkjet heads 202y to 202k are aligned in the sub-scanning direction and arranged side by side in the main scanning direction (the Y direction in the figure) perpendicular to the sub-scanning direction.

Further, the inks of the respective colors ejected from the inkjet heads 202y to 202k are the inks of the basic colors (process colors) used for color printing (for example, full-color printing). More specifically, the inkjet head 202y ejects yellow (Y) ink. The inkjet head 202m ejects magenta (M) ink. The inkjet head 202c ejects cyan (C) ink. In addition, the inkjet head 202k ejects black (K) ink. Further, in the following description, each of the inkjet heads 202y to 202k will simply be referred to as the inkjet head 202 when it is not distinguished which color each of the inkjet heads 202y to 202k corresponds to.

The platen 104 is a platform member that holds the medium 50 at a position facing the head section 102 . The main scanning driving unit 106 is a driving unit that causes the inkjet heads 202y to 202k in the head unit 102 to perform a main scanning operation. In this case, the main scanning operation is, for example, an operation of ejecting ink while moving relative to the medium 50 in the main scanning direction. In this example, the main scanning drive unit 106 moves the carriage 200 holding a plurality of inkjet heads 202y to 202k in the main scanning direction, thereby moving the inkjet heads 202y to 202y to the medium 50 whose position in the main scanning direction is fixed. The k side is moved in the main scanning direction.

The sub-scanning drive unit 108 is a drive unit that causes the inkjet heads 202y to 202k to perform sub-scanning operations. In this case, the sub-scanning operation is, for example, an operation of moving relative to the medium 50 in the sub-scanning direction. Further, in this example, the sub-scanning drive unit 108 moves the medium 50 side by, for example, conveying the medium 50 in the conveying direction parallel to the sub-scanning direction using a roller or the like (not shown). The inkjet heads 202y to 202k are caused to perform sub-scanning operations.

The camera unit 110 is a photographing device arranged at a position facing the medium 50 . The configuration of the camera unit 110 and the images acquired by the camera of the camera unit 110 will be described in more detail later.

The control unit 120 includes, for example, a CPU of the printing device 12 and controls the operation of each section of the printing device 12 . More specifically, the control unit 120 causes the inkjet heads 202yk to eject ink onto the medium 50 based on print input data received from the host PC 14, for example. Further, the control unit 120 causes the inkjet heads 202y to 202k to draw the print image indicated by the print input data. Further, in this example, the control unit 120 causes the inkjet heads 202y to 202k to draw a test pattern used for detecting defective nozzles in parallel with the operation of drawing a print image. In this case, the defective nozzle is, for example, a nozzle whose ejection characteristics are out of a predetermined normal range (ejection failure nozzle). Further, detection of defective nozzles means, for example, detecting the presence or absence of defective nozzles. In addition, in this example, in addition to detecting the presence or absence of a defective nozzle, it is also detected which nozzle is a defective nozzle among a plurality of defective nozzles.

Also, as described above, in this example, control unit 120 causes inkjet heads 202yk to draw a test pattern. In this case, causing the inkjet heads 202y to 202k to draw a test pattern means, for example, causing each of the inkjet heads 202y to 202k to draw a test pattern corresponding to each color. Also, the test pattern corresponding to each color can be considered as, for example, a pattern used for checking ejection characteristics of a plurality of nozzles in one inkjet head 202 . The test patterns to be drawn by the inkjet heads 202y to 202k will be described in more detail later.

Here, the operation of printing in the printing system 10 will be described in more detail. In this example, the printing device 12 prints on the medium 50 using a multipass method. In this case, the multi-pass method is, for example, a method in which main scanning operations are performed a plurality of times for each position in an area of the medium 50 where the print image is printed. Performing the main scanning operation multiple times for each position means, for example, performing the main scanning operation so that the inkjet heads 202y to 202k pass the position facing each position multiple times. In this case, between each main scanning operation, the sub-scanning driving unit 108 performs the sub-scanning operation with a feed amount determined according to the number of passes, which is the number of main scanning operations performed for each position. 202yk. More specifically, the width of the range (range in the sub-scanning direction) in which a plurality of nozzles are arranged in each of the inkjet heads 202y to 202k is defined as the nozzle line length L, and the number of passes is N (N is 2 or more). integer), the feed amount in the sub-scanning operation may be set to a distance corresponding to a value (L/N) obtained by dividing the nozzle row length by N, for example.

In this case, the host PC 14 also prepares, as print input data representing the print image, data for completing each part of the print image by a plurality of main scanning operations to the same position. For example, in this example, the host PC 14 generates print input data indicating ejection positions at which ink is to be ejected in each main scanning operation in accordance with multipass operation performed in the printing apparatus 12 . More specifically, for example, when main scanning data is defined as data specifying the ejection positions at which ink is ejected by each of the inkjet heads 202y to 202k in one main scanning operation, the host PC 14 draws a print image. print input data including main scanning data corresponding to each main scanning operation performed for printing.

In this case, the main scanning data can also be considered as data indicating ejection positions at which ink is ejected in one main scanning operation by one inkjet head 202, for example. Further, the print input data including such main scanning data can be considered, for example, as data indicating ejection positions at which ink is ejected in each main scanning operation for each color of ink used for printing. Further, the main scanning data can also be considered as a raster image or the like indicating an image corresponding to the ejection position by designating the ejection position, for example.

Further, in this example, the control unit 120 makes the inkjet heads 202y to 202k draw the test pattern by performing a correction to add the test pattern to the main scanning data. With this configuration, for example, ejection positions for ejecting ink for drawing a test pattern can be appropriately added to data specifying ejection positions in each main scanning operation. In addition, as a result, for example, even when printing is performed by the multipass method, it is possible to appropriately draw the test pattern. Further, the configuration for adding the test pattern in this manner can be considered, for example, as a configuration in which the test pattern is added in the printing device 12 according to the firmware of the printing device 12, or a configuration in which the test pattern is created by firmware. .

Next, the control unit 120 and the camera unit 110 in the printing device 12 will be explained in more detail. FIG. 2 is a diagram for explaining in more detail the control unit 120 and the camera unit 110 in the printing apparatus 12. As shown in FIG. FIG. 2A shows an example of a detailed configuration of the control unit 120. FIG. In this example, the control unit 120 has an input/output unit 302 , a CPU 304 , a defective nozzle detection unit 306 , a print control unit 308 , a carriage drive control unit 310 and a transport drive control unit 312 .

The input/output unit 302 is a part that performs input/output with the user, and receives user instructions for the printing system 10 (see FIG. 1) and the printing device 12 (see FIG. 1), and various information for the user. is displayed, etc. As the input/output unit 302, for example, an operation panel and a display unit can be used. The CPU 304 is an arithmetic device that performs various processes according to programs. Further, in this example, the CPU 304 controls each section of the control unit 120 (for example, the input/output section 302, the defective nozzle detection section 306, the print control section 308, and the carriage drive control) in accordance with firmware, which is a program for controlling the operation of the printing apparatus 12. 310 and the transport drive control unit 312). Further, the CPU 304 thereby controls the operation of each unit of the printing apparatus 12 . The firmware of the printing device 12 may be stored in, for example, a storage device (not shown).

The defective nozzle detection unit 306 is configured to detect defective nozzles. In this case, detecting a defective nozzle means detecting a defective nozzle having a defective ejection characteristic among the plurality of nozzles in the inkjet head 202 . Further, in this example, the defective nozzle detection unit 306 is installed in the apparatus main body (main body portion) of the printing apparatus 12, has an image processing unit 352 and an electronic recording medium 354, and is used to detect images captured by the camera unit 110. Based on this, defective nozzles are detected. Also, in the defective nozzle detection unit 306 , the electronic recording medium 354 stores image data representing an image captured by the camera unit 110 . Also, in this case, the electronic recording medium 354 stores the image at least until the processing of the image in the image processing unit 352 is completed. The image processing unit 352 also performs image processing based on the image data stored in the electronic recording medium 354 to determine whether or not there is a defective nozzle, and notifies the CPU 304 of the determination. Also, if there is a defective nozzle, the CPU 304 is notified by specifying the nozzle number indicating the defective nozzle. In this case, the nozzle number is, for example, a number set for each nozzle to distinguish each of the plurality of nozzles of the inkjet head 202 . As the nozzle number, for example, it is conceivable to use a number or the like that indicates which nozzle is counted from one end of the inkjet head 202 . The operation of detecting a defective nozzle in the defective nozzle detection unit 306 will be described in more detail later.

The print control unit 308 is configured to cause the plurality of inkjet heads 202 to perform operations for drawing print images and test patterns. In this example, the print control unit 308 controls the operations of the main scanning drive unit 106 and the sub-scanning drive unit 108 via the carriage drive control unit 310 and the transport drive control unit 312, and outputs the print image and the test pattern. Ink is ejected from the inkjet heads 202y to 202k to ejection positions required for drawing. In addition, the print control unit 308 causes the inkjet heads 202y to 202k to draw a print image and a test pattern on the medium 50 (see FIG. 1). In this case, the print control unit 308 can also be considered to function as a test pattern print instruction unit that instructs the printing of test patterns, for example.

Also, as described above, in this example, the main scanning data is corrected to cause the inkjet heads 202y to 202k to draw a test pattern. In this case, for example, the print control unit 308 corrects the main scanning data corresponding to at least one of the main scanning operations by adding ejection positions for ejecting ink for drawing a test pattern. . With this configuration, the test pattern can be appropriately drawn even when the print image is printed by the multi-pass method, for example. Also, as described above, in this example, the print input data is an example of ejection position designation data. Therefore, the operation of correcting the main scanning data as described above may be considered as an example of an operation of correcting the ejection position designation data by adding the ejection positions where ink is ejected in order to draw a test pattern. can.

The carriage drive control unit 310 is configured to control the movement of the carriage 200 (see FIG. 1) during the main scanning operation and the like. In this example, the carriage drive control section 310 moves the carriage 200 in the main scanning direction by controlling the operation of the main scanning drive section 106 . Further, the carriage drive control unit 310 thereby controls the movement of the inkjet heads 202y to 202k during the main scanning operation. The transport drive control unit 312 is configured to control transport of the medium 50 . In this example, the transport drive control unit 312 controls the sub-scanning operation by causing the sub-scanning drive unit 108 to transport the medium 50 .

With the above configuration, in this example, the control unit 120 causes the printing device 12 to draw a print image and a test pattern. Further, the control unit 120 detects defective nozzles based on the image captured by the camera unit 110 .

In addition, in FIG. 2A, for convenience of illustration and explanation, the configuration of the control unit 120 is divided for each function. However, in the control unit 120, it is conceivable that various functions are realized by the CPU 304 instead of necessarily using a different configuration for each function as described above. More specifically, for example, at least part of the image processing unit 352, the print control unit 308, the carriage drive control unit 310, and the transport drive control unit 312 in the defective nozzle detection unit 306 may be shared by the CPU 304. be done. In this case, the CPU 304 functions as an image processing unit 352, a print control unit 308, a carriage drive control unit 310, a transport drive control unit 312, etc. by operating according to firmware, for example.

Next, the configuration of the camera unit 110 will be explained. FIG. 2B shows an example of the configuration of the camera unit 110. As shown in FIG. In this example, camera unit 110 includes camera 402 , lighting 404 , and imaging control section 406 . Also, the camera 402 and the lighting 404 are attached to the apparatus body of the printing apparatus 12 by an attachment mechanism so as to face the medium 50 .

A camera 402 is a photographing device that photographs an image. In this example, the camera 402 is arranged so that a partial area of the medium 50 is within its field of view, and by performing photographing in accordance with an instruction from the photographing control unit 406, a part of the medium 50 can be captured. A partial area image, which is an image obtained by photographing an area, is acquired. More specifically, in this example, the camera 402 acquires an image showing a part of the test pattern drawn on the medium 50 as the partial area image. In addition, the camera 402 captures images while the printing apparatus 12 is printing a print image and a test pattern (during operation of the apparatus). to get Also, in this case, the camera 402 acquires a partial area image in which only a partial range in the sub-scanning direction of the test pattern is photographed by one shot. A partial range in the sub-scanning direction is a partial range in a direction parallel to the sub-scanning direction on the medium 50 during the operation of printing the print image and the test pattern.

A lighting 404 is a light source that irradiates an object to be photographed with light when the camera 402 is photographing. Also, in this example, the illumination 404 illuminates at least part of the test pattern.

The shooting control unit 406 is configured to control the shooting operation of the camera 402 . Also, in this example, the imaging control unit 406 causes the camera 402 to acquire a partial area image by controlling the operations of the camera 402 and the lighting 404 . Also, in this case, the imaging control unit 406 causes the camera 402 to perform imaging a plurality of times at different timings, thereby capturing a plurality of partial region images in which different ranges of the test pattern are captured. 402 to obtain. More specifically, in this example, the imaging control unit 406 causes the camera 402 to perform imaging a plurality of times by shifting the timing of imaging so that at least one sub-scanning operation is performed in between. The camera 402 acquires a plurality of partial region images such as

Further, the imaging control unit 406 supplies the plurality of partial area images acquired by the camera 402 to the defective nozzle detection unit 306 in the control unit 120 . Accordingly, the defective nozzle detection unit 306 detects defective nozzles based on the partial area image captured by the camera 402 . In this case, the defective nozzle detection unit 306 stores the partial area image received from the imaging control unit 406 in the electronic recording medium 354, and the image processing unit 352 performs predetermined image processing on the partial area image. Detect defective nozzles. According to this example, for example, it is possible to appropriately detect a defective nozzle using an image obtained by photographing a test pattern.

Next, a method for detecting defective nozzles using a test pattern will be described in more detail. FIG. 3 is a diagram for explaining in more detail the test pattern used in this example. FIG. 3A is a diagram showing an example of a printing area on the medium 50, showing an example of a print image 502 and a test pattern 504 drawn on the medium 50. FIG. In addition, in FIG. 3A, for convenience of illustration, the print image 502 and the test pattern 504 are illustrated by dashed lines that indicate areas where they are drawn.

As described above, in this example, in parallel with the operation of drawing the print image 502, the inkjet heads 202y to 202k are caused to draw a test pattern 504 used for detecting defective nozzles. More specifically, in this example, the print control unit 308 (see FIG. 2) causes the inkjet heads 202y to 202k to draw test patterns on areas outside the range in which the print image is drawn. With this configuration, the test pattern 504 can be appropriately drawn at a position that does not overlap with the print image 502, as shown in the figure, for example. Also, this makes it possible, for example, to appropriately draw the test pattern while avoiding the influence on the print image. Further, such an operation can be considered as, for example, an operation of drawing a test pattern on the margin of the print image that is originally printed on the medium 50 while the print image is being printed.

In this example, the range in which the test pattern 504 is drawn is set outside the range in which the print image 502 is drawn in the main scanning direction. More specifically, FIG. 3A shows an example of setting a range in which the test pattern 504 is drawn on one side of the range in which the print image 502 is drawn in the main scanning direction. The range in which the test pattern 504 is drawn may be set, for example, on both sides of the range in which the print image 502 is drawn in the main scanning direction.

FIG. 3B shows an example configuration of the test pattern 504 . In this example, the test pattern is a pattern comprising a start mark 602 , a plurality of vertical lines 604 , a pattern portion 606 and a plurality of position marks 608 . In addition, in FIG. 3B, for convenience of illustration, the pattern portion 606 is illustrated by a dashed line indicating an area where a predetermined pattern is drawn.

In addition, among these configurations, the start mark 602 is a pattern indicating the position where drawing of the test pattern 504 is started. In this example, a linear pattern (horizontal line pattern) extending in the main scanning direction is used as the start mark 602 . The start mark 602 indicates the start position of the test pattern 504 by being drawn at the most downstream position in the transport direction of the medium 50 in the test pattern 504 . In this case, the most downstream position in the transport direction of the medium 50 in the test pattern 504 can be considered, for example, as the position where ink is first ejected by the inkjet heads 202 y to 2 k in the operation of drawing the test pattern 504 . By using such a start mark 602, for example, it is possible to easily and appropriately detect that the beginning of the test pattern 504 has reached the field of view of the camera 402 (see FIG. 2). Also, this makes it possible to more reliably detect the starting position of the test pattern 504 in the plurality of partial area images acquired by the camera 402, for example. In this case, it is conceivable to use a partial area image acquired after the partial area image in which the start mark 602 is shown as the partial area image used for detecting the defective nozzle.

A plurality of vertical lines 604 are patterns indicating the range in which the test pattern 504 is drawn. In this example, each of the plurality of vertical lines 604 is a linear pattern (vertical line pattern) extending in the sub-scanning direction, and is aligned with the pattern portion 606 and the plurality of position marks 608 in the test pattern 504 in the main scanning direction. are drawn on one side and the other, respectively. By using such a plurality of vertical lines 604, the pattern drawn in the pattern portion 606 (for example, lines drawn by each nozzle) can be changed even when the magnification for capturing an image is changed due to adjustment of the camera 402, for example. ) (for example, the position in the main scanning direction) can be estimated more easily and appropriately. As for the positions where the plurality of vertical lines 604 are drawn, for example, left and right positions of the test pattern 504 can be considered.

A pattern portion 606 is a portion where a nozzle corresponding pattern, which is a pattern drawn by each of a plurality of nozzles, is drawn. In this case, the plurality of nozzles means, for example, the plurality of nozzles of at least one of the inkjet heads 202y to 202k (see FIG. 1). Also, the nozzle correspondence pattern can be considered as a pattern for checking whether or not each nozzle is a defective nozzle, for example. As the nozzle corresponding pattern, for example, a ladder pattern or the like can be preferably used. Ladder patterns are described in more detail later. Further, the nozzle corresponding pattern is not limited to the ladder-like pattern, and other patterns that are the same as or similar to known patterns used for detecting defective nozzles may be used.

A plurality of position marks 608 are patterns indicating reference positions preset in the test pattern 504 . Also, in this example, each of the plurality of position marks 608 is drawn at a position adjacent to the pattern section 606 in the main scanning direction so as to indicate the position of any of the nozzle corresponding patterns in the pattern section 606 . Further, in this case, each position mark 608 can be considered to indicate, for example, to which nozzle a nozzle correspondence pattern drawn at a predetermined relative position with respect to the position mark 608 corresponds. Also, the position mark 608 can be considered as a mark indicating the nozzle number of any nozzle in the inkjet head 202, for example. Also, the position mark 608 can be considered as a mark indicating a predetermined nozzle in the inkjet head 202, for example.

By using such a plurality of position marks 608, for example, for each nozzle corresponding pattern drawn in the pattern portion 606, it is possible to more appropriately identify which nozzle the pattern corresponds to. In addition, as a result, for example, defective nozzle detection using a partial area image can be performed more appropriately. The use of position marks 608 and the like are described in more detail below.

FIG. 4 is a diagram for explaining in more detail the operation of detecting a defective nozzle in the defective nozzle detection unit 306, how to use the position mark 608, and the like. shows an example of Also in FIG. 4, for convenience of illustration, the pattern portion 606 is illustrated by a dashed line indicating the area where the nozzle corresponding pattern is drawn.

As described above, in this example, the shooting control unit 406 (see FIG. 2) of the camera unit 110 causes the camera 402 (see FIG. 2) to shoot multiple times at different timings. Then, the camera 402 is caused to acquire a plurality of partial area images each showing a different range in the test pattern. In this case, as described above, each partial area image can be considered as an image showing a part of the test pattern, for example. Also, part of the test pattern can be considered as a range including nozzle corresponding patterns corresponding to only some nozzles in one inkjet head 202, for example. More specifically, in this example, the imaging control unit 406 mutually divides the imaging range in the sub-scanning direction, as indicated by the 1st to Nth images (N is an integer equal to or greater than 2) in the drawing. By causing the camera 402 to take N different images, the camera 402 is caused to acquire N partial area images.

Also, in this example, the test pattern 504 includes a plurality of position marks 608 drawn on the medium 50 with their positions shifted in the sub-scanning direction, as indicated by reference numerals 608-1 to N+1 in the figure. . In this case, shifting the position in the sub-scanning direction means shifting the position in the direction parallel to the sub-scanning direction during printing on the medium 50 . Also, in this case, a plurality of nozzle correspondence patterns corresponding to a plurality of nozzles are drawn in the range sandwiched between the two position marks 608 in the sub-scanning direction. More specifically, in the range sandwiched between the two position marks 608 in the sub-scanning direction, for example, a plurality of nozzles corresponding to a plurality of nozzles arranged continuously in a part of the nozzle row of one inkjet head 202 A corresponding pattern is drawn.

In this example, as shown in the drawing, the imaging control unit 406 controls two partial area images in which two or more position marks 608 appear in each partial area image and are continuously photographed. A plurality of partial area images are acquired by camera 402 such that any position mark 608 (any of two or more position marks 608) is commonly captured in the area images. For example, in the illustrated case, two position marks 608 appear in each partial area image, and one position mark 608 is common to two consecutively captured partial area images. The camera 402 is caused to acquire a plurality of partial area images so that the image can be captured by the camera 402 . By configuring in this way, for example, with respect to two partial region images that are continuously captured, the common portion of the images can be more reliably and appropriately recognized. In addition, this makes it possible to appropriately identify, for example, the position where two partial area images are connected. Also, for example, the correspondence relationship between the nozzle corresponding pattern in the pattern portion 606 and the position mark 608 can be determined more reliably.

Further, in this case, in image processing that is sequentially performed on a plurality of partial region images, a partial region image (previous image) for which image processing has been completed and a partial region image (current image) that is being processed. will always include one or more position marks 608. Then, the image processing unit 352 (see FIG. 2) in the defective nozzle detection unit 306 processes the position mark 608 that appears in common in the two partial area images captured in succession, and the two partial area images. The nozzles corresponding to the nozzle corresponding pattern appearing in the other of the two partial area images are identified based on the nozzle corresponding pattern appearing in one of them. In this case, for the second and subsequent partial area images, for example, the nozzle number corresponding to the lowest position mark 608 is matched among the position marks 608 in the previous partial area image. It is conceivable that determination is made as a nozzle number corresponding to one that With this configuration, for example, it is possible to appropriately identify the nozzles corresponding to the nozzle correspondence pattern appearing in the plurality of partial region images that are successively and sequentially acquired. In this case, identifying the nozzle corresponding to the nozzle correspondence pattern means identifying which nozzle drew the nozzle correspondence pattern.

In this example, the range captured by the camera 402 in one capturing is limited to only a part of the test pattern in the sub-scanning direction. Even when the camera 402 is used, it is possible to appropriately capture an image with accuracy that allows determination of a defective nozzle. Further, in this case, it is conceivable that the photographing range of the partial area image in the sub-scanning direction is narrower than the nozzle row length, for example. More specifically, it is possible to set the imaging range of the partial area image in the sub-scanning direction to, for example, half or less of the length of the nozzle row. Further, it is preferable that the imaging range of the partial area image in the sub-scanning direction is ⅓ or less of the length of the nozzle row. With this configuration, for example, the defective nozzle can be detected more appropriately using the inexpensive camera 402 .

In this case, when focusing on the relationship between the field of view of the camera 402 and the test pattern 504, it can be considered that the entire test pattern 504 is not within the field of view of the camera 402 in the vertical direction (sub-scanning direction). . Further, in this case, the relationship between the plurality of partial area images and the test pattern 504 is divided into multiple times by the camera 402 while the medium 50 is conveyed by the sub-scanning drive unit 108 (see FIG. 1), for example. It can be considered that the entire image of the test pattern 504 is obtained by photographing by and superimposing the upper portion of the partial region image that is photographed earlier and the lower portion of the partial region image that is photographed later. .

Next, the test pattern 504 used in this example will be described in more detail. FIG. 5 is a diagram showing an example of the detailed configuration of the test pattern 504, and shows an example of the configuration of the test pattern 504 including the nozzle corresponding patterns included in the pattern section 606. As shown in FIG. In the figure, the numbers shown in the pattern portion 606 are for showing an example of the correspondence relationship between the nozzle correspondence patterns and the nozzles, and the nozzle numbers of the nozzles corresponding to some nozzle correspondence patterns. is shown.

As described above, in this example, a ladder pattern is used as the nozzle corresponding pattern included in the pattern section 606 . In this case, the ladder-like pattern means that a plurality of nozzles are caused to draw a plurality of lines so that one nozzle draws one line in one main scanning operation, and adjacent nozzles draw lines. This pattern is formed by shifting in the main scanning direction. In this case, drawing a line with one nozzle in one main scanning operation means, for example, ejecting ink a plurality of times with a minimum ejection interval from one nozzle during a part of the main scanning operation. is to draw a line with Also, the ladder-like pattern is an example of a pattern in which printing is performed by ejecting ink using each nozzle to be detected. As the ladder-like pattern, the same or similar pattern as used in known test patterns can be used. Further, in this case, it can be considered that the linear pattern drawn by one nozzle in one main scanning operation is a nozzle correspondence pattern (nozzle correspondence pattern corresponding to each nozzle). When such a nozzle correspondence pattern is used, for example, the image processing unit 352 (see FIG. 2) in the defective nozzle detection unit 306 detects whether or not there is a line drawn by each nozzle. is a defective nozzle.

Also, as described above, in this example, the defective nozzle detection unit 306 detects defective nozzles based on a partial area image in which a part of the test pattern 504 is captured. More specifically, in this case, the defective nozzle detection unit 306 detects defective nozzles based on one partial area image with respect to the nozzles that draw the nozzle correspondence pattern included in the partial area image. Also, in this case, the defective nozzle detection unit 306 identifies by which nozzle each of the nozzle corresponding patterns appearing in the partial area image was drawn based on the position mark 608 appearing in the partial area image. By doing so, defective nozzles are detected based on the nozzle correspondence pattern.

More specifically, as described above, in the defective nozzle detection unit 306 of this example, the electronic recording medium 354 (see FIG. 2) stores image data representing a partial area image. Then, the image processing unit 352 reads the image data stored in the electronic recording medium 354 and performs image processing on the partial area image in which a part of the test pattern 504 is captured. In this image processing, the nozzle numbers of the nozzles that formed each nozzle corresponding pattern in the pattern portion 606 are identified based on the position marks 608 in the partial area image. In addition, the presence or absence of a defective nozzle and the position of the defective nozzle are detected by checking the state of the nozzle corresponding pattern and determining whether or not the ejection characteristics of each nozzle are normal.

Further, as described above, in this example, two or more position marks 608 appear in one partial area image with respect to the plurality of position marks 608 drawn on the side of the pattern portion 606, and One of the position marks 608 is arranged so as to appear in common in the two partial area images captured in succession. In this case, as described above, for example, the position where two partial area images are connected is appropriately identified, and each position mark 608 corresponds to any nozzle corresponding pattern in the pattern portion 606. You can make a more certain decision about whether to

Therefore, according to this example, for example, even if the entire test pattern 504 cannot be captured in one image in one shot, a plurality of images (partial area images) can be used to detect defective nozzles for all nozzles. It is possible to appropriately determine whether or not it is a nozzle. Further, as a result, for example, in a configuration in which the test pattern 504 is photographed a plurality of times, it is possible to detect a defective nozzle more appropriately.

Here, as illustrated in FIG. 5, it is more preferable to use marks having a plurality of types of shapes as the plurality of position marks 608 . In this case, it is preferable that at least the position marks 608 adjacent in the sub-scanning direction are different from each other. Making the position marks 608 adjacent in the sub-scanning direction different from each other means that, for each position mark 608, at least the position mark 608 one level below and the position mark one level above it, as shown in the drawing. It is different from 608 in shape. Further, such a configuration can also be considered as, for example, a configuration in which, for a plurality of position marks 608 drawn with their positions shifted in the sub-scanning direction, adjacent position marks 608 have different patterns. In this case, it is determined in advance at which position in the test pattern 504 the position mark 608 of each shape is to be drawn (for example, which nozzle corresponding pattern is adjacent to which position). With this configuration, for example, among a plurality of position marks appearing in one partial area image, it is possible to more easily and appropriately identify the position mark appearing in common with other partial area images. can. Also, this makes it possible to more reliably and appropriately identify the correspondence between the nozzle correspondence pattern and the nozzles, for example. Also, in this case, it is more preferable to draw the position marks 608 so that all of the plurality of position marks 608 appearing in one partial area image have different patterns.

Subsequently, supplementary explanations and the like regarding each configuration explained above will be given. As described above, in this example, defective nozzles are detected based on a plurality of partial area images obtained by photographing a part of the test pattern 504 . In this case, the defective nozzle detection unit 306 selects, for example, a partial range in the partial area image based on the position mark 608, and detects the defective nozzles with respect to the nozzles that draw the nozzle correspondence pattern within that range. Detection may be performed. More specifically, for example, when photographing a plurality of partial area images as shown in FIG. 4, in the image processing for the bottommost (first) partial area image, It is conceivable to determine whether or not the nozzles from (No. 1 nozzle) to the nozzle one position before the position mark 608 at the top in the image are defective nozzles. In the image processing for the uppermost (Nth) partial area image, for example, whether or not the nozzle corresponding to the position mark 608 at the bottom in the image to the last nozzle is defective is checked. It is conceivable to judge whether Further, in the image processing for other partial area images, for example, the nozzles from the nozzle corresponding to the bottom position mark 608 in the image to the nozzle one position before the top position mark are defective nozzles. It is conceivable to determine whether or not With this configuration, for example, defective nozzles are detected based on each of a plurality of partial area images obtained by photographing different portions of one test pattern 504, and the detected defective nozzles are detected. By summing the nozzle numbers for the entire test pattern 504 (for one test pattern 504), it is possible to appropriately determine whether or not all nozzles are defective nozzles.

Further, in image processing for each partial area image, a portion overlapping another partial area image may also be determined as a defective nozzle. In this case, if a nozzle to be determined in a plurality of partial area images is determined to be a defective nozzle in image processing based on any of the partial area images, it is preferable to treat that nozzle as a defective nozzle. .

Also, as described above, in this example, by using the test pattern 504 including the position mark 608, the nozzles corresponding to the nozzle corresponding patterns shown in the respective partial area images are appropriately identified. can do. Therefore, the operation of photographing the partial area image can be performed, for example, at a timing independent from the timing of the operation of drawing a print image or the like. More specifically, in this case, the imaging control unit 406 (see FIG. 2) in the camera unit 110, for example, performs imaging of a plurality of partial area images at timing independent of the timing at which the operation of drawing a print image is started. Let the camera 402 (see FIG. 2) do it. With this configuration, it is not necessary to notify the start timing of the operation of drawing a print image, for example, so it is possible to detect defective nozzles with a simpler configuration.

Further, as in this example, when using the printing apparatus 12 configured to create the test pattern 504 by firmware, a means ( For example, it is conceivable that the printer 12 does not have hardware or software for transmitting a photographing instruction. On the other hand, according to this example, even in the printing apparatus 12 having such a configuration, it is possible to appropriately detect a defective nozzle. In this case, for example, by adding the above-described defective nozzle detection function to a printing apparatus or printing system that does not have a function to detect defective nozzles, the manufacturing cost of the printing apparatus can be minimized. It is possible to easily and appropriately realize the printing apparatus 12 and the printing system 10 having a defective nozzle detection function while suppressing the problem.

Also, as described above, in this example, the printing device 12 performs printing in a multi-pass method, for example. In this case, creating the test pattern by firmware makes it possible to add the test pattern more appropriately. More specifically, as described above, when printing is performed using the multi-pass method, the host PC 14 performs RIP processing to correspond to each main scanning operation performed to draw a print image. print input data including main scanning data to be printed; In this case, for example, if a test pattern is added to the image data that is input to the RIP process, the test pattern will also be subject to the RIP process and will be developed into a plurality of main scanning data. However, when the test pattern is developed into a plurality of main scanning data, for example, a line extending in the main scanning direction may be drawn with a plurality of nozzles by a plurality of main scanning operations. As a result, it is conceivable that it becomes difficult to identify the correspondence between each part of the test pattern and the nozzles.

On the other hand, in this example, the printer 12 corrects the main scanning data by adding a test pattern according to the firmware. With this configuration, for example, it is possible to directly and more reliably specify the nozzles that draw each part of the test pattern (for example, each nozzle corresponding pattern). Therefore, according to this example, for example, even when printing is performed by the multi-pass method, it is possible to more reliably identify the correspondence between each portion of the test pattern and the nozzles.

Also, as described above, in this example, the test pattern 504 having the start mark 602 is used to detect defective nozzles. With respect to this point, for example, at the timing when the first partial area image is captured by the camera 402 (at the time of capturing the first image), the nozzle of the nozzle number 1 is drawn in the already printed test pattern 504 . If the spot where the test pattern 504 is detected passes through the field of view of the camera 402, it becomes difficult to detect a defective nozzle using the test pattern 504. FIG. Therefore, in such a case, for example, after the printing of the test pattern 504 is finished, the printing of the next test pattern 504 is newly started so that the start mark 602 in the next test pattern 504 is within the field of view of the camera 402. It is preferable to wait until it arrives and then use the next test pattern 504 to detect the defective nozzle. With this configuration, for example, defective nozzles can be detected more appropriately.

Next, a description of modifications of each configuration described above will be given. In the above, how to use the position marks 608 in the test pattern 504 is mainly based on the position marks 608 that appear in common in the two partial area images that are successively captured, and each nozzle corresponds to the position mark 608. The operation of identifying nozzles corresponding to a pattern has been described. In this case, it can be considered that the nozzles are identified using the plurality of position marks 608 instead of directly identifying the nozzles from the respective position marks 608 . However, in a modification of the operation of the defective nozzle detection unit 306, for example, based on each position mark 608 (only one position mark 608), the nozzles that draw the nozzle correspondence pattern near that position mark 608 are identified. you can go In this case, for example, as the plurality of position marks 608 included in one test pattern 504, patterns with different mark shapes may be used. More specifically, in this case, by storing in advance the nozzle number of the nozzle that draws the nozzle correspondence pattern drawn at a predetermined position for each mark shape, the position mark 608 of that mark shape is captured. During the image processing of the partial area image, it is possible to directly identify the nozzles that have drawn respective nozzle correspondence patterns.

Also, in further variations of the test pattern 504, the test pattern 504 may further comprise other patterns for identifying nozzle numbers, eg, in addition to the position marks 608 described above. FIG. 6 is a diagram for explaining a modified example of the test pattern 504. FIG. 6A and 6B show modified examples of the test pattern 504. FIG. It should be noted that, except for the points described below, in FIG. 6, the configurations denoted by the same reference numerals as in FIGS. 1-5 may have the same or similar features as the configurations in FIGS. 1-5.

In the variant shown in FIG. 6( a ), test pattern 504 further comprises a plurality of bit position markers 612 . In this case, each bit position marker 612 is drawn at a preset position relative to each position mark 608 to indicate the number indicating the corresponding position mark 608 in binary code. Also, for the bit position marker 612, for example, a pattern that indicates a position within the test pattern 504 by a code can be considered.

More specifically, in the case shown in FIG. 6A, each of the plurality of bit position markers 612 is drawn at a position sandwiching the pattern portion 606 between the corresponding position mark 608 in the main scanning direction. Also, the bottom bit position marker 612 indicates the number 0000001 in binary code. The second-to-bottom bit position marker 612 indicates the number 0000010 in binary code. The third bit position marker 612 from the bottom indicates the number 0000011 in binary code. By using such a test pattern 504, for example, it is possible to more reliably identify the number of each position mark 608 counted from the start mark 602 side. Also, this makes it possible to more easily and reliably identify the correspondence relationship between the nozzle correspondence patterns and the nozzles in the pattern section 606, for example.

6(b), the test pattern 504 further comprises a plurality of position marks 614. FIG. In this case, the plurality of position marks 614 are patterns that indicate positions within the test pattern 504 in a different manner than the plurality of position marks 608 . More specifically, in the case shown in FIG. 6B, each of the plurality of position marks 614 is drawn at a position sandwiching the pattern portion 606 with the corresponding position mark 608 in the main scanning direction. Also, each of the plurality of position marks 614 numerically indicates the nozzle number of the nozzle next to the corresponding position mark 608 . Even when such a test pattern 504 is used, the number of each position mark 608 counted from the start mark 602 side can be more reliably identified. Also, this makes it possible to more easily and reliably identify the correspondence relationship between the nozzle correspondence patterns and the nozzles in the pattern section 606, for example.

Further, regarding the printing apparatus 12, various modifications can be made to the specific configuration of the control unit 120 and the like. 7 and 8 show a variant of the configuration of the control unit 120. FIG. 7 and 8 with the same reference numerals as in FIGS. 1 to 6 may have the same or similar features as those in FIGS.

In the configuration shown in FIG. 7 , the defective nozzle detector 306 in the control unit 120 further has an imaging request signal generator 356 . The imaging request signal generation unit 356 is configured to generate a signal (imaging request signal) requesting imaging to the camera 402 (see FIG. 2) in the camera unit 110. By receiving from the driving unit 108, a photographing request signal is generated each time the medium is conveyed by a certain amount. In this case, for example, an output signal of an encoder attached to a motor that generates power for transporting the medium can be preferably used as the signal indicating the transport amount of the medium. With this configuration, for example, the timing of photographing the test pattern 504 can be appropriately controlled with high accuracy. In addition, this makes it possible, for example, to make the interval of photographing equal to minimize the overlapping portion of the partial region images.

In addition, in the configuration shown in FIG. 8, the control unit 120 further has a nozzle return processing section 322 . In this case, the nozzle restoration processing unit 322 controls, for example, the process of replacing a nozzle determined to be a defective nozzle (a nozzle corresponding to the nozzle number of the defective nozzle) with another nozzle. With this configuration, the printing operation can be appropriately continued even when a defective nozzle is detected, for example. Further, the nozzle recovery processing unit 322 may perform processing for improving ejection failures by cleaning the inkjet head 202 (see FIG. 1), for example.

Also, the various features described above in connection with the operation of detecting bad nozzles may be considered more general. More specifically, for example, when an area in which drawing is performed by the inkjet head 202 (see FIG. 1) on the medium is defined as an image printing area, the position mark is, for example, a preset reference position in the image printing area. can be considered as a mark or the like indicating Further, in this case, the operation of the print control unit 308 during drawing of the print image can be considered as, for example, an operation of causing the inkjet head 202 to further draw a position mark in the image printing area. Further, the operation of the imaging control unit 406 (see FIG. 2) can be considered, for example, as an operation of causing the camera 402 to acquire a plurality of partial area images each showing a different range in the image printing area. In this case, the camera 402 obtains, for example, a partial area image in which only a partial range in the sub-scanning direction of the image print area is captured by one shot. Further, the defective nozzle detection unit 306 identifies, for example, which range in the image printing region the range shown in the partial area image is based on the position mark shown in the partial area image. A nozzle that depicts at least a portion of the partial area image is identified. In addition, the defective nozzle detection unit 306 thereby detects defective nozzles.

Considering this, in a modified example of the printing system 10, for example, it is conceivable to detect a defective nozzle without using a nozzle corresponding pattern. Further, in this case, for example, it is conceivable to detect defective nozzles using a printed image. Detecting a defective nozzle using a print image means, for example, detecting a defective nozzle by identifying the nozzles that draw each part of the image nozzles. Also in this case, by using the position mark, it is possible to appropriately detect the defective nozzle, for example, using a camera with a narrow field of view.

INDUSTRIAL APPLICABILITY The present invention can be suitably used for printing systems.

DESCRIPTION OF SYMBOLS 10... Printing system, 12... Printing apparatus, 14... Host PC, 50... Medium, 102... Head part, 104... Platen, 106... Main scanning drive part, 108 110 Camera unit 120 Control unit 200 Carriage 202 Inkjet head 302 Input/output unit 304 CPU 306 . , 354... electronic recording medium, 356... photographing request signal generation unit, 402... camera, 404... illumination, 406... photographing control unit, 502... print image, 504... Test pattern 602 Start mark 604 Vertical line 606 Pattern part 608 Position mark 612 Bit position marker 614 Position mark

Claims (12)

A printing system that prints on a medium by an inkjet method,
an inkjet head having a plurality of nozzles for ejecting ink onto the medium;
a main scanning driving unit that causes the inkjet head to perform a main scanning operation of ejecting ink while moving relative to the medium in a preset main scanning direction;
a sub-scanning driving unit that causes the inkjet head to perform a sub-scanning operation of moving relative to the medium in a sub-scanning direction orthogonal to the main scanning direction;
a camera that acquires a partial area image that is an image obtained by photographing a partial area of the medium;
a shooting control unit that controls the shooting operation of the camera;
a print control unit that causes the inkjet head to draw a print image, which is an image to be printed, by controlling operations of the inkjet head, the main scanning driving unit, and the sub scanning driving unit;
a defective nozzle detection unit that detects a defective nozzle having defective ejection characteristics among the plurality of nozzles based on the partial area image captured by the camera;
When drawing the print image, the print control unit further causes the inkjet head to draw a test pattern used for detecting the defective nozzle,
The imaging control unit causes the camera to acquire a plurality of partial area images each showing a different range in the test pattern,
the camera acquires the partial area image in which only a partial area of the test pattern in the sub-scanning direction is captured by one shot;
The test pattern is
a nozzle corresponding pattern, which is a pattern drawn by each of the plurality of nozzles;
and a position mark, which is a pattern indicating a preset reference position in the test pattern,
The defective nozzle detection unit identifies which of the nozzles drew the nozzle corresponding pattern appearing in the partial area image based on the position mark appearing in the partial area image, A printing system, wherein the defective nozzle is detected based on the nozzle correspondence pattern. the test pattern includes a plurality of the position marks drawn on the medium with their positions shifted in the sub-scanning direction;
The photographing control unit is arranged such that two or more of the position marks appear in each of the partial area images, and two or more of the two or more of the partial area images are photographed in succession. causing the camera to acquire the plurality of partial region images so that any one of the position marks is captured in common;
The defective nozzle detection unit is adapted to correspond to the position mark commonly appearing in the two partial area images captured in succession and the nozzle appearing in one of the two partial area images. 2. The printing system according to claim 1, wherein the nozzles corresponding to the nozzle corresponding pattern appearing in the other of the two partial area images are identified based on the pattern. 3. The printing system according to claim 2, wherein among the plurality of position marks drawn with positions shifted in the sub-scanning direction, adjacent position marks have patterns different from each other. 4. The printing according to any one of claims 1 to 3, wherein the nozzle correspondence pattern corresponding to each of the nozzles is a linear pattern drawn by one nozzle in one main scanning operation. system. The print control section designates the ejection position at which ink is ejected to draw the test pattern with respect to the ejection position specification data, which is data indicating the print image, by specifying the ejection position at which the ink is ejected by the inkjet head. 2. The print image and the test pattern are drawn on the inkjet head by performing additional correction and causing the inkjet head to eject ink based on the corrected ejection position designation data. 5. The printing system according to any one of 4 to 4. printing on the medium by a multi-pass method in which the main scanning operation is performed a plurality of times for each position of an area where the print image is printed on the medium;
When the main scanning data is defined as data specifying the ejection position at which ink is ejected by the inkjet head in one main scanning operation, the ejection position specifying data is used for each operation for drawing the print image. including the main scanning data corresponding to the main scanning operation of
The print control unit is characterized in that the main scanning data corresponding to at least one of the main scanning operations is corrected by adding an ejection position for ejecting ink for drawing the test pattern. 6. The printing system of claim 5. 7. The imaging control unit according to any one of claims 1 to 6, wherein the imaging control unit causes the camera to perform imaging of the plurality of partial area images at a timing independent of a timing at which the operation of drawing the print image is started. The printing system according to 8. The printing system according to any one of claims 1 to 7, wherein the test pattern further includes a start mark, which is a pattern indicating a position at which drawing of the test pattern is started. The inkjet head has the plurality of nozzles arranged in a line with positions shifted from each other in the sub-scanning direction,
9. The printing system according to any one of claims 1 to 8, wherein an imaging range of the partial area image in the sub-scanning direction is narrower than a range in which the plurality of nozzles are arranged in the inkjet head. A printing method for printing on a medium by an inkjet method,
a main scanning operation in which an inkjet head having a plurality of nozzles for ejecting ink onto the medium ejects ink while moving relative to the medium in a preset main scanning direction; causing the inkjet head to draw a print image, which is an image to be printed, by performing a sub-scanning operation of moving relative to the medium in the sub-scanning direction,
and further causing the inkjet head to draw a test pattern used for detecting defective nozzles having defective ejection characteristics among the plurality of nozzles when drawing the print image,
causing a camera to acquire a partial area image, which is an image obtained by photographing a partial area of the medium;
detecting the defective nozzle based on the partial area image captured by the camera;
At the time of photographing with the camera, the camera acquires a plurality of the partial area images each of which is a different range of the test pattern, and the camera is caused to photograph the test pattern once. Acquiring the partial area image in which only a partial range in the sub-scanning direction is captured;
The test pattern is
a nozzle corresponding pattern, which is a pattern drawn by each of the plurality of nozzles;
and a position mark, which is a pattern indicating a preset reference position in the test pattern,
Based on the nozzle corresponding pattern, by identifying which of the nozzles drew the nozzle corresponding pattern reflected in the partial area image based on the position mark reflected in the partial area image, A printing method, comprising detecting the defective nozzle. A printing system that prints on a medium by an inkjet method,
an inkjet head having a plurality of nozzles for ejecting ink onto the medium;
a main scanning driving unit that causes the inkjet head to perform a main scanning operation of ejecting ink while moving relative to the medium in a preset main scanning direction;
a sub-scanning driving unit that causes the inkjet head to perform a sub-scanning operation of moving relative to the medium in a sub-scanning direction orthogonal to the main scanning direction;
a camera that acquires a partial area image that is an image obtained by photographing a partial area of the medium;
a shooting control unit that controls the shooting operation of the camera;
a print control unit that causes the inkjet head to draw a print image, which is an image to be printed, by controlling operations of the inkjet head, the main scanning driving unit, and the sub scanning driving unit;
a defective nozzle detection unit that detects a defective nozzle having defective ejection characteristics among the plurality of nozzles based on the partial area image captured by the camera;
At the time of drawing the print image, the print control unit causes the ink jet head to apply a reference preset in the image print region to the image print region, which is the region where drawing is performed by the ink jet head on the medium. Further draw a position mark indicating the position,
The imaging control unit causes the camera to acquire a plurality of partial area images each of which is a different range in the image printing area,
the camera acquires the partial area image in which only a partial area in the sub-scanning direction of the image printing area is photographed by photographing once;
The defective nozzle detection unit identifies, based on the position mark appearing in the partial area image, which area in the image printing area the area appearing in the partial area image is, A printing system, wherein the defective nozzle is detected by identifying the nozzle that has drawn at least part of the partial area image. A printing method for printing on a medium by an inkjet method,
a main scanning operation in which an inkjet head having a plurality of nozzles for ejecting ink onto the medium ejects ink while moving relative to the medium in a preset main scanning direction; causing the inkjet head to draw a print image, which is an image to be printed, by performing a sub-scanning operation of moving relative to the medium in the sub-scanning direction,
and a position indicating a preset reference position in the image printing area of the inkjet head with respect to the image printing area, which is the area where the inkjet head draws on the medium when the print image is drawn. Let the drawing of the mark be done further,
causing a camera to acquire a partial area image, which is an image obtained by photographing a partial area of the medium;
detecting the defective nozzle based on the partial area image captured by the camera;
At the time of photographing with the camera, the camera acquires a plurality of the partial area images each of which is a different range in the image printing area, and the image is printed by the camera by one photographing. Acquiring the partial area image showing only a partial range of the area in the sub-scanning direction;
By identifying which range in the image printing region the range captured in the partial area image is based on the position mark captured in the partial area image, at least the partial area image A printing method, wherein the defective nozzle is detected by identifying the partially drawn nozzle.

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