Image processing device, image processing method

Abstract

To provide a technology for suppressing false detections of periodic image defects that occur in printed materials. [Solution] The image processing device reads a recording medium on which an image based on print data is printed, and generates a scan image based on this scan image, and a difference image representing the difference between the amount of colorant corresponding to the scan image and the amount of colorant corresponding to the image. The image processing device then generates a diagnostic image used to diagnose image defects in printing based on the first difference image generated for the first print data and the second difference image generated for the second print data.

Description

TECHNICAL FIELD

[0001] The present invention relates to a diagnostic technique for image defects in printing.

BACKGROUND ART

[0002] Some image forming apparatuses used in the printing industry are equipped with an image inspection apparatus that automatically inspects output printed matter for image defects. The image inspection apparatus has an image reading unit that captures an image of the printed matter to acquire inspection image data in a paper discharge path of the image forming apparatus, and detects an image defect of the printed matter from a difference between document data and the inspection image data. In recent years, in this image inspection apparatus, a technique has been proposed for detecting minor image defects that occur in the initial stage of a failure of the image forming apparatus, which are not detected as image defects. With this technique, preparation for repair can be started at the initial stage of the failure, and the downtime of the image forming apparatus can be reduced. However, since minor image defects are likely to be buried in noise, it is necessary to separate actual image defects and noise from detected image defect candidates to detect the image defects. As a method for separating image defects and noise, for example, a method of inspecting a plurality of images and performing separation based on position identity is generally used. Patent Document 1 discloses a method of scanning the same position on the sample surface a plurality of times with temporal shifts, and determining whether an image defect exists on the sample based on a result of a logical product of luminance signals at the same position in each scan.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0003]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] In image forming apparatuses that use rotating members such as transfer belts to form printed materials, such as electrophotographic printers, scratches on the rotating members can cause periodic image defects on the printed material. For example, if there are scratches on the transfer belt, the colorant may adhere to or peel off the scratches, resulting in image defects on the printed material. Since the colorant that adheres or peels off varies depending on the printing timing, the image defects caused by the transfer belt may have different colors. Consider the case where multiple sheets are printed to separate image defects from noise, as described above. If the colorant attached to the first sheet is black and the colorant attached to the second sheet is yellow, using conventional technology, the former will have a large brightness difference and the latter a small brightness difference, leading to the detection of noise and potentially causing false detection. This invention provides a technology to suppress false detection of periodic image defects occurring in printed materials. [Means for solving the problem]

[0005] One aspect of the present invention is characterized by comprising: a scanned image obtained by reading a recording medium on which an image based on print data is printed; a first generation means that generates a difference image based on the scanned image, representing the difference between the amount of colorant corresponding to the scanned image and the amount of colorant corresponding to the image; and a second generation means that generates a diagnostic image used for diagnosing image defects in printing, based on a first difference image generated by the first generation means for first print data and a second difference image generated by the first generation means for second print data. [Effects of the Invention]

[0006] The present invention provides a technology for suppressing false detection of periodic image defects that occur in printed materials. [Brief explanation of the drawing]

[0007] [Figure 1] A diagram illustrating one of the problems that we are trying to solve. [Figure 2] A diagram showing an example configuration of an image processing device. [Figure 3] A block diagram showing an example of the hardware configuration of the image forming apparatus 201. [Figure 4] A block diagram showing an example of the hardware configuration of the image inspection device 202. [Figure 5] A block diagram showing an example of the functional configuration of the image forming apparatus 201 and the image inspection apparatus 202. [Figure 6] A flowchart of the processes performed by an image processing unit. [Figure 7] A flowchart showing the details of the process in step S603. [Figure 8] A diagram showing an example of the configuration of a conversion table. [Figure 9] A flowchart showing the details of the process in step S607. [Figure 10] A diagram illustrating the process from step S901 to step S905. [Figure 11] A flowchart of the processes performed by an image processing unit. [Figure 12] A diagram showing an example of the UI display. [Figure 13] A flowchart showing the details of the process in step S607. [Figure 14] A diagram illustrating the process from step S1301 to step S1305. [Modes for carrying out the invention]

[0008] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0009] [First Embodiment] First, let's explain one of the problems that this embodiment aims to solve, using Figure 1. First, let's explain the factors that cause the scanned image to have different colors due to image defects. In an image forming apparatus that uses rotating members such as a photosensitive drum, transfer belt, and fixing roller to transport a colorant image and form a printed material, if scratches occur on the rotating members, periodic image defects occur on the printed material due to these scratches. These periodic image defects have different colors.

[0010] Figure 1(a) is a schematic cross-sectional view showing an image defect. An ideal image 102 is formed in black pigment at a certain location on the recording medium 101, and an image defect 103 is formed in cyan pigment on top of the ideal image 102.

[0011] Figure 1(b) is a schematic cross-sectional view showing periodic image defects occurring in a location different from the location where image defect 103 occurs. An ideal image 104 is formed with yellow pigment at a certain location on the recording medium 101 (a location different from the location of the ideal image 102), and an image defect 105 is formed with cyan pigment on top of the ideal image 104. Since the location shown in Figure 1(a) and the location shown in Figure 1(b) are different, the pigments of the ideal image 102 and the ideal image 104 are considered to be different. In Figure 1(a) and Figure 1(b), the colors of the scanned images acquired due to the image defects are different because the pigments of the ideal image 102 and the ideal image 104 are different.

[0012] Figure 1(c) is a schematic cross-sectional view showing periodic image defects occurring in locations different from those where image defects 103 and 105 occurred. An ideal image 106 is formed with black pigment at a location on the recording medium 101 (different from the locations of the ideal images 102 and 104), and an image defect 107 is formed with yellow pigment on top of the ideal image 106.

[0013] Depending on the cause, such as when the cause of an image defect is a scratch on a transfer belt, the color material of a periodic image defect occurring at a different location may be a different color material. In Figure 1(a) and Figure 1(c), since the color material of the image defect 103 and the color material of the image defect 107 are different, the colors of the acquired scanned images are different.

[0014] Figure 1(d) is a cross-sectional view schematically showing a periodic image defect that occurred at a location different from the locations where the image defects 103, 105, and 107 occurred. An ideal image 108 is formed of black color material at a certain location on the recording medium 101 (a location different from the locations of the ideal images 102, 104, and 106), and an image defect 109 is formed of cyan color material over the ideal image 108. The image defect 109 is larger in size than the image defect 103. Since the scratch on the rotating member that is the cause of the image defect changes over time, the sizes of periodic image defects that occur at different locations may differ. Since the sizes of the generated image defects are different between Figure 1(a) and Figure 1(d), the colors of the scanned images acquired due to the image defects are different.

[0015] Due to such various factors, the colors of image defects differ. Therefore, depending on the image defect, such as when the color material of the image defect is yellow or when scattering is large, the luminance difference may be small or the luminance difference may be negative. In the conventional art, if the luminance difference is smaller than a threshold value, it is determined that the defect is not an image defect but noise. Further, if the luminance difference is negative, the determination itself cannot be performed. As described above, if the colors of the scanned images acquired due to image defects differ, the luminance difference may be small or negative, and the conventional method of distinguishing between image defects and noise using luminance may cause false detections.

[0016] Next, a configuration example of the image processing apparatus according to the present embodiment will be described with reference to Figure 2. As shown in Figure 2, the image processing apparatus according to the present embodiment includes an image forming apparatus 201, an image inspection apparatus 202, and a stacker 203. First, the image forming apparatus 201 will be described.

[0017] The operation panel 204 is an operation and display unit for the user to perform various operations and inputs to the image forming apparatus 201 and to display various screens, and for example, it has a touch panel screen.

[0018] Toner images are formed on the photoreceptor drums 205, 206, 207, and 208 by an imaging process that includes a charging step, an exposure step, a development step, a transfer step, and a cleaning step, and the formed toner images are transferred to the transfer belt 209.

[0019] In this embodiment, a yellow toner image, which is an image of yellow (Y) pigment, is formed on the photoconductor drum 205; a magenta toner image, which is an image of magenta (M) pigment, is formed on the photoconductor drum 206; a cyan toner image, which is an image of cyan (C) pigment, is formed on the photoconductor drum 207; and a black toner image, which is an image of black (K) pigment, is formed on the photoconductor drum 208.

[0020] The transfer belt 209 transports the toner images superimposed and transferred by the photoreceptor drums 205, 206, 207, and 208 to the secondary transfer position of the secondary transfer roller 210. In this embodiment, a toner image is transferred onto the transfer belt 209 by first transferring a yellow toner image by the photoreceptor drum 205, followed by a magenta toner image by the photoreceptor drum 206, a cyan toner image by the photoreceptor drum 207, and a black toner image by the photoreceptor drum 208, resulting in a superimposed toner image of yellow, magenta, cyan, and black toner images. However, the embodiment is not limited to this.

[0021] The paper feed unit 211 houses multiple recording media stacked on top of each other, and feeds these recording media sequentially to the subsequent stage. Various types of paper, such as plain paper and coated paper, can be used as recording media.

[0022] The transport roller pair 212 transports the recording medium fed by the paper feeding unit 211 along the transport path 215 in the direction indicated by arrow 216. The secondary transfer roller 210 transfers the toner image transferred on the transfer belt 209 onto the recording medium transported by the transport roller pair 212 at the secondary transfer position. At this time, the black toner image, cyan toner image, magenta toner image, and yellow toner image are sequentially superimposed and transferred onto the recording medium. The fuser roller 213 fixes the toner image to the recording medium by heating and pressurizing the recording medium on which the toner image has been transferred.

[0023] In the case of single-sided printing, the image forming apparatus 201 transports the recording medium with a toner image fixed on one side as a printed material to the image inspection apparatus 202, and in the case of double-sided printing, it sends the recording medium with a toner image fixed on one side to the inversion path 214.

[0024] The inversion path 214 reverses the front and back sides of the transmitted recording medium by switching it back and transports it in the direction indicated by the arrow 217. The recording medium transported by the inversion path 214 is transported again by the transport roller pair 212, and the toner image is transferred to the opposite side of the recording medium by the secondary transfer roller 210. After that, it is fixed by the fuser roller 213 and discharged as a printed material to the image inspection device 202.

[0025] Furthermore, the image forming apparatus 201 has rotary encoders 218 to 223 for acquiring the rotational position (phase) of various rotating members. The rotary encoders 218 to 223 can be composed of, for example, a marker attached to one location in the non-printing area of ​​the rotating member and a density sensor, and the phase of the rotating member is detected by acquiring the time the marker passes over it from the change in density of the density sensor. Rotary encoders 218, 219, 220, and 221 are attached to the photoreceptor drums 205, 206, 207, and 208, respectively. Rotary encoder 222 is attached to the transfer belt 209, and rotary encoder 223 is attached to the fixing roller 213. Note that these rotary encoders are not limited to the above method, and any that can identify the phase of the rotating member is acceptable.

[0026] Next, the image inspection device 202 will be described. The operation panel 225 is an operation display unit for the user to perform various operations and display various screens on the image inspection device 202, and for example, it has a touch panel screen.

[0027] Note that the operation panel 225 may be omitted. For example, the operation panel 204 may also serve as the operation panel 225, or a PC (personal computer) or tablet device connected to the image processing device may also serve as the operation panel 225.

[0028] The reading unit 224 optically reads one side of the printed material ejected from the image forming apparatus 201. Specifically, the reading unit 224 repeatedly irradiates the printed material with illumination light from an illumination device (not shown) and reads the amount of reflected light with an image sensor (not shown) each time the printed material is transported one line length in the transport direction. As the image sensor, a line sensor can be used in which multiple image sensors are arranged in parallel in the main scanning direction perpendicular to the transport direction of the printed material, but it is not limited to this, and an area sensor or the like may also be used. As the image sensors, for example, complementary metal-oxide-semiconductor CMOS or electrocoupled CCD equipped with red, green, and blue color filters can be used. As the illumination device, for example, one in which multiple light-emitting elements are arranged in parallel in the main scanning direction can be used. As light-emitting elements, for example, LEDs or organic EL elements can be used.

[0029] The image inspection device 202 ejects the printed material that has been read to the stacker 203. The image inspection device 202 may further include a reading unit that optically reads the other side of the printed material.

[0030] Next, the stacker 203 will be described. The stacker 203 ejects the printed materials discharged from the image inspection device 202 into the tray 226. However, the destination of the printed materials ejected by the stacker 203 is not limited to the tray 226.

[0031] Next, an example of the hardware configuration of the image forming apparatus 201 will be explained using the block diagram in Figure 3. As shown in Figure 3, the image forming apparatus 201 has a configuration in which the controller 301 and the engine 311 are connected by a PCI bus, which is a type of expansion bus. The controller 301 is a controller that performs various processes such as overall control of the image forming apparatus 201, drawing, communication, and control of input from and display on the operation display unit 309.

[0032] Engine 311 is a print engine that can be connected to a PCI bus. The print engine includes photoreceptor drums 205, 206, 207, and 208, a transfer belt 209, a secondary transfer roller 210, a paper feed unit 211, a transport roller pair 212, a fuser roller 213, and an inversion path 214. In addition to the above, the printer engine also includes rotary encoders 218, 219, 220, 221, 222, and 223, and a digital processing unit (not shown) that performs digital image processing such as halftone processing and gamma conversion on the printed image. The operation display unit 309 corresponds to the operation panel 204. Physical connection to the image inspection device 202 is made via USB 310.

[0033] The CPU 302 performs various processes using computer programs and data stored in the RAM 305. In this way, the CPU 302 controls the overall operation of the image forming apparatus 201 and executes or controls various processes described as being performed by the image forming apparatus 201. For example, the CPU 302 controls the reading and writing of computer programs and data to the system memory 303, and communication with peripheral devices connected via various buses. The CPU 302 is connected to the ASIC 306 via the AGP bus, a type of expansion bus for graphics cards, and the PCIe bus, another type of expansion bus. The CPU 302 is also connected to peripheral devices such as network interfaces (not shown) via the PCI bus.

[0034] The system memory 303 is a memory used for storing computer programs and data, for expanding computer programs and data, for drawing images based on print data, etc., and includes ROM 304 and RAM 305.

[0035] ROM304 stores configuration data for the image forming apparatus 201, computer programs and data related to the startup of the image forming apparatus 201, computer programs and data related to the basic operation of the image forming apparatus 201, and so on.

[0036] RAM305 has areas for storing computer programs and data loaded from ROM304, and areas for storing computer programs and data loaded from HDD308. Furthermore, RAM305 has a work area used by CPU302 and ASIC306 when executing various processes. For example, RAM305 can be used as memory for storing computer programs and data, memory for expanding computer programs and data, drawing memory, etc.

[0037] The ASIC306 is an integrated circuit for image processing applications that includes hardware elements for image processing. The ASIC306 has a memory controller that controls the local memory 307, and multiple direct memory access controllers that perform image rotation and other operations using hardware logic. The ASIC306 is also connected to the USB310 and engine 311 via the PCI bus. The operation display unit 309 is directly connected to the ASIC306. The local memory 307 is used as a copy image buffer and a code buffer.

[0038] HDD308 is a storage device capable of storing various types of data, including images, computer programs and data, font data, and forms. CPU302 can directly access this local memory 307 with high throughput via the AGP bus or PCIe bus. HDD308 also stores computer programs and data that cause CPU302 to execute or control various processes described as those performed by the image forming apparatus 201. These computer programs and data may also be stored in ROM304.

[0039] Next, an example of the hardware configuration of the image inspection device 202 will be explained using the block diagram in Figure 4. The configuration in Figure 4 is the same as the configuration in Figure 3, but with the engine 311 replaced by the reading unit 224. As shown in Figure 4, the image inspection device 202 has a configuration in which the controller 401 and the reading unit 224 are connected by a PCI bus, which is a type of expansion bus.

[0040] The controller 401 is a controller that performs various processes such as overall control of the image inspection apparatus 202, drawing, communication, and control of input from and display on the operation display unit 409. The operation display unit 409 corresponds to the operation panel 225. Physical connections to the image forming apparatus 201 and stacker 203 are made via USB 410.

[0041] The CPU 402 performs various processes using computer programs and data stored in the RAM 405. In this way, the CPU 402 controls the overall operation of the image inspection device 202 and executes or controls the various processes described as being performed by the image inspection device 202. For example, the CPU 402 controls the reading and writing of computer programs and data to the system memory 403, and communication with peripheral devices connected via various buses. The CPU 402 is connected to the ASIC 406 via the AGP bus, a type of expansion bus for graphics cards, and the PCIe bus, another type of expansion bus. The CPU 402 is also connected to peripheral devices such as network interfaces (not shown) via the PCI bus.

[0042] The system memory 403 is a memory used for storing computer programs and data, for expanding computer programs and data, for drawing images based on print data, etc., and includes ROM 404 and RAM 405.

[0043] ROM 404 stores configuration data for the image inspection device 202, computer programs and data related to the startup of the image inspection device 202, computer programs and data related to the basic operation of the image inspection device 202, and so on.

[0044] RAM405 has areas for storing computer programs and data loaded from ROM404, and areas for storing computer programs and data loaded from HDD408. Furthermore, RAM405 has a work area used by CPU402 and ASIC406 when performing various processes. For example, RAM405 can be used as memory for storing computer programs and data, memory for expanding computer programs and data, drawing memory, etc.

[0045] The ASIC406 has a memory controller that controls the local memory 407, and multiple direct memory access controllers that perform image rotation and other operations using hardware logic. The ASIC406 is also connected to a USB410 via the PCI bus. The operation display unit 409 is directly connected to the ASIC406. The local memory 407 is used as a copy image buffer and a code buffer.

[0046] HDD408 is a storage device capable of storing various types of data, including images, computer programs and data, font data, and forms. CPU402 can directly access this local memory 407 with high throughput via the AGP bus or PCIe bus. HDD408 also stores computer programs and data that cause CPU402 to execute or control various processes described as those performed by the image inspection device 202. These computer programs and data may also be stored in ROM304.

[0047] Next, Figure 5 shows block diagrams illustrating examples of the functional configurations of the image forming apparatus 201 and the image inspection apparatus 202. The RIP unit 501 and the image forming unit 502 can be implemented using, for example, a CPU 302 or an ASIC 306. The RIP unit 501 and the image forming unit 502 may be implemented in hardware or in software (computer program).

[0048] In the following, the RIP unit 501 and the image forming unit 502 may be described as the main components of the processing, but in reality, the CPU 302 and ASIC 306 execute the functions of the corresponding functional units, thereby realizing the functions of those functional units.

[0049] In the following, the acquisition unit 503, the generation unit 504, and the detection unit 505 can be implemented using, for example, a CPU 402 or an ASIC 406. The acquisition unit 503, the generation unit 504, and the detection unit 505 may be implemented in hardware or in software (computer program).

[0050] In the following, the acquisition unit 503, generation unit 504, and detection unit 505 may be described as the main components of the processing, but in reality, the CPU 402 and ASIC 406 execute the functions of the corresponding functional units, thereby realizing the functions of those functional units.

[0051] Next, the process performed by the image processing device to diagnose image defects in printing using a diagnostic image, and to notify the user of the diagnosis results, will be explained according to the flowchart in Figure 6.

[0052] In step S601, the image forming apparatus 201 performs the first printing. Specifically, first, the RIP unit 501 acquires the first print data transmitted from an external device such as a PC, tablet terminal, or smartphone. The RIP unit 501 then performs RIP processing based on the first print data to generate images corresponding to each color of the photoreceptor drums 205 to 208 (a total of four plane images: an image where each pixel has an 8-bit C pixel value, an image where each pixel has an 8-bit M pixel value, an image where each pixel has an 8-bit Y pixel value, and an image where each pixel has an 8-bit K pixel value) as the first RIP image (printed image).

[0053] The image forming unit 502 executes the printing process. Using rotating members such as the photoreceptor drums 205, 206, 207, 208, the transfer belt 209, and the fixing roller 213, the image forming unit 502 forms a first RIP image on the recording medium, thereby generating the recording medium on which the first RIP image is printed as a first printed material, and discharges the first printed material to the image inspection device 202.

[0054] Furthermore, the image forming unit 502 obtains the phase of the rotating member at the time the recording medium enters the rotating member (or, in the case of a photosensitive drum, the time exposure begins) from the output values ​​of the rotary encoders 218, 219, 220, 221, 222, and 223 attached to the rotating member, respectively, as the "phase of the rotating member corresponding to the first printed material".

[0055] In step S602, the acquisition unit 503 controls the reading unit 224 to scan the first printed material (first RIP image) ejected from the image forming unit 502 and acquire the first scanned image. In this embodiment, the scanned image obtained by scanning with the reading unit 224 is an RGB color image in which each pixel has three colors, R, G, and B, and the pixel values ​​of each color are quantized with 8 bits, but it is not limited to this.

[0056] In step S603, the generation unit 504 generates a difference image as the first difference colorant image, based on the first RIP image and the first scan image, which represents the difference between the amount of colorant corresponding to the first scan image and the amount of colorant corresponding to the first RIP image. Details of the processing in step S603 will be described later.

[0057] The processes in steps S604 to S606 are the same as those in steps S601 to S603 described above, except that the target print data is the second print data. The second print data may be the same as the first print data, or it may be different from the first print data.

[0058] In other words, in step S604, the image forming apparatus 201 performs a second print. Specifically, the RIP unit 501 performs RIP processing based on the second print data transmitted from the external device to generate a second RIP image (print image) consisting of a total of four planes: an image where each pixel has a pixel value of C, an image where each pixel has a pixel value of M, an image where each pixel has a pixel value of Y, and an image where each pixel has a pixel value of K.

[0059] The image forming unit 502 forms a second RIP image on the recording medium, thereby generating the recording medium on which the second RIP image is printed as a second printed material, and discharges the second printed material to the image inspection device 202.

[0060] Furthermore, the image forming unit 502 similarly obtains the "phase of the rotating member corresponding to the second printed material" from the output values ​​of the rotary encoders 218, 219, 220, 221, 222, and 223 attached to the rotating member.

[0061] In step S605, the acquisition unit 503 controls the reading unit 224 to scan the second printed material (second RIP image) ejected from the image forming unit 502 and acquire the second scanned image.

[0062] In step S606, the generation unit 504 generates a second difference colorant image based on the second RIP image and the second scan image, which represents the difference between the amount of colorant corresponding to the second scan image and the amount of colorant corresponding to the second RIP image (the difference between the ideal amount of colorant for the printed material and the actual amount of colorant). Details of the processing in step S606 will be described later.

[0063] In step S607, the detection unit 505 generates an image defect diagnostic image indicating whether or not there is an image defect, based on a first difference color image aligned based on "the phase of the rotating member corresponding to the first printed material" and a second difference color image aligned based on "the phase of the rotating member corresponding to the second printed material". The detection unit 505 then predicts the change in image defects over time based on the generated image defect diagnostic image and displays a message on the operation display unit 409 (operation panel 225) to enable automatic repair or action before it reaches a printing defect level. Details of the processing in step S607 will be described later.

[0064] Next, the details of the process in step S603 described above will be explained according to the flowchart in Figure 7. Note that in step S606, the process described in the flowchart in Figure 7 is applied, with "first" replaced by "second".

[0065] In step S701, the generation unit 504 acquires the first RIP image (RIP image after color separation). In step S702, the generation unit 504 acquires the first scan image.

[0066] In step S703, the generation unit 504 obtains a conversion table from the HDD 408 in which the correspondence between CMYK values ​​and RGB values ​​is registered. The conversion table can be created in advance by forming multiple printed materials with varying amounts of each colorant in the image forming unit 502, and then scanning the formed multiple printed materials with the reading unit 224, and saving it to the HDD 408.

[0067] Figure 8 shows an example of the configuration of the conversion table. The conversion table in Figure 8 includes a table containing the RGB values ​​corresponding to each CMY value when K=0, a table containing the RGB values ​​corresponding to each CMY value when K=10, and a table containing the RGB values ​​corresponding to each CMY value when K=255.

[0068] In step S704, the generation unit 504 obtains the CMY value corresponding to the RGB value of each pixel in the first scanned image from a table for each K. In step S705, the generation unit 504 selects one CMYK value from a plurality of CMYK values ​​obtained for each pixel in the first scanned image (each K value and the CMY value obtained from the table for that K). For example, for each pixel in the first scanned image, the generation unit 504 selects the CMYK value with the smallest difference between the plurality of CMYK values ​​obtained for that pixel and the CMYK value of the corresponding pixel that is positionally corresponding to that pixel in the first RIP image, as the selected CMYK value (amount of colorant) for that pixel. The generation unit 504 then generates an image as the first scanned colorant image in which the pixel value at the pixel position (x, y) is the selected CMYK value (amount of colorant) at the pixel position (x, y) of the first scanned image.

[0069] In step S706, the generation unit 504 generates a difference image of the first RIP image and the first scanned color material image for each of the C, M, Y, and K color materials, as the first difference color material image.

[0070] The pixel value of colorant C at pixel position (x, y) in the first difference colorant image is the difference between the pixel value of colorant C at pixel position (x, y) in the first RIP image and the pixel value of colorant C at pixel position (x, y) in the first scanned colorant image.

[0071] The pixel value of colorant M at pixel position (x, y) in the first difference colorant image is the difference between the pixel value of colorant M at pixel position (x, y) in the first RIP image and the pixel value of colorant M at pixel position (x, y) in the first scanned colorant image.

[0072] The pixel value of colorant Y at pixel position (x, y) in the first difference colorant image is the difference between the pixel value of colorant Y at pixel position (x, y) in the first RIP image and the pixel value of colorant Y at pixel position (x, y) in the first scanned colorant image.

[0073] The pixel value of colorant K at pixel position (x, y) in the first difference colorant image is the difference between the pixel value of colorant K at pixel position (x, y) in the first RIP image and the pixel value of colorant K at pixel position (x, y) in the first scanned colorant image.

[0074] In step S707, the generation unit 504 performs a process to align the phase of the first difference color material image based on the "phase of the rotating member corresponding to the first printed material". This is a process to align the phase with the second difference color material image obtained by processing according to the flowchart in Figure 7, using the second RIP image instead of the first RIP image and the second scan image instead of the first scan image. In step S708, the generation unit 504 saves the phase-aligned first difference color material image to the HDD 408.

[0075] Next, the details of the process in step S607 described above will be explained according to the flowchart in Figure 9. The processes in steps S901 to S904 are carried out similarly for the first difference color image and the second difference color image, respectively. First, the processes in steps S902 and S903 for the first difference color image will be explained.

[0076] In step S902, the detection unit 505 performs a binarization process on the first difference color material image to generate a first binary image. In the binarization process on the first difference color material image, for each of the C, M, Y, and K planes, the pixel value of each pixel in the first binary image corresponding to that plane is set to "1" if the pixel value of the plane of the corresponding pixel in the first difference color material image that is positionally corresponding to that pixel is greater than or equal to a threshold, and to "0" if the pixel value of the plane of the corresponding pixel is less than the threshold.

[0077] In step S903, the detection unit 505 calculates the logical OR of the colorants for the first binary images of the C, M, Y, and K planes. For example, the detection unit 505 calculates the logical OR of the pixel value at pixel position (x, y) of the first binary image of the C plane, the pixel value at pixel position (x, y) of the first binary image of the M plane, the pixel value at pixel position (x, y) of the first binary image of the Y plane, and the pixel value at pixel position (x, y) of the first binary image of the K plane, and obtains the result of this calculation as the first logical OR value at pixel position (x, y).

[0078] Next, the processing in steps S902 and S903 for the second difference color image will be described. In step S902, the detection unit 505 performs a binarization process on the second difference color image to generate a second binary image.

[0079] In step S903, the detection unit 505 calculates the logical OR of the colorants for the second binary images of the C, M, Y, and K planes. For example, the detection unit 505 calculates the logical OR of the pixel value at pixel position (x, y) of the second binary image of the C plane, the pixel value at pixel position (x, y) of the second binary image of the M plane, the pixel value at pixel position (x, y) of the second binary image of the Y plane, and the pixel value at pixel position (x, y) of the second binary image of the K plane, and obtains the result of this calculation as the second logical OR value at pixel position (x, y).

[0080] In step S905, the detection unit 505 generates an image for diagnosing image defects in which the pixel value at pixel position (x, y) is obtained by the logical AND of "the first logical OR value at pixel position (x, y)" and "the second logical OR value at pixel position (x, y)".

[0081] The processing from steps S901 to S905 will be explained using Figure 10 as an example. Graph 1001 shows the amount of cyan pigment corresponding to three locations A, B, and C in the first difference pigment image. Graph 1002 shows the amount of magenta pigment corresponding to three locations A, B, and C in the first difference pigment image. Graph 1003 shows the amount of yellow pigment corresponding to three locations A, B, and C in the first difference pigment image. Graph 1004 shows the amount of black pigment corresponding to three locations A, B, and C in the first difference pigment image.

[0082] The logical OR of the colorant amounts at position A (the result of binarizing the pixel values ​​of C, M, Y, and K) in each of the graphs 1001, 1002, 1003, and 1004 is shown as the colorant amount at position A in graph 1009. The same applies to positions B and C.

[0083] Graph 1005 shows the amount of cyan pigment corresponding to three locations A, B, and C in the second difference color image. Graph 1006 shows the amount of magenta pigment corresponding to three locations A, B, and C in the second difference color image. Graph 1007 shows the amount of yellow pigment corresponding to three locations A, B, and C in the second difference color image. Graph 1008 shows the amount of black pigment corresponding to three locations A, B, and C in the second difference color image.

[0084] The logical OR of the colorant amounts at position A (the result of binarizing the pixel values ​​of C, M, Y, and K) in each of graphs 1005, 1006, 1007, and 1008 is shown as the colorant amount at position A in graph 1010. The same applies to positions B and C.

[0085] The logical AND of the pigment amounts at position A in Graphs 1009 and 1010 is shown as the pigment amount at position A in Graph 1011. The same applies to positions B and C.

[0086] As explained using Figure 1, the color of scanned images obtained due to image defects varies depending on various factors. Therefore, depending on the image defect, such as when the colorant in the image defect is yellow or when there is significant scattering, the brightness difference may be small or even negative. However, even if the brightness difference is small, the value of the amount of each colorant will be large. Also, even if the brightness difference is negative, the amount of colorant will always be positive. Therefore, by using differential colorant images to detect image defects, false detections can be suppressed.

[0087] In step S906, the detection unit 505 predicts the change in image defects over time based on the image defect diagnosis image generated in step S905, and displays a message on the operation display unit 409 (operation panel 225) to enable automatic repair or action before it reaches a print defect level.

[0088] Furthermore, the method for generating messages based on images for image defect diagnosis, the method for notifying the user of the message, and the content of the notification to the user are not limited to specific cases. For example, the detection unit 505 may display the image for image defect diagnosis on the operation display unit 409 (operation panel 225), or it may display the first difference color material image or the second difference color material image on the operation display unit 409 (operation panel 225). Also, the message can be any message as long as it is a message that notifies the user of the result of the diagnosis of the rotating member based on the image defect diagnosis image. In this way, according to this embodiment, since image defects are detected by logical operations between color materials, it is possible to suppress false detection of results.

[0089] [Second Embodiment] The following describes the differences from the first embodiment, and unless otherwise specified, it will be assumed that it is the same as the first embodiment. In this embodiment, we will describe a case in which the type of colorant used for image defect detection is set according to the rotating member to be inspected, and image defects are detected.

[0090] The process performed by the image processing device to diagnose image defects in printing using a diagnostic image and to notify the user of the diagnosis results will be explained according to the flowchart in Figure 11. Steps S601 to S606 are as described above, so below we will explain steps S1101 and S1102 separately.

[0091] In step S1101, the detection unit 505 displays the UI (user interface) exemplified in Figure 12 on the operation panel 225. The UI exemplified in Figure 12 is a UI that allows the user to select one of the following as the rotating member to be inspected: the photosensitive drum 207 corresponding to C, the photosensitive drum 206 corresponding to M, the photosensitive drum 205 corresponding to Y, the photosensitive drum 208 corresponding to K, or the transfer belt 209. The user can specify the rotating member to be inspected by touching the check button corresponding to one of the rotating members. After specifying the rotating member to be inspected, touching the OK button proceeds the process to step S601. Note that the method of specifying the rotating member to be inspected is not limited to a specific method.

[0092] In step S1102, the detection unit 505 generates an image defect diagnostic image indicating whether or not there is an image defect, based on a first difference color image aligned based on "the phase of the rotating member corresponding to the first printed material" and a second difference color image aligned based on "the phase of the rotating member corresponding to the second printed material," in a manner appropriate to the rotating member being inspected.

[0093] For example, if a photosensitive drum corresponding to a color CL (where CL is one of C, M, Y, or K) is specified as the rotating member to be inspected, the detection unit 505 generates a first binary image of the first difference color material image of the CL plane and a second binary image of the second difference color material image of the CL plane in the same manner as in the first embodiment. It then generates an image for diagnosing image defects where the pixel value at the pixel position (x, y) is the value obtained by the logical AND of the pixel value at the pixel position (x, y) of the first binary image and the pixel value at the pixel position (x, y) of the second binary image. Also, for example, if a transfer belt 209 is specified as the rotating member to be inspected, the detection unit 505 generates an image for diagnosing image defects in the same manner as in step S607 described above.

[0094] The detection unit 505 then predicts the time-dependent changes in image defects based on the generated image for diagnosing image defects and displays a message on the operation display unit 409 (operation panel 225) to enable automatic repair or action before the image reaches a print defect level.

[0095] Thus, according to this embodiment, the colorant used for image defect detection can be narrowed down depending on the rotating member being inspected, making it possible to further suppress false detections.

[0096] [Third Embodiment] In step S607, a diagnostic image for image defects was generated by performing a logical OR followed by a logical AND; however, the same result can be obtained by performing a logical AND followed by a logical OR. The details of the process in step S607 described above will be explained according to the flowchart in Figure 13. The processes from steps S1301 to S1304 are performed each time a printed document is scanned. Below, we will explain a case where the first printed document was scanned in the past, and the second printed document is scanned this time.

[0097] In step S1302, the detection unit 505 performs a binarization process on the second difference color image, similar to step S902 above, to generate a second binary image for each of the C, M, Y, and K planes.

[0098] In step S1303, the detection unit 505 calculates a logical AND operation between the second binary image of plane C, the second binary image of plane M, the second binary image of plane Y, and the second binary image of plane K, respectively, and the first binary image of planes C, M, Y, and K generated in the previous step S1302. The logical AND operation between the binary images is performed between positionally corresponding pixels, as in the first embodiment.

[0099] In step S1305, the detection unit 505 generates an image for diagnosing image defects in which the pixel value at pixel position (x, y) is obtained by the logical OR of the "result of the logical AND at pixel position (x, y)" obtained in step S1303.

[0100] The process from steps S1301 to S1305 will be explained using Figure 14 as an example. A logical AND operation is performed between the amount of color pigment at positions A, B, and C in graph 1005 (the result of the binarization process of the pixel value of C) and the amount of color pigment at positions A, B, and C in graphs 1001, 1002, 1003, and 1004, respectively (the result of the binarization process of the pixel values ​​of C, M, Y, and K).

[0101] Similarly, for graphs 1006 to 1008, the logical AND operation is performed between the amount of color pigment at positions A, B, and C (the result of binarizing the pixel value of C) and the amount of color pigment at positions A, B, and C in graphs 1001, 1002, 1003, and 1004, respectively (the result of binarizing the pixel values ​​of C, M, Y, and K).

[0102] Graph 1401 shows the values ​​obtained by the logical OR of all logical AND values ​​calculated for position A, the values ​​obtained by the logical OR of all logical AND values ​​calculated for position B, and the values ​​obtained by the logical OR of all logical AND values ​​calculated for position C.

[0103] In step S906, the detection unit 505 predicts the change in image defects over time based on the image defect diagnosis image generated in step S905, and displays a message on the operation display unit 409 (operation panel 225) via the operation display unit 409 to enable automatic repair or action before it reaches a print defect level.

[0104] [Fourth Embodiment] In the above embodiment, the case of printing by electrophotography was described, but the printing method is not limited to electrophotography. In other words, the image forming apparatus 201 can be any image forming apparatus that produces periodic image defects, and may be an inkjet image forming apparatus that uses a rotating member to form an image. Alternatively, the image forming apparatus 201 may be an image forming apparatus such as an offset printer that uses a plate.

[0105] Furthermore, although the above embodiment describes a case where the image forming apparatus 201 and the image inspection apparatus 202 are separate devices, the invention is not limited to this, and for example, the image forming apparatus 201 and the image inspection apparatus 202 may be integrated to form a single image processing device. Also, one or more of the above functions described as having the function of the image forming apparatus 201 may be performed by other devices.

[0106] Furthermore, some of the processes described in the flowchart above may be performed on an external computer device such as a PC, tablet, or smartphone. In this case, the computer device may acquire information necessary for processing, such as RIP images, scan images, and phase data, from the image processing device, and transmit the diagnostic results based on the image for image defect diagnosis to the image processing device. In this case, the processing on such a computer device is achieved by a processor, such as a CPU, executing the processing using computer programs and data stored in memory.

[0107] The numerical values, processing timing, processing order, processing entity, data (information) structure / acquisition method / destination / source / storage location, etc., used in the above embodiment are given as examples for the purpose of providing a concrete explanation, and are not intended to limit the scope to such examples.

[0108] Furthermore, some or all of the embodiments described above may be used in appropriate combinations. Alternatively, some or all of the embodiments described above may be used selectively.

[0109] (Other embodiments) The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0110] The inventions described herein include the following image processing apparatus, image processing method, and computer program. (Item 1) A first generation means that generates a scanned image obtained by reading a recording medium on which an image based on print data is printed, and a difference image that represents the difference between the amount of colorant corresponding to the scanned image and the amount of colorant corresponding to the image, A second generation means generates a diagnostic image used for diagnosing image defects in printing, based on a first difference image generated by the first generation means for the first print data and a second difference image generated by the first generation means for the second print data. An image processing apparatus characterized by comprising: (Item 2) The image processing apparatus according to item 1, characterized in that the first generation means generates a scanned colorant image showing the amount of colorant in the scanned image based on the scanned image and the image, and generates the difference between the scanned colorant image and the image as the difference image. (Item 3) The image processing apparatus according to item 1 or 2, characterized in that the second generation means generates the diagnostic image based on the binary image for each color material of the first difference image and the binary image for each color material of the second difference image. (Item 4) The image processing apparatus according to item 3, characterized in that the second generation means generates the diagnostic image by the logical AND of the result of the logical OR of the binary images for each color material of the first difference image and the result of the logical OR of the binary images for each color material of the second difference image. (Item 5) The image processing apparatus according to item 3, characterized in that the second generation means calculates a logical AND of the binary images of each color material in the second difference image with the binary images of each color material in the first difference image, and generates the diagnostic image by the logical OR of the results of the logical AND obtained for the binary images of each color material in the second difference image. (Item 6) moreover, It includes a selection means for selecting a rotating member to be inspected, The second generating means is If a photoreceptor drum is selected as the rotating member to be inspected, the diagnostic image is generated based on the binary image of the color material corresponding to the photoreceptor drum in the first difference image and the binary image of the color material corresponding to the photoreceptor drum in the second difference image. When a transfer belt is selected as the rotating member to be inspected, the diagnostic image is generated based on the binary images of each color material in the first difference image and the binary images of each color material in the second difference image. An image processing apparatus according to any one of items 1 to 5, characterized by the features described herein. (Item 7) moreover, The image processing apparatus according to any one of items 1 to 6, characterized by comprising output means for generating and outputting the results of a diagnosis of a rotating member based on the aforementioned diagnostic image. (Item 8) moreover, An image processing apparatus according to any one of items 1 to 7, characterized by comprising a printing means for printing an image based on the aforementioned print data onto a recording medium. (Item 9) moreover, An image processing apparatus according to any one of items 1 to 8, characterized by comprising a reading means for reading the aforementioned recording medium. (Item 10) An image processing method performed by an image processing device, The first generation means of the image processing apparatus includes a first generation step of generating a scan image obtained by reading a recording medium on which an image based on print data is printed, and a difference image based on the scan image, which represents the difference between the amount of colorant corresponding to the scan image and the amount of colorant corresponding to the image. The second generation means of the image processing apparatus performs a second generation step which generates a diagnostic image used for diagnosing image defects in printing, based on the first difference image generated in the first generation step for the first print data and the second difference image generated in the first generation step for the second print data. An image processing method characterized by comprising: (Item 11) A computer program for causing a computer to function as one of the means of an image processing apparatus described in any one of items 1 through 7.

[0111] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention. [Explanation of Symbols]

[0112] 201: Image forming apparatus 202: Image inspection apparatus 501: RIP unit 502: Image forming unit 503: Acquisition unit 504: Generation unit 505: Detection unit

Claims

1. A first generation means that generates a scanned image obtained by reading a recording medium on which an image based on print data is printed, and a difference image that represents the difference between the amount of colorant corresponding to the scanned image and the amount of colorant corresponding to the image, A second generation means generates a diagnostic image used for diagnosing image defects in printing, based on a first difference image generated by the first generation means for the first print data and a second difference image generated by the first generation means for the second print data. An image processing apparatus characterized by comprising:

2. The image processing apparatus according to claim 1, characterized in that the first generation means generates a scanned colorant image showing the amount of colorant in the scanned image based on the scanned image and the image, and generates the difference between the scanned colorant image and the image as the difference image.

3. The image processing apparatus according to claim 1, characterized in that the second generation means generates the diagnostic image based on the binary image for each color material of the first difference image and the binary image for each color material of the second difference image.

4. The image processing apparatus according to claim 3, characterized in that the second generation means generates the diagnostic image by the logical AND of the result of the logical OR of the binary images for each color material of the first difference image and the result of the logical OR of the binary images for each color material of the second difference image.

5. The image processing apparatus according to claim 3, characterized in that the second generation means calculates a logical AND of the binary images of each color material in the second difference image with the binary images of each color material in the first difference image, and generates the diagnostic image by the logical OR of the results of the logical AND obtained for each binary image of each color material in the second difference image.

6. moreover, It includes a selection means for selecting a rotating member to be inspected, The second generating means is, If a photoreceptor drum is selected as the rotating member to be inspected, the diagnostic image is generated based on the binary image of the color material corresponding to the photoreceptor drum in the first difference image and the binary image of the color material corresponding to the photoreceptor drum in the second difference image. When a transfer belt is selected as the rotating member to be inspected, the diagnostic image is generated based on the binary images of each color material in the first difference image and the binary images of each color material in the second difference image. The image processing apparatus according to feature 1.

7. moreover, The image processing apparatus according to claim 1, further comprising output means for generating and outputting the diagnostic results of a rotating member based on the diagnostic image.

8. moreover, The image processing apparatus according to claim 1, further comprising printing means for printing an image based on the aforementioned print data onto a recording medium.

9. moreover, The image processing apparatus according to claim 1, further comprising a reading means for reading the aforementioned recording medium.

10. An image processing method performed by an image processing device, The first generation means of the image processing apparatus includes a first generation step of generating a scan image obtained by reading a recording medium on which an image based on print data is printed, and a difference image based on the scan image, which represents the difference between the amount of colorant corresponding to the scan image and the amount of colorant corresponding to the image. The second generation means of the image processing apparatus performs a second generation step which generates a diagnostic image used for diagnosing image defects in printing, based on the first difference image generated in the first generation step for the first print data and the second difference image generated in the first generation step for the second print data. An image processing method characterized by comprising:

11. A computer program for causing a computer to function as one of the means of an image processing apparatus according to any one of claims 1 to 7.

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