JP7787699B2 - Image forming device - Google Patents

Description

The present disclosure relates to an image forming apparatus .

Conventionally, in image forming devices that use electrophotography, for example, it is common to perform tone correction to reduce variations in color and density in printed images, and halftone processing to convert multi-level signals to binary signals on input image data before image formation. Tone correction involves converting input signals into corrected signals using, for example, a correction table selected according to the device's output characteristics. Halftone processing involves compressing the size of image data by binarizing the signal using, for example, error diffusion or a halftone screen.

Patent Document 1 discloses a technology that measures the output characteristics of a device when the power is turned on, when components such as toner cartridges are replaced, and when temperature or humidity fluctuates, and then calibrates a correction table based on the measurement results. Patent Document 2 discloses a technology that converts the color model of 8-bit input image data from RGB to CMYK, then performs gradation correction and halftone processing, and uses 1-bit image data for each CMYK for image formation.

JP 2016-92751 A Japanese Patent Application Laid-Open No. 2014-215333

However, the degree of variation in color and density of a printed image depends on the content of the input image data. In addition, the extent to which variation in color and density is acceptable depends on conditions such as the purpose of the printed image and the user's preferences. Therefore, if a job is in the middle of execution and there is a possibility that variation in color or density will occur in the printed image, stopping the job and redoing the gradation correction can actually be inconvenient for users who prioritize productivity.

The purpose of this disclosure is to provide a mechanism that allows users to flexibly choose between suppressing variations in color and density of printed images and maintaining image formation productivity in accordance with their needs.

According to one aspect, an image forming apparatus is provided, comprising: a conversion means for converting image data using conversion conditions for adjusting image quality; an image forming means for forming an image based on the image data converted by the conversion means; a calibration means for updating the conversion conditions based on measurement results of a proofreading image formed by the image forming means; a control means for temporarily suspending image formation by the image forming means to replace a component included in the image forming means; and a selection means used to select one of a plurality of operating modes , including a job stop mode in which the calibration means updates the conversion conditions and then causes the image forming means to resume image formation when replacement of the component is detected during execution of a job for forming images of multiple copies; and a job continue mode in which the calibration means causes the image forming means to resume image formation without updating the conversion conditions.

This disclosure allows users to flexibly choose between suppressing variations in color and density of printed images and maintaining image formation productivity to meet their needs.

FIG. 2 is a block diagram showing an example of the configuration of image processing that can be performed on image data used for image formation. 10A and 10B are explanatory diagrams for explaining some examples of signal conversion curves used for tone correction. 10A and 10B are explanatory diagrams for explaining variations in color tone and density caused by replacement of components. 10A and 10B are explanatory diagrams for explaining a decrease in productivity caused by re-executing calibration of the tone correction table. FIG. 1 is a block diagram showing an example of the configuration of an image forming apparatus according to an embodiment. 6 is a schematic cross-sectional view showing in more detail the configuration of the image forming unit of the image forming apparatus shown in FIG. 5 . 10A to 10C are explanatory diagrams showing examples of GUI configurations for allowing a user to select an operation mode. FIG. 10 is an explanatory diagram showing a further example of a GUI configuration for allowing a user to select an operation mode. FIG. 4 is an explanatory diagram for explaining the progress of image formation when a job stop mode is selected in a scenario similar to that of FIG. 3 . 5 is an explanatory diagram for explaining the progress of image formation when a job continuation mode is selected in a scenario similar to that of FIG. 4; 10 is a flowchart showing an example of the flow of a mode setting process according to an embodiment. 10 is a flowchart showing another example of the flow of the mode setting process according to an embodiment. 10 is a flowchart showing an example of the flow of image forming processing according to an embodiment.

The following describes the embodiments in detail with reference to the attached drawings. Note that the following embodiments do not limit the scope of the claimed invention. While the embodiments describe multiple features, not all of these features are necessarily essential to the invention, and multiple features may be combined in any desired manner. Furthermore, in the attached drawings, the same reference numbers are used to designate identical or similar components, and redundant explanations will be omitted.

<<1. Introduction>>
In this section, an example in which the technology according to the present disclosure is applied to a digital multifunction peripheral will be mainly described. However, the technology according to the present disclosure is not limited to such an example and can be widely applied to various types of image forming apparatuses such as printers, copiers, and facsimile receivers. Unless otherwise specified, each of the components such as apparatuses, devices, modules, and chips described below may be composed of a single entity or may be composed of multiple physically different entities.

First, we will explain the basic configuration of image processing and related issues using Figures 1 to 4. Figure 1 shows an example of the configuration of image processing 10 that can be performed on image data used in image formation. Referring to Figure 1, image processing 10 includes raster conversion 11, color conversion 13, tone correction 15, halftone processing 17, and switching processing 19.

Raster conversion 11 receives input image data 31, which is accepted as the target for job execution. The input image data 31 is, for example, image data written in a high-level page description language (PDL). Raster conversion 11 converts the input image data 31 into raster image data 32. The raster image data 32 represents an image in bitmap format. The raster image data 32 has, for example, a bit depth of 8 bits for each color component of each pixel. The processing time of raster conversion 11 varies depending on the content of the image represented by the input image data 31.

Color conversion 13 converts the color model (e.g., RGB) of the raster image data 32 into a color model (e.g., CMYK) suitable for image formation, generating pre-corrected image data 33. Tone correction 15 corrects the tone of each color component of each pixel of pre-corrected image data 33 using a correction table 16, generating corrected image data 34. Correction table 16 may be, for example, a lookup table that defines the signal conversion curve (e.g., a gamma curve or any other curve) to be used for tone correction. Halftone processing 17 converts the multilevel signal values of each color component of each pixel of corrected image data 34 into binary signal values using area gradation, generating compressed image data 35. The compressed image data 35 is output to the image formation unit and used for image formation.

Here, if a job being executed spans multiple copies, an image will be formed multiple times based on the same input image data 31. Therefore, the compressed image data 35 generated by the halftone process 17 is stored in memory 18, and for the second and subsequent copies, the compressed image data 35 retrieved from memory 18 is reused for image formation, thereby shortening processing time. The switching process 19 represents this reuse of image data. For example, under the control of the controller, when forming the first copy of an image based on the same input image data 31 for a certain job, the compressed image data 35 generated as a result of the halftone process 17 is output to the image forming unit. When forming the second and subsequent copies of an image based on the same input image data 31, the compressed image data 35 temporarily stored in memory 18 is read, and the read compressed image data 35 is output to the image forming unit.

The data size of image data after halftone processing 17 is generally reduced compared to the data size of image data before halftone processing 17. Therefore, by configuring in this way to reuse compressed image data 35, it is possible to reduce memory resource usage while shortening the execution time for jobs spanning multiple copies, thereby improving productivity.

Figure 2 is an explanatory diagram illustrating several examples of signal conversion curves represented by the correction table 16 used in the gradation correction 15. Figure 2(A) shows signal conversion curve 16a, and Figure 2(B) shows signal conversion curve 16b. Each of signal conversion curves 16a and 16b is a curve that converts the signal values of an input signal, which can take values within the range of 0 to 255, into signal values of a correction signal, which can also take values within the range of 0 to 255. Compared to signal conversion curve 16b, signal conversion curve 16a is defined as a conversion curve in which signal values in the central range of the input signal are converted to signal values of a larger correction signal.

It is generally known that in image forming devices, as the components of the image forming unit deteriorate, a decrease in print density occurs when image data having the same signal value is printed as is. Therefore, it is beneficial to selectively switch between signal conversion curve 16a and signal conversion curve 16b for use in gradation correction 15 depending on the degree of deterioration in print density, for example, by performing calibration at the start of a job. For example, by performing gradation correction using signal conversion curve 16b when the components have not deteriorated significantly and signal conversion curve 16a when the components have deteriorated significantly, variations in color and density caused by component deterioration can be suppressed. Naturally, the optimal curve for gradation correction may be selected from more than two signal conversion curves. These signal conversion curves may be stored in the form of a lookup table in which points on the curves are discretely sampled.

However, as in the example of Figure 1, if components in the image forming unit are replaced while a job involving multiple copies is being executed while reusing compressed image data 35, there is a risk of undesirable variations in color and density occurring. An example of such an event will be explained using Figure 3.

Figure 3 is an explanatory diagram illustrating variations in color and density due to component replacement. In the example of Figure 3, print jobs J11 and J12 are executed in sequence as time progresses from left to right. Print job J11 is a job for outputting three copies of a printed product based on input image data. Print job J12 is a job for outputting two copies of a printed product based on different input image data.

When print job J11 begins, toner cartridge CRG1 is already installed in the device. Because toner cartridge CRG1 is nearing the end of its life, a gradation correction table representing signal conversion curve 16a is used for gradation correction 15. When outputting the first printed copy of print job J11, compressed image data 35a is generated through gradation correction 15 and halftone processing 17. The print image for the first copy of print job J11 is formed based on this compressed image data 35a. The compressed image data 35a is also stored in memory 18. The print image for the second copy of print job J11 is formed based on compressed image data 35a read from memory 18. It is then assumed that toner cartridge CRG1 has reached the end of its life before printing the third copy of print job J11 begins. Execution of the job is paused in response to the end of its life. The user notices the job pause notification, replaces toner cartridge CRG1 with a new toner cartridge CRG2, and resumes execution of the job. The third print image of print job J11 is then formed based on compressed image data 35a read from memory 18. This third image is formed using new toner cartridge CRG2, reusing compressed image data 35a generated through gradation correction using signal conversion curve 16a that matches the old toner cartridge CRG1. As a result, the density of the third print image of print job J11 is excessively darker than would normally be expected. In other words, the image quality of the third print image is degraded compared to the first and second print images.

At the start of print job J12, toner cartridge CRG2 is installed in the device, and calibration process 20 is executed to update the gradation correction table. The gradation correction table is updated to represent signal conversion curve 16b suitable for toner cartridge CRG2. As a result, in print job J12, the gradation correction table representing signal conversion curve 16b is used for gradation correction 15. When outputting the first printed copy of print job J12, compressed image data 35b is generated through gradation correction 15 and halftone process 17. The first printed image of print job J12 is formed using toner cartridge CRG2 based on this compressed image data 35b. The compressed image data 35b is also stored in memory 18. The second printed image of print job J12 is formed using toner cartridge CRG2 based on compressed image data 35b read from memory 18. As a result, the density of these printed images returns to normal.

For users who prioritize print image quality, the density anomaly in the third print image of print job J11 in Figure 3 would be undesirable. In this case, if the entire job J11 had to be re-executed to obtain a print image with consistent color and density, paper and toner would be wasted. In contrast, if job J11 were paused when cartridge replacement was detected and then resumed after waiting until calibration of the gradation correction table was completed, fluctuations in color and density could be suppressed. However, in this case, it would take a longer time to complete the job. This reduction in productivity due to re-executing calibration of the gradation correction table is not limited to jobs that specify multiple copies, as shown in Figure 3, but can occur in general jobs that require image formation on multiple sheets of paper (i.e., image formation where at least one of the number of copies and the number of pages is two or more).

Figure 4 is an explanatory diagram illustrating the decrease in productivity caused by re-calibrating the tone correction table. In the example of Figure 4, print job J21 is executed along time progressing from left to right. Print job J21 is a job for outputting five pages of printed material based on input image data.

When print job J21 begins, toner cartridge CRG1 is already installed in the device. Because toner cartridge CRG1 is nearing the end of its life, a gradation correction table representing signal conversion curve 16a is used for gradation correction 15. When printing the first page of print job J21, compressed image data 35-1 is generated through gradation correction 15 and halftone processing 17, and the print image for page 1 is formed based on the compressed image data 35-1. Similarly, when printing the second page of print job J21, compressed image data 35-2 is generated through gradation correction 15 and halftone processing 17, and the print image for page 2 is formed based on the compressed image data 35-2. The same process is performed for page 3 of print job J21, with the print image for page 3 being formed based on compressed image data 35-3. Thereafter, it is assumed that toner cartridge CRG1 has reached the end of its life before printing page 4 of print job J21 begins. Execution of the job is paused in response to the end of its life. The user notices the job pause notification, replaces toner cartridge CRG1 with a new toner cartridge CRG2, and resumes job execution. At this time, in response to the detection of cartridge replacement, calibration process 20 is executed to update the gradation correction table, updating the gradation correction table to represent signal conversion curve 16b appropriate for toner cartridge CRG2. When printing the fourth page of print job J21, compressed image data 35-4 is generated through gradation correction 15 and halftone process 17, and the print image for page 4 is formed based on the compressed image data 35-4. Similarly, the print image for page 5 of print job J21 is formed based on compressed image data 35-5. In the example of FIG. 4, gradation correction is performed for every page of print job J21 based on the appropriately updated gradation correction table, thereby suppressing variations in color and density between pages. However, the delay associated with calibration process 20 increases the time it takes to complete job J21.

The degree of variation in color and density of the printed image depends on the content of the input image data. In addition, the extent to which variation in color and density is acceptable depends on conditions such as the purpose of the printed image and the user's preferences. For example, when printing or copying a document written in text, few users are concerned about variation in color and density. Therefore, rather than making a uniform decision on whether to perform proofreading process 20 before outputting the printed copies of pages 4 and 5 of print job J21, it is desirable to flexibly decide the operation according to the user's needs.

The embodiment, which will be described in more detail in the next section, takes these circumstances into consideration and aims to provide a mechanism that allows users to flexibly choose between suppressing variations in color and density of printed images and maintaining image formation productivity in accordance with their needs.

<<2. Configuration Example of Image Forming Apparatus>>
<2-1. Overall structure>
The multifunction peripheral 100 according to the embodiment described in this section is an image forming apparatus capable of forming a color image on paper (or a recording medium) through an electrophotographic process. Fig. 5 is a block diagram showing an example of the configuration of the multifunction peripheral 100. Fig. 6 is a schematic cross-sectional view showing in more detail the configuration of the image forming unit 120 of the multifunction peripheral 100 shown in Fig. 5.

Referring to FIG. 5, the multifunction device 100 includes a communication interface 101, a user interface (UI) 102, a memory unit 109, an image processing unit 110, an image forming unit 120, a characteristic acquisition unit 130, a reading unit 140, and a control unit 150.

The communication interface 101 is an interface for communication between the multifunction device 100 and other devices. The communication interface 101 may be a wired communication interface or a wireless communication interface.

The UI 102 is a unit for interaction between the multifunction peripheral 100 and the user. In the example of FIG. 5, the UI 102 includes a display 103, an operation unit 104, a microphone 105, and a speaker 106. The display 103 displays an image representing visual information based on an image signal from the control unit 150. The operation unit 104 accepts user input via, for example, one or more of a touch sensor, a button, a switch, and a keypad, and outputs an input signal representing the accepted user input to the control unit 150. The microphone 105 detects voice uttered by the user and outputs an input audio signal representing the content of the detected voice to the control unit 150. The speaker 106 outputs audio based on an output audio signal from the control unit 150. This embodiment will mainly describe an example in which the control unit 150 provides a graphical user interface (GUI) to the user via the display 103 and the operation unit 104. However, some or all of the described GUI may be replaced with an audio UI via the microphone 105 and speaker 106. In other embodiments, the control unit 150 may provide a UI to the user on another device (for example, on the screen of a terminal device such as a PC or smartphone) through a communication connection between the communication interface 101 and the other device.

The storage unit 109 stores one or more computer programs executed by the control unit 150, as well as various data such as configuration data and image data. The storage unit 109 may include volatile memory such as RAM (Random Access Memory) and non-volatile memory such as ROM (Read-Only Memory) and HDD (Hard Disk Drive).

Image processing unit 110 is a processing circuit that performs signal processing on image data input to image forming unit 120. The processing performed by image processing unit 110 will be described in detail later. Image forming unit 120 forms an image on a recording medium based on the image data input from image processing unit 110. In this embodiment, image forming unit 120 includes one or more replaceable members. The replaceable members may include, for example, toner cartridges. Characteristics acquisition unit 130 acquires image output characteristics related to the replaceable members of image forming unit 120 and notifies control unit 150 of the acquired image output characteristics. Reading unit 140 optically reads an original document and generates read image data.

The control unit 150 is a controller that controls the overall functions of the multifunction device 100. The control unit 150 may include one or more processors, such as a CPU (Central Processing Unit). For example, when a print job is received via the communication interface 101, the control unit 150 causes the image processing unit 110 to process the input image data and causes the image forming unit 120 to form an image based on the processed image data. Furthermore, when a scan job is instructed to be executed, the control unit 150 causes the reading unit 140 to read an original. Furthermore, when a copy job is instructed to be executed, the control unit 150 causes the reading unit 140 to read an original, causes the image processing unit 110 to process the read image data, and causes the image forming unit 120 to form an image based on the processed image data.

Referring to FIG. 6, the multifunction device 100 includes a cassette 51 that is retractably disposed within the housing. The cassette 51 stores a stack of paper (sheets) P. Any type of recording material may be used as the paper P, such as plain paper, cardboard, overhead projector sheets, coated paper, label paper, or perforated paper.

The multifunction device 100 also includes a transport mechanism including several rollers for transporting paper P. For example, the feed roller 52 picks up paper P from the cassette 51 and feeds it toward transport path Q1 (shown by the dashed line in the figure). The separation roller pair 53 separates the paper P picked up by the feed roller 52 from the stack of paper one by one. The registration roller pair 54 regulates the leading edge of the paper P transported from the separation roller pair 53 along transport path Q1 to correct any skew in the paper P. Although detailed explanation is omitted, the multifunction device 100 may also be capable of feeding paper from a manual paper feed tray 56 instead of the cassette 51. The jam sensor 58 is a sensor for detecting a jam of paper P in transport path Q1.

In this embodiment, the image forming unit 120 is capable of forming a color image on paper P using developers (also referred to as toner) of four color components: yellow (Y), magenta (M), cyan (C), and black (K). In the figures, the letters representing each color component are used as suffixes to identify components associated with each color component. However, to avoid duplication, components that are identical across these color components are described only once without the suffixes. The image forming unit 120 includes a photosensitive drum 61, a charging roller 62, a laser unit 63, a developing roller 64, and a primary transfer roller 65 for each color component. The image forming unit 120 may also include a drum cleaning member (not shown) for each color component. The photosensitive drum 61 is a rotatable image carrier. The charging roller 62 uniformly charges the surface of the photosensitive drum 61. The laser unit 63 exposes the surface of the photosensitive drum 61 to laser light in accordance with the image data to be printed, thereby forming an electrostatic latent image on the surface of the photosensitive drum 61. The developing roller 64 supplies toner of each color component from a toner storage chamber to the electrostatic latent image on the surface of the photosensitive drum 61, forming a toner image on the surface of the photosensitive drum 61 (i.e., developing a developer image, which is a visible image).

The image forming unit 120 further includes a transfer unit 70 that includes an intermediate transfer belt 71, a drive roller 72, a driven roller 73, a tension roller 74, and a belt cleaner 75. The intermediate transfer belt 71 is supported by the drive roller 72, the driven roller 73, and the tension roller 74, and is driven to rotate by the drive roller 72. Four primary transfer rollers 65Y, 65M, 65C, and 65K are disposed inside the intermediate transfer belt 71, facing the photosensitive drums 61Y, 61M, 61C, and 61K, respectively. These primary transfer rollers 65 transfer the toner images formed on the corresponding photosensitive drums 61 onto the intermediate transfer belt 71 in the order Y, M, C, and K, superimposing them on top of each other, thereby forming a multi-color toner image on the intermediate transfer belt 71.

A secondary transfer roller 76 is disposed opposite the drive roller 72 across the intermediate transfer belt 71. The area between the drive roller 72 and the secondary transfer roller 76 is called the secondary transfer nip T2. At the secondary transfer nip T2, the toner image on the intermediate transfer belt 71 is transferred to paper P being transported along the transport path Q1.

The belt cleaner 75 is disposed opposite the tension roller 74 and may be composed of, for example, a brush-like elastic body. A cleaning voltage of the opposite polarity to the residual toner is applied to the belt cleaner 75 by a power supply unit (not shown), and the belt cleaner 75 removes toner remaining on the intermediate transfer belt 71. Toner remaining on the surface of the photosensitive drum 61 can be collected by the drum cleaning member described above.

After passing through the secondary transfer nip T2, the paper P is transported to the fixing unit 77 by the secondary transfer roller 76. The fixing unit 77 has a pair of rollers that press against the paper P and a heater that heats the paper P. The fixing unit 77 heats the paper P while pressing against it, melting the toner image formed on the paper P and fixing it to the paper P. A voltage can be applied to the surfaces of the pair of rollers of the fixing unit 77 to prevent toner from adhering. After passing through the fixing unit 77, the paper P is further transported by the pair of discharge rollers 78 and discharged to the discharge tray 79.

Figure 6 also shows a schematic diagram of the physical configuration of the reading unit 140. The reading unit 140 includes, for example, a document tray 81 on which a document is placed, a group of transport rollers 82 that transport the document along transport path Q2, an image sensor 83 that optically reads the document, an output tray 84 to which the document is discharged after reading, and a document table 85. Depending on the reading mode, the image sensor 83 can read a document that remains stationary as it is transported along transport path Q2, or can read a document that is placed on the document table 85 while it is moving.

Figure 6 also shows a simplified circuit board 90 disposed inside the housing of the multifunction device 100. The circuit board 90 may be equipped with many circuit elements (e.g., a CPU, ROM, RAM, etc.) that implement the various functions described using Figure 5.

In this embodiment, the image forming unit 120 includes one or more replaceable components. The replaceable component may be, for example, a toner cartridge that can be attached to and detached from the housing of the multifunction peripheral 100. The toner cartridge may include, for example, at least one of a photosensitive drum 61 as an image carrier, a charging roller 62 as a charging device, a laser unit 63 as an exposure device, a developing roller 64 as a developing device, and a transfer unit 70 as a transfer device. When the control unit 150 determines that the life of a replaceable component has expired, it temporarily suspends operation of the image forming unit 120 and displays a message on the display 103 urging the user to replace the component. Upon noticing this message, the user, for example, opens the retractable cover of the housing of the multifunction peripheral 100, removes the old replaceable component from the housing, attaches a new replaceable component to the housing, and closes the cover. The end of the replaceable component's life may be determined based on the cumulative number of operations or operating time of the component, or the remaining amount of consumables contained in the component.

Note that this embodiment is not limited to an example in which the toner cartridge is replaceable. For example, any one or a combination of components such as the image carrier, charging device, exposure device, developing device, transfer device, and fixing device may be replaceable.

<2-2. Details of image processing>
5 , a detailed description will be given of the signal processing performed by the image processing unit 110 on image data prior to input to the image forming unit 120. The image processing unit 110 includes a raster conversion unit 111, a color conversion unit 113, a table storage unit 114, a gradation correction unit 115, a compression unit 117, and a memory 118.

The raster conversion unit 111 may correspond to a so-called raster image processor (RIP). The raster conversion unit 111 converts input image data accepted by the multifunction peripheral 100 as a target for job execution into raster image data and outputs the converted raster image data to the color conversion unit 113. The input image data may be received, for example, from an external device via the communication interface 101. As an example, if the input image data is PDL data, the raster conversion unit 111 may analyze the high-level PDL data to generate raster image data that represents the image in bitmap format. The PDL data may be data that defines the image content for each page using a set of printer control codes for drawing objects such as text, graphics, and images (photographs). Some objects in the PDL data may be described as vector data, and other objects may be described as raster data. The raster conversion unit 111 may generate raster image data by analyzing such PDL data and expanding the image content into a bitmap.

The color conversion unit 113 converts the color model of the raster image data input from the raster conversion unit 111 into a color model (e.g., CMYK) suitable for image formation and outputs the color-converted raster image data to the tone correction unit 115. The color model before color conversion may be any color model, such as grayscale or RGB. When converting the color model, the color conversion unit 113 may perform color adjustment based on an ICC (International Color Consortium) profile. The ICC profile may be composed of a source profile and a printer profile. The source profile is a profile for converting input image data to L*a*b* data. The source profile may include an RGB profile and a CMYK profile. In this case, if the input color model is RGB, the RGB profile is selected, and if the input color model is CMYK, the CMYK profile is selected. The printer profile is a profile for converting L*a*b* data into CMYK data suitable for the color characteristics of the image formation unit 120. These profiles are usually provided in the form of a lookup table, and the color conversion unit 113 can refer to the lookup table to convert the color vector of each pixel in the input raster image data into the color vector of the color model after color conversion.

The gradation correction unit 115 corrects the gradation of the raster image data input from the color conversion unit 113 by referencing the gradation correction table stored in the table storage unit 114 to generate corrected image data. The table storage unit 114 stores gradation correction tables corresponding to the output characteristics of the image forming unit 120 acquired by the characteristic acquisition unit 130. The gradation correction tables may be provided, for example, as lookup tables for each of the four color components, CMYK. Gradation correction may be performed to maintain the linearity of the printed image, which may differ for each image formation operation, and the results of the calibration described below may be reflected in these lookup tables. As an example, the table storage unit 114 may pre-store multiple gradation correction tables for each color component, each representing a conversion curve defining the relationship between the input signal and the correction signal, such as the signal conversion curves 16a and 16b described using Figure 2. In this case, the gradation correction unit 115 converts the input signal value of each color component of each pixel of the raster image data into a correction signal value in accordance with an optimal gradation correction table selected based on the output characteristics of the image forming unit 120. As another example, a gradation correction table may be dynamically generated for each color component based on the output characteristics of the image forming unit 120 and stored in the table storage unit 114. In this case, the gradation correction unit 115 converts the input signal value of each color component of each pixel of the raster image data into a correction signal value in accordance with the latest gradation correction table stored in the table storage unit 114. The gradation correction unit 115 outputs the corrected image data generated in this manner to the compression unit 117.

The compression unit 117 compresses the corrected image data input from the tone correction unit 115 to generate compressed image data. In this embodiment, the compression of the corrected image data by the compression unit 117 includes halftoning. That is, the compression unit 117 may compress the corrected image data by converting the multi-value (e.g., 8-bit) signal values of each color component of each pixel of the corrected image data into binary (i.e., 1-bit) signal values using area gradation. The compression unit 117 may selectively apply one of different types of screening methods to the corrected image data. For example, when executing a copy job, the compression unit 117 may use an error diffusion method, which is less likely to cause moiré, while when executing a print job, the compression unit 117 may use a halftone screen using a dither matrix to improve the reproducibility of characters and thin lines. The error diffusion method is a technique that distributes errors associated with the binarization of the signal value of a target pixel to surrounding pixels while maintaining gradation by weighting the target pixel and its surrounding pixels with an error filter. Halftone screening is a technique that uses a dither matrix to represent pseudo-intermediate gradations. The compression unit 117 may selectively switch between a low-line screen and a high-line screen depending on the content of the corrected image data. The compression unit 117 outputs the compressed image data generated in this way to the image forming unit 120.

Note that the compression unit 117 may perform any lossy compression process (e.g., simple bit depth reduction) instead of or in addition to halftoning.

Memory 118 is a storage unit capable of storing compressed image data output from compression unit 117. In this embodiment, when image formation for multiple copies is performed in a single job, memory 118 can temporarily store the compressed image data for each page of the first copy in preparation for reuse in printing the second copy and subsequent copies. Memory 118 may be a storage device separate from storage unit 109, or may be part of storage unit 109.

Although not shown in FIG. 5, the image processing unit 110 may perform further image processing before outputting the image data to the image forming unit 120. For example, the image processing unit 110 may perform edge detection based on pattern matching on the image data for each color component, and convert the detected edges into smoother patterns to smooth them and reduce jaggedness.

<2-3. Calibration of the gradation correction table>
The control unit 150 calibrates the gradation correction table when a calibration trigger is detected, such as when the multifunction device 100 is powered on, when a replaceable member of the image forming unit 120 is replaced, or when an environmental condition (e.g., environmental temperature or environmental humidity) changes beyond a threshold. To detect such a calibration trigger, the multifunction device 100 may be provided with one or more of a replacement detection sensor, a temperature sensor, and a humidity sensor (not shown).

When calibrating the gradation correction table, the control unit 150 causes the characteristic acquisition unit 130 to acquire the image output characteristics of the image forming unit 120. For example, the characteristic acquisition unit 130 may acquire the image output characteristics of the image forming unit 120 by measuring the density of a patch image of a predetermined pattern formed on paper by the image forming unit 120. Additionally or alternatively, the characteristic acquisition unit 130 may acquire the image output characteristics of the image forming unit 120 by reading characteristic data representing the characteristics associated with a component (e.g., a cartridge) newly installed in the image forming unit 120 from a memory built into the component. The control unit 150 then calibrates the gradation correction table stored in the table storage unit 114 according to the image output characteristics acquired by the characteristic acquisition unit 130.

As one example, the control unit 150 may select, for each color component, from among multiple gradation correction tables pre-stored in the table storage unit 114, a table that is suitable for the image output characteristics of the image forming unit 120 as the table to be used for gradation correction. As another example, the control unit 150 may dynamically generate a gradation correction table that is suitable for the image output characteristics of the image forming unit 120 and store the generated gradation correction table in the table storage unit 114.

In one variant, in addition to calibrating the tone correction table, the control unit 150 may also calibrate the profile (e.g., printer profile) used in the color conversion unit 113.

<2-4. Control of operation mode>
Next, the control performed by the control unit 150 will be described in detail. As described above, the control unit 150 controls the operation of the image forming unit 120 so as to form an image on paper based on image data after gradation correction by the gradation correction unit 115. When a job for forming images on multiple sheets of paper is executed, the control unit 150 monitors whether one or more replaceable parts of the image forming unit 120 are replaced during the execution of the job. When the control unit 150 detects the replacement of one or more replaceable parts, the control unit 150 determines, in accordance with a user selection, whether to cause the image forming unit 120 to continue forming an image that has been subjected to gradation correction based on the output characteristics acquired by the characteristics acquisition unit 130 before the replacement was detected.

In the first embodiment, the user may select one of multiple operation modes as an operation mode commonly set for multiple jobs. In this case, the control unit 150 presents the user with options corresponding to the multiple operation modes via the UI 102, for example, and allows the user to select one of the options.

For example, the first mode among the multiple operating modes is a job continuation mode that continues a job in progress when replacement of one or more replaceable components is detected. When job continuation mode is selected, the control unit 150 causes the image forming unit 120 to continue forming an image that has been subjected to gradation correction based on the output characteristics acquired by the characteristic acquisition unit 130 before the component replacement was detected, until the execution of the paused job is completed. Because the calibration of the gradation correction table is performed after the execution of the paused job is completed, delays associated with the execution of the calibration process can be avoided from extending the job execution time. In this case, the job resumed after the component replacement may experience the degradation in image quality described in relation to the third printed image of print job J11 in Figure 3, but it is assumed that such degradation in image quality is acceptable to the user.

The second of the multiple operating modes is a job stop mode, which stops a job in progress when replacement of one or more replaceable components is detected. When job stop mode is selected, the control unit 150 stops the job and calibrates the gradation correction table. In this case, the output characteristics acquired by the characteristic acquisition unit 130 before the component replacement was detected are not applied to the remaining image formation of the job. When the stopped job is re-executed, gradation correction is performed based on the output characteristics newly acquired by the characteristic acquisition unit 130, and the image that has undergone this gradation correction is formed on paper. Therefore, the image quality can be maintained the same before and after the job is re-executed.

7A shows an example of a GUI configuration for allowing a user to select an operation mode in the first embodiment. Referring to FIG. 7A, a user mode setting screen is displayed on the display 103. The user mode setting screen includes a common setting menu 511 for managing operation modes that can be set commonly for multiple jobs. The common setting menu 511 includes a menu item 512. The menu item 512 is an item for allowing a user to select an operation mode for handling a job when a cartridge change is detected during job execution. Below the menu item 512, an option 513 indicating "Continue" and an option 514 indicating "Stop" are displayed. The user can select one of the options 513 and 514 of the menu item 512 by, for example, touching the touch-panel display 103 or operating the directional keys 104a and buttons 104a and 104b. When the user selects option 513, the operation mode is set to the first mode described above, i.e., job continuation mode. If the user selects option 514, the operating mode is set to the second mode described above, i.e., job stop mode. The operating mode set here can be commonly applied to multiple image forming jobs (e.g., print jobs and copy jobs) that are started subsequently.

In the second embodiment, user selection can be made when component replacement is detected during job execution. That is, when replacement of one or more replaceable components is detected during execution of an image formation job, the control unit 150 prompts the user via the UI 102 to select whether or not to continue the job. If the user selects to continue the job, the control unit 150 causes the image forming unit 120 to continue forming images that have been subjected to gradation correction based on the output characteristics acquired before the component replacement was detected, until execution of the paused job is completed. If the user selects to stop the job, the control unit 150 stops the job and calibrates the gradation correction table. In this case, the output characteristics acquired by the characteristic acquisition unit 130 before the component replacement was detected are not applied to the remaining image formation of the job.

Figure 7 (B) shows an example of the configuration of a GUI that allows the user to select an operation mode in the second embodiment. Referring to Figure 7 (B), a mode selection screen is displayed on the display 103. The mode selection screen includes text that asks the user which operation mode should be applied to each job, and options 521 and 522. The user can select one of options 521 and 522, for example, by touching the display 103 or operating the directional keys 104a and buttons 104a and 104b. If the user selects option 521, the job continuation mode is applied to the job in progress. If the user selects option 522, the job stop mode is applied to the job in progress.

In a variation of the first embodiment, the plurality of operating modes selectable by the user may further include, as a third mode, an individual selection mode that allows the user to individually select an operating mode in response to detection of replacement of one or more replaceable components during job execution. When the individual selection mode is selected as a common setting for multiple jobs, the control unit 150 causes the display 103 to display the mode selection screen described in the second embodiment when replacement of a component is detected during job execution. Then, the control unit 150 controls the remaining image formation of the job in progress in accordance with the operating mode corresponding to the option selected by the user.

Figure 8(A) shows an example of the configuration of a GUI that allows the user to select an operation mode in this modified example of the first embodiment. Referring to Figure 8(A), the user mode setting screen displayed on the display 103 includes, below the menu item 512, an option 513 indicating "Continue" and an option 514 indicating "Stop," as well as an option 515 indicating "Individual Selection." If the user selects option 515, the operation mode is set to the third mode described above, i.e., the individual selection mode.

In the third embodiment, user selection can be made when execution of a specific job begins. That is, the control unit 150 allows the user to pre-select one of the above-mentioned multiple operating modes via the UI 102 as the operating mode to be set for the specific job to be executed. If the user selects to continue the job, even if the job is paused for component replacement after the job has started, the control unit 150 causes the image forming unit 120 to continue the remaining image formation without re-calibrating the gradation correction table after the replacement. If the user selects to stop the job, the control unit 150 stops the job and calibrates the gradation correction table when a component is replaced after the job has started.

Figure 8 (B) shows an example of the configuration of a GUI that allows the user to select an operation mode in the third embodiment. Referring to Figure 8 (B), a job setting screen is displayed on the display 103. The job setting screen includes a detailed setting menu 531 for setting setting items to be applied to the job when execution of the job begins. The detailed setting menu 531 includes a setting item 532. The setting item 532 is an item that allows the user to select an operation mode for handling the job when cartridge replacement is detected during job execution. Below the setting item 532, an option 533 indicating "Continue" and an option 534 indicating "Stop" are displayed. If the user selects option 533, the operation mode for the job is set to job continuation mode. If the user selects option 534, the operation mode for the job is set to job stop mode.

In a third embodiment, the control unit 150 monitors the lifespan of one or more replaceable components of the image forming unit 120, and if it predicts that the lifespan of any of the components will end during job execution, it may enable the setting item 532 described above and prompt the user to select an operating mode. For example, the control unit 150 monitors the lifespan of each replaceable component by measuring the cumulative number of image forming operations or operating time since the last replacement for each of the one or more replaceable components. The number of image forming operations may be measured, for example, by counting the number of sheets of paper consumed during job execution. The control unit 150 estimates the remaining lifespan of each replaceable component by subtracting the cumulative number of operations or operating time from a preset upper limit. Then, if it determines that the remaining lifespan is insufficient to complete the job based on setting values such as the number of pages of the input image data for the job, the specified number of copies, and the color mode, the control unit 150 predicts that the lifespan of any replaceable component will end during job execution. When it is predicted that the life of any replaceable component is about to end, the control unit 150 may cause the display 103 to display, enable, or highlight a setting item 532 such as the one shown in FIG. 8(B). This allows the user to be aware of the need to select an operation mode for the job that is about to be executed, and ensures that the appropriate operation mode is selected.

The UI for selecting the operating mode described in this section may also be realized by having a printer driver installed on an external terminal device (which may be connected to the multifunction device 100 via the communication interface 101) work in conjunction with the control unit 150 of the multifunction device 100.

<2-5. Spooling compressed image data>
Forming an image by image forming unit 120 based on image data after gradation correction (corrected image data) typically includes forming an image based on compressed image data whose data size has been compressed by compression unit 117. When a job for forming multiple copies of an image is executed, control unit 150 controls the operation of image forming unit 120 so that the image is formed by reusing compressed image data stored (i.e., spooled) in memory 118. By reusing compressed image data in this way, the job execution time can be shortened while reducing the amount of memory resources used.

The control of the operating mode based on user selection described above may also be applied to the spooling of compressed image data. That is, when the replacement of one or more replaceable components is detected during the execution of a job consisting of multiple copies, the control unit 150 may determine, in accordance with the user's selection, whether to continue forming images based on the compressed image data spooled before the replacement was detected. For example, when the user selects the job continuation mode in the first to third embodiments described above, the control unit 150 may determine to have the image forming unit 120 continue image formation. In this case, the control unit 150 may control the operation of the image forming unit 120 so that the compressed image data stored in memory 118 before the component replacement was detected is reused to form images (for the remaining copies of the paused job). On the other hand, when the user selects the job stop mode, the control unit 150 may not cause the image forming unit 120 to continue image formation, but may discard the spooled compressed image data and re-calibrate the gradation correction table before forming the remaining copies.

<2-6. Progress of image formation according to user needs>
FIG. 9 is an explanatory diagram for explaining the progress of image formation when a user who places importance on the quality of the printed image selects the job stop mode in a scenario in which a job similar to that shown in FIG. 3 is executed.

First, when print job J11 begins, toner cartridge CRG1 is already installed in the device. Because toner cartridge CRG1 is nearing the end of its life, a gradation correction table representing signal conversion curve 16a is used for gradation correction 15. When outputting the first printed copy of print job J11, compressed image data 35a is generated through gradation correction 15 and halftone processing 17. The print image for the first copy of print job J11 is formed based on this compressed image data 35a. The compressed image data 35a is also stored in memory 118. The print image for the second copy of print job J11 is formed based on compressed image data 35a read from memory 118. Thereafter, before printing the third copy of print job J11 begins, it is assumed that toner cartridge CRG1 has reached the end of its life. Execution of the job is temporarily suspended in response to the end of its life. The user notices the notification that the job has been temporarily suspended and replaces toner cartridge CRG1 with a new toner cartridge CRG2. When toner cartridge replacement is detected, the control unit 150 determines the operating mode according to the user's selection. In this example, it is assumed that the job stop mode is selected as a pre-defined common setting or as an individual setting for job J11. Therefore, the control unit 150 discards the compressed image data 35a spooled in memory 118 and stops execution of job J11.

After replacing the toner cartridge, the user instructs the multifunction device 100 to execute print job J11' (specifying one copy) to obtain the third print image of print job J11. Prior to the start of print job J11', a calibration process 20 is executed to update the gradation correction table. The gradation correction table is updated to represent the signal conversion curve 16b appropriate for toner cartridge CRG2. In print job J11', the gradation correction unit 115 performs gradation correction using the gradation correction table representing the signal conversion curve 16b to generate corrected image data, and the compression unit 117 compresses the corrected image data to generate compressed image data 35a'. The print image of print job J11' is formed based on this compressed image data 35a'. As a result, the color and density of the print image of print job J11' are equivalent to the color and density of the two print images output in print job J11, meaning that degradation of the image quality of the print image is suppressed.

At the start of the subsequent print job J12, the calibration process 20 is not performed, and the gradation correction table representing the signal conversion curve 16b suitable for the toner cartridge CRG2 continues to be used for gradation correction.

Figure 10 is an explanatory diagram showing the progress of image formation when a user who prioritizes productivity selects the job continuation mode in a scenario in which a job similar to that shown in Figure 4 is executed.

First, when print job J21 starts, toner cartridge CRG1 is already installed in the device. Because toner cartridge CRG1 is nearing the end of its life, a gradation correction table representing signal conversion curve 16a is used for gradation correction 15. When printing the first page of print job J21, compressed image data 35-1 is generated through gradation correction 15 and halftone processing 17, and the print image for page 1 is formed based on compressed image data 35-1. Similarly, when printing the second page of print job J21, compressed image data 35-2 is generated through gradation correction 15 and halftone processing 17, and the print image for page 2 is formed based on compressed image data 35-2. Similarly, for page 3, the print image is formed based on compressed image data 35-3. Thereafter, it is assumed that toner cartridge CRG1 has reached the end of its life before printing page 4 of print job J21 begins. Execution of the job is paused in response to the end of its life. The user notices the job suspension notification and replaces the toner cartridge CRG1 with a new toner cartridge CRG2. When the toner cartridge replacement is detected, the control unit 150 determines the operating mode according to the user's selection. Here, it is assumed that the job continuation mode is selected as a pre-defined common setting or as an individual setting for job J21. Therefore, regardless of the detection of the toner cartridge replacement, the control unit 150 resumes execution of job J21 without executing the calibration process 20. Therefore, shortly after the toner cartridge replacement is detected, compressed image data 35-4 is generated through the gradation correction 15 and halftone process 17, and the print image for page 4 of print job J21 is formed based on the compressed image data 35-4. Similarly, the print image for page 5 is formed based on the compressed image data 35-5. Thereafter, the calibration process 20 is executed, and the gradation correction table is updated to represent the signal conversion curve 16b suitable for the toner cartridge CRG2. In this way, in job continuation mode, re-execution of calibration process 20 is postponed until after the paused job is completed, shortening the time it takes to complete job J21 and improving productivity.

<<3. Processing flow>>
In this section, examples of processing flows that can be executed by the multifunction peripheral 100 according to the above-described embodiment will be described using the flowcharts in Figures 11 to 13. The processing shown in each flowchart can be performed by the various units of the multifunction peripheral 100 cooperating with each other under the control of the control unit 150, which executes a computer program stored in the storage unit 109. In the following description, processing steps will be abbreviated as S (step).

<3-1. Mode setting process>
Fig. 11 shows an example of the flow of the mode setting process. The mode setting process in Fig. 11 can be performed when accepting the setting of an operation mode common to a plurality of jobs in the first embodiment, when a component exchange is detected during the execution of a job in the second embodiment, and when the execution of a specific job is started in the third embodiment.

First, in S101, the control unit 150 displays a GUI including multiple operation mode options on the display 103 (or a display of a user terminal separate from the multifunction device 100). The GUI displayed here may be, for example, the user mode setting screen shown in FIG. 7(A), the mode selection screen shown in FIG. 7(B), or the job setting screen shown in FIG. 8(B). The GUI displayed in S101 may include at least a first option corresponding to the job continuation mode and a second option corresponding to the job stop mode.

Subsequent processing branches depending on which option corresponding to the operation mode was selected by the user in S102. If the first option corresponding to the job continuation mode was selected, processing proceeds to S104. On the other hand, if the second option corresponding to the job stop mode was selected, processing proceeds to S105.

In S104, the control unit 150 sets the operation mode for handling the job when cartridge replacement is detected during job execution to job continuation mode in accordance with the user selection. Meanwhile, in S105, the control unit 150 sets the operation mode for handling the job when cartridge replacement is detected during job execution to job stop mode in accordance with the user selection.

Figure 12 shows another example of the flow of the mode setting process. The mode setting process in Figure 12 can be performed, for example, in the modified example of the first embodiment described above, when accepting the setting of an operating mode common to multiple jobs.

First, in S101, the control unit 150 displays a GUI including multiple operation mode options on the display 103 (or a display of a user terminal separate from the multifunction device 100). The GUI displayed here may be, for example, the user mode setting screen shown in FIG. 8(A). The GUI displayed in S101 may include at least a first option corresponding to the job continuation mode, a second option corresponding to the job stop mode, and a third option corresponding to the individual selection mode.

Subsequent processing branches depending on which option corresponding to which operating mode was selected by the user in S102 and S103. If the first option corresponding to job continuation mode was selected (S102 - Yes), processing proceeds to S104. If the second option corresponding to job stop mode was selected (S102 - No, S103 - Yes), processing proceeds to S105. If the third option corresponding to individual selection mode was selected (S102 - No, S103 - No), processing proceeds to S106.

At S104, the control unit 150 sets the operation mode to job continuation mode in accordance with the user selection. At S105, the control unit 150 sets the operation mode to job stop mode in accordance with the user selection. At S106, the control unit 150 sets the operation mode to individual selection mode in accordance with the user selection.

<3-2. Image formation processing>
13 shows an example of the flow of image forming processing, which can be performed when the multifunction peripheral 100 receives a job for forming images on multiple sheets of paper.

First, in S111, the control unit 150 accepts a job requesting image formation, for example, via the UI 102 or from an external device via the communication interface 101. Here, it is assumed that a job for image formation on N sheets of paper (N>1) is accepted. If the number of pages in the input image data is M (M≧1) and the specified number of copies is equal to L (L≧1), then N = M×L. The control unit 150 passes the input image data specified by the accepted job to the raster conversion unit 111 of the image processing unit 110.

Next, in S112, processing is performed to generate image data from the input image data that is suitable for image formation by the image forming unit 120. The processing performed here may include raster conversion by the raster conversion unit 111, color conversion by the color conversion unit 113, gradation correction by the gradation correction unit 115, and compression by the compression unit 117. The gradation correction by the gradation correction unit 115 is performed using a gradation correction table that reflects the results of the most recent calibration and is stored in the table storage unit 114. The compression by the compression unit 117 may include halftone processing.

Next, in S113, the control unit 150 stores the compressed image data generated as a result of the processing in S113 in memory 118. That is, the control unit 150 spools the compressed image data using memory 118. Note that when forming images for the second or subsequent copies when the number of copies L is greater than 1, the compressed image data spooled in memory 118 is reused, so S112 and S113 can be skipped (these processing steps are therefore indicated by dashed lines in the figure).

Next, in S114, the image forming unit 120 forms an image on the ith sheet (i≦N) of paper based on the compressed image data generated in S112 or the compressed image data spooled in memory 118. Note that the initial value of variable i is 1, and i is incremented each time S114 is repeated (i←i+1).

Next, in S115, the control unit 150 determines whether execution of the accepted job has been completed. For example, if printing of all copies of all pages has been completed and the value of variable i has reached N, the control unit 150 may determine that execution of the accepted job has been completed. If execution of the job has not been completed, processing proceeds to S116. If execution of the job has been completed, processing proceeds to S119.

If the job execution is not complete, in S116 the control unit 150 determines whether replacement of one or more replaceable parts of the image forming unit 120 has been detected. If replacement has not been detected, the process returns to S112, and an image is formed on the next sheet of paper.

If replacement of one or more replaceable parts of the image forming unit 120 is detected in S116, job execution is temporarily suspended, and in S117, the control unit 150 determines the operating mode for handling the job in progress in accordance with the user's selection. Specifically, in the first embodiment, the control unit 150 applies to the job in progress an operating mode that is set commonly for multiple jobs based on a prior user selection. In the second embodiment (or in the individual selection mode of the modified first embodiment), the control unit 150 displays, for example, a mode selection screen such as that shown in FIG. 7B on the display, and determines the operating mode in accordance with the options selected by the user on this mode selection screen. In the third embodiment, the control unit 150 applies to the job the operating mode selected by the user at the start of the job.

Subsequent processing branches at S118 depending on the operating mode determined at S117. If the determined operating mode is job continuation mode, processing returns to S112, execution of the paused job is resumed, and image formation is performed on the next sheet of paper. On the other hand, if the determined operating mode is job stop mode, execution of the job is stopped, and processing proceeds to S119.

At S119, the control unit 150 discards the compressed image data spooled in the memory 118. Next, at S120, if a component replacement is detected during job execution, the control unit 150 updates or reselects the gradation correction table in the table storage unit 114 according to the image output characteristics of the image forming unit 120 associated with the new replaceable component. At this time, the control unit 150 may cause the characteristic acquisition unit 130 to measure the image output characteristics of the image forming unit 120, and update or reselect the gradation correction table according to the image output characteristics obtained as a result of the measurement. For example, if an old toner cartridge is replaced with a new one, a gradation correction table representing the signal conversion curve 16b, which may suppress the correction signal value, may be reselected compared to the signal conversion curve 16a, which was previously used and which is likely to output a larger correction signal value. If a component replacement is not detected during job execution, S120 may be skipped. The image formation process of FIG. 13 then ends.

Note that while Figure 13 shows a simplified flow of repetitive image formation operations, raster conversion, color conversion, tone correction, compression, and image formation for different copies or different pages may be performed in parallel as long as the circuit configuration allows, in order to improve productivity.

<<4. Summary>>
Various embodiments, examples, and modifications of the technology disclosed herein have been described above using FIGS. 5 to 13 . According to the above-described embodiments, in an image forming apparatus equipped with an image forming unit including one or more replaceable components, corrected image data is generated through gradation correction based on the output characteristics of the image forming unit, and an image based on the corrected image data is formed on paper. When a job for forming images on multiple sheets of paper is executed and a component replacement is detected during the job, whether to continue forming an image that has undergone gradation correction based on the output characteristics acquired before the detection is determined based on a user selection. Therefore, a user who prioritizes productivity can select to continue a job that was paused midway and quickly obtain a desired printed image. Furthermore, a user who prioritizes print image quality can select to update the output characteristics that serve as the basis for gradation correction before re-executing the remaining job, thereby obtaining a printed image with reduced variations in color and density. In this way, flexible selection is possible between print image quality and maintaining image formation productivity to meet the user's needs.

In the above-described embodiment, an image based on compressed image data generated from the corrected image data is formed by the image forming unit, and the compressed image data is stored in a storage unit. When a job for forming multiple copies of an image is executed, the image is formed by reusing the compressed image data stored in the storage unit. In this case, the process of generating compressed image data for image formation of the second and subsequent copies is omitted, significantly reducing the job execution time. If a component replacement is detected during the execution of the job for forming multiple copies of an image, a user-selected option is selected as to whether to continue image formation by reusing the compressed image data stored in the storage unit before the replacement was detected. Therefore, users who prioritize productivity can choose to significantly reduce time by reusing compressed image data, while users who prioritize print image quality can avoid reusing compressed image data and reduce variations in color and density among multiple copies.

In the above-described embodiment, the user selects one of multiple operating modes via the UI, including a first mode that continues a job in progress when a component replacement is detected. When the user selects the first mode, a decision is made to continue forming an image that has been subjected to gradation correction based on output characteristics acquired before the replacement is detected. The multiple operating modes further include a second mode that stops a job in progress when replacement of one or more replaceable components is detected. When an operating mode common to multiple jobs is selected in advance, it is possible to eliminate the need for the user to select an operating mode each time a component replacement is detected during actual job execution. When an operating mode is selected at the start of job execution, the user can select whether productivity or quality is prioritized for each individual job based on their current needs. Furthermore, when the user is prompted to select an operating mode when a component replacement is detected during job execution, the user does not need to select an operating mode unless a component replacement is detected, thereby reducing user complexity. In cases where the user is prompted to select an operation mode when it is predicted that a component's lifespan will end during job execution, if there is sufficient life left in the component, the user will not be prompted to select an operation mode, again reducing the hassle for the user.

<<5. Other embodiments>>
The above-described embodiment can also be realized in the form of a process in which a program for realizing one or more functions is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program, or by a circuit (e.g., an ASIC) that realizes one or more functions.

The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Therefore, the following claims are appended to clarify the scope of the invention.

100: Multifunction peripheral (image forming device), 61: Photosensitive drum (image carrier), 62: Charging roller (charging device), 63: Laser unit (exposure device), 64: Development roller (developing device), 70: Transfer unit (transfer device), 101: Communication interface, 102: User interface, 111: Raster conversion unit (raster image processor), 113: Color conversion unit, 115: Tone correction unit (correction unit), 117: Compression unit, 118: Memory (storage unit), 120: Image forming unit, 130: Characteristics acquisition unit, 150: Control unit

Claims (5)

a conversion means for converting image data using conversion conditions for adjusting image quality;
an image forming means for forming an image based on the image data converted by the converting means;
a calibration unit that updates the conversion conditions based on a measurement result of the calibration image formed by the image forming unit;
a control unit for temporarily suspending image formation by the image forming unit in order to replace a member included in the image forming unit;
a selection means for selecting one of a plurality of operation modes, including a job stop mode in which the proofreading means updates the conversion conditions and then causes the image forming means to resume the image formation when replacement of the member is detected during execution of a job for forming images for a plurality of copies, and a job continuation mode in which the proofreading means updates the conversion conditions and then causes the image forming means to resume the image formation without updating the conversion conditions;
An image forming apparatus comprising: the image forming apparatus,
a compression means for compressing the image data converted by the conversion means to generate compressed image data;
a storage means for storing the compressed image data;
Furthermore,
the image formation by the image forming means includes forming an image based on the compressed image data,
The control means
When the job for forming images for a plurality of copies is executed, the operation of the image forming means is controlled so that the compressed image data stored in the storage means is reused to form images.
The image forming apparatus according to claim 1 . The image forming apparatus of claim 2, wherein when replacement of the component is detected during execution of the job for forming images for multiple copies, and the selection means selects that the proofreading means cause the image forming means to resume the image formation without updating the conversion conditions, the control means controls the operation of the image forming means to form an image by reusing the compressed image data stored in the storage means before the replacement was detected. the conversion conditions are expressed by a gradation correction table according to the output characteristics of the image forming means,
the calibration means calibrates the gradation correction table in accordance with the output characteristics of the image forming means.
The image forming apparatus according to any one of claims 1 to 3 . The member included in the image forming unit is
Image carrier,
a charging device for charging the image carrier;
an exposure device that exposes the charged image carrier to light to form an electrostatic latent image on the image carrier;
a developing device that supplies a developer to the electrostatic latent image to form a developer image on the image carrier; and
a transfer device that transfers the developer image formed on the image carrier onto a sheet of paper;
5. The image forming apparatus according to claim 1 , further comprising at least one of: