Image formation device and information processing device

Abstract

To reduce a burden on a user relating to mount a sheet having a test image formed thereon.SOLUTION: An image formation device forms a test image on only one of the first surface and the second surface of a sheet and respectively reads the first surface and the second surface of the sheet to generate read data of the first surface and that of the second surface. The image formation device analyzes the read data of the first surface and that of the second surface, selects the read data of the first surface or that of the second surface which includes a result of reading the test image, and generates a gradation correction condition on the basis of the selected read data.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to image density control for controlling the density of an output image based on read data relating to a test image printed on a sheet. [Background technology]

[0002] In an image forming apparatus that forms an image on a sheet using ink or toner, the density of the image may change depending on changes in the usage environment and changes over time. Therefore, the image forming apparatus forms a test image on a sheet, has a reading device read the test image, and corrects the gradation correction conditions based on the read data of the test image. This is called gradation correction control in the calibration that adjusts the image quality. Patent Document 1 proposes gradation correction control that adjusts the gradation correction conditions so as to suppress the image formed on the front side of the sheet from being projected onto the back side of the sheet (so-called show-through). More specifically, the image forming apparatus forms a test image only on the front side (printing surface) of the sheet, and does not form a test image on the back side. A user places a sheet on the platen of an image reader used to read a document, and has the image reader read the test image formed on the front side of the sheet. Furthermore, the user turns the sheet over and places it on the platen, and has the image reader read the back side of the sheet on which the test image is not formed. Then, the density of the test image that does not cause show-through is determined, and gradation correction conditions are created such that the determined density is the maximum density. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-234354 A Summary of the Invention [Problem to be solved by the invention]

[0004] Although Patent Document 1 can prevent show-through, there is a risk that a gradation correction condition is created such that the gradation characteristics of the image formed on the front side of the sheet by the image forming device do not match the gradation characteristics of the input image. Some users may place more importance on the gradation characteristics of the image formed on the front side than on preventing show-through. For such users, the calibration of Patent Document 1 is not suitable. Furthermore, the user must open and close the pressure plate to place the sheet on the platen in order to invert the sheet on the platen. This may be troublesome for the user. On the other hand, there is known a method of having a reading device read a test image on a sheet using an auto document feeder (hereinafter referred to as ADF), which automatically transports a document placed on a tray to a reading position. When a sheet is read by a reading device using an ADF, opening and closing the pressure plate is not necessary, reducing the burden on the user. However, when only one side of a sheet transported by the ADF can be read, the readable side of the sheet is determined when the user places the sheet on the tray of the ADF. Therefore, if the user places the sheet upside down on the tray, the reading device cannot read the test image formed on the sheet. Therefore, an object of the present invention is to reduce the burden on the user when placing a sheet on which a test image is formed on the tray. [Means for solving the problem]

[0005] In order to solve the above problem, an image forming apparatus of the present invention has an image forming means for forming an image, a loading tray on which documents are loaded, a transport section for transporting the documents loaded on the loading tray, a first reading section for reading an image of the underside of the documents on the loading tray while the transport section transports the documents, a discharge section for discharging the documents read by the first reading section, and a discharge tray to which the documents are discharged by the discharge section, a platen on which documents are placed, and a second reading section, and when a document placed on the platen is to be read, the second reading section is moved while reading the document on the platen by the second reading section, and the document on the loading tray transported by the transport section is read by a document transport section. When reading a document, the document feeder has a reading means for reading an image of the upper surface of the document on the loading tray by the second reading unit while keeping the second reading unit stationary at a reading position; and when reading a test image formed on one side of a sheet by the image forming means while being transported by the document transporting means, the document feeder has a control means for causing both the first reading unit and the second reading unit to read the sheet, and adjusting the image quality of the image formed by the image forming means based on the read image of the side on which the test image is formed, from a first read image of the sheet on which the test image is formed by the first reading unit and a second read image of the sheet on which the test image is formed by the second reading unit. Effect of the Invention

[0006] According to the present invention, the burden on the user when the user places the sheet on which the test image is formed on the tray can be reduced. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view illustrating an image forming apparatus. [Diagram 2] Block diagram explaining the control unit [Diagram 3] Diagram explaining the test chart [Figure 4] Block diagram explaining the CPU functions [Diagram 5] Diagram explaining edge detection [Figure 6] Flowchart showing how to create a test chart [Figure 7] Flowchart showing a method for generating tone correction conditions [Figure 8] Flowchart showing a method for generating tone correction conditions [Figure 9] Flowchart showing a method for generating tone correction conditions [Figure 10] FIG. 13 is a schematic cross-sectional view illustrating a modified example of the image reader. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a plurality of features, not all of these features are essential to the invention, and the plurality of features may be combined in any manner. Furthermore, in the accompanying drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0009] First Embodiment [Image forming device] 1, the image forming apparatus 1 is a multifunction peripheral (MFP) having an electrophotographic printer 100 and an image reader 110. The electrophotographic system is merely an example, and other image forming systems such as an inkjet system may also be adopted.

[0010] ●Printer 100 The image forming unit 50 forms a color image by overlapping four color developers (toners): yellow (Y), magenta (M), cyan (C), and black (K). In Fig. 1, the letters YMCK indicating the toner colors are added to the end of the reference numbers, but the letters YMCK are omitted when matters common to all four colors are explained.

[0011] The feeding cassette 2 is a storage container that stores the sheets P. The feeding roller 4 feeds the sheets P from the feeding cassette 2 to a conveying path. The conveying roller pair 5 conveys the sheets P fed from the feeding cassette 2 further downstream in the conveying direction of the sheets P. The registration roller pair 6 is a conveying roller for matching the timing at which the sheets P arrive at the secondary transfer roller 19 with the timing at which the toner image arrives at the secondary transfer roller 19. The sheet sensor 22 is provided near the registration roller pair 6 and detects the arrival timing of the sheets P.

[0012] In the image forming section 50, the photosensitive drum 11 is an image carrier that carries an electrostatic latent image or a toner image. The charging roller 12 charges the surface of the photosensitive drum 11 so that the surface of the photosensitive drum 11 has a uniform potential. The exposure device 13 forms an electrostatic latent image by irradiating the surface of the photosensitive drum 11 with light. The development device 15 develops the electrostatic latent image using toner to form a toner image. The primary transfer device 16 transfers the toner image to the intermediate transfer body 17. The secondary transfer roller 19 transfers the toner image from the intermediate transfer body 17 to the sheet P. The fixing device 20 fixes the toner image to the sheet P using heat and pressure. The discharge roller 21 discharges the sheet P to a tray provided outside the image forming apparatus 1.

[0013] ●Image reader The image reader 110 has a reading unit 70 and a document transport device 80. The reading unit 70 has a platen 71 on which a document (sheet) is placed, and an image sensor 72 that reads the document (sheet) placed on the platen 71. In order to read the document (sheet) placed on the platen 71, the image sensor 72 reads the document (sheet) while moving from right to left in the drawing directly below the platen. The image sensor 72 of this embodiment has an LED as a light source and optical components including a lens, and reads the surface of the document (sheet) placed face down on the platen 71 by receiving reflected light from the document (sheet). The reading unit 70 has a housing equipped with an LED and optical components, and the image sensor 72, and may be configured such that the housing equipped with the LED and optical components moves without moving the image sensor 72. The document transport device 80 is rotatable with respect to the reading unit 70 so that a user can place a document (sheet) on the platen.

[0014] A configuration for reading an original (sheet) without a user placing the original (sheet) on the platen 71 will be described below. When the sheet sensor 82 detects that an original (sheet) has been placed on the original tray 81, the pickup roller 83 rotates and takes the sheet into the conveying path of the original conveying device 80. When multiple sheets are pulled in from the original tray 81, the separation roller 84 separates one sheet from the multiple sheets and conveys it to conveying rollers 85 and 86 located further downstream. The conveying rollers 85 and 86 correct the skew of the sheet by abutting the leading edge of the sheet against the registration roller 87. When the registration roller 87 starts to rotate, the sheet is conveyed to the reading unit 70. The conveying belt 88 conveys the sheet along the platen 71. At this time, the image sensor 72 is stationary at the original reading position and reads the image formed on the sheet conveyed along the platen 71. The conveying belt 88 and the paper discharge roller 89 discharge the sheet to the paper discharge tray 91. A paper discharge sensor 90 detects that the sheet has been discharged onto a paper discharge tray 91 .

[0015] ●Control unit As shown in FIG. 2, the control unit 10 controls the entire image forming apparatus 1. The control unit 10 is connected to the printer 100 via the device IF 116, and controls the printer 100 to form an image on a sheet. The control unit 10 is connected to the image reader 110 via the device IF 116, and acquires image data (read data) of a document generated by the image reader 110. The CPU 111 controls the image forming apparatus 1 based on a control program stored in the storage unit 112. The storage unit 112 has a RAM, a ROM, a hard disk drive, and the like. The CPU 111 receives a print job from a host computer or the like via the network IF 115. The CPU 111 displays a message on a display device of the operation unit 150 connected via the operation unit IF 117, and accepts a user instruction from an input device of the operation unit 150. The image processing unit 118 performs a predetermined image processing on the print data (image data for printing) received via the network IF 115. The image processing unit 118 expands the print data into bitmap data, converts the color space (RGB→YMCK) of the bitmap data, and performs gradation correction based on the gradation correction conditions. The image processing unit 118 converts the color space (RGB→YMCK) of the image data received from the image reader 110, and performs gradation correction based on the gradation correction conditions. The image memory 119 is a high-speed memory that temporarily stores image data for image processing. The gradation correction conditions are, for example, a one-dimensional table used to convert image signal values ​​included in the image data. The gradation correction conditions are used to correct the gradation characteristics of the image formed by the printer 100 to ideal gradation characteristics. The image data converted by the image processing unit 118 is transferred to the exposure device 13 of the printer 100. The exposure device 13 controls the light that exposes the photosensitive drum 11 based on the transferred image data.

[0016] [Surface judgment] The image reader 110 has a fixed reading mode and a running reading mode. In the fixed reading mode, the document transport device 80 is opened, a sheet is placed on the platen 71, and the document transport device 80 is closed. The lower surface of the document transport device 80 is a pressure plate that presses the sheet against the platen 71. In this case, the user places the sheet on the platen 71 with the surface on which the test image is formed facing the platen 71. On the other hand, in the running reading mode, the image on the sheet is read while the sheet placed on the document tray 81 of the document transport device 80 is transported by the document transport device 80. In this case, the user often wonders whether the sheet should be placed on the document tray 81 with the test image facing up, or the sheet should be placed on the document tray 81 with the test image facing down. If the user makes a mistake about the front and back of the sheet, the CPU 111 cannot create the correct gradation correction conditions. Therefore, in this embodiment, the user can place the sheet on the document tray 81 without intending the front and back of the test image. In this embodiment, the image reader 110 reads both the first and second sides of the sheet. Here, the first side is the side that is read by the image reader 110 first. The second side is the side that is read by the image reader 110 next to the first side. The user may first place the sheet on the document tray 81 so that the test image can be seen, and then place the sheet on the document tray 81 so that the test image cannot be seen. Alternatively, the user may first place the sheet on the document tray 81 so that the test image cannot be seen, and then place the sheet on the document tray 81 so that the test image can be seen. The CPU 111 analyzes the read data of the first side and the read data of the second side, and selects read data including the read result of the test image. Furthermore, the CPU 111 creates a gradation correction condition based on the selected read data. This reduces the burden on the user regarding placing the sheet on which the test image is formed.

[0017] [Test image] FIG. 3A shows a test image 301 formed on the printing surface 300a of the sheet P. FIG. 3B shows a non-printing surface 300b of the sheet P. A show-through image 302 on the non-printing surface 300b is an image in which the test image 301 formed on the printing surface 300a is seen through the non-printing surface 300b. The show-through image 302 is more likely to occur as the density of the test image 301 increases. In other words, the show-through image 302 corresponding to the low density area of ​​the test image 301 is less likely to occur. In this embodiment, the test image is formed on the printing surface 300a, and the test image is not formed on the non-printing surface 300b. Furthermore, the CPU 111 detects edges, marks, or histograms from the read data, and can distinguish the printing surface 300a from the non-printing surface 300b based on the detection result. A method for distinguishing the printing surface 300a from the non-printing surface 300b will be described in detail later.

[0018] As shown in FIG. 3(C), a mark 303a may be formed on the printing surface 300a together with the test image 301. As shown in FIG. 3(D), a mark 303b may be formed on the printing surface 300a together with the test image 301. The marks 303a and 303b are not formed on the non-printing surface 300b. Alternatively, the marks 303a and 303b may be formed on the printing surface 300a, and a mark different from the marks 303a and 303b may be formed on the non-printing surface 300b. Alternatively, no mark may be formed on the printing surface 300a, and a mark may be formed on the non-printing surface 300b. When marks are formed only on the printing surface 300a, the image forming apparatus 1 only needs to perform single-sided printing, so that the time required to form the test chart can be reduced. The test chart is the sheet P on which the test image 301 is formed. When marks are formed on the non-printing surface 300b, the image forming apparatus 1 must perform double-sided printing, so that the time required to form the test chart is increased.

[0019] [CPU functions] 4 shows functions that are realized by executing a control program by the CPU 111. However, all or part of these functions may be implemented by a hardware circuit such as an ASIC or FPGA.

[0020] The calibration unit 400 generates tone correction conditions based on the reading result of the test image 301. The test image unit 401 generates test data 451 or reads the test data 451 from the storage unit 112 and sends it to the image processing unit 118. The test data 451 is image data for forming the test image 301 on the sheet P. The mark unit 402 is optional, and generates image data for forming marks 303a and 303b on the sheet P or reads the image data from the storage unit 112 and sends it to the image processing unit 118. The generation unit 403 generates tone correction conditions (correction table 452) based on the reading result of the test image 301. The UI unit 404 displays a calibration guidance message on the display device of the operation unit 150 and receives user instructions from the input device. The calibration unit 400 controls the image reader 110 to read both the first and second sides of the sheet P on which the test image 301 is formed. The calibration unit 400 stores in the storage unit 112 first read data 453 which is the read result of the first side from the image reader 110 and second read data 454 which is the read result of the second side.

[0021] The selection unit 410 analyzes the first read data 453 and the second read data 454, and selects read data including the read result of the test image 301 from the first read data 453 and the second read data 454. The analysis unit 420 analyzes the first read data 453 and the second read data 454 to select read data including the read result of the test image 301. The reduction unit 421 reduces the first read data 453 to generate first reduced data 455. The reduction unit 421 reduces the second read data 454 to generate second reduced data 456. The first read data 453 and the second read data 454 are high-resolution images because they are used for calibration. On the other hand, such high-resolution images are not necessary to determine the printing surface 300a on which the test image 301 is formed. Therefore, the reduction unit 421 may be adopted to speed up the analysis process of the analysis unit 420. That is, the analysis unit 420 analyzes the first reduced data 455 and the second reduced data 456 instead of the first read data 453 and the second read data 454. In the following, the description regarding the first read data 453 and the second read data 454 also applies to the first reduced data 455 and the second reduced data 456. The edge detection unit 422 detects edges included in the first read data 453 and the second read data 454.

[0022] FIG. 5 is a schematic diagram showing image data of the test image 301 expanded in the image memory 119 by the CPU 111. The edge detection unit 422 refers to pixel values ​​of a plurality of pixels 502 to 505 spaced apart at a predetermined interval d from the tip of the image data expanded in the image memory 119 in the direction indicated by the arrow 501. The pixel values ​​may be luminance values ​​or density values. The edge detection unit 422 obtains a difference between the pixel values ​​of two adjacent pixels among the plurality of pixels 502 to 505. The edge detection unit 422 judges whether or not this difference exceeds a threshold value. If this difference exceeds a threshold value, the edge detection unit 422 judges that an edge exists between the two pixels. If this difference does not exceed a threshold value, the edge detection unit 422 judges that an edge does not exist between the two pixels. According to FIG. 5, it is judged that an edge exists between the pixel 503 and the pixel 504. The edge detection unit 422 judges whether or not the position of the edge or the position of the pixel 504 is within a predetermined range. The edge detection unit 422 determines that the read data includes the test image 301 when the edge position or the pixel 504 position is within a predetermined range. The edge detection unit 422 determines that the read data does not include the test image 301 when the edge position or the pixel 504 position is not within the predetermined range. Even if show-through occurs as shown in Fig. 3(B), the edge position or the pixel 504 position is not within the predetermined range, so the CPU 111 determines that the read data does not include the test image 301. This is because a high-density test image that causes show-through is formed outside the predetermined range as shown in Figs. 3(A) and 3(B).

[0023] The mark detection unit 423 analyzes the first read data 453 and the second read data 454, and determines whether the first read data 453 or the second read data 454 includes the mark 303a (or 303b). The mark 303a (or 303b) is also formed at a predetermined position on the sheet P. Therefore, the mark detection unit 423 selects the first read data 453 when the mark 303a (or 303b) is formed at a predetermined position on the first read data 453. The mark detection unit 423 selects the second read data 454 when the mark 303a (or 303b) is formed at a predetermined position on the second read data 454. The mark 303a (or 303b) may be formed to have a low density so that show-through does not occur. According to this configuration, the CPU 111 can select read data including the test image from the first read data and the second read data based on the detection result (selection result) of the mark detection unit 423. Alternatively, the mark detection unit 423 may compare the luminance of the area where the mark 303a (or 303b) is predicted to be formed, and make a judgment based on the result of the comparison of the luminance. If the luminance of the pixels of the predicted area of ​​the first read data is lower than the luminance of the pixels of the predicted area of ​​the second read data, the mark detection unit 423 selects the first read data 453. On the other hand, if the luminance of the pixels of the predicted area of ​​the second read data is lower than the luminance of the pixels of the predicted area of ​​the first read data, the mark detection unit 423 selects the second read data 454.

[0024] The histogram unit 424 calculates a histogram for each of the first read data 453 and the second read data 454. The test image 301 is formed on the print surface 300a of the sheet P, but the test image 301 is not formed on the non-print surface 300b. In other words, the histogram of the non-print surface 300b should be similar to the histogram of a blank sheet of paper. Alternatively, the histogram of the print surface 300a should be a unique histogram derived from the test image 301. Therefore, the histogram unit 424 may select read data including the read result of the test image 301 from the first read data 453 and the second read data 454 based on the histogram.

[0025] The determination unit 430 determines which of the first read data 453 and the second read data 454 includes the test image 301 based on the analysis result of the analysis unit 420. The determination unit 430 notifies the generation unit 403 which of the first read data 453 and the second read data 454 should be used.

[0026] [Calibration flow chart] ● Creating test charts 6 shows a method of creating a test chart executed by the CPU 111 according to a control program. The calibration is divided into a process of creating a test chart and a process of creating gradation correction conditions. When an instruction to execute the calibration is input from the operation unit 150 or the like, the CPU 111 executes the following process. In S601, the CPU 111 (test image unit 401) instructs the printer 100 to start printing. When the printer 100 is instructed to start printing, it executes preparatory operations required for executing printing and waits for image data (image signals) to be output from the control unit 10. In S602, the CPU 111 (test image unit 401) generates test data 451, which is image data of a test image. This process is a process of writing the test data 451 to the image memory 119 as image data. The test data 451 may be stored in advance in the storage unit 112. The test image unit 401 may generate the test data 451 according to a control program. In S603, the CPU 111 (test image unit 401) supplies the test data 451 expanded in the image memory 119 to the printer 100 via the device IF 116, thereby causing the printer 100 to create a test chart. The printer 100 forms the test image 301 on the sheet P, thereby creating the test chart. In S604, the CPU 111 (test image unit 401) instructs the printer 100 to end printing.

[0027] ●Generating tone correction conditions 7 shows a method of generating tone correction conditions executed in accordance with a control program by the CPU 111. When the creation of the test chart is completed, the CPU 111 executes the following process. In S701, the CPU 111 (calibration unit 400) instructs the image reader 110 to start reading. The CPU 111 may display a message on the display device of the operation unit 150 to prompt the user to place a test chart on the document tray 81. Note that the user may place the test chart on the document tray 81 so that the test image 301 is visible, or may place the test chart on the document tray 81 so that the test image is not visible. In S702, CPU 111 (calibration unit 400) acquires the reading result of the first side of the test chart from image reader 110. For example, CPU 111 receives first read data 453 output by image reader 110 and stores it in memory unit 112. As described above, CPU 111 may reduce first read data 453 to generate first reduced data 455 and store it in memory unit 112. CPU 111 may display a message on operation unit 150 prompting the user to flip the test chart over and place it on document tray 81. In S703, the CPU 111 (calibration unit 400) acquires the reading result of the second side of the test chart from the image reader 110. For example, the CPU 111 receives the second read data 454 output by the image reader 110, and stores it in the storage unit 112. As described above, the CPU 111 may reduce the second read data 454 to generate second reduced data 456, and store it in the storage unit 112. In S704, the CPU 111 (analysis unit 420) analyzes the first read data 453. Instead of the first read data 453, the first reduced data 455 may be analyzed. These read data may be expanded in the image memory 119 to speed up the analysis process. The analysis result may be any information useful for determining the presence or absence of the test image 301, such as an edge detection result (e.g., the presence or absence of an edge and the edge position), a mark detection result, or a histogram calculation result. In S705, the CPU 111 (determination unit 430) determines whether the first read data 453 includes the read result of the test image based on the analysis result. If the first read data 453 includes the read result of the test image, the CPU 111 advances the process to S706. If the first read data 453 does not include the read result of the test image, the CPU 111 advances the process to S710.

[0028] If the first scanned data 453 contains the scanned result of a test image In S706, the CPU 111 (the generation unit 403) performs sampling for creating a gradation correction condition for the first read data 453. The test image 301 has a plurality of gradation patterns (patch images) each having a different gradation. Therefore, the generation unit 403 performs sampling for each of the plurality of gradation patterns. In S707, the CPU 111 (generation unit 403) updates the tone correction conditions based on the sampling results. For example, the tone correction conditions for a certain tone are updated by comparing the sampling results for that tone with the test data 451 for that tone. As described above, the tone correction conditions may be a tone correction table (correction table 452). The generation unit 403 creates a new correction table 452 based on the sampling results, and overwrites the old correction table 452 stored in the storage unit 112. In step S708, the CPU 111 (UI unit 404) notifies the user of the completion of the correction. For example, the UI unit 404 may display a message indicating the completion of the correction on the operation unit 150. In S708, the CPU 111 (generation unit 403) deletes the read data (eg, first read data 453, second read data 454, first reduced data 455, second reduced data 456) from the storage unit 112 and image memory 119.

[0029] If the first scanned data 453 does not contain the scanned result of the test image In S710, the CPU 111 (analysis unit 420) analyzes the second read data 454. The second reduced data 456 may be analyzed instead of the second read data 454. These read data may be expanded in the image memory 119 to speed up the analysis process. The analysis result may be any information that is useful for determining the presence or absence of the test image 301, such as an edge detection result (e.g., the presence or absence of an edge and the edge position), a mark detection result, or a histogram calculation result. In S711, the CPU 111 (determination unit 430) determines whether the second read data 454 includes the read result of the test image based on the analysis result. If the second read data 454 includes the read result of the test image, the CPU 111 advances the process to S706. In this case, S706 to S709 are executed for the second read data 454. If the second read data 454 does not include the read result of the test image, the CPU 111 advances the process to S712.

[0030] If the second scanned data 454 does not contain the scanned result of the test image In S712, the CPU 111 (UI unit 404) notifies the user of the error. For example, the UI unit 404 may display a message indicating that an error has occurred on the operation unit 150. Normally, neither the first read data 453 nor the second read data 454 will include a test image. However, if the user forgets to invert the test chart, such an error may occur.

[0031] Second Embodiment Fig. 8 shows another method of generating gradation correction conditions executed by CPU 111 according to a control program. Fig. 8 differs from Fig. 7 in that S705, S706, S710, and S711 are replaced with S801 to S805. Here, S801 to S805 will be mainly described. To avoid duplication of explanation, the matters already described in Fig. 7 will be omitted. When S704 ends, CPU 111 advances the process to S801. In S801, the CPU 111 analyzes the second read data 454. S801 is the same process as S710. In S802, the CPU 111 determines whether the first or second side of the test chart includes the test image 301 based on the analysis result of the first read data 453 and the second read data 454. That is, the CPU 111 determines whether the first read data 453 or the second read data 454 includes the read result of the test image 301. As described above, the presence or absence of the test image 301 may be determined based on an edge, a mark, or a histogram. If either the first read data 453 or the second read data 454 includes the read result of the test image 301, the CPU 111 advances the process to S803. If neither the first read data 453 nor the second read data 454 includes the read result of the test image 301, the CPU 111 advances the process to S712. In S803, CPU 111 determines whether the first side includes test image 301. For example, determination unit 430 determines whether first read data 453 includes a read result of test image 301 based on the analysis result of first read data 453. As described above, the presence or absence of test image 301 may be determined based on an edge, a mark, or a histogram. If the first side includes test image 301, CPU 111 advances the process to S804. If the first side does not include test image 301 (if the second side includes test image 301), CPU 111 advances the process to S805. In S804, the CPU 111 (generation unit 403) executes sampling for creating a gradation correction condition for the first scanned data 453. S804 is the same process as S706. In S805, the CPU 111 (generation unit 403) executes sampling for creating a gradation correction condition for the second scanned data 454. S805 is the same process as S706.

[0032] <Third embodiment> Fig. 9 shows yet another method of generating tone correction conditions executed by CPU 111 according to a control program. Fig. 9 differs from Fig. 7 in that S703 to S705 are replaced by S901 to S903. Here, S901 to S903 will be mainly described. To avoid duplication of explanation, the matters already described in Fig. 7 will be omitted. When S702 ends, CPU 111 advances the process to S901. In S901, the CPU 111 analyzes the first read data 453. S901 is the same process as S704. At step S902, the CPU 111 (determination unit 430) determines whether the first read data 453 includes the read result of the test image based on the analysis result. If the first read data 453 includes the read result of the test image, the CPU 111 advances the process to step S706. If the first read data 453 does not include the read result of the test image, the CPU 111 advances the process to step S903. In S903, the CPU 111 obtains the read result of the second side of the test chart from the image reader 110. S903 is the same process as S703. After that, the CPU 111 advances the process to S710.

[0033] Thus, in Fig. 9, the reading process of the second side is performed only when the test image 301 is not formed on the first side. If the test image 301 is formed on the first side, the reading process of the second side is skipped. Compared to Figs. 7 and 8, the time from the start to the end of the calibration will be shortened in Fig. 9.

[0034] <Other embodiments> Image forming apparatus 1 may have a configuration including image reader 110 shown in FIG. 10, instead of image reader 110 shown in FIG. The configuration of image reader 110 in FIG. 10 will be described in detail. Image reader 110 in FIG. 10 has document transport device 80 and reading unit 70. Document transport device 80 of the image reader shown in FIG. 10 is different from document feed device 80 of image reader 110 shown in FIG. 1. Image sensor 72A has the same configuration as image sensor 72 in FIG. 1.

[0035] Pickup roller 83 feeds documents (sheets) loaded on document tray 81 into document transport device 80. Rotation of separation roller 84 is controlled so as to prevent multiple documents (sheets) from being fed simultaneously by pickup roller 83. The documents (sheets) fed to the transport path are transported toward reading position A by transport rollers 85 and 86a. Here, reading unit 70 has transparent glass 73 at a position facing reading position A. Note that glass 73 is provided separately from platen 71, but a configuration in which part of platen 71 overlaps with reading position A may also be used.

[0036] An opening is formed in the document transport device 80 so that the document (sheet) transported by the document transport device 80 is pressed against the glass 73 of the reading unit 70 at the reading position A. When the image sensor 72A reads the document (sheet) transported to the document transport device 80, the image sensor 72A of the reading unit 70 moves to a position directly below the glass 73. When the image sensor 72A reads the document (sheet) transported to the document transport device 80, the image sensor 72A stays directly below the reading position A. As a result, the document (sheet) passing through the reading position A by the document transport device is read by the image sensor 72A. Hereinafter, the surface of the document (sheet) read by the image sensor 72A is referred to as the first surface.

[0037] The document transport device 80 has a sensor that detects the leading edge of the document (sheet) transported on the transport path, upstream of the reading position A in the transport direction of the document (sheet). The control unit 10 controls the timing at which the image sensor 72A starts reading the document (sheet) based on the timing at which the sensor detects the leading edge of the document (sheet). The document transport device 80 also has a backup roller for suppressing fluttering of the document (sheet) passing through the reading position A.

[0038] The document (sheet) that has passed through the reading position A is transported toward the reading position B by the transport roller 86b. The document transport device 80 has an image sensor 72B that reads the document (sheet) transported to the reading position B. The longitudinal direction of the image sensor 72B is from the front to the back in FIG. 10. The image sensor 72B further includes an LED and optical components. The longitudinal direction of the image sensor 72B is a direction perpendicular to the sheet transport direction. The image sensor 72B has a plurality of pixels that receive R (red), G (green), and B (blue) light in the longitudinal direction. The image sensor 72B reads the second side, which is the reverse side of the first side of the document (sheet) that is read by the image sensor 72A.

[0039] The image sensor 72B reads the second side of the document (sheet) as follows. Specifically, an LED as a light source irradiates light onto the second side of the document (sheet). The reflected light from the document (sheet) passes through glass and reaches the optical components. The optical components guide the reflected light from the document (sheet) to the image sensor 72B. The image sensor 72B outputs analog read data based on the received reflected light. The image sensor 72B simultaneously reads one line of image in its longitudinal direction. Therefore, the image sensor 72B obtains analog read data for one page of the document (sheet) by performing reading multiple times while conveying the document (sheet). The analog read data is converted into digital read data (second read data) by an A / D conversion circuit (not shown) of the image sensor 72B and output to the control unit 10.

[0040] The timing at which image sensor 72B starts reading is also controlled based on the timing at which the sensor detects the leading edge of the document (sheet). The document (sheet) that has passed through reading position B is discharged onto discharge tray 91 by discharge rollers 89.

[0041] Moreover, the image sensor 72A of this embodiment has an LED as a light source and optical components including a lens, and receives reflected light from the original (sheet) to read the surface of the original (sheet) placed face down on the platen 71. Note that the reading unit 70 may have a housing including an LED and optical components, and an image sensor 72, and may be configured such that the housing including the LED and optical components moves without moving the image sensor 72.

[0042] Next, a method of generating tone correction conditions executed by the CPU 111 of this embodiment according to a control program will be described with a focus on differences from FIG. 7 of the first embodiment. The CPU 111 (calibration unit 400) of this embodiment acquires the reading result of the first side of the test chart from the image sensor 72A in step S702, and acquires the reading result of the second side of the test chart from the image sensor 72B in step S703. The CPU 111 acquires the first read data 453 acquired from the image sensor 72A and the second read data 454 acquired from the image sensor 72B, and stores them in the storage unit 112. The CPU 111 may generate the first reduced data 455 from the first read data 453, and may generate the second reduced data 456 from the second read data 454. At this time, the CPU 111 stores the first reduced data 455 and the second reduced data 456 in the storage unit 112. The processing of the other steps is the same as that of FIG. 7, and therefore will not be described here.

[0043] Furthermore, if the sheet sensor 82 does not detect that an original (sheet) has been placed on the original tray 81 and a read start command is input, it is presumed that an original (sheet) has been placed on the platen 71. Therefore, the image reader 70 executes a known fixed original reading. Since fixed original reading is a known technology, a detailed description will be omitted.

[0044] The document transport device 80 in FIG. 1 does not have a reading unit that reads the second side of the document (sheet) opposite to the first side of the document (sheet) read by the reading unit 70. Therefore, in the image reader 110 in FIG. 1, the user must place the sheet discharged to the discharge tray 91 on the document tray 81 again in order to obtain the read data of both sides of the sheet. On the other hand, in the image reader 110 in FIG. 10, a reading unit that reads the second side of the sheet is also arranged in the document transport device 80. This eliminates the need for the user to place the sheet discharged to the discharge tray 91 on the document tray 81 again. And, since the image reader 110 in FIG. 10 does not require the user to re-place the sheet after one side of the sheet has been read, the problem of both the first read data and the second read data being read data of the non-printed side on which the test image 301 is not formed does not occur.

[0045] Also, in the first to third embodiments and other embodiments, a configuration has been described in which the test chart used to generate the gradation correction conditions is transported and read by the document transport device 80. However, the test chart transported and read by the document transport device 80 is not limited to one for generating the gradation correction conditions, and may be, for example, a test chart for adjusting the transfer conditions for transferring a toner image. In the test chart for adjusting the transfer conditions for transferring a toner image, test images with different transfer conditions are also formed only on one of the first and second surfaces (printing surface 300a) of the sheet P.

[0046] The test chart for adjusting the transfer conditions for transferring the toner image is, for example, a sheet P on which a plurality of test images with different transfer conditions are formed. Here, the transfer conditions are, for example, a transfer voltage applied to the secondary transfer roller 19. The resistance values ​​of the secondary transfer roller 19 and the intermediate transfer body 17 change due to temperature, humidity, and accumulated driving time. If the resistance values ​​of the secondary transfer roller 19 and the intermediate transfer body 17 change, the transfer efficiency decreases, and the density of the output image formed by the image forming apparatus 1 changes. Therefore, the control unit 10 adjusts the transfer conditions based on the read data related to the test chart for adjusting the transfer conditions for transferring the toner image, thereby adjusting the image quality of the output image formed by the image forming apparatus 1.

[0047] <Technical ideas and effects derived from the first to third embodiments> [Point 1] As shown in FIG. 1, the printer 100 functions as an image forming unit that forms a test image 301 for determining gradation correction conditions only on one of the first and second surfaces (printing surface 300a) of the sheet P. The image reader 110 functions as a reading unit that generates read data of the first surface (first read data 453) and read data of the second surface (second read data 454) by reading the first and second surfaces of the sheet P, respectively. The selection unit 410 functions as a selection unit that analyzes the read data of the first surface and the read data of the second surface, and selects read data including the read result of the test image 301 from the read data of the first surface and the read data of the second surface. The generation unit 403 functions as a generation unit that generates gradation correction conditions (e.g., correction table 452) based on the selected read data. In this way, according to this embodiment, both the front and back surfaces of the sheet P are basically read. In particular, in the initial reading process, the user may place the sheet P on the document tray 81 so that the printed surface 300a is visible, or may place the sheet P on the document tray 81 so that the printed surface 300a is not visible. This reduces the burden on the user in placing the sheet P on which the test image is formed. Furthermore, the image forming apparatus 1 selects read data including the read result of the test image 301, and generates gradation correction conditions based on the selected read data. By using the generated gradation correction conditions, the image forming apparatus 1 can correct the gradation characteristics of the output image formed by the image forming apparatus 1 to ideal gradation characteristics.

[0048] [Point 2] The document transport device 80 is an example of an automatic document transport device. The document tray 81 is an example of a loading means on which the sheet P is loaded. The transport rollers 85 are an example of a transport means that transports the sheet loaded on the loading means to the reading means. After the sheet is loaded on the loading means so that the first side is read by the reading means, the sheet is loaded on the loading means so that the second side is read by the reading means. In other words, when the first reading process is completed, the user only needs to turn the sheet P over for the second reading process.

[0049] [Point 3] The display device of the operation unit 150 may function as an output means for outputting a message urging the user to turn the sheet over and place it on the placement means when the first side is read by the reading means. This will allow the user to turn the sheet over without hesitation.

[0050] [Point 4] As described in relation to Fig. 5, the selection unit 410 may perform edge detection on the scanned data of the first side, and select the scanned data of the first side if an edge is present at a predetermined position. The selection unit 410 may perform edge detection on the scanned data of the second side, and select the scanned data of the second side if an edge is present at a predetermined position. As shown in Fig. 5, an edge is present on the outer periphery of the test image 301. Thus, the presence or absence of the test image 301 may be determined by focusing on the edge.

[0051] [Point 5] There may be cases where the read data of the first side does not have an edge at a predetermined position, and the read data of the second side does not have an edge at a predetermined position. For example, such a case may occur if the user forgets to turn over the sheet, or places a sheet other than the test chart on the document tray 81. In this case, the selection unit 410 does not select either the read data of the first side or the read data of the second side. This makes it less likely that an incorrect gradation correction condition will be generated.

[0052] [Point 6] The printer 100 may form a test image and a first mark (e.g., marks 303a and 303b) on only one of the first and second sides. The selection unit 410 may analyze the read data of the first side and the read data of the second side, and select the read data including the first mark from the read data of the first side and the read data of the second side. By forming such a mark, the print side 300a and the non-print side 300b will be easily distinguished.

[0053] [Point 7] 3C, the printer 100 may form the first mark at a position away from the test image 301. This will make it less likely that the first mark will affect the creation of the tone correction conditions.

[0054] [Point 8] The printer 100 may form a second mark different from the first mark on the other of the first and second surfaces without forming the test image 301. By forming such a mark, the printing surface 300a and the non-printing surface 300b can be easily distinguished from each other.

[0055] [Point 9] The selection unit 410 may obtain a histogram for the read data of the first side, and if the histogram obtained for the read data of the first side is a histogram specific to blank paper, select the read data of the second side. The selection unit 410 may obtain a histogram for the read data of the second side, and if the histogram obtained for the read data of the second side is a histogram specific to blank paper, select the read data of the first side. In this embodiment, the test image 301 may be formed only on the print side 300a, and the non-print side 300b may be blank. Therefore, the print side 300a and the non-print side 300b may be easily distinguished based on the histogram.

[0056] [Point 10] The selection unit 410 may obtain a histogram for the read data of the first side, and if the histogram obtained for the read data of the first side is a histogram specific to the test image, select the read data of the first side. The selection unit 410 may obtain a histogram for the read data of the second side, and if the histogram obtained for the read data of the second side is a histogram specific to the test image, select the read data of the second side. In this embodiment, the test image 301 may be formed only on the print side 300a, and the non-print side 300b may be left blank. Therefore, the print side 300a and the non-print side 300b may be easily distinguished based on the histogram.

[0057] [Point 11] The gradation correction conditions may be a one-dimensional gradation correction table (e.g., correction table 452) that converts the gradation characteristics of the input image data to generate output image data. The image processing unit 118 uses the gradation correction table to convert the gradation characteristics of the input image data to generate output image data. The input image data is generated by an image reader or by developing a print job. Alternatively, the input image data may be generated by converting the color space of the image data. The output image data is image data generated to be supplied to a printer. This will bring the gradation characteristics of the input image and the gradation characteristics of the output image formed on the sheet P closer to each other.

[0058] [Point 12] As shown in FIG. 7 etc., the selection unit 410 may analyze the read data of the first side, and select the read data of the first side when the read data of the first side includes the read result of the test image 301. The generation unit 403 may generate the gradation correction condition based on the read data of the first side selected by the selection means. The selection unit 410 may analyze the read data of the second side when the read data of the first side does not include the read result of the test image, and select the read data of the second side when the read data of the second side includes the read result of the test image. The generation unit 403 may generate the gradation correction condition based on the read data of the second side selected by the selection means.

[0059] [Point 13] 8, the selection unit 410 may analyze the read data of the first side and the read data of the second side, respectively, and determine whether the read data of the first side or the read data of the second side includes the read result of the test image. In this way, the selection unit 410 may select the read data including the read result of the test image. The generation unit 403 generates a gradation correction condition based on the read data selected by the selection means.

[0060] [Point 14] 9, when the selection unit 410 selects the scanned data of the first side, the image reader 110 may skip scanning the second side of the sheet, which may reduce the time required for calibration.

[0061] [Point 15] As shown in Fig. 4, the reduction unit 421 functions as a reduction means for generating first reduced data obtained by reducing the read data of the first side and second reduced data obtained by reducing the read data of the second side. The analysis unit 420 functions as an analysis means for analyzing the first reduced data and the second reduced data. The selection unit 410 may select read data including the read result of the test image from the read data of the first side and the read data of the second side based on at least one of the analysis results of the first reduced data and the analysis results of the second reduced data. By analyzing the read data whose size has been reduced in this manner, the analysis time will be shortened.

[0062] [Point 16] The printer 100 functions as an image forming unit that forms an image based on image data. The image reader 110 has a tray on which a sheet is placed and a transport unit that transports the sheet on the tray, and functions as a reading unit that reads the sheet transported by the transport unit. The control unit 10 functions as an acquisition unit that causes the image forming unit to form a test image on one side of a sheet, causes the transport unit to transport the sheet on which the test image is formed, acquires first read data regarding the read result of the first side of the sheet on which the test image is formed, and acquires second read data regarding the read result of the second side different from the first side of the sheet on which the test image is formed. The selection unit 410 functions as a selection unit that selects read data regarding the read result of the test image from the first read data and the second read data acquired by the acquisition unit. The CPU 111 functions as a control unit that controls the density of the output image formed by the image forming unit based on the read data selected by the selection unit.

[0063] The image processing unit 118 may function as a conversion unit that converts image data based on the gradation correction conditions. The control unit (e.g., CPU 111) may generate the gradation correction conditions based on the read data selected by the selection unit. The image forming unit (e.g., printer 100) may form an output image based on the image data converted by the conversion unit.

[0064] The image forming unit (e.g., printer 100) may be controlled based on the image forming conditions (e.g., transfer conditions). The control unit (e.g., CPU 111) may determine the image forming conditions based on the read data selected by the selection unit.

[0065] As illustrated in FIG. 10, the reading means may have a first sensor (e.g., 72A) that reads a first side of the sheet transported by the transport unit, and a second sensor (e.g., 72B) that reads a second side of the sheet.

[0066] The control unit 10 is an example of an information processing device. The control unit 10 may be realized by a personal computer (PC). The control unit 10 may function as an acquisition unit that acquires first read data related to the read result of a first side of a sheet output from a reading device, and acquires second read data related to the read result of a second side of the sheet output from the reading device, which is different from the first side. The control unit 10 may function as a selection unit that selects read data related to the read result of a test image printed on one side of a sheet by a printer from the first read data and the second read data. The control unit 10 may function as a generation unit that generates a gradation correction condition for correcting the gradation characteristic of an image formed by a printer based on the read data selected by the selection unit. As shown in FIG. 10, the control unit 10 may acquire the first read data output from a first sensor of the reading device, and acquire the second read data output from a second sensor of the reading device.

[0067] 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. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0068] 1: image forming apparatus, 10: control unit, 100: printer, 110: image reader

Claims

1. An image forming means for forming an image; an original transport means including a loading tray on which originals are loaded, a transport section which transports the originals loaded on the loading tray, a first reading section which reads an image of the underside of the original on the loading tray while the transport section transports the originals, a discharge section which discharges the originals read by the first reading section, and a discharge tray to which the originals are discharged by the discharge section; a reading means having a platen on which an original is placed and a second reading unit, and when reading the original placed on the platen, reading the original on the platen with the second reading unit while moving the second reading unit, and when reading the original on the loading tray transported by the transport unit, reading an image of an upper surface of the original on the loading tray with the second reading unit while keeping the second reading unit stationary at a reading position; An image forming apparatus characterized in that, when a test image formed on one side of a sheet by the image forming means is read while being transported by the document transport means, the image forming apparatus has a control means for causing both the first reading unit and the second reading unit to read the sheet, and adjusting the image quality of the image formed by the image forming means based on the read image of the side on which the test image is formed, from a first read image of the sheet on which the test image is formed by the first reading unit and a second read image of the sheet on which the test image is formed by the second reading unit.

2. The image data is converted based on the gradation correction conditions. the control means generates the gradation correction condition based on the read image of the surface on which the test image is formed, 2. The image forming apparatus according to claim 1, wherein said image forming means forms an image based on the image data converted by said conversion means.

3. the image forming means is controlled based on image forming conditions, 2. The image forming apparatus according to claim 1, wherein the control unit determines the image forming conditions based on the read image on the surface on which the test image is formed.

4. 2. The image forming apparatus according to claim 1, further comprising a notification unit that notifies an error when neither the first read image nor the second read image is a read image of the surface on which the test image is formed.

5. An information processing device capable of communicating with an image forming device that forms an image, The image forming apparatus includes: an original transport means including a loading tray on which originals are loaded, a transport section which transports the originals loaded on the loading tray, a first reading section which reads an image of the underside of the original on the loading tray while the transport section transports the originals, a discharge section which discharges the originals read by the first reading section, and a discharge tray to which the originals are discharged by the discharge section; a reading means having a platen on which an original is placed and a second reading unit, and when reading the original placed on the platen, reading the original on the platen with the second reading unit while moving the second reading unit, and when reading the original on the loading tray transported by the transport unit, reading an image of an upper surface of the original on the loading tray with the second reading unit while keeping the second reading unit stationary at a reading position; The present invention provides The information processing device includes: an acquiring unit that acquires a first scanned image of a sheet on which a test image is formed by the first reading unit and a second scanned image of the sheet on which the test image is formed by the second reading unit; and a control means for adjusting the image quality of an image formed by the image forming device based on a read image of the surface on which the test image is formed from the first read image acquired by the acquisition means and the second read image acquired by the acquisition means.

6. The image data is converted based on the gradation correction conditions. the control means generates the gradation correction condition based on the read image of the surface on which the test image is formed, 6. The information processing apparatus according to claim 5, wherein the image forming apparatus forms an image based on the image data converted by the conversion means.

7. the image forming apparatus is controlled based on image forming conditions, 6. The information processing apparatus according to claim 5, wherein the control means determines the image forming conditions based on the read image on the surface on which the test image is formed.

8. 6. The information processing apparatus according to claim 5, further comprising a notification unit that notifies an error when neither the first read image nor the second read image is a read image of a surface on which the test image is formed.

Images