JP2006060713A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly read the inspection chart of printing density unevenness. <P>SOLUTION: A printing part 10 prints the inspection chart 200 in which a plurality of belt-like regions extending in a main scanning direction are arranged. Individual belt-like regions on the inspection chart 200 are read by one optical detector on a line sensor provided in a reading/inspection part 18 in accordance with reading vertical scanning by inserting the inspection chart 200 from a manual paper feed tray 14 by changing its direction by 90 degrees. Consequently, the printing density unevenness along the main scanning direction of printing is measured without being influenced by the variation of sensitivity by each optical detector. In the case of this reading, it becomes easy to perform user's work by displaying a guidance picture indicating how the direction of the printed and outputted inspection chart 200 is changed and set on the manual paper feed tray 14 by pattern diagrams. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus including a printing unit that performs color printing and an image reading unit, and more particularly, to correction processing for print density unevenness in a main scanning direction of the printing unit.

  The digital multi-function peripheral includes a printing unit and an image reading unit. Patent Document 1 proposes a method of monitoring the state of the printing unit by reading the print output of the printing unit by the image reading unit. . In this device, in order to correct the shading of the print head of an inkjet printer or LED printer, a test pattern is printed, and the print result is read by an attached image reading unit, so that the ink discharge amount of the inkjet nozzle and the LED emission Density unevenness due to intensity variation or the like is detected and corrected.

  On the other hand, in an electrophotographic laser color printer, the development gap, transfer performance, and the like may slightly change along the main scanning direction, that is, the axial direction of the photosensitive drum. In some cases, fine print density unevenness (in-plane unevenness) appeared. When high quality printing equivalent to offset printing is to be realized, it is necessary to accurately detect and correct such print density unevenness in the main scanning direction.

  For this purpose, for example, a test pattern having a uniform color and density in the main scanning direction is printed on the printing unit, and the printing result is read to measure the distribution of the printing density along the main scanning direction. Preparing a dedicated measuring device for this measurement is a place you would like to avoid if you can see it in terms of cost. As described above, the test pattern printed by the printing unit of the multifunction device is read by the attached reading unit to inspect unevenness. If possible, it is preferable not only in terms of cost but also in terms of work efficiency.

  In addition, in the digital printing system using a sheet as a sheet, the applicant provides a line sensor on a sheet conveyance path subsequent to the print engine, and the line sensor displays an image of the printed surface of the printed sheet being conveyed. A mechanism for determining the presence or absence of missing prints or smudges by comparing the read and read image with the image data of the printed document has been proposed (for example, Japanese Patent Application No. 2003-278091). Japanese Patent Application Laid-Open No. 2004-228561 discloses a mechanism for reading and inspecting an image at a later stage of a printing unit in a printing system using continuous paper. In these mechanisms, since an image reading unit such as a line sensor is provided on the paper conveyance path, it is convenient to be able to measure in-plane unevenness of printing using this.

  However, since the in-plane unevenness which is a problem is quite small, correct correction cannot be performed unless the reading unit reads the data accurately with high accuracy.

  Here, in the case of a reading unit that performs full-color reading, a sensor device is provided for each primary color of R, G, and B, and each of these sensor devices is typically a photosensor (pixel) of a photosensor array manufactured by a semiconductor process. Is covered with a color filter of a corresponding color. Even if the color filter has the same color, the transmittance changes as the thickness changes. A particular problem is that even with the same color filter, the spectral characteristics of the filter differ if the thickness is different. If there is a difference in spectral characteristics, there will be a particularly significant difference in the transparency of the base portion of the spectral response, and this will cause a large difference in sensitivity to light in the wavelength region of the base portion. In this way, even if the photosensor group under the filter is built with uniform performance, if the filter thickness differs between the photosensors, the sensitivity differs between the photosensors.

  For example, when a line sensor is used as the reading unit, if a horizontal width of A4 size is covered, a line sensor having that width is provided for each color of R, G, and B. In this case, in order to obtain a reading resolution of several hundreds dpi (dots per inch), each line sensor has a photosensor for several thousand pixels arranged in a line. It is difficult to form a color filter with a uniform thickness over the entire area of such a long width, and in fact, the filter gradually increases in thickness from one end of the line sensor toward the other end. The thickness of the film becomes uneven (hereinafter referred to as “filter density unevenness”). Since the in-plane unevenness of printing is minute as described above, the sensitivity difference between the photosensors due to the filter density unevenness greatly affects the in-plane unevenness measurement.

  Even with in-plane unevenness of printing, neutral density (grayscale) unevenness is not affected by the spectral characteristics of the filter, so it can be corrected satisfactorily by collecting and correcting the white reference and black reference within the page surface. .

  However, the color component unevenness directly affects the difference in the spectral characteristics of the filters of each photosensor due to the filter density unevenness. Therefore, the detection signal of each photosensor has an effect of the filter density unevenness on the in-plane unevenness of printing. Is superimposed. For this reason, in order to correct the in-plane unevenness, it is necessary to remove the error component due to the filter density unevenness included in the detection signal of the photosensor, so that the correction is not easy.

  FIG. 1 shows an example of spectral characteristics of the R, G, and B filters. This shows the spectral characteristics of the filter as a distribution in the wavelength direction of the relative sensitivity of the photosensor (here, normalized as sensitivity 1 of the photosensor with the R filter). For the sake of explanation, for B, a spectral response graph in the case where a filter with low sensitivity (that is, the filter density is high) is provided (broken line B ′). When the broken line B ′ is compared with the solid line B, there is a difference in relative sensitivity to the extent that it is close to the vicinity of the peak even at the spectral response base (near the wavelength of 500 nm). Accordingly, the detected intensity of the component having a wavelength of around 500 nm differs greatly between a photosensor with a filter with the characteristic of the solid line B and a photosensor with a filter with the characteristic of the broken line B ′. Also, the influence of such filter density unevenness has a difference in spectral characteristics even with the same color material, and varies depending on the print density.

  On the other hand, in Patent Document 3, in a reading apparatus using a multi-chip type sensor that covers a long main scanning section by connecting a plurality of line sensor chips, a correction circuit is provided at the output of each chip. An apparatus that corrects in an analog manner so that the output of each chip becomes uniform by appropriately adjusting the variable resistance is disclosed.

  Japanese Patent Laid-Open No. 2005-228561 prints a strip-shaped test pattern extending along the main scanning direction of the print head for each color of C, M, Y, and K for shading correction of the print head. A method of reading the longitudinal direction (main scanning direction of the print head) in accordance with the sub-scanning direction of the scanner is shown. In this method, the print density distribution along the main scanning direction of the print head can be read in the sub scanning direction with the same photodetector on the scanner's line sensor, so printing that is not affected by the difference in sensitivity of individual photodetectors. A concentration distribution can be obtained.

JP 2003-072206 A Japanese Patent Application Laid-Open No. 11-078183 Japanese Unexamined Patent Publication No. 62-293877

  When trying to realize the method of Patent Document 1, it is necessary to set a printed test pattern in an appropriate direction and cause the scanner to read it. However, Patent Document 1 does not consider measures from such a viewpoint.

  An image forming apparatus according to the present invention includes a printing unit that prints an image on a sheet and a line sensor in which a plurality of photodetectors are arranged, and the line sensor and a sheet to be read are read by the line sensor. An image reading unit that performs two-dimensional reading of the sheet by relative movement in a direction perpendicular to the scanning direction, a display unit that performs display for a user interface, and a density that extends in the main scanning direction of the printing unit A chart printing control unit that causes the printing unit to print an inspection chart including a uniform band-like region, and a print result of the inspection chart output by the printing unit under the control of the chart printing control unit is set in the image reading unit. A guidance display control unit for displaying a guidance screen for guiding the direction on the display on the display unit, and a printing result of the inspection chart by the printing unit, Based on the detection signal of each photodetector when the image reading unit reads the image in a state where the scanning direction is set to be the sub-scanning direction of the image reading unit, the band-shaped region in the inspection chart A main scanning print density distribution calculating unit for obtaining a print density distribution in the main scanning direction of the printing unit.

  An image forming apparatus according to the present invention includes a printing unit that prints an image on a sheet, and a line sensor in which a plurality of photodetectors are arranged, and the line sensor and a sheet to be read are connected to the line sensor. An image reading unit that performs two-dimensional reading of the sheet by relative movement in a direction perpendicular to the reading scanning direction, and an inspection chart that includes a band-like region having a uniform density extending in the main scanning direction of the printing unit. A chart printing control unit to be printed by the printing unit, and a printing result of the inspection chart by the printing unit in a state where the main scanning direction in the inspection chart is set to an orientation in which the sub scanning direction of the image reading unit is set. Based on the detection signal of each photodetector when the image reading unit reads the image, the print density distribution in the main scanning direction of the printing unit of the band-like region in the inspection chart is obtained. A main scanning print density distribution calculating unit, wherein the chart printing control unit includes a printing display on the inspection chart including a guidance display indicating a direction in which a printing result of the inspection chart is set in the image reading device. To print.

  An image forming apparatus according to the present invention includes a printing unit that prints an image on a sheet, and an image reading unit that is provided at a subsequent stage of the printing unit on a common sheet conveyance path with the printing unit. A line sensor in which photodetectors are arranged along the main scanning direction of the printing unit, and the line sensor and the sheet to be read are moved relative to each other in a direction perpendicular to the main scanning direction. An image reading unit that performs two-dimensional reading, a chart printing control unit that causes the printing unit to print an inspection chart including a strip-shaped region extending in the main scanning direction of the printing unit and having a uniform density, and on the paper conveyance path The inspection unit is provided between the printing unit and the image reading unit, and when the printing unit prints the inspection chart under the control of the chart printing control unit, the inspection chip is fed from a paper conveyance path from the printing unit. The test chart rotating unit that receives the print result of the print sheet and changes the orientation by 90 degrees and sends it to the paper conveyance path toward the image reading unit; and the inspection chart rotated by the inspection chart rotating unit Main scanning printing density for obtaining a printing density distribution in the main scanning direction of the printing portion of the band-like region in the inspection chart based on the detection signal of each photodetector when the image reading portion is caused to read the result A distribution calculation unit.

  The best mode for carrying out the present invention (hereinafter referred to as “embodiment”) will be described below with reference to the drawings.

  First, a configuration of an example of an image forming apparatus to which the present invention is applied will be described with reference to FIG. The image forming apparatus includes a printing unit 10, a paper feeding unit 12, a manual feed tray 14, a display unit 16, a reading / inspecting unit 18, and an output tray 19. The printing unit 10 incorporates an electrophotographic print engine, and prints digital print data in full color on a sheet. The print engine is of a tandem engine type having a photosensitive drum for each color of C, M, Y, K, for example. The paper feed unit 12 is a unit that stores paper and supplies the paper to the printing unit 10. The manual feed tray 14 is a tray for manually feeding paper and documents to the printing unit 10 and the reading / inspecting unit 18. The display unit 16 forms a part of a UI (user interface) device of the image forming apparatus, and displays an operation screen, an apparatus state, and the like. The reading / inspection unit 18 optically reads the printing result of the printing unit 10 and performs inspection processing such as collating the reading result with the original print data, thereby inspecting the quality of the printing result.

  The reading / inspecting unit 18 is provided with an image reading unit 28 (see FIG. 3) including line sensors for reading colors such as R, G, and B. The paper conveyance path of the image forming apparatus starts from the paper supply unit 12, passes through the print engine in the printing unit 10, and further passes through the reading target range of the image reading unit 28 in the reading / inspection unit 18 to the output tray 19. It extends. As shown in FIG. 4, the line sensors 102, 104, and 106 for R, G, and B colors in the image reading unit 28 have the arrangement direction of the photodetectors 110 (that is, the main scanning direction of the image reading unit 28). The sheet is disposed so as to be perpendicular to the sheet conveying direction in the sheet conveying path. Therefore, the image reading unit 28 generates the two-dimensional read image data of the printed paper by repeating the signal reading in the main scanning direction as the printed paper is conveyed. By checking the read image data against the original image to be printed indicated by the print data, inspection such as missing prints or dirt is performed.

  The output tray 19 is a tray that outputs a print result. Although only one output tray 19 is shown in the drawing, two or more output trays 19 are provided, and those determined as non-defective and defective as a result of inspection by the reading / inspection unit 18 are output to separate trays. You can also do it.

  In the present embodiment, in such an image forming apparatus, the reading / inspection unit 18 detects minute unevenness (in-plane unevenness) of the print density in the main scanning direction of the printing unit 10 so that it can be corrected. . The internal configuration of the image forming apparatus for this purpose is shown in FIG.

  In FIG. 3, the overall control unit 20 is a control unit that controls each unit of the image forming apparatus illustrated in FIG. 2 to realize the function of the image forming apparatus. In order to avoid complexity, the figure shows arrows indicating the flow of control only for the print control unit 24 and the image reading unit 28, but the overall control unit 20 also controls other units.

  The UI unit 22 is a user interface mechanism. In addition to the display unit 16 in FIG. 1, a key for inputting instructions and numerical values, and a mechanism for detecting the touch position of the user when the display unit 16 is a touch panel. Etc. A content instructed by the user from the UI unit 22 is closely related to the present embodiment, which includes a calibration mode instruction. The calibration mode is a mode for calibrating the registered data content of the print correction parameter 32. When this mode is instructed, the inspection chart is printed and read, and the print correction parameter 32 is calibrated based on the read result. Is done. A mode in which print data (or an original image read by a scanner device not shown) supplied from the outside via a network is printed on a sheet is referred to as a normal mode. In FIG. 3, the arrows connecting the functional blocks indicate the data flow, the solid line indicates the flow in the normal mode, and the alternate long and short dash line indicates the flow in the calibration mode.

  The print control unit 24 is a unit that controls the print engine 26 in the printing unit 10 to execute color printing. The image reading unit 28 is built in the reading / inspecting unit 18 and optically reads a printed sheet moving on the sheet conveyance path as described above to generate read image data.

  The storage device 30 is a nonvolatile storage device such as an EEPROM (Electronically Erasable and Programmable Read Only Memory) or a hard disk device. The storage device 30 stores data such as print correction parameters 32 and inspection chart information 34.

  The print correction parameter 32 is a group of parameters for correcting the print performance of the print engine 26. For example, a tone reproduction curve (or a look-up table for density conversion based thereon) of each primary color is a typical example. Further, in order to suppress minute in-plane unevenness, the pixel value of the print data is corrected according to the pixel position along the main scanning direction of the print engine 26, or the ROS (raster output scanner) for exposure is used. It is also possible to correct the laser output according to the pixel position along the main scanning direction, and correction data for each pixel position for that purpose is also stored as a part of the print correction parameter 32.

  The inspection chart information 34 is information such as image data of an inspection chart used for calibration of the print correction parameter 32 or a code that defines the image.

  FIG. 5 shows an example of an inspection chart. The inspection chart 200 shown in FIG. 5 includes belt-like regions 202-1, 202-2,..., 202-M (M is an integer) for each primary color. Expressed by the difference in pattern. Each belt-like region 202 is a belt long in the main scanning direction of the print engine 26, and the length along the main scanning direction is equal to the print width of the print engine 26 in the main scanning direction. In addition, the individual band-like regions 202 are uniform in color and density. When such data of the inspection chart 200 is supplied to the print engine 26 and printed, ideally, the individual band-like regions should have uniform colors and densities, but are minute along the main scanning direction. Print density unevenness may appear. A method for detecting such unevenness will be described later.

  It is also preferable that the inspection chart 200 includes a high-order color band-like region in which two or more primary colors are mixed. If the number of colors to be inspected is too large to fit on a single inspection chart, printing is performed on a plurality of sheets. When the inspection chart is printed on a plurality of sheets, it is preferable to print information indicating the order such as a serial number for each sheet.

  FIG. 6 shows an example of the types of colors placed on the inspection chart. Each “pattern” in the table shown in FIG. 6 is an individual single-color area (that is, a patch or a band-like area) in the inspection chart, and has a different print color. The color of each “pattern” is expressed by a combination of the densities of the color materials C, M, Y, and K. Here, the density levels of each color material are three levels of 0%, 50%, and 100%. However, the density level can be further increased, and the number of “patterns” in the inspection chart increases as the number of levels increases. Increase.

  The “color” of the pattern in the inspection chart is different from each other if the coordinates in the color space are different, but in the print engine that prints by performing halftone screening, even if the coordinates in the color space are the same, If the applied screenset changes, the visual color may change. Therefore, patterns with different screen sets may be handled as different colors.

  Returning to the description of FIG. 3 again, the parameter calibration processing unit 40 prints the print correction parameter based on the value of each pixel of the read image data output from the image reading unit 28 in the calibration mode (that is, the detection signal of each photodetector). Calibrate. In particular, in this embodiment, parameters for correcting print density unevenness in the main scanning direction of the print engine 26 are calibrated.

  FIG. 7 is a flowchart showing a procedure for correcting print density unevenness in the image forming apparatus of the present embodiment. Hereinafter, the print density unevenness correction process will be described with reference to FIG.

  In the image forming apparatus according to the present embodiment, when the user instructs the calibration mode from the UI unit 22, the overall control unit 20 instructs the print control unit 24 to print the inspection chart 200. In response to this, the print control unit 24 generates a raster image of the inspection chart 200 from the inspection chart information 34 in the storage device 30, and causes the print engine 26 to print it (S10).

  When the inspection chart 200 can be printed, as shown in FIG. 8, the user rotates the inspection chart 200 from the position on the output tray 19 by 90 degrees, sets the inspection chart 200 on the manual feed tray 14, and reads by the reading / inspection unit 18. (S14). As a specific processing system, for example, in the correction table calibration mode, when the user presses the start button of the image forming apparatus after the inspection chart printout is finished, the document set on the manual feed tray 14 is taken into the apparatus. The printing unit 10 may simply add it without printing, and the reading / inspection unit 18 may read the document.

  However, at this time, the user needs to set the inspection chart 200 on the manual feed tray 14 in the correct orientation. In order to support the user's work, in the present embodiment, the overall control unit 20 displays a guidance screen as shown in FIG. 9 on the display unit 16 (S12). The guidance screen 300 in FIG. 9 schematically shows how the inspection chart 200 is oriented in relation to the image forming apparatus, and further displays a message indicating the operation content to be performed by the user, for example, “output to output tray” "Turn the chart 90 degrees as shown in the figure below, place it in the manual feed tray, and press the start button." This display is performed after printing the inspection chart 200 (S10). When the user performs an operation according to this display, the reading process of S14 is performed.

  As described above, when the inspection chart 200 is rotated 90 degrees and read, in this image forming apparatus, the printing unit 10 and the reading / inspection unit 18 match the main scanning direction. And the reading of the reading / inspection unit 18 are interchanged between the main scanning and the sub scanning. Here, in the two-dimensional reading method in which the line sensor and the sub scanning are combined, each point on the line in the sub scanning direction is always read by the same photodetector. Therefore, according to this reading, each point on the line along the main scanning direction of printing of the inspection chart 200 is read in the sub-scanning direction by the same photodetector. Since it is not necessary to consider the density unevenness of the on-chip filter with the same photodetector, the series of detection signals (image data) along the sub-scanning direction of the photodetector is in the main scanning direction of printing. The data represents the print density unevenness along the line. The parameter calibration processing unit 40 creates the printing unevenness table 42 based on the image data output by the image reading unit 28 at this time (S16).

  FIG. 10 shows an example of data registered in the print unevenness table 42 at this time. In FIG. 10, a column number i is an index in the reading sub-scanning direction, for example, a serial number assigned to each main scanning line in the sub-scanning direction. On the other hand, the line number b is an index in the main scanning direction of reading, and the number of lines M is the total number of patterns printed on the inspection chart (the total number of patterns on each sheet when printing in plural sheets). is there. That is, in the inspection chart, the 1st to Mth band-like regions are arranged in the main scanning direction of reading, and therefore one row is assigned to each band-like region in the table 42.

  The value Dcbi ′ shown in the cell of each row and column is the light detector of the line sensor of the channel c (any one of R, G, and B) in the i-th main scanning line in the reading sub-scan. This is an average value of detection signals output from a group of photodetectors corresponding to the b-th band-shaped region (pattern) of the inspection chart 200.

  In other words, the arrangement order of the strip regions in the inspection chart 200 can be understood from the inspection chart information 34 stored in the storage device 30. Therefore, if the user has set the inspection chart 200 in the correct orientation according to the instruction shown on the display unit 16 or the like, the number of the detector group from the number to the number along the main scanning direction is the band number region. Can be determined by the parameter calibration processing unit 40. The parameter calibration processing unit 40 outputs the detection signals of the respective photodetectors sequentially supplied from the image reading unit 28 during one main scanning for a certain sub-scanning position, to the width of the band-like region (that is, the sub-scanning position). The number of detection signals of the number of consecutive photodetectors corresponding to the width in the scanning direction) is averaged, and the average value is written in the position corresponding to the band-like region b and the sub-scanning position i of the table 42. Note that the inspection chart 200 may be slightly tilted or displaced from the correct set state. In such a case, the photodetector corresponding to the vicinity of the boundary line of each belt-like region may have a band-like region to be originally read. It is possible to read the adjacent band-like area. Therefore, in such a case, in order to reduce the influence of such a reading error, in this averaging process, the detection signals of a predetermined number of photodetectors corresponding to the boundary portion of the band-like region are not considered in the averaging process. It is also preferable to do so. The printing unevenness table 42 is completed by repeating the above processing for the entire sub-scanning range. FIG. 10 shows a table for one line sensor channel, and this table is actually created for each of the R, G, and B channels.

  When the print unevenness table 42 is created, the parameter calibration processing unit 40 calibrates the correction parameter for the print density unevenness in the print correction parameter 32 based on the table 42 (S18). In the correction of the print density unevenness correction parameter, the correction parameter is corrected so that the value of each pixel along the main scanning direction of the read image data becomes uniform. The correction parameter to be corrected here may be a parameter for correcting the density of the pixels in the image data, or may be a parameter for correcting the laser output of the ROS according to the pixel position along the main scanning direction.

  According to the embodiment described above, the print density unevenness in the main scanning direction of the print engine 26 can be obtained from the series of detection signals in the sub-scanning direction of the same photodetector in the image reading unit 28. The print density unevenness can be obtained without being affected by the sensitivity variation due to the density unevenness of the on-chip color filter of the photodetector. By using such accurate print density unevenness information, it is possible to appropriately calculate and set parameters for correcting the print density unevenness. In the present embodiment, since the guidance screen 300 for explaining the direction in which the inspection chart 200 printed by the printing unit 10 is set on the image reading unit 28 is displayed on the UI unit 22, the user refers to it. Work properly.

  The embodiment described above is merely an example, and various modifications can be made within the scope of the present invention.

  For example, in the above-described embodiment, the guidance screen 300 is displayed on the UI unit 22 in order to support the operation of setting the inspection chart 200 printed by the printing unit 10 on the image reading unit 28. As shown in FIG. 5, if the inspection chart 200 itself includes a mark 204 indicating a position to be aligned with the reference position (“registration (registration)” position) of the manual feed tray 14, the print result is displayed. It is clear to the user which direction the paper should be set in the manual feed tray 14. Here, the portion of the four corners of the inspection chart 200 that is aligned with the registration position is indicated by the mark 204, but this is only an example. Any display may be used as long as it indicates the orientation (posture) in which the inspection chart 200 is set.

  The method for displaying the guidance screen 300 and the method for incorporating the mark 204 into the inspection chart 200 are not limited to the apparatus shown in FIG. 2 for loading a document to be read from the manual feed tray 14, but a general digital copying machine. The present invention can also be applied to an apparatus having a flat bed image reading unit or an image reading unit with an automatic document feeder on the upper surface of the apparatus.

  Further, in all of the above examples, the printed inspection chart 200 is set in the image reading unit 28 by the user in an appropriate orientation, but it is of course possible to execute it by a mechanical mechanism. is there. For example, Japanese Patent Laying-Open No. 05-301659 by the present applicant shows a paper direction changing device that changes the direction of a paper to be conveyed. This is to change the direction of the printed paper output from the print engine in a direction suitable for the subsequent processing when post-processing such as paper folding on the printed paper. It is diverted to change the direction for reading. In this case, the paper direction changing device is provided between the printing unit 10 and the reading / inspecting unit 18 of the image forming apparatus of FIG. The paper conveyance path reaches from the printing unit 10 to the reading / inspecting unit 18 through the paper direction changing device. When the calibration mode is designated, the overall control unit 20 causes the paper direction changing device to rotate the direction of the chart 200 by 90 degrees at the timing when the inspection chart 200 printed by the printing unit 10 reaches the paper direction changing device. Give instructions. According to such a configuration, the inspection chart 200 can be read in an appropriate orientation without intervention of the user's hand.

  In addition, the examples so far have dealt with the in-plane unevenness of the on-chip color filter, but the in-plane caused by the spectral field angle characteristics of the interference filter such as the color filter constituting the dichroic prism or the infrared cut filter. It can cope with unevenness as well.

  Further, the present invention is not limited to a reading device including a sensor having a plurality of reading lines in one sensor package, but can be applied to a reading device including independent sensors for each color, such as a dichroic prism system.

It is a figure for demonstrating the difference in the spectral characteristics of a photodetector. 1 is a diagram illustrating a schematic configuration of an image forming apparatus to which a technique of an embodiment is applied. 1 is a diagram illustrating a main part of a functional configuration of an image forming apparatus according to an embodiment. It is a schematic diagram which shows the example of the line sensor assembly provided in an image reading part. It is a figure which shows an example of an inspection chart. It is a figure which shows the example of the combination of the color of a test | inspection chart. 4 is a flowchart illustrating a procedure for correcting print density unevenness in the image forming apparatus according to the embodiment. It is a figure for demonstrating the direction at the time of setting an inspection chart to a manual feed tray. It is a figure which shows the example of a display of the guidance screen for assisting the operation | work which sets an inspection chart to a manual feed tray. It is a figure which shows an example of the data content of a printing nonuniformity table.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Print part, 12 Paper feed part, 14 Manual feed tray, 16 Display part, 18 Reading / inspection part, 19 Output tray, 20 Overall control part, 22 UI part, 24 Print control part, 26 Print engine, 28 Image reading part, 30 storage device, 32 printing correction parameter, 34 inspection chart information, 40 parameter calibration processing unit, 42 printing unevenness table.

Claims (3)

A printing section for printing an image on paper;
A line sensor having a plurality of photodetectors arranged therein, and two-dimensional reading of the sheet is performed by relatively moving the line sensor and the sheet to be read in a direction perpendicular to the reading scanning direction of the line sensor. An image reading unit for performing
A display unit for displaying for a user interface;
A chart printing control unit that causes the printing unit to print an inspection chart including a band-like region having a uniform density extending in the main scanning direction of the printing unit;
A guidance display control unit that displays on the display unit a guidance screen that guides the orientation when setting the print result of the inspection chart output by the printing unit under the control of the chart printing control unit in the image reading unit;
Each result when the image reading unit causes the image reading unit to read the print result of the inspection chart by the printing unit in a state in which the main scanning direction in the inspection chart is set to be in the sub-scanning direction of the image reading unit. A main scanning print density distribution calculating unit for obtaining a print density distribution in the main scanning direction of the printing unit of the belt-like region in the inspection chart based on a detection signal of a photodetector;
An image forming apparatus comprising: A printing section for printing an image on paper;
A line sensor having a plurality of photodetectors arranged therein, and two-dimensional reading of the sheet is performed by relatively moving the line sensor and the sheet to be read in a direction perpendicular to the reading scanning direction of the line sensor. An image reading unit for performing
A chart printing control unit that causes the printing unit to print an inspection chart including a band-like region having a uniform density extending in the main scanning direction of the printing unit;
Each result when the image reading unit causes the image reading unit to read the print result of the inspection chart by the printing unit in a state in which the main scanning direction in the inspection chart is set to be in the sub-scanning direction of the image reading unit. A main scanning print density distribution calculating unit for obtaining a print density distribution in the main scanning direction of the printing unit of the belt-like region in the inspection chart based on a detection signal of a photodetector;
And the chart printing control unit causes the printing unit to print the inspection chart including a guidance display indicating a direction in which the printing result of the inspection chart is set in the image reading apparatus. apparatus. A printing section for printing an image on paper;
An image reading unit provided at a subsequent stage of the printing unit on a common paper conveyance path with the printing unit, comprising a line sensor in which a plurality of photodetectors are arranged along a main scanning direction of the printing unit, An image reading unit that performs two-dimensional reading of the sheet by relatively moving the line sensor and the sheet to be read in a direction perpendicular to the main scanning direction;
A chart printing control unit that causes the printing unit to print an inspection chart including a band-like region having a uniform density extending in the main scanning direction of the printing unit;
On the paper conveyance path, provided between the printing unit and the image reading unit, and when the printing unit prints the inspection chart under the control of the chart printing control unit, from the paper conveyance path from the printing unit An inspection chart rotating unit that receives the print result of the inspection chart, changes the direction by 90 degrees, and sends it to the paper conveyance path toward the image reading unit;
The printing of the band-like region in the inspection chart based on the detection signal of each photodetector when the image reading unit reads the printing result of the inspection chart whose direction is changed by the inspection chart rotating unit. A main scanning print density distribution calculating unit for obtaining a print density distribution in the main scanning direction of the part;
An image forming apparatus comprising:

Images