JP2010098491A - Image forming apparatus, and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus etc., that enables a user who adjusts picture quality to easily balance a gradation and suitably adjust the picture quality even when operating without any special awareness. <P>SOLUTION: The image forming apparatus includes a storage section 500 which stores a test document for picture quality adjustment and optical reflection density information thereof, an image forming section 100 which outputs the test document as a printed image, an image read section 200 which optically reads the printed-out print image along a readout line, and a picture quality adjustment section which controls the print picture quality by comparing the optical reflection density of the stored test document with the optical reflection density of the printed-out print image. In the image forming apparatus, the test document includes two or more identical gradation patches, and the readout line of the image read section is put off a center virtual line in a gradation patch of the test document in a document width direction perpendicular to the conveying direction of the test document. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a test document for adjusting image quality and a storage unit for storing optical reflection density information thereof, an image forming unit for outputting the test document as a printed image, and optically printing the printed image printed according to a reading line. The present invention relates to an image forming apparatus having an image reading unit to be read and an image quality adjusting unit that controls the print image quality by comparing the optical reflection density of the test document with the optical reflection density of a printed image that has been printed out.

  In an electrophotographic image forming apparatus, in order to form a toner image, a one-component developing system using one-component toner, and a two-component developing apparatus using a two-component developer including a non-magnetic toner and a magnetic carrier It is divided roughly into.

  The one-component development method is suitable for downsizing, but is not suitable for high-speed development. Therefore, in a high-speed and long-life image forming apparatus, a two-component development device is almost adopted. In this type of developing apparatus using a two-component developer, the carrier itself in the two-component developer is not consumed and remains in the apparatus, but does not decrease. However, the toner is consumed and decreased. Therefore, in order to stabilize the image quality, the toner is appropriately replenished so that the toner concentration of the two-component developer is kept constant.

  Also, the image forming apparatus changes the print image quality under the influence of deterioration of the photoconductor and developer and changes in environmental conditions. Therefore, various image quality adjustments (process control or process control) are used to prevent this phenomenon. In recent years, these adjustment modes are implemented even when the image forming apparatus is not used for a long time. Also, during the period of regular maintenance, the service person adjusts the image quality using a test chart or the like.

  For example, in Patent Document 1, in a color image processing system including a color image scanner and a full color printer, a test sheet composed of a plurality of color patches is printed out from a printer, and the test sheet is automatically read by an image scanner. In performing color balance adjustment, a color balance adjustment pre-processing method is disclosed, in which when the test sheet on which the color patch is printed is read, the status of the printer or the test sheet is diagnosed.

Specifically, when the test sheet is set, if the front or back side or the positional relationship is not appropriate, a warning is issued to prompt the user to re-set or detect the position attached to the test sheet prior to reading the color patch. It is described that the read timing of the patch is adjusted while logically correcting the skew on the memory by reading the mark for use and setting the relative position of the color patch.
JP-A-9-186899

  However, since the cross balance is used as the position detection mark in the color balance adjustment pre-processing method of Patent Document 1, the position accuracy is very high, but the cross itself is an image forming condition caused by deterioration of the photoconductor and developer. Due to this, it gets thinner and thicker every time it is printed. Therefore, the position detection has a drawback that it is difficult.

  However, in order to increase the position detection accuracy, it is necessary to increase the resolution of the image reading unit (image scanner), which causes problems such as a decrease in reading processing speed and an increase in cost. there were.

  In view of the above-described problems, the present invention has an object that when a user performs image quality adjustment, even if an operation is performed without the user being particularly conscious, a simple gradation balance can be obtained and the image quality can be appropriately adjusted. It is to provide an image forming apparatus and the like that can be adjusted.

  In order to solve the above-described problems, an image forming apparatus according to the present invention includes a test document for adjusting image quality and a storage unit that stores optical reflection density information thereof, an image forming unit that outputs the test document as a print image, Image quality adjustment for controlling the print image quality by comparing the optical reflection density of the test document and the optical reflection density of the printed image printed with the image reading unit that optically reads the printed image printed according to the reading line The test document has two or more same gradation patches, and the reading line in the image reading unit is tested from the central virtual line in the gradation patch of the test document. The document is removed in the document width direction perpendicular to the document conveyance direction.

  The image forming apparatus according to the present invention is characterized in that when the reading line in the image reading unit is removed in the document width direction perpendicular to the document conveyance direction, the reading line is removed in different directions.

  In the image forming apparatus of the present invention, the test document further includes a position detection patch corresponding to a gradation patch, and the image reading unit sets a reading line based on the position detected by the position detection patch. It is characterized by determining.

  The image forming apparatus of the present invention is characterized in that the position detection patch is provided on a central virtual line of a gradation patch of a certain color.

  In the image forming apparatus according to the aspect of the invention, the image quality adjustment unit may perform tone correction using a dither value of each tone patch.

  An image forming method of the present invention stores a test document for adjusting image quality and optical reflection density information of the test document, outputs an image of the test document as a printed image, and optically prints the printed image printed according to a reading line. In the image forming method, the method includes: a reading step for reading the image; and an image quality adjustment step for controlling the print image quality by comparing the optical reflection density of the test document with the optical reflection density of the printed image printed. Has two or more of the same gradation patches, and the reading line in the reading step extends from the central virtual line in the gradation patch of the test document in the document width direction perpendicular to the conveyance direction of the test document. It is characterized by removing.

  According to the present invention, a test document for adjusting image quality and a storage unit that stores optical reflection density information thereof, an image forming unit that outputs the test document as a print image, and optically printing the printed image printed out according to a reading line. An image forming apparatus comprising: an image reading unit that automatically reads; and an image quality adjusting unit that controls the print image quality by comparing the optical reflection density of the stored test document with the optical reflection density of the printed image that has been printed out. The test document has two or more same gradation patches, and the reading line in the image reading unit is arranged in a direction perpendicular to the transport direction of the test document from the central virtual line in the gradation patch of the test document. It will be removed in the document width direction. As a result, even if the test document is placed obliquely, any gradation patch can be read, and gradation balance can be achieved with almost one operation.

  Further, according to the present invention, when the reading line in the image reading unit is removed in the document width direction perpendicular to the document conveyance direction, the reading line is removed in different directions. Therefore, even if the test document is tilted in any direction, the gradation patch can be read.

  According to the invention, the test document further includes a position detection patch corresponding to a gradation patch, and the image reading unit determines a reading line based on a position detected by the position detection patch. Can do. Thereby, the gradation patch can be read more reliably by using the position detection patch.

  Further, according to the present invention, the position detection patch is provided on the center virtual line of the gradation patch of a certain color. Accordingly, since the reading line can be used also as the position of the gradation patch of a certain color, it is not necessary to perform an extra position correction process.

  Further, according to the present invention, the image quality adjustment unit can easily perform correction with an exponent value by correcting the gradation with the dither value of each gradation patch.

  Embodiments of the present invention will be described below with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: It is not the thing of the character which limits the technical scope of this invention.

[1. Device configuration]
First, the configuration of the image forming apparatus 1 in the present embodiment will be described with reference to FIG. FIG. 1 is an explanatory diagram showing a simple configuration of an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 that is a main body apparatus forms multicolor and single color images on a sheet based on read image data of a document or image data transmitted through a network or the like. Here, the image forming apparatus 1 includes an image forming unit 100 and an image reading unit 200. First, the configuration of the image forming unit 100 will be described.

[1.1 Configuration of image forming unit]
The image forming unit 100 includes an exposure unit E, a photosensitive drum (corresponding to the image carrier of the present invention) 101 (101a to 101d), a developing device 102 (102a to 102d), a charging roller 103 (103a to 103d), Cleaning unit 104 (104a-104d), intermediate transfer belt 11, primary transfer roller 13 (13a-13d), secondary transfer roller 14, fixing device 15, paper transport paths P1, P2, P3, paper feed cassette 16, manual feed A paper tray 17 and a paper discharge tray 18 are provided.

  The image forming unit 100 corresponds to four hues of cyan (C), magenta (M), and yellow (Y), which are three subtractive primary colors obtained by color separation of a black (K) and color image. Image formation is performed in the image forming color portions Pa to Pd using the image data. The image forming color portions Pa to Pd have the same configuration. For example, the black image forming black portion Pa includes a photosensitive drum 101a, a developing device 102a, a charging roller 103a, a transfer roller 13a, a cleaning unit 104a, and the like. . The image forming color portions Pa to Pd are arranged in a line in the moving direction (sub-scanning direction) of the intermediate transfer belt 11.

  The charging roller 103 is a contact-type charger that uniformly charges the surface of the photosensitive drum 101 to a predetermined potential. Instead of the charging roller 103, a contact type charger using a charging brush or a non-contact type charger using a charging wire may be used. An exposure unit E which is an exposure apparatus of the present invention includes a semiconductor laser, a polygon mirror 4, a first reflection mirror 7, a second reflection mirror 8, and the like (not shown), and images of hues of black, cyan, magenta and yellow. Each of the photosensitive drums 101a to 101d is irradiated with a light beam such as a laser beam modulated by data. On each of the photosensitive drums 101a to 101d, an electrostatic latent image is formed based on image data of each hue of black, cyan, magenta, and yellow.

  The developing device 102 supplies toner to the surface of the photosensitive drum 101 on which the electrostatic latent image is formed, and develops the electrostatic latent image into a toner image. Each of the developing devices 102a to 102d contains toner of each hue of black, cyan, magenta, and yellow, and the electrostatic latent image of each hue formed on each of the photosensitive drums 101a to 101d is black, cyan. Then, the toner images are visualized as magenta and yellow toner images. The cleaning unit 104 removes and collects toner remaining on the surface of the photosensitive drum 101 after development and image transfer.

  The intermediate transfer belt 11 disposed above the photosensitive drum 101 is stretched between the driving roller 11a and the driven roller 11b to form a loop-shaped movement path. The outer peripheral surface of the intermediate transfer belt 11 faces the photosensitive drum 101d, the photosensitive drum 101c, the photosensitive drum 101b, and the photosensitive drum 101a in this order. Primary transfer rollers 13a to 13d are arranged at positions facing the respective photosensitive drums 101a to 101d with the intermediate transfer belt 11 interposed therebetween. Each of the positions where the intermediate transfer belt 11 faces the photosensitive drums 101a to 101d is a primary transfer position. The intermediate transfer belt 11 is formed of a film having a thickness of about 100 to 150 μm.

  The primary transfer rollers 13a to 13d have constant voltage control of a primary transfer bias opposite to the charging polarity of the toner in order to transfer the toner images carried on the surfaces of the photosensitive drums 101a to 101d onto the intermediate transfer belt 11. Applied. As a result, the toner images of each hue formed on the photosensitive drum 101 (101a to 101d) are sequentially transferred to the outer peripheral surface of the intermediate transfer belt 11, and a full color toner image is formed on the outer peripheral surface of the intermediate transfer belt 11. Is done.

  However, when image data of only a part of the hues of yellow, magenta, cyan, and black is input, some of the four photosensitive drums 101a to 101d corresponding to the hue of the input image data. Only the photosensitive drum 101 forms an electrostatic latent image and a toner image. For example, when forming a monochrome image, an electrostatic latent image and a toner image are formed only on the photosensitive drum 101 a corresponding to the black hue, and only the black toner image is transferred to the outer peripheral surface of the intermediate transfer belt 11. Is done.

  Each of the primary transfer rollers 13a to 13d is configured by covering the surface of a shaft made of a metal (for example, stainless steel) having a diameter of 8 to 10 mm with a conductive elastic material (for example, EPDM, urethane foam, or the like). A high voltage is uniformly applied to the intermediate transfer belt 11 by the elastic material.

  The toner image transferred to the outer peripheral surface of the intermediate transfer belt 11 at each primary transfer position is conveyed to a secondary transfer position that is a position facing the secondary transfer roller 14 by the rotation of the intermediate transfer belt 11. The secondary transfer roller 14 is pressed against the outer peripheral surface of the intermediate transfer belt 11 whose inner peripheral surface is in contact with the peripheral surface of the driving roller 11a at a predetermined nip pressure during image formation. When the paper fed from the paper feed cassette 16 or the manual paper feed tray 17 passes between the secondary transfer roller 14 and the intermediate transfer belt 11, the polarity of the toner charged on the secondary transfer roller 14 is opposite to that of the toner. The high voltage is applied. As a result, the toner image is transferred from the outer peripheral surface of the intermediate transfer belt 11 to the surface of the sheet.

  Of the toner adhering to the intermediate transfer belt 11 from the photosensitive drum 101, the toner remaining on the intermediate transfer belt 11 without being transferred onto the paper is removed by the cleaning unit 12 in order to prevent color mixing in the next process. Collected.

  The sheet on which the toner image has been transferred is guided to the fixing device 15, and passes between the heating roller 15a and the pressure roller 15b to be heated and pressurized. As a result, the toner image is firmly fixed on the surface of the paper. The paper on which the toner image is fixed is discharged onto the paper discharge tray 18 by the paper discharge roller 18a.

  In the image forming unit 100, a substantially vertical direction for feeding the paper stored in the paper feed cassette 16 to the paper discharge tray 18 between the secondary transfer roller 14 and the intermediate transfer belt 11 and via the fixing device 15. Paper transport path P1 is provided. In the paper transport path P1, a pickup roller 16a that feeds the paper in the paper feed cassette 16 one by one into the paper transport path P1, a transport roller r that transports the fed paper upward, and the transported paper A registration roller 19 that guides between the secondary transfer roller 14 and the intermediate transfer belt 11 at a predetermined timing, and a paper discharge roller 18 a that discharges the paper to the paper discharge tray 18 are disposed.

  Further, inside the image forming unit 100, a paper conveyance path P2 in which a pickup roller 17a and a conveyance roller r are arranged is formed between the manual paper feed tray 17 and the registration roller 19. Further, a paper transport path P3 is formed between the paper discharge roller 18a and the upstream side of the registration roller 19 in the paper transport path P1.

  The paper discharge roller 18a is rotatable in both forward and reverse directions, and is used for forming a single-sided image for forming an image on one side of a sheet and for forming a second-side image in forming a double-sided image for forming an image on both sides of a sheet. Driven in the forward direction, the paper is discharged to the paper discharge tray 18. On the other hand, when the first side image is formed in the double-sided image formation, the paper discharge roller 18a is driven in the normal rotation direction until the rear end of the paper passes the fixing device 15, and then the rear end of the paper is sandwiched. Driven in the reverse direction, the paper is guided into the paper transport path P3. As a result, the paper on which the image is formed on only one side when the double-sided image is formed is guided to the paper transport path P1 with the front and back surfaces and the front and rear ends reversed.

  The registration roller 19 performs secondary transfer of paper fed from the paper feed cassette 16 or the manual paper feed tray 17 or transported via the paper transport path P3 at a timing synchronized with the rotation of the intermediate transfer belt 11. Guided between the roller 14 and the intermediate transfer belt 11. For this reason, the registration roller 19 stops rotating when the operation of the photosensitive drum 101 and the intermediate transfer belt 11 is started, and the sheet fed or conveyed prior to the rotation of the intermediate transfer belt 11 has the front end at the registration roller 19. The movement in the sheet conveyance path P1 is stopped in a state where the sheet 19 is in contact with the sheet 19. Thereafter, the registration roller 19 is a position where the secondary transfer roller 14 and the intermediate transfer belt 11 are in pressure contact with each other, at a timing when the front end portion of the sheet and the front end portion of the toner image formed on the intermediate transfer belt 11 face each other. Start spinning.

  At the time of full color image formation in which image formation is performed in all the color portions Pa to Pd of image formation, the primary transfer rollers 13a to 13d press the intermediate transfer belt 11 against all of the photosensitive drums 101a to 101d. On the other hand, during monochrome image formation in which image formation is performed only in the image formation black portion Pa, only the primary transfer roller 13a is brought into pressure contact with the intermediate transfer belt 11 against the photosensitive drum 101a.

[1.2 Configuration of Image Reading Unit]
Next, the configuration of the image reading unit 200 provided on the upper part of the image forming unit 100 will be described. The image reading unit 200 is provided with a platen glass (original platen) 210 made of transparent glass on which an original is placed, and an automatic original reader 220 is attached to the upper side of the platen glass 210. The automatic document reader 220 automatically conveys the document on the platen glass 210.

  The automatic document reader 220 is configured to be rotatable in the direction of the arrow M, and the document can be placed manually by opening the top of the platen glass 210.

  The automatic document reader 220 includes a document tray on which a document is placed. The document placed on the document tray is fed and conveyed one by one by a pickup roller and a feeding roller. Then, the original is read as image data by passing through the original reading window.

  Specifically, when the document passes through the document reading window, the surface of the document is exposed by the light source lamp 201 of the scanning unit, and an image of the document surface is formed on a CCD (Charge Coupled Device) 202 via a mirror. To do. The CCD 202 repeatedly reads an image on the document surface in the main scanning direction, and outputs image data indicating the image on the document surface.

  When the document is placed on the platen glass (document placing table) 210, the scanning unit moves at a predetermined speed to expose the document surface on the platen glass 210, and similarly expose the document surface. Then, an image of the document surface is formed on the CCD 202 via the mirror.

[2. Functional configuration]
Next, the functional configuration of the image forming apparatus 1 will be described with reference to FIG. As shown in FIG. 2, the image forming apparatus 1 includes a CPU 1000, an image forming unit 100, an image reading unit 200, an operation unit 300, a display unit 400, a storage unit 500, and an image memory 600. It is configured.

  A CPU 1000 (Central Processing Unit) is a functional unit that performs various operations and controls of the image forming apparatus 1. Each process is realized by reading and executing various programs stored in the image forming apparatus 1.

  The image forming unit 100 is a functional unit for forming an image based on the image data stored in the image memory 600 and recording (printing) it on a recording sheet. The image reading unit 200 is placed on a document table. It is a functional unit that reads the read original and outputs it to the image memory 600 as image data. The image forming unit 100 and the image reading unit 200 are as described above.

  The operation unit 300 includes a display unit that displays information necessary for operation, a touch panel unit on which information such as a control command is input by a user operation, a numeric keypad, and the like. In addition, various setting information, operation status, and the like in the image forming apparatus 1 are displayed on the display unit 400, so that the user is notified.

  The storage unit 500 is a functional unit that stores various data and programs for operating the image forming apparatus 1. The CPU 1000 executes a control process by reading and executing a control program stored in the storage unit 500.

  The storage unit 500 stores an image quality adjustment program 510 and patch gradation data 520. The CPU 10 implements the image quality adjustment process (FIG. 3) by reading and executing the image quality adjustment program 510.

  The patch gradation data 520 stores gradation data relating to patches read by the image reading unit 200. By using the patch gradation data 520, the image quality in the image forming apparatus 1 is adjusted.

  The storage unit 500 stores image data of a test document for adjusting the image quality of the document. In response to an instruction from the user, the CPU 1000 outputs the test document stored in the storage unit 500 from the image forming unit 100.

  The image memory 600 is a memory that temporarily stores image data. Specifically, the image data generated by the image reading unit 200 is once stored in the image memory 600. Then, the image data to be printed is output to the image forming unit 100.

[3. Explanation of image quality adjustment operation]
Next, an operation for specifically adjusting image quality will be described with reference to the drawings. First, an example of a test document P200 for color adjustment is shown in FIG. In the present embodiment, the test document P200 has two yellow (Y), magenta (M), and cyan (C) colors, and two black (K) gradation patches (17 gradations). .

  Further, two position detection patches P210 and P212 are provided on the leading end side in the reading direction (conveyance direction) of the test document P200. Here, as shown in FIG. 3, the transport direction is the direction in which the test document is read, and the document width direction is the direction of the width of the test document that is perpendicular to the transport direction (in FIG. Direction).

  The position detection patch is provided on the same straight line as the gradation patch, and the center part of the gradation patch and the center part of the position detection patch are arranged on the same straight line. The line that virtually connects the center portions of the gradation patches is called a center virtual line, and the center virtual line passes through the center portions of the position detection patch and the gradation patch.

  First, in the case of FIG. 3, the image reading unit 200 reads an image (tone patch) using the central virtual line as a reading line. By reading the image along the center imaginary line, all the gradation patches used for image quality adjustment can be read.

  This will be specifically described with reference to FIG. As the test document is conveyed, the image reading unit 200 reads the test document. Then, first, the position detection patch P210 is detected. Here, a straight line passing through the center of the position detection patch P210 is detected as a central imaginary line, and a reading line L310 (two-dot chain line in FIG. 5) is set on the central imaginary line. Then, along the reading line L310, the image reading unit 200 reads the gradation patch P230 from the gradation patch P220.

  Similarly, when the position detection patch P212 is detected, a reading line L312 is set at the center of the position detection patch P212, and the gradation patches P222 to P232 are read along the reading line L312.

  FIG. 6 is a diagram for explaining a case where the test document is placed obliquely. In this case, when the center portion of the position detection patch is set as a reading line, all gradation patches cannot be read.

  That is, after the position detection patch P210 is detected, the reading line L310 is set at the center of the position detection patch P210. In this case, the gradation patch P220 can be read, but the gradation patch P230 cannot be read.

  Similarly, when the reading line L312 is set at the center of the position detection patch P212 after the position detection patch P212 is detected, the gradation patch P222 can be read, but the gradation patch P232 is read. I can't.

  Therefore, the case where the present invention is applied will be described with reference to FIG. As shown in FIG. 7, the central imaginary line passing through the center of the position detection patch P210 is L320. A reading line L330 is set at a position shifted from the test document by a predetermined amount. Similarly, the center imaginary line passing through the center of the position detection patch P212 is L322. A reading line L332 is set at a position shifted from the original width direction by a predetermined amount. That is, the reading line is set off the central virtual line.

  Here, the width (amount) for shifting the reading line from the central virtual line is set in advance, but may be variable by the user. Further, the maximum width shifted as the reading line is limited to a range in which the position detection patch can be detected.

  Furthermore, reading accuracy can be improved by making the readable area M210 smaller than that in FIG. In FIG. 7, as an example, by setting it as small as 4.1 mm square, it is possible to improve the reading accuracy as compared with FIG.

  Further, when there are two or more position detection patches, it is possible to cover the placed document in both directions by shifting the reading line in the opposite direction from the central virtual line.

  The entire document will be described with reference to FIG. When the position detection patch P210 is detected, the reading line L340 is set by shifting the position detection patch P210 from the center of the position detection patch P210 to the outside in the document width direction (upward of the paper) by a predetermined amount. When the position detection patch P212 is detected, the reading line L342 is set while being shifted from the center of the position detection patch P212 by a predetermined amount to the outside in the document width direction (downward of the sheet).

  Here, all the gradation patches cannot be read on the reading line L340, but all the gradation patches can be read on the reading line L342.

  In this way, by shifting the reading line from the center of the position detection patch in the document width direction (remove it from the center virtual line), even if the test document is not placed correctly, the gradation patch can be read at once. Therefore, it is possible to perform appropriate image quality adjustment.

  In the present embodiment, the two reading lines are described as being shifted. However, it is possible to shift only one reading line.

  Further, the two reading lines have been described as being shifted in opposite directions (outside the paper), but may be shifted in the same direction. For example, when the orientation of the test document is determined in the image reading unit 200, it is possible to accurately determine the placement error of the test document and to properly read the gradation patch by shifting in the same direction. Become.

[4. Process flow]
Next, image quality adjustment processing in the image forming apparatus 1 will be described with reference to FIG. The image quality adjustment processing of FIG. 9 is realized by the CPU 1000 reading and executing the image quality adjustment program 510.

  First, when it is detected that the image quality button on the operation unit 300 has been pressed by the user (step S10), a test document is printed (step S12). Then, it is determined whether or not the printed test document is placed on the image reading unit 200 (step S14).

  Here, when placed on the image reading unit 200 (step S14; Yes), the test document is scanned (step S16). Here, the fact that the test document is placed may be placed on the automatic document reading device 220 or on the platen glass (document placing table) 210, for example.

  If there is a test document placement error, the printed document is read again (step S18; Yes → step S14). On the other hand, if there is no test document placement error, the scanned patch gradation data is stored in the storage unit 500 (patch gradation data 520).

  Subsequently, 17 patch data of 4 colors (K, C, M, Y) are measured from the left to the right of the page, and the read patch data is analyzed for each measurement line, and the density gradually increases. The measured data is analyzed / extracted (step S22). Thereafter, the standard density value of the test document stored in advance and the measurement data are compared, and the correction amount is calculated (step S24).

  Specifically, the optical reflection density of each patch when the test document is normally arranged in advance is measured using an actual image forming apparatus, and the measured optical reflection density is stored as a standard value. Thereby, the difference from the standard value is calculated. Based on the calculated correction amount (correction value), solid density correction and gradation correction are performed (step S26), and the image quality adjustment process is terminated. As the implementation content, solid image density and halftone image density (gamma characteristic) taking development characteristics into consideration are performed.

  Here, various methods for correcting the image density of a specific halftone patch can be considered. In this embodiment, the dither values of 17 halftone patches are changed. . For example, as shown in FIG. 10, an index for the dither value max960 is preset for each color (K, C, M, Y). Control is performed so that the initial dither value is corrected at the time of image quality adjustment.

  Further, the scanning process in step S16 will be further described with reference to FIG. First, when a position detection patch is detected from a test document (step S50; Yes), a central virtual line is determined (step S52). Here, the center imaginary line is a straight line in the document transport direction passing through the center of the position detection patch.

  Subsequently, a reading line is determined by shifting a predetermined amount in the document width direction from the central virtual line (step S54). Here, for the reading line, for example, an amount to be shifted in the image forming apparatus 1 is specified in advance (for example, “3 mm”), and the reading line is determined at a position shifted outward from the central virtual line by the predetermined amount. The

  Various methods are conceivable as methods for determining the reading line. For example, a boundary portion (outside of the test document) of the position detection patch may be detected, and a position including the boundary portion may be used as the reading line.

  Subsequently, the gradation patch is read based on the reading line (step S56). Here, when all the gradation patches of the same gradation can be read, it is determined that the scanning is successful (step S58; Yes → step S60), and when all the gradation patches of the same gradation cannot be read, the scanning is failed. Determination is made (step S58; No-> step S62).

  In step S50, even when the position detection patch cannot be detected, it is determined that the scan has failed (step S50; No → step S62).

  As described above, according to the present embodiment, it is possible to appropriately read the gradation patch even when the test document is placed at an inclination due to a placement error. For this reason, even when a user with little knowledge of image quality adjustment performs, gradation balance can be achieved with almost one operation.

[5. Modified example]
The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  In the above-described embodiment, two gradation patches (position detection patches) have been described. Of course, three or more gradation patches may be provided. In this case, the gradation patch can be read more appropriately by shifting the position of the reading line corresponding to each gradation patch.

  In the above-described embodiment, the position detection patch is provided on the same straight line as the gradation patch, but the position of the position detection patch is shifted in the document width direction from the center line of the gradation patch. It does not matter.

1 is a cross-sectional view of an image forming apparatus in the present embodiment. FIG. 2 is a diagram for describing a functional configuration of an image forming apparatus in the present embodiment. It is a figure for demonstrating the test original document in this embodiment. It is a figure for demonstrating the operation | movement in this embodiment. It is a figure for demonstrating the operation | movement in this embodiment. It is a figure for demonstrating the operation | movement in this embodiment. It is a figure for demonstrating the operation | movement in this embodiment. It is a figure for demonstrating the operation | movement in this embodiment. It is a figure which shows an example of the image quality adjustment process in this embodiment. It is a figure which shows an example of the dither value in this embodiment. 6 is an operation flow for explaining document scanning processing in the present embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 100 Image forming part Pa-Pd Image forming each color part 200 Image reading part 300 Operation part 400 Display part 500 Storage part 510 Image quality adjustment program 520 Patch gradation data 600 Image memory

Claims (6)

A storage unit for storing image quality adjustment test originals and optical reflection density information thereof, an image forming unit for outputting the test originals as print images, and an image reading unit for optically reading the print output printed according to a read line And an image quality adjustment unit that controls the print image quality by comparing the optical reflection density of the test document and the optical reflection density of the printed image that is printed out.
The test document has two or more same gradation patches,
An image forming apparatus characterized in that a reading line in the image reading unit is removed from a central virtual line in a gradation patch of a test document in a document width direction perpendicular to the test document transport direction.   The image forming apparatus according to claim 1, wherein when the reading line in the image reading unit is removed in the document width direction perpendicular to the document conveyance direction, the image forming unit removes the reading line in different directions. The test document further includes a position detection patch corresponding to the gradation patch,
The image forming apparatus according to claim 1, wherein the image reading unit determines a reading line based on a position detected by the position detection patch.   The image forming apparatus according to claim 3, wherein the position detection patch is provided on a central virtual line of a gradation patch of a certain color.   The image forming apparatus according to claim 1, wherein the image quality adjustment unit performs gradation correction based on a dither value of each gradation patch. An image forming step for storing a test document for image quality adjustment and optical reflection density information thereof, and outputting the test document as a printed image, an image reading step for optically reading the printed image printed according to a reading line, and In an image forming method comprising: an image quality adjustment step for controlling a print image quality by comparing an optical reflection density of a test document and an optical reflection density of a printed image printed out;
The test document has two or more same gradation patches,
An image forming method characterized in that a reading line in the image reading step is removed from a central virtual line in a gradation patch of a test document in a document width direction perpendicular to the test document transport direction.

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