JP4274031B2 - Gradation adjustment apparatus, gradation adjustment method, gradation adjustment apparatus control program - Google Patents

Description

  The present invention relates to a gradation adjustment device, a gradation adjustment method, and a gradation adjustment device control program for an image forming apparatus, and more particularly to a technique for realizing a suitable gradation when a medium on which an image is formed is different from a standard one. .

  An image forming apparatus (such as a copying machine or a printer) that forms an image based on image data controls the amount of toner, the amount of ink, and the like based on the image data, thereby converting the image formed on the paper into the image data. A corresponding gradation is generated. For example, in an electrophotographic image forming apparatus, the amount of toner adhering to a latent image is adjusted by controlling the intensity of laser light that forms a charged latent image on a photoreceptor, thereby generating a gradation on a sheet. Is done. In order to perform this control, the image forming apparatus has a correspondence relationship (tone control characteristics) between image data (input value) and a target density (output value) that is a target value of density of toner or the like formed on a sheet. Has a conversion table. For example, in an image forming apparatus that forms an image using toners of four colors of cyan (C), magenta (M), yellow (Y), and black (K), gradation control characteristics are set for each CMYK component. Is done. Then, using these gradation control characteristics for each color component, each color component value of the image data is converted into a target density for each color component, and based on control conditions such as laser light intensity determined according to the target density. Thus, the amount of toner fixed on the sheet is controlled as described above.

  Here, even if an attempt is made to control each part of the image forming apparatus under a predetermined condition, the density of the image actually formed on the sheet is not necessarily constant due to the influence of the usage environment or the aging of the component parts. However, the target concentration is not always achieved. For this reason, the image forming apparatus conventionally holds a density correction table, adjusts the density of the image on the paper based on the table, and performs a process of adapting the actual tone characteristics on the paper to the target tone characteristics. Yes. A gradation adjustment process (calibration) is performed to obtain corrected density data to be stored in the density correction table. In this calibration, a patch chart is formed on a sheet by an image forming apparatus based on reference image data representing a predetermined gradation pattern, and the gradation pattern image represented on the patch chart is read by an image such as a scanner. The image data is converted again by the apparatus. Then, density data that cancels the difference between the gradation characteristics represented in the output image data and the target gradation characteristics is obtained and stored in the density correction table.

  Conventionally, the target gradation characteristics prepared for the image forming apparatus are only those for a predetermined standard paper determined by the manufacturer. One reason is that the load of work for adjusting the variation between image forming apparatuses of the same model performed at the time of shipment by a manufacturer increases unless the type and environment of the paper on which the work is performed are limited.

In order to support image formation on different types of paper, at the time of shipment from the factory, calibration is performed to achieve the target tone characteristics corresponding to standard paper, and a reference chart is created by the image forming device after calibration The following patent document discloses an idea of attaching this to the image forming apparatus. Here, the reference chart is obtained by forming a gradation pattern indicating a target gradation on the target paper on a paper (target paper) different from the standard paper. When the user performs calibration corresponding to the target paper, the patch chart is output by the image forming apparatus, and this is compared with the reference chart, for example, for each highlight section, halftone section, and shadow section. Adjust the image quality parameter so that the patch chart approaches the reference chart.
JP 2001-94809 A

  As described above, a manufacturer of an image forming apparatus assumes a predetermined standard sheet, and only the target gradation characteristics corresponding to the standard sheet are prepared in the image forming apparatus. However, the target paper used by the user is not always the same as the standard paper assumed by the manufacturer, but rather is generally not the same. When calibration for printing on the target paper is performed based on the target gradation characteristics suitable for the standard paper, generally, the gradation that is expressed and the range that is expressed in the color space are in the standard paper Is different. As a result, for example, even if the target paper has a wider color space range that can be output than the standard paper, it may not be fully utilized. Further, the target gradation characteristic indicates a suitable state that becomes a reference in calibration, and there is a problem that it is difficult for the user to perform calibration to adapt to the target paper regardless of the target gradation characteristic.

  Here, when the target sheet corresponds to the reference chart, a suitable state serving as a reference is indicated by the reference chart, so that the calibration work is facilitated. However, it is practically difficult for a manufacturer to prepare a reference chart for every sheet that can be used by the user.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and provides a gradation adjusting device that makes it possible to calibrate an image forming apparatus suitably and easily for various papers that can be selected by a user. The purpose is to provide.

  A gradation adjustment apparatus according to the present invention performs gradation adjustment on an image forming apparatus based on a target gradation characteristic that defines a correspondence relationship between an input value of image data and a target density for image formation. A reference image for inputting, to the image forming apparatus, gradation characteristic setting means for setting a reference gradation characteristic corresponding to a reference image medium, and image data representing a reference image including a predetermined gradation pattern to the image forming apparatus. Input means; and characteristic information acquisition means for acquiring realized gradation characteristic information relating to the gradation realized in the reference image based on the reference image formed on the target image medium in response to the input of the image data. And characteristic information storage means for storing the realized gradation characteristic information relating to the target image medium as medium characteristic information of the target image medium.

  Another gradation adjusting apparatus according to the present invention comprises gradation characteristic generation means for generating the target gradation characteristic corresponding to the target image medium based on the medium characteristic information stored in the characteristic information storage means. It is what you have.

  In the gradation adjustment device according to another aspect of the invention, the characteristic information acquisition unit acquires the realized gradation characteristic information for a sample image formed on a specific image medium, and the characteristic information storage unit includes the characteristic information storage unit. Realized gradation characteristic information is stored as sample image characteristic information.

  Furthermore, in the gradation adjusting apparatus according to the present invention, the characteristic information storage means stores medium identification information for identifying the specific image medium as the sample image characteristic information in association with the corresponding realized gradation characteristic information. To do.

  The gradation adjusting device according to another aspect of the present invention includes gradation characteristic reproducing means for reproducing the target gradation characteristic corresponding to the sample image based on the sample image characteristic information, and the gradation characteristic setting The means sets the reproduced target gradation characteristic in the image forming apparatus.

  A gradation adjustment method according to the present invention is a method for performing gradation adjustment on an image forming apparatus based on a target gradation characteristic that defines a correspondence relationship between an input value of image data and a target density for image formation. A gradation image setting step for setting a reference gradation characteristic corresponding to a reference image medium in the image forming apparatus, and a reference image for inputting image data representing a reference image including a predetermined gradation pattern to the image forming apparatus An input step; and a characteristic information acquisition step for acquiring realized gradation characteristic information relating to the gradation realized in the reference image based on the reference image formed on the target image medium in response to the input of the image data; A characteristic information storage step for storing the realized gradation characteristic information relating to the target image medium as medium characteristic information of the target image medium, and at the time of image formation on the target image medium, It has a gradation characteristic generating step of generating the target gradation characteristics corresponding to the target image medium based on 憶 been said medium characteristic information.

  A gradation adjustment apparatus control program according to the present invention is a gradation adjustment apparatus that performs gradation adjustment on an image forming apparatus based on a target gradation characteristic that defines a correspondence relationship between an input value of image data and a target density for image formation. A gradation characteristic setting procedure for setting a reference gradation characteristic corresponding to a reference image medium in the image forming apparatus, and image data representing a reference image including a predetermined gradation pattern in the image forming apparatus. Based on the reference image input procedure to be input to the image and the reference image formed on the target image medium according to the input of the image data, the acquired gradation characteristic information relating to the gradation realized in the reference image is acquired. A characteristic information acquisition procedure, and a characteristic information storage procedure for storing the realized gradation characteristic information relating to the target image medium as medium characteristic information of the target image medium.

  According to the present invention, the reference image is formed on the target image medium by the image forming apparatus in which the gradation control characteristic (reference gradation characteristic) capable of realizing the target gradation characteristic is set on the reference image medium corresponding to the standard paper. To do. The gradation (realized gradation characteristic information) realized in the reference image reflects characteristics such as the color and density of the target image medium, and this is stored as medium characteristic information of the target image medium. In the subsequent calibration at the time of image formation on the target image medium, the target gradation characteristic generated based on the medium characteristic information is used, so that the image forming apparatus corresponds to the characteristic of the target image medium. Calibration is performed appropriately and easily.

  In addition to the standard paper, the realized gradation characteristic information obtained from the sample image formed on the medium whose medium characteristic information is known (specific image medium) is the state of the image forming apparatus when the sample image is formed. Is stored as characteristic information of the sample image. By performing calibration using the target gradation characteristic generated based on the sample image characteristic information, it is possible to form an image that reproduces the same gradation as the sample image.

  Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings. FIG. 1 is a schematic block diagram of a system constituting a gradation adjusting apparatus according to the present invention. This system includes a multifunction machine 10, a server 12, a client computer 14, and a communication network 16 such as a local area network (LAN) that enables data transmission between them.

  The multifunction machine 10 has a copy function, a printer function, and a scanner function. In particular, with regard to the copy function and the printer function, for example, an image forming apparatus that prints on paper by electrophotography using four color toners of CMYK. is there. The client computer 14 issues a print instruction to the server 12 based on a user operation. The server 12 is a server related to the copy function and printer function of the multifunction device 10, and stores image data requested to be printed by, for example, the client computer 14 via the communication network 16 or the like. Send data to print. In particular, in this system, the server 12 has a function of inputting image data (reference image data) representing a patch chart (reference image) including a predetermined gradation pattern to the multifunction device 10. A gradation pattern is provided for each color of CMYK. Here, the patch chart may be displayed by changing the page for each color, or one page may include gradation patterns of all colors. In addition to the function of setting the gradation control characteristics for determining the correspondence between the image data and the target density for image formation in the multi-function peripheral 10, the server 12 performs arithmetic processing related to gradation adjustment and, as will be described later, It also has a function of generating new gradation control characteristics according to the color and density of the paper surface based on the tone characteristics.

  FIG. 2 shows an outline of processing for generating a target gradation characteristic (target paper gradation characteristic) corresponding to a paper (target image medium, hereinafter referred to as a target paper) used by a user in gradation adjustment using the present system. FIG. First, in this process, the reference gradation characteristics are set in the multifunction machine 10 (S30). The reference gradation characteristic is a gradation control characteristic corresponding to the standard paper (reference image medium) assumed by the manufacturer of the multifunction device 10, and is preset in the multifunction device 10 at the time of shipment from the manufacturer, and represents the characteristic. Information such as parameters is provided to the user by the manufacturer, and is installed in the server 12, for example, and is set from the server 12 to the multifunction device 10 according to the user's instruction. Note that the target gradation characteristics corresponding to the reference gradation characteristics may not be realized simply by setting the parameters representing the reference gradation characteristics in the multifunction apparatus 10 due to changes in each part of the multifunction apparatus 10 over time. More preferably, calibration is performed to adjust the gradation control characteristics of the multifunction machine 10 so that accurate target gradation characteristics are realized. This calibration can be performed by a method similar to the conventional method. That is, the patch chart is printed by the multifunction device 10 in which the parameters of the reference gradation characteristics are set, read by the scanner function of the multifunction device 10, and a density correction table is created based on the image data.

  When the reference gradation characteristics are set in the multifunction machine 10, the user sets the target paper in the paper feed tray of the multifunction machine 10 and instructs the server 12 from the client computer 14 to print the patch chart. Upon receiving an instruction from the client computer 14, the server 12 inputs the reference image data to the multifunction device 10, and the multifunction device 10 patches the target sheet based on the reference image data according to the currently set reference gradation characteristics. The chart is printed (S35).

  The user sets the target paper on which the patch chart is printed in the image reading unit of the multi-function peripheral 10 and instructs the multi-function peripheral 10 to read from the client computer 14. The multifunction machine 10 reads the patch chart printed on the target paper by the scanner function and generates image data realized on the target paper. This image data is transferred to the server 12. The server 12 acquires realized gradation characteristic information representing the gradation realized on the target sheet based on the image data (S40). The server 12 obtains the realized gradation characteristic information for each color of CMYK, and stores this as medium characteristic information of the target paper in a storage unit composed of a hard disk, a semiconductor memory, etc. (S45). In the storage unit, medium characteristic information can be registered for a plurality of types of target sheets.

  This medium characteristic information generation process will be described. FIG. 3 is a schematic graph showing gradations realized on the paper, in which the horizontal axis represents the image data I and the vertical axis represents the measured density D. The measured density D is a density realized on the paper and measured by a scanner or the like, and includes the influence of the color and density of the paper as a base. The multi-function device 10 performs density control in printing the patch chart in step S35 based on the reference gradation characteristics set in step S30. The realized gradation characteristic obtained from the printing result is a curve different from the target gradation characteristic for the standard paper depending on the difference in color and density between the target paper and the standard paper. For example, when the target paper is darker than the standard paper, when a patch chart formed on the target paper is scanned, a curve 50 (function D = fs (I)) representing the target gradation characteristics for the standard paper. ), A curve 52 (function D = ft (I)) having a higher measured density D is measured, and information representing this curve 52 is registered as medium characteristic information.

  The server 12 generates a target gradation characteristic corresponding to the target paper based on the registered medium characteristic information, and uses this to perform calibration when printing on the target paper. For example, the server 12 can use the medium characteristic information as it is as the target gradation characteristic for the target paper.

  Further, the server 12 may use a newly generated characteristic based on the medium characteristic information as the target gradation characteristic. As an example of generating a new characteristic, a target gradation characteristic that realizes a gradation similar to that of a standard sheet can be determined on the target sheet. In this case, the server 12 generates a new gradation control characteristic based on the gradation control characteristic for standard paper set in the multifunction machine 10 in step S30, and uses this as the initial value at the start of calibration of the target paper. By setting the state in the multifunction machine 10, the calibration can be completed promptly. Here, when the gradation control characteristic is expressed by a function of the instruction density D ′ for the multifunction machine 10 and the input data I, and the gradation control characteristic for standard paper is a function D ′ = gs (I), the server 12 For example, the tone control characteristic function gt for the target paper is generated based on the following equation.

(Equation 1)
gt (I) = gs (I) .fs (I) / ft (I)

  Further, the target gradation characteristic for the target paper based on the medium characteristic information may be generated in accordance with the user's designation, and the server 12 causes the user to designate the target gradation characteristic accordingly. May be configured to provide a user interface. For example, as shown in FIG. 3, a graph of medium characteristic information of the target paper or a target gradation characteristic of the standard paper is displayed on the screen, and a desired target gradation characteristic can be drawn on the graph using a mouse or the like. Each point of the curve 52 can be moved by a drag operation, and the curve obtained by the deformation can be taken in as a target gradation characteristic desired by the user.

  The target gradation characteristics for the target paper registered in the server 12 are presented to the user in a selectable manner. For example, when printing on a registered target sheet, the user selects a corresponding target gradation characteristic from the client computer 14, and the server 12 executes calibration based on this target gradation characteristic.

  In the above-described processing, target gradation characteristics are generated and registered for a target sheet that is not a standard sheet. Here, a target gradation characteristic that reflects the state of the image forming apparatus when the sample image is generated is generated from an image (sample image) printed in the past on a specific sheet (specific image medium). You can also In this case, the server 12 acquires the sample image characteristic information based on the image data obtained by reading the sample image representing the gradation with the scanner instead of the medium characteristic information, and registers the sample image characteristic information in the storage unit.

  The sample image characteristic information registered in the server 12 is used for calibration as a target gradation characteristic. By this calibration, it is possible to execute printing that reproduces the gradation characteristics in a situation where the sample image is generated on a specific sheet. This reproduction printing is basically performed on the same specific paper on which the sample image is formed. Therefore, the server 12 stores, as sample image characteristic information, the gradation characteristic read by the scanner and the information for identifying the specific sheet in a set and stores them in the storage unit, which is convenient for the user. As information for identifying a specific sheet, for example, identification information of medium characteristic information corresponding to the specific sheet can be given. In addition, when a sheet on which a sample image is formed is stored, information indicating the sheet can be used as the identification information.

  The above-described gradation adjustment processing is realized by the cooperation of the server 12 and the multifunction peripheral 10, but the processing in the server 12 is realized by a program executed by, for example, a CPU (Central Processing Unit). The program is held in a storage device such as a ROM (Read Only Memory) or a hard disk, and is read and executed when processing is executed.

1 is a schematic block diagram of a system constituting a gradation adjustment device according to the present invention. It is a general | schematic process flow figure regarding the process which produces | generates the media characteristic information in this system. It is a typical graph showing the gradation characteristic implement | achieved on a paper.

Explanation of symbols

  10 MFP, 12 server, 14 client computer, 16 communication network.

Claims (6)

A density correction table is prepared based on a target gradation characteristic that is prepared in advance by a manufacturer and defines a correspondence relationship between an input value of image data and a target density for image formation. A gradation adjustment device that performs gradation adjustment,
A gradation characteristic setting means for setting a reference gradation characteristic corresponding to a reference image medium in the image forming apparatus;
A reference image input means for inputting image data representing a reference image including a predetermined gradation pattern to the image forming apparatus;
Characteristic information acquisition means for acquiring realized gradation characteristic information relating to the gradation realized in the reference image based on the reference image formed on the target image medium in response to the input of the image data;
Characteristic information storage means for storing the realized gradation characteristic information relating to the target image medium as medium characteristic information of the target image medium;
Gradation characteristic generation for generating the target gradation characteristic corresponding to the target image medium from the medium characteristic information stored in the characteristic information storage unit and the reference gradation characteristic set by the gradation characteristic setting unit Means,
A gradation adjustment apparatus that performs gradation adjustment on the image forming apparatus based on the target gradation characteristic corresponding to the target image medium generated by the gradation characteristic generation unit. The gradation adjustment apparatus according to claim 1,
The characteristic information acquisition unit acquires the realized gradation characteristic information regarding the sample image formed on the specific image medium,
The characteristic information storage means stores the realized gradation characteristic information as sample image characteristic information;
The gradation adjusting device characterized by this. The gradation adjusting device according to claim 2,
The characteristic information storage unit stores medium identification information for identifying the specific image medium as the sample image characteristic information in association with the corresponding realized gradation characteristic information. In the gradation adjusting device according to claim 2 or 3,
Based on the sample image characteristic information, has gradation characteristic reproduction means for reproducing the target gradation characteristic corresponding to the sample image;
The gradation characteristic setting means sets the reproduced target gradation characteristic in the image forming apparatus;
The gradation adjusting device characterized by this. A density correction table is prepared based on a target gradation characteristic that is prepared in advance by a manufacturer and defines a correspondence relationship between an input value of image data and a target density for image formation. A gradation adjustment method for adjusting the gradation,
A reference gradation characteristic setting step for setting a reference gradation characteristic corresponding to a reference image medium in the image forming apparatus;
A reference image input step of inputting image data representing a reference image including a predetermined gradation pattern to the image forming apparatus;
A characteristic information acquisition step of acquiring realized gradation characteristic information related to the gradation realized in the reference image based on the reference image formed on the target image medium in response to the input of the image data;
A characteristic information storage step of storing the realized gradation characteristic information relating to the target image medium as medium characteristic information of the target image medium;
At the time of image formation on the target image medium, the target gradation characteristic corresponding to the target image medium from the medium characteristic information stored and the reference gradation characteristic set in the reference gradation characteristic setting step A gradation characteristic generation step for generating
A gradation adjustment method, wherein gradation adjustment is performed on the image forming apparatus based on the target gradation characteristic corresponding to the target image medium generated in the gradation characteristic generation step. A density correction table is prepared based on a target gradation characteristic that is prepared in advance by a manufacturer and defines a correspondence relationship between an input value of image data and a target density for image formation. To the computer that controls the gradation adjustment device that performs gradation adjustment.
A reference gradation characteristic setting procedure for setting a reference gradation characteristic corresponding to a reference image medium in the image forming apparatus;
A reference image input procedure for inputting image data representing a reference image including a predetermined gradation pattern to the image forming apparatus;
A characteristic information acquisition procedure for acquiring realized gradation characteristic information relating to the gradation realized in the reference image based on the reference image formed on the target image medium in response to the input of the image data;
A characteristic information storage procedure for storing the realized gradation characteristic information regarding the target image medium as medium characteristic information of the target image medium;
A gradation characteristic generation procedure for generating the target gradation characteristic corresponding to the target image medium from the stored medium characteristic information and the reference gradation characteristic set in the reference gradation characteristic setting procedure ;
Causing the image forming apparatus to execute a target gradation characteristic setting procedure for setting the target gradation characteristic corresponding to the target image medium generated by the gradation characteristic generation procedure;
A gradation adjusting apparatus control program for performing gradation adjustment on the image forming apparatus based on the target gradation characteristic corresponding to the target image medium generated by the gradation characteristic generating procedure. .

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