JP2013121152A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform optimal tone correction even for a special type of paper that is not plain paper such as glossy paper, or small size paper.SOLUTION: After confirming the set paper size in starting tone correction, it is made possible to perform tone correction for any of the set paper size. To accommodate every paper size, a plurality of layout patterns for a patch for density measurement for paper used for tone correction are stored in advance in a storage device in an image forming apparatus so that tone correction can be performed even if paper used for toner correction is divided into a plurality of pieces.

Description

  The present invention relates to an image forming apparatus having a gradation correction function for maintaining an optimum output image.

  Image forming apparatuses such as copiers, printers, and fax machines require tone reproducibility that faithfully reproduces the tone from the low density part to the high density part of the formed image, and always outputs the image density constant. There is a need. Various image forming apparatuses have an optimum relationship between input density and output density.

  However, in the current image forming apparatus, the gradation characteristics of the engine in the image forming apparatus may change depending on the environmental conditions in which the image forming apparatus is installed and changes with time. When the tone characteristics of the engine change, printing is performed in a state where the actual output with respect to the input is not optimal. Since it is difficult to always maintain the gradation characteristics using only the engine, a method of performing gradation correction using a controller in the apparatus is now available in image forming apparatuses. First, a specific patch with a predetermined input density is formed on the image carrier such as a photosensitive drum to recognize the state of the gradation characteristics of the engine, the formed patch is read, and the read density value is calculated. Notify the controller. The controller notified of the density value obtains the difference between the optimum density input / output relationship and the current engine input / output relationship, and changes the operation of the circuit that determines the image forming conditions in the controller to compensate for the difference. Tone correction is performed.

  As such a tone correction function, a tone correction patch indicating the current density state of the engine is applied to the paper at a fixed position, and then the paper output with the density measurement patch is output, Scan the paper, read the patches, and measure the density. Based on the input / output relationship between the actually measured density information and the optimum density, the controller performs tone correction to change the operation of the circuit that determines the image forming conditions so that printing can be continued with optimum image quality. Technology to make it out. However, depending on the characteristics of the image forming apparatus or the size of the paper, there are cases where a fixed patch cannot be transferred. In that case, there is a system in which gradation correction is made by changing the layout of patches for gradation correction, and gradation correction has been made possible (see, for example, Patent Document 1).

JP 2000-305730 A

  However, in the conventional gradation correction system, gradation correction can be performed by changing the layout of the density measurement patch. However, the size of the target medium is small, and all the density measurement patches are included in one sheet. If not, gradation correction cannot be performed. Therefore, if the paper is a special medium such as glossy paper instead of plain paper, and the size is also special, it is difficult to procure paper of the paper size used in the conventional gradation correction, and gradation correction cannot be performed. Or, even with gradation correction, correction is performed on another sheet, and gradation is corrected in accordance with the characteristics of the other sheet, so gradation correction cannot be performed along the characteristics of the special sheet. There was a problem.

An image forming apparatus having a function of reading a document and a function of performing gradation correction for suppressing fluctuations in color of an image,
Means for dividing and outputting a plurality of sheets on which density measurement patches embedded with density information necessary for gradation correction are printed;
An image forming apparatus characterized in that gradation correction is performed by scanning each sheet.

  Since gradation correction can be performed even on paper of a special size, it is possible to obtain an output with an optimum gradation maintained on any media.

FIG. 1 is a typical external view of an embodiment of an image forming apparatus according to the present invention. Overall flowchart from start to end of tone correction in the present invention An example of a screen displayed on the operation unit in the flow of S1 in FIG. An example of a screen displayed on the operation unit in the flow of S4 in FIG. A block diagram showing a basic configuration in an image forming apparatus that determines a layout of a density measurement patch during gradation correction An example of gradation correction paper layout when the number of gradation correction required is one sheet An example of gradation correction paper layout when the number of gradation correction required is two

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  The image forming apparatus forms an electrostatic latent image on an image carrier by an electrophotographic method, an electrostatic recording method, etc., and this electrostatic latent image is developed and visualized by a developing device using a two-component developer. Any configuration may be used as long as the configuration forms an image.

  FIG. 1 is an external view of an image forming apparatus according to the present invention. The image forming apparatus main body 100, an operation unit 101 for inputting settings to the user when display or gradation correction is performed for the setting state of the apparatus, processing in the current apparatus, or the like. A document table 102 for placing a gradation correction chart, a paper feed stage 103 for storing paper for gradation correction, paper fed from the paper feed stage 103, and printed according to the set conditions. A paper discharge stage 104 for storing the discharged paper.

  The printer controller 401 performs gradation correction by changing the operation of the circuit for determining the image forming conditions. The method for changing the operation of the circuit for determining the image forming conditions is an LUT (Look Up Table). Refers to generation.

  The LUT indicates an output density allocation table for input densities. In the present invention, the image forming apparatus is started from a state in which gradation correction is set from the operation unit 101 at an arbitrary timing on the user side. The image forming apparatus that has been set to perform gradation correction displays a UI on the operation unit 101 so that the user can select a paper feed stage that stores paper used for gradation correction (S1). The image forming apparatus selected by the user as the paper feed stage storing the paper used for gradation correction recognizes the size of the paper stored in the paper feed stage and is necessary for performing the gradation correction. The number of sheets and the patch layout corresponding to the number of sheets are set (S2). The image forming apparatus that has obtained the number of sheets necessary for the gradation correction notifies the user of the number of sheets necessary for the gradation correction through the operation unit 101 (S3). After the notification, the user is allowed to set whether or not gradation correction can be performed using the operation unit (S4).

  If not implemented is set, the gradation correction mode is terminated. When the execution is set, the paper is fed from the paper feed tray set in S1 (S5), and the correction patch is discharged in the image forming apparatus (S6). The discharged sheet is set on the document table 102, and the image forming apparatus whose scan start is pressed from the operation unit 101 scans the sheet (S7). In S2, since the layout for setting the number of sheets necessary for correction and the patch for density measurement is set in the image forming apparatus, it is determined whether or not the density measurement patch according to the layout is received (S8). If a sheet that does not match the layout is scanned, the user is notified to set the sheet having the appropriate patch applied, and the scanning is performed again (S9). If it is determined that an appropriate sheet has been scanned, an LUT necessary for gradation correction is generated based on the density information of the density measurement patch (S10). When S10 is completed, it is confirmed whether or not the number of scanned sheets has reached the number set in S2 (S11). Repeatedly (S12), if reached, the tone correction is terminated.

(Tone correction chart layout setting means)
FIG. 5 is a block diagram showing a basic configuration of the image forming apparatus according to the embodiment of the present invention.

  The image forming apparatus has a plurality of functions such as an image reading function, an image forming function, and an image communication function. By executing each function, it is possible to execute a print job for forming an image on a print medium and a scan job for reading an image from a document. Further, various jobs such as a fax job for performing image communication with an external apparatus and a copy job for forming an image read from a document on a print medium can be executed. The image forming apparatus includes a CPU 501, ROM 502, RAM 503, external storage device 504, display unit 505, operation unit 506, engine I / F 507, network I / F 508, external I / F 509, and system bus 510.

  The CPU 501 is a central processing unit that performs overall control or arithmetic processing of the image forming apparatus, and executes each process described below based on a program stored in the ROM 502. A ROM 502 is a read-only memory, and is a storage area for a startup program for starting the image forming apparatus, a program for controlling the printer engine, and character code information. A RAM 503 is a random access memory, and a program and data are loaded and executed for each of various processes in the image forming apparatus. The RAM 503 can also be used as a storage area for the chart layout pattern in the gradation correction of the present invention. The external storage area 504 is composed of a hard disk or the like and stores the layout pattern of the chart in gradation correction, parameters, various programs, information data, image data, attribute signals, etc., as well as the RAM 503, and a working area. Or used as

  The display unit 505 performs display using a liquid crystal or the like, and is used to display a setting state of the image forming apparatus, processing in the current image forming apparatus, an error state, and the like. The operation unit 506 is used for setting / changing or resetting various functions, and is used together with the display unit 505 when operating print settings during output. The engine interface 507 is an interface for actually exchanging commands and the like for notifying control and engine status between the printer controller and the printer engine. A network interface 508 is an interface for connecting the image forming apparatus to the network via the network interface 508. The external interface 509 is connected to the host computer via a serial or parallel interface. The system bus 510 should be a data path between the above-described components.

  The density measurement patch layout pattern for gradation correction confirms the size information of the paper loaded in the paper feed stage stored in the RAM 503 when the paper feed stage set by the user is selected on the operation unit 505. To do. After confirmation, an appropriate pattern is compared with the paper size set based on the layout pattern stored in the RAM 503 or the external storage device 504. Several types of layout patterns to be stored are prepared in advance, and the number of charts necessary for gradation correction corresponding to each layout pattern is also stored in advance as in the layout pattern. 6 and 7 are examples of the layout pattern of the density measurement patch. Needless to say, the layout pattern of the density measurement patch may be appropriately created in accordance with the characteristics of the image forming apparatus.

601 Density measurement patch
701 Density measurement patch

Claims (3)

An image forming apparatus having a function of reading a document and a function of performing gradation correction for suppressing fluctuations in color of an image,
Means for dividing and outputting a plurality of sheets on which density measurement patches embedded with density information necessary for gradation correction are printed;
An image forming apparatus comprising means for correcting gradation by scanning each sheet. Means (S1) for allowing the user to select a paper feed stage (103) on which paper used for gradation correction is mounted when performing gradation correction;
2. The image forming apparatus according to claim 1, further comprising means (S4) for grasping the required number of sheets and notifying the user of the number of sheets necessary for correction (S3) and allowing the user to confirm whether or not correction is performed. . And a means for changing the layout of the density measurement patch so that a density measurement patch suitable for the size can be applied after the size of the paper feed stage used for correction at the time of gradation correction is recognized (S2). The image forming apparatus according to 1.