JP2008058415A - Image forming apparatus and control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that makes a density adjustment by itself, the apparatus being designed so as to perform an adjustment process with appropriate content in accordance with the trigger of the density adjustment, and to provide a control method. <P>SOLUTION: The gradation value of image data for each color is corrected based on gradation correction information, and based on the corrected gradation value, the image forming apparatus forms an image. This image forming apparatus includes: a detection means that detects a state requiring a density adjustment process for updating gradation correction information; a determining means that, when the state is detected, determines the number of patch patterns for use as color examples according to the type of the detected state; and an adjusting means that, after the determination of the number of patch patterns, forms the determined number of patch patterns from image data for the corresponding patch patterns having the respective gradation values and updates the gradation correction information based on the colorimetry result of each of the formed patch patterns and the gradation value of the image data of each patch pattern. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and the like that perform density adjustment by itself, and more particularly, to an image forming apparatus and the like that can execute an adjustment process with appropriate contents according to the cause of execution of density adjustment.

  In general, in an image forming apparatus such as a printer, image formation is performed by discharging ink or supplying toner to a print medium based on image data represented by density gradation values of each color. For each density gradation value in the image data, the image forming process is performed so that the density (color value) of the image actually formed on the print medium becomes a predetermined standard value (target value). Made. In general, image forming apparatuses such as printers differ for each apparatus, and the relationship (density characteristics) between the density gradation value and the color value actually output to the density gradation value differs for each apparatus. . Therefore, when the apparatus is shipped, color correction information (for example, a gradation correction table) that matches the density characteristics of the apparatus is determined. At the time of image formation, for each density gradation value of the target image data, Color correction processing based on the color correction information is performed.

  However, even in such an image forming apparatus, use of the image causes changes in the environment, aging of each part, etc., and changes in the state of an engine part that actually forms an image on a print medium. Along with this, the above-described density characteristics also change, so that it is necessary to appropriately adjust the initial color correction information in order to keep the output result at the target value.

  Therefore, conventionally, calibration for density adjustment is performed at a predetermined timing. In such calibration, first, a plurality of patch patterns (color samples) are formed by changing the tone value of image data for each color of a color material (toner or ink) used in the image forming apparatus. Then, the density (color value) of each patch pattern is measured, and the color correction information (for example, for example) is corrected so that the difference between the target value planned for the gradation value of each patch and the actual measurement value is corrected. (Tone correction table) is updated.

For example, Patent Document 1 below proposes an apparatus and method that can appropriately perform density correction of a formed image in an image forming apparatus for all input density levels.
JP 2001-251510 A

  In the calibration for density adjustment described above, if the number of patch patterns used as color samples is increased, the accuracy of density adjustment can be improved. The time required for processing is in a trade-off relationship. In addition, there are various incentives for executing the density adjustment processing, such as turning on the image forming apparatus, printing a predetermined number of sheets, and user requests. It depends on these incentives.

  However, in the conventional image forming apparatus, the number of patch patterns to be used is fixed, and if the number is large, the density adjustment can be performed with high accuracy, but it always takes processing time. Although the processing can be completed in a short time, it is impossible to adjust the density with high accuracy. Therefore, it cannot be said that the conventional apparatus performs the density adjustment with the contents suitable for the respective incentives.

  Moreover, in the said patent document 1, although the patch pattern from which a density level differs is shown, the viewpoint of performing the process according to the said incentive is not shown.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus that performs density adjustment by itself, and that can perform adjustment processing with appropriate contents according to the cause of execution of density adjustment. That is.

  In order to achieve the above object, according to one aspect of the present invention, a tone value of each color included in image data to be image-formed is corrected based on tone correction information, and based on the tone value after correction. When the image forming apparatus that forms an image detects that an event that should execute density adjustment processing for updating the gradation correction information has occurred, and when the event is detected by the detecting unit, In accordance with the type of the detected event, a determination unit that determines the number of patch patterns used as a color sample in the density adjustment processing, and the determination is performed after the number of patch patterns is determined by the determination unit A plurality of patch patterns are formed from image data for each patch pattern having the gradation value, and the colorimetric results of the formed patch patterns and the images of the patch patterns are formed. Based on the gradation value of over data, and adjusting means for updating the tone correction information is to have a.

  Furthermore, in the above-described invention, a preferable aspect further includes a storage unit that stores the number of the patch patterns associated with each type of event for which the density adjustment process is to be executed, and the determination unit includes the determination unit The number of patch patterns is determined by acquiring the number of patch patterns stored in the storage unit associated with the type of detected event.

  Furthermore, in the above-described invention, a preferable aspect is that, when the detected event is replacement of consumables used in the image forming apparatus or an instruction to execute density adjustment processing by a user, The number of patch patterns, which is the largest among the number of patch patterns determined by the determining means, is determined for the event.

  In order to achieve the above object, another aspect of the present invention corrects the gradation value of each color included in image data to be image-formed based on gradation correction information, and based on the corrected gradation value. In the control method of the image forming apparatus for forming an image, it is detected that an event for executing the density adjustment process for updating the gradation correction information has occurred, and the density adjustment is performed according to the type of the detected event Determining the number of patch patterns used as color samples in the processing, forming the determined number of patch patterns from image data for each patch pattern having the gradation value, and forming each patch pattern The tone correction information is updated based on the color measurement result and the tone value of the image data of each patch pattern.

  Further objects and features of the present invention will become apparent from the embodiments of the invention described below.

  Embodiments of the present invention will be described below with reference to the drawings. However, such an embodiment does not limit the technical scope of the present invention. In the drawings, the same or similar elements are denoted by the same reference numerals or reference symbols.

  FIG. 1 is a configuration diagram according to an embodiment of a printer which is an image forming apparatus to which the present invention is applied. A printer 2 shown in FIG. 1 is an image forming apparatus to which the present invention is applied, and is an apparatus that forms an image on a predetermined print medium (paper) based on a print request from the host computer 1. When an event for executing the density adjustment processing of the image to be formed occurs, the printer 2 executes the density adjustment processing with the color sample having the number of patches corresponding to the generated event, in terms of adjustment accuracy and processing speed. Therefore, it is intended to adjust the concentration appropriately for each event.

  A host computer 1 shown in FIG. 1 is a host device that makes a print request to a printer 2 connected via a network 3 or the like, and transmits print data including image data and control commands to the printer 2 based on a user operation or the like. To do. The host computer 1 can be configured by a so-called personal computer.

  Next, as shown in FIG. 1, the printer 2 is a so-called four-cycle laser printer including a controller 4, an engine control unit 5, an engine 6, a user I / F unit 7, and the like.

  The controller 4 receives the print data transmitted from the host computer 1, interprets the control command included in the data, and performs predetermined processing on the image data included in the data to the engine 6 side. Generate the data to provide. As shown in FIG. 1, the controller 4 includes an I / F 41, a CPU 42, a ROM 43, a RAM 44, and an engine I / F 45.

  The I / F 41 is a part that receives the print data transmitted from the host computer 1, and the ROM 43 is a part that stores various programs for controlling the printer 2. Also, a patch number table, which is a feature of the printer 2, is stored here. The contents will be described later.

  The RAM 44 is a memory for storing the received print data and the like, and the image data of each page on which print processing is performed by the engine 6 is delivered to the engine I / F 45 from here. The RAM 44 also stores a gradation correction table, which will be described later, and performs density correction processing for each color using this table during image formation. Information about each consumable (toner cartridge 61, photoconductor 62, etc.) used in the printer 2 is held here and used for various controls.

  The CPU 42 controls various processes performed in the printer 2. In particular, the CPU 42 interprets the process for storing the image data included in the received print data in the RAM 44 and the control command included in the print data. It manages the process of instructing the engine control unit 5 to perform an appropriate printing process, the process of controlling the user I / F unit 7 that forms an interface with the user, and the like. The printer 2 is characterized by density adjustment processing (density calibration) performed mainly by the CPU 42, and the specific contents thereof will be described later. The processing executed by the CPU 42 is mainly performed according to a program stored in the ROM 43.

  Next, the engine I / F 45 reads the pixel data stored in the RAM 44 described above at a predetermined timing when printing is performed by the engine 6, performs a predetermined process on the pixel data, and delivers the pixel data to the engine 6 side. This is the part that controls the interface between the controller 4 and the engine 6 side. Although not shown, the engine I / F 45 includes a memory for temporarily storing data, a decompression unit, a screen processing unit, and the like. The pixel data read from the RAM 44 is compressed data. Decompression and screen processing to convert to dot data. Further, the engine I / F 45 is specifically composed of an ASIC.

  Next, although not shown, the engine control unit 5 includes a CPU, a ROM, a RAM, and the like, and controls the operation of each unit of the engine 6 described later. Further, when a later-described toner cartridge 61 or the like is replaced, it is detected and notified to the controller 4, and sensor values acquired by sensors 63 and 64 described later are notified to the controller 4.

  Next, the engine 6 includes a charging unit, an exposure unit, a developing device, a transfer unit, etc., but not all are shown in FIG. In the engine 6, first, the exposure unit forms an electrostatic latent image on the photosensitive member 62 charged by the charging unit in accordance with a signal transferred from the engine I / F 45. Thereafter, toner as a developer is supplied to the electrostatic latent image from the toner cartridge 61 of each color (here, C (cyan), M (magenta), Y (yellow), K (black)) detachably attached. Then, the toner image is developed, and the toner image is transferred onto a transfer target medium by a transfer unit, thereby forming an image.

  As described above, the toner cartridge 61 is detachable from the printer 2 and is replaced when there is no toner to be stored. In addition, the photosensitive member 62 is also removable as a consumable item, and is replaced when it reaches the end of its life. Further, in the printer 2, a patch pattern that becomes a color sample when density calibration is performed is formed on the photoconductor 62, and colorimetry is performed by the colorimetric sensor 63 provided on the photoconductor 62 side.

  The engine 6 is provided with a temperature / humidity sensor 64, and the measured value is reported as appropriate.

  Next, the user I / F unit 7 is a part that forms an interface between the user and the printer 2 such as when the user operates the printer 2, and includes a display panel, an operation panel, and the like. When the user wants to execute density calibration, the user I / F unit 7 instructs execution of density calibration by a predetermined operation.

  In the printer 2 according to the present embodiment having the configuration described above, the print data described in a predetermined language is supplied from the host computer 1 during printing, and is included in the print data on the controller 4 side. A predetermined process is performed on the image data to generate a signal for the engine 6, and the engine 6 side performs the above-described printing process based on the signal to form an image on a predetermined medium. The above-described gradation correction table is used in the process of image data processing performed on the controller 4 side. Here, the gradation correction table is represented by density gradation values (for example, 256 gradations) of each color (CMYK) for each pixel. It is assumed that tone correction using the tone correction table is executed on the obtained image data. That is, according to the density characteristics of the printer 2 at that time, the input tone value (original tone value) is corrected so as to have a density suitable for the input tone value when output on the engine 6 side. Is made. As a result of the density calibration process described below, this gradation correction table is updated to an appropriate one at that time.

  Next, the density adjustment process (density calibration) that is a feature of the printer 2 will be specifically described. FIG. 2 is a flowchart illustrating the procedure of density adjustment processing in the printer 2. In FIG. 2, it is described as processing performed by the CPU 42 of the controller 4.

  First, the CPU 42 periodically monitors the state of the engine 6 and the user I / F unit 7 and determines whether or not an event for executing the density adjustment process has occurred (step S1). Here, as an example, after the printer 2 is turned on, the density adjustment process has not yet been executed (A), the user has instructed the user I / F unit 7 to execute the density adjustment process (B), the toner The cartridge 61 or the photoconductor 62 has been replaced (C), the printer has returned from the power saving mode (D), the printing of a predetermined number of pages or more has been executed after the previous density adjustment processing (E), and the temperature / The fact that the environment such as humidity has changed significantly after the previous density adjustment process (F) is an event that should be executed.

  If the CPU 42 detects that any of the above events A to F has occurred (Yes in step S1), the patch pattern suitable for the event that has occurred (detected) is first executed to execute the density adjustment processing. Determine the number of. That is, the number of color samples to be formed for each color is determined. Specifically, referring to the patch number table stored in the ROM 43, the number of patches determined for the generated event is acquired (step S2).

  FIG. 3 is a diagram conceptually illustrating this patch number table. As shown in FIG. 3, in the patch number table, events that should be subjected to density adjustment processing (trigger types of density adjustment processing execution) correspond to the number of patches that should be formed in the density adjustment processing that is performed when the event occurs. It is included. For example, when the above event A occurs, the CPU 42 obtains information of 48 patches and determines the number of patches of each color as 48 in the density adjustment process to be executed.

  For the above events A, D, and E, it is unlikely that the environment of the engine 6 or the like has changed so much due to the occurrence of these events. Therefore, the time is shorter than when the concentration adjustment process is performed with high accuracy. Therefore, the number of patches is set to be small. On the other hand, for event B, the user has instructed the density adjustment process, and for event C, the occurrence of this event may cause a significant change in the environment related to the printing process. In this case, it is preferable to perform high-precision density adjustment processing, and accordingly, a large number of patches are set. In the event F, the change in the printing environment is considered to be larger than that in the case of the events A, D, and E, but is considered to be smaller than that in the case of the event C. The processing time is appropriate, and an intermediate number of patches is set.

  In this way, when the number of patches suitable for the event that has occurred is determined, the CPU 42 determines the gradation value of each patch (step S3). Here, each gradation value is determined by calculation so that the gradation values of the formed patches are equally spaced. Specifically, assuming that the gradation value of each color is expressed by 256 gradations, the range between the maximum gradation value of 255 and the minimum gradation value of 0 is determined according to the number of patches determined. The tone value of each patch is obtained by dividing the interval.

  FIG. 4 is a diagram illustrating patch patterns of each color and their gradation values. The patch pattern shown in FIG. 4 has a smaller number of patches than the actual pattern (in comparison with the value shown in the patch number table) for easy understanding. Indicates the case of 8 patches. In the figure, one rectangle of each color (CMYK) represents one patch pattern, and the numbers shown in each rectangle represent the tone values of the patch pattern.

  In the case of the four patches shown in FIG. 4A, one patch is assigned to the maximum gradation value “255” and the minimum gradation value “0”, respectively. -1) A patch having gradation values "170" and gradation values "85" is set by being equally divided. Similarly, in the case of 8 patches shown in FIG. 4B, one patch is assigned to the maximum gradation value “255” and the minimum gradation value “0”, respectively. The interval is divided into 7 (8-1), and the gradation value of each patch is set.

  In the case of other numbers of patches, for example, 48 patches, 96 patches, and 128 patches, the gradation value of each patch is determined by the same method. Note that the gradation value of each patch may be calculated in advance for each number of patches, stored in the ROM 43, and the like may be referred to.

  Next, the CPU 42 instructs density adjustment processing to the engine side (step S4). Specifically, the engine control unit 5 is instructed to start processing for measuring the color of the patch pattern formed by forming the patch pattern on the photoconductor 62. At this time, the determined number of patches is also designated on the engine side.

  Thereafter, the CPU 42 generates image data of each patch pattern in accordance with the determined gradation value of each patch, and sequentially transmits it to the engine side as a signal for the engine 6 to form each patch pattern on the photoreceptor 62. (Step S5). In accordance with the instruction, each patch pattern of each color is developed on the photoreceptor 62 under the control of the engine control unit 5.

  Each color patch pattern is formed on the photoreceptor 62 as shown in FIG. 4, for example. Note that the arrangement direction, arrangement location, and arrangement order of the patch pattern to be formed are not limited to this, and may be determined as appropriate.

  Thereafter, under the control of the engine control unit 5, the colorimetric sensor 63 measures the color value of each patch pattern formed on the photoconductor 62, the result is notified to the controller 4, and the CPU 42 determines these colorimetric values. Is acquired (step S6).

  Next, the CPU 42 updates the gradation correction table based on the obtained colorimetric value and the original gradation value of each patch (step S7). Specifically, since the colorimetric values are for the image on the photoreceptor 62, the colorimetric values are converted into colorimetric values when the image is transferred to a print medium such as paper. Such conversion is performed based on a conversion table or the like determined in advance based on actual measurement results. Then, from the original gradation value for each patch, that is, the determined gradation value (S3) and the measured color value after the conversion, that is, the color value that is actually output, The density characteristic of the printer 2 at the time is obtained. In other words, a relationship between each gradation value of the image data and the actual output density value is generated for each color. Thereafter, based on the density characteristics, each gradation value of the image data is converted into a gradation in which the actual output density value for the gradation value becomes a standard density value planned for the gradation value. A gradation correction table to be corrected to a value is generated, and the generated gradation correction table is held in place of the gradation correction table previously held in the RAM 44.

  FIG. 5 is a diagram for explaining the gradation correction table. In FIG. 5, as an example, the gradation correction table for C is represented by a graph, the horizontal axis indicates the original gradation value of the image data, and the vertical axis indicates the corrected gradation value. Yes. For example, a curve “a” in the drawing represents one gradation correction table, and each point on the curve indicates the original gradation value and the gradation value after correction for the original gradation value. Assuming that the new gradation correction table generated by the density calibration is the curve b in the figure, the gradation correction table based on the curve a held so far is updated to the gradation correction table based on the curve b. It will be. For YMK, the same gradation correction table is held and updated in the same manner.

  In this way, when the tone correction table reflecting the density characteristics of the printer 2 at that time is updated, the current density adjustment processing ends, and the CPU 42 again performs the engine 6 and the user I / F unit 7. And waits for an event to be executed for density adjustment processing (step S1).

  When the density calibration is performed as described above and the gradation correction table is updated, in subsequent printing, the gradation value of the original image data is maintained until the density characteristic of the printer 2 changes. It becomes possible to output at an appropriate density.

  In the above description, the patch pattern data is generated at the time of calibration based on the determined number of patches and gradation values, but may be generated in advance and stored in the ROM 43 or the like. In this case, for example, patch data for 48 patches, 96 patches, and 128 patches are prepared for each number of patches, and the CPU 42 determines the number of patches according to the event that has occurred, and then determines the number of patches. Patch data can be selected and used for patch formation.

  In the above description, the patch image on the photoconductor 62 is the target of colorimetry, but a patch pattern is output on paper as a so-called patch sheet, and the patch image of the output patch sheet is the target of colorimetry. It is also good as a method. Also in this case, determination of the number of patches according to the event that has occurred, determination of the gradation value of each patch, and the like can be performed in the same manner.

  In addition, the number of patches and the gradation value of each patch in the above description are examples, and other values may be used. The gradation value determination method for each patch is not necessarily equal.

  Further, the above-mentioned phenomenon that causes the concentration adjustment process is not meant to be limited to these.

  Further, the correction processing using the gradation correction table at the time of printing in the above description is an example, and correction may be performed at other processing timing. Further, the result of density calibration may be reflected as correction information in a format different from that of the gradation correction table.

  As described above, in the printer 2 according to the present embodiment, at the time of density adjustment processing, first, the number of patches to be formed is determined according to the type of the event that has caused the trigger, and a patch pattern of the number of patches is formed. Then, density calibration is executed. Therefore, the adjustment accuracy and processing time can be dynamically changed due to the cause of the density adjustment process, and the density adjustment process can be performed with appropriate contents for each cause.

  Specifically, when there is a possibility that the printing environment may have changed significantly, such as when consumables such as the toner cartridge 61 and the photoconductor 62 have been replaced, or when the user instructs calibration, priority is given to accuracy. Many patches are formed, and after power is turned on, calibration is performed with a small number of patches giving priority to processing in a short time. Therefore, the conventional problems such as excessive processing time and insufficient accuracy can be solved.

  In the embodiment, the image forming apparatus is a printer. However, the present invention can be applied to other image forming apparatuses such as a copying machine and a facsimile.

  The protection scope of the present invention is not limited to the above-described embodiment, but covers the invention described in the claims and equivalents thereof.

1 is a configuration diagram according to an embodiment of an image forming apparatus to which the present invention is applied. 4 is a flowchart illustrating an example of a density adjustment process in the printer 2. It is the figure which illustrated the patch number table notionally. It is the figure which illustrated the patch pattern of each color, and its gradation value. It is a figure for demonstrating a gradation correction table.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Host computer, 2 Printer, 3 Network, 4 Controller, 5 Engine control part (Adjustment means), 6 Engine (Adjustment means), 7 User I / F part, 41 I / F, 42 CPU (Detection means, Determination means, Adjustment means), 43 ROM (storage means), 44 RAM, 45 engine I / F, 61 toner cartridge, 62 photoconductor, 63 colorimetric sensor, 64 temperature / humidity sensor

Claims (4)

An image forming apparatus that corrects the gradation value of each color of image data to be image-formed based on gradation correction information and forms an image based on the corrected gradation value,
Detecting means for detecting the occurrence of an event for executing the density adjustment processing for updating the gradation correction information;
A determination unit that determines the number of patch patterns used as a color sample in the density adjustment process according to the type of the detected event when the event is detected by the detection unit;
After the number of patch patterns is determined by the determining means, the determined number of patch patterns is formed from image data for each patch pattern having the gradation value, and each of the formed patch patterns An image forming apparatus comprising: an adjustment unit that updates the gradation correction information based on a color measurement result and a gradation value of image data of each patch pattern. In claim 1, further comprising:
Storage means for storing the number of patch patterns associated with each type of event to be subjected to the density adjustment processing;
The image forming apparatus, wherein the determination unit determines the number of patch patterns by acquiring the number of patch patterns in the storage unit associated with the detected event type. In claim 1 or claim 2,
When the detected event is replacement of a consumable used in the image forming apparatus or an instruction to execute density adjustment processing by a user, the determining unit includes the number of patch patterns determined by the determining unit. An image forming apparatus characterized in that the number of patch patterns having the largest number is determined for the event. A control method for an image forming apparatus that corrects gradation values of each color of image data to be image-formed based on gradation correction information and forms an image based on the corrected gradation values,
Detecting that an event that should execute density adjustment processing for updating the gradation correction information has occurred,
According to the type of the detected event, determine the number of patch patterns used as color samples in the density adjustment process,
The determined number of patch patterns is formed from image data for each patch pattern having the gradation value, and the colorimetric results of the formed patch patterns and the gradation of the image data of each patch pattern The gradation correction information is updated based on the value. A control method for an image forming apparatus, comprising:

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