JP2005297408A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of carrying out a calibration by considering change of an output density with time. <P>SOLUTION: In this image forming apparatus, information of a colorant density with respect to a prescribed designation of image-forming is recorded as information of an output characteristic by each predetermined timing. When a setting value of the colorant density with respect to the designation of image-forming is corrected, a correction target is determined based on the information of the output characteristic and the determined correction target is corrected by the setting value of the colorant density with respect to the designation of image-forming. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a printer or a multifunction peripheral.

  It is desirable that the printer and the multifunction machine are set so that uniform print results can be output in response to the same image formation instruction. However, it is often difficult to maintain a constant image formation state due to environmental conditions such as temperature and humidity, the number of continuous outputs, the type of paper, and other factors.

  Therefore, for example, processing (calibration) for correcting the output result for a predetermined image formation instruction to the target result may be performed at regular intervals.

  Specifically, for this calibration, a host-based method that reads the output result of the printer with a scanner, and a printer-specific method that forms a patch in a portion of the printer that does not contact the paper on the transfer drum and reads it. There is. Each of these methods has advantages and disadvantages.

Therefore, density control is performed to create printer-specific calibration, and an error occurs when the difference between the print density value indicated by the obtained data and the calibration data downloaded from the host computer exceeds a predetermined threshold. There is a technique (Patent Document 1) that generates a correction table based on calibration data obtained by the printer.
JP 2001-018498 A

  However, the output result is subject to fluctuations due to complicated factors as described above, and even if calibration is performed, it may deviate from the allowable range immediately depending on the fluctuation state. Specifically, since the output result (for example, the output density corresponding to the predetermined pixel value) fluctuates with time as shown in FIG. 5, for example, the time t1 when the change is relatively flat in FIG. When the correction is made to the reference value B, the output density is within the allowable range even at time t2 (the correction result changes as indicated by the broken line indicated by X). On the other hand, if it is corrected to the reference value B at the time t3 when the output density is decreasing, it will already deviate from the allowable range at the time t4 (the correction result changes as indicated by a broken line indicated by Y). ).

  Thus, the conventional calibration process does not take into account the temporal change in the output density.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of performing calibration in consideration of a temporal change in output density.

  The present invention for solving the problems of the above conventional example is an image forming apparatus, which records information on color material density in response to a predetermined image formation instruction as output characteristic information at predetermined timings, and image formation When correcting the color material density setting value for the instruction, the correction target determining means for determining the correction target based on the output characteristic information and the color material density setting value for the image formation instruction are corrected to the determined correction target. And means for performing.

  Here, a rough correction unit that roughly corrects a set value of the color material density in response to the image formation instruction may be included, and the predetermined timing may be a timing immediately after the rough correction is performed.

  In addition, the present invention for solving the problems of the conventional example is an image forming apparatus, and when correcting a color material density setting value for an image formation instruction, the color material density for a predetermined image formation instruction is corrected. Information is measured a plurality of times, the measurement result is recorded as output characteristic information, correction target determination means for determining a correction target based on the output characteristic information, and a color material density setting value for an image formation instruction, And means for correcting the determined correction target.

  In these, the correction target determining means may determine a correction target value within a predetermined range from a predetermined target value based on the output characteristic information, and determine a correction target related to the correction target value. .

  The present invention for solving the problems of the above-described conventional example is an image forming method in which color material density information corresponding to a predetermined image formation instruction is recorded as output characteristic information at each predetermined timing, and image formation A step of determining a correction target based on the output characteristic information when correcting a set value of the color material density for the instruction, and a step of correcting the set value of the color material density for the image formation instruction to the determined correction target. It is characterized by including.

  The present invention for solving the problems of the above conventional example is an image forming method, and when correcting a color material density setting value for an image formation instruction, information on the color material density for a predetermined image formation instruction is obtained. A step of measuring a plurality of times and recording the measurement result as output characteristic information; a step of determining a correction target based on the output characteristic information; and a color material density setting value for an image formation instruction to the determined correction target And a step of correcting.

  The present invention for solving the problems of the above conventional example is a program executed by a computer of an image forming apparatus, and information on color material density in response to a predetermined image formation instruction is output characteristic information at predetermined timings. The recording procedure, the procedure for determining the correction target based on the output characteristic information when correcting the color material density setting value for the image formation instruction, and the color material density setting value for the image formation instruction were determined. And making the computer execute a procedure for correcting the correction target.

  The present invention for solving the problems of the above-described conventional example is a program executed by a computer of an image forming apparatus, and a predetermined image formation instruction when correcting a set value of color material density for an image formation instruction A procedure for measuring color material density information for a plurality of times and recording the measurement results as output characteristic information; a procedure for determining a correction target based on the output characteristic information; and a color material density setting value for an image formation instruction And a procedure for correcting the corrected target to the determined correction target.

  Embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the image processing apparatus according to the embodiment of the present invention includes a control unit 11, a storage unit 12, a program storage unit 13, a communication unit 14, and an image forming unit 15. Is done.

  The control unit 11 is realized by a CPU (Cetnral Processing Unit) or the like, operates according to a program stored in the program storage unit 13, and acquires color material density information from the image forming unit 15 at predetermined timing (characteristics). Acquisition processing), correction target determination processing for adjusting a correction target to determine a correction target, and calibration processing. In addition, the control unit 11 outputs an image formation instruction received from the outside via the communication unit 14 to the image forming unit 15 to perform image formation.

  The storage unit 12 is, for example, a RAM (Random Access Memory) or the like, and operates as a work memory that holds information generated during the execution of the control unit 11. The program storage unit 13 is a ROM (Read Only Memory), for example, and holds a program executed by the control unit 11.

  The communication unit 14 is connected to a network or the like, and outputs image formation data received via the network to the control unit 11. The image forming unit 15 forms an image on a predetermined recording medium (for example, paper) in accordance with an image forming instruction input from the control unit 11. Specifically, for example, as shown in FIG. 2, the image forming unit 15 includes a forming element 30 provided for each color material (for example, for each color toner of CMYK) (here, a tandem type example is shown). Each of the forming body elements includes a drum-type photosensitive member 31, a developing unit 32, and an image quality detecting unit 33. The forming element 30 of the image forming unit 15 originally includes a cleaning unit and a fixing unit in addition to the above, but here, only the parts related to the processing of the present embodiment will be described. I will do it.

  The photoconductor 31 rotates around its axis and carries an image formed by the developing unit 32. The photosensitive member 31 is brought into contact with a sheet as a recording medium conveyed by the sheet conveying unit 40 at a transfer point P, and transfers the carried image onto the sheet. The developing unit 32 forms an image on the photoreceptor 31 according to the image data. Specifically, as shown in FIG. 3, the developing unit 32 uses the color material of what density with respect to the input image element value (for example, pixel value) to form the image element on the photoreceptor 31. A setting table for setting whether to form an image corresponding to the image data is provided. The density value corresponding to the value of each pixel included in the input image data is read from the setting table, and the read density value is used. Form an image.

  Further, when the developing unit 32 receives a detection instruction input from the control unit 11, a portion of the photoconductor 31 that does not contact the paper (a portion called a non-image region or an observation region that does not correspond to the paper). At least one measurement latent image (an image having a density corresponding to a predetermined pixel value) is formed.

  When receiving the detection instruction from the control unit 11, the image quality detection unit 33 generates color material density information based on the measurement latent image formed on the photoconductor 31 and outputs the color material density information to the control unit 11. Here, the color material density information is a value representing the density of the latent image for measurement. For example, when the measurement latent image is formed of a color material having a density corresponding to a predetermined image formation instruction (for example, pixel value X), the density of the measurement latent image is measured and the predetermined image is measured. Color material density information representing the density corresponding to the formation instruction is output. Here, the density information for each color material corresponds to an example of output characteristic information. The sheet conveying unit 40 conveys a sheet as a recording medium from a sheet stack (not shown) to contact a photoconductor to form an image, and then conveys the sheet to a discharge tray.

  Here, a characteristic acquisition process, a correction target determination process, and a calibration process by the control unit 11 will be described. First, the specific acquisition process will be described. The control unit 11 outputs a detection instruction at every predetermined timing, acquires color material density information for each color material output by the image forming unit 15, and records these in the storage unit 12 as output characteristic information. As a result, at least the latest N pieces of output characteristic information acquired in the past are held in the storage unit 12 as shown in FIG.

  The control unit 11 determines a calibration correction target based on the output characteristic information stored in the storage unit 12 (correction target determination process). Specifically, the correction target is determined as follows. That is, the reference allowable range is determined in advance with the target reference value p as the center, p + r as the upper limit value, and p−s as the lower limit value.

  The control unit 11 outputs a detection instruction in order to acquire current output characteristic information (before calibration) (color material density of each color material), and the color material density information for each color material output by the image forming unit 15. To get. Then, with reference to the output characteristic information stored in the storage unit 12, the maximum value a and the minimum value b of the color material density information are acquired for each color material. Note that the control unit 11 separately holds the minimum and maximum values of the color material density measured in the past in the storage unit 12 for each color material regardless of whether the storage unit 12 stores them. When the color material density measured this time is smaller than the minimum value or larger than the maximum value, the color material density measured this time may be overwritten.

  When the current color material density is equal to the maximum value a, the control unit 11 determines the maximum value p + r of the reference allowable range as a correction target. When the current color material density is equal to the minimum value b, the minimum value ps of the reference allowable range is determined as the correction target. Further, if b <x <a, the correction target is set to a value obtained by linear interpolation between (p−s) and (p + r). As a result, the correction target value is determined within a predetermined range (within the allowable range) from the predetermined target value, and setting that deviates from the allowable range is prevented.

となる。これは、従来、補正ターゲットは常にｐであるのに対して、補正項αを加算することを意味する。なお、

である。 That is, if the current color material density is x, the equation for obtaining the correction target pA is:

It becomes. This means that the correction term α is added while the correction target is always p. In addition,

It is.

  After determining the correction target, the control unit 11 starts calibration processing, corrects the setting table of the developing unit 32, and corresponds to the measurement latent image forming instruction generated by the developing unit 32. Correct the density. Since this correction method is similar to a widely known calibration process, a detailed description thereof will be omitted.

として、補正ターゲットＰAを定める。 Further, in determining the correction target, consideration may be given to the variation direction of the color material density. That is, in the correction target determination process, the control unit 11 further includes the current color material density Dn indicated in the current output characteristic information and the previously acquired output characteristic for the correction target pA determined by the above equation (1). The difference from the previous color material density Dn-1 indicated in the information is calculated to obtain the fluctuation direction u = Dn-Dn-1. And if x> p + r,

The correction target PA is determined as follows.

  That is, if x> p + r and u> 0 (that is, the direction toward the maximum value), the correction target is the reference value p itself, and x> p + r and u ≦ 0 (that is, the maximum value is reached). In the direction of returning to the reference value), a value obtained by adding the correction term α to the reference value p is set as a correction target. Similarly, in the case of x <ps, if u <0 (that is, the direction toward the minimum value), the correction target is the reference value p itself, x <ps, and u ≧ 0 ( In other words, in the direction from the minimum value to the reference value), a value obtained by adding the correction term α to the reference value p is set as a correction target.

  By performing calibration with the correction target adjusted in this way as a target, in the example shown in FIG. 5, at time t3, x> p + r and u ≦ 0. Is added. Since the color material density is close to the maximum value at time t3, the correction target is set to a value offset to the p + r side from the original target p. Therefore, the correction amount becomes small, and the color material density can be maintained within the allowable range for a longer time than when the correction is made to p at time t3.

  The predetermined timing at which the control unit 11 acquires the output characteristic information through the characteristic acquisition processing may be, for example, a timing immediately after the image forming unit 15 roughly corrects the color material density setting value for the image formation instruction. . That is, the image forming unit 15 resets, for example, the setting table to a default state when receiving a correction instruction from the programming console during maintenance or the like. As a result, rough correction is performed, but the control unit 11 may execute characteristic acquisition processing after the rough correction to acquire output characteristic information. Further, as the predetermined timing, the control unit 11 may acquire the output characteristic information every predetermined time or every time a predetermined number of sheets are discharged.

  Further, in the examples so far, the example in which the control unit 11 acquires the output characteristic information in advance at every predetermined timing has been described. However, when performing calibration, the characteristic acquisition process is continuously performed a plurality of times. The correction target may be determined based on a plurality of pieces of output characteristic information acquired by the continuous characteristic acquisition process.

  For example, among the continuously acquired characteristic acquisition processes, the output characteristic information (first output characteristic information) acquired in the first characteristic acquisition process and the last (Nth) characteristic acquisition process Using the obtained output characteristic information (Nth output characteristic information), the fluctuation direction u is obtained, and the fluctuation direction from the first output characteristic information to the Nth output characteristic information (separately when the concentration is increasing or decreasing) is acquired. Then, the correction target may be determined by the mathematical formula shown in [Equation 3].

  In this embodiment, the case of color (in the case of using a plurality of color materials) has been described as an example. However, the same processing can be applied to a monochrome image forming apparatus.

1 is a configuration block diagram illustrating an example of an image processing apparatus according to an embodiment of the present invention. 2 is a schematic configuration diagram illustrating an example of an image forming unit. FIG. It is explanatory drawing showing the example of the setting table which sets a color material density | concentration. It is explanatory drawing showing the example of storage of output characteristic information. It is explanatory drawing showing the example of an effect at the time of correct | amending the setting table of color material density | concentration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Control part, 12 Memory | storage part, 13 Program memory | storage part, 14 Communication part, 15 Image forming part, 30 Forming element, 31 Photoconductor, 32 Developing part, 33 Image quality detection part, 40 Paper conveyance part

Claims (8)

Means for recording color material density information corresponding to a predetermined image formation instruction as output characteristic information for each predetermined timing;
Correction target determining means for determining a correction target based on the output characteristic information when correcting the set value of the color material density for the image formation instruction;
Means for correcting the set value of the color material density for the image formation instruction to the determined correction target;
An image forming apparatus comprising: The image forming apparatus according to claim 1,
Coarse correction means for roughly correcting the color material density setting value for the image formation instruction;
The image forming apparatus according to claim 1, wherein the predetermined timing is a timing immediately after the rough correction is performed. Means for measuring the color material density information for a predetermined image formation instruction a plurality of times when correcting the set value of the color material density for the image formation instruction, and recording the measurement result as output characteristic information;
Correction target determining means for determining a correction target based on the output characteristic information;
Means for correcting the set value of the color material density for the image formation instruction to the determined correction target;
An image forming apparatus comprising: The image forming apparatus according to any one of claims 1 to 3,
The correction target determining means determines a correction target value within a predetermined range from a predetermined target value based on the output characteristic information, and determines a correction target related to the correction target value. apparatus. A step of recording color material density information for a predetermined image formation instruction as output characteristic information for each predetermined timing;
A step of determining a correction target based on the output characteristic information when correcting the set value of the color material density for the image formation instruction;
Correcting the set value of the color material density for the image formation instruction to the determined correction target;
An image forming method comprising: When correcting the color material density setting value for the image formation instruction, measuring the color material density information for a predetermined image formation instruction a plurality of times, and recording the measurement result as output characteristic information;
Determining a correction target based on the output characteristic information;
Correcting the set value of the color material density for the image formation instruction to the determined correction target;
An image forming method comprising: In the computer of the image forming apparatus,
A procedure for recording color material density information for a predetermined image formation instruction as output characteristic information for each predetermined timing;
A procedure for determining a correction target based on the output characteristic information when correcting the set value of the color material density for the image formation instruction;
A procedure for correcting the set value of the color material density for the image formation instruction to the determined correction target,
A program characterized by having executed. In the computer of the image forming apparatus,
A procedure for measuring the color material density information for a predetermined image formation instruction a plurality of times when correcting the set value of the color material density for the image formation instruction, and recording the measurement result as output characteristic information;
Determining a correction target based on the output characteristic information;
A procedure for correcting the set value of the color material density for the image formation instruction to the determined correction target,
A program characterized by having executed.

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