JP2005010269A - Image forming apparatus and method for correcting image forming condition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct image forming conditions into optimum status by terminating a correction process by judging a correction limit regardless of an apparatus status and environment. <P>SOLUTION: A patch Pa is formed on paper P based on an exposure parameter. The toner image density of the patch Pa formed is detected. The present detection value of the toner image density of the patch Pa is compared with the past detection values including at least the previous detection value, and it is determined whether the result of the comparison has reached the correction limit or is close to the correction limit. In the case where it is determined that the result of the comparison has not reached the correction limit or is not close to the correction limit, the image forming apparatus repeats the correction process for correcting the exposure parameter so that the detection value reaches a predetermined reference value for each formation of the patch Pa. In the case where it is determined that the result of the comparison has reached the correction limit or is close to the correction limit, the correction process is terminated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine or a printer and an image forming condition correction method, and more particularly to an image forming apparatus and an image forming apparatus that detect a physical quantity related to the image quality of a reference image and correct the image forming condition based on the detection result. The present invention relates to a condition correction method.
[0002]
[Prior art]
Currently, the image quality of the output image by the image forming apparatus is remarkably improved, and as a result, the user's demand for image quality fluctuations has become more severe.
[0003]
For this reason, in many image forming apparatuses, density reproducibility, color reproducibility, and the like are stabilized by changing image forming conditions using a calibration function. As a calibration method, the image forming condition is corrected based on the detection result of the image quality state of the image, the image is re-formed under the corrected image forming condition, and the image quality state is detected again, and the target method is repeatedly performed. A Closed Loop system that approaches a state is known.
[0004]
An image forming apparatus that corrects image forming conditions using the Closed Loop method has means for detecting a toner adhesion amount of a predetermined pattern image and calculating a deviation between the detected toner adhesion amount and a reference value. Then, the image forming condition is changed from the deviation, the toner adhesion amount of the pattern image created under the changed image forming condition is detected again, and the deviation from the calculated reference value is determined to be within the reference range. In this case, an image forming apparatus that terminates the image forming condition changing process is known (for example, see Patent Document 1).
[0005]
[Patent Document 1]
JP-A-6-194918
[0006]
[Problems to be solved by the invention]
However, since the image forming apparatus and the environment in which the image forming apparatus is installed change the pattern image forming accuracy, the accuracy of the detection means for detecting the image quality state of the pattern image, the correction accuracy, and the like. When setting a reference range as a determination criterion for ending the image forming condition changing process (correction process) in the apparatus, it is necessary to set in consideration of such a variation in accuracy.
[0007]
For example, if the deviation reference range is set wide in consideration of such variations, the correction reaches the reference range before the actual correction ability of the device is demonstrated, and the correction ends. For reasons such as image creation unevenness, there is a problem that correction may end even if the correction result falls within the reference range.
[0008]
Hereinafter, the case where the deviation reference range is set wide will be described with reference to FIG. The illustrated color difference ΔE is a value indicating a deviation between the colorimetric value (color value) of the formed pattern image and the target reference value, and the color difference ΔE is plotted for each correction. Also, the deviation reference range (correction end range) E _th Is set to 3 or less.
[0009]
The color difference ΔE due to the first correction is outside the correction end range, but the color difference ΔE due to the second correction is within the correction end range. Therefore, in the conventional image forming apparatus, the correction ends when the second correction is performed.
[0010]
However, in the illustrated example, the color difference ΔE can be further reduced by repeating the correction process without completing the correction here.
[0011]
That is, there is a problem that if the correction end range is set to be wide even though the correction can be performed with higher accuracy, the correction processing ends without being corrected to the correction accuracy that can be originally realized.
[0012]
Conversely, when the correction end range is set to be narrower than the correction accuracy that can be actually realized (for example, the correction end range E in FIG. 12). _th Is set to 1 or less), the correction accuracy does not reach the correction end range, and there is a problem that the correction process is not repeated and ended even when the correction limit is reached.
[0013]
In order to deal with such a problem, a method of performing correction processing with a fixed number of corrections may be considered, but the correction processing is always repeated for the fixed number of corrections, so the limit of correction is reached before reaching the number of corrections. If it arrives, useless correction processing is repeated. Conversely, when the number of corrections is reached before the correction limit is reached, there is a problem that the correction process is terminated halfway without being corrected to the actual correction accuracy.
[0014]
The present invention has been proposed in order to solve the above-described problems. Regardless of the state or environment of the apparatus, the correction limit is judged and the correction process is terminated to correct the image forming conditions to an optimum state. It is an object of the present invention to provide an image forming apparatus and an image forming condition correction method that can be used.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, a first image forming apparatus according to the present invention is formed by a reference image forming unit that forms a reference image on an image carrier based on image forming conditions, and the reference image forming unit. A detection unit that detects a physical quantity related to the image quality of the reference image, and a correction limit by comparing a current detection value of the physical quantity related to the image quality detected by the detection unit with a past detection value including at least the previous detection value. A determination unit that determines whether or not the correction limit is approached, and a correction process that corrects the image forming condition so that the detection value approaches a predetermined reference value are repeatedly executed every time a reference image is formed. And processing means for ending the correction processing when the determination means determines that the correction limit or the correction limit is approached.
[0016]
The second image forming apparatus according to the present invention relates to a reference image forming unit that forms a reference image on an image carrier based on image forming conditions, and an image quality of the reference image formed by the reference image forming unit. A detection means for detecting a physical quantity; a difference between a current detection value of a physical quantity related to image quality detected by the detection means and a predetermined reference value; and a difference between a past detection value including at least the previous time and the reference value And a determination means for determining whether or not the correction limit or the correction limit is close, and a correction process for correcting the image forming condition so that the detected value approaches the reference value. And a processing means for ending the correction process when the determination means determines that the correction limit or the correction limit is close.
[0017]
In the present invention, the reference image forming unit forms the reference image on the image carrier based on the image forming conditions.
The physical quantity relating to the image quality may be, for example, the potential on the photoconductor, the toner image density, or the like when the reference image is formed on the photoconductor, or when the reference image is formed on the paper. The toner image density and color value may be used, and are not particularly limited.
[0018]
The detecting means detects a physical quantity related to the image quality of the reference image formed by the reference image forming means.
[0019]
The detection means is not particularly limited. For example, if the physical quantity related to the detected image quality is a color value, it can be a color sensor, and if the physical quantity related to the detected image quality is the toner image density, it can be a toner image density sensor. it can.
[0020]
The determination unit of the first image forming apparatus includes a difference between the current detection value of the physical quantity related to the image quality detected by the detection unit and a predetermined reference value, and a past detection value and a reference value including at least the previous time. The difference is compared to determine whether or not the correction limit or the correction limit is close.
[0021]
In addition, the determination unit of the first image forming apparatus is configured to calculate the difference between the current detection value and the previous detection value, and the current detection value and the previous detection value N (N is an integer equal to or smaller than the number of correction processes executed) times. Calculate any one of the difference between the average value of the previous detection values and the average value of the difference between the detection value from this time to the previous N times and the previous detection value for each detection value as a judgment value, Correction is made in either case where the judgment value falls below a predetermined threshold, and when the number of times the judgment value falls below a predetermined threshold reaches a predetermined number of times. It is possible to determine that the limit is close to the correction limit.
[0022]
For example, if the difference between the current detection value and the previous detection value is larger than the threshold value, it can be determined that the difference is likely to become smaller if the correction process is repeated further, and the correction limit or near the correction limit. It can be judged that it has not reached. In addition, when the difference between the current detection value and the previous detection value is less than or equal to the threshold value, it can be determined that even if the correction process is repeated further, the difference is unlikely to be further reduced. It can be determined that the correction is close to the limit.
[0023]
In this way, by using not only the current detection value but also the past detection value including at least the previous detection value, the correction limit or correction depends on the capability of the device at that time, regardless of the state or environment of the device. It is possible to determine whether or not it is close to the limit.
[0024]
The determination unit of the second image forming apparatus includes a difference between the current detection value of the physical quantity related to the image quality detected by the detection unit and a predetermined reference value, and a past detection value and a reference value including at least the previous time. The difference is compared to determine whether or not the correction limit or the correction limit is close.
[0025]
In addition, the determination unit of the second image forming apparatus may include a difference between a current detection value and the reference value, a difference between a previous detection value and the reference value, a current detection value and the reference value. The difference between the detected value and the average value of the difference between each reference value and the reference value up to N (N is an integer equal to or less than the number of correction processes executed) from the previous time, N times before this time A difference between each detected value up to and the reference value, and a difference between the previous detected value and the reference value with respect to each difference are calculated as a judgment value, When the judgment value is less than or equal to a predetermined threshold, when the number of times that the judgment value is less than or equal to the predetermined threshold has reached a predetermined number of times, and the current detection value and the reference value If the difference between the previous detection value and the reference value is larger, the correction limit or the correction limit It can be determined that close to.
[0026]
For example, if the difference between the current detection value and the reference value and the difference between the previous detection value and the reference value are larger than the threshold value, the difference may be further reduced if correction processing is further repeated. Can be determined to be high, and it can be determined that the correction limit or the correction limit is not reached. In addition, when the difference between the current detection value and the reference value and the difference between the previous detection value and the reference value is less than or equal to the threshold value, the difference is further increased even if correction processing is repeated further. It can be determined that the possibility of being small is low, and it can be determined that the correction limit or the correction limit is close.
[0027]
If the difference between the current detection value and the reference value is greater than the difference between the previous detection value and the reference value, the detection value is not close to the reference value. It can be judged that it is close to the limit.
[0028]
In this way, by using not only the difference between the current detection value and the reference value, but also the difference between the previous detection value including at least the previous time and the reference value, regardless of the state or environment of the device, It is possible to determine whether or not the correction limit or the correction limit is close according to the ability.
[0029]
Note that the threshold value to be compared with the determination value may be set in the apparatus in advance, or may be arbitrarily set by the user before starting the correction process. Similarly, the number of times of comparison with the number of times that the judgment value has become equal to or less than a predetermined threshold value may be set in advance in the apparatus, or may be arbitrarily set by the user before starting the correction process. Good.
[0030]
The processing means repeatedly executes a correction process for correcting the image forming condition so that the detected value approaches a predetermined reference value every time the reference image is formed, and the processing means performs a correction limit or correction by the determination means. If it is determined that the value is close to the limit, the correction process is terminated.
[0031]
The formation of the reference image and the correction process can be performed for each screen, for example, and can be performed for each image density.
[0032]
As described above, according to the image forming apparatus of the present invention, it is determined whether or not the correction limit or the correction limit is approached, and the end of the correction process is controlled. The correction process can be terminated by determining that the correction limit is approaching or approaching the limit, and the image forming conditions can be corrected to an optimum state.
[0033]
Further, the processing means terminates the correction process when it is determined that the correction limit or the correction limit is close, or is further determined in advance from the time when it is determined that the correction limit or the correction limit is close. It is also possible to end the correction process after repeatedly executing the correction process.
[0034]
The correction process is terminated when it is determined that the correction limit or the correction limit is approached, or the correction process is repeated a predetermined number of times from the determination that the correction limit or the correction limit is approached. Whether to end after execution may be set in the apparatus in advance, or may be set by the user before starting the correction process. In addition, the number of correction processes to be repeated from the time when it is determined that the correction limit or the correction limit is close may be set in the apparatus, for example, in advance by an experiment or the user may start the correction process. It may be arbitrarily set before.
[0035]
In addition, the processing unit may be configured such that when the number of corrections of the image forming condition reaches a predetermined upper limit, even if the determination unit does not determine that the correction limit or the correction limit is close, The correction process can also be terminated.
[0036]
If the upper limit of the number of corrections is set in advance, even if the correction accuracy is not stable, if the correction number reaches the predetermined upper limit, the correction process can be terminated, and the correction process is repeated unnecessarily. Can be prevented.
[0037]
The above-described image forming apparatus has a notification unit that notifies a warning when a difference between a detection value and a reference value that is determined to be close to a correction limit or near a correction limit exceeds a predetermined threshold value. It is also possible to further comprise.
[0038]
This allows the user to recognize that the expected correction accuracy has not been obtained. The threshold value to be compared with the difference between the detected value and the reference value may be set in the apparatus in advance, or may be set by the user before starting the correction process.
[0039]
The above-described image forming apparatus may further include a display unit that displays a correction result when the correction process is completed.
[0040]
Thereby, the user can visually recognize the state of the correction accuracy with reference to the displayed correction result.
[0041]
The displayed correction result is not particularly limited as long as the user can recognize the correction accuracy state, and the difference between the detection value and the reference value when it is determined that the correction limit or the correction limit is close. Or the difference between all the detected values detected during the correction process and the reference value. Further, it may be a detection value detected during the correction process, a difference between the previous detection value and the current detection value, a determination value used to determine a correction limit, or the like.
[0042]
The above-described image forming apparatus may further include an instruction unit that instructs to cancel the correction and repeat the correction process when the correction process is completed.
[0043]
As a result, when the user finishes the correction process, the user can be instructed to cancel the completion and repeat the correction process. Therefore, the number of correction processes can be easily increased as necessary, and the correction accuracy can be increased. Can be increased.
[0044]
When the correction process is completed, the above-described image forming apparatus holds either the image formation condition when the correction process is completed or returns the image formation condition to the state before the correction process is performed. A selection means for selecting one of these may be further included.
[0045]
Thus, the user can easily select whether to maintain the image forming conditions changed by the correction or to return the image forming conditions to the state before the correction is executed.
[0046]
A first image forming condition correction method according to the present invention relates to a reference image forming process for forming a reference image on an image carrier based on image forming conditions, and an image quality of the reference image formed by the reference image forming process. Whether the detection step for detecting the physical quantity and the current detection value of the physical quantity related to the image quality detected by the detection step are compared with the past detection value including at least the previous detection value, or whether the correction limit is close to the correction limit. A determination step of determining whether or not and a correction process for correcting the image forming condition so that the detected value approaches a predetermined reference value is repeatedly performed for each reference image formation, and correction is performed by the determination step. And a processing step of ending the correction process when it is determined that the limit or the correction limit is approached.
[0047]
The second image forming condition correction method according to the present invention relates to a reference image forming step for forming a reference image on an image carrier based on the image forming conditions, and an image quality of the reference image formed by the reference image forming step. A detection step for detecting a physical quantity; a difference between a current detection value of a physical quantity relating to image quality detected by the detection step and a predetermined reference value; and a difference between a past detection value including at least the previous time and the reference value And a determination process for determining whether or not the correction limit or the correction limit is close, and a correction process for correcting the image forming condition so that the detected value approaches the reference value And a process step of ending the correction process when the determination means determines that the correction limit or the correction limit is close.
[0048]
By executing the first and second image forming condition correction methods, it is possible to determine that the correction limit is near or close to the limit regardless of the state or environment of the apparatus, and to end the correction process. Can be corrected to an optimum state.
[0049]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
[0050]
[First Embodiment]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.
[0051]
The illustrated image forming apparatus 1 forms a latent electrostatic image by irradiating a laser beam after charging the surface of a photosensitive member with a charger, and a developing unit for developing the latent electrostatic image with toner is yellow (Y). , A tandem color electrophotographic full-color image forming apparatus provided for each color of magenta (M), cyan (C), and black (K).
[0052]
The image forming apparatus 1 includes a controller 10, a detection device 22, a UI display unit 16, a patch signal generator 18, and a laser driver 20.
[0053]
The controller 10 includes a microcomputer having a CPU, a ROM, and a RAM (not shown). The controller 10 controls and manages the entire apparatus based on a predetermined program. In a predetermined program, a reference image (hereinafter referred to as a patch) is formed, and correction processing for correcting image forming conditions such as exposure conditions and gradation characteristics used for image formation is executed and corrected. A processing routine program for determining the limit and terminating the correction process is included. Functions realized by executing this program include a calculation unit 12 for calculating a judgment value (described later) and an image formation condition correction unit 14 for correcting image formation conditions. A predetermined program including this program is stored in a ROM (not shown) in the microcomputer.
[0054]
The detection device 22 detects a physical quantity related to the image quality of the patch Pa formed on the paper P. For example, the detection device 22 can be a color sensor if the physical quantity relating to the detected image quality is a color value, and can be a toner image density sensor if the physical quantity relating to the detected image quality is the toner image density.
[0055]
The UI display unit 16 includes, for example, a touch panel display in which a touch panel is superimposed on a display, and can display various information or input desired information and instructions by user operation.
[0056]
When a patch formation instruction signal is input from the controller 10, the patch signal generator 18 generates an image signal for forming the patch Pa and outputs it to the laser driver 20.
[0057]
The laser driver 20 supplies a drive current to the laser output unit (ROS) 28 for each color based on the image signal input from the patch signal generator 18 to drive the ROS 28.
[0058]
The image forming apparatus 1 is further driven by a photoconductor 32 that rotates in the direction indicated by the arrow for each color of CMYK, a contact charger 30 that charges the surface of the photoconductor 32, and a laser driver 20. The surface is exposed with exposure light to form an electrostatic latent image on the photosensitive member 32, the ROS 28, the toner cartridge 24 for supplying toner, and the electrostatic latent image on the photosensitive member 32 are developed with each color developer and the photosensitive member 32 is developed. A developing unit 26 for forming a toner image thereon and a primary transfer unit 34 for transferring each color toner image on the photoreceptor 32 to the intermediate transfer belt 40 are provided.
[0059]
The image forming apparatus 1 further fixes a sheet feed unit 42 that supplies the sheet P, a secondary transfer unit 38 that transfers the toner image on the intermediate transfer belt 40 to the sheet P, and the toner image transferred to the sheet P. A fixing device 36 is provided.
[0060]
Next, a processing routine executed by the controller 10 of the present embodiment will be described using the flowchart of FIG.
[0061]
In the present embodiment, a case where a physical quantity relating to detected image quality is a toner image density and an image forming condition to be corrected is an exposure parameter (exposure amount exposed by ROS 28) will be described as an example. That is, here, the toner image density of the patch Pa formed on the paper P is detected, and the exposure parameter is corrected based on the detected toner image density, so that the target color is obtained. Since the physical quantity relating to the image quality to be detected is the toner image density, a toner image density sensor is used for the detection device 22.
[0062]
In step 100, the controller 10 resets the counter K. The counter K is a counter for counting the number of times the correction process is executed.
[0063]
In step 102, the controller 10 increments K.
[0064]
In step 104, the controller 10 causes the patch signal generator 18 to store image forming conditions stored in a memory (not shown) so that the patch Pa is formed on the image carrier (paper P in the present embodiment). A patch formation instruction signal is output together with information on (here, exposure parameter LD).
[0065]
When the patch formation instruction signal is input, the patch signal generator 18 outputs an image signal for forming the patch Pa to the laser driver 20 based on the image forming conditions. The laser driver 20 drives the ROS 28 based on the input image signal.
[0066]
The ROS 28 irradiates the surface of the photoconductor 32 uniformly charged by the contact charger 30 with a laser beam modulated by the image signal. As a result, an electrostatic latent image corresponding to the input image signal is formed on the photoreceptor 32. Next, the electrostatic latent image on the photoreceptor 32 is developed with toner by the developing device 26, and a toner image is formed on the photoreceptor 32.
[0067]
The toner image formed on the photoreceptor 32 is transferred to the intermediate transfer belt 40 by the primary transfer unit 34. After the toner image has been transferred to the intermediate transfer belt 40, the photoreceptor 32 is cleaned of adhering matter such as residual toner adhering to the surface by a cleaner (not shown), and the residual charge is removed by a static eliminator (not shown).
[0068]
The toner image on the intermediate transfer belt 40 is transferred onto the paper P conveyed from the paper feed unit 42 by the secondary transfer device 38. The toner image transferred onto the paper P is fixed by the fixing device 36, and the transfer of the toner image onto the paper P is completed. After the transfer is completed, the intermediate transfer belt 40 is cleaned of deposits such as residual toner adhered to the surface by a belt cleaner (not shown). The patch Pa is formed on the paper P by the above operation.
[0069]
In step 106, the controller 10 instructs the detection device 22 (here, toner image density sensor) to detect a physical quantity (here, toner image density) relating to the image quality of the patch Pa formed on the paper P. Output a signal. Accordingly, the detection device 22 detects the toner image density of the patch Pa formed on the paper P and outputs it to the controller 10.
[0070]
In Step 108, the controller 10 stores the toner image density input from the detection device 22 as a detection value in a memory (not shown).
[0071]
In step 110, the controller 10 determines whether or not the counter K is 1. When it is determined that the counter K is 1, the process proceeds to step 116, and the image forming condition (here, the exposure parameter LD) is corrected. Specifically, the corrected exposure amount ΔLD is calculated using the function of the image forming condition correction unit 14 so that the detection value approaches a predetermined reference value. The reference value refers to a predetermined target value for a physical quantity related to the detected image quality. The controller 10 stores the calculated corrected exposure amount ΔLD in a memory (not shown) and adds the calculated corrected exposure amount ΔLD to the exposure parameter LD to correct the exposure parameter LD. Thereafter, the process returns to step 102.
[0072]
The controller 10 performs the processing from step 102 to step 108 as described above, increments the counter K, forms a patch Pa, detects the toner image density, and stores a new detection value in the memory.
[0073]
If the controller 10 determines in step 110 that the counter K is not 1, the controller 10 calculates a determination value in step 112.
[0074]
The determination value is a parameter that is used to determine whether or not the correction limit is compared with a threshold value α that will be described later. Here, the controller 10 reads the current detection value and the previous detection value stored in the memory using the function of the calculation unit 12, calculates the difference, and uses the calculated difference as the determination value.
[0075]
In step 114, the controller 10 compares the calculated determination value with the threshold value α. The threshold value α is an index indicating whether or not the correction limit is reached, and is a preset value. If the judgment value is less than or equal to the threshold value α, the difference between the current detection value and the previous detection value is small, and therefore the rate at which the detection value approaches the reference value is small or close to the reference value even if correction processing is repeated further. Therefore, it can be determined that it is the limit of correction. On the other hand, if the determination value exceeds the threshold value α, it can be determined that the detection value can be made closer to the reference value by repeating the correction process, that is, it is not the limit of correction.
[0076]
If it is determined in step 114 that the determination value exceeds the threshold value α, the controller 10 determines that it is not the limit of correction, proceeds to step 116, and continues the correction process.
[0077]
If it is determined in step 114 that the determination value is equal to or smaller than the threshold value α, the controller 10 determines that the correction limit is reached, and ends the correction process.
[0078]
In this example, the case where the correction value is determined to be the limit of correction when the determination value is equal to or less than the threshold value α is described as an example. It may be determined that the limit is approached, and the correction process may be repeated a predetermined number of times before terminating. Thereby, the correction accuracy can be further improved. The number of repetitions of the correction process executed after it is determined that the correction limit is close can be arbitrarily set by the user. Further, the number of times until the correction limit is actually reached after it is determined to be close to the correction limit can be obtained in advance by experiments or the like, and that number can be set in the apparatus in advance.
[0079]
In this way, the current detection value and the previous detection value can be compared to determine whether or not the correction limit or the correction limit is close, so the correction limit is determined according to the capability of the device at that time. The image forming conditions can be corrected by repeating the correction process up to Therefore, the image forming conditions can be corrected to an optimum state. In addition, the correction process is not repeated unnecessarily, and the correction is not completed halfway before reaching the correction limit.
[0080]
In the present embodiment, an example has been described in which the difference between the current detection value and the previous detection value is obtained and used as a determination value. However, the determination value is not limited to this.
[0081]
For example, in step 112 described above, the difference between the average value of the detection values from the previous time to N times before and the current detection value may be calculated and used as the determination value. Here, N represents an integer equal to or less than the number of correction processes that have been executed. For example, when the average value of all the detected values in the past is obtained, the number obtained by subtracting 1 from the counter K used in the above-described processing routine is N. N may be a number set in advance in the apparatus, or may be a number set by the user before starting the correction process. In this case, the determination value calculation process in step 112 and the determination process in step 114 are not performed until K−1 becomes N or more.
[0082]
Further, in step 112, an average value of differences from the previous detection values for all detection values from this time to N times before may be calculated and used as a determination value. N represents an integer equal to or smaller than the number of correction processes executed as described above. Similarly, N may be a number set in advance in the apparatus, or may be a number set by the user before starting the correction process.
[0083]
By calculating the determination value in this way, the influence of detection unevenness of the detection device 22 can be reduced, and it is possible to accurately determine whether or not the correction limit or the correction limit is approached.
[0084]
Further, when the number of times that the determination value becomes equal to or less than the threshold value α reaches a predetermined number, it may be determined that the correction limit or the correction limit is approached, and the correction process may be terminated. In this case, steps 120, 122, and 124 shown in FIG. 3 are executed in place of step 114 of the above-described processing routine.
[0085]
Here, in addition to the counter K, the counter n is used. n is reset together with the counter K in step 100 described above (not shown).
[0086]
After calculating the determination value in step 112, in step 120, the controller 10 determines whether or not the determination value is less than or equal to the threshold value α. If the determination value is less than or equal to the threshold value α, the process proceeds to step 122 and the counter n is incremented.
[0087]
In step 124, the controller 10 determines that n is a preset threshold value n. _th It is determined whether or not this is the case. Threshold n _th If it is less than the limit, it is determined that the correction limit is not reached or is not close to the correction limit. n is the threshold value n _th If it is above, it is determined that the correction limit or the correction limit is close, and the correction process is terminated.
[0088]
By performing such processing, it is possible to reduce the influence of the detection unevenness of the detection device 22, and to determine whether or not the correction limit or the correction limit is close with high accuracy.
[0089]
In this embodiment, the example in which the toner image density of the patch Pa formed on the paper P is detected has been described. However, the toner image density of the patch Pa formed on the photoconductor 32 may be detected. The toner image density of the patch Pa formed on the intermediate transfer belt 40 may be detected, and the image carrier that forms the patch Pa is not particularly limited.
[0090]
Further, the physical quantity relating to the image quality to be detected is not particularly limited, and may be, for example, the potential on the photoconductor 32, the brightness or the saturation on the paper P, and not the toner image density. The image forming conditions to be corrected are not limited to exposure parameters. For example, charging parameters, development parameters, transfer parameters, toner supply parameters, LUT (Look Up) in which conversion characteristics used for conversion such as density and saturation are set. Table).
[0091]
For example, the physical quantity relating to the detected image quality can be the color (L * a * b *) value of the patch Pa, and the image forming condition to be corrected can be the LUT. Also in this case, the same processing as the processing routine described above is performed, the color value of the patch Pa formed on the paper P is detected, and the LUT is corrected by the detected color value of the patch Pa to obtain the target color. The correction can be performed so that Note that since the physical quantity related to the image quality to be detected is the color value of the patch Pa, a color sensor is used for the detection device 22.
[0092]
It is also possible to form a patch Pa for each screen and perform correction processing on each formed patch Pa. For example, there are various screens, such as a dot screen, a line screen, or a line screen, such as a 200-line line screen or a 300-line line screen, and there are various screens. , The judgment value is calculated for each patch, the correction limit is judged, and the correction processing can be terminated. In this case, a threshold value can be set for each screen to determine the correction limit.
[0093]
It is also possible to form a patch Pa for each image density and perform correction processing on each formed patch Pa. For example, a low-density patch, a medium-density patch, and a high-density patch can be formed, a judgment value can be calculated for each patch, a correction limit can be judged, and the correction process can be terminated. In this case as well, a threshold value can be set for each image density, and the correction limit can be determined.
[0094]
Further, a patch Pa may be formed for each combination of screen and image density, and a threshold value may be set.
[0095]
Further, the threshold α for determining whether or not the correction limit is close to the correction limit may be a value set in the apparatus in advance, or a value set by the user before the start of the correction process. Also good. FIG. 4 is a diagram showing an example of a setting screen for setting the threshold value α. The setting screen is displayed on the UI display unit 16, and the user can input a threshold value for each image density (low density part, medium density part, and high density part) according to the display. Although illustration is omitted, it is also possible to set a threshold value for each screen. A common threshold value may be set regardless of the image density and the screen.
[0096]
[Second Embodiment]
In the first embodiment described above, an example has been described in which the current detection value is compared with a past detection value including at least the previous detection value to determine whether or not the correction limit or the correction limit is close. However, in the following, a difference between the current detection value and a predetermined reference value is calculated, and the calculated difference is compared with a difference calculated in the past including at least the previous time, so that a correction limit or correction is made. A second embodiment for determining whether or not the limit is close will be described.
[0097]
Since the configuration of the image forming apparatus according to the present embodiment and the processing routine executed by the controller 10 are the same as those in the first embodiment, description thereof is omitted.
[0098]
However, in the present embodiment, the controller 10 (calculation unit 12) calculates the determination value as follows.
[0099]
In step 112 of the above-described processing routine, the controller 10 reads the current detection value and the previous detection value stored in the above-described memory (not shown), the difference between the current detection value and the reference value, and the previous time The difference between the detected value and the reference value is calculated.
[0100]
Hereinafter, for the sake of convenience, the difference between the current detected value and the reference value is referred to as the current calculated value, and the difference between the previous detected value and the reference value is referred to as the previous calculated value.
[0101]
Next, the controller 10 calculates the difference between the current calculated value and the previous calculated value. This value is used as a judgment value.
[0102]
Note that the difference between the current detection value and the reference value may be calculated when the patch Pa is detected. In this case, in step 108, the calculated value instead of the detected value is stored in the memory, and in step 112, the current calculated value and the previous calculated value are read from the memory, the difference is calculated, and the determination is made. A value may be obtained.
[0103]
After the determination value is calculated, similarly to the first embodiment, the controller 10 compares the calculated determination value with the threshold value α to determine whether or not the correction limit or the correction limit is close. If it is determined that the correction limit or the correction limit is approached, the correction process is terminated. If it is determined that the correction limit is not reached or is not close to the correction limit, the correction process is continued.
[0104]
In this way, the current calculated value and the previous calculated value can be compared to determine whether or not it is close to the correction limit or the correction limit. Therefore, the correction limit is determined according to the capability of the device at that time. The image forming conditions can be corrected by repeating the correction process up to Therefore, the image forming conditions can be corrected to an optimum state. In addition, the correction process is not repeated unnecessarily, and the correction is not completed halfway before reaching the correction limit.
[0105]
Here, an example has been described in which the difference between the current calculated value and the previous calculated value is obtained and used as the determination value, but the determination value is not limited to this.
[0106]
For example, the difference between the average value of the calculated values from the previous time to N times before and the current calculated value may be calculated and used as the determination value. Here, N represents an integer equal to or less than the number of correction processes that have been executed. For example, when obtaining the average value of all the calculated values in the past, the number obtained by subtracting 1 from the counter K used in the processing routine described above is N. N may be a number set in advance in the apparatus, or may be a number set by the user before starting the correction process. In this case, the determination value calculation process in step 112 and the determination process in step 114 are not performed until K−1 becomes N or more.
[0107]
Further, an average value of the difference between the calculated value from the current time to N times before and the previous calculated value may be calculated and used as the determination value. N represents an integer equal to or smaller than the number of correction processes executed as described above. Similarly, N may be a number set in advance in the apparatus, or may be a number set by the user before starting the correction process.
[0108]
By calculating the determination value in this way, the influence of detection unevenness of the detection device 22 can be reduced, and it is possible to accurately determine whether or not the correction limit or the correction limit is approached.
[0109]
Further, when the number of times that the determination value becomes equal to or less than the threshold value α reaches a predetermined number, it may be determined that the correction limit or the correction limit is approached, and the correction process may be terminated. In this case, as described in the first embodiment, steps 120, 122, and 124 shown in FIG. 3 are executed instead of step 114 of the processing routine described above.
[0110]
By performing such processing, it is possible to reduce the influence of the detection unevenness of the detection device 22, and to determine whether or not the correction limit or the correction limit is close with high accuracy.
[0111]
In addition to comparing the calculated judgment value with the threshold value, the current calculation value and the previous calculation value itself are compared with each other to determine whether the correction limit or the correction limit is close. You can also. For example, it is determined that the correction limit or the correction limit is close when either the calculated determination value falls within the threshold value or the current calculated value is larger than the previous calculated value. You just have to do it.
[0112]
In this case, steps 130 and 132 shown in FIG. 5 are executed in place of step 114 of the processing routine described above.
[0113]
After calculating the determination value in step 112, in step 130, the controller 10 determines whether or not the determination value is less than or equal to the threshold value α. If the determination value is equal to or less than the threshold value α, it is determined that the correction limit or the correction limit is approached, and the correction process is terminated.
[0114]
When the controller 10 determines in step 130 that the determination value exceeds the threshold value α, in step 132, the difference between the current detection value and the reference value (current calculation value) and the previous detection value are determined. And the difference (previously calculated value) between the reference value and the reference value. If the current calculated value is less than or equal to the previous calculated value, it is determined that it is not the limit of correction or is not close to the limit of correction, the process proceeds to step 116, and the correction process is continued. If the current calculated value is larger than the previous calculated value, it is determined that the correction limit or the correction limit is approached, and the correction process is terminated.
[0115]
Also by such a method, it is possible to determine whether the correction limit or the correction limit is approached.
[0116]
[Third Embodiment]
In the first and second embodiments, the example in which the correction process is repeatedly executed until it is determined that the correction limit or the correction limit is close is described. However, in this embodiment, the upper limit of the number of corrections is set in advance. An example will be described in which the correction process is terminated when the correction count reaches the upper limit even if it is not determined that the correction limit or the correction limit is approached.
[0117]
Since the configuration of the image forming apparatus according to the present embodiment is the same as that of the first embodiment, description thereof is omitted. Further, the processing routine executed by the controller 10 executes Steps 140 and 142 of FIG. 6 instead of Step 114 of the processing routine described in the first embodiment.
[0118]
After calculating the determination value in step 112, in step 140, the controller 10 determines whether or not the determination value is less than or equal to the threshold value α. When the determination value is equal to or less than the threshold value α, it is determined that the correction limit or the correction limit is approached, and the correction process is terminated (normal end).
[0119]
If it is determined in step 140 that the determination value exceeds the threshold value α, it is determined that it is not the limit of correction or is not close to the limit of correction, and the routine proceeds to step 142.
[0120]
In step 142, the controller 10 determines that the counter K for counting the number of executions of the correction process is K. _th It is judged whether it is over. K _th Is a value set as the upper limit of the number of corrections.
[0121]
In step 142, the counter K is K _th If it is determined that the value does not exceed, the process proceeds to step 116 to continue the correction process.
[0122]
In step 142, the counter K is K _th If it is determined that the value exceeds the correction value, the correction process is terminated. In this case, since the correction limit or near the correction limit is not reached, the process ends abnormally.
[0123]
Thus, if the limit of correction or the limit of correction is not reached even when the upper limit of the number of corrections set in advance is reached, it can be determined that the state where the correction accuracy is not stable continues. In the case of the state, it is possible to prevent the correction process from being repeated unnecessarily by terminating the correction process.
[0124]
Maximum number of corrections K _th May be preset in the apparatus, or may be arbitrarily set by the user before starting the correction process.
[0125]
FIG. 7 is a diagram showing an example of a setting screen for setting an upper limit (the maximum number of repetitions) of the number of corrections for each screen when the correction process is executed for each screen. The setting screen is displayed on the UI display unit 16, and the user can input the upper limit of the number of corrections in accordance with the instruction of the displayed setting screen. In this way, the user can set the upper limit of the number of corrections before starting the correction process.
[0126]
[Fourth Embodiment]
In the present embodiment, an example will be described in which a warning is notified when it is determined that the expected correction accuracy has not been obtained when the correction process is terminated.
[0127]
Since the configuration of the image forming apparatus according to the present embodiment is the same as that of the first embodiment, description thereof is omitted. Further, in the processing routine executed by the controller 10, steps 150, 152, and 154 in FIG. 8 are executed instead of step 114 of the processing routine described in the first embodiment.
[0128]
After calculating the determination value in step 112, in step 150, the controller 10 determines whether or not the determination value is less than or equal to the threshold value α. If the determination value is less than or equal to the threshold value α, the process proceeds to step 152 where the difference between the current detection value (that is, the detection value at the end of the correction process) and the reference value exceeds a preset threshold value β. Determine whether or not. The threshold β is an index for determining the correction accuracy, and may be set in advance in the apparatus, or may be arbitrarily set by the user before starting the correction process.
[0129]
If the difference is equal to or smaller than the threshold value β in step 152, the controller 10 determines that the expected correction accuracy has been obtained and ends the correction process. If the difference exceeds the threshold β in step 152, the controller 10 determines that the expected correction accuracy has not been obtained, and displays the abnormal end on the UI display unit 16 in step 154. The correction process is terminated.
[0130]
By performing such processing, the user can recognize that the expected correction accuracy has not been obtained.
[0131]
[Fifth Embodiment]
In the present embodiment, when the correction process ends, the difference between each detected value detected during the correction process and the reference value is displayed on the UI display unit 16 as the correction result, and the end of the correction process is canceled. An example in which the user inputs an instruction as to whether or not to execute the correction process repeatedly will be described.
[0132]
FIG. 9 shows an example of a screen displayed when the correction process is completed. This figure shows that the correction process has been completed four times. Further, as a correction result, a difference 52 between the detection value and the reference value is displayed for each image density from the first correction to the fourth correction. In addition to the difference 52 between the detected value and the reference value, an average value 54, a maximum value 56, and a minimum value 58 are displayed for each correction count. Further, this screen is provided with a Start button 60 for repeatedly executing the correction process and a Close button 62 for closing the screen without repeating the correction process.
[0133]
The user can visually recognize the correction accuracy state by referring to the displayed correction result, and can determine whether or not the correction is the limit. When the user determines that the correction is not at the limit and the difference between the detected value and the reference value can be reduced by performing further correction processing, the Start button 60 is executed so that the correction processing is repeatedly executed. Can be pressed. When the correction process is not executed, the Close button 62 can be pressed.
[0134]
When the Start button 60 is pressed, the controller 10 performs control so that the correction process is repeated a predetermined number of times. Note that when the upper limit of the number of corrections is set in advance as in the third embodiment, the correction process may be repeated up to the upper limit.
[0135]
As described above, when the correction process is completed, the correction result is displayed, and it is possible to instruct to cancel the correction end and repeatedly execute the correction process, so that the number of times of executing the correction process can be easily increased. It is possible to improve the correction accuracy.
[0136]
The correction result to be displayed may be only the difference between the detection value when it is determined that the correction limit or the correction limit is close and the reference value, or all detection values detected during the correction process. And a difference between the reference value and the reference value. Further, it may be a detection value detected during the correction process, a difference between the previous detection value and the current detection value, a determination value used to determine a correction limit, or the like.
[0137]
For example, as shown in FIG. 10, for each correction count, the judgment value used in the second embodiment (the difference between the current calculated value and the previous calculated value) is displayed in a graph. Also good. Further, the threshold value α used for determining whether or not the correction is the limit may be displayed on the graph so that the state of the correction accuracy can be shown more clearly.
[0138]
[Sixth Embodiment]
In the present embodiment, when the correction process is completed, the correction result is displayed on the UI display unit 16, and the image forming condition at the end of the correction is retained, or whether the image forming condition before executing the correction process is restored. An example in which the user selects either one of these will be described.
[0139]
FIG. 11 shows an example of a screen displayed when the correction process is completed. As a correction result, a reference value 70, a detection value 72 before correction, and a detection value 74 at the end of correction are displayed. Further, on this screen, an OK button 76 for validating the correction result (that is, holding the image forming condition at the time of completion of correction) and invalidating (that is, returning the image forming condition to before the correction processing is executed). ) Close button 78 is provided.
[0140]
The user can visually recognize the correction accuracy state based on the displayed correction result. If the user is satisfied with the result of the correction process, the user presses the OK button 76 to validate the correction result. If the user is not satisfied with the result of the correction process, the user presses the Close button 78 to invalidate the correction result. Can be pressed.
[0141]
When the OK button is pressed, the controller 10 controls to maintain the corrected image forming conditions. When the Close button 78 is pressed, the controller 10 returns the image forming conditions to the state before the correction processing. To control.
[0142]
By displaying the correction result in this way, the user can visually recognize the difference between the expected correction accuracy and the current correction accuracy, and retain the image forming conditions changed by the correction, or before executing the correction. It is easy to select whether to return to the current state.
[0143]
Note that the correction result to be displayed may be only the difference between the detection value detected at the end of the correction process and the reference value, as in the fifth embodiment, or all the detection results detected during the correction process. The difference between the detected value and the reference value may be used. Further, it may be a detection value detected during the correction process, a difference between the previous detection value and the current detection value, a determination value used to determine a correction limit, or the like.
[0144]
The present invention is not limited to the first to sixth embodiments described above, and various design changes can be made within the scope described in the claims.
[0145]
For example, in each of the above-described embodiments, an example in which the image forming apparatus is a laser printer has been described. However, an analog copying machine or the like may be used, and the present invention can be applied to various image forming apparatuses.
[0146]
【The invention's effect】
As described above, according to the present invention, the physical quantity related to the image quality of the reference image is detected, and the current detection value is compared with the past detection value including at least the previous detection value, or the current detection value. By comparing the difference between the reference value and the predetermined reference value and the difference between the previous detected value including at least the previous time and the reference value, to determine whether the correction limit or the correction limit is close Since the correction process is terminated, the correction process can be terminated by determining that the correction limit is approaching or close to the limit regardless of the state or environment of the apparatus, and the image forming conditions are optimized. There is an effect that it can be corrected.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention. .
FIG. 2 is a flowchart showing a processing routine executed by a controller.
FIG. 3 shows a step for ending a correction process when determining that the number of times that the judgment value has become equal to or less than the threshold value α reaches a predetermined number of times, and determining that the limit is close to the correction limit or the correction limit. FIG.
FIG. 4 is a diagram showing an example of a setting screen for setting a threshold value α.
FIG. 5 shows that the correction limit or the correction limit is close in either one of the case where the calculated judgment value falls within the threshold and the current calculation value exceeds the previous calculation value. It is the figure which showed the step which judges and complete | finishes a correction process.
FIG. 6 is a diagram showing a step for ending correction processing when the number of corrections reaches the upper limit even when it is not determined that the correction limit or the correction limit is approached.
FIG. 7 is a diagram showing an example of a setting screen for setting an upper limit of the number of corrections.
FIG. 8 is a diagram showing a step of notifying a warning when it is determined that the expected correction accuracy is not obtained when the correction process is terminated.
FIG. 9 is a diagram illustrating an example of a screen displayed when correction processing is completed.
FIG. 10 is a diagram illustrating a display example of a correction result.
FIG. 11 is a diagram illustrating an example of a screen displayed when correction processing is completed.
FIG. 12 is a diagram showing a conventional correction processing technique.
[Explanation of symbols]
1 Image forming device
10 Controller
12 Calculation unit
14 Image forming condition correction unit
16 UI display
18 Patch signal generator
20 Laser driver
22 Detector
32 photoconductor
40 Intermediate transfer belt
P paper
Pa patch (reference image)

Claims (12)

Reference image forming means for forming a reference image on the image carrier based on image forming conditions;
Detecting means for detecting a physical quantity related to the image quality of the reference image formed by the reference image forming means;
A determination unit that compares the current detection value of the physical quantity related to the image quality detected by the detection unit with a past detection value including at least the previous detection value to determine whether the correction limit or the correction limit is approached; ,
A correction process for correcting the image forming condition is repeatedly performed every time a reference image is formed so that the detected value approaches a predetermined reference value, and the determination unit determines that the correction limit or the correction limit is close. Processing means for ending the correction processing when
An image forming apparatus. The determination means includes the difference between the current detection value and the previous detection value, the current detection value and the average value of the detection values from the previous time to N (N is an integer equal to or less than the number of correction processes executed) , And a value obtained by averaging the difference between the detected value from the current time to the previous N times and the previous detected value for each detected value is calculated as a judgment value, and the judgment value is a predetermined threshold value. If it is less than or equal to the limit of correction or the limit of correction in any one of the cases where the number of times that the judgment value is equal to or less than a predetermined threshold has reached a predetermined number of times The image forming apparatus according to claim 1, wherein the determination is made. Reference image forming means for forming a reference image on the image carrier based on image forming conditions;
Detecting means for detecting a physical quantity related to the image quality of the reference image formed by the reference image forming means;
The difference between the current detected value of the physical quantity relating to the image quality detected by the detecting means and a predetermined reference value is compared with the difference between the past detected value including at least the previous time and the reference value to perform correction. A determination means for determining whether the limit or the limit of the correction is close;
When the correction processing for correcting the image forming condition so that the detected value approaches the reference value is repeatedly executed for each reference image formation, and the determination unit determines that the correction limit or the correction limit is close And a processing means for ending the correction process;
An image forming apparatus. The determination means includes
The difference between the current detection value and the reference value, the difference between the previous detection value and the reference value,
The difference between the current detection value and the reference value, and the average value of the difference between the detection value and the reference value from the previous time to N (N is an integer equal to or less than the number of correction processes executed) times before difference,
A value obtained by averaging the difference between each detected value and the reference value from N times before this time and the difference between the previous detected value and the reference value for each difference,
Any one of is calculated as a judgment value,
When the judgment value is less than or equal to a predetermined threshold, when the number of times the judgment value is less than or equal to the predetermined threshold reaches a predetermined number of times, and the current detection value and the reference value The image forming apparatus according to claim 3, wherein when the difference between the first detection value and the reference value is larger than the previous detection value, the correction limit or the correction limit is determined. The processing means terminates the correction process when it is determined that the correction limit or the correction limit is approached, or a predetermined number of times from when it is determined that the correction limit or the correction limit is close. 5. The image forming apparatus according to claim 1, wherein the image forming apparatus terminates after repeatedly executing the correction process. When the number of corrections of the image forming condition has reached a predetermined upper limit, the processing unit may perform the correction process even if the determination unit does not determine that the correction limit or the correction limit is close. The image forming apparatus according to claim 1, wherein the process ends. Claim 1 thru | or further including the alerting | reporting means which alert | reports a warning when the difference of the detection value when it is judged that it is near the limit of correction | amendment or the limit of correction | amendment and the said reference value exceeds the predetermined threshold value. The image forming apparatus according to claim 6. The image forming apparatus according to claim 1, further comprising a display unit that displays a correction result when the correction process is completed. 9. The image forming apparatus according to claim 1, further comprising: an instruction unit that instructs to cancel the correction and repeat the correction process when the correction process ends. Selection means for selecting, when the correction process is completed, whether to hold the image forming condition when the correction process is completed or to return the image forming condition to the state before the correction process is executed. The image forming apparatus according to claim 1, further comprising: A reference image forming step of forming a reference image on the image carrier based on image forming conditions;
A detecting step for detecting a physical quantity related to the image quality of the reference image formed by the reference image forming step;
A determination step of determining whether or not a correction limit or a correction limit is close by comparing a current detection value of a physical quantity related to image quality detected by the detection step with a past detection value including at least a previous detection value; ,
The correction process for correcting the image forming condition is repeatedly performed every time a reference image is formed so that the detected value approaches a predetermined reference value, and it is determined that the correction limit or the correction limit is close by the determination step. A processing step for ending the correction processing when
An image forming condition correction method including: A reference image forming step of forming a reference image on the image carrier based on image forming conditions;
A detecting step for detecting a physical quantity related to the image quality of the reference image formed by the reference image forming step;
The difference between the current detection value of the physical quantity related to the image quality detected by the detection step and a predetermined reference value is compared with the difference between the past detection value including at least the previous time and the reference value to perform correction. A determination step of determining whether the limit or the limit of correction is close;
When the correction processing for correcting the image forming condition so that the detected value approaches the reference value is repeatedly executed for each reference image formation, and the determination unit determines that the correction limit or the correction limit is close And a processing step of ending the correction processing;
An image forming condition correction method including:

Images