JP6459413B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a fax machine using electrophotographic technology.

  In an electrophotographic image forming apparatus, image forming conditions are adjusted in order to stabilize image quality such as image density and color. For example, an adjustment image is formed on the image carrier at a predetermined interval, and this is detected by an optical sensor to detect image density and color misregistration. Based on the detection result, image forming conditions (charging potential, development potential) , An exposure amount, an image forming position, an image processing pattern, etc.) are known.

  In order to reduce downtime, a method is also known in which such an adjustment image is formed in a non-image area (an area that is not transferred to a recording material) during printing, and the image forming conditions are adjusted.

However, in the conventional image forming condition adjusting method, and imaging the adjustment image determined in advance, to set the image forming condition based on the detection result, an image that the user used for printing before printing (hereinafter, print image In other cases , the adjustment operation is performed in consideration of areas of unnecessary colors and densities. As a result, adjustment time becomes long and unnecessary toner is consumed.

  In addition, because the specifications of the CPU and memory installed in the device are limited, it is difficult to correct the local imaging conditions if the imaging conditions are set in the entire density region, and the local image quality deteriorates. There was also.

  In Patent Document 1, in order to reduce the adjustment time of image forming conditions, when potential control for adjusting a solid density (maximum density) and gradation control for correcting gradation characteristics are continuously performed, A technique for limiting the number of adjustment images used for gradation control by utilizing information of adjustment images used in potential control is disclosed.

  The adjustment image is limited in order to reduce the adjustment time, but the user performs the adjustment operation in consideration of a color or density region that is not necessary for the print image. Therefore, there is room for improvement in terms of longer adjustment time, unnecessary toner consumption, local deterioration in image quality, and the like.

  Therefore, an object of the present invention is to realize an image forming apparatus that reduces the adjustment time, reduces unnecessary toner consumption, and improves the image quality.

In order to solve this problem, the present invention provides an image information acquisition unit that acquires density information of an image used for printing , and an adjustment that forms an image for adjusting image forming conditions based on the density information acquired by the image information acquisition unit. Adjustment image setting means for changing an image for use, image forming means for forming an image on an image carrier, image detection means for detecting an image formed by the image forming means, and detection results by the image detection means An image forming apparatus having an image forming condition adjusting unit that adjusts an image forming condition based on the image information acquisition unit, and using the highest density and the lowest density of the density information acquired by the image information acquiring unit, potential - concentration "relationship or" image processing pattern - from concentration "relationship, the patch image in a range that covers up the lowest concentration from the maximum density, the image forming apparatus characterized by selecting as the adjustment image To draft.

Image information such as an image density and an image processing pattern used in the print image is acquired from information on a print image before printing designated by the user in advance, and the adjustment image is changed based on the acquired image information. Therefore, it is possible to reduce the adjustment time of the image forming conditions, reduce unnecessary toner consumption, and improve the image quality.

1 is a schematic diagram illustrating an image forming apparatus according to an embodiment. It is the schematic which shows the example of the developing device in the apparatus. It is the schematic which shows the contact and separation | spacing to the transfer belt of a transfer roller. It is a block diagram which shows the structure of a controller. It is the schematic explaining the adjustment operation of potential control which is one of image formation condition adjustment. 5 is a flowchart of an image forming condition adjustment operation according to the embodiment of the present invention. It is a graph which shows the relationship between an electric potential and a density | concentration. 5 is a flowchart illustrating an adjustment image setting method (first embodiment) using a density gradation method. It is a figure which shows the patch image containing the patch image selected as an image for adjustment in this way. 10 is a flowchart illustrating another adjustment image setting method (second embodiment). It is a figure which shows the selection method of the electric potential corresponding to the image for adjustment in step 23 of FIG. 10 is a flowchart illustrating another adjustment image setting method (third embodiment). It is a figure which shows the selection method of the electric potential corresponding to the image for adjustment in step 33 of FIG. It is a schematic diagram of a typical area gradation pattern. FIG. 10 is a diagram illustrating a “pattern-density” relationship according to the fourth embodiment. 14 is a flowchart of an adjustment image setting method using an area gradation method according to the fourth embodiment. 10 is a flowchart of an adjustment image setting method (Embodiment 5) using an area gradation method. It is a figure which shows the method of selecting the pattern for every predetermined gradation step in step 54 of FIG. 17 as an image for adjustment. 14 is a flowchart of an adjustment image setting method (sixth embodiment) using an area gradation method. 18 is a flowchart of an adjustment image setting method (seventh embodiment) using an area gradation method. FIG. 10 is a diagram illustrating an image forming apparatus (Embodiment 8) capable of adjusting an image forming condition during printing. 19 is a flowchart of an adjustment image setting method in the image forming apparatus according to the eighth embodiment. FIG. 20 is a diagram illustrating setting of an update adjustment image and an update adjustment operation in Embodiment 8.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an image forming apparatus according to the embodiment, and FIG. 2 shows a developing device in the apparatus. The image forming apparatus 1 includes a developing device 2, a transfer belt 3 disposed above the developing device, stretching rollers 11 to 14 that stretch the transfer belt, a density sensor 4 disposed above the transfer belt, and a transfer belt. A belt cleaning unit 5 having a blade 6 in contact therewith, a transfer roller 7 that forms a nip portion facing the stretching roller 11 and the like.

  In FIG. 2, a developing device 22 including a charging roller 18 as a charging unit, a mirror 20 constituting a part of the optical scanning device, and a developing roller 22a around the photoconductor 8 in the rotation direction indicated by arrows. In addition, a transfer unit 10, a cleaning unit 24 including a cleaning blade 24a, and the like are disposed.

  The image forming operation in the image forming apparatus 1 is performed in the same manner as in the past. First, an image signal corresponding to an output image is transmitted to the controller 30 from a personal computer (hereinafter referred to as a PC), a scanner, a facsimile, or the like. The controller 30 converts this image signal into an appropriate output image signal and transmits it to the optical scanning device. In FIG. 2, exposure light Lb from the optical scanning device is irradiated to the exposure unit 26 on the photoconductor 8 through the mirror 20 and scanned, and a latent image is formed on the photoconductor 8. The formed latent image is developed as a toner image through a developing roller 22a of a developing device 22 having a developer such as toner, and is transferred onto the transfer belt 3 by transfer bias application by the transfer means 10 at the transfer portion N. . Residual toner remaining on the photosensitive member 8 without being transferred at the transfer portion N is scraped off by the cleaning blade 24a. Thereafter, the residual potential on the photoconductor 8 is removed by the charge eliminating means and prepared for the next image forming step.

  A plurality of developing devices 2 (four in this embodiment) are provided according to different colors of developers. For example, each developing device has a developer of black, cyan, magenta, and yellow, and a full-color image can be finally formed on the transfer belt 3 by superimposing the images of the respective colors.

  The image developed on the transfer belt 3 in this way is transferred onto the recording medium P at the nip formed by the transfer roller 7 and the stretching roller 11. Thereafter, the recording medium P is heated and pressurized by a fixing device on the downstream side in the transport direction, and the image is fixed on the recording medium P. Finally, the recording medium P is discharged and stacked on the paper discharge unit of the image forming apparatus 1. On the other hand, residual toner on the transfer belt 3 that has not been transferred at the nip portion is cleaned by the blade 6 of the belt cleaning means 5.

  Further, one or a plurality of density sensors 4 for measuring the toner image on the transfer belt 3 are arranged by a support member. In the example of FIG. 1, the density sensor 4 is disposed above the transfer belt 3 and between the stretching roller 11 and the belt cleaning unit 5, but is not limited to this position. As the concentration sensor 4, a conventional sensor as disclosed in Patent Document 1 can be used.

FIG. 3 is a schematic view showing contact and separation of the transfer roller with respect to the transfer belt.
The transfer roller 7 can be brought into contact with the transfer belt 3 (FIG. 3A) or separated (FIG. 3B) by the spring member 9 and the spring member driving means. As a result, a toner image that does not require printing, such as a measurement pattern to be described later, is not transferred to the recording medium P, but can be moved to a certain measurement position of the density sensor 4 (FIG. 3B).

  Other image forming apparatuses include those that directly transfer an image from a photoreceptor to a recording medium P, those that have only a single color developing device, and those that have five or more developing devices. In the present embodiment, the configuration of FIGS. 1 to 3 has been described as an example, but the present invention is not limited to the image forming apparatus having this configuration.

As shown in FIG. 4, the controller 30 provided in the image forming apparatus 1 includes image information for adjustment, and image information for acquiring density information of an image (hereinafter also referred to as a print image) used for printing before printing. An acquisition unit 32, an image forming condition adjusting unit 33 for adjusting an image forming condition based on a detection result by the density sensor 4, and an update adjustment image setting unit 34 are provided. Each means is electrically connected to the photoreceptor 8 and the optical scanning device that constitute the toner image forming apparatus.

FIG. 5 is a schematic diagram for explaining an adjustment operation of potential control, which is one of image forming condition adjustments.
Since the toner used for image formation is affected by the surrounding environment and deterioration with time, the charge amount changes. The characteristics of the photoconductor 8 also change due to deterioration with time. As a result, even if the same potential is always used in the image forming apparatus 1, the same amount of toner is not always developed. Therefore, a density adjustment operation is necessary.

Potential control is one of the density adjustment operations. In the potential control, first, the adjustment image 50 is formed on the transfer belt 3 as an image carrier by the developing device 2. Next, the adjustment image 50 is detected by the density sensor 4 serving as an image detection unit.
The adjustment image 50 is a plurality (four in this example) of patch images formed with a plurality of densities by changing the potential as shown in FIG. 5, for example. These patch images are detected by the density sensor 4, and density information of each patch image is acquired.

As illustrated in FIG. 5A, the image forming apparatus 1 may include one density sensor 4. In this case, the patch image is not limited to a single color image, and patch images of other colors may be formed and detected after these four patch images.
As shown in FIG. 5B, an image forming apparatus using a plurality of color developers has a plurality of density sensors 4 (three in this example) to shorten the adjustment operation time, and a plurality of color patch images. May be simultaneously formed and detected.

  These adjustment operations are performed at the timing when the number of prints from the previous adjustment operation exceeds a preset number, when the environment such as temperature and humidity changes suddenly, or when printing has not been performed for a certain period of time. The

FIG. 6 is a flowchart of the image forming condition adjusting operation according to the embodiment of the present invention.
When the image forming condition adjustment operation is performed at the timing as described above, first, an adjustment image to be formed is selected by the adjustment image setting means 31 (S1). Next, the selected adjustment image is imaged by the developing device 2 as image forming means (S2), and the imaged adjustment image is detected by the density sensor 4 as image detecting means (S3). Finally, the image forming condition adjustment unit 33 adjusts the image forming condition based on the detection result by the density sensor 4 (S4).
Hereinafter, an embodiment of the adjustment image setting method (S1) to be imaged will be described.

A potential setting method in potential control will be described with reference to FIG. FIG. 7 is a graph showing the relationship between potential and concentration.
A “potential-density” relationship represented by a straight line as shown in FIG. 7 can be obtained from the potential at the time of creating the patch image and the measured density value of the patch image by the density sensor 4. From this “potential-density” relationship, it is possible to calculate a set potential for the density desired in printing, and to change the subsequent image forming conditions. As a result, a stable image density can be maintained even when characteristics of the toner or the photoconductor 8 change with time.

  Since there is a possibility that noise is mixed in the measurement result of the concentration sensor 4, an approximate expression or the like is used for the measurement result in order to calculate the “potential-concentration” relationship. In this embodiment, it is assumed that the “potential-concentration” relationship is almost linear, and a first-order approximation is used. However, since this relationship is not strictly linear, a higher-order approximation is required when higher accuracy is required. You may express using. Further, in order to reduce the influence of noise, the number of patch images may be increased, or patch images may be formed a plurality of times at the same potential, and the average value of each measurement result may be used.

FIG. 8 is a flowchart illustrating an adjustment image setting method (first embodiment) using a density gradation method.
In the first embodiment, the adjustment image setting unit 31 is a patch corresponding to a plurality of predetermined potential levels based on information obtained from the image information acquisition unit 32 that acquires image information used for printing before printing. An adjustment image necessary for the print image is determined from the images.

  First, the image information acquisition unit 32 acquires information on the highest density and the lowest density from image information to be printed (S11). At this time, the image information acquisition unit 32 acquires a predetermined number of print image information. When the predetermined number of print image information does not exist, the image information acquisition unit 32 acquires the print image information for the presence. When the density gradation method is used, the image information acquisition unit 32 acquires the light emission amount and the light emission time per dot in the optical scanning device as the density information of the print image.

  Next, the adjustment image setting means 31 calculates a potential corresponding to the highest density and the lowest density of an image to be printed from the “potential-density” relationship set at the previous adjustment, and sets each potential to the highest potential. And it is set as the minimum potential (S12). Then, the adjustment image setting means 31 is within a range from a patch image corresponding to a potential equal to or higher than the highest potential and closest to the highest potential to a patch image corresponding to a potential equal to or lower than the lowest potential and closest to the lowest potential. A patch image is selected as the adjustment image 50 (S13). After the adjustment image 50 is selected, image formation (S2), measurement (S3), and image formation condition adjustment (S4) of the adjustment image 50 may be performed.

FIG. 9 is a diagram showing a patch image including the patch image selected as the adjustment image in this way.
In this example, among the 10 gradation patch images, 5 gradation patch images from the lowest density patch image 50a to the highest density patch image 50b are formed and detected. The density of these five tone patch images includes all the densities of the image to be printed. On the other hand, a patch image having a lower density than the patch image 50a and a patch image having a higher density than the patch image 50b are not formed. Thus, based on the density information acquired by the image information acquisition unit 32, the density, potential, or number of patches for the adjustment image 50 is changed. Therefore, since a patch image outside the density range necessary for the print image is not formed, unnecessary toner consumption can be reduced and adjustment time can be reduced.

Note that the minimum density does not include the density of the white background (the part without writing), and assumes the minimum density of an image other than the white background. For example, when the print image is a printer image and the text document has only a solid density, the minimum density and the maximum density are equal to each other because white paper is considered. At this time, the patch to be imaged is selected from the one that is higher than the highest density and closest to the highest density to the one that is lower than the lowest density and closest to the lowest density. As a result, only one solid patch is selected. Is done.
In the case of a single density other than the solid density, the minimum density and the maximum density are equal. In this case, if the image density and the patch density match, a single patch is selected, and if they do not match, the two front and rear patches are selected.

FIG. 10 is a flowchart showing another adjustment image setting method (second embodiment).
In the second embodiment, the adjustment image setting unit 31 is based on information obtained from the image information acquisition unit 32 that acquires image information used for printing and a predetermined number of one or more patches. The potential used for image formation is determined.
First, the image information acquisition unit 32 acquires information on the highest density and the lowest density of an image to be printed (S21). Next, the adjustment image setting means 31 calculates the highest potential and the lowest potential corresponding to the highest density and the lowest density of the image to be printed from the “potential-density” relationship set at the previous adjustment (S22). .

  Next, the adjustment image setting unit 31 selects potentials corresponding to the predetermined number of patches from the range of the calculated maximum potential and minimum potential (S23). In order to select the potential, for example, the interval between the highest potential and the lowest potential may be equally divided by the number of patches. Then, the adjustment image setting unit 31 selects a patch image corresponding to the selected potential as the adjustment image 50 (S24). After the adjustment image 50 is selected, image formation (S2), measurement (S3), and image formation condition adjustment (S4) of the adjustment image 50 may be performed.

FIG. 11 is a diagram illustrating a method of selecting a potential corresponding to the adjustment image in step 23 of FIG.
As shown in the figure, the adjustment image setting means 31 calculates the highest potential and the lowest potential corresponding to the highest density and the lowest density of the image to be printed from the “potential-density” relationship set at the previous adjustment ( FIG. 10, S22). Thereafter, the adjustment image setting unit 31 equally divides the interval between the highest potential and the lowest potential by the number of patches, and selects potentials for a predetermined number of patches (S23 in FIG. 10). In this example, the interval is divided into four equal parts, and five potentials are selected in total. However, the number is not limited to this number. Thus, based on the density information acquired by the image information acquisition unit 32, the density or potential for the adjustment image 50 is changed.

  The number of patches to be imaged may be determined in consideration of the downtime allowable time, or may be determined according to the number when the image forming apparatus has a plurality of density sensors. Alternatively, it may be determined so as to satisfy the required density accuracy. For example, the number of patches may be reduced in an apparatus having a “potential-concentration” relationship obtained by experiments or the like that is close to the first-order linearity. Otherwise, the number of patches may be increased.

  Further, as the number of patches, the number of patches that can provide the necessary correction accuracy when the minimum density of the printed image is a white background and the maximum density is a solid image is determined. This is the same as in the prior art. However, when the minimum density becomes deeper or the maximum density becomes lighter and the difference between the minimum density and the maximum density becomes small, precise correction is possible even with the same number of patches (density resolution is increased), and correction accuracy is improved. .

  In this method, since the number of patches is determined in advance, downtime cannot be reduced by reducing the patch image. However, since approximation is performed in the vicinity of the density range necessary for printing, the approximation accuracy of the “potential-density” relationship is improved. Can be improved.

FIG. 12 is a flowchart illustrating another adjustment image setting method (third embodiment).
In the third embodiment, the adjustment image setting unit 31 uses the information obtained from the image information acquisition unit 32 to acquire image information used for printing and one or more predetermined potential steps to adjust the adjustment image. The potential used for image formation is determined.
As in the second embodiment, first, the image information acquisition unit 32 acquires information on the maximum density and the minimum density of an image to be printed (S31). Next, the adjustment image setting means 31 calculates the highest potential and the lowest potential corresponding to the highest density and the lowest density of the image to be printed from the “potential-density” relationship set at the previous adjustment (S32). .

Next, the adjustment image setting unit 31 sets a predetermined potential for each potential step from the calculated lowest potential to the potential that is equal to or higher than the highest potential and closest to the highest potential as the potential at the time of patch creation (S33). ). On the contrary, the potential at the predetermined potential step from the calculated highest potential to the potential which is equal to or lower than the lowest potential and closest to the lowest potential may be used as the potential at the time of patch creation. Then, the adjustment image setting unit 31 selects a patch image corresponding to the selected potential as the adjustment image 50 (S34). After the adjustment image 50 is selected, image formation (S2), measurement (S3), and image formation condition adjustment (S4) of the adjustment image 50 may be performed.

FIG. 13 is a diagram illustrating a method of selecting a potential corresponding to the adjustment image in step 33 of FIG.
As shown in the figure, the adjustment image setting means 31 calculates the highest potential and the lowest potential corresponding to the highest density and the lowest density of the image to be printed from the “potential-density” relationship set at the previous adjustment ( FIG. 12, S32). Thereafter, the adjustment image setting unit 31 sets a potential for each predetermined potential step from the calculated minimum potential or maximum potential as the potential at the time of patch creation (FIG. 12, S33). According to the potential step of a predetermined width in this example, a total of five potentials are selected, but the present invention is not limited to this predetermined width and the corresponding potential (number of patches). Thus, based on the density information acquired by the image information acquisition unit 32, the density, potential, or number of patches for the adjustment image 50 is changed.

  The width of the potential step may be determined in consideration of an allowable downtime, or may be determined according to the number of density sensors 4 when the image forming apparatus has a plurality of density sensors 4. Alternatively, it may be determined so as to satisfy the required density accuracy. For example, the number of patches may be reduced in an apparatus having a “potential-concentration” relationship obtained by experiments or the like that is close to the first-order linearity. Otherwise, the number of patches may be increased.

  In this method, since the potential step is determined in advance, the number of patch images created can be reduced, especially when the density range of the printed image is narrow, reducing downtime and unnecessary toner consumption. Can do.

Next, an adjustment image setting method (Embodiment 4) using the area gradation method will be described with reference to FIGS. FIG. 14 is a schematic diagram of a typical area gradation pattern.
In the digitized image forming apparatus, density adjustment using the “potential-density” relationship as shown in FIG. 7 is not performed, but an area gradation method using image processing such as halftone dots as shown in FIG. The density is adjusted. FIG. 14A shows a dot-shaped area gradation pattern, and FIG. 14B shows a line-shaped area gradation pattern. In an image forming apparatus using such an area gradation method, an image is formed by making the density of a print image correspond to a plurality of preset image processing patterns. Therefore, when the area gradation method is used, not the light emission amount of the optical scanning device but the image processing pattern used for the print image is acquired as the density information of the print image.

  However, the image processing pattern for obtaining a desired density may change even when the same potential is used due to the change in the toner and the photoreceptor characteristics with time. Therefore, it is necessary to adjust the density even in the area gradation type image forming apparatus.

FIG. 15 is a diagram illustrating a “pattern-density” relationship according to the fourth embodiment.
In the image forming apparatus according to the present embodiment, the adjustment image setting unit 31 includes a pattern determining unit that determines an image processing pattern that achieves a desired density. The pattern determining means has a plurality of image processing patterns prepared in advance.
In the gradation control, first, the pattern determination unit of the adjustment image setting unit 31 selects several patterns from the plurality of image processing patterns. This step corresponds to step 1 in FIG. Next, the selected pattern is imaged as a patch image on the transfer belt 3 by the developing device 2 (FIG. 6, S2), and the density of the imaged patch image is measured by the density sensor 4 (FIG. 6, S3). .

  Based on the measurement result, the “pattern-density” relationship as shown in FIG. 15 can be obtained. This “pattern-density” relationship is not linear and varies with the environment. Therefore, correction by gradation control is necessary. By selecting a gradation corresponding to the target density from this “pattern-density” relationship, an image with the target density can be printed. However, the gradation is selected from predetermined ones. For example, in the fourth embodiment, the image forming apparatus 1 has 256 patterns of gradation. During actual printing, image formation is performed using a pattern from which a density closest to the target density can be obtained.

  Since there is a possibility that sensor noise exists in the measurement result of the density sensor 4, in order to calculate the “pattern-density” relationship, the measurement result is similar to the calculation of the “potential-density” relationship. An approximate expression is used. In this embodiment, it is assumed that the “pattern-density” relationship is almost a fourth-order relationship, and a fourth-order approximation is used. However, this relationship is not strictly linear. You may express using the above approximation. Conversely, when there is a restriction on the CPU or memory and it is desired to reduce the processing load, lower order approximation such as second order approximation may be used.

  Further, in order to reduce the influence of noise, the number of patches may be increased, or a patch image having the same potential may be formed a plurality of times, and the average value of each measurement result may be used.

FIG. 16 is a flowchart of an adjustment image setting method using the area gradation method according to the fourth embodiment.
In the fourth embodiment, the adjustment image setting unit 31 is based on the information obtained from the image information acquisition unit 32 that acquires image information used for printing, and includes patch images of several predetermined image processing patterns. From this, an adjustment image necessary for the print image is determined.
First, the image information acquisition unit 32 acquires information on an image to be printed (S41), and the adjustment image setting unit 31 acquires information on the maximum density and the minimum density used for the print image from the print image information. (S42). At this time, the adjustment image setting means 31 acquires print image information for a predetermined number of sheets. When the predetermined number of print image information does not exist, the adjustment image setting unit 31 acquires the print image information for the existing print image information.

  Next, the pattern determination unit of the adjustment image setting unit 31 calculates an image processing pattern corresponding to the highest density and the lowest density of an image to be printed from the “pattern-density” relationship set at the previous adjustment, Each image processing pattern is set to the highest density pattern and the lowest density pattern (S43). Then, the pattern determining means uses, as the adjustment image 50, a patch image having a density equal to or higher than the highest density pattern and closest to the highest density pattern to a patch image having a density equal to or lower than the lowest density pattern and closest to the lowest density pattern. Select (S44). As described above, the density, the number of patches, or the image processing pattern for the adjustment image 50 is changed based on the density information acquired by the image information acquisition unit 32. Thereafter, the selected patch image is formed on the transfer belt 3 by the developing device 2 (FIG. 6, S2), and the density of the formed patch image is measured by the density sensor 4 (FIG. 6, S3). The image condition may be adjusted (S4 in FIG. 6).

  Accordingly, since a patch image outside the density range necessary for the print image is not formed, unnecessary toner consumption can be reduced and adjustment time can be reduced.

FIG. 17 is a flowchart of another adjustment image setting method (Embodiment 5) using the area gradation method.
In the fifth embodiment, the adjustment image setting unit 31 is used to create an adjustment image based on information obtained from the image information acquisition unit 32 that acquires image information used for printing and a predetermined gradation step. An image processing pattern is determined.
First, the image information acquisition unit 32 acquires information on an image to be printed (S51), and the adjustment image setting unit 31 obtains information on the maximum density and the minimum density used for the print image from the print image information. Obtain (S52). Next, the adjustment image setting unit 31 calculates the highest density pattern and the lowest density pattern corresponding to the highest density and the lowest density of the image to be printed from the “pattern-density” relationship set at the time of the previous adjustment ( S53).

  Next, the adjustment image setting unit 31 cuts from the calculated minimum density pattern to the maximum density pattern for each predetermined gradation step, selects these image processing patterns as the adjustment image 50, and creates an image at the time of patch creation. A processing pattern is set (S54). After the adjustment image 50 is selected, image formation (S2), measurement (S3), and image formation condition adjustment (S4) of the adjustment image 50 may be performed.

FIG. 18 is a diagram showing a method of selecting a pattern for each predetermined gradation step in step 54 of FIG. 17 as an adjustment image.
As shown in the figure, the adjustment image setting means 31 calculates the highest density pattern and the lowest density pattern corresponding to the highest density and the lowest density of the image to be printed from the “pattern-density” relationship set at the previous adjustment. (FIG. 17, S53). Then, a pattern for each gradation step determined in advance from the calculated minimum density pattern is used as a pattern at the time of patch creation (FIG. 17, S54). According to the gradation step of a predetermined width in this example, three patterns are selected in total, but the predetermined width and the number of patches corresponding thereto are not limited. As described above, the density, the number of patches, or the image processing pattern for the adjustment image 50 is changed based on the density information acquired by the image information acquisition unit 32.

  The width of the gradation step may be determined in consideration of an allowable downtime, or may be determined according to the number of density sensors 4 when the image forming apparatus has a plurality of density sensors 4. Alternatively, it may be determined so as to satisfy the required density accuracy. For example, an apparatus having a “pattern-density” relationship that is obtained in advance by experiments or the like is close to a linear function, the number of patches may be small, and if not, the number of patches may be increased.

  In this method, since the gradation step is determined in advance, the number of patch images formed is reduced especially when the density range of the printed image is narrow, reducing downtime and unnecessary toner consumption. be able to.

  In the fifth embodiment, the pattern for each gradation step from the lowest density pattern is used as a pattern at the time of patch creation, but conversely, a pattern obtained by reducing only the gradation step from the highest density pattern may be used as a pattern at the time of patch creation. .

FIG. 19 is a flowchart of another adjustment image setting method (sixth embodiment) using the area gradation method.
In the present invention, since the image forming conditions are determined based on the image information to be printed, when the number of set pieces of image information is small, the adjustment operation is compared with a general adjustment operation performed for each preset number of prints. May increase in frequency. Therefore, only when there is a predetermined number of pieces of image information, the adjustment image selected according to the fourth or fifth embodiment may be used, and otherwise, a method using a predetermined adjustment image may be used.

  Specifically, first, the image information acquisition unit 32 acquires information on an image to be printed (S61), and the adjustment image setting unit 31 determines whether the number of printed sheets is N or more from the print image information. (S62). If the number is less than N (S62, NO), the adjusting operation is not performed. In the case of N sheets or more (S62, Yes), the adjustment image setting unit 31 acquires information on the maximum density and the minimum density used for the print image (S63), and selects the adjustment image 50 (S64).

  According to this method, although the adjustment of the image forming condition by the image forming condition adjusting unit 33 is limited to the case where printing of N sheets or more is required, the toner consumption and the downtime can be reduced.

FIG. 20 is a flowchart of another adjustment image setting method (Embodiment 7) using the area gradation method.
In this example, unlike Embodiment 6 of FIG. 19, the user can select the adjustment mode. For example, the user can select the normal adjustment mode or the shortening adjustment mode from the panel of the image forming apparatus 1. Therefore, only when the shortening adjustment mode is set (S72, Yes), the adjustment image selected by the adjustment image setting means 31 is used (S74), and a predetermined adjustment is performed in the normal adjustment mode (S72, No). Use the image.

FIG. 21 is a diagram illustrating an image forming apparatus (Embodiment 8) capable of adjusting an image forming condition during printing.
The image forming apparatus 1 according to the eighth embodiment includes the density sensor 4 at a position corresponding to the outside of the print image 52 area. In FIG. 21, the density sensor 4 is disposed at both ends of the print image area, but the density sensor 4 may be disposed at either one of them.

In this image forming apparatus 1, the adjustment image 50 is formed outside the print image area, the density is measured by the density sensor 4 (FIG. 6, S3), and the conditions are adjusted by the image forming condition adjusting means 33 (FIG. 6). 6, S4).
According to the present embodiment, the image forming apparatus 1 performs image information acquisition (new print image density information) by the image information acquisition unit 32 during printing without interrupting user printing, and performs an adjustment operation. Can do.

FIG. 22 is a flowchart of an adjustment image setting method in the image forming apparatus according to the eighth embodiment.
The image forming apparatus 1 according to the present exemplary embodiment also includes an update adjustment image setting unit 34 that sets an update adjustment image for image information acquired during printing. First, when printing by the image forming apparatus 1 is requested, the image information obtaining unit 32 obtains predetermined M pieces of print image information (S81). At this time, if the requested number of prints is less than M, the image information acquisition unit 32 acquires all image information.

  The number M may be determined in consideration of the processing time required to obtain the highest density and lowest density information from the image information. If the processing capability is sufficient, all print information requested at that time may be acquired.

  Next, the adjustment image setting means 31 selects the adjustment image 50 using the acquired image information (S82). If the number of printed sheets from the previous adjustment operation is equal to or greater than the predetermined number A (S83, Yes), the image forming condition adjusting unit 33 performs the image forming condition adjusting operation (S84). On the other hand, if it is less than A, it is assumed that the density fluctuation is small to some extent, and the image forming condition adjusting unit 33 does not perform the adjusting operation (No in S83).

  When the adjustment operation is not performed, the update adjustment image setting unit 34 determines whether an update adjustment image described later is set (S85). If the update adjustment image is set (S85, Yes), the image forming condition adjusting unit 33 performs the update image forming condition adjusting operation (S86). Details of the updated image forming condition adjustment method will be described later. When the update adjustment image is not set (S85, No), the printing operation is performed without the adjustment operation (S87).

  After printing, the image information acquisition unit 32 determines whether there is new print image information (whether a new print request has been made) (S88). If there is no new print image information (S88, No), it is determined whether printing is finished (S89). If it is not the end of printing (S89, No), the process returns to the determination of whether the number of printed sheets has become A or more (S83).

  When new print image information exists (S88, Yes), the image information acquisition unit 32 acquires the print image information (S90), and the update adjustment image setting unit 34 updates the maximum density and the minimum density. It is determined whether or not (S91). If not updated (S91, No), the process returns to the determination of whether the number of printed sheets has become A or more (S83).

  When the maximum density and the minimum density are updated (S91, Yes), the update adjustment image setting unit 34 sets an update adjustment image (S92). Details of the method for selecting the adjustment image for update will be described later. When the image forming condition adjustment is completed, the process returns to the determination of whether the number of printed sheets is A or more (S83).

  In the eighth embodiment, the adjustment operation is performed when the number of printed sheets from the previous adjustment operation (S84) is equal to or more than a predetermined number A, and the “updated image formation condition adjustment” (S86) It is not included in the “adjustment operation”. The reason for adjusting each A sheet is that it is assumed that the density fluctuation in the A sheet is small to some extent. In this embodiment, the correction for each A sheet only forms the necessary patch (S84). If printing at other densities is necessary (S91, Yes), the image formation for each A sheet is performed. Correction is performed by the updated image forming condition adjustment (S92) performed during the condition adjustment (S84).

FIG. 23 is a diagram illustrating setting of an update adjustment image and an update adjustment operation according to the eighth embodiment.
As shown in FIG. 23A, when the density of the new image 54 is outside the density range of the patch formed as the adjustment image 50, the update adjustment image setting means 34, the image forming means, and the image formation The condition adjustment means 33 executes the setting / creation and adjustment operations of the updated adjustment image 56. In this example, as shown in FIG. 23B, as the adjustment image 50, among the 10 gradation patch images, a 5 gradation patch image from the lowest density patch image 50a to the highest density patch image 50b is created. I was imaged. Then, a two-tone patch image is further formed as the updated adjustment image 56. At this time, the patch image to be imaged is selected according to the first to seventh embodiments using the updated maximum density or the minimum density, and as shown in FIG. Create an image.

  Accordingly, it is possible to maintain stable image quality even when the density range of the printed image is changed while preventing unnecessary toner consumption.

  According to the present embodiment, the image information for the newly requested printing is acquired during printing, and if necessary, the update adjustment operation is performed. Compared to the adjustment operation, toner consumption can be reduced. Further, unlike the first to seventh embodiments, less image information can be acquired at the start of printing.

  As described above, the present invention is characterized by a method for creating an adjustment image for adjusting image forming conditions. In other words, image information such as the color, image density, and image processing pattern used in the print image is acquired from the print image information specified in advance by the user, and the adjustment image is changed based on the acquired image information. is there.

  In the present invention, the photosensitive member 8 may be used as the image carrier, the developing device 22 may be used as the image forming unit, and the density sensor 4 disposed opposite to the photosensitive member 8 may be used as the image detecting unit.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Development apparatus (image forming means)
4 Density sensor (image detection means)
31 Adjustment image setting means 32 Image information acquisition means 33 Image forming condition adjustment means 50 Adjustment image

JP 2011-164240 A

Claims (9)

Image information acquisition means for acquiring density information of an image used for printing ;
An adjustment image setting means for changing an adjustment image to be formed for image formation condition adjustment based on the density information acquired by the image information acquisition means;
An image forming means for forming an image on the image carrier;
Image detecting means for detecting an image formed by the image forming means;
An image forming condition adjusting means for adjusting an image forming condition based on a detection result by the image detecting means;
An image forming apparatus having
Using the highest density and the lowest density of the density information acquired by the image information acquisition means, a patch image within a range that covers the range from the highest density to the lowest density from a preset “potential-density” relationship. Is selected as an adjustment image . Image information acquisition means for acquiring density information of an image used for printing;
An adjustment image setting means for changing an adjustment image to be formed for image formation condition adjustment based on the density information acquired by the image information acquisition means;
An image forming means for forming an image on the image carrier;
Image detecting means for detecting an image formed by the image forming means;
An image forming condition adjusting means for adjusting an image forming condition based on a detection result by the image detecting means;
An image forming apparatus having
Using a maximum density and a minimum density of the density information acquired by the image information acquisition means, a predetermined “image processing pattern-density” relationship is within a range that covers from the maximum density to the minimum density. An image forming apparatus, wherein a density pattern patch image is selected as an adjustment image. Select potentials corresponding to the predetermined number of patches from the range covering the highest density to the lowest density of the density information acquired by the image information acquisition means, and adjust the patch image corresponding to the selected potential. The image forming apparatus according to claim 1, wherein the image forming apparatus is selected as an image for use. A potential for each predetermined potential step is selected from a range covering from the highest density to the lowest density of the density information acquired by the image information acquisition means, and a patch image corresponding to the selected potential is adjusted. The image forming apparatus according to claim 1, wherein the image forming apparatus is selected as an image for use. A patch image of the selected image processing pattern is selected by selecting an image processing pattern for each predetermined gradation step from the range covering the highest density to the lowest density of the density information acquired by the image information acquisition means. The image forming apparatus according to claim 2, wherein the image is selected as an adjustment image. 6. The image forming apparatus according to claim 2, wherein the selected adjustment image is used only when there is information on an image used for printing a predetermined number or more. During printing, and retrieving the density information of the image used for the new print by the image information obtaining unit, according to claim 1-6, characterized in that to perform the adjustment of the image forming condition by the image forming condition adjusting means The image forming apparatus according to claim 1. An update adjustment image setting means for setting an update adjustment image for density information of an image used for new printing acquired during printing is provided, and the adjustment of the update image formation condition is adjusted by the image formation condition adjustment means. The image forming apparatus according to claim 7 , wherein: The user can select the normal adjustment mode or the shortening adjustment mode, and only when the shortening adjustment mode is set, the adjustment image selected by the adjustment image setting unit is used. In the normal adjustment mode, a predetermined adjustment image is used. the image forming apparatus according to any one of claims 1-8, characterized by using a.