JPH08275001A - Image adjustment method for multi-color image forming device - Google Patents

Abstract

PURPOSE: To realize the image adjustment method adjusting precisely image density in a multi-color image forming device. CONSTITUTION: A test pattern is formed on a latent image carrier by using the latent image carrier, a charge means for the latent image carrier and an exposure means for the latent image carrier provided in the multi-color image forming device (1001), after its contrast potential is stored and the test pattern is transposed and fixed on paper and an image read means reads the test pattern on the paper (1003), density information is obtained, a discrimination means discriminates the test pattern and a correction means to correct a gamma coefficient at image forming in response to the discrimination result of the discrimination means is used, a contrast potential corresponding to a desired object density is obtained for each color of the multi-image color (1005) and the correction amount of the gamma coefficient is decided based on the object density and the contrast potential (1006-1011).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image adjusting method for a multicolor image forming apparatus.

[0002]

2. Description of the Related Art A latent image carrier, charging means for charging the latent image carrier, exposure means for forming an electrostatic image by exposing the charged latent image carrier, and a test pattern output. A test pattern output means for reading the test pattern, a reading means for reading the test pattern, and a judging means for judging the test pattern, and a correcting means for correcting the γ coefficient at the time of image formation according to the judgment result of the judging means. There is a multicolor image forming apparatus that has. Examples of such a multicolor image forming apparatus include image forming apparatuses such as copying machines and printers. In such an image forming apparatus, as a method of increasing the image density, there are a method of changing the characteristics of the developer, a method of increasing the latent image potential on the latent image carrier to improve the adhesion of the developer, and the like. is there.

Regarding the above-mentioned method, the latent image potential on the latent image carrier such as the photosensitive drum is changed according to the characteristics of the developer such as toner to obtain the optimum maximum density (Japanese Patent Laid-Open No. Hei 4).
-268874). In this method, for example, the characteristic of the developer is detected, and the potential of the image portion is controlled according to the change in the characteristic of the developer. A rectangular test pattern, that is, a patch pattern, is formed on the latent image carrier. Then, the patch pattern is detected as a developer characteristic using a potential sensor, a density detection sensor, etc., and the contrast potential for obtaining the required maximum adhesion amount of toner suitable for representing the patch pattern is calculated, Create an image at that contrast potential.

Here, in a generally used reflection type optical density sensor, the output signal level also changes as the amount of developer attached to the image portion of the latent image carrier increases. The degree of this change does not change linearly indefinitely, and when it reaches a certain amount of adhesion, it does not increase more than the signal output at that time and reaches a so-called saturation level.

Therefore, it is not possible to directly detect the correct output signal level of the sensor corresponding to the maximum adhesion amount of the developer, which represents the test pattern on the latent image carrier, and the contrast potential is also detected. Can't be asked correctly.

[0006] Therefore, conventionally, as a convenient method, the maximum value is obtained by a substitute method in which the toner adhesion amount corresponding to the halftone before the sensor reaches the saturation level is used as a substitute, or an extrapolation method by calculation is used. A method of obtaining the contrast potential by obtaining the amount of adhesion is known.

[0007]

However, since the substitution method and the extrapolation method do not directly detect the required maximum adhesion amount, there is a problem in accuracy. In addition, since it is a method of controlling the amount of adhesion on the latent image bearing member, it is possible to reduce the density due to a process after the latent image bearing member, that is, a transfer process, a fixing process, or the like. , I can not fold the influence.

This is not a problem because the required accuracy is low in the case of a black-and-white recording apparatus mainly composed of characters, but when a high accuracy of image density is required in a full color system or the like. , It became a big problem, and sometimes it could be used for user work.

An object of the present invention is to provide an image adjusting method in a multicolor image forming apparatus capable of performing accurate image density adjustment.

[0010]

In order to achieve the above object, the present invention has the following constitution. (1) An image adjusting method for a multicolor image forming apparatus, which comprises a latent image carrier, a charging unit for charging the latent image carrier, and an electrostatic image by exposing the charged latent image carrier. Exposure means for forming a test pattern, a test pattern output means for outputting a test pattern, a reading means for reading the test pattern, a judging means for judging the test pattern, and an image forming time according to the judgment result of the judging means. Using a correction means for correcting the γ coefficient, a contrast potential corresponding to a predetermined target density is obtained for each color forming the multicolor image, and based on these target density and contrast potential,
The correction amount of the γ coefficient is decided (claim 1).

(2) In the image adjusting method of the multicolor image forming apparatus described in (1), after forming a plurality of patch patterns on the latent image carrier as a test pattern with a plurality of contrast potentials having mutually different values. , These patch turns are visualized on the same recording paper, and the plurality of visualized patch patterns are read by a reading means,
By comparing the read result with a predetermined reference value (predetermined target density) and making a determination, the contrast potential corresponding to the predetermined target density is selected from among the plurality of contrast potentials to obtain the predetermined target density. The corresponding contrast potential is determined (claim 2).

(3) In the image adjusting method for a multicolor image forming apparatus according to (1) or (2), a predetermined target density is set to
The maximum image density in the electrostatic image writing data written on the latent image bearing member by the exposing means when the test pattern was created (claim 3).

[0013]

The density of the toner image as a test pattern formed on the latent image carrier is not read, but is passed through a process such as transfer and fixing, which is a process after the image formation on the latent image carrier, and then, on the recording paper. It is possible to read the density of the test pattern formed on the sheet using the color sensor of the color image reading apparatus that does not cause toner adhesion.

[0014]

【Example】

(1) Example of multicolor image forming apparatus As an example of a multicolor image forming apparatus suitable for carrying out the present invention,
The color image forming apparatus will be described with reference to FIG.

A color image reading device (hereinafter referred to as a color scanner) 200 includes a contact glass 202.
The image of the upper original 180 is displayed on the illumination lamp 205 and the mirror group 2
04A, 204B, 204C, etc., and lens 206
An image is formed on the color sensor 207 via the, and the color image information of the document is, for example, blue (hereinafter, referred to as B),
Green (hereinafter referred to as G) red (hereinafter referred to as R) color-separated light is read for each color and converted into an electrical image signal.

The color sensor 207 is, in this example,
It is composed of B, G, and R color separation means and a photoelectric inter-pixel element such as a CCD (solid-state image pickup element), and performs the dynamic reading of three colors.

B, G, R obtained by the color scanner 200
A color conversion process is performed by an image processing unit (not shown) based on the color-separated image signal intensity level of, and black (hereinafter, BK), cyan (hereinafter, C), and magenta (hereinafter, hereafter). Color image data including color information of yellow (hereinafter referred to as Y) is obtained.

The operation method of the color scanner 200 for obtaining the image data of BK, C, M and Y by using the color image recording device (hereinafter referred to as a color printer) 400 using the color image data is as follows. In response to the operation of the color printer 400 and the scanner start signal in time, in FIG. 3, the illumination / mirror optical system including the illumination lamp 205 and the mirror groups 204A, 204B, and 204C scans the document in the left arrow direction, and Image data of one color is obtained every scanning. Then, each time, the images are sequentially visualized by the color printer 400, and these are superposed to form a full-color image of four colors.

Next, an outline of the color printer 400 will be described. Writing optical unit 40 as exposure means
Reference numeral 1 converts color image data from the color scanner 200 into an optical signal, performs optical writing corresponding to the original image, and forms an electrostatic latent image on the photosensitive drum 414 as a latent image carrier.

The optical writing optical unit 401 includes a laser emitting unit 441, an emission drive control unit (not shown) for driving the unit, a polygon mirror 443, a rotation motor 444 for driving the unit, a fθ lens 442, and a reflecting mirror 446.
Etc.

The photoconductor drum 414 rotates counterclockwise as shown by the arrow, and around it, the photoconductor cleaning unit 421, the discharging lamp 414M, the charger 419 as a charging means, and the photoconductor drum Sensor 414D for detecting the latent image potential of the developing device, the selected developing device of the revolver developing device 420, and the developing density pattern detector 4
14P, an intermediate transfer belt 415, and the like are arranged.

The revolver developing device 420 is a BK developing device 420K, a C developing device 420C, an M developing device 420M, a Y developing device 420Y, and a revolver rotation drive for rotating each developing device in a counterclockwise direction as shown by an arrow. (Not shown) and the like. These developing devices rotate the developing sleeves 420KS, 420 by bringing the brush of the developer into contact with the surface of the photosensitive drum 414 to develop the electrostatic latent image.
It is composed of CS, 420MS, 420, and a developing paddle that rotates for assembling and stirring the developer.

In the standby state, the revolver developing device 420 is set at the position where the BK developing device 420 develops, and when the copying operation is started, the color scanner 200 reads the BK image data from a predetermined timing. Based on this image data, optical writing and latent image formation by laser light starts (hereinafter, the electrostatic latent image based on the BK image data is referred to as BK latent image. C, M, Y
The same for each image data of. ).

In order to enable development from the front end of the BK latent image, the developing sleeve 420KS is started to rotate before the front end of the latent image reaches the developing position of the BK developing device 420K.
The K latent image is developed with BK toner.

Thereafter, the developing operation of the BK latent image area is continued, but when the trailing edge of the latent image passes the BK latent image position, the next color is immediately developed from the developing position by the BK developing device 420K. The revolver developing device 420 is driven and rotated to the developing position by the container. This rotating operation is completed at least before the leading edge of the latent image by the next image data arrives.

When the image forming cycle is started, the photosensitive drum 414 rotates counterclockwise as indicated by an arrow, and the intermediate transfer belt 415 rotates clockwise by a drive motor (not shown). Move.

As the intermediate transfer belt 415 rotates, B
K toner image formation, C toner image formation, M toner image formation, Y
Toner image formation is sequentially performed, and finally BK, C, M,
A toner image is formed by superimposing it on the intermediate transfer belt 415 in the order of Y.

The BK image is formed as follows. The charger 419 uniformly charges the photosensitive drum 414 with a negative charge to about −700 V in the dark by corona discharge. Subsequently, the laser diode 441 performs raster exposure based on the BK signal. When the raster image is exposed in this way, in the exposed portion of the photosensitive drum 414 that is initially uniformly charged, the charge proportional to the amount of exposure light disappears and an electrostatic latent image is formed.

The toner in the revolver developing device 420 is
It is negatively charged by stirring with a ferrite carrier, and the BK developing sleeve 420KS of this developing device
Is biased by a power supply means (not shown) with respect to the metal base layer of the photosensitive drum 414 to a potential in which a negative DC potential and an alternating current are superposed.

As a result, the toner does not adhere to the portion of the photosensitive drum 414 where the electric charge remains, and the BK toner is adsorbed to the portion having no electric charge, that is, the exposed portion, which is similar to the latent image. A BK visible image is formed.

The intermediate transfer belt 415 is connected to the drive roller 41.
5D, a transfer counter roller 415T, a cleaning counter roller 415C, and a driven roller group, are stretched and controlled by a drive motor (not shown).

Now, the B formed on the photosensitive drum 414
The K toner image is transferred onto the surface of the intermediate transfer belt 415, which is driven at a constant speed in contact with the photoconductor, by a belt transfer corona discharger (hereinafter referred to as a belt transfer unit) 416. Hereinafter, from the photosensitive drum 414 to the intermediate transfer belt 4
The toner image transfer to 15 is called belt transfer.

A small amount of untransferred residual toner on the photoconductor drum 414 is cleaned by the photoconductor cleaning unit 421 in preparation for reuse of the photoconductor drum 414. The toner collected here is stored in an exhaust toner tank (not shown) via a collection pipe.

On the intermediate transfer belt 415, the toner images of BK, C, M, and Y, which are sequentially formed on the photosensitive drum 414, are sequentially aligned on the same surface, and a belt transfer image of four-color overlapping is formed. Are formed, and thereafter, they are collectively transferred onto the transfer paper by a corona discharge transfer device.

On the side of the photosensitive drum 414, B
After the step of forming the K image, the process of forming the C image proceeds, but at a predetermined timing, the reading of the C image data by the color scanner 200 starts, and the formation of the C latent image is performed by writing the laser light with the image data. To do.

The C developing device 420C performs a rotating operation of the revolver developing device after the rear end of the previous BK latent image has passed and before the leading end of the C latent image has reached the developing position. , C latent image is developed with C toner.

After that, the development of the C latent image area is continued. At the time when the trailing edge of the latent image passes, the revolver developing device 420 is driven as in the case of the previous BK developing device to drive the C developing device 4.
20C is sent out and the next M developing device 420M is positioned at the developing position. This operation is also performed before the leading edge of the next M latent image reaches the developing section. The steps of forming the M and Y images are omitted because the operations of reading, forming the latent image, and developing the image data are similar to the steps of the BK image and the C image described above.

The belt cleaning device 415U comprises an inlet seal, a rubber blade, a discharge coil, and a contact / separation mechanism for these inlet seal and rubber blade. 1
After the BK image of the first color is transferred onto the belt, while the images of the second, third and fourth colors are transferred onto the belt, the entrance seal, the rubber blade, etc. are separated from the surface of the intermediate transfer belt by the blade contact / separation mechanism. .

A paper transfer corona discharger (hereinafter referred to as a paper transfer device) 417 is a corona discharge type AC to transfer the superimposed toner image on the intermediate transfer belt 415 to the transfer paper.
+ DC or DC component is applied to the transfer paper and the intermediate transfer belt.

The transfer paper cassette 482 in the paper supply bank stores transfer papers of various sizes. From the storage cassette that stores papers of a specified size, a paper feed roller 483 moves in the direction of the registration roller. Paper is fed and transported. Reference numeral 412B2 indicates a paper feed tray for manually inserting OHP paper or thick paper.

The transfer paper 190 is applied to the magnetism where the image formation is started.
Is fed from any one of the above-mentioned paper feed trays and stands by at the nip portion of the registration roll pair 418R. And
When the front end of the toner image on the intermediate transfer belt 415 reaches the paper transfer device 417, the registration roller pair 418R is set so that the front end of the transfer paper 190 exactly coincides with the front end of this image.
Is driven, and the registration of the paper and the image is performed.

In this way, the transfer paper is superposed on the color superposed image on the intermediate transfer belt and passes over the paper transfer device 417 which is connected to the positive potential. At this time, the transfer paper is positively charged by the corona discharge current, and most of the toner image is transferred onto the transfer paper. Subsequently, when passing through a separation static eliminator by AC + DC corona (not shown) arranged on the left side of the paper transfer device 417, the transfer paper is discharged, and the intermediate transfer belt 4 is discharged.
It is peeled from the sheet 15, and is transferred to the paper transport belt 422.

The transfer paper on which the four-color superposed toner images have been collectively transferred from the surface of the intermediate transfer belt is conveyed to the fixing device 423 by the paper conveying belt 422, and the fixing roller 423A and the pressure roller 423B controlled to a predetermined temperature. The toner image is melted and fixed in the nip portion of, and sent out of the main body by the discharge roll pair 424, and is stacked face up on a copy tray (not shown) to obtain a full color copy.

The photosensitive drum 414 after the belt transfer
Is cleaned on its surface by a photoconductor cleaning unit 421 including a brush roller and a rubber blade,
In addition, the static elimination lamp 414M uniformly eliminates static electricity.

The intermediate transfer belt 415 after the toner image is transferred onto the transfer paper is again cleaned by the cleaning unit 4.
The surface is cleaned by pressing the blade with a 15U blade contact / separation mechanism.

In the case of repeat copying, the operation of the color scanner and the image formation on the photosensitive member continue to the first color image process of the first sheet, and then proceed to the first color image process of the second sheet at a predetermined timing.

Further, the intermediate transfer belt 415 continues to the batch transfer process of the first four-color superimposed image onto the transfer paper, and the surface of the intermediate transfer belt 415 is cleaned by the belt cleaning device. Allow the image to be belt transferred. After that, the same operation as the first sheet is performed.

The above is the description of the copy mode for obtaining the four-color full-color copy. In the case of the three-color copy mode and the two-color copy mode, the same operation as described above is performed for the designated color and the number of times. Will be done.

In the single-color copy mode, only the developing device of the predetermined color of the revolver developing device 420 is placed in the developing position of the predetermined color and is in the developing operation state until the predetermined number of sheets is completed, and the belt is moved. The copying operation is continuously performed while the blade of the cleaning device 415U is being pressed against the belt.

(2) Embodiments corresponding to claims 1 to 3 A procedure for determining the correction amount of the γ coefficient will be described with reference to the flowchart of FIG. First, an outline will be described.

In step 1001, a first test pattern (described later with reference to FIG. 5) for determining the contrast potential is created on the transfer paper. The test pattern data is stored in the ROM 502 of the control device 1000 shown in FIG. Here, as shown in FIG. 6, the contrast potential is a potential that contributes to toner adhesion on the latent image carrier and is equal to or lower than the dark portion potential, and the remainder after subtracting the bright portion potential VL from the bias potential VB. Is the potential of.

The control device 1000 is an input / output terminal I
/ O 500, CPU 501, ROM 502, RAM 5
It consists of 03 etc. The test pattern is developed by expanding the ROM data in the RAM 503 via the CPU 501 and outputting it to the exposing unit of the multicolor image forming apparatus shown in FIG. 1 through the I / O 500 which is an input / output terminal. It is created by recording on transfer paper of the image forming apparatus.

That is, the first test pattern for determining the contrast potential created in step 1010 is as shown in FIG. One such test pattern is created for each of Y, M, C, and K colors.

The preparation procedure is as shown in FIG.
By using the patch pattern creation data stored in the ROM 502 of the control device 1000 shown in FIG. 1, a total of seven patch pattern latent images are formed on the photosensitive drum 414 while changing the contrast potential from 200V to 320V in 20V steps. And a developing bias potential value for patch pattern creation, and developed as a visible image of the patch pattern on the photosensitive drum 414.

This visible image is recorded on the transfer paper through the transfer and fixing steps, and finally a test pattern recording paper as shown in FIG. 5 is obtained. Since this test pattern has undergone each of the steps of transfer and fixing, unlike the conventional technique, it is different from the one formed on the latent image carrier, and the influence of the subsequent steps of transfer and fixing is folded in. Cage,
The error due to such influence is not included.

In step 1002, step 1001
The transfer sheet on which the test pattern has been formed in step 1 is used as a document in a normal copy operation, and is set on the contact glass 202 which is a document table.

In step 1003, the multicolor image forming apparatus is driven to scan the test pattern recording paper to read an original document, here, a CCD functioning as a means for reading a test pattern as the original document. The test pattern is read by the color sensor 207 as a test pattern reading unit configured by the above. Further, the read information relating to the density of each patch pattern obtained here is subjected to signal processing by an image processing unit (not shown) to obtain a density value for each patch pattern.

In step 1004, a predetermined reference value in the multicolor image forming data stored in advance in the ROM 502 shown in FIG. 2, for example, the maximum image density that is the target density in the data, more specifically, Makes a determination by comparing each value of IDmax and the density of the test pattern signal-processed in step 1003, that is, the density of each patch pattern forming the test pattern.

This determination is performed inside the control device shown in FIG. The procedure of this determination is conceptually performed as follows. In FIG. 4, the horizontal axis indicates the contrast potential from 200 V to 320 V in steps of 20 V. For each patch pattern, the photoconductor drum 414
Since the actual measurement value obtained by reading the above contrast potential with the potential sensor 414D is stored in the control device 100,
By correlating these values with the density values of the patch patterns obtained in step 1004, as shown in FIG.
You can draw one point.

These points are set to IDm which is the target density.
Ax target value is compared and judged. When all the values do not reach the level of the IDmax target value, the density value is insufficient, so it is determined that the value is an abnormal value, and the abnormal processing is performed in step 1011. The abnormality processing includes countermeasure processing for eliminating the cause of the abnormality. If it is not an abnormal value, it is a normal value and the process proceeds to the next step 1005.

In the example shown in FIG. 4, the contrast potential 26
Below 0V, the IDmax target value has not been reached, but 2
At the contrast potential of 60 V or higher, the target value is satisfied. Therefore, the process proceeds to the next step 1005.

At step 1005, the contrast potential is determined. That is, among the values exceeding the IDmax target value, only the value closest to the IDmax target value, in this example, the density of the patch pattern indicated by the symbol d corresponding to the contrast potential 260V is adopted as the normal value, and the contrast potential (preferably the contrast potential) is set. Based on the measured value), the optimum contrast potential corresponding to the predetermined target density is determined. Such a process is performed for each color of Y, M, C, and K, and the optimum contrast potential corresponding to a predetermined target density is determined for each color. Where I
The Dmax target value is different for each color.

As described above, the control device 1000 shown in FIG.
Is also a judging means, because it also functions to judge the test pattern.

When the contrast potential is determined in step 1005 of the flow chart shown in FIG. 1, the procedure for determining the correction amount of the γ coefficient is executed according to the process of step 1006 and subsequent steps.

In step 1006, step 1005
In order to realize the contrast potential determined for each color of Y, M, C, and BK in FIG. 3, the potential table corresponding to the potential contrast obtained by the potential contrast determination routine of step 1005 is used. By driving the multicolor image forming apparatus shown in FIG. 1 to form an electrostatic latent image on the photoconductor drum 414, and after visualizing the image, the image is transferred to a transfer sheet to create a test pattern for γ adjustment on the transfer sheet. .

FIG. 12 shows a test pattern for .gamma. Correction created on the transfer paper in this way. As shown in the figure, the patch patterns forming the test pattern are arranged in 10 gradations for each color of Y, M, C and BK.

With respect to the conveying direction indicated by the arrow, in order from the smallest number from 1 to 10 showing the gradation level in the direction at right angles,
The patch patterns are arranged in order from a thin (low toner adhesion amount) patch pattern to a dark (high toner adhesion amount) patch pattern.

In this example, the density of the patch pattern corresponding to number 10 matches or substantially matches the IDmax target value for each color. Note that the arrangement direction and the order of the density of the patch patterns are not limited to this example, and they can be arranged freely.

Next, step 1007 and step 10
08, steps 1002 and 100 in reading the test pattern for determining the contrast potential described above.
12, the patch pattern shown in FIG. 12 is read by the color sensor 207, and signal processing of the γ adjustment test pattern for correcting the γ coefficient is performed.

In step 1009, step 1008
At, the presence or absence of an abnormality in the density value for each color and gradation obtained by the signal processing is determined. If it is determined to be abnormal, an abnormal process for eliminating the abnormal situation is performed in step 1011. If it is determined not to be abnormal, a calculation for determining the correction amount of the γ coefficient is performed in step 1010. The correction amount is determined, and the correction curve (C) shown in FIG. 13 is finally created.

The calculation for determining the correction amount of the γ coefficient in step 1010 is performed by the control device 1000 shown in FIG. 2 according to the flow chart shown in FIG. Therefore, the control device 1000 constitutes a correction unit that corrects the γ coefficient referred to in claim 1.

The procedure for determining the correction amount of the γ coefficient for an arbitrary color will be described with reference to FIG. In FIG.
The horizontal axis is divided into 255 gradations (256 gradations when 0 is included). Therefore, 256 including the image data
It can be expressed in gradation. Of the 10 gradations shown in FIG. 12, 1 gradation corresponds to 1 gradation also in FIG. 13, and 10 gradations of 10 gradations shown in FIG. This corresponds to the gradation at the stage indicated by 255. This is IDma
x Corresponds to the target value.

As for the image design characteristic of the multicolor image forming apparatus, the density characteristic of an output image with respect to image data having gradation is ideally displayed as a straight line as shown by an ideal curve (A) in FIG. .

With respect to this ideal curve (A), the density value for each color and gradation already obtained by the signal processing in step 1008, that is, the result of reading the gradation patch pattern of 10 steps shown in FIG. Curve approximation to
The actual measurement curve (B) is plotted on the graph of No. 3. The correction curve (C) is obtained by plotting the values obtained by the calculation so that the ideal curve (A) can be obtained based on the measured curve (B). For each color,
A characteristic curve as shown in FIG. 12 is obtained.

Such a correction curve (C) is selected as a correction value for each image data by calculation.

(3) Another example of test pattern In step 1001, as described above, the first test pattern for determining the contrast potential is set for each color of Y, M, C and BK as shown in FIG. Since it was created, a total of 5 test patterns were required.

In this example, as shown in FIG. 7, Y, M,
A test pattern of each color of C and BK is formed on one sheet of transfer paper. By using this, the image adjustment of the present invention can be performed by a single operation in a multicolor image forming apparatus.

The second test pattern as shown in FIG. 7 is
The procedure is basically the same as that of the first test pattern shown in FIG. 5 described above, but each color is formed on the photosensitive drum 414 based on the output signal from the controller 1000. A plurality of patch patterns are sequentially formed for each two rows in the sub-scanning direction indicated by the arrow.

FIGS. 8, 9, 10 and 11 respectively show
The patch patterns for Y, M, C, and BK are shown. In these figures, one row is arranged on the potential sensor passage area in the center of the image indicated by the symbol SP, and the remaining one row is at an arbitrary position, but when the figures of FIGS. The positions of the patch pattern rows are different so that they do not overlap.

In each row, the two patch patterns arranged in the direction orthogonal to the sub-scanning direction have the same density.
The patch pattern located in the center of the image is the potential sensor 41.
4D is for reading the contrast potential on the photoconductor drum 414, and another patch pattern adjacent to the photosensitive drum 414 with the same density is used for reading the density by the color sensor 207 after being visualized and then transferred to the transfer paper. belongs to.

Specifically, on the photosensitive drum 414,
First, the Y patch pattern shown in FIG. 8 is created. In this example, as shown in FIG. 8, different contrast potentials (A), (B '), (C'), (D '), and (E') are 5 respectively.
One latent image pattern is formed in two rows, and the contrast potential at the latent image portion of each patch pattern is measured by the potential sensor 414D, then developed with Y toner, and the image is transferred onto the intermediate transfer belt 415. .

Similarly, patch patterns as shown in FIGS. 9, 10 and 11 are sequentially created for each color of M, C and BK, and these toner images are transferred onto the intermediate transfer belt 415 in an overlapping manner. After the final patch pattern of the K toner image is transferred onto the intermediate transfer belt 415 in an overlapping manner, the patch pattern is transferred onto a transfer sheet at once.

When this transfer paper is taken out after passing through the fixing device 423, a test pattern as shown in FIG. 7 is obtained. Code S
The patch pattern in the potential sensor passage area indicated by P is black due to subtractive color mixing because each color is superimposed and transferred.

The test pattern shown in FIG. 7 is set on the contact glass 202 in the same manner as the first test pattern shown in FIG.
Read at once by the reading means, Y, M, C, B
The optimum contrast potential is determined for each color by comparing with the IDmax value for each color of K, and the correction amount of the γ coefficient is determined according to the procedure performed in the first test pattern.

By the procedure according to FIG. 1 described above, the contrast potential and the image data can be corrected together. These methods can be carried out not only by the service person but also by the user side whenever necessary.

By directly reading the patch pattern recorded on the transfer paper as the test pattern recording paper, it is possible to make a judgment based on an image substantially similar to the final image obtained by the user, and it is possible to perform accurate image adjustment. . Further, conventionally, the adjustment such as γ correction has been performed by a service person having a specialized technique, but by substantially automating the scanning, the image adjustment can be performed when the user recognizes it as necessary.

[0087]

According to the present invention, since the image reading sensor is used as the sensor for reading the test pattern, it is not contaminated with toner and saturated, and the test pattern after transfer and fixing is used. However, the influence thereof has already been folded in, so that accurate image density adjustment can be performed.

[Brief description of drawings]

FIG. 1 is a flow chart suitable for implementing the present invention.

FIG. 2 is a block diagram illustrating a configuration of a control device suitable for implementing the present invention.

FIG. 3 is a diagram illustrating a configuration of a multicolor image forming apparatus suitable for implementing the present invention.

FIG. 4 is a diagram schematically illustrating a procedure for determining a contrast potential that satisfies an IDmax target value.

FIG. 5 is an explanatory diagram of a first test pattern.

FIG. 6 is a diagram illustrating a contrast potential.

FIG. 7 is an explanatory diagram of a second patch pattern.

FIG. 8 is an explanatory diagram of a test pattern of a Y image on the photoconductor drum in the second patch pattern creating process.

FIG. 9 is an explanatory diagram of an M image test pattern on a photosensitive drum in a second patch pattern creating process.

FIG. 10 is an explanatory diagram of a C image test pattern on the photosensitive drum in the second patch pattern creation process.

FIG. 11 is an explanatory diagram of a test pattern of a K image on the photosensitive drum in the second patch pattern creating process.

FIG. 12 is a diagram illustrating a test pattern for γ correction created on a transfer sheet.

FIG. 13 is a diagram illustrating a correction curve (C) for determining the correction amount of the γ coefficient.

[Explanation of symbols]

207 Color sensor 401 (as test pattern reading means) 401 Writing optical unit 414 (as exposure means) Photoconductor drum 419 (as latent image carrier) Charger 1000 (as charging means) 1000 (test pattern output means, test) Controller as pattern determining means and γ coefficient correcting means)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location G03G 15/02 102 B41J 3/00 B 15/043 G03G 15/04 120 15/04 H04N 1/40 101E H04N 1/407

Claims (3)

[Claims] 1. A method for adjusting an image in a multicolor image forming apparatus, comprising: a latent image carrier, charging means for charging the latent image carrier; and static exposure by exposing the charged latent image carrier. An exposure means for forming an electric image, a test pattern output means for outputting a test pattern, a reading means for reading the test pattern, a judging means for judging the test pattern, and an image forming according to the judgment result of the judging means. Using the correction means for correcting the γ coefficient at the time, a contrast potential corresponding to a predetermined target density is obtained for each color forming the multicolor image, and the correction amount of the γ coefficient is calculated based on the target density and the contrast potential. A multicolor image adjusting method characterized by determining. 2. The image adjusting method for a multicolor image forming apparatus according to claim 1, wherein a plurality of patch patterns are formed on the latent image carrier as a test pattern with a plurality of contrast potentials having mutually different values. These patch turns are visualized on the same recording paper, and a plurality of these visualized patch patterns are read by the reading means, and the read result is compared with a predetermined reference value (predetermined target density). The multi-color image adjusting method is characterized in that the contrast potential corresponding to the predetermined target density is obtained by selecting the contrast potential corresponding to the predetermined target density from the plurality of contrast potentials. 3. The image adjusting method for a multicolor image forming apparatus according to claim 1, wherein the predetermined target density is electrostatically written on the latent image carrier by the exposure means when the test pattern is created. A multicolor image adjusting method, which is the maximum image density in image writing data.