JP2003280316A - Color image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color image forming device which can form an excellent pattern without repeating pattern generation processing for position shift detection. <P>SOLUTION: The color image forming device which obtains a color image by transferring images, formed at a plurality of image formation parts installed along a conveyance body, to a recording medium one over another comprises a detecting means (steps S3, S5, S7, and S9) which detects the end of data writing and a density pattern generating means (steps S4, S6, S8, and S10) which generates a density pattern when the detecting means detects the end of writing and is characterized in that the pattern detecting means for position shift detection detects the generated density pattern (step S11) and if the detected density pattern is improper, a position shift pattern imaging condition is calculated (step S13) to carry out a position shift correcting means (step S14) according to the calculated pattern imaging condition. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color printer,
The present invention relates to a color image forming apparatus that forms a color image using an electrophotographic process such as color copier.

[0002]

2. Description of the Related Art In a color image forming apparatus, a color image is obtained on a recording medium by sequentially superposing and transferring the images formed by an image forming unit onto a single recording medium conveyed by a conveyor belt. A method called a tandem method is known.

The tandem type color image forming apparatus has an advantage that the printing speed is high, but has a drawback that it is difficult to match each color. Therefore, for example, when a user or a service person moves a part of the image forming units from the normal position due to a paper jam or an abnormal operation,
When returning to the original position again, a slight positional deviation occurs, which causes a color deviation of each color.

In recent years, various inventions have been proposed in order to prevent such color misregistration.

According to Japanese Patent Laid-Open No. 10-260567, a positional deviation detection pattern having a correct shape is formed due to a decrease in density of the positional deviation detection pattern or unevenness of density due to environmental changes due to fluctuations in temperature and humidity and changes over time. If it is not formed, accurate pattern detection cannot be carried out, and in order to solve the problem that color misregistration correction cannot be performed normally, density data is calculated, and when the density data is outside the proper range,
By changing the bias value for creating an image, the misregistration pattern detection value is held at a certain value or more.

[0006]

However, in the above-mentioned conventional method, when the pattern density variation occurs, it is necessary to execute the process of creating the misregistration detection pattern a plurality of times, and the misregistration correction process takes time. There is a problem of this.

In view of the above-mentioned problems, an object of the present invention is to create a density detection pattern immediately after writing of a print just before executing misregistration correction, and change an image forming parameter according to the output of the density detection pattern. It is an object of the present invention to provide a color image forming apparatus capable of forming a good pattern without repeating the position deviation detection pattern forming process a plurality of times by forming the position deviation detection pattern by using the color image forming apparatus.

Another object of the present invention is to create a density detection pattern immediately after writing of a print just before execution of the misregistration correction and to output the misregistration detection pattern according to the output of the density detection pattern. To provide a color image forming apparatus capable of correctly detecting a misregistration detection pattern by changing the misregistration detection pattern detection voltage threshold value without repeating the misregistration detection pattern creation processing a plurality of times. is there.

Another object of the present invention is to create a density detection pattern immediately after writing of a print just before execution of the misregistration correction, and determine whether or not to execute the density adjustment processing according to the output of the density detection pattern. Thus, the color misregistration pattern is accurately detected, and a color image forming apparatus with improved overall productivity is provided.

Another object of the present invention is to provide, when it is determined that the misregistration detection fails with the changed image forming parameter,
It is an object of the present invention to provide a color image forming apparatus capable of accurately performing the positional deviation pattern detection by executing the toner density adjustment.

Another object of the present invention is to make it possible to accurately detect a misalignment pattern by executing toner density adjustment when it is determined that misregistration detection fails with a changing threshold value. It is to provide a color image forming apparatus.

[0012]

The present invention employs the following means in order to solve the above problems.

A first means is a color image forming apparatus for obtaining a color image by sequentially superposing and transferring the images formed by the image forming units arranged along the carrier on a recording medium. A plurality of sets of position shift detection patterns for detecting the position shift of each color of the superimposed image are formed on the carrier, and the position shift detection pattern is detected by the position shift detection pattern detection means, and based on the detection result. And a density pattern creating unit that creates a density pattern when the end of writing is detected by the detecting unit and a position deviation correcting unit that corrects the position deviation of the superimposed image. The detected density pattern is detected by the position shift detection pattern detecting means, and if the detected density pattern is incorrect, the position Re calculates the pattern imaging condition, based on the calculated pattern imaging conditions, and executes the positional deviation correcting means.

A second means is a color image forming apparatus for obtaining a color image by sequentially superposing and transferring images formed by image forming units arranged along a carrier on a recording medium. A plurality of sets of position shift detection patterns for detecting the position shift of each color of the superimposed image are formed on the carrier, and the position shift detection pattern is detected by the position shift detection pattern detection means, and based on the detection result. And a density pattern creating unit that creates a density pattern when the end of writing is detected by the detecting unit and a position deviation correcting unit that corrects the position deviation of the superimposed image. The detected density pattern is detected by the position shift detection pattern detecting means, and if the detected density pattern is incorrect, the position Re calculates the pattern detection threshold based on the calculated positional deviation pattern detection threshold, and executes the positional deviation correcting means.

A third means is a color image forming apparatus for obtaining a color image by successively superimposing and transferring images formed by image forming units arranged along a carrier on a recording medium. A plurality of sets of position shift detection patterns for detecting the position shift of each color of the superimposed image are formed on the carrier, and the position shift detection pattern is detected by the position shift detection pattern detection means, and based on the detection result. And a density pattern creating unit that creates a density pattern when the end of writing is detected by the detecting unit and a position deviation correcting unit that corrects the position deviation of the superimposed image. The detected density pattern is detected by the position shift detection pattern detection means, and if the detected density pattern is incorrect, the density Performs integer processing, after density adjustment, and executes the positional deviation correcting means.

A fourth means is a color image forming apparatus for obtaining a color image by sequentially superposing and transferring the images formed by the image forming portions arranged along the carrier on a recording medium. A plurality of sets of position shift detection patterns for detecting the position shift of each color of the superimposed image are formed on the carrier, and the position shift detection pattern is detected by the position shift detection pattern detection means, and based on the detection result. And a density pattern creating unit that creates a density pattern when the end of writing is detected by the detecting unit and a position deviation correcting unit that corrects the position deviation of the superimposed image. The detected density pattern is detected by the position shift detection pattern detecting means, and if the detected density pattern is incorrect, the position If Re calculates the pattern image forming conditions can not be set further calculated pattern imaging conditions,
It is characterized in that the toner density is adjusted and the positional deviation correction means is executed.

A fifth means is a color image forming apparatus for obtaining a color image by sequentially superimposing and transferring images formed by a plurality of image forming units arranged along a carrier on a recording medium. A plurality of sets of position shift detection patterns for detecting the position shift of each color of the superimposed image are formed on the carrier, and the position shift detection pattern is detected by the position shift detection pattern detection means, and based on the detection result. And a density pattern creating unit that creates a density pattern when the end of writing is detected by the detecting unit and a position deviation correcting unit that corrects the position deviation of the superimposed image. The detected density pattern is detected by the position shift detection pattern detecting means, and if the detected density pattern is incorrect, the position Re calculates the pattern detection threshold, further if the calculated position shift pattern detection threshold can not be set, by adjusting the toner concentration, and executes the positional deviation correcting means.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a diagram showing the configuration of a color image forming apparatus of the present invention.

In the figure, Y, M, C and K added after the reference numerals respectively correspond to yellow, magenta, cyan and black colors, and 1Y to 1K correspond to four respective colors. First, second, third, and fourth stations of the image forming unit provided respectively, 2Y
2K are photosensitive drums of respective stations of the image forming unit, 3Y to 3K are chargers of respective stations of the image forming unit, 4Y to 4K are exposure devices of respective stations of the image forming unit, and 5Y to 5K are images. A developing device in each station of the forming unit, 6Y to 6K are photoconductor cleaners of each station of the image forming unit, 7Y to 7K are transfer devices of each station of the image forming unit, 8 is a conveyor belt, and 9 is a belt driving roller. Reference numeral 10 is a belt driven roller, 11 is a paper feed tray for accommodating recording paper, 12 is a fixing device, and 13 and 14 are detection devices each having a light emitting portion and a light receiving portion (not shown), which are light reflection type sensors. The detection devices 13 and 14 may be transmissive sensors.

In this color image forming apparatus, as shown in the figure, four stations 1Y to 1K of four image forming portions for forming different colors are arranged in a straight line along a conveyor belt 8, Each of these stations 1Y ~
1K includes a photosensitive drum 2Y that functions as an image forming medium.
˜2K, chargers 3Y to 3K arranged around the photosensitive drums 2Y to 2K, exposure devices 4Y to 4K, and developing devices 5Y to 5
K, photoconductor cleaners 6Y to 6K, and transfer devices 7Y to 7K are arranged.

The conveyor belt 8 is rotationally driven in the direction of arrow A by a belt driving roller 9.

The surface of each of the photosensitive drums 2Y to 2K is uniformly charged by each of the chargers 3Y to 3K and then exposed.
The patterns Y to 4K are exposed in a pattern corresponding to the image to be output, and electrostatic latent images are formed on the surfaces of the photosensitive drums 2Y to 2K. The electrostatic latent images formed on the photosensitive drums 2Y to 2K are developed by the developing devices 5Y to 5K to form toner images of respective colors.

The recording paper is sent out from the paper feed tray 11,
The transport belt 8 sequentially passes through the first station 1Y, the second station 1M, the third station 1C, and the fourth station 1K, and the respective color toner images formed on the photosensitive drums 2Y to 2K by the transfer devices 7Y to 7K are transferred. One color image is formed by sequentially transferring and superposing them on the same position on the recording paper. The recording paper on which the four color toner images have been transferred is peeled off from the conveyor belt 8 and fixed by the fixing device 12.

The toner remaining on the surface of each of the photosensitive drums 2Y to 2K after the transfer of each color toner image formed on each of the photosensitive drums 2Y to 2K is removed by each of the photosensitive member cleaners 6Y to 6K, and the next image forming cycle is performed. Be prepared.

FIG. 2 is a perspective view showing a main part of the color image forming apparatus shown in FIG.

In the figure, an arrow B indicates a main scanning direction perpendicular to the moving direction of the conveyor belt 8, and an arrow C indicates a sub-scanning direction parallel to the moving direction of the conveyor belt 8. Further, reference numerals 201 and 202 denote misregistration detection patterns transferred onto the conveyor belt 8, respectively.

FIG. 3 is a block diagram showing the configuration of the control unit of the color image forming apparatus.

In the figure, the detection devices 13 and 14 are used to detect the positional deviation detection patterns 201 and 202 shown in FIG.
Is detected, the detected analog signal is converted into a digital signal by the A / D converter 31 and acquired as a voltage value. The acquired voltage value is used by the alignment controller 34 to detect the misregistration patterns 201, 20.
The position 2 is calculated, the skew deviation amount, the main scanning registration deviation amount, the main scanning magnification deviation amount, the sub-scanning registration deviation amount and the correction amount are calculated, and the set values of the control signals such as the write clock and the write timing are set in the system. It transmits to the controller 35.

In the system controller 35, each color is aligned by changing each timing to the transmitted set value.

The above is the processing corresponding to the positional deviation correction processing in FIGS. 6 to 10 which will be described later in the control section.

Incidentally, FIG. 4 shows the pattern 2 for detecting the positional deviation.
It is a figure which shows an example of 01 and 202.

As shown in the figure, the misregistration detection pattern is formed on the conveyor belt 8 on the front side of the color image forming apparatus.
A plurality of sets (8 sets) are formed on the rear side.

Next, the case where the density processing according to the present invention is performed to perform the accurate positional deviation correction processing will be described with reference to FIGS. 3 and 5 to 6.

FIG. 5 is a view showing a density pattern formed at a predetermined position from the writing end position of each station on the conveyor belt 8.

In the figure, 41f and 41r are Y (mm) × Z (mm) square density detection patterns created at a position X (mm) from the writing end position by the first station, and 42f and 42r are Y (mm) × Z (mm) square density detection patterns created at positions X + Y + X (mm) from the writing end position by the second station, 43f and 43r are X + Y + X + Y + X (mm) from the writing end position by the third station. Y (mm) × Z (mm) square density detection patterns 44f and 44r are created at positions X + Y + X + Y + X + Y + X (mm) from the write end position by the fourth station. It is a density detection pattern of (mm) squares.

FIG. 6 is a flow chart showing a processing procedure for reading the density pattern and performing accurate positional deviation correction processing.

First, when printing is started, step S1
At the position adjustment controller 34 shown in FIG.
The output value T of 7 is monitored to determine whether or not the predetermined positional deviation correction execution condition is satisfied and the positional deviation correction execution timing is reached. Issue a shift correction execution request.

When the system controller 35 can perform the positional deviation correction, the printing process is interrupted in step S2, the writing of each station is monitored when the page to be interrupted is printed, and in step S3. It is judged whether the data writing of the 1st station is finished. If the writing is finished, X (mm) from the writing end position
The density detection patterns 41f and 41r of Y (mm) × Z (mm) squares are created at the positions. After that, the completion of writing in each station is sequentially monitored, and when the writing in the second station is completed, in steps S5 and S6, X + Y +
At the position of X (mm), the density detection patterns 42f, 42r,
When the writing in the third station is completed, in steps S7 and S8, the density detection patterns 43f and 43r are located at the positions of X + Y + X + Y + X (mm), and when the writing in the fourth station is completed, in steps S9 and S10.
Density detection patterns 44f and 44r are created at the positions of X + Y + X + Y + X + Y + X (mm), respectively, and the registration controller 34 is issued with registration execution permission and density pattern creation completion notification.

Next, in step S11, the alignment controller 34 detects the density patterns from the detection devices 13 and 14.
Output value D detected in step S12
(V) is compared with the reference value S (V), and when it is determined that the density is sufficient, in step S14, the series of positional deviation correction processing described above is performed without changing the image forming conditions. To execute. When it is determined that the density is insufficient, in step S13, the image forming condition including the charging bias, the developing bias, the transfer bias, and the exposure power for creating the displacement pattern is calculated, and the calculation result is obtained. Based on this, the positional deviation correction process in step S14 is executed. After the misregistration correction process is executed, printing is restarted.

FIG. 7 is a flowchart showing a processing procedure different from that of FIG. 6 for reading the density pattern and performing the accurate positional deviation correction processing.

Incidentally, step S21 to step S30
Are step S1 of the flowchart shown in FIG.
The explanation is omitted because it corresponds to step S10.

In step S31, the alignment controller 34 detects the density pattern with the detection devices 13 and 14, and in step S32, the detected output value D (V) is compared with the reference value S (V). If it is determined that the density is sufficient, in step S34, the series of positional deviation correction processing described above is executed without changing the detection threshold value.
When it is determined that the density is insufficient, the threshold value is newly calculated in step S33, and the positional deviation correction process in step S34 is executed based on the calculated threshold value. After the misregistration correction process is executed, printing is restarted.

FIG. 8 is a flow chart showing a processing procedure different from that of FIGS. 6 and 7 for reading the density pattern and performing the accurate positional deviation correction processing.

Incidentally, steps S41 to S50
Are step S1 of the flowchart shown in FIG.
The explanation is omitted because it corresponds to step S10.

In step S51, the alignment controller 34 detects the density pattern with the detection devices 13 and 14, and in step S52, the detected output value D (V) is compared with the reference value S (V). If it is determined that the density is sufficient, in step S54, the series of positional deviation correction processing described above is executed without performing the density adjustment processing.
If it is determined that the concentration is insufficient, step S
At 53, the density correction processing is executed, and then, at step S
The positional deviation correction process at 54 is executed. After the misregistration correction process is executed, printing is restarted.

FIG. 9 is a flowchart showing a processing procedure different from that of FIGS. 6, 7 and 8 for reading the density pattern and performing the accurate positional deviation correction processing.

Incidentally, steps S61 to S70.
Are step S1 of the flowchart shown in FIG.
The explanation is omitted because it corresponds to step S10.

In step S71, the alignment controller 34 detects the density pattern with the detection devices 13 and 14, and in step S72, the detected output value D (V) is compared with the reference value S (V). If it is determined that the density is sufficient, in step S76, the series of misregistration correction processing described above is executed without adjusting the image forming conditions and the toner density. If you determine that the concentration is insufficient,
In step S73, the image forming condition including the charging bias, the developing bias, the transfer bias, and the exposure power for creating the displacement pattern is calculated. Furthermore, step S
If it is determined in step 74 whether the calculated image forming condition can be set, and if the image forming condition can be set, in step S76, the positional deviation correction process is executed and the image forming condition cannot be set. In step S75, the toner density is adjusted, and the positional deviation correction process in step S76 is executed.
After the misregistration correction process is executed, printing is restarted.

FIG. 10 is a flow chart showing a processing procedure for reading the density pattern and performing accurate positional deviation correction processing, which is different from the processing procedure shown in FIGS. 6, 7, 8 and 9.

Incidentally, steps S81 to S90
Are step S1 of the flowchart shown in FIG.
The explanation is omitted because it corresponds to step S10.

In step S91, the alignment controller 34 detects the density pattern with the detection devices 13 and 14, and in step S92, the detected output value D (V) is compared with the reference value S (V). If it is determined that the density is sufficient, in step S96, the series of misregistration correction processing described above is executed without adjusting the detection threshold value and the toner density. If you determine that the concentration is insufficient,
In step S93, a new detection threshold value is calculated, and in step S94, it is determined whether the calculated threshold value is detectable. If yes, step S9 is performed.
In step 6, the positional deviation correction process is executed, and if it is not detectable, the toner density is adjusted in step S95, and the positional deviation correction process in step S96 is executed. After the misregistration correction process is executed, printing is restarted.

[0053]

According to the first aspect of the invention, a density pattern is created at the time of detecting the end of writing, and the created density pattern is detected by the positional deviation detection pattern detecting means.
When the detected density pattern is incorrect, the misregistration pattern image forming condition is calculated, and the position deviation correcting unit is executed based on the calculated pattern image forming condition. Without the adjustment process, the detection failure of the misalignment pattern during the alignment process is eliminated.
Productivity can be improved.

According to the second aspect of the present invention, a density pattern is created at the time of detecting the end of writing, and the created density pattern is detected by the positional deviation detection pattern detecting means, and the detected density pattern is incorrect. In this case, the misregistration pattern detection threshold is calculated, and the misregistration correction unit is executed based on the calculated misregistration pattern detection threshold. Therefore, after the printing is completed, without performing the density adjustment processing,
It is possible to improve productivity by eliminating the detection failure of the misalignment pattern during the alignment process.

According to the third aspect of the present invention, a density pattern is created when the writing end is detected, and the created density pattern is detected by the positional deviation detection pattern detecting means, and the detected density pattern is incorrect. In this case, the density adjustment process is performed, and after the density adjustment, the position deviation correction means is executed.Because the density adjustment is executed only when necessary before the alignment process, the redundant density adjustment process can be deleted. The productivity can be improved, and the alignment process after the density adjustment process is executed when necessary.
It is possible to eliminate pattern detection failure during the alignment process.

According to the fourth aspect of the present invention, a density pattern is created at the time of detecting the end of writing, and the created density pattern is detected by the positional deviation detection pattern detecting means, and the detected density pattern is incorrect. In this case, the misregistration pattern image forming condition is calculated, and if the calculated pattern image forming condition cannot be set, the toner density is adjusted and the position deviation correcting unit is executed. In addition, since the density adjustment is executed only when necessary, the extra density adjustment processing can be eliminated, so that the productivity can be improved, and further, the position adjustment processing after the density adjustment processing is executed when necessary. It is possible to eliminate a pattern detection failure during the matching process.

According to the invention described in claim 5, a density pattern is created at the time of detecting the end of writing, and the created density pattern is detected by the pattern detecting means for detecting the positional deviation, and the detected density pattern is incorrect. In this case, the misregistration pattern detection threshold is calculated, and if the calculated misregistration pattern detection threshold cannot be set, the toner density is adjusted and the misregistration correction unit is executed. In addition, since the density adjustment is performed only when necessary, the extra density adjustment process can be eliminated, so that the productivity can be improved, and the alignment process after the density adjustment process is performed when necessary, the alignment process can be performed. It is possible to eliminate the detection failure of the inside pattern.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a color image forming apparatus of the present invention.

FIG. 2 is a perspective view showing a main part of the color image forming apparatus shown in FIG.

FIG. 3 is a block diagram showing a configuration of a control unit of the color image forming apparatus.

FIG. 4 is a diagram showing an example of misregistration detection patterns 201 and 202.

FIG. 5 is a diagram showing a density pattern formed at a predetermined position from a writing end position of each station on the transport belt 8.

FIG. 6 is a flowchart showing a processing procedure for reading a density pattern and performing accurate positional deviation correction processing.

FIG. 7 is a flowchart showing a processing procedure different from that of FIG. 6 for reading a density pattern and performing accurate positional deviation correction processing.

FIG. 8 is a flowchart showing a processing procedure different from that of FIGS. 6 and 7 for reading a density pattern and performing accurate positional deviation correction processing.

FIG. 9 is a flowchart showing a processing procedure different from that of FIGS. 6, 7 and 8 for reading a density pattern and performing an accurate positional deviation correction processing.

FIG. 10 is a flowchart showing a processing procedure for reading a density pattern and performing accurate positional deviation correction processing, which is different from those in FIGS. 6, 7, 8 and 9.

[Explanation of symbols]

1Y to 1K ... 1st, 2nd, 3rd, and 4th stations of image forming unit, 2Y to 2K ... Photosensitive drums of respective stations of image forming unit, 3Y to 3K ... of image forming unit Charger of each station, 4Y to 4K ... Exposure device of each station of image forming unit, 5Y to 5K ... Developer of each station of image forming unit, 6Y to 6K ... Each station of image forming unit Photoconductor cleaner, 7Y to 7K ... Transfer device of each station of the image forming unit, 8 ... Conveyor belt,
9 ... Belt driving roller, 10 ... Belt driven roller, 11 ... Paper feed tray, 12 ... Fixing device, 13, 14 ... Detection device, 201,
202 ... Position shift detection pattern, 31 ... A / D converter, 32 ... ROM, 33 ... RAM,
34 ... Positioning controller, 35 ...
System controller, 36 ... Printed sheet counter,
37 ... Temperature sensor, 41f, 41r, 42f, 42
r, 43f, 43r, 44f, 44r ... Density detection pattern.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H027 DA09 DE02 EA01 EA02 EA03                       EA05 EB04 EC04 EC06 ED06                       EE07 ZA07                 2H200 FA01 FA04 GA12 GA23 GA34                       GA44 GA47 HA02 HB12 HB22                       JA02 JB06 JB16 JB50 PB16                       PB20 PB36                 2H300 EB04 EB07 EB12 EF02 EF06                       EH16 EH33 EH35 EH36 EJ09                       EJ25 GG23 GG26 GG27 QQ03                       QQ25 RR34 RR37 RR38 RR39

Claims (5)

[Claims] 1. A color image forming apparatus for obtaining a color image by sequentially superposing and transferring an image formed by a plurality of image forming units installed along a conveying body onto a recording medium. A plurality of sets of position deviation detection patterns for detecting the position deviation of each color are formed on the carrier, and the position deviation detection patterns are detected by the position deviation detection pattern detection means, and a superimposed image is obtained based on the detection result. The position shift correction means for correcting the position shift, the detection means for detecting the end of data writing, and the density pattern creation means for creating a density pattern when the end of writing is detected by the detection means are provided. If the density pattern detected by the position detection pattern detection means is not correct, the position deviation pattern is detected. Calculating the image condition based on the calculated pattern image forming conditions, the color image forming apparatus characterized by performing the positional deviation correcting means. 2. A color image forming apparatus for obtaining a color image by sequentially superposing and transferring images formed by an image forming unit arranged along a carrier on a recording medium. A plurality of sets of position deviation detection patterns for detecting the position deviation of each color are formed on the carrier, and the position deviation detection patterns are detected by the position deviation detection pattern detection means, and a superimposed image is obtained based on the detection result. The position shift correction means for correcting the position shift, the detection means for detecting the end of data writing, and the density pattern creation means for creating a density pattern when the end of writing is detected by the detection means are provided. If the density pattern detected by the position detection pattern detection means is not correct, the position deviation pattern is detected. Calculating the output threshold, based on the calculated positional deviation pattern detection threshold, the color image forming apparatus characterized by performing the positional deviation correcting means. 3. A color image forming apparatus that obtains a color image by sequentially superposing and transferring images formed by image forming units arranged along a carrier on a recording medium. A plurality of sets of position deviation detection patterns for detecting the position deviation of each color are formed on the carrier, and the position deviation detection patterns are detected by the position deviation detection pattern detection means, and a superimposed image is obtained based on the detection result. The position shift correction means for correcting the position shift, the detection means for detecting the end of data writing, and the density pattern creation means for creating a density pattern when the end of writing is detected by the detection means are provided. If the density pattern detected by the position detection pattern detection means is not correct, a density adjustment process is performed. After density adjustment, color image forming apparatus characterized by performing the positional deviation correcting means. 4. A color image forming apparatus for obtaining a color image by sequentially superimposing and transferring images formed by image forming units arranged along a carrier on a recording medium. A plurality of sets of position deviation detection patterns for detecting the position deviation of each color are formed on the carrier, and the position deviation detection patterns are detected by the position deviation detection pattern detection means, and a superimposed image is obtained based on the detection result. The position shift correction means for correcting the position shift, the detection means for detecting the end of data writing, and the density pattern creation means for creating a density pattern when the end of writing is detected by the detection means are provided. If the density pattern detected by the position detection pattern detection means is not correct, the position deviation pattern is detected. Calculating the image conditions, further when the calculated pattern image forming conditions can not be set, by adjusting the toner concentration, the color image forming apparatus characterized by performing the positional deviation correcting means. 5. A color image forming apparatus that obtains a color image by sequentially superposing and transferring images formed by image forming units arranged along a carrier on a recording medium. A plurality of sets of position deviation detection patterns for detecting the position deviation of each color are formed on the carrier, and the position deviation detection patterns are detected by the position deviation detection pattern detection means, and a superimposed image is obtained based on the detection result. The position shift correction means for correcting the position shift, the detection means for detecting the end of data writing, and the density pattern creation means for creating a density pattern when the end of writing is detected by the detection means are provided. If the density pattern detected by the position detection pattern detection means is not correct, the position deviation pattern is detected. Calculating the output threshold, further if the calculated position shift pattern detection threshold can not be set, by adjusting the toner concentration, the color image forming apparatus characterized by performing the positional deviation correcting means.