JPH1184759A - Method for measuring color slippage, and color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for measuring a color slippage capable of highly accurately measuring the color slippage, and a color image forming device even through the speed of a transfer belt is fluctuated. SOLUTION: A pattern 9A for measuring alignment slippage constituted of a K color is formed on an intermediate transfer belt 6 and detected by a pattern detector 2 so that the amount of the alignment slippage of the detector 2 in the main scanning direction X with respect to the pattern 9A is arithmetically calculated based on the detection result. A pattern B for measuring color slippage constituted of the respective colors of K, Y, M and C is formed on the belt 6 based on the amount of the alignment slippage and detected by the detector 2 so that the amount of color slippage is arithmetically calculated based on the detection result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color misregistration measuring method and a color image forming apparatus for determining a color misregistration amount using a color misregistration measuring pattern formed by a plurality of image forming units.

[0002]

2. Description of the Related Art Conventionally, as a color image forming apparatus for forming a color image at high speed, a plurality of images for forming toner images of respective colors of yellow (Y), magenta (M), cyan (C), and black (K) are known. Forming units are arranged along the transfer belt, and the toner images of each color formed by the plurality of image forming units are sequentially transferred onto transfer paper conveyed by the transfer belt, or the toner images of each color are transferred onto the transfer belt. Are transferred so as to sequentially overlap each other, and finally a toner image is collectively transferred onto transfer paper.

One of the main difficult problems in such a color image forming apparatus is color registration misregistration correction (registration) for adjusting the misregistration of each color of a color image. ROS (Raster Output S)
canner) Scan direction (main scanning direction) shift, belt conveyance direction (sub scanning direction) shift, image expansion and contraction in the main scanning direction,
There is an angle shift (skew) in the ROS scan direction.
The registration is adjusted to be below the allowable value at the time of shipment of the device, but the distortion of the device due to the difference in the floor surface between the time of the adjustment and the use, and the change of the environmental temperature and the temperature inside the device at the time of the adjustment and the use As a result, the positional relationship between the ROS, the photosensitive drum, and the transfer belt slightly changes, and a color shift exceeding an allowable value occurs.

Therefore, it is necessary to correct color misregistration in a timely manner. Such a conventional color image forming apparatus is disclosed in, for example, JP-A-6-118735. The color image forming apparatus includes a plurality of image forming units disposed along the intermediate transfer belt, and a pattern detector that detects a color misregistration measurement pattern including a plurality of chevron marks formed by the plurality of image forming units. ,
The image processing apparatus includes a calculation unit that calculates the amount of color shift based on the detection result of the pattern detector, and a correction unit that corrects the color shift based on the calculation result of the calculation unit.

FIGS. 9 and 10 show the color misregistration measurement patterns. The color misregistration measurement pattern includes a first chevron mark KK, a second chevron mark MM, and a third chevron mark KM. The first angle mark KK is the element K
K ₁ and KK ₂ , and the second chevron mark MM is
The third chevron mark KM, which is composed of elements MM ₁ MM ₂
Is composed of elements KM ₁ and KM ₂ . The elements KK ₁ ,
KK ₂ and KM ₁ are formed of K color toner, and the elements MM
₁ , MM ₂ and KM ₂ are formed with M color toner. The pattern detector includes optical sensors PD ₁ and PD ₂ , the center line L _{1 of which} is the center line L of the chevron marks KK, MM and KM.
It is fixed to the apparatus main body side by a sensor fixing member (not shown) so as to coincide with ₂ . And each Yamagata mark K
Using the data of the time when K, MM, and KM pass immediately below (or immediately above) the pattern detector and the speed V of the transfer belt in the sub-scanning direction Y, as described below, the K color M
The color shift amount C _{MKX in} the main scanning direction X and the color shift amount C _MKY in the sub-scanning direction Y can be measured.

That is, the color shift amount C _{MKX in} the main scanning direction X with respect to the M color K is obtained from the following equation (1). _{C MKX = 0.5V × (T 2MM} -T 1MM + T 1KK -T 2KK) ... (1) where, T _1KK: Time chevron KK has passed the optical sensor PD ₁ T _1MM: chevron MM optical sensor PD time T _2KK passed through the _1: chevron KK the time has passed the optical sensors PD ₂ T _2MM: time chevron MM has passed the optical sensors PD ₂ the color misregistration in the sub-scanning direction Y with respect to K color color M Quantity C
_MKY is obtained from the following equation (2). _{C MKY = V × [(T} 2KM -T 1KM) -0.5 × {(T 2KK -T 1KK) + (T 2MM -T 1MM)}] ... (2) where, T _1KM: chevron KM optical sensor PD time T _2KM passed through the _1: measurement of color shift amount for chevron KM is time Y color and C color K color which has passed through the optical sensor PD ₂ creates a chevron instead of the M color is detected Can be measured.

[0007]

However, according to the conventional color image forming apparatus, the belt width and the sensor fixing member are deformed due to a temperature change inside the apparatus, and the center line of the pattern detector is changed as shown in FIG. L ₁ and Yamagata mark KK, M
M, the center line L ₂ of KM is relatively displaced in the main scanning direction X, the measurement accuracy of the amount of deviation (misalignment amount) approximately in proportion to the amount of color shift in the x there is a problem that deteriorates.

FIG. 11 shows how the measurement accuracy is degraded. The accuracy of color misregistration measurement in the main scanning direction X when the amount of misalignment x of the pattern detector is a certain value (x = 0, 1, 2) is shown. Show qualitatively. The horizontal axis is a value obtained by dividing the speed fluctuation frequency f of the transfer belt by fc. Note that fc = V / S, V is the belt speed, and S is each chevron mark KK, MM, K
M is the pitch distance in the sub-scanning direction Y.

FIG. 12 is a diagram for explaining the reason why the measurement accuracy is deteriorated. In the figure, T _1A is changed from the angle mark KK to the angle mark MM in the optical sensor PD ₁ .
And T _2A is the transit time from the chevron mark KK to the chevron mark MM in the optical sensor PD ₂ .
The above equation (1) can be expressed by the following equation (3). C _MKY = 0.5 V × (T _2A −T _1A ) (3)

However, the belt speed V periodically fluctuates due to the eccentricity of the driving roller and the driven roller for driving the transfer belt, as shown in FIG. Actually, there are a plurality of speed fluctuation frequencies, but for simplicity of description, a case where the belt speed V fluctuates at a certain frequency as shown in FIG. Photosensor PD _1, PD ₂ of the center line L ₁ and the chevron KK, MM, the center line of KM L ₂ and the main scanning direction X
, The average belt speed at the passage times T _1A and T _2A becomes different. However, equation (3)
Since the calculation is performed with the belt speed V constant, the difference from the actual average speed appears as a color shift measurement error. This measurement error increases as the difference between the average belt speeds at the respective passing times T _1A and T _2A increases. The same can be said for the sub-scanning direction Y.

Accordingly, an object of the present invention is to provide a color misregistration measuring method and a color image forming apparatus which enable highly accurate color misregistration measurement even when the speed of the transfer belt fluctuates.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention forms a color misregistration measurement pattern image composed of a plurality of color materials on a transfer belt that moves around by a plurality of image forming units. In the color misregistration measuring method of detecting the color misregistration measurement pattern image by a pattern detector arranged at a position and calculating a color misregistration amount based on the detection result, at least one of the plurality of image forming units A first forming step of forming, on the transfer belt, an alignment misalignment measurement pattern image formed of the color material by an image forming unit; and a first detection step of detecting the alignment misalignment measurement pattern image by the pattern detector. Based on the detection result of the pattern image for alignment misalignment measurement by the pattern detector,
A first calculating step of calculating an amount of alignment shift in a direction perpendicular to a moving direction of the transfer belt with respect to the pattern image for alignment shift measurement of the pattern detector, and the plurality of image forming units based on the amount of alignment shift A second forming step of forming the color misregistration measurement pattern image composed of the plurality of color materials on the transfer belt, and a second detection step of detecting the color misregistration measurement pattern image by the pattern detector. A second calculating step of calculating the color shift amount based on a detection result of the color shift measuring pattern image by the pattern detector.

In order to achieve the above object, the present invention provides a color image forming apparatus for forming a color image composed of a plurality of color materials and a pattern image for color misregistration measurement by a plurality of image forming units on a transfer belt which rotates. A first forming unit configured to control at least one of the plurality of image forming units to form a pattern image for alignment deviation measurement made of the color material on the transfer belt;
The alignment misalignment measurement pattern image formed on the transfer belt, which is disposed at a predetermined position, is
A pattern detection unit that outputs a detection signal of the color shift measurement pattern formed on the transfer belt and outputs a second detection signal; and the first detection from the pattern detection unit. First calculating means for calculating an amount of alignment shift in a direction perpendicular to the direction of movement of the transfer belt with respect to the pattern image for alignment shift measurement of the pattern detecting means, based on the signal; A second forming unit that controls the plurality of image forming units to form the color misregistration measurement pattern image on the transfer belt on the transfer belt; and a second forming unit that controls the plurality of image forming units based on the second detection signal from the pattern detecting unit. There is provided a color image forming apparatus including a second calculating means for calculating a color shift amount.

[0014]

FIG. 1 shows a color image forming apparatus according to a first embodiment of the present invention. The color image forming apparatus includes a laser light source (not shown) that emits a laser beam modulated based on image data of each color of K (black), Y (yellow), M (magenta), and C (cyan);
Exposure devices 3K, 3Y, 3M, 3C having rotating polygon mirrors (not shown) for deflecting the emitted light, and charging devices (not shown).
Photoconductor drums 4K, 4 which form an electrostatic latent image on the surface by rotating while receiving exposure to laser light from M, 3C
Y, 4M, 4C and photosensitive drums 4K, 4Y, 4M, 4
Developing units 5K, 5Y, 5M and 5C for developing the electrostatic latent images formed on C with toners of K, Y, M and C, respectively;
And an intermediate transfer belt 6 on which the toner images developed on the photosensitive drums 4K, 4Y, 4M, and 4C are transferred, and the intermediate transfer belt 6 is stretched, and the intermediate transfer belt 6 is moved by a driving device (not shown). A driving roller 6A and a driven roller 6B that are driven to rotate in the direction of the arrow;
Transfer devices 7K, 7Y, 7M, and 7C for transferring the toner images developed by Y, 4M, and 4C to the intermediate transfer belt 6, and K color transferred onto the intermediate transfer belt 6 under the control of the controller 1. Alignment misalignment measurement pattern and K,
A pattern detector 2 for detecting a timing when a color misregistration measurement pattern composed of each of Y, M and C passes, and a transfer roll for transferring an image formed on an image area on the intermediate transfer belt 6 to a print sheet P 8 is provided.

FIG. 2 shows the pattern for measuring the misalignment and the pattern for measuring the misregistration transferred onto the intermediate transfer belt 6. Alignment deviation measurement pattern 9A
Is the image area I (I ₁ , I ₂ , I ₃ , I ₄ ,...)
Are formed on the outer sides A and B of the maximum length R in the main scanning direction X as a mountain-shaped mark made of K color toner. The color misregistration measurement pattern 9B is a chevron-shaped mark composed of a plurality of chevron marks described later, and one or a plurality of sets are provided on the outer sides A and B of the image area I outside the maximum length R in the main scanning direction X. It is formed in the sub scanning direction Y.

The pattern detector 2 is formed on one side A.
Alignment measurement pattern 9A and color misalignment
Detects chevron mark elements that compose measurement pattern 9B
The first sensor unit 20A and the other side B
9A and color misalignment
The elements of the chevron mark constituting the measurement pattern 9B are detected.
Out of the second sensor unit 20B.
You. The first sensor unit 20A includes an optical sensor PD_A1,
PD_A2And the second sensor unit 20B
Sensor PD_B1, PD_B2Consists of Also, the pattern detector 2
Is an optical sensor PD _A1And PD_A2Center line L₁And light sen
Sa PD_B1And PD_B2Center line L₁Is the color misregistration measurement pattern
Center line L of 9B chevron mark_TwoIllustrated to match
Is not fixed to the device body by the sensor
You. Each optical sensor PD_A1, PD_A2, PD_B1, PD_B2Is
Excessive or reflective sensor with misalignment
The measurement pattern 9A and the color shift measurement pattern 9B
Pulse signal when the constituent chevron mark element passes
Is output to the controller 1.

FIG. 3 is a block diagram showing the configuration of the controller 1. The controller 1 sends clock signals to the detection data storage units 16A to 16D for storing data of the time when the pulse signals S _A1 , S _A2 , S _B1 , and S _B2 arrive from the pattern detector ₂ , and to the detection data storage units 16A to 16D. The clock circuit 17 for transmitting the signal CK and time data are read from the detection data storage units 16A to 16D, and the amount of misalignment and the amount of color misalignment of the pattern detector 2 are calculated based on the read time data. Processor 10 for calculating the correction amounts for the exposure devices 3Y, 3M, 3C for the respective colors K, Y, M, and C based on the above, and the exposure device based on the correction amount data from the processor 10 and the pattern data from the pattern memory 11. Image signal output control circuit 12 for controlling the output timing and pixel clock at 3K, 3Y, 3M, 3C
And

Each of the detection data storage sections 16A to 16D is provided corresponding to the output destination of the optical sensors PD _A1 , PD _A2 , PD _B1 and PD _B2 , and receives the clock signal C from the clock circuit 17.
A counter circuit 13 for counting the number of K; a memory control circuit 15 for outputting a count value read control signal to the memory 14 each time a pulse signal S _A1 , S _A2 , S _B1 , S _B2 arrives from the pattern detector 2; A memory 14 for reading the count value of the counter circuit 13 by a count value read control signal from the memory control circuit 15 and sequentially storing the count value as time data.

The image signal output control circuit 12 includes a pattern memory 11 for storing pattern data for measuring misalignment and pattern data for measuring color misalignment, a pattern data for measuring misalignment, pattern data for measuring misregistration, and an image memory (not shown). The exposure devices 3K, 3 for K, Y, M, and C are stored on the basis of image data to be printed stored by the CPU 10 and correction amount data from the processor 10.
It controls the output timing and pixel clock in Y, 3M, 3C. The image signal output control circuit 12
When the latent image forming operation of the Y image area is completed, and the control signal H ₁ outputs it to the processor 10.

The processor 10 responds to the control signal H ₁ from the image signal output control circuit 12 to store each detected data storage unit 1.
Memory control circuit 15 outputs the time data request control signal H _2A to H _2D to within 6A～16D, time data from the memory control circuit 15 to output the time data read control signal to the memory 14 is stored in the memory 14 Is read, and the amount of alignment shift and the amount of color shift are calculated based on the read time data.

First, the calculation of the amount of misalignment will be described. Assuming that the amount of alignment shift is x, the amount of alignment shift x is obtained from the following equation (4). x = 0.5V × (T _2KK −T _1KK ) (4) where T _1KK is the time _{when the} chevron mark KK passes through the optical sensor PD _A1 T _2KK : the time _{when the} chevron mark KK passes through the optical sensor PD _A2 V : Speed of the intermediate transfer belt 6 in the sub-scanning direction Y

Next, the calculation of the color shift amount will be described with reference to FIGS.
This will be described with reference to FIG. Fig. 4 (a) shows a pattern for measuring color misregistration.
9B is shown. The color shift measurement pattern 9B has nine peaks.
Shape marks KK, YY, KY, MM. Chev at CC, KC
This constitutes a rhombic mark. Yamagata Mark KK
Element KK₁, KK_TwoConsisting of
₁, YY_TwoAnd the angle mark KY is an element KY₁, K
Y_TwoAnd the Yamagata mark MM is an element MM₁, MM_TwoOr
And the yamagata mark KM is the element KM₁, KM_TwoFrom
And the chevron mark CC is the element CC₁, CC_TwoConsisting of mountains
Shape mark KC is element KC₁, KC_TwoConsists of The figure is 1
Indicates one set, or one set or multiple sets
Is transferred to the intermediate transfer belt 6. Element KK₁, K
K_Two, KY_Two, KM_Two, KC_TwoIs the reference K color toner
Element YY ₁, YY_Two, KY₁Is the Y color
MM formed with the nut₁, MM_Two, KM₁Is the M color
Made of toner, element CC₁, CC, KC₁Is C color
It is formed with toner.

FIG. 4B shows a timing chart of the output signal of the pattern detector 2. Here, the first sensor unit 20A including the optical sensors PD _A1 and PD _A2 will be mainly described. The processor 10 includes an optical sensor P
D _A1, the time data based on the pulse signals S _A1, S _A2 of PD _A2 read from the memory 14, passing time data based on the time data _{(t KY11, t KY12, t} KM11, t KM12,
t _KC11 , t _KC12 , t _KY21 , t _KY22 , t _KM21 , t _KM22 , t
_KC21 , _tKC22 ), and the color shift amount is calculated based on the passing time data as described later. Similarly, the time data based on the pulse signals S _B1 , S _B2 of the optical sensors PD _B1 , PD _B2 constituting the second sensor unit 20B is read out from the memory 14 for the color shift measurement pattern 9B on one side. The transit time data is obtained based on the time data, and the color shift amount is calculated based on the transit time data. Based on the amount of color misregistration performed on the color misregistration measurement patterns 9B on both sides, deviations such as a margin in the main scanning direction, a margin in the sub scanning direction, and a main scanning magnification are calculated, and a correction amount corresponding to the calculation result is calculated.

FIG. 5 is a diagram for explaining the calculation of the color shift amount.
FIG. Ideal position of actually formed Yamagata mark KK
E in the main scanning direction X from the chevron mark KKr
_KKIs obtained from the following equation (5), similarly to equation (4). E_KK= 0.5V × (T_2KK-T_1KK) (5) Also, the peak at the ideal position of the actually formed chevron mark KK
Amount of deviation F in the sub-scanning direction Y from the shape mark KKr_KKIs
Is obtained from the equation (6). F_KK= 0.5V × (T_2KK+ T_1KK-2T₀)… (6) where T₀: The optical sensor P is the chevron mark KKr at the ideal position.
D_A1, PD_A2Similarly, the ideal position of the actually formed chevron mark YY
E in the main scanning direction X from the angle mark YYr_YY
Is obtained from the following equation (7). E_YY= 0.5V × (T_2YY-T_1YY)… (7) where T_1YY: Yamagata mark YY is optical sensor PD_A1Go through
Time T_2YY: Yamagata mark YY is optical sensor PD_A2When passing
Also, the peak at the ideal position of the actually formed chevron mark YY
Amount of deviation F in the sub-scanning direction Y from the shape mark YYr_YYIs
From the equation (8). F_KK= 0.5V × (T_2YY+ T_1YY-2T₀−2S / V) (8) where, S: pitch distance between chevron marks KK, YY Pitch distance S between chevron marks KK, YY is
It is obtained from equation (9). S = V × (T_2KY-T_1KK-T_1KY+ T_1YY…… (9) where T_1KY: Yamagata mark KY is optical sensor PD_A1Go through
Time T_2KY: Yamagata mark KY is optical sensor PD_A2When passing
Therefore, the main run of the Yamagata mark YY with respect to the Yamagata mark KK
Color shift amount C in inspection direction X _YKXIs given by the above equations (5) and (7)
It is obtained from the following equation (10). C_YKX= E_YY-E_KK = 0.5V × (T_2YY-T_1YY+ T_1KK-T_2KK) = 0.5V × (t_KY21-T_KY11) (10) Further, the sub-scanning of the chevron mark YY with respect to the chevron mark KK
Color shift amount C in direction Y_{YK Y}Equations (6), (8), (9)
It is obtained from the following equation (11) derived from the above equation. C_YKY= F_KK-F_KK = V × [(T_2KY−T_1KY) −0.5 × ｛(T_2KK−T_1KK) + (T_2YY−T_1YY)｝] = 0.5 V × (2t_KY22-2t_KY12+ T_KY21-T_KY11) (11) Yamagata mark of other Yamagata mark MM and Yamagata mark CC
Color shift in the main scanning direction X and sub scanning direction Y with respect to KK
The amount is determined similarly.

Next, the operation of the apparatus according to the first embodiment will be described with reference to the flowchart of FIG. FIG.
6 is a flowchart illustrating a procedure of color misregistration correction according to the first embodiment. When the color misregistration correction cycle starts, the image signal output control circuit 12
1 based on the data of the alignment deviation measurement pattern (hereinafter referred to as “pattern A”) 9A stored in
The output of the laser beam from the exposure device 3K is controlled. Exposure device 3
K irradiates the photosensitive drum 4K with a laser beam to form a latent image of the pattern A on the surface of the photosensitive drum 4K. The latent image of the pattern A on the photosensitive drum 4K is developed by the developing device 5K to be a toner image, and then transferred onto the intermediate transfer belt 6 by the transfer device 7K. Thus, a pattern A (9A) as shown in FIG. 4A is formed on the intermediate transfer belt 6 (S1).

The path transferred onto the intermediate transfer belt 6 is
Turn A (9A) is the pattern detection position of pattern detector 2.
Place 2_PIs reached, each element constituting pattern A is
When passing through the turn detector 2, the light of the pattern detector 2
Sensor PD_A1, PD_A2, PD _B1, PD_B2Is a pulse signal
S_A1, S_A2, S_B1, S_B2Is stored for each detection data of the controller 1.
Output to the units 16A to 16D (S2).

The counter circuit 13 provided in each of the detection data storage sections 16A to 16D is set to an initial value when starting a color misregistration correction cycle, and counts the number of clock signals CK from the clock circuit 17. To start. The memory control circuit 15 outputs a time data read control signal to the memory 14 every time the pulse signals S _A1 , S _A2 , S _B1 , S _B2 from the pattern detector 2 arrive, and
Reference numeral 4 sequentially inputs and stores the count value of the counter circuit 13 as time data.

At an appropriate time when the detection is completed, the processor 10 sends control signals H _{2A to} H ₂ to each memory control circuit 15.
Output _2D . These signals H _2A to H time data stored in each memory 14 of the detection data storage unit 16A~16D by _2D is: are transmitted to the processor 10. Based on the input time data, the processor 10 calculates the amount of alignment deviation x using the above equation (4) (S3), and outputs it to the image signal output control circuit 12. The data of the misalignment amount x is stored in the image signal output control circuit 12.

The image signal output control circuit 12 determines the exposure devices 3K and 3K based on the data of the misalignment amount x and the color misalignment measurement pattern (hereinafter referred to as “pattern B”) 9B stored in the pattern memory 11. 3Y, 3
The outputs of the M and 3C laser beams are controlled so that the amount of misalignment becomes zero. Exposure devices 3K, 3Y, 3M, 3
C irradiates a laser beam to each of the photosensitive drums 4K, 4Y, 4M, and 4C, and forms a latent image of the pattern B on the surface of each of the photosensitive drums 4K, 4Y, 4M, and 4C. Each photoconductor drum 4
The latent images of pattern B on K, 4Y, 4M, and 4C are developed into toner images by developing units 5K, 5Y, 5M, and 5C, and then orbitally moved by transfer units 7K, 7Y, 7M, and 7C. Are sequentially transferred onto the intermediate transfer belt 6. Thus, a pattern B (9B) as shown in FIG. 4A is formed on the intermediate transfer belt 6 (S5).

When the pattern B transferred on the intermediate transfer belt 6 reaches the pattern detection position 2 _P of the pattern detector 2, when each element constituting the pattern B passes through the pattern detector 2, the pattern is detected. The optical sensors PD _A1 , PD _A2 , PD _B1 , and PD _B2 of the detector 2 _output pulse signals S _A1 ,
S _A2 , S _B1 , and S _B2 are stored in each detection data storage section 16 of the controller 1.
A to 16D.

When the detection of the pattern B by the pattern detector 2 is completed, the processor 10 uses the equations (10) and (11) based on the time data input from each memory 14 to determine the Y color for the reference color K. _Calculate the shift amounts C _YKX and C _YKY , and similarly calculate the color shift amounts of the M color and the C color with respect to the K color (S7), the shifts in the main scanning direction margin, the sub scanning direction margin, the main scanning magnification, and the like. Is calculated, and a correction amount for the calculated value is calculated (S8). When there are a plurality of patterns B, an average value of each set may be obtained.

The processor 10 outputs the correction amount data obtained by the calculation to the image signal output control circuit 12. The image signal output control circuit 12 stores the correction amount data from the processor 10, and based on the correction amount data, Y, M, C
The correction of the writing timing (the position at which the electrostatic latent image is formed) in the exposure devices 3Y, 3M, and 3C corresponding to the respective colors, that is, changes in the settings of the main scanning direction margin, the sub scanning direction margin, the main scanning magnification, and the like are sequentially performed. (S9).

According to the above-described first embodiment, the formation and detection of the color shift measuring pattern 9B and the calculation of the color shift are performed after the alignment shift amount is set to zero. Even if the speed fluctuates, an accurate color shift amount can be obtained.

FIG. 7 shows a flowchart according to the second embodiment of the present invention. This second embodiment is similar to the first embodiment.
The flowchart of FIG. 5 showing the embodiment of the present invention is different from the flowchart of FIG. 5 in that a step S10 is provided between steps S3 and S4, and a correction amount of the pattern B is calculated when the amount of misalignment is equal to or greater than a threshold (S4) When the value is equal to or smaller than the threshold, the correction of the pattern B is omitted. This makes it possible to speed up color misregistration correction.

FIG. 8 shows an alignment deviation measuring pattern 9A according to a third embodiment of the present invention. In the first embodiment, the alignment deviation measurement pattern 9A
Is a single chevron mark of K color, but in the third embodiment, as shown in FIG. 10, the chevron marks KK, YY, MM, and CC are formed by toners of K, Y, M, and C colors. You may comprise. In this case, when calculating the amount of alignment deviation, the amount of alignment deviation is calculated for each of the chevron marks KK, YY, MM, and CC, and the average is calculated to obtain the total amount of alignment deviation. As a result, a highly reliable array deviation amount can be obtained.

The present invention is not limited to the above embodiment, but various embodiments are possible. For example, a light source and a rotary polygon mirror for deflecting the emitted light are used, but the present invention is not limited to this. For example, a liquid crystal shutter array or an LED array may be used. Further, a photoreceptor belt may be used instead of the intermediate transfer belt 6, and an electrostatic latent image may be formed directly on the photoreceptor belt. Further, instead of the intermediate transfer belt 6, a transport belt for transporting the recording medium P is used, and the recording medium P transported by the transport belt is used.
Transfer the toner image of each color on top to form an image image,
Pattern 9 for measuring misalignment on both sides of the conveyor belt
A and the color misregistration measurement pattern 9B may be formed.
Further, in the above embodiment, an example of correction at one element pitch by write timing correction as correction in the sub-scanning direction has been described. However, correction of the rotation phase of the rotating polygon mirror, tilt mirror, optical deflector, etc. The correction may be performed at a pitch of one element or less. Further, the pattern detector 2 has a CC
D or the like that detects a pattern as image information may be used. Further, the color misregistration measurement pattern 9B may be a mark of another form. Further, the pattern A for alignment misalignment measurement and the pattern B for color misregistration measurement are formed outside the maximum image forming region R. It may be formed inside R.

[0037]

As described above, according to the present invention, since the color misregistration measuring pattern is formed based on the amount of misalignment of the pattern detector (detecting means), the pattern detector (detecting means) is used. It is possible to eliminate a color shift measurement error based on the alignment shift. As a result, even if the speed of the transfer belt fluctuates, highly accurate color shift measurement can be performed, and a high-quality color image can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a color image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an alignment deviation measurement pattern and a color deviation measurement pattern transferred onto an intermediate transfer belt according to the first embodiment.

FIG. 3 is a block diagram illustrating a configuration of a controller according to the first embodiment.

4A shows a color misregistration measurement pattern, and FIG. 4B is a timing chart of an output signal of a pattern detector.

FIG. 5 is a diagram for explaining calculation of a color shift amount according to the first embodiment.

FIG. 6 is a flowchart illustrating a procedure of color misregistration correction according to the first embodiment.

FIG. 7 is a flowchart illustrating a procedure of color misregistration correction according to the second embodiment.

FIG. 8 is a diagram showing a pattern for measuring misalignment according to a third embodiment.

FIG. 9 is a diagram showing a conventional color misregistration measurement pattern.

FIG. 10 is a diagram showing a state in which alignment of a conventional pattern detector with respect to a color misregistration measurement pattern is misaligned.

FIG. 11 is a diagram illustrating a state in which measurement accuracy of a conventional color shift amount is deteriorated.

FIG. 12 is a diagram for explaining the reason why measurement accuracy deteriorates in a conventional configuration.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Controller 2 Pattern detector 2 _P pattern detection position 3K, 3Y, 3M, 3C Exposure device 4K, 4Y, 4M, 4C Photoconductor drum 5K, 5Y, 5M, 5C Developing device 6 Intermediate transfer belt 6A Drive roller 6B Follower roller 7K, 7Y, 7M, 7C Transfer unit 8 Transfer roll 9B Alignment misalignment measurement pattern 9B Color misalignment measurement pattern 10 Processor 11 Pattern memory 12 Image signal output control circuit 13 Counter circuit 14 Memory 15 Memory control circuit 16A to 16D Detected data storage part 17 clock circuit 20A first sensor unit 20B second sensor units a, B outer CK clock signal H ₁ control signal H _2A to H _2D time data request control signal I ₁ ~I ₄ image area KK, YY, MM, CC, KY, KM, KC Yamagata mark P print Paper _{PD A1, PD A2, PD B1} , PD B2 photosensor R maximum image forming area _{S A1, S A2, S B1} , S B2 pulse signal X main scanning direction Y subscanning direction

Claims (8)

[Claims] 1. A color shift measuring pattern image comprising a plurality of color materials is formed by a plurality of image forming units on a transfer belt that moves around, and the color shift measuring pattern is detected by a pattern detector arranged at a predetermined position. In a color misregistration measuring method for detecting an image and calculating a color misregistration amount based on the detection result, a pattern image for alignment misalignment measurement made of the color material by at least one of the plurality of image forming units. A first forming step of forming a pattern image on the transfer belt, a first detecting step of detecting the pattern image for alignment deviation measurement by the pattern detector, and a detection of the pattern image for alignment deviation measurement by the pattern detector. Based on the result, the pattern detector uses the pattern image for the alignment misalignment measurement. A first calculation step of calculating an amount of alignment shift in a direction perpendicular to the direction of movement of the transfer belt; and a method of measuring the color shift of the plurality of color materials by the plurality of image forming units based on the amount of alignment shift. A second forming step of forming a pattern image on the transfer belt; a second detecting step of detecting the color shift measuring pattern image by the pattern detector; and the color shift measuring pattern image by the pattern detector. A second calculating step of calculating the color shift amount based on the detection result of the color shift. 2. The color misregistration measurement pattern image includes a first chevron mark formed of a first color material among the plurality of color materials, and a first chevron mark among the plurality of color materials. A second chevron mark made of a different second color material, and a third chevron mark made of the first color material and the second color material, wherein the second calculation step comprises: Color material, the second
The color misregistration measuring method according to claim 1, wherein the color misregistration amount is calculated based on time data when the color material and the third color material pass through the pattern detector. 3. The method according to claim 2, wherein, if the amount of misalignment obtained in the first calculation step is equal to or less than a predetermined value, the color forming is performed without changing a preset pattern forming position. 2. The color shift measuring method according to claim 1, wherein the color shift measuring pattern image is formed. 4. The method according to claim 1, wherein the first forming step forms the misalignment measurement pattern image composed of the plurality of color materials by the plurality of image forming units. Calculating the amount of misalignment for each material, calculating an arithmetic average of the calculation result, the second forming step includes the step of measuring the color misalignment based on the arithmetic average of the amount of misalignment. 2. The color shift measuring method according to claim 1, wherein the color shift measuring method is configured to form an image. 5. A color image forming apparatus for forming a color image composed of a plurality of color materials and a pattern image for color misregistration measurement on a transfer belt rotating around by a plurality of image forming units, wherein at least one of the plurality of image forming units is provided. A first forming unit that controls one image forming unit to form a pattern image for alignment deviation measurement made of the color material on the transfer belt; and a first forming unit that is disposed at a predetermined position and is formed on the transfer belt. Detects the pattern image for alignment misalignment measurement and
A pattern detection unit that outputs a detection signal of the color shift measurement pattern image formed on the transfer belt and outputs a second detection signal; and the first detection from the pattern detection unit. A first calculating means for calculating an amount of misalignment in a direction perpendicular to a moving direction of the transfer belt with respect to the misalignment measuring pattern image of the pattern detecting means based on the signal;
Calculating means for controlling the plurality of image forming units based on the amount of misalignment to form the color misregistration measurement pattern image on the transfer belt on the transfer belt; and detecting the pattern. And a second calculating means for calculating the color shift amount based on the second detection signal from the means. 6. The color misregistration measurement pattern image includes a first chevron mark formed of a first color material among the plurality of color materials, and a first chevron mark of the plurality of color materials. A second chevron mark made of a different second color material, and a third chevron mark made of the first color material and the second color material; 6. The color image forming apparatus according to claim 5, wherein the color misregistration amount is calculated based on time data when the color material, the second color material, and the third color material pass through the pattern detection unit. 7. The image forming apparatus according to claim 1, wherein when the amount of misalignment obtained by the first calculating means is equal to or less than a predetermined value, the second forming means does not change a preset pattern forming position. The color image forming apparatus according to claim 5, wherein the color image forming apparatus is configured to form a shift measurement pattern image. 8. The first forming unit controls the plurality of image forming units to form the misalignment measurement pattern image formed of the plurality of color materials. Calculating the amount of alignment deviation for each of the plurality of color materials, calculating an arithmetic average of the calculation result, the second forming unit is configured to calculate the color deviation based on the arithmetic average of the amount of alignment deviation; 6. The color image forming apparatus according to claim 5, wherein the color image forming apparatus is configured to form a measurement pattern image.