JP2001005246A - Color image forming equipment - Google Patents

Abstract

(57) [Problem] To detect a color shift amount in an image forming apparatus used as an output device such as a computer because a registration pattern for detecting a color shift amount is not correctly drawn due to uneven conveyance or image formation. Cannot be performed correctly. SOLUTION: A plurality of registration patterns having different repetition frequencies are formed independently for each color, and sampling is performed at a sampling frequency corresponding to each registration pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a color image forming apparatus provided with a color misregistration detecting mechanism in a registration mechanism of a tandem engine type color image forming apparatus, and a color misregistration detecting method of the color image forming apparatus.

[0002]

2. Description of the Related Art In a conventional electrophotographic image forming apparatus, a uniform electrostatic charge of about 1 millicoulomb per square centimeter is applied to the surface of a photosensitive drum, and the photosensitive member is exposed to light in accordance with image information. To discharge only the charge of the irradiated portion to the photosensitive drum substrate, thereby forming an image (electrostatic latent image) based on the distribution of the resulting electrostatic charge, and developing the electrostatic latent image with colored charged particles (toner particles). After forming a powder image of toner particles by toner development to form a powder image, transferring the powder image to a sheet material or the like, applying heat and other energy to fix the image by fusing. Forming is being done.

On the other hand, with the colorization of images, a plurality of independent images are formed on the respective photosensitive drums by forming the respective color powder images of a cyan image, a magenta image, a yellow image, and more preferably a black image by the toner phenomenon. A tandem engine type color image forming apparatus that includes a forming station and superimposes and transfers and synthesizes a powder image formed on each photoconductor drum on an intermediate transfer material at a transfer position of each color powder image has also been proposed. I have. In the tandem engine type color image forming apparatus, since image formation is performed in parallel for each color, there is an advantage that the speed of image formation can be increased.

However, in the case of a tandem engine type color image forming apparatus, each powder image formed in a different image forming station is displaced due to a positional error or a timing deviation between the image forming stations, resulting in various colors. A shift occurs. In order to produce a high-quality color image forming apparatus, such a color shift becomes a very serious problem, and a technique for performing color shift correction (registration) is required.

FIG. 1 is a configuration diagram of a conventional color image forming apparatus, and FIG. 2 is a diagram showing types of color misregistration in a general color image forming apparatus.

In FIG. 1, the conventional color image forming apparatus is arranged such that four image forming stations Pa, Pb, Pc, and Pd are arranged side by side while being brought into contact with an upper portion of an intermediate transfer belt 7 rotated by driving rollers 14a and 14b. Each of the image forming stations has a photosensitive drum 1a, 1b, 1c, or 1d that comes into contact with the intermediate transfer belt 7 attached to the main body of the color image forming apparatus. Around the photosensitive drums 1a, 1b, 1c and 1d, charging means 2a, 2b, 2c and 2d for applying an electrostatic charge to each photosensitive drum are provided. Image forming stations Pa, Pb, Pc,
An exposure unit 3 which is a scanning optical system for exposing light corresponding to image information to each of the photosensitive drums 1a, 1b, 1c and 1d charged by the charging unit to form an electrostatic latent image is disposed above Pd. Has been established. Further, each photosensitive drum 1a, 1b, 1
developing means 4 for developing the electrostatic latent image formed by exposure with colored toner particles to form a powder image around c and 1d
a, 4b, 4c, 4d, developing means 4a, 4b, 4c, 4
transfer means 5 for superimposing and synthesizing each powder image formed in d on the intermediate transfer belt 7 at the transfer position of each color powder image
a, 5b, 5c, 5d, transfer means 5a, 5b, 5c, 5
d, cleaning means 6a, 6b, 6c, 6 for cleaning the surfaces of the photosensitive drums 1a, 1b, 1c, 1d after the respective powder images are transferred onto the intermediate transfer belt 7.
d are provided respectively.

The intermediate transfer belt 7 moves in the direction of arrow A shown in FIG. 1, and the respective photosensitive drums 1a, 1b, 1c, 1d
Rotates in the direction of arrow B shown in FIG. 1 without slipping on the intermediate transfer belt 7.

Next, the image forming operation of the above-described conventional color image forming apparatus will be described. First, at the image forming station Pa, the surface of the photosensitive drum 1a is uniformly charged with electrostatic charge by the charging means 2a, and then the electrostatic latent image corresponding to the image information of the black component is formed on the photosensitive drum 1a by the exposure means 3K. Is formed. This electrostatic latent image is developed on the photoreceptor drum 1a as a powder image by black toner particles by the developing means 4a, and the powder image is transferred as a black toner image onto the intermediate transfer belt 7 by the transfer means 5a. You. Photoreceptor drum 1 after transfer
On the surface a, the residual toner particles are removed by the cleaning unit 6a, and the surface a is prepared for the next image formation.

On the other hand, in parallel with the formation of the black toner image, the surface of the photosensitive drum 1b is uniformly charged with electrostatic charges by the charging means 2b in the image forming station Pb. An electrostatic latent image corresponding to the image information of the cyan component is formed on the photosensitive drum 1b by the means 3C. This electrostatic latent image is developed by the developing unit 4b.
As a result, the toner image is developed on the photosensitive drum 1b as a powder image of cyan toner particles, and is superimposed on the black toner image formed on the intermediate transfer belt 7 to form a composite toner image. Similarly, the magenta toner image is superimposed by the image forming station Pc and the yellow toner image is superimposed by the image forming station Pd.
And a composite toner image is formed thereon.

After the above-described superposition of the four color toner images is completed, the intermediate transfer belt 7 is brought into contact with the intermediate transfer belt 7 on the sheet material 9 such as the paper supplied from the paper supply cassette 10 by the paper supply roller 8. The composite toner image is transferred by a transfer roller 11 disposed at a position where the sheet material 9 is interposed between the belt 7 and the transfer roller 11, and is heated and fixed by a fixing unit 12 to form a color image on the sheet material 9. .

However, in the above-described tandem engine type image forming apparatus, when the temperature at the time of turning on the power is unstable, or when the image forming stations Pa, Pb, Pc,
Each image forming station Pa, Pb, P due to exchange of Pd, setting status of the image forming apparatus, temperature change in the apparatus, etc.
Various color shifts as shown in FIGS. 2A to 2E occur due to c, Pd, misalignment of the scanning optical system, and the like.

FIG. 2A shows an intermediate transfer belt 7.
Sub-scanning position shift due to parallel movement in the movement direction A of
(B) is a main scanning position shift that is shifted in parallel in the scanning direction of the exposure unit 3 (a direction perpendicular to the moving direction A of the intermediate transfer belt 7), and (c) is a deviation from the scanning direction of the exposure unit 3. A skew error in which the image is inclined obliquely, (d) is a magnification error in which the magnification of the exposure unit 3 in the scanning direction is shifted among the image forming stations Pa, Pb, Pc, and Pd, and (e) is a scanning direction of the exposure unit 3. Represents a curvature error in which the image is curved.

The main causes of various color misregistrations are the sub-scanning misalignment (a) and the main scanning misalignment (b) due to the misalignment of each image forming station Pa, Pb, Pc, Pd and the exposure means 3, or the exposure. The skew error (c) is caused by misalignment of a lens or a mirror (not shown) that constitutes the scanning optical system of the means 3.
a, Pb, Pc, Pd photosensitive drums 1a, 1b, 1
c, deviation of the mounting angles of the rotating shafts 1d and the exposure means 3
The magnification error (d) is an error in the optical path length from the scanning optical system of each of the exposure units 3K, 3C, 3M, and 3Y to the surface of each of the photosensitive drums 1a, 1b, 1c, and 1d. The curvature error (e) is caused by misalignment of a lens or a mirror (not shown) constituting a scanning optical system of each of the exposure units 3K, 3C, 3M, and 3Y.

Therefore, when the power is turned on, when each image station is replaced, or when the temperature inside the apparatus changes, a reference pattern (hereinafter referred to as a "registration pattern") is marked on the intermediate transfer belt 7 in advance. The registration pattern is detected by the color misregistration detecting means 13 using a plurality of sensors, the five types of color misregistration amounts are calculated from the detection results, and the color misregistration for adjusting the position of each color image according to the misregistration amount It is necessary to make corrections.

The operation of detecting and correcting a color shift of a conventional color image forming apparatus will now be described with reference to the drawings.

FIG. 3 is a block diagram of a conventional color misregistration detection unit, and FIG.
FIG. 5 is a layout diagram of a conventional registration pattern on the intermediate transfer belt and a misregistration detection unit, and FIG. 5 is a layout diagram of a registration pattern on the conventional intermediate transfer belt, a misregistration detection unit, and an output signal of the misregistration detection unit. FIG.

In FIG. 3, a color shift detecting means 13 disposed above the intermediate transfer belt 7 for detecting a positional shift of a registration pattern includes a light source 31 such as a lamp or a laser, and a sensor 33 for detecting the registration pattern. And a lens 32 for forming an image of the registration pattern irradiated on the light source 31 on the sensor 33.
It is composed of As shown in FIG. 4, the color misregistration detecting means 13 includes two color misalignment detecting means 13 near a scanning start position and a scanning ending position of the exposing means 3 on a line orthogonal to the moving direction A of the intermediate transfer belt 7. Color shift detecting means 13
b) It is provided. The sensors of the color shift detecting unit 13a and the color shift detecting unit 13b are arranged on a line orthogonal to the moving direction A of the intermediate transfer belt 7.

In the above-described configuration, in the color misregistration detecting operation, a registration pattern such as a predetermined straight line or graphic as shown in FIG. A straight line including a scanning start position and a straight line including a scanning end position of the exposure unit 3 arranged on a line orthogonal to A are formed as toner images 34, 35, 36, and 37 at predetermined intervals as an intermediate transfer belt. Then, the image is transferred onto the image 7, and the color misregistration detecting means 13a and 13b measure the amount of misregistration (color misregistration) of each color.

With respect to the sub-scanning position shift shown in FIG. 2A, as shown in FIG. 5A, the registration pattern of each color on the intermediate transfer belt 7 is detected by the color shift detecting means 13a.
ΔT (ΔTn = T−Tn: n = 1, ΔTn) between a time T1 passing through the sensor 33a and a predetermined design value T.
2, 3, 4) and the moving speed V of the intermediate transfer belt 7, the positional deviation ΔYn of each color (ΔYn = ΔTn × V: n = 1, 2, 3,
4) is calculated.

With respect to the main scanning position shift shown in FIG. 2B, for example, by setting the registration pattern as an oblique line, the registration pattern can be detected by the sensor 3 in the color shift detecting means 13a in the same manner as described above.
The position shift of each color is calculated from the time of passing through 3a and a predetermined design value and the moving speed V of the intermediate transfer belt 7.

With respect to the skew error shown in FIG. 2C, as shown in FIG. 5B, the registration pattern of the same color on the intermediate transfer belt 7 is detected by the color shift detecting means 13a.
And a time difference ΔTTn (n = 1,2,3,3) passing through the sensor 33a and the sensor 33b in the color shift detecting means 13b.
4) and the skew error ΔYYn of each color (ΔYYn = ΔTTn × V: n =
1,2,3,4) is calculated.

The magnification error shown in FIG. 2D is obtained by calculating the main scanning position shift in the color shift detecting means 13a and 13b as described above, and comparing the calculated value with a predetermined design value. The magnification error is calculated from the difference between.

The curvature error shown in FIG. 2E cannot be accurately measured by the conventional color misregistration detection operation using two sensors. Therefore, the error is reduced by increasing the assembling accuracy of the lens and the like in the exposure means 3.

Based on the four types of color misregistration amounts detected as described above, a color misregistration correction operation is performed next.

FIG. 6 is a configuration diagram of a conventional color misregistration correction mechanism of a scanning optical system in an exposure unit. In FIG. 6, the scanning optical system of the exposure unit 3 provided on the photosensitive drum 1 includes a polygon motor 61, a polygon mirror 62 mounted on the shaft of the polygon motor 61, an adjustment actuator 66, an adjustment actuator 67, And the mirror surface is held at a right angle, and a pair of substantially inverted C-shaped mirrors 63 and 64, and finally the scanning light beam is
And a return mirror 65 for irradiating the light. The adjusting actuator 66 includes the folding mirror 63,
64 is moved horizontally in the front-rear direction (the direction of arrow C in FIG. 6), and the adjustment actuator 67 is turned back.
64 is moved in the vertical direction (the direction of arrow D in FIG. 6).
As an actuator for performing these adjustments, a linear step actuator having a step motor, which is a drive source that moves linearly in a stepwise manner, or the like is used. The image data is optically modulated by a semiconductor laser (not shown),
The light enters the polygon mirror 62. Polygon mirror 62
The scanning light beams reflected by the mirrors are reflected by the mirrors 63, 64, 6
5, the light is sequentially reflected and irradiated on the surface of the photosensitive drum 1. The irradiation position of the scanning light beam is controlled by a polygon motor 61, an adjustment actuator 66, and an adjustment actuator 67 which are driven independently.

With the scanning optical system configured as described above, the correction of the sub-scanning position shift shown in FIG. 2A and the main scanning position shift shown in FIG. 2C, and the correction of the skew error shown in FIG. 2C and the correction of the magnification error shown in FIG. 2D are performed by the adjustment actuator 66 and the adjustment actuator 67. Position adjustment and optical path length adjustment.

[0027]

However, in the above-mentioned conventional configuration, when a registration pattern for examining the amount of color misregistration is transferred as a toner image onto the intermediate transfer belt, the eccentricity of the drive unit of the intermediate transfer belt or the like is reduced. Because the portion of the intermediate transfer belt where the toner image is transferred does not move at a constant speed (zero acceleration) due to shaft deviation of the driving unit or waving of the intermediate transfer belt, the toner image is transferred onto the intermediate transfer belt. The position of the registration pattern is not fixed and is shifted, resulting in a change in the position of the registration pattern. Further, the toner image itself may not be accurately formed on the image forming unit due to the eccentricity of the driving unit of the image forming unit or the axial deviation of the driving unit. As a result, if the registration pattern is used to detect the amount of color misregistration, a different amount of color misregistration from the actual one will be detected. As a result, there is a problem that the print quality is deteriorated.

The present invention has been made to solve this problem. By drawing a plurality of registration patterns and assigning a specific sampling frequency, it is possible to accurately detect a color shift based on a fluctuation component. An object of the present invention is to provide a color image forming apparatus capable of obtaining a high-quality image by enabling high-accuracy color misregistration correction.

[0029]

In order to solve the above-mentioned problems, the present color image forming apparatus comprises: an endless carrier for carrying and transporting an image on the surface; and an image transporter for transporting an image corresponding to image information of each color. A plurality of image forming means provided for each color to be formed on the means, and a signal for forming a registration pattern for each color on the endless carrier by the image forming means during a color misregistration detecting operation. The apparatus includes a registration pattern signal generation unit, a registration pattern signal control unit for controlling the registration pattern signal generation unit, and a color shift detection unit for detecting a color shift of an image from the registration pattern.

With this configuration, when a registration pattern is formed, a plurality of band-shaped registration patterns having different repetition frequencies in the sub-scanning direction are formed independently for each color, so that a plurality of periodic fluctuation components of each color are formed. By improving the color misregistration detection accuracy when only a predetermined component is detected from the inside, the accuracy of correction is also improved, and a color image forming apparatus capable of obtaining an image with high print quality can be provided.

In the image forming apparatus according to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the registration pattern signal control means controls the repetition frequency of each registration pattern to be equal to or smaller than that of the photosensitive drum. It is configured so that it can be set to at least twice or more the rotational drive frequency.

Further, in the image forming apparatus according to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the registration pattern signal control means may be configured so that the repetition frequency of each registration pattern is the endless shape. The rotation driving frequency of the carrier is set to be at least twice or more.

Further, in the image forming apparatus according to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, the registration pattern signal control means controls the repetition frequency of each registration pattern to be equal to the endless shape. The rotation frequency is set to be at least twice or more the rotation frequency for one rotation of the carrier.

Further, in the image forming apparatus according to a fifth aspect of the present invention, in the image forming apparatus according to the first aspect, the registration pattern signal control means controls the repetition frequency of each registration pattern so that the repetition frequency of the image formation is equal to or smaller than that of the image forming apparatus. The rotation driving frequency of the photosensitive drum of the means, the rotation driving frequency of the endless carrier, and the least common multiple of the rotation frequency of one rotation of the endless carrier are set to be equal to or more than the least common multiple.

Further, in the image forming apparatus according to a sixth aspect of the present invention, in the image forming apparatus according to the first aspect, the registration pattern signal control means determines that the order of forming each registration pattern is the same as that of the repetition frequency. The configuration is such that a pattern having a high repetition frequency can be formed in order from a pattern having a low repetition frequency.

[0036]

According to a first aspect of the present invention, there is provided a color image forming apparatus, comprising: an endless carrier for carrying and transporting an image on the surface; and an image transporting means for transporting an image corresponding to image information of each color. A plurality of image forming means provided for each color to be formed thereon; and a resist for generating a signal for forming a registration pattern for each color on the endless carrier by the image forming means during a color misregistration detecting operation. A registration pattern signal generation unit, a registration pattern signal control unit that controls the registration pattern signal generation unit, and a color shift detection unit that detects a color shift of an image from the registration pattern. By the configuration, a plurality of registration patterns having different repetition frequencies are formed independently for each color on the endless carrier. By assigning a frequency to be detected to each registration pattern, it is possible to detect a periodic rotation fluctuation occurring in the color image forming apparatus with high accuracy, and to measure the color misregistration amount with high accuracy. It has the action of:

According to a second aspect of the present invention, in the color image forming apparatus, an endless carrier for supporting and transporting an image on the surface, and an image corresponding to image information of each color are formed on the image transport unit. A plurality of image forming means installed for each color;
A registration pattern signal generation unit that generates a signal for forming a registration pattern for each color on the endless carrier by the image forming unit during a color misregistration detection operation, and a control of the registration pattern signal generation unit. Registration pattern signal control means for performing, and color misregistration detection means for detecting color misregistration of an image from the registration pattern. With this configuration, the repetition frequency of the registration pattern is set for each color. By setting the rotation driving frequency of the photosensitive drum of the image forming unit to at least twice or more, the minimum detection accuracy of the registration pattern can be obtained based on the sampling theorem.
This has the function of measuring the amount of color misregistration caused by fluctuations in the rotation of the photosensitive drum.

According to a third aspect of the present invention, there is provided a color image forming apparatus, wherein an endless carrier for carrying and transporting an image on the surface and an image corresponding to image information of each color are formed on the image transporting means. A plurality of image forming means installed for each color;
A registration pattern signal generation unit that generates a signal for forming a registration pattern for each color on the endless carrier by the image forming unit during a color misregistration detection operation, and a control of the registration pattern signal generation unit. Registration pattern signal control means for performing, and color misregistration detection means for detecting color misregistration of an image from the registration pattern, with this configuration, the repetition frequency of the registration pattern, the endless carrier of the endless By setting the rotation driving frequency at least twice or more, the minimum detection accuracy of the registration pattern can be obtained based on the sampling theorem, and the amount of color misregistration caused by the rotation fluctuation of the driving roller of the endless carrier can be obtained. It has the effect of being able to measure.

According to a fourth aspect of the present invention, there is provided a color image forming apparatus for forming an endless carrier for carrying and transporting an image on the surface, and forming an image corresponding to image information of each color on the image transporting means. A plurality of image forming means installed for each color;
A registration pattern signal generation unit that generates a signal for forming a registration pattern for each color on the endless carrier by the image forming unit during a color misregistration detection operation, and a control of the registration pattern signal generation unit. Registration pattern signal control means for performing, and color misregistration detection means for detecting color misregistration of an image from the registration pattern, with this configuration, the repetition frequency of the registration pattern, the endless carrier of the endless By making the rotation frequency at least twice the rotation frequency for one rotation, the minimum detection accuracy of the registration pattern can be obtained based on the sampling theorem, and the color caused by the rotation fluctuation in the circumference of the endless carrier is obtained. This has the effect that the amount of deviation can be measured.

According to a fifth aspect of the present invention, there is provided a color image forming apparatus for forming an endless carrier for carrying and carrying an image on the surface, and forming an image corresponding to image information of each color on the image carrying means. A plurality of image forming means installed for each color;
A registration pattern signal generation unit that generates a signal for forming a registration pattern for each color on the endless carrier by the image forming unit during a color misregistration detection operation, and a control of the registration pattern signal generation unit. A registration pattern signal control unit for performing the operation, and a color misregistration detecting unit for detecting a color misregistration of the image from the registration pattern. By setting the rotation drive frequency of the body drum and the rotation drive frequency of the endless carrier and the least common multiple of the rotation frequency of the endless carrier for one rotation, detection of a registration pattern can be efficiently obtained, Measurement of color shift caused by rotation fluctuation of endless carrier It has the effect of being able to.

According to a sixth aspect of the present invention, in the color image forming apparatus, an endless carrier for carrying and transporting an image on the surface, and an image corresponding to image information of each color are formed on the image transport unit. A plurality of image forming means installed for each color;
A registration pattern signal generation unit that generates a signal for forming a registration pattern for each color on the endless carrier by the image forming unit during a color misregistration detection operation, and a control of the registration pattern signal generation unit. Registration pattern signal control means for performing, and color misregistration detection means for detecting color misregistration of an image from the registration pattern. With this configuration, the order of forming the plurality of registration patterns is low in repetition frequency. From the pattern
By forming the pattern in the order of the higher repetition frequency and detecting the lower frequency of the image change first, the detection accuracy of the fluctuation component with the higher frequency can be improved.

(Embodiment 1) FIG. 7 is a functional block diagram of a color image forming apparatus according to Embodiments 1 and 2 of the present invention, and FIG. FIG. 4 is a diagram showing a ration pattern.

The configuration of the image forming section of the color image forming apparatus according to the present embodiment is the same as the conventional configuration as shown in FIG.

In FIG. 7, reference numeral 72 denotes a registration pattern signal generating means for generating a registration pattern signal under the control of the registration pattern control means 71;
b, Pc and Pd are the image stations, 7 is the intermediate transfer belt which is an image conveying means, and 13 is the color misregistration detecting means.

The color misregistration detecting means 13 has the same configuration as the conventional configuration as shown in FIG. 3, and a description of its configuration and operation will be omitted.

In this embodiment, as shown in FIG. 9, the registration pattern of each color linearly formed in the main scanning direction on the intermediate transfer belt 7 in order to detect the rotation fluctuation in the sub-scanning direction. The pattern is repeatedly formed at a constant fine interval along the sub-scanning direction.
This registration pattern is formed on both the front side and the back side of the intermediate transfer belt 7 in the width direction.
Depending on the fluctuation component to be detected, the intermediate transfer belt 7
A plurality of types of patterns are formed along the moving direction (sub-scanning direction) and are sampled. As described above, the fluctuation component of the registration is caused by the eccentricity of the driving unit of the intermediate transfer belt 7, the axial deviation of the driving unit, the waving of the intermediate transfer belt, the eccentricity of the driving unit of the image forming unit, the axial deviation of the driving unit, and the like. Occurs. Therefore, the frequency of these fluctuation components is
It covers various frequency components such as the cycle of the drive roller of the intermediate transfer belt, the cycle of the intermediate transfer belt, and the cycle of the photosensitive drum. However, if all the frequency components are to be detected, the detection method becomes complicated because the sampling frequency corresponds to the highest frequency component, the pattern width is set finely, and the calculation time is related. Therefore, attention is paid only to a variable component having a large amplitude, a plurality of registration patterns for detecting the variation component are formed, and the frequency of the variation component to be detected is assigned to each registration pattern. This can prevent the detection method from becoming complicated, and can improve the detection accuracy of the fluctuation component.

By the way, in order to detect a fluctuation component, it is more difficult to obtain the number of repetitive samples at a lower frequency due to the time required for the detection. Therefore, there is a problem how to improve the accuracy of low frequency sampling. Here, assuming that the plurality of fluctuation frequencies of the color image forming apparatus are Fa, Fb, and Fc (Fa>Fb> Fc), to detect a low frequency Fc, the sampling theorem requires at least a sampling frequency. If the frequency is set so as to be twice or more than Fc, the frequency of Fc can be detected. For example, Fa = 30 Hz, Fb = 20 Hz, Fc =
In the case of 3 Hz, the sampling frequency is set to 6 Hz or more. In this case, the sampling frequency Fs is set so as to satisfy 2Fc <Fs <Fb in order to make the frequency components of Fa and Fb fluctuate the dead band. By doing so, as shown in FIG. 8, the fluctuation components of the frequencies Fa and Fb can be ignored, the detection and analysis of only the fluctuation component Fc can be facilitated, and the sampling accuracy can be improved.

To detect a high frequency Fa, the sampling frequency is set to be at least twice as high as Fa. In this case, low frequency Fb, Fb
c is also detected at the same time, but the order of forming the registration patterns is changed from Fb, Fa to Fc corresponding to Fc.
In other words, from the registration pattern corresponding to the low-frequency fluctuation component, the pattern is formed in order of the registration pattern corresponding to the high-frequency fluctuation component, and the low-frequency fluctuation component is formed first. By detecting, the frequency of the fluctuation component on the low frequency side can be determined first, so that a high frequency Fa can be easily separated by a frequency analysis method such as FFT analysis. According to this method, a fluctuation component having a high frequency can be accurately detected.

FIG. 9 and FIG. 10 show the case where the fluctuation component of the photosensitive drum is detected based on the above concept.
This will be described in more detail with reference to the pattern diagram of FIG. Now, considering a case where the rotation frequency of the drive roller of the photosensitive drum is 2 Hz and the moving speed of the intermediate transfer belt in the sub-scanning direction is 100 mm / sec, the sampling frequency is at least 4 Hz.
The above may be set, but here, for convenience of calculation, 10H
Set to z. In this case, the interval between the registration patterns of the same color in the moving direction of the intermediate transfer belt is
100 (mm / sec) / 10 (Hz) = 10 (mm)
Set to. As a design value, a registration pattern with an interval of 10 (mm) is formed for each color in the moving direction of the intermediate transfer belt over the length of one circumference of the photosensitive drum as shown in FIGS. 9 and 10 (step S1). The registration pattern is read by the color misregistration detection sensor (step S2), and the registration pattern interval f (x) (where x is the number of patterns from the head position of the pattern in the moving direction of the intermediate transfer belt) according to (Equation 1) And x = 0 to N) is calculated (step S3).

[0050]

(Equation 1)

Next, the difference between the detected pattern interval f (x) and the designed pattern interval 10 (mm) is calculated, the one having the largest difference in the positive direction is obtained, and the difference is determined in the positive direction. The position from the top of the largest pattern (line) is determined by (Equation 2) (step S4).

[0052]

(Equation 2)

The above processing is performed for each color, and FIG.
As shown in FIG. 2, by determining the positions Tbk, Ty, Tm, and Tc of the maximum values of the rotational fluctuation components of the photosensitive drum for each color, the phases of the rotational fluctuation components of the photosensitive drums of BK, Y, M, and C are determined. You can know the relationship. In this embodiment, the rotation fluctuation component of the photosensitive drum has been described as an example. However, the rotation fluctuation component of the intermediate transfer belt roller or the rotation fluctuation component of one rotation of the intermediate transfer belt roller may be detected by the same method. Can be.

(Embodiment 2) In Embodiment 1, a method of assigning a unique sampling frequency to be detected to each of a plurality of registration patterns and detecting the frequency of a fluctuation component has been described. When a plurality of fluctuation components are detected by the registration pattern, the sampling frequency is set so that the component having the highest frequency can be detected. In this case, the sampling frequency is set so as to be the least common multiple of each fluctuation component, and a frequency analysis method such as FFT is used.
Each fluctuation component is detected. For example, when the rotation fluctuation component of the photoconductor drum, the rotation fluctuation component of the intermediate transfer belt roller, and the rotation fluctuation component of one rotation of the intermediate transfer belt roller are simultaneously detected, the frequency f1 of the rotation fluctuation component of the driving roller of the photoconductor drum and the intermediate frequency are calculated. The sampling frequency is set so as to be equal to or more than the least common multiple of the frequency f2 of the rotation fluctuation component of the transfer belt roller and the frequency f3 of the rotation fluctuation component of one rotation of the intermediate transfer belt roller. Further, the difference between the detected pattern interval f (x) and the designed pattern interval is calculated from the same registration pattern as that of FIG. 10 and (Equation 1), and the calculated color shift amount is calculated by the frequency using FFT or the like. When represented by a graph using an analysis method, waveforms having peaks at frequencies f1, f2, and f3 are obtained as shown in FIG. 13, so that the frequencies of these fluctuation components can be obtained.

[0055]

As described above, in the color image forming apparatus according to the first aspect of the present invention, an endless carrier that carries and conveys an image on the surface, and an image corresponding to image information of each color is formed on the image. A plurality of image forming units installed for each color to be formed on the conveying unit, and a signal for forming a registration pattern for each color on the endless carrier by the image forming unit during a color misregistration detecting operation. Registration pattern signal generating means for performing the control, the registration pattern signal control means for controlling the registration pattern signal generating means, and color shift detecting means for detecting a color shift of an image from the registration pattern. With this configuration, a plurality of registration patterns having different repetition frequencies are independently formed for each color on the endless carrier. Formed, for each registration pattern by assigning the frequencies to be detected can be detected periodic rotation fluctuation generated to the color image forming apparatus with high accuracy.

The color image forming apparatus according to the second aspect of the present invention forms an endless carrier for carrying and transporting an image on the surface, and forms an image corresponding to image information of each color on the image transport unit. A plurality of image forming means installed for each color;
A registration pattern signal generation unit that generates a signal for forming a registration pattern for each color on the endless carrier by the image forming unit during a color misregistration detection operation, and a control of the registration pattern signal generation unit. Registration pattern signal control means for performing, and color misregistration detection means for detecting color misregistration of an image from the registration pattern. With this configuration, the repetition frequency of the registration pattern is set for each color. By setting the rotation driving frequency of the photosensitive drum of the image forming unit to at least twice or more, the minimum detection accuracy of the registration pattern can be obtained based on the sampling theorem.
Phase detection corresponding to the fluctuation of the rotation of the photosensitive drum can be performed.

According to a third aspect of the present invention, there is provided a color image forming apparatus for forming an endless carrier for carrying and transporting an image on the surface, and forming an image corresponding to image information of each color on the image transporting means. A plurality of image forming means installed for each color;
A registration pattern signal generation unit that generates a signal for forming a registration pattern for each color on the endless carrier by the image forming unit during a color misregistration detection operation, and a control of the registration pattern signal generation unit. Registration pattern signal control means for performing, and color misregistration detection means for detecting color misregistration of an image from the registration pattern, with this configuration, the repetition frequency of the registration pattern, the endless carrier of the endless By setting the rotation driving frequency to at least twice or more, the minimum detection accuracy of the registration pattern can be obtained based on the sampling theorem, and the phase corresponding to the rotation fluctuation of the rotation fluctuation of the driving roller of the endless carrier can be obtained. Detection can be performed.

According to a fourth aspect of the present invention, there is provided a color image forming apparatus for forming an endless carrier for carrying and transporting an image on the surface, and forming an image corresponding to image information of each color on the image transporting means. A plurality of image forming means installed for each color;
A registration pattern signal generation unit that generates a signal for forming a registration pattern for each color on the endless carrier by the image forming unit during a color misregistration detection operation, and a control of the registration pattern signal generation unit. Registration pattern signal control means for performing, and color misregistration detection means for detecting color misregistration of an image from the registration pattern, with this configuration, the repetition frequency of the registration pattern, the endless carrier of the endless By setting the rotation frequency to at least twice the rotation frequency for one rotation, it is possible to obtain the minimum detection accuracy of the registration pattern based on the sampling theorem, and to reduce the rotation fluctuation in the rotation length in the circumference of the endless carrier. Corresponding phase detection can be performed.

According to a fifth aspect of the present invention, there is provided a color image forming apparatus for forming an endless carrier for carrying and transporting an image on the surface, and forming an image corresponding to image information of each color on the image transporting means. A plurality of image forming means installed for each color;
A registration pattern signal generation unit that generates a signal for forming a registration pattern for each color on the endless carrier by the image forming unit during a color misregistration detection operation, and a control of the registration pattern signal generation unit. A registration pattern signal control unit for performing the operation, and a color misregistration detecting unit for detecting a color misregistration of the image from the registration pattern. By setting the rotation drive frequency of the body drum and the rotation drive frequency of the endless carrier and the least common multiple of the rotation frequency of the endless carrier for one rotation, detection of a registration pattern can be efficiently obtained, Measurement of color shift caused by rotation fluctuation of endless carrier Can be.

According to a sixth aspect of the present invention, there is provided a color image forming apparatus for forming an endless carrier for carrying and transporting an image on the surface, and forming an image corresponding to image information of each color on the image transporting means. A plurality of image forming means installed for each color;
A registration pattern signal generation unit that generates a signal for forming a registration pattern for each color on the endless carrier by the image forming unit during a color misregistration detection operation, and a control of the registration pattern signal generation unit. Registration pattern signal control means for performing, and color misregistration detection means for detecting color misregistration of an image from the registration pattern. With this configuration, the order of forming the plurality of registration patterns is low in repetition frequency. From the pattern
By forming the pattern in the order of the higher repetition frequency and detecting the lower frequency of the image change first, it is possible to improve the detection accuracy of the fluctuation component having the higher frequency.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a conventional color image forming apparatus.

FIG. 2 is a diagram showing types of color misregistration in a general color image forming apparatus.

FIG. 3 is a configuration diagram of a conventional color misregistration detection unit.

FIG. 4 is a layout diagram of a conventional registration pattern and a displacement detection unit on an intermediate transfer belt.

FIG. 5 is a diagram showing a conventional arrangement pattern of a registration pattern on an intermediate transfer belt, a misregistration detection unit, and an output signal of a misregistration detection unit.

FIG. 6 is a configuration diagram of a color shift correction mechanism of a scanning optical system in a conventional exposure unit.

FIG. 7 is a functional block diagram of the color image forming apparatus according to the first embodiment of the present invention.

FIG. 8 is a fluctuation component waveform diagram for describing detection of a periodic fluctuation component according to the first embodiment of the present invention.

FIG. 9 is a configuration diagram of a pattern for detecting a periodic fluctuation component according to the first embodiment of the present invention.

FIG. 10 is a diagram showing a positional relationship of a pattern for detecting a periodic fluctuation component according to the first embodiment of the present invention;

FIG. 11 is a flowchart illustrating a process of obtaining a phase of a periodic fluctuation component according to the first embodiment of the present invention.

FIG. 12 is a diagram illustrating a phase relationship between periodic fluctuation components according to the first embodiment of the present invention.

FIG. 13 is a diagram showing a frequency analysis result by FFT analysis of a periodic fluctuation component according to the second embodiment of the present invention.

[Explanation of symbols]

1, 1a, 1b, 1c, 1d Photoreceptor drum 2a, 2b, 2c, 2d Charging means 3, 3K, 3C, 3M, 3Y Exposure means 4a, 4b, 4c, 4d Developing means 5a, 5b, 5c, 5d Transfer means 6a, 6b, 6c, 6d Cleaning means 7 Intermediate transfer belt 8 Paper feed roller 9 Sheet material 10 Paper feed cassette 11 Transfer roller 12 Fixing means 13 Color shift detecting means 14a, 14b Driving roller 31 Light source 32 Lens 33 Sensor 34-37 Resist Registration pattern 61 Polygon motor 62 Polygon mirror 63, 64, 65 Folding mirror 66, 67 Adjustment actuator 71a, 71b, 71c, 71d Image forming unevenness detecting means 72 Registration pattern signal generating means 73 Color shift correcting means 81 Image forming unevenness phase Matching means 91 Medium Transfer belt conveyance unevenness detecting means f1, f2, f3 rotation fluctuation component frequency Pa, Pb, Pc, Pd image forming stations Tbk, Ty, Tm, location of the maximum value of Tc rotation fluctuation component

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C362 BA50 BA52 CA23 CA39 CB59 CB73 CB80 2H027 DA50 DE02 DE07 EB04 EB06 EC03 ED04 EE01 EE02 EF09 HB07 ZA07 2H030 AA01 AB02 BB02 BB16 BB42 5C074 AA07 BB10 BB02 BB04 GG14

Claims (6)

[Claims] An endless carrier for carrying and transporting an image on the surface; a plurality of image forming means provided for each color for forming an image corresponding to the image information of each color on the image transporting means; A registration pattern signal generation unit that generates a signal for forming a registration pattern for each color on the endless carrier by the image forming unit during a color misregistration detection operation, and a control of the registration pattern signal generation unit. A color image forming apparatus comprising: a registration pattern signal control unit for performing the operation; and a color misregistration detecting unit configured to detect a color misregistration of an image from the registration pattern. By independently forming the registration pattern of each color for each color, a peripheral pattern generated in the color image forming apparatus is generated. Color image forming apparatus and detecting a rotation fluctuation. 2. A color image according to claim 1, wherein the repetition frequency of the registration pattern is at least twice as high as the rotational driving frequency of the photosensitive drum of the image forming means provided for each color. Forming equipment. 3. The color image forming apparatus according to claim 1, wherein a repetition frequency of the registration pattern is at least twice as high as a rotation driving frequency of the endless carrier. 4. The color image forming apparatus according to claim 1, wherein a repetition frequency of the registration pattern is at least twice as high as a rotation frequency of one rotation of the endless carrier. 5. The repetition frequency of the registration pattern is a minimum of a rotation driving frequency of the photosensitive drum of the image forming means, a rotation driving frequency of the endless carrier, and a rotation frequency of one rotation of the endless carrier. 2. The color image forming apparatus according to claim 1, wherein the number is a common multiple or more. 6. The method according to claim 1, wherein the plurality of registration patterns are formed in the order of a pattern having a low repetition frequency and a pattern having a high repetition frequency, and the pattern having a low image variation is detected first. The color image forming apparatus as described in the above.