JP2000162844A - Image-forming device and method for detecting positional deviation in main scanning direction in the image-forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect positional deviations in a main scanning direction with high accuracy by enlarging the detection amount of the positional deviations in the main scanning direction, so as to highly accurately detect the deviation, even when forming an in-dot multi-level image with high resolution. SOLUTION: Under the control of a CPU 18, a positional deviation detecting pattern is formed on a carrying belt by an image output part 23, without overlapping the patterns of every component, the pattern is constituted of plural linear elements extending opposite to each other in a rotating direction in the direction orthogonal to the moving direction of the carrying belt. Each element, constituting the positional deviation detecting pattern of every color component formed on the carrying belt, is detected by a pattern detecting part 20, and the positional deviation in the main scanning direction for every color component is calculated by a calculating part 22, based on the detection interval of each element constituting the positional deviation detecting pattern by every color component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plurality of image forming units provided for each color component on a plurality of image carriers provided for each color component. Forming a color component image on each image carrier, moving the color component image formed on each image carrier in a direction orthogonal to the main scanning direction of each image forming unit, TECHNICAL FIELD The present invention relates to an image forming apparatus capable of forming a multicolor image by superimposing and transferring a recording medium conveyed while being held on an endless moving body that sequentially passes through a body, and a method of detecting a displacement amount in the main scanning direction of the image forming apparatus. Things.

[0002]

2. Description of the Related Art In a conventional image forming apparatus such as an electrophotographic color printer, a plurality of image forming units are arranged in parallel in a conveying direction in order to output a full-color image at a high speed. Various methods have been proposed for sequentially transferring toner images of different colors formed on a recording material held on a transport belt.

In such a conventional image forming apparatus having a plurality of image forming units, unevenness in rotation and movement of the photosensitive drums and conveying belts of the plurality of image forming units occurs due to mechanical accuracy and the like. The deviation between the outer circumferential surface of the photosensitive drum and the moving amount of the conveyor belt at the transfer position of the image forming unit is generated separately for each image forming unit, and the toner image of each color formed on the photosensitive drum of each image forming unit When the image is transferred to the recording material, the toner images of the respective colors do not match, and a color shift (position shift) occurs.

Hereinafter, color misregistration in the main scanning direction will be described with reference to FIG.

FIG. 9 is a view for explaining an example of color shift in the main scanning direction of an image formed on a photosensitive drum.

In FIG. 1, reference numeral 7 denotes an original image position. Reference numerals 8a and 8b denote image positions when a color shift has occurred. Although FIG. 9 illustrates a case where there is a color shift in the main scanning direction, two lines are drawn apart in the transport direction for the sake of explanation.

FIG. 9A shows a color shift generated due to a variation in the width of the main scanning line in the image forming section for each color.
This is caused by a difference in the distance between the optical unit and the photosensitive drum. Such a color shift is likely to occur when the optical unit is a laser scanner. For example, the image frequency is finely adjusted (if the scanning width is long, the frequency is increased), and the length of the scanning line is changed to correct in the direction of the arrow in the figure.

FIG. 9B shows a color shift caused by an error in the writing position in the main scanning direction in the image forming section for each color. For example, if the optical unit is a laser scanner,
By adjusting the writing start timing from the beam detection position, correction is made in the direction of the arrow in the figure.

In order to correct these color shifts, a pattern for detecting a position shift for each color is formed on the conveyor belt, and a pair of optical sensors 6a and 6b provided on both sides of the downstream side of the conveyor belt. The pattern is detected, and various adjustments as described above are performed in accordance with the amount of displacement of the detected pattern.

Hereinafter, an example of a misregistration detection pattern for detecting misregistration in the main scanning direction in a conventional image forming apparatus will be described with reference to FIG.

FIG. 10 is a view for explaining an example of a misregistration detection pattern formed on a transport belt of a conventional image forming apparatus.

In FIG. 1, reference numerals 6a and 6b denote a pair of optical sensors for detecting a misregistration detection pattern formed on the conveyor belt 3. Reference numerals 9a to 9d and 10a to 10d are reference patterns which are not affected by positional deviation in the main scanning direction. 11a to 11d and 12a to 12d are detection patterns whose detection positions in the transport direction change in accordance with the amount of positional deviation in the main scanning direction. In this example, the inclinations are 45 degrees.

The patterns 9a to 12a are black (K), the patterns 9b to 12b are yellow (Y), the patterns 9c to 12c are magenta (M), and 9d to 12d. The pattern is cyan (C)
Of the image forming unit.

Tsf1 to tsf4 are timings at which the optical sensor 6a detects the reference patterns 9a to 9d. tm
In f1 to tmf4, the optical sensor 6a detects the detection pattern 11a to
This is the timing for detecting 11d. tsr1 to tsr
Reference numeral 4 denotes a timing at which the optical sensor 6b detects the reference patterns 10a to 10d. tmr1 to tmr4 are timings for detecting the optical sensors 12a to 12d. The arrow in the figure indicates the moving direction of the conveyor belt 3. The dashed line indicates the position of the optical sensors 6a and 6b.

The moving speed of the conveyor belt 3 is v [mm /
s], and the theoretical distance between the reference pattern and the detection pattern of each color is s [mm]. With respect to the main scanning direction, the positional shift amounts δemf and δemr of the respective left and right colors are:

[0016]

## EQU1 ## δemfK = s−v × (tmf1−tsf1) (1) δemfY = s−v × (tmf2−tsf2) (2) δemfM = s−v × (tmf3−tsf3). 3) δemfC = sv × (tmf4−tsf4) (4) δemrK = s−v × (tmr1−tsr1) (5) δemrY = s−v × (tmr2−tsr2) (6) δemrM = s−v × (tmr3−tsr3) (7) δemrC = s−v × (tmr4−tsr4) (8), and the direction of deviation from the sign of the calculation result, the writing position from δemf, and the writing position from δemr are δemr. An error in the main scanning width can be determined from −δemf.

If there is an error in the main scanning width, the writing start position is calculated not only by δemf but also by taking into account the amount of change in the image frequency that has changed with the correction of the main scanning width. If the position of a certain color is used as a reference, for example, if K is used as a reference, the difference between the amount of misalignment other than black (K) and the amount of misalignment of black (K) is calculated. The position of a color other than K is corrected based on the amount of displacement.

[0018]

However, in the above-mentioned conventional image forming apparatus, for example, one dot is 42.3 μm.
In order to obtain a high-quality image in which color misregistration is inconspicuous when forming an image with multiple gradations within a dot at a high resolution of 600 dpi or more, it is necessary to detect the amount of misregistration with high accuracy. However, in the above-described method of detecting the amount of displacement in the main scanning direction of the conventional image forming apparatus, one dot corresponds to four dots.
There is a problem that it is not possible to detect a positional deviation in the main scanning direction with sufficient accuracy when forming an image with multiple gradations within a dot at a high resolution of 2.3 μm or more at 600 dpi or more.

The present invention has been made to solve the above problems, and an object of the first to tenth inventions according to the present invention is to provide an endless moving body in a direction orthogonal to the moving direction. On the endless moving body, a misregistration detection pattern composed of a plurality of line-shaped elements extending in directions opposite to each other is formed on the endless moving body without overlapping each color component. Detecting the respective elements constituting the misregistration detection pattern for each color component formed in the main scanning direction based on the detected intervals of the respective elements constituting the detection pattern for each detected color component. In the case where the amount of displacement is calculated for each color component, the amount of displacement in the main scanning direction is detected, and the detection amount is detected with higher precision, and multi-tone image formation within dots with high resolution is performed. But main scanning with sufficient accuracy To provide a main scanning direction of the positional deviation amount detecting method of an image forming apparatus and an image forming apparatus capable of measuring the amount of positional displacement direction.

[0020]

According to a first aspect of the present invention, a plurality of images are provided for each color component (yellow (Y), magenta (M), cyan (C), black (K)). A plurality of image forming units (laser scanners 2a, 2b, 2c, 2d shown in FIG. 1 and laser scanners 2a, 2b, 2c and 2d shown in FIG. 1) provided on a carrier (photosensitive drums 1a, 1b, 1c and 1d shown in FIG. 1) for each color component. The image output unit 23) scans and exposes each of the color components in accordance with an image signal for each color component to form a color component image on each image carrier, and converts the color component image formed on each image carrier into each of the images. The transfer unit is moved in a direction perpendicular to the main scanning direction of the forming unit and is superimposed on a recording medium conveyed while being held on an endless moving body (a conveying belt 3 shown in FIG. 1) which sequentially passes through the image carriers. In an image forming apparatus capable of forming a multicolor image by
A plurality of line-shaped elements (elements 13a (13c), 13b constituting a position detection pattern shown in FIG. 3) extending in directions rotated in directions opposite to each other with respect to a direction orthogonal to the direction of movement of the endless moving body. (13d), the elements 14a (14) constituting the misregistration detection pattern shown in FIG.
c), 14b (14d) and the elements 14a (14c), 14b (14) constituting the misregistration detection pattern shown in FIG.
d)) controlling each of the image forming units so as to form the misregistration detection pattern constituted by (d)) on the endless moving body without overlapping each color component (as shown in FIG. 4); Control means (the CPU 18 shown in FIG.
And a detection means (FIG. 1) for detecting each element constituting a misregistration detection pattern for each color component formed on the endless moving body (see FIG. 1). And the detection interval (v × (tm11−tm1)) of each element constituting the misregistration detection pattern for each color component detected by the detection means. ) On the basis of the calculation means (calculation unit 22 shown in FIG. 2) for calculating the amount of displacement in the main scanning direction for each color component.

According to a second aspect of the present invention, the calculating means (the calculating unit 22 shown in FIG. 2) includes a detecting interval of each element constituting a misregistration detecting pattern for each color component detected by the detecting means. Based on the other reference color components (eg, black (K)) and other color components (yellow (Y),
This is for calculating the amount of positional deviation in the main scanning direction of magenta (M) and cyan (C).

According to a third aspect of the present invention, there is provided a second control means (an operation unit shown in FIG. 2) for controlling a writing position in the main scanning direction by each of the image forming units based on a calculation result of the calculation unit. A main scanning correction amount 22 is calculated, and the CP shown in FIG.
U18 is determined according to the main scanning correction amount calculated by the arithmetic unit 22.
(The writing position in the main scanning direction is controlled based on a program stored in the ROM 24).

According to a fourth aspect of the present invention, the first control means (CPU 18 shown in FIG. 2) uses the same color in the direction orthogonal to the moving direction of the endless moving body for the position shift detecting pattern. Each of the image forming units is controlled so as to form a plurality of components, and the detecting means (the optical sensors 6a and 6b shown in FIG. 1 and the pattern detecting unit 20 shown in FIG. 2)
It detects a plurality of misregistration detection patterns for each color component formed in a direction orthogonal to the direction of movement of the endless moving body on the endless moving body. The calculating means (the arithmetic unit 22 shown in FIG. 2) ) Calculates the main scanning width for each color component based on the detection interval of each element constituting a plurality of misregistration detection patterns for each color component detected by the detection means.

According to a fifth aspect of the present invention, there is provided a third control means (an operation unit shown in FIG. 2) for controlling a writing position in the main scanning direction by each of the image forming units based on a calculation result of the calculation unit. A main scanning correction amount 22 is calculated, and the CP shown in FIG.
U18 is determined according to the main scanning correction amount calculated by the arithmetic unit 22.
(The writing position in the main scanning direction is controlled based on a program stored in the ROM 24).

According to a sixth aspect of the present invention, there is provided a method for detecting a position shift (elements 13a (13c) and 13b (13d) constituting the position shift detecting pattern shown in FIG. 3) and a position shift detecting pattern shown in FIG. 14a that constitutes a pattern for use
(14c), 14b (14d), elements 14a (14c), 14b constituting the position shift detection pattern shown in FIG.
(14d)) is constituted by two line-shaped elements extending in a direction rotated in the opposite direction to the direction orthogonal to the moving direction of the endless moving body.

According to a seventh aspect of the present invention, there is provided a method of detecting a position shift (elements 13a (13c) and 13b (13d) constituting the position shift detecting pattern shown in FIG. 3) and a position shift detecting pattern shown in FIG. 14a that constitutes a pattern for use
(14c), 14b (14d), elements 14a (14c), 14b constituting the position shift detection pattern shown in FIG.
(14d)) is constituted by two line-shaped elements extending in directions rotated by 45 degrees opposite to each other with respect to a direction orthogonal to the moving direction of the endless moving body.

According to an eighth aspect of the present invention, the two line-shaped elements (elements 13a (13c) and 13b (13d) constituting the misregistration detection pattern shown in FIG. 3) and the misalignment shown in FIG. Element 14a constituting detection pattern
(14c), 14b (14d)) are two line segments extending from one point of the endless moving body.

According to a ninth aspect of the present invention, the two line-shaped elements (elements 15a (15c) and 15b (15d) constituting the misregistration detection pattern shown in FIG. 8) are provided.
Are two line segments extending from two different points of the endless moving body without intersecting with each other.

According to a tenth aspect of the present invention, a plurality of image forming units provided for each color component are provided on a plurality of image carriers provided for each color component in accordance with an image signal for each color component. Forming a color component image on each image carrier by scanning exposure, moving the color component image formed on each image carrier in a direction orthogonal to the main scanning direction of each of the image forming units. In the method for detecting a positional deviation amount in a main scanning direction of an image forming apparatus capable of forming a multicolor image by superimposing and transferring a recording medium conveyed while being held on an endless moving body that sequentially passes through an image carrier, The endless movement without overlapping a misregistration detection pattern composed of a plurality of line-shaped elements extending in directions rotated in directions opposite to each other with respect to a direction orthogonal to the moving direction of the endless moving body for each color component. The pattern form formed on the body And step (step of FIG. 6 (1)),
A detection step (step (2) in FIG. 6) for detecting each element constituting a misregistration detection pattern for each color component formed on the endless moving body; and a misregistration for each detected color component. And a calculation step (step (3) in FIG. 6) of calculating a positional shift amount in the main scanning direction for each color component based on a detection interval of each element constituting the detection pattern.

[0030]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

In this embodiment, a color printer having image forming units for four colors, that is, yellow (Y), magenta (M), cyan (C), and black (K) will be described as an example.

In the figure, reference numerals 1a to 1d denote photosensitive drums, the photosensitive drum 1a is black (K), the photosensitive drum 1b.
, An electrostatic latent image of magenta (M) is formed on the photosensitive drum 1c, and an electrostatic latent image of yellow (Y) is formed on the photosensitive drum 1d. Reference numerals 2a to 2d denote laser scanners, which are photosensitive drums 1a in accordance with image signals of respective color components (Y, M, C, K).
1d to form an electrostatic latent image on the photosensitive drums 1a to 1d.

The black image forming section comprises a photosensitive drum 1a, a laser scanner 2a and the like. The cyan image forming unit includes a photosensitive drum 1b, a laser scanner 2b, and the like. The magenta image forming unit includes the photosensitive drum 1
c, a laser scanner 2c and the like. The yellow image forming section includes a photosensitive drum 1d, a laser scanner 2d, and the like.

Reference numeral 3 denotes an endless conveying belt which moves in the direction of the arrow in the figure to sequentially convey paper as a recording medium (not shown) to the image forming units of each color, and also controls the photosensitive drums 1 for each color.
It also serves as a transfer belt for transferring the toner images formed on the recording media a to 1d onto a recording medium. Reference numeral 4 denotes a drive roller, which is connected to a drive unit including a motor and gears (not shown) to drive the transport belt 3. Reference numeral 5 denotes a driven roller which rotates in accordance with the movement of the conveyor belt 3 and applies a constant tension to the conveyor belt 3. Reference numerals 6a and 6b denote a pair of optical sensors (consisting of an LED light emitting unit and a photo sensor light receiving unit), which are provided on both sides of the conveyor belt 3 and which are formed on the conveyor belt 3 and used for detecting a positional shift. Position shift detection patterns 13a (13c) and 13b (1) shown in FIG.
3d), etc.) are detected.

Reference numeral 100 denotes a controller, which is an optical sensor 6
Based on the detection results of the misregistration detection patterns a and 6b, a misregistration amount in the main scanning direction is calculated, and a main scanning correction amount is calculated from the calculated misregistration amount. Image formation is controlled based on the correction amount. The details of the controller unit 100 are shown in FIG. 2 described later.

Hereinafter, the operation of the image forming apparatus of this embodiment will be described.

Data (print information) to be printed is sent from a computer (PC) or the like (not shown) to the color printer, and when image processing according to the printer engine system is completed and the printer is ready for printing, paper from a paper cassette (not shown) is taken out. Is supplied to the transport belt 3, and the transport belt 3 sequentially transports the paper to the image forming units of each color.

The image signals of the respective colors are supplied to the respective laser scanners 2a to 2a in synchronism with the sheet conveyance by the conveyor belt 3.
d, each of the laser scanners 2a to 2d irradiates a laser beam to form an electrostatic latent image on each of the photosensitive drums 1a to 1d, and a developing unit (not shown) is formed on each of the photosensitive drums 1a to 1d. The electrostatic latent image is developed with toner, and the toner images on the photosensitive drums 1 a to 1 d are transferred onto a sheet conveyed by the conveyor belt 3 by a transfer unit (not shown).

In the color printer shown in this embodiment, images are sequentially formed in the order of yellow (Y), magenta (M), cyan (C), and black (K). Thereafter, the sheet on which the toner image has been transferred is separated from the transport belt 3, and the toner image is fixed on the sheet by heat in a fixing device (not shown).
It is discharged outside.

Hereinafter, the operation of this embodiment will be described.

In order to reduce color misregistration (position misregistration), a pattern for detecting misregistration as shown in FIG. 3 to be described later is formed on the conveyor belt 3 and a pair of sensors 6a provided on both sides of the conveyor belt. , 6b to detect the amount of misregistration of each color.

Hereinafter, the controller section 100 shown in FIG. 1 will be described with reference to FIG.

FIG. 2 shows the controller unit 10 shown in FIG.
FIG. 4 is a block diagram illustrating a configuration of a zero.

In the figure, reference numeral 20 denotes a pattern detecting unit,
It comprises the optical sensors 6a and 6b shown in FIG. 1 comprising an ED light emitting section and a photo sensor light receiving section. 21 is A /
In the D section (analog-digital conversion section), the optical sensors 6a, 6
The analog signal output from the sensor such as b is digitized.

Numeral 22 denotes an arithmetic unit for arithmetically processing data from the optical sensors 6a and 6b digitized by the A / D unit 21 to calculate a main scanning position shift amount (main scanning width) and a correction value. Reference numeral 23 denotes an image output unit, which is a photosensitive drum 1 shown in FIG.
a to 1d, laser scanners 2a to 2d, and the like, and forms an image in accordance with the calculation result of the calculation unit 22. 1
Reference numeral 8 denotes a CPU, which controls the entire image forming apparatus based on a program stored in the ROM 24, and performs timing adjustments and various settings of the units 19 to 23.

A RAM 25 is used as a work area of the CPU 18. Reference numeral 19 denotes a timer, which controls the timing at which the pattern detection unit 20 detects a position shift pattern under the control of the CPU 18. Also, the CPU 18 has a ROM
The image output unit 23 is controlled based on the pattern data for position shift detection stored in 24, and a pattern for position shift detection shown in FIGS. Further, the CPU 18 controls the main scanning position of the image output unit 23 based on the calculation result of the calculation unit 22.

Referring to FIGS. 3 and 4, the shape and the like of the misregistration detection pattern formed on the conveyor belt 3 shown in FIG. 1 will be described.

FIG. 3 is a schematic diagram for explaining an example of a misregistration detection pattern formed on the conveyor belt 3 shown in FIG. In the present embodiment, FIG.
Similarly to the above, a misregistration detection pattern is formed on each of the left and right sides for each color. Here, for simplification of description, only one of the patterns, for example, a misregistration detection pattern of yellow is illustrated. I have.

In the figure, 13a (13c), 13b
(13d) is an element constituting a misregistration detection pattern, 13a and 13b correspond to a case where there is no misalignment in the main scanning direction, and 13c and 13d correspond to a case where there is misalignment in the main scanning direction. . Although 13c and 13d are shown by broken lines for convenience, they have the same shape as 13a and 13b.

Each element 13a of the displacement detection pattern
(13c) and 13b (13d) are oblique lines extending obliquely in opposite directions to each other in the transport direction. In the present embodiment, it is assumed that the inclination with respect to the transport direction is ± 45 degrees. Therefore, the detection positions in the transport direction change in directions opposite to each other according to the positional deviation amount in the main scanning direction. The elements 13c (13a) and 13d (13b) constituting the misregistration detection pattern are all formed of the same color, for example, yellow (Y).

That is, the misregistration detection pattern is 45 degrees from one point on the conveyor belt 3 in a direction orthogonal to the moving direction of the conveyor belt 3 (indicated by an arrow), that is, in a direction opposite to the main scanning direction. It is composed of line-shaped elements 13a (13c) and 13b (13d) extending in the direction of rotation.

Tm10 and tm11 are optical sensors 6a and 6b
Is detected by the timer 19 in accordance with an instruction from the CPU 18 at the timing of detecting the displacement detection patterns 13c and 13d. The dashed line indicates the position of the optical sensors 6a and 6b.
3c (13a) and 13d (13b) are detected.

Further, v [mm / s] is the moving speed of the conveyor belt 3, and s [mm] is the theoretical distance between the patterns.

FIG. 4 is a schematic diagram for explaining an example of a misregistration detection pattern formed on the conveyor belt 3 shown in FIG. 1. The same components as those in FIG. is there.

As shown in the figure, the misregistration detection pattern shown in FIG. 3 is formed on each of the left and right sides for each color component.

When there is a displacement in the main scanning direction, the displacement δemY calculated by the calculation unit 22 is

[0058]

ΔemY = {sv × (tm11−tm10)} / 2 (9), and the direction of deviation from the sign of the calculation result can be determined. When there is a displacement in the main scanning direction on the right side in FIGS. 3 and 4, the interval between the displacement detection patterns 13c and 13d becomes narrow, and “δemY” becomes positive. The transfer belt 3
The moving speed v [mm / s], the theoretical distance s [mm] between each pattern, and Expression (9) are calculated inside the arithmetic unit 22 or R
It is assumed that it is stored in the OM 24.

The calculating unit 22 calculates the write start position from the positional shift amount of the positional shift detecting pattern on the write start position side of the main scan among the positional shift detection patterns formed on the left and right sides of the transport belt 3. The main scanning width is calculated from the difference between the positional deviation amounts.

When there is an error in the main scanning width, the arithmetic unit 22 determines that the writing start position is not only the position shift amount of the position shift detection pattern on the writing start side, but also the image frequency changed with the main scanning width correction. Is calculated in consideration of the amount of change.

Further, if the position at which the color misregistration detection pattern of a certain color is detected is used as a reference, for example, if black (K) is used as a reference, a misalignment amount other than black (K) and black (K) are used. ) Is obtained, and the main scanning position of the color component other than black (K) is corrected and controlled based on the obtained difference.

Further, in the above equation (9), each of the elements 13c (13a) and 13d
In (13b), since the detection positions in the transport direction change in directions opposite to each other in accordance with the positional deviation amount in the main scanning direction, the detection amount is doubled with respect to the positional deviation amount in the main scanning direction, and more accurate. The displacement amount can be detected. Therefore, when one dot is 42.3 μm or more at 600 dpi or more, it is possible to detect the positional deviation with the accuracy required when forming multi-tone images within a dot.

Hereinafter, a method of reading a pattern in the image forming apparatus according to the present embodiment will be described with reference to FIG.

FIG. 5 shows the optical sensors 6a and 6b shown in FIG.
FIG. 7 is a diagram for explaining a method of determining a detection waveform of a positional deviation detection pattern read waveform output from the controller and a detection timing of the positional deviation detection pattern.

In FIG. 5, the detection timing t shown in FIG.
8 shows a specific example in which m10 and tm11 and detection timings tm20 and tm21 shown in FIG. 7 described later and detection timings tm30 and tm31 shown in FIG. 8 described later are determined.

In the drawing, reference numeral 17 denotes a read waveform of a positional deviation detection pattern output from the optical sensors 6a and 6b.

(A) corresponds to the case where the point in time ta when the pattern reaches the peak "Vp" is used as the detection timing of the pattern for detecting the positional deviation, and (b) corresponds to the case where the detected value is a constant level Vb.
Of the pattern exceeding “tb2 ｛= (tb3−tb
1) / 2} "corresponds to the detection timing of the misregistration detection pattern, and (c) corresponds to the case where the time" tc "at which the pattern detection level exceeds the threshold value" Vt "is the detection timing.

(A), (b) and (c) The appropriate pattern detection method is determined by the specifications required for the color printer, such as the development characteristics of the color printer and the circuit scale to be provided.

Hereinafter, referring to the flowchart of FIG.
The control processing operation of the image forming apparatus of the present invention will be described.

FIG. 6 is a flowchart showing a control processing procedure of the image forming apparatus according to the present invention, which is executed by the CPU 18 based on a program stored in the ROM 24. In addition, (1) to (5) indicate each step.

First, data to be printed is received from a computer (PC) or the like (not shown), and the printer becomes ready for printing. When the transport belt 3 is driven, the position shift shown in FIGS. A detection pattern is formed for each color component (1), and a pair of sensors 6a and 6b provided on both sides of the conveyor belt are used to form the misregistration detection pattern formed in step (1) for each color component. Detect (2).

Next, based on the detection result in step (2), the arithmetic unit 22 calculates the amount of positional deviation in the main scanning direction for each color component (or for a predetermined color component, for example, black (K)). (3), and based on the amount of positional deviation in the main scanning direction for each color component (or each color component with respect to a predetermined color component, for example, black (K)) calculated in step (3), Calculates the correction amount in the main scanning direction for each color component (4).

Next, the CPU 18 controls image formation based on print data received from a computer (PC) or the like by the image output unit 23 in consideration of the correction amount calculated by the calculation unit 22 in step (4) (5). ).

As described above, since the detected positions in the transport direction change in opposite directions to each other in accordance with the positional deviation amount in the main scanning direction, the detected amount is larger than the positional deviation amount in the main scanning direction. Thus, the displacement amount can be detected with higher accuracy, and one dot is 42.3 μm and 600 dp.
Even in the case of forming an image with multiple gradations within a dot at i or higher, sufficient positional deviation detection accuracy can be obtained.

[Second Embodiment] In the first embodiment,
Each element 13a (13
c) and 13b (13d) are combined on the left side with respect to the moving direction of the conveyor belt 3 and the right side is separated to form the misregistration detection pattern. However, the misalignment detection pattern is configured. The misalignment detection pattern may be formed in a shape in which the elements are separated on the left side and connected on the right side with respect to the moving direction of the transport belt 3. Hereinafter, the embodiment will be described.

FIG. 7 is a schematic diagram for explaining an example of a misregistration detecting pattern formed on the conveyor belt 3 of the image forming apparatus according to the second embodiment of the present invention.

In the figure, 14a (14c), 14b
(14d) is an element constituting a misregistration detection pattern, 14a and 14b correspond to a case where there is no misalignment in the main scanning direction, and 14c and 14d correspond to a case where there is misalignment in the main scanning direction. . 14c and 14d are indicated by broken lines for convenience, but have the same shape as 14a and 14b.

Each element 14a of the displacement detection pattern
(14c) and 14b (14d) are oblique lines extending obliquely in directions opposite to each other in the transport direction. In the present embodiment, it is assumed that the inclination with respect to the transport direction is ± 45 degrees. Therefore, the detection positions in the transport direction change in directions opposite to each other according to the positional deviation amount in the main scanning direction. Note that all the elements 14c (14a) and 14d (14b) constituting the misregistration detection pattern are formed in the same color, for example, yellow (Y).

That is, the misregistration detection pattern is formed such that a point on the conveyance belt 3 is in a direction opposite to the direction (in the direction opposite to the main scanning direction) orthogonal to the moving direction (indicated by an arrow) of the conveyance belt 3. Are formed by linear elements 14a (14c) and 14b (14d) extending in a direction rotated by 45 degrees.

Tm20 and tm21 are optical sensors 6a and 6b
Is detected by the timer 19 in accordance with an instruction from the CPU 18 at the timing of detecting the displacement detection patterns 14c and 14d. The dashed line indicates the position of the optical sensors 6a and 6b.
4c (14a) and 14d (14b) are detected.

Further, v [mm / s] is the moving speed of the conveyor belt 3, and s [mm] is the theoretical distance between the patterns.

The pattern 14a for detecting a displacement shown in FIG.
(14c) and 14b (14d) are basically the displacement detection patterns 13a and 13 shown in FIG. 3 of the first embodiment.
This is the case where the direction of b is reversed, and the positional deviation amount “δem” in the main scanning direction is basically the same as Expression (9) shown in the first embodiment. In the present embodiment, when there is a displacement in the main scanning direction on the right side in FIG. 7, the pattern interval is widened and δem is negative.

[Third Embodiment] In the above-described first and second embodiments, a case is described in which a misalignment detection pattern is formed in which each element constituting the misalignment detection pattern intersects at one end point. Has been described, it may be configured to form a misregistration detection pattern having a shape in which the elements constituting the misregistration detection pattern do not intersect at any end point. Hereinafter, the embodiment will be described.

FIG. 8 is a schematic diagram for explaining an example of a misregistration detection pattern formed on the conveyor belt 3 of the image forming apparatus according to the third embodiment of the present invention.

In the figure, 15a (15c), 15b
(15d) is an element constituting a misregistration detection pattern, 15a and 15b correspond to a case where there is no misalignment in the main scanning direction, and 15c and 15d correspond to a case where there is misalignment in the main scanning direction. . Although 15c and 15d are indicated by broken lines for convenience, they have the same shape as 15a and 15b.

Each of the elements 15a (15c) and 15b (15d) constituting the misregistration detection pattern is a diagonal line extending obliquely in the opposite direction to the transport direction. In the present embodiment, the inclination with respect to the transport direction is ± 45 degrees. Suppose there is. Therefore,
The detection positions in the transport direction change in directions opposite to each other according to the amount of displacement in the main scanning direction. Note that each of the elements 15c (15a) and 15d (15b) constituting the displacement detection pattern
Are all formed in the same color, for example, yellow (Y).

That is, the misregistration detection patterns are arranged at different points on the conveyor belt 3 in a direction perpendicular to the moving direction of the conveyor belt 3 (indicated by an arrow), that is, in a direction opposite to the main scanning direction. Linear elements 15a (15c), 1 extending in the direction rotated by degrees without intersecting each other
5b (15d).

Tm30 and tm31 are optical sensors 6a and 6b
Is detected by the timer 19 according to the instruction of the CPU 18 at the timing of detecting the displacement detection patterns 15c and 15d. The dashed line indicates the position of the optical sensors 6a and 6b, and the detection pattern 15c (1
5a) and 15d (15b) are detected.

Also, v [mm / s] is the moving speed of the conveyor belt 3, and s [mm] is the theoretical distance between the patterns.

The pattern 15a for detecting a displacement shown in FIG.
In (15c) and 15b (15d), the elements 13a (13c) and 13b (13d) constituting the misregistration detection pattern shown in FIG. 3 of the first embodiment are basically separated from each other (differences between them). ), And the amount of displacement “δem” in the main scanning direction is basically the same as the equation (9) shown in the first embodiment.

In the first to third embodiments, the oblique line (13a) which is an element constituting the misregistration detection pattern is used.
(13c), 14a (14c), 15a (15c)) and (13b (13d), 14b (14d), 15b (15
The angle between d) and d) is set to ± 45 degrees from the direction orthogonal to the conveyance direction of the conveyance belt 3, but is not necessarily set to ± 45 degrees.

However, in the case of a direction rotated by an angle smaller than 45 degrees from the direction orthogonal to the transport direction of the transport belt 3 (when the angle between the direction orthogonal to the transport direction and each oblique line is 45 degrees or less), the optical sensor The pattern reading waveforms 6a and 6b become sharper and the pattern detection accuracy is improved, but the ratio of the amount of detection in the transport direction to the displacement in the main scanning direction is reduced. On the other hand, in the case of a direction rotated by an angle larger than 45 degrees from the direction orthogonal to the transport direction of the transport belt 3 (when the angle between the direction orthogonal to the transport direction and each oblique line is 45 degrees or more), the rotation in the main scanning direction is performed. Although the ratio of the detected amount in the transport direction to the positional deviation increases, the pattern detection accuracy deteriorates. Therefore, approximately 45 degrees is desirable.

Although the two patterns are oriented in the opposite directions and at the same angle, they need not necessarily have the same direction and the same angle. However, two patterns of optical sensors 6a,
In order to make the 6b detection accuracy equivalent, it is desirable that they are substantially the same.

In each of the above embodiments, the optical sensor 6a,
Although 6b is provided on both sides, if the optical unit is not a laser scanner but an LED head and it is not necessary to correct the main scanning width, one may be provided at any position.

In this embodiment, a case has been described where image information is input from a computer (PC) or the like (not shown). However, the original is scanned optically by scanning the original with a document reading unit (not shown). Alternatively, a copy image based on the read image may be formed.

As described above, since the detection positions in the transport direction change in opposite directions to each other in accordance with the positional deviation amount in the main scanning direction in each of the positional deviation detection patterns, the detection amount is larger than the positional deviation amount in the main scanning direction. Thus, the displacement amount can be detected with higher accuracy, and one dot is 42.3 μm and 600 dp.
Even in the case of forming an image with multiple gradations within a dot at i or higher, sufficient positional deviation detection accuracy can be obtained.

Further, since each position shift detection pattern is set at approximately ± 45 degrees with respect to the transport direction, the position shift amount in the main scanning direction can be detected with higher accuracy and stability.

Further, since each of the misregistration detection patterns has the same angle in the opposite direction to the transport direction, the misregistration amount in the main scanning direction can be detected with higher accuracy and stability.

Note that the above embodiments may be combined and implemented.

As described above, the storage medium storing the program codes of the software for realizing the functions of the above-described embodiments is supplied to the system or the apparatus, and the computer (or CPU or MP) of the system or the apparatus is supplied.
It goes without saying that the object of the present invention is also achieved when U) reads out and executes the program code stored in the storage medium.

In this case, the program code itself read from the storage medium realizes the novel function of the present invention, and the storage medium storing the program code constitutes the present invention.

Examples of a storage medium for supplying the program code include a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, and C
DR, magnetic tape, nonvolatile memory card, RO
M, EEPROM and the like can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer based on the instruction of the program code. ) And the like perform part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instruction of the program code, The CPU provided in the function expansion board or function expansion unit performs part or all of the actual processing,
It goes without saying that a case where the function of the above-described embodiment is realized by the processing is also included.

Further, the present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one device. Needless to say, the present invention can be applied to a case where the present invention is achieved by supplying a program to a system or an apparatus. In this case, by reading a storage medium storing a program represented by software for achieving the present invention into the system or the apparatus, the system or the apparatus can enjoy the effects of the present invention. .

Further, by downloading and reading out a program represented by software for achieving the present invention from a database on a network using a communication program, the system or apparatus can be
It is possible to enjoy the effects of the present invention.

[0107]

As described above, the first embodiment according to the present invention is described.
According to the invention, a plurality of image forming units provided for each color component are respectively scanned and exposed on a plurality of image carriers provided for each color component in accordance with an image signal for each color component. A color component image is formed on the body, and the color component image formed on each image carrier is moved in a direction orthogonal to the main scanning direction of each of the image forming units and sequentially passes through each image carrier. In an image forming apparatus capable of forming a multicolor image by superimposing and transferring on a recording medium conveyed while being held on an endless moving body,
A position constituted by a plurality of line-shaped elements extending in directions rotated in directions opposite to each other with respect to a direction perpendicular to the direction of movement of the endless moving body by control of the first control means, The shift detecting pattern is formed on the endless moving body without overlapping for each color component, and the detecting means detects each element constituting the positional shift detecting pattern for each color component formed on the endless moving body. Since the calculating means calculates the amount of misregistration in the main scanning direction for each color component based on the detection interval of each element constituting the misregistration detection pattern for each color component detected by the detection means,
Since the detection position of each element of the pattern for detecting the position shift changes in the direction opposite to each other with respect to the transport direction in accordance with the amount of position shift in the main scanning direction, the amount of detection of the position shift amount in the main scanning direction is enlarged. Can be detected with higher accuracy.

According to the second aspect, the calculating means determines whether or not a predetermined reference color component is detected based on a detection interval of each element constituting a misregistration detection pattern for each color component detected by the detecting means. Is calculated in the main scanning direction, the amount of displacement in the main scanning direction of another color component with respect to a predetermined color component can be measured with high accuracy.

According to the third aspect, the second control means for controlling the writing position in the main scanning direction by each of the image forming units based on the calculation result of the calculation means is provided. The displacement can be corrected with high accuracy.

[0110] According to the fourth invention, the first control means is configured to form each of the plurality of patterns for detecting a displacement with the same color component in a direction orthogonal to a moving direction of the endless moving body. The image forming unit is controlled, and the detection unit detects a misregistration detection pattern for each color component formed in a plurality of directions in a direction orthogonal to a moving direction of the endless moving body on the endless moving body. The calculation means calculates the main scanning width for each color component based on the detection intervals of each element constituting a plurality of misregistration detection patterns for each color component detected by the detection means, The main scanning width can be measured with high accuracy.

According to the fifth aspect, the third control means for controlling the writing position in the main scanning direction by each of the image forming units based on the calculation result of the calculation means is provided. It can be corrected with high accuracy.

According to the sixth, ninth and ninth aspects of the present invention, the misregistration detecting pattern includes two patterns extending in the directions rotated in the directions opposite to each other in the direction orthogonal to the direction of movement of the endless moving body. Since it is composed of line-shaped elements, the amount of displacement in the main scanning direction can be stably measured with high accuracy.

According to the seventh aspect, the misregistration detection pattern has two line shapes extending in directions rotated by 45 degrees opposite to each other with respect to a direction orthogonal to the moving direction of the endless moving body. Since it is composed of elements, while maintaining the detection accuracy of the displacement detection pattern,
The amount of change of each element of the misregistration detection pattern in accordance with the misregistration amount in the main scanning direction can be enlarged, and the misalignment amount in the main scanning direction can be stably measured with higher accuracy.

According to the tenth aspect, a plurality of image forming units provided for each color component are scanned and exposed on a plurality of image carriers provided for each color component in accordance with an image signal for each color component. Forming a color component image on each image carrier, moving the color component image formed on each image carrier in a direction orthogonal to the main scanning direction of each image forming unit, In a method for detecting a displacement amount in the main scanning direction of an image forming apparatus capable of forming a multicolor image by superimposing and transferring a recording medium conveyed while being held on an endless moving body that sequentially passes through a body,
The endless moving pattern is not overlapped for each color component by a misregistration detection pattern composed of a plurality of line-shaped elements extending in directions rotated in directions opposite to each other with respect to a direction perpendicular to the moving direction of the endless moving body. Formed on a moving object,
Detecting each element constituting the misregistration detection pattern for each color component formed on the endless moving body, and detecting the detection interval of each element constituting the misregistration detection pattern for each detected color component. Since the amount of displacement in the main scanning direction is calculated for each color component based on the position, the detection positions of the elements of the pattern for detecting displacement in the main scanning direction are opposite to each other with respect to the transport direction. Therefore, the detection amount of the positional deviation amount in the main scanning direction can be expanded, and the detection can be performed with higher accuracy.

Therefore, even when the detection amount of the positional deviation amount in the main scanning direction is expanded and detected with higher accuracy, and a high-resolution multi-tone image formation within a dot is performed, the main accuracy is sufficiently high. This has the advantage that the amount of displacement in the scanning direction can be detected.

[Brief description of the drawings]

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

FIG. 2 is a block diagram illustrating a configuration of a controller unit illustrated in FIG.

FIG. 3 is a schematic diagram illustrating an example of a misregistration detection pattern formed on the transport belt illustrated in FIG.

FIG. 4 is a schematic diagram illustrating an example of a misregistration detection pattern formed on the transport belt shown in FIG.

5A and 5B are diagrams illustrating a method of determining a position shift detection pattern reading waveform output from the optical sensor illustrated in FIG. 1 and a detection timing of the position shift detection pattern.

FIG. 6 is a flowchart illustrating a control processing procedure of the image forming apparatus of the present invention.

FIG. 7 is a schematic diagram illustrating an example of a misregistration detection pattern formed on a transport belt of an image forming apparatus according to a second exemplary embodiment of the present invention.

FIG. 8 is a schematic diagram illustrating an example of a misregistration detection pattern formed on a conveyance belt of an image forming apparatus according to a third embodiment of the present invention.

FIG. 9 is a diagram illustrating an example of color misregistration of an image formed on a photosensitive drum in a main scanning direction.

FIG. 10 is a diagram illustrating an example of a misregistration detection pattern formed on a transport belt of a conventional image forming apparatus.

[Explanation of symbols]

1a, 1b, 1c, 1d Photosensitive drums 2a, 2b, 2c, 2d Laser scanner 3 Conveyor belt 6a, 6b Optical sensors 13a, 13b, 13c, 13d Elements constituting a misregistration detection pattern 18 CPU 20 Pattern detection unit 22 Operation unit 23 image output unit 24 ROM 25 RAM

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H027 DA32 DA38 DE02 DE07 DE09 EB04 EC03 EC06 EC08 EC09 EC20 ED04 EE02 EE07 EE08 EF06 FD06 FD08 2H030 AA01 AB02 AD05 AD16 BB02 BB16 BB23 BB56 9A001 BB06 KK31

Claims (10)

[Claims] An image forming unit provided for each color component scans and exposes a plurality of image forming units provided for each color component in accordance with an image signal for each color component. A color component image is formed thereon, and the color component images formed on each image carrier are moved in a direction orthogonal to the main scanning direction of each of the image forming units, and endlessly sequentially pass through each image carrier. An image forming apparatus capable of forming a multi-color image by superimposing and transferring on a recording medium conveyed while being held on an endless moving body, wherein the endless moving body has a direction opposite to a moving direction. A first control unit that controls each of the image forming units so that a misregistration detection pattern formed by a plurality of line-shaped elements extending in a rotated direction is formed on the endless moving body without overlapping each color component; Control means, on the endless moving body Detecting means for detecting each element constituting the formed misregistration detection pattern for each color component, based on a detection interval of each element constituting the misregistration detection pattern for each color component detected by the detection means. Calculating means for calculating the amount of displacement in the main scanning direction for each color component;
An image forming apparatus comprising: 2. The main scanning of another color component with respect to a predetermined reference color component based on a detection interval of each element constituting a misregistration detection pattern for each color component detected by the detection unit. 2. The image forming apparatus according to claim 1, wherein the amount of displacement in the direction is calculated. 3. The image forming apparatus according to claim 1, further comprising a second control unit that controls a writing position in the main scanning direction by each of the image forming units based on a calculation result of the calculation unit. apparatus. 4. The image forming unit according to claim 1, wherein the first control unit controls the image forming units so as to form a plurality of the misregistration detection patterns with the same color component in a direction orthogonal to a moving direction of the endless moving body. Wherein the detecting means detects a misregistration detection pattern for each color component formed in a plurality of directions in a direction orthogonal to a moving direction of the endless moving body on the endless moving body. 2. The apparatus according to claim 1, wherein said means calculates a main scanning width for each color component based on a detection interval of each element constituting a plurality of misregistration detection patterns for each color component detected by said detection means. The image forming apparatus as described in the above. 5. The image forming apparatus according to claim 4, further comprising a third control unit that controls a writing position in the main scanning direction by each of the image forming units based on a calculation result of the calculation unit. apparatus. 6. A method according to claim 1, wherein the misregistration detection pattern is constituted by two line-shaped elements extending in the directions rotated in opposite directions to be equal to each other with respect to a direction orthogonal to the moving direction of the endless moving body. The image forming apparatus according to claim 1, wherein: 7. The pattern for detecting a position shift is mutually shifted with respect to a direction orthogonal to a moving direction of the endless moving body.
2. The image forming apparatus according to claim 1, wherein the image forming apparatus is constituted by two linear elements extending in a direction rotated by 5 degrees in the opposite direction. 8. The image forming apparatus according to claim 6, wherein the two line-shaped elements are two line segments extending from one point of the endless moving body. 9. The image forming apparatus according to claim 6, wherein the two line-shaped elements are two line segments extending from two different points of the endless moving body without intersecting with each other. 10. A plurality of image forming units provided for each color component are respectively scanned and exposed on a plurality of image carriers provided for each color component in accordance with an image signal for each color component. A color component image is formed thereon, and the color component images formed on each image carrier are moved in a direction orthogonal to the main scanning direction of each of the image forming units, and endlessly sequentially pass through each image carrier. In a method for detecting a positional shift amount in a main scanning direction of an image forming apparatus capable of forming a multicolor image by superimposing and transferring a recording medium conveyed while being held on an endless moving body, the moving direction of the endless moving body is A pattern forming step of forming a misregistration detection pattern formed by a plurality of linear elements extending in directions rotated in directions opposite to each other on the endless moving body without overlapping each color component; And the endless movement A detection step of detecting each element constituting the misregistration detection pattern for each color component formed above, and a detection interval of each element constituting the detection pattern for each detected color component. A calculating step of calculating a displacement amount in the scanning direction for each color component, the method for detecting a displacement amount in the main scanning direction of the image forming apparatus.