JP2001324847A - Image forming device and color slurring detecting and processing method for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a dark state where a light emitting part is not lit, from being erroneously stored as the minimum value of a color slurring detection pattern and to prevent the deterioration of the position detecting accuracy on the color slurring detection pattern. SOLUTION: Before detecting a color slurring detection pattern image, the reset of a minimum value and a maximum value is started. Before releasing the reset, the light emitting part is lit and then the reset is released. Thereafter, the maximum value and the minimum value are sampled for an upper peak hold circuit 301 and a lower peak hold circuit 302. In the case of reading the color slurring detection pattern, a comparator circuit 305 generates position information based on a light quantity signal from the maximum value and the minimum value which are sampled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is capable of forming a color image by arranging a plurality of image forming stations side by side and sequentially superimposing and transferring the images formed in the respective image forming stations onto a recording sheet carried by a carrier. The present invention relates to a simple image forming apparatus and a color misregistration detection processing method of the image forming apparatus.

[0002]

2. Description of the Related Art An electrophotographic color image forming apparatus has a plurality of image forming units for speeding up and sequentially transfers images of different colors onto a recording material held on a conveyor belt. Have been proposed.

[0003] Problems with an apparatus having a plurality of image forming units include irregularities in the movement of a plurality of photosensitive drums and conveyor belts due to mechanical accuracy and the like, and the outer periphery of the photosensitive drum at the transfer position of each image forming unit. For example, the relationship between the surface and the movement amount of the transport belt may be different for each color, may not match when the images are superimposed, and may cause a color shift.

In particular, in a color image forming apparatus having a plurality of image forming units (image forming stations) each having a laser scanner and a photosensitive drum, there is an error in the distance between the laser scanner and the photosensitive drum in each image forming unit. Is different in each image forming unit, a difference occurs in the scanning width of the laser on the photosensitive drum, and a color shift occurs.

FIG. 12 is a view for explaining a color misregistration state in this type of color image forming apparatus.

In FIG. 12, reference numeral 7 denotes an original image position,
Reference numeral 8a denotes an image position when a color shift has occurred. In FIG. 12, (a), (b), and (c) show cases where there is color misregistration in the main scanning direction, but for the sake of explanation, two lines are drawn apart in the transport direction.

[0007] In particular, (a) shows the inclination deviation of the main scanning line, which occurs when there is an inclination between the optical unit and the photosensitive drum. For example, the position is corrected in the direction of the arrow by adjusting the position of the optical unit, the photosensitive drum, and the position of the lens.

FIG. 2B shows a color shift due to a variation in the width of the main scanning line, which is caused by a difference in the distance between the optical unit and the photosensitive drum. This 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). Then, correction is made in the direction of the arrow by changing the length of the scanning line.

FIG. 3C shows a writing position error in the main scanning direction. For example, if the optical unit is a laser scanner, correction is made in the direction of the arrow by adjusting the writing start timing from the beam detection position.

FIG. 3D shows a write start position error in the paper transport direction. For example, the correction is made in the direction of the arrow by adjusting the writing start timing of each color from the detection of the leading edge of the sheet.

In order to correct these color misregistrations, a pattern for color misregistration detection is formed for each color on the conveyor belt, and detected by a pair of optical sensors provided on both sides of the downstream portion of the conveyor belt. In accordance with the detected shift amount, a controller (not shown) electrically or mechanically performs the color shift correction control for the various adjustments as described above.

FIG. 13 is a diagram showing an example of a color misregistration detection pattern formed on a transport belt of this type of color image forming apparatus.

In FIG. 13, 9a to 9d and 10a to 1
0d is a pattern for detecting the color shift amount in the paper transport direction, and 11a to 11d and 12a to 12d are patterns for detecting the color shift amount in the main scanning direction orthogonal to the paper transport direction. In this example, The inclination is 45 degrees. Note that a to d
Indicates black (hereinafter Bk), yellow (hereinafter Y), magenta (hereinafter M), and cyan (hereinafter C), respectively.

Tsfl to tsf4, tmfl to tmf
4, tsrl to tsr4 and tmrl to tmr4 indicate the detection timing of each pattern, and the arrows indicate the moving direction of the conveyor belt 3. The moving speed of the conveyor belt 3 is Vmm / s, B
k as a reference color, each color of the paper transport direction pattern and Bk
The theoretical distance between patterns is dsYmm, dsMmm, ds
Cmm, the actual measured distance between the paper transport direction pattern and the main scanning direction pattern of each color is dmfBkmm,
dmfYmm, dmfMmm, dmfCmm, dmrB
km, dmrYmm, dmrMmm, dmrCmm, Bk as a reference color, and the color misregistration amount (color misregistration amount) δes of each color in the transport direction is the following (1) to (1).
As shown in equation 7), δesY = v * {(tsf2-tsfl) + (tsr2-tsrl)} / 2−dsY (1) δesM = v * t (tsf3-tsfl) + (tsr3-tsrl)} / 2-dsM (2) δesC = v * {(tsf4-tsfl) + (tsr4-tsrl)} / 2−dsC (3)

On the other hand, in the main scanning direction, the color misregistration amounts δemf and δemr of the left and right colors are dmfBk = v * (tmfl−tsfl) (4) dmfY = v * (tmf2−tsf2) (5) ) DmfM = v * (tmf3-tsf3) (6) dmfC = v * (tmf4-tsf4) (7) dmrBk = v * (tmrl-tsrl) (8) dmrY = v * (tmr2-) tsr2) (9) dmrM = v * (tmr3-tsr3) (10) dmrC = v * (tmr4-tsr4) (11)
From the equation, δemfY = dmfY−dmfBk (12) δemfM = dmfM−dmfBk (13) δemfC = dmfC−dmfBk (14)
ΔemrY = dmrY−dmrBk (15) δemrM = dmrM−dmrBk (16) δemrc = dmrC−dmrBk (17)
The deviation direction can be determined from the positive or negative of the calculation result, and the writing position is corrected from δemf, and the main scanning width is corrected from δemr-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.

FIG. 14 is a block diagram showing an example of a color misregistration detection processing circuit in this type of color image forming apparatus. In addition, a pair of optical sensors 6a and 6a in which the registration mark shown in FIG.
It shall be read by b.

In FIG. 14, the detection current from the light receiving elements in the optical sensors 6a and 6b, that is, the PD100 is I
The voltage is converted by the / V conversion circuit 101 into a voltage. Upper peak hold circuit 301 and lower peak hold circuit 30
3, the maximum value and the minimum value are respectively detected, and the voltage is divided by the resistors 302 and 304. I / V conversion circuit 1
A comparison circuit 305 determines the magnitude relationship between the output waveform 01 and the voltage values divided by the resistors 302 and 304 to generate a pulse signal corresponding to an output waveform (b) shown in FIG. .

Here, in order for the upper peak hold circuit 301 and the lower peak hold circuit 303 to obtain the maximum value and the minimum value, respectively, it is necessary to read one line in advance. A pulse conversion reference voltage is created from the maximum value and the minimum value acquired here. That is, it is necessary to create a registration mark for acquiring the maximum value and the minimum value immediately before the registration mark shown in FIG.

FIG. 15 is a characteristic diagram showing an example of a pattern detection waveform by the color misregistration sensor circuit shown in FIG.

FIG. 15A shows the width of the transport belt 3 in the transport direction at time t, and shows the transition of the output waveform (b) of the I / V conversion circuit and the positional relationship of the PD 100. The transport belt 3 has a high gloss, and most of the emitted light is specularly reflected, and is received by the PD 100.

The color misregistration detection pattern, which is a toner image, has low gloss, most of the emitted light is scattered, and the specularly reflected light received by the PD 100 is slight. The output waveform (b) is
It is high when the conveyor belt 3 is detected, and is low when the color misregistration detection pattern is detected. Note that the value of the threshold (c) is determined by the voltage division ratio of the resistors 302 and 304. This relationship is expressed by the formula of A: B = resistor 302: resistor 304.

A color misregistration detection pattern is formed on the conveyor belt 3 with yellow 9b, magenta 9c, cyan 9d, and black 9a, and is detected by the sensor 6 (6a, 6b). The light receiving element 52 outputs an output waveform (b) having four peaks as shown in FIG. The first corresponds to a yellow color misregistration detection pattern, the second corresponds to a magenta color, the third corresponds to a cyan color misregistration detection pattern, and the fourth corresponds to a black color misregistration detection pattern.

At this time, the waveforms for detecting the patterns of the four colors have the same shape. The first to fourth valleys are threshold (c)
The pulse signal (d) shown in FIG. Then, an arithmetic unit (not shown) obtains the center position of each of the first to fourth pulse signals (d) shown in FIG. 15, and further obtains the time difference between the respective center positions. A color shift amount is calculated from a difference between the obtained time difference and a preset time difference value.

[0025]

However, the comparison circuit 30 detects the maximum value and the minimum value of the color misregistration detection pattern and detects them.
5, a reference waveform is determined, a measured waveform is compared, a pulse waveform is generated, and color shift detection pattern position information is used.
There are problems as described below.

First, the reset function of the maximum value and the minimum value of the peak hold circuit is indispensable. When the reset is released and the color shift detection pattern is detected, the output in the dark state is set to the minimum value unless the LED is turned on. An erroneous detection causes an error in the reference level of the comparison circuit 305, which deteriorates the detection accuracy of the color misregistration detection pattern and makes it impossible to correct the color misregistration, or conversely promotes color misregistration.

Further, if the gloss of the toner of each color of the color misregistration detection pattern is larger than the toner forming the pattern for obtaining the maximum value or the minimum value before the color misregistration detection pattern, the held maximum value or minimum value is maintained. Between the maximum value and the minimum value of the toner pattern constituting the color shift detection pattern, the detection accuracy of the color shift detection pattern is deteriorated, and the color shift cannot be corrected, or conversely, the color shift is promoted. There is a problem that a case may occur.

In the case where color misregistration is corrected based on positional information from a plurality of color misregistration detection patterns, if the color misregistration detection patterns are far apart, the maximum value or the minimum value holding means of the peak hold circuit is held. Voltage fluctuates due to droop, the detection accuracy of the color misregistration detection pattern deteriorates, color misregistration cannot be corrected, and conversely, there is a problem that color misregistration is promoted. .

The present invention has been made to solve the above problems, and a first object of the present invention is to set a maximum value and a minimum value based on the amount of light received based on light reflected from a color misregistration detection pattern. When individually storing, the reset of the maximum value and the minimum value is released, and when detecting the color misregistration detection pattern,
By turning on the light emitting unit in advance, it is possible to prevent the dark state from being erroneously stored as the minimum value of the color shift detection pattern, and to prevent the position detection accuracy of the color shift detection pattern from deteriorating.

A second object is to detect the position information of a plurality of color misregistration detection patterns and to read the toner pattern immediately before the position detection of each color misregistration detection pattern, thereby obtaining the reflected light amount of the held toner. Is to recover the droop of the maximum value or the minimum value corresponding to the above, and prevent the accuracy of the position detection of the color misregistration detection pattern from deteriorating.

Further, a third object is to detect the position information of a plurality of color misregistration detection pattern groups, reset the maximum value and the minimum value once between the color misregistration detection patterns, and then execute the following. By reading the toner pattern immediately before the color misregistration detection pattern, the maximum and minimum values of the correct color misregistration detection pattern are sampled again to prevent the accuracy of position detection of the color misregistration detection pattern from deteriorating. An object of the present invention is to provide an image forming apparatus and a color misregistration detection processing method of the image forming apparatus that can realize misregistration correction.

[0032]

According to a first aspect of the present invention, a plurality of image forming stations are juxtaposed, and an image formed at each image forming station is sequentially superimposed on a recording sheet conveyed by a conveying body. An image forming apparatus capable of transferring and forming a color image, wherein the transfer of a reference color pattern image by a predetermined image forming station and a color misregistration detection pattern image by another image forming station among the plurality of image forming stations is performed. A pattern forming means (corresponding to the CPU 51 shown in FIG. 3) for controlling the image formation of each image forming station so as to form the image on the body, and a specular reflection of the series of color misregistration detection pattern images formed by the pattern forming means. The maximum value obtained by converting the light amount signal read by the light emitting unit and the light receiving unit into a voltage signal, which is read by the light emitting unit and the light receiving unit in which the optical system is formed, and Storage means for storing the small value (corresponding to the upper peak hold circuit 301 and the lower peak hold circuit 303 shown in FIG. 4); and reset means for resetting the maximum value and the minimum value stored in the storage means ( FIG.
And a first control unit (FIG. 1) for performing reset by the reset unit before detecting the color misregistration detection pattern image, turning on the light emitting unit during the reset, and then canceling the reset. CPU 51 shown in FIG.
And a reference value for generating a position information signal based on the light quantity signal from the maximum value and the minimum value stored in the storage means during the reset release state by the first control means. Generating means (comparing circuit 3 shown in FIG. 4)
05), calculating means for calculating the amount of color shift between the respective color images based on the position information signal generated by the generating means (corresponding to the calculating section 54 shown in FIG. 3), and calculating by the calculating means And a second control unit (corresponding to the CPU 51 shown in FIG. 3) for correcting and controlling the position of the image by each image forming station other than the reference color based on the color shift amount thus determined.

According to a second aspect of the present invention, the pattern forming means includes:
When a pattern group including a reference color pattern image by a predetermined image forming station and a color misregistration detection pattern image by another image forming station is formed on the carrier, an interval between each pattern group is one color misregistration detection. If it is longer than the interval between the pattern images, at least one dedicated pattern is formed immediately before each pattern group.

According to a third aspect of the present invention, the first control means includes detecting a reference color pattern image by a predetermined image forming station and a color misregistration by another image forming station among the plurality of image forming stations. When forming a pattern group including a pattern image on the carrier, if the interval between each pattern group is longer than the interval between one color misregistration detection pattern image, the previous pattern stored in the storage means is stored. The maximum value and the minimum value based on the group are reset by the reset means.

According to a fourth aspect of the present invention, in the above-mentioned first control means, after the reset by the reset means, a maximum of a surface reflected light of the image carrier of the carrier and a surface reflected light of the dedicated pattern is obtained. The value and the minimum value are stored in the storage means.

In a fifth aspect according to the present invention, the first control means stores in the storage means a dedicated pattern formed immediately before each pattern group or a maximum value based on the amount of reflected light received from the surface of the carrier. It is something to memorize.

In a sixth aspect according to the present invention, the first control means stores, in the storage means, a dedicated pattern formed immediately before each pattern group or a minimum value based on the amount of reflected light received from the surface of the carrier. It is something to memorize.

According to a seventh aspect of the present invention, the width of the dedicated pattern is equal to or larger than the image width of the color misregistration detection pattern.

According to an eighth aspect of the present invention, in the image forming apparatus, when the reflectance of the carrier is higher than the reflectance of the color misregistration detection pattern, the pattern forming means forms the dedicated pattern with toner having the lowest reflectance. If the reflectivity of the carrier is lower than the reflectivity of the toner, the dedicated pattern is formed with the toner having the highest reflectivity.

In a ninth aspect according to the present invention, the pattern forming means is configured such that the reflectance of light directly reflected from the carrier by turning on the light emitting portion is determined from a plurality of color toners formed on the carrier. When the exclusive pattern is included in the reflectance range of the reflected light, the dedicated pattern is formed with the toner of the same color as the toner having the highest reflectance or the toner color having the lowest reflectance.

According to a tenth aspect of the present invention, a plurality of image forming stations are juxtaposed, and an image formed in each image forming station is sequentially overlaid and transferred onto a recording sheet conveyed by a conveying body to form a color image. A color misregistration detection processing method of an image forming apparatus capable of forming, wherein, among the plurality of image forming stations, a reference color pattern image by a predetermined image forming station and a color misregistration detection pattern image by another image forming station are conveyed. A pattern forming step (step S103 shown in FIG. 7) for controlling the image formation of each image forming station so as to form the image on the body, and specular reflection optics for the series of color misregistration detection pattern images formed in the pattern forming step. The light is read by the light emitting unit and the light receiving unit where the system is formed, and the light amount signal read by the light receiving unit is converted into a voltage signal. A storage step (steps S103 and S104 shown in FIG. 7) for storing the value and the minimum value in a storage unit (corresponding to the upper peak hold circuit 301 and the lower peak hold circuit 303 shown in FIG. 4), and the storage unit A reset step (not shown) for resetting the maximum value and the minimum value, and a detection step for detecting a color shift detection pattern image.
A first control step (steps S101 and S101 shown in FIG. 7) for performing the reset in the reset step, turning on the light emitting unit during the reset, and then releasing the reset.
102) and generating a reference value for generating a position information signal based on the light amount signal from the maximum value and the minimum value stored in the storage unit during the reset release state by the first control step. Generation Step (Step S1 shown in FIG. 7)
05), a calculating step of calculating a color shift amount between the respective color images based on the position information signal generated by the generating step (step S109 shown in FIG. 7), and a color shift amount calculated by the calculating step And a second control step (step S110 shown in FIG. 7) of correcting and controlling the position of the image by each image forming station other than the reference color on the basis of.

According to an eleventh aspect of the present invention, in the pattern forming step, among the plurality of image forming stations, a reference color pattern image by a predetermined image forming station and a color misregistration detection pattern image by another image forming station. When forming a pattern group including on the carrier,
If the interval between each pattern group is longer than the interval between one color misregistration detection pattern image, at least one dedicated pattern (the pattern SG shown in FIG.
1, SG2).

According to a twelfth aspect of the present invention, the first control step includes the step of:
When a pattern group including a reference color pattern image by a predetermined image forming station and a color misregistration detection pattern image by another image forming station is formed on the carrier, an interval between each pattern group is one color misregistration detection. If the interval is longer than the interval between the pattern images, the maximum value and the minimum value based on the immediately preceding pattern group stored in the storage unit are reset by the reset step (step SS1 shown in FIG. 10).

According to a thirteenth aspect of the present invention, in the first control step, after the reset in the reset step, a maximum of a surface reflected light of the image carrier of the carrier and a surface reflected light of the dedicated pattern is obtained. The storage unit (the upper peak hold circuit 301 and the lower peak hold circuit 3 shown in FIG.
03 (corresponding to 03).

According to a fourteenth aspect of the present invention, in the first control step, the maximum value based on a dedicated pattern formed immediately before each pattern group or the amount of reflected light received from the carrier surface is stored in the storage unit. It is something to memorize.

According to a fifteenth aspect of the present invention, in the first control step, the minimum value based on the dedicated pattern formed immediately before each pattern group or the amount of reflected light received from the carrier surface is stored in the storage unit. It is something to memorize.

According to a sixteenth aspect of the present invention, the width of the exclusive pattern is equal to or larger than the image width of the color misregistration detection pattern.

According to a seventeenth aspect of the present invention, in the pattern forming step, when the reflectivity of the carrier is higher than the reflectivity of the color misregistration detection pattern, the dedicated pattern is formed of toner having the lowest reflectivity. If the reflectivity of the carrier is lower than the reflectivity of the toner, the dedicated pattern is formed with the toner having the highest reflectivity.

According to an eighteenth aspect of the present invention, in the pattern forming step, the reflectance of light directly reflected from the carrier by turning on the light emitting portion is determined from a plurality of color toners formed on the carrier. When the exclusive pattern is included in the reflectance range of the reflected light, the dedicated pattern is formed with the toner of the same color as the toner having the highest reflectance or the toner color having the lowest reflectance.

According to a nineteenth aspect of the present invention, a plurality of image forming stations are juxtaposed, and an image formed at each image forming station is sequentially transferred onto a recording sheet conveyed by a conveyer to transfer a color image. An image forming apparatus, comprising: a pattern forming unit configured to control the plurality of image forming stations so as to form a color misregistration detection pattern image of each color on the carrier; and a plurality of image forming stations on the carrier. Reading means for reading each color misregistration detection pattern image formed by the light emitting unit and the light receiving unit,
Storage means for storing a maximum value and a minimum value of the light amount signal output from the light receiving unit; reset means for resetting the maximum value and the minimum value stored by the storage means; and the color shift by the reading means. Performing a reset operation by the reset unit before performing the reading process of the detection pattern image and causing the light emitting unit to emit light during the reset,
First control means for canceling the reset operation thereafter;
Position detection for detecting the position of each color misregistration detection pattern image based on the maximum value and the minimum value stored in the storage means and a light amount signal output from the reading means in a reset release state by the first control means. Means for correcting the position of each color image formed by the plurality of image forming stations based on the output of the position detecting means.

[0051]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment FIG. 1 is a schematic perspective view illustrating an example of a color image forming apparatus according to a first embodiment of the present invention. For example, four colors, that is, yellow Y, magenta This corresponds to a color image forming apparatus in which M, cyan C, and black K image forming units (image forming stations) are juxtaposed.

In the figure, reference numerals 1a, 1b, 1c and 1d denote photosensitive drums for forming an electrostatic latent image (a, b, c and d indicate K, C, M and Y, respectively), 2a, 2b and 2c , 2d perform exposure in accordance with the image signal and perform exposure on the photosensitive drum 1 (1a, 1a).
b, 1c, 1d), a laser scanner for forming an electrostatic latent image thereon, and 3 an endless transport belt which also serves as a transfer belt for sequentially transporting the paper to the image forming units of each color, and is driven by a belt motor (not shown). The driving roller 4 is driven to rotate.

The driving roller 4 is connected to driving means, not shown, which includes a motor and gears, and drives the transport belt 3 at a predetermined speed. Reference numeral 5 denotes a driven roller which rotates according to 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 for detecting a color misregistration detection pattern formed on the conveyor belt 3, and are provided on the belt end side so as to be orthogonal to the conveying direction of the conveyor belt 3. I have. CONT is a control unit having a CPU, RAM, and ROM (not shown).
By executing a control program stored in the ROM, a sensor signal, image data, and the like input through an input port (not shown) are processed to control the driving of the engine unit.
The drive control of the laser scanner 2 (2a, 2b, 2c, 2d) is performed.

Data to be printed is sent from a personal computer (PC) constituted by a host computer (not shown) to the printer. When image formation according to the printer engine system is completed and the printer is ready for printing, the data is transferred from a paper cassette (not shown). The paper is fed and the conveyor belt 3
, And the sheet is sequentially conveyed by the conveying belt 3 to the image forming units of each color.

Then, the image signals of the respective colors are sent to the respective laser scanners 2 in synchronism with the sheet conveyance by the conveyor belt 3 to form an electrostatic latent image on the photosensitive drum 3, and the toner is developed by a developing unit (not shown). It is developed and transferred onto a sheet at a transfer unit (not shown).

In FIG. 1, images are sequentially formed in the order of Y, M, C, and K. Thereafter, the paper is separated from the conveyor belt 3,
The toner image is fixed on the paper by heat in a fixing device (not shown) and is discharged to the outside. Hereinafter, the operation of the present embodiment will be described.

In order to reduce color misregistration, a color misregistration detection pattern as shown in FIG. 13 is formed on each of the image forming stations on the transport belt 3 as described above. Pair of optical sensors 6 provided on the side
The colors are read at a and 6b, and the amount of color misregistration between the colors is detected.

FIG. 2 shows the optical sensors 6a and 6b shown in FIG.
FIG. 4 is a schematic explanatory diagram for explaining a detailed configuration of the present embodiment, and corresponds to a case where a pattern reading system is configured by a regular reflection optical system.

In the figure, reference numeral 51 denotes a light emitting element, for example, L
It is composed of ED. 52 is a light receiving element, for example, a photo sensor. 3 is a conveyor belt, 9, 10, 11,
Reference numeral 12 denotes a color misregistration detection pattern.

Reference numeral 53 denotes light emitted from the light emitting element 51.
Numeral 54 denotes a received light, which is received by the light receiving element 52 among the reflected light from the conveyor belt 3 or the color misregistration detection patterns 9, 10, 11, and 12.

In the present embodiment, the light emitting section and the light receiving section are formed of a regular reflection optical system using the transport belt 3 as a reflection surface, and the reflectance of the transport belt 3 and the reflectance of the regular reflection light of the color misregistration detection pattern are measured. The position of the color misregistration detection pattern is accurately detected based on the difference, that is, the difference in gloss. Therefore, even if the black toner is on the transport belt 3, the pattern can be detected from the difference in gloss, and the background image (patch image) can be detected by using another developing color toner for black as in the related art. Need not be formed, and the amount of toner to be collected during color misregistration correction can be significantly reduced.

When an object having a high gloss value is irradiated with light, a very large regular reflection light can be obtained. For example, the gloss value can be increased by subjecting the surface of the conveyor belt 3 to mirror finishing. I can do it. When a toner image is formed on the conveyor belt 3, the specularity of the toner image is lost and the gloss value is reduced. The change in the gloss value may be detected by the optical sensors 6a and 6b using the regular reflection optical system to detect the color shift detection pattern.

FIG. 3 is a block diagram for explaining a color misregistration processing mechanism in the color image forming apparatus according to the present invention.

As shown in FIG. 3, a calculation unit 34 for calculating the color misregistration amount and the correction value by calculating the detection data detected by the pattern detection unit 32 including an LED light emitting unit and a photo sensor light receiving unit. An image output unit 35 for forming an image according to the result, a timer 33 for adjusting the timing of each unit and various settings, a CPU 31, a RAM (not shown),
A ROM (not shown) is provided. Timer 33 and CP
It is assumed that the U31, the operation unit 34, the image output unit 35, and the pattern detection unit 32 are provided in the control unit CONT shown in FIG.

FIG. 4 is a block diagram showing an example of a color misregistration detection processing circuit in the color image forming apparatus according to the first embodiment of the present invention. Note that the same components as those in FIG. 14 are denoted by the same reference numerals.

The feature of this embodiment is that the reset signal input terminals for clearing the peak values stored in the upper peak hold circuit 301 and the lower peak hold circuit 303 are respectively provided by the upper peak hold circuit 301 and the lower peak hold circuit. This is the point added to the circuit 303. Less than,
The configuration and operation will be described.

When the image carrier is in the form of a belt as described above, the distance between the object to be measured and the color misregistration detection sensor is liable to fluctuate, depending on the configuration of the mounting portion, and the output voltage value fluctuates accordingly. It often happens. In such a case, the maximum and minimum values acquired by the peak hold circuits 301 and 303 may not always be optimal.

Therefore, in the present embodiment, the peak values acquired by the peak hold circuits 301 and 303 in a certain cycle are
For example, clearing a reset signal from the CPU 51 and reacquiring a new peak value enables more accurate registration mark detection.

In this embodiment, in order to reduce the color shift, a color shift detecting pattern as shown in FIG. 5 is formed on the transport belt 3, and a pair of light beams provided on both sides of the transport belt 3 are formed. The color is read by the sensors 6 (6a, 6b) and the amount of color shift between the colors is detected.

FIG. 5 is a diagram showing an example of a color misregistration detection pattern in the image forming apparatus according to the present invention. The toner having the smallest gloss (BK in this example) is provided before the color misregistration detection pattern described with reference to FIG. ) Are provided with at least a pair of minimum value reading patterns SG1 and SG2.

FIG. 6 is a timing chart for explaining the operation of the displacement detection circuit shown in FIG.

In FIG. 6,... Represent steps S101 to S101 in a flowchart shown in FIG.
It corresponds to 110.

FIG. 7 is a flowchart showing an example of the first color misregistration correction processing procedure in the image forming apparatus according to the present invention. In addition, S101 to S110 indicate each step.

Before executing the color shift correction, the upper peak hold circuit 301 and the lower peak hold circuit 303 are in a reset state. Here, the reset state in the upper peak hold state is a state where the voltage is fixed to the lowest voltage that the circuit can take. On the other hand, the reset state in the lower peak hold state is a state where the voltage is fixed to the highest voltage that the circuit can take.

When the color misregistration correction processing is started, the light emitting element (LED) 100 emits light (S101). Note that the light emitting element 100 can be turned on / off by turning on / off a switch provided between the light emitting element 100 and a power supply or GND by a signal from the CPU 51.

Next, the reset of the upper peak hold circuit 301 and the lower peak hold circuit 303 is released (S102). Next, a color misregistration detection pattern including at least a pair of minimum value reading patterns SG1 and SG2 made of the toner having the smallest gloss (BK in this example) shown in FIG. 5 is formed.

The light receiving element 1 as the color shift detecting means during this time
Since 00 is looking at the surface of the transport belt 3 with high gloss, the upper peak hold circuit 301 samples a large voltage corresponding to the gloss of the transport belt 3 (S103). Since this voltage is equal to or smaller than the reset level of the lower peak hold circuit 303, the lower peak hold circuit 303
Also sample the same voltage.

If the reset is released without causing the light emitting element such as an LED to emit light, the lower peak hold circuit 303 detects a dark state because there is no reflected light from the conveyor belt 3 or toner. , The comparison circuit 30
The slice level (threshold) of 5 exceeds the amplitude of the output of the light receiving element 100 as the color misregistration detecting means, or the margin between the slice level and the minimum value of the light receiving element 100 becomes small, resulting in damage to the transport belt 3 or the like. Although a problem occurs in that the noise becomes weaker, the present embodiment can avoid this problem.

After a lapse of time, the color misregistration detection pattern moves on the conveyor belt 3, and the light reflected from the minimum value reading patterns SG1 and SG2 prior to the color misregistration detection pattern enters the light receiving element 100. .

The gloss of the minimum value reading patterns SG1 and SG2 formed by the toner is lower than that of the transport belt 3, so that the upper peak hold circuit 301 does not change.
The lower peak hold circuit 303 samples the voltage corresponding to the gross of the patterns SG1 and SG2 for reading the minimum value (S104).

Thus, the upper peak hold circuit 3
When the maximum value and the minimum value are sampled in 01 and the lower peak hold circuit 303, respectively, the slice level of the comparison circuit 305 shown in FIG. 4 is determined by resistance division by the resistors 302 and 304 (S105).

Further, when the transport belt 3 advances (light from the transport belt 3 is incident during this time), the light receiving element 100 shown in FIG.
The reflected light from the color misregistration detection pattern shown in FIG.
Here, the color shift detection patterns of yellow 9, magenta 10, cyan 11, and black 12 are read one by one (S1).
06, S107). The output of the light receiving element 100 is
In order to cross the slice level, the comparison circuit 305 is inverted and a position information pulse is obtained.

Next, it is determined whether all color patterns have been read (S108). If it is determined that all color patterns have not been read, step S108 is performed.
Returning to step 107, from the obtained position information pulse, for example, the position of the center of the rise and fall is obtained as the position of each toner, and the color misregistration amount of each color is calculated by the above equations (1) to (16). (S109), color misregistration correction such as fine adjustment of the image frequency and adjustment of the writing start timing is performed (S110), and the process ends.

As described above, in the present embodiment, the upper peak hold circuit 301 and the lower peak hold circuit 30
3 is released, the light emitting element 51 as shown in FIG. 2 is turned on to prevent the dark state from being erroneously detected as the signal of the minimum value, and the correct maximum value and minimum value of the light receiving element 100 are prevented. Can hold the value.

For this reason, the slice level of the comparison circuit 305 for generating the position information detection signal cannot be set correctly, and the position information of the color misregistration detection pattern cannot be detected.
It is possible to avoid detecting noise due to a scratch on the transport belt 3 as a color shift detection pattern, and correct color shift can be accurately corrected.

In the present embodiment, the transport belt 3 serving as a transfer belt has been described as an example of the transport body. However, the same effect can be obtained even when the transport body is an intermediate transfer body and a separate paper transport system is provided. can get.

In FIG. 5, one pattern (SG1, SG2) for obtaining the minimum value is written, but it is needless to say that a plurality of patterns may be used.

However, if the width of the pattern is smaller than the width of the actual color shift detection pattern, the lower peak hold circuit 3
03 may be smaller than the actual color shift detection pattern, the position detection and the sampling of the lower peak hold circuit 303 are performed simultaneously at the first color shift detection pattern, and the value changes. The slice level of the comparison circuit 305 that generates a position information detection signal for the second and subsequent first color shift detection patterns and the first color shift detection pattern changes, resulting in an error in the obtained position information. Therefore, it is desirable that the toner patterns SG1 and SG2 for obtaining the minimum value be equal to or larger than the width of the color misregistration detection pattern.

When there is a difference in the gloss of each color toner for the same reason, it is desirable to form a pattern for obtaining the minimum value with the toner having the lowest gloss.

Further, the case where the gloss of the transport belt is higher than the gloss of the toner has been described above, but it goes without saying that the same effect can be obtained even in the opposite case, except that the magnitude of the signal is reversed.

When the difference in gloss between the toners of the respective colors is large, and there is a toner having a gloss larger than the gloss of the transport belt and a toner having a smaller gloss, the color misregistration detection pattern shown in FIG. The first pattern SG1 for peak-holding the minimum value added to 3
It is needless to say that the same effect can be obtained if the SG2 is divided into the toner having the maximum gloss and the toner having the minimum gloss.

[Second Embodiment] In the above embodiment, a case has been described in which one color shift detection pattern is detected and color shift correction is executed. However, a plurality of color shift detection patterns are provided to perform a plurality of detections. When performing color misregistration correction based on the results, if the gap between the color misregistration detection patterns is wide, the light receiving element for color misregistration detection between the color misregistration detection patterns is always looking at the transport belt and has an upper peak. The hold circuit is always in the sampling state, but the signal held in the lower peak hold circuit is not sampled for a long time, so the droop greatly fluctuates, and the slice level of the comparison circuit that generates the position information detection signal fluctuates, In some cases, a pattern for detecting color misregistration cannot be detected, or noise due to a scratch on the transport belt may be detected as a color misregistration detection pattern. There is a problem in that.

Further, since the lower peak hold circuit simultaneously performs the position detection and the sampling in the first pattern upon detection of the color misregistration detection pattern, the sampled value fluctuates. For this reason, the slice level of the comparison circuit that generates the position information detection signal for the second and subsequent first color shift detection patterns and the first color shift detection pattern changes, and the obtained position information is There is a problem that an error occurs and the accuracy of color misregistration correction deteriorates.

Therefore, when releasing the reset of the upper and lower peak hold circuits at the start of the color shift correction, in addition to turning on the light emitting elements in advance, prior to each of the plurality of color shift detection patterns, Patterns for obtaining the minimum value may be provided respectively so as to solve the above problem. Hereinafter, the embodiment will be described.

FIG. 8 is a diagram showing an example of a color misregistration detection pattern in the image forming apparatus according to the second embodiment of the present invention.

In FIG. 8, a plurality of color misregistration detection patterns are arranged in a necessary number to improve the accuracy of color misregistration detection of the color misregistration detection pattern shown in FIG. If the interval between groups is substantially equal to the interval between toners constituting each pattern, it is not necessary to particularly provide a pattern for acquiring the minimum value of the lower peak hold circuit 303 before the subsequent color shift detection pattern. In order to recover the voltage of the lower peak hold circuit 303 changed by the droop when the interval between the pattern groups is wide, the patterns SG1 and SG2 for obtaining the minimum value by the toner having the lowest gloss are provided before each color shift detection pattern. Provided.

In FIG. 8, 9a-9d, 10a-10
d is a pattern for detecting the amount of color misregistration in the sheet conveyance direction, and 11a to 11d and 12a to 12d are patterns for detecting the amount of color misregistration in the main scanning direction orthogonal to the sheet conveyance direction. In this example, The inclination is 45 degrees. Note that a to d indicate black (hereinafter, BK), yellow (hereinafter, Y), magenta (hereinafter, M), and cyan (hereinafter, C), respectively.

FIG. 9 is a flowchart showing an example of the second color shift correction processing procedure in the image forming apparatus according to the present invention. In addition, S101-S110, S201-S2
06, SN01 to SN06 indicate each step.

Before executing the color misregistration correction, the upper peak hold circuit 301 and the lower peak hold circuit 303 are in a reset state. Here, the reset state in the upper peak hold state is a state where the voltage is fixed to the lowest voltage that the circuit can take. On the other hand, the reset state in the lower peak hold state is a state where the voltage is fixed to the highest voltage that the circuit can take.

When the color misregistration correction processing is started, the light emitting element (LED) 100 emits light (S101). The light emitting element 100 can be turned on / off by turning on / off a switch provided between the light emitting element 100 and a power supply or GND by a signal from the CPU 31.

Next, the reset of the upper peak hold circuit 301 and the lower peak hold circuit 303 is released (S102). Next, a color misregistration detection pattern including at least a pair of minimum value reading patterns SG1 and SG2 made of the toner with the smallest gloss (BK in this example) shown in FIG. 5 is formed.

During this time, since the light receiving element 100 of the color misregistration detecting means looks at the surface of the transport belt 3 having high gloss, the upper peak hold circuit 301 samples a large voltage corresponding to the gloss of the transport belt 3 (S103). Since this voltage is equal to or lower than the reset level of the lower peak hold circuit 303, the lower peak hold circuit 303 also samples the same voltage.

If the reset is released without causing the light emitting element such as an LED to emit light, the lower peak hold circuit 303 detects a dark state because there is no reflected light from the conveyor belt 3 or toner. , The comparison circuit 30
5, the slice level (threshold) exceeds the amplitude of the output of the light receiving element 100, or the slice level and the light receiving element 1
A problem occurs in that the margin with respect to the minimum value of 00 becomes small and becomes weak to noise caused by a scratch or the like on the conveyor belt 3, but this problem can be avoided in the present embodiment.

After a lapse of time, the color misregistration detection pattern moves on the conveyor belt 3, and the light reflected from the minimum value reading patterns SG1 and SG2 prior to the color misregistration detection pattern enters the light receiving element 100. .

Since the gloss of the minimum value reading patterns SG1 and SG2 formed by the toner is lower than that of the transport belt 3, the upper peak hold circuit 301 does not change.
The lower peak hold circuit 303 samples the voltage corresponding to the gross of the patterns SG1 and SG2 for reading the minimum value (S104).

Thus, the upper peak hold circuit 3
When the maximum value and the minimum value are sampled in 01 and the lower peak hold circuit 303, respectively, the slice level of the comparison circuit 305 shown in FIG. 4 is determined by resistance division by the resistors 302 and 304 (S105).

Further, when the transport belt 3 advances (light from the transport belt 3 is incident during this time), the light receiving element 100 shown in FIG.
The reflected light from the color misregistration detection pattern shown in FIG.
Here, the color shift detection patterns of yellow 9, magenta 10, cyan 11, and black 12 are read one by one (S1).
06, S107). The output of the light receiving element 100 is
In order to cross the slice level, the comparison circuit 305 is inverted and a position information pulse is obtained.

Next, it is determined whether all color patterns have been read (S108). If it is determined that all color patterns have not been read, step S108 is performed.
Returning to step 107, if it is determined that all the color patterns have been read, the process proceeds to a process of detecting a second color misregistration detection pattern formed on the transport belt 3 at an interval.
The toner having the smallest gloss shown in FIG.
K), a second color misregistration detection pattern including at least a pair of minimum value reading patterns SG1 and SG2 is formed.

During this time, since the light receiving element 100 looks at the surface of the transport belt 3 with high gloss, the upper peak hold circuit 30
1 samples a large voltage corresponding to the gloss of the transport belt 3 (S201). Since this voltage is equal to or lower than the reset level of the lower peak hold circuit 303,
The lower peak hold circuit 303 also samples the same voltage.

If the reset is released without causing the light emitting element such as an LED to emit light, the lower peak hold circuit 303 detects a dark state because there is no reflected light from the conveyor belt 3 or toner. , The comparison circuit 30
5, the slice level (threshold) exceeds the amplitude of the output of the light receiving element 100, or the slice level and the light receiving element 1
There is a problem in that the margin with respect to the minimum value of 00 becomes small and becomes weak to noise caused by a scratch or the like on the transport belt 3, but this problem can be avoided in the present embodiment.

After a lapse of time, the color misregistration detection pattern moves on the conveyor belt 3, and the light reflected from the minimum value reading patterns SG1 and SG2 prior to the color misregistration detection pattern enters the light receiving element 100. .

Since the gross of the minimum value reading patterns SG1 and SG2 formed by the toner is lower than that of the transport belt 3, the upper peak hold circuit 301 does not change.
The lower peak hold circuit 303 samples the voltage corresponding to the gross of the patterns SG1 and SG2 for reading the minimum value (S202).

Thus, the upper peak hold circuit 3
When the maximum value and the minimum value are sampled by the first and lower peak hold circuits 303, respectively, the slice level of the comparison circuit 305 shown in FIG. 4 is determined by resistance division by the resistors 302 and 304 (S203).

Further, when the transport belt 3 advances (light from the transport belt 3 enters during this time), the light receiving element 100 shown in FIG.
The reflected light from the color misregistration detection pattern shown in FIG.
Here, the color shift detection patterns of yellow 9, magenta 10, cyan 11, and black 12 are read one by one (S2).
05). Then, the output of the light receiving element 100 crosses the slice level, the comparison circuit 305 inverts, and a position information pulse is obtained.

Next, it is determined whether all color patterns have been read (S206). If it is determined that all color patterns have not been read, step S206 is performed.
Returning to 205, when it is determined that all the color patterns have been read, the processing for detecting the N-th color misregistration detection pattern is started, and the process starts from the toner having the smallest gloss (BK in this example) shown in FIG. A second color misregistration detection pattern including at least a pair of minimum value reading patterns SG1 and SG2 is formed (SN01). Thereafter, steps similar to steps S202 to S206 (SN02 to SN
06) is repeated, and in step SN06, when it is determined that all the color patterns have been read, for example, the center position of the rise and fall is determined from the plurality of obtained position information pulses for each toner. The position is obtained, the color misregistration amount of each color is calculated by the above formulas (1) to (16) (S109), and color misregistration correction such as fine adjustment of image frequency and adjustment of write start timing is performed (S110). The process ends.

As described above, in the present embodiment, even if a plurality of color misregistration patterns are spaced apart from each other and a droop occurs in the voltage held by the lower peak hold circuit 303, the color misregistration pattern group starts at the top of each color misregistration pattern group. Since the minimum value is sampled again, the slice level of the comparison circuit that generates the position information detection signal can be the same for any of the color misregistration detection patterns, and accurate position information can be detected. Amount detection is possible. This means that the accuracy of the color misregistration correction also increases.

Although FIG. 8 shows a case where each of the patterns SG1 and SG2 for obtaining the minimum value is one, a plurality of patterns may be used. Also, it is desirable that the minimum value acquisition patterns SG1 and SG2 are equal to or larger than the width of the color misregistration detection pattern. If there is a difference in the gloss of the toner for the same reason, the minimum value of the toner with the lowest gloss is used. It is similar to the first embodiment that it is desirable to form a turn for acquisition.

Although the case where the gloss of the transport belt 3 is higher than the gloss of the toner has been described here, it is needless to say that the same effect can be obtained only by changing the magnitude of the signal in the opposite case. .

Further, when the difference in gloss between the toners of the respective colors is large and there are a toner having a gloss larger than the gloss of the transport belt and a toner having a smaller gloss, FIG.
If the first pattern for peak holding the minimum value added to FIG. 13 in the color misregistration detection pattern is divided into two, a toner having the maximum gloss and a toner having the minimum gloss, the same applies. It goes without saying that it is effective.

[Third Embodiment] In the second embodiment,
A case has been described in which a plurality of color misregistration detection pattern groups are provided, detection is performed a plurality of times, and color misregistration correction is performed based on the results. In the case of leakage, a constant value is always sampled because the light receiving element 100 looks at the surface of the conveyor belt between the patterns. Even if it is seen, the corresponding signal is small and is ignored, and a voltage different from the actual maximum value of the output of the light receiving element 100 is held.

On the other hand, the same applies to the lower peak hold circuit 303. When the pattern leaks to the GND side, the pattern is ignored because the output is large, and the actual light receiving element 100
A voltage different from the minimum value of the output is maintained.

Therefore, merely providing a pattern for obtaining a minimum value before each color shift detection pattern cannot correct an error in the slice level of the comparison circuit 305 for generating a position information detection signal, and the color shift detection pattern cannot be corrected. There is a problem that it becomes impossible to detect the noise, or noise due to the damage of the transport belt 3 is detected as a color shift detection pattern.

Therefore, when releasing the reset of the upper and lower peak hold circuits 301 and 303 at the start of the color shift correction, in addition to turning on the light emitting elements in advance, once the plurality of color shift detection patterns After resetting the upper and lower peak hold circuits 301 and 303, the maximum value and the minimum value of the output of the light receiving element 100 may be acquired again. Hereinafter, the embodiment will be described.

FIG. 10 is a flowchart showing an example of the third color shift correction processing procedure in the image forming apparatus according to the present invention. In addition, S101-S110, S201-S
207, SN01 to SN06, SS1, and SSN indicate respective steps. The timing with FIG. 6 is indicated by.

Before the color misregistration correction is performed, the upper peak hold circuit 301 and the lower peak hold circuit 303 are in a reset state. Here, the reset state in the upper peak hold state is a state where the voltage is fixed to the lowest voltage that the circuit can take. On the other hand, the reset state in the lower peak hold state is a state where the voltage is fixed to the highest voltage that the circuit can take.

When the color misregistration correction processing is started, the light emitting element (LED) 100 emits light (S101). The light emitting element 100 can be turned on / off by turning on / off a switch provided between the light emitting element 100 and a power supply or GND by a signal from the CPU 31.

Next, the reset of the upper peak hold circuit 301 and the lower peak hold circuit 303 is released (S102). Next, a color misregistration detection pattern including at least a pair of minimum value reading patterns SG1 and SG2 made of the toner with the smallest gloss (BK in this example) shown in FIG. 5 is formed (S103).

During this time, since the light receiving element 100 is looking at the surface of the transport belt 3 with high gloss, the upper peak hold circuit 30
1 samples a large voltage corresponding to the gloss of the transport belt 3 (S103). Since this voltage is equal to or lower than the reset level of the lower peak hold circuit 303, the lower peak hold circuit 303 also samples the same voltage.

If the reset is released without causing the light emitting element such as the LED to emit light, the lower peak hold circuit 303 detects a dark state because there is no reflected light from the conveyor belt 3 or toner. , The comparison circuit 30
5, the slice level (threshold) exceeds the amplitude of the output of the light receiving element 100, or the slice level and the light receiving element 1
A problem occurs in that the margin with respect to the minimum value of 00 becomes small and becomes weak to noise caused by a scratch or the like on the conveyor belt 3, but this problem can be avoided in the present embodiment.

After a lapse of time, the color misregistration detection pattern moves on the conveyor belt 3, and the light reflected from the minimum value reading patterns SG1 and SG2 prior to the color misregistration detection pattern enters the light receiving element 100. .

Since the gloss of the minimum value reading patterns SG1 and SG2 formed by the toner is lower than that of the transport belt 3, the upper peak hold circuit 301 does not change.
The lower peak hold circuit 303 samples the voltage corresponding to the gross of the patterns SG1 and SG2 for reading the minimum value (S104).

Thus, the upper peak hold circuit 3
When the maximum value and the minimum value are sampled in 01 and the lower peak hold circuit 303, respectively, the slice level of the comparison circuit 305 shown in FIG. 4 is determined by resistance division by the resistors 302 and 304 (S105).

Further, when the transport belt 3 advances (light from the transport belt 3 enters during this time), the light receiving element 100 shown in FIG.
The reflected light from the color misregistration detection pattern shown in FIG.
Here, the color shift detection patterns of yellow 9, magenta 10, cyan 11, and black 12 are read one by one (S1).
07). Then, the output of the light receiving element 100 crosses the slice level, the comparison circuit 305 inverts, and a position information pulse is obtained.

Next, it is determined whether or not all color patterns have been read (S108). If it is determined that all color patterns have not been read, the process proceeds to step S108.
Returning to step 107, if it is determined that all the color patterns have been read, the upper and lower peak hold circuits 301 and 303 are reset once before reading the next spaced second color shift detection pattern group. And then release (SS
1).

As a result, even if the peak hold circuit causes a droop in the power supply voltage direction between the color misregistration pattern groups,
Even if droop occurs in the ND direction, it is reset once,
After the reset is released, the reflected light of the belt surface and the reflected light of the toner for obtaining the minimum value are read again, so that the light receiving element 1 can be read.
The accurate maximum value and minimum value of 00 can be held, and an accurate slice level of the comparison circuit that detects the positional information of the color misregistration detection pattern can be obtained.

Next, a process for detecting a second color misregistration detection pattern formed on the transport belt 3 at intervals is started.
(In this example, BK)
A second color misregistration detection pattern including at least a pair of minimum value reading patterns SG1 and SG2 is formed.

During this time, since the light receiving element 100 looks at the surface of the transport belt 3 with high gloss, the upper peak hold circuit 30
1 samples a large voltage corresponding to the gloss of the transport belt 3 (S201). Since this voltage is equal to or lower than the reset level of the lower peak hold circuit 303,
The lower peak hold circuit 303 also samples the same voltage. Thereafter, step S202 is the same as in the second embodiment.
When it is determined in step S206 that all the color patterns have been read, the upper and lower peak hold circuits are once executed before reading the next spaced N-th color shift detection pattern group. After resetting 301 and 303, it is released (SSN).

Thereafter, the same step SN as in the second embodiment is performed.
01 to SN06, steps S109 and S110 are executed.

As described above, in the above embodiment, the intervals between the plurality of color misregistration pattern groups are wide, and a droop is generated in the voltage held by the lower peak hold circuit 303 in either the power supply or the GND direction. However, since both peak hold circuits 301 and 303 are reset once, the minimum value is sampled again at the head of each color shift pattern group, so that a comparison circuit for generating a position information detection signal for any color shift detection pattern. Since the slice level of 305 can be made the same and accurate position information is detected, it is possible to detect a color shift amount with higher accuracy. This means that the accuracy of the color misregistration correction also increases.

In the example of the color misregistration detection pattern shown in FIG. 8, the case where the number of the patterns for obtaining the minimum value is one is described. However, it is needless to say that a plurality of patterns may be obtained. Further, it is desirable that the pattern for obtaining the minimum value is equal to or larger than the width of the color misregistration detection pattern. If there is a difference in the gloss of the toner for the same reason, the toner having the lowest gloss is used for obtaining the minimum value. Desirable to form a pattern is the same as in the first embodiment.

The reset release timing of the peak hold circuit between the color shift detection pattern groups is as close as possible to the next color shift detection pattern after securing the sampling time of the upper and lower peak hold circuits 301 and 303. Is more advantageous in terms of droop.

Further, although the case where the gloss of the conveyor belt 3 is higher than the gloss of the toner has been described here, it is needless to say that the same effect can be obtained even in the opposite case, except that the magnitude of the signal is reversed. .

Further, when the difference in gloss between the toners of the respective colors is large and there are a toner having a gloss larger than the gloss of the transport belt and a toner having a smaller gloss, FIG.
In the color misregistration detection pattern shown in (1), if the first pattern for peak-holding the minimum value added to FIG. 13 is divided into two, a toner having the maximum gloss and a toner having the minimum gloss. It goes without saying that there is a similar effect.

According to each of the above embodiments, the light emitting device 100
A peak hold circuit is provided in a color misregistration correction device of a color image forming apparatus which holds a maximum value and a minimum value of a signal from a color image forming apparatus and determines a slice level of a comparison circuit for detecting position information based on the signal. Since the light emitting element is turned on before the resetting of the light receiving element is started, it is possible to prevent the dark state from being erroneously held by the lower peak hold circuit, so that the correct maximum value and minimum value of the light receiving element 100 can be held. Therefore, since the slice level of the comparison circuit that generates the position information detection signal can be set correctly, accurate position information of the color shift detection pattern can be obtained, and the accuracy of color shift correction can be improved.

Further, when color misregistration detection is performed using a plurality of color misregistration detection patterns, since a pattern for detecting a minimum value (or maximum value) is provided immediately before each color misregistration detection pattern, droop occurs in the peak hold circuit. Therefore, resampling can be performed and the slice level of the comparison circuit that generates the position information detection signal can be set correctly, so that accurate position information of the color misregistration detection pattern can be obtained and the accuracy of color misregistration correction can be improved Can be.

In the case of performing color shift detection using a plurality of color shift detection patterns, after resetting two peak hold circuits once immediately before each color shift detection pattern,
Since the maximum value and the minimum value are sampled again and the color misregistration detection pattern is read, resampling can be performed even if droop occurs in the power supply direction or the GND direction in the peak hold circuit, and a position information detection signal is generated. Since the slice level of the comparison circuit can be set correctly, accurate positional information of the color misregistration pattern can be obtained, and the accuracy of color misregistration correction can be improved.

In each of the above embodiments, the case where the color misregistration detection pattern is read using the regular reflection optical system has been described as an example. The invention is applicable.

In each of the above-described embodiments, the color misregistration detection pattern is read using the regular reflection optical system, and the image misregistration correction is performed by adjusting the image position of another image station based on the amount of misregistration from the reference color. Although the forming apparatus has been described as an example, the present invention can be applied to an image forming apparatus that adjusts the image position of each color to a predetermined reference position.

Hereinafter, the configuration of a data processing program readable by an image processing system to which the image forming apparatus according to the present invention can be applied will be described with reference to a memory map shown in FIG.

FIG. 11 is a view for explaining a memory map of a storage medium for storing various data processing programs which can be read by an image processing system to which the image forming apparatus according to the present invention can be applied.

Although not shown, information for managing a group of programs stored in the storage medium, such as version information and a creator, is also stored, and information dependent on the OS or the like on the program reading side, such as a program, An icon or the like for identification display may also be stored.

Further, data dependent on various programs is also managed in the directory. In addition, a program for installing various programs on a computer or a program for decompressing a program to be installed when the program to be installed is compressed may be stored.

The functions shown in FIGS. 7, 9 and 10 in the present embodiment may be executed by a host computer by a program installed from the outside. In this case, the present invention is applied even when a group of information including a program is supplied to the output device from a storage medium such as a CD-ROM, a flash memory, or an FD, or from an external storage medium via a network. Things.

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 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.

As storage media for supplying the program code, for example, a floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, C
D-ROM, CD-R, magnetic tape, nonvolatile memory card, ROM, EEPROM, etc. 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 into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instructions 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.

[0159]

As described above, the first embodiment according to the present invention is described.
According to the nineteenth aspect, before the detection of the color misregistration detection pattern image, the stored maximum value and the minimum value are reset, and then the light emitting unit forming the regular reflection optical system is turned on, and the color misregistration is detected. After the detection pattern image is read, the reset is released, and the light-emitting unit is turned off, and the position based on the light amount signal is obtained from the maximum value and the minimum value stored when the color misregistration detection pattern image is read. A reference value for generating an information signal is generated, a color shift amount between each color image is calculated based on the generated position information signal, and each image other than the reference color is calculated based on the calculated color shift amount. Since the position of the image is corrected and controlled by the forming station, it is possible to prevent a dark state in which the light emitting unit is not lit from being erroneously stored as the minimum value of the color misregistration detection pattern, and prevent the position detection accuracy of the color misregistration detection pattern from being deteriorated. This Can.

When detecting the position information of a plurality of color misregistration detection patterns, the pattern is read immediately before the position detection of each color misregistration detection pattern, so that the maximum value or the minimum value corresponding to the retained amount of reflected toner is maintained. By recovering the droop of the value, it is possible to prevent deterioration in the accuracy of position detection of the color misregistration detection pattern.

Further, when position information of a plurality of color misregistration detection patterns is detected, the maximum value and the minimum value are reset once between the color misregistration detection patterns, and then,
Since the pattern is read immediately before the next color misregistration detection pattern, the maximum value and minimum value of the correct color misregistration detection pattern are sampled again to prevent the accuracy of position detection of the color misregistration detection pattern from being deteriorated. This produces effects such as realizing deviation correction.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view illustrating an example of a color image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic explanatory diagram illustrating a detailed configuration of a sensor illustrated in FIG. 1;

FIG. 3 is a block diagram for explaining a color misregistration processing mechanism in the color image forming apparatus according to the present invention.

FIG. 4 is a block diagram illustrating an example of a color misregistration detection processing circuit in the color image forming apparatus according to the first exemplary embodiment of the present invention.

FIG. 5 is a diagram showing an example of a color misregistration detection pattern in the image forming apparatus according to the present invention.

FIG. 6 is a timing chart for explaining the operation of the color misregistration detection circuit shown in FIG.

FIG. 7 is a flowchart illustrating an example of a first color misregistration correction processing procedure in the image forming apparatus according to the present invention.

FIG. 8 is a diagram illustrating an example of a color misregistration detection pattern in an image forming apparatus according to a second embodiment of the present invention.

FIG. 9 is a flowchart illustrating an example of a second color misregistration correction processing procedure in the image forming apparatus according to the present invention.

FIG. 10 is a flowchart illustrating an example of a third color shift correction processing procedure in the image forming apparatus according to the present invention.

FIG. 11 is a diagram illustrating a memory map of a storage medium that stores various data processing programs that can be read by an image processing system to which the image forming apparatus according to the present invention can be applied.

FIG. 12 is a diagram illustrating a color misregistration state in this type of color image forming apparatus.

FIG. 13 is a diagram illustrating an example of a color misregistration detection pattern formed on a transport belt of a color image forming apparatus of this type.

FIG. 14 is a block diagram illustrating an example of a color misregistration detection processing circuit in this type of color image forming apparatus.

15 is a characteristic diagram showing an example of a pattern detection waveform by the color misregistration detection processing circuit shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Laser scanner 3 Conveyor belt 6 Optical sensor 9-12 Conventional color misregistration detection pattern 13, 14 Minimum value detection toner pattern 51 Light emitting element 52 Light receiving element CONT Control unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/29 G03G 21/00 372 F term (Reference) 2F065 AA14 AA49 AA56 BB02 CC02 DD03 DD04 FF42 GG07 JJ18 PP15 QQ02 QQ08 QQ25 QQ29 QQ34 2G020 AA08 DA24 DA34 DA43 DA65 2H027 DA09 DE02 DE07 EB04 ED04 ED16 EE08 EF09 2H030 AA01 AB02 AD17 BB16 BB44 BB56 5C074 AA07 AA10 AA15 DD15 DD16 DD24 EE11 GG19 GG19 GG19 GG15 GG11 GG19 GG15 GG11 GG19 GG15 GG11 GG19 GG15

Claims (19)

[Claims] 1. An image forming apparatus capable of forming a color image by arranging a plurality of image forming stations side by side and sequentially transferring the images formed in the respective image forming stations onto recording paper conveyed by a conveying body. Forming a reference color pattern image by a predetermined image forming station and a color misregistration detection pattern image by another image forming station on the carrier, among the plurality of image forming stations; A light emitting unit and a light receiving unit on which a regular reflection optical system is formed to read the series of color misregistration detection pattern images formed by the pattern forming unit, and a light amount signal read by the light receiving unit. Storage means for storing a maximum value and a minimum value obtained by converting into a voltage signal; and the maximum value and the minimum value stored in the storage means Reset means for resetting a value and a first control means for performing reset by the reset means before detecting the color misregistration detection pattern image, turning on the light emitting unit during the reset, and then canceling the reset. Generating means for generating a reference value for generating a position information signal based on the light amount signal from the maximum value and the minimum value stored in the storage means during a reset release state by the first control means; Calculating means for calculating a color shift amount between the respective color images based on the position information signal generated by the generating means; and forming each image other than the reference color based on the color shift amount calculated by the calculating means. An image forming apparatus comprising: a second control unit configured to perform correction control of a position of an image by a station. 2. The image forming apparatus according to claim 1, wherein the pattern forming unit is configured to transfer a pattern group including a reference color pattern image from a predetermined image forming station and a color misregistration detection pattern image from another image forming station among the plurality of image forming stations. At least one dedicated pattern is formed immediately before each pattern group when an interval between each pattern group is longer than an interval between one color misregistration detection pattern image. Item 2. The image forming apparatus according to Item 1. 3. The image processing apparatus according to claim 1, wherein the first control unit is configured to, among the plurality of image forming stations, generate a pattern group including a reference color pattern image by a predetermined image forming station and a color misregistration detection pattern image by another image forming station. When the distance between each pattern group is longer than the distance between one color misregistration detection pattern image when forming on the carrier, the maximum value and the minimum value based on the immediately preceding pattern group stored in the storage means. 2. The image forming apparatus according to claim 1, wherein the resetting is performed by the reset unit. 4. The first control means stores the maximum value and the minimum value of the surface reflected light of the image carrier of the carrier and the surface reflected light of the dedicated pattern in the storage means after the resetting by the resetting means. The image forming apparatus according to claim 3, wherein the image is stored. 5. The storage device according to claim 1, wherein the first control means stores a dedicated pattern formed immediately before each pattern group or a maximum value based on the amount of reflected light received from the surface of the carrier. Item 5. The image forming apparatus according to any one of Items 1, 3, and 4. 6. The storage device according to claim 1, wherein the first control means stores a dedicated pattern formed immediately before each pattern group or a minimum value based on the amount of reflected light received from the surface of the carrier. Item 5. The image forming apparatus according to any one of Items 1, 3, and 4. 7. The image forming apparatus according to claim 2, wherein the width of the dedicated pattern is equal to or larger than the image width of the color misregistration detection pattern. . 8. The method according to claim 1, wherein the pattern forming unit is configured to determine whether or not the reflectance of the carrier is higher than the reflectance of the color misregistration detection pattern.
The dedicated pattern is formed with toner having the lowest reflectance,
When the reflectance of the carrier is lower than the reflectance of the toner,
2. The image forming apparatus according to claim 1, wherein the dedicated pattern is formed with a toner having the highest reflectance. 9. The pattern forming means according to claim 1, wherein a reflectance of light directly reflected from said carrier by turning on said light emitting portion is a reflectance range of light reflected from a plurality of color toners formed on said carrier. 4. The image forming apparatus according to claim 3, wherein the special pattern is formed of a toner having the same color as the toner having the highest reflectance or the toner having the lowest reflectance. 10. A color image forming apparatus capable of forming a color image by arranging a plurality of image forming stations side by side and sequentially superimposing and transferring the images formed in each image forming station onto recording paper conveyed by a conveying body. A shift detection processing method, wherein, among the plurality of image forming stations, a reference color pattern image by a predetermined image forming station and a color shift detection pattern image by another image forming station are formed on the carrier. A pattern forming step of controlling image formation in the image forming station; and a series of color misregistration detection pattern images formed in the pattern forming step are read by a light emitting unit and a light receiving unit on which a regular reflection optical system is formed. A storage step of storing a maximum value and a minimum value obtained by converting a light amount signal read by the unit into a voltage signal in a storage unit; A resetting step of resetting the maximum value and the minimum value stored in the unit, and before the detection of the color misregistration detection pattern image, performing the resetting in the resetting step, turning on the light emitting unit during resetting, and thereafter resetting And a position information signal based on the light amount signal is generated from the maximum value and the minimum value stored in the storage unit during a reset release state by the first control step. A calculating step of generating a reference value for calculating a color shift amount between the respective color images based on the position information signal generated by the generating step; and a color shift amount calculated by the calculating step. A second control step of correcting and controlling the position of an image by each image forming station other than the reference color based on the reference color. Method. 11. The method according to claim 11, wherein, in the pattern forming step, a pattern group including a reference color pattern image by a predetermined image forming station and a color misregistration detection pattern image by another image forming station is selected from the plurality of image forming stations. When forming on top, the interval between each pattern group is 1
11. The color misregistration detection processing method for an image forming apparatus according to claim 10, wherein at least one dedicated pattern is formed immediately before each pattern group when the distance is longer than the interval between two color misregistration detection pattern images. 12. The image forming apparatus according to claim 1, wherein the first control step includes, among the plurality of image forming stations, a pattern group including a reference color pattern image by a predetermined image forming station and a color misregistration detection pattern image by another image forming station. When the distance between each pattern group is longer than the distance between one color misregistration detection pattern image when forming on the carrier, the maximum value and the minimum value based on the immediately preceding pattern group stored in the storage unit. 11. The method according to claim 10, wherein the resetting is performed in the resetting step. 13. The storage device according to claim 1, wherein the first control step stores, in the storage unit, a maximum value and a minimum value of the surface reflected light of the image carrier of the carrier and the surface reflected light of the dedicated pattern after the reset in the resetting step. 13. The color misregistration detection processing method for an image forming apparatus according to claim 12, wherein the color misregistration is stored. 14. The method according to claim 1, wherein in the first control step, a dedicated pattern formed immediately before each pattern group or a maximum value based on the amount of reflected light received from the surface of the carrier is stored in the storage unit. Item 14. A color misregistration detection processing method for an image forming apparatus according to any one of Items 10, 12, and 13. 15. The method according to claim 1, wherein the first control step stores the dedicated pattern formed immediately before each pattern group or a minimum value based on the amount of reflected light received from the surface of the carrier. Item 14. A color misregistration detection processing method for an image forming apparatus according to any one of Items 10, 12, and 13. 16. The image forming apparatus according to claim 11, wherein the width of the dedicated pattern is equal to or larger than the image width of the color misregistration detection pattern. Color misregistration detection processing method. 17. In the pattern forming step, when the reflectance of the carrier is higher than the reflectance of the color misregistration detection pattern, the dedicated pattern is formed with toner having the lowest reflectance. 13. The color misregistration detecting method according to claim 12, wherein, when is smaller than the reflectance of the toner, the dedicated pattern is formed by toner having the highest reflectance. 18. The pattern forming step, wherein the reflectance of light directly reflected from the carrier by turning on the light emitting unit is a reflectance range of light reflected from a plurality of color toners formed on the carrier. 13. The color misregistration detection processing method of the image forming apparatus according to claim 12, wherein, if included, the dedicated pattern is formed with a toner having the same color as the toner having the highest reflectance or the toner having the lowest reflectance. 19. An image forming apparatus in which a plurality of image forming stations are juxtaposed, and an image formed in each image forming station is sequentially overlaid and transferred onto a recording sheet conveyed by a conveying body to obtain a color image. Pattern forming means for controlling the plurality of image forming stations so as to form a color misregistration detection pattern image of each color on the carrier; and each color misregistration detection pattern formed on the carrier by the plurality of image forming stations. Reading means for reading an image with a light emitting unit and a light receiving unit, storage means for storing a maximum value and a minimum value of a light amount signal output from the light receiving unit, and a maximum value and a minimum value stored by the storage means Reset means for resetting the color shift detection pattern image by the reading means, A first control unit for performing a set operation and causing the light emitting unit to emit light during the reset, and thereafter releasing the reset operation; and the maximum value stored in the storage unit in a reset release state by the first control unit. Position detection means for detecting the position of each of the color misregistration detection pattern images based on a value and a minimum value and a light amount signal output from the reading means; formed by the plurality of image forming stations based on the output of the position detection means An image forming apparatus comprising: a correction unit configured to correct a position of each color image to be performed.