JP2001318501A - Image forming device and color slippage detection method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct a color slippage by detecting with a small amount of light a difference in reflection coefficient between a color slipped pattern which is transferred to a carrier body, and the carrier body without being affected by a state of the surface of the carrier body and without being affected by the color of the transfer side of the carrier body. SOLUTION: A reference voltage is variably set. The reference voltage is used for reading via a regular reflection optical system a series of color slippage detection pattern images based on a reflecting state of the ground of the carrying belt 3, which is detected by optical sensors 6a and 6b forming the regular reflection optical system. A control unit CONT compares the reference voltage with output signals from the optical sensors 6a and 6b to generate a pulse signal. The control unit then computes amounts of color slippages between the color images based on the generated pulse signals. Based on the computed amounts of the color slippages, the control unit then corrects the positions of the images, except a reference color image, which are formed at associated image forming stations.

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

In FIG. 16, reference numeral 7 denotes an original image position;
Reference numeral 8a denotes an image position when a color shift has occurred. In FIG. 16, (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) and the length of the scanning line is changed to correct in the direction of the arrow.

FIG. 3C shows a writing position error in the main scanning direction. For example, if the optical unit is a laser scanner, the 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) executes the various adjustments as described above electrically or mechanically to perform the color shift correction control.

FIG. 17 is a view for explaining a mechanism for detecting a color misregistration pattern formed on a transport belt of this type of color image forming apparatus. FIG. 17 shows a case where the light emitting element 51 and the light receiving element 52 are configured by a diffuse reflection optical system using the transport belt 3 as a reflection surface.

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, 9a-9d, 10a-
10d, 11a to 11d and 12a to 12d are color misregistration detection patterns. In addition, patterns 9, 10, 11, 12
Is shown as one, but it corresponds to a state of passing directly below the light receiving element 52, and is assumed to be originally formed on the transfer belt at a predetermined interval.

Reference numeral 53 denotes light emitted from the light emitting element 51.
54a is a conveyor belt or a color shift detection pattern 9, 1;
Among the reflected lights from 0, 11, and 12, the received light is received by the light receiving element 52.

[0015]

Since the color misregistration detecting mechanism in the conventional color image forming apparatus is configured as described above, in the case of using the irregular reflection optical system, the color shift detecting mechanism is compared with the irradiation light amount of the light emitting section. Since the amount of light received by the light receiving unit is small, it is difficult to obtain a sufficient amount of light for detection. As a countermeasure, for example, it is necessary to arrange a plurality of light emitting elements 51 around the light receiving element 52 or to use a light source having a large amount of emitted light. However, there is a problem that both measures cause a cost increase.

In addition, since it is affected by the spectral sensitivity of the transport belt 3 and the color shift detection patterns 9, 10, 11, and 12,
There are various restrictions on the wavelength of the light emitting element 51, the color of the transport belt 3, and the method of forming the color misregistration detection pattern. For example, the wavelength of the light emitting element 51 generally uses an infrared region that exhibits reflection characteristics for all three colors of YMC. In this case, Bk has absorption characteristics.

Therefore, the polarity of the detection waveform of the light receiving element 52 at the time of Bk measurement is opposite to that at the time of detection of other colors, and the detection level also needs to be different from the other colors. Note that the transport belt 3 generally has a large amount of black (Bk), but this makes it impossible to detect a color shift detection pattern of Bk formed on the transport belt 3.

As a countermeasure, the surface of the conveyor belt 3 is colored gray, or a solid pattern (patch image pattern) of any of YMC is formed below the color shift detection pattern of Bk to improve the reflectance of the base. However, the former countermeasure causes a cost increase, and the latter countermeasure has a problem that the amount of waste toner increases.

When a registration mark is detected through a diffuse reflection optical system, a pulse waveform is generated by comparing a predetermined reference voltage value with a measured waveform for a pattern, and the method is used as registration mark position information. There are problems as described below.

For example, an LED is often used as a light source of a sensor for detecting a registration mark. However, since the LED has a large individual variation in the amount of light emission, a mechanism for adjusting the amount of light emission or a sensitivity of an I / V conversion circuit is required. A mechanism for adjusting or a mechanism for adjusting the reference voltage value according to the light emission amount is required.

[0021] Then, although a method of performing adjustment in production by providing a volume, etc. on the circuit is commonly, a problem that costs absolutely since it takes labor increases occur in the regulation work.

In addition, when the light source reduces the light amount due to deterioration over time or the like, or when the gloss value of the object to be measured decreases due to deterioration over time, there arises a problem that the balance between the measured waveform and the reference voltage value is lost. .

As a solution to the above problem, there is a method in which a sensor detection waveform is read into an CPU through an A / D input port and the amount of light emitted from an LED or a reference voltage value is adjusted in accordance with the output. .

However, the A / D of the CPU, which tends to run short
It is not practical because it uses ports and cannot respond to fine fluctuations in output waveforms in terms of response speed.

Further, as described in the above conventional example,
In such a reflection type optical system, a regular reflection optical system that can increase the amount of light detected by the light receiving unit is often used, but on the other hand, since the regular reflection optical system responds to the magnitude of the gloss value, it is placed on the image carrier. It is also sensitive to the decrease in gloss value caused by the scratches. For this reason, in the case of an image carrier having been repeatedly used and having increased scratches, a case may occur in which the scratches are erroneously detected as registration marks.

The present invention has been made to solve the above problems, and an object of the present invention is to read a series of color misregistration detection pattern images formed on a carrier through a regular reflection optical system. At this time, a reference voltage for reading the series of color misregistration detection pattern images via the regular reflection optical system is variably set based on the detected base reflection state of the carrier, and the reference voltage and the reference voltage are output from the light receiving element. A pulse signal is generated by comparing the output signal with each other, a color shift amount between the respective color images is calculated based on the generated pulse signal, and each image other than the reference color is calculated based on the calculated color shift amount. By correcting and controlling the position of the image by the forming station, each color transferred to the carrier with a small amount of light without being affected by the surface condition of the carrier and without being affected by the transfer surface color of the carrier. With the shift pattern Detects the difference in reflectance from the transmitter itself, accurately calculates the amount of color misregistration with a simple and inexpensive configuration, and superimposes the color images formed in each image forming station with high accuracy to eliminate color misregistration. An object of the present invention is to provide an image forming apparatus capable of forming an image and a color misregistration detection processing method of the image forming apparatus.

[0027]

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 forming a color image by transferring, wherein, among the plurality of image forming stations, a reference color line pattern image by a predetermined image forming station and a color misregistration detection pattern image by another image forming station. A pattern forming unit (corresponding to the CPU 31 shown in FIG. 3) for controlling image formation of each image forming station so as to form the image on the carrier, and the series of color misregistration detection pattern images formed by the pattern forming unit; Pattern detecting means (CPU 31 shown in FIG. 3) for reading the background reflection state of the carrier through the regular reflection optical system
And setting means for variably setting a reference voltage for reading the series of color misregistration detection pattern images via a regular reflection optical system based on a base reflection state of the carrier detected by the pattern detection means. A signal generation means (corresponding to the CPU 31 shown in FIG. 3) for generating a color shift detection pulse signal by comparing the amount of reflected light detected by the pattern detection means with a reference voltage set by the setting means. And a calculating unit (calculating unit 3 shown in FIG. 3) for calculating the amount of color shift between the respective color images based on the color shift detection pulse signal generated by the signal generating unit.
4) and control means (CP 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 calculated by the calculation means.
U31).

According to a second aspect of the present invention, the signal generation means generates a pulse signal obtained by shaping a waveform of an output signal from the pattern detection means based on the reference voltage.

According to a third aspect of the present invention, in the above-mentioned first aspect, the arithmetic means includes a detecting means for detecting a pattern from the pattern detecting means obtained from the regular reflection optical system in which two light receiving elements adjacent to each other in the transport direction of the transport body are provided. The color shift amount is calculated by detecting the intersection of two output signals.

According to a fourth aspect of the present invention, in the image forming apparatus, the setting means is lower than an output signal amplitude value detected by the pattern detecting means at the time of reflection of the background of the carrier, and the series of color misregistration detections is performed. The reference voltage for enabling the pattern image to be read via the regular reflection optical system is variably set.

In a fifth aspect according to the present invention, the setting means corrects the series of color misregistration detection pattern images based on an output signal amplitude state detected by the pattern detection means at the time of reflection of the background of the carrier. The reference voltage for reading through the reflection optical system is variably set.

In a sixth aspect according to the present invention, the setting means detects a pulse width of an output signal detected by the pattern detection means at the time of reflection of the background of the carrier, and sets the detected pulse width to the detected pulse width. The reference voltage for reading the series of color misregistration detection pattern images via the regular reflection optical system is set variably.

According to a seventh aspect of the present invention, the setting means detects the number of pulses of the output signal at the time of reflection of the background of the carrier detected by the pattern detecting means, and determines the number of pulses as the number of detected pulses. The reference voltage for reading the series of color misregistration detection pattern images via the regular reflection optical system is set variably.

According to an eighth 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. 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 line pattern image by a predetermined image forming station and a color misregistration detection pattern image by another image forming station are used. A pattern forming step (step (5) shown in FIG. 7, step (16) shown in FIG. 8, etc.) for controlling image formation of each image forming station so as to form on a carrier, and the pattern forming step A pattern detecting step of reading the series of color misregistration detection pattern images or the base state of the carrier through a regular reflection optical system (see FIG. 7). Step (2), Step (12) shown in FIG. 8, etc.), and the series of color misregistration detection pattern images via the regular reflection optical system based on the base reflection state of the carrier detected in the pattern detection step. A setting step for variably setting a reference voltage for reading (step (15) shown in FIG. 8 and step (25) shown in FIG. 12), the amount of reflected light detected by the pattern detecting step, and the setting of the setting step A signal generation step of generating a color shift detection pulse signal by comparing with a reference voltage; and a calculation step of calculating a color shift amount between the respective color images based on the color shift detection pulse signal generated by the signal generation step (FIG. 7, step (18) shown in FIG. 8, step (28) shown in FIG. 12, and the color misregistration amount calculated in the calculation step. Control step of correcting control the position of the image by each image forming station is one having a (step (41) shown in FIG. 13).

According to a ninth aspect of the present invention, in the signal generating step, a pulse signal is generated by shaping a waveform of an output signal from the pattern detecting step based on the reference voltage.

According to a tenth aspect of the present invention, in the calculation step, the pattern detecting means provided from the regular reflection optical system in which two light receiving elements adjacent to each other in the transport direction of the transport body are provided. The point of intersection of the two output signals (shown in FIG. 11) is detected to calculate the amount of color shift.

According to an eleventh aspect of the present invention, in the setting step, the output signal amplitude value detected when the pattern detection step detects the background of the carrier and the series of color misregistration detections is performed. The reference voltage for enabling the pattern image to be read via the regular reflection optical system is variably set.

According to a twelfth aspect of the present invention, in the setting step, the series of color misregistration detection pattern images is corrected based on an output signal amplitude state at the time of reflection of the background of the carrier detected in the pattern detection step. The reference voltage for reading through the reflection optical system is variably set.

According to a thirteenth aspect of the present invention, the setting step (step (14), step (15) shown in FIG. 8)
Detects a pulse width of an output signal at the time of base reflection of the carrier detected by the pattern detection step, and, based on the detected pulse width, transmits the series of color misregistration detection pattern images via a regular reflection optical system. The reference voltage for reading by reading is variably set.

The fourteenth invention according to the present invention is directed to the setting step (step (24) shown in FIG. 12, step (2)
5)) detecting the number of pulses of the output signal at the time of reflection of the base of the carrier detected in the pattern detection step, and forming the series of color misregistration detection pattern images on the basis of the detected number of pulses; The reference voltage for reading through the system is variably set.

According to a fifteenth aspect of the present invention, an image is obtained by arranging a plurality of image forming stations side by side and sequentially transferring the images formed at each image forming station onto a recording medium conveyed by a conveying body. An image forming apparatus, comprising: a pattern forming unit configured to control an image forming process of the plurality of image forming stations so as to form a pattern image for alignment on the carrier; A light emitting unit for irradiating, reading means for reading the reflected light of the carrier or the pattern image formed on the carrier by the light emitting unit, and a threshold value according to a reading output of the reflected light of the carrier by the reading means Is formed by the plurality of image forming stations based on the threshold value and the output of reading the pattern image by the reading unit. A color misregistration detecting means for detecting a color misregistration amount between the images, and a correction for compensating the color misregistration between the images formed by the plurality of image forming stations based on the color misregistration amount detected by the color misregistration detecting means. Means.

In a sixteenth aspect of the present invention, the color misregistration detecting means compares the threshold value with a read output signal of the pattern image, and detects the color misregistration amount based on the comparison result. .

According to a seventeenth aspect of the present invention, the color misregistration detecting means has a comparing means for comparing the threshold value with a read output signal of the reflected light of the carrier and generating a pulse based on the comparison result. Then, the threshold value is set based on a pulse output by the comparing means.

According to an eighteenth aspect of the present invention, the color shift detecting means sets the threshold value in accordance with the number of the pulses.

According to a nineteenth aspect of the present invention, the color shift detecting means sets the threshold value in accordance with the pulse width.

[0046]

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 Reference numeral 2d denotes a laser scanner that performs exposure in accordance with an image signal to form an electrostatic latent image on the photosensitive drum 1, and 3 denotes an endless transport belt that also serves as a transfer belt that sequentially transports a sheet to an image forming unit of each color. , Driven by a driving roller 4 driven by a belt motor (not shown).

The driving roller 4 is connected to a driving means including a motor and gears (not shown) 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, which are provided on the belt end side so as to be orthogonal to the conveyance direction of the conveyance belt 3 for detecting a color misregistration detection pattern formed on the conveyance belt 3. A control unit CONT includes a CPU, a RAM, and a ROM (not shown).
By executing the control program stored in M,
A sensor signal input through an input port (not shown),
By processing image data and the like, engine unit drive control, laser scanner 2 drive control, and the like are performed.

Data to be printed is sent from a personal computer (PC) constituted by a host computer (not shown) to the printer, and when image formation according to the printer engine system is completed and the printer is ready for printing, a paper cassette (not shown) is used. 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 1, 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. 4 is formed on each of the image forming stations on the transport belt 3 as described above. Sensor 6a, 6 provided on the side
b, and the amount of color misregistration between the colors is detected.

FIG. 2 is a schematic explanatory view for explaining the detailed configuration of the sensors 6a and 6b shown in FIG. 1, and corresponds to a case where the pattern reading system is constituted 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 pattern for detecting a color shift.

Reference numeral 53 denotes light emitted from the light emitting element 51.
Reference numeral 54b denotes received light, which is received by the light receiving element 52 from the reflected light from the conveyor belt 3 or the color shift detection pattern images (color shift detection patterns) 9, 10, 11, and 12.

In the present embodiment, the light emitting portion and the light receiving portion 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 regular reflection light of the color misregistration detection pattern is 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, 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 variation of the gloss value may be detected by the sensors 6a and 6b using a regular reflection optical system to detect the color misregistration 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 shift amount and the correction value by calculating the detection data detected by the pattern detection unit 32 including the LED light emitting unit and the 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 diagram showing an example of a color misregistration detection pattern formed on the transport belt shown in FIG. Hereinafter, FIG.
Will be described in detail below.

In FIG. 4, 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 represent 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 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, and Bk as a reference color, and in the transport direction, the color shift amount δes of each color is as shown in the following equations (1) to (17): 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, with respect to 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. 5 is a block diagram showing an example of a first light receiving processing circuit including the light receiving element 52 shown in FIG.

In FIG. 5, reference numeral 100 denotes a photodetector, which is a conveyor belt or a color misregistration detection pattern 9, 10, or 1.
The light received by the light receiving element 52 is detected from the light reflected from the light receiving elements 1 and 12. An I / V conversion circuit 101 converts a current value proportional to the received light into a voltage signal. A comparison unit 102 compares the voltage signal output from the I / V conversion circuit 101 with the reference voltage 103, and outputs the result signal to the CPU.
Output to 104.

In the image forming apparatus thus configured, the color shift detection pattern detected by the light receiving element 52 shown in FIG. 2 is converted from current to voltage by the I / V conversion circuit 101 as shown in FIG. (I / V conversion) and the comparison unit 1
At 02, the pulse signal is compared with the reference voltage 103, and a positive pulse signal is output as shown in FIG. 7 while the signal level is lower than the reference voltage.

FIG. 6 is a block diagram showing an example of a second light receiving processing circuit including the light receiving element 52 shown in FIG. 2, and the same components as those in FIG. 5 are denoted by the same reference numerals.

In FIG. 6, the color misregistration detection pattern detected by the light receiving element 52 is converted from current to voltage by the I / V conversion circuit 101 (I / V conversion), and the clamp circuit 110
, The detection level (base level) of the conveyor belt 3 when there is no color misregistration detection pattern is converted to a constant value, compared with the reference voltage 103 by the comparison unit 102, and the signal level is lower than the reference voltage. (For example, during detection of a color misregistration pattern or detection of a flaw on the conveyor belt 3 as described later), a positive pulse is output.

FIG. 7 shows the comparison section 102 shown in FIGS.
It is a diagram for explaining the characteristics of the pulse signal output from the
This corresponds to a pulse signal (including a state of detection of a flaw on the transport belt 3) output at the time of reading a detection pattern of a color misregistration detection pattern formed on the transport belt 3 shown in FIG. In FIG. 7, the horizontal axis indicates time.

FIG. 7A shows a state in which the pattern width of the light receiving element 52 in the transport direction of the transport belt 3 is indicated by time t. (B) is an output waveform after the output of the light receiving element 52 is subjected to I / V conversion by the I / V conversion circuit 101 and then the background level is converted to a constant value by the clamp circuit 110.
The transport belt 3 has a high gloss, and most of the emitted light 53 shown in FIG.
Is received.

The color misregistration detection pattern, which is a toner image, has a low gloss, most of the emitted light 53 is scattered, and the specularly reflected light 54b received by the light receiving element 52 is slight. The characteristic of ()) shows a remarkable waveform characteristic that it is high when the transport belt 3 itself is detected and becomes low when the color misregistration detection pattern is detected.

The output waveform (b) shown in FIG. 7 has four valleys. Of these, the first and third colors counted from the left side in the figure are regular color misregistration detection patterns (formed on the transport belt 3 at each image forming station shown in FIG. 1). The second and fourth waveforms when the light passes through the light receiving element 5
2 is a waveform when the light beam has passed through No. 2.

(C) and (d) are threshold values for specifying the reference voltage 103, and the threshold value (c) corresponds to the initially set threshold value. (E) is generated. The threshold value (d) corresponds to a threshold value variably set in order to avoid erroneous detection due to a flaw or the like. In this case, the pulse signal (f) based on normal pattern detection that does not include an error is output from the comparing unit 102. Generated.

When the transport belt 3 is scratched as described above,
The light emitting section 53 has such a characteristic that the specularly reflected light 54b received by the light receiving element 52 is scattered, and the output waveform b is reduced. However, compared to the color misregistration detection pattern, the portion of the gloss unevenness due to the scratch or the like of the transport belt 3 has a smaller amount of scattering of the light emitting portion 53 and has a narrow (narrow) range. The specularly-reflected light 54b received and received increases.

However, the light amount of the light emitting unit 51 varies greatly, and the threshold value is initially set so that the color misregistration detection pattern can be detected even when the light amount decreases due to individual differences of the LEDs, environment, changes over time, or the like. It is set to the level of the threshold (c) (for example, it is set by the CPU 31 shown in FIG. 3). Hereinafter, the color misregistration detection processing in the image forming apparatus according to the present invention will be described with reference to the flowchart shown in FIG.

FIG. 8 is a flowchart showing an example of a first data processing procedure in the image forming apparatus according to the present invention, and corresponds to a color misregistration detection processing procedure. In addition, (1)-
(7) shows each step.

First, the threshold is set to a high level corresponding to the threshold (c) shown in FIG. 7 (1). Next, the conveyor belt 3 on which the color misregistration detection pattern is not formed is detected by the color misregistration detection optical sensor 6 (2). At this time, the conveyor belt 3
If there is a flaw, as shown in FIG. 7, the output waveform (b) corresponding to the second and fourth is output from the light receiving element 52, and as shown in FIG. The corresponding pulse signal (e) is output from the comparing unit 102.

In step (3), it is determined whether or not the pulse signal (e) is output. If it is determined that the pulse signal (e) is output, the threshold value (c) is output as shown in FIG.
Is variably set so as to gradually decrease to a level corresponding to the threshold value (d) (4), and the process returns to step (2), where the transport belt 3 on which the color misregistration detection pattern is not formed is again formed.
Is detected by the optical sensor 6 for detecting color misregistration.

On the other hand, when it is determined in step (3) that the pulse signal (e) is not output (when returning from step (4) to step (2),
The output levels from the light receiving element 52 corresponding to the second and fourth output waveforms (b) shown in (b) are higher than the threshold (d), so that no pulse is output). , 10, 11 and 12 are formed (5), and are detected by the color misregistration detecting optical sensor 6 shown in FIG. 1 (6). Then, based on the pulse signal (f) according to the detected color misregistration detection pattern, the arithmetic section 34 performs an arithmetic process based on the above-described equations (formulas (1) to (17) to obtain color misregistration). The amount is calculated (7), and the process is terminated.After step (7), the black image forming station is used as a reference in accordance with the calculated color shift amount.
The CPU 31 in the control unit CONT corrects and controls the image forming timing so as to cancel the color misregistration of other colors, and controls a color image forming sequence without color misregistration.

As a result, the light receiving element 52 outputs four waveforms corresponding to the output waveform (b) shown in FIG. Of these, the first and third waveforms are obtained when the normal color misregistration detection pattern passes through the light receiving element 52.
The fourth and fourth waveforms show waveforms when the flawed portion of the transport belt 3 passes through the light receiving element 52.

The first corresponds to the color shift detection pattern of the reference color, and the third corresponds to the color shift detection pattern of the detected color. The first and third valleys are lower than the threshold value (d), and the second and fourth valleys are higher than the threshold value (d). As a result, the pulse signal (f) shown in FIG. Is output from the comparison unit 102.

In response, operation unit 34 shown in FIG.
Then, the center position of each of the first and second pulses of the pulse signal (f) in FIG. 7 is obtained, the time difference between the respective center positions is obtained, and the obtained time difference is compared with a predetermined time difference. The color shift amount is calculated from the difference between the values.

According to the first embodiment, the output from the light receiving element 52 due to the influence of the gloss unevenness is shown in FIG. The pulse signal (e) is not output, the pulse signal (f) is output only for the output waveform based on the original color shift detection pattern, and the color shift amount is calculated. 6 enables highly accurate color misregistration detection that is not affected by the color or flaw of the transport belt 3.

[Second Embodiment] In the first embodiment, by the step (3) shown in FIG. 8, the output waveform caused by the flaw included in the output waveform (b) shown in FIG. A case has been described in which the threshold value (c) is detected and variably set so as to gradually decrease to the threshold value (d). However, when the widths of the second and fourth detected pulses are measured, the threshold value ( As compared with c), when the level of the flaw is sufficiently low, the pulse width becomes long, and when the level is slightly low, the pulse width becomes short. Therefore, based on the measurement result, the width of the second and fourth pulses is determined according to the pulse width to determine how much the threshold (c) should be reduced, and the color shift detection pulse can be normally detected. May be adjusted by one error pulse detection. Hereinafter, the embodiment will be described.

Since the configuration and the like are the same as those of the first embodiment, the description will focus on the differences from the first embodiment.

FIG. 9 is a flowchart showing an example of the second data processing procedure in the image forming apparatus according to the present invention, and corresponds to the second color misregistration detection processing procedure. In addition,
(11) to (18) show each step.

First, the threshold value is set to a high level corresponding to the threshold value (c) shown in FIG. 7 (11). Next, the transport belt 3 on which the color misregistration detection pattern is not formed is detected by the color misregistration detection optical sensor 6 (12). At this time, if the transport belt 3 is flawed, the output waveform (b) corresponding to the second and the fourth is output from the light receiving element 52 as shown in FIG. The pulse signal (e) corresponding to the fourth and fourth pulse signals is output from the comparison unit 102.

In step (13), the comparison unit 1
If it is determined that there is a pulse output from the comparison unit 102 in the determination of the presence or absence of the pulse output from the second unit 02, the second and fourth error pulse signals (e) are determined in step (14). The width of the third pulse is measured by, for example, a count process based on a reference clock (not shown).

At this time, compared to the threshold value (c), the transport belt 3
If the level of the above flaw is sufficiently low, the pulse width at the time of the error becomes long, and if the level is slightly low, the pulse width becomes short. ) Can be determined. Therefore, in step (15), the threshold is set to a variable level threshold (d1 (not shown)) according to the pulse width, and the process proceeds to step (16).

On the other hand, in step (13), the comparing section 102
If it is determined that there is no pulse output from the printer, in step (16), the color misregistration detection patterns 9, 10, 11, and 12 are continuously formed on the conveyor belt 3, and the process proceeds to step (1).
7), when detected by the optical sensor 6 for detecting color misregistration, the current light receiving element 52 outputs four waveforms corresponding to the output waveform (b) shown in FIG. Of these, the first (the first is a color shift detection pattern of the reference color) and the third (the color shift detection pattern of the detected color) are waveforms when a normal color shift detection pattern passes through the light receiving element 52. The second and fourth waveforms are obtained when the flawed portion of the conveyor belt 3 passes through the light receiving element 52. The first and third valleys are lower than the threshold (d1), and the second and fourth valleys are lower than the threshold (d1). The second and fourth valleys are higher than the threshold value (d1), and the pulse signal (f) shown in FIG. 7 is output from the comparison unit 102 shown in FIG.

Then, in step (18), the arithmetic unit 34 shown in FIG. 3 calculates the center position of each of the first and second pulses of the pulse signal (f) shown in FIG. A time difference between the center positions is obtained, and a color shift amount is calculated from a difference between the obtained time difference and a preset time difference value. The subsequent data processing and color shift correction processing are the same as in the first embodiment.

Thus, according to the second embodiment, the first
Unlike the embodiment, a process of repeatedly detecting the output waveform including a flaw or the like of the transport belt 3 to lower the threshold stepwise,
That is, it is not necessary to repeat steps (2) to (4) shown in FIG. 8, and it is possible to shift to a state where color misregistration can be detected in a short time.

[Third Embodiment] In the first and second embodiments, the case where the color shift detection pattern formed on the transport belt 3 is detected by one light receiving element 52 has been described. May be configured by two light receiving elements. Hereinafter, the embodiment will be described.

FIG. 10 is a view for explaining an example of a color misregistration pattern detecting mechanism in the color image forming apparatus according to the third embodiment of the present invention. is there. Note that this corresponds to a case where the 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. 52a and 52b are light receiving elements,
For example, a photo sensor. Reference numeral 3 denotes a conveyor belt;
Reference numerals 0, 11, and 12 are color misregistration detection patterns.

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

FIG. 11 is a block diagram showing an example of a color misregistration detection processing circuit in a color image forming apparatus according to the third embodiment of the present invention. is there.

In FIG. 11, light receiving elements 52a, 52b
The color misregistration detection patterns detected by the light receiving elements 120 and 130 corresponding to the I / V conversion circuits 121 and 131
, The current is converted into a voltage signal. The difference between the light receiving sensitivities of the two light receiving elements 52a and 52b is determined by adjusting the conversion rate of the I / V conversion circuits 121 and 131.
The result is the same after / V conversion.

Next, in the clamp circuits 122 and 132,
The conversion is performed such that the detection level (base level) of the transport belt 3 when there is no color misregistration detection pattern becomes a constant value. Note that the levels of the clamp circuits 122 and 132 are set to the same value.

After the clamping, only the signal corresponding to the light receiving element 120 is clipped to a high level by the clipping circuit 123.

Then, in the comparing section 124, the light receiving element 12
0 and the signal level corresponding to the light receiving element 130 are compared with each other, and a positive pulse is output while the signal level corresponding to the light receiving element 130 is lower than the signal level corresponding to the light receiving element 120.

On the other hand, in the comparing section 134, the light receiving element 130
Is compared with the reference voltage, and the light receiving element 130
Are output during a period in which the signal level corresponding to is lower than the reference voltage.

In the pulse generator 125, when the comparator 134 outputs a positive pulse, the comparator 124 outputs a positive pulse having a constant width only when a positive pulse rise is output.

FIG. 12 is a characteristic diagram for explaining the operation of the color misregistration detection processing circuit shown in FIG. 10, and the same components as those in FIG. 7 are denoted by the same reference numerals.

FIG. 12C shows the light receiving element 52a.
Is converted by the I / V conversion circuit 121 into I / V, and the background level is converted to a constant value by the clamp circuit 122.
This is an output waveform after a high level has been clipped by the clipping circuit 123.

FIG. 11B shows a case where the output of the light receiving element 52b is subjected to I / V conversion by the I / V conversion circuit 131, and then the clamp circuit 132
Is an output waveform after the background level has been converted to a constant value.

The threshold value (d) shown in FIG.
The reference voltage of the comparison unit 134 shown in FIG.
(E) shows a pulse signal output from the comparison unit 134, and (g) shows a pulse signal output from the pulse generation unit 125 shown in FIG.

Each of the output waveforms (b) and (c) shown in FIG. 12 has four valleys. Of these, the first and third from the left side in the figure are the normal color shift detection
2a and 52b, the second and fourth waveforms
The third is that the flaws on the conveyor belt 3 are light receiving elements 52a, 52
It is a waveform when passing through 2b.

In the example shown in FIG. 10, the light receiving elements 52a, 52
2b are arranged adjacent to each other along the transport direction of the transport belt 3, so that the color misregistration detection patterns 9, 10, 11, 1
2, the light receiving elements 52a, 5
When passing through 2b, when the signal level of the output waveform of the light receiving element 52a rises, at the same time, the signal level of the output waveform of the light receiving element 52b falls.

Therefore, the I / V conversion circuit 1 shown in FIG.
At 21 and 131, the difference between the light receiving sensitivities of the two light receiving elements 52a and 52b is adjusted, and the levels of the clamp circuits 122 and 132 are set to the same value.
The characteristic is such that the rise and the fall intersect at an intermediate level of the amplitude of the signal corresponding to a and 52b.

For this reason, the pulse signal (f) shown in FIG.
Shows the output of the comparison unit 124 shown in FIG. 11, but since the signal levels after passing through the clamp circuits 122 and 132 have the same background level, if they are input to the comparison unit 124 such as a comparator, the output will be Chattering occurs.

Therefore, the high level (base level) of the signal corresponding to the light receiving element 52a is clipped to a predetermined level by the clipping circuit 123 so as to have a linear characteristic (output waveform (c) shown in FIG. 12) in the figure. The background level of the signal is set to a different value.

Thus, the rise of the positive pulse of the pulse signal (f) in FIG.
The timing at which the center of 11 and 12 passes through the center of the light receiving elements 52a and 52b indicates the timing of the fluctuation of the line width of the color misregistration detection patterns 9, 10, 11 and 12, and the fluctuation of the light quantity of the light emitting element 51. Not affected.

Therefore, the pulse signal (g) is transmitted to the light receiving element 5
When the signal level corresponding to 2b is lower than the threshold (d),
The signal level corresponding to the light receiving element 52b is
The signal is output only when a transition is made from a higher level to a lower level as compared with the signal level corresponding to a. That is,
It is output only when the regular color misregistration detection pattern passes through the light receiving elements 52a and 52b.

The color misregistration detection sequence is almost the same as that of FIG. 8 shown in the first embodiment. First, in step (1), the threshold value is set to the threshold value (c) shown in FIG. 7 (FIG. 12). (D) higher than the threshold (d) shown in FIG.
From the detection of the color shift to the detection of the color misregistration detection pattern.
This is the same as the embodiment.

According to the present embodiment, in the processing for calculating the color shift amount, the rising of the pulse signal (g) in FIG. 12 indicates the detection position of the color shift detection pattern.
The processing amount of the calculation unit 34 shown in (1) is smaller than that of the first embodiment, and the color misregistration calculation processing can be greatly reduced.

[Fourth Embodiment] FIG. 13 is a flowchart showing an example of a third data processing procedure in the image forming apparatus according to the present invention, and corresponds to a third color misregistration detection processing procedure. Note that (21) to (28) indicate each step.

First, the threshold value is set to a high level corresponding to the threshold value (c) shown in FIG. 7 (21). Next, the conveyor belt 3 on which the color misregistration detection pattern is not formed is detected by the optical sensor 6 (22).

At this time, if the transport belt 3 is damaged, waveforms corresponding to the second and fourth output waveforms (c) and (b) in FIG. 12 are output from the light receiving elements 52a and 52b.
Pulse signals corresponding to the second and fourth pulse signals (e) shown in FIG. 7 are output from the comparison unit 124 shown in FIG.

The CPU 31 or the like determines whether these pulses have been detected (23). If it is determined that there is a pulse output, the number of detected pulses is counted (24). If the level of the flaw is sufficiently lower than the set threshold value, the number of pulses increases, and if the level is slightly lower, the number of pulses decreases. It is possible to determine how much the threshold should be reduced according to the number of pulses.

Therefore, the threshold is set to (d) according to the number of pulses counted in step (24) (25).

Next, color shift detection patterns 9, 10, 11, and 12 are formed on the conveyor belt 3 (26), and detected by the optical sensor 6 (27).

As a result, four waveforms corresponding to the output waveforms (c) and (b) in FIG. 12 are output from the light receiving elements 52a and 52b. Of these, the first and third waveforms are obtained when the normal color misregistration detection pattern has passed through the light receiving elements 52a and 52b, and the second and fourth waveforms indicate that the scratched portion of the transport belt 3 is a light receiving element. It is a waveform when passing through 52a and 52b.

In particular, the first corresponds to the color shift detection pattern of the reference color, and the third corresponds to the color shift detection pattern of the detected color. The valleys corresponding to the first and third light receiving elements 52b are lower than the threshold value (d), and the comparison unit 1 shown in FIG.
From FIG. 34, a positive pulse (e) is output at the timing shown in FIG. 12, but the valleys corresponding to the second and fourth light receiving elements 52b become higher than the threshold value (d), and the comparison shown in FIG. The positive pulse is not output from the unit 134. As a result, the pulse generation unit 125 shown in FIG.
The pulse signal (g) is output as a total of two positive pulses at the timing shown in FIG.

Accordingly, the operation unit 34 shown in FIG.
An image formed by the reference color image forming station and another image based on the time difference between the rises of the two positive pulses which are the pulse signals (g) shown in FIG. 2 and the difference between the preset time differences. The amount of color misregistration with the image formed by the forming station is calculated (28), and the process ends. The subsequent data processing and color shift correction processing are the same as in the first embodiment.

Thus, unlike the third embodiment, in the present embodiment, it is not necessary to repeat the detection of the base of the transport belt.

In the present embodiment, although the pulse is output from the color misregistration pattern detecting section, it is also possible to output an analog signal, perform A / D conversion, and perform similar processing according to the output level. good.

FIG. 14 is a flowchart showing an example of an image processing procedure in the image forming apparatus according to the present invention.
Note that (31) to (44) indicate each step.

First, the control unit CONT
It is determined whether or not it is the registration correction timing of each image forming station (31). If it is not the registration correction timing, the process proceeds to step (42) to wait for reception of image data to be output. Is received at the current correction timing stored in the nonvolatile memory in the control unit CONT, while controlling the image writing in each image forming station,
An image is formed (43). Then, the image formation is repeated until it is determined that the image formation is completed (44), and when the image formation is completed, the processing is completed. The number of image formations formed by image formation is stored in the non-volatile memory,
It is referred to at the time of the next registration correction timing.

The registration correction timing in step (31) is determined for each fixed number of image formations, for a registration correction instruction from an operation panel or an external host (not shown), or for the time elapsed since the last registration correction execution. The registration correction timing is determined based on the number of prints and the like.

On the other hand, if it is determined in step (31) that it is the registration correction timing, the control unit CONT sets the color misregistration correction mode and reads out the color misregistration detection pattern data from the ROM or the like ( 3
2) In each image forming station, a color misregistration detection pattern (see FIG. 3) corresponding to each color is formed (33).

Next, when the color misregistration detection pattern formed in each image forming station is transferred to the transport belt 3, (3
4), a color shift pattern image is converted into a regular reflection optical system, for example, FIG.
The color misregistration detection pattern is detected by the light receiving element 52 constituting the read toner image detection sensor shown in (3) (35), and the current value based on the detected pattern image is converted to the I / V conversion circuit 1.
I / V conversion is carried out by using 01 (36).

Next, the I / V conversion circuit 101
By comparing the converted output waveform with a reference voltage value (the level of which is variably set by the above-described procedure), it is determined whether or not the reference voltage value exceeds the output waveform value (3).
7) If it is determined that the color difference is exceeded, a pattern detection pulse signal is generated for each color (38), and the reading of the color misregistration detection pattern transferred onto the transport belt 3 is completed N times (39). ), When the reading is completed, the arithmetic processing is added to the pattern detection pulse signal for each color,
The color shift amount between the black line pattern 1 as the reference color and the line pattern of another color is calculated (40).

Next, the image writing timing of each image forming station is determined based on the calculated color misregistration amount, and, for example, the previous correction timing data stored in the non-volatile memory is replaced with the currently calculated correction timing data. After rewriting (41), the process ends.

According to the above embodiment, since a large amount of reflected light can be ensured by the color misregistration detecting means using the regular reflection optical system, the amount of light emitted from the light source can be suppressed. Furthermore, Y
Since the toners of four colors of MCK can be similarly detected, the light emission frequency of the light source can be freely selected. further,
Since one point of the output signal from the color shift detecting means indicates the position information of the color shift detection pattern, the color shift amount can be calculated with a small amount of calculation.

Further, by providing a reference voltage value correcting mechanism, erroneous detection of a registration mark due to a scratch on the image carrier can be prevented.

Further, according to the present embodiment, the threshold value is adjusted in the color misregistration detection processing using the regular reflection optical system according to the detection result of the background level prior to the detection of the color misregistration detection pattern. With a simple configuration, it is possible to reduce the detection error due to the influence of the light amount fluctuation of the portion and the influence of the gloss unevenness due to the scratch or the like of the color misregistration detection pattern forming medium.

Furthermore, since one point of the output signal from the color misregistration detecting means indicates the position information of the color misregistration detection pattern, the color misregistration amount can be calculated with a small amount of calculation.

Further, since the adjustment of the threshold value is not repeated by the background detection or the like, an appropriate threshold value can be set in a short time.

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. 15 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.

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

Further, data subordinate to 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.

In this embodiment, FIGS.
The functions shown in FIG. 14 may be performed 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 code of the software for realizing the functions of the above-described embodiment 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 a new function of the present invention, and the storage medium storing the program code constitutes the present invention.

As a storage medium 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 codes, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer based on the instructions of the program codes. ) 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 instruction of the program code, The CPU provided in the function expansion board or function expansion unit performs part or all of the actual processing,
It goes without saying that a case where the function of the above-described embodiment is realized by the processing is also included.

[0151]

As described above, the first embodiment according to the present invention is described.
According to the nineteenth aspect, when a series of color misregistration detection pattern images formed on the carrier is read through the regular reflection optical system, the series of color misregistration detection patterns are detected based on the detected base reflection state of the carrier. A reference voltage for reading the color misregistration detection pattern image via the regular reflection optical system is variably set, and a pulse signal is generated by comparing the reference voltage with an output signal output from the light receiving element. By calculating the amount of color misregistration between the respective color images based on the pulse signal and correcting and controlling the position of the image by each image forming station other than the reference color based on the calculated amount of color misregistration, the surface condition of the conveyance body Detects the difference between the reflectance of each color misregistration pattern transferred to the carrier with a slight amount of light and the carrier itself, regardless of the transfer surface color of the carrier, regardless of the transfer surface color of the carrier. , And inexpensive configuration The effect of such may be forming a color image without color misregistration superimposed accurately the color image formed by calculating the color shift amount accurately by the image forming stations.

[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 the optical sensor shown in FIG.

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 diagram illustrating an example of a color misregistration detection pattern formed on the transport belt illustrated in FIG. 1;

FIG. 5 is a block diagram showing an example of a first light receiving processing circuit including the light receiving element shown in FIG.

FIG. 6 is a block diagram showing an example of a second light receiving processing circuit including the light receiving element shown in FIG.

FIG. 7 is a diagram illustrating characteristics of a pulse signal output from a comparison unit illustrated in FIG. 6;

FIG. 8 is a flowchart illustrating an example of a first data processing procedure in the image forming apparatus according to the present invention.

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

FIG. 10 is a diagram illustrating an example of a color misregistration pattern detection mechanism in a color image forming apparatus according to a third embodiment of the present invention.

FIG. 11 is a block diagram illustrating an example of a color misregistration detection processing circuit in a color image forming apparatus according to a third embodiment of the present invention.

FIG. 12 is a characteristic diagram illustrating an operation of the color misregistration detection processing circuit illustrated in FIG. 11;

FIG. 13 is a flowchart illustrating an example of a third data processing procedure in the image forming apparatus according to the present invention.

FIG. 14 is a flowchart illustrating an example of an image processing procedure in the image forming apparatus according to the present invention.

FIG. 15 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. 16 is a diagram illustrating a color misregistration state in this type of color image forming apparatus.

FIG. 17 is a diagram illustrating a mechanism for detecting a color misregistration pattern formed on a transport belt of a color image forming apparatus of this type.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Laser scanner 3 Conveyor belt 6 Optical sensor 9-12 Color shift detection pattern 51 Light emitting element 52 Light receiving element CONT Control unit

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. The image of each image forming station is formed such that a reference color line pattern image by a predetermined image forming station and a color misregistration detection pattern image by another image forming station are formed on the carrier. Pattern forming means for controlling the formation; pattern detecting means for reading the series of color misregistration detection pattern images formed by the pattern forming means or the base reflection state of the carrier through a regular reflection optical system; The series of color misregistration detection pattern images are corrected based on the background reflection state of the carrier detected by the means. Setting means for variably setting a reference voltage for reading via a projection optical system; and comparing a reflected light amount detected by the pattern detecting means with a reference voltage set by the setting means to generate a color shift detection pulse signal. A signal generating means for generating; a calculating means for calculating a color shift amount between the respective color images based on a color shift detecting pulse signal generated by the signal generating means; and a color shift amount calculated by the calculating means. Control means for correcting and controlling the position of an image by each image forming station other than the reference color. 2. The image forming apparatus according to claim 1, wherein the signal generation unit generates a pulse signal obtained by shaping a waveform of an output signal from the pattern detection unit based on the reference voltage. 3. The arithmetic unit detects an intersection of two output signals from the pattern detection unit obtained from the regular reflection optical system in which two light receiving elements adjacent to each other in the transport direction of the transport body are provided. 2. The image forming apparatus according to claim 1, wherein the amount of color misregistration is calculated. 4. The method according to claim 1, wherein the setting unit detects a series of color misregistration detection pattern images that is lower than an output signal amplitude value of the carrier detected by the pattern detection unit when the background is reflected, and that uses a regular reflection optical system. The image forming apparatus according to claim 1, wherein a reference voltage that can be read through the image forming apparatus is variably set. 5. The system according to claim 1, wherein the setting unit reads the series of color misregistration detection pattern images via a regular reflection optical system based on an output signal amplitude state detected by the pattern detection unit when the substrate is reflected on the base. 2. The image forming apparatus according to claim 1, wherein the reference voltage is variably set. 6. The setting means detects a pulse width of an output signal at the time of reflection of the base of the carrier detected by the pattern detecting means, and based on the detected pulse width, the series of color misregistration detection patterns. 2. The image forming apparatus according to claim 1, wherein a reference voltage for reading an image via a regular reflection optical system is variably set. 7. The color misregistration detection pattern based on the number of pulses of an output signal detected by the pattern detection means when the substrate is reflected by the base, and based on the detected number of pulses. 2. The image forming apparatus according to claim 1, wherein a reference voltage for reading an image via a regular reflection optical system is variably set. 8. A color image forming apparatus capable of forming a color image by arranging a plurality of image forming stations in parallel and sequentially superimposing and transferring the images formed in the respective image forming stations onto recording paper conveyed by a conveying body. A shift detection processing method, wherein, among the plurality of image forming stations, a reference color line 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 of each image forming station; and a pattern detecting step of reading the series of color misregistration detection pattern images formed in the pattern forming step or a base state of the carrier via a regular reflection optical system. And detecting the series of color shifts based on a reflection state of the base of the carrier detected in the pattern detection step. A setting step of variably setting a reference voltage for reading a pattern image via a specular reflection optical system; and comparing a reflected light amount detected in the pattern detection step with a reference voltage set in the setting step to perform color shift. A signal generation step of generating a detection pulse signal; a calculation step of calculating a color shift amount between the respective color images based on the color shift detection pulse signal generated by the signal generation step; and a color shift calculated by the calculation step A control step of correcting and controlling the position of the image by each image forming station other than the reference color based on the amount. 9. The color misregistration detection of an image forming apparatus according to claim 8, wherein the signal generation step generates a pulse signal obtained by shaping a waveform of an output signal from the pattern detection step based on the reference voltage. Processing method. 10. The computing step detects an intersection of two output signals from the pattern detection means obtained from the regular reflection optical system in which two light receiving elements adjacent to each other in the transport direction of the transport body are provided. 9. The color misregistration detection processing method for an image forming apparatus according to claim 8, wherein the color misregistration amount is calculated. 11. The method according to claim 1, wherein the setting step includes a step of lowering an output signal amplitude value of the carrier detected at the time of reflection of the substrate detected by the pattern detection step, and converting the series of color shift detection pattern images into a regular reflection optical system. 9. The color misregistration detection processing method for an image forming apparatus according to claim 8, wherein a reference voltage that can be read through the image forming apparatus is variably set. 12. The setting step is for reading the series of color misregistration detection pattern images via a regular reflection optical system based on an output signal amplitude state at the time of substrate reflection of the carrier detected in the pattern detection step. 9. The color misregistration detection method for an image forming apparatus according to claim 8, wherein the reference voltage is variably set. 13. The color shift detection pattern according to claim 1, wherein the setting step detects a pulse width of an output signal detected by the pattern detection step at the time of reflection of the base of the carrier, and based on the detected pulse width. 9. The color misregistration detection processing method for an image forming apparatus according to claim 8, wherein a reference voltage for reading an image via a regular reflection optical system is variably set. 14. The method according to claim 1, wherein the setting step detects a pulse number of an output signal at the time of reflection of the base of the carrier detected by the pattern detecting step, and based on the detected pulse number, detects the series of color misregistration detection patterns. 9. The color misregistration detection processing method for an image forming apparatus according to claim 8, wherein a reference voltage for reading an image via a regular reflection optical system is variably set. 15. An image forming apparatus in which a plurality of image forming stations are juxtaposed and images formed by the respective image forming stations are sequentially transferred onto a recording medium conveyed by a conveying body to obtain images. A pattern forming unit that controls image forming processes of the plurality of image forming stations so as to form a pattern image for alignment on a carrier, a light emitting unit that irradiates light on the carrier, A reading unit that reads reflected light of the pattern image formed on the carrier or the carrier by the unit; and a threshold is set according to a reading output of the reflected light of the carrier by the reading unit. Detecting the amount of color misregistration between the images formed by the plurality of image forming stations based on the read output of the pattern image by the reading means; And a correcting unit that corrects a color shift between images formed by the plurality of image forming stations based on the amount of color shift detected by the color shift detecting unit. Image forming apparatus. 16. The image according to claim 15, wherein the color misregistration detecting means compares the threshold value with a read output signal of the pattern image, and detects the color misregistration amount based on a result of the comparison. Forming equipment. 17. The color misregistration detecting means includes a comparing means for comparing the threshold value with a read output signal of the reflected light of the carrier, and generating a pulse based on the comparison result. 16. The image forming apparatus according to claim 15, wherein the threshold is set based on a pulse to be applied. 18. The apparatus according to claim 1, wherein said color shift detecting means sets said threshold value according to the number of said pulses.
8. The image forming apparatus according to 7. 19. The apparatus according to claim 1, wherein said color misregistration detecting means sets said threshold value according to a width of said pulse.
8. The image forming apparatus according to 7.