JPH02153377A - Image forming device - Google Patents

Abstract

PURPOSE:To always form an appropriate color image free of misregistration by providing a correction control means, executing the inspection by a detecting means a set number of times and controlling the actual correcting execution from a set number of obtained detecting signals. CONSTITUTION:A controller 13 serves as a correcting means and a correction control means, and forcibly adjusts misregistration in all image stations to a cyan misregistration according to the difference between detecting timings of when mark detectors 5 and 6 detect picture data of resist marks (11, 12) in a cyan picture station and of when the detectors 5 and 6 detect resist marks in subsequent picture stations. The controller 13 instructs the detectors 5 and 6 to execute detection a set number of times, controls the actual correcting execution from a set number of detecting signals obtained by detecting actions, and corrects color slurring while dealing with an unexpected and instantaneous color slurring, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an image forming apparatus that forms an image by exposing an image carrier to light using an electrophotographic method, such as a laser beam copying machine or a facsimile machine. In particular, the present invention relates to an apparatus that forms multiple, multicolor, or color images by disposing a plurality of optical scanning means.

(Prior Art) Conventionally, as an image forming apparatus having a plurality of optical scanning means, for example, the one shown in FIG. 11 is known.

FIG. 11 is a schematic diagram illustrating the configuration of a four-drum full-color image forming apparatus.

101M, 10IY, and 1018 are image forming stations (hereinafter referred to as image stations or simply stations) that form images of cyan, magenta, yellow, and black colors, respectively, and each image forming station 10IC, 101M, 10IY, and 10IBK are J: and optical scanning means 103C, 103M, 103Y, 1 on the photosensitive drums 102C, 102M, 102Y, 1028, respectively.
038, and further includes a developing device, a cleaner, etc., and on the transfer material S conveyed in the direction of arrow A by the transfer belt 112, cyan, magenta,
Yellow, black images 104C, 104M, 104
A color image is formed by sequentially transferring Y and 1048K. In this way, multiple image forming stations l0IC
, 101M, 101 Y, 1018 K all ft
Since images of different colors are sequentially transferred onto the same surface of the same transfer material S, each image forming station 10
If the transferred image position in 1C, 101M, 1018K, and 1018K deviates from the ideal position, for example, in the case of a multicolor image, the image intervals of different colors will shift or overlap,
In addition, in the case of a color image, differences in color tone and, in severe cases, color shift appear, which significantly deteriorates the quality of the image.

By the way, the first type of positional deviation of the transferred image is
Positional deviation (top margin deviation) of the transfer material S in the transport direction (input direction in the figure) as shown in Fig. 2(a), Fig. 12(a)
Positional deviation (left margin deviation) in the scanning direction (direction B in the figure) as shown in b), tilt deviation in the diagonal direction as shown in Fig. 12(c), and deviation as shown in Fig. 12(d). There are magnification errors, etc., and in reality, each of the above-mentioned positional deviations does not occur individually, but a combination of these positional deviations, that is, a superposition of four types of positional deviations appears.

In the case of the top margin (see FIG. 12(a)), the main cause of the image position shift is each image forming station 101C, 101M.

This occurs due to the difference in the timing of writing each image at 101Y and 1018, and the left margin (Fig. 12 (b)
), each image forming station 101C,
This occurs due to a shift in the writing timing of each image to IOIM, 10IY, and 1018, that is, the scanning start timing for one scanning line, and the tilt shift in the diagonal direction (
In the case of (see FIG. 12(C)), the scanning optical system is attached with an angular deviation θ (see FIGS. 13(a) to (C)).

Angular deviation θ2 of the rotation axis at 1028 (Fig. 14(a)
-(C)), and the deviation due to magnification error (see FIG. 12(d)) is caused by each image forming station l.
From the optical scanning optical system of 0IC, IOIM, 101Y, 10IBK to the photosensitive drums 102C, 102M, 102Y, 10
This occurs due to the error ΔL in the optical path length up to 28K, that is, due to the scanning line length deviation 2×δS (see FIGS. 15 and 16).

Therefore, in order to eliminate the deviations of the above-mentioned 4 fffi types, conventionally, the top margin and left margin that occur as the image forming apparatus changes over time.

Tilt 9 Misalignment due to magnification error is corrected by adjusting electrical or optical scanning means (scanner), photosensitive drum, reflection mirror, etc. For example, during the adjustment process before the start of the normal image forming sequence, A registration mark for detecting positional deviation is transferred to a conveyance body, and a predetermined one registration mark image detection timing among a plurality of registration mark images for each image carrier transferred to the conveyance body and each remaining registration mark image are detected. The irradiation start position of the light beam on each remaining image carrier based on the relative difference with the mark,
A method has been proposed in which the color shift is corrected by individually correcting the irradiation angle of the light beam to each remaining image carrier and the optical path length of the light beam to each remaining image carrier. That is, the mounting position of the optical scanning means (scanner, etc.) and the photosensitive drum is determined by the tilt deviation and the magnification error deviation, which vary depending on the mounting angle, etc. of the optical scanning means (scanner),
The mounting position or angle of the reflection mirror on the photosensitive drum or the light beam optical path is changed, and the deviation of the top margin and left margin is corrected by electrically adjusting the timing of light beam scanning.

[Problems to be Solved by the Invention] However, in such conventional examples, color misalignment that gradually increases, such as color misalignment due to changes over time due to the use of the image forming apparatus and color misalignment due to environmental changes, cannot be solved using high-definition technology. However, it is difficult to make high-precision adjustments for dynamic color shifts, such as sudden color shifts or momentary color shifts caused by disturbances such as external vibrations or shocks, and errors may occur. There were serious problems that led to adjustments, readjustments, and divergence of adjusted values.

This invention was made in order to solve the above-mentioned problems, and includes a plurality of image carriers, and at the stage of adjustment processing before the start of a normal image sequence, a conveyance body that is conveyed is used to detect positional deviation. multiple image formation in which the amount of color misregistration on each image carrier is individually measured, and the positional shift on each image carrier is corrected according to the measured color shift of a given image station. By performing the registration mark reading and detection operation a preset number of times in the device,
Misadjustment and readjustment 1 even for sudden and momentary color shifts, etc.
It is an object of the present invention to provide an image forming apparatus that can form optimal color images without divergence or other misalignment at all times.

(Means for Solving the Problems) An image forming apparatus according to the present invention provides a method for detecting a predetermined one registration mark image among a plurality of registration mark images for each image carrier transferred to a conveying member, which is sequentially detected by a detection means. Based on the relative difference between the detection timing and the detection timing of each remaining registration mark image, the irradiation start position of the light beam to each remaining image carrier, the irradiation angle of the light beam to each remaining image carrier, and the irradiation angle of the light beam to each remaining image carrier a correction means for individually correcting the optical path length of the light beam; and a correction means for performing a detection operation of the detection means an arbitrary set number of times and executing a correction process by the correction means based on a detection signal obtained by the detection operation for the set number of times. A correction control means for controlling the correction control means is provided.

[Operation] In the present invention, the correction control means executes the detection operation of the detection means an arbitrary set number of times, and limits the actual execution of correction processing by the correction means based on the detection signals obtained by the detection operation for the set number of times.

〔Example〕

FIG. 1(a) is a perspective view illustrating the configuration of a four-drum full-power single-type image forming apparatus showing an embodiment of the present invention, in which IC, IM, IY, and IBK are photosensitive drums, and cyan, cyan, and IBK are photosensitive drums, respectively. Each image forming station is provided with developer (toner) of each color: magenta, yellow, and black.

2C, 2M, 2Y, and 2BK are scanning mirrors, and optical scanning systems 3C, 3M, and 3 are provided for each image forming station.
The light emitted from Y and 38K is transmitted to each photosensitive drum IC and IM.
, IY, and IBK. Reference numeral 4 denotes a conveyor belt serving as a conveyor, on which registration marks 11 and 12 for each color formed by the photosensitive drums IC, IM, IY, and IBK are transferred. The registration marks 11 and 12 are transferred parallel to a straight line orthogonal to the conveyance direction of the conveyor belt 4.

In particular, the image forming station for cyan, that is, the photosensitive drum iC1 scanning mirror 2C and optical scanning system 3C, are fixedly disposed at predetermined positions in the main body of the apparatus at the time of assembly, and are not provided with an actuator mechanism to be described later.

On the other hand, the photosensitive drums IM, IY, IBK, scanning mirrors 2M, 2Y, 28, and optical scanning systems 3M, 3Y, 38, which constitute the remaining image forming stations, can be moved in predetermined directions by actuator mechanisms described later. It becomes.

Reference numeral 5.6 denotes a mark detector composed of a charge-coupled device such as a CCD, and the mark detector 5 receives the reflected light of the light exposed to the conveyor belt 4 from the lamp 7 via the condensing lens 9. The image data of the registration marks 11 detected in synchronization with the detection timing signal output from the controller 13 (each registration mark 11 is composed of, for example, four medium-sized mark images) is output to the controller 13 and sent to the mark detector 6. receives the reflected light of the light exposed to the conveyor belt 4 from the lamp 7 via the condensing lens 1o;
Image data of the detected registration marks 12 (each registration mark 12 is composed of, for example, four medium-sized mark images) is output to the controller 13 in synchronization with a detection timing signal output from the controller 13.

A crease member 8 collects toner images corresponding to the registration marks 11 and 12 transferred to the conveyor belt 4.

Note that the controller 13 also serves as a correction means and a correction control means of the present invention, and detects the mark detection timing detected in the registration mark image data of the cyan image station output from the mark detector 5.6 and the sequential mark detection. The optical scanning systems 3M, 3Y, 38
Each photosensitive drum IM, IY, of the light beam emitted from K
Optical path length and scan length for IBK.

By adjusting the drive of the actuator provided in the image stations other than cyan in the scanning direction (with respect to the axial direction of the photosensitive drums IM, 1Y, and IBK), the positional deviation at all image stations is forcibly adjusted to the positional deviation state for cyan. . At this time, the controller 13 executes the detection operation of the mark detector 5.6 an arbitrary set number of times, and controls the actual correction process execution as described later from the detection signals obtained by the detection operation for the set number of times. , suddenly.

To perform color shift correction while dealing with instantaneous color shift, etc.

Note that the controller 13 executes the detection operation of the mark detector 5.6 an arbitrary set number of times, and is unable to perform correction operation based on the detection signal obtained by the detection operation for the set number of times (for example, when the mark detector 5.6 detects the registration mark 11 .12 cannot be detected), the correction process described below is stopped or the mark detection process is repeated again. 2 is a perspective view illustrating the arrangement of the scanning mirror and optical scanning system shown in FIG. 1, and the same components as in FIG. 1(a) are given the same reference numerals.

Note that the same configuration as this is provided for each image station, and the magenta and yellow black stations are particularly shown.

In this figure, 20 is an fθ lens, and a laser light source 22
A polygon mirror 21 that is fired from and rotates at a constant speed.
The laser beam (light beam) L deflected by the laser beam L is imaged, for example, on the photosensitive drum 1C at a constant speed. 23 is an optical box, and the above-mentioned 20 to 22 are housed integrally. Note that the laser beam emitted from the laser light source 22 is emitted from the aperture 23a via the fθ lens 20. Reference numeral 24a designates a first reflecting mirror, and a second reflecting mirror 24b provided substantially perpendicularly to the first reflecting mirror 24a provides reflections corresponding to the scanning mirrors 2M, 2Y, and 28K shown in FIG. 1(a). A body 24 is constructed. Note that the laser beam emitted from the laser light source 22 is reflected by a first reflecting mirror 24a,
For example, the photosensitive drum IM
.

It is configured to form images on IY and IBK.

Reference numeral 25 denotes a linear step actuator (actuator) composed of, for example, a stepping motor, and a reflector 24 in which a first reflecting mirror 24a and a second reflecting mirror 24b are integrally supported according to the step amount output from the controller 13 is shown in the figure. vertically move in steps in the a direction. 26.27 is a linear step actuator (actuator) composed of, for example, a stepping motor, which moves the reflector 24 in which the first reflecting mirror 24a and the second reflecting mirror 24b are integrally supported according to the step amount output from the controller 13. They are each independently horizontally moved in the b direction in the figure. The linear step actuators 25 to 27 are used to linearly move the output shaft of a stepping motor, and have a trapezoidal screw structure inside the motor rotor and the output shaft, and are mainly used for moving heads of floppy disks, etc. It corresponds to what is normally used for the purpose. In addition, instead of the linear step actuators 25 to 27 mentioned above, a lead screw (threaded shaft) is used on the shaft of a normal stepping motor.
It is possible to function in the same way by using a movable member having a thread formed thereon corresponding to the lead screw.

Specifically, the screw formed on the lead screw is 4P0.
．． 5 (nominal diameter 4 mm, pitch 0.5 mm).

When the step angle of the stepping motor is 48 steps/one revolution, the advance amount S of the output section is S=0.5/4
8=10.42μm/step, and this 10.42
It becomes possible to drive and control the reflector 24 with a feeding amount of every μm/step.

Next, the driving operation of the actuators 25 to 27 shown in FIG. 2 will be explained with reference to FIGS. 3(a) to 3(C).

FIGS. 3(a) to 3(C) are schematic diagrams illustrating image shift on the image carrier, and S indicates a transfer material, and this transfer material S is conveyed in the direction of arrow A (the conveyance direction of the conveyor belt 4). be done.

Here, by driving the actuator 25 in the direction a, which is the emission direction of the light beam L from the scanning optical device, the reflector 24 is moved approximately parallel to the direction a, and the photosensitive drum 1
Shorten the optical path length up to C and move the actuator 25 to a2.
By driving in the direction, the optical path length can be adjusted to be long.

In this way, by adjusting the optical path length, the length of the scanning line on the photosensitive drum 1C of the light beam L having a predetermined spread angle can be changed to mo (solid line) as shown in FIG. 3(a), for example.
can be varied from m+ (broken line).

Further, by driving the actuators 26 and 27 in the same direction at the same time, for example, in the directions, the reflector 24 is moved in parallel in the b direction, which is a direction substantially perpendicular to the a1 direction,
As a result, scanning line m0 in FIG. 3(b) is changed to scanning line m2 (
It can be moved in parallel to the position indicated by the broken line). Also,
When either one of the actuators 26 and 27 is driven, or when the actuators 26 and 27 are driven in opposite directions, such as driving the actuator 26 in the direction b2 and the actuator 27 in the direction b2, as shown in FIG. 3(C). scanning line m.

The slope of the scanning line m3 (broken line) can be varied.

In this way, the reflector 24, which is a pair of reflective mirrors incorporated at approximately right angles, is disposed in the optical beam path from the scanning optical device to the photosensitive drum 1C, and the position of the reflector 24 is adjusted by adjusting the position of the reflector 24 from the actuator 2.
5 or actuators 26 and 27, the optical path length or the light beam scanning position can be adjusted independently. That is, by moving the reflector 24 having a pair of reflecting mirrors arranged in a V-shape in the direction a, the light beam L can be adjusted without changing the position of the scanning line imaged on the photosensitive drum 1C. Only the optical path length can be corrected, and the image formation position and angle on the photosensitive drum 1C can be corrected without changing the optical path length of the light beam L by moving the reflector 24 in the b direction. can.

In this embodiment, a four-drum full-color printer is provided with the reflector 24 and an actuator mechanism for adjusting the position of the reflector 24, respectively.
A photosensitive drum IC, IM is provided independently for each image carrier serving as each image forming means.

In IY and IBK, magnification errors, top margins, and left margins based on scanning line inclinations and optical path length differences are individually corrected to eliminate color misregistration between each color toner that is sequentially transferred to the transfer material S. has been done.

The reading operation of the registration marks 11 and 12 for detecting color misregistration and the color misregistration correction feedback control operation executed based on this reading will be described below with reference to FIG. 4 (a).
) and (b).

FIG. 4(a) is a control block diagram illustrating the internal configuration of the controller 13 shown in FIG.
Components that are the same as those are given the same reference numerals.

In this figure, 31a is an amplifier that amplifies the mark image signal output from the mark detector 5. 32a is a binarization circuit which converts the analog signal output from the amplifier 31a into digital data and outputs image data CCD2P to the exclusive logic gate 35b and the third counter circuit 42. 32b is a binarization circuit which converts the analog signal outputted from the amplifier 31b into digital data and converts the image data CCDIP into exclusive logic gate 35b and the second
It is output to the counter circuit 39. 33 beam lock generator generates one main scanning period signal CDHSYNC,
This one main scanning period signal CDHSYNC is sent to the mark detector 5.
, 6 as a reading synchronization signal, and outputs it as a read synchronization signal of VS
Clock is output to YNC counter 3'ZC, 37M, 37Y, and 378 manually. Note that, for example, the mark detectors 5 and 6 are each placed at a preset position corresponding to the reference 1.2,
1.12 starts writing accurately From the reference position, the scanning line slope is 1
When the registration mark 11.12 is formed at a regular position with no magnification error, left margin error, or top margin shift, the center of the registration mark 11.12 is precisely adjusted and placed at a position where it can be read by the center pixel of the mark detector 5.6. ing. That is, the reflector 24 or Adjust and fix the position of the optical scanning system 3C. By this fixing, the center of the registration mark image developed and transferred with the cyan toner serving as the reference color can always be detected by the center pixel of the mark detectors 5 and 6, and the center of the detected registration mark image for cyan and The center deviation from the registration mark images formed by the second to fourth stations, which are sequentially detected, is detected with high accuracy, and the actuators 25 to 27 are driven and controlled in accordance with the detected amount of positional deviation.

34 is a first counter circuit, which receives one main scanning period signal CDHS.
Image data CCDI for the registration mark image for cyan, which is the reference color constituting the registration mark 12, detected by the mark detector 6 at the YNC sending timing ■
P is obtained, and one main scanning period signal CDH is generated in synchronization with a start signal 5 TARTI which is an exclusive OR output of this image data CCDIP and one main scanning period signal CDHSYNC.
Start counting 5YNC, 1 main scanning period signal CD)
! Mark detector 5 at the time of 5YNC sending timing ■
Image data CC for the registration mark image for cyan, which is the reference color constituting the registration mark 11 detected by
1 in synchronization with stop signal STOP 2, which is the exclusive OR output of D2P and 1 main scanning period signal CDHSYNC
Counting of the main scanning period signal CDHSYNC ends.

The count data counted from the start to the end of the count is obtained as the scanning line inclination amount N0 of the reference color cyan, and the scanning line inclination amount N0, that is, the inclination amount of the reference color cyan, is used as a reference value to sequentially detect the scanning line inclination amount N0. The image shift amount is calculated by comparing the scanning line inclination amount NM corresponding to the second to fourth stations. The above operation is repeated n times for a preset arbitrary number of trials, and the obtained NMi, NM
The data of each scanning line inclination amount of □, . . . +NMn are compared, and a representative value N is determined. As a method for determining the representative value N2, it is preferable to take an average value excluding the maximum value and the minimum value.

Similarly, the calculated image shift amounts for the second to fourth stations are NN, NY, and Nax is in the lth ROM 3 in the subsequent stage.
5 (each actuator 26 of the second to fourth stations)
．． 27 in a specified direction is stored as a selection signal. Note that the first counter circuit 34 is enabled based on a station select signal output from a CPU (not shown). 36 is a selector circuit, and each control value ADM, ADY, ADBK read from the first ROM 35 drives the reflector 24 of the second to fourth image stations, actuators 26 and 27.
is output to.

37C is a VSYNC counter, which receives a registration mark write signal output at the timing when a cyan registration mark (a cyan registration mark image serving as a reference color constituting registration marks 11 and 12) is written at the first image station. Synchronized with 1 main scanning period signal CDH3
The image data CC is output when the mark detector 6 starts counting YNC and detects the registration mark image for cyan, which is the reference color constituting the registration mark 12.
When the start signal 5TARTI is output from the exclusive OR gate 35a in synchronization with D1, the count of one main scanning period signal CDHSYNC is finished, and the count value, that is, the top margin correction standard of the reference color cyan is Obtain the value CO. Then, the top margin values MO of the subsequent second to fourth stations are obtained by the same counting process by the VSYNC counters 37M, 37Y, and 378K, and the top margin correction reference value CO and the top margin value MO are compared, The controller 13 calculates the amount of image shift caused by the top margin shift between cyan and magenta, between cyan and yellow, and between cyan and black.

Repeat the above operation for a preset number of trials n
Repeatedly, the obtained M. l+ MO2+...MOn
Compare the data of each top margin value of M
Determine 0. As a method for determining the representative value M0, it is preferable to use the average value of data obtained by excluding the maximum value and minimum value from the obtained data. The similarly calculated image shift amounts Mo, Yo, and BKo for the second to fourth stations are output as selection signals to the subsequent third ROM 38 (in which control values for correcting the top margin are stored in advance).

The third ROM 3B sends delay signals DELAYM, DELAYY, and DELAYBK for correcting the top margin to the actuators 26 of each of the second to fourth image stations.
．． Output to 27.

39 is a second counter circuit, which receives one main scanning period signal CDHS.
XICL starts counting XICLOCK which is input in synchronization with YNC, and when the mark detector 6 detects the registration mark image for cyan, which is the reference color constituting the registration mark 12, and outputs the image data CCDIP, XICL starts counting.
The OCK count ends and the count value t. I is held in a register (not shown), and one main scanning period signal C
DHSYNC1: Synchronized and manually operated XICLOCK
starts counting XICLOCK, and when the mark detector 6 detects the registration images for the second to fourth stations constituting the registration mark 12 and outputs the image data C0DIP, the counting of XICLOCK ends and the count value t
Get 1.

Repeat the above operation for a preset number of trials n
Repeatedly, the obtained tl. The data of each count value of +t11+...jln are compared to obtain a representative value t1. Representative value 1. The determination method uses the average value of the data obtained by excluding the maximum and minimum values. Similarly, the calculated count values for the second to fourth stations are 1. is output to the subsequent comparator 4o. The comparator 40 has a count value t held in the register.
. 1 and the count value t1, and according to the difference Δt1, the actuators 2 of the second to fourth image stations
Optimum control values A2 to A4 for driving 5 are output, respectively.

42 is a third counter circuit, which receives one main scanning period signal CDHS.
XICL starts counting manually in synchronization with YNC, and when the mark detector 5 detects the registration mark image for cyan, which is the reference color constituting the registration mark 11, and outputs the image data C0D2P, XICL starts counting.
The OCK count ends and the count value t. 2 is held in a register (not shown), and 1 main scanning period signal C
The mark detector 5 starts counting the XICLOCK input manually in synchronization with DHSYNC, and the mark detector 5 detects the registration mark 11.
When the registration mark images for the second to fourth stations constituting the station are detected and the image data CCD2P is output, the XICLOCK count ends and a count value t2 is obtained.

Repeat the above operation for a preset number of trials n
The data of each count value of t2°, t2□, . . . The method for determining the representative value t2 uses the average value of data obtained by excluding the maximum value and minimum value from among the obtained data. The count value t2 for the second to fourth stations calculated in the same manner is output to the comparator 43 at the subsequent stage.

The comparator 43 compares the count value t02 held in the register with the count value t2 counted by the third counter circuit 42, and stores the difference Δt2 in the second ROM 4.
1 as a selection signal. The second ROM 41 contains an optimum delay control value DMI for driving the actuators 26 and 27 of the second to fourth image stations according to the difference Δt2.
, DYl, and DBKI, respectively, or adjust the vertical period signal output timing that determines the image writing timing according to the difference Δt2. Note that the mark detector 5
．． 6 is positioned so as to start reading in the main scanning direction from the reference 1.2 shown in FIG. 4(a).

FIG. 4(b) is a flowchart illustrating an example of the correction execution control procedure of the present invention. Note that (1) to (8) indicate each step.

When the correction process is started under the control of the controller 13, it is determined whether the registration mark 11, 12 detection process has reached a preset number of trials n (1).
Once reached, execute the comparison calculation process described later 2)
Determine whether the correction impossible flag is already set to 11 (3), and if YES, the correction process will be canceled (4).
), the process ends.

On the other hand, if the judgment in step (3) is No, it is determined whether the correction process is impossible5) If it is YES, the correction impossible flag is set6), and the process returns to step (1) to detect registration marks 11 and 12 again. Resume processing.

On the other hand, if the determination in step (5) is No, a correction process to be described later is executed (7). Next, the process waits for the correction processing at all stations to be completed (8), and when the correction processing is completed, the processing is terminated and the process proceeds to normal image forming processing.

Next, the operation shown in FIG. 4(a) will be explained with reference to FIGS. 5 and 6.

FIG. 5 is a diagram for explaining the reading operation of the registration marks 11.12 by the mark detector 5.6 shown in FIG. It is attached.

In this figure, IA indicates the write output for cyan (with respect to the writing start reference position fa2A), and IB indicates the second to fourth write outputs.
The write output (with respect to the writing start reference position 2B) corresponding to the station is shown. 3A is mark reading data,
This corresponds to the binary output for the write output IA for the cyan registration mark image forming the registration marks 11 and 12 formed at the cyan station serving as the reference color. 3B is mark reading data, which corresponds to the binary output for the write output IB for the registration mark images formed at the second to fourth stations. Conveyor belt 4
Registration marks 11 and 12 transferred to predetermined positions on both ends of
is detected by the mark detector 5.6, first, image data CCD2P, C for the cyan registration mark image is detected.
The center pixel of CDIP receives one main scanning period signal CDHSYN.
From C, time toe and to2 (count value t
. A resist image signal for cyan is obtained at a time position of 1° to 2). However, the write output IB for the registration mark images formed at the second to fourth stations
When the writing position shifts as shown in the figure, the count value t. Even if 1 and count value t1 match, count value t. 2 and the count value t2 no longer match, and when to2>t2, the second to fourth station images become smaller than the reference color cyan image, and this reduction magnification error is reflected by the comparator 4.
0, a selection signal for selecting a magnification control value for driving and controlling the actuators 25 provided at the second to fourth image stations is output to the second ROM 41.

FIG. 6 is a timing chart explaining the operation of FIG. 4(a), and the same parts as in FIG. 4(a) are given the same reference numerals.

The magnification error and left margin shift amount detection operations will be described below.

The mark detectors 5 and 6 receive one main scanning period signal C outputted from the clock generator 33 at sending timings ■ to ■.
The cyan registration mark image corresponding to the reference color constituting the registration mark 11.12 conveyed in synchronization with DHSYNC (Fig. 4 (a)) is read, and the image data CCDIP and CCD2P shown in Fig. 6 are sequentially read. Outputs, but
Regarding the sending timing ■, 1. Since the mark detector 5.6 has not read the registration mark 11.12, no cyan image signal is output. Then, at the sending timing (3), a cyan registration mark constituting the registration mark 12 detected by the mark detector 6 at a time tl (equal to to+ shown in FIG. 5) from one main scanning period signal CDHSYNC. Image data CCDIP is obtained by binarizing the detection signal for the image. and,
At sending timing ■, 1 main scanning period signal CDHS
Time t from YNC. At time point 2, image data CCD2P is obtained by binarizing the detection signal for the cyan registration mark image constituting the registration mark 11 detected by the mark detector 5.

In this way, when the image data CCDIP and CCD2P are obtained from the binarization circuits 32a and 32b, the second counter circuit 39. The counting process by the third counter circuit 42 is started as described above, and the count value t. l+
t02 is temporarily saved in the register, and the comparator 40.
43. Therefore, first comparator 4
0 is a count value obtained by counting the input count value t01 (writing position reference of the reference color cyan) and the detection timing of each registration mark image formed at the second to fourth stations that are sequentially manually operated by the second counter circuit 39. t, and the reference color difference Δt.

(content 0) is output to the second ROM 41 as a selection signal. In response, a magnification correction control signal is output from the second ROM 41 to each actuator 27 of the second to fourth stations.

On the other hand, the comparator 43 receives the input count value to2.
(writing position reference for the reference color cyan) is compared with the count value t2 counted by the third counter circuit 42 of the detection timing of each registration mark image formed at the second to fourth stations that are sequentially manually operated. Reference color difference Δt
2 (content-1) is output to the second ROM 41 as a selection signal.

As a result, the optimum movement control values (control values A2 to A4) for driving the actuator 25 of each image station are output from the table in which the magnification movement amount and left margin movement amount are set, which are stored in advance in the second ROM 41. At the same time, the delay control values DMl, DYI, and DBKI, which are the amount of movement of the left margin, are sequentially outputted in accordance with the station select signal manually input to the selection port S of the second ROM 41.

Therefore, by this correction, the magnification error and the left margin deviation are corrected by moving the image without causing image deviation from the cyan image, which is the reference color.

Next, the scanning line tilt amount correction process will be explained.

Similarly to the above, the cyan registration mark image constituting the registration mark 12 is read by the mark detector 6 in synchronization with the 1 main scanning period signal CDHSYNC sent at the sending timing ①, and the image data is sent from the binarization circuit 32b. When C0DIR is obtained, the subsequent exclusive OR gate 3
5a, one main scanning period signal CDHSYNC, which is one manual input, is erased and the start signal 5TARTI is erased.
is generated, and this start signal 5TARTI is applied to the 5TART signal terminal of the first counter circuit 34 and the clock signal CLK of the VSYNC counters 37C, 37M, 37Y, and 378. In response, the first counter circuit 34 starts counting one main scanning period signal CDHSYNC.

Next, at sending timing (3), the mark detector 5 reads the cyan registration mark image constituting the registration mark 11, and converts the image data C from the binarization circuit 32a.
Output CD2P. Next, by manually inputting the stop signal 5TOP2 from the exclusive OR gate 35b at the subsequent stage to the 5Top terminal of the first counter circuit 34, the counting process of one main scanning period signal CDHSYNC is stopped, and the count number counted so far is That is, the scanning line slope ff1N of the reference color cyan. is obtained, and this scanning line inclination amount N
. and a stop signal 5T output from the exclusive OR gate 35b corresponding to the registration mark images corresponding to the second to fourth stations sequentially detected by the mark detector 11.
The scanning line tilt amount NM corresponding to the second to fourth stations counted by the first counter circuit 34 before OP2 is input is compared to calculate the difference of each image shift, and the subsequent first ROM 35 (7 A selection signal is output to the output terminal (in which control values for moving the cutiuators 26 and 27 in eight specified directions are stored). According to this scanning line tilt correction control value, the second to
Each actuator 26, 27 of the fourth station positions the reflector 24 at the proper position. By similarly performing this operation for each of the magenta, yellow, and black registration marks, each control value ADM is determined according to the station select signal inputted to the selector circuit 36.

ADY and ADBK are output to actuators 26 and 27 of each image station to position each reflector 24 at a proper position and correct the amount of scanning line inclination, respectively.

Next, a top margin shift correction process will be described.

The second to fourth top margin correction controls and controls for the top margin for cyan, which is the reference station, are performed at the time when registration marks 11 and 12 are started to be written on the photosensitive drum 1C, that is, when the C registration mark write signal is output from the VSYNC counter 37C. It starts from the time when the C registration mark write signal is sent to the 5TAR terminal, and after this C registration mark write signal is sent to the 5TART terminal of the VSYNC counter 37C, the vs
The counting operation by the yNC counter 37C starts.

Next, when the mark detector 6 detects the first mark of the cyan registration mark image constituting the registration mark 12, the binarization circuit 32b outputs the image data C.
Start signal 5TARTI output according to CDIP
While ``1'' is being output, the value of one main scanning period signal CDHSYNC counted by the 5YNC counter 37C, that is, the difference ic1 is obtained. This difference amount C1 becomes the top margin correction reference value for the second to fourth stations.

Therefore, similarly, when the mark detector 6 detects the first mark of the registration mark image for the second to fourth stations constituting the registration mark 12, the binarization circuit 32
VSY while the start signal 5TARTI is output in accordance with the image data CCDIP output from b.
The values of one main scanning period signal CDHSYNC counted by the NC counters 37M, 37Y, and 37BK, that is, the difference amounts Ml, Yl, and BKI, are individually compared with the difference amount C1, and the relative difference thereof is calculated.

Then, each relative difference value is calculated by each VSYNC counter 37.
It is output to the third ROM 38 by M, 37Y, and 378. Accordingly, the delay signals DELAYM, DELAYY, and DELAYBK, which are the top margin correction values (difference values compared with the values output when writing the cyan registration mark) stored in advance in the third ROM 38, are - Execute top margin correction by outputting to the actuators 26 and 27 of the fourth station or by adjusting the vertical synchronization signal output timing specified for each image station. Thereby, the top margins of the second to fourth stations remaining in the top margin of the image station for cyan can be subjected to dependent correction.

Note that each VSYNC counter 37C, 37M.

At 37Y and 378, a start signal 5T based on the image data C0DIP output from the registration mark images of each image station sequentially detected by the mark detector 6.
Counting operation is ended by ARTI,
In order to continuously detect registration mark images, it is necessary to monitor accurately so that the counting operation does not end with image data CCDIP at an unnecessary position.

Also, the registration mark 11. is detected by the mark detector 5.6.
When the detection of step 12 is completed, the registration mark image transferred to the conveyor belt 4 is cleaned by the cleaner member 8 in preparation for writing the next registration mark.

In the above actual Mi example, as shown in FIG. 1(a), a reference station, that is, a station for cyan, is fixedly arranged, and the registration mark image transferred at this fixedly arranged image station is used as a reference. In the case where the optical path length, scanning length, and scanning direction of the light beam L emitted from the optical scanning system of each of the second to fourth stations are dependently corrected by driving the actuators 25 to 27 of each of the second to fourth stations. However, as shown in FIG. 1(b) and FIG. 1(C), that is, in FIG. 1(b), the manual adjustment screws 45 to 47 are set at the positions of each actuator 25 to 27. By providing them at corresponding positions, inspection, maintenance, and fine adjustment work for the image forming apparatus main body can be reduced. Furthermore, as shown in FIG. 1(C), actuators 25 to 27 are also mounted on the cyan station.
In addition to reducing inspection, maintenance, and fine adjustment work for the main body of the image forming apparatus, it is also possible to intentionally adjust the positional deviation of the reference station and reduce the burden of correction adjustment ranges on dependent stations.

Next, an image forming apparatus to which the present invention can be applied will be described with reference to FIGS. 7 to 10.

FIGS. 7(a) and 7(b) are a perspective view and an enlarged perspective view of essential parts for explaining an example of an image forming apparatus to which the present invention is applied, and the same parts as in FIG. 1(a) are designated by the same reference numerals. It is attached.

In these figures, reference numerals 51 and 52 are actuators constituted by, for example, stepping motors, and the actuator 51 moves the optical box 23 with reference to the center 1 of a rotating shaft (not shown) inserted into the free through hole of the optical box 23. arrow a
the photosensitive drum 1 from the laser light source 22.
The optical path length of the light beam L emitted to C is adjusted to correct the magnification error. The actuator 52 rotates the optical box 23 with reference to the center °C of a rotating shaft (not shown) inserted into a free through hole of the optical box 23, and rotates the photosensitive drum 1C.
Correct the slope of the scan line drawn in .

As can be seen from these figures, the reflector 2 shown in FIG.
The present invention can also be applied to an image forming apparatus that moves the optical box 23 instead of moving the optical box 23, and the scanning line inclination and magnification correction can be performed in the same manner as described above.

8(a) to 8(C) are a perspective view, an enlarged perspective view of a main part, and a sectional view of a main part, illustrating an example of an image forming apparatus to which the present invention is applied, and FIG. 1(a) and FIG. Components that are the same as those are given the same reference numerals.

In these figures, 61C, 61M, 61Y, 618
There are flanges on the photosensitive drums 1C11M, 1Y, I.
Fixed to both ends of BK, flanges 61C, 61M, 6
Axis 62C162M, 62Y, 628K to 1Y, 618
are rotatably supported by bearings 64C, 64M, 64Y, and 648K of bearing devices 63C, 63M, 63Y, and 638.

The inner case 6 is attached to the bearings 64C, 64M, 64Y, and 648 so as to be movable in the AA force direction by guide grooves (not shown).
It is supported by 5. Bearing 64C inside each inner case 65
, 64M, 64Y, and 648 are biased by respective springs 66 and abut against protrusions of an actuator 67 composed of, for example, a stepping motor.
Apply 48K in AA force direction 8 times. On the 6th, a spring energizes the inner case 65 housed in the outer case 70.

69 is an actuator composed of a stepping motor, which moves the inner case 65 urged by the spring 68 in the BB force direction A.
(orthogonal to the direction of force A). In addition, the inner case 65
is supported by a guide groove (not shown) in the outer case 70 so as to be movable in the BB force direction, which is perpendicular to the AA force direction.

As shown in FIG. 8(a), bearing devices 63C, 63M, 6
3Y, 638, the photosensitive drums 1C, IM, IY, IBK are aligned with the AA force direction horizontally and the BB force direction vertically.
When the pair of actuators 69 are simultaneously driven in the same direction, that is, in the BB force direction, the photosensitive drum, for example, the photosensitive drum 1C, is moved approximately parallel to the direction in which the light beam L is emitted from the scanning optical device, and the optical path length is increased. It can be varied to correct magnification errors.

Furthermore, when either one of the pair of actuators 67 is moved, each actuator 67 is driven in opposite directions, so that the scanning line inclination can be corrected. Further, by driving the pair of actuators 67 simultaneously, it becomes possible to move the scanning line drawn on the photosensitive drum 1C by the light beam L in parallel, and top margin correction becomes possible.

In this way, the reflector 24 shown in FIG. In addition to driving the optical box 23 individually, the photosensitive drum IC, IM,
It is also possible to add correction processing for the amount of color misregistration according to the present invention to an image forming apparatus that serves as a mechanism for individually moving IY and IBK in a predetermined direction.

Furthermore, as shown in FIG. 9, the present invention can be easily applied to a four-drum color printer having an intermediate transfer member 81, and as shown in FIG. 10, roll paper 82 is used as the transfer agent. The present invention can be easily applied to a four-drum type color printer, and color misregistration occurring in each image forming process can be optimally corrected.

Although the above application example has been explained for a four-drum color printer, for example, by applying the present invention to two- or three-color image forming processing and multiple image forming apparatuses, it is possible to produce clear images without image shift. It becomes possible to form an image.

In addition, in the above embodiment, a case has been described in which the reflector 24 is integrally formed in a U-shape, and a mirror surface is disposed on the opposing surface to scan the light beam L onto the photoreceptor. The angle and the number of mirror surfaces are not limited to those in the above embodiments, and can be freely set. For example, the reflector 24 may be formed in an L-shape.

Furthermore, in each of the above embodiments, the case where the actuator mechanism is configured with a linear step motor, for example, has been explained, but it may also be a normal stepping motor with a threaded shaft, a cam fixed to it, or a linear motor, etc. The actuator mechanism of the present invention can also have a similar function.

Furthermore, in the above embodiment, the case where the registration marks 11 and 12 are transferred using the conveyor belt 4 as the conveyor is explained, but if a known electrophotographic process is used, the transfer material to be conveyed can be transferred. The upper position and shape are not limited to the registration marks 11 and 12; for example, marks such as rr4 may be used, and marks such as r-", MJ, etc. may be individually transferred to detect image position shift. A similar effect can be expected.

Further, in the above embodiment, the registration marks 11 and 12 transferred to the conveyor belt 4 are cleaned using the cleaner member 8 such as a cleaning blade, but it is also possible to use a fur brush method or an air suction method. As a result, the toner transferred and attached to the conveyor belt 4 can be collected with high precision, and errors can be prevented from forming and reading the registration marks 11 and 12 for detecting image position deviation. Alternatively, the image may be reversely transferred onto the photosensitive drum by a transfer charger and collected by a cleaner member for the photosensitive drum.

Furthermore, in the above embodiment, a case has been described in which the registration mark 11.12 is read by the mark detector 5.6, but the number of mark detectors installed is not limited to two, and more mark detectors can be installed simultaneously. By disposing a pair of registration marks 11, 12 or similar marks on a single straight line or on different straight lines and reading the registration marks 11, 12 or similar marks, it is possible to detect image positional deviations of the respective photosensitive drums IC, 1M, IY, and IBK with high precision.

〔Effect of the invention〕

As described above, the present invention is capable of detecting a predetermined one registration mark image detection timing among a plurality of registration mark images for each image bearing member transferred to a conveying body sequentially detected by a detection means, and detecting each remaining registration mark image. Based on the relative difference with the timing, the irradiation start position of the light beam to each remaining image carrier, the irradiation angle of the light beam to each remaining image carrier, and the optical path length of the light beam to each remaining image carrier are individually determined. A correction means for performing the correction, and a correction control means for performing the detection operation of the detection means an arbitrary set number of times and controlling execution of correction processing by the correction means based on detection signals obtained by the detection operation for the set number of times. Therefore, not only color shifts due to normal changes over time, but also sudden color shifts and instantaneous color shifts due to external disturbances such as vibrations and shocks to the main body of the device.

High-definition adjustment is possible for dynamic color shifts, and it also prevents false detections and reading errors during reading.

Therefore, the images of all the image stations can be overlapped with high precision, and an optimal color image can be outputted efficiently.

[Brief explanation of the drawing]

FIG. 1(a) is a perspective view illustrating the configuration of a 4-drum full-power single-type image forming apparatus showing an embodiment of the present invention, and FIGS. 1(b) and 1(C) FIG. 2 is a perspective view illustrating the configuration of an image forming apparatus according to an embodiment of the present invention, and FIG. ) to (C) are schematic diagrams explaining the image shift of the image carrier, and FIG.
) is a control block diagram explaining the internal configuration of the controller shown in FIG. 4(b) is a flow chart explaining an example of the correction execution control procedure according to the present invention, and FIG. 6 is a timing chart illustrating the operation of FIG. 4(a), and FIGS. 7(a) and 7(b) are diagrams illustrating the registration mark reading operation by the mark detector. A perspective view and an enlarged perspective view of essential parts of an example of the apparatus, FIGS. 8(a) to 8(C) are perspective views of an example of an image forming apparatus to which the present invention is applied,
An enlarged perspective view of a main part, a cross-sectional view of a main part, FIGS. 9 and 10 are cross-sectional views illustrating an example of an image forming apparatus to which the present invention is applied,
FIG. 11 is a schematic diagram illustrating the configuration of a four-drum full-power single-type image forming apparatus, FIG. 12 is a schematic diagram illustrating types of image displacement, and FIG. 13 is an image resulting from positional displacement of the optical scanning system. FIG. 14 is a schematic diagram illustrating the misalignment of the photosensitive drum shaft, and FIG.
The figure is a schematic diagram illustrating an image shift caused by an optical path length error of a light beam, and FIG. 16 is a schematic diagram illustrating a magnification error caused by an optical path length error. In the figure, IC, IM, IY, 18 are photosensitive drums, 2
C, 2M, 2Y, 28 have scanning mirrors 3C, 3M, 3
Y, 38 is an optical scanning system, 4 is a conveyor belt, 5.6 is a mark detector, 11.12 is a registration mark, and 13 is a controller. lμ；Archer゛Fig. (a) (b) (c) (d) Figure Figure Mouth A Figure

Claims (1)

[Claims] In an image forming apparatus having a plurality of image carriers arranged at predetermined intervals and a detection means for detecting each registration mark image sequentially transferred to a conveying body formed by each image carrier, the detection means Each remaining image is determined based on the relative difference between the detection timing of a predetermined one registration mark image among the plurality of registration mark images for each image carrier transferred to the conveyance body and the detection timing of each remaining registration mark image, which are sequentially detected. a correction means for individually correcting the irradiation start position of the light beam to the carrier, the irradiation angle of the light beam to each of the remaining image carriers, and the optical path length of the light beam to each of the remaining image carriers; and detection by the detection means. and a correction control means for controlling execution of correction processing by the correction means based on detection signals obtained by the detection operation for the set number of times by executing the operation an arbitrary set number of times. Device.