JPH09120233A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an image without positional deviation by detecting the position of an image formed on a photoreceptor and controlling an optical system based on output from a detection means. SOLUTION: A reflector 24 in which a pair of reflection mirrors 24a and 24b are incorporated nearly at right angles is disposed in the optical path of a light beam from a scanning optical device to the photoreceptor drum 1. By adjusting the position of the reflector 24 by an actuator 27 or actuators 28 and 29, optical path length or a light beam scanning position is independently adjusted. Namely, by moving the reflector 24 provided with a pair of reflection mirrors 24a and 24b disposed in chevron-shape in a direction (a), only the optical path length of the light beam L is corrected without changing the position of a scanning line forming an image on the drum 1. By moving the reflector 24 in a direction (b), an image forming position and angle on the drum 1 are corrected without changing the optical path length of the light beam L.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for forming an image by irradiating a photoconductor with a light beam.

[0002]

2. Description of the Related Art Conventionally, as a multiplex image forming apparatus having a plurality of optical scanning means, for example, one shown in FIG. 11 is known. FIG. 11 is a schematic view showing a 4-drum full-color image forming apparatus. In FIG.
Reference numerals 1M, 101Y, and 101BK are image forming stations that form images of cyan, magenta, yellow, and black, respectively.
C, 101M, 101Y and 101BK respectively include photosensitive drums 102C, 102M, 102Y and 102BK, optical scanning means 103C, 103M, 103Y and 103BK, a developing device and a cleaner, and a transfer material S that moves in the direction of arrow A by a transfer belt 106. Cyan, magenta, yellow, black images 31C, 31M, 31Y, 31 on top
BK is sequentially transferred to form a color image.

As described above, in an apparatus having a plurality of image forming stations, images of different colors are sequentially transferred onto the same surface of the same transfer material S. Therefore, when the transferred image position in each image forming station deviates from the ideal position, For example, in the case of a multicolor image, the image intervals of different colors are shifted or overlapped, and in the case of a color image, the difference in tint, and when the degree is worse, the color shift appears, significantly deteriorating the image quality. Was there.

By the way, as shown in FIGS. 12 (a), 12 (b), 12 (c) and 12 (d), the types of positional deviation of the transferred image are positions in the transfer material S transport direction (direction A in the drawing). Deviation (top margin) ((a) in the figure), scanning direction (A in the figure)
Misalignment (left margin) in the B direction orthogonal to the direction
(The same figure (b)), the inclination shift of the diagonal direction (the same figure (c)),
There is a deviation in magnification error ((d) in the figure), and in practice
It appears that the types of misalignment are superimposed.

The main cause of the image shift is a shift in the image writing timing of each image forming station in the case of the top margin shown in FIG.
In the case of the left margin, it is the deviation of the writing timing of each image of each image forming station, that is, the scanning start timing in one scanning line, and in the case of the inclination deviation in the oblique direction in FIG. Angle deviation θ ₁ (formed in order of FIGS. 13A, 13B, and 13C) or angular deviation θ ₂ of the rotation axis of the photosensitive drum (FIGS. 14A, 14B, and 14C).
In the case of the deviation due to the magnification error of FIG. 12D, the deviation of the scanning line length due to the error ΔL of the optical path length from the optical scanning optical system of each image forming station to the photosensitive drum. 2 × δS (FIGS. 15 and 1)
6).

Therefore, in order to eliminate the above four types of deviations,
Regarding the top margin and left margin, the timing of the light beam scanning is electrically adjusted to correct the deviation,
Regarding the inclination deviation and the deviation due to the magnification error, the position and the mounting angle of the optical scanning unit and the photosensitive drum when assembled into the apparatus are carefully adjusted so that the positional deviation does not occur. That is, the tilt deviation and the magnification error deviation, which vary depending on the mounting position and angle of the optical scanning unit (scanner or the like) and the photosensitive drum, are corrected by the optical scanning unit (scanner), the photosensitive drum, or the reflection mirror in the light beam optical path. The adjustment was done by changing the mounting position and angle.

[0007]

However, in such a conventional example, although the electrically adjustable top margin and the left margin can be almost completely eliminated, the optical scanning means (scanner), the photosensitive drum, or the optical margin is used. There is a problem in that it is difficult to adjust the inclination shift and the magnification error due to the adjustment of the mounting position of the reflection mirror in the beam optical path, and it is very laborious.

A further extremely important problem is the stability of image position deviation. That is, the running stability of the transfer belt as a moving body (meandering,
Misalignment), positional reproducibility when attaching / detaching the photosensitive drum, top margin in the case of a laser beam printer, instability of the left margin, etc.
It greatly affects the image quality.

Further, the relationship between the main body and the optical system, the photosensitive drum, etc., which is once adjusted when the main body is installed, requires complicated and difficult readjustment due to, for example, a slight distortion generated when the main body is moved to another floor. turn into.

Further, in an apparatus for forming a highly accurate image which cannot be compared with such a conventional electrophotographic apparatus, thermal expansion due to the ambient temperature of the main body frame, positional displacement due to thermal contraction, temporal change, etc. The positional deviation due to the was also a big problem.

Therefore, the present invention has been made in order to solve the above-mentioned problems of the prior art, and an object thereof is to provide an image forming apparatus capable of forming an image without displacement.

[0012]

[Means for Solving the Problems] In order to solve the above problems,
In order to achieve the above-mentioned object, the present invention is an optical system that irradiates a light beam for forming an image on a photoconductor, and a detection unit that detects the position of the image formed on the photoconductor.
And a control unit that controls the optical system based on the output of the detection unit.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] The present invention will be described below based on the illustrated embodiment. FIG. 1 is a block diagram showing a four-drum full-color image forming apparatus of the embodiment. In FIG.
1Y and 1BK are cyan, magenta, yellow,
The photosensitive drum in each image forming station is provided with a developer (toner) of each color of black. These photosensitive drums 1C, 1M, 1Y, 1BK rotate in the direction of the arrow in the figure, and these photosensitive drums 1C, 1M, 1Y, 1BK
A primary charger for uniformly charging, a scanning optical device 3C as image writing means (latent image forming means),
3M, 3Y, 3BK, a developing device that visualizes a latent image with toner, a cleaner, and a transfer charging device are provided. In addition, the transfer material S is supported on the transfer belt 6a and the arrow A
Direction, the toner images of the respective colors are sequentially transferred at the image forming stations to form a color image, and the image is fixed by the fixing device 8 after completion of the transfer process, and the tray 9
Is discharged on top.

On the other hand, on the transfer belt 6a, in addition to the image formed on the transfer material S, image register marks 34 and 35 for detecting the image position are fixed for each color by an electrophotographic process. It is formed with a space.
In this embodiment, a cross-shaped register mark as shown in the figure is used. Also, 14 and 15 are sensors for reading these register marks, which are normally CC
D is used. A CCD is a linear sensor that converts an optical signal into an electric signal, and is generally used in facsimiles and similar to a well-known image reading sensor. The register marks 34 and 35 formed on the transfer belt 6a are C through the lamps 16 and 17 and the condenser lenses 18 and 19 arranged on the downstream side of the final station.
The color misregistration is read by the CDs 14 and 15, and the correction is performed by the feedback control described later.

The scanning optical devices 3C, 3M, 3
As shown in FIG. 2, each of Y and 3BK is configured by arranging an fθ lens 20, a polygon mirror 21, and a laser light source 22 at a predetermined position of an optical box 23, and the light beam L emitted from the laser light source 22 is The light is reflected and scanned by the polygon mirror 21, and emitted from the opening 23a of the optical box 23 through the fθ lens 20. On the other hand, above the optical box 23, a reflector 2 serving as a light reflecting means provided with a first reflecting mirror 24a and a second reflecting mirror 24b facing each other at substantially right angles.
4 is fixed to the apparatus main body (not shown) so that the first reflecting mirror 24a is located on the opening 23a.
The emitted light beam L is configured to reach the photosensitive drum 1 through the first reflecting mirror 24a and the second reflecting mirror 24b in this order. The reflector 24 can be adjusted in its mounting position independently in the arrow a direction and the arrow b direction with respect to the main body of the apparatus, and is a driving source that linearly moves stepwise as an adjusting means for performing these adjustments. Actuators 27, 28, 29 such as a linear step actuator having a certain step motor are equipped.

The linear step actuator used here is a device for linearly moving the output shaft of a stepping motor, and has a structure in which a trapezoidal screw is formed inside the motor rotor and the output shaft. Often used for head feeding. In addition, as a method similar to this, a lead screw shaft (having a thread on the shaft) is used for the shaft of the stepping motor, and a movable member having a screw formed thereon can be used to perform the same actuator function. .

For example, the screw formed on the lead screw is 4P0.5 (nominal diameter 4 mm, pitch 0.5 mm),
Assuming that the step angle of the step motor is 48 steps / circle, S = 0.5 / 48 as the advance amount S of the output unit.
The feed amount can be controlled with an accuracy of 10.42 μm / step.

In the present specification, these are also referred to as an actuator. Here, the actuator 2
7 is the direction of emission of the light beam L from the scanning optical device a ₁
By driving in the direction, the reflector 24 is moved substantially parallel to the a direction, and the optical path length to the photosensitive drum 1 is shortened, and by driving the actuator 27 in the a ₂ direction, the optical path length can be adjusted to be long. it can. By adjusting the optical path length in this manner, the length of the scanning line on the photosensitive drum of the light beam L having a predetermined divergence angle can be adjusted, for example, as shown in FIG.
Can be changed from m ₀ to m ₁ .

Further, by simultaneously driving the actuators 28 and 29 in the same direction, for example, in the b ₁ direction, the reflector 24 is translated in the b direction, which is a direction substantially perpendicular to the a ₁ direction. The scanning line m ₀ of 3 (b) can be moved in parallel to the position of the scanning line m ₂ . Also,
When either one of the actuators 28 and 29 is moved, or when the actuators 28 are driven in the b ₁ direction and the actuators 29 are driven in the b ₂ direction, driving in the opposite directions is performed. The inclination of the scanning line m ₀ can be changed like the scanning line m ₃ .

As described above, the reflector 24 in which a pair of reflecting mirrors are installed at a substantially right angle is arranged in the light beam optical path from the scanning optical device to the photosensitive drum, and the position of the reflector 24 is set to the actuator 27 or the actuator 28. , 29, 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 a direction, the position of the scanning line imaged on the photosensitive drum is not changed and the light beam L It is possible to correct only the optical path length, and by moving the reflector 24 in the b direction, it is possible to correct the image forming position and angle on the photosensitive drum without changing the optical path length of the light beam L.

In the present embodiment, the four-drum color printer is provided with the reflector and the position adjusting means for the reflector, and each image forming means independently has a magnification based on the inclination of the scanning line on the photosensitive drum and the optical path length. The error, the top margin, and the left margin are corrected to eliminate the color shift between the toners sequentially transferred to the transfer material S.

Above, the actual register mark reading method and feedback method will be described in detail by taking a cyan image as an example.

FIG. 4 shows a block diagram for performing feedback control to each station after detecting a register mark detecting portion.

FIG. 4 shows an example of reading the written register mark in the state where the above-mentioned scanning line inclination and magnification error occur.

The sensors 14 and 15 for reading the register marks 34 and 35 are CCDs 1 and 2, respectively. Since the outputs of CCDs 1 and 2 converted to electric signals are very low signal levels,
The electric signal CCD1 which is amplified by each amplifier A and corresponds to the accurate position of the register mark by the binarization circuits 50 and 51.
P, CCD2P is obtained. The CCDs 1 and 2 are installed at predetermined positions of the reference 1 and 2 respectively, and when the register mark is formed at a normal position from the reference position at which writing is started correctly, there is no scanning line inclination and magnification error, and The center of the mark is arranged so that it can be read by the center pixel of the pixels of the CCDs 1 and 2. Also, the main scanning start position (left margin) of each CCD is the reference 1,
The directions of the CCDs 1 and 2 are also set so as to start from 2.

FIG. 5 shows an example of a case where a magnification error and a left margin shift occur, and a case where data is normally written, together with the positional relationship between the CCDs 1 and 2. In the figure, 1A is the output when writing at the regular position, and 1B
This is the case where the misalignment occurs.

CCDs 1 and 2 when register marks 34 and 35 on both sides are read after writing 1A and 1B, respectively.
The output waveforms after binarization are shown in 3A and 3B. The output of 3A obtained by 1A is the normal position, so CCDs 1, 2
Is output as a register mark image signal at a time position t ₀ from the main scanning start position (hereinafter referred to as CDHSYNC). However, like 1B, the register mark written at the shifted position is the CCD as shown in 3B.
The image signal of the register mark is obtained at the regular position on the 1st side, and on the CCD 2 side at a time t ₂ inside the regular position and shorter than t ₀ . Therefore, when t ₀ > t ₂ in this way, the magnification is small, and if the magnification is to be adjusted normally, it is possible to predict that the left margin will also deviate from the reference position 2A to the position 2B.

Referring to FIG. 4, in more detail, a method for detecting a magnification error and a left margin deviation amount and a correction method will be described.
It will be described together with the timing chart of FIG.

The CDHSYNC generator 70 supplies a CDHSYNC signal for one main scanning period to the CCD1 and CCD2.
, And can be converted into an image signal in this cycle. Register marks 34 and 35 are CCD1 and CCD2
The signal outputs obtained by reading in the order of CDHSYNC, are CCD1P and CCD2P in FIG. In the case of CDHSYNC, no image signal can be obtained because neither CCD has read the register mark yet. CCD during the next CDHSYNC cycle
As the output on the 1st side, the image signal of the CCD 1P is obtained at the position of t ₁ . The time of t ₁ is as described in the example of FIG.
It is equal to the time t _{0 at} the predetermined position.

In the further CDHSYNC cycle, the image signal of the CCD 2P is obtained at the position of t ₂ as the output of the CCD ₂ . This is as described in the example of FIG.
Shorter than t ₀ . Counters 2 (62) and 3 are counters for measuring the times t ₁ and t ₀ , respectively.
(63). Each of the counters 62 and 63 has a CLOCK terminal, and X1 CLOCK is input to this terminal. Since the CLOCK frequency of X1 is to see the shift amount at this frequency, the higher frequency is more advantageous.
Counter 1 (54), Counter 2 (62) STA
The C signal of the CDHSYNC generator 70 is connected to the RT signal terminal.
The DHSYNC signal is input. Also, the STOP
The output signal of the CCD 1P is input to the counter 2 and the output signal of the CCD 2P is input to the counter 3 at the signal terminals. Therefore, at counter 2 CDHSYNC
Start counting the clock frequency of X1 and
It stops when the image signal of 1P is input, and the count number is output t
Obtained as ₁ . Also, at counter 3, CDHSYN
Start counting the clock frequency of X1 from C, CC
It stops when the image signal of D2P is input, and the count number is obtained as the output t ₂ . The obtained values of t ₁ and t ₂ are compared with the value of the center value t _{0 by} the comparators CP1 and CP2, and the differences Δt ₁ and Δt ₂ are Δt ₁ = 0 and Δt ₂ = −1. . A ROM in which a magnification movement amount and a left margin movement amount are set in advance in accordance with each value of Δt.
The optimum movement control value of the actuator 27 for magnification error control, which is the first control amount in 2, is selected and output. Furthermore, the moving amount of the left margin, which is the second control amount, is also selected and output as DELAY (CH).

Therefore, by this correction, the magnification error and the left margin shift can be moved and corrected to the normal position. All stations are corrected by repeating the operation of these examples for the following magenta, yellow, and black register marks. The station select signals to the E terminals of the counters 2 and 3 and the S terminal of the ROM 2 are for that selection.

Next, the correction of the scanning line inclination amount will be described.

When CCD1P is obtained by reading register mark 34 when CCD1 is CDHSYNC, CDHSYNC is obtained by EXCLUSIVE-OR of EX1.
The C signal is erased to obtain the START1 signal. By inputting this signal to the START signal terminal of the counter 1, counting of the CDHSYNC signal input to the CLOCK terminal is started. Next, CDHSY by CCD2
When NC, read register mark 35, CCD2P
Since it becomes the signal of STOP2 by the same EX2 as above.
Get the signal. By inputting this signal to the STOP terminal of the counter 1, counting of CDHSYNC is stopped. Therefore, the value of CDHSYNC, that is, the scanning line inclination amount N is obtained at the output of the counter 1, and in this example, N
= 1. In accordance with this deviation amount, the control values of the actuators 28 and 29 for moving the scanning lines in the designated direction are selected from the ROM 1 set in advance, the station is designated by the selector, and the actuators 28 and 29 are designated.
Move. Therefore, the scanning line inclination amount is corrected by this correction and the scanning line is moved to the normal position. This operation is repeated for the subsequent magenta, yellow, and black register marks to correct all stations. The station select signal to the E terminal of the counter 1 is for that selection.

Next, the correction of the top margin shift will be described.

The VSYNC-C counter detects the position of the register mark first written by the first station. By inputting the timing signal at which the register mark is written to the START terminal, the CDHSYNC input to the CLK terminal starts counting. . This signal is not limited to CDHSYNC, but if it is set to a completely different higher frequency, the resolution can be further improved. Then, by stopping at the START signal of the register mark read by the CCD 1 first, the CDHS
Stop YNC counting. This value C'is introduced to the ROM 3 which selects and outputs the difference amount by comparing with the value obtained when the register mark is written in a predetermined position.
The output of the ROM 3 is the DELAY (CV) top margin control output. Therefore, the top margin shift is corrected by this correction, and it is moved to the regular position. By repeating this operation for the following magenta, yellow, and black register marks, all stations are corrected. Since the register marks are continuous in the operation of each VSYNC counter, it is needless to say that a control signal is necessary so as not to stop at a register mark signal at an unnecessary position although not shown. Further, even if the control value selected from the ROM 3 is used as the control value of the actuators 28 and 29, the top margin deviation can be corrected in the same manner.

By combining the operations described above, it is possible to automatically and quickly correct an image in which various color shifts have occurred.

After passing through the CCD reading section, the register mark formed on the transfer belt is cleaned by a belt cleaning device such as the cleaning blade 7 shown in FIG. 1, and the next register mark is written. Provide.

[Second Embodiment] FIG. 7 shows a second embodiment of the present invention. In this embodiment, the scanning optical device (that is, the scanner) detects the above-described color shift scanning line inclination, magnification error, and the like.
Optical box 23 (fθ lens 20, polygon mirror 2)
1, a box in which the laser light source 22 is integrated, and the mounting position of the laser light source 22 can be corrected by a position moving means that is adjustable with respect to the apparatus body. The mechanism will be described below.

In FIG. 7, reference numerals 40 and 41 denote stepping motors or actuators such as the linear step actuator described in the first embodiment.

By driving the actuator 40 in the a ₁ direction, which is the direction in which the light beam L is emitted from the scanning optical device, the optical box 23 is configured to be moved substantially parallel to the a direction along the axis l. ing. As a result, the optical path length to the photosensitive drum 1 is shortened, and the actuator 40
The optical path length can be adjusted to be long by driving a in the a ₂ direction. Thus, similarly to the first embodiment, the magnification error can be corrected.

By driving the actuator 41, the optical box 23 is moved around the axis l as a center of rotation,
Thereby, the inclination amount of the scanning line can be adjusted.

As described above, it is possible to correct the amount of color shift described above also by correcting the position of the scanning optical device itself. The register mark below this is read, the feedback control of the correction amount to these actuators 40 and 41, the reading method, etc. are all the same as the method described in the first embodiment.

[Third Embodiment] FIG. 8 shows a third embodiment of the present invention. In the present embodiment, the image carrier (that is, the photosensitive drum) causes the above-described color shift scanning line inclination, magnification error, and the like.
It is configured so that it can be corrected by the position moving means. The mechanism will be described below.

In FIG. 8A, 10C, 10M, 1
0Y and 10BK are photosensitive drums 1C, 1M, 1Y and 1B.
Flange fixed to both ends of K, each of which is
The shaft support device 11C, 11M, 11 shown in FIG.
Y, 11BK is pivotally supported, and the shaft support device 11C,
11M, 11Y, and 11BK are fixed to support members corresponding to the respective photosensitive drums. The photosensitive drum is driven by a drive transmission mechanism (not shown).

FIGS. 8B and 8C are detailed views of the shaft support device 11. In this figure, the shaft 10a of each flange 10
Are supported by bearings 601. The bearing 601 is supported by the inner case 604 so as to be movable in the direction of arrow A by a guide groove (not shown), and the actuator 6
The spring 602 is biased by 03. In addition, the inner case 604 is also provided with a guide groove (not shown) to form the outer case 6
07 is movably supported in the direction of arrow B, which is perpendicular to the direction of arrow A.
It is urged by 05. The actuators 603 and 606 in this case are preferably linear step actuators and the like as described in the previous embodiment.

As shown in FIG. 8 (a), for example, when the axial support device 11 is mounted so that the A direction is horizontal and the B direction is vertical, the front and rear actuators 6 are mounted.
When 06a and 606b are simultaneously driven in the same direction, that is, in the B direction, the photosensitive drum 1 is moved substantially parallel to the emission direction of the light beam L from the scanning optical device, and the optical path length is changed.
Thereby, the magnification error can be corrected.

Further, the actuators 603a and 603b
The scanning line inclination amount can be corrected by moving either one of them or by driving the actuators 603a and 603b in opposite directions.

Further, the actuators 603a and 603b
If the scanning lines are simultaneously driven in the same direction, the scanning lines are moved in parallel, that is, the top margin can be adjusted.

As described above, it is possible to correct the amount of color misregistration described above also by correcting the position of the photosensitive drum itself. The register mark below this is read, and the feedback control of the correction amount to these actuators 603 and 606, the reading method, etc. are all the same as the method described in the first embodiment.

The method described above is used in the intermediate transfer member 1.
The present invention can be applied to other image forming apparatuses such as the image forming apparatus of FIG. 9 including 0 and the image forming apparatus of FIG. 10 using the roll paper 11 as a transfer material. In the case of FIG. 9, the register mark is formed on the intermediate transfer member 10 or the transfer material S, and in the case of FIG. 10, it is formed on the roll paper 11.

The present invention can be applied not only to a 4-drum color printer, but also to a multi-color image forming apparatus of two colors or three colors or a multiple image forming apparatus.

Furthermore, in the first embodiment described above, the case where a reflector having a V-shaped reflecting mirror is used as an optical system for defining the optical path of the light beam L has been described, but the present invention is not limited to this. However, the mounting position and angle of the reflecting mirrors and the number of reflecting mirrors may be freely selected, or a pair of reflecting mirrors may be integrally formed in an L shape.

Further, in each of the embodiments, the linear step actuator has been described as an example of the actuator. However, in addition to this, for example, a normal stepping motor with a threaded shaft, gum, linear motor, etc. Any material may be used as long as it has a similar function.

Further, the position of the register mark to be formed may be any position on the moving body as long as it can be formed by the electrophotographic method, and the shape of the register mark is also the same as in the present embodiment. Not limited to the one used in, any form may be used as long as the image shift as described above can be detected.

Further, as described above, the cleaning on the belt after writing the register mark is more effective by using the fur brush method or the air suction method in addition to the cleaning blade method.

Further, as the number of sensors such as CCD used for reading, in the present invention, the image is read at two places on the front side and the back side, but this is, for example, three places and four places. Needless to say, if the number is increased, the image shift can be read with higher accuracy.

[0057]

As described above, according to the present invention,
By controlling the optical system, for example, it becomes possible to adjust the inclination and magnification of the image with high accuracy.

[Brief description of the drawings]

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

FIG. 2 is a perspective view of a main part of the first embodiment.

FIG. 3 is an explanatory diagram showing an image shift of a transfer material.

FIG. 4 is a block diagram showing feedback control of a phone embodiment.

FIG. 5 is an explanatory diagram of a CCD reading unit.

FIG. 6 is a timing chart showing the feedback control of this embodiment.

FIG. 7 is a perspective view of a second embodiment.

FIG. 8 is a perspective view of a third embodiment.

FIG. 9 is a diagram showing another embodiment.

FIG. 10 is a diagram showing another embodiment.

FIG. 11 is a diagram showing another embodiment.

FIG. 12 is a diagram showing an image shift.

FIG. 13 is an explanatory diagram of an image shift due to a position shift of the optical scanning device.

FIG. 14 is an explanatory diagram of an image shift due to an axis shift of a photosensitive drum.

FIG. 15 is an explanatory diagram showing an optical path length error.

FIG. 16 is an explanatory diagram showing a magnification error due to an optical path length error.

[Explanation of symbols]

 1 Photosensitive Drum 3 Scanning Optical Device 6a Transfer Belt 14 Sensor

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yukio Sato 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Yoichi Kubota 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Co., Ltd. (72) Inventor Ken Miyagi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hirose ▲ Yoshi ▼ hiko 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. In-house (72) Inventor Kunihiko Matsuzawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroyuki Miyake 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72 ) Inventor Tomohiro Aoki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Setsu Uchida 3-30-2 Shimomaruko, Ota-ku, Tokyo Roh emissions within Co., Ltd. (72) inventor Kanakura Kazunori Ota-ku, Tokyo Shimomaruko 3-chome No. 30 No. 2 Canon within Co., Ltd.

Claims (7)

[Claims] 1. An optical system for irradiating a light beam for forming an image on a photoconductor, a detection unit for detecting the position of an image formed on the photoconductor, and an output based on the output of the detection unit. An image forming apparatus comprising: a control unit that controls the optical system. 2. The image according to claim 1, wherein the optical system includes a generation unit that generates the light beam, and a mirror unit that reflects the light beam and guides the light beam onto the photoconductor. Forming equipment. 3. The image forming apparatus according to claim 2, wherein the control unit has an actuator that adjusts a position of the mirror unit, and adjusts the actuator according to a position of the image. 4. A writing control means for controlling the optical system to form a resist mark on the photoconductor, and a moving body for moving the resist mark formed on the photoconductor at a transfer position. The image forming apparatus according to claim 1, further comprising: 5. The detection means has mark detection means for detecting the position of a registration mark on the moving body, and detects the position of the image based on the output of the mark detection means. The image forming apparatus according to claim 4. 6. The image forming apparatus according to claim 1, comprising a plurality of the photoconductors and a plurality of the optical systems. 7. The image forming apparatus according to claim 6, wherein the control unit controls the plurality of optical systems to correct a positional deviation between images formed on the plurality of photoconductors. .