JP2001249523A - Image forming device, control method for image forming device and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an image of high definition without any color slurring by matching variation in magnification in a main scanning direction of an image that is formed on each photoreceptor drum and decreasing deviation in the image in the main scanning direction. SOLUTION: In the device, photoreceptor drums 1C, 1M, 1Y and 1BK are installed separated by an integral multiple of a circumference 'd' of the photoreceptor drum so that phases of cycle of variation in position of laser scanning surfaces on surfaces of photoreceptor drums 1C, 1M, 1Y and 1BK are the same in the photoreceptor drums 1C, 1M, 1Y and 1BK.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive drum and a method for scanning and exposing the photosensitive drum with a light beam which is modulated in accordance with an image signal inputted to the photosensitive drum to form an image on the photosensitive drum surface. An image forming apparatus having a plurality of sets with an exposure device for forming an image, and capable of forming a multiplexed image by superimposing images formed on the respective photosensitive drum surfaces, a control method of the image forming apparatus, and a storage medium Things.

[0002]

2. Description of the Related Art Conventionally, in a laser exposure apparatus used for a laser beam printer, a digital copying machine, or the like, a light beam which is light-modulated from a light source means in accordance with an image signal and emitted is, for example, a rotating polygon mirror (polygon mirror) or the like. The light is deflected periodically by an optical deflector and is focused on a photosensitive recording medium (photosensitive drum) surface in a spot shape by a scanning optical element (imaging element) having fθ characteristics. The image is recorded by scanning.

FIG. 13 is a schematic view of a main part of a scanning optical system of a conventional image forming apparatus.

In FIG. 1, reference numeral 91 denotes light source means for emitting divergent light. Reference numeral 92 denotes a collimator lens which converts a divergent light beam emitted from the light source means 91 into a substantially parallel light beam. Reference numeral 93 denotes an aperture for limiting the light flux (light amount) of the substantially parallel light flux output from the collimator lens 92. Reference numeral 94 denotes a cylinder lens (cylindrical lens) which has a predetermined refractive power only in the sub-scanning direction, and out of the substantially parallel light beam incident on the cylinder lens 94, exits as a substantially parallel light beam in the main scanning section. .

The light deflector 95 rotates in the direction of arrow A in the figure, and deflects and reflects the light beam incident from the cylinder lens 94 on a deflecting surface 95a.

Reference numeral 96 denotes a scanning optical element (fθ lens).
The light flux having the θ characteristic and being deflected by the optical deflector 95 is guided onto a photosensitive drum surface 98 as a surface to be scanned.

The operation of each unit will be described below.

The divergent light beam emitted from the light source means 91 is converted into a substantially parallel light beam by a collimator lens 92, and the light beam (light amount) is restricted by a stop 93. ) 94.

[0009] Of the substantially parallel light beams incident on the cylinder lens 94, they are emitted as they are in the state of substantially parallel light beams in the main scanning section. In the sub-scanning section, the light deflector 95 is formed by focusing and rotating a polygon mirror.
Is formed as a substantially linear image on the deflecting surface (reflection surface) 95a.

The light beam deflected and reflected by the deflecting surface 95a of the optical deflector 95 is converted into a scanning optical element (f
The light is guided on a photosensitive drum surface 98 as a surface to be scanned via a θ lens) 96, and the light deflector 95 is rotated in the direction of arrow A, whereby the light is scanned on the photosensitive drum surface 98 in the direction of arrow B. I do.

As a result, the photosensitive drum surface 9 as a recording medium
8 is recorded.

FIG. 14 shows a color image obtained by using a plurality of scanning optical systems shown in FIG. 13 at the same time, recording image information for each color component on a photosensitive drum for each color component, and superimposing an image for each color component. FIG. 1 is a cross-sectional view schematically illustrating a main part of a color image forming apparatus that forms a color image.

In the figure, 111, 112, 113, 1
Numeral 14 denotes a scanning optical device shown in FIG. 13
Reference numerals 1, 132, 133, and 134 denote photosensitive drums as image carriers, respectively, and scanning optical devices 111, 112, and 11 are provided.
3, 114 hold the electrostatic latent image. 12
Reference numerals 1, 122, 123, and 124 denote developing units, respectively, which develop the electrostatic latent images held on the photosensitive drums 131, 132, 133, and 134 with a developer such as toner. Reference numeral 141 denotes a conveyor belt which conveys a recording medium such as recording paper in the direction of the arrow in the figure, and transports the recording medium to the photosensitive drums 131, 132, 133, and 1
34 are sequentially fed.

The color image forming apparatus shown in the figure is a scanning optical apparatus (111, 112, 113, 11) shown in FIG.
4), each of which corresponds to each color of C (cyan), M (magenta), Y (yellow), and BK (black), and is parallel to the photosensitive drums 131, 132, 133, respectively.
Image information is recorded on the surface 134, and a color image is printed at high speed.

In such a color image forming apparatus, since a plurality of scanning lines are overlapped to form an image, it is particularly important to reduce scanning line deviation between colors (hereinafter, also referred to as "color deviation"). is there.

[0016]

FIG. 15 is a schematic diagram when optical scanning is performed on the photosensitive drum surface 98 by the scanning optical system shown in FIG. 13. The same components as those in FIG. It is attached.

In the figure, L is the optical path length from the optical deflector 95 to the photosensitive drum surface 98, W is the print width of the image to be formed, θ is the angle at which the light beam enters the photosensitive drum surface 98, T is the center of the image in the transfer material feed direction. The arrow C in the drawing indicates the transfer material feeding direction.

If the image center T in the transfer material feed direction is not shifted between the colors, no color shift occurs between the colors if the printing width W is the same between the colors.

However, the optical path length L fluctuates by ΔL due to a static scanning surface deviation due to the distance accuracy between the laser exposure device and the photosensitive drum surface 98, or a dynamic scanning surface deviation due to deflection or eccentricity of the photosensitive drum itself. At this time, as shown in the figure, the print width W changes by “e (= ΔLcosθ) × 2”. That is, the overall magnification changes.

FIG. 16 is a schematic diagram when optical scanning is performed on the photosensitive drum surface 98 by the scanning optical system shown in FIG. 13, and particularly shows a vertical line continuous in the transfer material feeding direction.

As shown in the figure, when there is no scanning plane shift,
An ideal line (reference) represented by a two-dot chain line in FIG. However, as described above, if the scanning plane is shifted by ΔL, the scanning line becomes a line meandering at the period of the photosensitive drum as shown by a broken line or a dashed line in the drawing.

At this time, if the other three colors at the time of color image formation do not change and are ideal lines, only the color scanned by this scanning optical system will cause a color shift of "e" in the main scanning direction. become.

Further, when a change (shift) occurs in which one color is reversed to another color, a color shift of “2 × e” occurs between these two colors. Become. However, even if all colors deviate from the ideal line, no color misregistration occurs if they are similarly changed.

On the other hand, in recent years, the size of the apparatus has been reduced, and the optical path length L has become shorter than that of a conventional scanning optical apparatus. Further, image forming requirements for a transfer material of A3 noble size or larger are increasing, and the maximum printing width is increasing.

Accordingly, the incident angle θ on the photosensitive drum surface 98
Is smaller, and even if the scanning plane shift ΔL is the same as the conventional one, the color shift “e” in the main scanning direction increases, and it is increasingly difficult to suppress the color shift in the main scanning direction between colors. There was a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the first to twelfth inventions according to the present invention to solve the problem of positional fluctuation of a laser scanning surface on a photosensitive drum surface of each color. By arranging the photosensitive drums of the respective colors such that the phase of the cycle is the same between the photosensitive drums of the respective colors, for example, by arranging the photosensitive drums of each color at an integer multiple of the circumferential length of the photosensitive drum,
An image forming apparatus and an image capable of forming a high-quality image without color shift by reducing the image shift in the main scan direction by matching the fluctuation of the magnification in the main scanning direction of the image formed on each photosensitive drum. An object of the present invention is to provide a method of controlling a forming apparatus and a storage medium.

[0027]

According to a first aspect of the present invention, there is provided a photosensitive drum (photosensitive drums 1C, 1M, 1M shown in FIG. 1).
Y, 1BK) and an exposure device (FIG. 1) that scans and exposes the photosensitive drum with a light beam that is light-modulated in accordance with an input image signal corresponding to the photosensitive drum to form an image on the surface of the photosensitive drum. The laser exposure devices 51, 52, 53,
54) In an image forming apparatus which has a plurality of sets and which can form a multiplex image by superimposing images formed on the respective photosensitive drum surfaces, the position of the exposure scanning surface on each of the photosensitive drum surfaces The photosensitive drums are arranged so that the phase of the fluctuation period is the same between the photosensitive drums.

According to a second aspect of the present invention, there is provided a photosensitive drum (the photosensitive drums 1C, 1M, 1Y, 1BK shown in FIG. 1) and light modulated in accordance with an image signal inputted thereto corresponding to the photosensitive drum. A plurality of sets of exposure apparatuses (laser exposure apparatuses 51, 52, 53, and 54 shown in FIG. 1) for scanning and exposing the photosensitive drum with a beam to form an image on the surface of the photosensitive drum are provided. In an image forming apparatus capable of forming a multiplex image by superimposing images formed on photosensitive drum surfaces, a plurality of driving means (drive motors 90C, 90M, 9M shown in FIG. 9) for independently driving the respective photosensitive drums.
0Y, 90BK) and a plurality of detecting means (sensors 14C, 14M, 14Y, 14 shown in FIG. 9) for respectively detecting the phase of the position fluctuation cycle of the exposure scanning surface on each photosensitive drum surface.
BK) and the detection results of the plurality of detection means,
Control means (CPU 101 shown in FIG. 2) for controlling the driving means so that the phase of the position variation cycle of the laser scanning surface on each photosensitive drum surface is the same between the photosensitive drums.
7 is driven and controlled based on a program stored in the ROM / RAM 1030).

According to a third aspect of the present invention, there is provided a photosensitive drum (photosensitive drums 1C, 1M, 1Y, 1BK shown in FIG. 1) and light modulated in accordance with an image signal inputted thereto corresponding to the photosensitive drum. A plurality of sets of exposure apparatuses (laser exposure apparatuses 51, 52, 53, and 54 shown in FIG. 1) for scanning and exposing the photosensitive drum with a beam to form an image on the surface of the photosensitive drum are provided. In an image forming apparatus capable of forming a multiplexed image by superimposing images respectively formed on photosensitive drum surfaces, a plurality of detecting means for detecting a phase of a position change cycle of an exposure scanning surface on each photosensitive drum surface (FIG. And control means for adjusting an image signal input to each of the exposure devices in accordance with a preset adjustment amount, based on detection results of the plurality of detection means, and sensors 14C, 14M, 14Y, and 14BK shown in FIG. CPU1017 is RO shown in Figure 2
Adjustment based on a program stored in the M / RAM 1030).

According to a fourth aspect of the present invention, a plurality of detecting means (sensors 14C and 1C shown in FIG. 9) for detecting the phase of the position fluctuation cycle of the exposure scanning surface on each photosensitive drum surface, respectively.
4M, 14Y, 14BK) and control means (CPU 1017 shown in FIG. 2) for adjusting an image signal input to each of the exposure devices according to a preset adjustment amount based on the detection results of the plurality of detection means. Is ROM / RAM1030
Is adjusted based on the program stored in the program.).

According to a fifth aspect of the present invention, the plurality of detecting means include a mark (mark 13C shown in FIG. 9) attached at the same phase position of the position fluctuation cycle of the exposure scanning surface on each photosensitive drum surface. , 13M, 13Y, 13BK) as sensors (sensors 14C, 14M, 14Y, 14B shown in FIG. 9).
K).

According to a sixth aspect of the present invention, there is provided a control means for adjusting an image signal input to each of the exposure devices according to a preset adjustment amount based on the detection results of the plurality of detection means. CPU 1017 shown in FIG.
1030, which performs adjustment control based on a program stored in 1030).

According to a seventh aspect of the present invention, the control means determines a modulation frequency of an image signal input to each of the exposure devices and an input timing of the image signal based on detection results of the plurality of detection means. The adjustment is performed in accordance with a preset eccentric amount of the center of the photosensitive drum (an eccentric amount Δr shown in FIG. 8).

According to an eighth aspect of the present invention, each of the photosensitive drums is set so that the distance between the photosensitive drums is an integral multiple of the circumferential length of the photosensitive drum (the circumferential length d of the photosensitive drum shown in FIG. 6). It is something to arrange.

According to a ninth aspect of the present invention, there is provided a photosensitive drum which can be driven independently and scans and exposes the photosensitive drum with a light beam which is light-modulated in accordance with an input image signal corresponding to the photosensitive drum. A method for controlling an image forming apparatus, comprising a plurality of sets with an exposure device for forming an image on a photosensitive drum surface, and capable of forming a multiplex image by superimposing images formed on the respective photosensitive drum surfaces, A detection step (step S102 in FIG. 10) for detecting the phase of the position variation cycle of the exposure scanning surface on each photosensitive drum surface, and the position of the exposure scanning surface on each photosensitive drum surface based on the detection result. An adjusting step (step S103 in FIG. 10) of adjusting the driving of each of the photosensitive drums so that the phase of the fluctuation cycle is the same among the photosensitive drums.

According to a tenth aspect of the present invention, the photosensitive drum is scanned and exposed by a photosensitive drum and a light beam light-modulated in accordance with an image signal input to the photosensitive drum, and the photosensitive drum is scanned and exposed on the photosensitive drum surface. An image forming apparatus having a plurality of sets with an exposure device for forming an image on each photosensitive drum surface, wherein an image formed on each photosensitive drum surface can be overlapped to form a multiplex image. A detecting step (step S202 in FIG. 11) for detecting the phase of the position variation cycle of the exposure scanning surface, and, based on the detection result, changing the image signal input to each of the exposure apparatuses according to a preset adjustment amount. Adjustment step (Step S203 in FIG. 11)
And

According to an eleventh aspect of the present invention, there is provided a photosensitive drum which can be independently driven, and the photosensitive drum is scanned and exposed by a light beam which is modulated in accordance with an image signal inputted to the photosensitive drum. An image forming apparatus having a plurality of sets with an exposure device for forming an image on a photosensitive drum surface and capable of forming a multiplex image by superimposing images formed on the respective photosensitive drum surfaces is provided with the respective photosensitive devices. Based on a detection process (step S102 in FIG. 10) for detecting the phase of the position fluctuation cycle of the exposure scanning surface on the drum surface, respectively,
And performing an adjustment step (step S103 in FIG. 10) of adjusting the drive of each of the photosensitive drums so that the phase of the position variation cycle of the exposure scanning surface on each of the photosensitive drum surfaces becomes the same between the respective photosensitive drums. A program for causing a computer to read the program is stored in a storage medium so as to be readable by a computer.

According to a twelfth aspect of the present invention, the photosensitive drum is scanned and exposed by a photosensitive drum and a light beam light-modulated according to an image signal inputted to the photosensitive drum, and the surface of the photosensitive drum is exposed to light. An image forming apparatus having a plurality of sets with an exposure device for forming an image on each photosensitive drum surface, and capable of forming a multiplex image by superimposing images formed on the respective photosensitive drum surfaces of the respective sets, A detecting step (step S202 in FIG. 11) for detecting the phase of the position variation cycle of the exposure scanning surface, and, based on the detection result, changing the image signal input to each of the exposure apparatuses according to a preset adjustment amount. The program for executing the adjustment step (step S203 in FIG. 11) for making the adjustment is stored in a storage medium in a computer-readable manner.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment FIG. 1 is a sectional view schematically showing a main part of an image forming apparatus according to a first embodiment of the present invention.

In the figure, reference numerals 51, 52, 53, and 54 denote laser exposure devices each having the structure shown in FIG. 2 to be described later. Reference numerals 1C, 1M, 1Y, and 1BK denote photosensitive drums, respectively, and cyan (C) and magenta. (M), yellow (Y),
Corresponds to black (BK).

Reference numerals 3C, 3M, 3Y, and 3BK denote cyan (C), magenta (M), yellow (Y), and black (BK) scanning units, each of which is light-modulated based on input image information. Laser light) LC, LM, LY, L
Emit BK.

Reference numerals 10C, 10M, 10Y and 10BK denote cyan (C), magenta (M), yellow (Y) and black (BK) diffractive optical elements (details of which will be described later), and scanning units 3C, 3M, 3Y, Each light beam emitted from 3BK is diffracted.

Reference numerals 2C, 2M, 2Y, and 2BK denote primary chargers, and photosensitive drums 1C, 1M, 1Y, and 1BK before image formation.
Is primarily charged. Reference numerals 4C, 4M, 4Y, and 4BK denote cyan (C), magenta (M), yellow (Y), and black (BK) developing units, respectively, and diffractive optical elements 10C, 10M, and 1B.
The latent images formed on the photosensitive drums 1C, 1M, 1Y, and 1BK by the laser beams irradiated through 0Y and 10BK are developed into cyan (C), magenta (M), yellow (Y), and black (BK). Visualize with the agent.

7 is a transfer belt, 5C, 5M, 5Y, 5B
K is cyan (C), magenta (M), yellow (Y),
Developing devices 4C, 4M, and black (BK) transfer rollers
The visible images developed by 4Y and 4BK are sequentially electrostatically transferred to the transfer material P conveyed on the transfer belt 7.

A fixing device 25 thermally fixes the color image formed on the transfer material P to the transfer material P. Reference numeral 26 denotes a paper discharge roller which conveys the transfer material P fixed by the fixing device 25 and outputs it to the outside of the apparatus.

Reference numerals 6C, 6M, 6Y, and 6BK denote cyan (C), magenta (M), yellow (Y), and black (BK) cleaners.
The residual toner remaining on the 1M, 1Y, and 1BK surfaces is removed and collected.

Reference numeral 21 denotes a paper feed tray on which transfer materials P are stacked. A paper feed roller 22 sequentially feeds the transfer materials P stacked on the paper feed tray 21 one by one. Reference numeral 23 denotes a registration roller, which feeds the transfer material P fed by the paper feed roller 22 onto the transfer belt 7 in synchronization with the image writing timing.

Reference numeral 24 denotes a drive roller, which is connected to a drive motor (not shown) having a small rotation unevenness, and feeds the transfer belt 7 accurately.

The operation of each section will be described below.

In the present embodiment, each light flux (laser light) LC, LM, L
Y, LBK emit the respective scanning units 3C, 3M, 3Y, 3BK, and the diffractive optical elements 10C, 10M, 10Y, 10B
K, the corresponding photosensitive drums 1C, 1M,
Irradiation is performed on the 1Y, 1BK plane to form a latent image.

This latent image is stored in the primary chargers 2C, 2M, 2
The photosensitive drums 1C, 1M, 1Y, and 1BK, which are uniformly charged by Y and 2BK, respectively, are visualized as cyan (C), magenta (M), yellow (Y), and black (BK) images and transferred. A color image is formed by being electrostatically transferred to the transfer material P conveyed on the belt 7 by the transfer rollers 5C, 5M, 5Y, and 5BK in order.

Thereafter, the photosensitive drums 1C, 1M, 1Y, 1
The residual toner remaining on the BK surface is the cleaner 6C or 6C.
M, 6Y, and 6BK, the primary chargers 2C, 2M, 2Y, and 2 are again used to form the next color image.
It is uniformly charged by BK.

The transfer material P is stacked on a paper feed tray 21, is fed one by one by a paper feed roller 22, and is transferred onto a transfer belt 7 by a registration roller 23 in synchronization with an image writing timing. Will be sent to
A cyan (C) image, a magenta (M) image, and a yellow (Y) image formed on the surfaces of the photosensitive drums 1C, 1M, 1Y, and 1BK while being accurately conveyed on the transfer belt 7.
And the black (BK) image are sequentially transferred onto the transfer material P to form a color image.

The color image formed on the transfer material P is heat-fixed by the fixing device 25, and then conveyed by a paper discharge roller 26 and output outside the apparatus.

FIG. 2 is a block diagram illustrating the configuration of the image forming apparatus according to the first embodiment of the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals.

In the image forming apparatus, reference numeral 1001 denotes a controller, which is a control program or the like stored in a program ROM of a ROM 1013 by a CPU 1012 or a control stored in an external memory 1014 such as a hard disk, a floppy (registered trademark) disk, or a magneto-optical disk. Based on a program or the like, access to various devices connected to the system bus 1015 is comprehensively controlled, and an image signal as output information is output to a printer engine unit (engine) 1016. The font ROM of the ROM 1013 stores font data and the like used when generating the output information. Further, the ROM 101
The data ROM 3 stores information and the like used on the host computer 2000 for a printer that does not include the external memory 1014 such as a hard disk.

The CPU 1012 has an input unit 1018,
Host computer 2 via interface 2100
000, and is capable of notifying the host computer 2000 of information and the like in the image forming apparatus. Reference numeral 1019 denotes a RAM.
Twelve main memories, work areas, etc., are configured so that the memory capacity can be expanded by an optional RAM connected to an additional port (not shown). Also, the CPU 1012 in the controller 1001
The CPU 1017 in the engine 1016 has a timer inside, and can measure time.

The RAM 1019 is used as an output information development area, an environment data storage area, and a nonvolatile memory such as an NVRAM. Hard disk (H
D), access to the external memory 1014 such as an IC card is controlled by a memory controller (MC) 1020. The external memory 1014 is connected as an option and stores font data, an emulation program, form data, and the like. An operation unit 1021 includes switches for operation and various settings and an LED display.
An LCD display and the like are provided.

Further, the above-mentioned external memory 1014 stores
The number of external memories is not limited to one, but is provided so that a plurality of external memories storing an option card and a program for interpreting a printer control language of a different language system in addition to the built-in fonts can be connected. Further, a nonvolatile memory (not shown) may be provided to store various setting information from the operation panel 1021.

In order to print an image signal sent from the CPU 1012 of the controller 1001, the engine 1
And a control program executed by the CPU 1017 for performing a control by operating the CPU 022 and feeding back signals from various detection systems 1023 (including various sensors such as optical sensors) taken in during the operation to the operation. , And each scanning unit 3C, 3M,
ROM / RAM 1 for temporarily storing 3Y, 3BK write timing data (correction data) and data read from detection system 1023 (various sensors)
030 is provided. This ROM / RAM 1030
RAM includes a non-volatile memory (not shown).

FIG. 3 shows the laser exposure apparatus 51 shown in FIG.
It is a figure explaining composition of -54.

Hereinafter, a laser exposure apparatus 5 for cyan (C)
1, laser exposure devices 52 to 5 for magenta (M), yellow (Y), and black (BK) will be described.
4 has the same configuration.

In the figure, reference numeral 1 denotes a semiconductor laser, which emits a divergent light beam light-modulated according to an input image signal.
A collimator lens 2 converts a divergent light beam emitted from the semiconductor laser 1 into a substantially parallel light beam. Reference numeral 3 denotes an aperture stop that limits the light flux (light amount) of the substantially parallel light flux converted by the collimator lens 2. Reference numeral 4 denotes a cylindrical lens. Of the substantially parallel light beams incident on the cylindrical lens 4, the light is emitted as it is on the main scanning section, and converges on the sub-scanning section to form a substantially linear image on the mirror surface 5a of the polygon mirror 5. (A line image elongated in the main scanning direction).

The polygon mirror 5 rotates in the direction of arrow E, deflects the light beam formed by the cylindrical lens 4 and guides it on the surface of the photosensitive drum 1C via the toric lens 61 and the diffractive optical element 10c. Then, optical scanning is performed on the surface of the photosensitive drum 1C in the direction of arrow F in the figure.

The operation of each section will be described below.

In the laser exposure device 51, the divergent light beam emitted from the semiconductor laser 1 is converted into a substantially parallel light beam by the collimator lens 2, and the light beam (light amount) is restricted by the aperture stop 3 and is incident on the cylindrical lens 4. .

Of the substantially parallel light beam incident on the cylindrical lens 4, it is emitted as it is in the main scanning section, and converges in the sub-scanning section to form a substantially linear image (main scanning section) on the mirror surface 5 a of the polygon mirror 5. (A line image elongated in the direction).

Then, the mirror surface 5a of the polygon mirror 5
The light beam deflected by the above is guided on the surface of the photosensitive drum 1C via the toric lens 61 and the diffractive optical element 10c, and by rotating the polygon mirror in the direction of arrow E,
Optical scanning is performed in the direction of arrow F on the surface of the photosensitive drum 1C.

As described above, for example, the latent images of cyan (C), magenta (M), yellow (Y), and black (BK) correspond to the corresponding photosensitive drums 1C, 1M, 1
The image is formed on the Y, 1BK plane, and thereafter, is multiplex-transferred onto the transfer material P to form one full-color image.

FIG. 4 shows the laser exposure device 51 shown in FIG.
4 is a schematic diagram when optical scanning is performed on the surface of the photosensitive drum 1C, and the same components as those in FIG. 3 are denoted by the same reference numerals.

Hereinafter, a laser exposure apparatus 5 for cyan (C) will be described.
1, laser exposure devices 52 to 5 for magenta (M), yellow (Y), and black (BK) will be described.
4 has the same configuration.

In the drawing, L is the optical path length from the polygon mirror 5 to the surface of the photosensitive drum 1C, θ is the angle at which the light beam enters the surface of the photosensitive drum 1C, H is the exposure point at the extreme end, and the arrow F indicates the scanning direction. The arrow G in the figure indicates the transfer material feeding direction.

FIG. 5 is a schematic diagram when optical scanning is performed on the surface of the photosensitive drum by the scanning optical system shown in FIG. 3, particularly showing a vertical line continuous in the transfer material feeding direction.

If the center of the image in the transfer material feed direction is not shifted between the colors, no color shift occurs between the colors if the printing width is the same between the colors.

In the present embodiment, since the incident angle θ at the extreme end is “60 °” and the displacement ΔL of the scanning surface of the photosensitive drum 1C is “70 μm”, the latent image formed on the photosensitive drum 1C The image is enlarged by “e = 41 μm” and the overall magnification is increased by “2e = 82 μm”.

FIG. 6 shows the photosensitive drums 1C and 1 shown in FIG.
FIG. 2 is a diagram showing eccentric states of M, 1Y, and 1BK, and the same components as those in FIG. 1 are denoted by the same reference numerals.

As shown in the figure, the photosensitive drums 1C, 1M,
As shown in the drawing, each of 1Y and 1BK has an eccentricity of “Δr” with respect to a radius “r” (reference radius).
C, 12M, 12Y, and 12BK are driven to rotate. d is the distance between adjacent photosensitive drums, and corresponds to the circumference of each photosensitive drum 1C, 1M, 1Y, 1BK.

As described above, the laser exposure devices 51 and 5
Light beams emitted from 2, 53, and 54 are scanned and exposed on the photosensitive drum surface.

When an exposure scan is performed on the photosensitive drum surface when the radius is "r", an image is written at a predetermined magnification as a whole magnification because the exposure length L remains the reference size as shown in FIG. It is.

However, when the photosensitive drum surface is exposed when the radius is smaller by “Δr”, ie, when “r−Δr”, the exposure length “L” is “ Δ
r ”. Therefore, the overall magnification increases. If −Δr is ΔL (= 70 μm) described above, the magnification increases e (= 41 μm) on one side. Similarly, when the photosensitive drum surface is exposed when the radius is r + Δr, the magnification is reduced by e (= 41 μm) on one side.

Referring now to FIG. 7, Δr shown in FIG.
The fluctuation of the scanning exposure surface of the photosensitive drums 1C, 1M, 1Y, and 1BK having the eccentricity will be described.

FIG. 7 is a diagram showing the fluctuation of the scanning exposure surface of the photosensitive drums 1C, 1M, 1Y, and 1BK having the eccentricity Δr shown in FIG.

The vertical axis indicates the amount of deviation of the exposure point H at the end shown in FIG. 4 for each color (C: cyan, M: magenta, Y: yellow, BK: black), and the horizontal axis indicates Time, that is, the transport direction G of the transfer material P is shown.

Here, cyan (C) will be described.
When the photosensitive drum having an eccentricity of −Δr rotates, the scanning exposure surface changes from “0 (reference)” → “−Δr” → “0” → “+ Δ”.
r ”→“ 0 ”→“ −Δr ”in one drum cycle.

Then, since the magnification varies as described above, the point H becomes larger (+ in the graph) or smaller (− in the graph) as shown in FIG.
Direction) and a waveform having a period of one rotation of the photosensitive drum. This is the meandering in the main scanning direction described above, and an image deviation from an ideal position (also a position fluctuation of the laser scanning surface).
Represents

Similarly, magenta (M), yellow (Y),
The waveform of one cycle of the drum is also shown for each color of black (BK). Further, if −Δr is the same, the amplitude of each color of cyan (C), magenta (M), yellow (Y), and black (BK) is also the same.

Here, in the present invention, although there is a variation of the H point in each color, the waveforms of the cyan (C), magenta (M), yellow (Y), and black (BK) colors (position variation of the laser scanning surface) As described above, by adjusting the phases of the waveforms, the color shift between the cyan (C), magenta (M), yellow (Y), and black (BK) colors does not occur.

Specifically, as shown in FIG. 6, the distance between the photosensitive drums is configured to be the same as the photosensitive drum circumference "d" (or an integral multiple of the circumference), and the phase of the eccentricity of the photosensitive drum is determined by exposure scanning. This is achieved by making each color the same phase with respect to the surface (making the phase of each color exposure scanning plane fluctuation waveform the same).

In the present embodiment, the distance between the photosensitive drums is the same as the circumferential length of the photosensitive drum. However, even if the distance between the photosensitive drums and the circumferential length of the photosensitive drum are different, as shown in FIG. The eccentric phase of the photosensitive drum may be adjusted so that the phases of the waveforms become the same.

With the above configuration, even if the magnification of each color in the main scanning direction changes, each color similarly changes, so that it is possible to prevent a color shift between the colors.

[Second Embodiment] In the first embodiment,
The distance between the photosensitive drums is configured to be the same as the photosensitive drum circumference "d", but a mark is provided on the side surface of each color photosensitive drum, and the mark position of each color photosensitive drum is changed based on the detection signal of the mark. Alternatively, the driving motor for driving the photosensitive drum may be controlled so that each color has the same phase. Hereinafter, the embodiment will be described.

FIG. 8 is a diagram showing a schematic configuration of the image forming apparatus shown in FIG. 1, and the same components as those in FIG. 6 are denoted by the same reference numerals.

The photosensitive drums 1C, 1M, 1Y, 1BK
As shown in the figure, each has an eccentricity of “Δr” with respect to the radius “r” (reference radius), and has 12C, 12M, and 12C, respectively.
It is driven to rotate around Y, 12BK. As described above, the light beams LC, LM, LY, and LBK emitted from the laser exposure devices 51, 52, 53, and 54 are applied to the photosensitive drum 1C,
Scanning exposure is performed on the 1M, 1Y, and 1BK planes.

Reference numerals 13C, 13M, 13Y, and 13BK denote marks provided on the side surfaces of the eccentric positions of the photosensitive drums 1C, 1M, 1Y, and 1BK at the same phase position. Note that, in the figure, each color is provided in a portion whose radius is longer by Δr.

Note that the distance between adjacent photosensitive drums is the circumference d of each of the photosensitive drums 1C, 1M, 1Y, and 1BK, as in FIG.

FIG. 9 is a diagram showing a schematic configuration around the photosensitive drum of the image forming apparatus shown in FIG. 8, and the same components as those in FIG. 8 are denoted by the same reference numerals.

In the figure, 14C, 14M, 14Y, 1
4BK are sensors (for example, optical sensors) for detecting the marks 13C, 13M, 13Y, and 13BK, respectively, as shown in FIG. 90C, 90M, 90Y, and 90BK are drive motors, respectively, and each of the photosensitive drums 1C, 1M, 1
A single drive motor is provided for each of Y and 1BK.

The sensors 14C, 14M, 14Y, 1
4BK is included in the detection system 1023 shown in FIG.
The CPU 1017 of the engine 1016 shown in FIG.
14M, 14Y, 14BK) to control the driving of the drive motors 90C, 90M, 90Y, 90BK.

The image forming apparatus according to the present invention comprises a yellow (Y), magenta (M), cyan (C), black (B
k) Each color has an image shift in the main scanning direction, and furthermore, the color shift is reduced by adjusting the phase as described in the first embodiment. In the second embodiment of the present invention, the following configuration is used to realize the above-described phase matching.

The photosensitive drums 1C, 1M, 1Y, 1B of each color
K is rotated first, and the marks 13C,
13M, 13Y, and 13BK are converted to sensors 14C, 14M, and 1
Detected at 4Y, 14BK.

Next, the sensors 14C, 14M, 14Y, 1
4BK mark 13C, 13M, 13Y, 13BK
The CPU 1017 shown in FIG. 2 controls the drive motors 90C, 90M, 90Y, and 90BK based on the detection signals of FIG.

In the present embodiment, the distance between the photosensitive drums is configured to be the same as the circumferential length of the photosensitive drums. Therefore, as described in the first embodiment, the positions of the marks are in the same phase with respect to the scanning exposure surface. Is controlling the drive motor. At this time, it is desirable that the transfer belt 7 is separated from the drum.

In this embodiment, the distance between the photosensitive drums is the same as the circumferential length of the photosensitive drum, as in the first embodiment. However, even if the distance between the photosensitive drums and the circumferential length of the photosensitive drum are different, each color is different. The drive motor of the photosensitive drum may be controlled so that the phase of the waveform of the image shift (waveform of the position fluctuation of the laser scanning surface) becomes the same.

Hereinafter, with reference to the flow chart shown in FIG. 10, the phase matching operation of the photosensitive drum of each color will be described.

FIG. 10 is a flowchart for explaining an example of the first control processing procedure of the present invention. The flowchart corresponds to an example of the phase adjustment processing procedure of each color photosensitive drum, and corresponds to the CP shown in FIG.
U1017 executes based on the program stored in ROM in ROM / RAM1030 or other storage media not shown. In addition, S101 to S103 indicate each step.

First, in step S101, the photosensitive drums 1C, 1M, 1Y, 1BK are rotationally driven by the drive motors 90C, 90M, 90Y, 90BK. In step S102, the sensors 14C, 14M, 14Y, 1
4BK, marks 13C, 13 provided on the photosensitive drum
M, 13Y, and 13BK are detected.

Next, at step S103, the mark 13 by the sensors 14C, 14M, 14Y, 14BK
Based on the detection signals of C, 13M, 13Y, and 13BK,
The drive motors 90C, 90M, 90Y, 9 are so adjusted that the phases of the eccentricities of the photosensitive drums 1C, 1M, 1Y, 1BK of the respective colors match.
0BK is controlled.

With this configuration, it is not necessary to adjust the phase of the eccentricity of the photosensitive drum in advance, and even if the eccentricity phase of the photosensitive drum is shifted for some reason, if the above-described control is performed, the original state of the photosensitive drum can be maintained. Can be returned to.

With the above arrangement, even if the magnification of each color in the main scanning direction changes, each color similarly changes, so that color shift between the colors can be prevented.

[Third Embodiment] In the second embodiment,
A configuration has been described in which a drive motor that drives a photosensitive drum is controlled based on a mark detection signal of a mark provided at the same phase position of eccentricity of each photosensitive drum so that each photosensitive drum has the same phase. An image signal input to each laser scanning system may be adjusted based on the mark detection signal. Hereinafter, the embodiment will be described.

First, magnification shift is corrected by changing the modulation frequency for performing light modulation of a light beam for each color. In addition to the magnification correction, the image writing timing (that is, the image signal input timing to the semiconductor laser 1) is adjusted and adjusted in the left-right direction (left end position shift).

The adjustment amount can be calculated by measuring the amount of eccentricity in advance.

Hereinafter, the operation of the image shift adjustment processing of each color will be described with reference to the flowchart of FIG.

FIG. 11 is a flow chart for explaining an example of the second control processing procedure of the present invention. The flowchart corresponds to an example of the image shift adjustment processing procedure of each color, and corresponds to the CPU 10 shown in FIG.
17 is executed based on a program stored in the ROM in the ROM / RAM 1030 or another storage medium (not shown). S201 to S203 indicate each step.

First, in step S201, the photosensitive drums 1C, 1M, 1Y, 1BK are rotationally driven by the drive motors 90C, 90M, 90Y, 90BK. In step S202, the sensors 14C, 14M, 14Y, 1
4BK, marks 13C, 13 provided on the photosensitive drum
M, 13Y, and 13BK are detected.

Next, at step S203, the mark 13 by the sensors 14C, 14M, 14Y, 14BK
Based on the detection signals of C, 13M, 13Y, and 13BK,
The modulation frequency of the image signal for performing the light modulation of each color and the timing of writing the image of each color (that is, the timing of inputting the image signal to the semiconductor laser 1) are measured in advance and the ROM / RAM is measured.
The amount of eccentricity (Δ) of the center of the photosensitive drum stored in 1030
Adjustment control is performed in accordance with r) to correct the magnification and correct the positional deviation (left end positional deviation) in the horizontal direction (main scanning direction). That is, based on the phase difference between the photosensitive drums and the amount of eccentricity (Δr) of the photosensitive drums, the modulation frequency of each color image signal and the image writing timing of each color are adjusted and controlled.

By the above processing, each of the color images can be made to coincide with the reference image, so that high-precision printing in which the occurrence of color misregistration between the colors can be suppressed can be achieved.

In this embodiment, an image signal and an image forming timing to be input to each laser scanning system are adjusted based on a mark detection signal of a mark provided at the same phase position of eccentricity of each photosensitive drum. I explained,
First, as described in the second embodiment, a drive motor for driving the photosensitive drums is controlled based on the mark detection signal so that the phases of the photosensitive drums are in the same phase.
The modulation frequency and the image forming timing of the image signal input to each laser scanning system may be adjusted based on the mark detection signal to perform the overall magnification correction and the scanning position correction in the main scanning direction.

As a result, it is possible to prevent color misregistration between the respective colors in the main scanning direction, adjust the magnification, and prevent meandering of the image in the main scanning direction (shown in FIG. 5), thereby achieving high-precision color printing. Can be.

Further, the image forming apparatus of the present invention is designed to record color image information or the like while suppressing the scanning line deviation between each color. In addition to the color laser beam printer shown in FIG. The present invention is also suitable for an apparatus such as a color digital copying machine having an electrophotographic process, and can perform high-precision color printing while suppressing color shift in the main scanning direction between colors.

As described above, even if the magnification in the main scanning direction is changed for each color, each color is similarly changed, so that the color shift in the main scanning direction can be reduced.

Further, since the magnification can be adjusted, color misregistration in the main scanning direction can be reduced, and high-precision printing can be achieved.

With the above arrangement, the magnification in the main scanning direction of each color can be adjusted, and the meandering of the image edge in the sub-scanning direction in the main scanning direction can be prevented.

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

FIG. 12 is a view for explaining a memory map of a storage medium for storing various data processing programs readable by the image forming apparatus according to the present invention.

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. Also, if the programs and data to be installed are compressed,
A program for decompressing may also be stored.

The functions shown in FIGS. 10 and 11 in this embodiment 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 the novel 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 disk, hard disk, optical disk, magneto-optical disk, CD-ROM, C
DR, DVD-ROM, magnetic tape, non-volatile memory card, ROM, EEPROM, silicon disk and the like can be used.

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

Further, after the program code read from the storage medium is written 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.

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

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

[0136]

As described above, the first embodiment according to the present invention is described.
According to the invention, the respective photosensitive drums are arranged so that the phase of the position variation cycle of the exposure scanning surface on each photosensitive drum surface is the same between the respective photosensitive drums. Even if the magnification of the image in the main scanning direction changes, the magnification in the main scanning direction of each image formed on each photosensitive drum can be similarly changed to reduce the image shift in the main scanning direction.

According to the second aspect of the present invention, the plurality of detecting means respectively detect the phase of the position fluctuation cycle of the exposure scanning surface on each photosensitive drum surface, and control means based on the detection results of the plurality of detecting means. However, since a plurality of drive units that independently drive the respective photosensitive drums are controlled such that the phase of the position fluctuation cycle of the exposure scanning surface on the respective photosensitive drum surfaces becomes the same between the respective photosensitive drums, Even if the magnification in the main scanning direction of the image formed on the photosensitive drum changes, the magnification in the main scanning direction of each image formed on each photosensitive drum is similarly changed to reduce image deviation in the main scanning direction. be able to.

According to the third aspect of the present invention, the plurality of detecting means detect the phase of the position variation cycle of the exposure scanning surface on each photosensitive drum surface, and the control means based on the detection results of the plurality of detecting means. Adjusts the image signal input to each of the exposure devices according to a preset adjustment amount, so that the magnification in the main scanning direction of the image formed on each photosensitive drum is adjusted, and the image in the main scanning direction is adjusted. The displacement can be reduced and a highly accurate image can be formed.

According to the fourth aspect, a plurality of detecting means for respectively detecting the phase of the position fluctuation cycle of the exposure scanning surface on each of the photosensitive drum surfaces, and the detecting means based on the detection results of the plurality of detecting means. Since control means for adjusting an image signal input to each exposure device in accordance with a preset adjustment amount is provided, the main scanning direction magnification of an image formed on each photosensitive drum is adjusted to perform main scanning. It is possible to reduce the image displacement in the direction and to form a highly accurate image.

According to the fifth aspect of the present invention, the plurality of detecting means detect the marks attached at the same phase position in the position fluctuation cycle of the exposure scanning surface on each photosensitive drum surface by the sensor. By adjusting the magnification in the main scanning direction of the image formed on the drum, it is possible to reduce image deviation in the main scanning direction and to form a highly accurate image.

According to the sixth aspect, there is provided control means for adjusting an image signal input to each of the exposure devices in accordance with a preset adjustment amount based on the detection results of the plurality of detection means. Therefore, by adjusting the magnification of the image formed on each photosensitive drum in the main scanning direction, it is possible to reduce image deviation in the main scanning direction and to form a highly accurate image.

According to the seventh aspect, the control means presets a modulation frequency of an image signal input to each of the exposure devices and an input timing of the image signal based on the detection results of the plurality of detection means. Adjustment according to the amount of eccentricity of the center of the photosensitive drum, the magnification of the image formed on each photosensitive drum in the main scanning direction is adjusted to reduce the image shift in the main scanning direction and to achieve a highly accurate image. Can be formed.

According to the eighth aspect, the photosensitive drums are arranged so that the distance between the photosensitive drums is an integral multiple of the circumferential length of the photosensitive drums. Even if the magnification in the main scanning direction varies, the magnification in the main scanning direction of each image formed on each photosensitive drum can be similarly varied to reduce image deviation in the main scanning direction.

According to the ninth and eleventh aspects, the phase of the position fluctuation cycle of the laser scanning surface on each photosensitive drum surface which can be driven independently is detected, and based on the detection result, the phase on each photosensitive drum surface is detected. The phase of the position fluctuation cycle of the laser scanning surface of
Since the drive of each of the photosensitive drums is adjusted so as to be the same among the respective photosensitive drums, even if the magnification in the main scanning direction of the image formed on each of the photosensitive drums changes, the photosensitive drum is formed on each of the photosensitive drums The image displacement in the main scanning direction can be reduced by changing the magnification in the main scanning direction of each image in the same manner.

According to the tenth and twelfth aspects, the phase of the position variation period of the laser scanning surface on each photosensitive drum surface is detected, and based on the detection result, the image signal input to each of the exposure devices is detected. Is adjusted in accordance with a preset adjustment amount, so that the magnification in the main scanning direction of the image formed on each photosensitive drum is adjusted to reduce image deviation in the main scanning direction and to form a highly accurate image. can do.

Accordingly, the variation in the magnification in the main scanning direction of the image formed on each photosensitive drum can be matched to reduce the image deviation in the main scanning direction, and a high-quality image without color deviation can be formed. And so on.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a main part of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of an image forming apparatus according to the first exemplary embodiment of the present invention.

FIG. 3 is a diagram illustrating the configuration of the laser exposure apparatus shown in FIG.

FIG. 4 is a schematic diagram when optical scanning is performed on a photosensitive drum surface by the laser exposure device shown in FIG. 3;

FIG. 5 is a schematic diagram when optical scanning is performed on the surface of the photosensitive drum by the scanning optical system shown in FIG. 3;

6 is a diagram showing an eccentric state of the photosensitive drum shown in FIG.

FIG. 7 is a diagram showing a scanning exposure surface variation of the photosensitive drum having the eccentricity of Δr shown in FIG. 6;

FIG. 8 is a diagram illustrating a schematic configuration of the image forming apparatus illustrated in FIG. 1;

9 is a diagram illustrating a schematic configuration around a photosensitive drum of the image forming apparatus illustrated in FIG. 8;

FIG. 10 is a flowchart illustrating an example of a first control processing procedure according to the present invention.

FIG. 11 is a flowchart illustrating an example of a second control processing procedure according to the present invention.

FIG. 12 is a diagram illustrating a memory map of a storage medium that stores various data processing programs that can be read by the image forming apparatus according to the present invention.

FIG. 13 is a schematic view of a main part of a scanning optical system of a conventional image forming apparatus.

14 uses a plurality of scanning optical systems shown in FIG. 13 at the same time, records image information for each color component on a photosensitive drum for each color component, and forms a color image by superimposing an image for each color component. FIG. 2 is a cross-sectional view schematically illustrating a main part of the color image forming apparatus.

15 is a schematic diagram when optical scanning is performed on a photosensitive drum surface by the scanning optical system shown in FIG.

FIG. 16 is a schematic diagram when optical scanning is performed on the surface of the photosensitive drum by the scanning optical system shown in FIG.

[Explanation of symbols]

1C, 1M, 1Y, 1BK Photosensitive drum 12C, 12M, 12Y, 12BK Center of rotation of photosensitive drum 13C, 13M, 13Y, 13BK Mark 14C, 14M, 14Y, 14BK Sensor 51, 52, 53, 54 Laser exposure device 90C, 90M, 90Y, 90BK Drive motor 1017 CPU 1030 ROM / RAM 1023 Detection system d Distance between adjacent photosensitive drums (perimeter of photosensitive drum) r Reference radius of photosensitive drum Δr Eccentricity of photosensitive drum

 ──────────────────────────────────────────────────続 き Continued on front page F-term (reference) 2C362 BA32 BA33 BA39 BA52 BA68 BA70 BB37 BB39 BB40 CA22 CA23 CA39 CB59 2H027 DA22 DE02 DE07 DE10 EB04 ED02 ED06 EE04 EE07 ZA07 2H030 AA01 AB02 AD11 AD17 BB02 BB12 BB12 BB12 BB12 BB12 CC26 DD11 DD12 DD15 DD24 EE04 EE06 FF15 GG09 GG12 HH02 9A001 HH34 JJ35 KK16 KK42

Claims (12)

[Claims] An exposure apparatus for scanning and exposing the photosensitive drum with a light beam that is modulated in accordance with an image signal input to the photosensitive drum and that is input to the photosensitive drum to form an image on the surface of the photosensitive drum; In the image forming apparatus having a plurality of sets, the images formed on the respective photosensitive drum surfaces can be overlapped to form a multiplex image, An image forming apparatus, wherein each of the photosensitive drums is arranged so that a phase is the same between the photosensitive drums. 2. An exposure apparatus for scanning and exposing a photosensitive drum with a light beam modulated according to an image signal input to the photosensitive drum and corresponding to an image signal input to the photosensitive drum to form an image on the surface of the photosensitive drum. An image forming apparatus capable of forming a multiplexed image by superimposing images formed on the photosensitive drum surfaces of the respective sets, wherein a plurality of driving units independently drive the respective photosensitive drums, A plurality of detecting means for respectively detecting a phase of a position variation cycle of the exposure scanning surface on each of the photosensitive drum surfaces; and a position of the exposure scanning surface on each of the photosensitive drum surfaces based on detection results of the plurality of detecting means. An image forming apparatus comprising: a control unit that controls each of the driving units so that a phase of a fluctuation cycle is the same among the photosensitive drums. 3. An exposure apparatus which scans and exposes the photosensitive drum with a light beam which is modulated in accordance with an image signal inputted thereto corresponding to the photosensitive drum and forms an image on the surface of the photosensitive drum. In the image forming apparatus having a plurality of sets, the images formed on the respective photosensitive drum surfaces can be overlapped to form a multiplex image, A plurality of detection means for respectively detecting a phase, and a control means for adjusting an image signal input to each of the exposure apparatuses according to a preset adjustment amount based on detection results of the plurality of detection means. An image forming apparatus comprising: 4. A plurality of detecting means for respectively detecting a phase of a position change cycle of an exposure scanning surface on each of the photosensitive drum surfaces, and a signal inputted to each of the exposure devices based on a detection result of the plurality of detecting means. 2. An image forming apparatus according to claim 1, further comprising control means for adjusting an image signal according to a preset adjustment amount. 5. The sensor according to claim 3, wherein the plurality of detection units detect a mark attached to an in-phase position of a position variation cycle of an exposure scanning surface on each of the photosensitive drum surfaces by a sensor. The image forming apparatus as described in the above. 6. A control means for adjusting an image signal input to each of said exposure devices according to a preset adjustment amount based on detection results of said plurality of detection means. Item 3. The image forming apparatus according to Item 2. 7. The control device according to claim 1, wherein the control unit sets a modulation frequency of an image signal and an input timing of the image signal, which are input to each of the exposure devices, at a center of the photosensitive drum based on detection results of the plurality of detection units. 7. The image forming apparatus according to claim 4, wherein the adjustment is performed according to the amount of eccentricity. 8. The image forming apparatus according to claim 1, wherein said photosensitive drums are arranged such that a distance between said photosensitive drums is an integral multiple of a peripheral length of the photosensitive drums. apparatus. 9. A photosensitive drum which can be independently driven and a light beam which is modulated in accordance with an image signal input to the photosensitive drum to scan and expose the photosensitive drum to form an image on the surface of the photosensitive drum A plurality of sets with the exposure apparatus to
In the control method of an image forming apparatus capable of forming a multiplex image by superimposing images formed on the respective photosensitive drum surfaces, detecting a phase of a position variation cycle of an exposure scanning surface on each of the photosensitive drum surfaces. And adjusting the driving of each of the photosensitive drums based on the detection result such that the phase of the position variation cycle of the exposure scanning surface on each of the photosensitive drum surfaces is the same between the photosensitive drums. And a control method of the image forming apparatus, comprising: an adjusting step. 10. An exposure apparatus for scanning and exposing a photosensitive drum with a light beam optically modulated according to an image signal input to the photosensitive drum to form an image on the surface of the photosensitive drum. A method of controlling an image forming apparatus capable of forming a multiplex image by superimposing images formed on the photosensitive drum surfaces of the respective sets, wherein a position of an exposure scanning surface on each of the photosensitive drum surfaces A detection step of detecting a phase of a fluctuation cycle, and an adjustment step of adjusting an image signal input to each of the exposure apparatuses according to a preset adjustment amount based on the detection result. A method for controlling an image forming apparatus. 11. A photosensitive drum which can be driven independently and scans and exposes the photosensitive drum with a light beam optically modulated in accordance with an image signal input to the photosensitive drum to form an image on the surface of the photosensitive drum. An image forming apparatus having a plurality of sets with an exposure device to be formed, and capable of forming a multiplexed image by superimposing images formed on the respective photosensitive drum surfaces of the respective sets, A detection step of detecting the phase of the position fluctuation cycle, and based on the detection result, the phase of the position fluctuation cycle of the exposure scanning surface on each of the photosensitive drum surfaces is set to be the same between the respective photosensitive drums. A storage medium in which a program for executing the adjusting step of adjusting the drive of each photosensitive drum and a computer are readable. 12. An exposure apparatus for forming an image on the surface of the photosensitive drum by scanning and exposing the photosensitive drum with a light beam modulated in accordance with an image signal input to the photosensitive drum. An image forming apparatus that has a plurality of sets and that can form a multiplexed image by superimposing images formed on the photosensitive drum surfaces of the respective sets, the position variation period of the exposure scanning surface on each photosensitive drum surface A computer-readable storage medium storing a program for executing a detection step of detecting a phase, and an adjustment step of adjusting an image signal input to each of the exposure apparatuses based on the detection result according to a preset adjustment amount. A storage medium stored in a readable form.