JPS6240475A - Image forming device - Google Patents

Abstract

PURPOSE:To correct positional deviation and to form an image having high quality by providing a detecting device that detects positional deviation in the direction of shifting of a transferred material and in the direction intersecting orthogonally with the direction of shifting and a controlling device that corrects the position of an image forming in the direction of shifting of the transferred material and in the direction intersecting orthogonally with the direction of shifting by operating a shift device. CONSTITUTION:Copying operation is made by detecting the amount of positional deviation in (x) direction and (y) direction of fed paper by an optical detecting unit 130 and controlling a lens block 8 for variable power, the first carriage and an exposure lamp 4 according to the amount of positional deviation. Accordingly, the original image can be copied at the specified position of a paper even when the positional deviation is occurred in the fed paper, and the quality of copied image can be improved. Furthermore, when a cassette selector key is operated at the optical detecting unit 130, the specified part of an optical sensor 133 is moved so as to coincide with the reference position Re of selected paper. Accordingly, the positional deviation of the paper can be detected even when the size of the paper is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to an image forming apparatus applied to, for example, an electronic copying machine.

(Technical background of the invention and its problems) As is well known, in conventional copying machines, misalignment of paper supplied to the transfer unit (misalignment relative to the direction of paper movement, or misalignment perpendicular to the direction of movement) There was no means for detecting or correcting the directional positional deviation.

Generally, the paper supplied from the paper cassette has a voltage of ±3V.
A positional shift of about n may occur. however,
Conventional copying machines are unable to detect and correct misalignment of paper that has been supplied, and in some cases, the image is formed on one side of the paper, resulting in a misalignment of the formed image. There were times when the quality deteriorated. Therefore, it is desired to develop a means that can detect and correct the positional deviation of the supplied paper. Moreover, it would be convenient in practice if this paper positional shift detection and correction could be performed even when the paper size changes.

[Purpose of the invention]

This invention was made based on the above circumstances,
The purpose is to
It is an object of the present invention to provide an image forming apparatus that is capable of correcting positional deviations and forming high-quality images.

[Summary of the invention]

This invention provides, for example, an optical detection unit that is movable in a direction perpendicular to the paper movement direction in front of the registration roller and detects a positional shift of the supplied paper, and detects the position of the paper according to the output signal of the optical detection unit. , the lens block for variable magnification is moved in a direction perpendicular to the moving direction of the first carriage to correct the image forming position relative to the paper, and in particular, the optical detection unit is set to a standard according to the paper size. It is designed to be set at a certain position.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 4 and 5 schematically show an image forming apparatus of the present invention, such as a copying machine. A document table (transparent glass) 2 for supporting a document is fixed to the top surface of the copying machine main body 1. The document table 2 is provided with a fixed scale 2 that serves as a reference for setting the document, and furthermore, a document cover 11 and a work table 12, which can be opened and closed, are provided near the document table 2. The original placed on the original platen 2 is processed by an optical system consisting of an exposure lamp 4 and mirrors 5, 6, and 7.
Exposure scanning is performed by reciprocating in the direction of arrow a along the lower surface of document table 2. in this case,
Mirror 6.7 is 1/1/2 of mirror 5 to maintain the light exposure length.
It is moved at a speed of 2.

The light reflected from the original by the scanning of the optical system, that is, the light reflected from the original by the light irradiation of the exposure lamp 4, is reflected by the mirror 5, 6, 7, passes through the variable magnification lens block 8, and is further reflected by the mirror. 9 and guided to the photoreceptor drum 10, so that an image of the document is formed on the surface of the photoreceptor drum 10.

The photosensitive drum 10 is rotated in the direction of arrow C in the figure, and first, the surface thereof is charged by the charging device 11. Thereafter, the image is exposed to slit light to form an electrostatic latent image on the surface. This electrostatic latent image is made visible by applying toner by the developing device 12.

On the other hand, the paper (transfer material) P is taken out one by one from the selected upper paper feed cassette 13 or lower paper feed cassette 14 by the delivery roller 15 or 16, and the taken out paper is taken out from the paper guide path 17 or 18 to one pair of registration rollers, and is guided to a transfer section by this pair of registration rollers 19. Here, the paper feed cassettes 13 and 14 are removably provided at the lower right end of the main body 1, and one of them can be selected from an operation panel to be described later. The cassette size of each of the paper feed cassettes 13 and 14 is detected by a cassette size detection switch 601 and 602, respectively. The cassette size detection switch 6o1.602 is composed of a plurality of microswitches that are turned on and off according to the insertion of cassettes of different sizes.

The paper P sent to the transfer section is brought into close contact with the surface of the photoreceptor drum 10 at the transfer charger 20, and
The toner image on the photoreceptor drum 10 is transferred by the action of 0. The transferred paper P is electrostatically peeled off from the photosensitive drum 10 by the action of a peeling charger 21, and is sent by a conveyor belt 22 to a fixing roller 23 as a fixing device provided at the end thereof. The transferred image is fixed by passing through this, and the fixed paper P is discharged to a tray 25 outside the main body 1 by a pair of paper discharge rollers 24 . Further, the photoreceptor drum 10 after the transfer is transferred to a charger 2 for removing static electricity.
6, residual toner on the surface is removed by a cleaner 27, and afterimages are roughly erased by a static elimination lamp 28, so that the initial state is restored. Note that 29 is a cooling fan for preventing the temperature inside the main body 1 from rising.

FIG. 6 shows the operation panel 30 provided on the main body 1. 301 is a copy key for instructing the start of copying; 302
is a numeric keypad for setting the number of copies, etc.; 303 is a display unit that displays the operating status of each section and paper jams; 304 is a cassette selection key for selecting the upper and lower paper feed cassettes 13 and 14; 305 is a selected key. A cassette display section for displaying the cassette, 306 a magnification setting key for setting the enlargement and reduction magnification of copies in a predetermined relationship, 307 a zoom key for steplessly setting the enlargement and reduction magnification, and 30a for displaying the set magnification. The display section 30B is a density setting section for setting copy density.

FIG. 7 shows an example of the drive source configuration of each drive unit of the copy line configured as described above, and is configured with the following motors. That is, 31 is a lens motor, which is a motor for moving the position of the lens block 8 for performing magnification change. 32 is a mirror motor;
This is a motor for changing the distance device (optical path length) between the mirror 5 and the mirror 6.7 for changing the magnification.

A scanning upper 33 is a motor for moving the exposure lamp 4, the mirror 5, and the mirror 6.7 for scanning the original. A shutter motor 34 is a motor for moving a shutter (not shown) for adjusting the charging width of the photosensitive drum 10 by the charger 11 during zooming. A developing motor 35 is a motor for driving the developing roller of the developing device 12 and the like. 36 is a drum motor, which is a motor for driving the photosensitive drum 10. Reference numeral 37 denotes a fixing motor, which is a motor for driving the paper conveyance path 22, the pair of fixing rollers 23, and the pair of paper discharge rollers 24.

38 is a paper feed motor, and the feed roller 15, 16
This is a motor for driving. A paper feeding motor 39 is a motor for driving the registration roller pair 19. A fan motor 40 is a motor for driving the cooling fan 29.

FIG. 8 shows a drive mechanism for reciprocating the optical system. That is, the mirror 5 and the exposure lamp 4 are supported by a first carriage 411, and the mirror 6.7 is supported by a second carriage 422, and these carriages 411 and 412 are guided by guide rails 421 and 422 in the direction of arrow a. It is said to be able to move in parallel. Further, the four-phase pulse motor 33 drives a pulley 43. An endless belt 45 is stretched between the pulley 43 and the idle pulley 44, and one end of a first carriage 411 that supports the mirror 5 is fixed to a midway portion of the belt 45. On the other hand, the second mirror supporting mirror 6.7
Two pulleys 47.47 are rotatably provided on the guide portion 46 of the carriage 422, spaced apart in the axial direction of the rail 422, and a wire 48 is connected between these pulleys 47.47.
is being handed over. One end of this wire 48 is a fixed part 49
The other end is connected to the fixing part 4 via a coil spring 50.
are fixed respectively. Further, one end of a first carriage 411 is fixed to a midway portion of the wire 48. Therefore, by rotating the pulse motor 33, the belt 45 rotates and the first carriage 411 is moved, and the second carriage 422 is also moved accordingly. At this time, since the pulleys 47, 47 serve as movable pulleys, the second carriage 422 is moved in the same direction as the first carriage 411 at 1/2 the speed. The moving directions of the first and second carriages 41 and 412 are as follows:
It is controlled by switching the rotation direction of the pulse motor 33.

Further, on the document table 2, a copyable range corresponding to the specified paper is displayed. That is, the cassette selection key 304
Let the paper size specified by (Px, Py) be,
If the copy magnification specified by the magnification setting keys 305 and 307 is K, the copyable range (X, V) is rx=P
x/KJ.

rV-Py/Kl. This copyable range (X.

y), the X direction is indicated by the distance between the pointers 51 and 52 provided on the back surface of the document table 2, and the y direction is indicated by the distance between the scale 53 provided on the upper surface of the first carriage 41 and the It is displayed based on the distance between two fixed scales.

As shown in FIG. 9, the above-mentioned pointers 51.
55 via a spring 56. The pulley 55 is rotated by a motor 58, and the distance between the pointers 51 and 52 is changed by driving the motor 58 in accordance with the determined copyable range in the X direction. It looks like this.

Further, the first carriage 411 is moved to a predetermined position (home position according to the magnification) by driving the motor 33 according to the paper size and magnification. When the copy key 301 is pressed, the first carriage 411 is first moved toward the second carriage 412, and then the lamp 4 is turned on and moved away from the second carriage 412. When scanning of the original is completed, the lamp 4 is turned off and the first carriage 41
1 is returned to the home position.

FIG. 10 shows a drive mechanism for the variable magnification lens block 8. As shown in FIG. The motor 31 is connected to a first carriage 411
A lead screw 61 arranged along the moving direction (y direction) is rotated. Bushes 63 and 632 provided at one end of the board 62 are screwed into the lead screw 61.
1 is rotated, the substrate 62 is moved in the y direction.

A guide member 62r is provided at the other end of the substrate 62, and the guide member 621 is slidably engaged with the guide rail 64. Further, the substrate 62 includes a substrate 62 .
A movable body 65 is provided, which is movable in a direction (X direction) orthogonal to the above, and to which the variable magnification lens block 8 is attached. That is, supports 651. are provided at both ends of the moving body 65.
652 are provided, and these supports 651 and 652 are guided and held by guide members 661 and 662 provided on the substrate 62. Further, a rack 653 is provided on the longitudinal side surface of the support body 651, and a pinion 68 rotated by a pulse motor 67 provided on the base plate 62 is meshed with this rack 653. Therefore, the variable power lens block 8 is moved in the X direction by driving the motor 67. In addition, the micro switches 691 and 692 are connected to the substrate 62 and the moving body 6, respectively.
This is to detect the initial position of No. 5.

Next, the relationship between the operation of the variable magnification lens block 8 and the image formed will be explained. In FIG. 11<a), the focal length of the variable power lens block 8 is f, and the optical path length from the document table 2 to the variable power lens block 8 is ya1. When the optical path length is yb1 and the total optical path length from the document table 2 to the photosensitive drum 10 is yc, the optical formula is expressed as follows.

1/f-1/ya+1/yb Also, the magnification is expressed as -yb/ya. Since the focal length f of the variable power lens block 8 is constant, it is understood that in order to focus during variable power, it is necessary not only to change the total optical path length yc but also to change ya or yb. This ya, yb
can be changed by moving the variable power lens block 8 in the y direction. Further, the total optical path length yc can be changed by moving the second carriage 412' and changing the position of the mirror 6.7.

On the other hand, as shown in FIG. 11(b), the distances between the document table 2, the variable magnification lens block 8, and the photosensitive drum 10 are kept constant, and the variable magnification lens block 8 is moved in the X direction by the motor 67, for example, by a distance x When the image on the photosensitive drum 10 is moved by 1, the image on the photosensitive drum 10 is moved by a distance x 2 expressed by the following equation.

X2-xl XVb/Va Also, in the case of a same size copy, it becomes X2-2Xt. In this way, by moving the variable magnification lens block 8 in the X direction, the center of the copied image can be moved.

FIG. 12 shows the overall control circuit.

The main processor group 71 detects inputs from the operation panel 30 and input devices 75 such as various switches and sensors, for example, the cassette size detection switches 601 and 602, and includes a high-voltage transformer 76 that drives the various chargers, and the static elimination lamp. 28, the blade solenoid 27a1 of the cleaner 27, the heater 23a1 of the fixing roller pair 23, the exposure lamp 4, and each of the motors 31-40.58
．． 67 and the like to perform the above-mentioned copying operation, the light emitting element 132 of the optical detection unit 130, the optical sensor 133, and the pulse motor 138 are used to detect the misalignment of the paper, and depending on the state, the paper An operation is performed to compensate for the image forming position relative to the image forming position. Note that details of the optical detection unit 130 and the like will be described later.

Among the motors 31 to 40, 58, 67, and 138, the motor 35, 37, and 40 and the toner motor 77 that supplies toner to the developing device 12 are controlled by the main processor group 71 via a motor driver 78. 31-3
4.67.138 are controlled by the first sub-processor 72 via a pulse motor driver 79, and motors 36.
39, 38, and 58 are controlled by the second sub-processor group 73 via the pulse motor driver 80. Further, the exposure lamp 4 is controlled by the main processor group 71 via the lamp regulator 81, and the heater 23a is controlled by the main processor group 71 via the heater control section 82. Then, from the main processor group 71, the first. Commands to drive and stop each motor are sent to the second sub-processor group 72, 73, and status signals indicating the driving and stopping states of each motor are sent from the first and second sub-processor groups 72, 73 to the main processor group 71. It will be done. Further, the first sub-processor details 72 receives position information from a position sensor 83 that detects the initial positions of the motors 31 to 34, 67, and 138.

FIG. 13 shows an example of the configuration of the main processor group 71. That is, the one-chip microcomputer 91 (
(hereinafter simply referred to as microcontroller), the input/output board 9
2, key human force detection and various display controls on an operation panel (not shown) are performed. Further, the microcomputer 91 is expanded by input/output ports 93-96. and,
A high voltage transformer 76, a motor driver 78, a lamp regulator 81, and other outputs are connected to the input/output boat 93. A size switch for detecting paper size and other inputs are connected to the input/output boat 94. is connected to the copy condition setting switch and other inputs. Note that the input/output port 96 is an option.

FIG. 14 shows an example of the configuration of the first sub-processor group 72. The microcomputer 101 is the main processor group 7
1 is connected. Programmable interval
The timer 102 controls the phase switching interval time of the pulse motor, and when a setting value is set from the microcomputer 101, counting of reference clock pulses is started based on the set value, and when the timer 102 is counted out, the end pulse is sent to the microcomputer 101. It is designed to output to the interrupt line. The microcomputer 101 also includes the position sensor 8.
3, and input/output boats 103 and 104 are connected. The input/output boat 104 is connected to the motors 31 to 34, 67, and 138 via the pulse motor driver 79. The input/output board 103 is used, for example, to output status signals of each pulse motor to the main processor group 71.

FIG. 15 shows the configuration of the second sub processor C tether group 73. The microcomputer 111 is connected to the main processor group 71
is connected to. The programmable interval timer 112 controls the phase switching interval time of the pulse motor, and when a set value is set from the microcomputer 111, it starts counting reference clock pulses based on it, and when the count is out, it starts counting the end pulse. It is designed to be output. This termination pulse is latched by the latch circuit 113, and its output is supplied to the interrupt line and input/output board input line of the microcomputer 111. Further, an input/output boat 114 is connected to the microcomputer 111, and this input/output boat 114 is connected to the pulse motor driver 8.
Motors 36.38.39.58 are connected via 0.

Figure 16 shows the control circuit of the pulse motor.
The input/output boat 121 (corresponding to the input/output boats 104 and 114 in FIGS. 14 and 15) has a pulse motor driver 1.
22 (seven pulse motor drivers of the 12th factor, equivalent to 80) are connected to this pulse motor driver 122, and a pulse motor 123 (the pulse motors 31 to 34.
6.38.39.58.67.138) are connected to each other.

FIG. 17 shows a method for controlling the speed of a pulse motor, in which (a) shows the speed curve of the pulse motor, and (b) shows the phase switching interval.

As is clear from this figure, the ° phase switching interval is long at first, then gradually becomes equal intervals, becomes gradually longer again, and then stops. In other words, this indicates the through-up and through-down of the pulse motor, starting from the self-starting region, being used in the high-speed region, and finally falling down. Note that tl, t2, . . . tx indicate the time of the phase switching interval.

Next, main parts of the present invention will be explained. In this embodiment, it is possible to correct paper misalignment. That is,
As shown in FIG. 1(a), the above-mentioned registration roller pair 1
9 and the photoreceptor drum 1o (not shown), the optical detection unit 13 detects a lateral positional deviation of the paper P.
0 is set. This optical detection unit 130 is
A case 131 having a substantially U-shape, and a light emitting element 132 and a plurality of light receiving elements 133a to 133d disposed inside the case 131 at predetermined intervals in a direction perpendicular to the front and back sides of the paper P, for example. It is constituted by an optical sensor 133 consisting of. The case 131
is a guide shaft 13 disposed along a pair of registration rollers 19.
The case 131 is movably provided at the timing belt 1 disposed along the guide shaft 134.
It is fixed at 35. This timing belt 135 is stretched between pulleys 136 and 137, of which pulley 137 is driven by a pulse motor 138. Therefore, when the pulse motor 138 is driven, the optical detection unit 130
is moved along the guide shaft 134. Further, a microswitch 139 is provided near one end of the guide shaft 134, and the initial position of the optical detection unit 130 is detected by this microswitch 139. Although the registration roller pair 19 and the guide shaft 134 are shown separated from each other in FIG. 1(a), the distance yp between them is extremely narrow.

In the above configuration, a paper misalignment detection operation using the optical detection unit 130 will be described.

When the copy key 301 of the operation panel 30 is operated,
The main processor group 71 performs operations as shown in FIG. That is, first, in step ST1, by operating the cassette selection key 304 on the operation panel 30, the upper paper feed cassette 13 and the lower paper feed cassette 14 are selected.
It is determined which paper feed cassette is selected. As a result, if it is determined that the upper paper feed cassette 13 is being operated, the control moves to step ST2, and if it is determined that the lower paper feed cassette 14 is being operated, the control is The process moves to step ST3. In steps ST2 and ST3, the optical detection unit 130 is moved to a reference position corresponding to the selected paper size. Figure 1(b)
As shown in FIG.
If detection is to be performed between the 33 light emitting elements 133b and 133C, the reference position Re between the light emitting elements 133b and 1330 is determined according to the size of the selected paper.
will be moved to Note that the paper P is fed so that its center in the width direction is aligned with the center in the longitudinal direction of the pair of registration rollers 19. Furthermore, when the paper is changed by operating the cassette selection key 304, the optical detection unit 13
0 moves from the reference position Re of one paper to the reference position Re of the other paper, as shown in FIG. If the widths of are xl and x2, respectively, then S-(Xl-X2)/2 is obtained.

As described above, the optical detection unit 130 detects the selected paper reference position i! In the state of being moved to Re, in step ST4, paper is fed from the selected paper feed cassette, and the amount of positional deviation of the fed paper is detected by the optical detection unit 130. Here, the amount of positional deviation of the paper in the X direction (width direction) and the positional deviation direction are determined by the light emitting elements 133a to 133a forming the optical sensor 133.
It is detected by the output signal of 133d. For example, if there is no positional shift in the fed paper, the light emitting elements 133a and 133b are blocked by the fed paper, and an output signal is detected only from the light emitting element 133C1133d. On the other hand, if the fed paper is misaligned in the X direction, the light emitting elements 133a to 133 of the optical sensor 133
The number of output signals obtained from d changes. Therefore, the amount and direction of paper misalignment can be detected from changes in this output signal.

Furthermore, the positional deviation in the y-direction (movement direction) of the paper changes the timing from when the paper starts being fed until an output signal is detected from any of the light emitting elements 133a to 133d forming the optical sensor 133. It can be detected by detecting. This detection method involves counting the number of pulses supplied to the motor 39 that drives the pair of registration rollers 19 until the optical sensor 133 detects the paper, and comparing this counted value with a preset reference value. By doing so, the amount of positional deviation in the y direction can be detected. When positional deviations in the X and y directions are detected in this way, in step ST6, the variable magnification lens block 8 is moved in accordance with the detected positional deviation l in the X direction, and the first carriage is moved. 411 and exposure lamp 4
The operation timing is controlled according to the amount of positional deviation in the y direction, and the copying operation described above is performed in step ST7. Therefore, the position at which an image is formed on the paper is changed depending on the misalignment of the paper, and the original image is formed at a predetermined position on the paper. In this way, the paper on which the original image has been copied is transferred to the paper output tray 2 in step ST8.
The paper is ejected at 5, and all processing is completed.

According to the embodiment described above, the optical detection unit 130 detects the amount of positional deviation of the fed paper in the X direction and the y direction. , the exposure lamp 4 is appropriately controlled to perform the copying operation. Therefore, even if a misalignment occurs in the fed paper, the original image can be copied at a predetermined position on the paper, and the quality of the copied image can be improved. Moreover, the optical detection unit 130 is configured such that when the cassette selection key 304 is selectively operated (6), the predetermined portion of the optical sensor 133 is moved so as to match the reference position Re of the selected sheet. . Therefore, even when the paper size is changed, it is possible to reliably detect paper misalignment.

Further, since the positional deviation of the paper in the X direction and the y direction can be detected by one optical detection unit 130, the configuration is relatively easy and it is possible to prevent the device from becoming large in size.

In the above embodiment, the optical sensor 133 was configured by a plurality of light emitting elements 133a to 133d, but as shown in FIG.
You may also use 0.

With such a configuration, it is possible to detect the positional deviation l of the paper with even higher accuracy.

It goes without saying that various other modifications can be made without departing from the gist of the invention.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to correct positional deviation regardless of the size of the transfer material, and image formation is possible in which a high-quality image can be formed. equipment can be provided.

[Brief explanation of the drawing]

Figure 1 shows an embodiment of the image forming apparatus according to the present invention, in which figure (a) is a perspective view of the main part showing an optical detection unit, and figure (b) is a perspective view of the main part showing the optical detection unit. ), FIG. 3(C) is a plan view for explaining the movement of the optical detection unit, FIG. 2 is a diagram showing misalignment detection and corrected copying operations, Figures a) and (b) show other embodiments of the present invention, in which figure (a) is a perspective view showing an optical detection unit, and figure (b) is a plane view showing the main parts of figure (a). 4 and 5 respectively show the configuration of the image forming apparatus, FIG. 4 is an external perspective view, FIG. 5 is a side sectional view, and FIG. 6 is a plan view showing the configuration of the operation panel. , FIG. 7 is a perspective view showing the configuration of the drive section, FIG. 8 is a perspective view schematically showing the drive mechanism of the optical system, FIG. 9 is a perspective view schematically showing the drive mechanism of the pointer, and FIG. FIG. 10 is a perspective view of the main parts showing the configuration of the variable power lens block, FIG. 11 is a diagram shown to explain the operation of the variable power lens block, and FIG. 12 is a configuration diagram showing the overall control circuit. , Fig. 13 is a block diagram of the main processor group, Fig. 14 is a block diagram of the first sub-processor group, Fig. 15 is a block diagram of the second sub-processor group, and Fig. 16 is a schematic diagram showing the control circuit of the pulse motor. The configuration diagram, FIG. 17, is a diagram for explaining the speed control method of the pulse motor. DESCRIPTION OF SYMBOLS 1... Main body, 2... Original table, 10... Photosensitive drum, 19... Registration roller pair, 30... Operation panel, 304... Cassette selection key, 71... Main processor Group, 130... Optical detection unit, 133
...Optical sensor, 138...Pulse motor, P...
・Paper. Applicant's agent Patent attorney Takehiko Suzue Figure 1 (C) Figures 2, 3 (a) 261 4rA yjS16 Figure 17

Claims (3)

[Claims] (1) A scanning device that optically scans a document placed on a document table, an image carrier on which an image of the document guided by the scanning device is formed, and a document imaged on the image carrier. An image forming apparatus comprising a moving means for changing the position of an image, a transfer means for transferring the image formed on the image carrier onto a transfer material, and a supply means for supplying the transfer material to the transfer means. , a detection means that is provided near the supply means and is movable in a direction perpendicular to the moving direction of the transferred material and detects the moving direction of the supplied transferred material and the positional deviation in the direction orthogonal to the moving direction; , the operation timing of the scanning means is controlled according to the moving position and output signal of the detecting means, and the moving means is operated to correct the moving direction of the transferred material and the image forming position in a direction perpendicular to the moving direction. An image forming apparatus comprising a control means. (2) The image forming apparatus according to claim 1, wherein the detection means includes a plurality of light receiving elements. (3) The image forming apparatus according to claim 1, wherein the detection means comprises a CCD line sensor.