JP2003316208A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for preventing visual image deviation when forming a double-sided image on a sheet or a double image on the sheet. <P>SOLUTION: The image forming apparatus comprises: a CCD 605 for detecting an image size and a position to the sheet after fixing images on the first surface of the sheet; a controller 602 for correcting the image size of the second surface in the sheet and the position to the sheet according to the detection signal of the CCD 605; and a reference position input section 614 for arbitrarily setting the correction reference of each controller 602 to a sheet transport direction and a direction that orthogonally crosses the sheet transport direction. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a printer, a facsimile, a copying machine, or a multifunctional machine having a combination of these functions.

[0002]

2. Description of the Related Art For example, in an image forming apparatus such as a copying machine, a printer or a facsimile, a sheet (transferring material) which is a recording material is transferred by an appropriate image forming process mechanism such as an electrophotographic method, an electrostatic recording method, a magnetic recording method. An image in which an unfixed toner image formed and carried by a transfer method (indirect method) or a direct method on a material, photosensitive paper, electrostatic recording paper, printing paper, etc. is heat-fixed. Forming equipment is widely used.

In such an image forming apparatus, an image is formed again on the back side of a sheet on which one side of the image is formed (both sides), or an image is formed again on the same side of the sheet on which the one side of image is formed. There have been proposed many image forming apparatuses capable of performing (multiplexing).

In such an image forming apparatus, the sheet is reversed inside the image forming apparatus and conveyed again to the image forming section, or the sheet discharged by the user to the outside of the image forming apparatus is again placed on the sheet stacking section. There is something to put.

When two-sided or multiple image formation is performed, the image shift on the front and back sides of the sheet occurs in the case of both sides, and the image shift on the same side of the sheet occurs in the case of multiple side, which deteriorates the quality of the printed matter. Is.

The main causes of this image shift are the absolute shift of the position from the edge of the sheet and the expansion and contraction due to the heat effect of the sheet which occurs when the first side of the sheet fixes the image.

With respect to the absolute displacement of the sheet from the edge portion, the sheet is once abutted against the nip of the pair of registration rollers which are stopped, and then the sheet is conveyed in synchronization with the image of the image forming section. The ones that start the sheet, those that use a shutter instead of the registration rollers, and those that synchronize the image by accelerating and decelerating without stopping the sheet conveyance are used to prevent the deviation of the sheet conveyance direction. ing.

As for the deviation of the sheet in the direction orthogonal to the conveying direction, the sheet is abutted against one side wall by an oblique feeding roller to correct the position, or the position of the sheet end is detected by a sensor. , A method of correcting the image position is adopted.

Regarding the expansion and contraction of the sheet, since paper is mainly used as the sheet, in the case of paper, the image on the second side becomes larger than that on the first side due to the contraction due to the evaporation of water.

When a resin sheet is used, the sheet expands due to thermal expansion, and the image on the second side becomes smaller. Therefore, the image on the second side of the sheet is uniformly predicted and scaled for correction on the first side of the sheet, or the size of the sheet after the image is fixed is detected in the conveyance path, and uniformly corrected. Such an image forming apparatus has been proposed.

[0011]

In recent years, in the case of printing a small number of copies, such an image forming apparatus, which does not require plate making, is sometimes used as a printing machine. Performance of 0.1 mm or less) is required. In addition to so-called copy paper, there is a demand for a wide variety of sheet materials, and examples of sheets include thick paper (150 / m ² or more) and coated paper.

However, the expansion and contraction due to the fixing of the above-mentioned sheet is not constant depending on the paper type and the paper thickness, and the length and the width are different depending on the fibers of the paper.
It also depends on the density of the image on the first side. In the case of paper, the maximum shrinkage is within 1%, but with respect to the maximum size A3 (420 mm) that is mainly used in such image forming apparatus, even a shrinkage of 0.1% is 0.42 mm. Therefore, it is necessary to consider 0.01% of 1/10 of the target level.

To solve this problem, the method of detecting or predicting the degree of shrinkage of the paper and uniformly applying the correction is not sufficient to achieve the performance of a printing press.

In the case of printing, the output is often bound into a book. For example, as shown in FIG. 10, the left-open 6-page booklet is excluded from the front and back covers from the sheets 1001 and 1002 on which images are formed on two sides. Will be described.

In FIG. 11 (a), the letter "a" is drawn on the pages 1 and 2 of the spread, and in FIG.
11 (c) is a booklet in which "i" is drawn on page 4, and "u" is drawn on pages 5 and 6, and the central portion is stapled at two places.

In such a case, as shown in FIG. 12A, an image of the left half of "a" and the right half of "u" is drawn on the table of the first sheet 1001. As shown in FIG. 12 (b), the character (image) of “I” is displayed on the front side of the second sheet 1002, and the right half of “A” and “U” are further displayed on the back side of the second sheet 1002. The image on the left half is drawn.

However, if the centers of the first sheet 1001 and the second sheet 1002 deviate from each other, as shown in FIG. Parallel lines are misaligned.

The difference in magnification between the front and back images due to the expansion and contraction of the sheet also causes a shift. Such a deviation is very noticeable even if it is a minute deviation, and the request for the printing machine is intended for such a case. Therefore, it is not necessary to suppress the deviation in the entire area except for special applications. .

The present invention has been made to solve the above-mentioned problems with the prior art, and its purpose is to:
An object of the present invention is to provide an image forming apparatus capable of preventing visual image shift during double-sided image formation on a sheet or multiple image formation on sheets.

[0020]

To achieve the above object, an image forming apparatus of the present invention comprises an image forming means for forming an image on a sheet, and a fixing means for fixing the image on the sheet on which the image is formed. In an image forming apparatus that forms an image again on the back surface or the same surface of the sheet on which the image is fixed by the fixing unit, the image size and the position with respect to the sheet after the image is fixed on the first surface of the sheet are detected. A detection unit, a correction unit that corrects the image size of the second surface of the sheet and a position with respect to the sheet according to a detection signal of the detection unit, and a conveyance direction of the sheet and a direction orthogonal to the conveyance direction, respectively. And a setting unit capable of arbitrarily setting the correction reference of the correction unit.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a sectional view showing the schematic arrangement of an image forming apparatus (for example, an electrophotographic color copying machine) according to this embodiment.

The image forming apparatus shown in FIG. 1 photoelectrically converts the image information read by the reader unit 1 having a scanning optical system, transfers the image information to the image forming unit 2, and the sheet S fed by the paper feeding unit 3. On the other hand, the image forming unit 2 forms an image. The sheet S on which the image has been formed is conveyed to the fixing device 4, where heat and pressure are applied to fix the transferred image. Since a series of electrophotographic process steps are known, detailed description thereof will be omitted.

(Reader Section) The document D placed on the document table glass 11 is irradiated with light by a scanning optical system 12 having a light source and a reflection mirror group, and the reflected light is reduced by a reduction lens 13.
An image is formed on the CCD 14 via the and photoelectric conversion is performed.
After (analog) / D (digital) conversion, this image information is transferred to the memory. The maximum document size is LT
R or A3. An automatic document feeder 5 is installed on the platen glass 11. Document tray 51
The documents placed on the document are separated one by one by a separation unit (not shown), and then fed onto the document table glass 11 by an endless conveyor belt 52. The original is read on the scanning optical system 12 and then returned to the original tray 51.

(Feeding Unit) A sheet feeding cassette 31 in which sheets S are stacked and stored is detachably attached to the lower portion of the copying machine. A solenoid (not shown) connected to the pickup roller 32 is turned on during standby, and the pickup roller 32 is separated from the surface of the sheet S. Next, when the sheet S is fed, the solenoid is turned off (OF
After that, the pickup roller 32 comes into contact with the surface of the sheet S. Then, the first sheet S is fed by the pickup roller 32 that is being rotationally driven. The drive of the pickup roller 32 is transmitted from a conveyance roller (not shown) via a timing belt (not shown).

The picked-up sheet S is nipped and conveyed by the conveying roller and the retard roller (not shown). The transport roller is rotationally driven in the transport direction of the sheet S, and the retard roller is rotationally driven in the opposite direction to the transport direction of the sheet S via a torque limiter (not shown). Therefore, since there is only one sheet between the conveying roller and the retard roller on the leading edge side of the first sheet S, the torque limiter loses the frictional force between the sheet S and the retard roller, and the retard The roller rotates in the sheet S conveyance direction.

Next, when the two sheets S are overlapped, when the sheets S reach the nip between the conveying roller and the retard roller, the first and second sheets S are placed.
Friction force is lost by the torque limiter, and the retard roller rotates in the reverse direction with respect to the sheet S conveyance direction.
Only the uppermost sheet S is separated and fed first.
Even if a plurality of sheets S are picked up, only the one sheet located at the top is separated and fed in advance by the same operation as described above.

By the sheet S sheet feeding operation as described above,
It is possible to feed the stacked sheets S one by one.

(Conveying Section) The sheet S fed by the sheet feeding section 3 is temporarily stopped at its leading end by the registration roller 22,
The image is fed again according to the image formed by the image forming unit 2, and the image is transferred at the transfer unit. The rotation of the registration rollers 22 is performed by connecting a clutch (not shown), and the control is performed by the controller of the image forming apparatus main body.

(Image Forming Section) After the document image is read and image processed by the reader section 1, the laser emitting section 21 emits a laser beam by a laser driver (not shown) from the stored information in the image memory. . The rotation of the polygon mirror 20 causes the photosensitive drum 23 to rotate.
To form a latent image on the outer peripheral surface of the photosensitive drum 23 that has been previously charged by the charger 24.
This latent image is developed by the developing device 25 provided around the photosensitive drum 23.
The toner image is transferred by the transfer charger 26 onto the sheet S that has been developed by and is placed on the transfer belt (not shown). After the image is transferred onto the sheet S, the toner remaining on the outer peripheral surface of the photosensitive drum 23 is removed by the cleaning device 27.

In this image forming apparatus, four (cyan, magenta, yellow, and black) image forming units having the same structure are continuously arranged, and each read image is color-separated into multiple colors and transferred in multiple. By doing so, a color image is formed.

(Fixing Section) The sheet S to which the toner image has been transferred in the image forming section 2 is guided to the fixing device 4 by the conveyor belt 8 and, when passing through the fixing roller and the pressure roller of the fixing device 4, Heat and pressure are applied to fuse the toner image to the sheet S.

(Double-sided Conveying Section) The sheet S which has passed through the fixing device 4 passes through the inner paper discharging roller 61 and is guided to the outer paper discharging roller 63 side by the flapper 62 in the case of the one-sided printing and the second side of the double-sided printing. The external paper discharge roller 63 discharges the image to the outside of the image forming apparatus (see FIG. 2). In the case of the first side of double-sided printing, the flapper 62 is rotated counterclockwise by a solenoid (not shown) and guided to the lower path (see FIG. 3). The operation of the flapper 62 is performed at the same time as the sheet S pushes down the flag 64 after the image is fixed on the sheet S, and the photo interrupter 65 changes to an undetected signal of the flag 64.

The inner paper discharge roller 61, as shown in FIG.
It is composed of a large-diameter roller 61a to which drive is input and two small-diameter rollers 61b that rotate together, and the curl of the sheet S is corrected while curving the sheet S and passing the sheet. Further, since the lengths of the rollers 61a and 61b in the longitudinal direction are set to be equal to or longer than the maximum size, a so-called roller trace due to a non-uniform temperature difference or a pressure difference after the image is fixed on the sheet S is generated. It never happens.

The sheet S on the first side in the double-sided image formation deflected by the flapper 62 is a switchback unit 66.
When the trailing edge of the sheet S has passed a predetermined position, the reversing roller 67 is reversed to convey the sheet S to the double-sided conveying path 69. When the sheet S reaches the position of the sheet re-feed roller 70, the conveyance of the sheet S is temporarily stopped, and the sheet S
If the image of the first side is prepared in the memory, the conveyance of the sheet S is started again, and the image is formed on the second side like the first side. If the image for the second side is not prepared in the memory, the stopped state is maintained until the OK signal is output from the controller of the image forming apparatus main body.

Next, the operation of detecting the sheet size in the image forming apparatus according to this embodiment will be described with reference to FIG.

FIG. 4 is a perspective view in which a part of the arrangement state from the registration roller 22 to the first photosensitive drum 23 (the photosensitive drum located at the rightmost end in FIG. 2) is omitted.

As described above, when the leading edge of the sheet S is abutted against the nip portion (not shown) of the registration roller 22, the waist of the sheet S causes the leading edge of the registration roller 2 to move.
The skew feeding is corrected in parallel with 2. Registration roller 22
An illumination 28 and a line CCD 29 are arranged downstream of the sheet, and the length thereof is set to be longer than the width of the maximum sheet size and capable of detecting the length of the entire sheet width. Therefore, the sheet S becomes the registration roller 22.
When the sheet S is conveyed again by the line CCD 29, the absolute position of the sheet S in the direction orthogonal to the conveying direction, the width of the sheet S, and the leading end of the sheet S in the conveying direction can be detected.

The laser emitted from the laser emitting section 21 has its writing start timing corrected by the absolute position in the direction orthogonal to the sheet S conveying direction, and moves from P1 along the generatrix of the photosensitive drum 23 in the arrow direction 400 in the figure. Form an image. The laser writing timing in the transport direction of the sheet S starts writing after a lapse of a predetermined time from the time when the leading edge of the sheet S is detected, but it is transferred from the leading edge detection position of the sheet S rather than the length L1 from the laser emitting portion 21 to the transfer portion. Since the length L2 to the copy is longer, it is possible to correct the laser writing timing after detecting the leading edge of the sheet S. Of course, the sheet S for double-sided image formation
The above correction is performed on both the first surface and the second surface.

As for image formation, as described above, the copy mode in which the document is read by the reader unit 1 of the image forming apparatus and copied, and the image data is directly transferred from an external device such as a personal computer (personal computer) to the image memory unit. And a print mode to transfer to.

As described above, the type and thickness of the sheet S,
Since the amount of expansion and contraction of the sheet S varies depending on the image, in the present embodiment, a test print is performed and this is printed by the leader unit 1.
The front and back images on both sides of the sheet S are matched by being read in.

First, when the image of the first side to be copied or printed is output in the test print mode, the flapper 71 (rotated clockwise by a solenoid (not shown) after passing through the inner paper discharge roller 61 shown in FIG. The sheet S is guided upward along the one-dot chain line in FIG. 5 (see FIG. 5). The test print is sent to the platen glass 11 through the transport path 72 shown in FIG. 1 and then placed at a predetermined position by the transport belt 52. In the test print, an image is read by the CCD 14 via the scanning optical system 12 as in the normal copying. After being read, the test print is discharged to the outside of the automatic document feeder 5. Of course, the test print may be manually performed by the user without being automatically sent to the reader unit 1. CCD 14 is 600d
Since the resolution is pi, about 40 μm of one pixel is the resolution. Of course, a CCD having a higher resolving power may be used, and the resolving power in the scanning direction can be increased by decreasing the scanning speed. Therefore, the scanning speed may be decreased in the test print mode.

FIG. 6 is a block diagram showing the configuration of the electric system of the image forming apparatus according to this embodiment. In FIG. 6, 601 is a computer, 602 is a controller, and 6 is a controller.
03 is an image pattern recognition unit (image pattern recognition means),
Reference numeral 604 is a page recognition unit (page recognition means), and 605 is C.
CD (corresponding to CCD 14 in FIG. 1: detection means), 6
Reference numeral 06 is an A / D conversion unit, 607 is an image processing unit, 608 is an image scaling unit, 609 is an image position calculation unit, 610 is a shrinkage ratio calculation unit, 611 is a shrinkage ratio memory, 612 is a paper type setting unit, 6
13 is an operation unit, 614 is a reference position input unit, 615 is an image memory, 616 is a video controller, 617 is a laser driver, 618 is an image forming unit, and 619 is a line CC.
D (corresponding to the line CCD 29 in FIG. 4: detection means)
Is.

The controller 602 has CCDs 605, 6
It has a function of correcting the image size of the second surface of the sheet S and the position with respect to the sheet S according to the detection signal of 19. The image pattern recognizing unit 603 has a function of recognizing a blank portion without an image, a page layout, etc. between pages, and a sheet S.
It has a function of recognizing a line serving as a scaling reference in a direction orthogonal to the conveyance direction of. In addition, the page recognition unit 604
It has a function of recognizing the one-page area of the original image on the output sheet S. Further, the pattern recognition unit 603 and the page recognition unit 604 are configured to recognize an image spanning between pages or a blank space between pages. The reference position input unit 614 can arbitrarily set the correction reference of the controller 602 for the conveyance direction of the sheet S and the direction orthogonal to the conveyance direction of the sheet S.

The test print is shown in FIG. 12A of the conventional example.
Taking the first sheet of the sample shown in FIG. 7 as an example, as shown in FIG. 7, in addition to the image, cross marks A, C,
Draw cross marks B, D, E and G on F and H and their centers.
In FIG. 7, the arrow 700 indicates the conveyance direction of the sheet S.

After the document image is read by the reader unit 1, a line X0 connecting BG is connected as a reference of the sheet S conveying direction, and a line D-E is connected as a reference of a direction orthogonal to the sheet S conveying direction. The line position Y0, the distances X1, X2, Y1, Y2 to the cross marks at the four corners of the sheet S and the distances Y3, X3, X4 to the ends of the sheet S are calculated by the image position calculation unit 609 based on the respective references.

Next, the shrinkage rate calculation unit 61 is compared with X1, X2, Y1, and Y2 by comparing the distances drawn in advance for each.
The shrinkage rate is calculated by 0, and the calculated value is stored in the shrinkage rate memory 611.

At the time of actual output using the above shrinkage ratio, the image scaling unit 608 performs image scaling processing on the second surface of the sheet S, but the Y0 position on the second surface of the sheet S is line CC.
It is determined by Y3 from the absolute position of the sheet S on the P1 side detected by D619. Since the sheet S has variations in its original size other than heat shrinkage,
Unless the leading edge reference of the sheet S on the second side is set to be the same, a deviation occurs due to the size variation. Therefore, the second surface X0 of the sheet S is determined by X4 from the front end of the sheet S detected by the line CCD 619 because the front end of the sheet S is inverted. Next, the image multiplied by the above contraction rate is written with Y0 and X0 as references. That is, since the bookbinding image is used here, the two images "the left half of (A) and the right half of (U) and the Y0 'line" are printed by controlling the writing timing so that the Y0 and X0 lines become the reference.

By forming images on both sides of the sheet S as described above, it is possible to prevent the image misalignment between the front and back sides of the sheet S.

The contraction rate memory 611 may be provided with a memory for a plurality of types of sheets S and may be appropriately called by user input.

Further, the sheet S is calculated by using the calculated shrinkage ratio.
It is also possible to make the first side of the image a scaled (enlarged) image and not to scale the second side.

Further, in order to improve the quality, in the present embodiment, not only the center of the image, but also X0 and Y0, which are the reference positions for zooming, can be arbitrarily changed.

In FIG. 7, the most noticeable misalignment at the time of bookbinding is the line 701 extending over the page over the character. Therefore, the page recognition unit 604 and the pattern recognition unit 60
When an image straddling the central portion between pages is found by 3 and 3, that point is used as a reference for scaling.

In FIG. 7, the line is recognized and Y0 'is changed to Y'.
Y3 ′ is used as the Y0 ′ reference for the second surface of the sheet S by calculating the shrinkage ratios of Y1 ′ and Y2 ′ as the directional scaling reference.

FIG. 8 is a diagram showing a state in which four pages are allocated on the surface of one sheet S. In the present embodiment, X01, X02, Y01, Y0 are placed at the center of each page.
A plurality of two standards are provided, the shrinkage rate is calculated by the shrinkage rate computing unit 610, and the correction process for the second surface of the sheet S is performed.

FIG. 9 is a diagram showing an example in which a large number of references are set for X and Y, the shrinkage rate calculation unit 610 calculates the shrinkage rates in a matrix, and the correction processing for the second surface of the sheet S is performed.

As described above, when a plurality of standards are set,
Mismatches occur in the image scaling processing by the image scaling section 608, but the pattern recognition section 603 recognizes a blank area with no image, such as between pages, and eliminates the mismatch at the blank area. Further, the pattern recognizing unit 603 may recognize page layout, determine adjacent pages, and use the read expansion / contraction data for correction processing of different sheets S.

In the present embodiment, the pattern recognition and the reference position determination are automatic. However, the user may manually input the point to be the reference by the operation unit 613. Further, in the printer mode in which image data is directly transferred from the personal computer to the image forming apparatus, after reading the test print, the position information and the calculated shrinkage ratio data are sent back to the personal computer, and the user can use the printer driver software. Various settings may be made possible.

Further, in the present embodiment, the image is read by the reader unit 1, but an image recognizable sensor is arranged in the middle of the double-sided conveyance path after the image is fixed on the sheet S.
You may make it read the image of a face.

Further, in the present embodiment, the image processing is performed when the image is scaled. However, for example, by changing the conveying speed of the sheet S or changing the rotation speed of the polygon mirror 20. Alternatively, the magnification of the image may be changed.

The same sheet S can be used also in the case of performing multiple image formation in which a large number of formats are first copied and then another image or character is added and copied.
The present invention can be applied since the above is passed twice.

Further, in the present embodiment, the double-sided image formation of the color copying machine or the color printer has been described, but the present invention can be applied to the multiple copying or the multiple printing in which the sheet S is not switched back. It is also applicable to monochrome copiers and monochrome printers.

[0063]

As described above, according to the image forming apparatus of the present invention, the image size after the first image fixing and the detection signal of the detection unit for detecting the position with respect to the sheet are set to 2
When correcting the image size and the position with respect to the sheet for the second time, it is possible to set the correction reference of the correction means arbitrarily in the sheet conveyance direction and the direction orthogonal to the sheet conveyance direction, so that the image deviation is most noticeable. Since the magnification can be applied based on the part, visual image shift can be prevented, and a high-quality image can be formed.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a double-sided conveyance section in the image forming apparatus according to the embodiment of the present invention.

FIG. 3 is an enlarged view of a double-sided conveyance section in the image forming apparatus according to the embodiment of the present invention.

FIG. 4 is a perspective view showing a configuration of a sheet size detection unit in the image forming apparatus according to the embodiment of the present invention.

FIG. 5 is an enlarged view of a double-sided conveyance section in the image forming apparatus according to the embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of an electric system of the image forming apparatus according to the present embodiment.

FIG. 7 is a diagram showing a sheet alignment reference in the image forming apparatus according to the embodiment of the present invention.

FIG. 8 is a diagram showing a sheet alignment reference in the image forming apparatus according to the embodiment of the present invention.

FIG. 9 is a diagram showing a sheet alignment reference in the image forming apparatus according to the embodiment of the present invention.

FIG. 10 is a diagram showing a general bookbinding example.

FIG. 11 is a diagram illustrating a general bookbinding example.

FIG. 12 is a diagram showing a general bookbinding example.

FIG. 13 is a diagram illustrating a general bookbinding example.

[Explanation of symbols]

1 Reader Unit 2 Image Forming Unit 3 Paper Feeding Unit 4 Fixing Device 5 Automatic Document Feeding Device 11 Document Platen Glass 12 Scanning Optical System 14 CCD (Detecting Means) 22 Registration Rollers 23 Photosensitive Drum 29 Line CCD (Detecting Means) 28 Illumination 61 Paper discharge roller 62 Flapper 63 External paper discharge roller 65 Photo interrupter 69 Double-sided conveyance path 70 Refeed roller 71 Flapper S sheet 601 Computer 602 Controller 603 Image pattern recognition unit (image pattern recognition unit) 604 Page recognition unit (page recognition unit) 605 CCD (corresponding to CCD 14: detection means) 606 A / D conversion unit 607 Image processing unit 608 Image scaling unit 609 Image position calculation unit 610 Shrinkage ratio calculation unit 611 Shrinkage ratio memory 612 Paper type setting unit 613 Operation unit 614 Reference position Input unit 615 Image memory 616 Video Controller 617 laser driver 618 an image forming unit 619 line CCD (corresponding to the line CCD 29: detecting means)

Continued front page    F term (reference) 2H027 DB04 DB09 DC04 DC05 DC10                       DE02 DE07 DE09 EC02 EC06                       EC09 ED17 ED25 FA13 FB05                       FB11 FB12 FB14 FD03 FD08                       FD10 ZA08                 2H028 BA06 BA09 BA16 BB02 BB04                       BB06

Claims (12)

[Claims] 1. An image forming means for forming an image on a sheet, a fixing means for fixing the image on the sheet on which the image is formed, and a rear surface or the same surface of the sheet on which the image is fixed by the fixing means. In an image forming apparatus for forming an image, a detection unit that detects an image size after fixing the image on the first surface of the sheet and a position with respect to the sheet, and a second surface of the sheet according to a detection signal of the detection unit. A correction unit that corrects an image size and a position with respect to the sheet; and a setting unit that can arbitrarily set a correction reference of the correction unit with respect to a conveyance direction of the sheet and a direction orthogonal to the conveyance direction. Characteristic image forming apparatus. 2. The image forming apparatus according to claim 1, wherein an image reading apparatus for copying which communicates with the image forming apparatus also serves as the detecting means. 3. The image forming apparatus according to claim 2, further comprising a conveying unit that conveys the sheet after the image is fixed on the first surface to the image reading apparatus for copying. 4. A page recognizing means for recognizing a one-page area of the image on the sheet is provided.
The image forming apparatus according to item 1. 5. The image forming apparatus according to claim 1, further comprising image pattern recognition means for recognizing a margin portion of the sheet. 6. The image forming apparatus according to claim 1, further comprising image pattern recognition means for recognizing a line serving as a scaling reference in a direction orthogonal to the sheet conveying direction. 7. The image forming apparatus according to claim 4, further comprising a calculation unit that automatically corrects the correction reference according to information from the page recognition unit. 8. The image forming apparatus according to claim 5, further comprising a calculation unit that automatically corrects the correction reference according to information from the image pattern recognition unit. 9. A communication means for communicating with an external computer, and a control means for controlling to form an image based on image data transferred from the external computer. The image forming apparatus according to item 1. 10. The image forming apparatus according to claim 9, further comprising a transfer unit that transfers the information detected by the detection unit to the external computer. 11. The image forming apparatus according to claim 1, wherein the detection unit detects downstream of the registration roller. 12. The detection means detects after fixing an image on the sheet.
10. The image forming apparatus according to any one of 10.