JPH10246992A - Image forming device controlling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device and a controlling method improved in image forming positional accuracy, particularly, in the accuracy of both side copying time. SOLUTION: In several sections on both aides of a paper sheet, '#' is printed. The deviation value is decided by reading the several original printed on the both side. Based on the decided deviation value, as for the deviation in a direction orthogonal to the transporting direction, the mounting position of the paper sheet on the either side unit 19 is shifted so as to correct to the extent of a portion of the deviation. Then, as for the deviation in the transporting direction, the portion of the deviation is corrected by letting the timing of the paper sheet feeding to the image forming section deviated by driving resist rollers 18. Contrary to this, the deviation can be corrected by shifting the image forming position corresponding to the paper sheet.

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 for forming an image on a recording medium, for example, and a control method therefor.

[0002]

2. Description of the Related Art Heretofore, with respect to the alignment (phase) of images on both sides, the position at which an image is formed has been determined by regulating the leading end of the paper position with a registration roller or the like. The regulation in the horizontal direction is determined by a regulation plate in a cassette, a regulation plate of a duplex unit on which a sheet on which one side is recorded is once placed, or another regulation plate.

[0003]

In this method, it is possible to stabilize the image position to some extent, but an error always occurs. For this reason, in some color copying machines,
It has been pointed out that the image forming position at the time of double-sided copying is shifted between the front side and the back side. The image shift at the time of double-sided copying occurs on both sides. Therefore, depending on the direction of the shift, the amount of the shift is doubled by adding the amounts of the front and back sides. For example, in double-sided copying, usually, the front and back are reversed with respect to an axis parallel to the front and rear edges of the sheet in the sheet conveyance direction. For this reason, the amount of displacement is doubled. As described above, since the amount of displacement is large during double-sided copying, highly accurate alignment is required.

However, in the prior art, the error of the image forming position is large, and the image forming position may be deviated only by replenishing the sheet cassette. As described above, the error generated at the time of double-sided copying is doubled, and a positional deviation may be pointed out at the time of cutting or bookbinding after creating a double-sided copied original.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus and a control method which have been made in view of the above-mentioned conventional example, and have improved image forming position accuracy, particularly, accuracy in duplex copying.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional example, and has the following configuration. That is, after forming an image on a first surface of a print medium by an image forming unit, the image forming apparatus reverses the medium and forms an image on the second surface of the medium also by the image forming unit.
An output unit that prints out a predetermined image on both sides, and an image on each surface is formed based on a displacement of the image on the first surface and the image on the second surface output by the output unit. Correction means for moving the positions to each other by the amount of the displacement to make the positions coincide with each other.

Alternatively, after an image is formed on a first surface of a printing medium by an image forming unit, the image forming apparatus reverses the medium and forms an image on the second surface of the medium by the image forming unit. A control method, comprising: an output step of printing and outputting a predetermined image on both sides; and an output image of each surface based on a displacement of an image position between a first surface and a second surface. A correcting step of moving the formed positions by the amount of the displacement to make the positions coincide with each other.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the outline of the present invention will be described.

First, a predetermined image is formed on the first side using a copying machine. This image indicates an image forming range, is fixed, and is conveyed to a double-sided tray. Paper is re-fed from the double-sided tray, and printing on the second side is performed. Note that the image formed on the second surface is ideally shifted by a predetermined amount with respect to the image formed on the first surface, and is predetermined so that the front and back can be identified when read later. The density difference of the values is given. In order to simplify the processing, the graphic on the first side and the graphic on the second side are mirror-like figures symmetrical with respect to the sheet, and are desirably recorded at the same density. 2
When the image is formed on the front side, the sheet is fixed and discharged. The images thus formed should overlap if they are originally at correct positions.

Next, the original printed on both sides in this manner is set on an image reading section of a copying machine by a user, and is read by a reading system using a CCD.

The copying machine reads the symbol (hereinafter, symbol 1) indicating the image forming range on the first side recorded as described above, and checks the image forming range from the signal. At the same time, the second side symbol (symbol 2) that is shown off on the paper is read. Symbols 1 and 2 are distinguished so that they can be clearly read as a difference in signal value when read by a CCD. From this signal,
The start position of the image on the second side during duplex copying is matched with the start position of the first side. (First Embodiment) As a first embodiment, a copying machine having a duplex copying mechanism will be described. <Configuration of Copying Machine> In FIG. 1, a document placed on a document placing glass 2 is scanned by a document illumination lamp 3. The scanned optical signal is transmitted through the lens 4 to the CCD 5
Is converted into an electric signal, subjected to necessary image processing by the control unit 1, and then output as a video signal. The control unit 1 performs image processing and controls the entire apparatus including the engine unit. The laser scanner 6 emits laser light based on a video signal and a timing signal from the engine unit to scan the photosensitive drum 7. To form an electrostatic latent image. The photosensitive drum 7 is uniformly charged by the pre-exposure lamp 8 and the primary charger 9 before the laser scanning.

The formed latent image is subjected to YMCK
Is developed in one of the colors. The developed toner image is conveyed from the cassettes 14, 15, 16, the paper feed tray 17 or the duplex unit 19, and is transferred onto the paper wound around the transfer drum 12. This latent image formation-development-
The transfer process is sequentially repeated for each of the YMCK colors to form a full-color image. The transported paper is
The transfer timing is defined by the registration rollers 18, and the transfer is performed in synchronization with the formation of the image on the photosensitive drum.

The sheet on which the image has been transferred is separated from the transfer drum by the separation claw 13. Second on one side or both sides
When the recording of the front side (called the back side) is completed, the sheet is discharged to the discharge tray 20. When the recording of the first side (referred to as the front side) of the double-sided copy is completed, the sheet is transferred to the transport path 21.
, And are placed once on the duplex unit 19 with the front and rear and the top and bottom (front and back) being switched with respect to the transport direction. That is, the sheet is turned over to record the back side, and the transport direction for the sheet is also reversed accordingly.

In this manner, the steps of latent image formation, development and transfer are repeated for each of the YMCK colors on the back surface.

FIG. 5 shows the configuration of the control unit 1. In FIG. 5, a CPU 101 executes a program stored in a ROM 102 to implement a predetermined control procedure. ROM102
Stores the pattern for correction shown in FIG. 2 in addition to the program and data. The RAM 103 stores data and programs used by the CPU 101. Image data read by the scanner 53 is stored in the image memory 104. The image processing unit 105 performs predetermined processing on the image data, receives a signal TOP indicating a page timing and a signal BD indicating a scan line timing from the engine unit 51, and synchronizes them with a video clock (not shown). The video signal to the engine unit 51
To supply.

The CPU 101 is connected to the input panel 52 and the scanner 53 via the I / O interface 106 to exchange data, and outputs a control signal to be described later to the engine unit to correct the position of the sheet.

FIG. 6 is a schematic diagram showing a schematic configuration of the duplex unit 19. A sheet on which only one side is recorded is placed on the duplex unit 19, and the sheet size varies. Control plates 191L and 191R that move left and right (in the direction of the arrow) are provided to correspond to these various sizes and to hold the paper at an appropriate position in the horizontal direction. These restriction plates can be moved independently of each other. Note that the direction perpendicular to the transport direction is called the left-right direction,
When viewed from the front side of the sheet (the surface on which recording is first performed), the right side and the left side with respect to the transport direction are simply called the right side and the left side, respectively.

FIG. 7 is a diagram showing a configuration for controlling the duplex unit 19 and the registration roller 18 from the control unit 1. Although the engine unit has many other control points, only the parts considered to be relevant to the present invention are illustrated in the figure. The control unit 1 includes a motor driver 193,1
The control unit 94 moves the regulating plates 191R and 191L to adjust the size of the sheet and adjust the position of the sheet in the left-right direction.

M, a motor driver 181 for driving the registration roller 18 is controlled to be driven at a predetermined timing. That is, the registration roller 18
Is driven at predetermined time intervals, and the sheet is fed to the image forming section composed of the developing drum 7 and the transfer drum 12 at the drive timing. <Correction of Image Position During Double-Side Recording> In the above configuration, the correction of the image position during double-side recording is performed as follows. The procedure will be described with reference to FIGS.

The operator operates the input panel 52 in a predetermined procedure to set the execution of the correction sequence. Thereby, the procedure of FIG. 8 is executed. Each flowchart is executed by the CPU 101 of the control unit 1.

Referring to FIG. 8, the control unit 1
03 is set (step S
81). Next, the pattern 10 stored in the ROM 102
2a is read, developed into an image, stored in the image memory 104, and this pattern is printed on both sides. FIG. 2 shows an example of this pattern. If the figure is symmetrical on the left and right as described above, if the image is recorded on both sides, the images on both sides should exactly overlap. However, if the position of the image recorded on the paper is shifted, a double-sided printed matter in which the front and back images are shifted from each other is output as shown in FIG. However, as described later, there are cases where slightly different images are recorded on the front surface and the back surface.

The operator places the printed matter on the original placing glass 2 and presses a copy button. Then, the procedure of FIG. 9 is started. For the sake of simplicity, it is assumed that the original is placed on the scanner such that the transport direction at the time of recording matches the sub-scanning direction at the time of reading. <Execution of Correction Sequence> First, in step S91, a correction flag is tested. If it is on, it is determined that the correction sequence is being performed, and the process proceeds to step S93. If it is off, the process proceeds to step S92 to execute a normal copying process.

In step S93, the scanner 53
To read the image. At this time, if the recording paper output in FIG. 8 has a basis weight of about 65 g / m @ 2 or less, the # -type symbol can show through. That is, both sides of the image can be read by scanning one side as shown in FIG. At this time, the image of the show-through surface, that is, the upper surface of the original placed on the original placing glass 2 can be read as a weaker signal than the image of the directly read surface (hereinafter, referred to as a scan surface). Becomes This is read using the image reading device of the copying machine.

A column containing the symbols of the read data;
Alternatively, for a row, FIG. 4 shows a signal value on the vertical axis and a position on the horizontal axis. That is, the signal of the first surface (downward surface) is strong, and the signal of the second surface (upward surface) is weak. By identifying this signal, the shift between the image positions of the first surface and the second surface is determined. It should be noted that the signal is of the # type for the purpose of improving the accuracy, and may be in another form. However, when the correction is performed in both the vertical and horizontal directions, it is preferable that the image includes a line orthogonal to both directions. The same purpose is also provided at five locations, and it is sufficient if at least one location.

In order to make corrections to be described later, it is necessary to determine the front and back of the surface of the sheet placed on the document table during recording and the transport direction of each surface. Therefore, if the image of FIG. 2 is recorded on both sides of the sheet, even if it is sufficient to use for correction of misalignment, it is not possible to grasp the direction and surface when it was recorded from only the printed matter, so the mark for grasping is used. It is desirable to add FIG. 12A shows an example thereof. That is, the image of FIG. 2 is recorded at the time of recording on the front side, and the image of FIG. 2 is recorded with an arrow 121 added in the sheet conveyance direction at the time of recording on the back side. In this way, the transport direction during backside recording can be determined based on the position of arrow 121, and the relationship between front and back can be determined based on arrow 121.

This determination may be made by an operator or a copier. When the operator makes a determination, the operator places the sheet on the table 2 in a predetermined direction by looking at the arrow. When the apparatus determines, it determines based on the position of the arrow and its reading level (any of the strengths shown in FIG. 4). This mark 1
In the case where there is no 21, it is necessary for the operator to place correction paper on the document mounting table so as to have a predetermined directional relationship with the direction of the paper discharged to the discharge tray 20.
Hereinafter, description will be made assuming that a mark (arrow) indicating the paper transport direction is printed at the time of recording on the back side, and the direction of the document is determined by the copying machine.

In step S94, predetermined rows (in the main scanning direction of the scanner) and columns (in the sub-scanning direction) are sampled from the read image data. The sampling rows and columns include approximate positions where the symbols included in the pattern 102a exist. An example of this sampling is shown in FIG.
This is shown in (B). That is, from the read image data, rows A1 to A3 and columns A
4 to A6 are sampled.

Next, it is determined whether the pattern read in step S95 matches the pattern written in step S83. This determination may be made using the data sampled in step S94. That is, a signal as shown in FIG. 12C is obtained for a row, and a characteristic signal is obtained for a column according to a pattern. Therefore, from this feature, it can be determined whether the pattern should have been recorded.

If it is determined in step S95 that the patterns match, in step S96, a shift between the patterns on both surfaces is detected, a correction amount is determined, and the correction amount is stored in a predetermined area.

Thus, the correction sequence is completed.

FIG. 10 shows the contents of step S96.

In step S101, the amount of deviation between the front and the back is obtained from the sampled row and column data. For this shift, for example, a peak position is obtained by differentiating a signal, a signal level at the peak position is used to determine whether or not the signal is an image of a show-through image, and a shift distance of each of the front and rear images is obtained. it can. By performing this for rows and columns, a shift in the transport direction and a shift in the left-right direction can be obtained. This shift amount is obtained for each of the “Δ” symbols in the image of FIG.

In step S102, the deviation of the deviation obtained for the symbol at each position is checked. If the variation is equal to or greater than the predetermined amount, the correction may be performed due to an amount that cannot be corrected, that the sheet is skewed, or that the image is originally different from the image for correction. Interrupt. If the variation is equal to or less than the predetermined amount, step S1
In step 04, the state in which the original is placed is determined.

This determination will be described with reference to FIG. FIG. 12C shows the image of FIG.
FIG. 3 is an example of sampled rows A1 and A3 when the image of FIG. 2 is recorded on the surface. In the case of the example of FIG. 12B, the signal of row A1 has a stronger signal at arrow 121 when the back side (the surface on which arrow 121 is recorded) is a scan surface, and becomes signal 122 when the back surface is the scan surface. Arrow 12
One part becomes weak and becomes a signal 123. Row A3 is signal 1
24, and the arrow 121 does not appear.

For this reason, from the rows A1 to A3 and the columns A4 to A6, it is determined whether or not the back side constitutes the scan plane.
It is possible to determine which of the 1 side and the A3 side corresponds to the front side transport direction and the back side transport direction, respectively.

Finally, in step S104, as a correction amount in the vertical direction (transport direction), one half of the displacement amount in the transport direction obtained in step S101 is stored in a predetermined storage area, and the correction amount in the horizontal direction (right / left direction) is stored. In this example, the shift amount in the left-right direction obtained in step S121 is stored as the correction amount of the LBP main scanning direction. The signs of these correction amounts are determined according to the state of the document obtained in step S104. The reason why the transport direction is halved and the lateral direction is left as it is is that the transport direction is corrected for both the front and back surfaces, but is corrected only for the rear surface in the horizontal direction.

Here, the direction (sign) of the correction amount will be described with reference to FIG. In the present embodiment, the shift is corrected by changing the position of the sheet in the transport direction and the left and right direction without changing the image position on the photosensitive drum. Therefore, FIG.
In 3, the transport direction will be described as the timing of adjusting the transport of the sheet by the registration roller, and the horizontal direction will be described as the direction in which the regulating plate in the duplex unit moves. FIG. 13 shows that, in short, if the direction of the original at the time of recording and the direction of the original at the time of reading are known, the direction of deviation can be determined according to the sampled signal. This correction direction is for the apparatus shown in FIG. 1. If the reversal axes of the front and back sides during double-sided recording are different,
There are also different results.

FIG. 13A is a diagram for defining the direction on the document table 2. The direction D is the sub-scanning direction, and the direction C is the main scanning direction.

FIG. 13B will be described as an example. 13A is an example in which the direction D in FIG. 13A is the conveyance direction of the back surface during recording, and the back surface is the upper side, that is, the front surface is the scan surface. In this case, if the direction D is higher among the peaks indicating the front and back included in the sampled column signal, as in the upper row of the cell, it is determined that the paper has advanced too far with respect to the image. That is. Therefore, if the sheet conveyance timing is delayed, the front and back sides can be matched. Conversely, if the peak on the direction D side is low, it means that the conveyance of the sheet is delayed with respect to the image. Therefore, if the timing for transporting the paper is advanced, the front and back sides can be matched.

The remaining three cells can be considered in exactly the same way. That is, if the state of the upper left cell is turned over without changing the orientation of the original with respect to the direction D, or the orientation of the original is exchanged with respect to the direction D, the table shown in FIG. 13A is obtained.

FIG. 13C is a table for explaining the direction of correcting the deviation in the left-right direction. The correction in the left-right direction is performed by moving the regulating plates 191L and 191R of the duplex unit 19 in FIG. Therefore, the direction of movement for correction is
This is shown in the directions of arrows L and R in FIG. The arrow A indicates the direction in which the sheet is transported.

In FIG. 13C, the square at the upper left is
The direction D of 3 (A) is the conveyance direction of the back surface during recording, and is an example in which the back surface is the upper side, that is, the front surface is the scan surface. In this case, if the direction C (see FIG. 13A) is higher among the peaks indicating the front and back included in the sampled row signal, as in the upper row of the cell,
This means that the paper has passed the L side in FIG. 6 during backside recording. Therefore, the regulating plate 191 is moved in the R direction by a shift amount. Conversely, if the peak on the direction C side is low,
This means that the paper has passed the R side in FIG. 6 during backside recording. Therefore, the regulating plate 191 is moved in the L direction by a displacement amount.

The remaining three squares can be considered in exactly the same way. That is, when the state of the upper left cell is turned over without changing the direction of the original with respect to the direction D, or the direction of the original is exchanged with respect to the direction D, a table shown in FIG. 13C is obtained.

The direction of correction determined as described above is stored as a code with the correction amount attached. <Duplex Copying of Original> When the correction amount is determined as described above, the original is copied while correcting the position of the sheet according to the correction amount during copying. FIG. 11 shows a control procedure at the time of copying.

First, in step S111, it is determined whether or not double-sided copying is performed. If it is double-sided, the interval between the regulating plates 192R and 192L is adjusted to the paper size according to the set original size, and the procedure shown in FIG. The positions of both regulating plates are moved according to the determined correction amount. Of course, this operation may be simultaneous.

Next, double-sided copying is performed in step S113. At this time, the drive timing of the registration roller 18 is
The correction is performed as shown in FIG. 13B according to the correction amount determined in FIG. Thereby, the shift in the transport direction is eliminated. Since the position of the regulating plate of the duplex unit has been corrected in step S112, the image on the back surface is formed at the same position as the image on the front surface.

As described above, the image on each side during double-sided printing is determined by the signal level, and the image shift between the two sides can be detected based on the signal level. Based on the detected deviation, the position of the recording paper during the double-sided recording can be corrected, and the deviation of the image during the double-sided recording can be prevented.

Further, a symbol for determining the direction of the recorded image is formed together, and the symbol is also read in a corrected manner, so that the direction of the sheet at the time of image recording and the direction of reading the recorded image are read. The correction value can be determined by automatically determining the direction of the document.

In FIG. 10, step S104
The correction amount can be determined by always keeping the original direction at the time of recording and the original direction at the time of reading even if there is no step of determining the state of the placed original. For example, if the upper left cell is positioned as shown in FIG. 13B, it is unnecessary to determine the direction of the read original.

Further, by repeating the above procedure and outputting, reading, and adjusting the same pattern one or more times, the accuracy can be further improved.

Further, the correction of the position in the transport direction has an effect that the image position can be formed at a more accurate position even during one-sided copying.

As a result, it is possible to accurately align images on both sides. As a result, electronic publishing in DTP or the like and editing functions when using an editor are enhanced, and users can make full use of the double-sided functions. Can be created.

By aligning the image positions, the quality of the finished copy when a multi-page publication is copied is improved. (Second Embodiment) In the first embodiment, the position of the image is corrected by changing the position of the recording paper relative to the position of the image to be formed. However, conversely, by changing the image forming position without changing the position of the recording paper, it is also possible to correct the image misalignment during double-sided printing. In this case, the procedure up to the determination of the correction value is almost the same. However, since the moving mode is not the sheet but the position of the image formed on the photosensitive drum, the correction direction shown in FIG. 13 is opposite. The image forming position is corrected to this correction amount.

FIG. 14 shows the procedure of the copying process. In step S142, unlike the first embodiment, only the regulation plate 191 is adjusted to the paper size. Also,
In step S143, an image is formed. At this time, the output timing of the video signal is adjusted by the image processing unit 105.

FIG. 15 shows a mechanism for generating two timing signals BD and TOP in the engine unit 51. The signal BD detects a laser beam emitted from the laser scanner 6 by the optical sensor 601 at a predetermined position, and outputs the detected timing. Therefore, the signal BD is generated every main scanning.

The signal TOP is detected by the sensor 602 to detect the passage of a predetermined portion provided on the outer peripheral portion of the photosensitive drum 7 by the sensor 602, and is output by the sensor 602. Therefore, the signal TOP is generated for each sub-scan.

The image processing section 105 outputs a video signal at the timing shown in FIG. FIG. 17 is an enlarged view of this in the time direction.

First, with reference to FIG. 16, a description will be given of the correction of the position of the image with respect to the paper transport direction. In FIG.
Formation of an image of one page, that is, output of a video signal,
After detecting the TOP signal, the process is started after a predetermined number of pulses of the BD signal are detected. Since one cycle of the BD signal indicates one main scan, image formation is started after a line corresponding to the number of pulses is made. Normally, the output of the video signal is started at the timing T161 after the standard pulse number is left. However, when the vertical correction amount is given in the procedure of FIG. 10, the BD signal corresponding to the correction amount is given. Timing T when the number of signal pulses is increased or decreased to the standard number of pulses
At 162, image formation is started.

In FIG. 13, if the paper conveyance is delayed, the image formation is relatively advanced. Therefore, in this embodiment, the image formation is advanced earlier than the standard timing, and the paper conveyance is advanced. If so, image formation is delayed.

Next, the correction of the position of the image in the left and right directions of the sheet will be described with reference to FIG. The formation of each line at the time of image formation is started after a predetermined number of video clocks are generated after the signal BD is detected. That is, usually, the output of the video signal is started from the timing T171 after the standard delay. If the correction amount is set,
At the time of backside recording of double-sided copying, the delay is increased or decreased by the horizontal correction amount, and main scanning is started at the timing T172.

Here, it is assumed that the laser beam is scanned in the direction from the R side to the L side in FIG. Then,
Moving the regulating plate 191 to the R side is relatively the same as accelerating the scanning start timing. Therefore,
In FIG. 13, when the regulating plate is moved to the R side, the main scanning timing is advanced in the present embodiment, and when it is moved to the L side, the main scanning timing is delayed. this is,
If the main scanning direction is reversed, it is naturally reversed.

As described above, similarly to the first embodiment, it is possible to correct the positional deviation of the image during single-sided and double-sided printing. Further, in the present embodiment, since the correction is performed in the image formation, the position can be corrected in pixel units in the vertical direction and the horizontal direction, and finer position adjustment can be performed. (Third Embodiment) In the above-described example, a copying machine having a scanner is used. However, in the case of an analog copying machine having no independent reading mechanism, a mechanism for manually adjusting by a user is provided.

That is, the deviation of the image recorded on both sides recorded as shown in FIG. 4 is measured by an operator using a ruler or the like. The user inputs the measured value itself or the amount by which the writing position obtained from the measurement is shifted from the input panel. The amount to be displaced when the measured value itself is input is calculated in the same manner as in the first embodiment, and when the amount to be displaced is input, the value is stored, and when the amount is calculated, the value is stored. Keep it.

In accordance with the first and second embodiments, the sheet feeding timing and the regulating plate, or the image forming timings in the main scanning and sub-scanning directions are shifted in accordance with the stored shift amounts. Thus, the image forming position is corrected. (Fourth Embodiment) One of the first and second embodiments
When discriminating between the signals on the front side and the second side, not only the strength of the signal but also the difference in color can be used.

In a copying machine such as a color copying machine capable of reproducing a plurality of colors, the symbols on the first and second surfaces are made different in color, and the symbols are read by a CCD or other reading device having a function of distinguishing colors. . At this time, the symbols on the first surface and the second surface are distinguished based on the difference between the signal values of RGB.

After the distinction, the image forming position is corrected in the same manner as in the first to third embodiments.

By distinguishing the front and back by the color in this way,
The back and front images can be more accurately distinguished.

[0068]

[Other Embodiments] Even if the present invention is applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), an apparatus (for example, a copying machine) Machine, facsimile machine, etc.).

Further, an object of the present invention is to provide a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or an apparatus, and to provide a computer (or CPU) of the system or apparatus.
Or MPU) reads and executes the program code stored in the storage medium.

In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, 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, CD
-R, a magnetic tape, a nonvolatile memory card, a ROM, or 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. ) Performs 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 instructions of the program code, The case where the CPU of the function expansion board or the function expansion unit performs part or all of the actual processing, and the function of the above-described embodiment is realized by the processing.

[0074]

As described above, according to the present invention,
This has the effect of improving the image forming position accuracy, especially the accuracy during duplex copying.

As a result, it is possible to accurately align the images on both sides, and as a result, the electronic publishing in DTP or the like and the editing function when using the editor are enhanced, and the user can make full use of the double-sided function. Can be created.

By adjusting the image positions, it is possible to improve the finish when copying a multi-page publication.

[0077]

[Brief description of the drawings]

FIG. 1 is a sectional view of a copying machine according to the present invention.

FIG. 2 is a diagram illustrating an example of a correction pattern.

FIG. 3 is a diagram illustrating a state in which a correction pattern is recorded and read on both sides.

FIG. 4 is a diagram illustrating an example of a signal obtained by reading an image copied on both sides.

FIG. 5 is a diagram showing a configuration of a control unit 1.

FIG. 6 is a schematic diagram showing a schematic configuration of a duplex unit 19;

FIG. 7 is a diagram showing a configuration for controlling a duplex unit 19 and a registration roller 18 from a control unit 1.

FIG. 8 is a flowchart of a correction sequence.

FIG. 9 is a flowchart of an image reading processing procedure at the time of correction.

FIG. 10 is a flowchart of a procedure for setting a correction value based on a shift amount of a two-sided image.

FIG. 11 shows a control procedure at the time of copying.

FIG. 12 is a diagram illustrating another example of a correction pattern.

FIG. 13 is a diagram illustrating an example of how to give a correction value.

FIG. 14 shows a procedure of a copying process according to the second embodiment.

FIG. 15 is a schematic diagram illustrating scanning of a photosensitive drum by a laser beam.

FIG. 16 is a timing chart showing how the image forming timing in the vertical direction is corrected.

FIG. 17 is a timing chart showing how the image forming timing in the vertical direction is corrected.

Claims (20)

[Claims] An image forming apparatus that forms an image on a first surface of a print medium by an image forming unit, and then reverses the medium to form an image on the second surface of the medium by the image forming unit. Output means for printing and outputting a predetermined image on both sides; and an image on the first surface and a second image output by the output means.
An image forming apparatus comprising: a correction unit that moves a position where an image of each surface is formed by an amount corresponding to the shift based on a shift of an image position of the surface to match the positions. 2. A reading device for simultaneously reading images on a first surface and a second surface formed on a recording medium, and a determining device for determining a deviation between images on each surface read by the reading device. 2. The image forming apparatus according to claim 1, further comprising a correction unit that matches an image position based on the displacement determined by the determination unit. 3. The printing apparatus according to claim 1, further comprising a conveying unit configured to convey the medium to the image forming unit, wherein the correcting unit controls a timing of conveying the recording medium to the image forming unit, and a position of the recording medium in a lateral direction with respect to the conveying direction. 2. The method according to claim 1, wherein the position of the image is matched with at least one of moving the image.
Or the image forming apparatus according to 2. 4. The image according to claim 1, wherein the correction unit matches an image position by shifting an image forming position when the image forming unit forms an image. Forming equipment. 5. The image processing apparatus according to claim 1, wherein the output unit outputs, as the predetermined image, an image including two line segments arranged in at least one position on the recording medium in directions orthogonal to each other. An image forming apparatus according to any one of claims 1 to 4. 6. The output unit also outputs, as a predetermined image, an image for identifying a direction in which image formation is started on one of a first surface and a second surface of the recording medium. 6. The image forming apparatus according to claim 5, wherein the determining unit determines a direction of an image shift between the first surface and the second surface based on the tracking of the image read by the reading unit. Image forming apparatus. 7. The reading means is an optical scanner for optically reading an image, and reads an image on a medium through one side directly and through the medium through the other side. 3. The image forming apparatus according to claim 2, wherein a difference between an image on the first surface and an image on the second surface is determined based on a level difference between a density signal of the image read through the medium and an image read through the medium. Image forming device. 8. The color reading means for reading at least two colors, wherein the output means outputs an image of a first surface in one of the two colors and an image of a second surface in the other color. The image forming apparatus according to claim 2, wherein the determination unit determines a positional shift of the image between the two sides based on a difference in color. 9. The image forming apparatus according to claim 1, wherein the correcting unit shifts an image forming position when forming an image by the image forming unit by moving at least one of a medium conveying direction and a direction orthogonal to the medium conveying direction. The image forming apparatus according to claim 4, wherein the values match. 10. An image forming apparatus for forming an image on a first surface of a print medium by an image forming unit and then inverting the medium to form an image on the second surface of the medium by the image forming unit. A control method, comprising: an output step of printing out a predetermined image on both sides; and an image on each side of the output image based on a displacement of an image position between a first side and a second side. And a correction step of moving the positions where are formed to each other by the amount of the displacement to make the positions coincide with each other. 11. A recording medium comprising a first surface and a second surface formed on a recording medium.
A reading step of simultaneously reading the images of the surfaces, and a discriminating step of discriminating a displacement between the read images of the respective surfaces. The control method according to claim 10, wherein the control is made to coincide. 12. The image forming unit includes a conveying unit that conveys a medium, and the correcting step includes a step of moving the position of the recording medium in a direction transverse to a conveying direction and a direction of conveying the recording medium. The control method according to claim 10, wherein the positions of the images are matched at least on one side. 13. The control according to claim 10, wherein, in the correcting step, when forming an image by the image forming unit, the position of the image is matched by shifting the image forming position. Method. 14. The output step includes the steps of:
14. The control method according to claim 10, wherein an image including two line segments arranged in directions orthogonal to each other is output to at least one location on the recording medium. 15. The output step includes the steps of:
On one of the first surface and the second surface of the recording medium,
An image for identifying a direction in which image formation is started is also output, and the determining step includes the step of shifting the image between the first surface and the second surface based on the image read by the reading unit. The control method according to claim 14, wherein the direction is determined. 16. The reading step includes optically reading an image on a medium, with one surface being direct and the other surface being transparent to the medium. 12. The control method according to claim 11, wherein a difference between an image on the first surface and an image on the second surface is determined based on a level difference between density signals of the read image. 17. The reading step reads at least two colors, and the outputting step outputs an image of a first surface in one of the two colors and an image of a second surface in the other color. The control method according to claim 11, wherein the determining step determines a shift in the position of the image between the two surfaces based on a difference in color. 18. The image forming apparatus according to claim 18, wherein the image forming position when forming an image by the image forming unit is shifted by moving at least one of a medium conveying direction and a direction orthogonal to the medium conveying direction. 14. The control method according to claim 13, wherein the control is made to coincide. 19. The image forming apparatus according to claim 1, wherein the predetermined image is a graphic image having a predetermined shape. 20. The control method according to claim 10, wherein the predetermined image is a graphic image having a predetermined shape.