JP2003080790A - Imaging apparatus and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus which can register even rotated images to papers as desired. SOLUTION: In addition to a reference correction value 152 at a time of imaging without rotating images, correction values 154-158 corresponding to rotation angles 90 deg., 180 deg. and 270 deg. respectively are registered as correction value data 150 for image registration. A control routine of the imaging apparatus reads out from a nonvolatile memory 136 the correction value corresponding to the rotation angle of an object image at an imaging time, and corrects a registration state of the image by moving image write start points in a horizontal scanning direction and in a vertical scanning direction by an amount corresponding to the correction value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for aligning an image on a sheet in an image forming apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a printer, generally, the paper accumulated in a paper feed tray is provided with a photoconductor (in the case of a xerographic system), an ink jet head (in the case of an ink jet printer) or the like. The image is formed on the sheet by being conveyed to the engine section, and by the combination of the image writing processing on the sheet in the main scanning direction by the engine section and the conveying operation of the sheet in the sub-scanning direction.

In such an image forming apparatus, a sheet is temporarily stopped by a registration gate (also called a registration roller) provided at the front stage of the engine section to adjust the posture of the sheet, and then the sheet is synchronized in synchronization with the operation of the engine section. By restarting the conveyance, the control is performed so that the image is formed at the correct position on the sheet in the correct posture.

In this control, the position of the image in the sub-scanning direction is adjusted by adjusting the timing of restarting the sheet conveyance by driving the registration gate and the timing of starting the image writing process in the engine section. For example, in the case of the xerographic method, an image is written on a photoconductor and transferred onto a sheet of paper being conveyed. At that time, the leading edge of the image writing range on the photoconductor in the sub-scanning direction is The difference between the two timings is set so as to coincide with the leading edge of the sheet in the sub-scanning direction during transfer. Image alignment in the main scanning direction is performed by adjusting the image writing start position in the main scanning direction. For example, in the case of the xerographic method, the image writing start position in the main scanning direction when writing an image on the photoconductor is set so as to have a fixed relationship with the side edge of the sheet on the start position side.

In such an image forming apparatus, a correction value for alignment can be set in the main scanning direction and the sub scanning direction. This is because, in part, it absorbs individual differences in actual devices.

That is, for example, in the case of the sub-scanning direction, if there is a variation in the sheet conveyance speed due to individual differences in the performance of the sheet conveyance motor and the like, the difference between the sheet conveyance resumption timing and the engine section writing start timing is determined. If the control is performed using the design value as it is, the positional relationship between the image and the sheet may be displaced. In the case of popular machines, such individual differences are unavoidable to some extent, and in order to absorb this, a correction value for correct alignment is obtained by inspection at the time of factory shipment, etc. and stored in the image forming apparatus, and the image forming processing is performed. At this time, the control timing is adjusted by the correction value. The same applies to the case of the main scanning direction, and if there is a deviation in the alignment state in the main scanning direction due to individual differences in the device, correct alignment can be performed by shifting the image writing start position in the main scanning direction by the correction value. I am trying. Hereinafter, the correction value in the sub-scanning direction will be referred to as a sub-scanning correction value, and the correction value in the main-scanning direction will be referred to as a main-scanning correction value.

The correction value for alignment is also used when the position of the image on the paper is intentionally adjusted. For example, when a document having a strict format is printed, the correction value is adjusted to realize the adjustment of the image position according to the format.

[0008]

On the other hand, in a digital copying machine or the like, an image once captured in the apparatus is
Some have a function of rotating a predetermined angle such as 180 ° or 270 ° to form an image. For example, if an A4 size portrait original is read but there is only A4 landscape paper, this function is used to rotate the original image 90 ° or 270 ° to match the orientation of the paper and form an image. ing.

However, in the conventional image forming apparatus, when the image is formed by rotating the image in such a manner, there is a problem that the image cannot be precisely aligned. This problem will be described below with reference to FIG.

FIG. 9A schematically shows the image formation result of the character "A" when the image is not rotated (that is, the rotation angle is 0 °). Here, the sub-scanning correction value 100a is set with reference to the leading edge of the paper in the paper conveyance direction, and the main scanning correction value 102a is set with reference to the right side of the paper with respect to the paper conveyance direction. .

On the other hand, the same image is reproduced at 270 ° and 180 °.
Schematic diagrams of the image formation results when rotated by 90 ° (rotation angle is positive in the counterclockwise direction) are shown in (b), (c), and (d), respectively. Also in these cases, as in the case of the rotation angle of 0 °, the sub-scanning correction values 100b, 100
c and 100d are set with reference to the leading edge of the sheet in the conveyance direction, and the main-scanning correction values 102b, 102c, and 102d are set with reference to the right side of the sheet.

As can be seen from this figure, when the rotation angle of the image changes, the relative positions of the sub-scanning correction value and the main-scanning correction value with respect to the image ("A") change. This causes the displacement of the image.

For example, when the rotation angles are 0 ° and 180 °, it is possible to use the papers in the same paper tray. In this case, the conventional apparatus corresponds to the paper tray regardless of which rotation angle. Image position correction is performed using the same sub-scanning correction value and main scanning correction value that have been set. In this case, as can be seen by comparing (a) and (c) of FIG.
Since the same correction value is applied to the image from different positions, the position of the image “A” on the paper differs between the rotation angles of 0 ° and 180 °. In the case of 90 ° rotation or 270 ° rotation, for the same reason, the position of the image with respect to the paper is slightly deviated as compared with the case where the rotation angle is 0 °.

For the same reason, in the case of double-sided printing,
When an image is formed with different rotation angles of the image on the front side and the back side (for example, the front side is rotated by 90 ° with respect to the read image and the back side is rotated by 270 °), the image is slightly deviated between the front side and the back side. There was a problem.

Although such a shift is delicate, there are situations where high alignment accuracy is required, and it is required to reduce this shift as much as possible.

The present invention has been made to solve such a problem, and an object of the present invention is to provide an apparatus capable of aligning images with high accuracy in consideration of image rotation.

[0017]

To achieve the above object, an image forming apparatus according to the present invention comprises an image forming means capable of rotating an acquired image to form an image on a sheet, and the image forming means for the sheet. A position correction unit that corrects the formation position of the image by the image forming unit, and a correction unit that performs correction using an individual correction value for each rotation angle of the image.

In a preferred aspect of the present invention, the correcting means performs the correction by controlling an image writing timing in the image forming means.

In another preferred aspect, the correction means performs the correction by electronically operating the image on the memory.

In another preferred aspect, the image forming means has a double-sided image forming function, and the correcting means has a correction value for each rotation angle for forming a back side image.

In another preferred aspect, a correction value setting means for accepting a setting operation of the correction value for each rotation angle by the correction means, and an authentication for authenticating a person who intends to use the correction value setting means. And means.

The image forming apparatus control method according to the present invention is an image forming apparatus capable of rotating an acquired image to form an image on a sheet, when correcting the image forming position on the sheet. The correction is performed using the individual correction value for each rotation angle of the image.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

In the image forming apparatus of this embodiment, the correction value for image alignment can be set individually for each rotation angle of the image. Then, the image forming position is corrected using the correction value according to the rotation angle of the image at the time of image formation, so that the image can be correctly aligned with respect to the sheet at any rotation angle.

First, referring to FIG. 1, the structure of the mechanical mechanism portion of the image forming apparatus to which the control of this embodiment is applied will be described.

In the example of this figure, a double-sided printing module 2 is connected to a housing 1 of the main body of the image forming apparatus.
In this example, two paper trays 3 are provided in the housing 1, and the tray 3 is provided with a feed roll 4 that sends the paper to the paper transport path. Also, in this device,
A manual feed tray 21 is provided, and paper of a size that is not in the paper tray 3 can be supplied from this tray 21. The manual feed tray 21 is also provided with a feed roll 22. Also, the paper tray 3 and the manual feed tray 2
1 is provided with a paper sensor 25 for determining the presence or absence of paper on those trays.

This example is an xerographic image forming apparatus in which a photosensitive drum 7 is provided along a paper transport path. After the photoconductor drum 7 is charged by the charging unit 9, image writing (exposure) by a raster output scanner or the like is performed.
The unit 10 forms a latent image of an image to be formed on the surface of the drum 7. This latent image is developed by attracting the toner supplied from the toner attracting portion 11, and this is transferred to the transfer portion 1.
2 is transferred to the paper. The residual toner after transfer is cleaned by the photoconductor cleaning unit 8. The sheet on which the image is transferred is fixed to the sheet by heat or the like in the fixing unit 13.

The gate 14 is a means for allocating the fixed paper to a path on the side of the discharge tray 16 or the discharge tray 19, and the gate 17 is for discharging the paper conveyed from the gate 14 side to the discharge tray 19 or. It is a means for allocating to the path in the duplex unit 2. The discharge roll 18 is a roll for discharging the image-formed sheet on the discharge tray 19. The paper reversing roll 15 is a roll that can perform a reversing operation when the paper is discharged onto the discharge tray 16 and when the paper is reversed during double-sided printing.

In the case of double-sided printing, after the image transfer and fixing on the front surface, the paper is once discharged halfway onto the discharge tray 16. After that, the paper reversing roll 15 is reversed and the gate 1
By switching 7 to the duplex unit 2 side, the orientation of the paper is reversed by the switchback method. The sheet conveyed through the path in the duplex unit 2 is temporarily stopped by the double-sided gate 20, and when the sheet can enter the main conveyance path 5 in the main body, the double-sided gate 20 is driven and the sheet is mainly conveyed. Route 5 is sent. The paper sensor 27 is connected to the gate 14
And a sheet reversing roll 15 for detecting the presence or absence of the sheet at the installation position. Further, the paper sensor 24 detects the presence / absence of paper in the duplex unit 2.

A registration gate (hereinafter abbreviated as "registration gate") 26 is provided to temporarily tilt the sheet conveyed from the tray 3 or 21 or the double-sided unit 2 to the main conveying path 5 so that the sheet is inclined during conveyance. Is corrected, and when the image forming preparation is completed on the photoconductor drum 7 or the like, the sheet is sent toward the photoconductor drum 7.
The paper sensor 23 is a sensor that detects whether or not paper exists at the position of the registration gate 26.

The configuration of FIG. 1 illustrated above is an example of a general image forming apparatus, and this is merely an example for explaining the image alignment control below. Therefore, the application of the image registration control according to the present embodiment is not limited to the configuration shown in FIG. 1, and it should be noted in advance that it can be widely applied to general image forming apparatuses having an image rotation function.

Next, with reference to FIG. 2, the overall configuration including the control system of the image forming apparatus of this embodiment will be described.

ROM (Read Only Memory) 132
The control program of the image forming apparatus and the like are stored in. The CPU (Central Processing Unit) 131 uses this RO
The image forming apparatus is controlled by executing the program of M132. RAM (random access
The memory) 133 is used as a storage area for data associated with the execution of this program and also for storing image data to be printed.

The I / O port 134 is a port that serves as an interface between the CPU 131 and an input / output device in the image forming apparatus. The I / O port 134 is connected with the image writing unit 10, the feed rolls 4 and 22, the resist gate 26, the paper reversing roll 15 and the like, and the sensors such as the paper sensors 23, 24, 25 and 27. The sensor signal 145 is input. The I / O port 134 also includes an image input unit 140 such as a document reading device (scanner) and an external input unit 14 that receives print data from a host computer via a network or a cable.
1 is connected. The image data acquired by the input unit 140 or 141 is accumulated in the RAM 133, and is written on the photosensitive drum 7 by the image writing unit 10 under the control of the CPU 131. The external input unit 14
The print data input from 1 is often described in a page description language. In such a case, the CPU 13
1 executes a program stored in the ROM 132 to develop the print data into image data in a format that can be handled by the image writing unit 10.

In addition to the above, the I / O port 134 is connected with units such as an input destination detection unit 137, a time measurement unit 138, a touch panel 139, and the like. Input destination detection unit 1
37 is a means for detecting the supply source of the image forming target data. For example, in the case of a digital multi-function peripheral, a plurality of input devices such as a facsimile are provided as a local image input unit 140 in addition to a scanner, and an external input unit 141 is further provided. Which one of them. The input destination detection unit 137 is provided for each image supply source in order to provide finer image position deviation correction according to the characteristics thereof (details will be described later). Therefore, the input destination detection unit 137 is not necessary when it is not necessary. The time measuring unit 138 is a means such as a timer for measuring the time when controlling the image forming apparatus. The touch panel 139 is a user interface unit of the image forming apparatus, displays various operation screens on a display according to a control program executed by the CPU 131, and acquires a user's operation instruction input by touching the display with the user. To the control program.

The image rotation processing section 135 is means for rotating the image held in the RAM 133 to change its direction. When the state of being unfolded on the RAM 133 from the image input unit 140 is 0 °, the rotation angles such as 90 °, 180 ° and 270 ° can be selected counterclockwise. The image rotation may be performed in response to an explicit instruction from the user via the touch panel 139, or may be automatically performed by a control program of the image forming apparatus. In the latter case, for example, when an A4 portrait original is read and there is only A4 landscape paper on the tray, the direction of the image is automatically rotated by 90 ° so that an image can be formed on the paper. Is. In addition, when the booklet is created by stapling the double-sided printing result, it is necessary to reverse the top and bottom of the image depending on the assumed way of opening the booklet. In such a case, the image on the back side is automatically displayed according to the opening instruction input by the user.
Control such as rotation by 80 ° is performed.

The non-volatile memory 136 is, for example, EEPR.
The OM stores various setting values of the image forming apparatus. The non-volatile memory 136 stores the correction value data 150 for image alignment. This correction value data 150 includes when the image is not rotated (rotation angle 0
In addition to the reference correction value 152, which is the correction value of 90 °), the correction value 154 at 90 ° rotation, the correction value 156 at 180 ° rotation,
The correction value 158 at the time of 270 ° rotation is included. The correction values 152 to 158 of the respective rotation angles have a sub-scanning correction value which is a correction value in the sub-scanning direction and a main scanning correction value which is a correction value in the main scanning direction. In this example, the rotation angles of the image are 0 °, 90 °, 180 °,
This is a case of an image forming apparatus capable of a rotation angle of 270 °, and if there is another apparatus capable of a rotation angle, a correction value corresponding to the rotation angle may be obtained and stored.

The correction value for each rotation angle is set, for example, at the time of factory shipment, at the time of maintenance and inspection by a support engineer, or before the start of individual image forming processing. This setting is performed, for example, by calling the correction value setting screen from the user interface screen on the touch panel 139 or by calling the correction value setting screen by accessing the image forming apparatus from a computer via a network such as a LAN. FIG. 3 is a diagram showing an example of the correction value setting screen. The correction value setting screen 201 of FIG.
It is a screen for setting a correction value at the time of 0 ° rotation. This screen can be called by hierarchically selecting from the main user interface screen,
At this time, a correction value setting screen for a desired rotation angle may be selected and called. On this setting screen, for example, the numeric keypad 221
A correction value can be input by operating.
For example, by touching the “sub-scanning” column of the correction value setting column 220, the sub-scanning correction value is input and selected, and the value input by the ten key 221 is displayed in the sub-scanning correction value column. When nothing is entered in the correction value field, the image forming apparatus interprets that a default value stored in advance in the apparatus is instructed and performs processing. By touching the test print button 222 as necessary, test printing is performed using the sub-scanning correction value and the main-scanning correction value displayed in the correction value setting field 220. In this test printing, a test image, such as a lattice pattern, in which the positional relationship between the image and the paper is easy to grasp is printed and output on the paper. The operator can confirm the suitability of the set correction value by looking at the test print result. When the correction value is not appropriate, the numeric keypad 221 is operated to input the correction value again, or the plus button 223 or the minus button 2
The correction value can be adjusted until the desired alignment between the paper and the image is obtained by an operation such as changing the correction value by a predetermined amount in the plus or minus direction by 24.

Also, by touching the "Default restore" button 225, the current value displayed in the correction value setting field 220 can be returned to the default value (for example, the factory default value).

When the correction value setting is completed by such an operation, the set value is stored in the non-volatile memory 136.

It is also possible to limit the authority of work for setting / changing the correction value to a specific person. For example, only a service engineer of a company that sells or leases an image forming apparatus, a specific system administrator of an organization on the image forming apparatus introducing side, or the like can set or change the correction value. For this purpose, for example, in order to access the correction value setting screen, it is necessary to input authentication information such as a password. Of course, if such authentication means is not provided, anyone can change this correction value as needed.

Correction values 154-1 for each rotation angle
It is also preferable to store 58 as an offset value with respect to the reference correction value 152 when not rotating. By doing this, when there are a plurality of paper trays, if only the reference correction value is set for each paper tray, the correction values 154 to 156 for the remaining rotation angles can use the values common to those paper trays. The size of the correction value data can be reduced. Since the correction value at the time of rotation is basically based on a common mechanism such as sheet conveyance that does not depend on the sheet tray, such a collective handling is possible. In this case, the correction value to be actually applied is a value obtained by adding the reference correction value 152 to the stored correction value 154. When printing on the back side in double-sided printing mode, the paper conveyance path is different from that for front-side printing (and in single-sided printing mode), so the reference correction value corresponding to the back side (and other rotation angle corrections if necessary) It is preferable to set (value).

When there are a plurality of image input destinations (ie, supply sources) such as a scanner and a facsimile,
It is also possible to set the correction value data 150 for each rotation angle for each of these input destinations. By doing so, it is possible to realize individual desired image alignment states for each image input destination. In this case, the correction value for each rotation angle is determined based on a certain input destination,
It is also preferable to store only the offset value for the correction value of the other input destination with respect to the correction value of the reference input destination.

In the above description, the correction value for image alignment is expressed by two parameters, the sub-scanning correction value and the main-scanning correction value. However, depending on the structure of the image forming apparatus, the correction value may be corrected by a larger number of parameters. In some cases it is better to express the value, in other cases it can be expressed by a single value. It is preferable that the correction value can be set in an expression format suitable for the structure of the applied image forming apparatus.

Next, the flow of the image forming process in this embodiment will be described with reference to FIGS. Here, processing in the double-sided printing mode will be described as an example.

When an image forming start instruction is given by the user through the operation means such as the touch panel 139, the control routine for image formation of the image forming apparatus is executed by the touch panel 13.
It is determined from the processing mode information input from 9 whether the instructed processing is single-sided printing or double-sided printing. Here, the description will proceed assuming that double-sided printing is instructed. When there are a plurality of image input destinations such as a scanner and a facsimile, the input destination detection unit 137 detects the input destination and notifies the control routine of this. This input destination detection is performed based on whether the processing function instructed by the user on the touch panel 139 or the like is copying, receiving facsimile printing, or the like. The control routine stores the information of the input destination thus detected.

Next, the control routine determines the rotation angle of the image based on the document size information input from the image input unit 140, the paper size information existing in the paper tray, various designation contents input from the touch panel 139, and the like. Ask (S
10). When there are a plurality of paper trays, it is also determined which paper tray is used. If the rotation angle cannot be obtained due to an exception of the processing, it is assumed that the reference rotation angle (for example, 0 °) is designated for the purpose of preventing the abnormality, and the process proceeds to the following processing.

Next, the control routine is executed by the non-volatile memory 13
From the correction value data 150 in FIG. 6, the image alignment correction value (FIG. 2) corresponding to the rotation angle obtained in step S10.
In this example, the sub-scanning correction value and the main-scanning correction value are read (S1
2). If there are a plurality of paper trays, the correction value information of the rotation angle is read from the correction value data 150 corresponding to the paper tray to be used. When the correction values 154 to 158 for each rotation angle are registered as offset values for the reference correction value 152, the correction value actually used is obtained by adding the correction value for the rotation angle to the reference correction value 152. Further, when there are a plurality of image input destinations (suppliers), the correction value of the rotation angle is read from the correction value data 150 corresponding to the input destination obtained by the input destination detection unit 137.

When the correction value is obtained in this way, the feeding of the paper is started from the paper tray (S14). The control routine waits until the fed sheet advances along the conveying path and is detected by the sheet sensor 23 (S16). When the paper sensor 23 is turned on, the control routine starts time measurement using the time measurement unit 138 (S18), waits for the elapse of a predetermined fixed time (S20), and once the fixed time elapses, the paper is once conveyed. Stop (S22). This is because the paper is pressed firmly against the resist gate 26 so that the attitude of the paper can be properly adjusted in accordance with the resist gate 26. Therefore, the fixed time of waiting in S20 is also predetermined according to this purpose.

Next, the control routine waits until the image to be written is ready (S24). When the image is ready, the driving of the resist gate 26 is started, the conveyance of the sheet is restarted, and the time measurement is started using the time measurement unit 138 (S26). Then, wait for a certain time (S2
8) After a certain period of time, the image writing unit 10 is instructed to start writing an image on the photosensitive drum 7 (S3).
0). The standby for a certain time at this time is the timing when the paper reaches the position of the transfer unit 12 from the resist gate 26, and the beginning of the image written on the photosensitive drum 7 by the image writing unit 10 is the photosensitive drum 7. Transfer part 1 by rotation
This is done to match the timing until reaching the position 2. In this example, the image written on the photosensitive drum 7 is not transferred until the paper reaches the transfer unit 12.
Since it takes longer to reach 2, the paper transport is restarted first and the image writing is started after that, but this may be reversed depending on the design of the image forming apparatus. .

The correction of the image position adjustment in the sub-scanning direction is performed by correcting the waiting time (time difference from the restart of sheet conveyance to the start of image writing) in step S28 with the sub-scanning correction value obtained in step S12. . When the waiting time is reduced by this correction, the sheet reaches the transfer unit 12 quickly. In this case, the formed image arrives at the transfer unit 12 with a relative delay as compared with the case where no correction is made.
The image formed on the paper is the paper conveyance direction (sub-scanning direction)
Move down against. On the contrary, when the waiting time is extended due to the correction, the image on the paper comes higher in the paper conveyance direction than when the image is not corrected.

On the other hand, the correction of the image position in the main scanning direction is performed by adjusting the image writing start position in the main scanning direction by the image writing unit 10. Here, as is well known, in the process of writing an image on the photosensitive drum 7, the writing is performed from the image writing start position determined with the origin (the position corresponding to the sheet edge in the main scanning direction) as a reference. Is started and writing is performed for a predetermined number of pixels according to the paper width, writing of one line is completed, and by repeating this for the number of lines of one page, an image of one page is written on the photosensitive drum 7. In the image position correction in the main scanning direction, the interval from the origin to the image writing start position (generally counted in the number of pixels) is corrected by the main scanning correction value obtained in step S12. This correction is performed in the writing control of all lines for one page.
By this correction, the entire image written on the photosensitive drum 7 is shifted in the main scanning direction by the main scanning correction value, and as a result, an image is formed on the sheet at a position corrected by the main scanning correction value. To be done.

The process flow after this will be described with reference to FIG. When the paper sensor 23 is turned off while the image writing and the transfer to the paper are progressing as described above, the control routine starts the time measurement by the time measuring unit 138 (S
32) When a certain period of time has passed, the writing of the image on the photosensitive drum 7 by the image writing unit 10 is completed (S34, S).
36). That is, OFF of the paper sensor 23 means that the rear end of the paper has passed the position of the sensor 23, and the image writing process is completed after a certain time from this point, so that the rear end of the image in the paper transport direction is ended. Can be correctly positioned with respect to the trailing edge of the paper in the same direction.

In this way, the transfer of the image onto the surface of the paper is completed, and the fixing unit 13 fixes the image on the paper. At this time, the sheet is discharged through the gate 14 to the discharge tray 16
Is sent to the side transport path. During this period, the control routine waits for the paper sensor 27 to be turned on (S38), and when the same sensor 27 is turned off thereafter (S40), it is determined that the paper has reached the reversing roll 15 and time measurement is started (S4).
2). Then, after a lapse of a certain time (S44), the rotation of the reversing roll 15 is reversed, and the paper is reversed in the reverse direction.
Transport towards.

The processing shifts to the flow shown in FIG. 6, and the control routine follows that the paper sensor 24 in the duplex unit 2 is turned on.
It waits until it becomes, and when it becomes ON, the sheet conveyance is stopped (S48). Here, the preparation of the data of the image to be formed on the back side is waited, and if there is another sheet on the sheet conveyance path in front of the registration gate 26 of the image forming apparatus main body, it is waited until it disappears (S50). During this time, the rotation angle of the image on the back side is obtained, and the image alignment correction value (sub scanning and main scanning) corresponding to this rotation angle is acquired (S52,
S54). This is the step S10 and S for surface
Basically, it may be the same as the processing of 12. However, here, the correction value for the back surface is acquired.

When the image is ready, the double-sided gate 20 is driven to restart the sheet conveyance (S56). Thereafter, the processing from step S58 to step S76 shown in FIG. 7 is the same as the processing from step S16 to step S36 described above. However, here, the standby time in step S68 and the image writing start position of each line are corrected by the sub-scanning correction value and the main-scanning correction value for the back surface (corresponding to the obtained rotation angle, of course).

After the image writing is completed (S76), the control routine waits for the paper sensor 27 on the conveying path to the discharge tray 16 to detect the paper (S78), and this sensor 27 turns off.
The sheet reversing roller 15 is rotated in the sheet discharging direction as it is even after detecting N and turning off thereafter (S80), and the sheet is discharged to the discharge tray 16.

The processing procedure of this embodiment has been described above by taking the case of double-sided printing as an example. However, in the case of single-sided printing, the same control as the processing at the time of front-side printing in double-sided printing may be performed. It will be obvious to the trader.

As described above, according to the image forming apparatus of the present embodiment, it is possible to register the correction value for the image alignment for each rotation angle of the image, and it is possible to register the correction value according to the rotation angle of the image when the image is formed. Since the alignment of the image is corrected using the correction value, it is possible to align the image correctly on the paper even when the image is formed by rotating the image.
It is possible to make it difficult for image shifts and chippings to occur. Then, by appropriately setting the correction value for each rotation angle, it is possible to obtain an image formation result in which the registration state of the image with respect to the paper is the same regardless of which rotation angle the same image is rotated to form the image ( Of course, even if you use the same size paper).

Further, in the present embodiment, the relative positional relationship between the images on the front surface and the back surface during double-sided printing can be corrected in detail. That is, when an image developed on the RAM 133 is rotated by 90 ° on the front side and 270 ° on the back side to form an image (for example, when it is assumed that the print result is stapled and opened and read vertically, such processing is performed). However, in the related art, the front and back image positions may deviate from each other due to the difference in the acting portion of the correction value described in FIG. 8, but in the present embodiment, the rotation angles of the image on the front surface and the back surface are different. By performing the correction using the corresponding correction value, the shift can be reduced. If the correction value can be set appropriately, it is not impossible to eliminate the deviation.

Further, in this embodiment, the correction value for each rotation angle can be set for each paper tray, so that the image alignment error due to the difference in the transport mechanism for each paper tray can be corrected. . Further, also in the case of back side printing, by making it possible to set the correction value for each rotation angle, it is possible to improve the accuracy of the image alignment correction during double sided printing.

Further, in the present embodiment, the correction value for each rotation angle can be set for each input destination (supply source) of the image to be image-formed, so that desired image alignment can be performed for each input destination. Can be realized.

Further, in the present embodiment, by providing the user authentication means for the correction value setting, only the service engineer or the predetermined system administrator can set / change the correction value. As a result, it is possible to prevent erroneous setting of the correction value by a general user.

In the present embodiment, the correction of the image position adjustment is performed by adjusting the image writing start timing in the control routine and the writing start position at the time of each line writing (this "position" is also a kind of timing). Can be done by. Even if no hardware is added to the conventional image forming apparatus, the image alignment correction of the present embodiment can be realized only by software change, which is excellent in cost.

Alternatively, if a sufficiently large size memory is used as a memory for expanding the image data to be written, the image is stored in such an address that a sufficient margin is formed around the image. The same image alignment correction can be realized by expanding the read start and end addresses by the sub-scanning correction value and the main-scanning correction value when reading the image from this memory when writing the image. is there.

Further, in the correction value setting screen (see FIG. 3) exemplified in the above embodiment, the main scanning correction value and the sub scanning correction value are shown by numerical values, but the correction value setting screen and the correction value are affected by the values alone. The part may be difficult to understand intuitively.
Therefore, for example, by graphically displaying as illustrated in FIG. 8, a user interface that is easy for the setting person to understand can be provided. In the example of FIG. 8, the image writing start positions indicated by the main-scanning correction value and the sub-scanning correction value are indicated by arrows 252 and 262 on the gauges 250 and 260, respectively. The gauges 250 and 260 are set in the directions in which the respective correction values act on the image of the document set on the document table (platen) of the image forming apparatus, and are intuitively easy to understand. In addition, since the default value of each correction value and the direction of the paper edge in the vicinity are shown, it is easy to understand which direction the correction value should be adjusted. In this example, the "+" and "-" buttons are provided for changing and adjusting the correction value, but in addition to this, a numeric keypad as shown in FIG. 3 may be provided.

Even if the detailed display is not as shown in FIG. 8, the correction value increasing / decreasing direction and the image writing start position moving direction (moving toward the edge of the paper, or toward the center of the paper) It would be a great help to the setter just to provide a display that shows the correspondence with (whether it moves to the one with the image).

In the above example, the xerographic image forming apparatus using the laser raster output scanner as the image writing means is taken as an example, but the concept of the image alignment correction processing of the present embodiment is other than that. It is also applicable to various types of image forming apparatuses, for example, apparatuses such as a xerographic method using an LED head, an inkjet method, a dot impact method, a silver salt photography method, and a lithography method.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an example of an image forming apparatus to which an image alignment correction process according to the present invention is applied.

FIG. 2 is a diagram showing a schematic configuration of a control system of the image forming apparatus.

FIG. 3 is a diagram showing a display example of a correction value setting screen.

FIG. 4 is a flowchart showing a processing procedure at the time of double-sided printing of the image forming apparatus of the embodiment.

FIG. 5 is a flowchart showing a processing procedure for double-sided printing of the image forming apparatus of the embodiment.

FIG. 6 is a flowchart showing a processing procedure for double-sided printing of the image forming apparatus of the embodiment.

FIG. 7 is a flowchart illustrating a processing procedure for double-sided printing of the image forming apparatus according to the embodiment.

FIG. 8 shows a correction value setting screen for each rotation angle,
It is a figure which shows another example of the display form of a correction value.

FIG. 9 is a diagram for explaining how a relative positional relationship with respect to an image of a portion on which an image alignment correction value acts changes with a rotation angle of the image.

[Explanation of symbols]

10 image writing means, 26 resist gate, 133
RAM, 135 image rotation processing unit, 136 non-volatile memory, 150 correction value data, 152 reference correction value, 1
54 90 ° rotation correction value, 156 180 ° rotation correction value, 158270 ° rotation correction value.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 21/14 G03G 21/00 390 5C074 G06T 3/60 372 5C076 H04N 1/23 B41J 3/00 S 1 / 387 MF Term (reference) 2C062 RA06 2C087 AC08 BD20 CB12 2C362 BB27 BB28 BB46 CB39 CB41 2H027 EJ01 FA11 FA30 FD00 FD08 ZA07 5B057 AA11 BA02 BA23 CD04 CE20 CH07 CH11 CH18 5C074 5A04 AA CC CC26 CH07 CH11 CH18 5C074 AA07 CC26 DD26

Claims (6)

[Claims] 1. An image forming unit capable of rotating an acquired image to form an image on a sheet, and a position correcting unit for correcting a formation position of the image on the sheet by the image forming unit, An image forming apparatus, comprising: a correction unit that performs correction by using a correction value for each rotation angle of the image. 2. The image forming apparatus according to claim 1, wherein the correction unit performs the correction by controlling an image writing timing in the image forming unit. 3. The image forming apparatus according to claim 1, wherein the correction unit performs the correction by electronically operating the image on the memory. 4. The image forming apparatus according to claim 1, wherein the image forming unit has a double-sided image forming function, and the correcting unit has a correction value for each rotation angle for forming a back side image. apparatus. 5. A correction value setting means for accepting a correction value setting operation for each rotation angle by the correction means, and an authentication means for authenticating a person who intends to use the correction value setting means. The image forming apparatus according to item 1. 6. An image forming apparatus capable of rotating an acquired image to form an image on a sheet, wherein when correcting the image forming position on the sheet, individual correction is performed for each rotation angle of the image. A method of controlling an image forming apparatus, which corrects using a value.