JP2011186241A - Image forming apparatus, image forming method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly precisely detect shifting of printing positions on a front side and a back side in both sides printing that performs printing on the front side and the back side even when a recording medium has large paper thickness and to correct it with high precision. <P>SOLUTION: An image forming apparatus includes: a plotter device 24 as a both sides printing means for printing correction patterns on the front side and the back side of the recording medium; a reader 10 as a both sides reading means for reading the correction patterns that are printed on both sides of the recording medium at a time; a CPU18 as a correction pattern detection means for detecting the positions of respective correction patterns read from both sides of the recording medium; the CPU 18 as a calculation means for calculating the amount of correction for the shifting of the printing positions from the correction patterns on both sides that are detected by the correction pattern detection means; and the CPU 18 as the correction means for correcting the shifting of printing positions on the front side and the back side when printing on both sides, on the basis of the amount of correction that is calculated by the calculation means. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, an image forming method, and a program.

  In a conventional image forming apparatus, the image forming position at the time of double-sided printing is determined by restricting the front position of the paper with a registration roller or the like, and the horizontal position is a regulating plate in the paper cassette, It is determined by restricting with a restricting plate of a duplex unit on which a sheet on which one side is recorded is once placed or other restricting plate.

  However, in the image forming apparatus configured as described above, an error in the image forming position is large, and the image forming position may be shifted even if only paper is supplied to the paper feeding cassette. Therefore, in another image forming apparatus, after outputting a correction pattern printed on both sides on a recording medium, the correction pattern is read on both sides of the correction pattern by the reading unit of the own machine, thereby preventing a printing position shift during double-sided printing. A technique of correcting separately is known.

  In addition, the image forming apparatus disclosed in Patent Document 1 prints and outputs a predetermined image on both sides of a print medium for the purpose of correcting a printing position shift between the front and back sides during double-sided printing. Disclosed is a correcting means for matching the printing positions on both sides by reading the front side and back side image by single-sided reading, and moving the image forming positions on each side by the amount shifted from each other. Has been.

  However, in the other image forming apparatus, after the correction pattern printed on both sides of the recording medium is output, the correction pattern is read one side at a time on both sides by the reading unit of the own machine, so Since the printing position deviation was corrected separately, it was necessary to consider the reading accuracy of the front and back surfaces, and there was a problem that the correction accuracy was lowered accordingly.

  Further, in the image forming apparatus disclosed in Patent Document 1, since the show-through was read when the correction pattern printed on both sides of the recording medium was read by the reading unit, the correction pattern was printed on the recording medium having a paper thickness. Then, there was a problem that the show-through could not be read and the desired correction could not be made.

  The present invention has been made in view of the above, and even when a recording medium having a paper thickness is printed on the front surface and the back surface, the printing position deviation between the front surface and the back surface can be accurately detected, and high accuracy can be achieved. It is an object of the present invention to provide an image forming apparatus, an image forming method, and a program that can be accurately corrected.

  In order to solve the above-described problems and achieve the object, the present invention provides a double-sided printing unit that prints a correction pattern on the front and back surfaces of a recording medium, and reads the correction pattern printed on both sides of the recording medium at a time. A correction amount of a printing position deviation from a correction pattern on both sides detected by the correction pattern position detection unit, a correction pattern position detection unit that detects the position of each correction pattern read from both sides of the recording medium And a correction unit that corrects the printing position deviation between the front and back sides during duplex printing based on the correction amount calculated by the calculation unit.

  In order to solve the above-described problems and achieve the object, the present invention is an image forming method executed by an image forming apparatus, the image forming apparatus including a double-sided printing unit, a double-sided reading unit, A correction pattern position detection unit; a calculation unit; and a correction unit, wherein the double-sided printing unit prints a correction pattern on the front and back surfaces of the recording medium, and the double-sided reading unit prints on both sides of the recording medium. A step of reading the corrected pattern at a time, a step of detecting the position of each correction pattern read from both sides of the recording medium, and a step of correcting the detected both sides of the correction unit. The step of calculating the correction amount of the printing position deviation from the pattern position, and the correction unit compensates for the printing position deviation of the front side and the back side during duplex printing based on the calculated correction amount. Characterized in that it comprises the steps of, a.

  In order to solve the above-described problems and achieve the object, the present invention is a program installed in an image forming apparatus, and a computer for printing a correction pattern on the front and back surfaces of a recording medium; A double-side reading means for reading correction patterns printed on both sides of the recording medium at a time, a correction pattern position detecting means for detecting positions of the respective correction patterns read from both sides of the recording medium, and the correction pattern position detection Calculating means for calculating the correction amount of the printing position deviation from the correction patterns on both sides detected by the means, and correcting the printing position deviation on the front and back sides during duplex printing based on the correction amount calculated by the calculating means. This is a program that functions as correction means.

  According to the present invention, the correction patterns printed on the front and back surfaces of the recording medium are read at a time by the double-sided reading means, the positions of the respective correction patterns are detected, and the printing position deviation is detected from the detected correction patterns on both sides. A correction amount is calculated, and based on the calculated correction amount, a printing position shift between the front surface and the back surface during double-sided printing is corrected. As a result, the present invention can accurately detect a printing position shift between the front surface and the back surface during double-sided printing for printing on the front surface and the back surface even with a paper-thick recording medium, and can correct this with high accuracy. There is an effect that can be done.

FIG. 1 is an overall configuration diagram of the image forming apparatus according to the first embodiment. FIG. 2 is a cross-sectional view showing the configuration of the reading device of FIG. FIG. 3 is a flowchart of the correction pattern output operation. FIG. 4A is a diagram illustrating an example of a correction pattern output on the surface. FIG. 4B is a diagram illustrating an example of the correction pattern output on the back surface. FIG. 4C is a diagram illustrating an example of the correction pattern output on both sides. FIG. 5 is a flowchart of a printing misalignment correction operation during duplex printing according to the first embodiment. FIG. 6A is a diagram illustrating another example of the correction pattern output on the surface. FIG. 6B is a diagram illustrating another example of the correction pattern output on the back surface. FIG. 6C is a diagram illustrating another example of the correction pattern output on both sides. FIG. 6-4 is a diagram illustrating an example in which a correction pattern for avoiding shock jitter is output. FIG. 7 is a diagram showing changes in the conveyance speed of the ADF apparatus. FIG. 8 is a flowchart of a printing misalignment correction operation during duplex printing according to the second embodiment. FIG. 9 is an enlarged view of the vicinity of the front end of the recording medium after outputting the correction pattern. FIG. 10 is a flowchart of a printing misalignment correction operation during duplex printing according to the third embodiment.

  Exemplary embodiments of an image forming apparatus, an image forming method, and a program according to the present invention are explained in detail below with reference to the accompanying drawings. The present invention is not limited to these embodiments, and various modified embodiments are possible without departing from the spirit of the present invention.

(First embodiment)
FIG. 1 is an overall configuration diagram of the image forming apparatus according to the first embodiment. In this embodiment, an example in which the image forming apparatus according to the present invention is applied to a digital image forming apparatus (MFP: Multi Function Peripherals) in which a plurality of functions such as copying, faxing, and printers are housed in one housing. Although shown, the present invention is not limited to this. For example, the image forming apparatus according to the present invention can be applied to any apparatus provided with a scanner function, such as a copying machine, a facsimile apparatus, and a scanner apparatus.

  As shown in FIG. 1, the image forming apparatus 8 includes a reading device 10 as a double-sided reading unit, an image data processing unit 12, a bus control unit 14, an HDD (Hard Disk Drive) 16, a correction pattern position detection unit, a calculation unit, CPU (Central Processing Unit) 18 as correction means, memory 20, plotter I / F device 22, plotter device 24 as double-side printing means, operation display device 26 as error notification means, line I / F device 28, external I / F device 30, S.P. B. (South Bridge) 32, a ROM (Read Only Memory) 34, a slot 36 for external media, and the like, and are connected via a general-purpose expansion bus 38.

  The reading device 10 includes a line sensor composed of a CCD (Charge Coupled Device), an A / D converter, and a drive circuit thereof, and is obtained by scanning a document that has come to a reading position. It generates and outputs digital image data of 8 bits for each RGB from the density information of the document.

  The image data processing device 12 performs processing that unifies the digital image data output from the reading device 10 with predetermined characteristics and outputs the digital image data. The characteristic to be unified is a characteristic suitable for image conversion of an output destination when image data is stored in the HDD 4 and reused.

  The bus control device 14 is a data bus control device that exchanges various data such as image data and control commands necessary in the digital color multifunction peripheral, and also has a bridge function between a plurality of types of bus standards.

  The HDD 16 is a large-sized storage device for storing electronic data that is also used in personal computers and the like, and is mainly digital image data and accompanying information (for example, setting mode) in the digital color multifunction peripheral. Is to accumulate. In this embodiment, an ATA bus connection hard disk standardized by expanding IDE is used.

  The CPU 18 is a microprocessor that controls the entire control of the digital color multifunction peripheral. Since high-speed processing is required, the CPU 18 starts up the system with a boot program stored in the ROM 34 during normal startup, and thereafter performs processing with a program developed in the memory 20 that can be accessed at high speed. In the present embodiment, a DIMM used in a standardized personal computer is used.

  The memory 20 stores temporarily exchanged data in order to absorb a speed difference when bridging between a plurality of types of bus standards and a difference in processing speed of connected components themselves, or the CPU 18 performs a digital color composite. It is a volatile memory that temporarily stores programs and intermediate processing data when controlling the machine.

  When the plotter I / F device 22 receives digital image data composed of CMYK sent via the general-purpose standard I / F via the CPU 18, the plotter I / F device 22 performs a bus bridge process that outputs the digital image data to the dedicated I / F of the plotter device 24. is there. The general-purpose standard I / F used in the present embodiment is a PCI-Express bus.

  When the plotter device 24 receives digital image data composed of CMYK, the plotter device 24 outputs the image data received on the transfer paper using an electrophotographic process using a laser beam.

  The operation display device 26 is a part that performs a user interface with the digital color multifunction peripheral. A key switch group including an LCD (liquid crystal display device) provided with a touch panel, various processing mode setting keys, numeric keys, a start key, and the like. It displays the various states and operation methods of the device on the LCD, and detects input from the user via the touch panel or key switch group. In this embodiment, it is also used as an error notification means for displaying on the LCD and informing the user that a reading error has occurred.

  The line I / F device 28 is a device for connecting a PCI-Express bus and a telephone line. The line I / F device 10 allows the digital color multi-function peripheral to exchange various data with the FAX 50 that is an image output device (image processing unit) via a telephone line.

  The external I / F device 30 is a device that is connected to a PCI-Express bus and a PC (personal computer) 52 that is an image output device. The external I / F device 30 is also a device that is connected to an external medium 54 such as an SD card via the slot 36. The external I / F device 11 enables the digital color multifunction peripheral to exchange various data with the PC 52 and the external medium 54. In this embodiment, a network (Ethernet: registered trademark) is used for the connection I / F. That is, the image forming apparatus 8 is connected to the network via the external I / F device 30. The external medium 54 performs various controls and input / output of image data to / from the digital color multifunction peripheral via the external media slot 36 for the installed application software and driver.

  S. B. Reference numeral 32 denotes one of chip sets used for the PC 52, which is a general-purpose electronic device called South Bridge. Mainly a bus bridge function often used in constructing a CPU system including a PCI-Express and an ISA bridge is formed as a general-purpose circuit. In this embodiment, the bus is bridged with the ROM 13. .

  The ROM 34 is a memory that stores various programs (including a boot program) when the CPU 18 controls the digital color multifunction peripheral. In the present embodiment, the ROM 34 and the CPU 18 are connected via a PCI-Express bus.

  In the present embodiment, the image data processing device 12 and the CPU 18 are connected by a PCI-Express bus, and are connected to the HDD 4 by an ATA bus and are made into an ASIC. Further, the CPU 18, the operation display device 26, the line I / F device 28, the external I / F device 30, and the S.P. B. 32 is connected by a general-purpose standard expansion bus 38.

  Note that the program executed by the image processing apparatus 8 according to the present embodiment is provided by being incorporated in advance in the ROM 34 or the like. Further, the program executed by the image processing apparatus 8 of the present embodiment can be installed in a file in an installable format or an executable format, a CD-ROM, a flexible disk (FD), a CD-R, a DVD (Digital Versatile Disk). For example, the program may be recorded on a computer-readable recording medium.

  Further, the program executed by the image processing apparatus 8 of the present embodiment may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Further, the program executed by the image processing apparatus 8 of the present embodiment may be configured to be provided or distributed via a network such as the Internet.

  A program executed by the image processing apparatus 8 according to the present embodiment includes a module including the above-described units (double-sided printing unit, double-sided reading unit, correction pattern position detection unit, calculation unit, correction unit, error notification unit, etc.). As actual hardware, the CPU (processor) 18 reads out the program from the ROM 34 and executes the program, so that the above-described units are loaded on the main storage device, and a duplex printing unit, a duplex reading unit, and a correction pattern are loaded. Position detection means, calculation means, correction means, error notification means, and the like are generated on the main storage device.

  Examples of the program include a copy operation process program (copy application), a scanner distribution process program (scanner distribution application), and a fax transmission process program (fax application).

  The processing modes that can be selected by the user include a color / monochrome mode, an application mode, and an image quality mode. Specifically, the color / monochrome mode includes a full color mode, a single color mode, a monochrome mode, and the like. Application modes include a copy mode, a scanner mode, a FAX mode, and a scanner delivery mode. The image quality mode includes a character mode, a character photo mode, and a photo mode. In addition to this, there is notch information such as making the original darker or thinner.

  FIG. 2 is a cross-sectional view showing the configuration of the reading device of FIG. The reading apparatus 10 shown in FIG. 2 is an ADF apparatus (automatic document feeding) including a document tray 100 on which documents are placed, a pickup roller 153 that feeds documents one by one, a conveying drum 104, a paper discharge roller 124, and the like. The document is discharged to the discharge tray 126 through the apparatus. A front-side image sensor 118 that reads the front side of the original through the reading window 106 and a rear-side image sensor 120 that reads the back side of the original are arranged in the middle of the conveyance path.

  The back side image sensor 120 uses a CIS (Contact Image Sensor) that reads back side image data of a document and converts it into an analog electric signal. The CIS includes an LED light source, a Selfoc lens array, an image sensor element, an A / D conversion circuit, a digital processing circuit, and the like (not shown). A reference white roller 122 is disposed at a position facing the back surface image sensor 120.

  A CCD (Charge Coupled Device) is used for the surface image sensor 118. The surface image sensor 118 includes a CCD and a sensor board unit (SBU) on which a signal processing unit for processing signals from the CCD is mounted. The surface image of the document transported by the transport drum 104 includes a first carriage 112 having a mirror 110a and two mirrors 110b, the surface image illuminated by the xenon lamp 108 when the document passes through the reading window 106. The image is read by the surface image sensor 118 through the lens 116 through the second carriage 114 having 110c. Further, a reference white plate 128 is disposed near the reading window 106.

  As described above, since the reading apparatus 10 according to the present embodiment includes the ADF apparatus, the image can be read while continuously conveying a plurality of documents set in the ADF apparatus. The reading device 10 is an ADF device that can simultaneously read both sides of a document. The front side image sensor 118 and the back side image sensor 120 are used to transfer image data on the front and back sides of a double-sided document with a single document feed. Can be read.

  FIG. 3 is a flowchart of the correction pattern output operation, FIG. 4A is a diagram illustrating an example of a correction pattern output on the front surface, and FIG. 4B is an example of a correction pattern output on the back surface. FIG. 4C is a diagram illustrating an example of correction patterns output on both sides. The correction pattern output operation will be described with reference to FIGS. 1, 3, and 4.

  First, as shown in FIG. 3, when the user presses the correction pattern output button of the operation display device 26 of FIG. 1 (step S100), the correction pattern stored in the ROM 34 is developed in the memory 20 (step S102). A correction pattern is output to both sides of the recording medium by the plotter device 24 (S104). At this time, five “+” reference points as shown in FIG. 4C are printed on the front and back surfaces of the recording medium. As shown in FIGS. 4A and 4B, the printing position of the reference point is at a distance of Da to Di from the front end of the recording medium, and the front and back patterns do not overlap. (See FIG. 4-3).

  In the present embodiment, as shown in FIG. 4, the number of reference points on one surface is five. However, the number of reference points is not necessarily limited to this. The detection accuracy can be maintained if the distance between the reference points is as far as possible at the four corners.

  FIG. 5 is a flowchart of a printing misalignment correction operation during duplex printing according to the first embodiment. As shown in FIG. 5, the correction pattern output by the correction pattern output operation of FIG. 3 is set on the document tray 100 of the ADF apparatus of the reading apparatus 10 of FIG. 2 (step S200). When the user presses the reading start button of the operation display device 26 (step S202), the CPU 18 causes the reading device 10 to start reading the correction pattern.

  First, the surface of the correction pattern (FIG. 4-1) is detected by the surface image sensor 118 of the reading device 10 (step S204). If the correction pattern on the surface is not detected (No in step S204), it is determined whether or not the predetermined time Ta has elapsed (step S206), and if not, the process returns to step S204. If the predetermined time Ta has elapsed, error processing 1 is performed. The error process 1 is a process for displaying on the LCD of the operation display device 26 that a correction pattern reading error has occurred.

  In step S204, when the front surface of the correction pattern (FIG. 4-1) is detected by the front surface image sensor 118 of the reading apparatus 10 (Yes in step S204), the process proceeds to step S208, and the back surface of the correction pattern ( FIG. 4B is detected by the back surface image sensor 120 of the reading device 10. If the back side correction pattern is not detected (No in step S208), it is determined whether or not the predetermined time Tb has passed (step S210). If not, the process returns to step S208. If the predetermined time Tb has elapsed, error processing 2 is performed. The error process 2 displays on the LCD that a correction pattern read error has occurred, as in the error process 1.

  In step S208, when the back surface of the correction pattern (FIG. 4-2) is detected by the back surface image sensor 120 of the reading apparatus 10 (Yes in step S208), the process proceeds to step S212, and the front surface of the correction pattern is detected. If the difference in detection time between the front surface and the back surface is not less than the predetermined time Tc with reference to the detected timing (No in step S212), error processing 3 is performed. Error processing 3 displays on the LCD that a correction pattern reading error has occurred, as in error processing 1.

  If the difference in detection time between the front surface and the back surface is less than the predetermined time Tc with reference to the timing at which the front surface of the correction pattern is detected in step S212 (Yes in step S212), the detection time between the front surface and the back surface If there is no difference in detection time, no correction is necessary and no correction is performed.

  In step S214, if there is a difference in detection time between the front and back surfaces (No in step S214), a correction amount is calculated based on the detection time difference between the front and back surfaces (step S216). The calculation of the correction amount is executed from the relative detection time difference between the front surface and the back surface of the correction pattern, and an average value of the detection time differences between the front surface and the back surface of a plurality of correction patterns is used. Then, by correcting the image forming position on the back side during double-sided printing in the sub-scanning direction from the correction amount (step S218), the image forming positions on the front side and the back side that are the object of the present invention can be matched.

The above-mentioned “difference in detection time between the front surface and the back surface” means a physical interval (distance) between the reading window 106 that is the detection position of the front surface image sensor 118 and the detection position of the back surface image sensor 120. This is the time calculated from Ds (the interval shown in FIG. 2) and the speed at which the reading device 10 reads the correction pattern. Further, the position of the correction pattern (printing position of the reference point “+”) between the front surface and the back surface to be printed on the recording medium according to the distance Ds between the front surface and the back surface of the image sensor is expressed by the following equation (1). By disposing the equations so as to hold, the measurement error due to the difference in detection timing at which the front and back surfaces of the correction pattern are detected by each image sensor can be reduced.
Ds = (Dg−Da) × A = (Dh−Db) × B = (Di−Dc) × C (1)
(A, B, C: any constant)

  As described above, in the first embodiment, the correction pattern formed on the front surface and the back surface of the recording medium can be detected by one transport using the front surface image sensor and the back surface image sensor. It is not necessary to consider the reading accuracy of the back surface, and the detection accuracy can be increased.

  In the first embodiment, the printing position of the reference point in the correction pattern is arranged at a position where the front and back patterns of the recording medium do not overlap. Adverse effects (for example, poor toner fixing, ink bleeding, etc.) due to printing on the printer can be prevented.

  In the first embodiment, the correction patterns for the front and back surfaces to be printed on the recording medium are arranged in correspondence with the distance (Ds) between the front surface image sensor and the back surface image sensor. A measurement error due to a difference in detection timing between the front surface and the back surface of the pattern can be reduced.

  Furthermore, in the first embodiment, when the correction pattern cannot be read for a certain period of time, a reading error is displayed on the operation screen, so that the user can be notified that reading of the correction pattern has failed. Here, the error display is performed on the operation screen. However, the present invention is not limited to this, and any error notification may be used as long as the user can recognize the error using a means such as voice or light.

(Second Embodiment)
The feature of the second embodiment is that the correction pattern can be detected more appropriately. The basic configuration of the image forming apparatus is the same as that in FIGS. 1 and 2 of the first embodiment, and a description thereof will be omitted.

  FIG. 6A is a diagram illustrating another example of the correction pattern output on the front surface, FIG. 6B is a diagram illustrating another example of the correction pattern output on the back surface, and FIG. FIG. 6-4 is a diagram showing another example of correction patterns output on both sides, FIG. 6-4 is a diagram showing an example of outputting a correction pattern for avoiding shock jitter, and FIG. 7 is a diagram showing a change in the conveyance speed of the ADF device. FIG. 8 is a flowchart of the printing position deviation correction operation during duplex printing according to the second embodiment, and FIG. 9 is an enlarged view of the vicinity of the front end of the recording medium after the correction pattern is output. It is.

  First, as in the first embodiment, when the user presses the correction pattern output button of the operation display device shown in the flowchart of FIG. 3 (step S100), the correction pattern stored in the ROM is expanded in the memory. (Step S102), the correction pattern is output to both sides of the recording medium by the plotter device 24 (S104). At this time, as shown in FIG. 6-3, five “+” reference points are printed on the front and back surfaces of the recording medium. As shown in FIGS. 6A and 6B, the printing position of the reference point is at a distance of Da to Di from the end of the recording medium, and is in a position where the front and back patterns do not overlap. (See FIG. 6-3).

The correction pattern shown in FIG. 6 is characterized in that the distance from the edge of the recording medium is shorter on the back surface than on the front surface compared to the correction pattern in FIG. That is, when comparing the magnitude relationship of the distances from the edge of the recording medium to the reference point of the “+” mark of each correction pattern, the relationships of Dg> Da, Dh> Db, and Di> Dc are established. In the second embodiment, with respect to the distance Ds between the front surface image sensor and the back surface image sensor shown in FIG. "Printing position" is arranged so that the relationship of the following equation (2) is satisfied.
Ds = Dg−Da = Dh−Db = Di−Dc (2)
By arranging the correction patterns in this way, the correction patterns on the front surface and the back surface can be detected simultaneously by the two image sensors.

  This is because, as shown in FIG. 7, the transport speed of the ADF apparatus constantly changes due to transport unevenness. Therefore, if the detection timings of the correction patterns on the front surface and the back surface are different, the detection results of the correction patterns are also different. That is, if the transport speed of the ADF device at the time of detecting the correction pattern is different between the front surface and the back surface as shown in FIG. 7, a difference in transport speed appears as a difference in detection distance, resulting in poor detection accuracy. On the other hand, in the second embodiment, since the correction pattern is arranged so that the front and back surfaces can be detected at the same timing by each image sensor, uneven conveyance due to variation in the conveyance speed can be avoided, Detection accuracy can be improved.

  Also, as shown in FIG. 6-4, when reading an original with the ADF apparatus, the influence of shock jitter at the front end and the rear end (portions shown by hatching in FIG. 6-4) in the recording medium conveyance direction. It becomes easy to receive. Shock jitter refers to a phenomenon in which the conveyance speed changes abruptly when the leading end of the recording medium enters between the pressurizing members and when the trailing end of the recording medium exits between the pressurizing members. For this reason, when the correction pattern is printed in the hatched portion shown in FIG. 6-4, it is assumed that the detection timing of the correction pattern is shifted due to the influence of shock jitter. Therefore, in the second embodiment, the effect of shock jitter can be avoided by printing a correction pattern on a location of the recording medium that is not affected by shock jitter (location other than hatching in FIG. 6-4). The correction pattern can be read stably by the front surface image sensor 118 and the back surface image sensor 120.

  The second embodiment is configured as described above. Hereinafter, an operation for correcting a printing position deviation during double-sided printing will be described with reference to FIG. First, based on the correction pattern output flowchart of FIG. 3, the correction patterns are printed on both sides of the recording medium as shown in FIG. 6-3. When the user sets the recording medium on which the correction pattern is printed on the ADF device of the reading device 10 (step S300) and presses the reading start button of the operation display device 26 (step S302), reading of the correction pattern is started. .

  Here, when the front / back surfaces of the correction pattern are simultaneously detected by the image sensors of the reading device 10, no correction is necessary (Yes in step S304). If the front / back surfaces of the correction pattern are not detected at the same time in step S304 (No in step S304), the process proceeds to step S306 to detect whether the front surface of the correction pattern is detected. If the front surface of the correction pattern is not detected (No in step S306), the process proceeds to step S308 to detect whether the back surface of the correction pattern is detected. If the back surface of the correction pattern is not detected (No in step S308) and the predetermined time Ta has not elapsed (No in step S310), the process returns to step S304. In addition, if the back surface of the correction pattern is not detected (No in step S308) and the predetermined time Ta has elapsed (Yes in step S310), error processing 1 for displaying on the LCD that a correction pattern reading error has occurred is displayed. Is done.

  If the back surface of the correction pattern is detected in step S308 (Yes in step S308), it is determined whether or not the front surface of the correction pattern is detected (step S312). Here, when the surface of the correction pattern is not detected (No in step S312) and the predetermined time Tc has not elapsed (No in step S314), the process returns to step S312. If the surface of the correction pattern is not detected (No in step S312) and the predetermined time Tc has elapsed (Yes in step S314), error processing 2 for displaying on the LCD that a correction pattern reading error has occurred is displayed. Is done. In step S312, when the surface of the correction pattern is detected (Yes in step S312), the process proceeds to step S320 described later.

  In step S306, if the front surface of the correction pattern is detected (Yes in step S306) and the back surface of the correction pattern is not detected (No in step S316), it is determined whether or not a certain time Tb has elapsed (step S306). S318) If the predetermined time Tb has not elapsed, the process returns to step S316. If the predetermined time Tb has elapsed, error processing 3 for displaying on the LCD that a correction pattern reading error has occurred is performed.

  If the front surface of the correction pattern is detected in step S306 (Yes in step S306) and the back surface of the correction pattern is detected in step S316 (Yes in step S316), the front surface and back surface of the correction pattern are detected in step S320. It is determined whether or not the difference in detection time is less than a predetermined time Tc. If the detection time difference between the front surface and the back surface is less than Tc (Yes in step S320), the CPU 18 calculates the correction amount from the detection time difference between the front surface and the back surface (step S322), but the detection time difference between the front surface and the back surface is If it is not less than Tc (No in step S320), error processing 4 for displaying on the LCD that a correction pattern reading error has occurred is performed.

  Here, the correction direction to the sub-scanning changes depending on whether the front surface or the back surface of the correction pattern is detected first (step S324). That is, when the back side is detected first (Yes in step S324), correction is performed so that the back side printing position is in the sub-scan rear end direction (step S326), and when the front side is detected first ( No in step S324), correction is performed so that the back surface printing position is in the sub-scanning front end direction (step S328). Thereby, the image formation position of the front surface and the back surface at the time of duplex printing can be adjusted to an appropriate position.

  Further, when the correction pattern is read by the ADF device, if the detection of the correction pattern is not confirmed even after the predetermined time Ta, Tb, Tc has passed, the fact that the correction pattern reading error has occurred is displayed on the LCD of the operation display device 26. Although it is displayed, the detection method of occurrence of a reading error can be detected not only by time but also by whether or not the detection interval between the front surface and the back surface is within a predetermined number of lines.

  Furthermore, it is assumed that the front and back surfaces of the correction pattern are mistakenly set in the ADF apparatus. For this reason, in the second embodiment, as shown in FIG. 9, “↑ Please set this in the direction of the arrow” on the upper end of the recording medium on which the correction pattern is printed. The user can set the correction pattern in the ADF apparatus with the correct orientation and surface by printing the warning message.

  As described above, in the second embodiment, since the correction pattern is arranged so that it can be detected simultaneously on the front surface and the back surface, unevenness of conveyance when the correction pattern is conveyed by the ADF apparatus is avoided, and detection accuracy is increased. be able to.

  In the second embodiment, since the correction pattern is printed on the portion of the recording medium that is not affected by the shock jitter, the correction pattern can be read stably and the detection accuracy can be improved. it can.

  In the second embodiment, when the correction pattern cannot be read for a certain period of time, or when the detection pattern detection interval between the front surface and the back surface is not within a predetermined number of lines, the operation screen displays Since a reading error is displayed, the user can be notified that reading of the correction pattern has failed.

(Third embodiment)
In the first embodiment, the detection time between the front surface and the back surface of the correction pattern is based on the surface detected first, and the time until the back surface is detected is measured, but the third embodiment However, this method is characterized in that the detection time until the correction pattern is measured using the end of the recording medium (hereinafter also referred to as a paper edge) as a reference.

  FIG. 10 is a flowchart of a printing misalignment correction operation during duplex printing according to the third embodiment. First, based on the correction pattern output flowchart of FIG. 3, for example, correction patterns as shown in FIG. 4-3 are printed on both sides of the recording medium. The user sets the recording medium on which the correction pattern is printed on the ADF device of the reading device 10 (step S400), and when the reading start button of the operation display device 26 is pressed (step S402), reading of the correction pattern starts. Is done.

  Here, based on the read image data, the CPU 18 determines whether or not an end of the recording medium on which the correction pattern is printed, that is, a paper edge is detected (step S404). If no paper edge is detected (No in step S404) and the predetermined time Ta has not elapsed (No in step S406), the process returns to step S404. If the predetermined time Ta has elapsed (Yes in step S406), error processing 1 for displaying on the LCD that a correction pattern reading error has occurred is performed.

  If the paper edge of the correction pattern is detected (Yes in step S404), the surface of the correction pattern (FIG. 4-1) is detected by the surface image sensor 118 of the reading device 10 (step S408). If the correction pattern on the surface is not detected (No in step S408) and the predetermined time Tb has not elapsed (No in step S410), the process returns to step S408. If the predetermined time Tb has elapsed (Yes in step S410), error processing 2 is performed to display on the LCD that a correction pattern reading error has occurred.

  In step S408, when the front surface of the correction pattern (FIG. 4-1) is detected by the front surface image sensor 118 of the reading apparatus 10 (Yes in step S408), the process proceeds to step S412 and the back surface of the correction pattern ( FIG. 4B is detected by the back surface image sensor 120 of the reading device 10. If the back side correction pattern is not detected (No in Step 412) and the predetermined time Tc has not elapsed (No in Step S414), the process returns to Step S412. If the predetermined time Tc has elapsed (Yes in step S414), error processing 3 for displaying on the LCD that a correction pattern reading error has occurred is performed.

  In step S412, when the back surface of the correction pattern (FIG. 4-2) is detected by the back surface image sensor 120 of the reading apparatus 10 (Yes in step S412), the process proceeds to step S416 and the paper edge of the correction pattern is detected. If the difference in detection time between the front surface and the back surface is not less than the predetermined time Td (No in step S416), the fact that a correction pattern reading error has occurred is displayed on the LCD with the timing at which (edge) is detected as a reference. Error processing 4 is performed.

  If the difference between the detection times of the front surface and the back surface is less than the predetermined time Td with reference to the timing at which the paper edge of the correction pattern is detected in step S416 (Yes in step S416), the front and back surface correction patterns are detected. It is determined whether or not there is a difference between the detection times (step S418). If there is a difference in the detection time (No in step S418), the correction amount is calculated based on the difference in detection time between the front surface and the back surface (step S420). If there is no difference in the detection time, correction is unnecessary and correction is performed. Not.

  In addition, since the calculation of the correction amount in step S420 is executed based on the value detected with reference to the paper edge that is the edge of the recording medium on which the correction pattern is printed, the front and back surfaces of the correction pattern are the same. It becomes possible to manage in time series, and the detection accuracy can be improved. Then, by correcting the image forming position on the back side during duplex printing in the sub-scanning direction from the calculated correction amount (step S422), it is possible to match the image forming positions on the front side and the back side that are the object of the present invention.

  As described above, in the third embodiment, when the position of the correction pattern is detected, the detection is performed based on the end portion (paper edge) of the recording medium. Since the correction patterns can be managed in the same time series, the detection accuracy can be increased. In the image forming apparatus according to the third embodiment, the CPU 18 calculates a correction amount based on the detected value, and can correct the image forming positions on both sides at the time of duplex printing to an appropriate position.

8 Image forming device 10 Reading device 12 Image data processing device 14 Bus control device 16 HDD
18 CPU
20 Memory 22 Plotter I / F Device 24 Plotter Device 26 Operation Display Device 28 Circuit I / F Device 30 External I / F Device 32 B.
34 ROM
36 slots 38 expansion bus 118 image sensor for front surface 120 image sensor for back surface

Japanese Patent Laid-Open No. 10-246992

Claims (9)

A double-sided printing means for printing a correction pattern on the front and back surfaces of the recording medium;
Double-sided reading means for reading correction patterns printed on both sides of the recording medium at a time;
Correction pattern position detection means for detecting the position of each correction pattern read from both sides of the recording medium;
A calculation means for calculating a correction amount of the printing position deviation from the correction patterns on both sides detected by the correction pattern position detection means;
Based on the correction amount calculated by the calculation means, correction means for correcting the printing position deviation of the front surface and the back surface during double-sided printing;
An image forming apparatus comprising:   The double-sided printing unit prints the correction pattern on the front surface and the back surface of the recording medium so that the distance from the end of the recording medium to the correction pattern is different between the front surface and the back surface. The image forming apparatus according to claim 1, wherein:   In the double-sided printing unit, the correction patterns on the front and back sides of the recording medium are arranged corresponding to the distance between the front-side image sensor and the back-side image sensor that detects the correction pattern installed in the double-sided reading unit. The image forming apparatus according to claim 1, wherein printing is performed as described above.   The double-sided printing unit is configured so that when the double-sided reading unit reads the correction pattern, the front-side image sensor and the back-side image sensor can simultaneously detect the correction pattern printed on each side. The image forming apparatus according to claim 1, wherein printing is performed by adjusting the positions of the correction patterns on the front and back surfaces to be printed on the medium.   The double-sided printing unit prints the correction pattern except for a fixed area at the leading end and the trailing end of the recording medium in the conveyance direction when the double-side reading unit reads the correction pattern. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The double-sided reading means, when reading the correction pattern printed on both sides of the recording medium, reads the end of each surface of the recording medium and the correction pattern,
6. The correction pattern position detecting means detects the position of the correction pattern printed on the surface of each side of the recording medium with reference to the end of the recording medium. The image forming apparatus according to any one of the above. Error notification means for notifying the user of the occurrence of an error,
The double-sided reading means reads the correction pattern printed on the recording medium, and when the detection interval of the correction patterns on the front and back surfaces of the recording medium does not fall within a predetermined number of lines, the error notification means The image forming apparatus according to claim 1, wherein a user is notified of the occurrence of a reading error. An image forming method executed by an image forming apparatus,
The image forming apparatus includes a double-sided printing unit, a double-sided reading unit, a correction pattern position detection unit, a calculation unit, and a correction unit.
The double-sided printing means prints a correction pattern on the front and back surfaces of the recording medium;
The double-sided reading means reads the correction pattern printed on both sides of the recording medium at a time;
The correction pattern position detecting means detects the position of each correction pattern read from both sides of the recording medium;
The calculating means calculates a correction amount of a printing position deviation from the detected positions of the correction patterns on both sides;
The correcting unit correcting the printing position deviation between the front surface and the back surface during double-sided printing based on the calculated correction amount;
An image forming method comprising: A program installed in an image forming apparatus,
A double-sided printing means for printing a correction pattern on the front and back surfaces of a recording medium;
Double-sided reading means for reading correction patterns printed on both sides of the recording medium at a time;
Correction pattern position detection means for detecting the position of each correction pattern read from both sides of the recording medium;
A calculation means for calculating a correction amount of the printing position deviation from the correction patterns on both sides detected by the correction pattern position detection means;
A program for functioning as a correcting unit that corrects a printing position shift between the front and back sides during double-sided printing based on the correction amount calculated by the calculating unit.

Images