Patent Publication Number: US-11644783-B2

Title: Image forming apparatus that adjusts image forming area based on read test image

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of International Patent Application No. PCT/JP2018/007101, filed Feb. 27, 2018, which claims the benefit of Japanese Patent Application No. 2017-039704, filed Mar. 2, 2017 and Japanese Patent Application No. 2018-031751, filed Feb. 26, 2018, all of which are hereby incorporated by reference herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure relates to a technology for adjusting an image formation area (print position) in which an image can be formed. 
     Background Art 
     In an image forming apparatus of recent years, a position of an image to be formed on a sheet and a shape of the image are required to be more accurate. However, due to abrasion of a conveying member configured to convey the sheet, a change in environment (temperature or humidity), or a change in a moisture content of the sheet, a size of the image to be formed on the sheet varies, the image rotates, or the image is distorted. Under a state in which the image to be formed on the sheet is at a position different from an ideal position, a character or letter image formed on a preprint sheet having ruled lines printed thereon in advance overlaps the ruled lines. Additionally, under a state in which a shape of the image to be formed on the sheet is different from a predetermined shape, misalignment occurs between an image formed on a front surface of the sheet and an image formed on a back surface of the sheet. Moreover, at a joint between images formed on facing pages, misalignment between the images becomes clearly visible. 
     To correct the position and shape of the image to be formed on the sheet, an image forming apparatus has a function of adjusting an image formation area in which an image can be formed. For example, an image forming apparatus described in Japanese Patent Laid-Open No. 2003-173109 includes a scanner configured to read an original and adjust an image formation area based on a result of reading with the scanner a reference image formed on a sheet. Meanwhile, for example, an image forming apparatus described in Japanese Patent Laid-Open No. 2005-221582 includes a reading sensor along a conveyance path for conveying a sheet and adjusts an image formation area based on a result of reading a pattern image with the sensor. 
     CITATION LIST 
     Patent Literature 
     PTL 1 Japanese Patent Laid-Open No. 2003-173109 
     PTL 2 Japanese Patent Laid-Open No. 2005-221582 
     However, depending on a type of printed materials, it may be impossible to appropriately adjust the image formation area. When the printed material is to be cut, the image forming apparatus is required to correct the image formation area into a rectangular shape. Meanwhile, when the printed material is a full-page printed material, the image forming apparatus is required to correct the image formation area such that each of margins of the sheet having the image formed thereon has a predetermined width. However, depending on the printed material, it may be impossible to appropriately adjust a print position. 
     SUMMARY OF THE INVENTION 
     According to at least one embodiment of the present disclosure, there is provided an image forming apparatus including: an image forming unit configured to form an image on a sheet; and a controller configured to: cause the image forming unit to form a test image on the sheet; obtain read data, which is obtained by reading the test image formed on the sheet; and control a predetermined image formation area, in which the image forming unit is able to form an image, based on the read data. The controller is configured to perform a first adjustment process of adjusting the predetermined image formation area to a first area and a second adjustment process of adjusting the predetermined image formation area to a second area. The first area has a rectangular shape, and the second area has a shape similar to a shape of the sheet having the test image formed thereon. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is an overall configuration diagram of a printing system. 
         FIG.  2    is a configuration diagram of an image forming apparatus according to at least one embodiment of the present disclosure. 
         FIG.  3    is an explanatory diagram of a printer. 
         FIG.  4    is a configuration diagram of a stacker. 
         FIG.  5    is a configuration diagram of a reading device. 
         FIG.  6    is a hardware configuration diagram of a control system for the image forming apparatus. 
         FIG.  7    is a hardware configuration diagram of a control system for an information processing apparatus. 
         FIG.  8    is a functional configuration diagram of the printing system. 
         FIG.  9    is a diagram for illustrating an example of a job management application screen. 
         FIG.  10    is a diagram for illustrating an example of a print setting screen. 
         FIG.  11    is a diagram for illustrating an example of an interface screen for performing an operation on a sheet library. 
         FIG.  12    is an explanatory diagram of the sheet library. 
         FIG.  13    is an explanatory diagram of adjustment charts. 
         FIG.  14    is a diagram for illustrating an example of an instruction screen for giving an instruction to implement a print position adjustment method. 
         FIG.  15    is an explanatory diagram of a process of determining print position misalignment amounts. 
         FIG.  16 A  is an explanatory diagram of an image after print position adjustment. 
         FIG.  16 B  is an explanatory diagram of the image after the print position adjustment. 
         FIG.  16 C  is an explanatory diagram of the image after the print position adjustment. 
         FIG.  17    is a flow chart for illustrating a process of calculating print position misalignment amounts. 
         FIG.  18    is a flow chart of an image formation process including a print position adjustment process. 
         FIG.  19    is a diagram for illustrating an example of a warning screen. 
         FIG.  20    is a flow chart for illustrating the image formation process including the print position adjustment process. 
         FIG.  21    is a flow chart for illustrating the image formation process including the print position adjustment process. 
         FIG.  22    is a flow chart for illustrating the image formation process including the print position adjustment process. 
         FIG.  23    is an explanatory diagram of the warning screen. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Now, with reference to the drawings, at least one embodiment of the present disclosure is described in detail. 
     Configuration of Printing System 
       FIG.  1    is an overall configuration diagram of a printing system including an image forming apparatus according to at least one embodiment of the present disclosure. A printing system  1  includes an image forming apparatus  101  and an information processing apparatus  102 . The image forming apparatus  101  and the information processing apparatus  102  are connected to be communicative to/from each other via a network  103 . The information processing apparatus  102  is, for example, a server. The information processing apparatus  102  performs job management and processes such as raster image processor (RIP) processing and imposition and transmits a print job to the image forming apparatus  101 . 
       FIG.  2    is a configuration diagram of the image forming apparatus  101 . The image forming apparatus  101  includes a sheet feeder  201 , a printer  202 , a stacker  203 , and a reading device  204  (sensing device). 
     The sheet feeder  201  can contain a large number of sheets (for example, 3,000 sheets). The sheet feeder  201  feeds the sheets to the printer  202 . The printer  202  forms an image in accordance with the print job on each of the sheets, to thereby perform printing. To the printer  202 , the sheets are fed not only from the sheet feeder  201 , but also from an associated sheet cassette. The use of the sheet feeder  201  allows the printer  202  to perform printing a large number of sheets without interruption. The stacker  203  is a delivery device configured to allow a large number of printed materials resulting from image formation on the sheets in the printer  202  to be accumulated therein in such a manner as to follow an instruction given by the print job. The stacker  203  is used mainly when large-volume printing using the sheet feeder  201  is performed. The reading device  204  reads adjustment charts described later, which are printed for the adjustment of an image formation area (print position), from a printed material delivered from the printer  202 . The adjustment charts are used to sense print position misalignment. A result of the reading (read data) is used for print position adjustment described later. 
       FIG.  3    is an explanatory diagram of the printer  202 . The printer  202  includes an auto document feeder (ADF)  301 , a scanner  302 , and an operation panel  323 . The printer  202  is not necessarily configured to include the ADF  301 , the scanner  302 , and the operation panel  323 . 
     The ADF  301  conveys, on a one-by-one basis, each of originals in a stack of originals placed on an original tray to a reading position of the scanner  302 . The scanner  302  reads an original image from each of the originals conveyed by the ADF  301  to generate original image data (image data corresponding to the original image). The scanner  302  also reads the original image from each of the originals placed on an original table  300  to generate the original image data. 
     The printer  202  includes a photosensitive drum  304 , on which a toner image is to be formed, a transfer drum  305  serving as an intermediate transfer member configured to transfer the toner image formed on the photosensitive drum  304  onto each of the sheets, and a fixing device  308  configured to fix the toner image to the sheet. 
     The photosensitive drum  304  is a drum-shaped photosensitive member and has a surface on which the toner images are to be formed by a charging device, an exposing device  303 , and developing devices. The photosensitive drum  304  rotates clockwise in  FIG.  3   . The photosensitive drum  304  has a surface thereof uniformly charged by the charging device and irradiated with a laser beam from the exposing device  303  to have an electrostatic latent image formed on the surface. The exposing device  303  irradiates the photosensitive drum  304  with the laser beam modulated in accordance with the image data to form the electrostatic latent image in accordance with the image data on the photosensitive drum  304 . The developing devices cause toner to be deposited on the electrostatic latent image formed on the photosensitive drum  304  to develop the electrostatic latent image, to thereby form the toner image on the surface of the photosensitive drum  304 . The developing devices are provided individually for yellow (Y), magenta (M), cyan (C), and black (K) colors. 
     The transfer drum  305  rotates in a direction opposite to the direction of rotation of the photosensitive drum  304 , while holding the sheet. To the sheet held by the transfer drum  305 , the toner image having one of the colors is transferred every time the transfer drum  305  rotates once. A sequential image formation process from the charging of the photosensitive drum  304  to the transfer of the toner image is repeated four times to allow a full-color toner image to be formed on the sheet. The sheet having the toner image formed thereon is removed from the transfer drum  305  by a separation claw  306  and conveyed to the fixing device  308  via a conveyance path  307 . 
     The fixing device  308  includes a combination of rollers and belts, and has a heat source, for example, a halogen heater, embedded therein. The fixing device  308  applies heat and pressure to the sheet having the toner image transferred thereon to fix the toner image to the sheet. The sheet delivered from the fixing device  308  is conveyed to a flapper  309 . The flapper  309  is configured to be swingable around a swing axis to change a direction in which the sheet is to be conveyed depending on a direction in which the flapper  309  swings. When the sheet is conveyed by the flapper  309  to rollers  310 , the sheet is output by the rollers  310  to the outside of the image forming apparatus. 
     The printer  202  includes a sheet cassette  317 , a sheet cassette  318 , and a sheet tray  320  each configured to contain sheets to be used in the image formation process, a conveyance path, and a double-side conveying portion. 
     Feeding of the sheets is performed by the sheet cassettes  317  and  318 , the sheet tray  320 , and the sheet feeder  201 . Each of the sheet cassettes  317  and  318  and the sheet feeder  201  can contain sheets of various sizes and various materials. The sheet tray  320  is configured such that various sheets including special sheets, for example OHP sheets, can be stacked thereon. Along the conveyance path, various rollers configured to convey the fed sheets are provided. 
     For the sheet cassettes  317  and  318 , the sheet feeder  201 , and the sheet tray  320 , respective rollers  321  are provided. Each of the rollers  321  feeds each of the sheets on a one-by-one basis. The sheets contained in the sheet cassette  317  are sequentially fed out by a pick-up roller, and a separating roller provided to face the roller  321  prevents multi-feeding of stacked sheets. Thus, each of the sheets is fed out on a one-by-one basis to the conveyance path. To the separating roller, a drive force for rotating the separating roller in a direction opposite to the direction of conveyance is supplied via a torque limiter (not shown). When only one of the sheets has entered a nip portion formed between the separating roller and the roller  321 , the separating roller rotates in a direction of conveyance while following the sheet. When the multi-feeding has occurred, the separating roller rotates in a direction opposite to the direction of conveyance to retract the multi-fed sheets. This process allows only one uppermost sheet to be fed. 
     The fed sheet is conveyed by a plurality of conveying rollers to registration rollers  316 . At this time, the registration rollers  316  are stopped. The registration rollers include a pair of rollers. A leading end of the sheet abuts against a nip portion between the registration rollers  316  to correct skew feeding of the sheet. The registration rollers  316  start to rotate at a time when the toner image is formed on the photosensitive drum  304  to resume the conveyance of the sheet. The sheet conveyed by the registration rollers  316  is electrostatically adsorbed by an adsorbing roller  322  onto the surface of the transfer drum  305 . 
     The double-side conveying portion is a conveyance path for conveying the sheet having a first surface (front surface) on which image formation has been completed when double-side printing is performed. The sheet having the toner image fixed thereto by the fixing device  308  is conveyed by the flapper  309  to the double-side conveying portion. The double-side conveying portion includes a flapper  311 , rollers  312 , a reverse guide  313 , and a double-side tray  314 . The flapper  311  is configured to be swingable around a swing axis, and changes the direction of conveyance of the sheet. In the case of double-side printing, the sheet having the image formed on the front surface is conveyed by the flapper  311  to the reverse guide  313 . After a rear end of the sheet passes through the flapper  311 , the rollers (not shown) provided in the reverse guide  313  temporarily stop. Subsequently, the flapper  311  swings clockwise in FIG.  3  to change a destination to which the sheet is to be conveyed to the double-side tray  314 . Then, the rollers  312  rotate in the opposite direction. Thus, the sheet is switch-back conveyed. The sheet is conveyed to the double-side tray  314  under a state in which the rear and leading ends thereof have been switched. 
     On the double-side tray  314 , the sheet is temporarily placed. The sheet placed on the double-side tray  314  is conveyed again to the registration rollers  316  by rollers  315 . At this time, the sheet has a second surface (back surface) opposite to the first surface (front surface) facing the photosensitive drum  304 . Then, on the back surface of the sheet, an image is formed by the same process as that performed on the front surface. The sheet having the images formed on both surfaces thereof is discharged by the rollers  310  to the outside of the image forming apparatus. 
     The operation panel  323  is a user interface including various operation buttons, a numeric keypad, a display device, for example, a liquid crystal display (LCD), a touch panel, and the like. An operator can input a command and print settings to the printer  202  via the operation panel  323 . The operation panel  323  causes the display device to display a setting screen and a job status. 
     The printer  202  includes a network connector  324  for communication via the network  103 . The network connector  324  has a shape in accordance with a communication interface. 
     The sheet feeder  201 , the sheet cassettes  317  and  318 , and the sheet tray  320  are supporting members configured to support sheets. Depending on from which one of the plurality of supporting members the sheet is fed, a surface of the sheet on which the image is to be formed in single-side printing is determined. Likewise, depending on from which one of the plurality of supporting members the sheet is fed, a front surface (first surface) on which a first image is to be formed in double-side printing is determined. The sheets contained in the sheet cassettes  317  and  318  are placed with print surfaces (front surfaces) thereof facing downward. The sheets contained in the sheet feeder  201  and the sheet tray  320  are placed with print surfaces (front surfaces) thereof facing upward. When a sheet for which it is required to pay attention to the orientations of the front and back surfaces thereof, for example a carbonless sheet, is to be fed, the user is required to pay attention to the print surfaces when placing the sheet. 
       FIG.  4    is a configuration diagram of the stacker  203 . The stacker  203  includes a straight path  401 , an escape path  402 , and a stack path  403  as conveyance paths. Along each of the conveyance paths, a plurality of sensors for detecting a situation in which the sheet is conveyed and a jam are provided. 
     The straight path  401  is a conveyance path for conveying the sheet discharged from the printer  202  to a device (post-processing device) in a subsequent stage (not shown). The escape path  402  is a conveyance path for outputting the sheet discharged from the printer  202  to an escape tray  404 . For example, when an operation of checking a printed material (print check) or the like is performed, a sheet for the print check is output to the escape tray  404 . The stack path  403  is a conveyance path for conveying the sheet discharged from the printer  202  to a stack tray  405 . For example, when the print job requires a process of stacking printed materials, the sheets after printing (printed materials) are stacked on the stack tray  405 . 
     The stack tray  405  is a stack unit placed over extendable stays  406 . In joint portions between the stack tray  405  and the stays  406 , shock absorbers or the like are provided. The stays  406  are provided on a wagon  407 . To the wagon  407 , a handle (not shown) is attached to allow the wagon  407  to carry the sheets stacked on the stack tray  405  to another offline finisher or the like. When a front door of the stacker  203  is closed, the stays  406  lift the stack tray  405  to a position at which the sheets are easily stacked. When the front door is opened, the stays  406  lower the stack tray  405  to allow the sheets to be easily retrieved. 
     Thus, the stacker  203  can allow a large number of printed materials to be stacked on the stack tray  405  and also allow a small number of printed materials for the print check or the like to be delivered to the escape tray  404 . 
       FIG.  5    is a configuration diagram of the reading device  204 . The reading device  204  includes a reading controller  501 , sheet detecting sensors  502 , and line sensors  503 . The reading device  204  reads a test image (hereinafter referred to as “adjustment chart”) for print position adjustment, which is formed in the printer  202 , while conveying the adjustment chart along a conveyance path  504 . Details of the adjustment chart are described later. 
     Each of the sheet detecting sensors  502  detects the sheet conveyed along the conveyance path  504  in a direction of the arrow. The conveyance path  504  is formed of a black conveying belt. The adjustment chart is formed on a white sheet. Each of the sheet detecting sensors  502  detects a leading edge of the sheet in a direction of conveyance of the sheet. By conveying the white sheet over the black conveying belt, the accuracy of the detection of the sheet is improved. 
     The plurality of sheet detecting sensors  502  are provided in a direction perpendicular to the direction of conveyance of the sheet. Each of the sheet detecting sensors  502  detects the leading edge of the sheet and notifies the reading controller  501  of the detection of the leading edge. The reading controller  501  determines an amount of the skew feeding of the sheet based on the timing of the notification from each of the sheet detecting sensors  502  and on a speed of conveyance of the sheet. The reading controller  501  also controls the line sensors  503  through use of the notification from each of the sheet detecting sensors  502  as a trigger, and reads the images (adjustment charts) formed on the sheet. To simultaneously read both surfaces of the sheet, the two line sensors  503  are provided with the conveyance path  504  being interposed therebetween. The reading controller  501  transmits the angle of skew feeding of the sheet and image data representing the images read by the line sensors  503  to a control system described later, which is configured to control an operation of the printer  202 . 
     Control System for Image Forming Apparatus  101   
       FIG.  6    is a hardware configuration diagram of the control system for the image forming apparatus  101 . The control system includes a central processing unit (CPU)  607 , a read only memory (ROM)  609 , and a random access memory (RAM)  610 . The CPU  607  executes a program stored in the ROM  609  through use of the RAM  610  as a work area, to thereby control an operation of the image forming apparatus  101 . To the CPU  607 , an ADF controller  603 , a scanner controller  604 , an image processor  605 , a printer controller  606 , a reading device controller  608 , an operation panel controller  611 , and a stacker controller  612  are connected. Those components are configurations for controlling respective operations of the individual components of the image forming apparatus  101 . To the CPU  607 , a storage interface (I/F)  613  and a network interface (I/F)  614  are also connected. Such a control system can be implemented by, for example, a micro-processing unit (MPU), an application specific integrated circuit (ASIC), or a system-on-a-chip (SoC). 
     The ADF controller  603  controls an operation of the ADF  301 . The ADF controller  603  causes the ADF  301  to convey an original to the reading position of the scanner  302 . The scanner controller  604  controls an operation of the scanner  302 . The scanner controller  604  causes the scanner  302  to read an original image and transmits original image data to the image processor  605 . When the adjustment charts are read by the scanner  302 , the scanner controller  604  transfers read data obtained by reading the adjustment charts to the CPU  607 . When the original is read by the scanner  302 , the image processor  605  performs image processing on the original image data obtained from the scanner controller  604  based on a predetermined image processing condition, and transmits the original image data to the printer controller  606 . When the image data is transferred from the information processing apparatus  102  via the network  103 , the image processor  605  performs image processing on the transferred image data, and transmits the image data to the printer controller  606 . The printer controller  606  causes the printer  202  to print an image on a sheet based on the image data obtained from the image processor  605 . 
     The reading device controller  608  controls an operation of the reading device  204  based on an instruction from the CPU  607 . In print position adjustment described later, the reading device  204  uses the sheet detecting sensor  502  and the line sensors  503  to detect the edge of the sheet and read the adjustment charts. The reading device  204  transmits read data obtained by reading the adjustment charts to the CPU  607  via the reading device controller  608 . The image forming apparatus  100  is capable of executing a mode in which the adjustment charts are read through use of the reading device  204  described above and a mode in which the adjustment charts are read through use of the scanner  302 . 
     The operation panel controller  611  performs interface control between the operation panel  323  and the CPU  607 . The operation panel controller  611  transmits to the CPU  607  data input thereto via the operation panel  323 . The operation panel controller  611  also displays, based on the instruction from the CPU  607 , an image of a setting screen or the like on the operation panel  323 . 
     The stacker controller  612  controls an operation of the stacker  203 . The stacker  203  outputs, based on an instruction from the stacker controller  612 , each of the sheets output from the printer  202  to an output destination (escape tray  404  or stack tray  405 ) specified by the instruction. 
     The storage I/F  613  is connected to a large-capacity storage  615 , such as a hard disk drive (HDD) or a solid state drive (SSD). The storage I/F  613  performs interface control between the storage  615  and the CPU  607 . The CPU  607  writes data in the storage  615  via the storage I/F  613  or reads data from the storage  615  via the storage I/F  613 . The network I/F  614  is an interface configured to control communication to/from an external apparatus (information processing apparatus  102 ) via the network  103 . The printer  202  performs communication to/from the information processing apparatus  102  via the network I/F  614 . 
     Control System for Information Processing Apparatus  102   
       FIG.  7    is a hardware configuration diagram of a control system for the information processing apparatus  102 . The control system for the information processing apparatus  102  is a computer system including a CPU  701 , a ROM  707 , and a RAM  708 . The CPU  701  executes a program stored in the ROM  707  through use of the RAM  708  as a work area, to thereby perform various processes in the information processing apparatus  102 . The CPU  701 , the ROM  707 , and the RAM  708  are connected to be communicative to/from each other via a bus  713 . 
     To the bus  713 , a video random access memory (VRAM)  703  to be connected to a display device  702 , a keyboard  704 , and a pointing device (PD)  705  are connected. The display device  702 , the keyboard  704 , and the PD  705  are user interfaces. In the VRAM  703 , the CPU  701  draws an image to be displayed on the display device  702 . The image drawn in the VRAM  703  is transformed into a predetermined format, transmitted to the display device  702 , and displayed thereon. The display device  702  displays, for example, a window, an icon, a message, a menu, and other user interface information. The keyboard  704  includes various keys for inputting characters. The keyboard  704  transmits a result of a key input to the CPU  701 . The PD  705  is used to specify an object such as the icon or the menu to be displayed on a display screen of the display device  702 . For example, the PD  705  is a mouse. The PD  705  transmits, to the CPU  701 , the result of the specification. 
     To the bus  713 , a media drive  706 , a storage  709 , and an external storage interface (I/F)  710  connected to an external storage device are connected. The media drive  706  is a device configured to read or write various control programs and data from and to media such as a compact disc (CD) and a DVD. The CPU  701  is allowed by the media drive  706  to access the media. The storage  709  is an internal storage device embedded in the information processing apparatus  102 , such as an HDD or an SSD, and stores the various control programs and data. The CPU  701  can execute a computer program stored in the storage  709 . The external storage I/F  710  is an interface configured to allow data to be read and written from and to the external storage device, for example, a universal serial bus (USB) memory. The CPU  701  is allowed by the external storage I/F  710  to access the media. 
     To the bus  713 , a network interface (I/F)  711  is connected. The network I/F  711  is an interface configured to control communication to/from the external apparatus via the network  103 . The information processing apparatus  102  communicates to/from the image forming apparatus  101  via the network I/F  614 . 
     After being activated, the CPU  701  executes the control programs stored in the storage  709  and the media to cause the information processing apparatus  102  to implement various functions. For example, the information processing apparatus  102  implements a function of performing RIP processing on image data and transmitting the image data to the image forming apparatus  101 . 
     Functional Configuration of Printing System  1   
       FIG.  8    is a functional configuration diagram of the printing system  1 . Referring to  FIG.  8   , function of the information processing apparatus  102  causing the image forming apparatus  101  to perform image formation is described. 
     The execution of the computer program by the CPU  607  allows the image forming apparatus  101  to function as each of a user interface (UI) processor  801 , a device controller  802 , a reception processor  803 , and a network controller  804 . 
     The UI processor  801  receives input via the operation panel  323 . The UI processor  801  also causes the operation panel  323  to display an image. For example, when the operation of the image forming apparatus  101  is to be set, the UI processor  801  causes the operation panel controller  611  to display a setting screen on the operation panel  323 . The UI processor  801  uses the storage I/F  613  to store, in the storage  615 , a set value input via the operation panel  323 . 
     The device controller  802  causes the image forming apparatus  101  to perform processes such as an image formation process (printing) and device information setting management. For example, the reception processor  803  inputs, on a page basis, the image data after the RIP processing received from the information processing apparatus  102  via the network controller  804  to the device controller  802 . The network controller  804  uses the network I/F  614  to communicate to/from the information processing apparatus  102  via the network  103 . 
     The execution of the control program by the CPU  701  allows the information processing apparatus  102  to function as each of a UI processor  805 , a job controller  806 , a transmission processor  807 , a network controller  808 , and the RIP processor  809 . 
     The UI processor  805  causes the display device  702  to display an image and also receives input via the keyboard  704  and the PD  705 . The UI processor  805  causes, for example, a job management application screen to be displayed on the display device. The job management application is described later. The UI processor  805  receives job settings via the job management application screen, and inputs the job settings to the job controller  806 . 
     The job controller  806  performs a process, for example, generation of a print job to be executed by the image forming apparatus  101 . The transmission processor  807  transmits, on a page basis, the image data subjected to the RIP processing in the RIP processor  809  to the image forming apparatus  101  via the network controller  808 . The network controller  808  uses the network I/F  711  to communicate to/from the image forming apparatus  101  via the network  103 . 
     When the image data subjected to the RIP processing in the information processing apparatus  102  is to be printed in the image forming apparatus  101 , the following process is performed. 
     The job controller  806  of the information processing apparatus  102  causes the RIP processor  809  to render the image data and causes the transmission processor  807  to transmit the image data subjected to the RIP processing to the image forming apparatus  101 . The job controller  806  also causes the network controller  808  to transmit job setting information to the image forming apparatus  101 . The job setting information is information including various settings related to, for example, the print job. 
     The device controller  802  of the image forming apparatus  101  inputs, to the image processor  605 , the image data subjected to the RIP processing and obtained by the reception processor  803 . The device controller  802  is also caused by the network controller  804  to receive the job setting information. The device controller  802  gives, to the printer controller  606 , instructions relating to an output destination, a feeding source, and a condition for print position adjustment based on the job setting information. The device controller  802  also gives, to the image processor  605 , an instruction to transmit the image data to the printer controller  606 . At this time, in preparation for a case in which a print check request is input to the device controller  802  via the operation panel  323 , the device controller  802  temporarily stores the image data in the storage  615 . The device controller  802  deletes the image data from the storage  615  at a time when it is no longer required to store the image data, for example, when a job is completed. 
     Job Management Application 
       FIG.  9    is a diagram for illustrating an example of the job management application screen to be displayed on the display device  702  of the information processing apparatus  102 . The job management application screen includes a name bar  901 , an end button  902 , an active window  903 , and a job history window  904 . 
     The name bar  901  displays a name of a job management application. The end button  902  is pressed when the job management application is to be ended. Through the pressing of the end button  902 , the job management application is ended, and the job management application screen is closed. 
     The active window  903  is a display area for displaying a list of print jobs stored by the information processing apparatus  102 . The active window  903  in this case displays a print job named “CONTRACT.pdf” stored by the information processing apparatus  102 . In association with the job displayed in the active window  903 , a property  905  for executing “PRINT” and “PRINT SETTINGS” can be displayed. When the “PRINT” is selected, printing for the print job is performed. When the “PRINT SETTINGS” is selected, print settings can be changed. 
     The job history window  904  is a display area for displaying a history of the print jobs for which processing has been completed. The job history window  904  in this case displays a print job named “QUOTATION.pdf” as a job history of the print job for which printing has been completed. For the print job displayed in the job history window  904 , print settings cannot be changed and printing cannot be performed, unlike for the print job displayed in the active window  903 . 
       FIG.  10    is a diagram for illustrating an example of a print setting screen to be displayed on the display device  702  of the information processing apparatus  102  when the “PRINT SETTINGS” for the job is selected in the active window  903 . The print setting screen includes tags  1001 , an “OK” button  1006 , and a “CANCEL” button  1007 . The information processing apparatus  102  generates the job setting information based on details of settings made to the print setting screen. 
     The tags  1001  include five types of tags, which are a “GENERAL” tag, a “JOB INFORMATION” tag, a “SHEET” tag, a “LAYOUT” tag, and a “FINISHING” tag. Setting items in accordance with the type of the selected tag  1001  are displayed. The setting items for the “SHEET” tag are displayed in this case. The “SHEET” tag displays the setting items for making settings relating to a sheet on which an image is to be printed. For example, the “SHEET” tag allows the type of sheet to be used for the print job, the size thereof, a tray (feeding source), and a print position adjustment method to be selected. 
     A “SHEET TYPE” menu  1002  is a pull-down menu for setting the type of sheet to be used for the print job. For example, the “SHEET TYPE” menu  1002  allows “AUTO SELECT” or “PLAIN SHEET” to be set. A “SHEET TRAY” menu  1003  is a pull-down menu for setting a feeding source of the sheet to be used for the print job. For example, the “SHEET TRAY” menu  1003  allows “AUTO SELECT”, “CASSETTE 1”, or “MANUAL FEEDING” to be set. The print job allows an image to be formed on the sheet fed from the feeding source set in the “SHEET TRAY” menu  1003 . A “SHEET SIZE” menu  1004  is a pull-down menu for setting the size of the sheet to be used for the print job. For example, the “SHEET SIZE” menu  1004  allows “A3”, “A4”, “B4”, “B5”, or “LTR” to be set. A “SHEET MIX” button  1005  is pressed when, for one print job, images are to be formed on a plurality of types of sheets having different sheet sizes and contained in different sheet trays. 
     A “POSITION ADJUSTMENT” menu  1008  is a pull-down menu for selecting a print position adjustment method. The printer  202  can adjust a print position on a sheet by a plurality of print position adjustment methods. In at least one embodiment, the printer  202  can adjust the print position by a print position adjustment method for adjusting the print position so as to maintain perpendicularity and by a print position adjustment method for adjusting the print position so as to set uniform margins. In the following description, the adjustment method for adjusting the print position so as to maintain perpendicularity is referred to as “first adjustment process”, in which a predetermined image formation area in which the printer  202  can form an image is adjusted to a first area having a rectangular shape. Meanwhile, in the following description, the adjustment method for adjusting the print position so as to set uniform margins is referred to as “second adjustment process”, in which the predetermined image formation area in which the printer  202  can form an image is adjusted to a second area having a shape similar to a shape of the sheet. In the “POSITION ADJUSTMENT” menu  1008 , in addition to those print position adjustment methods, a “NO ADJUSTMENT” process, in which no print position adjustment is performed, can be set. 
     The “OK” button  1006  is a button for allowing the details of the setting made to the print setting screen to be reflected on printing. The “CANCEL” button  1007  is a button for canceling the details of the setting made to the print setting screen. Through the pressing of the “OK” button  1006  or the “CANCEL” button  1007 , the print setting screen is closed. 
     Print Position Adjustment 
     By the print position adjustment, each of a print position of an image to be formed on a first surface of the sheet and a print position of an image to be formed on a second surface of the sheet is adjusted to an ideal print position. This adjustment allows correction of misalignment between the print position of the image to be formed on the first surface of the sheet and the print position of the image to be formed on the second surface of the sheet. 
       FIG.  11    is a diagram for illustrating an example of an interface screen for performing an operation, for example editing, on a sheet library. The sheet library is a database for managing sheets that can be used for printing in the image forming apparatus  101 . The sheet library is stored in the storage  615  of the image forming apparatus  101  to be subjected to, for example, reading or updating as required. Details of the sheet library are described later. 
     An interface screen  1100  for performing an operation on the sheet library is displayed on the operation panel  323  of the printer  202 . The interface screen  1100  includes a sheet list  1101 , an “ADD NEW SHEET” button  1111 , an “EDIT” button  1112 , a “DELETE” button  1113 , and an “ADJUST PRINT POSITION” button  1114 . 
     The sheet list  1101  displays a list of sheets managed in the sheet library. The sheet list  1101  has, depending on types of individual sheets, such sheet attributes as shown in columns  1102  to  1107 . The column  1102  shows names of the sheets. The names of the sheets are displayed so as to be distinguishable from each other. The columns  1103  and  1104  show sizes of the sheets. The column  1103  shows widths of the sheets, while the column  1104  shows lengths of the sheets. The column  1105  shows basis weights of the sheets. The column  1106  shows surface properties of the sheets. The surface properties represent physical properties of surfaces of the sheets. Examples of the surface properties include “COATED” indicating that coating treatment has been performed on the surface of a sheet to increase glossiness thereof and “EMBOSSED” indicating that depressions and projections have been formed on the surface of a sheet. The column  1107  shows colors of the sheets. 
     A touch operation performed on the operation panel  323  or the like allows a sheet to be selected in the sheet list  1101 . The sheet attributes of the selected sheet are displayed to be highlighted to clearly show the selected sheet. In  FIG.  11   , a case in which “XYZ PAPER COLOR 81” is selected is illustrated by way of example. When the number of sheets managed in the sheet library is larger than the number of sheets that can be displayed simultaneously in the sheet list  1101 , an operation performed on a scroll bar  1108  allows the sheet attributes to be displayed and selected. 
     The “ADD NEW SHEET” button  1111  is a button for allowing a new sheet to be added to the sheet library. The “EDIT” button  1112  is a button for allowing the sheet attributes of the sheet selected in the sheet list  1101  to be edited. The “DELETE” button  1113  is a button for allowing the sheet selected in the sheet list  1101  to be deleted from the sheet library. The “ADJUST PRINT POSITION” button  1114  is a button for allowing print position adjustment to be performed on the sheet selected in the sheet list  1101 . 
       FIG.  12    is an explanatory diagram of the sheet library. The sheet library is stored in a file format such as an extensible markup language (XML) or comma-separated values (CSV) in the storage  615  of the image forming apparatus  101 . The sheet library includes the sheet attributes of each sheet type and print position misalignment amounts thereof. 
     Rows  1201  to  1205  show respective sheet attributes of individual sheets registered in the sheet library. Columns  1211  to  1221  show individual items of the sheet attributes. Each of the items is input to the interface screen through the operation panel  323 . The column  1211  shows names of the sheets. The columns  1212  to  1215  show physical properties of the sheets. The column  1212  shows widths of the sheets. The column  1213  shows lengths of the sheets. The column  1214  shows basis weights of the sheets. The column  1215  shows surface properties of the sheets. The column  1216  shows colors of the sheets. The column  1217  shows the number (n) of sheets required to calculate the print position misalignment amounts. On each of the n sheets, adjustment charts described later are formed and, based on the result of measuring the adjustment charts, the print position misalignment amounts are determined. 
     The columns  1218  and  1219  show the respective print position misalignment amounts on front surfaces and back surfaces of the sheets at the time when adjustment is performed through use of the scanner  302 . The columns  1220  and  1221  show the respective print position misalignment amounts on the front surfaces and the back surfaces of the sheets at the time when adjustment is performed through use of the reading device  204 . Each of the print position misalignment amounts shows an amount of position misalignment from an ideal print position. In at least one embodiment, each of the print position misalignment amounts is represented by a perpendicularity correction amount, a keystone (trapezoidal) correction amount, a skew feeding correction amount, a lead position, a side position, a main scanning magnification, and a sub-scanning magnification. When adjustment is performed through use of the reading device  204 , the perpendicularity correction amount is not included in the print position misalignment amounts. Each of the print position misalignment amounts corresponds to an adjustment amount for allowing the image position with respect to each of the sheets to be adjusted to an ideal print position. The print position misalignment amount also corresponds to an adjustment amount for adjusting the image formation area in which the printer  202  can form an image. During actual printing, the image forming apparatus  101  performs print position adjustment based on the print position misalignment amount such that each image is formed at the ideal print position. In other words, the image forming apparatus  101  performs adjustment so as to cancel out the print position misalignment amount and forms an image. For example, the image processor  605  performs affine transformation on the image data based on the print position misalignment amounts, to thereby correct the print position of each of the images to be formed on the sheet to the ideal print position. This correction also adjusts the predetermined image formation area, to thereby correct the size of the image, the rotation of the image, and the distortion of the image. 
     The perpendicularity correction amount represents an amount of misalignment between respective perpendicularities of print orientations in a sub-scanning direction and a main scanning direction with respect to the sheet. The “main scanning direction” as used herein refers to a direction in which a laser beam from the exposing device  303  scans a surface of the photosensitive drum  304 , while the “sub-scanning direction” refers to a direction orthogonal to the main scanning direction. The sub-scanning direction corresponds to a direction (direction of sheet conveyance) in which each of the sheets is conveyed in the printer  202 . For example, the perpendicularity correction amount is represented by an amount of misalignment between an ideal perpendicular line calculated with respect to a straight line printed in the sub-scanning direction and a straight line printed in the main scanning direction. The keystone correction amount represents an amount of misalignment between elongation and contraction of the sheet. For example, the keystone correction amount is represented by an amount of misalignment between a straight line printed, in the sub-scanning direction, from a position on a sheet at which printing is started to a rear end of sub-scanning and a straight line printed, in the sub-scanning direction, from a position on the sheet corresponding to a rear end of main scanning performed on the sheet to the rear end of the sub-scanning. The lead position and the side position represent respective print position misalignment amounts with respect to the sheet in the sub-scanning direction and the main scanning direction. The lead position is adjusted by changing a position at which the printing of the image is started, which begins at a leading end portion of the sheet in the direction of conveyance thereof. The side position is adjusted by changing a position at which printing of an image is started, which begins at a left end portion of the sheet in the direction of conveyance thereof. Specifically, the lead position and the side position are adjusted by adjusting a time when emission of the laser beam toward the photosensitive drum  304  is started. The sub-scanning magnification represents image length misalignment (magnification with respect to an ideal length) in the sub-scanning direction. The sub-scanning magnification is adjusted by controlling a rotation speed of the transfer drum  305 . The main scanning magnification represents image length misalignment (magnification with respect to an ideal length) in the main scanning direction. 
     The print position misalignment amount is determined by printing the adjustment charts (position measurement images) on which predetermined marks are disposed on a sheet and detecting the positions of the marks on the adjustment charts. An initial value of each of the items of the print position misalignment amounts is “0”. When a new sheet is registered in the sheet library or when the print position has not been adjusted even though the sheet has been registered in the sheet library, the initial value is used as the print position misalignment amount. 
       FIG.  13    is an explanatory diagram of the adjustment chart. After the print position adjustment is started, the adjustment chart is printed on a sheet based on an instruction from the CPU  607 . On each of a front surface  1300  and a back surface  1301  of the sheet, the same adjustment chart is printed.  FIG.  14    is a diagram for illustrating an example of an instruction screen for giving an instruction to specify a print position adjustment method. A user inputs an instruction to such an instruction screen as displayed on the operation panel  323 . In response to the instruction given to the instruction screen, the CPU  607  obtains user instruction information and gives an instruction to print the adjustment chart. When any of a “CORRECT USING SCANNER” button  1401  or a “CORRECT USING READING DEVICE” button  1402  is pressed, the adjustment chart is printed. When a “CANCEL” button  1403  is pressed, a print position adjustment process is canceled. 
     An image  1310  is an arrow and characters to be printed on the front surface  1300 . The image  1310  is used to identify the direction of conveyance of the sheet on which the adjustment charts are printed and the front and back surfaces thereof. An image  1311  is an arrow and characters to be printed on the back surface  1301 . The image  1311  is used to identify the direction of conveyance of the sheet on which the adjustment charts are printed and the front and back surfaces thereof. When the scanner  302  is caused to read the adjustment charts, the images  1310  and  1311  are printed so as to prevent an operator from making a mistake in identifying an orientation. The images  1310  and  1311 , which are not directly related to the determination of the print position misalignment amounts, are not necessarily required to be printed. 
     Marks  1320  are images printed at specific positions on the adjustment charts. The marks  1320  are formed through use of a toner in a color having a large reflectance difference with the sheet. In at least one embodiment, the marks  1320  are formed with a black toner. In at least one embodiment, the marks  1320  are formed at the total of eight positions on the respective four corners of the front surface  1300  and the back surface  1301  of the sheet. When the print positions are ideal, the marks  1320  are formed at positions each at a predetermined distance from an end portion of the sheet. Relative positions of the marks  1320  on the adjustment charts are measured to allow the print position misalignment amounts to be determined. A distance of each of the marks  1320  from a reference side of the sheet is measured to allow a shape of the image formation area, the size of the image formation area, and a positional relationship between the reference side of the sheet and the image formation area to be sensed. 
     In at least one embodiment, when the print position adjustment is performed through use of the reading device  204 , distances C to R are measured while, when the print position adjustment is performed through use of the scanner  302 , distances A to V are measured. The distances A to V of  FIG.  13    are measured. The distance A is a length of the adjustment chart in the sub-scanning direction. The distance B is a length of the adjustment chart in the main scanning direction. Ideal lengths of the distances A and B are sheet lengths set in the sheet library. The distances C to V are lengths between the respective marks  1320  and respective end portions of the sheet that are closest to the marks  1320 . 
     The front surface  1300  is divided by a chart middle line  1340  into two areas  1351  and  1352 . The back surface  1301  is divided by a chart middle line  1341  into two areas  1353  and  1354 . Of the adjustment chart, the front surface  1300  and the back surface  1301  are divided into the regions  1351 ,  1352 ,  1353 , and  1354 , which are individually read by the scanner  302 . Triangular marks  1331  to  1334  indicate the order in which the areas  1351 ,  1352 ,  1353 , and  1354  are read and serve as guide marks indicating a position on the scanner  302  at which the sheet is placed. The operator causes the scanner  302  to read the adjustment charts in the order corresponding to the numbers of the triangular marks. The adjustment charts in this case are read in the order of the area  1352 , the area  1351 , the area  1354 , and the area  1353 . After the adjustment charts divided into the individual areas  1351  to  1354  are read, reading results are combined with each other. By thus reading the adjustment charts divided into the individual areas, the scanner  302  can read the adjustment charts even when the size of each of the adjustment charts is too large to be placed on the original table  300 . 
     A process of determining the print position misalignment amounts based on the measured distances A to V is now described.  FIG.  15    is an explanatory diagram of the process of determining the print position misalignment amounts. 
     Each of the print position misalignment amounts is represented by items for the front surface and items for the back surface. The items for the front surface include a lead position  1501 , a side position  1502 , a main scanning magnification  1503 , a sub-scanning magnification  1504 , a perpendicularity correction amount  1505 , and a keystone correction amount  1506 . The items for the back surface include a lead position  1507 , a side position  1508 , a main scanning magnification  1509 , a sub-scanning magnification  1510 , a perpendicularity correction amount  1511 , and a keystone correction amount  1512 . For each of the items common to the front surface and the back surface, a measurement value  1520  and a print position misalignment amount  1522  are calculated based on the same calculation formula, and a common ideal value  1521  is set. 
     The respective measurement values  1520  of the individual items are calculated from the respective actually measured values of the distances A to V described with reference to  FIG.  13    through use of respective calculation formulae set for the individual items on a one-by-one basis. The respective measurement values  1520  of the lead positions  1501  and  1507  correspond to respective average values of the distances C and E (K and M) from the leading end portions of the sheet in the direction of conveyance thereof to the corresponding marks  1320 . The respective measurement values  1520  of the side positions  1502  and  1508  correspond to respective average values of the distances F and J (N and R) from the left end portions of the sheet in the direction of conveyance thereof to the corresponding marks  1320 . The respective measurement values  1520  of the main scanning magnitudes  1503  and  1509  correspond to the respective average values of the distances between the marks  1320  aligned on the same line in the main scanning direction. The respective measurement values  1520  of the sub-scanning magnitudes  1504  and  1510  correspond to the respective average values of the distances between the marks  1320  aligned on the same line in the sub-scanning direction. The respective measurement values  1520  of the perpendicularity correction amounts  1505  and  1511  correspond to respective average values of misalignment amounts S and T (U and V) in the sub-scanning direction between the marks  1320  on a reading rear end side and lines perpendicular to straight lines connecting the marks  1320  on a reading lead end side, which are aligned on the same scanning lines in the main scanning direction. The respective measurement values  1520  of the keystone correction amounts  1506  and  1512  correspond to the differences between the distances between the marks  1320  aligned on the same scanning lines in the sub-scanning direction. 
     The respective ideal values  1521  of the individual items are obtained based on the marks  1320  formed at positions each spaced apart by 1 cm from an end portion of the sheet. The ideal value  1521  of each of the lead positions  1501  and  1507  and the side positions  1502  and  1508  is 1 cm. The ideal value  1521  of each of the main scanning magnifications  1503  and  1509  is obtained by subtracting 2 cm from the length of the sheet registered in the sheet library. The ideal value  1521  of each of the sub-scanning magnifications  1504  and  1510  is obtained by subtracting 2 cm from the width of the sheet registered in the sheet library. The ideal value  1521  of each of the perpendicularity correction amounts  1505  and  1511  and the keystone correction amounts  1506  and  1512  is 0 cm. 
     The respective print position misalignment amounts  1522  of the individual items are calculated from the corresponding measurement values  1520  and the corresponding ideal values  1521  through use of respective calculation formulae set on a one-by-one basis for the individual items. The respective print position misalignment amounts  1522  of the lead positions  1501  and  1507 , and the side positions  1502  and  1508  are calculated by subtracting the ideal values  1521  from the measurement values  1520  (in units of millimeter). The respective print position misalignment amounts  1522  of the main scanning magnifications  1503  and  1509  and the sub-scanning magnifications  1504  and  1510  are calculated by dividing values obtained by subtracting the ideal values  1521  from the measurement values  1520  by the ideal values (in units of percent). As the respective print position misalignment amounts  1522  of the perpendicularity correction amounts  1505  and  1511  and the keystone correction amounts  1506  and  1512 , the measurement values  1520  are used without alteration. The respective calculated print position misalignment amounts  1522  of the individual items are managed in the columns  1218  to  1221  of the sheet library illustrated in  FIG.  12   . 
     When the scanner  302  is used, the distances A to V can be measured through use of the adjustment charts read by the scanner  302 . Accordingly, the respective print position misalignment amounts  1522  of all the items can be calculated. When the reading device  204  is used, the distances C to R can be measured through use of the adjustment charts read by the reading device  204 . Accordingly, the respective print position misalignment amounts  1522  of the items other than the perpendicularity correction amounts  1505  and  1511  can be calculated. The reading device  204  reads the adjustment charts, while allowing the sheet to be conveyed. It may be possible that, due to a non-uniform speed of conveyance of the sheet or the like, the reading device  204  does not have a sufficient accuracy required for the print position adjustment. Consequently, the number of items of distances that can be read by the reading device  204  is smaller than the number of items of distances that can be read by the scanner  302 . 
       FIG.  16 A ,  FIG.  16 B , and  FIG.  16 C  are explanatory diagrams of the print position adjustment process. In  FIG.  16 A ,  FIG.  16 B , and  FIG.  16 C , image formation areas  1602 ,  1604 , and  1606  on respective sheets  1601 ,  1603 , and  1605  are illustrated. Due to elongation and contraction of the sheets  1601 ,  1603 , and  1605 , each of the sheets  1601 ,  1603 , and  1605  no longer has a rectangular shape. Each of the image formation areas  1602 ,  1604 , and  1606  is an area in which an image can be formed. In  FIG.  16 A , the image formation area  1606  obtained when the print position adjustment is not performed is illustrated. When the print position adjustment is not performed, perpendicularity of the image formation area  1606  is not maintained. In addition, the respective distances (margins) between the four sides of the image formation area  1606  and edges of the sheet  1605  are non-uniform. In  FIG.  16 B , an image obtained when the first adjustment process is performed is illustrated. In the first adjustment process, the print position misalignment amounts  1522  of the perpendicularity correction amounts  1505  and  1511  are also used. In  FIG.  16 C , an image obtained when the second adjustment process is performed is illustrated. In the second adjustment process, the print position misalignment amounts  1522  of the perpendicularity correction amounts  1505  and  1511  are not used. In each of  FIG.  16 A ,  FIG.  16 B , and  FIG.  16 C , respective distortions of the sheets resulting from heat from the fixing device  308  are represented in an exaggerated manner to allow a difference between the individual processes to be easily recognized. 
     As illustrated in  FIG.  16 B , when the respective print position misalignment amounts  1522  of the perpendicularity correction amounts  1505  and  1511  are included in the items of the print position adjustment, respective print positions on the front and back surfaces are adjusted so as to allow the perpendicularity of the image formation area  1602  to be maintained. However, distances (margin widths) between four sides of the image formation area  1602  and edges of the sheet  1601  are non-uniform. The image formation area  1602  has a rectangular shape of ideal dimensions. This corresponds to a case in which the print position adjustment is performed based on the result of reading the adjustment chart placed on the original table  300  through use of the scanner  302 . 
     As illustrated in  FIG.  16 C , when the respective print position misalignment amounts  1522  of the perpendicularity correction amounts  1505  and  1511  are not included in the items of the print position adjustment, respective print positions on the front and back surfaces are adjusted so as to allow uniformity of the margins to be maintained. In other words, the distances (margin widths) between four sides of the image formation area  1604  and edges of the sheet  1603  have a predetermined value and are uniform, but the perpendicularity of the image formation area  1604  is not maintained. The image formation area  1604  has a shape similar to that of the sheet  1603 , on which the test images are formed. This corresponds to a case in which the print position adjustment is performed through use of the reading device  204 . 
     When the distances are calculated from the adjustment charts through use of the reading device  204 , the reading device  204  first scans the sheet passing through respective reading positions of the line sensors  503  to read the adjustment charts. Data read from the adjustment charts is transmitted to the CPU  607 . The CPU  607  detects, based on a density difference in the adjustment charts, end portions of the sheet and edges (boundaries between a sheet base and the marks  1320 ) of the marks  1320 . The CPU  607  calculates the distances C to R from the detected end portions of the sheet and the detected edges of the marks  1320 . 
     When the distances are calculated from the adjustment chart through use of the scanner  302 , the scanner  302  reads each of the front and back surfaces of the adjustment chart placed on the original table  300  in two steps. The reading is performed in the order of the triangular marks  1331  to  1334  in response to the instruction given by the operator. The results (read data) of reading the adjustment chart are transmitted to the CPU  607 . The CPU  607  combines the result of reading the area  1351  and the result of reading the area  1352  with each other to produce a front-surface adjustment chart. The CPU  607  combines the result of reading the area  1353  and the result of reading the area  1354  with each other to produce a back-surface adjustment chart. The CPU  607  detects, from the density difference between the adjustment charts based on the results of the combinations, the end portions of the sheet and the edges of the marks  1320 . The CPU  607  calculates the distances A to V from the detected end portions of the sheet and the detected edges of the marks  1320 . 
       FIG.  17    is a flow chart for illustrating a process of calculating the print position misalignment amounts. In at least one embodiment, the operator selects one of the sheets in the interface screen of  FIG.  11    displayed on the operation panel  323  and presses the “ADJUST PRINT POSITION” button  1114  to cause the instruction screen of  FIG.  14    to be displayed on the operation panel  323 . The operator selects a print position adjustment method from among the print position adjustment methods in the instruction screen to cause the operation panel controller  611  to receive user instruction information. As a result, the CPU  607  starts the process of calculating the print position misalignment amounts. The print position misalignment amounts are calculated in this case through use of the reading device  204 . Accordingly, the “CORRECT USING READING DEVICE” button  1402  is selected, and the process of calculating the print position misalignment amounts is started. The process of calculating the print position misalignment amounts may also be automatically started by a specific trigger. 
     The CPU  607  obtains, from the sheet library, the number (n) of sheets required to calculate the print position misalignment amounts of the sheet selected by the operator (Step S 1701 ). When the print position adjustment process is input, the CPU  607  automatically obtains, from the sheet library, the number of the sheets on which the adjustment charts are to be printed when the print position adjustment is performed on the sheet. The CPU  607  may also perform display control for the operation panel  323  so as to cause, every time the print position adjustment process is input, the operator to input the number of the sheets on which the adjustment charts are to be printed. 
     The printer  202  prints, on both surfaces of each of the sheets selected by the operator, the adjustment charts illustrated by way of example in  FIG.  13    and having the marks  1320  disposed therein, and outputs the sheet to the outside of the image forming apparatus (Step S 1702 ). The output sheet is conveyed to the reading device  204 . The CPU  607  causes the reading device  204  to scan images on both surfaces of the sheet having the adjustment charts printed thereon. The reading device  204  causes the two line sensors  503  to simultaneously read the adjustment charts from both surfaces of the sheet. The CPU  607  obtains, from the reading device  204 , the data read from the adjustment charts (Step S 1703 ). 
     The CPU  607  extracts, based on the data read from the adjustment charts, respective positions of the end portions of the sheet and the marks  1320 , and obtains the distances C to R illustrated in  FIG.  13   . The CPU  607  calculates, through use of the obtained distances C to R, the print position misalignment amounts based on the calculation formulae of  FIG.  15    (Step S 1704 ). The CPU  607  stores, in the storage  615 , the calculated print position misalignment amounts. 
     The CPU  607  determines whether or not the calculation of the misalignment amounts is performed for each of the sheets, the number (n) of which is obtained in the process of Step S 1701  (Step S 1705 ). When the calculation of the misalignment amounts is not performed for each of the n sheets (“N” in Step S 1705 ), the CPU  607  repeatedly performs the process of Steps S 1702  to S 1704  until the calculation of the misalignment amounts corresponding to each of the n sheets is performed. 
     When the calculation of the misalignment amounts corresponding to each of the n sheets is performed (“Y” in Step S 1705 ), the CPU  607  calculates an average value of the misalignment amounts stored in the storage  615  (Step S 1706 ). The CPU  607  stores, in the sheet library, the calculated average value as the print position misalignment amounts of the sheets selected in the interface screen of  FIG.  11    (Step S 1707 ). In the process of Step S 1707 , the CPU  607  updates information on the print position misalignment amounts in the sheet library, which is to be stored in the storage  615 . Based on the print position misalignment amounts determined as described above, the CPU  607  adjusts respective positions (print positions) at which images are to be formed when images are formed on a sheet of a similar type. 
     When the print position misalignment amounts are calculated through use of the scanner  302 , the “CORRECT USING SCANNER” button  1401  is selected, and a process of calculating the print position misalignment amounts is started. Due to the use of the scanner  302 , the adjustment charts are not automatically read unlike when the reading device  204  is used, and consequently the operator performs a reading operation. The process is the same as that performed when the reading device  204  is used, but the CPU  607  obtains the distances A to V illustrated in  FIG.  13    based on data read from the adjustment charts. The CPU  607  calculates, through use of the obtained distances A to V, the print position misalignment amounts based on the calculation formulae of  FIG.  15   . The CPU  607  stores the calculated print position misalignment amounts in the storage  615 . 
     The print position misalignment amounts calculated in the process of  FIG.  17    serve as correction amounts for adjusting the positions at which images are to be formed when the print position adjustment process is performed. The printer  202  uses, as conditions for adjusting the print positions, the print position misalignment amounts (correction amounts). The printer  202  performs the print position adjustment process based on the corresponding print position misalignment amounts in the sheet library. In the sheet library of  FIG.  12   , the columns  1218  to  1221  correspond to individual print position adjustment conditions. The printer  202  selects an appropriate condition from among the plurality of adjustment conditions and performs the print position adjustment process. In the following, four examples of an image formation process including the print position adjustment process are described. 
     Image Formation Process 1 
       FIG.  18    is a flow chart for illustrating the image formation process including the print position adjustment process. The process is started when the operator makes print settings in the print setting screen of  FIG.  10    and presses the “OK” button  1006 . As a result, the information processing apparatus  102  transmits, to the image forming apparatus  101 , an instruction to perform the image formation process including job setting information for a print job. 
     When receiving the instruction to perform the image formation process, the CPU  607  of the image forming apparatus  101  determines the print position adjustment method set in the “POSITION ADJUSTMENT” menu  1008  based on the job setting information (Step S 1801 ). As described above, in the “POSITION ADJUSTMENT” menu  1008 , any of the first adjustment process, the second adjustment process, and the “NO ADJUSTMENT” process, in which no print position adjustment is performed, can be selected. When the “NO ADJUSTMENT” process is selected (“ABSENT” in Step S 1801 ), the CPU  607  performs normal printing without performing any of the print position adjustment processes (Step S 1812 ). 
     When the first adjustment process is selected (“FOR MAINTAINING PERPENDICULARITY” in Step S 1801 ), the CPU  707  determines the presence or absence of correction values for the first adjustment process (Step S 1802 ). The CPU  607  refers to the sheet library of  FIG.  12    to determine the presence or absence of the correction values for the first adjustment process based on whether or not the correction values for the first adjustment process corresponding to the type of sheet to be used for printing are set in the columns  1218  and  1219 . When the correction values for the first adjustment process are set (“PRESENT” in Step S 1802 ), the CPU  607  adjusts the print positions based on the correction values set in the columns  1218  and  1219  of the sheet library, and performs printing (Step S 1804 ). 
     When the correction values for the first adjustment process are not set (“ABSENT” in Step S 1802 ), the CPU  607  displays, on the operation panel  323 , a warning screen for notifying the user that the correction values for the first adjustment process are not registered (Step S 1805 ).  FIG.  19    is a diagram for illustrating an example of the warning screen. The warning screen displays a button  1901  for stopping a print job, a “PRINT AFTER ADJUSTMENT” button  1902  for allowing printing to be performed after the correction values for the first adjustment process are registered, and a button  1903  for allowing printing to be performed through use of the correction values for the second adjustment process. The “PRINT AFTER ADJUSTMENT” button  1902  is a button for giving an instruction to obtain the correction values for the first adjustment process through use of the scanner  302  and perform printing through use of the obtained correction values. The button  1903  is selectable when the correction values for the second adjustment process are present, but is displayed in grayout and is unselectable, for example, when the correction values for the second adjustment process are absent. The CPU  607  determines which button is selected by the operator in the warning screen (Step S 1806 ). When the button  1901  is selected (“CANCEL” in Step S 1806 ), the CPU  607  stops the print job and ends the process. 
     When the “PRINT AFTER ADJUSTMENT” button  1902  is selected (“CORRECT” in Step S 1806 ), the CPU  607  performs the print position adjustment using the scanner  302  (Step S 1807 ). The print position adjustment using the scanner  302  is the same as in the process performed when the “CORRECT USING SCANNER” button  1401  is selected in the instruction screen of  FIG.  14    described above. After the print position adjustment, the CPU  607  adjusts the print positions based on the correction values set in the columns  1218  and  1219  of the sheet library, and performs printing (Step S 1804 ). 
     When the button  1903  is selected (“SET UNIFORM MARGINS” in Step S 1806 ), the CPU  607  adjusts the print positions based on the correction values set in the columns  1220  and  1221  of the sheet library, and performs printing (Step S 1808 ). 
     When the second adjustment process is selected in the “POSITION ADJUSTMENT” menu  1008  (“SET UNIFORM MARGINS” in Step S 1801 ), the CPU  607  determines the presence or absence of the correction values for the second adjustment process (Step S 1803 ). The CPU  607  refers to the sheet library of  FIG.  12    to determine the presence or absence of the correction values for the second adjustment process based on whether or not the correction values for the second adjustment process corresponding to the type of sheet to be used for printing are set in the columns  1220  and  1221 . When the correction values for the second adjustment process are set (“PRESENT” in Step S 1803 ), the CPU  607  adjusts the print positions based on the correction values set in the columns  1220  and  1221  of the sheet library, and performs printing (Step S 1808 ). 
     When the correction values for the second adjustment process are not set (“ABSENT” in Step S 1803 ), the CPU  607  displays, on the operation panel  323 , a warning screen for notifying the user that the correction values for the second adjustment process are not registered (Step S 1809 ). The warning screen is a screen after “MAINTAIN PERPENDICULARITY” of  FIG.  19    is changed to “SET UNIFORM MARGINS” and the button  1903  of  FIG.  19    is changed to “PRINT USING CORRECTION VALUES FOR FIRST ADJUSTMENT PROCESS”. The CPU  607  determines which button is selected by the operator in the warning screen (Step S 1810 ). When the button  1901  is selected (“CANCEL” in Step S 1810 ), the CPU  607  stops the print job and ends the process. 
     When the “PRINT AFTER ADJUSTMENT” button  1902  is selected (“CORRECT” in Step S 1810 ), the CPU  607  performs the print position adjustment using the reading device  204  (Step S 1811 ). The print position adjustment using the reading device  204  is the same as in the process performed when the “CORRECT USING READING DEVICE” button  1402  is selected in the instruction screen of  FIG.  14    described above. After the print position adjustment, the CPU  607  adjusts the print positions based on the correction values set in the columns  1220  and  1221  of the sheet library, and performs printing (Step S 1808 ). 
     When the button  1903  is selected (“MAINTAIN PERPENDICULARITY” in Step S 1810 ), the CPU  607  adjusts the print positions based on the correction values set in the columns  1218  and  1219  of the sheet library, and performs printing (Step S 1804 ). 
     According to Image Formation Process 1, the image forming apparatus  101  performs the print position adjustment through use of the correction values specified by the operator from among the correction values for a plurality of print positions, and forms an image. This process allows print position adjustment appropriate for a printed material to be performed depending on post-treatment, for example cutting. 
     Image Formation Process 2 
     Displaying the warning screen may cause feeling of annoyance when it is only required to align the respective print positions on the front and back surfaces with each other. By allowing for automatic selection of the correction values for the print positions, it is possible to reduce an operation to be performed by the operator in response to the warning screen. The automatic selection of the correction values is performed when, for example, “AUTO SELECT” is added as an option to the “POSITION ADJUSTMENT” menu  1008  in the print setting screen of  FIG.  10   , and the operator selects “AUTO SELECT”.  FIG.  20    is a flow chart for illustrating the image formation process including the print position adjustment process to be performed in such a process. This process is also started when the operator makes print settings in the print setting screen of  FIG.  10    and presses the “OK” button  1006 . 
     When receiving an instruction to perform the image formation process, the CPU  607  of the image forming apparatus  101  determines the print position adjustment method set in the “POSITION ADJUSTMENT” menu  1008  based on the job setting information (Step S 2001 ). The process (Steps S 2002  to S 2012 ) performed when any of the first adjustment process, the second adjustment process, and the “NO ADJUSTMENT” process is set is the same as the process (Steps S 1802  to S 1812 ) of  FIG.  18   . Therefore, a description of the process performed in such cases is omitted. 
     When “AUTO SELECT” is set as the print setting (“AUTOMATICALLY SELECTED” in Step S 2001 ), the CPU  607  determines the presence or absence of the correction values for adjusting the print positions (Step S 2013 ). The CPU  607  refers to the sheet library of  FIG.  12    and determines, depending on the type of sheet to be used for printing, the presence or absence of the correction values for adjusting the print positions based on whether or not the correction values are set in the columns  1218  to  1221 . When only the correction values for the first adjustment process are present (“FOR MAINTAINING PERPENDICULARITY” in Step S 2013 ), the CPU  607  performs the process of Step S 2004 . When only the correction values for the second adjustment process are present (“FOR SETTING UNIFORM MARGINS” in Step S 2013 ), the CPU  607  performs the process of Step S 2008 . When the correction values are absent (“ABSENT” in Step S 2013 ), the CPU  607  performs the print position adjustment, and performs the image formation process (Step S 2014 ). In this case, the CPU  607  causes the instruction screen illustrated by way of example in  FIG.  14    to be displayed on the operation panel  323 , and performs the print position adjustment based on the instruction given via the instruction screen. The CPU  607  adjusts the print positions based on the correction values determined by the print position adjustment and performs printing. When both of the correction values for the first adjustment process and the correction values for the second adjustment process are present, the CPU  607  uses, for example, the correction values for the adjustment process set in advance to perform printing. 
     According to Image Adjustment Process 2, the image forming apparatus  101  automatically determines the correction values to be used for the print position adjustment from among the correction values for the plurality of print positions, performs the print position adjustment, and forms an image. This process can relieve the operator from a troublesome operation. 
     Image Formation Process 3 
     When a printed material is cut in the post-treatment, it is preferred to maintain a perpendicularity of the printed material. In addition, the printed material having uniform margins is visually attractive. In this process, in the consideration of the resulting printed material, the correction values are appropriately selected automatically.  FIG.  21    is a flow chart for illustrating the image formation process including the print position adjustment process to be performed in such a process. This process is also started when the operator makes print settings in the print setting screen of  FIG.  10    and presses the “OK” button  1006 . 
     When receiving an instruction to perform the image formation process, the CPU  607  of the image forming apparatus  101  determines the print position adjustment method set in the “POSITION ADJUSTMENT” menu  1008  based on the job setting information (Step S 2101 ). The process (Steps S 2102  to S 2112 ) performed when any of the first adjustment process, the second adjustment process, and the “NO ADJUSTMENT” process is set is the same as the process (Steps from S 1802  to S 1812 ) of  FIG.  18   . Therefore, a description of the process in such cases is omitted. 
     When “AUTO SELECT” is set as the print setting (“AUTOMATICALLY SELECTED” in Step S 2101 ), the CPU  607  determines a job type included in the print job based on the print settings (Step S 2113 ). The CPU  607  determines, based on the job type, the correction values to be used for the print position adjustment process. For example, when the job type includes cutting (“CUTTING” in Step S 2113 ), the CPU  607  performs the process of Step S 2102  and the steps subsequent thereto. For example, when the job type is full-page printing and margins are required to be uniform (“SETTING UNIFORM MARGINS” in Step S 2113 ), the CPU  607  performs the process of Step S 2103  and the steps subsequent thereto. Such settings are exemplary, and it may also be possible to allow setting of which ones of the correction values are to be used to perform printing every time a job is set. 
     According to Image Formation Process 3, the image forming apparatus  101  automatically determines the correction values to be used for the print position adjustment from among the correction values for the plurality of print positions based on the setting of the print job, performs the print position adjustment, and forms an image. Accordingly, appropriate print position adjustment is performed. 
     Image Formation Process 4 
     In the description of Image Formation Processes 1, 2, and 3, the first adjustment process and the second adjustment process are used as examples of the print position adjustment process. However, the print position adjustment process may also be selected from among a plurality of print position adjustment processes other than the first adjustment process and the second adjustment process. Consequently, the CPU  607  performs the process from among the plurality of print position adjustment processes based on the user instruction information. In the following description, the first adjustment process is referred to as “first mode process”, and the second adjustment process is referred to as “second mode process”.  FIG.  22    is a flow chart for illustrating the image formation process including the print position adjustment process. The process is started when the operator makes print settings in the print setting screen of  FIG.  10    and presses the “OK” button  1006 . As a result, the information processing apparatus  102  transmits, to the image forming apparatus  101 , an instruction to perform the image formation process including job setting information for a print job. In the print setting screen of  FIG.  10   , any of the first mode process and the second mode process is selectable. The operator selects any of the first mode process and the second mode process in the print setting screen and makes print settings. 
     When receiving the instruction to perform the image formation process, the CPU  607  of the image forming apparatus  101  determines, based on the job setting information, whether or not the first mode process is selected in the “POSITION ADJUSTMENT” menu  1008  (Step S 2201 ). In the “POSITION ADJUSTMENT” menu  1008 , any of the first mode process, the second mode process, and the “NO ADJUSTMENT” process, in which no print position adjustment is performed, can be set. 
     When the first mode process is selected (“Y” in Step S 2201 ), the CPU  607  determines the presence or absence of the correction values for the first mode process (Step S 2202 ). The CPU  607  refers to the sheet library of  FIG.  12    and determines, depending on the type of sheet to be used for printing, the presence or absence of the correction values for the first mode process based on whether or not the corresponding correction values are set. When the correction values for the first mode process are present (“Y” in Step S 2202 ), the CPU  607  adjusts the print positions based on the correction values for the first mode process and performs printing (Step S 2203 ). 
     When the correction values for the first mode process are absent (“N” in Step S 2202 ), the CPU  607  displays on the operation panel  323  the warning screen for notifying that the correction values for the first mode process have not been set (Step S 2204 ).  FIG.  23    is a diagram for illustrating an example of such a warning screen. In the warning screen, a button  2301  for performing printing without performing the print position adjustment, a button  2302  for performing printing after performing the print position adjustment, and a button  2303  for performing printing through use of another adjustment mode (second mode process) are provided. The warning screen is a screen for allowing the correction values (image processing conditions) corresponding to the process in the selected mode to be selected. 
     The CPU  607  determines which one of the buttons is selected by the operator in the warning screen (Step S 2205 ). When the button  2301  is selected in Step S 2205  (“PRINT WITHOUT ADJUSTMENT” in Step S 2205 ), the CPU  607  performs printing without performing the print position adjustment (Step S 2207 ). 
     When the button  2302  is selected in Step S 2205  (“PRINT AFTER ADJUSTMENT” in Step S 2205 ), the CPU  607  performs the print position adjustment in the first mode process (Step S 2206 ). After the print position adjustment in accordance with the first mode process, the CPU  607  adjusts the print positions based on the correction values for the first mode process and performs printing (Step S 2203 ). 
     When the button  2303  is selected in Step S 2205  (“ANOTHER ADJUSTMENT MODE” in Step S 2205 ), the CPU  607  performs the process to be performed when the second mode process is selected. This process is described later. 
     When the first mode process is not selected in the process of Step S 2201  (“N” in Step S 2201 ), the CPU  607  determines whether or not the second mode process has been selected in the “POSITION ADJUSTMENT” menu  1008  (Step S 2208 ). When the second mode process has not been selected (“N” in Step S 2208 ), the CPU  607  performs printing without performing the print position adjustment (Step S 2207 ). 
     When the second mode process is selected (“N” in Step S 2208 ), the CPU  607  determines the presence or absence of the correction values for the second mode process (Step S 2209 ). The CPU  607  refers to the sheet library of  FIG.  12    and determines, depending on the type of sheet to be used for printing, the presence or absence of the correction values for the second mode process based on whether or not the corresponding correction values for the second mode process are set. Even when the button  2303  is selected in the process of Step S 2205 , the CPU  607  performs the determination process of Step S 2209 . When the correction values for the second mode process are present (“Y” in Step S 2209 ), the CPU  607  adjusts the print positions based on the correction values for the second mode process, and then performs printing (Step S 2210 ). 
     When the correction values for the second mode process are absent (“N” in Step S 2209 ), the CPU  607  displays on the operation panel  323  the warning screen for notifying that the correction values for the second mode process have not been set (Step S 2211 ). The warning screen is the same as that of  FIG.  23   . The CPU  607  determines which one of the buttons on the warning screen has been selected by the operator (Step S 2212 ). 
     When the button  2301  is selected in Step S 2212  (“PRINT WITHOUT ADJUSTMENT” in Step S 2212 ), the CPU  607  performs printing without performing the print position adjustment (Step S 2207 ). 
     When the button  2302  is selected in Step S 2212  (“PRINT AFTER ADJUSTMENT” in Step S 2212 ), the CPU  607  performs the print position adjustment in the second mode process (Step S 2213 ). After the print position adjustment in accordance with the second mode process, the CPU  607  adjusts the print positions based on the correction values for the second mode process and performs printing (Step S 2210 ). 
     When the button  2303  is selected in Step S 2212  (“ANOTHER ADJUSTMENT MODE” in Step S 2212 ), the CPU  607  performs the process of Step S 2202  to be performed when the first mode process is selected. 
     According to Image Formation Process 4, the image forming apparatus  101  performs the print position adjustment through use of the correction values specified by the operator from among the correction values for a plurality of modes, and forms an image. This process allows print position adjustment appropriate for a printed material to be performed depending on post-treatment, for example cutting. 
     According to at least one embodiment of the present disclosure, there is provided an image forming apparatus configured to allow different adjustment processes to be executed. Further, according to at least one embodiment of the present disclosure, it is possible to allow different adjustment processes to be executed. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.