Abstract: An image forming apparatus includes an accommodating portion, an image forming unit, a skew correcting portion, a conveyance unit, a detection unit, a re-conveyance unit, and a control unit. The control unit controls the re-conveyance unit such that the re-conveyance unit stops a sheet in the second conveyance path temporarily and starts to convey the sheet at a first timing after a second timing and before a third timing, where the second timing is a timing such that if the sheet is started to convey to the first conveyance path at the second timing, the conveyance unit decelerates the conveyance speed when the sheet reaches to the detection unit, and the third timing is a timing such that if the sheet is started to convey to the first conveyance path at the third timing, the conveyance unit decelerates the conveyance speed when the sheet reaches to the skew correcting portion.

Abstract: The multifunction peripheral of the present invention includes an ADF document crop function. According to this ADF document crop function, front side image shaping processing for cutting out a front side document image corresponding to the image on the front side of a document, from a front side read image of the document and for correcting the tilt of the front side document image is performed. Then, on the basis of shaping information in the front side image shaping processing, back side image shaping processing for cutting out a back side document image from a back side read image of the document and for correcting the tilt of the back side document image is performed.

Abstract: A document feeder includes a lift plate, a pickup roller, a lift motor, a retard roller, and a control unit. In a manual feed mode, the control unit rotates the retard roller to feed a document in a document conveyance direction. Further, the control unit causes the lift motor to start lowering the lift plate while the pickup roller is feeding a document after the rotation of the pickup roller is started.

Abstract: An image forming apparatus includes a drive source, a driving gear provided on an output shaft of the drive source, a first gear engaging with the driving gear, a first drive transmission portion for transmitting a driving force from the first gear to an image bearing member, a second gear engaging with the driving gear, and a second drive transmission portion for transmitting a driving force from the second gear to a feeding portion. The first gear and the second gear are provided coaxially with each other. A positional relationship between the first gear and the second gear with respect to an axial direction is that the first gear is disposed closer to the drive source than the second gear is.

Abstract: Whether there exists a side area image within side areas of the recording medium is determined. When it is determined that there exists no image within the side areas, a command is transmitted to a printer. The command causes a printer to start conveying of the recording medium at an earlier timing. The side areas of the recording medium are difficult to be heated by a heater arranged at a central portion of a fixing roller. Therefore, in order to heat the side areas, a long time for heating by the heater is necessary. When there is no image within the side areas, the heating time is shortened. Thereby, it is possible to start conveying the recording medium at an early timing, and a time period for completing a printing operation can be shortened.

Abstract: Methods for printing using printing systems comprising a flexible intermediate transfer member (ITM) disposed around a plurality of guide rollers at which encoders are installed, and an image-forming station at which ink images are formed by droplet deposition by print bars onto the ITM, can include measuring a local velocity of the ITM under one of the print bars, determining a stretch factor for a portion of the ITM based on a relationship between an estimated stretched length fixed physical distance between print bars, controlling an ink deposition parameter according to the stretch factor so as to compensate for stretching of the reference portion of the ITM.

Abstract: An image forming apparatus includes an image former configured to form an image on a recording medium, and a hardware processor, wherein the hardware processor, before the image is formed on the recording medium by the image former, determines a medium type of a subject medium that is the recording medium on which the image is to be formed by the image former, and before the medium type of the subject medium is determined, determines whether an image forming speed at which the image former forms the image is a medium speed that is predetermined with respect to the medium type of the subject medium.

Abstract: An image forming apparatus includes a toner image supporting section and a medium transfer section. The toner image supporting section includes first and second toner image supporting member that support first and second toner images at first and second linear speeds, respectively. The medium transfer section transfers, onto a medium, the first and second toner images respectively supported by the first and second toner image supporting members, to thereby cause the first and second toner images to be superimposed on each other. The following conditional expression (1) is satisfied when the medium transfer section transfers the first and second toner images onto the medium, (Vd1?Vt1)/(Vt1>(Vd2?Vt2)/Vt2??(1) where Vd1 is the first linear speed, Vt1 is a first conveyance speed of the medium, Vd2 is the second linear speed, and Vt2 is a second conveyance speed of the medium.

Abstract: A controller: generates a first corrected pulse signal by correcting a received first pulse signal or generate a second corrected pulse signal by correcting a received second pulse signal, based on a difference value between a first rotation cycle of a first roller and a second rotation cycle of a second roller such that a difference between a first pulse cycle of the received first pulse signal and a second pulse cycle of the received second pulse signal is reduced; upon generating the first corrected pulse signal, controls first print timings in respective first print mechanisms of a first printer based on the generated first corrected pulse signal; and upon generating the second corrected pulse signal, controls second print timings in respective second print mechanisms of a second printer based on the generated second corrected pulse signal.

Abstract: A scale is configured to measure a displacement or velocity of a rotating object. The scale includes a first region that includes a first mark row including a plurality of marks arranged in a first period, and a second region that includes a second mark row including a plurality of marks arranged in a second period having a phase continuity with the first mark row formed in the first region. A periodic mark row including the first mark row and the second mark row is formed over an entire circumference of the rotating object including the first region and the second region.

Abstract: An image forming apparatus including a first sensor configured to output a signal in response to detecting passage of each sheet fed by a sheet feeder, a second sensor configured to output a signal in response to detecting passage of each sheet re-conveyed by a re-conveyance unit, and a controller configured to acquire a passing time period during which a preceding sheet fed by the sheet feeder is passing through the first sensor, based on the signal from the first sensor, determine an adjustment time period between a time when a leading end of the preceding sheet re-conveyed by the re-conveyance unit is detected based on the signal from the second sensor and a time for the sheet feeder to feed a subsequent sheet toward the image forming unit, and control the sheet feeder to feed the subsequent sheet toward the image forming unit with timing adjusted based on the determined adjustment time period.

Abstract: An image forming apparatus comprises a first roller, a second roller and a control section. The first roller is arranged on a conveyance path of a sheet. The second roller is arranged downstream side of the first roller in the conveyance path. The control section calculates a deflection amount of the sheet nipped by the first roller and the second roller based on a conveyance speed of the sheet conveyed along the conveyance path, and controls a rotation speed of at least one of the first roller and the second roller based on the calculated deflection amount.

Abstract: A method of controlling a printing apparatus, comprises printing an image on a sheet; measuring a printing speed of the printing; and storing, for each printing speed measured in the measuring, a number of sheets printed in the printing.

Abstract: In a constitution in which a power source exclusively for primary-transfer is omitted and a predetermined voltage is generated in an intermediary transfer member, in a test mode in which a test voltage is applied to a secondary-transfer member in advance in order to obtain a proper secondary transfer voltage, in the case where the test voltage is low, a proper secondary-transfer voltage cannot be obtained in some cases. In a period of the test mode, the power source is controlled in order to maintain a Zener breakdown voltage, so that the proper secondary-transfer voltage can be obtained.

Abstract: A transporting device includes a detecting portion that detects a load applied to a driving portion provided for transporting a medium, an identifying portion that identifies a type of the medium from a result of detection performed by the detecting portion, and a correcting portion that fits, if a predetermined instruction is made, the result of detection to a predetermined reference characteristic of the load applied to the driving portion.

Abstract: An image forming apparatus including a driving source, a planetary gear mechanism including first, second and third elements, a rotation restraint member configured to switch the planetary gear mechanism between a locked state where rotation of the second element is locked and a released state where the second element is capable of rotating, and a switching mechanism configured to switch the planetary gear mechanism between a first state where any two elements of the first, second and third elements are separated and a second state where the two elements are coupled, wherein the third element is configured to rotate in a first direction when the planetary gear mechanism is in the locked state and first state and to rotate in a second direction opposite to the first direction when the planetary gear mechanism is in the released state and second state.

Abstract: A motor control device includes a detecting unit configured to detect rotation of a motor to be controlled and output a rotation detection value related to the rotation; a drive control unit configured to perform drive control to rotate the motor at a control target value increasing with time based on the rotation detection value; and an abnormality detection unit configured to perform an abnormality detection process for detecting an abnormality in the drive control based on the rotation detection value and a predetermined threshold. The drive control unit performs control to stop rotation of the motor when the abnormality is detected.

Abstract: An image forming apparatus includes a detection unit, a determination unit, and a control unit. The detection unit detects a length of a conveyed recording medium. The determination unit determines the number of recording media conveyable in double-sided image formation, on the basis of a result of detection by the detection unit. The control unit controls, on the basis of a result of determination by the determination unit, the order in which image forming operations are performed when the double-sided image formation is performed on a plurality of recording media.

Abstract: An image forming apparatus includes an image forming unit configured to form a measurement image on a sheet, a measurement unit configured to emit light to the measurement image, and measure light reflected from the measurement image, a selection unit configured to select one of a first mode for feeding a sheet, forming a measurement image on the sheet with the image forming unit, and measuring the measurement image on the sheet with the measurement unit, and a second mode for feeding a chart on which a measurement image has already been formed, and measuring the measurement image on the chart with the measurement unit without performing image formation with the image forming unit, and a control unit configured to control the measurement unit to perform measurement of the measurement image according to the mode selected by the selection unit.

Abstract: An image forming apparatus including a transmission mechanism transmitting a driving force in a transmission direction from a driving source to an output unit, the transmission mechanism including a movable gear configured to move between a transmission position where, when the driving source generates the driving force in a first rotational direction, and a clutch is in a rotating state, the movable gear is allowed to rotate without contacting a lock member, and a restriction position where, when the driving source generates the driving force in a second rotational direction, the clutch is in an idling state, the movable gear is restricted from rotating by contact with the lock member.

Abstract: An improved image forming apparatus is described in which, even when a conveyance unit is switched from a pressure engaged state to a disengaged state, misalignment of a sheet during conveyance can be inhibited. A control unit conveys a sheet between a transfer unit and paper stop rollers, while forming a loop of the sheet therebetween, by setting the speed of conveying the sheet passing between the paper stop rollers to be higher than the speed of conveying the sheet passing through the transfer unit. In addition to this, when the pair of rollers serving as the paper stop rollers are switched from a pressure engaged state to a disengaged state, the paper stop rollers are controlled to reduce the speed of conveying the sheet therethrough in advance of this switching operation.

Abstract: An ink jet printing control method and device, the method comprising: judging whether the interval distance between a detected current color code on a print stock and the previous color code of the current color code is smaller than a time delay distance; if yes, then recording the interval distance, and printing the content corresponding to the current color code after the print stock has moved for a period of time required for the interval distance from the time when the content corresponding to the previous color code is completely printed.

Abstract: An image forming apparatus has an image bearing member bearing a toner image, a transfer part transferring the toner image from the image bearing member onto a sheet, a separation/feeding part separating and feeding sheets stacked on a sheet stacking member, and a transport part transporting the sheet fed by the separation/feeding part to the transfer part, in which a transporting operation of the transport part is changed according to a length of the sheet to be transported in a transport direction of the sheet. A control is configured to control so that a timing to decelerate to the transfer speed by the transport part with respect to a start of image formation is changed according to a length of the transported sheet in a transport direction of the sheet.

Abstract: An image forming apparatus including an image forming unit configured to form an image on the image bearing member, a transfer unit configured to transfer the image on the image bearing member to a recording material, a conveyance unit configured to convey the recording material to the transfer unit, a controller configured to form a test sheet by causing a test image to be formed on the image bearing member such that the test image has a predetermined density and causing the test image to be transferred to the recording material, and a determination unit configured to determine a conveyance speed of the recording material such that a density difference between a density of the test image on the test sheet and the predetermined density is less than or equal to a threshold value.

Abstract: An image forming apparatus includes a pre-transfer conveying portion that conveys a recording medium, an image bearing member that moves while bearing a toner image, a conveying belt that attracts the recording medium conveyed from the pre-transfer conveying portion and conveys the recording medium at the same speed as the image bearing member, a detecting portion that detects the recording medium attracted to the conveying belt, and a control unit that controls the speed at which the pre-transfer conveying portion conveys the recording medium. On the basis of the detection of the recording medium, the control unit changes the speed of the pre-transfer conveying portion from a speed slower than the speed of the conveying belt to a speed equal to or faster than the speed of the conveying belt, and thereby causes the leading edges of the toner image and the recording medium to coincide.

Abstract: An image forming apparatus includes a rotatable image bearing member provided with a mark; a driving portion for rotationally driving the image bearing member; a first detecting portion for detecting speed information of the image bearing member by detecting the mark moved in a predetermined first distance; a second detecting portion for detecting speed information of the image bearing member by detecting the mark moved in a second distance shorter than the predetermined first distance; a filter circuit for suppressing a high-frequency part of an output from the detecting portion and a low-frequency part of an output from the second detecting portion; a calculating portion for calculating a speed of the image bearing member detected from an output from the filter circuit; and a controller for controlling the driving portion so that the calculated speed of the image bearing member is a set speed.

Abstract: An actual sheet interval from a preceding sheet to a succeeding sheet is detected by a top sensor. A registration roller is accelerated or decelerated such that the sheet interval from the preceding sheet to the succeeding sheet is an ideal value by the time that the leading edge of the succeeding sheet reaches a transfer nip part. Note that a time period during which acceleration or deceleration is applied and a sub-scan synchronization signal output timing are determined from the actual sheet interval. Note that a recording sheet P does not stop at the registration roller.

Abstract: The image forming apparatus detects a color deviation amount in a timing when a developing roller separates from or contacts a photosensitive drum to set a difference in peripheral velocities between the photosensitive drum and an intermediate transfer belt or a transfer material conveying belt based on the color deviation amount and information about the use degree of the intermediate transfer belt.

Abstract: An image forming apparatus and method are provided. The image forming apparatus includes a communication interface unit that receives printing data, an image forming unit that performs an ordinary printing to form an image on printing paper based on the printing data, a paper supplying unit that provides the printing paper to the image forming unit along with a paper supplying route, a determination unit that determines whether a functional printing may be performed on the paper supplying route in an interval section between sheets of the printing paper, and a controller that controls the image forming unit to perform a functional printing, wherein the ordinary printing is a printing performed on one or more sheets of printing paper, and the functional printing is a printing performed in an interval section between the sheets of printing paper.

Abstract: The speed at which transfer-material enters a transfer region is controlled to prevent a phenomenon in which a toner image on an intermediate transfer belt is scraped by the leading edge of the transfer-material when the toner image is transferred onto the transfer-material. While the conveying speed of the transfer-material in a transfer nip coincides with the speed of the intermediate transfer belt, the transfer-material is conveyed at a speed lower than the peripheral speed of the intermediate transfer belt when the leading edge of the transfer-material comes into contact with the intermediate transfer belt, and the conveying speed of the transfer-material is increased by the time when the transfer-material enters the transfer nip.

Abstract: A duplex scanning apparatus and a sheet-feeding control method thereof are provided. The duplex scanning apparatus includes a sheet feeding channel, a sheet transfer channel, an inverting channel, and a sheet sensing module. A first end of the inverting channel is connected to a junction between said sheet feeding channel and the sheet transfer channel. A second end of the inverting channel is connected to the sheet transfer channel. A distance between the sheet sensing module and the first end of the inverting channel is greater than a distance between the sheet sensing module and the second end of the inverting channel. When a document is transferred through the sheet sensing module at the second time, a next document is fed into the sheet feeding channel through a sheet entrance.

Abstract: An image processing apparatus includes: a transport roller for transporting a sheet subjected to image processing; a motor that drives the transport roller to rotate; and a speed reduction unit that performs a speed reduction control on the motor to temporarily stop the sheet, the speed reduction control being performed in a manner that a stopping time and a stopping distance each satisfy a corresponding target range, wherein the speed reduction control includes: a first control that is a control of reducing a rotation speed of the motor to a reference speed through at least two operations from among a braking operation, a powering operation, and a free running operation; and a second control that is a control of, after a rotation amount of the motor from the start of the speed reduction control reaches a reference value, continuously performing the braking operation until the stop of the motor.

Abstract: An image forming apparatus includes: an intermediate transfer member onto which a image is primarily transferred from an image forming unit; a transfer unit to secondarily transfer the image from the intermediate transfer member to a media at a secondary-transfer position; a conveying unit configured to convey the media to the secondary-transfer position; and a conveying speed controller to control a speed of conveying the media. The conveying unit includes a first detector and a second detector downstream the first detector and upstream the secondary-transfer position. Based on a detection of the media by the first detector and a timing at which the image forming unit forms the image, the conveying speed controller changes the conveying speed until the second detector detects the media and changes, after the second detector detects the media, the conveying speed to a speed substantially the same as the intermediate transfer member speed.

Abstract: A printer having an imaging drum rotatable around its longitudinal axis, receives a pattern of ink corresponding to an image to be printed. A transfix roller rotates around its longitudinal axis, and is selectively held against the imaging drum by a transfix force, the interface of the imaging drum and the transfix roll forms a transfix nip. An image is formed on the substrate passed through the transfix nip by the marking ink on the imaging drum. A motor drives the imaging drum through a power train with a speed and direction controlled by a motor drive unit. A substrate sensor detects the substrate at the transfix nip, and outputs a signal to the motor drive. The motor drive varies the torque applied to the imaging drum in response to the signal, to maintain a constant rotational speed of the imaging drum.

Abstract: According to the present invention, skew feeding of a sheet is corrected while conveying the sheet, positioning of a side edge of the sheet in the width direction is carried out, and an image is formed on the sheet by an image forming portion 90. Two steering mechanisms 120a and 120b are disposed upstream of the image forming portion along the conveying direction, and the steering mechanisms 120a and 120b can feed a sheet on the skew in any direction with respect to the sheet conveying direction. Two CISs 100a and 100b are disposed along the sheet conveying direction corresponding to the steering mechanisms. A skew feeding angle and a skew feeding velocity of each of the steering mechanisms is changed according to differential value between a side edge position detected by the CISs 100a and 100b and a target position of a side edge of a sheet.

Abstract: An image forming apparatus has an intermediate transfer member to which an image on an image bearing member is primarily transferred. The image primarily transferred to the intermediate transfer member is secondarily transferred to a recording medium. The velocity at which the recording medium is conveyed is switched to a velocity different from the image forming velocity before the recording medium is conveyed to the transfer position.

Abstract: An image forming apparatus has an intermediate transfer member to which an image on an image bearing member is primarily transferred. The image primarily transferred to the intermediate transfer member is secondarily transferred to a recording medium. The velocity at which the recording medium is conveyed is switched to a velocity different from the image forming velocity before the recording medium is conveyed to the transfer position.

Abstract: An image forming apparatus receives input of sheet information of a print sheet designated as a print destination of print data by a predetermined information processing apparatus as first sheet information, and stores therein sheet information of a print sheet designated as a print destination in advance by the image forming apparatus as second sheet information. A feed-timing determining unit compares the first sheet information with the second sheet information and determines the feed timing of a print sheet contained in a feed tray in accordance with the comparison result.

Abstract: Provided is an image forming apparatus for driving a cassette pickup roller (17) and a registration roller (18) by using the same driving source, in which a conveyance control portion (221) starts conveyance speed control for a subsequent sheet, which is fed from a sheet feeding position subsequently to a preceding sheet fed therefrom earlier, when it is determined that a trailing edge of the preceding sheet has passed through the registration roller (18).

Abstract: An image forming apparatus includes an image carrying belt for carrying a toner image; an image forming station for forming toner image on the image carrying belt; a sheet feeding belt for feeding a sheet; a transfer member for transferring the toner image from the carrying belt onto the sheet fed on the feeding belt; and a controller for controlling speeds of the carrying belt and the feeding belt. The controller is capable of controlling a relative speed between the carrying belt and the feeding belt at multiple levels. The image forming station forms a first toner pattern on the carrying belt in a state that the relative speed is at a first level, and forms a second toner pattern on the carrying belt in a state that the relative speed is at a second level which is different from the first level. The transfer member transfers the first toner pattern and the second toner pattern onto the sheet carried on the feeding belt.

Abstract: The present invention provides an image forming apparatus including an upstream conveying portion, a downstream conveying portion, and a loop detector, wherein the image forming apparatus further includes a driving portion which moves the contact portion to a projecting position where the sheet conveying path is in contact with a conveyed sheet and to a retracted position where the sheet conveying path is not in contact with the conveyed sheet, and a controlling portion which controls the driving portion such that the contact portion is moved from the projecting position to the retracted position before a tip end of a sheet which enters the sheet conveying path from the upstream conveying portion reaches the contact portion.

Abstract: An image forming apparatus includes a paper cassette feeding a recording material, an image forming unit forming an image on a photosensitive member, a primary transfer roller transferring the image onto an intermediate transfer belt, a secondary transfer roller transferring the image onto the recording material, and a sensor detecting the size of the recording material. The timing of starting feeding the recording material is earlier than the timing of starting forming the image. When image formation on the recording material is started, until the sensor detects the size of the recording material, a plurality of images are formed on the intermediate transfer belt at a first interval according to a predetermined recording material size, and after the sensor detects the size of the recording material, a plurality of images are formed on the intermediate transfer belt at a second interval according to the detected recording material size.

Abstract: A method and system for insuring printing accuracy in simplex imaging or duplex imaging, including a media sheet in a media path adapted to move the media sheet through the system. The media path includes sensors and a datum. The sensors include a leading edge sensor and a trailing edge sensor adapted to record the time of arrival of the edge. The edge arrival time difference is determined between the arrival time of the edge using output from the trailing edge sensor and the arrival time of the edge using output from the leading edge sensor. A correction factor is based upon the time difference. The time of arrival of the media sheet at the datum is determined using the correction factor to align items printed on both side of the media sheet.

Abstract: An image forming apparatus including an image forming apparatus and an image checking apparatus. The image forming apparatus includes a transport control unit which transports a recording medium at a transport speed, and forms an image on the recording medium. The image checking apparatus includes a transport-speed acquisition unit, a detector, a reading unit, and an operation-state notification unit. The transport-speed acquisition unit acquires transport-speed information from the image forming apparatus. The detector detects a mark shown on the recording medium. The reading unit reads a checking-target image formed by the image forming apparatus at a position distant from the mark, on the basis of the transport-speed information and information concerning a positional relationship between the mark and the checking-target image. The operation-state notification unit notifies the image forming apparatus of an operation state of the image checking apparatus.

Abstract: A controlled velocity decoupling device for improved media registration at transfer in a reprographic device includes a one-way clutch in a drive roll of a registration subsystem to decouple velocities between the registration subsystem and a charge retentive surface. The one-way clutched drive roll prevents the formation of a buckle in a sheet prior to the sheet engaging the charge retentive surface, and thus allowing for more controlled registration of the sheet to the charge retentive surface. The drive roll is set to a lower speed than the charge retentive surface in order to allow for variability in the velocity differences and ensure that no buckle is formed prior to transfer.

Abstract: A printing machine includes: a reception unit configured to receive image data; a printing unit configured to print on a print medium based on the image data received by the reception unit; a first paper feeding unit configured to take out and convey a print medium on a paper feed tray one by one; a second paper feeding unit configured to convey a print medium conveyed by the first paper feeding unit to the printing unit; and a print control unit configured to drive the first paper feeding unit to start conveyance of a print medium upon start of reception of the image data by the reception unit.

Abstract: In an image forming apparatus when a transfer material is fed at a first speed, a moving speed of an image bearing member, an exposure speed of an exposure device in a moving direction of the image bearing member, and a moving speed of an intermediary transfer member are equal to the first speed. When the transfer material is fed at a second speed which is lower than the first speed, the moving speed of the image bearing member is equal to the first speed, and the exposure speed of the exposure device and the moving speed of the intermediary transfer member are equal to the second speed.

Abstract: A sheet feeding device includes a first roller configured to feed a sheet in a first direction along a first feed path, a second roller arranged on a downstream side of the first roller and configured to feed the sheet in the first direction along the first feed path, a sheet detection unit arranged between the first roller and the second roller. A rotation amount of the second roller from detection of the leading end of the sheet by the sheet detection unit to arrival of the sheet at a predetermined position on the downstream side is compensated based on the rotation speed of the first roller within a first period, which is a period from start of feeding of the sheet as the first roller is started to be driven to the detection of the leading end of the sheet by the sheet detection unit.

Abstract: A semiconductive polyimide resin belt that exhibits excellent electrical properties, including the ability to achieve accurate image transfer in a color image-forming unit, and the ability to prevent variations in resistance due to the transfer voltage, enabling high-quality transfer images to be stably produced over an extended period of time; and excellent physical properties, including resistance to deterioration in flatness due to plastic deformation caused by loads applied in the width direction of the belt, excellent durability, and stable operation even after extended use; and an intermediate transfer belt made of the semiconductive polyimide resin belt. The semiconductive polyimide resin belt comprises carbon black and a polyimide resin.

Abstract: A length L of the test pattern string is determined so as to satisfy a condition L?{P?(Q1+Q2)}×V, where a time Q is a total time of a time Q1 for which the test pattern string is transferred from an exposure position of the test pattern string to a sensor and a time Q2 from when the test pattern is detected by the sensor until a color misregistration correction value calculated on the basis of a result of detecting is reflected in image formation; a time P is a time from a timing of starting to write the test pattern string to a timing of starting to write an image in which the correction value should be reflected; and a driving speed of a second image carrier is V.