JP2016155247A - Image formation apparatus, image formation method and image formation program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust an image position shift due to the difference in the drive nozzle numbers.SOLUTION: An image formation apparatus 1 comprises: a reference pattern formation part 302 which forms a reference pattern composed of two reference lines by causing a discharge part 304 to drive nozzles in a predetermined reference nozzle number with a reference drive waveform generated by a drive waveform generation part 301; an adjustment pattern formation part 303 which causes the discharge part 304 to form a plurality of adjustment patterns composed of a reference line by driving with the reference drive waveform of the nozzles in the reference nozzle number and a plurality of adjustment lines by driving with combination of the nozzles in the plurality of adjustment object nozzle numbers being the nozzle number different from the reference nozzle number and the plurality of adjustment drive waveforms; a distance acquisition part 305 which acquires a reference distance between the reference lines and adjustment distances between each reference line and the adjustment lines; and a waveform determination part 306 which determines a correction value to the reference drive waveform of the drive waveform driving the nozzles in the adjustment object nozzle numbers on the basis of the reference distance and the plurality of adjustment distances.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an image forming apparatus, an image forming method, and an image forming program. More specifically, the present invention relates to an image forming apparatus, an image forming method, and an image forming program that simultaneously drive a plurality of nozzles to eject liquid droplets. .

  Conventionally, a liquid ejection type image forming apparatus, in particular, printing (image formation) in both forward and backward directions by reciprocating a carriage mounted with a recording head on which a plurality of nozzles for ejecting droplets are formed. There is an image forming apparatus to perform. Such an image forming apparatus intermittently conveys a sheet as a recording medium in the sub-scanning direction, and simultaneously stops a plurality of nozzles of the recording head in the main scanning direction while the conveyance of the sheet is stopped. The image is formed by driving.

  In order to improve the image forming speed, the image forming apparatus forms an image by ejecting liquid droplets in both the forward and backward directions of the carriage.

  However, when the image forming apparatus forms an image in both the forward and backward directions of the carriage, the landing positions of the droplets ejected from the recording head mounted on the carriage on the recording medium are misaligned between the forward and backward paths. However, there is a problem that image degradation occurs. In particular, the conventional image forming apparatus has a problem that when the formed image is a ruled line or the like, the image quality deterioration due to the misalignment is easily noticeable.

  Therefore, conventionally, an image forming apparatus prints a test pattern for automatic adjustment of ruled line printing position deviation on a recording medium, reads the test pattern with a reflective sensor, and adjusts the ejection timing based on the read result. ing.

  For example, conventionally, a recording head having a nozzle hole array in which a plurality of nozzle holes that eject ink droplets by driving a piezoelectric element are arranged, a recording head driving unit that drives the piezoelectric element of the recording head, and the recording head driving unit In addition, an image data signal and a drive waveform output signal for driving the piezoelectric element of the recording head in response to the image data signal are sent to control the ejection of ink droplets from the nozzle holes of the recording head In the image forming apparatus including the head control unit, the recording head control unit counts the number of nozzle holes for simultaneously ejecting ink droplets from the image data signal, and the image data count unit counts the nozzle holes. A first correction table storing a correction amount of an output timing of a drive waveform output signal for driving the piezoelectric element according to the number of nozzle holes And a drive waveform control section that sends the drive waveform output signal to the recording head drive section at an output timing based on the first correction table has been proposed (see Patent Document 1). ).

  In other words, this conventional technique adjusts the output timing of the drive waveform output signal according to the number of nozzles to be ejected simultaneously based on a correction table prepared in advance, thereby reducing undershoot, overshoot, and rise / fall delay. Trying to control.

  However, in the above prior art, a correction table generation method for determining the output timing of the drive waveform output signal according to the number of nozzles to be discharged at the same time is not described, and the number of nozzles that are simultaneously driven by experiments or the like is not described. The determination of the drive waveform signal and the output timing according to the above has a problem of poor workability.

  Further, the positional deviation due to the difference in the number of drive nozzles is caused not only by the ejection speed of the droplets ejected from each nozzle but also by the variation in the ejection amount depending on the number of drive nozzles. However, the conventional technique does not take into account fluctuations in the droplet discharge amount due to the difference in the number of drive nozzles, and improves the image quality by adjusting the displacement of the droplet landing position. There was a need for improvement.

  Accordingly, an object of the present invention is to adjust the positional deviation of the landing position of a droplet caused by the number of drive nozzles.

  In order to achieve the above object, an image forming apparatus according to claim 1, wherein a plurality of nozzles are driven by a drive signal having a predetermined drive waveform to discharge droplets onto a recording medium; Drive waveform generation means for generating a reference drive waveform and a plurality of adjustment drive waveforms different from the reference drive waveform; and at least 2 by causing the ejection means to drive the nozzles of a predetermined reference nozzle number with the reference drive waveform. A reference pattern forming means for forming a reference pattern comprising a plurality of reference lines, a reference line by driving the nozzles of the reference nozzle number with the reference drive waveform, and a plurality of adjustments of the number of nozzles different from the reference nozzle number A plurality of adjustment patterns including a plurality of adjustment lines driven by a combination of the number of target nozzles and a plurality of the adjustment drive waveforms are provided as the ejection hand. An adjustment pattern forming means to be formed, a distance acquisition means for acquiring a reference distance of the reference line, an adjustment distance between each reference line and the adjustment line, and the adjustment based on the reference distance and the plurality of adjustment distances. Drive waveform determining means for determining a correction value for the reference drive waveform of the drive waveform for driving the nozzles of the number of target nozzles.

  According to the present invention, it is possible to adjust the positional deviation of the landing position of the droplet due to the number of drive nozzles.

1 is a schematic perspective view of an image forming apparatus to which an embodiment of the present invention is applied. The top view of a carriage part. FIG. 3 is a block diagram of a main part of the image forming apparatus. FIG. 3 is a configuration diagram around a misregistration detection unit. The block block diagram of FPGA. The figure which shows an example of a reference | standard drive waveform and a 1.2 times drive waveform. 1 is a functional block diagram of an image forming apparatus. The figure which shows an example of a pattern. The figure which shows the relationship between the number of drive nozzles, a droplet discharge speed, and a droplet discharge amount. The figure which shows an example of the flat bridge to the image by the number of drive nozzles. The figure which shows the relationship between the number of drive nozzles, and the image density for every drive waveform magnification. The flowchart which shows an image position shift detection process. The flowchart which shows a sensor calibration process. The figure which shows an example of a pattern formation procedure. FIG. 4 is a diagram illustrating a pattern formation example when the reading sensor is at the center position of the recording head. The figure which shows pattern formation in case a reading sensor reads in multiple places of a recording head. The figure which shows the example of pattern formation in the case of forming multiple patterns of the same drive waveform magnification. The flowchart which shows a pattern data reading process. The figure which shows the relationship between the passage of the reading spot of a reading sensor, and the width | variety of a putter. The figure which shows the relationship between a reading light spot, a pattern, and a sensor output voltage. The enlarged view of a reference pattern and an adjustment pattern. The figure which shows the relationship between the drive waveform magnification of a reference pattern and an adjustment pattern, and distance. FIG. 23 is a diagram showing an example of an image formed with a drive waveform magnification of 1.15 when the number of drive nozzles in the adjustment pattern of FIG. The figure which shows the relationship between the number of drive nozzles, and drive waveform magnification.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, since the Example described below is a suitable Example of this invention, various technically preferable restrictions are attached | subjected, However, The range of this invention is unduly limited by the following description. However, not all the configurations described in the present embodiment are essential constituent elements of the present invention.

  1 to 24 are diagrams showing an embodiment of an image forming apparatus, an image forming method, and an image forming program according to the present invention. FIG. 1 shows an image forming apparatus, an image forming method, and an image forming program according to the present invention. 1 is a schematic perspective view of an image forming apparatus 1 to which an embodiment is applied.

  In FIG. 1, an image forming apparatus 1 is an image forming apparatus of a serial type liquid discharge method (ink discharge method), and a main body casing 2 is disposed on a main body frame 3. In the image forming apparatus 1, a main guide rod 4 and a sub guide rod 5 are stretched in a main body housing 2 in the main scanning direction indicated by a double arrow A in FIG. The main guide rod 4 movably supports the carriage 6, and the carriage 6 is provided with a connecting piece 6 a that engages with the sub guide rod 5 to stabilize the posture of the carriage 6.

  In the image forming apparatus 1, an endless belt-like timing belt 7 is disposed along a main guide rod 4, and the timing belt 7 is stretched between a driving pulley 8 and a driven pulley 9. The drive pulley 8 is rotationally driven by the main scanning motor 10 and is disposed in a state in which a predetermined tension is applied to the timing belt 7. The driving pulley 8 is rotationally driven by the main scanning motor 10 to rotate and move the timing belt 7 in the main scanning direction according to the rotation direction.

  The carriage 6 is connected to the timing belt 7 by a belt holding portion 6b (see FIG. 2), and the timing belt 7 is rotated and moved in the main scanning direction by the drive pulley 8 so that the main belt 4 is moved along the main guide rod 4. Reciprocates in the scanning direction.

  In the image forming apparatus 1, the cartridge unit 11 and the maintenance mechanism unit 12 are accommodated at both end positions in the main scanning direction in the main body housing 2. In the cartridge unit 11, cartridges that respectively store yellow (Y), magenta (M), cyan (C), and black (K) liquids (inks) are exchangeably stored. Each cartridge of the cartridge unit 11 is connected to recording heads 20y, 20m, 20c, and 20k (see FIG. 2) of the corresponding color of the recording head 20 mounted on the carriage 6 by a pipe (not shown). Each cartridge supplies a liquid (ink) of a corresponding color to the recording heads 20y, 20m, 20c, and 20k through a pipe. In the following description, the recording heads 20y, 20m, 20c, and 20k are collectively referred to as the recording head 20.

  As will be described later, the image forming apparatus 1 moves on the platen 14 (see FIG. 2) in the sub-scanning direction (arrow B direction in FIG. 1) perpendicular to the main scanning direction while moving the carriage 6 in the main scanning direction. An image is recorded and output on the recording medium P by ejecting liquid onto the recording medium (such as paper) P that is intermittently conveyed.

  That is, the image forming apparatus 1 according to the present embodiment intermittently conveys the recording medium P in the sub-scanning direction, and performs the main scanning of the carriage 6 while the conveyance of the recording medium P in the sub-scanning direction is stopped. While moving in the direction, liquid is ejected from the nozzle rows of the recording heads 20y, 20m, 20c, and 20k onto the recording medium P on the platen 14, and an image is formed on the recording medium P.

  The maintenance mechanism unit 12 performs cleaning of the ejection surface of the recording head 20, capping, ejection of unnecessary liquid, and the like to discharge unnecessary liquid from the recording head 20 and maintain the reliability of the recording head 20. .

  The image forming apparatus 1 is provided with a cover 13 that can open and close a conveyance portion of the recording medium P. When the image forming apparatus 1 is maintained or when a jam occurs, the cover 13 is opened so that the inside of the main body housing 2 can be opened. Maintenance work and removal of the jammed recording medium P can be performed.

  As shown in FIG. 2, the carriage 6 is mounted with recording heads 20y, 20m, 20c, and 20k. The recording heads 20y, 20m, 20c, and 20k are piped to the cartridges of the corresponding colors of the cartridge unit 11, respectively. Are connected to each other, and liquids of corresponding colors are discharged onto the recording medium P facing each other. That is, the recording head 20y is a yellow (Y) liquid, the recording head 20m is a magenta (M) liquid, the recording head 20c is a cyan (C) liquid, and the recording head 20k is a black (K). Each liquid is discharged.

  The recording head 20 is mounted on the carriage 6 so that the ejection surfaces (nozzle surfaces) of the recording heads 20y, 20m, 20c, and 20k face downward (recording medium P side) in FIG. A liquid is discharged onto the medium P.

  In the image forming apparatus 1, an encoder sheet 15 is disposed in parallel with the timing belt 7, that is, the main guide rod 4 over at least the movement range of the carriage 6. An encoder sensor 21 that reads the encoder sheet 15 is attached to the carriage 6. The image forming apparatus 1 controls the movement of the carriage 6 in the main scanning direction (arrow A direction in FIG. 2) by controlling the driving of the main scanning motor 10 based on the reading result of the encoder sheet 15 by the encoder sensor 21. .

  The main guide rod 4 and the sub guide rod 5 are bridged between the left and right side plates 2a, 2b of the main body housing 2 and fixed.

  As shown in FIG. 2, the recording heads 20 mounted on the carriage 6 are each composed of a plurality of nozzle rows 20y, 20m, 20c, and 20k. The recording head 20 forms an image on the recording medium P by ejecting liquid from the nozzle row onto the recording medium P conveyed on the platen 14 in the sub-scanning direction (the direction of arrow B in FIG. 2). In the image forming apparatus 1, in order to ensure a wide width of an image that can be formed on the recording medium P by one scan of the carriage 6, and to improve the black printing speed, the upstream recording is performed on the carriage 6. A head 20 and a recording head 20 on the downstream side are mounted.

  A reading sensor 30 is attached to the carriage 6, and the reading sensor 30 reads patterns Tk and Tc (see FIG. 8 and the like) recorded on the recording medium P during image position deviation detection processing described later. The reading sensor 30 will be described later. In the following description, the reference pattern Tk and the adjustment pattern Tc are also collectively referred to as a pattern T as appropriate.

  The image forming apparatus 1 is configured as a block as shown in FIG. The image forming apparatus 1 includes a control unit 100, a carriage 6, a main scanning motor 10, an encoder sensor 21, a rotary encoder 201, a sub-scanning motor 202, a feeding motor 203, a discharge motor 204, an image reading unit 205, an operation display unit 206, and the like. It has. The carriage 6 is equipped with a reading sensor 30 and recording heads 20y to 20k. In addition to the above, the image forming apparatus 1 includes a maintenance / recovery motor that drives the maintenance mechanism unit 12, a recovery system drive unit that drives the maintenance / recovery motor, and a solenoid drive unit that drives various solenoids. Although not shown, a clutch drive unit for driving the motor is provided. Further, in the image forming apparatus 1, detection signals of other various sensors are input to the main control unit 101, but the illustration is omitted.

  The control unit 100 includes a main control unit 101, an external I / F 102, a head drive control unit 103, a main scan drive unit 104, a sub scan drive unit 105, a feed drive unit 106, a discharge drive unit 107, a scanner control unit 108, and the like. I have. The main control unit 101 includes a CPU (Central Processing Unit) 111, a ROM (Read Only Memory) 112, a RAM (Random Access Memory) 113, an NVRAM (Non-Volatile Random Access Memory) 114, an ASIC (Application Specific Integrated Circuit) 115, and An FPGA (Field Programmable Gate Array) 116 or the like is mounted.

  The main control unit 101 stores a basic program as the image forming apparatus 1 and a program such as an image forming program for detecting an image misregistration of the present invention and necessary data in the ROM 112. In the main control unit 101, the CPU 111 controls each unit of the image forming apparatus 1 based on a program in the ROM 112 to execute basic processing as the image forming apparatus 1, and detects image misregistration of the present invention described later. An image forming method involving processing is executed. In this operation process, the CPU 111 uses the RAM 113 as a work memory.

  The NVRAM 114 stores and reads data to be stored even when the power of the image forming apparatus 1 is off under the control of the CPU 111. In particular, the NVRAM 114 stores data necessary for executing the image forming method of the present invention, such as a drive waveform correction value based on an adjustment pattern described later.

  The ASIC 115 performs image processing such as various signal processing and rearrangement on the image data, and the FPGA 116 processes input / output signals for controlling the entire image forming apparatus 1.

  The external I / F 102 interfaces communication with other devices and the main control unit 101 via a network such as a LAN (Local Area Network) or a communication line such as a dedicated line, and sends data from an external device to the main control unit 101. Send it out. The external I / F 102 outputs the data generated by the main control unit 101 to the external device. The external I / F 102 can be loaded with a removable storage medium, and is distributed via a state where the program is stored in the storage medium or an external communication device.

  The head drive control unit 103 controls the recording heads 20y to 20k onto the recording medium P by controlling the presence or absence of the liquid ejection of each of the recording heads 20y to 20k, the droplet ejection timing when ejecting, and the drive waveform of the drive signal. Record an image. The head drive control unit 103 has a head data generation array conversion ASIC (head driver) for driving and controlling the recording heads 20y to 20k, and based on the print data (dot data subjected to dithering processing, etc.) A drive signal having a drive waveform indicating the presence / absence of a droplet and the size of the droplet is generated and supplied to the recording heads 20y to 20k. Each of the recording heads 20y to 20k has a switch for each nozzle of the recording heads 20y, 20m, 20c, and 20k, and is turned on / off based on a drive signal, whereby the recording medium P specified by the print data. A droplet of the size specified at the position of is landed. The head driver of the head drive control unit 103 may be provided on the recording heads 20y to 20k side, or the head drive control unit 103 and the recording heads 20y to 20k may be integrated. Further, the head drive control unit 103 controls the drive of the recording heads 20y to 20k to record a pattern T, which will be described later, on the recording medium P as an image.

  The main scanning drive unit 104 drives the main scanning motor 10 that moves and scans the carriage 6 in the main scanning direction under the control of the main control unit 101.

  The main control unit 101 receives a reading result signal from the encoder sensor 21 that reads the encoder sheet 15, and the main control unit 101 detects the position of the carriage 6 in the main scanning direction based on the reading result signal. The main control unit 101 drives and controls the main scanning motor 10 via the main scanning driving unit 104 to reciprocate the carriage 6 to an intended position in the main scanning direction.

  The sub-scanning drive unit (motor driver) 105 drives the sub-scanning motor 202 that conveys the recording medium P.

  The main control unit 101 receives a detection signal (pulse) from a rotary encoder 201 that detects the rotation of the sub-scanning motor 202. The main control unit 101 detects the amount of movement of the recording medium P in the sub-scanning direction based on this detection signal, that is, the medium feed amount, and drives and controls the sub-scanning motor 202 via the sub-scanning driving unit 105. The conveyance control of the recording medium P is performed via a conveyance roller (not shown).

  The feed driving unit 106 drives a feed motor 203 that feeds the recording medium P from a feed tray (not shown).

  The discharge drive unit 107 drives a discharge motor 204 that drives a discharge roller that discharges a printed (image-formed) recording medium P onto a discharge tray (not shown). The discharge driving unit 107 may be substituted by the sub-scanning driving unit 105.

  The scanner control unit 108 controls the driving operation of the image reading unit 205. As the image reading unit 205, for example, an image scanner using a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) is used. The image reading unit 205 scans the document, reads an image of the document with a predetermined resolution, and outputs the scanned image to the scanner control unit 108.

  The operation display unit 206 includes various keys necessary for causing the image forming apparatus 1 to perform various operations, and includes a lamp such as a display (for example, a liquid crystal display) or an LED (Light Emitting Diode). When various operations for causing the image forming apparatus 1 to perform various functional operation processes are performed from the operation keys, the operation display unit 206 passes the operation content to the main control unit 101. The operation display unit 206 also displays on the display display information delivered from the main control unit 101, that is, command contents input from the operation keys and various types of information notified to the user from the image forming apparatus 1. In particular, the operation display unit 206 performs various setting operations necessary for execution of an image forming method that involves an image displacement detection process described later.

  Then, the main control unit 101 drives the recording heads 20y to 20k via the head drive control unit 103 to form the pattern T (reference pattern Tk, adjustment pattern Tc) on the recording medium P. The main control unit 101 calculates a positional deviation amount based on the result of reading the pattern T by the reading sensor 30 and executes a positional deviation adjustment process that determines the drive waveforms of the recording heads 20y to 20k. First, the main control unit 101 performs recording based on the interval (distance between edges or center position distance) of the pattern T recorded on the recording medium P by the head drive control unit 103 and the reading result of the pattern T by the reading sensor 30. A calculation process is performed to calculate a drive waveform correction amount for correcting the displacement of the landing position of the droplets ejected from the heads 20y to 20k and landed on the recording medium P. The main control unit 101 determines a drive waveform correction amount based on the number of nozzles that are simultaneously driven when an image is actually formed, corrects the reference drive waveform with the drive waveform correction amount, and the head drive control unit 103. The recording heads 20y to 20k are driven.

  Specifically, the main control unit 101 generates a reference drive waveform and a plurality of adjustment drive waveforms different from the reference drive waveform as drive waveforms for driving the nozzles. Further, the main control unit 101 drives a nozzle having a predetermined reference number of nozzles with a reference drive waveform via the head drive control unit 103 to form a reference pattern Tk composed of at least two reference lines Lk. Further, the main control unit 101 controls the reference line Lk by driving with the reference drive waveform of the nozzles of the reference nozzle number, the nozzles having a plurality of adjustment target nozzles having the number of nozzles different from the reference nozzle number, and the plurality of adjustment driving A plurality of adjustment patterns Tc including a plurality of adjustment lines Lc driven by a combination with the waveform are formed via the head drive control unit 103. Then, the main control unit 101 causes the reading sensor 30 described later to acquire a reference distance between the reference lines Lk of the reference pattern Tk and an adjustment distance between the reference line Lk and the adjustment line Lc of each adjustment pattern Tc. Based on the plurality of adjustment distances, a correction value for the reference drive waveform when simultaneously driving the nozzles of the adjustment target nozzle number is determined.

  The main control unit 101 adjusts the positional deviation (landing positional deviation) of the image by correcting the drive waveforms of the recording heads 20y to 20k by the positional deviation adjustment unit 120 shown in FIG.

  The main part of the misalignment adjusting unit 120 is mounted on the main control unit 101. The CPU 111, the light emission control unit 121, the smoothing circuit 122, the drive circuit 123, the photoelectric conversion unit 124, the low-pass filter circuit 125, and the A / D (Analog). / Digital) conversion circuit 126, FPGA 116, shared memory 127, head drive control unit 103, read sensor 30, and the like.

  In the reading sensor 30, a light emitting element 31 and a light receiving element 32 are fixed in a holder 33, and a lens 34 is provided at an emitting part of reading light from the light emitting element 31 and an incident part to the light receiving element 32. Yes. The light emitting element 31 and the light receiving element 32 are arranged side by side in a sub-scanning direction (conveying direction of the recording medium P) orthogonal to the main scanning direction. As a result, the reading sensor 30 can detect the patterns Tk and Tc in a state where the influence due to the movement speed fluctuation of the carriage 6 is reduced.

  In FIG. 4, the holder 33 is fixed to a side surface position of the carriage 6 that coincides with the black (K) recording head 20 k mounted on the carriage 6 in the main scanning direction.

  In FIG. 4, the reading sensor 30 is for detecting an image position deviation of the recording head 20k, and is coincident with the recording heads 20y to 20c in the main scanning direction for detecting an image position deviation of the other recording heads 0y to 20c. It is preferable to mount a reading sensor at a position where the reading is performed. However, the image forming apparatus 1 is provided with a moving mechanism that slides the reading sensor 30 between a position that coincides with the recording head 20k in the main scanning direction and a position that coincides with the recording heads 20y to 20c in the main scanning direction. In this case, it is possible to detect misalignment of all the recording heads 20y, 20m, 20c, and 20k using only one reading sensor 30. Alternatively, the image forming apparatus 1 conveys the recording medium P, on which the pattern T is formed by the recording heads 20y, 20m, and 20c, to the position of the reading sensor 30 in the counter-conveying direction, so that only one reading sensor 30 is provided. By using this, it is possible to detect image positional deviations in all the recording heads 20y, 20m, 20c, and 20k.

  In the reading sensor 30, a relatively simple and inexpensive light emitting element that emits visible light such as an LED (Light Emitting Diode) is used as the light emitting element 31, and a photosensor is used as the light receiving element 32. It is used. Further, the spot diameter d of the reading light spot on the recording medium P by the light emitting element 31 is not a high-precision lens 34, but an inexpensive one is used, and the cost of the image forming apparatus 1 is reduced. In order to make it cheaper, the detection range is on the order of mm.

  The CPU 111 sets a PWM value for driving the light emitting element 31 of the reading sensor 30 in the light emission control unit 121 while moving the carriage 6 in the main scanning direction, and the light emission control unit 121 sets the light emission pulse signal of the PWM value. Is output to the smoothing circuit 122. The smoothing circuit 122 smoothes the light emission pulse signal and outputs it to the drive circuit 123. The drive circuit 123 drives the light emitting element 31 to emit light in accordance with the light emission pulse signal, and the recording target on which the pattern T is formed. The medium P is irradiated with emitted light from the light emitting element 31.

  The reading sensor 30 irradiates the pattern T on the recording medium P with the light emitted from the light emitting element 31, so that the reflected light reflected from the pattern T is incident on the light receiving element 32. The light receiving element 32 outputs an analog detection signal corresponding to the amount of reflected light from the pattern T to the photoelectric conversion unit 124.

  The photoelectric conversion unit 124 photoelectrically converts the detection signal input from the light receiving element 32 of the reading sensor 30 and outputs the photoelectric conversion signal (sensor output voltage) So to the low-pass filter circuit 125.

  The low-pass filter circuit 125 removes noise from the sensor output voltage data and outputs it to the A / D conversion circuit 126, and the A / D conversion circuit 126 converts the sensor output voltage data into digital and outputs it to the FPGA 116.

  The FPGA 116 stores the digitally converted sensor output voltage data in the shared memory 127. The shared memory 127 may be another memory in the main control unit 101, or may be the RAM 113 or the NVRAM 114.

  Then, as will be described later, when the CPU 111 forms a pattern, the reference pattern consisting of at least two reference lines Lk is generated by driving the recording heads 20y to 20k with a reference drive waveform for a predetermined number of reference nozzles. Tk is formed. The CPU 111 also includes a reference line Lk driven by a reference drive waveform of the nozzles of the reference nozzle number, a plurality of adjustment target nozzles having a number of nozzles different from the reference nozzle number, and a plurality of adjustment drive waveforms. The recording heads 20y to 20k are formed with a plurality of adjustment patterns Tc composed of a plurality of adjustment lines Lc driven by the combination of the above.

  The CPU 111 reads the sensor output voltage data from the shared memory 127, detects the center position of the pattern T (reference pattern Tk, a plurality of adjustment patterns Tc), and calculates the deviation amount (difference in distance between patterns) on the actual print. calculate. That is, the CPU 111 calculates the difference between the distance between the reference pattern Tk and each adjustment pattern Tc.

  The CPU 111 drives to drive the nozzles corresponding to the number of nozzles to be adjusted based on the calculated shift amount (difference in distance between patterns), the number of drive nozzles when the pattern T is formed, and the drive waveform (drive waveform magnification). A drive waveform correction value for the reference drive waveform of the waveform is determined. The CPU 111 stores the determined drive waveform correction value as a drive waveform correction table in the internal memory (not shown) of the FPGA 116 or the NVRAM 114 for each of the recording heads 20y to 20k in correspondence with the number of drive nozzles.

  Then, when forming an image, the image forming apparatus 1 corrects the drive waveform from the drive waveform correction value determined by the CPU 111 and the number of drive nozzles determined by the image data, and causes the head drive control unit 103 to record the print heads 20y to 20k. Drive.

  The FPGA 116 has a block configuration as shown in FIG. 5, and includes an image data output unit 131, a drive count unit 132, a drive waveform correction value calculation unit 133, a drive waveform correction unit 134, a drive waveform table 135, and the like. ing.

  The image data output unit 131 holds image data to be ejected in the next cycle. The image data output unit 131 outputs the image data to the recording heads 20 y to 20 k and also outputs it to the drive count unit 132.

  The drive count unit 132 counts the number of drive nozzles based on the image data, and outputs the drive nozzle number to the drive waveform correction value calculation unit 133.

  Based on the number of drive nozzles, the drive waveform correction value calculation unit 133 refers to the internal memory of the FPGA 116 or the drive waveform correction table of the NVRAM 114, determines the drive waveform correction value, and corrects the determined drive waveform correction value to the drive waveform. Output to the unit 134.

  A drive waveform table 135 is connected to the drive waveform correction unit 134, and the drive waveform table 135 stores a reference drive waveform.

  The drive waveform correction unit 134 corrects the reference drive waveform of the drive waveform table 135 with the drive waveform correction value, generates a drive waveform, passes the generated drive waveform to the head drive control unit 103 in FIG. The drive control unit 103 outputs a drive signal having the drive waveform to the recording heads 20y to 20k.

  Specifically, for example, as illustrated in FIG. 6, the drive waveform correction unit 134 multiplies the reference drive waveform by a drive waveform correction value (for example, 1.2), thereby multiplying the correction value (1). .2) drive waveform is generated.

  The recording heads 20y to 20k drive the nozzles corresponding to the image data from the image data output unit 131 based on the drive signal of the drive waveform corrected by the drive waveform correction unit 134 to cause the droplets to be recorded on the recording medium P. To form an image.

  The image forming apparatus 1 includes a ROM, an EEPROM (Electrically Erasable and Programmable Read Only Memory), an EPROM, a flash memory, a flexible disk, a CD-ROM (Compact Disc Read Only Memory), a CD-RW (Compact Disc Rewritable), and a DVD. (Image Versatile Disk), SD (Secure Digital) Card, MO (Magneto-Optical Disc), etc. Recorded on a Computer-Readable Recording Medium, Image Forming for Executing Image Forming Method with Detection of Misalignment of the Present Invention By loading the program and introducing it into the ROM 112 or the like, it is constructed as an image forming apparatus that executes an image forming method accompanied by an image misregistration adjustment method for accurately performing image misregistration adjustment of a formed image, which will be described later. This image forming program is a computer-executable program written in a legacy programming language such as assembler, C, C ++, C #, Java (registered trademark) or an object-oriented programming language, and is stored in the recording medium. Can be distributed.

  In this embodiment, the CPU 111 mainly performs the image misregistration detection process, but part or all of the image misregistration detection process may be performed by an LSI (Large Scale Integration) such as the FPGA 116 or the ASIC 115. Further, in the following description, it is assumed that the main control unit 101 including these performs image positional deviation detection processing.

  In the image forming apparatus 1, the functional blocks as shown in FIG. 7 are constructed by introducing the image forming program. That is, as shown in FIG. 7, the image forming apparatus 1 includes a drive waveform generation unit 301, a reference pattern formation unit 302, an adjustment pattern formation unit 303, an ejection unit 304, a distance acquisition unit 305, a waveform determination unit 306, and head drive control. The unit 307 and the like are constructed.

  The ejection unit 304 is constructed by the recording heads 20y to 20k. The ejection unit 304 ejects droplets onto the recording medium P by driving a plurality of nozzles with a drive signal having a predetermined drive waveform. Therefore, the discharge unit 304 functions as a discharge unit.

  The drive waveform generation unit 301 is constructed by the main control unit 101, in particular, the CPU 111, the NVRAM 114, and the like, and generates a reference drive waveform and a plurality of adjustment drive waveforms different from the reference drive waveform as drive waveforms. Therefore, the drive waveform generation unit 301 functions as drive waveform generation means. That is, the NVRAM 114 or the ROM 112 stores, for example, a reference drive waveform as shown in FIG. 6A in advance, and the CPU 111 sets various magnifications as shown in FIG. 6B to the reference drive waveform. The multiplied adjustment drive waveform is generated and stored in the NVRAM 114.

  The reference pattern forming unit 302 is constructed by the main control unit 101 and the head drive control unit 103. The reference pattern forming unit 302 causes the ejection unit 304 to drive a predetermined number of reference nozzles with a reference drive waveform to form a reference pattern Tk including at least two reference lines Lk. Therefore, the reference pattern forming unit 302 functions as a reference pattern forming unit.

  For example, the reference pattern forming unit 302 sets 100 nozzles as the number of reference nozzles, and, as shown in FIG. 8, two reference lines Lk with 100 nozzles are recorded on the ejection unit 304 with a reference drive waveform. A reference pattern Tk is formed on P. In FIG. 8, the reference pattern Tk is a pattern formed only by the reference line Lk described as 100 ch-100 ch with a drive waveform magnification of “1”.

  Further, in FIG. 8, as indicated by the region L, the drive waveform magnification is also in the columns of “1”, “1.05”, “1.1”, “1.15”, “1.2”. , A reference pattern Tk in which nozzles of 100 ch to 100 ch are driven at a driving waveform magnification “1” is described. The image forming apparatus 1 can also acquire the reference distance by the distance acquisition unit 305 described later without forming the region L. However, the image forming apparatus 1 generates a yawing error in the main scanning direction when the distance acquisition unit 305 acquires a distance. Therefore, the image forming apparatus 1 reduces the influence of the yawing error due to the main scanning position by forming the reference pattern Tk having the drive waveform magnification “1” as shown in the region L as the reference of each drive waveform magnification. Can do.

  The adjustment pattern forming unit 303 is constructed by the main control unit 101 and the head drive control unit 103. The adjustment pattern forming unit 303 includes a reference line Lk driven by a reference drive waveform of nozzles having a reference number of nozzles, a plurality of adjustment target nozzles having a number of nozzles different from the reference nozzle number, and a plurality of adjustment drive waveforms. A plurality of adjustment patterns Tc composed of a plurality of adjustment lines Lc by driving in combination with are formed in the ejection unit 304. Therefore, the adjustment pattern forming unit 303 functions as an adjustment pattern forming unit.

  The adjustment pattern forming unit 303 forms a pattern including the reference line Lk and the adjustment line Lc, for example, a pattern other than the reference pattern Tk shown in FIG. 8 as the adjustment pattern Tc. For example, in the case of the adjustment pattern Tc shown as 100 ch-150 ch, the adjustment pattern forming unit 303 sets one line as a reference line Lk and 150 nozzles as an adjustment line Lc, which is a reference drive waveform and 1.05 times the reference drive waveform. , 1.1 times, 1.15 times, and 1.2 times of the adjustment line Lc having the adjustment drive waveform are formed as a pair.

  The distance acquisition unit 305 is constructed by the reading sensor 30 and the main control unit 101. The distance acquisition unit 305 acquires a reference distance between the reference lines Lk of the reference pattern Tk and an adjustment distance between the reference line Lk of each adjustment pattern Tc and each adjustment line Lc. Therefore, the distance acquisition unit 305 functions as a distance acquisition unit.

  The waveform determination unit 306 is constructed by the main control unit 101, and determines a correction value for the reference drive waveform of the drive waveform for driving the nozzles of the number of adjustment target nozzles based on the reference distance and the plurality of adjustment distances. Therefore, the waveform determining unit 306 functions as drive waveform determining means.

  The head drive control unit 307 is constructed by the main control unit 101. The head drive control unit 307 acquires the number of nozzles that the ejection unit 304 drives simultaneously based on the image data, and acquires the correction value determined by the waveform determination unit 306 based on the number of nozzles and the number of adjustment target nozzles. . Then, the head drive control unit 307 outputs a drive signal having a drive waveform obtained by correcting the reference drive waveform with the correction value to the ejection unit 304. Therefore, the head drive control unit 307 functions as drive control means.

  Next, the operation of this embodiment will be described. The image forming apparatus 1 according to the present embodiment adjusts the positional deviation of the landing position of the liquid droplets due to the number of drive nozzles.

  That is, the image forming apparatus 1 forms the image on the recording medium P by driving the recording heads 20 y to 20 k while causing the carriage 6 to reciprocate in the main scanning direction to eject droplets toward the recording medium P. To do. Therefore, in the image forming apparatus 1, the landing position of the droplet on the recording medium P differs depending on the number of nozzles to be driven.

  The image forming apparatus 1 changes the droplet discharge speed and the droplet discharge amount depending on the number of nozzles that are simultaneously driven among the nozzles formed in the sub-scanning direction in the recording heads 20y to 20k. The landing position on the recording medium P is different. That is, the recording heads 20y to 20k have different driving waveform overshoots and undershoots depending on the number of nozzles that are driven simultaneously (hereinafter, appropriately referred to as the number of drive nozzles). Affects the voltage amplitude of the waveform. In the recording heads 20y to 20k, the larger the voltage amplitude of the drive waveform, the faster the droplet ejection speed and the more the droplet ejection amount. As a result, the number of drive nozzles affects the droplet discharge speed Vj and the droplet discharge amount Mj as shown in FIG. If the droplet discharge speed Vj and the droplet discharge amount Mj vary, a print deviation and a density difference occur, and this causes image deterioration. In FIG. 9, when the number of drive nozzles is “100”, both the droplet discharge speed Vj and the droplet discharge amount Mj are the largest, and the droplet discharge speed Vj and the droplet discharge amount Mj are approximately proportional. There is a relationship.

  The peaks of the droplet discharge speed Vj and the droplet discharge amount Mj vary depending on the image forming apparatus, but are approximately the same, and can be obtained by evaluation in advance.

  Then, when the droplet discharge speed Vj and the droplet discharge amount Mj vary, for example, as shown in FIG. 10, the image density recorded on the recording medium P changes. FIG. 10A shows landing droplets when FIG. 10A repeats 100 nozzle (100 ch) driving and 100 nozzle driving. FIG. 10B shows a landing droplet when 100 nozzle driving and 50 nozzle driving are repeated. As can be seen in FIG. 10B, in the case of 50 nozzle driving, the droplet discharge speed Vj is slower than in the case of 100 nozzle driving, so the position is in the direction opposite to the moving direction (the right direction in FIG. 10). Landing out of position. Further, as can be seen from FIG. 10B, in the case of 50 nozzle driving, the droplet discharge amount Mj is smaller than in the case of 100 nozzle driving, so the dot size of landing is reduced and the density of the formed image is reduced. descend. In FIG. 10, odd-numbered rows are formed with 100 nozzles (100 ch), and even-numbered rows are formed with 100 nozzles (100 ch) or 50 nozzles (50 ch).

  As described above, since the droplet discharge speed Vj and the droplet discharge amount Mj vary depending on the number of nozzles that are driven simultaneously, by adjusting the drive waveform of the nozzles by the recording heads 20y to 20k according to the number of drive nozzles, The droplet discharge speed Vj and the droplet discharge amount Mj can be adjusted.

  That is, as shown in FIG. 11, the image density of the formed image varies depending on the number of drive nozzles and the drive waveform magnification. In FIG. 11, the number of drive nozzles is 100 nozzles-100 nozzles (100 ch-100 ch), the image density of the reference drive waveform (drive waveform magnification 1) is the reference density, and the number of drive nozzles is 100 nozzles-30 nozzles, 100 Nozzle-50 nozzles, 100 nozzles-150 nozzles, 100 nozzles-192 nozzles, drive waveform, reference drive waveform, magnification is 1.05 times, 1.1 times, 1.15 times, 1.2 times The state of the image density when the image is formed while changing to is shown. In FIG. 11, when driving with a drive signal of 1.15 times for 30 nozzles, 1.1 times for 50 nozzles, 1.1 times for 150 nozzles, and 1.15 times for 192 nozzles, It is shown that the image density is equivalent to that when 100 nozzles are driven by the drive signal of the reference drive waveform.

  That is, the image forming apparatus 1 sets the drive waveform to an appropriate multiple of the reference drive waveform based on the number of nozzles that are driven simultaneously, thereby changing the image density of the formed image to the reference nozzle number ( For example, the density is corrected when driving 100 nozzles) with a reference driving waveform.

  That is, when the drive waveform magnification is changed, the droplet discharge speed Vj and the droplet discharge amount Mj also change, and the image density of the formed image is corrected by adjusting the drive waveform magnification based on the number of drive nozzles. be able to.

  The drive waveform magnification here means maintaining the intermediate potential of the drive waveform and changing the other drive waveform portions by the magnification, as shown in FIG. That is, the drive waveform can be corrected by multiplying a value other than the intermediate potential of the reference drive waveform stored in the drive waveform table 135 by the drive waveform correction value (magnification).

  Therefore, when a misregistration detection instruction is generated by a preset misregistration detection timing or an operation of the operation display unit 206, the image forming apparatus 1 performs an image misregistration detection process shown in FIG.

  The main control unit 101 drives the sub-scanning drive unit 105 to transport the recording medium P to a predetermined position (step S101).

  The main control unit 101 performs a calibration process for the reading sensor 30 (step S102).

  The main control unit 101 performs the calibration process of the reading sensor 30 as shown in FIG.

  That is, when entering the calibration process, the main control unit 101 first causes the light emitting element 31 of the reading sensor 30 to emit light with a preset initial light emission amount (step S201). Specifically, the main control unit 101 sets a PWM value for causing light emission at the initial light emission amount in the light emission control unit 121, and the light emission control unit 121 outputs a light emission pulse signal of the PWM value via the smoothing circuit 122. Output to the drive circuit 123. The drive circuit 123 drives the light emitting element 31 to emit light based on the light emission pulse signal of the PWM value.

  When the main control unit 101 causes the light emitting element 31 to emit light, the amount of reflected light from the recording medium P received by the light receiving element 32, that is, the range of the specified output value in which the output value of the light receiving element 32 is set in advance. It is determined whether it is within (step S202). Specifically, for example, the main control unit 101 determines whether or not the output value of the light receiving element 32 is within a range of 4V ± 0.2V.

  When the output value of the light receiving element 32 is not within the range of the specified output value (in step S202, when NG), the main control unit 101 resets the output light amount (step S203). The main control unit 101 repeatedly performs the process of determining the output value by causing the light emitting element 31 to emit light with the reset output light amount until the output value of the light receiving element 32 falls within the specified output value range (steps S201 to S201). S203).

  When the output value of the light receiving element 32 falls within the specified output value range in step S202 (when OK in step S202), the main control unit 101 ends the calibration process.

  Returning again to FIG. 6, the main control unit 101 performs an adjustment pattern T forming process. That is, in the image forming apparatus 1, the drive waveform generation unit 301 generates a reference drive waveform and a plurality of adjustment drive waveforms different from the reference drive waveform. The reference pattern forming unit 302 causes the ejection unit 304 to drive the nozzles having the number of reference nozzles with a reference drive waveform to form a reference pattern Tk including at least two reference lines Lk. Further, the adjustment pattern forming unit 303 includes a reference line Lk driven by a reference drive waveform of nozzles having a reference number of nozzles, a plurality of adjustment target nozzles having a number of nozzles different from the reference nozzle number, and a plurality of adjustments. A plurality of adjustment patterns Tc composed of a plurality of adjustment lines Lc by driving in combination with the driving waveform are formed in the ejection unit 304.

  The image forming apparatus 1 drives the recording heads 20y to 20k in the order shown by the arrows in FIG. 14, for example, when all the reference patterns Tk and the adjustment patterns Tc shown in FIG. 8 are formed. Thus, the reference pattern Tk and the adjustment pattern Tc are formed on the recording medium P. FIG. 14 shows an example of pattern formation when the reading sensor 30 is disposed on the upper side of FIG. 14 when the pattern formation and the next pattern data reading process are performed simultaneously. That is, FIG. 14 shows a state in which patterns Tk and Tc are formed by driving from the upper side by the number of drive nozzles among all nozzles arranged in a row in the sub-scanning direction. When the reading sensor 30 is attached to the carriage 6 so as to be at the center position of the recording heads 20y to 20k, the image forming apparatus 1 is arranged in a row in the sub-scanning direction as shown in FIG. Among all the nozzles, the nozzles dispersed in the vertical direction by the number of drive nozzles from the central position are driven to form the patterns Tk and Tc. Further, when the reading sensor 30 performs reading at a plurality of locations of the recording heads 20y to 20k, the image forming apparatus 1 forms patterns Tk and Tc at the sub-scanning positions where reading is performed as illustrated in FIG. . In this case, when only one reading sensor 30 is attached to the carriage 6, the image forming apparatus 1 reads the patterns Tk and Tc while moving the recording medium P to a position corresponding to the reading position. I do. Further, as shown in FIG. 17, the image forming apparatus 1 may form a plurality of patterns having the same drive waveform magnification in the main scanning direction as the reference pattern Tk and the adjustment pattern Tc. In this case, the image forming apparatus 1 calculates an average value of a plurality of reading results, calculates a positional deviation, and reduces the influence due to variation.

  When the image forming apparatus 1 forms an adjustment pattern, the distance acquisition unit 305 constructed by the main control unit 101 and the reading sensor 30 performs a pattern data reading process (step S104).

  The main control unit 101 executes this pattern data reading process as shown in FIG.

  That is, the main control unit 101 causes the light emitting element 31 of the reading sensor 30 to emit light based on the result of the calibration (step S301), and starts capturing sensor data that is an output value output from the light receiving element 32 (step S302). ).

  Next, the main control unit 101 starts moving the carriage 6 in the main scanning direction (step S303), and sensor data output from the light receiving element 32 in the area where the pattern T is recorded while moving the carriage 6. Is taken in (step S304).

  When the main control unit 101 completes the acquisition of the sensor data output from the light receiving element 32 in the pattern T recording area, the main control unit 101 stops the movement of the carriage 6 and ends the pattern data reading process (step S305).

  In the pattern data reading process shown in FIG. 18, the movement of the carriage 6 is started after the light emitting element 31 emits light. However, the movement of the carriage 6 is started first, and the carriage 6 is accelerated. In addition, the light emitting element 31 may emit light and prepare for reading.

  The main control unit 101 sets the PWM data for driving the light emitting element 31 of the reading sensor 30 in the light emission control unit 121 as described above, specifically, the light emission control unit 121 as described above. Outputs the light emission pulse signal of the PWM value to the smoothing circuit 122. The smoothing circuit 122 smoothes the light emission pulse signal and outputs it to the drive circuit 123. The drive circuit 123 drives the light emitting element 31 to emit light in accordance with the light emission pulse signal, and the recording target on which the pattern T is formed. The medium P is irradiated with emitted light from the light emitting element 31.

  The reading sensor 30 irradiates the pattern T on the recording medium P with the light emitted from the light emitting element 31, so that the reflected light reflected from the pattern T is incident on the light receiving element 32. In the reading sensor 30, the light receiving element 32 outputs an analog detection signal corresponding to the amount of reflected light from the pattern T to the photoelectric conversion unit 124.

  The photoelectric conversion unit 124 photoelectrically converts the detection signal input from the light receiving element 32 of the reading sensor 30 and outputs the photoelectric conversion signal (sensor output voltage) to the low-pass filter circuit 125.

  The low-pass filter circuit 125 removes noise from the sensor output voltage data and outputs it to the A / D conversion circuit 126, and the A / D conversion circuit 126 converts the sensor output voltage data into digital and outputs it to the FPGA 116.

  In this pattern data reading process, the main control unit 101 appropriately sets the pattern width L of the pattern T to the spot diameter d of the reading light spot Y on the recording medium P of the reading sensor 30, as shown in FIG. Is output to the head drive control unit 103. Therefore, for example, the reading sensor 30 sets the spot diameter d of the reading light spot Y to the same size as the pattern width L of the pattern T, so that the reading light with the same spot diameter d as the pattern width L of the pattern T can be obtained. The pattern T can be read. In FIG. 19 and FIG. 20, one line of the patterns Tk and Tc is shown as a pattern T.

  In this case, as shown in FIG. 20A, the reading light spot Y crosses the pattern T as the reading sensor 30 moves in the main scanning direction together with the carriage 6 from the reading light spot Y1 to the reading light spot Y5. . 20B is a sensor output voltage output from the light receiving element 32 of the reading sensor 30 corresponding to the positional relationship between the reading light spot Y and the pattern T in FIG. 20A, and FIG. The absorption area by the reading light pattern T in the reading light spot Y, FIG. 20D shows the increase rate of the absorption area obtained by differentiating the absorption area of FIG.

  That is, at the position of the reading light spot Y1, the end of the reading light spot Y1 in the moving direction coincides with the edge of the pattern T, does not overlap the pattern T, and the reading sensor 30 does not detect the pattern T. Accordingly, the sensor output voltage of the reading sensor 30 at this time is a voltage value when no image exists, as shown in FIG.

  At the position of the reading light spot Y2, half of the moving direction of the reading light spot Y2 overlaps the pattern T, and the reading sensor 30 detects the pattern T, and the reduction rate of the reflected light becomes the largest. That is, the rate of change in the positive direction per unit time of the area where the reading light spot Y overlaps the pattern T is the largest.

  At the position of the reading light spot Y3, the entire reading light spot Y3 overlaps with the pattern T, and as described above, the spot diameter d of the reading light spot Y and the width (pattern width) L of the pattern T coincide with each other. Is set. Therefore, at this moment, the intensity of the reflected light of the reading light irradiated from the reading sensor 30 to the recording medium P becomes the smallest, and the sensor output voltage of the reading sensor 30 has a minimum value as shown in FIG. It has become.

  At the position of the reading light spot Y4, the half opposite to the moving direction of the reading light spot Y2 overlaps the pattern T, and the reading sensor 30 detects the pattern T, and the increase rate of the reflected light becomes the largest. That is, the rate of change in the negative direction per unit time of the area where the reading light spot Y overlaps the pattern T is the largest.

  At the position of the reading light spot Y5, contrary to the position of the reading light spot Y1, the end opposite to the moving direction of the reading light spot Y1 coincides with the edge of the pattern T and does not overlap the pattern T. The reading sensor 30 does not detect the pattern T. Accordingly, the sensor output voltage of the reading sensor 30 at this time is a voltage value when no image exists, as shown in FIG.

  Thus, the reduction rate of the reflected light on the recording medium P at the reading light spot Y2 becomes the largest, and the reflected light on the recording medium P decreases at the position of the reading light spot Y4. The rate is the largest. Therefore, as shown in FIG. 20D, the inflection point at which the increase rate of the absorption area changes from the increasing tendency to the decreasing tendency coincides with the reading light spot Y2. Further, the inflection point at which the increasing rate of the absorption area changes from the decreasing tendency to the increasing tendency coincides with the reading light spot Y4.

  Therefore, when the sensor output voltage of the reading sensor 30 indicates an inflection point, the reading light spot Y coincides with the edge position of the pattern T. As a result, the sensor output voltage of the reading sensor 30 accurately detects the inflection point, so that the edge position of the pattern T can also be detected with high accuracy.

  FIG. 20 shows a state in which the pattern T is read by the reading sensor 30 while the carriage 6 is moved in the main scanning direction while the recording medium P is being conveyed at a constant speed in the sub-scanning direction. Yes. In the image misalignment detection process, the carriage 6 is moved in the main scanning direction while the recording medium P is stopped at a position where the reading sensor 30 can read the pattern T on the recording medium P. However, the pattern T may be read by the reading sensor 30.

  Then, the edge position of the pattern T can be detected based on the inflection point of the increase rate or decrease rate of the absorption area.

  Returning to FIG. 12 again, when the main control unit 101 performs the pattern data reading process, the main control unit 101 performs the drive waveform correction value calculation process. That is, the main control unit 101 obtains the reference distance of the reference pattern Tk. Next, the main control unit 101 obtains an adjustment distance between the reference line Lk and the adjustment line Lc of each adjustment pattern Tc. For each adjustment pattern Tc, the main control unit 101 determines the drive waveform magnification of the adjustment distance closest to the reference distance as the drive waveform magnification when driving the nozzles of the number of drive nozzles of the adjustment pattern Tc to form an image. .

  That is, the reference pattern Tk and the adjustment pattern Tc can be shown as shown in FIG. In FIG. 21, an adjustment pattern Tc of 100 nozzles-30 nozzles, an adjustment pattern Tc of 100 nozzles-50 nozzles, and a reference pattern Tk of 100 nozzles-100 nozzles at a predetermined drive waveform magnification are described as examples. Although not shown in FIG. 21, the same adjustment pattern Tc and the adjustment pattern Tc of the drive waveform magnification are recorded on the recording medium P.

  In the image forming apparatus 1, the main control unit 101 moves the carriage 6 at a constant speed, and the main control unit 101 sets the reference line Lk (line with 100 nozzles) and the adjustment line Lc (line with 30 nozzles, 50 nozzles, etc.) of the adjustment pattern Tc. The adjustment distances K1, K2,. The main control unit 101 measures the adjustment distances of the adjustment patterns Tc having the same number of drive nozzles and different drive waveform magnifications as the adjustment distances K1, K2,. Further, the main control unit 101 measures a distance (reference distance) K0 between the reference lines Lk of the reference pattern Tk. The main control unit 101 calculates the reference distance and the adjustment distance based on the moving speed of the carriage 6 and the detection time from detection of one line to be detected until detection of the next line.

  Then, the main control unit 101 adjusts the adjustment pattern Tc, the reference line Lk of the reference pattern Tk, and the adjustment line Lc read in the reading process, the adjustment closest to the reference distance for each number of drive nozzles of the adjustment pattern Tc Determine the drive waveform magnification of the distance.

  For example, as shown in FIG. 22A, the adjustment distance of the adjustment pattern Tc of 100 nozzles-30 nozzles varies depending on the drive waveform magnification, and the adjustment distance when the drive waveform magnification is 1.15. It is the shortest and closest to the reference distance shown in FIG. Therefore, when the number of drive nozzles is 30, and the drive waveform magnification is corrected to 1.15 and an image is formed, as shown in FIG. 23, as shown in FIG. In addition, the image quality can be improved.

  When the main control unit 101 determines the drive waveform magnification of the adjustment distance closest to the reference distance for each number of drive nozzles of the adjustment pattern Tc, the main control unit 101 associates the drive waveform magnification with the number of drive nozzles and drives the drive waveform correction table. Is stored in the NVRAM 114 or the like (step S106).

  When the main control unit 101 stores the drive waveform correction table, the image position deviation detection process ends.

  Then, at the time of image formation, the image forming apparatus 1 acquires the number of drive nozzles based on the image data, and acquires the drive waveform magnification corresponding to the number of drive nozzles from the drive waveform correction table. The image forming apparatus 1 corrects the drive waveform and drives the recording heads 20y to 20k with the drive signal having the corrected drive waveform to form an image. The image forming apparatus 1 corrects the drive waveform by adjusting the drive waveform magnification based on the number of drive nozzles under the control of the CPU 111 as shown in FIG. Good.

  The image forming apparatus 1 creates an adjustment pattern Tc and stores the drive waveform magnification with respect to the number of nozzles in the adjustment pattern Tc as a drive waveform correction table. May form.

  In this case, in the image forming apparatus 1, the drive waveform correction value calculation unit 133 corresponds to the number of drive nozzles that do not exist in the drive waveform correction table from the relationship between the number of drive nozzles and the drive waveform magnification, for example, as shown in FIG. This is determined by complementing the drive waveform magnification to be performed.

  As described above, the image forming apparatus 1 according to the present exemplary embodiment includes the ejection unit (ejection unit) 304 that ejects droplets onto the recording medium P by driving a plurality of nozzles with a drive signal having a predetermined drive waveform, and the drive. As a waveform, a drive waveform generation unit (drive waveform generation unit) 301 that generates a reference drive waveform and a plurality of adjustment drive waveforms different from the reference drive waveform, and a predetermined reference nozzle in the discharge unit 304 with the reference drive waveform A reference pattern forming section (reference pattern forming means) 302 that drives a number of the nozzles to form a reference pattern Pk composed of at least two reference lines Lk, and the reference drive number of the nozzles in the reference drive waveform A combination of a reference line Lk by driving, a plurality of adjustment target nozzles having a number of nozzles different from the reference nozzle number, and a plurality of the adjustment drive waveforms. An adjustment pattern forming section (adjustment pattern forming means) 303 that causes the ejection section 304 to form a plurality of adjustment patterns Pc including a plurality of adjustment lines Lc by driving, a reference distance between the reference lines Lk, and the reference lines. A distance acquisition unit (distance acquisition unit) 305 that acquires an adjustment distance between Lk and the adjustment line Lc, and a drive waveform that drives the nozzles of the adjustment target number of nozzles based on the reference distance and the plurality of adjustment distances. A waveform determination unit (drive waveform determination means) 306 that determines a correction value for the reference drive waveform.

  Accordingly, the correction value for the reference drive waveform can be determined according to the difference between the number of drive nozzles and the reference nozzle number, and the positional deviation of the landing positions of the droplets due to the number of drive nozzles can be adjusted.

  The image forming apparatus 1 according to the present exemplary embodiment also includes a discharge processing step in which a plurality of nozzles are driven by a drive signal having a predetermined drive waveform to discharge droplets onto the recording medium P, and a reference drive waveform as the drive waveform. And a drive waveform generation processing step for generating a plurality of adjustment drive waveforms different from the reference drive waveform, and at least two nozzles of a predetermined reference nozzle number are driven in the ejection processing step by the reference drive waveform. A reference pattern forming process step for forming a reference pattern Pk composed of a reference line Lk, a reference line Lk obtained by driving the nozzle of the reference nozzle number with the reference driving waveform, and a plurality of nozzles different from the reference nozzle number From a plurality of adjustment lines Lc driven by a combination of the number of adjustment target nozzles and a plurality of adjustment drive waveforms Adjustment pattern formation processing step for forming a plurality of adjustment patterns Pc in the ejection processing step, and distance acquisition processing step for acquiring a reference distance between the reference lines Lk and an adjustment distance between each reference line Lk and the adjustment line Lc. And a waveform determination processing step for determining a correction value for the reference drive waveform when simultaneously driving the nozzles of the number of adjustment target nozzles based on the reference distance and a plurality of the adjustment distances. Execute.

  Accordingly, the correction value for the reference drive waveform can be determined according to the difference between the number of drive nozzles and the reference nozzle number, and the positional deviation of the landing positions of the droplets due to the number of drive nozzles can be adjusted.

  Furthermore, the image forming apparatus 1 according to the present exemplary embodiment includes a discharge process in which a control processor such as the CPU 11 drives a plurality of nozzles with a drive signal having a predetermined drive waveform to discharge droplets onto the recording medium P, and the drive. A drive waveform generation process for generating a reference drive waveform and a plurality of adjustment drive waveforms different from the reference drive waveform, and driving the nozzles of a predetermined reference nozzle number in the ejection process with the reference drive waveform. A reference pattern forming process for forming a reference pattern Pk composed of at least two reference lines Lk, a reference line Lk obtained by driving the nozzle with the reference drive waveform with the reference drive waveform, and a nozzle different from the reference nozzle number A plurality of adjustment lines Lc driven by a combination of a plurality of adjustment target nozzles and a plurality of the adjustment drive waveforms. An adjustment pattern forming process for forming a plurality of adjustment patterns Pc by the discharge process; a distance acquisition process for acquiring a reference distance between the reference lines Lk and an adjustment distance between the reference lines Lk and the adjustment line Lc; An image forming program that executes a waveform determination process that determines a correction value for the reference drive waveform when simultaneously driving the nozzles of the number of adjustment target nozzles based on a reference distance and a plurality of the adjustment distances is mounted. ing.

  Accordingly, the correction value for the reference drive waveform can be determined according to the difference between the number of drive nozzles and the reference nozzle number, and the positional deviation of the landing positions of the droplets due to the number of drive nozzles can be adjusted.

  Further, the image forming apparatus 1 according to the present exemplary embodiment acquires the number of nozzles that are simultaneously driven by the discharge unit 304 based on image data, and the waveform determination unit 306 determines the number of nozzles and the number of adjustment target nozzles based on the number of nozzles. A drive control unit (drive control unit) 307 that acquires the determined correction value and outputs a drive signal having a drive waveform obtained by correcting the reference drive waveform with the correction value to the ejection unit 304 is further provided.

  Accordingly, the drive nozzle can be driven with a drive waveform obtained by correcting the reference drive waveform with a correction value corresponding to the image data, and the positional deviation of the landing position of the droplet due to the number of drive nozzles can be adjusted to improve the image quality. A good image can be formed.

  Furthermore, in the image forming apparatus 1 of the present embodiment, the plurality of adjustment drive waveforms for the number of adjustment target nozzles are used as the drive waveforms when the waveform determination unit 306 drives the nozzles for the number of adjustment target nozzles. The adjustment driving waveform having the smallest difference between the adjustment distance and the reference distance is determined.

  Therefore, it is possible to determine the correction value of the driving waveform that minimizes the positional deviation of the landing position of the droplet due to the number of driving, and more appropriately adjust the positional deviation of the landing position of the droplet due to the number of driving nozzles. can do.

  Furthermore, in the image forming apparatus 1 of the present embodiment, the drive waveform generation unit 301 generates a drive waveform having the same waveform shape as the reference drive waveform and a different potential magnification as the adjustment drive waveform.

  Therefore, it is possible to generate a driving waveform for adjustment similar to the driving waveform at the time of actual driving, detect a positional deviation, and determine a correction value for the reference driving waveform for correcting the positional deviation. As a result, it is possible to more appropriately adjust the positional deviation of the landing positions of the droplets due to the number of drive nozzles.

  Further, in the image forming apparatus 1 according to the present embodiment, the distance acquisition unit 305 irradiates the recording medium P on which the reference pattern Pk and the adjustment pattern Pc are formed with reading light, and reflects the reflected light. , The reference distance between the reference line Lk and the adjustment distance between the reference line Lk and the adjustment line Lc are acquired.

  Therefore, it is possible to automatically acquire the reference distance and the adjustment distance, determine the correction value for the reference drive waveform, and improve workability.

  The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to that described in the above embodiments, and various modifications can be made without departing from the scope of the invention. It goes without saying that it is possible.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Main body housing | casing 3 Main body frame 4 Main guide rod 5 Sub guide rod 6 Carriage 6a Connection piece 6b Belt holding part 7 Timing belt 8 Drive pulley 9 Driven pulley 10 Main scanning motor 11 Cartridge part 12 Maintenance mechanism part 13 Cover 14 Platen 15 Encoder Sheet 20 Recording Head 20y, 20m, 20c, 20k Recording Head 21 Encoder Sensor 30 Reading Sensor 31 Light Emitting Element 32 Light Receiving Element 33 Holder 34 Lens 100 Control Unit 101 Main Control Unit 102 External I / F
DESCRIPTION OF SYMBOLS 103 Head drive control part 104 Main scanning drive part 105 Subscanning drive part 106 Feeding drive part 107 Discharge drive part 108 Scanner control part 111 CPU
112 ROM
113 RAM
114 NVRAM
115 ASIC
116 FPGA
121 light emission control unit 122 smoothing circuit 123 drive circuit 124 photoelectric conversion unit 125 low-pass filter circuit 126 A / D conversion circuit 116 FPGA
127 Shared Memory 131 Image Data Output Unit 132 Drive Count Unit 133 Drive Waveform Correction Value Calculation Unit 134 Drive Waveform Correction Unit 135 Drive Waveform Table 201 Rotary Encoder 202 Sub-Scanning Motor 203 Feeding Motor 204 Ejection Motor 205 Image Reading Unit 206 Operation Display Unit DESCRIPTION OF SYMBOLS 301 Drive waveform generation part 302 Reference pattern formation part 303 Adjustment pattern formation part 304 Discharge part 305 Distance acquisition part 306 Waveform determination part 307 Head drive control part P Recording medium Tk Reference pattern Tc Adjustment pattern Lk Reference line Lc Adjustment line 1 Hand scanner Housing 2 Input document 3 One-dimensional image sensor 4 Wide lens 5 Illumination lamp

JP 2011-148287 A

Claims (7)

Discharge means for driving a plurality of nozzles by a drive signal of a predetermined drive waveform to discharge droplets onto a recording medium;
Drive waveform generating means for generating a reference drive waveform and a plurality of adjustment drive waveforms different from the reference drive waveform as the drive waveform;
A reference pattern forming means for causing the ejection means to drive the nozzles of a predetermined reference nozzle number with the reference drive waveform to form a reference pattern composed of at least two reference lines;
A reference line by driving the nozzles of the reference nozzle number with the reference drive waveform, and a combination of the nozzles of a plurality of adjustment target nozzles having a number of nozzles different from the reference nozzle number and a plurality of the adjustment drive waveforms An adjustment pattern forming unit that forms a plurality of adjustment patterns composed of a plurality of adjustment lines by driving in the discharge unit;
Distance acquisition means for acquiring a reference distance between the reference lines and an adjustment distance between each of the reference lines and the adjustment line;
Drive waveform determining means for determining a correction value for the reference drive waveform of a drive waveform for driving the nozzles of the number of adjustment target nozzles based on the reference distance and a plurality of adjustment distances;
An image forming apparatus comprising: The image forming apparatus includes:
Based on the image data, the number of nozzles that are simultaneously driven by the ejection unit is acquired, the correction value determined by the waveform determination unit is acquired based on the number of nozzles and the number of nozzles to be adjusted, and the correction value is Drive control means for outputting a drive signal of a drive waveform obtained by correcting the reference drive waveform to the ejection means;
An image forming apparatus, further comprising: The waveform determining means includes
As the drive waveform when driving the nozzles of the adjustment target nozzle number, the adjustment drive waveform having the smallest difference between the adjustment distance and the reference distance by the plurality of adjustment drive waveforms in the adjustment target nozzle number The image forming apparatus according to claim 1, wherein the image forming apparatus is determined. The drive waveform generation means includes
4. The image forming apparatus according to claim 1, wherein a drive waveform having the same waveform shape as the reference drive waveform and having a different potential magnification is generated as the adjustment drive waveform. 5. . The distance acquisition means includes
By irradiating the recording medium on which the reference pattern and the adjustment pattern are formed with reading light and receiving the reflected light, a reference distance between the reference lines, and between the reference line and the adjustment line The image forming apparatus according to claim 1, wherein an adjustment distance is acquired. A discharge processing step of driving a plurality of nozzles by a drive signal having a predetermined drive waveform to discharge droplets onto a recording medium;
A drive waveform generation processing step for generating a reference drive waveform and a plurality of adjustment drive waveforms different from the reference drive waveform as the drive waveform;
A reference pattern forming process step of driving a predetermined number of reference nozzles in the ejection processing step with the reference drive waveform to form a reference pattern composed of at least two reference lines;
A reference line by driving the nozzles of the reference nozzle number with the reference drive waveform, and a combination of the nozzles of a plurality of adjustment target nozzles having a number of nozzles different from the reference nozzle number and a plurality of the adjustment drive waveforms An adjustment pattern forming process step for forming a plurality of adjustment patterns including a plurality of adjustment lines by driving in the ejection process step;
A distance acquisition processing step of acquiring a reference distance between the reference lines and an adjustment distance between each of the reference lines and the adjustment line;
A waveform determination processing step for determining a correction value for the reference drive waveform when simultaneously driving the nozzles of the number of adjustment target nozzles based on the reference distance and a plurality of the adjustment distances;
An image forming method characterized by comprising: To the control processor,
An ejection process in which a plurality of nozzles are driven by a drive signal having a predetermined drive waveform to eject droplets onto a recording medium;
As the drive waveform, a drive waveform generation process that generates a reference drive waveform and a plurality of adjustment drive waveforms different from the reference drive waveform;
A reference pattern forming process for forming a reference pattern including at least two reference lines by driving the nozzles of a predetermined reference nozzle number in the ejection process with the reference driving waveform;
A reference line by driving the nozzles of the reference nozzle number with the reference drive waveform, and a combination of the nozzles of a plurality of adjustment target nozzles having a number of nozzles different from the reference nozzle number and a plurality of the adjustment drive waveforms An adjustment pattern forming process for forming a plurality of adjustment patterns including a plurality of adjustment lines by driving in the discharge process;
A distance acquisition process for acquiring a reference distance between the reference lines and an adjustment distance between each of the reference lines and the adjustment line;
Based on the reference distance and a plurality of adjustment distances, a waveform determination process for determining a correction value for the reference drive waveform when simultaneously driving the nozzles of the number of adjustment target nozzles;
An image forming program for executing