JP2008073852A - Image forming apparatus, program, storing medium, image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that the occurrence of a positional deviation for forming the dots, when the contour part is to be corrected by substituting blank dots or image dots with dots with a relatively smaller size, causes the quality of the image to be deteriorated as the dots with the smaller size not located at required positions. <P>SOLUTION: By performing a correction processing by selecting a predetermined correction pattern from information related to factors generating deviation on dot forming positions such as temperature and humidity, lapse of years, and lapse of time from the previous time of use, information on the amount of deviation on the actual dot forming positions detected, or information related to the amount of deviation on the dot forming positions inputted, a correction pattern for correcting the contour part of the image is changed from the information related to the deviation on the dot forming positions, the information on the amount of deviation on the actual dot forming positions detected, or the information related to the amount of deviation on the dot forming positions inputted, to perform the correction processing. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  As an image forming apparatus such as a printer, a facsimile machine, a copying machine, or a multifunction machine of these, for example, a liquid (e.g., a liquid ejecting apparatus) including a recording head composed of a liquid ejecting head that ejects liquid droplets of recording liquid (liquid) is used. Hereinafter, although it is also referred to as “paper”, the material is not limited, and a recording medium as a liquid (hereinafter, referred to as “recording medium”, “recording medium”, “transfer material”, “recording paper” and the like is also used synonymously). Some of them perform image formation (recording, printing, printing, and printing are also used synonymously) by attaching the ink to the paper.

  The image forming apparatus means an apparatus for forming an image by discharging a liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc. The term “not only” means not only giving an image having a meaning such as a character or a figure to a medium but also giving an image having no meaning such as a pattern to the medium. Further, the liquid is not limited to the recording liquid and ink, and is not particularly limited as long as it is a liquid capable of forming an image. The “image forming apparatus” includes both a serial type image forming apparatus that forms an image while scanning by mounting a liquid discharge head on a carriage and a line type image forming apparatus that includes a line type liquid discharge head.

  By the way, in the serial type image forming apparatus, the printing speed is determined by the resolution of the image, the nozzle density, the driving frequency for forming dots, the sub-scanning speed, and the like. Among these, the nozzle density is limited by the processing accuracy of the nozzle, liquid chamber, flow path, and actuator. In particular, in the case of a liquid discharge head using a piezoelectric element, in order to divide and form channels corresponding to nozzles, there is only a thin film PZT formed by mechanical processing such as dicing or printing, and so-called thermal formed by a semiconductor process. The nozzle density is relatively low compared to the mold liquid discharge head. The upper limit of the nozzle density of the piezoelectric liquid discharge head is currently about 360 dpi.

  On the other hand, in order to improve the printing speed, it is preferable to form the printing area by one main scanning. For example, when an image with a nozzle density of 300 dpi and a resolution of 300 dpi in the sub-scanning direction is formed, it can be created by one scan in the head movement direction (main scanning direction). On the other hand, when an image of 600 dpi is created, it is necessary to fill the image by a so-called interlace method in which two main scans and one sub-scan (paper conveyance) are performed. Non-interlace method) prints images at a high speed. Also, in the main scanning direction, as a method of forming one line in the main scanning direction, a method of forming by one main scanning (one pass printing) and a method of forming by a plurality of main scanning (so-called multi-pass printing). However, of course, the printing speed is faster in the one-pass printing that can be formed by one main scanning.

  However, in the case of an image forming apparatus using a piezoelectric head, since the nozzle density itself is low as described above, in order to increase the printing speed, it is inevitable that an image is formed by a one-pass non-interlace method. In particular, the resolution of the image is lowered. When the image density is low, a method of multi-value one pixel is effective for improving the image quality. Examples of the multivalued method include a method of changing the size of one dot itself, a method of forming one pixel by discharging a plurality of small dots, or a method of changing the density of the ink itself.

  However, high image quality by multi-value is effective for image images such as photographs, but is hardly effective for graphics and characters. This is because, in the case of characters and graphics, a dot size larger than that of the background portion is necessary, and when a small-sized dot is used, a low-density character or graphics image is obtained. Therefore, in binary images such as character graphics, a problem peculiar to low resolution occurs, and particularly in the case of characters, character quality deteriorates and characters are difficult to read.

  The problem specific to the low resolution will be described in detail. A liquid ejection type recording image is represented by dots formed in a matrix in the scanning direction of the head and in the conveyance direction of the paper, which is a direction perpendicular thereto. Here, when a character is printed as a dot image, the quality of the character varies greatly depending on the resolution of the image to be printed. For example, when a character of the same size is printed at 300 dpi and when printed at 600 dpi, the number of dots constituting the character differs by about 4 times, so that the details when printed at 600 dpi are expressed in detail. Yes, of course, the character quality is improved. In particular, since dots increase (or decrease) in a staircase pattern according to the resolution in the shaded part (inclined part) of the character, it is easier to be recognized as jagged (jaggy) when printed at 300 dpi. .

  A smoothing method called anti-aliasing is a method for reducing the contour jaggy that appears at the time of low resolution. However, this method changes the dot with a very large number of gradations, so that high-precision smoothing can be achieved, but the processing is very complicated and requires processing time. Thus, it is not suitable for an image forming apparatus that requires high throughput.

Therefore, Patent Document 1 compares the bit pattern of the sample window in the character bitmap image with a predetermined bit pattern and corrects the center pixel in the sample window to a small dot if they match. It is described to do.
Japanese Patent No. 2886192

Japanese Patent Application Laid-Open No. 2004-228561 describes that an edge portion of an image is discriminated from black dot data to reduce the size of print dots other than edge dots and black dots.
Japanese Patent No. 3029533

Japanese Patent Application Laid-Open No. 2004-228561 describes that the jaggy of the contour portion is reduced by changing the size of the dots constituting the contour portion according to the inclination of the contour or by forming dots in the blank portion around the contour. Has been.
JP 2003-334938 A

Japanese Patent Application Laid-Open No. 2004-228561 describes that a means for forming the periphery of a step-like change portion of dots forming an outline portion of an image with dots having a size smaller than dots forming an image is provided.
JP 2004-114303 A

Patent Document 5 describes that smoothing processing using small dots is performed when the image data of characters and graphics is black, and smoothing processing is not performed when the image data is not black.
JP 2004-017552 A

Patent Document 6 discloses that the periphery of a stepped change portion of a dot that forms a contour portion of characters and graphics is converted into dot data of a size smaller than the dots that form other than the periphery of the stepwise change portion, and the contour portion It is described that the conversion method for converting data into small-sized dot data differs according to the inclination of the image.
JP 2004-017546 A

Patent Document 7 discloses a detection step of detecting a stepped change portion of a dot that forms a contour portion of a character and graphics subjected to halftone processing, and a stepped change portion around the stepped change portion detected by the detection step. A conversion process for converting to dot data of the same or smaller size as the dots forming the changed portion, and the conversion method to the dot data of the same or smaller size in the conversion process is different depending on the inclination of the contour portion. An image processing method is described.
JP 2005-193384 A

  The techniques of Patent Documents 1 and 2 described above effectively work for LED printers and laser printers, as exemplified by the examples in the specification. This is because LED printers and laser printers use toner having a particle size of 10 μm or less, so that there is almost no spread on plain paper and small dots as specified can be obtained. This is also because a laser printer can form dots of a specified size at an optimal position by slightly changing the light emission position and length of the laser.

  However, the liquid ejection type image forming apparatus has a larger ink spread than a laser printer. In addition, since it takes time to form dots compared to LED printers and laser printers, it is difficult to change the dot size that changes according to the number and length of drive pulses during the drive cycle. The dot size changes. For the same reason, dot formation positions can be formed only at almost fixed positions within one pixel, and it is difficult to change the position within one pixel relatively freely like LED printers and laser printers. .

  The technique of Patent Document 3 is a technique for reducing jaggies in an ink jet recording system. However, when printing is performed by changing the dot size in the ink jet recording system, the dot forming position on the medium differs depending on the dot size. Also occurs. This problem will be described in detail.

  As described above, as a liquid discharge head used in a liquid discharge type image forming apparatus, as a pressure generating unit that applies pressure to ink as liquid in a liquid chamber, a thermal that uses a heating resistor for generating bubbles is used. There is a type head and a piezoelectric type head that uses a piezoelectric element that is an electromechanical conversion element that deforms the wall surface of the liquid chamber. In order to change the dot diameter, a method of changing the supply energy to the pressure generating means is generally used. Is. Specifically, the magnitude of the driving voltage of the pressure generating means is changed, or the pulse width and the number of pulses of the driving pulse are changed.

  Among these, the method of changing the drive voltage requires a signal destination corresponding to the drive voltage, and requires switching means for switching and selecting the plurality of drive voltages for each channel. As a result, the drive element (driver IC) becomes large. On the other hand, when controlling by the pulse width and the number of pulses, it is possible to change the pulse width and the number of pulses by controlling the switching means according to the time, so that one switching means is required for each channel. In particular, an image forming apparatus using a piezoelectric head uses this pulse width modulation method or pulse number modulation method.

  However, the ink droplet amount differs depending on the pulse width modulation method or the pulse number modulation method. In other words, when forming ink droplets with different dot diameters, the length of the drive pulse is different, so even when the drive pulse is input and the meniscus starts to rise, the time for the drive pulse to expire and eject as droplets is the same. Because of the difference, the time until reaching the medium surface is different, and as a result, the dot formation position on the medium varies depending on the dot size. For this reason, even if it is attempted to improve the image quality by replacing the dots in the outline with small dots, the small size dots are not formed at the desired position, which may result in a poor image. is there.

  Further, the deviation of the dot formation position also occurs when the ink viscosity resistance changes depending on environmental conditions such as temperature and humidity. Furthermore, the influence of the displacement of the dot formation position varies depending on the conditions for forming the image (paper used, resolution, etc.).

  The present invention has been made in view of the above-described problems, and an image forming apparatus and an image contour portion that improve image quality by performing correction that is not easily affected by the displacement of the dot formation position when correcting the image contour portion. A program that can improve image quality by performing correction that is not easily affected by misalignment of dot formation when correcting the image, a storage medium that can provide this program, and the effect of misalignment of dot formation when correcting the image contour An object of the present invention is to provide an image forming method capable of improving image quality by performing correction that is difficult to receive.

  In order to solve the above-described problems, the image forming apparatus according to the present invention is configured such that when an image is formed by ejecting droplets having different sizes to form dots having different sizes on the medium, In the image forming apparatus that corrects the dots by replacing the dots in the image, based on the factors that cause fluctuations in the formation positions of the dots formed by the landing of the droplets or the amount of deviation of the dot formation positions on the medium, A configuration is provided that includes means for changing the manner of replacement of dots around the contour portion.

  Here, the factors that cause fluctuations in the dot formation position are at least one of environmental temperature, environmental humidity, elapsed time since the device was manufactured, and elapsed time since the previous image formation, dot formation It is possible to adopt a configuration provided with means for detecting a positional deviation amount, and a configuration in which information regarding the positional deviation amount of the dot formation is input from the outside. Further, it is possible to change the dot replacement method based on the printing conditions when image formation is performed. In this case, the printing conditions can be at least one of resolution and medium type. The means for changing the dot replacement method uses a droplet of a size that is relatively less likely to cause a shift in the dot formation position, or reduces the usage ratio of a droplet that is likely to cause a shift in the dot formation position. And can. Further, the change of the dot replacement method may include a configuration in which the dot replacement is not performed.

  The program according to the present invention corrects by replacing dots around the contour of an image when discharging droplets of different sizes to form dots of different sizes on a medium to form an image. In the program that causes the computer to execute the above, based on the factors that cause fluctuations in the formation position of dots formed by the landing of droplets or the amount of deviation of the dot formation position on the medium, The computer is configured to execute processing for changing the replacement method.

  Here, a factor causing fluctuation in the dot formation position may be at least one of an environmental temperature, an environmental humidity, an elapsed time since the device was manufactured, and an elapsed time since the previous image formation. In addition, it is possible to perform a process of changing the way of dot replacement based on the printing conditions when performing image formation. In this case, the printing conditions can be at least one of resolution and medium type. Also, when changing the dot replacement method, use droplets of a size that is relatively difficult to cause a shift in the dot formation position, or reduce the usage ratio of droplets that are a size that is likely to cause a shift in the dot formation position. It can be configured to perform processing. Further, the change of the dot replacement method may include a configuration in which the dot replacement is not performed.

  The storage medium according to the present invention stores the program according to the present invention.

  In the image forming method according to the present invention, when droplets having different sizes are ejected to form dots having different sizes on a medium to form an image, correction is performed by replacing the dots around the outline of the image. In the image forming method, the replacement of dots around the contour of the image is based on factors that cause fluctuations in the formation position of the dots formed by the landing of droplets or the amount of deviation of the dot formation position on the medium. The configuration is changed.

  According to the image forming apparatus of the present invention, based on a factor that causes variation in the dot formation position formed by the landing of a droplet or a deviation amount of the dot formation position on the medium, Since there is a means for changing the dot replacement method, when the dot formation position shift occurs, the replacement method can be changed to make corrections that are not easily affected by the dot formation position shift. Quality is improved.

  According to the program of the present invention, the dots around the contour portion of the image are based on factors that cause fluctuations in the formation position of the dots formed when the droplets land or on the amount of deviation of the dot formation position on the medium. Since the computer performs a process to change the replacement method, if there is a shift in the dot formation position, the replacement method can be changed to make corrections that are not easily affected by the shift in the dot formation position. Will improve.

  According to the storage medium according to the present invention, the program according to the present invention is stored. Therefore, when the dot formation position deviation occurs, the replacement method is changed to perform correction that is not easily affected by the dot formation position deviation. Accordingly, a program that improves image quality can be provided.

  According to the image forming method of the present invention, based on a factor that causes variation in the dot formation position formed by the landing of a droplet or the amount of deviation of the dot formation position on the medium, Since the dot replacement method is changed, if the dot formation position is shifted, the replacement method can be changed to make corrections that are hardly affected by the dot formation position shift, and the image quality is improved.

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an example of an image forming apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is an explanatory side view for explaining the overall structure of the mechanism section of the image forming apparatus, and FIG. 2 is a plan view for explaining the mechanism section.
In this image forming apparatus, a carriage 3 is slidably held in a main scanning direction by a guide rod 1 and a guide rail 2, which are guide members horizontally mounted on left and right side plates (not shown), and a driving pulley 6A is driven by a main scanning motor 4. 2 is moved and scanned in the direction indicated by the arrow (main scanning direction) in FIG. 2 via a timing belt 5 stretched between the roller and the driven pulley 6B.

  The carriage 3 includes, for example, four recording heads 7y, 7c, 7m, which are liquid ejection heads that eject ink droplets of yellow (Y), cyan (C), magenta (M), and black (K), respectively. A plurality of ink ejection openings are arranged in a direction crossing the main scanning direction, and the ink droplet ejection direction is directed downward.

  The liquid discharge head constituting the recording head 7 includes a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses a phase change caused by liquid film boiling using an electrothermal transducer such as a heating resistor, and a metal phase change caused by a temperature change. A shape memory alloy actuator using an electrostatic force, an electrostatic actuator using an electrostatic force, and the like provided as pressure generating means for generating a pressure for discharging a droplet can be used. In addition, the configuration is not limited to an independent head for each color, and may be configured with one or a plurality of liquid ejection heads having a nozzle row composed of a plurality of nozzles that eject droplets of a plurality of colors.

  The carriage 3 is also equipped with sub-tanks 8 for each color for supplying ink of each color to the recording head 7. Ink is supplied to the sub tank 8 from a main tank (ink cartridge) (not shown) via an ink supply tube 9.

  On the other hand, as a paper feeding unit for feeding paper 12 stacked on a paper stacking unit (pressure plate) 11 such as a paper feeding cassette 10, a half-moon roller (for separating and feeding the paper 12 one by one from the paper stacking unit 11) A separation pad 14 made of a material having a large friction coefficient is provided facing the sheet feeding roller 13 and the sheet feeding roller 13, and the separation pad 14 is urged toward the sheet feeding roller 13 side.

  In order to convey the sheet 12 fed from the sheet feeding unit below the recording head 7, a conveyance belt 21 for electrostatically attracting and conveying the sheet 12 and a guide 15 from the sheet feeding unit. A counter roller 22 for transporting the sheet 12 fed between the conveyor belt 21 and the conveyor belt 21, and for shifting the sheet 12 fed substantially vertically upward by approximately 90 ° to follow the conveyor belt 21. A conveyance guide 23 and a pressing roller 25 urged toward the conveyance belt 21 by a pressing member 24 are provided. In addition, a charging roller 26 as a charging unit for charging the surface of the transport belt 21 is provided.

  Here, the conveyance belt 21 is an endless belt, is stretched between the conveyance roller 27 and the tension roller 28, and the conveyance roller 27 rotates from the sub-scanning motor 31 via the timing belt 32 and the timing roller 33. By doing so, it is configured to circulate in the belt conveyance direction (sub-scanning direction) of FIG. A guide member 29 is disposed on the back side of the conveying belt 21 corresponding to the image forming area by the recording head 7. The charging roller 26 is disposed so as to come into contact with the surface layer of the transport belt 21 and rotate following the rotation of the transport belt 21.

  Further, as shown in FIG. 2, a slit disk 34 is attached to the shaft of the transport roller 27, and a sensor 35 for detecting the slit of the slit disk 34 is provided. A rotary encoder 36 is configured.

  Further, as a paper discharge unit for discharging the paper 12 recorded by the recording head 7, a separation claw 51 for separating the paper 12 from the transport belt 21, a paper discharge roller 52 and a paper discharge roller 53, and a discharge And a paper discharge tray 54 for stocking the paper 12 to be printed.

  A double-sided paper feeding unit 55 is detachably mounted on the back. The double-sided paper feeding unit 55 takes in the paper 12 returned by the reverse rotation of the transport belt 21, reverses it, and feeds it again between the counter roller 22 and the transport belt 21.

  Further, as shown in FIG. 2, a maintenance / recovery mechanism 56 for maintaining and recovering the nozzle state of the recording head 7 is disposed in the non-printing area on one side of the carriage 3 in the scanning direction.

  The maintenance / recovery machine 56 is provided with caps 57 for capping each nozzle surface of the recording head 7, a wiper blade 58 as a blade member for wiping the nozzle surface, and for discharging the thickened recording liquid. An empty discharge receiver 59 for receiving droplets when performing an empty discharge for discharging droplets that do not contribute to recording is provided.

  In the image forming apparatus configured as described above, the sheets 12 are separated and fed one by one from the sheet feeding unit, and the sheet 12 fed substantially vertically upward is guided by the guide 15, and includes the transport belt 21 and the counter roller 22. The leading end is guided by the conveying guide 23 and pressed against the conveying belt 21 by the pressing roller 25, and the conveying direction is changed by approximately 90 °.

  At this time, a control unit (not shown) applies an alternating voltage that alternately repeats positive and negative to the charging roller 26 from the AC bias supply unit, and a charging voltage pattern that alternates the conveying belt 21, that is, a sub-scanning direction that is a circumferential direction. In addition, charging is performed with a pattern in which plus and minus are alternately repeated with a predetermined width. When the paper 12 is fed onto the charged transport belt 21, the paper 12 is attracted to the transport belt 21 by electrostatic force, and the paper 12 is transported in the sub-scanning direction by the circular movement of the transport belt 21.

  Therefore, by driving the recording head 7 according to the image signal while moving the carriage 3 in the forward and backward directions, ink droplets are ejected onto the stopped paper 12 to record one line. After transporting a predetermined amount, the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the paper 12 has reached the recording area, the recording operation is finished and the paper 12 is discharged onto the paper discharge tray 54.

  In the case of double-sided printing, when recording on the front surface (surface to be printed first) is completed, the recording belt 12 is fed into the double-sided paper feeding unit 61 by rotating the conveyor belt 21 in the reverse direction. The paper 12 is reversed (with the back surface being the printing surface), fed again between the counter roller 22 and the transport belt 21, controlled in timing, and transported onto the transport bell 21 as described above. After recording on the back side, the sheet is discharged onto the discharge tray 54.

  During printing (recording) standby, the carriage 3 is moved to the maintenance / recovery mechanism 55 side, and the nozzle surface of the recording head 7 is capped by the cap 57, and the nozzles are kept in a wet state. To prevent. In addition, the recording liquid is sucked from the nozzle in a state where the recording head 7 is capped by the cap 57, and a recovery operation is performed to discharge the thickened recording liquid and bubbles, and the ink adhered to the nozzle surface of the recording head 7 by this recovery operation. Wiping is performed with a wiper blade 58 in order to clean and remove. In addition, an idle ejection operation for ejecting ink not related to recording is performed before the start of recording or during recording. Thereby, the stable ejection performance of the recording head 7 is maintained.

  Next, an example of the liquid discharge head constituting the recording head 7 will be described with reference to FIGS. 3 is a cross-sectional explanatory diagram along the longitudinal direction of the liquid chamber of the head, and FIG. 4 is a cross-sectional explanatory diagram of the head along the lateral direction of the liquid chamber (nozzle arrangement direction).

  This liquid discharge head includes, for example, a flow path plate 101 formed by anisotropic etching of a single crystal silicon substrate, a vibration plate 102 formed by, for example, nickel electroforming bonded to the lower surface of the flow path plate 101, a flow path A nozzle plate 103 joined to the upper surface of the plate 101 is joined and laminated, and a nozzle communication path 105 that is a flow path through which a nozzle 104 that discharges droplets (ink droplets) communicates therewith and a liquid chamber that is a pressure generation chamber. 106, an ink supply port 109 communicating with a common liquid chamber 108 for supplying ink to the liquid chamber 106 through a fluid resistance portion (supply path) 107 is formed.

  In addition, two rows (only one row is shown in FIG. 6) of stacked piezoelectric elements as electromechanical conversion elements that are pressure generating means (actuator means) for pressurizing ink in the liquid chamber 106 by deforming the diaphragm 102. An element 121 and a base substrate 122 to which the piezoelectric element 121 is bonded and fixed are provided. Note that a column portion 123 is provided between the piezoelectric elements 121. This support portion 123 is a portion formed simultaneously with the piezoelectric element 121 by dividing and processing the piezoelectric element member. However, since the drive voltage is not applied, the support portion 123 becomes a simple support. Further, an FPC cable 126 equipped with a drive circuit (drive IC) (not shown) is connected to the piezoelectric element 121.

  The peripheral edge of the diaphragm 102 is joined to a frame member 130, and the frame member 130 serves as a through-hole 131 and a common liquid chamber 108 that house an actuator unit composed of the piezoelectric element 121 and the base substrate 122. A recess and an ink supply hole 132 for supplying ink from the outside to the common liquid chamber 108 are formed. The frame member 130 is formed by injection molding with a thermosetting resin such as an epoxy resin or polyphenylene sulfite, for example.

  Here, the flow path plate 101 is formed by, for example, subjecting the single crystal silicon substrate having a crystal plane orientation (110) to anisotropic etching using an alkaline etching solution such as an aqueous potassium hydroxide solution (KOH), so that the nozzle communication path 105, Although a recess or a hole serving as the liquid chamber 106 is formed, the invention is not limited to a single crystal silicon substrate, and other stainless steel substrates, photosensitive resins, and the like can also be used.

  The vibration plate 102 is formed from a nickel metal plate, and is manufactured by, for example, an electroforming method (electroforming method). Alternatively, a metal plate or a joining member between a metal and a resin plate may be used. it can. The piezoelectric element 121 and the support post 123 are bonded to the diaphragm 102 with an adhesive, and the frame member 130 is further bonded with an adhesive.

  The nozzle plate 103 forms a nozzle 104 having a diameter of 10 to 30 μm corresponding to each liquid chamber 106 and is bonded to the flow path plate 101 with an adhesive. The nozzle plate 103 is formed by forming a water repellent layer on the outermost surface of a nozzle forming member made of a metal member via a required layer.

  The piezoelectric element 121 is a stacked piezoelectric element (here, PZT) in which piezoelectric materials 151 and internal electrodes 152 are alternately stacked. An individual electrode 153 and a common electrode 154 are connected to each internal electrode 152 drawn out to different end faces of the piezoelectric element 121 alternately. In this embodiment, the ink in the liquid chamber 106 is pressurized using the displacement in the d33 direction as the piezoelectric direction of the piezoelectric element 121. However, the pressure in the d31 direction is used as the piezoelectric direction of the piezoelectric element 121. The ink in the liquid chamber 106 may be pressurized. Alternatively, a structure in which one row of piezoelectric elements 121 is provided on one substrate 122 may be employed.

  In the liquid discharge head having such a configuration, for example, by lowering the voltage applied to the piezoelectric element 121 from the reference potential, the piezoelectric element 121 contracts, and the diaphragm 102 descends to expand the volume of the liquid chamber 106. Then, the ink flows into the liquid chamber 106, and then the voltage applied to the piezoelectric element 121 is increased to extend the piezoelectric element 121 in the stacking direction, and the diaphragm 102 is deformed in the direction of the nozzle 104, so that the volume / volume of the liquid chamber 106 is increased. By contracting the volume, the recording liquid in the liquid chamber 106 is pressurized, and droplets of the recording liquid are ejected (jetted) from the nozzle 104.

  Then, by returning the voltage applied to the piezoelectric element 121 to the reference potential, the diaphragm 102 is restored to the initial position, and the liquid chamber 106 expands to generate a negative pressure. The recording liquid is filled in 106. Therefore, after the vibration of the meniscus surface of the nozzle 104 is attenuated and stabilized, the operation proceeds to the next droplet discharge.

  Note that the driving method of the head is not limited to the above example (drawing-pushing), and striking or pushing can be performed depending on the direction of the drive waveform.

Next, an outline of the control unit of the image forming apparatus will be described with reference to the block diagram of FIG.
The control unit 200 forms the contour portion of the image based on a factor that causes variation in the formation position of the dots formed by the landing of the liquid droplet according to the present invention or the amount of deviation of the actual dot formation position. A CPU 211 for controlling the entire apparatus, which also serves as a means for changing the correction method for correcting the dot size, a program including the program according to the present invention executed by the CPU 211, and a ROM 202 for storing other fixed data , A RAM 203 for temporarily storing image data, a rewritable nonvolatile memory 204 for retaining data even while the apparatus is powered off, and an image process for performing various signal processing and rearrangement on the image data And an ASIC 205 for processing input / output signals for controlling the entire apparatus.

  The control unit 200 also includes an I / F 206 for transmitting and receiving data and signals to and from the host, data transfer means for driving and controlling the recording head 7, and drive waveform generation means for generating a drive waveform. A print control unit 207; a head driver (driver IC) 208 for driving the recording head 7 provided on the carriage 3 side; a motor driving unit 210 for driving the main scanning motor 4 and the sub-scanning motor 31; An AC bias supply unit 212 that supplies an AC bias to the roller 34, detection signals from the encoder sensors 43 and 35, and various sensors such as a temperature sensor 215 that detects an environmental temperature as a factor causing a shift in the dot formation position. An I / O 213 for inputting a detection signal is provided. The control unit 200 is connected to an operation panel 214 for inputting and displaying information necessary for the apparatus.

  Here, the control unit 200 transmits image data from the host side such as an information processing device such as a personal computer, an image reading device such as an image scanner, an imaging device such as a digital camera, etc. via an I / F 206 via a cable or a network. Receive.

  Then, the CPU 201 of the control unit 200 reads and analyzes the print data in the reception buffer included in the I / F 206, performs necessary image processing, data rearrangement processing, and the like in the ASIC 205, and drives the image data to the head drive. The data is transferred from the control unit 207 to the head driver 208. Note that generation of dot pattern data for outputting an image is performed by a printer driver on the host side as will be described later.

  The print control unit 207 transfers the above-described image data to the head driver 208 as serial data, and transmits a transfer clock, a latch signal, a droplet control signal (mask signal), and the like necessary for the transfer of the image data and confirmation of the transfer. In addition to the output to the head driver 208, a drive waveform generator and a head driver composed of a D / A converter, a voltage amplifier, a current amplifier, etc. for D / A converting the pattern data of the drive signal stored in the ROM Drive waveform selection means for generating a drive waveform composed of one drive pulse (drive signal) or a plurality of drive pulses (drive signal) and outputting the drive waveform to the head driver 208.

  The head driver 208 selectively selects droplets of the recording head 7 based on image data corresponding to one line of the recording head 7 input serially, and forms a driving signal provided from the print control unit 207. The recording head 7 is driven by applying it to a driving element (for example, a piezoelectric element as described above) that generates energy to be discharged. At this time, by selecting a driving pulse constituting the driving waveform, for example, dots having different sizes such as large droplets (large dots), medium droplets (medium dots), and small droplets (small dots) can be distinguished. it can.

  Further, the CPU 201 detects a speed detection value and a position detection value obtained by sampling a detection pulse from the encoder sensor 43 constituting the linear encoder, and a speed target value and a position target value obtained from a previously stored speed / position profile. Based on this, a drive output value (control value) for the main scanning motor 4 is calculated, and the main scanning motor 4 is driven via the motor driving unit 210. Similarly, based on the speed detection value and position detection value obtained by sampling the detection pulse from the encoder sensor 35 constituting the rotary encoder, and the speed target value and position target value obtained from the previously stored speed / position profile. Then, a drive output value (control value) for the sub-scanning motor 31 is calculated, and the sub-scanning motor 31 is driven via the motor driver 210 and the motor driver.

Next, an example of the print control unit 207 and the head driver 208 will be described with reference to FIG.
As described above, the print control unit 207 generates a drive waveform (common drive waveform) composed of a plurality of drive pulses (drive signals) within one printing cycle, and outputs a print waveform. And a data transfer unit 302 that outputs a clock signal, a latch signal (LAT), and droplet control signals M0 to M3.

  The droplet control signal is a 2-bit signal that instructs each droplet to open and close an analog switch 317, which will be described later, of the head driver 208. The droplet control signal is a waveform to be selected according to the printing cycle of the common drive waveform. State transition is made to level (ON), and state transition is made to L level (OFF) when not selected.

  The head driver 208 receives a transfer clock (shift clock) and serial image data (gradation data: 2 bits / CH) from the data transfer unit 302, and each register value of the shift register 311 by a latch signal. A latch circuit 312 for latching, a decoder 313 that decodes gradation data and control signals M0 to M3 and outputs the result, and a logic level voltage signal of the decoder 313 is converted to a level at which the analog switch 315 can operate. Level shifter 314, and an analog switch 316 that is turned on / off (opened / closed) by the output of the decoder 313 provided via the level shifter 314.

  The analog switch 316 is connected to the selection electrode (individual electrode) 154 of each piezoelectric element 121, and the common drive waveform from the drive waveform generation unit 301 is input thereto. Accordingly, when the analog switch 316 is turned on in accordance with the result of decoding the serially transferred image data (gradation data) and the control signals MN0 to MN3 by the decoder 313, a required drive signal constituting the common drive waveform is obtained. Passing (selected) is applied to the piezoelectric element 121.

Next, an example of the drive waveform will be described with reference to FIGS.
As shown in FIG. 7, the drive waveform generator 301 is fair within one printing cycle (one drive cycle), such as a waveform element that falls from the reference potential Ve and a waveform element that rises from the state after the fall. A drive signal (drive waveform) composed of eight drive pulses P1 to P8 is generated and output. On the other hand, the driving pulse to be used is selected by the droplet control signals M0 to M3 from the data transfer unit 302.

  Here, the waveform element in which the potential V of the drive pulse falls from the reference potential Ve is a drawing waveform element in which the piezoelectric element 121 contracts and the volume of the pressurized liquid chamber 106 expands. Further, the waveform element that rises from the state after the fall is a pressurizing waveform element that causes the piezoelectric element 121 to expand and the volume of the pressurized liquid chamber 106 to contract.

  Then, when forming a small droplet (small dot) by the droplet control signals M0 to M3 from the data transfer unit 302, the drive pulse P1 is selected as shown in FIG. 8A to form a medium droplet (medium dot). When driving, the driving pulses P4 to P6 are selected as shown in FIG. 8B, and when forming large droplets (large dots), the driving pulses P2 to P8 are selected as shown in FIG. When the meniscus is vibrated without droplet ejection, the fine drive pulse P2 is selected as shown in FIG. 8D and applied to the piezoelectric element 121 of the recording head 7 respectively.

  When forming a medium droplet, the first droplet is ejected by the drive pulse P4, the second droplet is ejected by the drive pulse P5, and the third droplet is ejected by the drive pulse P6. At this time, if the natural vibration period of the pressure chamber (liquid chamber 106) is Tc, the interval between the ejection timings of the drive pulses P4 and P5 is preferably 2Tc ± 0.5 μs. Since the drive pulses P4 and P5 are configured by simple strike waveform elements, if the drive pulse P6 is also set to the same simple strike waveform element, the ink droplet velocity becomes too large, and the landing positions of other droplet types are affected. There is a risk of shifting. Therefore, the drive pulse P6 reduces the pull-in voltage (decreasing the falling potential) to reduce the meniscus pull-in and suppress the ink drop speed of the third drop. However, the startup voltage is not reduced in order to increase the necessary ink droplet volume.

  That is, in the drawing waveform element of the final drive pulse among the plurality of drive pulses, by reducing the drawing voltage relatively, the droplet discharge speed by the final drive pulse is relatively reduced, and the landing position is set to other droplets. It can be combined with the seed as much as possible.

  The fine drive pulse P2 is a drive waveform that vibrates the meniscus without ejecting ink droplets in order to prevent drying of the meniscus of the nozzle. This fine driving pulse P2 is applied to the recording head 7 in the non-printing area. In addition, by using the drive pulse P2 which is the fine drive waveform as one of the drive pulses constituting the large droplet, it is possible to achieve a shortened (higher speed) drive cycle.

  Furthermore, by setting the interval between the ejection timings of the fine drive pulse P2 and the drive pulse P3 within the range of the natural vibration period Tc ± 0.5 μs, the volume of ink droplets ejected by the drive pulse P3 can be increased. In other words, by superimposing the expansion of the pressurized liquid chamber 6 by the drive pulse P3 on the pressure vibration of the pressurized liquid chamber 106 by the vibration cycle generated by the fine drive pulse P2, the droplet volume of the droplet that can be ejected by the drive pulse P3 is driven. It can be made larger than when applying P3 alone.

A description will be given of correction control of the contour portion of the image in the image forming apparatus configured as described above.
As described above, when different widths and different numbers of driving pulses are applied to the recording head to discharge droplets having different dot diameters, the timing at which the meniscus starts to rise when the driving pulses are input is the same. Since the drive pulse is cut and the time for ejecting the droplet is different, the time to reach the paper is different. As a result, the dot formation position on the paper may be different depending on the dot size.

  In addition, if the ambient temperature and ambient humidity change, the ink viscosity resistance changes, so even if a drive pulse is applied to the head, the meniscus cannot be controlled, resulting in misalignment of the dot landing position or dot size. As a result of not being able to maintain the sheath shape normally, the dot formation position is shifted. In addition, when the device has not been used for a long time, dry ink has accumulated around the nozzles, and when the device has been used for many years since it was manufactured, the head characteristics have changed. This affects the drop landing accuracy and causes the dot formation position to shift.

  Here, the piezoelectric type head is described as an example, but the thermal type head, the electrostatic type that pressurizes the liquid chamber by using the vibration plate with the electrostatic force between the vibration plate and the electrode facing it. Even when a head or the like is used as a liquid ejection head, the dot formation position is displaced. For example, when a thermal head is used, multi-value dots can be ejected by controlling the resistance value of the electrothermal transducer, but the present invention can also be applied to such a case.

  Here, correction of the contour portion of the image will be described with reference to FIG. FIG. 9A shows an example of a contour portion that has not been subjected to correction processing. However, when the resolution is not sufficiently high, unevenness is conspicuous in the stepped portion of the contour portion, and a good quality image cannot be obtained. Therefore, the unevenness of the stepped portion is reduced by replacing the dots in the stepped peripheral portion with other dots.

  For example, FIG. 9B shows an example in which one blank dot in the stepped portion of the outline is replaced with an image dot and the image dot is a small size dot (dot added), as shown in FIG. 9C. Fig. 4D shows an example in which two blank dots in the stepped portion of the outline are replaced with image dots and the image dots are medium-sized dots and small-sized dots (dots are added). In addition to (2), two image dots in the stepped peripheral portion are replaced with medium-sized dots and small-sized dots.

  However, as described above, when the dot formation position fluctuates (displaces), the image quality may be deteriorated by performing such correction processing. For example, as shown in FIG. 10A, when correction processing for adding the dot Dh is performed as shown in FIG. 10B in order to make the jaggy in the contour portion inconspicuous, the droplet landing position is displaced. When this occurs, the formation position of the dots Dh formed by the liquid droplets is shifted as shown in FIG. 4C, and double line formation and blurring occur due to the deviation of the dot formation positions. As a result, the image quality deteriorates. As a specific example, when the deviation of the dot formation position shown in FIG. 11B is large as compared to the case where the deviation of the dot formation position shown in FIG. Become.

  Therefore, in the present invention, factors that cause fluctuation (deviation) in the dot formation position due to the deviation of the landing position of the droplet, such as environmental temperature, environmental humidity, elapsed time since the manufacture of the apparatus, elapsed time since the previous image formation, etc. Do not use dots that are misaligned to the extent that they cause image quality problems based on the amount of misalignment of the dot formation position on the actual medium. The replacement method is changed. Here, the dot replacement method is changed by selecting a correction pattern to maintain the quality of the output image.

  For example, FIG. 12A shows an example in which the contour correction processing is not performed as in FIG. 9A described above, but the concavities and convexities in the contour are conspicuous. Therefore, as shown in FIG. 12B, contour correction processing using droplets of different sizes (medium droplet and small droplet: medium dot and small dot) is performed. At this time, the landing position of the droplet to be used When the displacement occurs, for example, when the droplet landing position displacement occurs, the dot formation position is displaced (the small dot Ds is displaced by 1 dot) as shown in FIG. Not only the correction effect cannot be obtained, but also the image quality is deteriorated such as double line, mist and blur.

  Therefore, for example, when the landing position deviation of the small droplet is large, as shown in FIG. 12 (d), the correction of the contour portion is performed using the correction pattern of only the middle droplet that does not use the small droplet, When the landing position deviation of the medium droplet is large, as shown in FIG. 12 (e), by correcting the contour portion using the correction pattern of only the small droplet that does not use the middle droplet, the deviation occurrence state ( Alternatively, contour correction processing (dot replacement processing) is performed with an optimal correction pattern according to the cause of deviation. Here, an example using three types of large (medium) and small (size) droplets is described here, but examples of droplet types, sizes, and correction patterns are not limited thereto.

Next, factors that cause variation (deviation) in the dot formation position and detection or input thereof will be described.
As described above, the factors causing the deviation of the dot formation position include the environmental temperature, the environmental humidity, the elapsed time since the manufacture of the apparatus, the elapsed time since the previous image formation, and the like. Therefore, by providing means (such as the above-described temperature sensor 215) for detecting the environmental temperature and environmental humidity, the elapsed time since the manufacture of the device and the elapsed time since the previous image formation are time-counting means (such as a timer). These factors can be detected by updating and storing in the nonvolatile RAM 204 of the control unit 200 described above.

  It is also possible to detect the amount of deviation of the dot formation position on the actual medium. For example, a dot pattern (for example, a ruled line pattern formed with dots of different sizes) that can detect the amount of deviation of the dot formation position during image formation is printed on the medium, and the printed dots Reading the pattern with a photo sensor or scanner unit, obtaining dot formation position information (landing accuracy information), density information, and brightness information, and calculating how much the dot formation position is misaligned (deviation amount) Can be detected.

  In this case, if the configuration for detecting the amount of deviation of the actual dot formation position becomes complicated, the user may input information regarding the amount of deviation of the dot formation position. In this case as well, a dot pattern that can detect the amount of deviation of the dot formation position during image formation is printed on the medium, and the amount of deviation is determined by looking at the dot pattern that the user has output. Enter information about the quantity. For example, the amount of deviation is divided into the first to nth stages in advance, the user determines which stage the output image belongs to, and displays information (for example, numbers) indicating the corresponding stage on the operation panel. Enter from.

Next, the relationship between the shift of dot formation position and resolution, the type of medium, and the image quality will be described.
As described above, the correction of the stepped change portion in the contour portion of the image is required when the resolution is low, and a considerable image quality can be obtained when the resolution is high. Therefore, it is necessary to correct the contour portion in the first place. There is no. Even when the contour portion is corrected, the unevenness at the step-like change portion becomes relatively conspicuous as the resolution is lowered. Therefore, it is preferable to change the correction method (dot replacement method) according to the resolution of the image to be formed.

  In addition, depending on the type of medium, it is likely that the medium with less smearing of the landed droplets is easier to recognize the deviation of the dot formation position and the image quality is poor. For example, even when the amount of displacement at the dot formation position is the same, generally, glossy paper or the like does not bleed ink droplets that have landed and has high contrast, so that the landing displacement tends to affect the image quality as it is. Therefore, it is preferable to change the correction method (dot replacement method) according to the type of medium to be used.

Therefore, the correction control of the contour portion of the image performed by the control unit will be described with reference to the flowchart of FIG. This correction control is performed by the CPU 201 executing a program according to the present invention stored in the ROM 202.
Here, it has a correction pattern that performs pattern matching with the contour portion of the image in advance, and when the correction pattern matches the contour portion of the image, the peripheral dots of the step-like change portion of the contour portion have the size specified by the correction pattern. It is assumed that correction is performed by replacing with dots. The correction of the contour portion means that the dots in the peripheral portion of the step-like change portion are replaced from blank dots to image dots, or the dot size of the image dots is changed.

  First, it is determined whether or not the resolution of the print mode to be printed is equal to or lower than a predetermined value, and it is checked whether or not the contour portion needs to be corrected. As described above, if the printing resolution is sufficiently high so that the unevenness of the contour portion is not conspicuous, it is not necessary to correct the contour portion. In this case, the unevenness of the contour may not be noticeable depending on the type of the paper (medium). Therefore, it is determined whether or not to correct the contour depending on the type of medium in addition to the resolution or instead of the resolution. You can also

  On the other hand, when the contour portion is corrected, a factor that causes the deviation of the dot formation position (this is referred to as “dot deviation information”) is acquired. As described above, temperature, humidity, aging time, elapsed time information from the previous use, or the actual dot formation position deviation obtained by printing the dot pattern, or the input dot formation position deviation. Information about quantity.

  The obtained dot formation position deviation information (temperature, humidity, aging time, etc., or the deviation amount itself) and the set resolution (or medium type) are compared with a predetermined correction pattern selection condition. Based on the result, a correction pattern corresponding to the condition is selected, and a correction process for correcting the contour portion with the selected correction pattern is performed. If none of the correction pattern use conditions is satisfied, the correction process itself may not be performed, that is, the dot replacement may not be performed.

  For example, as shown in FIG. 14, according to the combination of the resolution and the environmental temperature, when the resolution is 600 dpi × 600 dpi or higher, no contour correction is performed regardless of the environmental temperature, and if the environmental temperature T is lower than the set temperature T1, the resolution If the environmental temperature T is equal to or higher than the set temperature T1 and lower than the set temperature T2, the patterns C and D correspond to the resolution. If the environmental temperature T is equal to or higher than the set temperature T2, the pattern depends on the resolution. E and pattern F are preset.

  In terms of the environmental temperature, generally, when the operating environment of the apparatus is low, the viscosity resistance of the ink increases, and ejection failure of small droplets may occur. Therefore, in an environment where the temperature is low, a pattern (A, B) in which small droplets that are likely to cause ejection failure are not used or the usage ratio of small droplets is reduced is used. At room temperature where dot discharge failure is unlikely to occur, optimum correction patterns (C, D) using all types of dots are used. On the other hand, at high temperatures, the viscosity of the ink decreases, and the amount of ejected ink increases, the ejection speed increases, and the landed ink scatters in a mist shape. It ’s possible that you ’ll land on the ground. Therefore, a correction pattern (E or F) that does not use such droplets that are likely to cause defects even at high temperatures or that uses a reduced ratio is used. An optimum correction pattern is prepared for each printing condition (resolution, type of medium).

  The correction pattern may be selected based on the amount of misalignment of the dot formation position itself, or may be performed based on a factor causing the misregistration of the dot formation position, such as the environmental temperature described above. Basically, a correction pattern under ideal conditions with little deviation is prepared for each printing condition (including resolution and paper), and droplets of that droplet size are not used under conditions that cause defects in specific size dots. It is switched to such a correction pattern (the pattern that does not use the droplet has the most correction effect). In addition, when an effective contour correction cannot be performed using any correction pattern, a correction pattern in which the contour portion is not corrected can be used.

  In the above description, as a method for changing the correction method, a plurality of correction patterns corresponding to factors that cause deviation in the dot formation position are provided in advance, and correction is performed according to the detection result of the factor that causes deviation in the dot formation position. The correction pattern is changed by selecting a pattern, but the correction pattern itself is not changed. For example, when matching is performed by pattern matching, a factor that causes a shift in the dot formation position is compared with the setting condition ( For example, the detected environmental temperature is compared with the set temperature), and the size of the replaced dot may be changed.

  In this way, based on factors that cause variation in the formation position of the dots formed by the landing of the liquid droplets or the amount of deviation of the dot formation position on the medium (given as a detection result or an external input), By providing means for changing the way of replacing the dots forming the contour of the image (for example, a correction pattern), if there is a deviation in the dot formation position, the way of replacing the dots (how to correct) is changed. Correction that is not easily affected by the displacement of the dot formation position can be performed, and the image quality is improved.

  Also, based on factors that cause variation in the formation position of the dots formed by the landing of the droplets or the amount of deviation of the actual dot formation position, how to replace the dots that form the outline of the image (for example, correction) If a dot formation position shift occurs by using a program that causes a computer to change the pattern), the dot replacement method (correction method) is changed and the dot formation position shift is affected. Difficult correction can be performed and image quality is improved.

  By storing such a program in a storage medium, if a dot formation position shift occurs, the dot replacement method (correction method) is changed to make it difficult to be affected by the dot formation position shift. It is possible to provide a program that can improve image quality.

  In addition, based on factors that cause variation in the formation position of dots formed by the landing of droplets or the amount of deviation of the actual dot formation position, how to replace the dots that form the contour of the image (correction pattern) ) Is changed so that if the dot formation position shift occurs, the dot replacement method (correction method) is changed to make correction that is not easily affected by the dot formation position shift. Image quality is improved.

  Further, in the image forming apparatus, depending on various kinds of information such as temperature, humidity, dot landing information (information on misalignment of dot formation position), the apparatus user and administrator are informed of the status, state, or state of the apparatus. It may have a function of presenting a method for improving the information through an information presentation device such as a display installed in the device or a host computer (information processing device) connected to the device.

  For example, as described above, there are cases where effective contour correction (correction that reduces jaggies) cannot be performed even if a correction pattern that the apparatus has (stored) in advance is applied. In such a case, it cannot be handled as a function of the image forming apparatus itself. Therefore, when the apparatus is in a state where effective contour correction cannot be performed due to environmental temperature, humidity, dot landing information (information regarding dot formation position deviation), and other factors that cause fluctuations in dot position deviation, the image forming apparatus Information correlating that effective contour correction cannot be performed with the function of the image forming apparatus itself can be notified through the operation unit of the image forming apparatus or the printer driver of the information processing apparatus on the host side.

  Here, the information correlated with the fact that effective contour correction cannot be performed by the function of the image forming apparatus itself may be only a notification that the apparatus is in such a state, or the environmental temperature, the environment Information on the environmental conditions in which the device is located, such as humidity, resolution, and amount of displacement acquired, information on the device itself, or a message prompting a change in the operating environment, head cleaning, head position adjustment, etc. It may be information including contents for improving the performance of the apparatus, such as a message prompting maintenance of the device or a message prompting contact with service or support, and these may be notified alone or in combination.

  If it has such a function, it will suggest how to maintain the device according to the conditions so as to eliminate dot misalignment, prompt the user to adjust the calibration and settings of the device, It is possible to promote use in a use environment (temperature, humidity, etc.) that can improve the condition.

  In addition, the function of transmitting information related to the situation and state of the image forming apparatus as described above and the fact that the image forming apparatus itself cannot perform effective contour correction via the network to the support department of the apparatus. You may have.

  With such a function, when an abnormal state occurs in the apparatus such as a failure, the abnormal part of the apparatus can be automatically identified and quick support can be developed.

  By having these functions, not only can the optimal correction process be performed in accordance with the state of the device, but also how to maintain the state of the device optimally and the state of the device so that the device can perform at its best. You can build a support system to keep it optimal.

  In the above embodiment, the present invention has been described with reference to an example in which the present invention is applied to an image forming apparatus having a printer configuration. The same can be applied to the forming apparatus.

1 is an explanatory side view illustrating an overall configuration of a mechanism unit of an image forming apparatus according to the present invention. It is principal part plane explanatory drawing of the mechanism part. FIG. 3 is an explanatory cross-sectional view along the longitudinal direction of the liquid chamber showing an example of the recording head of the apparatus. FIG. 4 is an explanatory cross-sectional view of the recording head along the lateral direction of the liquid chamber. It is a block diagram which shows the outline | summary of the control part of the apparatus. It is a block diagram which shows an example of the printing control part of the control part. It is explanatory drawing which shows an example of the drive waveform produced | generated and output by the drive waveform production | generation part of the same printing control part. It is explanatory drawing explaining each drive signal of the small droplet, medium droplet, large droplet, and fine drive selected from the same drive waveform. It is explanatory drawing with which it uses for description of jaggy correction | amendment (contour part correction | amendment). FIG. 10 is an explanatory diagram for explaining a correction result when there is no dot formation position deviation and a correction result when a dot formation position deviation occurs before contour correction; It is explanatory drawing with which it uses for description of the specific example when the case where the dot formation position shift has not generate | occur | produced in the character by which the outline correction | amendment was performed, and it generate | occur | produced. It is explanatory drawing with which it uses for description of the example of application of a correction pattern. It is a flowchart with which it uses for description of correction | amendment control processing. It is explanatory drawing with which it uses for description of the example of correction | amendment pattern selection.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 ... Carriage 7 ... Recording head 207 ... Print control part 208 ... Head driver

Claims (16)

  In the image forming apparatus that corrects by replacing dots around the outline of the image when forming droplets of different sizes to form dots of different sizes on the medium by ejecting droplets of different sizes, the liquid Means for changing the manner of replacement of dots around the contour of the image based on factors that cause variation in the formation position of dots formed when the droplets land or on the amount of deviation of the dot formation position on the medium An image forming apparatus comprising:   2. The image forming apparatus according to claim 1, wherein the factors that cause fluctuations in the dot formation position are environmental temperature, environmental humidity, elapsed time since the apparatus was manufactured, and elapsed time from the previous image formation. An image forming apparatus characterized by being at least one of them.   2. The image forming apparatus according to claim 1, further comprising means for detecting a shift amount of the dot formation position.   The image forming apparatus according to claim 1, wherein information regarding a shift amount of the dot formation position is input from the outside.   5. The image forming apparatus according to claim 1, wherein the dot replacement method is changed based on a printing condition when performing the image formation.   6. The image forming apparatus according to claim 5, wherein the printing condition is at least one of a resolution and a medium type.   7. The image forming apparatus according to claim 1, wherein the means for changing the dot replacement method uses droplets having a size that is relatively difficult to cause displacement of dot formation positions, or dot formation. An image forming apparatus characterized in that a use ratio of droplets having a size that is likely to cause positional deviation is reduced.   8. The image forming apparatus according to claim 1, wherein changing the dot replacement method includes not performing dot replacement.   A program for causing a computer to execute a correction process by replacing dots around the outline of the image when discharging droplets of different sizes to form dots of different sizes on a medium to form an image. The method of replacing dots around the contour portion of the image on the basis of a factor causing fluctuation in the formation position of dots formed by the landing of the liquid droplets or the amount of deviation of the dot formation position on the medium A program for causing a computer to execute a process of changing the value.   10. The program according to claim 9, wherein the factors causing fluctuation in the dot formation position are at least one of environmental temperature, environmental humidity, elapsed time since the device was manufactured, and elapsed time since the previous image formation. A program characterized by   The program according to claim 9 or 10, wherein a process for changing a method of replacing the dot based on a printing condition when performing the image formation is performed.   12. The program according to claim 11, wherein the printing condition is at least one of a resolution and a medium type.   13. The program according to claim 9, wherein when the method of replacing the dots is changed, a droplet having a size that is relatively difficult to cause a dot formation position deviation or a dot formation position deviation is used. A program for causing a process to reduce the use ratio of droplets of a size that is likely to cause a drop.   13. The program according to claim 9, wherein changing the dot replacement method includes not performing dot replacement.   15. A storage medium storing the program according to claim 9.   In the image forming method, the liquid is corrected by replacing dots around the outline of the image when forming droplets of different sizes to form dots of different sizes on the medium. Changing the manner of replacement of dots around the contour of the image based on factors that cause variation in the formation position of dots formed by the landing of droplets or the amount of deviation of the dot formation position on the medium An image forming method.