JP2019161625A - Image processing apparatus, apparatus for discharging liquid, image processing method, and program - Google Patents

Abstract

To enable maintaining halftone gradation even when a dot is displaced.SOLUTION: From a highlight part to a middle part, an anchor pattern is formed with a first dot of the resolution and dot size that does not overlap even when the dot position shift occurs, and from the middle part to a shadow part, distribution arrangement is performed such that a gap of the anchor pattern is filled with a second dot of a size that maintains the overlap of dots even when the dot position shift occurs, and a threshold value is arranged such that the distribution pattern has high-frequency characteristics in the anchor pattern and a composite pattern of the anchor pattern and the second dot.SELECTED DRAWING: Figure 13

Description

  The present invention relates to an image processing apparatus, an apparatus for ejecting liquid, an image processing method, and a program.

  In order to output an input image with a device that outputs an image using a liquid discharge head, for example, a plurality of dots of different sizes are combined with the input image to generate halftone image data that expresses gradation. Halftone processing is performed.

  Conventionally, when an image is formed by an electrophotographic method, a highlight pattern is created with a sufficient interval that the gradation is not destroyed even if dot gain occurs, and dots are collected around the highlight pattern as a core. A method of growing halftone dots is known (Patent Document 1).

JP 2002-337401 A

  However, in an apparatus for ejecting liquid, landing position deviation of, for example, about several tens of μm to 100 μm may occur due to a liquid ejection bend, a change in a mechanism portion associated with a main / sub scanning operation, and the like. Therefore, even when trying to form a halftone dot by solidifying a droplet around a highlight dot as in the past, the halftone dot can be larger or smaller than the target due to the impact of the landing position shift, so halftone There is a problem that gradation characteristics change.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to suppress a change in halftone gradation characteristics even when a dot displacement occurs.

In order to solve the above problems, an image processing apparatus according to the present invention provides:
An image processing apparatus that performs halftone processing for expressing gradation by combining dots of a plurality of sizes,
In a gradation region less than a predetermined value, even if a dot position shift occurs, a pattern is formed by distributing and arranging first dots of resolution and dot size that do not overlap at least part of the dots,
In a gradation area of a predetermined value or more, halftone processing is performed in which the gaps of the pattern are dispersedly arranged so as to fill in the gaps of the pattern with the second dots having a size in which at least a part of the dots is kept overlapping even when the dot position shift occurs. It was set as the structure provided with the means.

  According to the present invention, halftone gradation can be maintained even if dot misalignment occurs.

It is a plane explanatory view of a mechanism part in an example of a device which discharges liquid concerning the present invention. It is a principal part side surface explanatory drawing similarly. FIG. 6 is an explanatory cross-sectional view in a direction (liquid chamber longitudinal direction) orthogonal to a nozzle arrangement direction of an example of a liquid discharge head. It is a cross-sectional explanatory drawing of a nozzle arrangement direction (liquid chamber short direction) similarly. It is block explanatory drawing of the control part of the apparatus. It is a block explanatory diagram of an example of an image processing device according to the present invention. It is block explanatory drawing with which the example of performing the halftone process which concerns on this invention on the image processing apparatus side is provided. FIG. 6 is a block diagram for explaining an example in which halftone processing according to the present invention is executed on the printing apparatus side. It is explanatory drawing with which it uses for description of the image nonuniformity in the apparatus which discharges a liquid. It is explanatory drawing of the head arrangement | positioning of a connection structure. It is explanatory drawing of the phase shift of the head of the same connection structure. It is explanatory drawing of the texture nonuniformity by the phase shift of the head of the same connection structure. It is explanatory drawing with which it uses for description of the landing position shift of a droplet, and dot size (dot diameter). It is explanatory drawing of the recording resolution and dot position shift with which it uses for description of construction | assembly of an anchor pattern. It is explanatory drawing with which it uses for description of an example of a halftone process. It is explanatory drawing with which it uses for description of threshold value mask and pattern formation of a droplet. It is explanatory drawing with which it uses for description of formation of the threshold value mask of a medium drop, and the pattern following FIG. It is explanatory drawing with which it uses for description of formation of the threshold value mask of a large droplet, and the pattern following FIG.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an example of an apparatus for ejecting a liquid that outputs image data generated by image processing according to the present invention will be described with reference to FIGS. FIG. 1 is an explanatory plan view of a mechanism portion of a printing apparatus as an apparatus for discharging the liquid, and FIG.

  The printing apparatus 100 is a serial type apparatus. A carriage 105 is held so as to be movable in the main scanning direction by a guide mechanism such as a main guide member 102 and a sub guide plate 103 that span the left and right side plates 101A and 101B.

  The carriage 105 is equipped with three liquid ejection units 110 (110a to 110c). The liquid discharge unit 110 is configured by integrating a liquid discharge head (head) 111 serving as a liquid discharge unit and a sub tank 112 that supplies liquid to the head 111.

  On the apparatus main body side, a cartridge holder 121 to which a plurality of main tanks (liquid cartridges) 120 containing liquids of respective colors are mounted in a replaceable manner is disposed. The liquid of each color is supplied from the main tank 120 mounted on the cartridge holder 121 to the head 111 of each liquid discharge unit 110 through a liquid path 123 formed of a supply tube of each color by a liquid feed pump or the like.

  On the other hand, in order to convey the sheet material 130 in the conveyance direction, a conveyance unit 140 that sucks the sheet material 130 and conveys the sheet material opposite the head 111 is provided.

  The conveyance unit 140 is configured to convey the sheet material 130 via the conveyance roller 141, the pressure roller 142 that is pressed against and in contact with the conveyance roller 141, the platen member 143 that faces the head 111, and the suction hole 143 a of the platen member 143. The suction mechanism unit 144 and the like are configured to adsorb. In the drawing, the suction hole 143a is partially illustrated, but is disposed on the entire platen member 143.

  A maintenance / recovery mechanism 150 that performs maintenance / recovery (maintenance) of the head 111 is disposed on one side of the carriage 105 in the main scanning direction.

  The maintenance / recovery mechanism 150 includes, for example, a cap 151 for capping the nozzle surface 111a of the head 111, a web 154 for wiping the nozzle surface 111a, and a wiper unit 152 including a wiper member 155. The wiping unit 152 is disposed on the main frame 156.

  In the printing apparatus 100, the sheet material 130 is conveyed in the conveyance direction while adsorbing on the platen member 143 by the conveyance roller 141 and the pressure roller 142.

  Therefore, by driving the head 111 according to the print signal while moving the carriage 105 in the main scanning direction, a liquid of a required color is ejected onto the stopped sheet material 130 to print one line, and the sheet After the material 130 is conveyed by a predetermined amount, the printing of the next line is repeatedly performed, and the sheet material 130 is discharged.

  Next, an example of the liquid discharge head will be described with reference to FIGS. 3 is a cross-sectional explanatory diagram in a direction (liquid chamber longitudinal direction) orthogonal to the nozzle arrangement direction of the head, and FIG. 4 is a cross-sectional explanatory diagram in the same nozzle arrangement direction (liquid chamber short direction).

  The liquid discharge head 111 joins the nozzle plate 1, the flow path plate 2, and the vibration plate member 3. And the piezoelectric actuator 11 which displaces the diaphragm member 3 and the frame member 20 are provided as a common flow path member.

  Thereby, an individual liquid chamber (also referred to as a pressure chamber or a pressurizing chamber) 6 that communicates with a plurality of nozzles 4 that discharge droplets, and a liquid supply that also serves as a fluid resistance unit that supplies the liquid to the individual liquid chamber 6 A path 7 and a liquid introduction part 8 communicating with the liquid supply path 7 are formed. Adjacent individual liquid chambers 6 are separated by a partition wall 6A in the nozzle arrangement direction.

  Then, the liquid is supplied to the plurality of individual liquid chambers 6 through the liquid introduction part 8 and the liquid supply path 7 through the filter part 9 formed in the diaphragm member 3 from the common flow path 10 as the common flow path of the frame member 20. .

  The piezoelectric actuator 11 is disposed on the opposite side of the individual liquid chamber 6 across a deformable vibration region 30 that forms the wall surface of the individual liquid chamber 6 of the diaphragm member 3.

  The piezoelectric actuator 11 has a plurality of stacked piezoelectric members 12 joined on a base member 13. The piezoelectric member 12 is grooved by half-cut dicing, and a piezoelectric element 12A as a columnar pressure generating element for giving a driving waveform and a support column 12B are formed in a comb shape at a predetermined interval.

  The piezoelectric element 12 </ b> A is bonded to the island-shaped convex portion 3 a formed in the vibration region 30 of the diaphragm member 3. Further, the support column 12 </ b> B is joined to the convex portion 3 b of the diaphragm member 3.

  This piezoelectric member 12 is formed by alternately laminating piezoelectric layers and internal electrodes, and each internal electrode is pulled out to the end face and provided with an external electrode, which can be used to give a drive waveform to the external electrode of the piezoelectric element 12A. An FPC 15 as a flexible wiring board having flexibility is connected.

  The frame member 20 is formed with a common flow path 10 through which liquid is supplied from a head tank or a liquid cartridge.

  In this liquid discharge head 111, for example, the piezoelectric element 12A contracts by lowering the voltage applied to the piezoelectric element 12A from the intermediate potential Ve, the vibration region 30 of the diaphragm member 3 descends, and the volume of the individual liquid chamber 6 increases. By expanding, the liquid flows into the individual liquid chamber 6.

  Thereafter, the voltage applied to the piezoelectric element 12A is increased to extend the piezoelectric element 12A in the stacking direction, and the vibration region 30 of the diaphragm member 3 is deformed in the nozzle 4 direction to contract the volume of the individual liquid chamber 6. Thereby, the liquid in the individual liquid chamber 6 is pressurized, and the liquid is ejected (injected) from the nozzle 4.

  Then, by returning the voltage applied to the piezoelectric element 12A to the reference potential, the vibration region 30 of the diaphragm member 3 is restored to the initial position, and the individual liquid chamber 6 expands to generate a negative pressure. The liquid is filled into the individual liquid chamber 6 through the liquid supply path 7. Therefore, after the vibration of the meniscus surface of the nozzle 4 is attenuated and stabilized, the operation for the next discharge is started.

  Next, an outline of the control unit of the printing apparatus will be described with reference to FIG. FIG. 5 is a block diagram of the control unit.

  The control unit 500 includes a CPU 501 that controls the entire apparatus, a ROM 502 that stores fixed data such as various programs including a program for executing processing according to the present invention executed by the CPU 501, and temporarily stores image data and the like. A main controller 500A including a RAM 503.

  In addition, the control unit 500 includes a rewritable nonvolatile memory (NVRAM) 504 for holding data while the apparatus is powered off, image processing for performing various signal processing, rearrangement, and the like on image data. In addition, an image processing unit 505 that processes input / output signals for controlling the entire apparatus is provided.

  Further, the control unit 500 includes a head drive control unit 508 including a head control unit for driving and controlling the head 111 and a drive waveform generation unit. The head drive control unit 508 drives and controls the head 111 via a head driver (driver IC) 509 provided on the carriage 105 side.

  In addition, the control unit 500 includes a carriage driving unit 510 that drives a main scanning motor 551 that moves and scans the carriage 105, a feed motor 552 that drives the conveyance roller 141, and a conveyance system driving unit 511 that drives the suction mechanism unit 144. I have.

  Further, the control unit 500 includes a supply system driving unit 512 that drives a liquid feeding pump unit 553 that feeds liquid from the liquid cartridge 120 to each head 111 side, and a maintenance driving unit 515 that drives the maintenance and recovery mechanism 150. I have.

  In addition, the control unit 500 includes an I / O unit 513. The I / O unit 513 acquires a reading signal from the reading sensor 560 and information from various sensor groups 570, extracts information necessary for controlling the apparatus, and uses it for various controls.

  The control unit 500 is connected to an operation panel 514 for inputting and displaying information necessary for the apparatus.

  The control unit 500 also includes an I / F 506 for transmitting and receiving data and signals to and from the printer driver 421 of the host 400 such as an information processing apparatus such as a personal computer, an image reading apparatus, and an imaging apparatus.

  Then, the CPU 501 of the control unit 500 reads and analyzes the print data in the reception buffer included in the I / F 506, performs necessary image processing, data rearrangement processing, and the like in the image processing unit 505. Is transferred to the head driver 509 via the head drive control unit 508.

  The head drive control unit 508 transfers image data as serial data, and outputs a transfer clock, a latch signal, a control signal, and the like necessary for transferring the image data and confirming the transfer to the head driver 509.

  The head drive control unit 508 includes a drive waveform generation unit including a D / A converter that performs D / A conversion on drive waveform data read from the ROM 502, a voltage amplifier, a current amplifier, and the like. A drive waveform composed of one drive pulse or a plurality of drive pulses is generated and output to the head driver 509.

  The head driver 509 selects a drive pulse constituting a drive waveform supplied from the head drive control unit 508 based on image data corresponding to one row of the head 111 input serially, and applies it to the piezoelectric element 12A of the head 111. To give. Thereby, the head 111 is driven. At this time, by selecting part or all of the pulses constituting the drive waveform or all or part of the waveform elements forming the pulse, for example, the size (size) of large droplets, medium droplets, small droplets, etc. Different dots can be distinguished.

  Next, an image processing apparatus equipped with a program that causes a computer to execute image processing according to the present invention for outputting a print image by the above-described printing apparatus will be described with reference to a block diagram of FIG.

  In the image processing apparatus 400, a CPU 401 and various ROMs 402 and RAM 403, which are memory means, are connected by a bus line. A storage device 406, an input device 404 such as a mouse or a keyboard, a monitor 405, and the like are connected to the bus line via a predetermined interface, and communicate with a network such as the Internet or an external device such as a USB. A predetermined interface (external I / F) 407 to be performed is connected.

  The storage device 406 of the image processing apparatus 400 stores an image processing program including a program for executing the processing according to the present invention. This image processing program may operate on a predetermined OS, or may form part of specific application software.

  Here, an example of executing the halftone processing (image processing) according to the present invention by the program on the image processing apparatus 400 side will be described with reference to the functional block diagram of FIG.

  A printer driver 421 including a program for causing the CPU 401 to perform image processing according to the present invention on the image processing apparatus 400 (PC) side records image data 410 given from application software or the like from a monitor display color space (image device). CMM (Color Management Module) processing unit 412 that performs conversion (RGB color system → CMY color system) to a color space for forming apparatus), BG / UCR (black) that performs black generation / under color removal from CMY values generation / under color removal) processing unit 413, a total amount regulating unit 414 that corrects the CMYK signal according to the maximum total amount value of the recording color material that can be printed by the printing apparatus 100 with respect to the CMYK signal serving as a recording control signal, and the characteristics of the printing apparatus 100 And a gamma correction unit 415 that performs input / output correction reflecting user's preference, and enlargement processing according to the resolution of the printing apparatus 100 Zooming processing, halftone processing unit 416 that replaces image data with a pattern arrangement of dots ejected from printing apparatus 100, and dot pattern data that is print image data obtained by halftone processing is used as data for each scan. It includes a rasterizing unit 417 that divides and further develops data in accordance with the positions of nozzles that perform recording, and outputs an output 418 of the rasterizing unit 417 to the printing apparatus 100.

  A part of such image processing can also be executed on the printing apparatus 100 side. This example will be described with reference to the functional block diagram of FIG.

  The printer driver 421 on the image processing apparatus 400 (PC) side sends the image data generated by performing the processing up to the above-described γ correction to the printing apparatus 100.

  On the other hand, the control unit 500 of the printing apparatus 100 configures a halftone processing unit 616 and a rasterizing unit 617, and provides an output 618 of the rasterizing unit 617 to the head drive control unit 508. In this case, the program according to the present invention is stored in the ROM 502.

  Image processing (halftone processing) according to the present invention can be applied to any of the configurations shown in FIGS.

  Next, image unevenness in the apparatus for ejecting liquid will be described with reference to FIGS. FIG. 9 is an explanatory diagram of image unevenness when multipass printing is performed. FIG. 10 is an explanatory diagram of the arrangement of the heads in the connection configuration, FIG. 11 is an explanatory diagram of the phase shift of the heads in the connection configuration, and FIG. 12 is an explanatory diagram of texture unevenness due to the phase shift of the heads in the connection configuration.

  When an image is formed by the liquid discharge method, image unevenness may occur due to variations in droplet discharge bending and sheet material conveyance control. This image unevenness can be reduced by performing so-called multi-pass printing in which a unit area is overwritten by using different nozzles in a plurality of scans.

  However, in multi-pass printing, the printing time increases as the number of scans increases, and productivity decreases. In addition, when a large head unit having a “connected configuration” in which a plurality of heads of the same color are arranged, in addition to the above-described image unevenness, unevenness due to phase shift between the heads occurs.

  Therefore, even in multi-pass printing with a small number of scans, it is required to reduce image unevenness while suppressing a decrease in graininess.

  In this case, as described above, when a halftone dot is formed by solidifying a droplet around the highlight dot, the halftone dot becomes larger or smaller than the target due to the influence of the deviation of the landing position of the droplet. As a result, halftone gradation cannot be maintained. Further, since the number of printed lines (almost image resolution) is fixed by the highlight dot pattern, the graininess is deteriorated.

  For example, as shown in FIG. 9, when multi-pass printing is performed, a dot short (overlap) occurs in the vertical direction in the second scan, and a dot short occurs in the vertical direction even in the third scan. There is a gap in the fourth time.

  That is, when the number of scans is small, the landing position deviation (vertical deviation in FIG. 9) is not distributed and a gap is generated as in the fourth and eighth scans. This may occur evenly in the main scanning direction (looks like banding), or the occurrence and disappearance of a deviation like a sine curve may be repeated in synchronization with head fluctuations (rolling or yawing). (In this case, it looks like a moire pattern).

  In addition, as shown in FIG. 10, when the heads HA to HC that discharge the same color are arranged in a “connecting configuration” in the vertical direction (sheet material feeding direction), the heads are discharged with a deviation in trigger timing. The dot positions formed by the droplets change as shown in FIG. 11 (a landing phase shift occurs).

  Due to the phase shift of the landing, texture unevenness as shown in FIG. 12 occurs. The texture unevenness caused by this phase shift does not always occur repeatedly at a fixed position, and the generation site also changes due to a sheet material transfer shift (shift in the sub-scanning direction) or the like.

  In this case, the reverse phase method of shifting the dots to the reverse phase of the phase shift has a disadvantage that a new texture is generated when the phase is slightly shifted from the assumed position.

  Therefore, in the present embodiment, a dot having a size that maintains at least a part of overlap between dots even when a landing position shift (dot position shift) occurs is a large dot (second dot). For small dots and medium dots (hereinafter referred to as “first dots”) that are smaller in size than large dots, the resolution is calculated such that at least some of the dots do not overlap even if a dot position shift occurs.

  Then, from the highlight portion to the middle portion, that is, in the gradation region less than the predetermined value, the first dots having the resolution and the dot size are distributed so that at least a part of the dots does not overlap even if the dot position shift occurs. A gradation pattern (this is referred to as “anchor pattern”) is arranged. For the formation of the anchor pattern, a threshold mask having a threshold value, for example, an FM mask is used.

  In addition, from the middle part to the shadow part, that is, in the gradation region of a predetermined value or more, the anchor pattern is dispersedly arranged so as to fill the gap of the anchor pattern with the second dot. The arrangement of the large dots uses a threshold mask, for example, an FM mask, in which thresholds are arranged so as to disperse the large dots so as to fill the gaps in the anchor pattern.

  At this time, it is preferable to use an FM mask in which a threshold value is arranged so that the anchor pattern and the combined pattern obtained by combining the anchor pattern and the large dot have high frequency characteristics (blue noise characteristics).

  In other words, in the present embodiment, when halftone processing that expresses gradation by combining dots of a plurality of sizes is performed, an anchor constructed with a recording resolution having a margin for landing position error (dot position deviation) When a dot with a size that includes a mask to form a pattern and has a sufficient margin for landing position error is defined as a large dot, small and medium dots smaller than the large dot are distributed according to the anchor pattern. The large dots themselves are dispersedly arranged so as to fill the gaps in the anchor pattern, and the threshold value mask is arranged so that the dispersion tendency of the anchor pattern and the combined pattern of the anchor pattern and the large dot has high frequency characteristics. Use to process.

  In this case, even if the head has the above-described connection configuration, even if the landing position is shifted by the landing phase shift, the tone density is maintained by forming an anchor pattern in which the dots do not overlap each other, Texture unevenness can be suppressed.

  Here, the landing position deviation (dot position deviation) and the dot size (dot diameter) of the droplet will be described with reference to FIG. FIG. 13 is an explanatory diagram for explaining the same.

  As shown in FIG. 13A, when dots are arranged at a resolution (recording resolution) of 900 dpi × 600 dpi, the dots D1 can be filled if there is no landing position deviation.

  However, if there is a deviation in the landing position, for example, as shown in FIG. 13B, a gap S occurs in the dot D1 having a diameter of 70 μm. On the other hand, as shown in FIG. 13C, when a dot D2 having a diameter of 105 μm is used, even if a landing position shift occurs, it can be overlapped without causing a gap. At this time, the dot D2 becomes a large dot having a sufficient margin for maintaining the overlap between the dots with respect to the landing position deviation.

  Next, the construction of the anchor pattern will be described with reference to FIG. FIG. 14 is an explanatory diagram of dot position deviation with respect to the recording resolution provided for the description.

  As shown in FIG. 14, the resolution and the dot diameter are calculated so that the dot position does not reverse (superimpose) even if the dot position shifts due to the variation factor from the droplet landing accuracy. Here, the dot diameter of a small droplet is 49 μm, and the dot diameter of a medium droplet is 63 μm.

  Then, an anchor pattern is constructed in which dots are arranged with a resolution and a dot diameter (dot size) at which at least a part of the dots does not overlap even if a dot position shift occurs.

  Next, an example of halftone processing will be described with reference to FIG. FIG. 15 is an explanatory diagram for explaining the same.

  As for the gradation from the highlight part to the middle part (gradation area less than a predetermined value), as shown in FIGS. 15A and 15B, small dots (“small”) are used. (Inscription) to medium dots (indicated as “medium”) are distributed. In addition, italic characters indicate that they are arranged later.

  Here, FIG. 15B shows the final arrangement in the anchor pattern. That is, the anchor pattern is arranged so as to be sequentially replaced from a small dot (small dot) to a large dot (medium dot).

  In forming the anchor pattern, it is specified that the dot (first dot) having a size smaller than the large dot (second dot) is formed using a liquid having a lower density than the large dot liquid. You can also.

  For the gradation from the middle part to the shadow part (gradation area of a predetermined value or more), as shown in FIG. 15C, large dots are dispersedly arranged so as to fill the gaps in the anchor pattern. Are replaced with large dots as shown in FIG.

  Next, an example of the formation of an FM mask for small / medium / large drops and an anchor pattern will be described with reference to FIGS. FIG. 16 to FIG. 18 are explanatory diagrams for the same description.

  In general, the landing position deviation (dot position deviation) is about half of the resolution pitch, but in the anchor pattern of this embodiment, even if the landing is shifted up to 1.5 pixel pitch, most of the dots are separated. Is set to an interval where the dots do not overlap, that is, an interval where the dots do not overlap substantially (including a case where the dots do not overlap at all). However, it is sufficient that at least a part of the dots do not overlap.

  16A shows an example of a small drop (small dot) anchor pattern, FIG. 16B shows an example of a medium drop (medium dot) anchor pattern, and FIG. 16C shows an example of a large drop (large dot) anchor pattern. It is an example of a pattern.

  FIG. 16A shows an example of an FM mask threshold table as a threshold mask for arranging small droplets (small dots). In the present embodiment, small dots are dispersedly arranged at a resolution that does not overlap even if a dot position shift occurs in gradation values 1 to 44, for example, a resolution that is 1.5 times the resolution of the apparatus (see FIG. 16B). To do.

  Thereby, for example, at the gradation value 44, an anchor pattern of a droplet as shown in FIG. 16B is created. Thereafter, as shown in FIG. 16 (c), the process proceeds to the creation of an anchor pattern including a medium droplet from a small droplet.

  FIG. 17A shows an example of an FM mask threshold value table as a threshold mask for arranging medium drops (medium dots). In the present embodiment, medium dots are dispersedly arranged at a resolution that does not overlap even if a dot position deviation occurs in the gradation values 45 to 74, for example, 1.5 times the resolution of the apparatus (small droplets). The anchor pattern is the same as the distributed arrangement.

  Thereby, for example, at the gradation value 74, as shown in FIG. 17B, an intermediate drop anchor pattern in which all the small drops are replaced with the middle drops is created. Thereafter, as shown in FIG. 17C, the process proceeds to the creation of an anchor pattern including a medium droplet from a medium droplet.

  FIG. 18A shows an example of an FM mask threshold value table as a threshold mask for arranging large droplets (large dots). In the present embodiment, large dots are dispersedly arranged at a gradation value of 75 or more so as to fill the gaps in the anchor pattern up to the middle droplet.

  As a result, as shown in FIGS. 18B and 18C, the space of the anchor pattern up to the middle droplet is sequentially filled with large dots, and finally becomes a large dot solid.

  In this way, even when landing position deviation (dot misalignment) occurs, an anchor pattern is formed from small dots to medium dots, and the minimum gradation characteristics from the highlight portion to the middle portion are ensured.

  Then, large dots having a size larger than necessary in terms of recording resolution are dispersedly arranged at pixel positions where dots are not formed, so that gaps generated due to landing position deviation are filled with a dot diameter margin.

  At this time, since the large dots in which the positional deviation has occurred are partially superimposed on the anchor pattern, the excessive dot size becomes inconspicuous, and the reduction in graininess can be suppressed. And since the pattern disperses and arranges dots, the image resolution does not decrease.

  As a result, even with multi-pass printing with a small number of scans, it is possible to obtain an image with less unevenness and good graininess.

  In the present application, the liquid to be ejected is not particularly limited as long as it has a viscosity and surface tension that can be ejected from the head, and the viscosity becomes 30 mPa · s or less at room temperature, normal pressure, or by heating and cooling. It is preferable. More specifically, solvents such as water and organic solvents, colorants such as dyes and pigments, functional materials such as polymerizable compounds, resins, and surfactants, and biocompatible materials such as DNA, amino acids, proteins, and calcium. , Edible materials such as natural pigments, solutions, suspensions, emulsions, and the like. These include, for example, inkjet inks, surface treatment liquids, components of electronic devices and light emitting devices, and formation of electronic circuit resist patterns. It can be used in applications such as liquids for use, three-dimensional modeling material liquids, and the like.

  As energy generation sources for discharging liquid, piezoelectric actuators (laminated piezoelectric elements and thin film piezoelectric elements), thermal actuators using electrothermal transducers such as heating resistors, electrostatic actuators consisting of a diaphragm and counter electrode are used. To be included.

  In addition, the “device for ejecting liquid” includes not only a device capable of ejecting a liquid to an object to which the liquid can adhere, but also a device that ejects the liquid in the air or in the liquid. .

  This “apparatus for discharging liquid” may include means for feeding, transporting, and discharging a liquid to which liquid can adhere, as well as a pre-processing apparatus and a post-processing apparatus.

  For example, as a “liquid ejecting device”, an image forming device that forms an image on paper by ejecting ink, a powder is formed in layers to form a three-dimensional model (three-dimensional model) There is a three-dimensional modeling apparatus (three-dimensional modeling apparatus) that discharges a modeling liquid onto the powder layer.

  Further, the “apparatus for ejecting liquid” is not limited to an apparatus in which significant images such as characters and figures are visualized by the ejected liquid. For example, what forms a pattern etc. which does not have a meaning in itself, and what forms a three-dimensional image are also included.

  The above-mentioned “applicable liquid” means that the liquid can be attached at least temporarily and adheres and adheres, or adheres and penetrates. Specific examples include recording media such as paper, recording paper, recording paper, film, and cloth, electronic parts such as electronic substrates and piezoelectric elements, powder layers (powder layers), organ models, and test cells. Yes, unless specifically limited, includes everything that the liquid adheres to.

  The material of the above-mentioned “material to which liquid can adhere” is not limited as long as liquid such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics can be adhered even temporarily.

  In addition, the “device for ejecting liquid” includes a device in which the liquid ejection head and the device to which the liquid can adhere move relatively, but is not limited thereto. Specific examples include a serial type apparatus that moves the liquid discharge head, a line type apparatus that does not move the liquid discharge head, and the like.

  In addition, as the “device for ejecting liquid”, other than the above, a treatment liquid coating apparatus that ejects a treatment liquid onto a sheet in order to apply the treatment liquid to the surface of the sheet for the purpose of modifying the surface of the sheet, There is an injection granulation apparatus that granulates raw material fine particles by spraying a composition liquid in which raw materials are dispersed in a solution through a nozzle.

  Note that the terms “image formation”, “recording”, “printing”, “printing”, “printing”, “modeling” and the like in the terms of the present application are all synonymous.

DESCRIPTION OF SYMBOLS 100 Printing apparatus 105 Carriage 111 Liquid discharge head 400 Image processing apparatus 500 Control part 515 Image processing part

Claims (7)

An image processing apparatus that performs halftone processing for expressing gradation by combining dots of a plurality of sizes,
In a gradation region less than a predetermined value, even if a dot position shift occurs, a pattern is formed by distributing and arranging first dots of resolution and dot size that do not overlap at least part of the dots,
In a gradation area of a predetermined value or more, halftone processing is performed in which the gaps of the pattern are dispersedly arranged so as to fill in the gaps of the pattern with the second dots having a size in which at least a part of the dots is kept overlapping even when the dot position shift occurs. An image processing apparatus comprising: means. The first dots forming the pattern include two or more dots having different sizes,
The image processing apparatus according to claim 1, wherein the patterns are arranged so that dots of a small size are sequentially replaced with dots of a large size. The liquid constituting the first dot is designated to be the same as the liquid constituting the second dot or a liquid having a lower concentration than the liquid constituting the second dot. The image processing apparatus according to claim 1. The means for performing the halftone process includes:
In a gradation region less than a predetermined value, a threshold value is arranged so that a pattern is formed by dispersing and arranging first dots having a resolution and a dot size in which at least some of the dots do not overlap even if a dot position shift occurs. A mask,
In a gradation region of a predetermined value or more, threshold values are arranged so as to be distributed so as to fill the voids of the pattern with second dots of a size that can maintain at least part of the overlap between dots even when a dot position shift occurs. The image processing apparatus according to claim 1, further comprising a threshold value mask. An apparatus for discharging a liquid that performs halftone processing for expressing gradation by combining dots of a plurality of sizes,
In a gradation region less than a predetermined value, even if a dot position shift occurs, at least a part of the dots forms a pattern by distributing and arranging first dots of resolution and dot size,
In a gradation area of a predetermined value or more, halftone processing is performed in which the gaps of the pattern are dispersedly arranged so as to fill in the gaps of the pattern with the second dots having a size in which at least a part of the dots is kept overlapping even when the dot position shift occurs. An apparatus for ejecting liquid, characterized by comprising means. An image processing method for performing halftone processing for expressing gradation by combining dots of a plurality of sizes,
In a gradation region less than a predetermined value, even if a dot position shift occurs, a pattern is formed by distributing and arranging first dots of resolution and dot size that do not overlap at least part of the dots,
In a gradation region of a predetermined value or more, halftone processing is performed in which the gaps of the pattern are dispersedly arranged so as to fill in the gaps of the pattern with the second dots having a size in which at least part of the overlap is maintained even when the dot position shift occurs. An image processing method characterized by the above. A program that causes a computer to perform halftone processing for expressing gradation by combining dots of a plurality of sizes,
In a gradation region less than a predetermined value, even if a dot position shift occurs, a pattern is formed by distributing and arranging first dots of resolution and dot size that do not overlap at least part of the dots,
In a gradation region of a predetermined value or more, a halftone process is performed in which a halftone process is distributed so as to fill the voids of the pattern with second dots having a size that maintains at least a part of the overlap between dots even when a dot position shift occurs. A program to be executed.

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