JP7800064B2 - Processing device, image forming device, image forming operation setting method and program - Google Patents

Description

This invention relates to a processing device, an image forming device, an image forming operation setting method, and a program.

Image forming devices form images by operating recording elements that have a large number of nozzles arranged in rows and drive elements such as piezoelectric elements that cause pressure fluctuations in the ink inside the nozzles, thereby generating dots. As the number of recording elements increases in response to demands for higher image resolution and precision, the probability of malfunctioning recording elements also increases. To address this issue, there is technology that complements the image by operating recording elements located nearby, such as those next to the malfunctioning recording element, in its place.

However, simply compensating for malfunctioning recording elements by using other recording elements in the same way as the operational settings of the malfunctioning recording elements does not necessarily result in the desired image quality. In response to this, Patent Document 1 discloses a technology that reduces uneven density in the formed image by determining the amount of gradation correction according to the density gradation of the image in the area to be corrected, performing gradation correction, and then performing halftone processing.

JP 2012-45831 A

However, even within the range of what is considered to be normal operation, minute irregularities can occur due to variations in dot generation position or differences in the characteristics of the medium on which the image is formed. Even if the difference is not a problem if all recording elements are operating, when compensating for a malfunctioning recording element, there may be areas that are not fully covered by the formed dots due to differences from the original dot generation position of the malfunctioning recording element. This poses the issue of not being able to adequately prevent degradation in image quality, even if the density of the original image is adjusted and then converted into ejection data using halftoning or other methods. Furthermore, because the density gradation of the formed image changes nonlinearly depending on factors such as the state of the recording medium and image forming device, the amount of gradation correction required to compensate for malfunctioning recording elements must be continually readjusted depending on the above conditions, which is a time-consuming process.

The object of this invention is to provide a processing device, image forming device, image formation operation setting method, and program that can perform settings related to compensating for malfunctioning recording elements in a more stable manner to minimize degradation of image quality.

In order to achieve the above object, the invention described in claim 1 comprises:
a position determination means for determining dot generation positions on a recording medium, where dots are generated on the recording medium by a plurality of recording elements arranged in a first direction and moving relative to the recording elements in a second direction intersecting the first direction, based on gradation data of each pixel of an image to be formed in accordance with an image formation command;
a replacement number determination means for determining a number of corrected dots by adding an offset number, which is an additional number of dots, to the number of dot generation positions of the malfunctioning recording elements that are set as the recording elements where dots are not normally generated;
position change means for determining the dot generation positions of the corrected number of dots within a range in which dots can be generated by recording elements other than the malfunctioning recording elements;
The processing device is characterized by comprising:

The invention described in claim 2 is the processing apparatus described in claim 1,
The image forming apparatus is characterized by comprising a change determining means for determining the offset number based on the gradation data.

The invention described in claim 3 is the processing apparatus described in claim 2,
The gradation data associated with the offset number is characterized in that it is determined by the number of dot generation positions set in a predetermined range surrounding the generation range of dots corresponding to the malfunctioning recording element.

The invention according to claim 4 provides the processing apparatus according to claim 2 or 3,
a storage means for storing a correspondence relationship between a value relating to the gradation of the pixel and the offset number;
The correspondence relationship is changeable.

The invention described in claim 5 is the processing apparatus described in claim 4,
An operation receiving means is provided,
the storage means stores a plurality of types of the correspondence relationships;
The change determining means determines the offset number based on one of the correspondence relationships selected based on the input operation received by the operation receiving means.

The invention of claim 6 is a processing apparatus according to any one of claims 2 to 5,
The change determining means determines the offset number based on the type of recording medium on which the image is to be formed.

The invention of claim 7 is a processing apparatus according to any one of claims 2 to 6,
The change determining means determines the offset number based on the color of the dots generated by the recording elements.

The invention of claim 8 is a processing apparatus according to any one of claims 2 to 7,
the plurality of recording elements belong to any of a plurality of recording heads,
The change determining means determines the offset number depending on the recording head.

The invention of claim 9 provides a processing apparatus according to any one of claims 2 to 7,
the plurality of recording elements belong to a recording head,
The change determining means determines the offset number in accordance with a plurality of regions into which the print head is divided.

The invention of claim 10 is a processing apparatus according to any one of claims 1 to 9,
The offset number is a positive value.

The invention according to claim 11 further comprises:
a recording head to which the plurality of recording elements belong;
A processing device according to any one of claims 1 to 10;
a driving unit that causes the recording head to generate dots at the dot generation positions determined by the position changing unit;
The image forming apparatus is characterized by comprising:

The invention according to claim 12 is as follows:
a position determination step of determining dot generation positions on a recording medium, where dots are generated on the recording medium by a plurality of recording elements arranged in a first direction and moving relative to the recording elements in a second direction intersecting the first direction, based on gradation data of each pixel of an image to be formed by an image formation command;
a substitution number determination step for determining a number of corrected dots by adding an offset number, which is the number of dots to be generated additionally, to the number of dot generation positions of the malfunctioning recording elements that are set as the recording elements where dots are not normally generated;
a position change step of determining the dot generation positions of the corrected number of dots within a range in which dots can be generated by recording elements other than the malfunctioning recording element;
The image forming operation setting method is characterized by including the steps of:

The invention according to claim 13 further comprises:
a position determination means for determining dot generation positions on a recording medium, which causes a plurality of recording elements arranged in a first direction to generate dots on the recording medium, which moves relative to the recording elements in a second direction intersecting the first direction, based on gradation data of each pixel of an image to be formed by an image formation command;
an alternative number determination means for determining a corrected dot number by adding an offset number, which is the number of dots to be generated additionally, to the number of dot generation positions of the malfunctioning recording element that is set as the recording element where dots are not normally generated;
a position change means for determining a dot generation position of the corrected number of dots within a range in which dots can be generated by recording elements other than the malfunctioning recording element;
The program is characterized by functioning as follows.

The present invention has the advantage of enabling settings related to compensating for malfunctioning recording elements to more stably prevent degradation of image quality.

1 is a schematic diagram illustrating the overall configuration of an image forming apparatus including a processing apparatus according to an embodiment of the present invention. FIG. 2 is a bottom view of the ink ejection surface of the head unit. FIG. 2 is a block diagram showing the functional configuration of the image forming apparatus. 10 is a flowchart showing an outline of the flow of a discharge data generation process. FIG. 10 is a diagram illustrating a missing part complement process. FIG. 10 is a diagram illustrating setting of an offset number. 10 is a flowchart showing a control procedure for missing part completion processing.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
1 is a schematic diagram showing the overall configuration of an image forming apparatus 1 including a processing apparatus according to this embodiment, as viewed from the front.

This image forming device 1 is an inkjet recording device that ejects ink from nozzles, and is a printer that has a line head and can record color images by ejecting multiple colors of ink at appropriate times while moving a recording medium M relative to the line head.
The image forming apparatus 1 includes a medium supply unit 10, a forming operation unit 20, a medium discharge unit 30, and a control unit 40 (position determination means, replacement number determination means, position change means, change determination means), etc. In this image forming apparatus 1, based on the control of the control unit 40, the recording medium M stored in the medium supply unit 10 is transported and moved along a predetermined transport path to the forming operation unit 20, and after an image is recorded, it is discharged to the medium discharge unit 30.

The medium supply unit 10 sends the recording media M stored therein one by one to the forming operation unit 20 .
Examples of the recording medium M include printing paper of various thicknesses, as well as various materials such as cell, film, and fabric, and in this case, materials that can be curved and carried on the outer peripheral surface of the image forming drum 21.

The medium supply unit 10 has a supply tray 11 that stores recording media M, and a feeder board 12 that transports the recording media M from the supply tray 11 to the forming operation unit 20. The supply tray 11 is a plate-shaped member that is capable of loading one or more recording media M. The supply tray 11 is configured to move up and down depending on the amount of recording media M loaded on the supply tray 11, and in the direction of the up and down movement, the topmost recording media M is held at a position where it can be transported by the feeder board 12.
The feeder board 12 has a conveying mechanism that drives a ring-shaped belt 123 carried by a plurality of (for example, two) rollers 121 and 122 on the inside to convey the recording medium M on the belt 123, and a supply unit that transfers the top recording medium M placed on the supply tray 11 onto the belt 123. The feeder board 12 conveys the recording medium M transferred onto the belt 123 by the supply unit so as to follow the belt 123.

The forming operation unit 20 includes an image forming drum 21, a transfer unit 22, a drum heater 231, a head unit 24 (discharge operation unit), an irradiation unit 25, an imaging unit 26, a delivery unit 27, and the like.

The image forming drum 21 has a cylindrical outer shape and carries up to three sheets of recording media M on the outer surface of the cylindrical portion, transporting the recording media M in response to rotation about the central axis of the cylinder.

The transfer unit 22 transfers the recording medium M transferred from the medium supply unit 10 to the image forming drum 21. The transfer unit 22 has a swing arm unit 221 that supports one end of the recording medium M transported by the feeder board 12, and a cylindrical transfer drum 222 that transfers the recording medium M supported by the swing arm unit 221 to the image forming drum 21. The swing arm unit 221 picks up the recording medium M on the feeder board 12 and transfers it to the transfer drum 222, guiding the recording medium M in a direction along the outer circumferential surface of the image forming drum 21 and transferring it to the image forming drum 21.

The drum heater 231 is located near the outer peripheral surface of the image forming drum 21 and heats this outer peripheral surface and the recording medium M. Here, the drum heater 231 is installed in the rotational direction of the image forming drum 21, between the position where the delivery unit 22 transfers the recording medium M to the image forming drum 21 and the position where the head unit 24 forms an image on the recording medium M. The outer peripheral surface of the image forming drum 21 is heated by the drum heater 231, and the recording medium M it carries is kept at an appropriate temperature. This maintains an appropriate curing speed for the recording medium M when ink lands on the recording medium M, allowing for stable, high-quality images to be recorded. For example, an infrared heater is used for this drum heater 231.

The head unit 24 ejects ink droplets at appropriate timing from multiple nozzle openings provided on the surface (nozzle opening surface) of the head unit 24 facing the image-forming surface of the recording medium M, which moves in response to the rotation of the image-forming drum 21, onto the image-forming surface of the recording medium M. The droplets land on the image-forming surface of the recording medium M, thereby recording an image. In the image forming device 1 of this embodiment, multiple head units 24 are positioned at predetermined intervals in the transport direction of the recording medium M; here, four head units 24 are arranged side by side, one for each of the four colors of ink. The four head units 24 output C (cyan), M (magenta), Y (yellow), and K (black) ink, respectively. These inks may, for example, undergo a phase change between a sol state and a gel state depending on the temperature, or may be cured by exposure to ultraviolet light. This type of ink is often in a gel state at room temperature and becomes a sol state when heated. Therefore, the ink is heated and maintained at an appropriate temperature inside and/or outside the head unit 24 by an ink heater 232 (see Figure 3) to become a sol state.

FIG. 2 is a bottom view of the ink ejection surface of the head unit 24. As shown in FIG.
Each of the head units 24 has, for example, a plurality of recording heads 240 arranged in a width direction (first direction) perpendicular to the transport direction (second direction) of the recording medium M transported on the image forming drum 21. The bottom surface of each recording head 240 has a plurality of nozzle openings N arranged at equal intervals in the width direction, and the array range of the nozzle openings N in each recording head 240 is continuous, spanning the entire image formation width of the recording medium M (i.e., as long as they are arranged at appropriate intervals in the width direction, the positions of the nozzle openings N may be dispersed in a plurality of locations in the transport direction). This makes it possible to form an image in a single pass by ejecting ink from the nozzle openings onto the recording medium M to generate dots while moving the recording medium M in the transport direction (relative movement), i.e., the head unit 24 is a line head.

The irradiation unit 25 irradiates energy rays (electromagnetic waves) of a predetermined wavelength, in this case ultraviolet light in the near-ultraviolet region (wavelength of approximately 400 nm), to cure and fix the ink (i.e., the image recorded with the ink) ejected from the head unit 24 and landed on the recording medium M. The irradiation unit 25, for example, has a light-emitting diode (LED 251) that emits ultraviolet light, and irradiates ultraviolet light by applying a voltage to the LED 251 to pass a current through it. The irradiation unit 25 is positioned downstream of the landing position of the ink ejected from the head unit 24 relative to the recording medium M transported by the rotation of the image forming drum 21, and upstream of the position where the recording medium M is delivered to the delivery unit 27, so that the ink fixing position, i.e., the recording medium M, can be irradiated with ultraviolet light.

Note that the configuration for emitting ultraviolet light in the irradiation unit 25 is not limited to LEDs. The irradiation unit 25 may include, for example, a mercury lamp. Furthermore, if the ink has the property of being cured when exposed to energy rays other than ultraviolet light, various light sources that emit energy rays with a wavelength that cures the ink can be provided instead of the above-mentioned configuration for emitting ultraviolet light.

The imaging unit 26 captures an image of the surface of the recording medium M where ink droplets land from the head unit 24 and are fixed by the irradiation unit 25. The imaging unit 26 has a line sensor with, for example, a CCD sensor or CMOS sensor. By capturing one-dimensional images in the width direction of the recording medium M transported by the operation of the transport unit at appropriate timing, it is possible to capture an image of a desired position on the recording medium M. The imaging unit 26 is capable of capturing images in, for example, each of the RGB wavelength bands, and image data in one of the wavelength bands can be selected as needed, or these image data can be combined and used for inspection processing, etc.

The delivery unit 27 transports the recording medium M to the medium discharge unit 30 after the image formation operation is completed and the deposited ink has hardened. The delivery unit 27 includes a cylindrical delivery roller 271, multiple (e.g., two) rollers 272 and 273, and a ring-shaped belt 274 supported on the inner surface by the rollers 272 and 273. The delivery roller 271 receives the recording medium M from the image forming drum 21 and guides it onto the belt 274. The delivery unit 27 transports the recording medium M delivered from the delivery roller 271 onto the belt 274 by moving it together with the belt 274, which moves in a circular motion as the rollers 272 and 273 rotate, and sends it to the medium discharge unit 30.

The medium ejection unit 30 stores the recording medium M sent from the forming operation unit 20 by the delivery unit 27 until it is removed by the user. The medium ejection unit 30 has a plate-shaped ejection tray 31, on which the recording medium M after image formation is placed.

The control unit 40 controls the operation of the medium supply unit 10, the forming operation unit 20, and the medium discharge unit 30, and forms an image on the recording medium M according to the data of the image to be formed by the image formation command (job) and settings related to the image forming operation.

Of the above components, the image forming drum 21, the transfer unit 22, and the delivery section 27 constitute the conveying section of this embodiment.

FIG. 3 is a block diagram showing the functional configuration of the image forming apparatus 1. As shown in FIG.
In addition to the head unit 24, the irradiation unit 25, the imaging unit 26 and the control unit 40, the image forming apparatus 1 also includes a heating unit 23, a conveying drive unit 29, a memory unit 42 (memory means), a communication unit 51, a display unit 52, an operation reception unit 53 (operation reception means), etc.

The control unit 40 includes a CPU (Central Processing Unit) 401 and RAM (Random Access Memory) 402. The CPU 401 is a processor that performs various arithmetic operations. The RAM 402 provides the CPU 401 with working memory space and stores temporary data.

The storage unit 42 includes a non-volatile memory such as a flash memory, and stores various setting data and programs 421. The programs 421 include a processing program related to the missing nozzle completion process described below. The setting data includes a malfunctioning nozzle list 422 and offset amount data 423.

The transport drive unit 29 operates each unit that transports the recording medium M, such as the image forming drum 21. The transport drive unit 29 outputs drive signals to each unit involved in the transport operation based on control signals output from the control unit 40.

The heating unit 23 includes an ink heater 232 in addition to the drum heater 231 described above. The ink heater 232 heats and maintains the ink supplied from an ink supply unit (such as an ink tank) (not shown) that is stored and flows within the head unit 24, within a predetermined set temperature range, maintaining the ink in a sol state with an appropriate viscosity. The temperature of the ink and the temperature of the outer surface of the image forming drum 21 are measured by a temperature measurement unit (not shown), such as a thermistor, and the operation of the drum heater 231 and ink heater 232 can be controlled based on the measurement results. Operation control may involve simply switching them on and off according to the measurement value, or control processing based on well-known techniques such as PID control may be performed.

The head unit 24 includes a head driver 241 and nozzles N. The head driver 241 includes an electromechanical transducer P and outputs an electrical signal that causes the electromechanical transducer P to deform in a predetermined deformation mode, direction, and magnitude. The electromechanical transducer P deforms in response to the electrical signal, thereby deforming the ink supply path (particularly the pressure chamber) that communicates with the nozzle N, and is provided for each nozzle N. The electromechanical transducer element P is, for example, a piezoelectric element. A pair of an electromechanical transducer element P and a nozzle N constitutes a recording element R in this embodiment.

The waveform of the electrical signal (voltage) that the head driver 241 outputs to the electromechanical transducer element P is not particularly limited here. That is, the waveform may be a rectangular wave or a trapezoidal wave. The output timing is synchronized, for example, with the output cycle of a predetermined clock signal. At each output cycle, whether or not a signal with a waveform that causes ink to be ejected is output to the electromechanical transducer element P is switched depending on data indicating whether or not each nozzle is ejecting, which is generated based on image data of the printing target, etc.

As described above, the irradiation unit 25 has an LED 251, and selectively lights up the LED 251 while the area where ink has landed on the recording medium M passes through the irradiation range.

The transport drive unit 29 includes a rotary motor and other components that synchronize and rotate the components involved in the transport movement of the recording medium M, such as the image forming drum 21 and rollers, at a rotational speed that corresponds to the appropriate transport speed of the recording medium M.

The communication unit 51 controls the exchange of signals between the image forming apparatus 1 and the outside. The communication unit 51 has, for example, a network card and sends and receives signals to and from the outside using a predetermined communication standard. An example of the predetermined communication standard is TCP/IP. The communication unit 51 may also have a predetermined connection terminal, such as one of various USB connection terminals, allowing direct data transmission and reception with peripheral devices via a USB cable or the like.

The display unit 52 displays various information under the control of the control unit 40. The display unit 52 may be equipped with, for example, an LCD screen, and may appropriately display image formation operation menus, status, and the like. The LCD screen may be positioned over a touch panel, and the control unit 40 may detect the operation content by correlating the display content of the LCD screen with the detected position of the touch operation. The display screen is not limited to an LCD display, but may also be an organic EL (Electro-Luminescent) screen, etc. The display unit 52 may also have an LED lamp, etc. The LED lamp may be used to notify, for example, the power supply status, data transmission/reception status, and/or the occurrence of an operational abnormality.

The operation reception unit 53 receives input operations from an external device, such as a user, and outputs the input signals to the control unit 40. The operation reception unit 53 may, for example, include a touch panel and output information about the detected position while detecting a touch operation. The operation reception unit 53 may also include a key operation reception unit such as a numeric keypad, or a push button switch.

Of the above components, at least the control unit 40 is included in the processing device of this embodiment, and the memory unit 42, operation reception unit 53, etc. may also be included in the processing device.

Next, the generation of ejection data and the missing ink complement process related to the image forming operation setting method in the image forming apparatus 1 of this embodiment will be described.
4 is a flowchart showing the outline of the discharge data generation process. Some or all of this process may be performed by a dedicated circuit, or may be performed entirely by software using a CPU.

The ejection data is generated based on the image data of the output target. This image data is, for example, image data in which graphics (including character shapes and designs) are vector-represented. This image data is first rasterized and converted into array data (raster image data) of RGB values for each pixel (Step S11). This array data is then converted (color conversion) into data with ink colors, i.e., CMYK gradation values, (Step S12). This image data (CMYK color image data; gradation data for each pixel) undergoes adjustments such as shading correction and limiting the total ink ejection amount (Step S13), and then undergoes halftone processing (Step S14) to convert it into a binary dot representation corresponding to the presence or absence of ink ejection at each transport position of each nozzle N (i.e., ink ejection indicates the distribution of dot generation positions) (position determination step, position determination means). If the ink ejection amount from nozzle N can be switched between multiple levels, each position may be represented by a value corresponding to the number of levels (three steps for two levels, large and small droplets). This generates the initial ejection data.

The nozzles N corresponding to the ejection data determined in this way may include malfunctioning nozzles (malfunctioning recording elements) that are experiencing malfunctions related to ink ejection. If this initial ejection data is used as is to eject ink from a nozzle N that includes a malfunctioning nozzle, the ink will not be ejected normally from the malfunctioning nozzle, resulting in abnormalities in the ink ejection amount/position in the corresponding area. In particular, if the malfunction results in very little ink ejection or no ink being ejected at all, a continuous area where ink does not land (white streak) will appear along the width direction corresponding to the nozzle N, significantly reducing the image quality of the output image. To reduce this degradation in image quality, a defect compensation process is performed in which the ink that the malfunctioning nozzle is set to eject is replaced by the surrounding nozzles (step S15).

Based on the ejection data generated and adjusted in this way, the head drive unit 241 outputs a drive signal to each electromechanical conversion element P, controlling whether or not ink is ejected from the corresponding nozzle N.

FIG. 5 is a diagram illustrating the missing part completion process of this embodiment.
5A, the horizontal direction corresponds to the width direction, i.e., the nozzle N is defined. The vertical direction corresponds to the transport direction, and indicates whether or not ink is being ejected from each nozzle N for each specified transport amount (time interval). In other words, the two-dimensional matrix of ejection data represents the dot generation positions within a two-dimensional plane.

If the sixth nozzle N from the left in Figure 5(a) is a malfunctioning nozzle that is unable to eject ink, ink will not be ejected normally continuously into the vertical area Di corresponding to this nozzle N. Therefore, the ink for the dot generation positions that were originally set to be ejected into this area Di is covered by being ejected instead by the normal nozzles N on the left and right.

As shown in Figure 5(b), four ink ejection locations are initially set within area Di. In image forming device 1, these four ejection settings are distributed among surrounding nozzles N, and three additional dot generation positions are set. If the same number of ejection settings as the number of ejection settings canceled due to an operational abnormality are assigned to surrounding nozzles N, adjacent nozzles may not be able to completely cover area Di due to slight deviations within the normal range of the ink ejection direction from nozzle N or variations in landing area. If white streaks or other defects remain due to such ink landing conditions, a significant deterioration in image quality will continue. Therefore, here, a number of dot generation positions (corrected dot number; in other words, the offset number is positive) greater than the number of dot generation positions set in area Di by a predetermined number (offset number) are assigned as ink ejection positions.

As shown in Figure 5(c), seven dot generation positions, including the four dot generation positions set within area Di plus the four dot generation positions corresponding to the added offset number, are assigned to additionally assignable positions (within the possible generation range) within a predetermined range around the original area Di. As with conventional methods, priority is given to the adjacent dot generation positions in the width direction based on the dot generation positions originally set within area Di. If these positions have already been set as dot generation positions, they may be assigned to adjacent positions or positions before and after in the transport direction. If the ink droplet volume to be ejected can be set in multiple stages, it may be possible to change a dot generation position that has already been set as a dot generation position but is set to an ejection setting that is not the maximum droplet volume to an ejection setting that is higher. The allocation of the additional offset number may be set appropriately in a balanced manner so as not to be biased toward other dot generation positions already set. Conventional methods may be used as the criteria for setting these dot generation positions.

FIG. 6 is a diagram illustrating the setting of the offset number.
Generally, density unevenness is more noticeable when ink is not ejected from certain positions than when ink is ejected in duplicate at the same position, which means that it has a greater adverse effect on image quality. In particular, when the density (ejection ratio within a unit area) is medium, for example, and ink droplets that land from adjacent nozzles N do not connect (or overlap) on the recording medium M where they should. Because the size of the ink droplets that land on the recording medium M is larger than the distance between the dot generation positions, slight variations in the ejection direction and landing size of a regular nozzle N do not pose a problem. However, when complementary ejection is performed by the adjacent nozzle N, if the ejection direction is shifted to the opposite side of the complementary side or the landing size is small, the expected connection or overlap may not occur, as described above. Therefore, as shown in FIG. 6A , the offset amount (offset rate), which is the additional amount per unit area of dots allocated from malfunctioning nozzles to surrounding nozzles N, may be changed depending on the density gradation value of the target area (the original CMYK gradation data) and the number of dot generation positions per unit area (a predetermined range surrounding the dot generation range corresponding to the malfunctioning nozzle). The correspondence between the offset amount (or density gradation; collectively, values related to pixel gradation) and the number of dot generation positions (offset number) to be added is predetermined and stored in the storage unit 42 as offset amount data 423. Furthermore, since this correspondence may change over time due to use, it may be re-specified using an appropriate method, and the offset amount data 423 may be updated or changed. Furthermore, when the offset amount is changed using the density gradation value, it is preferable that the correspondence between the dot generation positions and the positions of the CMYK pixel data before the halftone process be stored so that it can be easily specified.

In addition, the degree of ink spread varies depending on the type of ink (color, dye, pigment, etc.) and the type of recording medium M on which the ink lands, so these factors may be taken into consideration when changing the offset amount. Furthermore, the visibility of density unevenness due to variation may also depend on the type of halftone processing (e.g., error diffusion or blue noise). Therefore, the offset amount data 423 may include multiple types of correspondence relationships, for example, for each type of ink, each type of recording medium M, and each type of halftone processing.

6(b), the unit area for counting the number of dot generation positions is set as an appropriate range Ag relative to the target position T. The range Ag does not necessarily have to be a square (the same number of positions in the transport direction and the width direction), and the target position T does not have to be the center position of the range Ag. For the sake of explanation, a range of 7 x 7 dots is shown as an example here, but it may be a completely different size (for example, a larger size that corresponds to a scale visible to humans or the pattern size of the actual image).
Furthermore, compared to individual variations in the nozzles N, large changes in trends within the head unit 24, for example variations between recording heads 240, are often more noticeable. Therefore, the offset number may be determined for each recording head 240 in the width direction, or for each region obtained by dividing the recording head 240 into multiple regions. In this case, there may be cases where the gradation value (the number of dot generation positions) varies greatly within the recording head 240, but even in such cases, the offset number may be determined based on a representative value (average value, median value, etc.).

Fig. 7 is a flowchart showing the control procedure for the missing portion complement process called in the ejection data generation process of Fig. 4. Here, the missing portion complement process will be described as being executed by the CPU 401 as software.
When the missing part complement process is called, the CPU 401 acquires information on the type of recording medium M (step S101), and then acquires the malfunctioning nozzle list 422 (step S102).

The CPU 401 selects an unselected malfunctioning nozzle from the acquired malfunctioning nozzle list 422 (step S103). The CPU 401 then acquires information on the type of ink ejected by the selected malfunctioning nozzle (step S104).

The CPU 401 counts the number of dot generation positions set within a predetermined range from the reference position for the selected malfunctioning nozzle (step S105). The CPU 401 acquires the gradation values within the predetermined range (or counts the number of dot generation positions for all nozzles N) (step S106). The CPU 401 references the offset amount data 423 to acquire the determined gradation values and the offset numbers corresponding to the previously acquired type of recording medium M and type (color) of ink (step S107; substitution number determination step, substitution number determination means, change determination means). Note that if the CPU 401 cannot determine which correspondence relationship to use because the type of halftone processing to be applied to the image data to be formed has not yet been determined, the correspondence relationship to be used may be selected based on user input to the operation reception unit 53. In this case, the CPU 401 simply causes the display unit 52 to display a display for accepting the selection operation.

The CPU 401 determines destination dot generation positions, including those corresponding to the offset number, within a range determined for the dot generation position of the selected malfunctioning nozzle (step S108; position change step, position change means). The determined range is typically a position range that is adjacent to the dot generation position of the malfunctioning nozzle, but is not limited to this.

The CPU 401 determines whether all of the predetermined ranges corresponding to the length of the image in the transport direction have been set for the selected malfunctioning nozzle (step S109). If it is determined that there are still predetermined ranges that have not been set ("NO" in step S109), the CPU 401 returns to step S105.

If it is determined that all the predetermined ranges corresponding to the length of the image have been set ("YES" in step S109), the CPU 401 determines whether all malfunctioning nozzles have been selected (step S110). If it is determined that there are malfunctioning nozzles that have not been selected ("NO" in step S110), the CPU 401 returns to step S103. If it is determined that all malfunctioning nozzles have been selected ("YES" in step S110), the CPU 401 ends the missing nozzle completion process and returns to the ejection data generation process.

As described above, the control unit 40 as a processing device of this embodiment serves as a position determination means, determining dot generation positions at which dots are generated on the recording medium M by a plurality of recording elements R (nozzles N and electromechanical conversion elements P) arranged in the width direction based on the gradation data (CMYK data) of each pixel of the image to be formed, which moves relative to the recording elements R in a transport direction intersecting (orthogonal to) the width direction; as a replacement number determination means, determining a correction dot number by adding an offset number to the number of dot generation positions by malfunctioning recording elements set in the malfunctioning nozzle list 422 as recording elements R at which dots are not generated normally; and as a position change means, determining the dot generation positions of the correction dot number within the range in which dots can be generated by recording elements R other than the malfunctioning recording elements.
In this way, when a malfunctioning recording element is complemented by the operation of another recording element R, the dot generation position is increased or decreased by the offset number in dot units, thereby compensating for the incompleteness of the complement due to variations in the operation of the recording element R within the normal range, which is difficult to cover by simply adjusting the density of the original image, and this allows the control unit 40 to generate ejection data that can more appropriately suppress deterioration in image quality.
Furthermore, after generating the ejection data representing the dot generation position in this manner, the number of dots can be directly increased or decreased using the offset number when making adjustments for malfunctioning nozzles, thereby eliminating the need to adjust the image data itself of the original object to be formed.As an extension of conventional processing, it is possible to more reliably prevent degradation of image quality due to white spots and white streaks caused by ink not reaching the area where it should land and cover the recording medium M.

Furthermore, the control unit 40 may determine the offset number based on the gradation data as a means for determining the change. When the density gradation is medium or higher, if gaps remain in areas that should be covered with coloring material such as ink, these will be very noticeable and will significantly reduce image quality. On the other hand, if areas that originally had many gaps are filled in too much, the original density gradation will deviate significantly, resulting in noticeable density unevenness. Therefore, by changing the offset number according to the density gradation, it is possible to appropriately reduce the degradation of image quality in each case.

Furthermore, the gradation data associated with the offset number is determined by the number of dot generation positions set in a predetermined range surrounding the dot generation range corresponding to the malfunctioning recording element. In other words, even if the range is based on the dot generation positions set for the malfunctioning recording element, the offset number is determined based on the number of surrounding dot generation positions rather than the density gradation of the original image, making it possible to perform interpolation that more appropriately reflects the coverage state of the recording medium M according to the number of dots. Therefore, this processing device can generate more appropriate ejection data that minimizes degradation of image quality.

The processing device also includes a storage unit 42 that stores the correspondence between pixel gradation values and offset numbers as offset amount data 423. This offset amount data 423 is changeable. The correspondence changes over time due to factors such as continuous use of the recording element R, so by updating it as appropriate, it is possible to continuously prevent degradation in image quality. By storing and retaining such correspondence in advance, it is possible to easily perform missing part completion processing.

The processing device also includes an operation reception unit 53. The memory unit 42 stores multiple types of the above-mentioned correspondence relationships, and the control unit 40, as a change determination means, determines the offset number based on one of the correspondence relationships selected based on the input operation received by the operation reception unit 53. Since the spread of the generated dots changes depending on various conditions, multiple types of correspondence relationships are prepared depending on those conditions, and by being able to select one as appropriate, degradation of image quality can be stably and effectively suppressed by appropriate missing part completion that reflects the conditions.

Furthermore, the control unit may, as a change determination means, determine the offset number based on the type of recording medium M on which the image is formed. The above conditions include, for example, the type of recording medium M, and by changing the offset number according to the recording medium M, ejection data is generated that can prevent the occurrence of white streaks and other defects on the recording medium and prevent degradation of image quality.

Furthermore, the control unit may, as a change determination means, determine the offset number based on the color of the dots generated by the recording element R. In particular, when the recording element R includes a nozzle N and ejects ink, the physical properties of the ink tend to vary depending on the ink color, and therefore the way the ink spreads on the recording medium after landing also varies. Therefore, by changing the offset number according to the dot color, this processing device can generate ejection data that can more appropriately minimize degradation of image quality.

Furthermore, the multiple recording elements R belong to one of multiple recording heads 240, and the control unit may determine the offset number according to the recording head 240 as a change determination means. Since dot generation characteristics often vary for each recording head 240, which is the manufacturing unit, by varying the correspondence between the number of dot generation positions and the offset number for each recording head 240 in this way, it is possible to generate ejection data that is less likely to result in uneven images.

Furthermore, multiple recording elements R belong to the recording head 240, and the control unit, as a change determination means, may determine the offset number according to multiple regions into which the recording head 240 is divided. In this way, by dividing the recording head 240 into even smaller regions, it is possible to generate ejection data that can more accurately respond to temperature differences between the center and edges of the recording head, etc., and achieve more uniform image quality.

The offset number may also be a positive value. As mentioned above, it is more noticeable when ink does not cover necessary areas, leaving white streaks, than when too much ink is ejected and overlaps more than necessary. Therefore, by setting the offset number to a positive value, it is possible to create ejection data that can more reliably prevent significant degradation in image quality.

In addition, the image forming apparatus 1 of this embodiment includes a recording head 240 to which multiple recording elements R belong, a control unit 40 as the processing device, and a head driving unit 241 that causes the recording head 240 to generate dots at dot generation positions determined by the control unit as a position changing means.
According to the image forming apparatus 1, it is possible to form an image with reduced degradation in image quality by appropriately generated and compensated ejection data.

Furthermore, the image forming operation setting method of this embodiment includes a position determination step for determining dot generation positions at which dots are generated on the recording medium M by a plurality of recording elements arranged in the width direction, based on the gradation data (CMYK pixel data) of each pixel of the image to be formed, which move relative to the recording elements in a transport direction intersecting (orthogonal to) the width direction; a substitution number determination step for determining a number of corrected dots by adding an offset number to the number of dot generation positions by malfunctioning recording elements that are set in the malfunctioning nozzle list 422 as recording elements at which dots are not generated normally; and a position change step for determining the dot generation positions of the corrected dot number within a range in which dots can be generated by recording elements other than the malfunctioning recording elements.
This image formation operation setting method makes it possible to more appropriately adjust for missing dots due to variations in recording elements within the normal range, something that could not be adequately covered by conventional technology, on a dot generation position basis, and generates ejection data that more reliably suppresses degradation of image quality due to remaining white streaks, etc.

Furthermore, by installing the program 421 related to the image formation operation settings described above in a computer having a control unit 40 and having the control unit 40 (CPU 401) execute it, ejection data, which is drive data for image formation, can be generated easily and more appropriately without requiring special hardware and without reducing image quality.

The present invention is not limited to the above-described embodiment, and various modifications are possible.
For example, in the above embodiment, halftone processing is used to generate ejection data according to binary values or the number of steps of ink droplet size, but this is not limited to this. Other well-known methods such as dithering may also be used.

In addition, in the above embodiment, the width direction, which is the arrangement direction of the nozzles N, and the transport direction of the recording medium M are described as being perpendicular to each other, but this is not limited to this. Images can be formed in the same way even if they intersect at an angle other than 90 degrees.

Furthermore, the operation of ejecting ink from a malfunctioning nozzle may be canceled when it is assigned to another nozzle N, but if no ink is ejected at all, there is no need to bother with canceling the operation.

In addition, in the above embodiment, the correspondence between the number of dot generation positions and the number of offsets was described as being set according to the type of recording medium, the color of ink (dots), the type of halftone processing, etc., but some or all of these do not necessarily have to be determined. Furthermore, when setting correspondences for two or more of these, correspondences may be found for all combinations, or a representative value (such as the average or median) of the number of offsets obtained for each of the corresponding correspondences may be set as the final number of offsets.

In addition, in the above embodiment, the offset number is described as a positive value, but this is not limited to this. Depending on the situation, the adverse effects of overlapping dots may be greater, so it may be possible to set a negative offset number. Furthermore, as long as the offset number is not zero, it does not necessarily have to be variable depending on factors such as the density gradation (number of dot generation positions). If the offset number is variable, it may include a portion where the offset number is zero within a certain range of the density gradation (number of dot generation positions).

In addition, while the above embodiment has been described as a line head with multiple recording heads arranged in the width direction, this is not limited to this. A single recording head may be used. Alternatively, the image forming device may be a scan-type device in which the head unit 24 scans the recording medium M. Furthermore, the recording medium M does not have to be transported by the image forming drum 21. The recording medium M may be transported on a flat surface. Furthermore, in the above embodiment, the image forming device has been described as having four colors of ink: CMYK, but the ink colors may be different, and the number of colors may be more or less than this. Furthermore, the same color ink with different components, such as two types of black, may be ejected.

In addition, in the above embodiment, the image forming device 1 was described as an inkjet recording device, but if the image forming device has multiple recording elements arranged in a row, each of which forms dots, the missing part completion processing described in the above embodiment can be applied.

In addition, in the above embodiment, the ejection data generation process, including the missing part completion process, is described as being performed by the control unit 40 of the image forming apparatus 1, but this is not limited to this. The final ejection data obtained by performing the missing part completion process, etc., on an external terminal device may be transmitted to the image forming apparatus 1, and the image forming apparatus 1 may simply perform image formation operations based on the ejection data. Furthermore, the ejection data generation process may be distributed and executed by multiple electronic devices, etc.

In the above description, the storage unit 42, which is a nonvolatile memory such as a flash memory, is used as an example of a computer-readable medium for storing the program 421 related to the defect complementation control of the present invention. However, the present invention is not limited to this. Other computer-readable media include HDDs, other nonvolatile memories such as EEPROMs and MRAMs, and portable recording media such as CD-ROMs and DVDs. Furthermore, a carrier wave is also applicable to the present invention as a medium for providing program data related to the present invention via a communication line.
In addition, the specific configurations, contents and procedures of the processing operations shown in the above embodiments can be modified as appropriate without departing from the spirit of the present invention. The scope of the present invention includes the scope of the invention described in the claims and its equivalents.

REFERENCE SIGNS LIST 1 Image forming apparatus 10 Medium supply section 11 Supply tray 12 Feeder boards 121, 122 Roller 123 Belt 20 Forming operation section 21 Image forming drum 22 Transfer unit 221 Swing arm section 222 Transfer drum 23 Heating section 231 Drum heater 232 Ink heater 24 Head unit 240 Recording head 241 Head driving section 25 Irradiation section 251 LED
26 Imaging unit 27 Delivery unit 271 Delivery rollers 272, 273 Roller 274 Belt 29 Conveyance drive unit 30 Medium discharge unit 31 Discharge tray 40 Control unit 401 CPU
402 RAM
42 Storage unit 421 Program 422 Malfunctioning nozzle list 423 Offset amount data 51 Communication unit 52 Display unit 53 Operation acceptance unit Ag Range Di Area M Recording medium N Nozzle P Electromechanical conversion element R Recording element

Claims (13)

a position determination means for determining dot generation positions on a recording medium, where dots are generated on the recording medium by a plurality of recording elements arranged in a first direction and moving relative to the recording elements in a second direction intersecting the first direction, based on gradation data of each pixel of an image to be formed in accordance with an image formation command;
a replacement number determination means for determining a number of corrected dots by adding an offset number, which is an additional number of dots, to the number of dot generation positions of the malfunctioning recording elements that are set as the recording elements where dots are not normally generated;
position change means for determining the dot generation positions of the corrected number of dots within a range in which dots can be generated by recording elements other than the malfunctioning recording elements;
A processing device comprising: The processing device described in claim 1, further comprising a change determination means for determining the offset number based on the gradation data. A processing device as described in claim 2, characterized in that the gradation data associated with the offset number is determined by the number of dot generation positions set in a predetermined range surrounding the generation range of dots corresponding to the malfunctioning recording element. a storage means for storing a correspondence relationship between a value relating to the gradation of the pixel and the offset number;
4. The processing device according to claim 2, wherein the correspondence is changeable. An operation receiving means is provided,
the storage means stores a plurality of types of the correspondence relationships;
5. The processing device according to claim 4, wherein the change determining means determines the offset number based on one of the correspondence relationships selected based on the input operation received by the operation receiving means. The processing device described in any one of claims 2 to 5, characterized in that the change determination means determines the offset number based on the type of recording medium on which the image is formed. The processing device described in any one of claims 2 to 6, characterized in that the change determination means determines the offset number based on the color of the dots generated by the recording elements. the plurality of recording elements belong to any of a plurality of recording heads,
8. The processing device according to claim 2, wherein the change determining unit determines the offset number depending on the print head. the plurality of recording elements belong to a recording head,
8. The processing device according to claim 2, wherein the change determining unit determines the offset number in accordance with a plurality of regions obtained by dividing the print head. A processing device according to any one of claims 1 to 9, characterized in that the offset number is a positive value. a recording head to which the plurality of recording elements belong;
A processing device according to any one of claims 1 to 10;
a driving unit that causes the recording head to generate dots at the dot generation positions determined by the position changing unit;
An image forming apparatus comprising: a position determination step of determining dot generation positions on a recording medium, where dots are generated on the recording medium by a plurality of recording elements arranged in a first direction and moving relative to the recording elements in a second direction intersecting the first direction, based on gradation data of each pixel of an image to be formed by an image formation command;
a substitution number determination step for determining a number of corrected dots by adding an offset number, which is an additional dot number, to the number of dot generation positions of the malfunctioning recording elements that are set as the recording elements where dots are not normally generated;
a position change step of determining the dot generation positions of the corrected number of dots within a range in which dots can be generated by recording elements other than the malfunctioning recording element;
10. An image forming operation setting method comprising: a position determination means for determining dot generation positions on a recording medium, which causes a plurality of recording elements arranged in a first direction to generate dots on the recording medium, which moves relative to the recording elements in a second direction intersecting the first direction, based on gradation data of each pixel of an image to be formed by an image formation command;
a replacement number determination means for determining a number of corrected dots by adding an offset number, which is an additional number of dots, to the number of dot generation positions of the malfunctioning recording elements that are set as the recording elements at which dots are not normally generated;
a position change means for determining a dot generation position of the corrected number of dots within a range in which dots can be generated by recording elements other than the malfunctioning recording element;
A program characterized by functioning as