Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/015—Ink jet characterised by the jet generation process
  • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
  • B41J2/045—Ink jet characterised by the jet generation process generating single droplets or particles on demand by pressure, e.g. electromechanical transducers
  • B41J2/04501—Control methods or devices therefor, e.g. driver circuits, control circuits
  • B41J2/04508—Control methods or devices therefor, e.g. driver circuits, control circuits aiming at correcting other parameters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/015—Ink jet characterised by the jet generation process
  • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
  • B41J2/045—Ink jet characterised by the jet generation process generating single droplets or particles on demand by pressure, e.g. electromechanical transducers
  • B41J2/04501—Control methods or devices therefor, e.g. driver circuits, control circuits
  • B41J2/0451—Control methods or devices therefor, e.g. driver circuits, control circuits for detecting failure, e.g. clogging, malfunctioning actuator
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/015—Ink jet characterised by the jet generation process
  • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
  • B41J2/045—Ink jet characterised by the jet generation process generating single droplets or particles on demand by pressure, e.g. electromechanical transducers
  • B41J2/04501—Control methods or devices therefor, e.g. driver circuits, control circuits
  • B41J2/0458—Control methods or devices therefor, e.g. driver circuits, control circuits controlling heads based on heating elements forming bubbles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/015—Ink jet characterised by the jet generation process
  • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
  • B41J2/045—Ink jet characterised by the jet generation process generating single droplets or particles on demand by pressure, e.g. electromechanical transducers
  • B41J2/04501—Control methods or devices therefor, e.g. driver circuits, control circuits
  • B41J2/04581—Control methods or devices therefor, e.g. driver circuits, control circuits controlling heads based on piezoelectric elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/015—Ink jet characterised by the jet generation process
  • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
  • B41J2/045—Ink jet characterised by the jet generation process generating single droplets or particles on demand by pressure, e.g. electromechanical transducers
  • B41J2/04501—Control methods or devices therefor, e.g. driver circuits, control circuits
  • B41J2/04593—Dot-size modulation by changing the size of the drop
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/21—Ink jet for multi-colour printing
  • B41J2/2121—Ink jet for multi-colour printing characterised by dot size, e.g. combinations of printed dots of different diameter
  • B41J2/2128—Ink jet for multi-colour printing characterised by dot size, e.g. combinations of printed dots of different diameter by means of energy modulation

Definitions

• the present invention relates to a technique for printing an image on a print medium by discharging ink.
• the present invention has been made to solve the above-mentioned problems in the prior art, and it is an object of the present invention to provide a technique for improving color reproducibility by compensating for an error in the amount of ink for each type of ink droplet. Aim.
• the present invention provides a method for printing ink on a print medium.
• Printing is performed using a printing unit that can form N types of dots of different sizes in the area of one pixel by selectively discharging N types (N is an integer of 2 or more) of different amounts of ink droplets.
• An error information receiving unit that receives error information representing the dot data, and a dot data generating unit that processes the given original image data to generate dot data representing the dot formation state of each pixel in the print image.
• the dot data generating unit is configured to generate dot data in which the error in the ink amount is compensated for each of the specific types of ink droplets, according to the error information. It is characterized by.
• the dot data is compensated for each specific type of ink droplet so as to compensate for an error in the ink amount. Because the ink can be generated, the color can be reproduced more accurately even when the error of the ink amount varies for each type of ink droplet.
• the dot data generation unit converts a color system of the original image data using a color conversion table, so that a color represented by a plurality of color components that can be used by the printing unit.
• a color conversion unit that generates converted image data; and a correspondence relationship in which a tone value of the color conversion image data is input and a combination of recording rates of the N types of dots is output.
• a halftone processing unit that converts a tone value of the color-converted image data into one of N tone values for each pixel based on the corrected correspondence in which the error information is reflected,
• the halftone processing unit determines a reference between a gradation value of the color-converted image data prepared in advance assuming that there is no error in the ink amount and a recording rate combination of each of the N types of dots.
• the correspondence and the error information It has preferred to so as to generate the corrected correspondence relationship. In this way, the amount of ink can be compensated by correcting the correspondence in which the tone values of the color-converted image data are input and the combinations of the recording rates of the N types of dots are output.
• the halftone processing unit may include a first ink amount ejected per unit area when the error of the ink amount is not included and a unit area per unit area when the error of the ink amount is included.
• a second ink amount to be ejected is calculated for each gradation value of the color-converted image data based on the reference correspondence relationship, and the first ink amount is divided by the second ink amount. It is preferable that the corrected correspondence is generated by multiplying the corrected value by the gradation value. This makes it possible to quickly determine the corrected correspondence with a simple configuration.
• the halftone processing unit may calculate the first amount of ink ejected per unit area when the error of the amount of ink is not included in the color-converted image data based on the reference correspondence relationship. And the reference correspondence is adjusted such that the second ink amount ejected per unit area when the ink amount error is included approaches the first ink amount. In this case, it is preferable to generate the corrected correspondence described above. In this way, a more accurate corrected correspondence can be generated.
• the dot data generation unit converts the color system of the original image data using a corrected color conversion table in which the error information is reflected, so that the print unit can be used.
• a halftone processing unit that converts the tone value of the color-converted image data into one of N tone values for each pixel based on a correspondence relationship in which the combinations of the recording rates of the dots are output.
• the color conversion unit generates the corrected color conversion table according to the reference color conversion table set assuming that there is no error in the ink amount and the error information. Is preferred.
• the gradation can be expressed by using the combination of the dot recording rates set in advance. Colors can be accurately reproduced without excessively reducing the features.
• FIG. 1 is a block diagram showing the configuration of a printing system as one embodiment of the present invention.
• FIG. 2 is a schematic configuration diagram of the color printer 20.
• c 4 is an explanatory diagram showing a purine evening head of a schematic configuration into dot Bok recording of the present invention is an explanatory diagram showing a dot Bok formation principle in the printer of the present invention.
• FIG. 5 is a flowchart showing the flow of the dot formation control routine.
• FIG. 6 is a flowchart showing the flow of the half-in process.
• FIG. 7 is an explanatory diagram showing a dot recording rate table.
• FIG. 8 is an explanatory diagram showing the concept of dot on / off determination by the dither method.
• FIG. 9 is an explanatory diagram showing a relationship between a dither matrix used for determining a large dot and a dither matrix used for determining a small dot.
• FIG. 10 is an explanatory diagram showing a method of correcting the dot recording rate table performed in the first embodiment of the present invention.
• FIG. 12 is an explanatory diagram showing a method for compensating for an error in the amount of ink in the second embodiment of the present invention.
• FIG. 13 is an explanatory diagram showing a method of calculating a correction coefficient used for compensating for an error in the amount of ink in the second embodiment of the present invention.
• FIG. 14 is an explanatory diagram showing a method for compensating for an error in the amount of ink in the third embodiment of the present invention.
• FIG. 15 is an explanatory diagram showing the dot recording rate table and the ink ejection amount according to the third embodiment of the present invention.
• FIG. 16 is a correspondence table used for adjusting a gradation value in the third embodiment of the present invention.
• FIG. 1 is a block diagram showing a configuration of a printing system as one embodiment of the present invention.
• This printing system includes a computer 88 as a printing control device, and a color printer 20 as a printing unit.
• the combination of the color printer 20 and the computer 88 can be called a “printing device” in a broad sense.
• an application program 95 runs under a predetermined operating system.
• the operating system incorporates a video driver 94 and a printer driver 96, and the application program 95 supplies a print data PD for transfer to the color printer 20 via these drivers. Will be output.
• the application program 95 performs desired processing on the image to be processed, and displays the image on the CRT 21 via the video driver 94.
• the printer driver 96 of the computer 88 receives the image data from the application program 95 and converts it into print data PD to be supplied to the color printer 20. I do.
• a resolution conversion module 97 inside the printer driver 96, a color conversion module 98, a half I-one module 99, a print data generation module 100, A color conversion table LU, an ink amount compensator 10 #, and an error information receiver 102 are provided. These functions will be described later.
• the printer driver 96 is equivalent to a program for realizing a function of generating the print data PD.
• a program for realizing the function of the printer driver 96 is supplied in a form recorded on a recording medium that can be read all over the computer.
• recording media include flexible disks, CD-ROMs, magneto-optical disks, IC cards, ROM cartridges, punched cards, printed materials on which codes such as bar codes are printed, and internal storage devices (RAMs) of computers.
• RAMs internal storage devices
• FIG. 2 is a schematic configuration diagram of the color printer 20.
• the color printer 20 includes a sub-scan feed mechanism that conveys the printing paper P in the sub-scan direction by the paper feed motor 22, and a sub-scan feed mechanism 27 that the carriage 30 includes in the sub-scan feed mechanism by the carriage motor 24.
• a main scanning feed mechanism that reciprocates in the axial direction (main scanning direction) of the printer and a print head unit 60 (also referred to as a “print head assembly”) mounted on the carriage 30 drive ink ejection and discharge.
• the head drive mechanism that controls the dot formation, and exchanges signals with these paper feed motors 22, carriage motors 24, print head units 60, and operation panel 32.
• a control circuit 40 is connected to a computer 88 via a connector 56.
• the print head unit 60 has a memory (not shown) in which error information indicating an error in the ink ejection amount is stored.
• the control circuit 40 reads out the error information from this memory and sends it to the computer 88 via the connector 56.
• the transmitted error information is received by the error information receiving unit 102 (FIG. 1) in the computer 88.
• the sub-scan feed mechanism that conveys the printing paper P includes a gear train that transmits the rotation of the paper feed motor 22 to the sub-scan feed mechanism 27 and a paper conveyance roller (not shown) (not shown). .
• the main scanning feed mechanism for reciprocating the carriage 30 includes a sliding shaft 34 erected in parallel with the axis of the sub-scanning feed mechanism 27 for holding the carriage 30 slidably, and a carriage motor 24.
• a pulley 38 on which an endless drive belt 36 is stretched is provided, and a position sensor 39 for detecting the origin position of the carriage 30 is provided.
• FIG. 3 is an explanatory diagram showing a schematic configuration inside the ink ejection head 28.
• the heads 6 1 to 66 of each color of the printing head 28 provided in the printer (the heads 62 to 66 of each color are not shown).
• the ink cartridge is installed for the first time, the ink is drawn into the heads 61 to 66 of each color by a dedicated pump.
• a pump for suction a cap for covering the print head 28 at the time of suction, and the like are omitted.
• the heads 61 to 66 of each color are provided with a plurality of nozzles Nz for each color, and a piezo element PE, which is one of the electrostrictive elements and has excellent response, is provided for each nozzle. It is located.
• FIG. 4 shows the structure of the piezo element PE and the nozzle Nz in detail. As shown in the upper part of FIG. 4, the piezo element PE is installed at a position in contact with the ink passage 68 that guides the ink to the nozzle Nz.
• the piezo element PE is an element that distorts the crystal structure due to the application of a voltage and converts electro-mechanical energy at an extremely high speed.
• the piezo element PE expands only for the duration of the voltage application as shown in the lower part of FIG. Deform one side wall of passage 6 8.
• the volume of the ink passage 68 contracts in accordance with the expansion of the piezo element PE, and the ink corresponding to this contraction becomes an ink droplet Ip, and is discharged from the tip of the nozzle Nz at high speed.
• Printing is performed by the ink droplets Ip penetrating into the paper P mounted on the platen 26.
• the size of the ink droplet Ip can be changed by a method of applying a voltage to the piezo element PE. This makes it possible to form, for example, three types of large, medium and small dots.
• the size of the ink droplet Ip also fluctuates due to a manufacturing error of the ink passage 68 or an individual difference of the piezo element PE.
• the amount of this variation is stored as error information in a memory provided in the print head unit 60.
• the error information is information for each ink droplet IP for forming each of the large, medium, and small dots. The embodiment described later aims at performing accurate color reproduction by compensating this variation amount for each type of ink droplet IP.
• the carriage 30 is transported by the paper feed motor 23 (hereinafter referred to as “sub-scan”), and the carriage 30 is moved by the carriage. It is reciprocated by the motor 24 (hereinafter referred to as main scanning), and simultaneously drives the piezo elements PE of each color head 6 1 to 66 of the print head 28 to discharge each color ink and form a dot. To form a multicolor image on paper P.
• main scanning the motor 24
• main scanning simultaneously drives the piezo elements PE of each color head 6 1 to 66 of the print head 28 to discharge each color ink and form a dot.
• FIG. 5 is a flowchart showing the flow of the dot formation control routine in this embodiment. This processing is executed in the computer 88.
• the printer driver 96 receives the image data of RGB.
• This image data is data passed from the application program 95 shown in FIG. 1 and has a value of 0 to 255 for each color of R, G, and B for each pixel constituting the image. This is data having six gradation values.
• step S 105 the resolution conversion module 97 converts the resolution of the input image data into the resolution in the printer 20. If the image data is lower than the print resolution, the resolution conversion is performed by generating new data between adjacent original image data by linear interpolation. Conversely, if the image resolution is higher than the printing resolution, the resolution conversion is performed by thinning out the data at a fixed rate.
• the color conversion module 98 performs a color conversion process.
• the color conversion process is a process of converting image data composed of R, G, and B gradation values into multi-gradation data representing gradation values of C, M, ⁇ , and K colors used in the printer 20. .
• This processing is performed using a color conversion table LUT (see Fig. 1) that stores the combinations of C, M, ⁇ , and K for expressing the color composed of each combination of R, G, and B on the printer 20. Done. Note that this multi-gradation data corresponds to the color conversion image data in the claims.
• step S200 the half I-one module 99 performs an eight-one I-one process on the image data thus color-converted.
• the half-in process means that the tone value of the original image data (256 m in this embodiment) is represented by the pixel 20 for each pixel.
• This refers to a process of reducing colors to possible gradation values.
• color reduction refers to reducing the number of gradations expressing colors. In the present embodiment, color reduction to four gradations of “no dot formation”, “small dot formation”, “medium dot formation”, and “large dot formation” is performed.
• FIG. 6 is a flowchart showing the flow of the half-in process in this embodiment.
• step S210 the half I-line module 99 receives multi-tone data from the color conversion module 98.
• the multi-tone data input here is subjected to color conversion processing (step S110 in FIG. 5), and is data having 256 gradations for each color of C, M, Y, ⁇ .
• step S220 large dot level data LVL is determined as follows in accordance with the gradation of the image data.
• FIG. 7 is an explanatory diagram showing a dot recording rate template used for determining the level data of each of the large, medium, and small dots.
• the horizontal axis is the gradation value (0 to 255)
• the left vertical axis is the dot recording rate (%)
• the right vertical axis is the level data (0 to 255).
• the “dot recording rate” means the proportion of pixels in the area where dots are formed, when a uniform area is reproduced according to a certain gradation value.
• the curve SD in FIG. 7 shows the recording rate of small dots
• the curve MD shows the recording rate of medium dots
• the curve LD shows the recording rate of large dots.
• the level data refers to data obtained by converting the dot recording rate into 256 levels of values from 0 to 255.
• the level data LVL corresponding to the gradation value is read from the large dot curve LD.
• the curve D is stored in a memory (not shown) as a ⁇ -dimensional table, and the level data is obtained by referring to this table. This table is referred to herein as the recording rate table DT.
• step S230 it is determined whether or not the level data LVL thus set is larger than the threshold value THL.
• THL the threshold value
• the determination of the talent of the dot by the dither method is performed.
• the threshold H is set for each pixel by so-called dither matrix. Are set to different values. In this embodiment, a matrix in which values 0 to 254 appear in a 16 ⁇ 16 square pixel block is used.
• FIG. 8 is an explanatory diagram showing the concept of dot on / off determination by the dither method. For convenience of illustration, only some pixels are shown. As shown in FIG. 8, each pixel of the level data LV is compared with the corresponding portion of the dither table. When the level data LVL is larger than the threshold value THL indicated in the dither table, the dot is turned on, and when the level data LVL is smaller, the dot is turned off. In FIG. 8, the pixels with eight dots indicate the pixels that turn on the dots.
• One module 9 When the level data LVL is greater than the threshold value THL, the module 9 determines that the large dot should be turned on, and assigns the value 1 in binary to the variable RE indicating the result value. Substitute 1 (step S300).
• the result value RE is a variable representing the size of the dot formed in the pixel. Pixels with this variable 11 form a large dot.
• step S230 the half-in-one module 99 determines that a large dot should not be formed if the level data LVL is smaller than the threshold value THL. Proceed to 240.
• step S240 the middle dot level data LVM is set.
• the medium dot level data LVM is set based on the gradation value by the above-described recording rate table DT.
• the setting method is the same as the setting of the large dot level data LVL.
• step S250 the magnitude relationship between the level data LVM of the middle dot and the threshold value THM is compared to determine whether the middle dot is on or off.
• the method of judging ON / OFF is the same as in the case of large dots, but the threshold value LVM used for judgment is different from the threshold value LVL of large dots as shown below.
• the pixels for which the dot is likely to turn on coincide with each other.
• the middle dot will be turned off when the large dot becomes talented.
• the middle dot The recording rate may be lower than the desired recording rate.
• the dither matrix is changed for both. In other words, the positions of the pixels that are likely to be turned on are changed between the large dot and the middle dot to ensure that each is formed appropriately.
• FIG. 9 is an explanatory diagram showing the relationship between dither matrices used for determining large dots and dither matrices used for determining medium dots.
• the first dither matrix TM is used for large dots
• the second dither matrix UM is used for medium dots by shifting these threshold values symmetrically in the sub-scanning direction. Is used.
• a 64 ⁇ 64 matrix is used as described above, but FIG. 9 shows a 4 ⁇ 4 matrix for convenience of illustration. Note that a completely different dither matrix may be used for the large dot and the medium dot.
• step S250 If the middle dot level data LVM is larger than the threshold value THM in step S250, it is determined that the middle dot should be turned on, and the value 10 is substituted into the result value RE in binary. (Step S290). On the other hand, when the middle dot level data LVM is smaller than the threshold value THM in step S250, it is determined that the middle dot should not be formed, and the process proceeds to step S255.
• step S255 the small dot level data LVS is set in the same manner as the setting of the large dot and medium dot level data.
• step S260 the half I module 99 determines that the small dot should be turned on when the level data LVS is greater than the threshold value THS, and stores the result value in the variable RE as a binary number. The value 0 1 is substituted (step S280).
• step S280 the small dot level data LVS is smaller than the threshold value THS in step S260, it is determined that a dot should not be formed, and the variable RE indicating the result value has a binary value of 0. 0 is substituted (step S270).
• the dither matrix for small dots differs from that for medium dots and large dots in order to suppress the drop in the recording rate of small dots as described above. It is preferred that
• the half I-one module 99 repeats the processing of steps S220 to S300 until the processing is completed for all pixels (step S310).
• the processing routine for the I-one is temporarily terminated, and the processing returns to the dot formation control processing routine.
• step S400 the print data generation module 100 generates print data PD from the half I ⁇ 1 data thus generated.
• the print data PD is data including raster data indicating a dot recording state during each main scan and data indicating a sub-scan feed amount, and is output to the printer 20 (S410).
• the printer 20 receives this data, forms large, medium, and small dots on each pixel, and prints an image. Note that the above half-in process is performed on the assumption that there is no error in the ink amount of the ink droplet, so that if the ink amount contains an error, the color will not be accurately reproduced.
• FIG. 0 is an explanatory diagram showing a method of correcting the dot recording rate table performed in the first embodiment of the present invention.
• the curves SD and SDc in Fig. 10 (a) show the dot recording rates of small dots, and the curves MD and MDc show the dot recording rates of medium dots, and the curves LD and LDc show the dot recording rates of large dots. Each is shown. Dotted lines SD, MD, and LD show the dot recording rates before correction, and solid lines SDc, MDc, and LDc show the dot recording rates after correction.
• the dot recording rate table is corrected to compensate for variations in the amount of ink caused by individual differences of the print head unit 60 for each type of dot.
• Figure 10 (b) shows the target value of the ink amount of the ink droplet for forming dots of each size, error information, the estimated value of the ink weight, the correction coefficient, and the corrected ink amount. Is shown.
• the target value of the ink amount is the ink weight of the ink droplet assuming that the ink droplet is ejected without error.
• the error information is information indicating an error in the ink weight of the ink droplet ejected by the print head unit 60 used for printing. For example, in the case of an ink drop for forming a small dot, the target value of the ink weight is 10 ng (nanogram), and the error information is 0.1.
• the correction coefficient is determined such that the ink weight approaches the target value by multiplying the predicted value of the ink weight.
• the correction in this embodiment is performed by adjusting the dot recording rate of each size dot according to the correction coefficient. That is, it is performed by directly adjusting the number of dots formed per unit area. Specifically, as shown in FIG. 10 (a), for a small dot, for example, the curve SDc representing the dot recording rate after correction is the curve SDc representing the dot recording rate before correction. Is multiplied by the correction coefficient 0.91.
• Such adjustment can be implemented, for example, by adding a step of multiplying the level data of the dots of each size by the respective correction coefficients.
• the printing process in this embodiment is performed as follows.
• the computer 88 first reads the error information from the memory of the print unit 60 via the control circuit 40 of the printer 20.
• the error information is received by the error information receiving unit 102 in the computer 88 and sent to the ink amount compensating unit 101.
• the ink amount compensating unit 101 obtains a correction coefficient from the error information and multiplies the correction coefficient by the level data of the dot recording rate table DT provided in the halftone module 99. In this way, the dot recording rates of the large, medium and small dots are adjusted.
• the printer driver 96 receives the image data from the application program 95 and sends the image data to the print data PD for supplying it to the color printer 20. conversion I do.
• the error in the ink amount can be compensated for each ink droplet having a different ink weight, so that even when the error in the ink amount varies for each ink droplet, Colors can be reproduced more accurately. Further, by performing such correction for each of the ink colors, an accurate color balance can be realized.
• the resolution conversion module 97, the color conversion module 98, the halftone module 99, and the ink amount compensator 101 correspond to a dot data generator in the claims.
• the second embodiment differs from the first embodiment in that the amount of ink is compensated by adjusting the gradation value of the multi-gradation data by multiplying the dot level data of each size by a correction coefficient. .
• FIG. 11 is an explanatory diagram showing a dot recording rate table and ink ejection amounts according to the second embodiment of the present invention.
• FIG. 11 (a) is a diagram showing the relationship between the gradation value of multi-gradation data and the dot recording rate of dots of each size, and the curves SD, MD, and 0 are shown in FIG. a) The dotted line in the middle is the same as SD, MD, LD.
• FIG. 11B is an explanatory diagram showing the relationship between the gradation value and the weight of ink ejected to a predetermined area. This figure is a figure generated using the predicted values of the ink drop weight in the table shown in FIG. 10 (b).
• the ink ejection amount increases from 0 ng to 7650 ng along the straight line W i.
• the ink weight ejected to a predetermined area and the gradation value have a linear relationship.
• the weight of the ink ejected to the predetermined area increases as follows with an increase in the gradation value. (1) In the region from the gradation value 0 to the gradation value G1, the ink weight increases linearly as the dot recording rate of the small dot increases.
• the dot recording rate for small dots is constant, and the ink weight linearly increases as the dot recording rate for medium dots increases. Increase.
• such a profile is generated as a result of the following trade-off.
• the profile is set with the upper limit of the dot recording rate for small dots being 25% and the upper limit of the dot recording rate for medium dots being 50%.
• FIG. 12 is an explanatory diagram showing a method of compensating for an error in the amount of ink in the second embodiment of the present invention.
• FIG. 12 (a) is an explanatory diagram showing how an error in the ink amount is compensated by adjusting the gradation value of the multi-gradation data.
• Dotted line W i is a line indicating the relationship between the gradation value and the ideal ink ejection amount when there is no error, and is shown in FIG. 11 (b). Is the same as the straight line W i.
• the solid line We is a line showing the relationship between the gradation value and the estimated ink ejection amount when the ink amount error is considered.
• the solid line We is a diagram generated by using the estimated values of the ink droplet weights in the table shown in FIG. 10 (b), and is shifted from the dotted line Wi by the ink amount error.
• the gradation value of the multi-gradation data is adjusted as follows. For example, if the gradation value is G, the ideal ink ejection amount is Rt on the dotted line W i assuming that there is no error in the ink amount. The ink discharge amount is Re. As a result, it is expected that a difference occurs between the ideal ink ejection amount Rt and the predicted ink ejection amount Re at the gradation value G. This difference results in an error in the amount of ink to be compensated.
• FIG. 12B is an explanatory diagram showing a calculation formula for adjusting a gradation value to compensate for an error.
• the gradation value Gc adjusted by multiplying the gradation value G by a value obtained by dividing the ideal ink ejection amount Rt by the predicted ink ejection amount Re is obtained.
• the ink ejection amount corresponding to the tone value Gc thus obtained is Rc.
• the compensated ink ejection amount Rc is closer to the ideal ink ejection amount Rt than the predicted ink ejection amount Re, it can be seen that the error in the ink amount is suppressed.
• the ideal ink ejection amount Rt corresponds to the first ink amount in the claims
• the predicted ink ejection amount Re corresponds to the second ink amount in the claims.
• FIG. 13 is an explanatory diagram showing a method for calculating a correction coefficient (R t RR e) used for compensating for an error in the amount of ink in the second embodiment of the present invention.
• FIG. 13 (a) is an explanatory diagram showing the relationship between the gradation value and the distribution rate of the ink amount for forming dots of each size. This figure shows the ratio of the amount of ink ejected to a predetermined area for each dot of each size. For example, when the gradation value is G1, only the ink drops for forming the small dots are ejected, so the distribution ratio of the small dots is 100%, and the distribution ratio of the medium dots and the large dots is Are all 0%.
• the distribution ratios of large, medium, and small dots are 0%, 80%, and 20%.
• the distribution ratio for each dot of each size can be obtained from the product of the weight of each ink droplet (for example, 10 ng for a small dot) and the dot recording rate.
• the product of the weight of the ink droplet and the dot recording rate is 10 ng X 25% for a small dot, and 20 ng X 50% for a medium dot.
• the dot recording rate is 0% for large dots, the ratio of the ink amounts of small, medium, and large dots is 250: 1 000: 1.
• the correction coefficient for adjusting the gradation value using the distribution ratio can be obtained by the following method.
• FIG. 13B is an explanatory diagram showing a relationship between a gradation value and a correction coefficient for adjusting the gradation value.
• This correction coefficient can be obtained from the correction coefficient for the dots of each size shown in FIG. 10B and the ink amount distribution ratio. Specifically, the correction coefficient is obtained by calculating the product of the correction coefficient and the ink amount distribution ratio for each size dot, and then calculating the sum of these values.
• the correction coefficient is 0.91 which is the same as the correction coefficient for the small dot.
• the correction coefficient for the small dot is the product of 20%, which is the ink distribution ratio of the small dot, and 0.9 mm of the correction coefficient for the small dot.
• the correction coefficient for the medium dot is 0.94, which is the product of the ink distribution ratio of the medium dot of 80% and the correction coefficient of the medium dot of 1.18. As a result, the correction coefficient is 1.12.
• the tone value is adjusted using this value.
• the gradation value of G2 is 100
• the gradation value is replaced with 1 12 which is the product of the correction coefficients. This replacement By generating the level data using the obtained gradation values as input values, it is possible to compensate for errors in the amount of ink.
• the compensation can be made by adjusting the P-tone value, so that the combination of the dot recording rates of the dots of each size is not changed.
• the combination of the dot recording ratios is set so as to reduce, for example, graininess (image roughness) and banding (streak-like image quality deterioration), such a dot recording ratio can be obtained.
• the advantage is that colors can be reproduced more accurately without excessively reducing the characteristics of the recording rate combinations.
• the third embodiment differs from the second embodiment in that the ink amount is compensated by adjusting the gradation value without changing the combination of the dot recording rates of the dots of each size. Common. However, this embodiment is different from the second embodiment in the method of adjusting the gradation value.
• FIG. 14 is an explanatory diagram showing a method for compensating for an error in the amount of ink in the third embodiment of the present invention.
• the dotted line Wi is a line indicating the relationship between the gradation value and the ideal ink ejection amount
• the solid line We is a line indicating the relationship between the gradation value and the predicted ink ejection amount.
• the solid line We, the dotted line, and W i are the same as the solid line We and the dotted line W i shown in Fig. 12 (a), respectively.
• the gradation value is adjusted as follows.
• the ideal ink ejection amount is the ink ejection amount Rt corresponding to the point Pt on the dotted line Wi.
• the point Pc is determined by searching the solid line We for a gradation value capable of discharging the ink amount closest to the ink discharge amount Rt.
• the gradation value Gc corresponding to the point Pc is the adjusted output gradation value.
• the input tone value G is converted into the output tone value Gc.
• FIG. 15 shows a dot recording rate table DT and ink ejection according to the third embodiment of the present invention. It is explanatory drawing which shows an output amount.
• Fig. 15 (a) is a table generated using the target values of the ink amount. For example, when the input gradation value is 106, 64 small dots are formed and 128 medium dots are formed, but large dots are not formed.
• the target value of the ink droplet weight is 10 ng for small dots and 20 ng for medium dots.
• FIG. 16 is a correspondence table used for adjusting a gradation value in the third embodiment of the present invention.
• This correspondence table is a table for adjusting the gradation value so that the ink amount predicted to be ejected approaches the ink amount desired to be ejected. For example, when the input gray scale value to be expressed is 106, 1 15 corresponds to the output gray scale value. As a result, it can be seen that the amount of ink predicted to be ejected is changed from 288 ng to 3204 ng, and approaches the desired ink amount of 3200 ng.
• this embodiment is similar to the above-described second embodiment in that compensation can be performed by adjusting the gradation value, but the input gradation value and the output gradation value can be arbitrarily set. Therefore, there is an advantage that an error in the ink ejection amount can be minimized.
• compensation is made for all ink droplets for forming large dots, medium dots, and small dots, but compensation is made for some types of ink droplets. May be. For example, compensation may be made only for a specific type of ink droplet (for example, a small ink droplet), but not for other types of ink droplets.
• the compensation of the ink amount is performed by adjusting the gradation value of the recording rate table DT, but the gradation value of the color conversion table LUT is adjusted. You may go. Alternatively, compensation may be performed by generating a color conversion table LUT in which the P tone values have been adjusted and performing color conversion using this. The color conversion table LUT in which the gradation value has been adjusted corresponds to a corrected color conversion template in the claims.
• the color conversion table LUT may be created in the memory when a printer is selected or when the printer driver is started, or may be created when the printer driver is installed or when the print unit is replaced, and stored in the computer hard disk. You may save it.
• the former has the advantage of avoiding confusion about the correspondence between printers and color conversion tables when multiple printers are available, while the latter reduces the time required to select printers and start the printer driver. Shortening There is an advantage that you can.
• the error of the ink amount is compensated in the half-toning process.
• the compensation may be performed in the color conversion process, or the gradation value of the original image data before the color conversion is performed. May be compensated by adjusting.
• the compensation of the ink amount performed in the present invention may be performed in any of the processes of processing the given original image data into the dot data.
• the method of dither diffusion processing is used for halftone processing, but error diffusion processing may be used.
• the half-in-one processing method may be any method as long as it can reduce the number of tones that can be formed by N types of dots from the multi-tone data of each ink color.
• a printer having a head for discharging ink using a piezo element is used, but a printer for discharging ink by another method may be used.
• the present invention may be applied to a printer of a type in which a heater disposed in an ink passage is energized and ink is ejected by bubbles generated in the ink passage.
• the processing in the printing apparatus described above can also be realized by a computer program.
• Examples of recording media on which such computer programs are recorded include flexible disks, CD-ROMs, magneto-optical disks, IC cards, ROM cartridges, punched cards, printed materials on which codes such as barcodes are printed, and internal storage in computers.
• Various computer-readable media, such as devices (memory such as RAM and ROM) and external storage devices, can be used.
• an embodiment as a program supply device that supplies a computer program for performing the above-described image processing or the like via a communication path at a short time is also possible.
• the present invention is applicable to an output device of a computer.

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• 2001
  • 2001-12-18 JP JP2001384968A patent/JP2003182120A/ja active Pending
• 2002
  • 2002-12-11 EP EP02786090A patent/EP1457336A4/en not_active Withdrawn
  • 2002-12-11 WO PCT/JP2002/012987 patent/WO2003051636A1/ja not_active Ceased
  • 2002-12-11 US US10/475,048 patent/US7137681B2/en not_active Expired - Lifetime
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