JP2004345124A - Printing apparatus, printing method, program for printing, and pattern for printing correction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply adjust printing irregularities even when an image to be printed is dividedly drawn by a plurality of scannings. <P>SOLUTION: A printing apparatus (printer 22 and computer 90) for dividedly printing the image to be printed on a printing medium by a plurality of the number of scannings has a pattern printing means for feeding rate correction (printing head 12) which prints a pattern for feeding rate correction so as to correct a feeding rate of the printing medium (printing paper P), and a feeding rate correcting means (computer 90) which corrects the feeding rate of the printing medium (printing paper P) on the basis of the pattern for feeding rate correction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a printing apparatus, a printing method, a printing program, and a printing correction pattern.
[0002]
[Prior art]
2. Description of the Related Art In recent years, as a kind of output device of a computer, a printer that ejects several colors of ink from a plurality of nozzles provided in a print head to form dots on a print medium and prints an image processed by a computer has been widely used. ing.
[0003]
By the way, in such a printer, the landing position of the ink droplet ejected from the nozzle may be shifted due to the processing accuracy of the nozzle or the like. In such a case, for example, when the ink droplet is displaced in the sub-scanning direction (a direction perpendicular to the scanning direction (main scanning direction) of the print head), if the ink droplets are normal, the dots should be arranged neatly in a matrix. Are partially shifted in the sub-scanning direction, and density unevenness such as white stripes may occur in a printed image.
[0004]
Therefore, conventionally, a print correction pattern printed by a printer is converted into an electric signal by a CCD (Charge Coupled Device) or the like and input, and density unevenness detected by weighting by an error diffusion method is corrected. (See Patent Document 1).
[0005]
[Patent Document 1]
JP-A-02-54676 (abstract)
[0006]
[Problems to be solved by the invention]
However, in recent years, a drawing method such as an interlace method has been proposed in which an image to be printed is drawn in a plurality of scans. FIG. 20 is a diagram illustrating an example of an interlaced printing method.
[0007]
In this figure, the circles indicate dots formed on the print medium, and the numbers inside the circles indicate the numbers of the nozzles that formed the dots. First, first to fifth dots indicated by white circles are formed by the first scan. Then, after the paper is fed by a predetermined amount L, a circle dot with a vertical hatching line is printed by the second scanning. Similarly, after the paper is fed by a predetermined amount L, a dot with a circle with oblique hatching is printed by the third scan.
[0008]
By the way, as shown in FIG. 21, when the paper feed amount is smaller than the predetermined amount L by d (error) (when there is a deviation), the dots are printed with a deviation in the upward direction in the figure. As a result, a blank portion in the vertical direction of the dot, that is, a white stripe may be generated.
[0009]
In such a case, even if the density unevenness is to be corrected by the above-described method, the density unevenness caused by both the error of the paper feed amount and the error of the nozzle is mixed. Is difficult.
[0010]
In recent years, printers having a plurality of different dot sizes and increasing the number of reproducible gradations by appropriately selecting the dots of the plurality of sizes are becoming widespread.
[0011]
Such a printer has a problem that it is very difficult to correct the density unevenness because the output characteristics, that is, the flight trajectory of the ejected ink droplets vary depending on the dot size.
[0012]
The present invention has been made based on the above circumstances, and an object thereof is to easily adjust print unevenness even when an image to be printed is divided into a plurality of scans and drawn. It is intended to provide a possible printing device, printing method, printing program, and print correction pattern.
[0013]
[Means for Solving the Problems]
In order to solve the problem, the present invention provides a printing apparatus that prints an image to be printed on a print medium by dividing the image to be printed into a plurality of scans by using a feed amount correction pattern for correcting a feed amount of the print medium. Feed amount correction pattern printing means for printing, feed amount correction means for correcting the feed amount of the print medium based on the feed amount correction pattern, and print correction comprising a plurality of patterns having different dot recording rates per unit area. And a dot recording rate determining means for determining a relationship between a gradation value and a dot recording rate based on the printing correction pattern.
[0014]
For this reason, it is possible to easily adjust the printing unevenness even when the image to be printed is drawn in a plurality of scans.
[0015]
According to another embodiment of the present invention, in addition to the above-described invention, N (N ≧ 2) kinds of ink droplets having different ink amounts are selectively ejected onto a print medium to have different sizes in one-pixel regions. N types of dots can be formed, and the print correction pattern printing unit prints the same print correction pattern composed of a plurality of patterns having different dot recording rates per unit area for at least one of the N types of ink droplets. Printing is performed using different types of inks, and the dot recording rate determining means determines the relationship between the gradation value and the dot recording rate for each of the N types of ink droplets based on the print correction pattern. . Therefore, even when one pixel is constituted by N types of ink droplets, it is possible to easily adjust the printing unevenness.
[0016]
According to another invention of the present invention, in addition to the above-described inventions, the feed amount correction pattern printing means repeats an operation of discharging ink from a predetermined nozzle when a print medium is fed, thereby performing printing. A plurality of line segments are printed on the medium, and the feed amount correction unit corrects the feed amount based on the plurality of line segments constituting the feed amount correction pattern. Therefore, it is possible to accurately determine the feed amount of the print medium based on the plurality of line segments.
[0017]
According to another aspect of the present invention, in addition to the above-described invention, the image forming apparatus further includes a reading unit that optically reads a plurality of line segments constituting a feed amount correction pattern printed on a print medium, The means corrects the feed amount of the print medium based on the information read by the reading means. Therefore, it is possible to easily and accurately determine the feed amount of the printing medium based on the plurality of line segments.
[0018]
According to another aspect of the present invention, in addition to the above-described invention, the reading unit optically reads the print correction pattern, and the dot recording rate determining unit performs dot printing based on the information read by the reading unit. The recording rate is determined. Therefore, not only the feed amount but also the dot recording rate can be easily and accurately obtained.
[0019]
Also, the present invention provides a printing apparatus that prints an image to be printed on a print medium by dividing the image to be printed into a plurality of scans, by feeding a feed amount correction pattern for correcting a feed amount of the print medium. Amount printing means, feed amount correcting means for correcting the feed amount of the print medium based on the feed amount correction pattern, and printing a print correction pattern comprising a plurality of patterns each having a different dot recording rate per unit area. Print correction pattern printing means, dot recording rate determining means for determining the relationship between the tone value and dot recording rate based on the print correction pattern, and the tone value and dot determined by the dot recording rate determining means Detecting means for detecting the occurrence of banding when the print correction pattern is printed according to the relationship with the recording rate; and detecting the occurrence of banding by the detecting means. If it is has a repeating means for repeatedly executing the determination processing by the dot recording rate determining means.
[0020]
For this reason, it is possible to easily adjust the printing unevenness even when the image to be printed is drawn in a plurality of scans.
[0021]
According to another aspect of the present invention, in addition to the above-described aspect, the repetition means corrects the feed amount correction when banding is detected even when the determination processing by the dot recording rate determination means is repeatedly executed. The correction processing of the feed amount by the means is repeatedly executed. For this reason, the feed amount causing the banding can be corrected without fail.
[0022]
According to another aspect of the present invention, in addition to the above-described aspect, the repetition means corrects the feed amount in a direction to reduce the feed amount when banding due to the presence of a portion having a low density occurs. I am trying to do it. For this reason, it is possible to reliably correct the feed amount that causes the occurrence of banding due to the presence of the low density portion.
[0023]
Also, the present invention provides a printing method for printing an image to be printed on a print medium by dividing the image to be printed into a plurality of scans, wherein a feed amount correction pattern for printing a feed amount correction pattern for correcting a feed amount of the print medium is provided. Print pattern, a feed correction step for correcting the feed amount of the print medium based on the feed correction pattern, and printing a print correction pattern including a plurality of patterns having different dot recording rates per unit area. A print correction pattern printing step, a dot recording rate determining step of determining a relationship between a tone value and a dot recording rate based on the print correction pattern, and a tone value and a dot determined by the dot recording rate determining step. A detection step for detecting the occurrence of banding when the print correction pattern is printed according to the relationship with the recording rate; and a detection step. What, if the occurrence of banding is detected, so that has a repeating step of repeatedly executing the determination processing by the dot recording rate determining step.
[0024]
For this reason, it is possible to easily adjust the printing unevenness even when the image to be printed is drawn in a plurality of scans.
[0025]
Also, the present invention provides a printing method for printing an image to be printed on a print medium by dividing the image to be printed into a plurality of scans, wherein a feed amount correction pattern for printing a feed amount correction pattern for correcting a feed amount of the print medium is provided. Print pattern, a feed correction step for correcting the feed amount of the print medium based on the feed correction pattern, and printing a print correction pattern including a plurality of patterns having different dot recording rates per unit area. The method includes a print correction pattern printing step and a dot recording rate determining step of determining a relationship between a gradation value and a dot recording rate based on the print correction pattern.
[0026]
For this reason, it is possible to easily adjust the printing unevenness even when the image to be printed is drawn in a plurality of scans.
[0027]
According to another aspect of the present invention, there is provided a computer-readable printing program for causing a computer to perform a process of printing an image to be printed on a print medium by dividing the image into a plurality of scans. Feed amount correction pattern printing means for printing a feed amount correction pattern for performing printing, feed amount correction means for correcting the feed amount of a print medium based on the feed amount correction pattern, and dot recording rates per unit area are different from each other. A print correction pattern printing unit that prints a print correction pattern including a plurality of patterns, and a dot recording rate determining unit that determines a relationship between a gradation value and a dot recording rate based on the print correction pattern.
[0028]
For this reason, it is possible to easily adjust the printing unevenness even when the image to be printed is drawn in a plurality of scans.
[0029]
According to another aspect of the present invention, there is provided a computer-readable printing program for causing a computer to perform a process of printing an image to be printed on a print medium by dividing the image into a plurality of scans. Feed amount correction pattern printing means for printing a feed amount correction pattern for performing printing, feed amount correction means for correcting the feed amount of a print medium based on the feed amount correction pattern, and dot recording rates per unit area are different from each other. A print correction pattern printing unit that prints a print correction pattern including a plurality of patterns; a dot recording ratio determination unit that determines a relationship between a gradation value and a dot recording ratio based on the print correction pattern; Band print when the print correction pattern is printed according to the relationship between the tone value determined by the means and the dot recording rate Detecting means for detecting the occurrence of ring, by the detection means, when the occurrence of banding is detected, so that to function repeating means for repeatedly executing the determination processing by the dot recording rate determining means as.
[0030]
For this reason, it is possible to easily adjust the printing unevenness even when the image to be printed is drawn in a plurality of scans.
[0031]
Further, according to the present invention, N types of dots having different sizes can be formed in one pixel region by selectively discharging N (N ≧ 2) types of ink droplets having different ink amounts on a print medium, In a print correction pattern used in a printing apparatus capable of printing an image to be printed in a plurality of scans, a feed amount correction pattern for correcting a feed amount of a print medium and N types of ink droplets And a print correction pattern in which a plurality of patterns having different dot recording rates per unit area are printed using the same type of ink.
[0032]
For this reason, it is possible to easily adjust the printing unevenness even when the image to be printed is drawn in a plurality of scans.
[0033]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0034]
First, an outline of a printing apparatus will be described with reference to FIGS. Hereinafter, a combination of the printer 22 and the computer 90 is referred to as a “printing device”.
[0035]
FIG. 1 is a schematic configuration diagram of a printer 22 constituting a printing apparatus, and FIG. 2 is a block diagram illustrating a configuration example of a main part of the printer 22 with a control circuit 40 at the center.
[0036]
As shown in FIG. 1, the printer 22 includes a sub-scan feed mechanism that conveys the printing paper P by a paper feed motor 23 and a main scan feed mechanism that reciprocates a carriage 31 in the axial direction of a paper feed roller 26 by a carriage motor 24. And Here, the feeding direction of the printing paper P by the sub-scanning feed mechanism is called a sub-scanning direction, and the moving direction of the carriage 31 by the main scanning feed mechanism is called a main scanning direction.
[0037]
The printer 22 includes a print head unit 60 mounted on the carriage 31 and including the print head 12, a head drive mechanism that drives the print head unit 60 to control ink ejection and dot formation, and paper The control circuit 40 is provided with a feed motor 23, a carriage motor 24, a print head unit 60, and a control circuit 40 which controls exchange of signals with the operation panel 32.
[0038]
Next, the configuration of the print head 12 corresponding to the feed amount correction pattern printing unit and the print correction pattern printing unit will be described with reference to FIG.
[0039]
As shown in FIG. 1, the carriage 31 has a cartridge 71 containing black (K) ink, a cartridge 72 containing cyan (C) ink, a cartridge 73 containing magenta (M) ink, and a yellow ( The four ink cartridges 71 to 74 of the cartridge 74 containing the ink of Y) are detachably mounted.
[0040]
The print head 12 is provided below the carriage 31. In the print head 12, nozzles as ink discharge locations are arranged in a row in the transport direction of the printing paper P, and form a nozzle row corresponding to each color ink.
[0041]
In the nozzle row provided below the carriage 31 and associated with each ink, a piezo element, which is one of the electrostrictive elements and has excellent responsiveness, is arranged for each nozzle. The piezo element is installed at a position in contact with a member that forms an ink passage that guides ink to the nozzle. The crystal structure of a piezo element is distorted by the application of a voltage, and converts electric-mechanical energy very quickly.
[0042]
In the present embodiment, by applying a voltage having a predetermined time width between the electrodes provided at both ends of the piezo element, the piezo element expands by the voltage application time and deforms one side wall of the ink passage. As a result, the volume of the ink passage contracts in accordance with the expansion of the piezo element, and the ink corresponding to the contraction is ejected at high speed from the tip of the nozzle as an ink droplet. The ink droplets permeate the printing paper P along the paper feed roller 26 to form dots and perform printing. The size of the ink droplet can be changed by a method of applying a voltage to the piezo element. This makes it possible to form three types of dots of different sizes, large, medium, and small.
[0043]
The control circuit 40 is connected to the computer 90 via the connector 56. The computer 90, which is a feed amount correction unit, a dot recording rate determination unit, and also a repetition unit, is equipped with a driver program for the printer 22 as described later, And a user interface for presenting various information in the printer 22 on a screen display of the display device.
[0044]
The sub-scan feed mechanism that transports the printing paper P includes a gear train (not shown) that transmits the rotation of the paper feed motor 23 to the paper feed roller 26 and the paper transport roller (not shown).
[0045]
The main scanning feed mechanism for reciprocating the carriage 31 has an endless drive between a carriage shaft 24 and a slide shaft 34 laid parallel to the axis of the paper feed roller 26 and slidably holding the carriage 31. A pulley 38 on which the belt 36 is stretched, and an optical sensor 39 for detecting the origin position of the carriage 31 and detecting a printing correction pattern described later are provided. The optical sensor 39 serving as a reading unit and a detecting unit includes a light source that projects light onto the printing paper P, and a line sensor (or CCD) that converts reflected light from the printing paper P into a corresponding image signal. Element).
[0046]
2, the control circuit 40 includes a CPU (Central Processing Unit) 41, a programmable ROM (P-ROM (Read Only Memory)) 43, a RAM (Random Access Memory) 44, and a character that stores a dot matrix of characters. It is configured as an arithmetic and logic operation circuit including a generator (CG (Character Generator)) 45 and an EEPROM (Electrically Erasable and Programmable ROM) 46.
[0047]
The control circuit 40 further drives an I / F dedicated circuit 50 that is an interface (I / F (Interface)) with an external motor or the like, and drives a print head unit 60 connected to the I / F dedicated circuit 50. And a motor drive circuit 54 for driving the paper feed motor 23 and the carriage motor 24.
[0048]
The I / F dedicated circuit 50 has a built-in parallel interface circuit and can receive the print signal PS supplied from the computer 90 via the connector 56.
[0049]
Next, the configuration of the computer 90 will be described with reference to FIG.
[0050]
As shown in FIG. 3, the computer 90 includes a CPU 91, a ROM 92, a RAM 93, a hard disk drive (HDD) 94, a video circuit 95, an I / F 96, a bus 97, a display device 98, an input device 99, and an external storage device 100. Have been.
[0051]
Here, the CPU 91 is a control unit that executes various types of arithmetic processing according to programs stored in the ROM 92 and the HDD 94 and controls each unit of the apparatus.
[0052]
The ROM 92 is a memory that stores basic programs and data executed by the CPU 91. The RAM 93 is a memory for temporarily storing programs being executed by the CPU 91, data being calculated, and the like.
[0053]
The HDD 94 is a recording device that reads data and programs recorded on a hard disk, which is a recording medium, in response to a request from the CPU 91, and records data generated as a result of arithmetic processing of the CPU 91 on the aforementioned hard disk.
[0054]
The video circuit 95 is a circuit that executes a drawing process according to a drawing command supplied from the CPU 91, converts the obtained image data into a video signal, and outputs the video signal to the display device 98.
[0055]
The I / F 96 is a circuit that appropriately converts the expression format of the signal output from the input device 99 and the external storage device 100, and outputs a print signal PS to the printer 22.
[0056]
The bus 97 is a signal line that interconnects the CPU 91, the ROM 92, the RAM 93, the HDD 94, the video circuit 95, and the I / F 96, and enables data transmission and reception between them.
[0057]
The display device 98 includes, for example, an LCD (Liquid Crystal Display) monitor or a CRT (Cathode Ray Tube) monitor, and is a device that displays an image corresponding to a video signal output from the video circuit 95.
[0058]
The input device 99 is configured by, for example, a keyboard and a mouse, and is a device that generates a signal according to a user operation and supplies the signal to the I / F 96.
[0059]
The external storage device 100 includes, for example, a CD-ROM (Compact Disk-ROM) drive unit, an MO (Magneto Optical) drive unit, and an FDD (Flexible Disk Drive) unit, and is recorded on a CD-ROM disk, an MO disk, and an FD. This is a device that reads out data and programs stored therein and supplies them to the CPU 91. In the case of the MO drive unit and the FDD unit, it is a device for recording data supplied from the CPU 91 on an MO disk or FD.
[0060]
FIG. 4 is a diagram illustrating functions of a program and a driver installed in the computer 90. Note that these functions are realized by the cooperation of the hardware of the computer 90 and the software recorded on the HDD 94. As shown in the figure, an application program 121, a video driver program 122, and a printer driver program 130 are mounted on a computer 90, and these operate under a predetermined operating system (OS).
[0061]
Here, the application program 121 is, for example, an image processing program. After processing an image captured from a digital camera or the like or processing an image drawn by a user, the printer driver program 130 and the video Output to the driver program 122.
[0062]
The video driver program 122 is a program for driving the video circuit 95. For example, after performing gamma processing and white balance adjustment on image data supplied from an application program, the video driver program 122 generates a video signal. The data is supplied to the display device 98 to be displayed.
[0063]
The printer driver program 130 includes a resolution conversion module 131, a color conversion module 132, a color conversion table 133, a halftone module 134, a recording rate table 135, a print data generation module 136, and an error information receiving unit 137. The image data generated by the program 121 is subjected to various processes described later to generate print data, and the print data is supplied to the printer 22. Further, the printer driver program 130 executes a process of updating the recording rate table 135 based on a print correction pattern (described later) printed by the printer 22.
[0064]
Here, the resolution conversion module 131 performs a process of converting the resolution of the image data supplied from the application program 121 according to the resolution of the print head 12.
[0065]
The color conversion module 132 converts the image data expressed by the RGB (Red, Green, Blue) color system into a CMYK (Cyan, Magenta, Yellow, Black) color system image with reference to the color conversion table 133. Performs processing to convert to data.
[0066]
The halftone module 134 converts the image data represented by the CMYK color system by dither processing into bits composed of a combination of three types of large, medium, and small dots by referring to the recording rate table 135 as described later. Convert to map data.
[0067]
The print data generation module 136 generates, from the bitmap data output from the halftone module 134, print data including raster data indicating a dot recording state during each main scan and data indicating a sub-scan feed amount. And supplies it to the printer 22.
[0068]
The error information receiving section 137 receives correction pattern data (error information) detected by the printer 22 and supplies the data to the recording rate table 135.
[0069]
Next, with reference to FIG. 5, the flow of processing when forming dots will be described. This process is a process executed by the computer 90. When this flowchart is started, the following steps are executed.
[0070]
Step S10: The printer driver program 130 receives the image data represented by the RGB color system from the application program 121. This image data is data having 256 gradation values of values 0 to 255 for each color of R, G, B for each pixel. This image data is data having 256 gradation values of values 0 to 255 for each color of R, G, B for each pixel. The image data may be data having 32 gradation levels (0 to 31) out of 64 gradation levels (0 to 63). A description will be given of the tone value.
[0071]
Step S11: The resolution conversion module 131 converts the resolution of the input image data into the resolution of the printer 22 (hereinafter, referred to as “print resolution”). When the resolution of the image data is lower than the printing resolution, the resolution conversion is performed by generating new data between adjacent original image data by linear interpolation or the like. Conversely, when the resolution of the image data is higher than the print resolution, the resolution conversion is performed by performing processing such as thinning out the image data at a fixed rate.
[0072]
Step S12: The color conversion module 132 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, Y, and K colors used in the printer 22. This process is performed using a color conversion table 133 that stores a combination of C, M, Y, and K for expressing a color composed of each combination of R, G, and B on the printer 22.
[0073]
Step S13: The halftone module 134 performs a halftone process on the image data color-converted in step S12. The halftone process refers to a process of reducing the gradation value (256 gradations in the present embodiment) of the original image data to a gradation value that can be expressed by the printer 22 for each pixel. Here, “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. Details of the halftone process will be described later with reference to FIG.
[0074]
Step S14: The print data generation module 136 executes a process of generating print data from the bitmap data generated by the halftone process. Here, the print data is data including raster data indicating a dot recording state during each main scan and data indicating a sub-scan feed amount.
[0075]
Step S15: The print data generation module 136 outputs the print data generated by the print data generation processing to the printer 22. Then, the process ends.
[0076]
Next, details of the halftone process, which is step S13 in the flowchart shown in FIG. 5, will be described with reference to FIG. FIG. 6 is a flowchart illustrating details of the halftone process. When this flowchart is started, the following steps are executed.
[0077]
Step S30: The halftone module 134 receives the multi-tone data from the color conversion module 132. The multi-tone data input here is data that has been subjected to a color conversion process (step S12 in FIG. 5) and is expressed in 256 tones for each of C, M, Y, and K colors.
[0078]
Step S31: The halftone module 134 sets the large dot level data LVL according to the gradation of the image data as follows. That is, FIG. 7 is a diagram showing a plurality of recording rate tables used for determining the level data of each of the large, medium, and small dots. In FIG. 7, the horizontal axis represents the gradation value (0 to 255), the left vertical axis represents the dot recording rate (%), and the right vertical axis represents the level data (0 to 255). Here, the “dot recording rate” means a ratio of pixels in which dots are formed among pixels in a uniform area when a uniform area is reproduced according to a certain gradation value. In FIG. 7, the profile SD indicated by a solid thin line indicates the recording rate of small dots, the profile MD indicated by a thick solid line indicates the recording rate of medium dots, and the profile LD indicated by a dotted line indicates the recording rate of large dots. The rates are shown respectively. The level data refers to data obtained by converting the dot recording rate into 256 levels of values 0 to 255. The method of setting the dot recording rate table will be described later.
[0079]
That is, in step S31, the level data LVL corresponding to the gradation value is read from the large-dot profile LD. For example, as shown in FIG. 7, when the gradation value of the multi-gradation data is gr, the level data LVL is obtained as 1d using the profile LD. Actually, the profile LD is stored in the RAM 93 as a one-dimensional table, and the level data is obtained by referring to this table. This table is the recording rate table 135 (see FIG. 4).
[0080]
Step S32: The halftone module 134 determines whether or not the level data LVL set as described above is larger than the threshold value THL. Here, for example, dot on / off determination is performed by the dither method. As the threshold value THL, a different value is set for each pixel by a so-called dither matrix. In this embodiment, a matrix in which values from 0 to 254 appear in a 16 × 16 square pixel block is used.
[0081]
FIG. 8 is a diagram showing a state 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 LVL 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 hatched pixels indicate the pixels that turn on the dots. If the level data LVL is larger than the threshold value THL, the halftone module 134 proceeds to step S40, otherwise proceeds to step S33.
[0082]
Step S33: The halftone module 134 sets medium dot level data LVM. The medium dot level data LVM is set by the above-described recording rate table 135 based on the gradation value. The setting method is the same as the setting of the large dot level data LVL. That is, in the example shown in FIG. 7, the level data LVM is obtained as 2d.
[0083]
Step S34: The level relationship between the medium dot level data LVM and the threshold value THM is compared to determine whether the medium dot is on or off. The on / off determination method is the same as that for the large dot, but the threshold value THM used for the determination is different from the threshold value THL for the large dot as shown below. That is, when on / off determination is made for the large dot and the medium dot using the same dither matrix, the pixels where the dots are likely to be on coincide with each other. That is, when the large dot is turned off, the medium dot is also likely to be turned off. As a result, there is a possibility that the recording rate of the medium dot becomes lower than the desired recording rate. In the present embodiment, in order to avoid such a phenomenon, the dither matrix is changed between them. That is, by changing the position of the pixel that is likely to be turned on between the large dot and the medium dot, it is ensured that each is appropriately formed.
[0084]
FIG. 9 is a diagram illustrating a relationship between a dither matrix used for determining a large dot and a dither matrix used for determining a medium dot. In this embodiment, as shown in FIG. 9, the first dither matrix TM is used for large dots, and the second dither is obtained by symmetrically moving the respective threshold values about the center in the sub-scanning direction for medium dots. The matrix UM is used. In this embodiment, 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 large dots and medium dots.
[0085]
If the medium dot level data LVM is larger than the threshold value THM, it is determined that the medium dot should be turned on, and the process proceeds to step S39. Otherwise, the process proceeds to step S35.
[0086]
Step S35: The small dot level data LVS is set in the same manner as the setting of the large dot and medium dot level data. It is preferable that the dither matrix for small dots is different from that for medium dots and large dots in order to suppress a decrease in the recording rate of small dots as described above.
[0087]
Step S36: The halftone module 134 proceeds to step S38 if the level data LVS is larger than the threshold value THS for a small dot, otherwise proceeds to step S37.
[0088]
Step S37: The halftone module 134 determines that a dot should not be formed, and stores the binary value “00” in the variable RE for storing the result value.
[0089]
Step S38: The halftone module 134 determines that the small dot should be turned on, and stores the binary value “01” in the variable RE storing the result value.
[0090]
Step S39: The halftone module 134 determines that the middle dot should be turned on, and stores the binary value “10” in the variable RE storing the result value.
[0091]
Step S40: The halftone module 134 determines that the large dot should be turned on, and stores the binary value “11” in the variable RE that stores the result value.
[0092]
Step S41: Since it is determined which dot should be formed for one pixel by the above processing, the halftone module 134 repeats the processing of steps S31 to S40 until the processing is completed for all pixels. . When the processing for all the pixels is completed, the halftone processing (step S13) ends, and the process returns to the print data generation processing (step S14).
[0093]
Next, the paper feed amount correction process will be described.
[0094]
FIG. 10 is a flowchart illustrating an example of a process for correcting the paper feed amount. When this flowchart is started, the following processing is executed.
[0095]
Step S60: The CPU 91 supplies a paper feed command to the printer 22. As a result, the control circuit 40 of the printer 22 drives the paper feed motor (not shown) and the paper feed motor 23 to suck only one print sheet P from the sheet feed tray.
[0096]
Step S61: The CPU 91 assigns “1” as an initial value to a variable i for counting the number of processes.
[0097]
Step S62: The CPU 91 supplies to the printer driver program 130 a command requesting printing of a ruled line having a predetermined length in the main scanning direction and a predetermined width in the sub-scanning direction. As a result, the control circuit 40 ejects ink from predetermined nozzles of the print head 12 (for example, nozzles located at the top of black (K)) to draw ruled lines. In the following processing, the ruled line is drawn using the same nozzle when printing the ruled line.
[0098]
FIG. 11 is a diagram showing an example of ruled lines forming a print correction pattern 150 corresponding to the feed amount correction pattern printed at this time. For example, when i = 1, ruled lines 151 are printed, and when i = 2, 3,..., 8, ruled lines 152 to 158 are printed, respectively.
[0099]
Step S63: The CPU 91 requests the printer 22 to feed the paper by a predetermined amount L (see FIG. 11). Note that L corresponds to the paper feed amount (see FIG. 20) when printing in the interlace mode. As a result, the control circuit 40 drives the paper feed motor 23 to feed the print paper P by a predetermined amount L.
[0100]
Step S64: The CPU 91 determines whether or not the value of the variable i for counting the number of processes is “1”. If the value is “1”, it is the first process, so that only one ruled line is provided. It is determined that printing has not been performed, and the process proceeds to step S68; otherwise, the process proceeds to step S65.
[0101]
Step S65: The CPU 91 reads, by the optical sensor 39, ruled lines vertically adjacent to each other, that is, ruled lines newly printed in the process in step S62 and ruled lines printed in the immediately preceding process, and supplies the read lines to the CPU 91. The optical sensor 39 has a length (length in the sub-scanning direction) in which two vertically adjacent ruled lines can be read by one scan, and the ruled line read by the optical sensor 39 has a length. A corresponding electric signal is supplied to the CPU 91.
[0102]
Step S66: The CPU 91 refers to the distance between the ruled lines read in step S65 and determines whether or not the paper feed amount is appropriate. If the paper feed amount is appropriate, the process proceeds to step S70; Goes to step S67. In order to determine whether or not the paper feed amount is appropriate, referring to the electric signal supplied from the optical sensor 39, the ruled line printed immediately before and the ruled line printed by the previous process are used. The determination is made based on whether or not the distance between the ruled lines, that is, the distance between the light receiving elements detecting these ruled lines is appropriate.
[0103]
Step S67: The CPU 91 causes the print data generation module 136 to change the set value so that the paper feed amount becomes appropriate. That is, when the paper feed amount is larger than the specified value, the set value is set smaller by a predetermined amount, and when the paper feed amount is smaller than the specified value, the set value is set larger by a predetermined amount.
[0104]
Step S68: The CPU 91 increments the value of the variable i for counting the number of processes by one.
[0105]
Step S69: The CPU 91 determines whether or not the value of the variable i is equal to or smaller than a predetermined constant value N (for example, N = 10), and if so, returns to step S62 and repeats the same processing. If not, the process proceeds to step S70.
[0106]
Step S70: The CPU 91 supplies a command requesting the printer 22 to discharge the printing paper P. As a result, the control circuit 40 of the printer 22 drives the paper feed motor 23 to discharge the printing paper P.
[0107]
With the above processing, the paper feed amount L can be set accurately.
[0108]
Next, a method of setting the recording rate table 135 will be described.
[0109]
FIG. 12 is a diagram illustrating a relationship between the recording rate table 135 and the ink ejection amount. FIG. 12A is a diagram showing the relationship between the gradation values of the multi-gradation data and the dot recording rates of dots of each size, and is the same as FIG. FIG. 12B is a diagram illustrating a relationship between the gradation value and the weight of ink ejected to a predetermined area. The predetermined area is an area composed of 255 pixels. The ink weight is 10 ng for small dots, 20 ng for medium dots, and 30 ng for large dots.
[0110]
Specifically, FIG. 12B plots the product of the following values (1), (2), and (3) for each gradation value.
(1) Recording rate of dots of each size (for example, in gradation value G2, small dots are 25%, medium dots are 50%)
(2) Ink weight (10 ng for small dots, 20 ng for medium dots, 30 ng for large dots)
(3) Number of pixels in predetermined area (255 pixels)
[0111]
For example, when the gradation value is 255 (maximum gradation value), the above product is 7650 ng (= 100% × 30 ng × 255 pixels).
[0112]
In FIG. 12B, when the gradation value increases from “0” to “255”, the ink ejection amount increases from 0 ng to 7650 ng along the straight line Wi. As described above, in the present embodiment, for simplicity of description, the weight of ink ejected to a predetermined area and the gradation value have a linear relationship.
[0113]
As shown in FIGS. 12A and 12B, the weight of the ink ejected to the predetermined area increases as follows in accordance with the increase in the gradation value.
(1) In the region from the gradation value “0” to the gradation value G1, the ink weight linearly increases as the recording rate of the small dots increases. This area is occupied only by small dots.
(2) In the region from the gradation value G1 to the gradation value G2, the dot recording rate of the small dots becomes constant, and the ink weight linearly increases as the dot recording rate of the medium dots increases. This area is composed of small dots and medium dots.
(3) In the region from the gradation value G2 to the gradation value G3, the recording rates of the small dots and the medium dots become constant, and the ink weight linearly increases as the dot recording rate of the large dots increases. This area is composed of three types of small dots, medium dots, and large dots.
(4) In the region from the gradation value G3 to the maximum gradation value, the dot recording rates of the small dots and the medium dots start to decrease, and by replacing the small dots and the medium dots with the large dots, the ink is linearly printed. Weight increases. This area is also composed of three types of small dots, medium dots, and large dots.
[0114]
Such a dot recording rate profile needs to be determined in consideration of the following trade-offs.
(1) In order to suppress graininess (roughness of an image), it is desirable to lower the dot recording rate of relatively large dots that are easily visible and increase the dot recording rate of relatively small dots. Such characteristics are particularly remarkable in a low gradation region.
(2) In order to reduce banding (streak-like image quality deterioration), it is desirable to lower the dot recording rate of relatively small dots by replacing relatively small dots with relatively large dots. Such characteristics are particularly remarkable in a high gradation region.
[0115]
FIGS. 13 and 14 are diagrams showing the relationship between the dot recording rate and banding. FIG. 13A shows a state in which small dots are printed at a dot recording rate of 33% in an 8 × 6 matrix. FIG. 13B similarly shows a state in which small dots are printed at a dot recording rate of 44% in an 8 × 6 matrix. FIG. 14A shows a state in which small dots are recorded at a dot recording rate of 100%. In these figures, the numbers in the circles indicate the numbers of the nozzles that have formed the dots. In this example, the dots formed by the fifth nozzle are shifted upward due to a manufacturing error or the like.
[0116]
As is clear from these figures, the white streak is not so noticeable when the dot recording rate is 33%, but starts to be slightly noticeable at about 44% and becomes noticeable at about 100%. FIG. 14B shows a state in which some of the dots in FIG. 13B are replaced with medium dots. In this case, since the fourth dot and the fifth nozzle form a medium dot in the portion where the white streak shown in FIG. 13B is generated, the white streak is divided by these and becomes inconspicuous. ing.
[0117]
As described above, in order to suppress the occurrence of white streaks and other banding, it is desirable to perform printing by replacing dots with a relatively large size in the vicinity of the dot recording rate where banding is conspicuous. However, it is desirable to individually and specifically set the recording rate at which the switching should be performed in accordance with the error characteristics of each printer, the printing purpose, and the like.
[0118]
Therefore, in the present embodiment, the dot size switching timing is set by the following method.
[0119]
FIG. 15 is a flowchart illustrating a flow of a process for setting the recording rate table 135 (see FIG. 4) for determining the timing of switching the dot size. When this flowchart is started, the following steps are executed.
[0120]
Step S80: The CPU 91 sends a control command to the control circuit 40 of the printer 22 to request that only one print sheet P be sucked. As a result, the control circuit 40 drives the paper feed motor 23 and a paper feed motor (not shown) to suck only one print sheet P.
[0121]
Step S81: The CPU 91 sets “1” as an initial value to each of the variables i and j in order to count the number of processes. As a result, the control circuit 40 drives the paper feed motor 23 and a paper feed motor (not shown) to suck only one print sheet P.
[0122]
Step S82: The CPU 91 proceeds to step S83 if the value stored in the variable i is “1”, to step S84 if it is “2”, or to step S85 if it is “3”. Each branch.
[0123]
Step S83: The CPU 91 selects a small dot as a dot to be printed. That is, the fact that the value of the variable i is "1" means that the value of the variable RE is "01" in the above example.
[0124]
Step S84: The CPU 91 selects a medium dot as a dot to be printed. At this time, the fact that the variable i has a value of “2” means that the value of the variable RE has a value of “10” in the above example.
[0125]
Step S85: The CPU 91 selects a large dot as a dot to be printed. The selection of “3” as the variable i in this way means that the value of the variable RE is “11” in the above example.
[0126]
Step S86: The CPU 91 sets the j-th recording rate as a recording rate for printing a print correction pattern described later. For example, to describe a small dot as an example, as shown in FIG. 16, the dot recording rate of the small dot is set between “0%” and “ds%” according to the gradation value. Sample points are selected at four points a1 to a4 in the section, and these are set as first to fourth recording rates, respectively. Then, as described later, a correction pattern is printed at each of the first to fourth recording rates, and the occurrence of white streaks is observed. For example, if j = 1, the first recording rate (that is, the dot recording rate at a1 in FIG. 16) is set.
[0127]
Step S87: The CPU 91 supplies data for printing the print correction pattern to the printer driver program 130. As a result, the print correction pattern corresponding to the recording rate set in step S86 is printed by the printer 22. At this time, each print correction pattern is printed not by one scan but by a plurality of scans having a predetermined amount L of paper feed.
[0128]
FIG. 17 is a diagram illustrating an example of the print correction pattern 200 corresponding to the print correction pattern printed at this time. In the example of this figure, at the top, the recording rate is set so as to increase in order from left to right, and print correction patterns 210 to 213 printed only with small dots are printed. In the same manner, print correction patterns 220 to 223 with medium dots are printed, print correction patterns 230 to 233 with large dots are printed on the third row, and large, medium, and small print patterns are printed on the fourth row. Print correction patterns 240 to 243 printed by mixing dots are printed. In this example, since j = 1 and i = 1, the print correction pattern 210 is printed.
[0129]
Step S88: The CPU 91 transmits a command for instructing the printer 22 to detect the density of the print correction pattern printed immediately before. As a result, the control circuit 40 of the printer 22 drives the carriage motor 24 to move the carriage 31 in the main scanning direction, scans the immediately preceding print correction pattern in the main scanning direction, Detect concentration.
[0130]
FIG. 18 is a diagram illustrating an example of a signal output from the optical sensor 39 at this time. In this figure, the horizontal axis indicates the position of the nozzle provided on the print head 12, and the horizontal axis indicates the output of the optical sensor 39. More specifically, the optical sensor 39 has, for example, line sensors arranged in a line in the sub-scanning direction, and this line sensor converts reflected light from the print correction pattern into an electric signal. In this embodiment, the obtained electric signal has a small value when the intensity of the reflected light from the printing paper P is high, and has a large value when the intensity is low. Therefore, when a white stripe or the like occurs in the correction pattern, the level of a part of the output from the line sensor of the optical sensor 39 is lower than that of the other part as shown in FIG. By detecting a portion (hereinafter, referred to as a “depressed portion”), the occurrence of white streaks can be detected.
[0131]
Step S89: The CPU 91 refers to the output signal of the optical sensor 39, calculates the ratio (Ld / La) between the average level La of the signal and the level Ld of the depressed portion, and this is a predetermined value (for example, 10%). If the above is true, it is determined that a white stripe has occurred. When it is determined that a white stripe has occurred, the process proceeds to step S90, and otherwise, the process proceeds to step S91.
[0132]
Step S90: The CPU 91 records the dot recording rate at the time point when the white stripe is detected in the RAM 93.
[0133]
Step S91: The CPU 91 increments the value of the variable j for counting the number of processes by one.
[0134]
Step S92: The CPU 91 determines whether or not the processing for all recording rates has been completed. If the processing has not been completed, the flow returns to step S86 to repeat the same processing. Otherwise, the processing proceeds to step S93. For example, in the case of small dots, as described above, when printing of all the print correction patterns 210 to 213 for the first to fourth dot recording rates (recording rates corresponding to a1 to a4) is completed. Proceeds to step S93, otherwise returns to step S86 to repeat printing of the print correction pattern.
[0135]
Step S93: The CPU 91 increments the value of the variable i indicating the type of dot by one. As a result, the processing shifts to the print correction patterns 220 to 223 for medium dots. If the print dot recording rate for medium dots is, for example, four, the above-described print correction patterns 220 to 223 are printed, and the recording rate at the time of occurrence of white stripes is recorded. Thereafter, the variable i is further increased by one. Then, the print correction patterns 230 to 233 using large dots are printed.
[0136]
Step S94: The CPU 91 determines whether or not the processing for all the dots has been completed. If the processing has not been completed, the processing returns to step S82 to repeat the same processing. Otherwise, the processing proceeds to step S95. More specifically, if the printing of the print correction pattern for all of the small, medium, and large dots is completed, the process proceeds to step S95; otherwise, the process returns to step S82 to repeat the printing of the print correction pattern. It is.
[0137]
Step S95: The CPU 91 executes a process of resetting the recording rate table 135. For example, if a white streak is detected at the point a3 in FIG. 16, it is necessary to increase the generation rate of medium dots at the point where the gradation is lower than a3. Therefore, as shown in FIG. 19, at a5 which is an intermediate point between a2 and a3, the upper limit of the recording rate of small dots is set, and a profile of medium dots is set so that medium dots are generated from a5. As a result, when small dots are always printed at a recording rate lower than the recording rate at a3 at which white streaks occur, at the tone value of a3 at which white streaks have occurred only with the small dots, the medium Are mixed, so that generation of white stripes can be suppressed. The generation of white stripes can be suppressed. Note that the same processing is performed between a medium dot and a large dot. With the above processing, the setting of the new recording rate table 135 is completed.
[0138]
Step S96: The CPU 91 prints a correction pattern using all of the small, medium and large dots by using the newly set recording rate table 135. As a result, the print correction patterns 240 to 243 shown in FIG. By referring to such print correction patterns 240 to 243, a user or a setter in a manufacturing process can confirm whether or not the generation of white stripes has been suppressed by the above-described processing. At this time, the print correction patterns 210 to 213, 220 to 223, and 230 to 233 for each dot may be printed again.
[0139]
The above-described print correction patterns 210 to 213, 220 to 223, 230 to 233, and 240 to 243 may be printed with ink of each color and corrected for each color.
[0140]
Through the above processing, most of the banding can be eliminated. However, if the paper feeding error cannot be completely eliminated due to the detection error of the optical sensor 39, for example, and the occurrence of banding cannot be eliminated only by correcting the recording rate, the process returns to the flowchart shown in FIG. Then, the paper feed amount may be adjusted again. In this case, for example, when banding due to a low density portion is detected, that is, when the optical sensor 39 detects a portion with high light reflection (white stripe), the target value of the paper feed amount is set. Is set smaller than the current value, and the processing shown in FIG. 10 is repeated. According to such a method, for example, even when there is a detection error caused by the optical sensor 39, it is possible to eliminate the occurrence of banding. When banding caused by a portion having a high density is detected, it can be usually solved by lowering the dot recording rate. However, if the problem cannot be solved even by lowering the dot recording rate, for example, the target value of the paper feed amount may be set to be larger than the current value, and the process shown in FIG. 10 may be repeated.
[0141]
In general, it is often impossible to completely eliminate the paper feed error due to the accuracy of the optical sensor 39 and the like. However, according to the present invention, by correcting the dot recording rate, it is possible to prevent banding from occurring even when a paper feed error is included to some extent, including the amount due to the error. it can.
[0142]
According to the above embodiment, after printing the print correction pattern 150 shown in FIG. 11 and correcting the feed amount, the print correction patterns 210 to 213 and 220 to 223 are changed by changing the dot recording rate for each dot. , 230 to 233, 240 to 243, and by referring to these, the recording rate table 135 is reset, so that banding due to an error in the feed amount is prevented, and errors in the nozzles are reduced. It is possible to suppress the occurrence of banding due to the above. In addition, since the switching timing of the dot size can be set at a point just before the occurrence of white streaks, it is possible to obtain high quality image with less graininess by preferentially selecting smaller dots.
[0143]
As mentioned above, although one Embodiment of this invention was described, this invention can be variously deformed besides this. For example, in the above embodiment, four types of patterns are printed for each dot as the print correction patterns 210 to 213, 220 to 223, 230 to 233, and 240 to 243. The following patterns may be printed. For example, when three or less types of patterns are printed, the printing time of the patterns can be reduced as compared with the case of printing four types. When five or more types of patterns are printed, it is possible to more accurately determine the dot switching point (for example, a5 shown in FIG. 19).
[0144]
Further, in the above embodiment, after correcting the paper feed amount by the pattern for correcting the paper feed amount, the dot recording rate is corrected by the print correction pattern for correcting the dot recording rate. Only the pattern for correcting the paper feed amount may be printed to correct only the paper feed amount.
[0145]
Further, in the above embodiment, the pattern for correcting the paper feed amount shown in FIG. 11 and the print correction pattern for determining the dot recording rate shown in FIG. However, it is also possible to record them on the same printing paper. According to such a method, useless consumption of the printing paper P can be prevented.
[0146]
Further, in the above embodiment, the color of the ink for printing the print correction pattern shown in FIG. 17 is not particularly mentioned, but printing is performed using only a specific color (for example, black (K)). Alternatively, it is also possible to print a print correction pattern for each color. In the former case, printing unevenness can be detected with high accuracy by using an ink having a high light absorption rate (black (K) ink). In the latter case, by obtaining the dot recording rate for each color, it is possible to obtain a high-quality image with no printing unevenness for all colors.
[0147]
Further, in the above-described embodiment, the recording rate table 135 used for the entire image is changed according to the occurrence state of the white streak. A recording rate table used only for one or more nozzles in the vicinity may be prepared, and only this recording rate table may be changed. In this case, since it is necessary to use a plurality of recording rate tables, the processing load increases, but the setting of only the nozzles that generate white streaks or the nozzles and one or more nozzles near the nozzles is required Since the adjustment can be made only by changing, the white streak can be surely suppressed without changing the image quality of the entire image.
[0148]
Further, in the above embodiment, the print correction pattern 150 is a ruled line. However, the print correction pattern 150 is not limited to the ruled line only, as long as the pattern can read the feed amount. It may be a pattern like a letter.
[0149]
In the above embodiment, the print correction patterns 210 to 213, 220 to 223, 230 to 233, and 240 to 243 are detected by the optical sensor 39 provided in the printer 22. May be converted into an electric signal and read by an optical scanner or the like connected to the device. According to such an embodiment, even when the printer 22 does not have the optical sensor 39, it is possible to optimally set the dot recording rate.
[0150]
In the above embodiment, the print correction patterns 210 to 213, 220 to 223, 230 to 233, and 240 to 243 are read by the optical sensor 39, and the recording rate table 135 is automatically set. For example, the recording rate table 135 may be set manually by referring to the detection result of the optical sensor 39. According to such a method, it is possible for the user or the like to optimally set the recording rate table 135 while actually checking with eyes, taking into account the increase and decrease of the granularity.
[0151]
Further, in the above embodiment, the upper limit of the target dots is set to a dot recording rate smaller than the dot recording rate at which banding is detected. However, as shown by a dashed line in FIG. It is also possible to set the upper limit to a value equal to or higher than the dot recording rate at which banding is detected. Further, the start point of a larger dot may be set to a value equal to or higher than the dot recording rate at which banding is detected. Specifically, in FIG. 19, a5 may be set at a point a3, which is the start point of the medium dot, or at a point equal to or more than a3. Even in such a case, dot switching occurs as shown in FIG. 12B, and banding is reduced. According to such a setting, the granularity can be reduced by increasing the recording rate of small-sized dots as compared with the case of FIG.
[0152]
Further, in the above embodiment, four colors of CMYK are used as the inks. However, in addition to this, light-colored inks (light cyan (LC), light magenta (LM), dark yellow (DY)) are used. Ink may be used.
[0153]
Further, in the above-described embodiment, the printer 22 including the head that ejects ink using the piezo element is used. However, as the ejection driving element, various types other than the piezo element can be used. is there. For example, the present invention can be applied to a printer including a discharge drive element of a type in which a heater disposed in an ink passage is energized and ink is discharged by bubbles generated in the ink passage.
[0154]
Further, in the above embodiment, the above-described processing is executed by a printer driver program stored in the HDD 94 (or the external storage device 100). However, a program having an equivalent function is stored in the P-ROM 43 of the printer 22, and the above-described processing is executed by the program, or the computer 90 and the printer 22 share and execute the processing. It is also possible.
[0155]
The program describing the above processing functions can be recorded on a computer-readable recording medium. Computer-readable recording media include magnetic recording devices, optical disks, magneto-optical recording media, and semiconductor memories. The magnetic recording device includes a hard disk device (HDD), a flexible disk (FD), a magnetic tape, and the like. The optical disc includes DVD, DVD-RAM (Random Access Memory), CD-ROM, CD-R (Recordable) / RW (ReWritable), and the like. The magneto-optical recording medium includes an MO.
[0156]
When distributing the program, portable recording media such as DVDs and CD-ROMs on which the program is recorded are sold. Alternatively, the program may be stored in a storage device of a server computer, and the program may be transferred from the server computer to another computer via a network.
[0157]
The computer that executes the program stores, for example, the program recorded on the portable recording medium or the program transferred from the server computer in its own storage device. Then, the computer reads the program from its own storage device and executes processing according to the program. The computer can also read the program directly from the portable recording medium and execute processing according to the program. Further, the computer may execute the processing according to the received program each time the program is transferred from the server computer.
[0158]
【The invention's effect】
According to the present invention, it is possible to easily adjust the printing unevenness even when an image to be printed is divided into a plurality of scans and drawn.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a schematic configuration of a main part of a printing apparatus according to an embodiment.
FIG. 2 is a block diagram illustrating a configuration of a main part of the printer centering on a control circuit in the printing apparatus illustrated in FIG. 1;
FIG. 3 is a block diagram illustrating a detailed configuration of a computer in the printing apparatus illustrated in FIG.
FIG. 4 is a diagram showing details of various programs installed in a computer in the printing apparatus shown in FIG. 1;
FIG. 5 is a flowchart illustrating a detailed processing flow of a printer driver program installed in a computer in the printing apparatus illustrated in FIG. 1;
FIG. 6 is a flowchart for explaining a detailed processing flow of a halftone process shown in the flowchart of FIG. 5;
7 is a diagram showing the contents of the recording table shown in FIG. 4, and is a diagram showing details of a recording rate table used for determining level data of each of large, medium, and small dots.
FIG. 8 is a diagram showing a state of dot on / off determination by a dither method executed in the halftone module shown in FIG. 4;
9 is a diagram illustrating a dither matrix used for dither processing performed in the halftone module illustrated in FIG. 4, showing a relationship between a dither matrix used for determining a large dot and a dither matrix used for determining a medium dot. FIG.
FIG. 10 is a diagram illustrating a flow of a process performed when correcting the paper feed amount in the printing apparatus illustrated in FIG. 1;
11 is a diagram illustrating an example of a print correction pattern for correcting a paper feed amount printed by the process illustrated in FIG. 10;
12A and 12B are diagrams showing the contents of a recording rate table shown in FIG. 4 and ink ejection amounts corresponding to the contents, and FIG. 12A is a diagram showing a recording rate table in which a gradation value and a dot recording rate are related (B) is a diagram showing the relationship between the gradation value and the ink ejection amount.
13A and 13B are diagrams illustrating a relationship between a dot recording rate and banding in the printing apparatus illustrated in FIG. 1; FIG. 13A illustrates a case where small dots are printed at a dot recording rate of 33% in an 8 × 6 matrix; (B) shows a state in which a small dot is printed at a dot recording rate of 44% in an 8 × 6 matrix.
14A and 14B are diagrams illustrating a relationship between a dot recording rate and banding in the printing apparatus illustrated in FIG. 1; FIG. 14A illustrates a case where small dots are printed at a dot recording rate of 100% in an 8 × 6 matrix; FIG. 13B shows a state in which some small dots are replaced with medium dots in FIG.
FIG. 15 is a flowchart illustrating a flow of a process for setting a recording rate table for determining a dot size switching timing in the printing apparatus illustrated in FIG. 1;
FIG. 16 is an example of the recording rate table shown in FIG. 4, showing a relationship between dot recording rates of small dots and medium dots.
FIG. 17 is a diagram illustrating an example of a correction pattern printed by the printing apparatus illustrated in FIG. 1;
18 is a diagram illustrating a result of reading the single print correction pattern illustrated in FIG. 17 by the optical sensor illustrated in FIG. 1, and is a diagram illustrating a relationship between a nozzle position and an optical sensor output.
19 is a diagram illustrating an example of a new recording rate table obtained by correcting the recording rate table illustrated in FIG. 16 by the processing illustrated in FIG. 15;
FIG. 20 is a diagram illustrating an example of an interlaced printing method.
FIG. 21 is a diagram illustrating a state in which the paper feed amount is smaller than a predetermined amount L by d in interlaced printing.
[Explanation of symbols]
12 Print head (feed amount correction pattern printing means, print correction pattern printing means)
39 Optical sensor (reading means, detecting means)
90 Computer (feed amount correction means, dot recording rate determination means, repetition means)
150 Print correction pattern (feed amount correction pattern)
200 Print correction pattern (Print correction pattern)

Claims (13)

In a printing apparatus that prints an image to be printed on a print medium by dividing the image into multiple scans,
Feed amount correction pattern printing means for printing a feed amount correction pattern for correcting the feed amount of the print medium,
Feed amount correction means for correcting the feed amount of the print medium based on the feed amount correction pattern,
A print correction pattern printing unit for printing a print correction pattern including a plurality of patterns each having a different dot recording rate per unit area,
Dot recording rate determining means for determining the relationship between the tone value and the dot recording rate based on the print correction pattern,
A printing apparatus comprising: N types of dots having different sizes can be formed in one pixel area by selectively discharging N (N ≧ 2) types of ink droplets having different ink amounts on the print medium;
The print correction pattern printing means prints, using at least one of the N types of ink droplets, a print correction pattern including a plurality of patterns having different dot recording rates per unit area using the same type of ink. ,
The dot recording rate determining unit determines a relationship between a gradation value and a dot recording rate for each of the N types of ink droplets based on the print correction pattern.
The printing apparatus according to claim 1, wherein: The feed amount correction pattern printing means repeats the operation of discharging ink from a predetermined nozzle when performing the feeding operation of the print medium, prints a plurality of line segments on the print medium,
The printing apparatus according to claim 1, wherein the feed amount correction unit corrects the feed amount based on the plurality of line segments forming the feed amount correction pattern. A reading unit for optically reading the plurality of line segments constituting the feed amount correction pattern printed on the print medium,
4. The printing apparatus according to claim 3, wherein the feed amount correcting unit corrects the feed amount of the print medium based on information read by the reading unit. The reading means also optically reads the print correction pattern,
The printing apparatus according to claim 4, wherein the dot recording rate determination unit determines a dot recording rate based on information read by the reading unit. In a printing apparatus that prints an image to be printed on a print medium by dividing the image into multiple scans,
Feed amount correction pattern printing means for printing a feed amount correction pattern for correcting the feed amount of the print medium,
Feed amount correction means for correcting the feed amount of the print medium based on the feed amount correction pattern,
A print correction pattern printing unit for printing a print correction pattern including a plurality of patterns each having a different dot recording rate per unit area,
Dot recording rate determining means for determining the relationship between the tone value and the dot recording rate based on the print correction pattern,
Detecting means for detecting the occurrence of banding when printing the print correction pattern according to the relationship between the tone value and the dot recording rate determined by the dot recording rate determining means;
Repeating means for repeatedly executing the determination process by the dot recording rate determining means when the occurrence of banding is detected by the detection means;
A printing apparatus comprising: The repetition means, even when the determination processing by the dot recording rate determination means is repeatedly executed, when the occurrence of banding is detected, causes the feed amount correction means to repeatedly execute the feed amount correction processing. 7. The printing apparatus according to claim 6, wherein: 8. The printing method according to claim 7, wherein the repetition unit corrects the feed amount in a direction to decrease the feed amount when banding due to the presence of a low-density portion occurs. apparatus. In a printing method of printing an image to be printed on a print medium by dividing the image into a plurality of scans,
A feed amount correction pattern printing step of printing a feed amount correction pattern for correcting the feed amount of the print medium,
A feed amount correction step of correcting the feed amount of the print medium based on the feed amount correction pattern,
A print correction pattern printing step of printing a print correction pattern including a plurality of patterns having different dot recording rates per unit area,
A dot recording rate determining step of determining a relationship between a tone value and a dot recording rate based on the print correction pattern;
A printing method comprising: In a printing method of printing an image to be printed on a print medium by dividing the image into a plurality of scans,
A feed amount correction pattern printing step of printing a feed amount correction pattern for correcting the feed amount of the print medium,
A feed amount correction step of correcting the feed amount of the print medium based on the feed amount correction pattern,
A print correction pattern printing step of printing a print correction pattern including a plurality of patterns having different dot recording rates per unit area,
A dot recording rate determining step of determining a relationship between a tone value and a dot recording rate based on the print correction pattern;
A detection step of detecting the occurrence of banding when the print correction pattern is printed according to the relationship between the tone value and the dot recording rate determined by the dot recording rate determining step;
When the occurrence of banding is detected by the detection step, a repetition step of repeatedly executing a determination process by the dot recording rate determination step;
A printing method comprising: In a computer-readable printing program that causes a computer to perform a process of printing an image to be printed on a print medium by dividing the image into a plurality of scans,
Computer
Feed amount correction pattern printing means for printing a feed amount correction pattern for correcting the feed amount of the print medium,
Feed amount correction means for correcting the feed amount of the print medium based on the feed amount correction pattern,
A print correction pattern printing unit that prints a print correction pattern including a plurality of patterns having different dot recording rates per unit area,
A dot recording rate determining unit that determines a relationship between a gradation value and a dot recording rate based on the print correction pattern,
A computer-readable printing program for functioning as a computer. In a computer-readable printing program that causes a computer to perform a process of printing an image to be printed on a print medium by dividing the image into a plurality of scans,
Computer
Feed amount correction pattern printing means for printing a feed amount correction pattern for correcting the feed amount of the print medium,
Feed amount correction means for correcting the feed amount of the print medium based on the feed amount correction pattern,
A print correction pattern printing unit that prints a print correction pattern including a plurality of patterns having different dot recording rates per unit area,
A dot recording rate determining unit that determines a relationship between a gradation value and a dot recording rate based on the print correction pattern,
Detecting means for detecting the occurrence of banding when the print correction pattern is printed according to the relationship between the tone value and the dot recording rate determined by the dot recording rate determining means;
When the occurrence of banding is detected by the detection means, a repetition means for repeatedly executing the determination processing by the dot recording rate determination means,
A computer-readable printing program for functioning as a computer. It is possible to selectively discharge N (N ≧ 2) types of ink droplets having different ink amounts on a print medium to form N types of dots having different sizes in an area of one pixel, and to print an image to be printed. In a print correction pattern used in a printing apparatus capable of printing in a plurality of scans,
A feed amount correction pattern for correcting the feed amount of the print medium,
For at least one of the N types of ink droplets, a print correction pattern in which a plurality of patterns having different dot recording rates per unit area are printed using the same type of ink;
A print correction pattern, comprising:

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