JP2005041078A - Printer, correction pattern, computer program, and computer system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a printer or the like in which impact position of an ink drop can be corrected precisely in the main scanning direction. <P>SOLUTION: In the printer comprising an ejection head for forming dots on a body to be printed by ejecting ink drops, and a density reading means movable in the main scanning direction together with the ejection head and printing a correction pattern having a plurality of subpatterns for correcting deviation in dot forming position using the ejection head, the density reading means reads out the density of the correction pattern while moving in the main scanning direction and corrects deviation based on two or more subpatterns having a peak in density out of the plurality of subpatterns. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a printing apparatus and a computer system.
[0002]
[Prior art]
In recent years, as an output device of a computer, a print head that ejects ink is provided in a carriage that scans in the main scanning direction, and an ink jet printer that performs printing by ejecting ink while the carriage scans has become widespread. Some ink jet printers have a function of performing so-called “bidirectional printing” in which ink is ejected in each of the forward path and the backward path in order to improve the printing speed.
[0003]
When bi-directional printing is performed, if the landing positions of the ink droplets in the main scanning direction in the forward path and the backward path are different, the image deteriorates. Therefore, it is necessary to correct the landing positions of the ink droplets in the forward path and the backward path. Therefore, a plurality of correction amounts can be set in the printer, and a user or the like selects an appropriate correction amount and sets it in the printer.
[0004]
As a method for selecting the correction amount, for example, by printing in the forward path, a plurality of vertical lines extending in the sub-scanning direction with a certain interval in the main scanning direction are printed using the nozzles on the front end side of the print head. Next, when printing is performed at the ideal position by printing in the return path, a plurality of vertical lines that are different from each other in the direction in which the correction amount is increased and the direction in which the correction amount is decreased are based on the vertical line that is linearly connected to the vertical line. Is printed using a nozzle on the rear end side of the print head. The user or the like visually confirms that the vertical line printed by the forward printing and the vertical line printed by the backward printing of the printed pattern obtained in this way are printed in a straight line, and selects the correction amount. .
[0005]
[Patent Document 1] Japanese Patent Laid-Open No. 11-5301
[0006]
[Problems to be solved by the invention]
However, since the amount of correction is extremely small, it is difficult to visually determine whether the two vertical lines arranged in front and back are arranged in a straight line or whether a shift has occurred, and the user or the like may select it incorrectly. There is.
Further, such a problem arises when correcting the deviation between the landing position of one color ink droplet and the landing position of another color ink droplet when ejecting a plurality of color ink droplets to one pixel. Also occurs.
The present invention has been made to solve the above-described problems, and realizes a printing apparatus capable of accurately correcting the landing position of ink droplets in the main scanning direction, and a computer system having the printing apparatus. The purpose is to do.
[0007]
[Means for Solving the Problems]
The main present invention has an ejection head for ejecting ink droplets to form dots on a printing medium, and a density reading means that can move in the main scanning direction together with the ejection head, and shifts the dot formation position. In a printing apparatus for printing a correction pattern having a plurality of sub-patterns for correction on a printing medium by the ejection head, the density reading unit moves in the main scanning direction while moving the density of the correction pattern. And the deviation is corrected based on two or more sub-patterns having a peak in density among the plurality of sub-patterns.
[0008]
Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
=== Summary of disclosure ===
At least the following will be made clear by the description of the present specification and the accompanying drawings. An ejection head for ejecting ink droplets to form dots on a printing medium; and a density reading unit movable in the main scanning direction together with the ejection head, for correcting a deviation in dot formation position, In a printing apparatus that prints a correction pattern having a plurality of sub-patterns on a printing medium using the ejection head, the density reading unit reads the density of the correction pattern while moving in the main scanning direction, The printing apparatus, wherein the deviation is corrected based on two or more subpatterns having a peak in density among the subpatterns.
[0010]
According to the present invention, for example, when printing the sub-pattern, when the ideal dot formation position in the forward path of the main scan and the ideal dot formation position in the backward path are the same position, the dot formation position in the forward path When there is no deviation from the dot formation position in the return pass, the forward pass dot and the return pass dot overlap, and when a shift occurs, these dots are printed at different positions. Therefore, when there is no deviation, the amount of ink occupying the surface of the printing medium is small and the density is low, and when the deviation occurs, the amount of ink occupying the surface of the printing medium is large and the density is high. In addition, when the ideal dot formation position in the forward path and the backward path is a position shifted by half the inter-dot distance, when there is no deviation between the dot formation position in the forward path and the dot formation position in the backward path, In the center between the forward dots, the backward dots are printed and the density increases, and when a deviation occurs, the distance between the dots varies and the density decreases. For this reason, the deviation amount between the dot formation position in the forward path and the dot formation position in the backward path appears as a density difference of the sub-pattern. That is, the density of the sub-pattern when there is no deviation is the highest peak or the lowest peak. For this reason, it is possible to correct the deviation based on the sub-pattern having a peak in density. Furthermore, since two or more subpatterns are used when correcting the deviation, it is possible to perform correction with higher accuracy than when correcting based on one subpattern.
[0011]
The same effect can also be obtained when correcting the deviation between the landing position of one color ink droplet and the landing position of another color ink droplet when ejecting multiple color ink droplets to one pixel. It is done.
[0012]
Further, since the density detection member that can move in the main scanning direction together with the ejection head reads the density of the correction pattern while moving in the main scanning direction, the density of the sub-patterns has a peak in the second density. It is possible to effectively specify two or more sub patterns.
[0013]
In the printing apparatus, the correction pattern may be a correction pattern having a plurality of sub-patterns for correcting a deviation between a dot formation position in the forward pass of main scanning and a dot formation position in the return pass. .
In such a printing apparatus, each sub pattern may be configured by arranging dots in the main scanning direction and the sub scanning direction.
According to such a printing apparatus, since each of the sub-patterns is configured by arranging dots in the main scanning direction and the sub-scanning direction, it is possible to form a correction pattern with good visibility or density detection. Become.
[0014]
Further, in the printing apparatus, the sub-pattern has a plurality of correction amounts for performing the correction, and each of the sub-patterns is a forward dot formed at a predetermined interval in the main scanning forward path and a return path of the main scanning. In other words, the amount of deviation between the forward dot formation position and the backward dot formation position may be the correction amount that is different for each sub-pattern.
According to such a printing apparatus, the amount of deviation between the dot formation position on the forward path and the dot formation position on the return path is the correction amount that differs for each sub-pattern. It becomes possible to recognize the correction pattern with good characteristics.
[0015]
In the printing apparatus, it is preferable that the correction amount is an integral multiple of a distance obtained by equally dividing the ideal inter-dot distance in the main scanning direction, and the number of sub-patterns included in the correction pattern is larger than the division number.
According to such a printing apparatus, since the product of the correction amount and the number of divisions is the ideal inter-dot distance, and the number of subpatterns is larger than the number of divisions, at least all of the correction amounts that can be set are included in the correction pattern. Are included as sub-patterns with a deviation amount between the dot formation position in the forward path and the dot formation position in the backward path, and it is possible to include two or more sub-patterns having peaks in these sub-patterns. Therefore, highly accurate correction can be performed based on two or more sub-patterns having peaks.
[0016]
In the printing apparatus, the correction patterns are arranged so that the correction amount sequentially changes in the main scanning direction, and two sub patterns are extracted based on the density distribution of the correction pattern in the main scanning direction. Then, it is desirable that the median value of the correction amounts of the extracted sub patterns is a correction amount for correcting the deviation.
According to such a printing apparatus, the correction pattern has periodic changes in shading in the main scanning direction. When the correction amount is selected based on the density of the sub-pattern, even if the adjacent sub-pattern is selected by mistake, the correction pattern is arranged so that the correction amount is sequentially changed in the main scanning direction. Two sub-patterns are extracted based on the density distribution of the sub-pattern, and the median of the correction amounts of the extracted sub-patterns is used as a correction amount for correcting the deviation, thereby reducing the error due to the sub-pattern selection error by half. It becomes possible to.
[0017]
Further, in the printing apparatus, the two sub-patterns are a sub-pattern that protrudes most in the density distribution in the main scanning direction of the correction pattern and a sub-pattern positioned away from the sub-pattern by the number of divisions. It is good.
The sub-patterns that are located apart from the most protruding sub-pattern in the density distribution in the main-scanning direction by the number of divisions are different from the most protruding sub-pattern in the main-scanning direction in terms of the amount of deviation between the forward-passing dots and the return-passing dots. Since it is shifted by the ideal inter-dot distance, the sub-pattern is shifted by one period in the density distribution. Therefore, these two sub-patterns have a peak in density, and it becomes possible to perform high-precision correction by setting the median value of the correction amounts of these sub-patterns as a correction amount for correcting the shift.
[0018]
Further, in the printing apparatus, a predetermined sub-pattern and a sub-pattern located apart from the number of divisions among the correction patterns are sub-pattern pairs, and the sub-pattern most protruding in average density among the sub-pattern pairs. The pair may be the two sub-patterns.
In the sub-pattern pair, the deviation amount between the forward and backward dots of the other sub-pattern with respect to one of the sub-patterns is shifted by the ideal inter-dot distance in the main scanning direction. The sub pattern is shifted. Therefore, the most prominent sub-pattern pair in the average density of the sub-pattern pair has a peak in density, and the median of the correction amounts of these sub-patterns is used as a correction amount for correcting the deviation, thereby correcting with high accuracy. Can be performed.
[0019]
In the printing apparatus, when there are a plurality of the most prominent sub-pattern pairs at the average density, the sub-pattern pair including the sub-pattern having the most prominent density among the sub-patterns constituting each sub-pattern pair. May be the two sub-patterns.
By setting the median value of the correction amounts of the sub-pattern pairs including the sub-pattern having the most protruding density among the sub-patterns constituting the most protruding sub-pattern pair as the correction amount for correcting the deviation. Accurate correction can be performed.
[0020]
In the printing apparatus, it is preferable that the density distribution of the correction pattern is a curve interpolated based on the density of each sub-pattern.
According to such a printing apparatus, since the density distribution is represented by continuous data, correction can be performed with a more accurate correction amount.
[0021]
In such a printing apparatus, when there are no two sub-patterns having a peak in the density distribution in the main scanning direction of the correction pattern, the correction amount of the sub-pattern positioned at the end in the main scanning direction is changed. It is desirable to print a new correction pattern whose correction amount sequentially changes in the main scanning direction.
According to such a printing apparatus, it is possible to print at least two sub patterns having a peak in the density distribution in the sub patterns included in the correction pattern.
[0022]
In the printing apparatus, it is preferable that the correction amount for printing a new correction pattern is changed according to the position of the sub-pattern having the peak with respect to the sub-pattern serving as a reference for the correction amount.
Since the correction amount when printing a new correction pattern is changed according to the position of the sub pattern forming the peak with respect to the sub pattern serving as a reference for the correction amount, a peak in the density distribution is used as a new correction pattern. It is possible to include at least two sub-patterns forming
[0023]
The printing apparatus further includes an extraction unit that extracts a sub-pattern having a peak based on density information read by the density reading unit, and the extraction unit cannot extract two or more sub-patterns having a peak. In this case, it is desirable to print a new correction pattern by changing the correction amount of the sub-pattern located at the end in the main scanning direction.
According to such a printing apparatus, even when the correction pattern does not have two or more sub-patterns having a peak, the dot position deviation in the main scanning direction is corrected without bothering the user. It becomes possible to do.
[0024]
A discharge head for discharging ink droplets to form dots on the printing medium; and a density reading unit that can move in the main scanning direction together with the discharge head; In a printing apparatus that prints a correction pattern having a plurality of sub-patterns on a printing medium using the ejection head for correcting a deviation from a dot formation position in a return pass, each sub-pattern is a main scan forward pass The forward pass dots formed at predetermined intervals and the backward pass dots formed at predetermined intervals in the main scanning return pass are arranged in the main scanning direction and the sub-scanning direction, and the correction pattern is formed by the forward dot formation. Sub-pattern printed by sequentially changing a plurality of correction amounts that form an integral multiple of the distance obtained by equally dividing the ideal inter-dot distance in the main scanning direction between the position and the dot formation position in the return pass Are arranged in the main scanning direction more than the number of divisions, and the density reading unit reads the density of the correction pattern while moving in the main scanning direction, and the density of the correction pattern in the main scanning direction. The most prominent sub-pattern in the distribution and the sub-pattern located away from the sub-pattern by the number of divisions are extracted, and the median value of the correction amount of the extracted sub-pattern is a correction amount for correcting the deviation. The printing apparatus characterized by performing.
[0025]
According to such a printing apparatus, it is possible to realize a printing apparatus that can easily correct the landing positions of ink droplets in the main scanning direction in the forward path and the backward path.
[0026]
In the printing apparatus, the correction patterns are arranged such that the correction amount sequentially changes in the main scanning direction, and a peak appears on the higher density side in the density distribution of the correction pattern in the main scanning direction. Two sub-patterns having one and one sub-pattern having a peak on the lower density side may be extracted, and the deviation may be corrected based on the extracted sub-patterns.
[0027]
Further, a computer main body and a printing apparatus that is connected to the computer main body and performs printing on a print medium, the discharge head for discharging ink droplets to form dots on the print medium; and Printing that includes a density reading unit that can move in the main scanning direction together with the ejection head, and prints a correction pattern having a plurality of sub-patterns on the printing medium by the ejection head to correct a deviation in dot formation position. In the computer system having the apparatus, the density reading unit reads the density of the correction pattern while moving in the main scanning direction, and two or more sub-patterns having a peak in density among the plurality of sub-patterns. A computer system characterized by correcting the deviation based on a pattern can also be realized.
[0028]
=== Overview of Printing Apparatus ===
First, an outline of the printing apparatus will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic configuration diagram of a printing system including an inkjet printer 22. FIG. 2 is a block diagram showing the configuration of the printer 22 with the control circuit 40 as the center.
[0029]
The printer 22 has a sub-scan feed mechanism that transports the printing paper P by the paper feed motor 23 and a main scan feed mechanism that reciprocates the carriage 31 in the axial direction of the platen 26 by the carriage motor 24. Here, the feed direction of the printing paper P by the sub-scan feed mechanism is called a sub-scan direction, and the moving direction of the carriage 31 by the main scan feed mechanism is called a main scan direction. The carriage 31 is provided with a reflection type optical sensor 29 that forms density reading means for a correction pattern, which will be described later.
[0030]
The printer 22 drives a discharge head unit 60 (also referred to as “discharge head assembly”) mounted on the carriage 31 to control ink discharge and dot formation, and these paper feed motors 23. And a carriage motor 24, a discharge head unit 60, a reflective optical sensor 29, and a control circuit 40 that controls the exchange of signals with the operation panel 32. The control circuit 40 is connected to the computer 90 via the connector 56. The computer 90 is equipped with a driver for the printer 22, accepts user commands by operating a keyboard or mouse as input means, and presents various information in the printer 22 to the user by display on the display screen. Has an interface.
[0031]
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 platen 26 and a paper transport roller (not shown). The main scanning feed mechanism for reciprocating the carriage 31 is an endless drive belt 36 between the carriage motor 24 and a slide shaft 34 that is installed in parallel with the axis of the platen 26 and slidably holds the carriage 31. And a position detection sensor 39 for detecting the origin position of the carriage 31.
[0032]
As shown in FIG. 2, the control circuit 40 is configured as an arithmetic logic circuit including a CPU 41, a programmable ROM (PROM) 43, a RAM 44, and a character generator (CG) 45 storing a dot matrix of characters. ing. The control circuit 40 further includes an I / F dedicated circuit 50 dedicated to interface with an external motor and the like, and a head that is connected to the I / F dedicated circuit 50 and drives the ejection head unit 60 to eject ink. A drive circuit 52, a motor drive circuit 54 for driving the paper feed motor 23 and the carriage motor 24, and a control circuit 53 for controlling the reflective optical sensor are provided. The I / F dedicated circuit 50 incorporates a parallel interface circuit and can receive a print signal PS supplied from the computer 90 via the connector 56.
[0033]
=== Configuration Example of Reflective Optical Sensor ===
Next, a configuration example of the reflective optical sensor will be described with reference to FIG. FIG. 3 is a schematic diagram for explaining an example of the reflective optical sensor 29.
The reflective optical sensor 29 is attached to the carriage 31, and includes a light emitting unit 29a formed of, for example, a light emitting diode and a light receiving unit 29b formed of, for example, a phototransistor. Light emitted from the light emitting unit 29a, that is, incident light is reflected by the printing paper P, and the reflected light is received by the light receiving unit 29b and converted into an electrical signal. The magnitude of the electrical signal is measured as the output value of the light receiving sensor corresponding to the intensity of the received reflected light. Accordingly, the reflective optical sensor 29 functions as a density detection member that detects the density of the pattern printed on the printing paper P.
[0034]
In the above description, as shown in the figure, the light emitting unit 29a and the light receiving unit 29b are integrated to form a device called the reflective optical sensor 29. However, like the light emitting device and the light receiving device, respectively. A separate device may be configured.
In the above, in order to obtain the intensity of the received reflected light, the magnitude of the electric signal is measured after converting the reflected light into an electric signal. However, the present invention is not limited to this. It is only necessary to measure the output value of the light receiving sensor according to the intensity of the reflected light.
[0035]
=== Configuration of Discharge Head ===
Next, the configuration of the ejection head will be described with reference to FIGS. 4, 5, and 6. FIG. 4 is an explanatory diagram showing a schematic configuration inside the ejection head. FIG. 5 is an explanatory diagram showing in detail the structure of the piezo element PE and the nozzle Nz. FIG. 6 is an explanatory diagram showing the arrangement of the inkjet nozzles Nz in the ejection heads 61-66.
[0036]
The carriage 31 (FIG. 1) is supplied with a black ink (K) cartridge 71 and inks of five colors, cyan (C), light cyan (LC), magenta (M), light magenta (LM), and yellow (Y). The stored color ink cartridge 72 can be mounted.
[0037]
A total of six ejection heads 61 to 66 are provided in the lower part of the carriage 31, and an introduction pipe 67 (see FIG. 4) that guides ink from the ink tank to the ejection heads for each color is provided at the bottom of the carriage 31. Is provided. When the black (K) ink cartridge 71 and the color ink cartridge 72 are mounted on the carriage 31 from above, the introduction pipe 67 is inserted into the connection hole provided in each cartridge, and the ejection heads 61 to 66 are inserted from each ink cartridge. Ink can be supplied to the printer.
[0038]
When the ink cartridges 71 and 72 are mounted on the carriage 31, the ink in the ink cartridge is sucked out through the introduction pipe 67 as shown in FIG. 4 and the ejection heads 61 to 66 provided below the carriage 31. Led to.
[0039]
Piezoelectric elements PE, which are one of electrostrictive elements and excellent in responsiveness, are arranged for each nozzle in the discharge heads 61 to 66 of the respective colors provided at the lower part of the carriage 31. As shown in the upper part of FIG. 5, the piezo element PE is installed at a position in contact with the ink passage 68 that guides ink to the nozzle Nz. As is well known, the piezo element PE is an element that transforms electro-mechanical energy at a very high speed because the crystal structure is distorted by application of a voltage. In the present embodiment, by applying a voltage having a predetermined time width between the electrodes provided at both ends of the piezo element PE, the piezo element PE extends for the voltage application time as shown in the lower part of FIG. One side wall of 68 is deformed. As a result, the volume of the ink passage 68 contracts according to the expansion of the piezo element PE, and the ink corresponding to the contraction becomes an ink droplet Ip and is ejected from the tip of the nozzle Nz at high speed. The ink droplet Ip soaks into the paper P mounted on the platen 26, whereby dots are formed and printing is performed.
[0040]
As shown in FIG. 6, the arrangement of the inkjet nozzles Nz in the ejection heads 61 to 66 is black (K), cyan (C), light cyan (LC), magenta (M), light magenta (LM), yellow (Y). It consists of six sets of nozzle arrays that eject ink for each color, and each of the 48 nozzles Nz is arranged in a line at a constant nozzle pitch k.
[0041]
The printer 22 having the hardware configuration described above reciprocates the carriage 31 by the carriage motor 24 while conveying the paper P by the paper feed motor 23, and simultaneously drives the piezo elements PE of the ejection heads 61 to 66, Each color ink is ejected to form dots and form a multicolor image on the paper P.
[0042]
Here, as described above, the printer 22 having the head for ejecting ink using the piezo element PE is used. However, various ejection drive elements other than the piezo element can be used. It is. For example, the present invention can be applied to a printer provided with an ejection drive element of a type that energizes a heater arranged in an ink passage and ejects ink by bubbles generated in the ink passage. The configuration of the control circuit 40 also supplies a drive signal to each ejection drive element, and generates a drive signal so that the ejection order of ink droplets with time is kept the same in the forward and backward passes of main scanning. Anything can be used.
[0043]
=== Driving Head Drive ===
Next, driving of the ejection heads 61 to 66 will be described with reference to FIG. FIG. 7 is a block diagram showing a configuration of a drive signal generator provided in the head drive circuit 52 (FIG. 2).
[0044]
In FIG. 7, the drive signal generation unit includes a plurality of mask circuits 204, an original drive signal generation unit 206, and a drive signal correction unit 230. The mask circuit 204 is provided corresponding to a plurality of piezo elements for driving the nozzles n1 to n48 of the ejection head 61, respectively. In FIG. 7, the number in parentheses at the end of each signal name indicates the number of the nozzle to which the signal is supplied. The original drive signal generator 206 generates an original drive signal ODRV that is commonly used for the nozzles n1 to n48. The original drive signal ODRV is a signal including two pulses, a first pulse W1 and a second pulse W2, within the main scanning period for one pixel. The drive signal correction unit 230 performs correction by shifting the timing of the drive signal waveform shaped by the mask circuit 204 back and forth in the entire return path. By correcting the timing of the drive signal waveform, the deviation of the ink droplet landing position in the forward path and the backward path is corrected, that is, the deviation of the dot formation position in the forward path and the backward path is corrected.
[0045]
=== Overview of Correction Pattern Used for Dot Formation Position Deviation Correction ===
Next, an outline of dot formation position deviation correction in the main scanning direction will be described with reference to FIG. FIG. 8 is a diagram for explaining an outline of a method for determining a correction value for misalignment adjustment based on a correction pattern.
[0046]
The method of correcting the dot formation position deviation described below is to intentionally shift the ink droplet ejection timing in the return path so that the deviation of the dot formation position in the forward path and the return path becomes inconspicuous. is there. The ink droplet ejection timing in the forward path may be intentionally shifted throughout the forward path, and the ink droplet ejection timing in the forward path and the backward path may be intentionally shifted in the entire forward path and the entire backward path. Also, the cause of misalignment of the dots in the main scanning direction in the forward path and the backward path is due to variations in the ejection speed of ink droplets, backlash of the driving mechanism in the main scanning direction, and warping of the platen that supports the printing paper underneath. Etc.
[0047]
As shown in FIG. 8A, this correction pattern has, for example, 11 sub patterns P1 to P11. Each of the sub-patterns P1 to P11 is printed by causing the ejection head 28 to reciprocate in the main scanning direction and forming dots on the printing paper P by a specific row of nozzles (for example, the nozzles of the ejection head 61) during that time. is there.
[0048]
In the forward path, ink droplets are ejected onto the printing paper P at the same interval (= 1/180 inch). On the other hand, in the return path, ink droplets are similarly ejected at the same interval (= 1/180 inch), but the ejection timing is changed for each of the sub-patterns P1 to P11, and the amount of change in the main scanning direction is sequentially Print side by side to change. At this time, the amount of change in the ejection timing is set so that the amount of deviation between the forward dot and the backward dot changes by a unit correction amount temporarily set to select the correction amount. Here, the unit correction amount deviates from the ideal inter-dot distance (= 1/180 inch) in the main scanning direction, for example, by dividing into eight equal parts, that is, (1/180 inch) ÷ 8 = 1/1440 inch. As described above, the sub-patterns P1 to P11 are formed by shifting the discharge timing of the return path.
[0049]
For example, regarding the sub-pattern P1 and the sub-pattern P2, the difference between the forward ejection timing and the backward ejection timing in the sub-pattern P1 is ΔP1, and the forward ejection timing and the backward ejection timing in the sub-pattern P2 are When the deviation is ΔP2, | ΔP1−ΔP2 | = 1/1440 inch. Further, 1/180 inch is equal to 8/1440 inch. Therefore, assuming that the difference between the discharge timing of the forward path and the discharge timing of the return path in the sub-pattern P1 and the eight adjacent sub-patterns P9 is ΔP9, | ΔP1 | = | ΔP9 |.
[0050]
Here, the reason why the number of sub-patterns constituting the correction pattern is 11 is that the correction pattern includes two or more sub-patterns having peaks in density. For example, since the unit correction amount is set to 1/8 of the ideal inter-dot distance in the main scanning direction, when the forward pass dot and the backward pass dot forming the first sub pattern overlap, the unit is set for each sub pattern. When the correction amount is multiplied by an integer and sequentially increased, a sub-pattern in which the forward pass dot and the backward pass dot overlap again is printed in the eighth sub pattern counted from the first sub pattern. That is, a correction pattern in which shading occurs periodically every 8 patterns is printed. For this reason, it is necessary to set the number of sub-patterns more than the number of divisions obtained by equally dividing the ideal inter-dot distance in the main scanning direction.
[0051]
In the subpatterns P1 to P11 formed in this way, the larger the overlap between the dots formed on the printing paper P in the forward path and the dots formed on the printing paper P in the backward path, the larger the subpattern. The sub-pattern becomes darker as the overlap between the dots formed on the printing paper P in the forward path and the dots formed on the printing paper P in the backward path becomes smaller. In FIG. 8B, the darkness of each sub-pattern is indicated by ●, and the correction pattern shown in FIG. 8A is shown as a curve by interpolation based on the data of ●. , The subpattern P6 is the thinnest, the subpattern P2 and the subpattern P10 are the darkest, and the subpattern P6, the subpattern P2, and the subpattern P10 have a peak in density. In FIG. 8B, the peak marked with ● matches the peak of the curve, but by interpolating based on the data marked with ●, discrete data can be regarded as continuous data. The accuracy can be improved.
[0052]
=== Method of selecting a correction amount using a correction pattern ===
In the present embodiment, the density of each sub-pattern shown in FIG. 8A is read by the reflective optical sensor 29 and converted into an electrical signal, and has a peak in density based on the electrical signal as density information. Two sub-patterns are extracted by the control circuit 40 constituting sub-pattern extracting means. The actual printing of the return path is performed at the ejection timing in the return path when the sub pattern located at the center of the two extracted sub patterns is printed.
[0053]
That is, with reference to sub-patterns positioned at the ends of a plurality of sub-patterns arranged in the main scanning direction, it is detected how many sub-patterns having a peak in the density are located with respect to the reference. . The sub-pattern located in the center of the detected sub-pattern is specified, the ejection timing in the return pass when the specified sub-pattern is printed is stored as a correction value, and the ejection timing of ink droplets in the entire return pass is intentionally set by the correction value The dot formation position is corrected by shifting to. At this time, when the center of the two sub-patterns is the boundary of the sub-patterns, the center value of the ejection timings of the two sub-patterns forming the boundary is set as the correction value. Further, the median value of the ejection timings of both detected sub-patterns may be used as the correction value.
[0054]
Although there is a method in which the thinnest sub-pattern is selected using a sensor or visually recognized by the user and the formation condition of the sub-pattern is set to the optimum value, in terms of accuracy, as described above, the peak having a high concentration is used. It is preferable to select two sub-patterns having, and set the median value of the ejection timing in the return path when these two sub-patterns are printed to the optimum value. The reason is as follows.
[0055]
When the thinnest sub-pattern is selected using a sensor or visually recognized by the user and the sub-pattern formation condition is set to the optimum value, if the next sub-pattern is selected by mistake, the ejection timing of the return path Deviates from the optimum value by 1/1440 inch.
[0056]
On the other hand, in the case of a method in which two subpatterns having a high concentration peak are selected and the formation condition of the subpattern located between the two subpatterns is set to the optimum value, the adjacent subpattern is erroneously set. However, if the sub-pattern P11 adjacent to P2 and the sub-pattern P11 adjacent to P10 are selected by mistake, or the sub-pattern P3 and P10 next to P2 are erroneously selected. Even when P9 is selected, the median value of the return timing of the return path of the two sub patterns is the optimum value. Here, an example has been shown in which a sub-pattern having a high density peak is selected. However, when the ideal dot formation position on the return path with respect to the forward path is set to be shifted by half the ideal inter-dot distance, the low density peak is set. Two sub-patterns having “” are selected.
[0057]
Also, if the sub-pattern P2 is correctly selected but the other sub-pattern is wrongly selected as the sub-pattern P11, or the sub-pattern P10 is correctly selected but the other sub-pattern is wrongly selected as the sub-pattern P1. Even in such a case, the median value of the discharge timing of the return path of the two sub-patterns is only deviated by half of 1/1440 inch from the optimum value.
[0058]
In this correction method, it is not always necessary to perform printing using all the nozzles in the nozzle row. That is, in this correction method, it is only necessary to know the shade of each sub-pattern, so as long as the condition is satisfied, the sub-pattern may be printed by some nozzles in the nozzle row. For example, the sub-pattern may be formed by ejecting ink droplets only to the nozzles at the end or center of the nozzle row. By doing so, it is possible to save ink required for printing the correction pattern.
[0059]
As an example of extracting two or more sub-patterns having a peak in density from a plurality of sub-patterns included in the correction pattern, in the above example, two sub-patterns having a peak on the higher density side in the density distribution are selected. However, the present invention is not limited to this, and the following method may be used.
For example, the most prominent sub pattern in the density distribution in the main scanning direction of the correction pattern, that is, the sub pattern having the highest or the lowest density is selected, and eight sub patterns (in the main scanning direction) are selected from the selected sub patterns. The sub-patterns that are separated by the number of equal divisions of the ideal inter-dot distance and the selected pattern may be extracted.
[0060]
In addition, among the correction patterns, a predetermined sub-pattern and a sub-pattern that is located at a distance of eight sub-patterns are used as a sub-pattern pair, and one of the sub-patterns is sequentially formed from the sub-pattern at the end of the correction pattern It may be changed to extract a plurality of sub-pattern pairs and extract the most prominent sub-pattern pair at the average density of each sub-pattern pair. At this time, when there are a plurality of sub-pattern pairs that protrude most in the average density, each sub-pattern located in the center of the sub-pattern pairs is extracted, and the sub-pattern located in the center of the two sub-pattern pairs is extracted. The actual printing of the return pass may be performed at the discharge timing in the return pass when printing, and the center of the sub-pattern pair including the sub-pattern having the most protruding density among the sub-patterns constituting each sub-pattern pair. The actual printing of the return path may be performed at the discharge timing of the return path when the sub-pattern located at the position is printed.
[0061]
Furthermore, from two or more sub-patterns of the correction pattern, an attempt was made to extract two or more sub-patterns having a peak in density, but when two sub-patterns forming a peak did not exist and could not be extracted, At the end of the main scanning direction, change the correction amount of the sub pattern that serves as a reference for the correction amount, print a new correction pattern, and then create two or more sub patterns having a peak in density from the new correction pattern. Extract the pattern. At this time, the correction amount of the sub pattern serving as the reference of the correction amount is changed according to the position of the sub pattern forming the peak with respect to the sub pattern serving as the reference of the correction amount, and a new correction pattern is printed. For example, when recognizing the position where the darkest sub-pattern is positioned from the reference, and changing the correction amount of the reference sub-pattern to the correction amount of the sub-pattern and printing, the two sub-patterns that have a peak in density are printed. A correction pattern having a pattern can be printed.
[0062]
=== Dot formation position correction process ===
Next, the dot formation position correction process will be described with reference to FIGS. FIG. 9 is a flowchart for explaining the dot formation position correction process. FIG. 10 is a schematic diagram illustrating an example of a UI window for the user to instruct print misalignment adjustment.
[0063]
First, FIG. 10 shows a command to perform print misalignment adjustment for adjusting misalignment of the dot formation position in the forward pass and the return pass in the main scanning direction when the user perceives image quality degradation in bidirectional printing. This is performed from the UI window as shown (step S2). A screen for instructing such adjustment exists in the utility of the printer properties, etc., and the user clicks a button corresponding to print misalignment adjustment (the square button shown in the upper left of the figure) with the mouse to adjust the print misalignment. Let it begin.
[0064]
A command for print misalignment adjustment by the user is transmitted to the printer 22 as a command. Based on the received command, the printer 22 feeds the printing paper P by driving the paper feed motor 23 by the motor driving circuit 54 (step S4).
Subsequently, the printer 22 prints a correction pattern by driving the carriage motor 24 and the paper feed motor 23 by the head drive circuit 52 and the motor drive circuit 54.
[0065]
First, ink droplets are ejected from the ejection head 61 to print the correction patterns shown in FIG. 8, that is, the sub patterns P1 to P11 (step S6).
Next, each of the sub-patterns P1 to P11 is irradiated with light from the light emitting unit 29a of the reflective optical sensor 29, and the reflected light reflected is received by the light receiving unit 29b, and the light is reflected according to the intensity of the received reflected light. Based on the output value of the light receiving unit 29b, the darkness of each of the sub-patterns P1 to P11 is detected (step S8), and the detected darkness data is interpolated to interpolate the darkness peak from the darkness distribution shown in FIG. Two sub patterns forming a value are extracted (step S9).
Next, in the sub-patterns P1 to P11, the control circuit 40 determines whether there are two sub-patterns having a dark peak value (step S10).
[0066]
If there are two sub-patterns having a dark peak value in the sub-patterns P1 to P11, the sub-pattern located at the center of the two sub-patterns is specified (step S12), and the specified sub-pattern is printed. In this case, the discharge timing in the return path is stored as a correction value (step S13).
[0067]
In the sub-patterns P1 to P11, when there is only one sub-pattern having a dark peak value, the ink ejection timing in the return path is such that there are two sub-patterns having a dark peak value. Are appropriately changed as a whole (step S14), and a new correction pattern is printed (S6). At this time, the position of one sub-pattern having the peak value detected by the reflective optical sensor 29 is recognized from the end of the correction pattern, and printing is performed according to the correction amount of the sub-pattern having the peak value. When the correction amount of the sub-pattern located at the end of the correction pattern is changed so that the sub-pattern and the eighth sub-pattern counted from the sub-pattern are included in the correction pattern, Thereafter, the waste of ink can be prevented without repeatedly printing the correction pattern.
[0068]
Finally, the printer 22 discharges the printing paper P by driving the paper feed motor 23 by the motor driving circuit 54 (step S16).
[0069]
=== Others ===
As described above, the printing apparatus and the like according to the present invention have been described based on one embodiment. However, the above-described embodiment is intended to facilitate understanding of the present invention and is not intended to limit the present invention. Absent. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes the equivalents thereof.
[0070]
Although the printing paper has been described as an example of the printing material, a film, a cloth, a thin metal plate, or the like may be used as the printing material.
[0071]
Also, a computer main body, the printer according to the above-described embodiment connected to the computer main body, an input device such as a mouse and a keyboard provided as necessary, a display device such as a CRT, a flexible disk drive device, and a CD A computer system having a ROM drive device can also be realized, and the computer system realized in this way is an overall system that is superior to conventional systems.
[0072]
The printer according to the above-described embodiment may have a part of functions or mechanisms respectively included in the computer main body, the display device, the input device, the flexible disk drive device, and the CD-ROM drive device. For example, the printer includes an image processing unit that performs image processing, a display unit that performs various displays, and a recording medium attachment / detachment unit for attaching / detaching a recording medium that records image data captured by a digital camera or the like. Also good.
[0073]
In the above embodiment, a color ink jet printer has been described. However, the present invention can be applied to a monochrome ink jet printer, and can also be applied to printers other than the ink jet system. The present invention is generally applicable to a printing apparatus that prints on a printing medium, and can also be applied to, for example, a facsimile machine and a copier. However, in a so-called ink jet type printing apparatus that performs printing by discharging ink from the print head, a high image quality of the printing result is particularly required, so that the merit of the above-described means is further increased.
In the above description, the print misalignment adjustment is performed based on the user's request. However, it may be automatically performed without any user instruction. Further, the adjustment inspection may be performed before the printing apparatus reaches the user's hand, for example, at the time of shipment.
[0074]
For all nozzles of each color, correction may be performed according to one correction value for each dot size, or for each nozzle group that can independently correct ink droplet ejection timing, a correction value for each dot size is set. Also good. Further, the correction value may be set independently for each group of nozzle rows that eject the same ink. For example, when two sets of nozzle rows for ejecting specific ink are provided, the same correction value may be applied to the two sets of nozzles.
[0075]
In the above embodiment, the positional deviation is corrected by adjusting the discharge timing of the return path. However, the positional deviation may be corrected by adjusting the discharge timing of the forward path. Further, the positional deviation may be corrected by adjusting both the discharge timing of the forward path and the return path. That is, the positional deviation may be corrected by adjusting at least one of the discharge timing of the forward path and the backward path.
[0076]
In the above embodiment, the correction of the misalignment of the dot formation position when performing bidirectional printing has been described. However, the present invention relates to the dot formation position of one color and the dot of another color when performing unidirectional printing. The present invention can also be applied to correction of misalignment of formation position (so-called “UNI-D correction”). In this case, a correction pattern having a plurality of sub-patterns for correcting the deviation between the dot formation position of the first color ink and the dot formation position of the second color ink is applied to the printing medium by the ejection head. The density reading unit prints and reads the density of the correction pattern while moving in the main scanning direction. Based on two or more sub-patterns having a peak in density among the plurality of sub-patterns, the shift is performed. What is necessary is just to correct | amend.
[0077]
As another embodiment, the correction patterns are arranged such that the correction amount sequentially changes in the main scanning direction, and the correction pattern has a higher density in the density distribution in the main scanning direction. Two sub-patterns having a peak and one sub-pattern having a peak on the lower density side may be extracted, and the shift may be corrected based on these extracted sub-patterns.
[0078]
In this case, first, in the sub-patterns P1 to P11, two sub-patterns having a peak value on the dark side and a sub-pattern having a peak on the thin side are extracted. Next, the sub-pattern located at the center of the two sub-patterns having the peak value on the extracted dark side is specified, and the ejection timing in the return path when the specified sub-pattern is printed is set as the first correction value. . Furthermore, the ejection timing in the return path when the extracted sub-pattern having a peak on the thin side is printed is set as the second correction value. Then, the average value of the first correction value and the second correction value may be stored as the final correction value (note that the sub-pattern located at the center of the two sub-patterns having the peak value on the dark side, When the sub-pattern having a peak on the thin side is the same sub-pattern, the first correction value and the second correction value are naturally the same value). In this manner, in addition to the two sub-patterns having a peak on the higher density side, one sub-pattern having the peak on the lower density side is also used, so that the deviation can be corrected with higher accuracy. .
[0079]
In the above embodiment, a part of the configuration realized by hardware may be replaced by software, and conversely, a part of the configuration realized by software may be replaced by hardware. .
[0080]
【The invention's effect】
According to the present invention, it is possible to realize a printing apparatus capable of accurately correcting the landing position of ink droplets in the main scanning direction, and a computer system having this printing apparatus.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a printing system including an inkjet printer.
FIG. 2 is a block diagram showing the configuration of the printer 22 with a control circuit 40 as the center.
FIG. 3 is a schematic diagram for explaining an example of a reflective optical sensor 29;
FIG. 4 is an explanatory diagram showing a schematic configuration inside the ejection head.
FIG. 5 is an explanatory diagram showing in detail the structure of a piezo element PE and a nozzle Nz.
6 is an explanatory diagram showing an arrangement of inkjet nozzles Nz in the ejection heads 61 to 66. FIG.
FIG. 7 is a block diagram showing a configuration of a drive signal generator provided in the head drive circuit 52 (FIG. 2).
FIG. 8 is a diagram for explaining an outline of a method for determining a correction value for misalignment adjustment based on an example of a correction pattern and a correction pattern;
FIG. 9 is a flowchart for explaining dot forming position correction processing using the reflective optical sensor 29;
FIG. 10 is a schematic diagram illustrating an example of a UI window for a user to instruct print misalignment adjustment.
[Explanation of symbols]
22 Color printer 23 Paper feed motor
24 Carriage motor 26 Platen
29 Reflective optical sensor 29a Light emitting part
29b Light receiver 31 Carriage
32 Operation panel 34 Sliding shaft
36 Drive belt 38 Pulley
39 Position detection sensor 40 Control circuit
41 CPU 43 PROM
44 RAM 45 Character generator (CG)
50 I / F dedicated circuit 52 Head drive circuit
53 Reflective optical sensor control circuit 54 Motor drive circuit
56 Connector 60 Discharge head unit
61-66 Discharge head 67 Introduction pipe
68 Ink passage 71, 72 Ink cartridge
90 computer 204 mask circuit
206 Original drive signal generator 230 Drive signal correction unit

Claims (17)

An ejection head for ejecting ink droplets to form dots on a printing medium; and a density reading unit movable in the main scanning direction together with the ejection head, for correcting a deviation in dot formation position, In a printing apparatus that prints a correction pattern having a plurality of sub-patterns on a substrate by the ejection head,
The density reading unit reads the density of the correction pattern while moving in the main scanning direction,
The printing apparatus, wherein the deviation is corrected based on two or more sub patterns having a peak in density among the plurality of sub patterns. The printing apparatus according to claim 1,
The printing apparatus according to claim 1, wherein the correction pattern is a correction pattern having a plurality of sub-patterns for correcting a shift between a dot formation position in a forward pass of main scanning and a dot formation position in a return pass. The printing apparatus according to claim 1 or 2,
Each sub-pattern is configured by arranging dots in a main scanning direction and a sub-scanning direction. The printing apparatus according to claim 2,
Each of the sub-patterns has a plurality of correction amounts for performing the correction, and each of the sub-patterns is a forward pass dot formed at a predetermined interval in the main scan forward pass, and a return pass formed at a predetermined interval in the main scan return pass A printing apparatus having dots, wherein a deviation amount between a dot formation position in the forward path and a dot formation position in the backward path is set to the correction amount that is different for each sub-pattern. The printing apparatus according to claim 4,
The printing apparatus is characterized in that the correction amount is an integral multiple of a distance obtained by equally dividing the ideal inter-dot distance in the main scanning direction, and the number of sub-patterns included in the correction pattern is larger than the division number. The printing apparatus according to any one of claims 1 to 5,
The correction patterns are arranged so that the correction amount sequentially changes in the main scanning direction, two sub patterns are extracted based on the density distribution of the correction pattern in the main scanning direction, and the extracted sub patterns A printing apparatus, wherein a median value of correction amounts is a correction amount for correcting the shift. The printing apparatus according to claim 6.
A printing apparatus characterized in that a sub pattern that protrudes most in the density distribution in the main scanning direction of the correction pattern and a sub pattern that is located apart from the sub pattern by the number of divisions are the two sub patterns. The printing apparatus according to claim 6.
Among the correction patterns, a predetermined sub-pattern and a sub-pattern located apart by the number of divisions are sub-pattern pairs, and the sub-pattern pair that protrudes most in the average density among the sub-pattern pairs is the two sub-patterns. A printing apparatus characterized by the above. The printing apparatus according to claim 8, wherein
In the case where there are a plurality of sub-pattern pairs that protrude most at the average density, each of the sub-patterns located at the center of the sub-pattern pair is set as the two sub-patterns. The printing apparatus according to claim 8, wherein
When there are a plurality of subpattern pairs that protrude most at the average density, a subpattern pair that includes a subpattern having the highest protrusion density among the subpatterns constituting each subpattern pair is defined as the two subpatterns. A printing apparatus characterized by the above. The printing apparatus according to claim 6.
The printing apparatus, wherein the density distribution of the correction pattern is a curve interpolated based on the density of each sub-pattern. The printing apparatus according to any one of claims 6 to 11,
When there are no two sub-patterns having a peak in the density distribution in the main scanning direction of the correction pattern, the correction amount of the sub-pattern located at the end in the main scanning direction is changed so that the correction amount is the main scanning direction. A printing apparatus for printing a new correction pattern that sequentially changes. The printing apparatus according to claim 12, wherein
A printing apparatus, wherein a correction amount for printing a new correction pattern is changed according to a position of the sub-pattern that forms the peak with respect to a sub-pattern serving as a reference for the correction amount. The printing apparatus according to claim 1,
Based on the density information read by the density reading means, it has an extracting means for extracting a sub-pattern having a peak, and when two or more sub-patterns having a peak cannot be extracted by the extracting means, the main scanning direction A printing apparatus that prints a new correction pattern by changing a correction amount of a sub-pattern positioned at the edge of the print pattern. An ejection head for ejecting ink droplets to form dots on a printing medium; and a density reading unit that can move in the main scanning direction together with the ejection head. In a printing apparatus that prints a correction pattern having a plurality of sub-patterns on a substrate by the ejection head in order to correct a deviation from a dot formation position.
Each of the sub-patterns is configured by arranging forward dots formed at a predetermined interval in the main scanning forward pass and return dots formed at a predetermined interval in the main scanning backward pass in the main scanning direction and the sub-scanning direction. And
The correction pattern was printed by sequentially changing a plurality of correction amounts that are an integral multiple of a distance obtained by equally dividing the distance between ideal dots in the main scanning direction between the forward dot formation position and the backward dot formation position. More sub-patterns are arranged in the main scanning direction than the number of divisions,
The density reading unit reads the density of the correction pattern while moving in the main scanning direction,
A sub pattern that protrudes most in the density distribution in the main scanning direction of the correction pattern and a sub pattern that is located away from the sub pattern by the number of divisions are extracted, and the median value of the correction amount of the extracted sub pattern is A printing apparatus having a correction amount for correcting the shift. The printing apparatus according to claim 1,
The correction patterns are arranged so that the correction amount sequentially changes in the main scanning direction,
In the density distribution in the main scanning direction of the correction pattern, two sub patterns having a peak on the higher density side and one sub pattern having a peak on the lower density side are extracted,
A printing apparatus that corrects the deviation based on the extracted sub-patterns. A computer body, and
A printing apparatus that is connected to the computer main body and performs printing on a printing medium. The ejection head ejects ink droplets to form dots on the printing medium, and the ejection head together with the ejection head in the main scanning direction. A computer system having a printing device that prints a correction pattern having a plurality of sub-patterns on a printing medium with the discharge head for correcting a shift of a dot formation position. ,
The density reading unit reads the density of the correction pattern while moving in the main scanning direction,
The computer system characterized by correcting the deviation based on two or more subpatterns having a peak in density among the plurality of subpatterns.

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