JP4900437B2 - Printing device - Google Patents

Description

  The present invention relates to a printing apparatus and a computer system.

  In recent years, color printers that eject several colors of ink from a head have become widespread as output devices for computers. Some ink jet color printers have a function of performing so-called “bidirectional printing” in order to improve printing speed.

  In addition, the ink jet printer can only reproduce each pixel with binary values of on / off, but recently, a multi-value printer capable of reproducing three or more multi-values with one pixel has been proposed. Multi-valued pixels can be formed, for example, by ejecting ink droplets of a plurality of sizes of the same color for one pixel.

Japanese Patent Laid-Open No. 11-5301

When bi-directional printing is performed using a multi-value printer that discharges a plurality of ink droplets for one pixel, the image quality may be deteriorated due to a difference in printing characteristics between the forward path and the backward path. For example, if the landing positions in the main scanning direction of the ink droplets of the respective sizes differ between the forward path and the backward path, the image deteriorates due to this.
Further, when a plurality of colors of ink droplets are ejected to one pixel, the image quality deteriorates if a deviation occurs between the landing position of a certain color ink droplet and the landing position of another color ink droplet.
The present invention has been made to solve the above-described problems, and an object of the present invention is to prevent deterioration in image quality due to a deviation in ink landing position.

  The main present invention includes an ejection head for selectively ejecting ink droplets of a plurality of sizes to form dots on a printing medium, and a density detection member that can move in the main scanning direction together with the ejection head. In the printing apparatus that prints the correction pattern for correcting the deviation of the dot formation position on the printing medium, the dots constituting the correction pattern printed by discharging ink droplets of a certain size from the discharge head The interval in the sub-scanning direction is different from the interval in the sub-scanning direction of dots constituting the correction pattern printed by ejecting ink droplets of other sizes from the ejection head. The density of the correction pattern is detected while moving in the main scanning direction.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  According to the present invention, it is possible to prevent the deterioration of the image quality due to the deviation of the ink landing position.

1 is a schematic configuration diagram of a printing system including an inkjet printer 22. FIG. FIG. 3 is a block diagram illustrating a configuration of a printer 22 with a control circuit 40 as a center. The schematic diagram for demonstrating an example of the reflection type optical sensor 29. FIG. FIG. 3 is an explanatory diagram showing a schematic configuration inside the ejection head. Explanatory drawing which showed in detail the structure of the piezo element PE and the nozzle Nz. Explanatory drawing which shows the arrangement | sequence of the inkjet nozzle Nz in the discharge heads 61-66. FIG. 3 is a block diagram showing a configuration of a drive signal generator provided in a head drive circuit 52 (FIG. 2). The timing chart which shows operation | movement of a drive signal generation part. The figure for demonstrating the outline of the method of determining the correction value of deviation adjustment based on the pattern for a correction | amendment. The figure for demonstrating the correction pattern comprised by a large dot. The figure for demonstrating the correction pattern comprised by a medium dot. The figure for demonstrating the correction pattern comprised by a small dot. 10 is a flowchart for explaining dot forming position correction processing. FIG. 3 is a schematic diagram illustrating an example of a UI window for a user to instruct print misalignment adjustment. The figure which showed an example of the pattern for a correction | amendment.

[Outline 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 selectively ejecting ink droplets of a plurality of sizes to form dots on a printing medium; and a density detection member that can move in the main scanning direction together with the ejection head, In a printing apparatus that prints a correction pattern for correcting misalignment on a printing medium, dots in the sub-scanning direction of the correction pattern that is printed by discharging ink droplets of a certain size from the discharge head. The interval is different from the interval in the sub-scanning direction of dots constituting the correction pattern printed by ejecting ink droplets of other sizes from the ejection head, and the density detection member moves in the main scanning direction. A printing apparatus that detects the density of the correction pattern.

  If the size of the ink droplets ejected from the ejection head is different, the size of the dots formed on the printing medium is different accordingly, and the density of the correction pattern is also different. Therefore, even if the density of the correction pattern formed according to an ink droplet of a certain size is preferable, the density of the correction pattern formed according to an ink droplet of another size may not be preferable.

  According to the present invention, the correction pattern printed by ejecting ink droplets of other sizes is arranged such that the dots in the sub-scanning direction of the correction pattern printed by ejecting ink droplets of a certain size are printed. Therefore, it is possible to form a correction pattern having a darkness corresponding to the size of the ink droplet. Further, since the density detection member that can move in the main scanning direction together with the ejection head detects the density of the correction pattern while moving in the main scanning direction, the correction pattern appropriately formed according to the dot size The density in the main scanning direction can be efficiently detected using the density detecting member.

  In the printing apparatus, the correction pattern may be a correction pattern for correcting a deviation between a dot formation position in the forward path of main scanning and a dot formation position in the backward path.

  In the printing apparatus, the correction pattern may include a plurality of sub patterns, and 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, the correction pattern has a plurality of sub-patterns, and each sub-pattern is configured by arranging dots in the main scanning direction and the sub-scanning direction. It is possible to form a good correction pattern.

  Further, in the printing apparatus, the sub-pattern has forward dots formed at a predetermined interval in the main scanning forward pass, and return pass dots formed at a predetermined interval in the main scanning backward pass, The amount of deviation between the forward pass dot formation position and the backward pass dot formation position may be different for each sub-pattern.

  According to such a printing apparatus, the sub-pattern has forward dots formed at predetermined intervals in the main scanning forward pass, and return pass dots formed at predetermined intervals in the main scanning forward pass, Since the amount of deviation between the forward pass dot formation position and the backward pass dot formation position differs for each sub-pattern, it is possible to form a correction pattern with good visibility or density detectability in shading.

In such a printing apparatus, the intervals in the main scanning direction of the dots constituting the correction pattern may be the same regardless of the size.
If the interval in the main scanning direction of the dots constituting the correction pattern is reduced in order to increase the density of the correction pattern formed by ejecting small-sized ink droplets, adjacent dots in the main scanning direction A blurring phenomenon occurs when they are connected to each other. According to the printing apparatus, since the intervals in the main scanning direction of the dots constituting the correction pattern are the same regardless of the size, it is possible to suppress the occurrence of the bleeding phenomenon.

In the printing apparatus, the predetermined interval may be twice or more the dot interval in the sub-scanning direction.
When the dot interval in the main scanning forward path and the backward path is reduced, adjacent dots in the main scanning direction are coupled to each other, resulting in a bleeding phenomenon. According to the printing apparatus, since the predetermined interval is at least twice the dot interval in the sub-scanning direction, it is possible to suppress the occurrence of bleeding.

In this printing apparatus, the deviation between the dot formation position in the forward pass of the main scanning and the dot formation position in the return pass may be corrected based on the density detection result by the density detection member.
According to such a printing apparatus, it is possible to perform accurate dot position deviation correction based on a correction pattern whose density is optimized according to the dot size.

In addition, the printing medium has an ejection head that selectively ejects ink droplets of a plurality of sizes to form dots on the printing medium, and a correction pattern for correcting dot position deviation in the forward and backward passes of main scanning In the printing apparatus that prints on, the interval in the sub-scanning direction of the dots constituting the correction pattern printed by discharging ink droplets of a certain size is printed by discharging ink droplets of other sizes. Unlike the interval in the sub-scanning direction of the dots constituting the correction pattern, it accepts user instruction information based on the correction pattern, and based on the instruction information, the dot formation position in the forward path of main scanning and the dot in the return path A printing apparatus characterized by correcting a deviation from the formation position can also be realized.
According to such a printing apparatus, it is possible to perform accurate dot position deviation correction based on user instruction information based on a correction pattern with good visibility.

  And a discharge head for selectively discharging ink droplets of a plurality of sizes to form dots on the printing medium, and a density detection member that can move in the main scanning direction together with the discharge head, In a printing apparatus that prints a correction pattern for correcting a deviation between a dot formation position in the forward path and a dot formation position in the backward path on a printing medium, printing was performed by ejecting ink droplets of a certain size from the ejection head. The intervals in the sub-scanning direction of the dots constituting the correction pattern are the intervals in the sub-scanning direction of the dots constituting the correction pattern printed by ejecting ink droplets of other sizes from the ejection head. The correction pattern has a plurality of sub-patterns, and each sub-pattern is configured by arranging dots in the main scanning direction and the sub-scanning direction. The sub-pattern has a forward dot formed at a predetermined interval in the main scanning forward path and a backward dot formed at a predetermined interval in the main scanning backward path. The amount of misalignment differs for each sub-pattern, and the intervals in the main scanning direction of the dots constituting the correction pattern are the same regardless of the size, and the predetermined interval is twice the dot interval in the sub-scanning direction. As described above, it is possible to realize a printing apparatus that corrects the deviation between the dot formation position in the forward pass of the main scanning and the dot formation position in the return pass based on the density detection result by the density detection member.

  Also, in order to correct the misalignment between the dot formation position in the forward path of the main scanning and the dot formation position in the backward path by the ejection head for selectively ejecting ink droplets of a plurality of sizes to form dots on the printing medium. In the correction pattern, the intervals in the sub-scanning direction of the dots constituting the correction pattern printed by discharging an ink droplet of a certain size from the discharge head are different from each other. A correction pattern that is different from the interval in the sub-scanning direction of the dots constituting the correction pattern that is ejected and printed can also be realized.

  In addition, the apparatus has a discharge head for selectively discharging ink droplets of a plurality of sizes to form dots on a printing medium, and a density detecting member that can move in the main scanning direction together with the discharge head, and forms dots In a printing apparatus that prints a correction pattern for correcting a positional deviation on a printing medium, dots that constitute the correction pattern printed by ejecting ink droplets of a certain size from the ejection head are overprinted. The number of times is different from the number of overprinting dots constituting the correction pattern printed by ejecting ink droplets of other sizes from the ejection head, and the density detection member moves in the main scanning direction. Also, it is possible to realize a printing apparatus characterized by detecting the density of the correction pattern.

  A computer main body and a printing apparatus that is connected to the computer main body and performs printing on a printing medium, and selectively ejects ink droplets of a plurality of sizes to form dots on the printing medium. And a density detecting member that can move in the main scanning direction together with the ejection head, and a printing device that prints a correction pattern for correcting a deviation in dot formation position on a printing medium. In the computer system, the interval in the sub-scanning direction of dots constituting the correction pattern printed by ejecting ink droplets of a certain size from the ejection head ejects ink droplets of other sizes from the ejection head. Unlike the interval in the sub-scanning direction of the dots constituting the correction pattern printed in this way, the density detection member moves in the main scanning direction. While, the computer system characterized in that to detect the density of the correction pattern.

[Overview of printing device]
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.

  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 reflective optical sensor 29 described later.

  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 control circuit 40 for exchanging signals with the carriage motor 24, the ejection head unit 60, and the operation panel 32. The control circuit 40 is connected to the computer 90 via the connector 56.

  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.

  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 and a motor drive circuit 54 for driving the paper feed motor 23 and the carriage motor 24 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.

[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.

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.

[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.

  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.

  A total of six ejection heads 61 to 66 are provided at the lower portion 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 ejected from each ink cartridge. Ink can be supplied to the printer.

  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 at the lower portion of the carriage 31. Led to.

  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 under 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.

  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.

  The printer 22 includes a nozzle Nz having a constant diameter as shown in FIG. 6, and a plurality of types of ink droplets having different ink amounts can be formed using the nozzle Nz. This is done by changing the drive waveform for driving the piezo element PE. Specifically, the rate of change when the drive voltage of the piezo element PE is made negative or the peak voltage of the drive waveform is changed. By changing, it is possible to form ink droplets having different ink amounts with one nozzle.

  The printer 22 having the hardware configuration described above, while transporting the paper P by the paper feed motor 23, reciprocates the carriage 31 by the carriage motor 24 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.

  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 selectively ejects one or more ink droplets from each nozzle, so that a plurality of types of dots having different sizes are provided at each pixel position. Any one of them can be recorded, and a drive signal can be generated so as to keep the same order of discharge over time for a plurality of types of ink droplets in the forward and backward passes of main scanning. Something like that.

[Driving head drive]
Next, driving of the ejection heads 61 to 66 will be described with reference to FIGS. 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 timing chart showing the operation of the drive signal generator shown in FIG.

  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.

  As shown in FIG. 7, the input serial print signal PRT (i) is input to the mask circuit 204 together with the original drive signal ODRV output from the original drive signal generator 206. The serial print signal PRT (i) is a 2-bit serial signal per pixel, and each bit corresponds to the first pulse W1 and the second pulse W2.

  The mask circuit 204 is a gate for masking the original drive signal ODRV in accordance with the level of the serial print signal PRT (i) (i = 1 to 48). That is, when the serial print signal PRT (i) is 1 level, the mask circuit 204 passes the corresponding pulse of the original drive signal ODRV as it is and supplies it as the drive signal DRV to the piezo element, while the serial print signal PRT (i ) Is 0 level, the corresponding pulse of the original drive signal ODRV is cut off.

  At the time of printing, as shown in FIG. 8 (a-1), as the pulse of the original drive signal ODRV, the first pulse W1 and the second pulse W2 are generated in this order in each pixel section T1, T2, T3. . The “pixel section” has the same meaning as the main scanning period for one pixel. As described above, the mask circuit 204 (FIG. 7) passes the pulse of the original drive signal ODRV as it is when the serial print signal PRT (i) is 1 level, and the original when the serial print signal PRT (i) is 0 level. The pulse of the drive signal ODRV is cut off.

  Therefore, as shown in FIGS. 8A-2 and 8A-3, when the two bits of the serial print signal PRT (i) in each pixel section are “1, 0”, only the first pulse W1 is present. Output in the first half of one pixel interval. Thereby, small dots having a small size are formed on the printing medium. Further, when “0, 1”, only the second pulse W2 is output in the latter half of one pixel interval. As a result, medium dots of medium size are formed on the substrate. When “1, 1”, both the first pulse W1 and the second pulse W2 are output. Thereby, large dots having a large size are formed on the printing medium.

  As can be understood by looking at the forward drive signal waveform shown in FIG. 8 (a-3), the three types of drive signals DRV (i) for recording the three types of dots are the drive signals over one pixel section. It is shaped so that the waveforms are different from each other, that is, at least one of the size and number of ink droplets ejected from the nozzles is different. That is, the drive signal DRV (i) in one pixel section is shaped to have three different waveforms depending on three different values of the print signal PRT (i).

  The same drive signal waveform corresponding to each dot is used in both the forward and backward passes of the main scanning. That is, small ink droplets, medium ink droplets, and large ink droplets ejected from one nozzle in one pixel section are ejected in the same order and time interval in the forward path and the backward path. However, although the same drive signal waveforms are used for the forward and return passes of main scanning, the timing is shifted back and forth by the drive signal correction unit 230 (FIG. 7) and corrected for the entire return pass. By correcting this timing, the landing position of the ink droplet is intentionally shifted in the entire return path, and the deviation of the landing position of the ink droplet in the forward path and the return path is corrected.

[Outline of dot position correction in the main scanning direction]
Next, an outline of dot formation position shift correction in the main scanning direction will be described with reference to FIG. FIG. 9 is a diagram for explaining an outline of a method for determining a correction value for misalignment adjustment based on a correction pattern.

  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.

  As shown in FIG. 9A, this correction pattern has eleven 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.

  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 shifted by 1/1440 inch in the sub-scanning direction for each of the sub-patterns P1 to P11. ing.

  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 |.

  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. FIG. 9B shows the darkness of each sub-pattern, but the correction pattern shown in FIG. 9A is the thinnest in the sub-pattern P6, and in the sub-pattern P2 and the sub-pattern P10. It is the darkest.

  In this embodiment, among the sub-patterns shown in FIG. 9A, two darkest sub-patterns are selected, and the intermediate values of the respective ejection timings in the return path when these two sub-patterns are printed. The actual printing of the return path is performed. That is, the intermediate value of the ejection timing in the return path when each sub-pattern is printed is stored as a correction value, and the dot formation position is determined by intentionally shifting the ejection timing of the ink droplets in the entire return path by the correction value. to correct.

  Although there is a method of selecting the thinnest sub-pattern by using a sensor or by visual recognition by the user and setting the sub-pattern formation condition to an optimum value, in terms of accuracy, as described above, the darkest sub-pattern It is preferable to select an intermediate value of the discharge timing in the return path when the two sub-patterns are printed and the two sub-patterns are printed. The reason is as follows.

  In the method of selecting the thinnest sub-pattern using a sensor or by visual recognition by the user and setting the sub-pattern formation condition to the optimum value, if the adjacent sub-pattern is selected by mistake, the discharge timing of the return path Deviates from the optimum value by 1/1440 inch.

  On the other hand, in the method of selecting the two darkest sub-patterns and setting the sub-pattern formation condition located in the middle of the two sub-patterns to the optimum value, select the next sub-pattern by mistake. 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 P9 adjacent to P2 and P10 adjacent to P2 is selected by mistake. Even in such a case, the intermediate value of the return timing of the return path of the two sub-patterns is an optimum value.

  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 this case, the intermediate 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.

  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.

[Method for forming correction pattern according to dot size]
Next, a correction pattern forming method corresponding to the dot size will be described with reference to FIGS. FIG. 10 is a diagram for explaining a correction pattern composed of large dots. FIG. 11 is a diagram for explaining a correction pattern composed of medium dots. FIG. 10 is a diagram for explaining a correction pattern composed of small dots.

  As described above, the shift of the dot formation position is corrected based on the correction pattern. Here, when the intervals of the dots constituting the correction pattern in the main scanning direction and the sub-scanning direction are the same, the correction pattern configured by large dots is darker than the correction pattern configured by medium dots, and the medium dots The correction pattern constituted by is darker than the correction pattern constituted by small dots.

  Accordingly, in a correction pattern composed of small dots formed at a certain interval, even if the difference in shading of each sub-pattern is appropriate, in a correction pattern composed of large dots formed at the same interval Therefore, the difference in shade between the sub-patterns becomes inappropriate, that is, since each sub-pattern is extremely dark, the difference in shade between the sub-patterns becomes small.

  Therefore, in the present embodiment, the intervals in the sub-scanning direction of the dots constituting the correction pattern are different depending on the dot size. More specifically, the intervals in the sub-scanning direction of the dots constituting the correction pattern are increased in the order of small dots, medium dots, and large dots.

  Each sub-pattern P1 to P11 shown in FIG. 10A, FIG. 11A, and FIG. 12A is printed at the same ejection timing in both the forward path and the backward path. That is, assuming that the deviation between the forward discharge timing and the backward discharge timing when printing each sub-pattern Pi (i = 1 to 11) is ΔPi, ΔPi is as shown in FIGS. 10 (A) and 11 (A). This is the same in FIG. FIG. 10B, FIG. 11B, and FIG. 12B show the darkness for each sub-pattern. Both the vertical axis and the horizontal axis show FIG. 10B and FIG. ) And the same scale in FIG. As is clear from a comparison of FIGS. 10B, 11B, and 12B, the sub-pattern formed by large dots is generally darker than the sub-pattern formed by medium dots. The sub pattern composed of medium dots is generally darker than the sub pattern composed of small dots.

  In FIG. 10B, the circled plots show a resolution of 180 dpi in the main scanning direction and a resolution of 1440 dpi in the sub scanning direction, that is, the dot interval in the main scanning direction is (1/180) inch and the sub scanning. It shows the darkness of each sub-pattern when each sub-pattern is configured with the direction dot interval of (1/1440) inches.

  Also, what is plotted with square marks is a resolution of 180 dpi in the main scanning direction and a resolution of 720 dpi in the sub scanning direction, that is, a dot interval in the main scanning direction of (1/180) inches and a dot interval in the sub scanning direction. The density of each sub-pattern when each sub-pattern is configured as (1/720) inches is shown.

  Also, what is plotted with rhombus marks is a resolution of 180 dpi in the main scanning direction and 360 dpi in the sub scanning direction, that is, a dot interval in the main scanning direction of (1/180) inches and a dot interval in the sub scanning direction. The density of each sub-pattern when each sub-pattern is configured as (1/360) inches is shown. Note that the relationship between the circle mark, the square mark, and the rhombus mark and the dot interval in the main scanning direction and the sub scanning direction is the same in FIGS. 11B and 12B.

  As shown in FIG. 10, in each of the sub-patterns P1 to P11 composed of large dots, if the resolution in the sub-scanning direction is set to 1440 dpi, any sub-pattern becomes dark and the difference in shading between the sub-patterns becomes small. . On the other hand, as the resolution in the sub-scanning direction is lowered to 720 dpi and 360 dpi, the light / dark difference of each sub-pattern increases. Therefore, when a correction pattern is configured with large dots, the resolution is 180 dpi in the main scanning direction and 360 dpi in the sub-scanning direction.

  As shown in FIG. 11, in each of the sub-patterns P1 to P11 composed of medium dots, if the resolution in the sub-scanning direction is 720 dpi, the difference in shade of each sub-pattern becomes the largest. Therefore, when a correction pattern is configured with medium dots, the resolution is 180 dpi in the main scanning direction and 720 dpi in the sub-scanning direction.

  As shown in FIG. 12, in each of the sub-patterns P1 to P11 composed of small dots, if the resolution in the sub-scanning direction is set to 360 dpi, any sub-pattern becomes thin, and the light / dark difference of each sub-pattern becomes small. . On the other hand, as the resolution in the sub-scanning direction is increased to 720 dpi and 1440 dpi, the difference in shade between the sub-patterns increases. Therefore, when a correction pattern is configured with small dots, the resolution is 180 dpi in the main scanning direction and 1440 dpi in the sub-scanning direction.

  Note that the interval in the main scanning direction of the dots constituting the correction pattern is constant (for example, 180 dpi) regardless of the dot size. When the dot interval in the main scanning direction is reduced, the correction pattern becomes darker. However, if the interval in the main scanning direction of the dots constituting the correction pattern is reduced in order to increase the density of the correction pattern, the dots adjacent to each other in the main scanning direction are combined with each other to cause a bleeding phenomenon. End up. From this point of view, in this embodiment, the occurrence of the blurring phenomenon is suppressed by making the intervals in the main scanning direction of the dots constituting the correction pattern the same regardless of the dot size.

  Further, from the viewpoint of suppressing the occurrence of the bleeding phenomenon, it is preferable that the dot interval in the main scanning direction is not less than twice the dot interval in the sub-scanning direction regardless of the dot size.

[Dot formation position correction]
Next, dot forming position correction processing will be described with reference to FIGS. 13, 14, and 15. FIG. 13 is a flowchart for explaining the dot formation position correction process. FIG. 14 is a schematic diagram illustrating an example of a UI window for a user to instruct print misalignment adjustment. FIG. 15 is a diagram illustrating an example of a correction pattern.

  First, FIG. 14 shows an instruction 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.

  An instruction 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. An example of the correction pattern will be described with reference to FIG.

  First, a correction pattern composed of large dots, that is, sub-patterns P1 to P11, is printed by ejecting large ink droplets from the ejection head 61 (step S6). The dot resolution at this time is 180 dpi in the main scanning direction and 360 dpi in the sub scanning direction, that is, the dot interval in the main scanning direction is (1/180) inch, and the dot interval in the sub scanning direction is (1). / 360) inches. As described above, when a correction pattern is configured with large dots, the density of each of the sub-patterns P1 to P11 becomes most noticeable when printing is performed at such a resolution.

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, 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).
Next, in the sub-patterns P1 to P11, it is determined whether there are two sub-patterns having a dark peak value (step S10).
In the case where there are two sub-patterns having a darkness peak value in the sub-patterns P1 to P11, the intermediate value of the respective ejection timings in the return pass when the two sub-patterns are printed is used as the large dot correction value. Store (step S12).
In the case of sub-patterns P1 to P11, if there are no two sub-patterns having a darkness peak value, the ink ejection timing in the return path is appropriately set as a whole so that there are two sub-patterns having a darkness peak value. Shift (step S14).

Subsequently, a medium pattern ink droplet is ejected from the ejection head 61 to print a correction pattern composed of medium dots, that is, sub-patterns P1 to P11 (step S16). The dot resolution at this time is 180 dpi in the main scanning direction and 720 dpi in the sub scanning direction, that is, the dot interval in the main scanning direction is (1/180) inch, and the dot interval in the sub scanning direction is (1). / 720) inches. As described above, when a correction pattern is configured with medium dots, the density of each of the sub-patterns P1 to P11 becomes most noticeable when printing is performed at such a resolution.
Next, using the sub-patterns P1 to P11, medium dot correction values are stored in the same manner as in the case of large dots (step S18).

Further, a small pattern of ink droplets is ejected from the ejection head 61 to print correction patterns composed of small dots, that is, sub-patterns P1 to P11 (step S20). The dot resolution at this time is 180 dpi in the main scanning direction and 1440 dpi in the sub scanning direction, that is, the dot interval in the main scanning direction is (1/180) inch, and the dot interval in the sub scanning direction is (1). / 1440) inches. As described above, when the correction pattern is configured with small dots, the density of each of the sub-patterns P1 to P11 becomes most prominent when printing is performed at such a resolution.
Next, using the sub-patterns P1 to P11, small dot correction values are stored in the same manner as in the case of large dots (step S22).
Finally, the printer 22 discharges the printing paper P by driving the paper feed motor 23 by the motor drive circuit 54 (step S24).

  In the correction process described above, in step S8, 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 reflected light is received by the light receiving unit 29b. The density of each of the sub patterns P1 to P11 is detected based on the output value of the light receiving unit 29b corresponding to the intensity of the received reflected light. However, the user visually recognizes the density of each sub pattern. It is good to do. In this case, the user visually recognizes the sub-patterns P1 to P11 and selects two sub-patterns having a dark peak value. The printer 22 receives, as instruction information, information specifying the sub pattern selected by the user, and based on the instruction information, an intermediate value of each ejection timing in the return path when printing two sub patterns is used as a correction value. Just remember.

[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.

  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.

  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.

  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.

  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.

  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.

  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.

  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 the formation position (so-called “UNI-D correction”). In this case, when the correction pattern 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 printed on the printing medium, the first color ink is used. The intervals in the sub-scanning direction of the dots constituting the correction pattern printed by ejecting ink droplets of a certain size from the ejection head for ejecting and the ejection head for ejecting the second color ink are different from these ejection heads. The interval in the sub-scanning direction of the dots constituting the correction pattern printed by ejecting ink droplets of a size may be different.

  In the above-described embodiment, the interval in the sub-scanning direction of dots constituting the correction pattern printed by ejecting ink droplets of a certain size from the ejection head is different from the ejection head in other sizes. The correction pattern printed by ejecting ink droplets of a certain size is different from the interval in the sub-scanning direction of the dots constituting the correction pattern printed by ejecting the ink droplets. The number of times of overprinting dots constituting the pattern for use may be different from the number of times of overprinting dots constituting the correction pattern printed by ejecting ink droplets of other sizes from the ejection head.

  By appropriately setting the interval between dots in the sub-scanning direction according to the dot size, the difference in pattern shading can be made appropriate, but the number of dot overstrikes can be set appropriately according to the dot size. This also makes it possible to make the difference in pattern shading appropriate. For example, two or three small dots are formed at the same position on the medium, and only one large dot is formed at the same position on the medium. An appropriate shading pattern can be created for both dots.

  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. .

  22 Color printer, 23 Paper feed motor, 24 Carriage motor, 26 Platen, 29 Reflective optical sensor, 29a Light emitting unit, 29b Light receiving unit, 31 Carriage, 32 Operation panel, 34 Slide 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, 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 corrector.

Claims (5)

An ejection head for selectively ejecting ink droplets of a plurality of sizes to form dots on the substrate;
A density detecting member movable in the main scanning direction together with the ejection head;
A sub-scan feed mechanism for transporting the substrate to be printed in a sub-scan direction intersecting the main scan direction;
Have
In a printing apparatus that prints a correction pattern for correcting a deviation in dot formation position in the main scanning direction on a printing medium,
The density detection member corrects the deviation of the dot formation position based on the result of detecting the density of the correction pattern,
The correction pattern includes a first correction pattern composed of dots of a first size and a second correction pattern composed of dots of a second size,
The first size is smaller than the second size;
The printing apparatus, wherein the number of overstrikes of the first size dots constituting the first correction pattern is greater than the number of overstrikes of the second size dots constituting the second correction pattern . The printing apparatus according to claim 1 ,
The correction pattern has a plurality of sub-patterns,
Each sub-pattern is configured by arranging dots in the main scanning direction and the sub-scanning direction. The printing apparatus according to claim 2 ,
Each of the sub-patterns includes forward dots formed at predetermined intervals in the main scanning forward path, and backward dots formed at predetermined intervals in the main scanning backward path,
The printing apparatus, wherein the amount of deviation between the forward pass dot formation position and the backward pass dot formation position varies depending on each of the sub-patterns. The printing apparatus according to claim 3.
When information specifying two sub-patterns selected by the user is received, a correction for correcting the deviation of the dot formation position is performed using an intermediate value of the ejection timing at which the return pass dot included in each of the two sub-patterns is formed A printing device characterized by a value. The printing apparatus according to any one of claims 1 to 4,
The dot interval in the sub-scanning direction of the first correction pattern is smaller than the dot interval in the sub-scanning direction of the second correction pattern,
The dot interval in the main scanning direction of the first correction pattern is the same as the dot interval in the main scanning direction of the second correction pattern,
  The dot interval in the main scanning direction of the first correction pattern is at least twice the dot interval in the sub-scanning direction of the first correction pattern,
  The printing apparatus, wherein a dot interval in the main scanning direction of the second correction pattern is twice or more a dot interval in the sub-scanning direction of the second correction pattern.

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