JP2000318144A - Printing apparatus, printing method, and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly adjust a positional deviation when two-way printing is carried out by forming a plurality of comparison images on a printing medium while changing every image at a discharge timing of ink drops at a first half or a second half of reciprocation, and correcting the discharge timing of ink drops on the basis of the discharge timing when selected one comparison image is formed. SOLUTION: A printing head 41 loaded to a carriage 40 of the printing apparatus is relatively reciprocated to a printing medium, whereby images are formed both at a first half and at a second half of the reciprocation. In this printing apparatus, when a discharge timing of the printing apparatus is to be corrected by a control device 60, a plurality of predetermined images having a predetermined gradation width are formed while at least either one of a discharge timing of ink drops at the reciprocation, and a discharge timing of ink drops at the second half is changed for every image. One image is selected from the plurality of formed images. A discharge timing of ink drops when forming printing images is corrected on the basis of the discharge timing when the selected image is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for printing an image while moving a head for ejecting ink droplets relatively to a print medium.

[0002]

2. Description of the Related Art A printing apparatus (hereinafter referred to as an ink jet printer) for printing an image on a printing paper while moving a head for discharging ink droplets relatively to the printing paper.
Are widely used as recording devices for images output from computers and the like. Ink jet printers form a raster of ink dots on printing paper by reciprocating the head while discharging ink droplets,
The image is printed by shifting the position of the printing paper little by little in accordance with the formation of the raster.

Some ink-jet printers eject ink droplets only when the head moves forward. However, if ink droplets are ejected not only when the head moves forward but also when the head moves backward, the printing speed can be improved. Printers capable of performing such bidirectional printing are widely used.

In such an ink jet printer capable of bidirectional printing, ink dots are formed both when the head is moved forward and backward, so that the printing time can be shortened accordingly, but on the other hand, the print quality is maintained. In order to prevent the displacement of the dots between the ink dots formed during the forward movement and the ink dots formed during the backward movement,
It is necessary to precisely adjust the ejection timing of ink droplets. That is, the ink droplets ejected from the moving head form ink dots on the print medium after traveling a certain distance in the moving direction of the head. In an inkjet printer that performs bidirectional printing, the head movement direction is reversed between forward movement and backward movement, so if ink droplets are not ejected at the appropriate timing considering the head movement direction, the forward movement The displacement of the ink dots occurs between the time and the backward movement, thereby deteriorating the image quality.

As a method of accurately adjusting the ink droplet ejection timing at the time of forward movement and the backward movement, a predetermined image is actually printed while changing the ejection timing of the ink droplet at the time of backward movement little by little. Conventionally, a method of selecting an ejection timing that minimizes the displacement has been performed.
Since it is considered important to adjust the ejection timing accurately in order to avoid deterioration in image quality during bidirectional printing, ruled lines and the like that can detect even a slight misalignment in order to increase the adjustment accuracy are considered. In general, the discharge timing is adjusted using the simple image described above. Also, Japanese Patent Application Laid-Open No. 7-8119
No. 0 discloses a technique for adjusting the ejection timing with higher accuracy by detecting a positional deviation finer than the printing resolution.

[0006]

However, various technologies have been developed, such as a technology for printing while actively controlling the size of ink dots and a technology for printing by using inks having different densities. As the print quality of inkjet printers improves as a result, simply reducing the displacement of the ink dot formation position during forward movement and backward movement while printing ruled lines for adjustment is equivalent to that in unidirectional printing. In some cases, high-quality images cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art, and a technique for enabling high-quality printing by appropriately adjusting the positional deviation during bidirectional printing. The purpose is to provide.

[0008]

Means for Solving the Problems and Their Functions and Effects In order to solve at least part of the above-mentioned problems, the printing apparatus of the present invention employs the following configuration. That is, a printing apparatus which forms a print image by ejecting ink droplets from the head during both the forward movement and the backward movement while reciprocating the head relative to the print medium, Adjustment image storage means for storing image data of an image having a gradation width of, and a comparison image as an image formed on the print medium based on the image data, the ejection timing of ink droplets during forward movement or A comparative image forming means for forming a plurality of images while changing at least one of the ejection timings of the ink droplets at the time of the backward movement for each image; The gist of the invention is to provide an ejection timing correction unit that corrects the ejection timing of the ink droplet when forming the print image based on the ejection timing.

Further, the method of correcting the ejection timing according to the present invention corresponding to the above-mentioned printing apparatus is characterized in that the head is reciprocated relative to the printing medium while the head is moved forward and backward.
A method of correcting a discharge timing of a printing apparatus that forms a print image by discharging ink droplets from the head, wherein image data of an image having a predetermined gradation width is stored, and the printing is performed based on the image data. A plurality of comparative images, which are images formed on the medium, are formed while changing at least one of the ink droplet ejection timing at the time of forward movement and the ink droplet ejection time at the time of backward movement for each image. The gist of the invention is to correct the ejection timing of ink droplets when forming the print image based on the ejection timing when one comparative image selected from images is formed.

In such a printing apparatus and a method of correcting the ejection timing, image data of an image having a predetermined gradation width is stored in advance, and the ejection timing of the ink droplet at the time of forward movement or backward movement is changed little by little. While forming a plurality of such images. When one image is selected from a plurality of images formed by changing the ejection timing for each image in this manner, the printing apparatus performs image processing based on the ejection timing used when forming this image. The ejection timing used when forming the image is corrected.

If the ink droplet ejection timing is adjusted using an image having a predetermined gradation width, it is possible to adjust the ejection timing to an appropriate one. Therefore, high-quality printing can be performed even in bidirectional printing. it can.

Here, in order to more clearly explain the reason why it is possible to improve the image quality in bidirectional printing by making adjustments using an image having a predetermined gradation width, in order to explain more clearly, The reason why a sufficient print quality may not be ensured even if the positions of the ink dots are accurately matched will be described below.

FIG. 23A shows the principle that, when bidirectional printing is performed, the dot positions of the ink dots during the forward movement and the ink dots during the backward movement are matched by adjusting the ejection timing of the ink droplets. FIG. As shown on the left side of the drawing, the ink droplets are ejected from the position A toward the print medium at the speed Vi while the head moves from the left to the right on the paper surface at the speed Va (this direction is referred to as the forward movement direction). Suppose you did. The ejected ink droplets fly at the velocity component Vc toward the direction of movement of the head, and at the same time fly at the velocity component Vi toward the print medium. As a result, they fly at the combined velocity Va as shown in the drawing. An ink dot is formed at a position C on the print medium. Assuming that the time from when the ink droplet is ejected to when the ink dot is formed is dT, the position C where the ink dot is formed is a distance L (= Vc × dT) from the position A where the head ejected the ink droplet.
Just be away.

Next, as shown on the right side of FIG. 23A, consider the case where the head ejects ink droplets while moving from right to left on the paper (this direction is referred to as a backward direction). Since the head moves in the opposite direction at the speed Vc and the ink droplets are ejected toward the print medium at the speed Vi, in order to form an ink dot at the same position C as in the forward movement,
It is necessary to eject ink droplets when the head passes a position B that is a distance L before the position C (a distance 2L before the position A where the ink droplets were ejected during the forward movement).

When bidirectional printing is performed as described above, it is necessary to adjust the ejection timing of the ink droplets so that the positions of the ink dots ejected during the forward movement and the ink dots ejected during the backward movement do not shift. There is. Normally, this adjustment is performed so that the ink droplets at the time of the forward movement and the ink dots at the time of the backward movement are at the same position while ejecting ink droplets during the forward movement and the backward movement to actually form an image. This is performed by adjusting the ejection timing of the ink droplet at the time of the return movement.

However, no matter how precisely the ejection timing is adjusted in this way, it has been found that image quality equivalent to that of unidirectional printing cannot be maintained when bidirectional printing is performed. This will be described below.

In FIG. 23A, it is assumed that the velocity Vi of the ink droplet ejected from the head toward the print medium is always constant. However, the inventor of the present application has found that the speed of ink droplets ejected from the head is not always constant when an image is actually printed.
Various reasons can be considered as a factor that causes the ejection speed of the ink droplet to fluctuate. For example, a mechanism (for example, an actuator or a heater) that generates a driving force for discharging ink droplets for each nozzle also has manufacturing variations. It is considered that there is. In an ink jet printer that can perform color printing using several types of inks, physical characteristics such as ink viscosity and surface tension slightly differ for each color. Because it depends on these physical properties of the ink,
It is considered that the ejection speed of the ink droplet may slightly differ depending on the type of the ink.

Further, the discharge speed of ink droplets may be different between a case where ink droplets are simultaneously discharged from a plurality of nozzles provided in the head and a case where ink droplets are discharged from only some of the nozzles. This is because the electric load for driving the actuators and the like is different between the case where the ink droplets are ejected from all the nozzles and the case where the ink droplets are ejected from some of the nozzles. When ejecting ink droplets from all nozzles,
Although a large amount of ink must be supplied to the nozzles in accordance with the discharge amount of the entire head, the supply of the ink cannot be performed in time, and the discharge speed of the ink droplets may fluctuate. Further, in the case of ejecting ink droplets from all nozzles and the case of ejecting ink droplets from some nozzles, for example, in the method of ejecting ink droplets by deforming the head with an actuator, the rigidity of the head changes, or the heater is used. In the method of ejecting ink droplets by generating bubbles in the ink passages, the speed of the ink droplets ejected from the nozzles may be different due to the influence of the heat capacity of the head or the like. At the time of actual image printing, these various reasons are superimposed on each other depending on the printing conditions, and the speed of the ink droplet is slightly different for each nozzle.

FIG. 23B is an explanatory diagram showing the positions of ink dot formation, assuming that the speed of ink droplets differs for each nozzle. On the left side of the figure, when the head ejects ink droplets from position A while moving in the forward movement direction,
This shows how ink dots are formed. FIG.
In (b), the fastest speed is represented by Vif, and the slowest speed is represented by Vis. The droplets are distributed in a certain range over the position Cs1 where the droplet forms the dot. The right side of FIG. 23B shows a case where the head ejects ink droplets from the position B while moving in the backward movement direction. Also in this case, the formation positions of the ink dots are distributed from the position Cf2 where the fastest ink droplet forms a dot to the position Cs2 where the slowest ink droplet forms a dot. As is clear from FIG.
Considering that the ink droplet has a certain velocity distribution, as shown in FIG. 23A, no matter how precisely the ink droplet ejection timing is adjusted assuming that the ink droplet velocity takes a constant value Vi. It can be seen that the timing is not adjusted to the optimal discharge timing. In contrast, as in the present invention,
By adjusting the ejection timing of ink droplets when performing bidirectional printing using an image having a predetermined gradation width, it is possible to determine the position of ink dots formed by ink droplets of various speeds, The timing can be adjusted to obtain a good image quality.

The head used in such a printing apparatus may be a head capable of discharging a plurality of types of ink droplets. The plurality of types of ink droplets include, for example, ink droplets of different sizes, ink droplets of inks of different colors, and ink droplets of ink of the same color and different densities.

The flying speed of the ink droplet may be different depending on the difference in the size of the ink droplet and the type of the ink to be ejected. If adjusted, it is possible to adjust to an appropriate ejection timing in consideration of a difference in ejection speed due to a difference in the type of ink droplet. By performing the bidirectional printing with the ejection timing adjusted in this manner, a high-quality image can be printed, which is preferable.

In a printing apparatus capable of discharging a plurality of types of ink droplets, the timing of discharging the ink droplets may be adjusted using an image having a gradation width such that a plurality of types of ink droplets are formed.

If the image used for adjusting the ejection timing of the ink droplets is an image formed by a plurality of types of ink droplets, good image quality can be obtained in consideration of the effect of positional deviation due to the difference in the type of ink. This is preferable because the discharge timing can be adjusted to a desired value.

In such a printing apparatus, a printing apparatus having a head for ejecting ink droplets of each color capable of expressing an achromatic image by being used in combination with each other is provided.
The image having the predetermined gradation width may include at least an achromatic region.

If the positions of the ink dots formed by the ink droplets of each color are slightly deviated, the achromatic region will show any color. Therefore, the discharge timing using the image including the achromatic region is determined. By performing the adjustment, it is possible to adjust the discharge timing to a more appropriate one.

In such a printing apparatus, a plurality of types of images having a predetermined gradation width are stored, and a plurality of images are selected from the plurality of images while changing the ejection timing at the time of forward movement or backward movement. May be formed.

By storing data of a plurality of types of images in this way, it is possible to select an appropriate image according to the image to be printed, and to adjust the ejection timing of ink droplets using this image. it can. It is preferable to print an image at the ejection timing adjusted in this way, since a higher quality image can be printed.

In such a printing apparatus, at least image data corresponding to a natural image such as a photograph and image data corresponding to a character image such as a character, a figure, a table, or a graph may be stored. good.

When printing an image such as a photograph, the ejection timing of ink droplets is adjusted using an image corresponding to the natural image. Adjust using By doing so, it is possible to adjust the ejection timing to an appropriate one according to the image, so that it is possible to obtain a high quality print image while performing bidirectional printing, which is preferable.

In such a printing apparatus, one image may be selected from a plurality of stored image data and used based on the image data of the image to be printed. For example, the type of the application program that created the image may be determined from the extension of the image data to be printed, and the image used for adjusting the ejection timing may be selected based on the determination result. .

An image to be used for adjusting the ejection timing is selected based on the image data of the image to be printed, and if the adjustment is performed using the selected image, the image is printed at an appropriate ejection timing according to the print image. Therefore, a high-quality image can be obtained, which is preferable.

In such a printing apparatus, a gradation value distribution of an image to be printed may be obtained, and an image whose discharge timing is to be adjusted may be selected based on the gradation value distribution.

When selecting an image for which the ejection timing is to be adjusted, for example, an appropriate image is selected by paying attention to a range in which the grayscale values are distributed, or a grayscale value with the highest frequency is focused. Then, an appropriate image can be selected based on the gradation value distribution. It is preferable to perform printing with the ejection timing adjusted using an appropriate image in this manner, since high-quality printing can be performed.

In such a printing apparatus, a plurality of image data are stored for adjusting the ejection timing, and the adjustment result of the ejection timing is stored for each of the plurality of image data. When the adjustment result of the ejection timing is stored in the image data for adjusting the ejection timing selected according to the image to be printed, the ejection timing of the print image is determined based on the stored adjustment result. May be corrected.

As long as the ejection timing is adjusted using the same image data, it can be considered that the adjustment results for each time are almost the same. Therefore, the adjustment result of the ejection timing is stored for each adjustment image data, and when the adjustment is performed using the adjustment image data next time, the adjustment is not actually performed but the stored adjustment is performed. Even if the result is read, almost the same result can be obtained. Adjusting the ejection timing during bidirectional printing in this way is preferable because a high-quality image can be obtained while saving the time required for the adjustment.

Further, in this printing apparatus, if the adjustment result of the ejection timing is not stored in the adjustment image data selected according to the image to be printed,
The ejection timing may be adjusted using the selected adjustment image.

This is preferable because bidirectional printing can always be performed using an appropriate ejection timing, even if the adjustment result of the ejection timing is not necessarily stored for all the image data for adjustment. .

Further, in this printing apparatus, a plurality of images of the image data selected for adjusting the ejection timing are formed while changing the ejection timing at the time of forward movement or at the time of backward movement, and the images are compared as a comparison. It may be formed by unidirectional printing.

The image formed by unidirectional printing does not deteriorate in image quality due to the reversal of the head movement direction. It can also be considered an image that is a target for improvement. From this, when selecting a preferable image from a plurality of images formed by changing the ejection timing,
If a selection is made in comparison with an image formed by unidirectional printing, the selection can be made appropriately and easily.

The method of correcting the ejection timing of the printing apparatus according to the present invention can also be realized by combining the printing apparatus with a computer that controls the printing apparatus, and causing the computer to perform necessary processing. Therefore, the ejection timing correction method of the present invention also includes the following mode as a recording medium on which a program for causing a computer to execute necessary processing is recorded. That is, while the head is reciprocated relative to the print medium, the ejection timing of a printing apparatus that forms a print image by ejecting ink droplets from the head during both the forward movement and the backward movement is corrected. A computer-readable recording medium for recording a program for realizing the method, the method comprising controlling the printing apparatus to print a predetermined image having a predetermined gradation width at a time when ink droplets are ejected at the time of forward movement or at the time of backward movement. A function of forming a plurality of images while changing at least one of the ejection timings of the ink droplets for each image, and a method for forming an image when one image is selected from the plurality of formed images. According to another aspect of the present invention, there is provided a recording medium storing a program for realizing a function of correcting a discharge timing of an ink droplet when forming the print image based on the discharge timing.

A computer reads a program recorded on such a recording medium, and realizes each of the above functions while controlling the printing apparatus, so that the ejection timing of ink drops during bidirectional printing can be appropriately corrected. However, a high-quality image can be obtained.

[0042]

DETAILED DESCRIPTION OF THE INVENTION Configuration of Apparatus An embodiment of the present invention will be described based on an example. FIG. 1 is an explanatory diagram illustrating a configuration of a printing apparatus as an embodiment of the present invention. As shown, this printing device
The color printer 20 is connected to the computer 80, and a predetermined program is loaded and executed on the computer 80 to function as a printing apparatus as a whole. The color original to be printed is captured using the color scanner 21 connected to the computer 80, or an image created by the application program 91 on the computer 80 is used. The data ORG of these images is stored in the computer 8
The image data is converted into image data that can be printed by the color printer 20 by the CPU 81 in the image data 0 and output to the color printer 20 as image data FNL. Color printer 20
Forms ink dots of each color on a print medium in accordance with the image data FNL, so that a color image corresponding to a color original is printed on printing paper.

The computer 80 includes a CPU 81 for executing various arithmetic processing and a RAM for temporarily storing data.
82, a ROM 83 for storing various programs, a hard disk 26, and the like. Also, SIO
If 88 is connected to the public telephone line PNT via the modem 24, it becomes possible to download necessary data and programs from the server SV on the external network to the hard disk 26.

The color printer 20 is a printer capable of printing a color image. In this embodiment, a total of cyan, light cyan (light cyan), magenta, light magenta (light magenta), yellow and black is printed on the printing paper. An inkjet printer that prints a color image by forming dots of six colors is used. The ink ejection method of the ink jet printer used in this embodiment employs a method using a piezo element PE as described later, but a printer having a head for ejecting ink by another method may be used. . For example, the present invention may be applied to a printer of a system in which a heater arranged in an ink passage is energized and ink is ejected by bubbles generated in the ink passage.

The color printer 20 according to the present embodiment is a variable dot printer, that is, a large-sized printer having different sizes.
The printer is capable of forming three types of dots, medium and small, for each color. By changing the size of dots to be formed using a variable dot printer, it is possible to express multi-valued gradations for each dot, so that an image with rich gradation expression can be printed. The color printer 20 of this embodiment forms dots of three different sizes by using a single ink discharge nozzle by devising an ink discharge method. The method of discharging such ink will be described later.

FIG. 2 is a block diagram conceptually showing a software configuration of the printing apparatus. In the computer 80, all application programs 91 operate under an operating system. A video driver 90 and a printer driver 92 are incorporated in the operating system, and image data output from each application program 91 is output to the color printer 20 via these drivers.

When the application program 91 issues a print command, the printer driver 9 of the computer 80
2 receives image data from the application program 91, performs predetermined image processing, and converts the image data into image data that can be printed by a printer. As conceptually shown in FIG. 2, the image processing performed by the printer driver 92 includes a resolution conversion module 93, a color conversion module 94, a halftone module 95, and an interlace module 9.
It is composed of six large four modules. Although the contents of the image processing performed by each module will be described later, the image data received by the printer driver 92 is converted by these modules and then output to the color printer 20 as final image data FNL. Note that the color printer 20 of this embodiment only plays a role of forming dots in accordance with the image data FNL, and does not perform image processing, but, of course, performs part of image conversion by the color printer 20. There may be.

FIG. 3 shows a schematic configuration of the color printer 20 of this embodiment. As shown, the color printer 20 drives a print head 41 mounted on a carriage 40 to eject ink and form dots.
The carriage 40 includes a mechanism for reciprocating the carriage 40 in the axial direction of the platen 36 by the carriage motor 30, a mechanism for conveying the printing paper P by the paper feed motor 35, and a control circuit 60.

The mechanism for reciprocating the carriage 40 in the axial direction of the platen 36 includes a sliding shaft 33 that slidably holds the carriage 40 erected in parallel with the axis of the platen 36.
Between the endless drive belt 3 and the carriage motor 30
1 and a position detection sensor 34 for detecting the origin position of the carriage 40.

The mechanism for transporting the printing paper P is a platen 3
6, a paper feed motor 35 for rotating a platen 36,
It comprises a paper feed auxiliary roller (not shown) and a gear train (not shown) for transmitting the rotation of the paper feed motor 35 to the platen 36 and the paper feed auxiliary roller. Printing paper P
Is set so as to be sandwiched between the platen 36 and the paper feed auxiliary roller, and is fed by a predetermined amount according to the rotation angle of the platen 36.

The control circuit 60 includes a computer 8
PC interface 6 for exchanging data with 0
4, a peripheral device input unit (PIO) 65 for exchanging data with the paper feed motor 35, the carriage motor 30, etc.
A drive buffer 67 for supplying dot on / off signals to the ink ejection heads 44 to 49, a CPU 61 for controlling these, a RAM 63 for temporarily storing data, and the like are provided. The control circuit 60 also includes an oscillator 70 that outputs a drive waveform, and a distribution output device 69 that distributes the output of the oscillator 70 to the ink ejection heads 44 to 49 at a predetermined timing.

When the computer 80 outputs the image data FNL to the color printer 20, the dot on / off signals are temporarily stored in the RAM 63 in the control circuit 60.
The CPU 61 in the color printer 20 controls the oscillator 70, the carriage motor 30, and the paper feed motor 35, and outputs dot data in the RAM 63 to the drive buffer 67 while synchronizing with the oscillator 70, the carriage motor 30, and the paper feed motor 35. Is discharged.

The carriage 40 includes an ink cartridge 42 for storing black (K) ink, cyan (C), light cyan (LC), magenta (M), and light magenta (L).
M) and an ink cartridge 43 containing a total of five color inks of yellow (Y). Of course, K
The ink, the LC ink and the LM ink may be stored in the same ink cartridge, or the K ink and the Y ink may be stored in the same ink cartridge. If a plurality of inks can be stored in one cartridge, the ink cartridge can be made compact. When the ink cartridges 42 and 43 are mounted on the carriage 40, the respective inks in the cartridges are supplied to the ink discharge heads 44 to 49 for the respective colors through introduction pipes (not shown). The ink supplied to each head is discharged from the print head 41 by a method described below, and forms dots on printing paper.

FIG. 4A is an explanatory diagram showing the internal structure of each color head. The ink discharge heads 44 to 49 of each color are provided with 48 nozzles Nz for each color, and each nozzle is provided with an ink passage 50 and a piezo element PE on the passage. As is well known, the piezo element PE is an element that distorts the crystal structure due to the application of a voltage and converts electro-mechanical energy very quickly. In this 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 expands by the voltage application time as shown in FIG. One side wall of the ink passage 50 is deformed. As a result,
The volume of the ink passage 50 expands and contracts in accordance with the expansion of the piezo element PE, and ink corresponding to the contraction is ejected from the nozzle Nz as particles Ip at a high speed. This ink Ip
Penetrates into the printing paper P mounted on the platen 36, thereby forming dots on the printing paper P.

FIG. 5 shows the ink ejection heads 44 to 4.
FIG. 9 is an explanatory diagram showing an arrangement of inkjet nozzles Nz in No. 9; As shown in the figure, on the bottom surface of the ink ejection head, six sets of nozzle arrays for ejecting ink of each color are formed, and 48 nozzles Nz per one set of nozzle arrays are arranged at a constant nozzle pitch k. They are arranged in a staggered pattern. The 48 nozzles N included in each nozzle array
z does not need to be arranged in a staggered manner, and may be arranged in a straight line. However, the arrangement in a staggered manner as shown in FIG. 5A has the advantage that the nozzle pitch k can be easily set small in manufacturing.

As shown in FIG. 5, the ink discharge heads 44 to 49 of the respective colors are displaced in the transport direction of the carriage 40. Also, the nozzles of each color head are displaced in the transport direction of the carriage 40 due to the staggered arrangement of the nozzles. The control circuit 60 of the color printer 20 ejects ink droplets by driving each head at an appropriate timing in consideration of these nozzle positions while transporting the carriage 40.

The color printer 20 of this embodiment is provided with nozzles Nz having a constant diameter as shown in FIG. 5, but it is necessary to form three types of dots having different sizes from each other using the nozzles Nz. Can be. Hereinafter, this principle will be described. FIG. 6 is an explanatory diagram showing the relationship between the driving waveform of the nozzle Nz when the ink is ejected and the ejected ink Ip. The drive waveform indicated by a broken line in FIG. 6 is a waveform when a normal dot is ejected. In the section d2, once a voltage lower than the reference voltage is applied to the piezo element PE, the piezo element PE is deformed in a direction to increase the cross-sectional area of the ink passage 50, contrary to the description of FIG. Since the supply speed of ink to the nozzle is limited,
The supply amount of the ink becomes insufficient with respect to the expansion of the ink passage 50, and as a result, as shown in the state A of FIG. 6, the ink interface Me is depressed inside the nozzle Nz. Also,
When the voltage is rapidly lowered as shown in the section d1 using the driving waveform shown by the solid line in FIG.

Next, when a high voltage is applied to the piezo element PE (section d3), the ink in the ink passage 50 is compressed due to the decrease in the cross-sectional area of the ink passage 50, and ink droplets are ejected from the nozzles. At this time, from the state in which the ink interface is not much depressed inward (state A), large ink droplets are ejected as shown in states B and C, and from the state in which the ink interface is largely dented (state a), state b And state c
A small ink droplet is ejected as shown in FIG. As described above, the dot diameter can be changed by changing the rate of change when the drive voltage is reduced (section d1, d2).

The color printer 20 continuously outputs two types of driving waveforms. This state is shown in FIG. The drive waveforms W1 and W2 correspond to the small ink droplet Ips and the large ink droplet Ipm, respectively. When the carriage 40 outputs the drive waveform W1 while moving in the main scanning direction and then outputs the drive waveform W2, the small ink droplet Ips ejected by the drive waveform W1 has a relatively low flying speed,
Since the large ink droplet Ipm ejected by the driving waveform W2 has a high flying speed, the large ink droplet Ipm ejected later catches up with the small ink droplet Ips ejected earlier. Therefore, the driving waveform W1 and the driving waveform W2
Is adjusted, the ink dot of the small ink droplet Ips and the ink droplet of the large ink droplet Ipm are adjusted as shown in FIG.
And the same ink dot can be formed in the same pixel.

In the color printer 20 of this embodiment, small dots are formed by supplying only the driving waveform W1 to the piezo element PE, and medium dots are formed by supplying only the driving waveform W2 to the piezo element PE. W2
Are supplied together, and two ink droplets are ejected to the same pixel to form a large dot. Of course, by increasing the types of driving waveforms, it is also possible to form dots of various sizes.

Here, the ink discharge heads 44 to 49
However, a mechanism for ejecting ink droplets at appropriate timing while synchronizing with the movement of the carriage 40 under the control of the CPU 61 of the color printer 20 will be described.
FIG. 8 shows that the CPU 61 controls the carriage motor 3 to eject ink droplets in synchronization with the movement of the carriage 40.
FIG. 4 is an explanatory diagram conceptually showing a state in which the ink ejection heads 44 to 49, the oscillator 70, and the like are controlled. still,
Although the color printer 20 of the present embodiment can perform bidirectional printing, for convenience of explanation, first, an operation at the time of unidirectional printing will be described.

The CPU 61 reads out dot data from the RAM 63 and outputs a dot on / off signal to the drive buffer 67 while outputting a drive pulse and a trigger signal to the carriage motor 30 and the oscillator 70, respectively. The carriage motor 30 rotates by a predetermined angle corresponding to the number of drive pulses received from the CPU 61, and accordingly, the carriage 40 is transported by a predetermined amount. Upon receiving the trigger signal from the CPU 61, the oscillator 70 outputs a drive signal including the two drive waveforms W1 and W2 shown in FIG. Distribution output device 69
When receiving the driving signal from the oscillator 70, the driving signal is output to each nozzle row of the ink ejection heads 44 to 49 at a predetermined timing. The function of the distribution output device 69 will be described later. The nozzle arrays of the ink ejection heads 44 to 49 are provided in a circuit in which the drive buffer 67 is on the source side and the distribution output unit 69 is on the sink side. When output, only the nozzles receiving the ON signal from the drive buffer 67 are driven, and ink droplets are simultaneously ejected. C
An operation in which the PU 61 outputs a drive pulse of the carriage motor 30, a trigger signal of the oscillator 70, etc.
The operation of setting the dot data to 7 or the operation of outputting the drive signal by the distribution output device 69 are performed in synchronization with the clock signal which is the reference of the operation of the CPU 61.

As described above, when the distribution output device 69 receives the driving waveform from the oscillator 70, it outputs the driving waveform to each nozzle row of the ink discharge heads 44 to 49 of each color at an appropriate timing. Will be described. As shown in FIG. 8, five registers reg1 to reg5 and r
A total of seven registers of egA and regBD are provided, and an appropriate value can be set to each register by the CPU 61. In each of the registers reg1 to reg5, a value indicating how many clocks the optimal drive timing of each color ink ejection head is shifted is set. To be more specific with reference to FIG. 5, for example, at the time of forward movement, the carriage 40 is transported from left to right on the paper surface, so that the ejection head 44 for K ink is driven first, Next, C ink, M ink, Y
The ejection head of each color ink is driven in the order of ink, LC ink, and LM ink. In order to drive each ejection head at such a timing, the distribution output device 69 performs the following operation. First, when a drive signal is received from the oscillator 70, the signal is output to the ejection head 44.
Next, a drive signal is output to the ejection head 45 with a delay by the number of clocks set in reg1. further,
A drive signal is output to the ejection head 46 with a delay of the number of clocks set in reg2. Similarly, reg3
Or delay by the number of clocks set in reg5,
Drive signals are sequentially output to the ejection heads 47 to 49. The above description focuses on the ejection head of each color,
Since two nozzle rows are formed in the ink discharge head, it is necessary to discharge ink droplets at an optimum timing for each nozzle. Re in the distribution output device 69 of FIG.
gA is a register for setting the timing difference between the nozzle rows formed on the same head. For example, the distribution output device 69 outputs a drive signal to the nozzle row on the right side of the ink ejection head 44, and then outputs a drive signal to the nozzle row on the left side with a delay of the number of clocks set to regA. Similarly, for other ink ejection heads, a drive signal is output to each nozzle row with a delay by the number of clocks set to regA. Since the timing difference between the nozzle rows is so small that the difference between the ink ejection heads of each color is negligible, the same setting value is used.

As described above, when the CPU 61 outputs a trigger signal to the oscillator 70, the oscillator 70 outputs a drive signal to the distribution output device 69, and the distribution output device 69 divides the drive signal into an optimal signal for each nozzle row. Output at appropriate timing. When the nozzle array receives the drive signal, ink droplets are simultaneously ejected from the nozzles for which the dot ON signal is set in advance. The CPU 61 synchronizes the transport of the carriage 40 and the ejection of ink droplets by synchronizing and outputting the drive pulse of the carriage motor 30 and a trigger signal to the oscillator 70.

Next, a mechanism for ejecting ink droplets while synchronizing with the movement of the carriage 40 during bidirectional printing will be described. At the time of bidirectional printing, it is necessary to eject ink droplets both at the time of forward movement and at the time of backward movement of the carriage 40, and at the time of forward movement and at the time of backward movement, the transport direction of the carriage 40 is reversed. 69 performs different operations by distinguishing between forward movement and backward movement. The CPU 61 outputs an identification signal at the time of forward movement and at the time of backward movement to the distribution output device 69, and the distribution output device 69 switches the operation based on the identification signal.

When the ink droplets are ejected during the forward movement of the carriage 40, the operation of the distribution output unit 69 is the same as the operation in the above-described unidirectional printing. When ink droplets are ejected when the carriage 40 moves backward, it can be considered that the operation is substantially the reverse of the forward movement. However, when the carriage 40 moves backward, the portion that outputs the drive signal while referring to the set value of regBD differs. ing. Hereinafter, a specific description will be given with reference to FIG. At the time of the backward movement, the carriage 40 is conveyed from right to left on the paper surface. Therefore, the ejection head 49 for the LM ink is driven first, and then the LC ink, the Y ink, the M ink, the C ink, and the K ink are driven. Must be driven in this order. First, upon receiving the drive signal from the oscillator 70, the distribution output device 69 counts the number of clocks set in the regBD, and then counts the number of clocks set in the regBD.
The drive signal is output to the nozzle row on the left side of No. 9. Next, with a delay of the number of clocks set in reg5,
A drive signal is output to the nozzle row on the left side of the ejection head 48 for LC ink. Hereinafter, similarly, reg4 to reg1
The driving signal is output to the nozzle row on the left side of the ejection head of each color with a delay of the number of clocks set in the above. In addition, for the right nozzle row of each ejection head, the drive signal is output to the left nozzle row, and then the drive signal is automatically output with a delay of the number of clocks set to regA.

When the ink droplets are ejected at the time of the backward movement, the distribution output device 69 receives the drive signal from the oscillator 70, and outputs the first drive signal with a delay by the number of clocks set in regBD. The drive signal is output to each nozzle row based on the drive signal. Therefore, by changing the value set in the regBD, the timing of the drive signal output to each nozzle row can be advanced or delayed as a whole. As will be described later, the color printer 20 of the present embodiment adjusts the ink droplet ejection timing at the time of backward movement in bidirectional printing. It is done by rewriting.

The color printer 20 having the above-described hardware configuration drives the carriage motor 30 so that the ink discharge heads 44 to 4 of each color are driven.
9 is moved in the main scanning direction with respect to the printing paper P, and the paper feed motor 35 is driven to move the printing paper P in the sub-scanning direction. Under the control of the control circuit 60, while repeating the main scanning and the sub-scanning of the carriage 40,
By driving the print head 41 at an appropriate timing, the color printer 20 prints a color image on printing paper.

B. Overview of Printing Process As described above, the color printer 20 uses the image data FN
It has a function of printing a color image in response to the supply of L, and the image data FNL to be supplied to the color printer 20 is generated by the computer 80 performing predetermined image processing on the color image. Prior to the start of the image processing, the computer 80 needs to acquire information on various conditions that are presupposed to start the image processing. FIG. 9 is a flowchart illustrating an outline of a process in which the computer 80 outputs image data FNL to the color printer 20 and prints an image. This processing is realized using the functions of the CPU 81 in the printer driver 92 of the computer 80. Hereinafter, the outline of the printing process will be described with reference to FIG.

As shown in FIG. 9, when the printing process is started, the CPU 81 first acquires various printing conditions (step S100). In this processing, various conditions necessary for generating image data FNL by performing image processing, for example, printing such as whether to give priority to image quality, to give priority to quick printing, or to perform bidirectional printing. This is the condition set by the user. These conditions are set for each application program 91 and are usually transmitted from the application 91 to the printer driver 92 at the same time as the print command. Prior to printing, it is also possible to make settings for adjusting the ejection timing during bidirectional printing.

In step 102, it is detected whether or not the setting for adjusting the ejection timing during bidirectional printing has been made prior to printing. If the setting has been made to perform the ejection timing adjustment, the ejection timing adjustment process (S10) is performed. If the setting has not been made to perform the ejection timing adjustment, the image data input process is performed without performing the adjustment process. Start. There are several forms of the discharge timing adjustment processing, which will be described later. In FIG. 9, for convenience of explanation, the ejection timing adjustment routine is described as being performed within the printing processing routine.
U81 temporarily suspends the print processing routine, shifts the processing to the discharge timing adjustment processing, and returns to the print processing routine of FIG. 9 again when the discharge timing adjustment is completed, and proceeds to step S1.
04 and subsequent processes are executed.

Subsequently, the CPU 81 inputs image data (step S104). The image data is data supplied from the application program 91 as described with reference to FIG.
This is data having 256 gradations of values of 0 to 255 for each color B. The resolution of the image data changes according to the resolution of the original image data ORG and the like.

The CPU 81 converts the resolution of the input image data into a resolution for printing by the color printer 20 (step S106). If the image data is lower than the printing resolution, resolution conversion is performed by generating new data between adjacent original image data by linear interpolation. Conversely, if the image data is higher than the print resolution, resolution conversion is performed by thinning out the data at a fixed rate.

Next, the CPU 81 performs a color conversion process (step S108). The color conversion process is a process of converting image data composed of R, G, and B gradation values into gradation value data of each color such as C, M, and Y used in the color printer 20. This processing is performed using a color conversion table LUT (see FIG. 2). A combination of K, LC, and LM is stored. Various known techniques can be applied to the process of performing color conversion using the color conversion table.
For example, processing by interpolation calculation can be applied.

When the color conversion processing is completed, a multi-value processing is performed (step S110). In this embodiment, the image data after the color conversion is a 256-gradation image of 6 colors of C, M, Y, K, LC, and LM. On the other hand, in the color printer 20 of the present embodiment, only four states of “do not form a dot”, “form a small dot”, “form a medium dot”, and “form a large dot” can be taken. . Therefore, it is necessary to convert an image having 256 gradations into an image represented by four gradations that can be represented by the color printer 20. The process of performing such conversion is a multi-value process. That is, by changing the ease of forming each of the large, medium, and small dots on the recording medium according to the gradation value of the original image, the color printer 20 can express 256 gradations of the original image. It is expressed by gradation values.

When the multi-level processing is completed, the CPU 81 starts the interlace processing (step S112). This process is a process of rearranging the image data, which has been converted into a format indicating the presence or absence of dot formation by the multi-value processing, into an order in which the image data should be transferred to the color printer 20. That is, the color printer 20 drives the print head 41 to form a dot row (raster) on the printing paper P while repeating the main scanning and the sub-scanning of the carriage 40 as described above. As described with reference to FIG. 4, the ink discharge heads 44 to 49 for each color are provided with a plurality of nozzles Nz, so that a plurality of rasters can be formed by one main scan. However, the rasters are separated from each other by the nozzle pitch k. Therefore, in one main scan, it is necessary to first form a plurality of rasters separated by the nozzle pitch k, and then to slightly shift the head position to form a new raster between the rasters. . When such control is performed, the order in which the color printer 20 actually forms dots is different from the order of pixels on the image data. Therefore, the image data is rearranged in the interlace processing.

As mentioned in step S100, the color printer 20 of this embodiment can be set to perform bidirectional printing. In the case of bidirectional printing, the order of image data to be transferred to the color printer 20 must be taken into account in order to form dots during both the forward movement and the backward movement of the carriage 40. In the process of step S112, such image data rearrangement is also performed according to whether or not to perform bidirectional printing.

When the interlacing process is completed, the image data is converted into image data FNL printable by the printer.
Output to the color printer 20 (step S11
4). An image is printed on printing paper by the color printer 20 forming dots in accordance with the image data FNL.

C. Processing for Adjusting Discharge Timing (1) First Embodiment Hereinafter, processing for adjusting the discharge timing of ink droplets in bidirectional printing in the color printer 20 will be described. FIG. 10 is a flowchart showing the overall flow of adjusting the ejection timing. When the screen of the computer 80 for controlling the color printer 20 instructs the printer driver 92 to adjust the ejection timing of ink droplets during bidirectional printing, the ejection timing adjustment process shown in FIG. 10 is started. . Hereinafter, the contents of the discharge timing adjustment processing will be described with reference to the flowchart of FIG.

When the discharge timing adjustment process is started, first, an adjustment image is selected on the screen of the CRT 23 of the computer 80 (step S200). The adjustment image is an image used for adjusting the ink ejection timing. FIG. 11 shows a state in which an adjustment image is selected on the screen of the CRT 23. As shown in the figure, on the screen, a photographic image, a character image, an image (hereinafter referred to as a patch image) in which several small rectangles are separately painted with a predetermined gradation value, and the like are displayed. I have.

These adjustment images are not selected at random, but are selected as representatives of respective characteristic images. The image denoted by (1) in FIG. 11 is a photographic image that is bright overall and has a bluish hue. If the image to be printed is a bright image as a whole or a bluish photographic image, the adjustment image is selected to adjust the ejection timing of the ink droplets. The image labeled (2) in FIG. 11 is an adjusted image used to adjust a standard photographic image. This image includes a bright part to a dark part evenly, and various colors are included in the image. The image labeled (3) in FIG. 11 is an adjustment image used especially for printing a portrait of a person. In order to print natural-looking human skin, it is necessary to adjust the ejection timing of the ink droplets particularly appropriately. Therefore, an adjusted image for human skin is particularly provided. FIG.
The image labeled (4) in 1 is an adjustment image for printing an image (hereinafter, referred to as a text image) including characters, tables, graphs, and the like. If none of the above images is considered appropriate, the ejection timing is adjusted using the patch image labeled (5) in FIG. The patch image prepared from the beginning is an achromatic color, but it is also possible to specify the color of the patch image if it is desired to adjust with a specific color image according to the image to be printed. When a color is designated for a patch image, when a button “designate” in FIG. 11 is selected, a color designation screen as shown in FIG. 13 appears on the screen of the CRT 23,
It is possible to select one of the colors according to the print image.

Here, a brief description will be given of how each gradation value forming the patch image of FIG. 11 is selected. FIG. 12 is an explanatory diagram conceptually showing the characteristics of the dot recording rate with respect to the gradation values set in the color printer 20. The dot recording rate is a value indicating the ratio of the number of pixels where dots are actually formed to the total number of pixels included in a solid image when a solid image having a certain gradation value is printed. For example, a dot recording rate of 33% indicates a state in which dots are recorded in about one third of the pixels in the area. As described above, the color printer 20 of this embodiment includes six color inks, and can form large, medium, and small dots for each color ink. Among the six color inks, the magenta and cyan colors include dark ink and light ink. The color printer 20 greatly improves the expressiveness of an image by controlling the size of dots formed for each of these color inks. As is clear from FIG. 12, the dot recording rate of each dot is set for each tone value, but the tone value represented by a single type of dot and the dot recording rate expressed by a plurality of types of dots It can be seen that there are different grayscale values. The gradation values (A to E) represented by a plurality of types of dots are selected as the gradation values constituting the patch image in FIG. If the patch image is configured with such gradation values, the ejection timing can be selected in consideration of the effect on image quality caused by forming a plurality of dots. In the setting example of the dot recording rate shown in FIG. 12, there is no gradation value at which three or more types of dots are formed at the same time. It is of course possible to set the dot recording rate so that the tone value of the patch image may be set to such a tone value.

In step S200 of FIG. 10, one adjustment image is selected as described above. When the adjustment image is selected, whether or not to print using the existing values is specified (step S202). In the ejection timing adjustment processing of this embodiment, the ejection timing that is considered to be optimal for each adjusted image is set in advance, and when printing using this set value, printing using an existing value is specified in step S202. do it. The designation of printing using the existing values is performed by selecting a button “use existing values” on the screen on which the adjustment image was selected (see FIG. 11). If it is specified in step S202 that an existing value is to be used,
After reading the correction amount stored corresponding to the selected adjustment image (step S204), the ink droplet ejection timing at the time of reverse movement in bidirectional printing is updated (step S21).
4), the discharge timing adjustment processing ends. The update of the ink droplet ejection timing at the time of the return movement is performed by rewriting the set value of the regBD in the output distributor 69 as described above with reference to FIG. As described above, if the adjustment image corresponding to the image to be printed is selected and printing is performed using the ejection timing set in advance corresponding to the selected adjustment image, the ejection timing suitable for the print image can be easily determined. Can be selected.
For this reason, it is possible to easily obtain a high-quality print image by bidirectional printing.

If it is specified in step S202 that the existing value is not to be used, that is, if the button "Adjust ejection timing" is selected on the above-mentioned adjustment image selection screen (see FIG. 11), the selection is made. The ejection timing of the ink droplets is adjusted using the adjusted image thus adjusted. Although the details will be described later, the adjustment processing of the present embodiment performs optimal printing while actually printing a plurality of adjustment images by changing the ejection timing of ink droplets at the time of backward movement when performing bidirectional printing. This is performed by the user selecting the ejection timing at which image quality is obtained. It is necessary to adjust the ejection timing at the time of the backward movement with high accuracy. Is roughly divided into two stages, that is, a stage of roughly performing and a stage of fine adjustment. That is, as shown in the flowchart of FIG. 10, the ejection timing correction range is selected (step S206), the correction range is roughly narrowed, and then the ejection timing correction amount is finely selected in the vicinity of the correction range (step S206). Step S208). This makes it possible to adjust the ejection timing quickly and accurately.

When the selection process of the correction range of the ejection timing is started (step S206), the screen shown in FIG.
Is displayed, and the color printer 20 automatically prints an image as shown in FIG. FIG.
FIG. 5 is an explanatory diagram showing an image printed by the color printer 20 in order to select a correction range of the ejection timing. FIG.
Shows a case where an achromatic patch image is selected as the adjustment image. As described above, the color printer 20 includes the black ink. However, in the ejection timing adjustment processing of the present embodiment, the color printer 20 has no color except for an achromatic color having a predetermined gradation or more (the rightmost portion in the example of FIG. 15). A colored image is expressed not by black ink but by C, M and Y color inks. This is because, by expressing the achromatic color using the C, M, and Y color inks, the ejection timing of each color ink can be collectively and accurately adjusted for the following reasons.

When ink dots of each color of C, M, Y are formed uniformly on white printing paper so as not to overlap with each other,
As a result of the additive color mixture of the respective color dots evenly on the human retina, the printing paper is recognized as exhibiting an achromatic color. However, when the formation positions of the ink dots are shifted and overlapping the ink dots of each specific color, the printing paper is recognized as exhibiting some color instead of an achromatic color. If there is no thread at the positions of the ink dots or the deviation is small, the deviation of the overlap of each color dot is small, so the printing paper will show a color close to an achromatic color. Conversely, if the deviation of the ink dot position deviation is large, printing will be performed. The paper becomes a color different from the achromatic color. In the ejection timing adjustment process of the present embodiment, by utilizing this phenomenon, achromatic colors having a predetermined gradation or less are represented by C, M, and Y inks, so that the positional deviation of each color ink dot can be accurately adjusted. I have. The achromatic color having a predetermined gradation or higher is expressed by using black ink.
This is because if all the achromatic colors are expressed only by the C, M, and Y inks, it is not possible to adjust the displacement of the K ink dots.

As shown in FIG. 15, the color printer 20
The reference image is printed at the top of the printed image.
The reference image is an image obtained by printing the previously selected adjustment image by unidirectional printing. When performing bidirectional printing, it is considered difficult to obtain an image quality exceeding the unidirectional printing image, no matter how the ejection timing at the time of return is adjusted, so the ejection timing at the time of return is determined based on the image quality. It is printed as a reference when making adjustments. Below the reference image, a plurality of adjustment images are printed by bidirectional printing, and in each image, the ink droplet ejection timing at the time of the backward movement is slightly changed. In the example shown in FIG. 15, the adjustment images of the five correction ranges A to E are printed. However, each correction range is set by shifting the discharge timing at the time of the backward movement by four pixels by the number of pixels. I have.

In the selection process of the ejection timing correction range in step S206 (see FIG. 10), while viewing the image (see FIG. 15) automatically printed by the color printer 20, the adjusted image having the image quality closest to the reference image is set to 1 And input the correction range corresponding to the selected image from the screen of the CRT 23,
Select the "Confirm" button (see FIG. 14).

When the "confirm" button in FIG. 14 is selected, the process of selecting the discharge timing correction range in step S206 is completed, and subsequently, the process of selecting the discharge timing correction amount (step S208).
To start. When this process starts, the color printer 2
0 automatically prints the image shown in FIG.

The image printed at the top of FIG.
Similar to FIG. 15, this is a reference image printed by unidirectional printing. A plurality of adjustment images are printed below the reference image, and these adjustment images are printed by bidirectional printing. FIG. 16 shows a case where “A” is selected as the correction range. In each adjustment image printed below the reference image, the ejection timing at the time of the backward movement is set to be shifted by one pixel from each other. ing. That is, in the correction range selection process (step S206), the number of pixels is roughly selected in units of four pixels, and then in the correction amount selection process (step S208), the optimal ejection timing is obtained in units of one pixel. Adjust as follows.

In the selection process of the ejection timing correction amount in step S208, one of the adjustment images closest to the reference image in image quality is selected while viewing the print image shown in FIG. 16, and the code of the selected image (for example, A -2) is input on the CRT screen (see FIG. 14).

When the code of the image is input in step S208, it is once confirmed whether or not readjustment is to be performed (step S210). That is, even after the code of the image selected on the screen shown in FIG. 14 is input, if the button “Re-adjustment” is selected, the ejection timing correction range is selected again from the selection processing (step S206). It is possible to fix it. If the image quality of the selected adjustment image is almost equal to the image quality of the reference image, it is not necessary to readjust the ejection timing, so the “confirm” button is selected on the screen of FIG. If it is determined that re-adjustment is unnecessary, the ejection timing of the finally selected adjustment image is stored in the memory of the computer 80 in association with the used adjustment image (step S212). The final ejection timing selected in this way is stored in association with the adjustment image, and is used in the next and subsequent adjustments of the ejection timing. That is, the aforementioned step S
If it is specified in step 202 that printing is to be performed using the existing values of the adjustment image, the ejection timing is determined in step S204.
Is read in.

When the selected ejection timing is stored in association with the adjusted image, the ejection timing of the ink droplet when actually printing the image is changed to the selected ejection timing (step S214). Is completed. As described above, the discharge timing is changed by changing the set value of regBD in the distribution output device 69 (FIG. 8).
reference).

In the above-described method of adjusting the ejection timing, an adjustment image having a predetermined gradation width is selected according to an image to be printed, and bidirectional printing is actually performed using the adjustment image. A target image is printed by using the ejection timing of ink droplets that can provide an image of high quality. Therefore, even if the speed of ink droplets ejected from the head fluctuates according to the print image, bidirectional printing can always be performed using the optimal ejection timing, so that a high-quality image can be obtained. Will be done.

Particularly when printing a color image, the optimum ejection timing is not determined only by the positional deviation of the entire ink dots, but is affected by complicated factors such as the dispersibility between the color dots. By applying the method, it is possible to obtain a great effect of improving the image quality. The reason will be described in some detail. For example, consider the case of printing a light blue image. In order to print a very light blue color, it is necessary to form C dots and M dots sparsely on a print medium. However, since both the C dot and the M dot are relatively conspicuous dots, if they are formed close to each other, they become conspicuous as if they are one large dot, resulting in an image with a rough feeling, that is, a so-called poor granularity. . Therefore, when adjusting the ejection timing of the ink droplets at the time of the backward movement, not only the positional deviation of the ink dots is reduced, but also the distance between the dots is increased as much as possible, that is, the dispersibility of the dots is improved. By adjusting the ejection timing in such a manner, a high quality image can be obtained. As described above, particularly in the case of printing a color image, in order to obtain a high-quality image, complicated factors such as the dispersibility of each color dot are not limited to merely reducing the positional deviation of the dots. Therefore, according to the method of the present embodiment, by selecting the ejection timing at which the image quality is the best while actually printing the adjustment image, a large image quality improvement effect can be obtained.

As described above, the ejection timing at which the optimum image quality is obtained is stored for each adjustment image, and the next time the image corresponding to this adjustment image is printed, the stored ejection timing is stored. If printing is performed using the timing, it is not necessary to adjust the ejection timing every time printing is performed, and it is possible to suppress an increase in printing time due to the adjustment of the ejection timing.

(2) Second Embodiment In the first embodiment described above, the ejection timing in bidirectional printing is adjusted using the adjustment image corresponding to the image to be printed. The adjustment may be performed using the image itself. FIG. 17 is a flowchart showing the flow of processing when adjusting the ejection timing using an image to be printed. Hereinafter, the second embodiment will be described with reference to the flowchart of FIG.

When the discharge timing adjustment process is started, first, image data to be printed is read and displayed on the CRT 23 screen of the computer 80 (step S30).
0). In the adjustment processing of the second embodiment, the ejection timing is adjusted while actually printing this image. However, printing the entire image requires a long printing time and requires a large amount of printing paper. However, if the image is reduced and printed, it becomes impossible to determine the quality of the image between the printed images.
Therefore, from the image read in step S300, an area to be used for adjusting the ejection timing is designated, and adjustment is performed using the image of the designated area. The process of selecting an adjustment region in step S302 is a process of designating such a region.

FIG. 18 is an explanatory diagram showing a state in which an image to be printed is displayed on the screen of the computer 80, and an area used for adjusting the ejection timing is specified on the screen. The area surrounded by the broken line in FIG. 18 is the area of the designated image. An arbitrary range of the image to be printed can be specified, but the size of the area that can be specified is fixed and cannot be changed. This is because it is necessary to print an image at its original size in order to accurately adjust the ejection timing. Once the area to be specified is determined, select the "OK" button at the bottom of the screen. If you want to re-specify, just click the "Reset" button.

When the "OK" button is selected on the screen shown in FIG. 18, the process of step 302 is terminated and the process of selecting the subsequent ejection timing correction range is started (step S30).
4). When this process is started, the color printer 20 automatically prints the image shown in FIG.
The display on the 23 screen is also switched to the display similar to FIG. In the selection process of the discharge timing correction range in the second embodiment, the correction range of the discharge timing is roughly selected as in the first embodiment.

FIG. 19 shows a state in which the correction range of the ejection timing is selected while actually printing the image of the designated area. As in the case of the first embodiment, a unidirectional printing image is printed as a reference image on the top of the printing paper. Under the reference image, the images of the correction ranges A to E are printed by bidirectional printing, and between each correction range, the ejection timing of the ink droplet at the time of the backward movement is converted into the number of pixels and shifted by 4 pixels. Is set. Select the image with the highest image quality from the images in the correction ranges A to E,
When the input is made on the screen of the computer 80 and the "confirmation" button is selected (see FIG. 14), the process of selecting the ejection timing correction range in step 304 is terminated, and the process of selecting the subsequent ejection timing correction amount is started (step S30). S306).

When the process of selecting the ejection timing correction amount in step S306 is started, the color printer 20 automatically
Print an image like 0. That is, a reference image printed in one direction is printed on the uppermost row, and a plurality of images are printed below the reference image by changing the ejection timing at the time of the backward movement of the bidirectional printing. In these images, the ejection timing at the time of the backward movement is converted into the number of pixels from the previously selected correction range by 1 pixel.
It is set shifted by the number of pixels. While comparing with the reference image, one image having the best image quality is selected and input from the screen of the computer 80 (see FIG. 14).

When the code of the image is input in step S206, it is once confirmed whether or not readjustment is performed (step S308). That is, "Readjustment" is performed on the screen of FIG.
By selecting the button, it is possible to perform adjustment again from the adjustment area selection processing (step S302). When the "confirm" button is selected on the screen of FIG. 14, the discharge timing at the time of actual image printing is changed so that the selected image is printed at the same discharge timing as when the image was printed (step S310). The process of adjusting the ejection timing is ended. As described above, the discharge timing is changed by changing the set value of regBD in the distribution output device 69 (see FIG. 8).

In the adjustment processing of the second embodiment described above,
Since the ejection timing is adjusted during bidirectional printing using a part of the image to be printed, the ejection timing is adjusted using an image having an appropriate gradation width according to the characteristics of the printed image. As a result, a high-quality image can be obtained.

Further, since a part of the image to be printed is selected, printing time and printing paper can be saved when printing while changing the ejection timing in various ways.

(3) Third Embodiment In the first embodiment or the second embodiment described above, the operator of the color printer 20 intentionally adjusts the ejection timing before printing an image. Although it has been described that the ejection timing is performed, the ejection timing adjustment process may be incorporated in the image printing process so that the operator can naturally adjust the ejection timing in the process of printing the image. FIG. 21 is a flowchart showing the overall flow when the ejection timing adjustment processing is incorporated in the printing processing. Hereinafter, description will be made according to this flowchart.

In the third embodiment, when the operator instructs the printer driver 92 to print an image from the application program 91 running on the computer 80, the processing shown in FIG. 21 is started. When the process is started, the type of the print image is first identified (step S
400). That is, it is determined whether the image to be printed is an image composed of characters, figures, graphs, and the like (hereinafter, referred to as a text image) or a photographic image. This identification is performed by identifying the application program that has issued the print command. For example, if printing is performed from a document creation program, it is determined to be a text image, and if printing is performed from a photo retouching application program, it is determined to be a photographic image. Alternatively, it is possible to determine the type of the application program that created the image data from the extension of the image data, and to identify the type of the image based on the determination result.

If the image to be printed is a text image, the ejection timing set as a standard for printing a text image is read from the memory (step S402).
Printing is executed using the ejection timing (step S41).
0). Details of the discharge timing set as standard will be described later. If the image to be printed is a photographic image, it is specified whether or not to print using the ejection timing set as standard for photographic image printing (step S40).
6). This designation is made by selecting a predetermined button on the box of the computer 80 when a dedicated display (dialog box) appears on the screen of the computer 80 when it is determined in step S400 that the image is a photographic image. . If it is specified to print using the standard ejection timing, the standard ejection timing for the photographic image is read from the memory (step S404), and printing is executed using this ejection timing (step S410).

If it is determined in step S406 that the standard ejection timing is not used, the screen is automatically switched to start the ejection timing adjustment processing (step S408). Since the content of the discharge timing adjustment process is almost the same as the process described as the first embodiment, only the outline will be described with reference to FIG.

First, an adjustment image used for adjusting the ejection timing is selected (corresponding to step S200). At this stage, since the various adjustment images shown in FIG. 11 are displayed on the screen, an adjustment image suitable for the image to be printed is selected from the various adjustment images. Next, it is designated whether to print using the existing ejection timing of the selected adjustment image or to adjust the ejection timing again (corresponding to step S202). As described above, since the ejection timing is stored in advance as a standard value for each adjustment image, whether or not to use this ejection timing is selected. In the case where the direction of re-adjustment is designated, the correction range of the ejection timing is selected (corresponding to step S206).
The process of selecting the ejection timing correction amount (corresponding to step S208) is performed (see FIGS. 15 and 16). When the selection of the ejection timing is completed in this way, the setting of the ejection timing at the time of printing the image is changed to the selected ejection timing (corresponding to step S214), and the process exits the adjustment process of the ejection timing and executes printing as shown in FIG. (Step S410).

The standard values for the text image read in step S402 of FIG. 21 or the standard values for the photographic image read in S404 are as follows. As described in the first embodiment, the adjustment image labeled (2) in the adjustment image shown in FIG. 11 is an image used for adjusting a typical photographic image. The encoded adjustment image is an image used for adjusting the text image. The ejection timing is stored in advance for each adjustment image. That is, what is read in step S402 is the ejection timing recorded in association with the adjustment image of (4), and what is read in step S404 is stored in association with the adjustment image of (2). Discharge timing.

As described above as the third embodiment, if the ejection timing adjustment processing is incorporated in the printing operation, the print image can be printed even if the operator does not intentionally perform the ejection timing adjustment processing. Printing can be performed using an appropriate ejection timing.

Further, by judging the type of image data to be printed and selecting an appropriate ejection timing for bidirectional printing based on the adjusted image according to the type, a high quality image can be obtained by bidirectional printing. Can be obtained.

(4) Fourth Embodiment In the various embodiments described above, the operator selects the adjustment image in accordance with the image to be printed. By performing the analysis, it is also possible to automatically select the adjustment image based on the analysis result. FIG. 22 is a flowchart illustrating a flow of the fourth embodiment as an example of a mode of automatically selecting an adjustment image. Hereinafter, description will be given according to the flowchart of FIG.

From the application program 91,
When the operator issues an image print command to the printer driver 92, the printer driver 92 receives the image data (step S500) and analyzes the image data to create a frequency distribution of gradation values (step S502). . Since the color printer 20 of this embodiment can form six color ink dots as described above, the frequency distribution of the gradation values is also created for each color. A tone value having the highest frequency (hereinafter, this tone value is referred to as a main tone value in the present specification) may be considered as a tone value that strongly controls the image quality of an image to be printed. it can. Therefore, an appropriate adjustment image is selected based on such a main gradation value determined for each color (step S504). The method of selecting the adjustment image from the main gradation value is unavoidably based on trial and error, but for example, the following method can be used.

For each of the adjusted images shown in FIG. 11, a main gradation value is obtained for each color. After obtaining the main gradation value for the image to be printed, the distance (for example, the absolute value of the difference) between the adjustment image and the main gradation value between the printed image is obtained for each color, and the sum of the distances for each color is determined to be minimum. Is selected.
Here, it is also effective to multiply the distance value for each color by the weighting factor for each color in order to enhance the consistency with the visual evaluation.

Further, instead of selecting the adjustment image based on the main gradation value as described above, instead of selecting the adjustment image based on the gradation value distribution of the image to be printed, the minimum gradation value having a frequency equal to or higher than a predetermined value is obtained. The value and the maximum value may be obtained (this range is referred to as a gradation value range in the present specification), and the adjustment image having the closest gradation value range may be selected.

After the adjustment image is selected (step S504), the ejection timing is adjusted using the adjustment image (step S506). The content of the discharge timing adjustment process is the same as the process performed in the third embodiment, and thus the description is omitted. When the adjustment of the ejection timing is completed, printing of an image is executed according to the adjusted ejection timing (step S50).
8).

Depending on the image to be printed, it may be difficult to determine which adjustment image should be used for adjustment. If the ejection timing is adjusted using an inappropriate adjustment image, it is difficult to obtain a high-quality print image. On the other hand, as shown in the fourth embodiment, if the adjustment image is selected based on the analysis result of the image, it is possible to always select the optimum adjustment image.
It is possible to stably obtain a high-quality print image.

Although various embodiments have been described above, the present invention is not limited to all the above embodiments, and can be implemented in various modes without departing from the gist of the invention. For example, a software program (application program) that implements the above functions
May be supplied to a main memory or an external storage device of the computer system via a communication line and executed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a printing apparatus according to an embodiment.

FIG. 2 is an explanatory diagram illustrating a configuration of software.

FIG. 3 is a schematic configuration diagram of a printer according to the present embodiment.

FIG. 4 is an explanatory diagram showing a dot formation principle in the printer of the present embodiment.

FIG. 5 is an explanatory diagram showing a nozzle arrangement in the printer of the embodiment.

FIG. 6 is an explanatory diagram illustrating the principle of forming dots having different sizes by the printer of the present embodiment.

FIG. 7 is an explanatory diagram showing a driving waveform of a nozzle and dots formed by the driving waveform in the printer of the embodiment.

FIG. 8 is an explanatory diagram showing a mechanism in which the printer head of this embodiment forms dots while synchronizing with the movement of the carriage.

FIG. 9 is a flowchart illustrating a flow of a print processing routine according to the present exemplary embodiment.

FIG. 10 is a flowchart illustrating a flow of a discharge timing adjustment process according to the first embodiment.

FIG. 11 is an explanatory diagram illustrating a screen for selecting an adjustment image during the ejection timing adjustment processing according to the present embodiment.

FIG. 12 is an explanatory diagram conceptually showing a dot recording rate of each dot set in the color printer of the present embodiment.

FIG. 13 is an explanatory diagram showing a screen for specifying a color of a patch image selected as an adjustment image.

FIG. 14 is an explanatory diagram showing a screen displayed when the discharge timing adjustment process is being performed.

FIG. 15 is an explanatory diagram showing an image printed by a color printer in order to select a correction range of ejection timing in the first embodiment.

FIG. 16 is an explanatory diagram showing an image printed by a color printer in order to select a correction amount of ejection timing in the first embodiment.

FIG. 17 is a flowchart illustrating a flow of a discharge timing adjustment process as a second embodiment.

FIG. 18 is an explanatory diagram illustrating a state in which an adjustment image area is designated from among images to be printed.

FIG. 19 is an explanatory diagram showing an image printed by a color printer in order to select a correction range of ejection timing in the second embodiment.

FIG. 20 is an explanatory diagram showing an image printed by a color printer in order to select a correction amount of ejection timing in the first embodiment.

FIG. 21 is a flowchart showing a flow of a discharge timing adjustment process as a third embodiment.

FIG. 22 is a flowchart illustrating a flow of an ejection timing adjustment process as a fourth embodiment.

FIG. 23 is an explanatory diagram for explaining the reason for adjusting the ink droplet ejection timing at the time of backward movement in order to eliminate positional displacement of ink dots in bidirectional printing.

[Explanation of symbols]

 Reference Signs List 20 color printer 21 color scanner 23 CRT 24 modem 26 hard disk 30 carriage motor 31 drive belt 32 pulley 33 sliding shaft 34 position detection sensor 35 paper feed motor 36 platen 40 carriage 41 ... Print heads 42, 43 ... Ink cartridge 44 ... Ink ejection head 50 ... Ink path 60 ... Control circuit 61 ... CPU 63 ... RAM 64 ... PC interface 67 ... Drive buffer 69 ... Distribution output device 70 ... Oscillator 80 ... Computer 81 ... CPU 82 RAM 83 ROM 88 SIO 90 Video driver 91 Application program 92 Printer driver 93 Resolution conversion module 94 Color conversion module 95 Halftone module 96 Interleave The scan module

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C056 EA04 EB27 EB29 EB58 EC07 EC28 EC37 EC42 FA11 KD10 2C057 AF30 AG12 AL31 AL36 AM16 AM17 AM40 AN02 CA01

Claims (13)

[Claims] 1. A printing apparatus that forms a print image by ejecting ink droplets from a head during both forward movement and backward movement while reciprocating a head relative to a print medium. Adjusting image storage means for storing image data of an image having a predetermined gradation width; and a comparison image as an image formed on the print medium based on the image data, A comparison image forming means for forming a plurality of images while changing at least one of the ejection timing and the ejection timing of the ink droplet at the time of return for each image; and forming one comparison image selected from the plurality of comparison images. And a discharge timing correction unit configured to correct the discharge timing of the ink droplets when forming the print image based on the discharge timing. 2. The printing apparatus according to claim 1, wherein the head is a head that can discharge a plurality of types of ink droplets. 3. The printing apparatus according to claim 3, wherein the image having the predetermined gradation width is an image formed by ejecting the plurality of types of ink droplets. 4. The printing apparatus according to claim 2, wherein the head is a head that ejects ink droplets of each color capable of expressing an achromatic image when used in combination with each other, and stores the adjusted image. The printing apparatus is means for storing image data of an image including at least an achromatic region. 5. The printing apparatus according to claim 1, wherein the adjustment image storage unit is a unit that stores a plurality of types of the image data, and the comparison image forming unit is a storage device that stores the plurality of types of the image data. A printing apparatus that forms a plurality of the comparison images based on the image data selected from. 6. The printing apparatus according to claim 5, wherein the adjustment image storage unit stores, as the image data, image data corresponding to a natural image such as a photograph and an image corresponding to a character image such as a character or a figure. A printing device that is means for storing at least data. 7. The printing apparatus according to claim 5, wherein one image data is selected from the plurality of image data stored in the adjustment image storage unit based on the image data of the print image. A printing apparatus comprising: an adjustment image selecting unit; and the comparison image forming unit is a unit that forms a plurality of the comparison images based on the selected image data. 8. The printing apparatus according to claim 7, wherein the adjustment image selection unit obtains a gradation value distribution of an image to be printed, and the image processing unit determines the image based on the obtained gradation value distribution. A printing device that is a means for selecting data. 9. The printing apparatus according to claim 5, wherein the ejection timing corresponding to one comparison image selected from the plurality of comparison images is stored in the adjustment image storage unit. And an ejection timing storage unit that stores the ejection timing when the image data whose ejection timing is stored in the ejection timing storage unit is selected. A printing device that is a unit that performs the correction based on time. 10. The printing apparatus according to claim 9, wherein the comparison image forming unit is configured to, when at least image data for which the ejection timing is not stored in the ejection timing storage unit is selected, select the image data. A printing device that is a unit that forms a corresponding image as the comparison image. 11. The printing apparatus according to claim 1, wherein an ink droplet is ejected only to one of the forward movement and the backward movement, and the ink droplet is formed based on image data stored in the adjustment image storage means. A reference image forming unit that forms a reference image serving as an image on the print medium, wherein the ejection timing correction unit compares the correction of the ejection timing with the reference image, A printing device, which is a means for performing based on the ejection timing. 12. A discharge device of a printing apparatus which forms a print image by discharging ink droplets from the head during both the forward movement and the backward movement while reciprocating the head relative to the print medium. A timing correction method, wherein image data of an image having a predetermined gradation width is stored, and a comparative image, which is an image formed on the print medium based on the image data, is stored in an ink droplet during forward movement. A plurality of ejection timings or at least one of the ejection timings of ink droplets at the time of return movement are changed for each image, and the ejection is performed when one comparison image selected from the plurality of comparison images is formed. An ejection timing correction method for correcting the ejection timing of ink droplets when forming the print image based on the timing. 13. A discharge device of a printing apparatus for forming a print image by discharging ink droplets from the head during both the forward movement and the backward movement while reciprocating the head relative to the print medium. A computer-readable recording medium that records a program for implementing a timing correction method, wherein the control unit controls the printing apparatus to output a predetermined image having a predetermined gradation width at an ink droplet ejection timing during forward movement or A function of forming at least one of the ejection timings of ink droplets at the time of return movement while changing the timing for each image, and forming an image when one image is selected from the plurality of formed images A program for realizing a function of correcting the ejection timing of ink droplets when forming the print image based on the ejection timing at the time of printing.