JPH11188898A - Ink jet recorder and recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single pulse system ink jet recorder in which generation of join streak is suppressed at the boundary of band through processing based on a binarized image data on the ink jet recorder side. SOLUTION: At least one of the first or last rasters of one band being recorded through single scanning of a recording head is divided into a plurality of unit regions each comprising predetermined number of dots and the ink jet quantity is recognized for each unit region based on a binarized image data (S22, S23). Based on the recognized ink jet quantity, ink dots to be jetted are decimated to reduce the ink jet quantity in the unit region (S24). Decimation is carried out with reference to a predetermined correction table 28 of ink jet quantity for a concerned color depending on the sum of the ink jet quantity for the concerned color and for other colors in each unit region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ink jet recording apparatus which performs recording by a single pass method.

[0002]

2. Description of the Related Art In an ink jet recording apparatus, an image recording is usually performed by repeatedly scanning a recording head having a plurality of discharge ports (nozzles) for discharging ink in a direction different from the arrangement direction of the discharge ports. A scan-like image area (band) is formed by the scanning. At this time, the ink may bleed depending on the material and surface condition of the recording medium. In that case, the so-called "connecting stripe"
May occur.

To prevent this, a multi-pass system in which the same band is recorded a plurality of times may be adopted, but the multi-pass system has a problem that the recording speed is reduced.

[0004]

As a technique for preventing a connecting streak in a single-pass type ink jet recording apparatus, there is a technique disclosed in, for example, JP-A-7-89099. This is to reduce bleeding by reducing the signal value of a signal (multi-level signal) recorded at the boundary between bands, thereby preventing a connecting streak.

However, in the above conventional example, since the correction is performed at the image signal level, there are the following disadvantages.

That is, first, most of the commonly used ink jet recording apparatuses are connected to a computer terminal apparatus, perform image processing such as binarization by the computer terminal apparatus, transfer the image processing to the ink jet recording apparatus, and perform recording. doing. However, if an ink jet recording apparatus is provided with an image input unit or an image processing unit for handling multi-valued signals, the cost and processing time increase, and this is not common in popular devices. Therefore, if the inkjet recording apparatus performs correction at the image signal level, the process of converting a multi-tone image into a binary image wastes time, and the recording speed is reduced. The inkjet recording apparatus of the present invention does not correct multi-level signal levels, but targets binary image data for correction processing.

Secondly, it is difficult in the above-mentioned conventional example to correct these differences because the individual difference in the error of the paper feed amount and the amount of ink bleeding vary depending on the individual ink jet recording apparatus or recording medium. Further, when the correction process is performed by a computer terminal device or the like, the process becomes difficult if the accurate boundary between the bands of the ink jet recording apparatus is not known.

In view of the above, the present invention has been made to solve the above-described problem, and the processing on the ink jet recording apparatus side based on the binarized image data alleviates the generation of the connecting streak at the boundary between the bands. It is an object of the present invention to provide a single-pass type ink jet recording apparatus that can perform the operation.

Another object of the present invention is to provide a single-pass type ink jet recording capable of alleviating the occurrence of streaks at a boundary portion in accordance with individual differences of the ink jet recording apparatus and differences in the amount of bleeding inherent in the recording medium. It is to provide a device.

[0010]

In order to achieve the above object, the present invention is directed to a printing head in which a plurality of ejection openings for ejecting ink are repeatedly scanned in a direction different from the arrangement direction of the ejection openings to sequentially form a band. In an ink jet recording method for performing image recording in units, at least one of a first raster and a final raster of one band recorded by one scan of the recording head is converted into a plurality of unit areas each including a predetermined number of dots. In accordance with the binarized image data, an ink ejection amount is recognized for each unit area, and based on the recognized ink ejection amount, the ink ejection amount in the unit area is reduced. By performing thinning processing of ink dots to be ejected, occurrence of a connecting streak at a boundary between bands is reduced.

According to this configuration, the amount of ink ejected at the boundary between the bands can be corrected using the binarized image data. By performing correction processing on the apparatus side, it is possible to alleviate the occurrence of streaking at the boundary between scans (bands).

Further, by limiting the target area of one correction process to a relatively small unit area, the processing load can be reduced without lowering the print quality.

According to another aspect of the present invention, a recording head having a plurality of ejection openings for ejecting ink is used for each of a plurality of colors, and the recording head is repeatedly arranged in a direction different from the arrangement direction of the ejection openings. In an ink-jet recording method for sequentially performing image recording in band units by scanning, at least one of a first raster and a final raster of one band recorded by one scan of the recording head is converted from a predetermined number of dots each. Divided into a plurality of unit areas, and based on the binarized image data, in accordance with the ink discharge amount of the target color in each unit area and the sum of the ink discharge amounts of other colors in the unit area. The correction is performed so as to reduce the ink ejection amount of the target color, and the correction is sequentially and repeatedly performed for the other colors in the unit area. The above-described correction is sequentially and repeatedly performed for the unit area, and the ink dots to be ejected of the target color in the unit area are discharged so as to perform the ink discharge of the target color with the corrected ink discharge amount for each unit area. The thinning process is performed.

[0014] Preferably, the thinning process of the ink dots is performed in accordance with a sum of an ink ejection amount of a target color in each unit area and a total of ink ejection amounts of other colors in the unit area. This is performed by referring to a predetermined correction table for the color ink ejection amount. By using the correction table, quick correction processing can be performed. By providing the correction table separately according to the area to be corrected, the color, the type of the recording medium, and the like, it is possible to perform a more appropriate correction process for mitigating a connection streak.

[0015] The ink jet recording apparatus according to the present invention comprises:
In an inkjet printing apparatus that repeatedly scans a print head in which a plurality of ejection openings for ejecting ink are arranged in a direction different from the arrangement direction of the ejection openings to sequentially perform image recording in band units, based on binarized image data, Means for dividing at least one of the first raster and the final raster of each band into a plurality of unit areas each consisting of a predetermined number of dots, and calculating an ink ejection amount in each unit area;
Thinning means for thinning out ink dots to be ejected so as to reduce the ink ejection amount in the unit area based on the obtained ink ejection amount. It is characterized in that the occurrence of connecting streaks is reduced.

It is preferable that the thinning means performs the thinning process by using a correction table in which an ink ejection amount and a corrected ink ejection amount corresponding thereto are predetermined.

The correction table may be separately provided for each color of the ink to be corrected. By using the correction table, quick correction processing can be performed.

The correction table is based on, for example, the binarized image data, and is based on the ink discharge amount of a target color in each unit area and the total of the ink discharge amounts of other colors in the unit area. Thus, the corrected ink ejection amount of the noted color is determined.

A plurality of correction tables may be provided according to recording conditions including at least the type of the recording medium, and may be selectively used according to the conditions.

In the thinning of the ink dots in the unit area, it is preferable that the priority order of the dots to be thinned is predetermined according to the dot position of each unit area.
At this time, when some of the dots in the unit area are thinned out, it is preferable to determine the priority order so that the thinned out dots are spatially dispersed.

When the first raster and the last raster of a band are to be subjected to dot thinning, it is preferable that the priority of the dots to be thinned be different between the first raster and the last raster.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the ink jet recording apparatus of the present invention. In FIG. 1, reference numeral 11 denotes a CPU for controlling the operation of the entire apparatus, and 12 denotes a RAM used as a work area of the CPU 11 and a temporary storage area for data. Reference numeral 13 denotes a ROM in which a program and data for driving the ink jet recording apparatus are written.
Used by the CPU 11. Reference numeral 14 denotes an interface unit for connecting to an external computer terminal device or the like (not shown), through which binary data is transferred. Reference numeral 15 denotes an LCD display device for performing display for a man-machine interface, and reference numeral 16 denotes a key operation unit for selecting various settings of the ink jet recording apparatus. Reference numeral 17 denotes a printing unit using an ink jet head, and reference numeral 18 denotes a system bus that connects the CPU 11 to other components.

In the ink jet head of the printing unit 17,
There are four colors, black (K), cyan (C), magenta (M), and yellow (Y).
It has 28 nozzles and ejects ink droplets corresponding to binarized image data.

FIG. 2 is a processing flow from reception of input data to printing.

First, input data is received from the outside (S2).
1) Analyze the received data to prepare print data for one band suitable for recording by the inkjet head (S22). Next, the ink ejection amount (the number of ejection dots) of each unit area of the first and final rasters is recognized for each color (S23), and based on this, the print data is corrected by referring to the correction table 28 (S23). S24). Each head is driven based on the corrected image data of the band obtained as described above to perform a printing process (S25). This process is repeated until all bands are completed (S2
6) Execute repeatedly.

FIG. 3 is a diagram for explaining the correction processing of the ink ejection amount in the present embodiment. In this example,
The last raster of the first scan (first band) and the second raster (second band)
The correction of the ink ejection amount is performed in the first raster and the final raster after the band. In the last band, only the first raster is corrected.

For example, assuming that the number of nozzles of the head per one color involved in recording of one band is 128, the first and the first
The ink droplets ejected by the 28 nozzles are to be corrected. The nozzles involved in one-band recording need not be all the nozzles provided in the head. That is,
The nozzles for which the ink droplet ejection is to be corrected are not limited to the first and last nozzles of the one-row nozzle group provided in the head.

In this embodiment, the rasters to be corrected are the first and last rasters of the band. However, at least one of the rasters can be two or more rasters. In particular, when the bleeding is large, the correction in units of two rasters is effective. That is, whether the correction target raster of one side of the band is one raster or two rasters can be determined by the individual difference of the inkjet recording apparatus and the amount of ink bleeding (that is, paper quality) of the recording medium.

Next, a description will be given of a process of correcting the ink ejection amount at the boundary portion in this embodiment.

First, the boundary of the band is divided so as to have a constant shape and area. From the relationship between workload and effectiveness,
In the present embodiment, the boundary is a single raster at the beginning and end of the band, and each raster is divided into a unit area of 5 horizontal dots × 1 vertical dot. However, the present invention is not limited to this. As described above, the number of rasters in the unit area may be a plurality of rasters instead of one according to the recording medium, and the number of dots per raster is not limited to five.

FIG. 4 schematically shows data of one raster constituted by a unit area of 5 dots × 1 dot of each color of Y, M, C, and K. In the present embodiment, portions less than the rightmost five dots are excluded from the correction processing in this embodiment because uniform processing cannot be performed and the effect is small even if the correction processing is not performed.

The correction process is performed for each color for each unit area. For example, when the ink ejection amount of Y in a certain unit area is to be corrected, the number x (0 ≦ x ≦ 5) of ejection dots of yellow Y in that unit area is determined, and the other colors M,
The total value y (0) of the number of ejection dots in the same unit area of C and K
≤ x ≤ 15). The appropriate number of Y ejection dots z (0 ≦ x ≦ 5) that minimizes the connecting streak in accordance with the combination of the ink ejection amount x of the target ink color and the ink ejection amount y of the other ink colors. Is experimentally determined in advance,
These relationships are stored in a correction table corresponding to the color. Therefore, four correction tables Y, M, C, and K are provided. Thus, an appropriate correction value can be set for each color. However, in the present invention, when a common correction table is used for all colors, or when Y, M, C
This does not exclude the case where a common correction table is used for K and a dedicated correction table is used for K.

At the time of the correction processing of the ink ejection amount of the unit area of a certain color, by referring to the correction table of the color according to the values of x and y given by the binarized image data, the corresponding correction value is obtained. z is obtained. The ink ejection amount of the color in the unit area is reduced so that the ejection amount of the correction value is obtained. For example, the dot number x of yellow Y is 5,
When the total value y of the numbers of dots of other colors is 3, the number of dots of yellow Y after correction is set to 1. The same correction process is performed for other colors by sequentially changing the color of interest. When the number of dots of a certain color is reduced, which dots in the unit area are thinned will be described later.

FIG. 7 shows a specific example of the correction table 28 when the number of dots in the unit area is 5. As aforementioned,
For each color (Y, M, C, K) of the correction target of interest, any combination of the ink discharge amount x of that color in a given unit area and the total y of the ink discharge amounts of other colors is , The corrected ink ejection amount z of the color is determined in advance. x,
The preferred relationship between y and z can be determined experimentally.

Further, as the correction table, separate tables may be prepared for the first raster and the final raster of the band. As a result, the correction values of the two rasters can be made different, so that more detailed correction processing can be performed.

FIG. 5 is a diagram showing the order of priority for reducing the ink ejection amount (dot thinning) in a unit area. In one unit area, the numerical values adjacent to each other in priority order are arranged in a dispersed manner so as not to be spatially continuous. In addition, the priority is different between the final raster of a certain band (the raster above the boundary) and the first raster of the next band (the raster below the same boundary). In this example, the priority order of the ejection dot thinning is 1, 3, 5, 2, 4 from the left end in the unit area for the last raster, and 5, 3, 1, 4, 4 for the first raster. It is set to 2 (the younger number is thinned out first). The reason why the numerical values of the priorities are discontinuously dispersed is to prevent deterioration in image quality as a result of thinning. Note that the positions of the numerical values of these priorities are merely examples, and the present invention is not limited to these.

Here, a specific example will be considered. For example, the ink ejection amount of the target ink color in the unit area of the last raster of one band given the input image data is 4, and the correction amount in the correction table 28 is 1 based on the combination with other ink ejection amounts. Assume that In this case, since the ink ejection amount decreases from 4 to 1 by 3 dots, it is necessary to thin out 3 dots. Therefore, if the dot at the left end of the input image data in the unit area is to be checked and printed, this dot is not printed. If printing is not to be performed, the second dot from the right is examined next. If printing is to be performed, this dot is not printed. In this way, until the three dots are thinned out (that is, the ink ejection amount is set to 1), the ejection dots to be thinned out are searched according to the priority order. For the first raster of the band, the dots are thinned out at different priorities as described above.

FIG. 6 shows the configuration of a unit area according to another embodiment of the present invention. FIG. 6A shows that the unit area is located above the boundary, where the final n-th raster and the n-th raster of the band are arranged.
The area of 5 horizontal dots × 2 vertical dots for 2 rasters of −1 raster is set, and the horizontal 5 dots for one raster similar to FIG.
This is an area of dots × one vertical dot. Conversely, the upper side of the boundary may be one raster and the lower side may be two rasters.

FIG. 6B shows an example in which both the upper and lower sides of the boundary are defined as an area of 5 horizontal dots × 2 vertical dots for two rasters.

The configuration of the unit area shown in FIG. 6 is effective when applied to a recording medium in which ink bleeds greatly. An example of the priority of the thinning of the ejection dots in each unit area is shown in the figure by numerical values. Also in this case, the numerical values adjacent to the priority are set so as not to be spatially continuous.

While the preferred embodiment of the present invention has been described above, various modifications can be made.

For example, as a modification of the present invention, it is possible to correct the ink ejection amount only on one of the upper side and the lower side of the boundary.

It is preferable that the correction table described above is prepared separately according to the amount of ink bleeding on the recording medium, and the corresponding correction table is selected according to the selection of the paper type by the user. In general, there are various types of recording media such as plain paper, coated paper, glossy paper, and film, and the corresponding correction table can be switched and used according to each individual or group.

Further, when the correction amount of the correction table experimentally obtained does not conform to the remaining amount of ink at printing, temperature, humidity, individual differences of the recording medium, etc., 0 is set to each numerical value of the correction table. A number of correction tables obtained by multiplying by a coefficient of about 0.5 to 1.5 (the fraction is rounded off, etc.) are prepared (or calculated) so that they can be selected before actual printing. It is more effective.

In the above description, the corrected ink ejection amount is determined as the output of the correction table, but the number of thinned dots may be defined instead.

[0047]

According to the present invention, the amount of ink discharged at the boundary between bands can be corrected using the binarized image data, so that there is no need to change the processing in an external computer terminal or the like. By performing correction processing on the ink jet recording apparatus side, it is possible to alleviate the occurrence of connecting streaks at boundaries between scans (bands). In addition, by limiting the target area for one correction process to a relatively small area, the processing load can be reduced without lowering the print quality. Further, by using the correction table, quick correction processing can be performed. By providing the correction table separately according to the area to be corrected, the color, the type of the recording medium, and the like, it is possible to perform a more appropriate correction process for mitigating a connection streak.

[0048]

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of an inkjet recording apparatus according to the present invention.

FIG. 2 is a flowchart showing a processing flow from input data reception to printing of the inkjet recording apparatus of FIG. 1;

FIG. 3 is a diagram for describing a process of correcting an ink ejection amount according to the embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a unit area of 5 dots × 1 dot of each color of Y, M, C, and K according to the embodiment of the present invention;
FIG. 4 is a diagram schematically illustrating raster data.

FIG. 5 is a diagram illustrating a priority order of ink ejection amount reduction (dot thinning) in a unit area according to the embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a unit area according to another embodiment of the present invention.

FIG. 7 is a diagram showing a specific example of a correction table when the number of dots in a unit area is set to 5 in the embodiment of the present invention.

[Explanation of symbols]

11 CPU, 12 RAM, 13 ROM, 14 interface (I / F), 15 liquid crystal display (LC
D), 16: key operation unit (KEY), 17: printing unit, 1
8: system bus, 28: correction table.

Claims (10)

[Claims] 2. An ink jet recording method according to claim 1, wherein a recording head having a plurality of ejection ports for ejecting ink is repeatedly scanned in a direction different from the arrangement direction of the ejection ports to sequentially record an image in band units. At least one of the first raster and the last raster of one band recorded by one scan of is divided into a plurality of unit areas each composed of a predetermined number of dots, and based on the binarized image data, For each unit area, an ink ejection amount is recognized, and based on the recognized ink ejection amount, the ink ejection amount in the unit area is reduced.
An ink jet recording method characterized by reducing the occurrence of a connecting streak at a boundary between bands by performing a thinning process of ink dots to be ejected. 2. A printing head having a plurality of ejection ports for ejecting ink is used for each of a plurality of colors, and the recording head is repeatedly scanned in a direction different from the arrangement direction of the ejection ports to sequentially record images in band units. In the inkjet recording method, at least one of the first raster and the last raster of one band recorded by one scan of the recording head is divided into a plurality of unit areas each including a predetermined number of dots, Based on the binarized image data, the amount of ink ejection of the target color in each unit area and the total amount of ink ejection of other colors in the unit area correspond to the amount of ink ejection of the target color. This correction is sequentially and repeatedly performed for the other colors in the unit area, and the correction is performed for all the unit areas in the raster to be corrected. The next iteration is performed, and for each unit area, the thinning process of the ink dots to be ejected of the noticed color in the unit area is performed so as to perform the ejection of the noticed color with the corrected ink ejection amount. An inkjet recording method characterized by the above-mentioned. 3. The thinning-out process of the ink dots is performed in accordance with the ink discharge amount of a target color in each unit area and the total of the ink discharge amounts of other colors in the unit area. 3. The ink jet recording method according to claim 2, wherein the ink ejection amount is determined by referring to a predetermined correction table. 4. An ink jet recording apparatus for recording an image sequentially in band units by repeatedly scanning a recording head having a plurality of ejection openings for ejecting ink in a direction different from the arrangement direction of the ejection openings. Means for dividing at least one of the first raster and the last raster of each band into a plurality of unit areas each including a predetermined number of dots, and calculating an ink ejection amount in each unit area; Thinning means for thinning out ink dots to be ejected so as to reduce the ink ejection amount in the unit area based on the obtained ink ejection amount, and connecting the bands at the boundary between the bands by the thinning process. An ink jet recording apparatus characterized by reducing the occurrence of streaks. 5. The thinning-out unit according to claim 4, wherein the thinning-out unit performs the thinning-out process using a correction table in which an ink ejection amount and a corrected ink ejection amount corresponding thereto are predetermined. Ink jet recording device. 6. An ink jet recording apparatus according to claim 5, wherein said correction table is provided separately for each color of ink to be corrected. 7. The correction table according to the binarized image data, the amount of ink ejection of a target color in each unit area and the total amount of ink ejection of other colors in the unit area. 7. The ink jet recording apparatus according to claim 5, wherein the corrected ink ejection amount of the noted color is determined. 8. The ink jet recording apparatus according to claim 5, wherein a plurality of correction tables are provided according to recording conditions including at least the type of a recording medium, and are selectively used according to the conditions. 9. The thinning out of ink dots in the unit area, wherein the priority order of the dots to be thinned out is predetermined according to the dot position of each unit area. The inkjet recording device according to any one of the above. 10. When the first raster and the last raster of a band are to be subjected to dot thinning, the priority of the dots to be thinned is made different between the first raster and the last raster. 10. The ink jet recording apparatus according to 9.