JP2000108386A - Method and device for ink jet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single pulse type ink jet recorder capable of suppressing occurrence of a connection stripe at an interface section of a band by an operation based on binarized image data at a side of this ink jet recorder in comparatively simple method and structure. SOLUTION: A unit region is classified to plural kinds of conditions A, B, C in accordance with an aggregation condition of an ejection dot of binary image data by each unit region in terms of at least one of the first raster and the last raster in one band which is recorded in one scanning of a recording head (S23). A thinning operation of ink dots to be ejected is executed in order to lower an ejection quantity of ink in each unit region by using a correction table 28 wherein a mask pattern having a length predetermined by each unit region is stored. As a result, it is possible to suppress a connection stripe at an interface between bands.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus, and more particularly, 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 particular, image irregularities called so-called "connecting stripes" may occur at the boundary between bands.

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 the signal value of the signal (multi-level signal) recorded at the boundary between the bands, thereby suppressing ink bleeding and preventing a streak.

However, in this 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. are 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 corrects the image signal level, the process of converting a multi-tone image into a binary image wastes time, resulting in a decrease in recording speed. The inkjet recording apparatus of the present invention does not correct multi-level signal levels, but targets binary image data for correction processing.

Secondly, since the individual difference of 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, it is difficult to correct these in the above-mentioned conventional example. 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.

As another technique for preventing the connecting streaks, there is one disclosed in Japanese Patent Application No. 9-368844 previously proposed by the present applicant. This is, for example, on the binarized image data, by reducing a predetermined number of ink dots on the line on the boundary between the bands, to reduce the print density between the bands, to suppress the blur, There are some that prevent the connecting streaks. In this prior art, a corrected ink ejection amount is determined by referring to a correction table in accordance with an instructed ink ejection amount in a unit area, and ink dots are thinned by an excess amount. However, in this prior art, since a strict correction is performed in consideration of the combination of all the dots in the unit area on / off for each color, the correction table becomes large, and the processing load using the table is relatively large. became.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and it is an object of the present invention to reduce the occurrence of a connecting streak at a band boundary by processing on an ink jet recording apparatus based on binarized image data. It is an object of the present invention to provide a single-pass type ink jet recording apparatus capable of performing the following.

It is another object of the present invention to provide a single-pass type ink jet recording apparatus which can reduce the occurrence of connecting streaks by a relatively simple method and configuration.

[0011]

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 recording an image in units, at least one of a first raster and a final raster of one band recorded by one scan of the recording head has a discharge dot of binarized image data for each unit area. The ink dots to be ejected are classified into a plurality of states according to the state of aggregation, and using a mask pattern having a predetermined length for each of the states so as to reduce the amount of ink ejected in each unit area. Is performed, the generation of the connecting streak at the boundary between the bands is reduced.

According to this method, the mask pattern for thinning out the ink dots is determined for each unit area of the image raster according to the state, so that the configuration (for example, the table configuration) for determining the mask pattern is simplified. You. Also,
This is because the amount of ink discharged at the boundary between the bands can be corrected using the binarized image data. There is no need to change the processing in the external computer terminal, etc.
The correction processing is performed on the ink jet recording apparatus side, so that the occurrence of the connecting streak at the boundary between the scans (bands) can be reduced.

The plurality of types of states are, for example, a first state in which a predetermined number of discharge dots are continuous in a unit area, and a second state in which a predetermined number of discharge dots are present in a unit area but not a predetermined number.
And a third state in which no ejection dot exists in the unit area.

According to the apparatus of the present invention for carrying out such a method, a recording head in which a plurality of ejection openings for ejecting ink are arranged is repeatedly scanned in a direction different from the arrangement direction of the ejection openings to sequentially perform band unit printing. In an ink jet recording apparatus for recording an image, a set of ejection dots of binary image data for each unit area for at least one of a first raster and a final raster of one band recorded by one scan of the recording head. Means for classifying the state into a plurality of types of states, a correction table storing a mask pattern of a predetermined length for each of these states, and a mask pattern corresponding to the state of each unit area from the correction table, The thinning process of the ink dots to be ejected is performed so that the ink ejection amount in the unit area is reduced by the mask pattern. And a stage, by the thinning processing, characterized in that to alleviate the occurrence of the banding in the band and the band boundaries.

By using the correction table, quick correction processing can be performed. The same correction table may be used for each color of the ink to be corrected, but if provided separately, a different mask pattern can be set for each color.

The correction table may determine a mask pattern for each color according to a combination of states of a plurality of ink colors in a unit area. As a result, it is possible to determine the thinning state of each color according to the state of the other color, instead of performing the closed correction only within one ink color.
A good result of the thinning process of the ink dots is obtained as a whole.

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

When the first raster and the last raster of the band are to be subjected to dot thinning, even if the mask pattern has the same thinning rate, the mask pattern is made different between the first raster and the last raster. Is also good.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred 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 an ink jet recording apparatus according to 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, 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.

The ink jet head of the printing unit 17 includes:
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 shows a processing flow from input data reception to printing. At the time of printing, first, input data is received from the outside (S21), and the received data is analyzed to prepare print data for one band suitable for recording by the inkjet head (S22). Next, the first and last rasters are sequentially read from the top of the raster for each color, one raster area is divided into predetermined unit areas, and these unit areas are classified into three types of states (S2).
3). For example, a first state in which the ejection dots continue for a predetermined threshold number or more, a second state in which the ejection dots exist but do not continue for a predetermined threshold number or more, and a third state in which the ejection dots do not exist.
Are classified into three types. Next, referring to the correction table 28 prepared in advance according to each type of the unit area,
The print data is corrected (S24). Each head is driven based on the corrected image data of the band obtained as described above to perform a printing process (S25). Such processing is repeatedly executed until all the bands are completed (S26).

FIG. 3 is a diagram for explaining the correction processing of the ink ejection amount according to the present embodiment.

In this example, the ink ejection amount is corrected in the last raster of the first scan (first band) and the first raster and the last raster after the second scan (second band). In the last band, only the first raster is corrected. For example, assuming that the number of nozzles of the head per color involved in recording of one band is 128, ink droplets ejected by the first and 128th nozzles are to be corrected.

However, the nozzles involved in one band printing need not be all the nozzles provided in the head. Therefore, 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 them 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 band boundary is divided so as to have a constant shape and area. In the present embodiment, the boundary is a single raster at the beginning and at the end of the band, and each raster is divided into a unit area of 16 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 raster depending on the recording medium, and the number of dots per raster is not limited to 16 dots.

FIG. 4 schematically shows data of one raster composed of a unit area of 16 dots × 1 dot of each color of Y, M, C, and K. The correction process is performed for each color for each of the divided unit areas.

First, the state of the unit area is recognized. For example, when the ejection amount of the yellow Y ink in a certain unit area is to be corrected, if a predetermined number of consecutive ejection dots of Y in the unit area is determined, this is the state A. FIG. 8A illustrates an example of a dot ejection state in the unit area in the state A.

If ejection dots exist in the unit area but do not continue for a predetermined number of times, it is determined that the ejection state is the state B. FIG. 8B illustrates an example of a dot ejection state in the unit area in the state B.

If there is no ejection dot in the unit area (all "0"), it is determined that this is the state C. FIG. 8C illustrates an example of a dot ejection state in the unit area in the state C.

For each of these states, a mask pattern that can reduce the connecting streak most commonly is experimentally obtained and stored in a correction table corresponding to the color. As described above, in the present embodiment, the state of each unit area is classified into three types, A, B, and C, and the correction value for each of these states may be stored in the correction table. It is reduced and the processing is simplified. However, the present invention is not limited to three types of states, and may be, for example, two types or four or more types.

In the present embodiment, as will be described later with reference to FIG. 7, correction tables are provided for four colors of Y, M, C, and K. This makes it possible to specify an appropriate correction mask pattern for each color. However, in the present invention, when a common correction table is used for all colors, or when Y, M,
This does not exclude the case where a common correction table is used for C and a dedicated correction table is used for K.

FIG. 7 shows a specific example of the correction table 28 when the number of dots in the unit area is 16. As shown in the drawing, the correction tables 28a to 28d for each of the colors (Y, M, C, and K) to be corrected have 16-bit values used for the correction process for the state of the color in a given unit area. Are determined in advance. In the figure, "0x" indicates that the following numerical value is a hexadecimal number. By thinning the data ("1" dots) by ANDing the mask pattern with the data using this correction table.

Further, the correction table 28 may be prepared as separate tables for the first raster and the final raster of the band. This makes it possible to use different correction methods for both rasters. More detailed correction processing becomes possible.

Further, as shown in FIG. 9, when this determination is made for a certain unit area of a certain color, the correction table is used in accordance with the state of the unit area at the same position of another color. In this case, a different mask pattern may be set. As a result, although the size of the correction table is increased, finer correction processing can be performed without impairing the processing speed of the correction processing.

FIG. 5 is a diagram showing an example of a discharge dot thinning mask pattern used for correcting the ink discharge amount in a unit area in state A in which all dots are discharge dots. In this example, in one unit area, a mask pattern is formed so that adjacent dots are not spatially continuously thinned out.
0 bits are dispersed (“0” in the mask pattern)
The bits that have become thinned out). Here, as a result of the thinning, 25% of the ejection dots are thinned. Even if the thinning rate is the same, the mask pattern 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 mask pattern is 0xFF55 for the final raster and 0x55FF for the first raster. The reason why the “0” bit positions of the mask pattern are dispersed in this way is to prevent the image quality from deteriorating as a result of thinning. Note that the examples of these mask patterns are merely examples, and the present invention is not limited to these.

FIG. 6 shows the structure of a unit tilt according to another embodiment of the present invention.

FIG. 6A shows that the unit area is an area of 16 horizontal dots × 2 vertical dots corresponding to two rasters of the last nth raster and the (n-1) th raster of the band above the boundary. On the lower side, 16 dots horizontally x 1 vertically for one raster as in FIG.
This is a dot area. Conversely, 1 above the boundary
The raster and the lower side may be two rasters.

FIG. 6B shows upper and lower sides of the boundary.
Both areas are 16 raster dots by 2 raster dots for two rasters. The configuration of the unit area in FIG. 6 is effective when applied to a recording medium in which ink bleeds greatly. An example (corresponding to state A) of a mask pattern used for thinning the ejection dots in each unit area is shown in the figure.
In this case as well, the bit arrangement of the mask pattern is considered and determined so that the dots to be masked are not spatially continuous.

Although the preferred embodiment of the present invention has been described above, various changes 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.

The above-mentioned correction table 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. You may. 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 match due to the remaining amount of ink at printing, the temperature, humidity, individual differences of the recording medium, etc., more dots are masked. It would be more effective if several correction tables having mask patterns were prepared so that they could be selected before actual printing.

[0045]

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. The correction processing is performed on the ink jet recording apparatus side, so that the occurrence of the connecting streak at the boundary between the scans (bands) can be reduced.

Further, the processing load can be reduced without deteriorating the print quality by limiting the target area of one correction process to a relatively small unit area. The unit area does not consider the combination of on / off of all the dots in it, but considers the state of each unit area according to the state of aggregation of the ejection dots in the unit area. It can be simplified.

Further, since the process is only to AND the mask pattern with the data using the correction table, a quick correction process 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 schematically showing one raster data composed of a unit area of 16 dots × 1 dot of each color of Y, M, C, and K in the embodiment of the present invention.

FIG. 5 is a diagram illustrating an example of a mask pattern used for reducing the ink ejection amount (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 16 in the embodiment of the present invention.

FIG. 8 is a diagram for explaining a classification process based on a continuous state of ejection dots in a unit area according to the embodiment of the present invention.

FIG. 9 is a diagram showing a modification of the correction table according to 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.

Continued on front page F-term (reference) 2C056 EA08 EA09 EB58 EC71 FA10 2C057 AF31 AL31 AM28 AN01 DA09 DB03 2C262 AA02 AA18 AB03 BC01 EA04 EA06 EA08 EA10 EA11 GA29 5C074 AA02 AA05 BB16 CC26 DD08 DD24 DD01 FF08 EA08

Claims (8)

[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 is classified into a plurality of states according to the aggregation of the ejection dots of the binarized image data for each unit area. Using a mask pattern of a predetermined length for each band, the thinning process of the ink dots to be ejected is performed so as to reduce the ink ejection amount in each unit area, so that the connecting streak at the boundary between the bands is performed. An ink jet recording method characterized by alleviating occurrence. 2. The plurality of states include a first state in which all dots in a unit area are ejection dots, a second state in which ejection dots and non-ejection dots are mixed in the unit area,
2. The ink jet recording method according to claim 1, wherein the third state is that there is no ejection dot in the unit area. 3. An ink jet recording apparatus which performs image recording 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 classifying at least one of the first raster and the last raster of one band recorded by one scan into a plurality of types of states according to a collection state of ejection dots of binary image data for each unit area; And a correction table storing a mask pattern of a predetermined length for each state, a mask pattern corresponding to the state of each unit area is obtained from the correction table, and the ink ejection amount in the unit area is determined by the mask pattern. Means for performing thinning processing of ink dots to be ejected so as to reduce the number of ink dots to be ejected. An ink jet recording apparatus characterized in that occurrence of a connecting streak at a boundary between bands is reduced. 4. The plurality of types of states include a first state in which a predetermined number of discharge dots are continuous in a unit area, a second state in which a predetermined number of discharge dots are present in a unit area, and a predetermined number of discharge dots are not continuous. 4. The ink jet recording apparatus according to claim 3, which is in a third state in which no ejection dots exist in the area. 5. An ink jet recording apparatus according to claim 3, wherein said correction table is provided separately for each color of ink to be corrected. 6. The ink jet recording apparatus according to claim 4, wherein the correction table defines a mask pattern for each color according to a combination of states of a plurality of ink colors in a unit area. 7. The ink jet recording apparatus according to claim 3, 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. 8. When the first raster and the last raster of a band are to be subjected to dot thinning, the mask pattern is made different between the first raster and the last raster even if the mask patterns have the same thinning rate. Claims 3 to
8. The ink jet recording apparatus according to any one of 7.