JP3168131B2 - Image recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus,
More specifically, the present invention relates to correction of uneven density occurring in an ink jet print image.

[0002]

2. Description of the Related Art Conventionally, as one of image recording apparatuses,
2. Description of the Related Art An ink jet printing apparatus that performs recording by discharging ink onto a printing material is known. An ink jet recording apparatus is a non-impact type recording apparatus, and has advantages such as low noise and easy recording of a color image by using a plurality of types of inks. Spreading.

FIG. 8 is a schematic perspective view of an ink jet printing apparatus according to a conventional example.

In FIG. 8, a print material 5 wound in a roll shape is conveyed by conveying rollers 1 and 2 and is sandwiched by a feeding roller 3 composed of a pair of rollers. It is sent in the direction f in the figure with the driving of 50. Guide rails 6 and 7 are provided in parallel with each other so as to traverse the printing material 5, and a carriage 8 on which a head unit 9 is mounted is slidably engaged with the guide rails 6 and 7, whereby the carriage 8 scans are possible. The head unit 9 has four inkjet heads 9Y of four colors, yellow, magenta, cyan, and black.
9M, 9C, 9Bk, and ink tanks for supplying inks of the colors corresponding to them. Printed material 5
Is intermittently fed by a length corresponding to a predetermined print width of each ink jet head, and during a period in which the printing material 5 is stopped during the intermittent feeding, the head unit 9 scans in the arrow P direction in the figure. And ejects ink droplets corresponding to the image signal.

In such a so-called serial scan type ink jet printing apparatus, stripe-shaped density unevenness occurs in a portion corresponding to a joint between each scan of an ink jet head in an output image, which causes deterioration in image quality of the output image. Some things are well known. On the other hand, as an image recording apparatus that solves the above-described density unevenness, a configuration that corrects an image signal for an end portion of a plurality of ink ejection ports of an inkjet head to reduce the streak at the seam, or that one pixel is used 2. Description of the Related Art A configuration in which joint streaks are made inconspicuous by so-called multi-scan printing formed by ink ejected from different ink ejection ports has been conventionally proposed.

[0006]

However, in the above-mentioned conventional example, although the joint streak is reduced to some extent, the effect may be low depending on the type of the printing material.
The reason for this is that, in the conventional example, the configuration for reducing the joint streak was to cope with variations in the feed amount of the printing material and bleeding of the ink in the printing material, which were dealt with. The effect may vary depending on the type of print material.

[0007] According to the results of experiments and studies by the present inventor, it has been found that streaks are generated due to a cause different from the above. In other words, the main cause of the occurrence of seam streaks based on the results of experiments and studies by the present inventor is that adjacent ink droplets come into contact with each other from the moment when the ink droplet lands on the printing material to the time when its suction is completed, and It has been found that these ink droplets are united due to surface tension (hereinafter, this phenomenon is referred to as "being").

FIGS. 9 and 1 show details of the beading that occurs on the printing material, which is the cause of the occurrence of the joint streak.
0 will be described below.

Each of the ink jet heads 9C, 9M, 9Y
9 and 9Bk are provided with 128 ink ejection ports, respectively, as shown in FIG. 9, and these ejection ports can print a line having a print width d by scanning of each inkjet head.

FIGS. 10A to 10C are schematic views showing how ink droplets land when printing is performed by the ink jet head shown in FIG.

As shown in FIG. 10A, when a plurality of ink droplets having a print width d are recorded in a short time as shown in FIG. 10B, beading occurs between the plurality of ink droplets. . That is, since the ink droplets near the center of the ink droplets arranged with the print width d have the ink droplets on the left and right, the forces applied to the ink droplets are balanced, and the ink droplets themselves do not move. However, the ink droplets at both ends of the print width d have ink droplets on the inner side but have no ink droplets on the outer side, and thus come into contact only with the inner ink droplets. As a result, the outer ink droplet is pulled inward by the surface tension when the two ink droplets come into contact with each other, resulting in a larger ink droplet. That is, a phenomenon similar to the phenomenon occurs (see FIG. 10).
(C)). The density unevenness of the image corresponding to the end of the ink-jet head thus formed is opposed to the density unevenness which similarly occurs at the end of the next scan, and as a result, stripes due to the density unevenness at the joint between scans occur. I do.

[0012] As is clear from the above description, the seam streak due to the above-mentioned beading becomes more remarkable as the image density printed by each ink jet head increases and the amount of ink ejected by each ink jet head increases.
Such a phenomenon is more likely to appear in a printing material having a lower ink absorption speed. When such a printing material is used in a serial scan type ink jet printing apparatus, a streak occurs in a printed image at a joint of each scan. Sometimes.

As described above, the streak at the joint is
Since it is caused by various factors, including conventionally known factors, it is necessary to deal with joint streaks corresponding to each factor.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to deal with a joint streak caused by a plurality of causes in a serial scan type image recording apparatus. It is an object of the present invention to provide an image recording apparatus capable of obtaining an image with reduced joint streaks by performing the above-mentioned correction.

[0015]

According to the present invention, there is provided:
Using a recording head in which a plurality of recording elements for ejecting ink are arranged in a predetermined direction, while moving a recording material relative to the recording head, an image signal indicating a density value corresponding to each pixel is obtained. In an image recording apparatus that performs recording by discharging a plurality of colors of ink onto a recording material based on the recording element, a recording element positioned at an end of the arrangement among the plurality of recording elements arranged in the recording head A first correction unit for correcting a density value indicated by the image signal corresponding to the image signal according to the density value, wherein the image signal corresponding to each of the plurality of colors is individually corrected, and the image signal is A first correction unit that increases a correction amount for reducing the density value of the image signal when the image signal indicates a high density compared with a case where the image signal indicates a low density, and is corrected by the first correction unit. According to a plurality of correction coefficients obtained based on density values indicated by the image signals corresponding to the plurality of colors, among the image signals corresponding to the plurality of colors corrected by the first correction unit, A second correction unit for correcting the image signal corresponding to the recording element located at the end, and a switching unit for enabling or disabling the correction by each of the first and second correction units. It is characterized by having.

[0016]

According to the above arrangement, each of the first causes of the line unevenness which may occur at the boundary of the scanning area of the print head is firstly set.
Correction means and second correction means are provided, and for the image signal corresponding to the recording element positioned at the end of the recording element array of the recording head, the first correction means determines whether the image signal has a high density. The correction for increasing the correction amount for reducing the density value of the signal is performed for each of a plurality of colors for each of the plurality of colors so as to increase the correction amount more than when the image signal indicates a lower density. Since the image signal is corrected according to the correction coefficient obtained based on the value, the first
The bleeding at the above boundary can be reduced by the correction by the correction unit, and the beading that can be caused by the ink of each color overlapping by the correction by the second correction unit can be reduced. At the same time, these corrections can be switched and executed.

[0017]

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

(First Embodiment) FIG. 1 shows a first embodiment of the present invention and is a block diagram of a control unit applicable to the ink jet printing apparatus shown in FIG.

Here, 11C, 11M, 11Y, 11B
k is an input image signal for each pixel, and is a signal corresponding to cyan, magenta, yellow, and black ink ejected by the inkjet head, respectively. An image processing unit 12 performs processing such as masking and gamma conversion, and outputs image signals 13C, 13M, 13Y, and 13Bk of four colors of cyan, magenta, yellow, and black.

Reference numeral 14 denotes a first image correction unit which performs correction processing to be described later on the input image signals 13C, 13M, 13Y, and 13Bk.
C, 15M, 15Y, and 15Bk are output. That is,
The first image correction unit 14 performs image correction to reduce, for example, joint streaks caused by ink bleeding in the print material. Reference numeral 16 denotes a second image correction unit which inputs image signals 15C, 15M, 15Y, and 15Bk.
, The image signals 19C, 19M, 19Y, and 19Bk are output as a result.
That is, the second image correction unit 16 performs image correction to reduce a joint streak generated due to a cause different from that of the first image corrector, for example, the joint streak caused by the above-described beading.

Reference numeral 18 denotes a control unit, and the first image correction unit 14
The control unit 17 outputs control signals 17a and 17b to the second image correction unit 16 for controlling selection of the presence or absence of each correction for each pixel. For example, since the cause of the occurrence of the joint streak differs depending on the types of a plurality of printing materials, when the type of the printing material to be used needs to be corrected only by the first image correction unit, the processing of the first image correction unit is performed. Is turned on and the processing of the second image correction unit is turned off. Further, in the case of a printing material in which a joint streak does not occur due to any of the above factors, the processing of both the first image correction unit and the second image correction unit is turned off, and the respective input signals are output as they are, and conversely, both of them are output. In the case of a printing material in which a joint streak occurs due to the above, the processes of both the first image correction unit and the second image correction unit are turned on. However, in the above-described switching, even in the correction unit whose processing is turned on, in the present embodiment, when the pixel position is located at a position other than the end of the above-described print width d (see FIG. 10),
The process is turned off, that is, a process of outputting the input signal as it is is performed.

FIG. 2 is a diagram showing an example of the above-described correction switching in accordance with the printing material.

The type of the printing material can be automatically detected by a known method using an optical sensor or the like, or can be specified by an operator from an operation unit of the image recording apparatus main body. The control unit 18 outputs control signals 17a and 17b with reference to the table and the pixel position as shown in FIG. 2 in response to the detection or designation, and outputs the control signals 17a and 17b in the first image correction unit 14 and the second image correction unit 16, respectively. Set processing on or off.

Referring again to FIG. 1, the corrected image signals 19C, 19M, 19Y, and 19Bk are binarized by a binarization circuit 20 using a dither method, an error diffusion method, or the like, and then output as ejection signals. And drives them.

The head 9 includes, for example, a cyan head 9C, a magenta head 9M, a yellow head 9Y, and a black head 9Bk, as shown in FIG.
Each has 128 ink ejection ports. The ink jet heads 9C and 9 arranged as shown in FIG.
M, 9Y, and 9Bk can perform full-color image recording while performing serial scanning.

Next, the processing in the first image correction unit and the second image correction unit will be described in detail.

First, the first image correction unit will be described with reference to FIG.

The cyan, magenta, yellow, and black signals 13C, 13M, 1 output from the image processing unit 12
3Y and 13Bk are gamma conversion units 2 of the first image correction unit 14
4 is input to the gamma selection unit 22.
The gamma selector 22 outputs the image signals 13C, 13M, 13
Y, 13Bk, 8-bit gamma selection signals 23C, 23 for selecting a gamma conversion table described later.
M, 23Y and 23Bk are output. On the other hand, the gamma conversion unit 24 performs gamma conversion on the image signals 13C, 13M, 13Y, and 13Bk. The gamma converter 24 includes:
A0 to A255 as shown in FIG.
56 gamma conversion tables are stored. When the input is X and the output is Y, for example, in the low-density part to the medium-density part, these tables A0 to A255 are: A0; Y = XA1; Y = 0.998XA2; Y = 0.996X :: : An; Y = (1−0.002n) X The conversion is performed such that the gradient becomes smaller as the density becomes higher. This is because the amount of ink bleeding increases in the high-density portion and stripes easily occur, so that the correction amount is increased and the correction amount is reduced in the low-density portion.

The gamma conversion tables used for each pixel of each color are gamma selection signals 23C, 23M, 23Y, and 23.
When Bk is "0", A0 is set, and when Bk is "1", A1,.
.., "N", An ... is selected.

Here, the selection signal of the gamma selection unit 22 shown in FIG. 3 is controlled by the above-mentioned control signal 17a. As described above, basically, the first correction unit needs correction. In this case, the control signal 17a is set to "1", but this is applied only to the pixel at the end of the print width d. That is, when the control signal 17a is "0", that is, when the pixel is other than the end pixel, the selection signal of the gamma selector 22 always outputs "0" to select the table A0, and the control signal 17a becomes "1". ", The image signals 13C, 13C
A gamma selection signal corresponding to M, 13Y, 13Bk is output, and a table corresponding to the gamma selection signal is selected.

The image signal 15 thus corrected
C, 15M, 15Y, and 15Bk are input to the second image correction unit 16, and when the control signal 17b is "0", the image signals 19C, 19M, and 19C are not corrected as described above.
Y, 19Bk, and when the control signal is "1", the image signals 19C, 19M, 19Y, 19Bk corrected by performing the correction shown in FIG. After that, the image signals 19C, 19M, 19Y, 19
Bk is binarized by the binarization processing unit 20, and cyan,
Input to the magenta, yellow, and black heads 9,
By driving this, color image recording is performed.

As a result, the amount of ink ejected from the ejection port at the head end having a print width d can be reduced by the correction of the first correction section 14, and the seam caused by the bleeding of the ink in the printing material can be reduced. Streaks are greatly reduced.
Further, when the density value indicated by the image signal is small, the correction amount is reduced, so that the density of the end dots in the low density portion is reduced, and no white stripe is generated.

Next, referring to FIG.
Will be described in detail.

The image signals 15C, 15M, 15Y, and 15Bk output from the first image correction unit 14 are corrected
And to the correction coefficient selection unit 26.

In the correction operation unit 28, the first image correction unit 14
, Magenta, yellow, and black signals 15C, 15M, 15Y, and 15Bk for each pixel output from
Performs the following conversion based on the 16 coefficients αij output from the correction coefficient selection unit 26, and outputs corrected image signals 19C, 19M, 19Y, and 19Bk.

That is, the input image signals 15C, 15M,
15Y and 15Bk are C, M, Y and Bk, respectively.
Assuming that the corrected image signals 19C, 19M, 19Y, and 19Bk are C ', M', Y ', and Bk', respectively, conversion represented by the following matrix operation is performed.

[0037]

[Outside 1]

Where C '<0, M'<0, Y '<0,
When Bk ′ <0, C ′ = 0, M ′ = 0, Y ′ = 0,
A process for setting Bk '= 0 is performed.

Here, the selection and switching of the image signal to be corrected is controlled by a control signal 17b output from the control unit 18 according to the pixel position, similarly to the first image correction unit 14.
When the control signal is "0", the following conversion is performed: C '= CM' = MY '= YBk' = Bk, and when the control signal is "1", that is,
Only in the case of the image signal of the pixel at the end of the print width d (see FIG. 10), the conversion by the above-described matrix operation is selectively performed.

The correction coefficient selecting section 26 outputs the coefficient in the calculation of the above equation (1). That is, the correction coefficient selection unit 26 outputs the cyan, magenta, yellow, and black signals 15C, 15M, 1 output from the first image correction unit 14.
Input 5Y, 15Bk and change coefficient according to their values

[0041]

[Outside 2]

Is output. Collecting these coefficients, αij (i = c, m, y, bk, j = c, m, y, b
αij, represented by k), is set to take a range of 0 ≦ αij ≦ 1. αij is LU in accordance with the values of the input image signals 15C, 15M, 15Y and 15Bk.
It is output with reference to T (lookup table).

The contents of this LUT are based on the control signal 17b.
Are "1" and the input image signals 15C, 15M, 15Y, 15
When the value of Bk is small and when the control signal 17b is "0", αij = 1 (when i = j) and αij = 0 (when i ≠ j) are output. Further, the input image signals 15C, 15M, 15
As the values of Y and 15Bk increase, αij is set to be small when i = j and large when i ≠ j.

FIG. 6 shows the relationship between the input image signal and the coefficient αij, that is, the contents of the LUT. The horizontal axis represents the input image signal 15C, 15M, 15 for each pixel.
Y, the total T of the density values indicated by 15Bk, and the vertical axis represents the coefficient αij
And That is, the contents of the LUT related to αij are such that when the total value T of the density values indicated by the input image signals 15C, 15M, 15Y, and 15Bk is small, αij = 1 (when i = j) αij = 0 (i ≠) j) is output.

That is, as is apparent from the contents of the LUT shown in FIG. 6, the input image signals 15C, 15M, 15Y, 1
When the value of 5Bk is small (and when the control signal 17b is "0"),

[0046]

[Outside 3]

That is, an operation is performed such that C ′ = CM ′ = MY ′ = YBk ′ = Bk.

Similarly, as is clear from the contents of the LUT shown in FIG. 6, the input image signals 15C, 15M, 15
As the total T of Y and 15Bk increases, αij is set to be small when i = j and large when i ≠ j. For example, when the input image signal is represented by 8 bits 0 to 255, C = 250, M = 200, Y = B
If k = 0, the sum of the input image signals is 450, so
With reference to the graph of FIG. 6, αij is, for example,

[0049]

[Outside 4]

Is as follows. Then, C ', M', Y ', Bk
From equation (1), C ′ = 0.98 * 250−0.20 * 200−0.01 * 0−0.00 * 0 = 205 M ′ = − 0.02 * 250 + 0.95 * 200−0.02 * 0−0.02 * 0 = 185Y '= -0.00 * 250 -0.05 * 200 + 0.95 * 0 -0.04 * 0 = -10 → 0 Bk' = -0.00 * 250 -0.00 * 200 -0.01 * 0 + 1.00 * 0 = 0. In other words, cyan becomes 250 → 205, magenta becomes 200 → 185, yellow and black become 0, and this is an operation to decrease the value of the input image signal.

When the correction operation is performed on the pixel corresponding to the discharge port at the end of the ink jet head according to the control signal 17b "1", the discharged ink droplets (in this case, yellow and black) are thinned out. Also, the density value decreases. As a result, in the high density portion of the output image, the joint streak caused by the above-mentioned beading is reduced.

In the above-described embodiments, different corrections are performed by the first image correction unit and the second image correction unit.
There is only one, but the number of image correction units is not limited to this. In other words, when it is considered that the joint streak has occurred due to n physical phenomena, the first image correction unit,
By providing the second image correction unit to the n-th image correction unit, it is considered that the joint streak can be more effectively reduced.

As can be seen from the above description, the first
In the correction, the correction is performed for each color independently, and in the second correction, the correction is performed for each color. This is because a streak caused by a beading which is likely to occur when a printing material having a low ink absorption speed is used is affected by inks of the respective colors which have not yet been absorbed on the printing material, and the state changes.

(Second Embodiment) In a second embodiment of the present invention, the same circuit configuration (FIG. 1) as that of the above-described first embodiment is adopted, and the gamma selection unit of the first image correction unit 14 is used. Method of selecting gamma conversion table at 22 and second image correction unit 1
6 is different from the method of selecting a correction coefficient in the correction coefficient selection unit 26 of FIG.

That is, in the first embodiment, the image correction method is switched in accordance with each of a plurality of joint streak occurrence factors. However, the joint streak occurrence factors are the same, but the degree of the joint streak is large or small. In order to perform correction in response to a plurality of printing materials having different Gamma conversion tables, a gamma conversion table and a correction coefficient are provided for each degree. Selection of the gamma conversion table and the correction coefficient are made variable according to the printing material, and are selected by a control signal from the control unit.

According to the structure of this embodiment, the joint streak can be further reduced optimally in accordance with a plurality of printing materials.

(Third Embodiment) In a third embodiment of the present invention, the same circuit configuration as that of the first embodiment (FIG. 1) is employed, and the gamma selection section 22 of the first image correction section 14 is used. 5 is different from the method of selecting the gamma conversion table and the method of selecting the correction coefficient in the correction coefficient selection unit 26 of the second image correction unit 16.

In the second embodiment, a plurality of gamma conversion tables and correction coefficients corresponding to a plurality of materials to be printed are provided, each having the same joint streak generation factor but different in the degree of the joint streak. However, in the present embodiment, in order to perform correction according to the environmental temperature and humidity inside or around the image recording apparatus main body, a plurality of gamma conversion tables and correction coefficients are provided. That is,
A temperature sensor and a humidity sensor are provided inside the image recording apparatus main body, and a plurality of gamma conversion tables and correction coefficients for performing correction in accordance with the output values of these sensors are selected and selected by a control signal from a control unit.

FIG. 7 shows NO. 1 to NO.
9 shows an example of switching the gamma conversion table of FIG.

This embodiment is particularly effective for an ink jet type image recording apparatus. In other words, in the inkjet image recording apparatus, when printing is performed on a printing material whose moisture content changes according to the surrounding temperature and humidity, the degree of ink bleeding or the degree of beading in the printing material is reduced in the surrounding area during printing. This is because it changes according to the temperature and humidity. This configuration is effective in reducing streak streaks in various environments.

In the first to third embodiments,
The pixel to be corrected is 1 at the end of each inkjet head.
Although the pixels are used, the invention is not limited to this, and two or more pixels may be used. In that case, it is not always necessary to include the pixel at the end, and the selection may be made according to the type of the printing material. In this way, streaking may be more effectively prevented by making the pixel to be corrected variable.

Further, the present invention can be effectively applied not only to a color image recording apparatus but also to an apparatus which performs gradation recording in a single color. In this case, for example, in an ink-jet printing apparatus, a plurality of ink-jet heads having different ink ejection amounts or a single ink-jet head is used, and printing is performed a plurality of times, or gradation recording is performed by changing driving conditions and the like. It may be something.

In the above embodiment, an image recording apparatus of an ink jet system has been described as an example. However, the present invention is not limited to this system, but can be applied to a thermal transfer system and a heat sensitive system.

(Others) It should be noted that the present invention includes a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for discharging ink, particularly in an ink jet recording system. An excellent effect is obtained in a recording head and a recording apparatus of a type in which the state of ink is changed by the thermal energy. This is because according to such a method, it is possible to achieve higher density and higher definition of recording.

The typical configuration and principle are described in, for example, US Pat. Nos. 4,723,129 and 4,740.
It is preferable to use the basic principle disclosed in the specification of Japanese Patent No. 796. This method is a so-called on-demand type,
Although it can be applied to any type of continuous type, in particular, in the case of the on-demand type, it can be applied to a sheet holding liquid (ink) or an electrothermal converter arranged corresponding to the liquid path. By applying at least one drive signal corresponding to the recorded information and giving a rapid temperature rise exceeding the nucleate boiling, heat energy is generated in the electrothermal transducer, and film boiling occurs on the heat acting surface of the recording head. Liquid (ink) corresponding to this drive signal on a one-to-one basis.
This is effective because air bubbles inside can be formed. The liquid (ink) is ejected through the ejection opening by the growth and contraction of the bubble to form at least one droplet. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of a liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further, if the conditions described in US Pat. No. 4,313,124 relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed.

As the configuration of the recording head, in addition to the combination of the discharge port, the liquid path, and the electrothermal converter (linear liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned respective specifications, U.S. Pat. No. 4,558,333 and U.S. Pat. No. 44,558 which disclose a configuration in which a heat acting portion is arranged in a bending region.
A configuration using the specification of Japanese Patent No. 59600 is also included in the present invention. In addition, Japanese Unexamined Patent Application Publication No. 59-123670 discloses a configuration in which a common slit is used as a discharge portion of an electrothermal converter for a plurality of electrothermal converters. The effect of the present invention is effective even if the configuration is based on JP-A-59-138461, which discloses a configuration corresponding to a discharge unit. That is, according to the present invention, recording can be reliably and efficiently performed regardless of the form of the recording head.

Further, the present invention can be effectively applied to a full-line type recording head having a length corresponding to the maximum width of a recording medium on which a recording apparatus can record. Such a recording head may have a configuration that satisfies the length by a combination of a plurality of recording heads, or a configuration as one integrally formed recording head.

In addition, even in the case of the serial type as described above, the recording head fixed to the apparatus main body or the electric connection with the apparatus main body and the ink from the apparatus main body can be provided by being mounted on the apparatus main body. The present invention is also effective when a replaceable chip-type recording head that can be supplied or a cartridge-type recording head in which an ink tank is provided integrally with the recording head itself is used.

Further, it is preferable to add ejection recovery means for the recording head, preliminary auxiliary means, and the like as the constitution of the recording apparatus of the present invention since the effect of the present invention can be further stabilized. If these are specifically mentioned, the recording head is heated using capping means, cleaning means, pressurizing or suction means, an electrothermal transducer, another heating element or a combination thereof. Pre-heating means for performing the pre-heating and pre-discharging means for performing the discharging other than the recording can be used.

The type and number of recording heads to be mounted are, for example, different from those provided with only one ink corresponding to a single color ink and those corresponding to a plurality of inks having different recording colors and densities. A plurality may be provided. That is, for example, the printing mode of the printing apparatus is not limited to a printing mode of only a mainstream color such as black, but may be any of integrally forming a printing head or a combination of a plurality of printing heads. The present invention is also very effective for an apparatus provided with at least one of the recording modes of full color by color mixture.

In addition, in the embodiments of the present invention described above, the ink is described as a liquid. However, an ink which solidifies at room temperature or lower and which softens or liquefies at room temperature may be used. In general, the ink jet method generally controls the temperature of the ink itself within a range of 30 ° C. or more and 70 ° C. or less to control the temperature so that the viscosity of the ink is in a stable ejection range. Sometimes, the ink may be in a liquid state. In addition, in order to positively prevent temperature rise due to thermal energy by using it as energy for changing the state of the ink from a solid state to a liquid state, or to prevent evaporation of the ink, the ink is solidified in a standing state and heated. May be used. In any case, the application of heat energy causes the ink to be liquefied by the application of the heat energy according to the recording signal and the liquid ink to be ejected, or to start solidifying when it reaches the recording medium. The present invention is also applicable to a case where an ink having a property of liquefying for the first time is used. In such a case, the ink
JP-A-54-56847 or JP-A-60-7
As described in Japanese Patent Publication No. 1260, it is also possible to adopt a form in which the sheet is opposed to the electrothermal converter in a state where it is held as a liquid or solid substance in the concave portion or through hole of the porous sheet. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition, the form of the ink jet recording apparatus of the present invention is not limited to those used as image output terminals of information processing equipment such as computers, copying apparatuses combined with readers and the like, and facsimile apparatuses having a transmission / reception function. It may take a form.

[0073]

As described above, according to the present invention,
A first correction unit and a second correction unit are provided for each of the causes of streak unevenness that may occur at the boundary of the scan area of the print head, and an image signal corresponding to a print element located at an end of the print element array of the print head The first correction means performs correction for each color for a plurality of colors so that the correction amount for reducing the density value of the image signal when the image signal indicates high density is larger than that for the case where the image signal indicates low density. The second correction unit corrects the image signal according to the correction coefficient obtained based on the density values indicated by the image signals of the plurality of colors, so that the bleeding at the boundary can be reduced by the correction by the first correction unit. In addition, it is possible to reduce the breathing by the correction by the second correction unit. At the same time, these corrections can be switched and executed.

As a result, high-quality image recording in which streak-like density unevenness is further reduced becomes possible.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an image processing unit of an inkjet printing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating on / off switching of a first image correction unit and a second image correction unit according to the type of a printing material shown in the embodiment.

FIG. 3 is a block diagram illustrating details of a first image correction unit according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a gamma conversion table of the first image correction unit.

FIG. 5 is a block diagram illustrating details of a second image correction unit according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating a table in the second image correction unit, that is, a relation between a correction coefficient and a total of input image signals.

FIG. 7 is a diagram illustrating switching of a gamma conversion table according to temperature and humidity according to a third embodiment of the present invention.

FIG. 8 is a perspective view illustrating a configuration example of an inkjet printing apparatus as a recording apparatus to which the present invention can be applied.

FIG. 9 is a layout diagram of an ink jet head used in the apparatus.

FIG. 10 is an explanatory diagram for explaining a generation mechanism of a joint streak which is an object of the present invention.

[Explanation of symbols]

 Reference Signs List 5 Printed material 9 Inkjet head 12 Image processing unit 14 First image correction unit 16 Second image correction unit 18 Control unit 20 Binarization processing unit 22 Gamma selection unit 24 Gamma conversion unit 26 Correction coefficient selection unit 28 Correction calculation unit

Claims (5)

(57) [Claims] [Claim 1] using a recording head in which a plurality of recording elements in a predetermined direction for ejecting ink, while relatively moving the recording medium relative to the recording head, in each pixel
Multiple colors of b on the basis of the image signal indicating the corresponding density value
In an image recording apparatus that performs recording by discharging ink onto a recording material, the plurality of recording elements arranged in the recording head are used.
That is, the image corresponding to the recording element located at the end of the array
A first method of correcting the density value indicated by the signal according to the density value
Correction means corresponding to each of the plurality of colors.
The image signal is individually corrected and the image signal is high.
Reduce the density value of the image signal when indicating density
The amount of correction to be performed than when the image signal indicates a lower density.
The first correction means, and the plurality of colors corrected by the first correction means.
Are obtained based on the density values indicated by the corresponding image signals.
The first correction means compensates for a plurality of correction coefficients according to
The image signals corresponding to each of the plurality of corrected colors
The image corresponding to the recording element located at the end of the array
A second correction unit for correcting the image signal; and a first correction unit and a second correction unit.
An image recording apparatus, comprising: switching means for enabling or disabling correction . 2. The first correction by the switching means.
Validity and invalidity of the correction of each of the means and the second correction means
Is controlled in accordance with the type of the recording material.
2. The image recording apparatus according to claim 1 , further comprising control means . 3. The first correction means and the second compensation means.
3. The image recording apparatus according to claim 1 , wherein the correction amount of the image signal by the corrector is made variable in accordance with the temperature and humidity inside or around the image recording apparatus. 4. The apparatus according to claim 1, wherein said first correcting means is provided at an end of said array.
Image signals located in the plurality of colors.
And independently corrects the corresponding image signal.
The correction means of (2) uses the image signal located at the end of the array
There the image recording apparatus according to any one of claims 1 to 3, characterized in that to correct dependent on image signals corresponding to the plurality of colors. 5. The recording element according to claim 1, wherein the recording element applies heat energy to the ink.
Heat energy generating means, wherein the recording head is
Bubbles are generated in the ink by the thermal energy generating means
And discharging the ink.
5. The image recording apparatus according to any one of claims 1 to 4.