JPH08156287A - Recorder - Google Patents

Abstract

PURPOSE: To obtain a recorder capable of performing a high-quality image recording while suppressing beading. CONSTITUTION: A correction factor selection part 14 selects an optimum correction factor on the basis of a total density T of image signals 13C, 13M, 13Y, 13Bk per color component for every pixel subjected to image processing and transmits it to a correction operation part 18. On the other hand, a control part 17 checks whether or not a pixel to be recorded on inputted image signals is to be printed with ink delivered from an end of a nozzle of a recording head and outputs the result to the correction operation part 18 as a control signal Z. In the correction operation part 18, image signals for a pixel judged to have a high density and to be printed by an ink delivery from a nozzle end on the basis of the control signal Z and the transmitted correction factor are corrected by a matrix operation to be lowered in density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording device, and in particular,
The present invention relates to a printing apparatus that prints according to an inkjet method.

[0002]

2. Description of the Related Art A recording apparatus according to an ink jet method for recording by ejecting ink onto a recording medium is a non-impact type recording apparatus with less noise and color image recording using multicolor ink is easy. Therefore, it has been rapidly spreading in recent years. FIG. 5 is an external perspective view showing a schematic configuration of a conventional inkjet recording apparatus. In FIG. 5, the recording paper 5 wound on a roll is nipped by the feeding roller 3 via the conveying rollers 1 and 2, and is driven in the f direction in accordance with the driving of the sub-scanning motor 50 coupled to the feeding roller 3. Sent. Now, guide rails 6 and 7 are placed parallel to each other in a direction perpendicular to the conveying direction of the recording sheet 5 so as to face the recording sheet 5, and the recording head unit 9 mounted on the carriage 8 is provided.
Moves along the guide rails 6 and 7. Carriage 8
Yellow (Y), magenta (M), cyan (C), black (Bk) four-color heads 9Y, 9M, 9C, 9B
k is mounted, and ink tanks of four colors are arranged on it.

The recording paper 5 is intermittently fed by the recording width of the recording head unit 9, but when the recording paper 5 is stopped, the recording head unit 9 scans in the P direction and ink droplets corresponding to the image signal are discharged. Is discharged. In such an inkjet type recording apparatus, the characteristics of the recording paper are important, and in particular, the ink absorption speed of the recording paper has a great influence on the image quality. In particular, when ink droplets are ejected from a recording element onto a recording sheet having a low ink absorption speed, "beading" of the ink occurs. That is, adjacent ink droplets overlap each other during the time from the moment when the ink droplets reach the recording paper until the absorption ends, and the surface tension of the ink causes the ink droplets to continue to stick together. In this way, the ink droplets move from the arrival point on the recording paper in the direction in which the adjacent ink droplets exist, and the image quality deteriorates. This phenomenon becomes more remarkable as the image density recorded on the recording paper by each recording head is higher, that is, as the number of ink droplets recorded on the recording paper is larger.

For the above reasons, in order to form a high quality image, it is required to increase the ink absorption speed of the recording medium such as recording paper.

[0005]

However, since the time from the arrival of an ink droplet on a recording medium such as a recording sheet to the occurrence of ink beading is very short, the time from the arrival to the occurrence of beading is shorter than that. Recording media that absorb ink faster are limited. When the ink absorption speed of the recording medium is slow, beading of the ink occurs and the image quality deteriorates, but this causes another problem as described below.

In the conventional serial scan type ink jet recording apparatus shown in FIG. 5, for example, a recording width formed by arranging a plurality of nozzles corresponding to respective inks in parallel in the moving direction of the carriage 8 as shown in FIG. When image recording is performed by mounting the multi-nozzle head of d, streak-like unevenness (joint streak, banding) at each joint of each recording scan
Occurs. Through experiments and examination of the results, it has been verified that the main cause of the occurrence of the seam stripes is the beading of the ink on the recording medium. Here, the recording width d
Is determined by the number of nozzles in the head and the recording density. The number of nozzles is 128 and the recording density is 400 dots / inch (dpi).
In the case of the multi-nozzle head of, d = 128 × 25.4
/400=8.128 (mm).

Next, the beading of the ink on the recording medium, which is the cause of the seam streak, will be described in detail with reference to FIG. First, as shown in FIG. 7A, a plurality of ink droplets having a recording width d are ejected from a recording element of a recording head and fly toward a recording medium, and then as shown in FIG. When the ink droplets of 1 are approached and recorded in a short time, beading occurs between the plurality of ink droplets.
Since the ink droplets in the vicinity of the center of the plurality of ink droplets arranged in the recording width d have ink droplets on the left and right sides, the force applied to the ink droplets is almost equal in both the left and right directions, and the ink droplets move. There is no.

However, the ink droplets at both ends of the recording width d are
Although there is an ink droplet inside the ink droplet, but no ink droplet outside the ink droplet, it contacts only the ink droplet inside. When two ink droplets come into contact with each other, a force is applied due to the surface tension in the direction in which the ink droplets pull each other, and a phenomenon similar to a phenomenon (beading) that finally becomes one large ink droplet occurs. That is, as shown in FIG. 7B, the ink droplets at both ends of the recording width d have an inward pulling force, but do not have an outward pulling force. Therefore, the ink droplets at both ends move inward, As a result, as shown in FIG. 7C, the ink swells near the ends of the recording width d due to the concentration of the ink droplets. And as a result, this appears as a joint line. The seam streak due to this beading becomes more remarkable as the image density recorded by each recording head increases and the amount of ink recorded by each recording head increases.

Such a phenomenon is caused by the fact that the recording medium such as recording paper has a slow ink absorption speed. When recording is performed using a recording paper having a low ink absorption speed, for the above reasons, A streak is generated in the output image at the joint of each recording scan. Next, a seam line due to beading that occurs when color recording is performed using a plurality of inks will be described. In the following description, the total amount of ink ejected by a plurality of recording heads in a unit area on the recording medium is called the total amount of ink.

First, as described with reference to FIGS. 7A to 7C, a plurality of ink droplets of the first color (Y) are recorded by the first recording head (for example, the recording head 9Y). The ink droplets having a width d are ejected onto the recording medium, and beading of ink droplets occurs in the regions at both ends of the recording width d. Then, the second recording head (for example, the recording head 9M) ejects a second color (M) ink droplet onto the recording medium before the first color ink is completely absorbed by the recording medium. The ink of the second color is ejected after the ink of the first color has been absorbed to some extent by the recording medium and the ink absorption speed on the surface of the recording medium has slowed down. Becomes longer. That is, the ink of the second color behaves as if it was ejected onto the recording medium having a slow ink absorption speed, and the beading of the ink becomes more remarkable. As a result, as shown in FIG. 7D, the ink droplet at the end of the second color moves further inward than the ink droplet at the end of the first color.

When the ink thus moved is completely absorbed and fixed on the recording medium, as shown in FIG. 7 (e), a streak-like density unevenness and color unevenness of the first color appear at the end of the recording width d. A seam line is formed so as to face the unevenness caused by the next recording scan. Also in this case, as the image density increases and the total amount of ink recorded by a plurality of recording heads per unit time increases, the seam lines due to beading on the recording medium become more remarkable.

However, when recording on a recording medium with a plurality of recording heads, there is a difference in the ejection time of the ink of each color, so that the ink is absorbed in the recording medium to some extent during that time, and even if the same total ink amount is used, recording with a plurality of color inks is performed. In this case, the seam lines due to beading on the recording medium are less noticeable than in the case of recording with a single color ink. Further, for the same reason, in the image formation of a plurality of color inks or a single color ink, when recording of one pixel is divided into a plurality of times and is performed by scanning a plurality of times, it depends on the number of scans (= n) of the print head. The state of the seam line changes. That is, since the ink to be printed at one time by one scan is ejected by scanning the print head n times and dividing it into n times, there is a difference in the ejection time of each scan, and the ink amount printed per unit time is one time. Since it is 1 / n of that when printing is performed by scanning, the joint lines due to beading on the recording medium are less noticeable.

Therefore, in order to prevent the seam streaks, it is sufficient to use a recording medium having a high ink absorption speed, reduce the amount of ink recorded per unit time, or reduce the total amount of ink used for recording. . The present invention has been made in view of the above conventional example, and an object of the present invention is to provide a recording apparatus capable of performing high-quality image recording without causing image quality deterioration.

[0014]

In order to achieve the above object, the recording apparatus of the present invention has the following constitution. That is, a recording apparatus that performs image recording using a recording head that performs recording by discharging a recording material onto a recording medium from a plurality of nozzles arranged in a predetermined direction corresponding to each of a plurality of recording elements. Image processing means for inputting and performing image processing, and determination means for determining whether or not a nozzle for discharging and recording the recording material on the basis of the image-processed data exists at the end of the array, A correction unit that corrects the value of the input image data according to the value of the input image data and the determination result of the determination unit, and a scanning unit that scans the recording head in a direction different from the predetermined direction are provided. However, when the value of the input image data is high density and the nozzle for performing image recording based on the input image data is at the end portion of the array, the correction means outputs the input image data Corrected to reduce, by a plurality of scanning by said scanning means, a recording apparatus characterized by performing color recording by the recording head.

[0015]

According to the present invention having the above-described structure, the image recording is performed by using the recording head for recording by discharging the recording material onto the recording medium from the plurality of nozzles arranged in the predetermined direction corresponding to each of the plurality of recording elements. When performing, it is determined whether or not a nozzle for discharging a recording material and performing recording is present at the end of the nozzle array based on the image-processed input image data, and according to the value of the input image data and the determination result. , When the value of the input image data is high density and the nozzle for performing image recording based on the input image data is at the end of the nozzle array, the value of the input image data is corrected so as to decrease, and the recording head Color recording is performed by scanning a plurality of times.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the external schematic configuration of the recording apparatus according to the inkjet method used in the following description is shown in FIG.
The recording apparatus is the same as the conventional recording apparatus shown in FIG. 5, and the respective constituent elements in FIG. 5 will be referred to as necessary. Further, the structure of the recording head has the same structure as shown in FIG.

FIG. 1 is a block diagram showing the arrangement of a control unit of a recording apparatus according to the ink jet system which is a typical embodiment of the present invention. In FIG. 1, 11C, 11M, 11
Y and 11Bk are color components (cyan (C), magenta (M), yellow (Y), and black (Bk) of input image data transmitted from an image reading unit (not shown) such as a host computer or a scanner. ) Signal, 12 is an image processing unit for performing processing such as UCR masking and gamma conversion on the input image signal, 13C, 13M, 13Y, 1
3Bk is each color component (cyan, magenta, yellow, and black) of the image signal corrected by the image processing unit 12.
Is.

Reference numeral 14 is a correction coefficient selecting section for inputting the corrected image signal color components 13C, 13M, 13Y, 13Bk and selecting an appropriate correction coefficient in accordance with the input data. Reference numeral 17 is shown in FIG. Each recording head 9C, 9M, 9
A control unit for outputting a control signal for controlling selection of presence / absence of correction to an image signal recorded by a Y, 9Bk recording element;
Reference numeral 18 denotes corrected four color image signals 13C, 13M, 13Y, 13Bk of cyan, magenta, yellow and black.
Is input, and a correction calculation unit that executes the correction calculation of the image signal according to the correction coefficient selected by the correction coefficient selection unit 14 and the control signal from the control unit 17. 19C, 19M,
19Y and 19Bk are the color components of the corrected image signal output by the correction calculator 18.

Now, the control unit 17 includes a correction coefficient selection unit 14
Image signals 13C, 13M, 13Y, 13B input to
When k is an image signal recorded by the recording element at the end of each recording head 9C, 9M, 9Y, 9Bk, Z = 1 is recorded as the control signal (Z) and recording is performed by the recording element other than one end. In the case of an image signal, Z = 0 is output to the correction calculator 18. Further, the calculation in the correction calculator 18 is selectively executed only on the image signals recorded by the recording elements at the ends of the recording heads 9C, 9M, 9Y, 9Bk, and the other image signals. On the other hand, the input image signals 13C, 13M, 13Y and 13Bk are directly output as the output image signals 19C, 19M, 19Y and 19Bk without performing any calculation.

The calculation for the image signal to be corrected executed here is a correction calculation for reducing the image signal in order to reduce the recording ink amount (details will be described later). It is changed according to the input signals of the heads 9C, 9M, 9Y and 9Bk, and the result of the correction calculation is reflected in the corrected image signals 19C, 19M, 19Y and 19Bk which are the outputs.

Corrected image signal 1 obtained as described above
9C, 19M, 19Y and 19Bk are binarized by a binarization circuit 20 using a dither method, an error diffusion method or the like, and then input to the recording head unit 9 for color recording. Reference numeral 30 is an instruction button that allows the apparatus user to set a recording mode described later.

As shown in FIG. 6, the recording head unit 9 is composed of recording heads 9C, 9M, 9Y and 9Bk each having 128 recording elements. 1 to No. 128 is attached. Then, full-color image recording is performed by serial scanning by the recording device. Next, the function of the correction coefficient selection unit 14 will be described in detail.

In the correction coefficient selection unit 14, the image processing unit 12
The cyan, magenta, yellow, and black signals 13C, 13M, 13Y, and 13Bk output from are input, and the coefficients a _cc , a _cm , a _cy , which vary according to these values,
a _cbk , a _mc , a _mm , a _my , a _mbk , a _yc , a _ym , a _yy ,
_{a ybk, a bkc, a bkm} , a bky, to output _a bkbk. Collecting these coefficients, a _ij (i = c, m, y, bk; j
= C, m, y, bk), a _ij is 0 ≦ a _ij ≦ 1
Set to take the range of. Then, a _ij is output by referring to the LUT according to the values of the input image signals 13C, 13M, 13Y, 13Bk.

Here, the correction coefficient selecting section 14 has a _ij = 1 (when i = j) or a _ij = 0 when the values of the input image signals 13C, 13M, 13Y and 13Bk are small.
(When i ≠ j) is output. In addition, the input image signal 13
As the values of C, 13M, 13Y, and 13Bk increase, the value of a _ij decreases when i = j, while i _ij decreases.
When ≠ j, the value is set in the LUT so that the value becomes large.

In the correction calculation unit 18, the image processing unit 1
The cyan, magenta, yellow, and black signals 13C, 13M, 13Y, and 13Bk output from 2 and the 16 coefficients a _ij output from the correction coefficient selecting unit 14 are input, and the corrected image signals 19C, 19M, 19Y, 19Bk
Is output. Here, the input image signals 13C, 13M,
When 13Y and 13Bk are C, M, Y and Bk respectively and the corrected image signals 19C, 19M, 19Y and 19Bk are C ′, M ′, Y ′ and Bk ′ respectively, the following matrix calculation is performed.

[0026] However, when C '<0, M'<0, Y '<0, Bk'<0, C '= 0, M' = 0, Y '= 0, Bk' = 0 are converted.

Here, the selection switching of the image signal to be corrected is
It is controlled by the control signal Z output from the control unit 17.
In this embodiment, when the control signal Z = 0, no correction calculation is performed, and C ′ = C, M ′ = M, Y ′ = Y, and Bk ′ = Bk. On the other hand, when Z = 1, that is, the recording heads 9C, 9M, and 9 that constitute the recording head unit head 9
Only in the case of the image signals of the recording pixels of the nozzles at the ends of Y and 9Bk, the above matrix calculation is selectively performed.

FIG. 2 shows the total sum T of the input image signals of this embodiment.
It is a figure which shows the relationship of the correction coefficient _aij . In FIG.
Each recording head 9C, 9M, 9 for the unit pixel on the horizontal axis
Y, 9Bk input image signals 13C, 13M, 13Y, 1
The total sum of 3Bk is T, and the vertical axis is the correction coefficient a _ij . As shown in FIG. 2, the input image signals 13C, 13M,
When the sum T of 13Y and 13Bk is small, i and j
A _ij = 1 is output regardless of the value of.

That is, when the values of the input image signals C, M, Y and Bk are small, the matrix calculation as shown below is performed. By this calculation, C ′ = C, M ′ = M, Y ′ = Y, B
k ′ = Bk.

Next, consider a case where the values of the input image signals C, M, Y and Bk are large. As shown in FIG. 2, as the total value T of the input image signals 13C, 13M, 13Y, 13Bk increases, a _ij decreases so that i = j, and If ≠ j, the value is set to be large. For example, when the input image signal is represented by an 8-bit signal (its value is an integer value of 0 to 255), C = 250, M = 200, Y = Bk
= 0, the total T of the input image signals is 450, so
The relationship shown in FIG. 2 is expressed more concretely, and a _ij is set as follows, for example.

[0031] When this matrix is applied to the above-described matrix calculation formula to perform calculation, C ′, M ′, and Y′Bk ′ are obtained by calculating the following formulas.

C ′ = 0.98 × 250 −0.20 × 200 −0.01 × 0 −0.00 × 0 = 205 M ′ = 0.00 × 250 −0.95 × 200 −0.02 × 0 −0.02 × 0 = 185 Y ′ = 0.98 × 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 That is, cyan is 250 → 205, magenta is 200 →
185, yellow, and black are 0, and the value obtained with respect to the value of the input image signal is reduced.
By applying such a correction calculation to the input image signal, each recording head 9 that constitutes the recording head unit 9
The amount of ink droplets ejected from the recording elements at the end portions of C, 9M, 9Y, and 9Bk is reduced, and as a result, it is possible to reduce the seam stripes in the high density portion of the output image.

Each element forming the matrix has the following physical meaning. That is, the diagonal component [a _ij (i = j)] of the matrix is reduced by directly multiplying each input signal of C, M, Y, and Bk by a coefficient of 1 or less, and the non-diagonal component [a _ij (a _ij (i = j)] is obtained. i ≠ j)] becomes a coefficient of the other signal, and the value of the input signal is further reduced by subtraction. This serves to reduce the value of the image signal in order to reduce the streaks caused by the diagonal components of C, M, Y, and Bk's own ink, and the non-diagonal components before the pixel currently considered. Alternatively, it plays a role of reducing streaks that are worse than the ink ejected to the subsequent pixels.

In the present embodiment, a plurality of recording heads 9 are used.
The C, 9M, 9Y, and 9Bk recording scans on the recording sheet are configured to record a plurality of times for each of a plurality of colors. In FIG. 5, the first forward scan of the carriage 8 (scan in the direction of arrow P in FIG. 5) records with two heads of cyan and black ink (recording heads 9Bk and 9C), and the second time after carriage return. Magenta and yellow ink (recording head 9M,
Recording is performed with two heads (9Y). As described above, the same row is subjected to print scanning for every two inks, and a total of two forward scans are repeated to form a color image for one row.

When the recording for one line is completed in this way, the sub-scanning motor 50 is driven to execute the sheet feeding for one line,
Scanning for each of the two colors is repeated in the same manner as described above to form a color image in that row, and thereafter, color recording is successively performed in the same manner. With such scanning control, the amount of ink ejected per unit time is halved compared to when printing is performed using cyan, magenta, yellow, and black inks in one scan, so that seam lines are reduced. It

However, if the image formation for one line is performed by scanning a plurality of times, the quality of image recording is improved but the throughput is lowered. Therefore, in this embodiment, the instruction button 30 is provided in the main body of the recording apparatus to make a plurality of recordings. The mode is set by the user so that the user can select the number of scans for image formation for one line. For example, a normal mode with a high recording speed but a medium image quality and a high quality mode with a low recording speed but a high image quality are provided. In the normal mode, the number of scans required to form an image for one line is set to one. In the mode, control is performed so that the number of scans required to form an image on one line is changed to twice or more.

At this time, even when the same image is output in the normal mode and the high quality mode, the correction coefficient necessary for the correction calculation is controlled so as to switch between the normal mode and the high quality mode. This is because the beading level changes between the normal mode and the high quality mode, and in order to cope with this change, two kinds of correction coefficients corresponding to each mode are provided.
It is set to 4 in advance and is switched by the control signal X from the control unit 17.

With the above configuration, the seam streak can be reduced in the normal mode and further reduced in the high quality mode. Therefore, according to this embodiment,
With respect to the pixels to be printed from the nozzles at the end of the print head, the correction calculation is performed on the image signal so as to reduce the density value especially when the density value of the input image signal is high
The amount of recording ink at the end of the recording head is reduced, and the occurrence of beading can be suppressed. This makes it possible to obtain a high-quality recorded image.

In addition, two modes are provided for changing the relationship between the scanning of the recording head and the ejection of each ink in accordance with the recording operation, and even when the speed priority or the image quality priority recording is performed, the input suitable for each mode is performed. Since the density correction is performed on the image signal, the image quality can be improved in that mode. In this embodiment, the correction coefficient aij is selected according to the total value T of the input image signals for the unit pixel, but the present invention is not limited to this. For example, even with the circuit configuration shown in FIG. 1, the correction coefficient selection control in the correction coefficient selection unit 14 can be performed as follows.

That is, the correction coefficient selection unit 14 selects the correction coefficient aij according to the total value T of the input image signals and the ratio of the input image signals recorded in the unit pixel by the recording element of each recording head. That is, when the correction coefficient selection unit 14 inputs the image signals 13C, 13M, 13Y, and 13Bk and sets them C, M, Y, and Bk, the total value (T = C + M + Y + Bk) of the input image signals and the input image signal The ratio (C / T, M / T, Y / T, Bk / T) is calculated. Since C ≦ T, M ≦ T, Y ≦ T, and Bk ≦ T are always satisfied, the ratio (R) of the input image signal is 0 ≦ R ≦ 1. Also, a value RB that can express the ratio R in 2 bits
When represented by (0, 1, 2, 3), for example, the relationship between the value of the ratio R and the value of RB is as follows.

When 0.00 ≦ R <0.25, RB = 0 0.25 ≦ R <0.50, RB = 1 0.50 ≦ R <0.75, RB = 20. When 75 ≦ R ≦ 1.00, RB = 3, and the correction coefficient a _ij shown in FIG. 2 and the correction coefficient (a _ij ) shown in FIG. 2 are switched so that the correction coefficient a _ij is selectively switched according to the value of RB. ), The T-a _ij graph showing the relationship is set. That is, one of the four T-a _ij graphs is selected according to the ratio of the input image signal, and the correction coefficient a _ij corresponding to the total T of the input image signals is selected based on the selected graph. is there.

As described above, by performing the correction calculation on the input image signal, the ink ejection amount can be suppressed more appropriately for the output images having various print duties, which contributes to the reduction of the seam stripes. In this case as well, it goes without saying that, as described above, the apparatus can be configured so that different correction coefficients are set in the normal mode and the high quality mode and the correction coefficients are switched according to the mode.

[0043]

Other Embodiments Here, a case will be described in which the correction calculation of the input image signal is performed using gamma conversion. FIG. 3 is a block diagram showing the configuration of the control unit of the recording apparatus according to the inkjet method according to the present embodiment. In FIG. 3, the same components as those of the control unit shown in FIG. 1 described in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted. Here, only characteristic parts of the present embodiment will be described.

The cyan, magenta, yellow, and black image signals 13C, 13M, output from the image processing unit 12,
13Y and 13Bk are input to the gamma selection unit 24. The gamma selection unit 24 includes image signals 13C, 13M, 13Y,
For example, 8-bit gamma selection signals 23C, 23M, 23Y, and 23Bk are output according to 13Bk. on the other hand,
The image signals 13C, 13M, 13Y, 13Bk are also input to the gamma conversion unit 28, where the image signals 13C, 13C
Gamma conversion is performed on M, 13Y, and 13Bk.

As shown in FIG. 4, the gamma conversion unit 28 stores a total of 256 gamma conversion tables from A0 to A255. Here, when the input for the gamma conversion is X and the output is Y, A0 to 0 indicating the relationship between X and Y
A255 has the following relationship, for example.
That is, A0; Y = X, A1; Y = 0.998X, A2;
Y = 0.996X, ..., An (n = 0 to 255); Y =
(1-0.002n) X.

Here, the closer the value of n is to "0", the lower to medium density portion of the image is shown, while the closer to "255",
The high density part of the image is shown. As described above, the gamma conversion function used in this embodiment is a linear function, and its slope becomes gentler toward the high density portion. This is to increase the correction amount of eye streaks that are likely to occur in the high density portion and decrease the correction amount of eye streaks that are less likely to occur in the low density portion. In this embodiment, the gamma conversion selection signal 2 output by the gamma selection unit 24
The gamma conversion table to be used is selected according to 3C, 23M, 23Y, and 23Bk. That is, when the gamma conversion selection signals 23C, 23M, 23Y and 23Bk are "0", A0 is selected, when "1", A1 is selected, and when "255", A255 is selected.

On the other hand, the gamma selection section 24 always outputs "0" when the control signal Z output from the control section 17 is "0", that is, when the pixel is not the end pixel, and the control signal is "0". 1 ", the image signals 13C, 13M, 13Y, 1
A gamma selection signal is output according to 3Bk. The relationship between the image signals 13C, 13M, 13Y, 13Bk and the gamma selection signal in this embodiment is such that the value of the gamma selection signal increases as the density value of the image signal increases, and the correction rate of the image signal increases.

Further, similarly to the above-mentioned embodiment, the gamma conversion table is set separately for the normal mode and the high quality mode, and this table is switched according to the selected mode. The image signal 19C corrected in this way,
19M, 19Y, and 19Bk are binarized by the binarization processing unit 20 and input to the recording heads 9C, 9M, 9Y, and 9Bk that form the recording head unit 9, and these recording heads are driven to record a color image. Is done.

Therefore, according to the present embodiment, the nozzles at the end of the print head depend on the density value of the input image signal and which nozzle of the print head ejects the ink ejected according to the image signal. Since the gamma conversion is applied to the input image signal so as to reduce the amount of ink ejected from, the seam streak in the recorded image can be significantly reduced.
Further, when the density value of the image signal is small, the gamma correction amount is set small, so that white dots are not generated by thinning the end dots in the low density portion.

In the described embodiment, the pixel to be corrected is not limited to one pixel at the end of each recording head, but may be two or more pixels. In that case, it is not always necessary to include the pixels at the ends, and the pixels may be selectable according to the type of the recording medium. In this way, by making the pixel to be corrected variable, it is possible to prevent streaks more effectively.

Furthermore, the present invention is applicable not only to a color image recording apparatus but also to an apparatus for performing gradation recording in a single color, such as an ink jet recording apparatus equipped with a plurality of recording heads having different ink discharge amounts, or a single recording head. The present invention can be effectively applied to an inkjet recording apparatus that performs gradation recording by using a plurality of times of printing and different driving conditions. The present invention is provided with a means (for example, an electrothermal converter or a laser beam) that generates thermal energy as energy used for ejecting ink, particularly in the inkjet recording system, and the state of the ink is determined by the thermal energy. Although the printing apparatus of the type that causes a change has been described, such a method can achieve high density and high definition of recording.

With regard to its typical structure and principle, for example, US Pat. Nos. 4,723,129 and 4,740 are applicable.
What is done using the basic principles disclosed in 796 is preferred. This method can be applied to both the so-called on-demand type and continuous type, but especially in the case of the on-demand type, liquid (ink)
By applying at least one drive signal to the electrothermal converter arranged corresponding to the sheet or liquid path in which the liquid crystal is held, which corresponds to the recorded information and causes a rapid temperature rise exceeding film boiling. Since the electrothermal converter is caused to generate heat energy to cause film boiling on the heat-acting surface of the recording head, as a result, bubbles in the liquid (ink) corresponding to the drive signal in a one-to-one relationship can be formed. It is valid. The liquid (ink) is ejected through the ejection openings by the growth and contraction of the bubbles to form at least one droplet. It is more preferable to make this drive signal in a pulse shape, because bubbles can be grown and contracted immediately and appropriately, and thus a liquid (ink) with excellent responsiveness can be achieved.

As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. If the conditions described in US Pat. No. 4,313,124 of the invention relating to the rate of temperature rise on the heat acting surface are adopted, more excellent recording can be performed. As the structure of the recording head, in addition to the combination structure (straight liquid flow path or right-angled liquid flow path) of the ejection port, the liquid path, and the electrothermal converter as disclosed in the above-mentioned specifications, a heat acting surface is also provided. A configuration using US Pat. No. 4,558,333 and U.S. Pat. No. 4,459,600, which disclose a configuration in which is arranged in a bending region, is also included in the present invention. In addition, Japanese Unexamined Patent Application Publication No. Sho 5-5 discloses a configuration in which a common slot for a plurality of electrothermal converters is used as a discharge portion of the electrothermal converters.
Japanese Patent Application Laid-Open No. 9-123670 and Japanese Patent Application Laid-Open No. Sho 5 (1993) -58
The configuration may be based on Japanese Patent Publication No. 9-138461.

Further, as a full line type recording head having a length corresponding to the maximum recording medium width that can be recorded by the recording apparatus, a combination of a plurality of recording heads as disclosed in the above-mentioned specification provides the length. Either of the structure satisfying the requirement or the structure as one recording head integrally formed may be used. In addition, the ink is integrated into the replaceable chip-type recording head, or the recording head itself, which can be electrically connected to the apparatus main body and can supply ink from the apparatus main body by being attached to the apparatus main body. A cartridge-type recording head provided with a tank may be used.

Further, it is preferable to add a recovery means for the recording head, a preliminary auxiliary means, etc., provided as a configuration of the recording apparatus of the present invention, because the effect of the present invention can be further stabilized. . Specific examples thereof include capping means, cleaning means, pressurizing or suctioning means for the recording head, preheating means using an electrothermal converter or another heating element or a combination thereof, and recording. It is also effective to perform a stable recording by performing a preliminary discharge mode in which another discharge is performed.

Further, the recording mode of the recording apparatus is not limited to the recording mode only for the mainstream color such as black, but the recording head may be integrally formed or a plurality of combinations may be used. Alternatively, the device may be provided with at least one of full-color mixed colors. In the embodiments of the present invention described above, the ink is described as a liquid, but an ink that solidifies at room temperature or lower, or one that softens or liquefies at room temperature may be used, or an ink jet system may be used. Generally, the temperature of the ink itself is adjusted within the range of 30 ° C to 70 ° C to control the temperature of the ink so that the viscosity of the ink is within the stable ejection range. Anything can be used.

In addition, in order to positively prevent the temperature rise due to thermal energy from being used as the energy for the state change of the ink from the solid state to the liquid state,
Alternatively, in order to prevent the ink from evaporating, an ink that solidifies in a standing state and liquefies by heating may be used. In any case, by applying heat energy, such as ink that is liquefied by applying heat energy according to the recording signal and liquid ink is ejected, or that begins to solidify when it reaches the recording medium. The present invention can be applied to the case where an ink having a property of being liquefied for the first time is used. In such a case, the ink is retained as a liquid or solid in the recesses or through holes of the porous sheet as described in JP-A-54-56847 or JP-A-60-71260. It may be configured to face the electrothermal converter. 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, as the form of the recording apparatus according to the present invention, in addition to the one provided integrally or separately as an image output terminal of information processing equipment such as a computer, a copying apparatus combined with a reader or the like, and further transmission / reception It may take the form of a facsimile machine having a function. The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0059]

As described above, according to the present invention, there is provided a recording head for performing recording by ejecting a recording agent onto a recording medium from a plurality of nozzles arranged in a predetermined direction corresponding to each of a plurality of recording elements. When performing image recording using, it is determined whether or not a nozzle for ejecting a recording material to perform recording based on the image-processed input image data is present at the end of the nozzle array, and the value of the input image data, When the value of the input image data is high density and the nozzle for performing image recording based on the input image data is at the end of the nozzle array, the value of the input image data is corrected according to the result of the determination. Therefore, there is an effect that it is possible to perform high-quality recording in which no streak is generated even in a high density portion of a recorded image.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a control unit of a recording apparatus according to an inkjet system which is a typical embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a total sum T of input image signals and a correction coefficient a _ij .

FIG. 3 is a block diagram showing a configuration of a control unit of a recording apparatus according to an inkjet method according to another embodiment.

FIG. 4 is a diagram showing a gamma conversion function for gamma conversion.

FIG. 5 is an external perspective view showing a schematic configuration of a conventional inkjet type recording apparatus.

FIG. 6 is a diagram showing a configuration of a multi-nozzle head.

FIG. 7 is a diagram illustrating beading of ink on a recording medium.

[Explanation of symbols]

 5 recording sheet 9 recording head unit 12 image processing unit 14 correction coefficient selection unit 18 correction calculation unit 20 binarization processing unit 24 gamma selection unit 28 gamma conversion unit 30 instruction button

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area B41J 3/04 103 X

Claims (13)

[Claims] 1. A recording apparatus for recording an image using a recording head for recording by discharging a recording material onto a recording medium from a plurality of nozzles arranged in a predetermined direction corresponding to each of a plurality of recording elements. An image processing unit for inputting image data and performing image processing, and a determination for determining whether or not a nozzle for ejecting the recording material to perform recording based on the image-processed data is present at the end of the array. Means, a correction means for correcting the value of the input image data according to the value of the input image data, and a determination result by the determination means, and a scanning means for scanning the recording head in a direction different from the predetermined direction. The correction means has a high density value of the input image data, and when the nozzle for performing image recording based on the input image data is at the end of the array, Corrected to reduce the value of the data, by a plurality of times of scanning by said scanning means, recording device and performing color recording by the recording head. 2. The recording apparatus according to claim 1, wherein the number of times of scanning by the scanning unit is variable. 3. The recording apparatus according to claim 2, wherein the correction amount by the correction unit is controlled according to the number of scans. 4. The recording head comprises a plurality of recording heads for recording with a plurality of color inks, and the input image data is density data of a plurality of color components. The recording device described. 5. The recording apparatus according to claim 4, wherein the plurality of colors are cyan, magenta, yellow and black. 6. The method according to claim 1, wherein the correction by the correction unit is performed on a pixel-by-pixel basis, and the determination as to whether or not the value of the input image data has a high density is based on the density value on the pixel-by-pixel basis. The recording device described. 7. The correction by the correction unit is performed in pixel units, and the determination as to whether or not the value of the input image data is high density is performed by summing the density values of density data of a plurality of color components related to the pixel unit. The recording device according to claim 4, wherein the recording device is based on 8. The recording apparatus according to claim 7, wherein the correction amount by the correction unit is determined in consideration of a ratio between a density value of each of the plurality of color components and a sum of the density values. . 9. An instructing means for instructing a first recording mode giving priority to recording speed or a second recording mode giving priority to recording quality, and according to the recording mode instructed by the instructing means,
The control means for controlling the number of scans for the same scan area in the recording operation is further included.
The recording device according to 1. 10. The recording apparatus according to claim 9, wherein the correction amount of the correction unit is changed according to the recording mode instructed by the instruction unit. 11. The recording apparatus according to claim 1, wherein gamma conversion is used for the correction by the correction means. 12. The recording apparatus according to claim 1, wherein the recording head is an inkjet recording head that performs recording by ejecting ink. 13. The recording head is a recording head which ejects ink by utilizing thermal energy, and is provided with a thermal energy converter for generating thermal energy applied to the ink. Item 2. The recording device according to item 1.