JP2003211647A - Inkjet recorder, and method for correcting ink concentration of the apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To record good gradational images by a cost-saving simple method. <P>SOLUTION: Concentration determination patterns in which regions recorded by a combination of an object ink and an ink having a lower concentration than that of the ink, and regions recorded by a combination of inks lower in the concentration than the object ink are recorded in a form of teeth of a comb are recorded to transmission films. A pattern which makes densities of two regions visually approximately equal is selected, thereby obtaining an ink relative concentration. The relative concentration of every ink to be used is obtained, and a combination of kinds of ink and the number of ink drops to be used for recording each gradation is determined to correct the concentration in accordance with the obtained relative concentrations. <P>COPYRIGHT: (C)2003,JPO

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 an ink density correction method for the apparatus, and more specifically, it uses a plurality of types of inks having different densities for the same color, and The present invention relates to correction of ink density in an inkjet recording apparatus that performs multi-gradation recording by changing the type of ink used during recording and the number of ink droplets.

[0002]

2. Description of the Related Art With the spread of information processing equipment such as copying machines, word processors, computers, etc., and communication equipment, an image is recorded using an ink jet recording head as a recording equipment for outputting information from these equipment. Recorders are rapidly spreading. Further, along with the higher quality and colorization of visual information in the above information processing equipment and communication equipment, there is an increasing demand for higher image quality and colorization in a recording apparatus.

As a recording apparatus to meet such a demand, there is a recording element array in which a plurality of recording elements are integrated and arranged in order to cope with the miniaturization of recording pixels, and an ink ejection port and a liquid path. Recording heads that integrate multiple
To support colorization, for example, cyan, magenta,
Generally, a plurality of inks are provided for each of yellow and black inks.

However, there is a certain limit in integrating the ink discharge ports and the liquid passages at a high density, and therefore there is also a certain limit in miniaturization of recorded pixels. In an image recorded by such a recording device, the dots forming each pixel are relatively large, so that graininess may be given in an image highlight portion having a low density and the image quality may become a problem.

On the other hand, instead of increasing the integration density of the ink ejection ports and the liquid passages, that is, instead of reducing the size of one pixel, the amount of ejected ink droplets is reduced and one pixel is recorded. A so-called multi-drop method is known in which the ink droplets are formed according to the density.
In the multi-drop method, the diameter of the ink dots recorded on the recording paper can be made relatively small, so that the graininess in the low density portion such as the highlight portion can be improved.

However, as the amount of ink droplets decreases, ejection becomes unstable, so there is a certain limit to the miniaturization of ink dots and a limit to high image quality. Further, in this method, the higher the recording gradation degree, the more ink droplets should be ejected per pixel, which leads to a decrease in recording speed, and the recording speed decreases as the image quality increases. A relationship occurs.

Further, as another method for improving the image quality without increasing the discharge port integration density, a density recording method using two kinds of inks of similar colors having different ink densities is known. In this method, a highlight portion or the like is recorded with a low-density light ink to make the graininess of the ink dots inconspicuous, and a high-density portion is recorded with a dark ink. Therefore, it is possible to form the high-density portion without increasing the number of ink droplets to be ejected as in the multi-drop method, and it is possible to suppress an increase in the amount of ink droplets used for recording and a decrease in recording speed. it can.

Further, as a pseudo halftone processing method by the above-described binarization processing or multivalued processing, a dither method, an error diffusion method, an average density preservation method, etc. are known.

The dither method is to binarize the data of each pixel by a threshold value for each pixel defined by a dither matrix.

The error diffusion method is described in, for example, the document R. FLOYD
& L.A. STEINBERG, "ANAADAPTIVE
ALGRITHM FOR SPETIAL GRA
YSCALE ”, SID 75 DIGEST, PP3
6 to 37, the multi-valued image data of the pixel of interest is binarized (converted to the darkest level or the lightest level), and the difference between the binarized level and the value before binarization. (error)
Is distributed to peripheral pixels and added.

An average density preservation method is disclosed in, for example, Japanese Patent Laid-Open No.
As described in Japanese Patent Laid-Open No. 210962, a threshold value is obtained based on already binarized binary data in the vicinity of a pixel of interest, or data including a binarized pixel of interest of black or white. The image data of the target pixel is binarized by this threshold value.

Further, multi-valued processing can be performed by making some changes or modifications to these various binarized processing methods.

However, even if these methods are used,
Problems arise depending on the type of image to be recorded.

For example, when recording a medical image, particularly a transparent image such as a chest X-ray image which is monochrome but requires extremely high gradation, it is a transparent image and therefore a visual effect on the density cannot be obtained. The resolution is improved. As a result, even when the dark and light inks are used, the density difference of each pixel is recognized, and the image is rough.
That is, it is necessary to further increase the number of recording gradations.

In the above method, in order to further increase the gradation of each pixel, the number of dark and light inks is increased, and a large number of multi-heads are required accordingly. That is, the cost will increase significantly.

Therefore, the inventors of the present invention have disclosed in Japanese Patent Laid-Open No. 10-3.
As described in Japanese Patent No. 24002, a plurality of types of ink having different densities can be ejected for one color, and ink droplets are selectively ejected a plurality of times within a predetermined limit for one pixel. A gradation recording method is proposed in which the number of gradations represented by this pixel is increased by ejecting (overlapping). According to this method, more gradations can be expressed without drastically increasing the number of dark and light inks and multi-heads.

[0017]

However, even in the above gradation recording method, the following problems occur.

For example, in the ink stored in the apparatus for a long period of time, there arises a problem that the concentration of the ink changes due to the influence of evaporation of water or the like in the supply system route.
In order to prevent this, it is conceivable that the ink supply system is made of an airtight material that shuts off all vapors. However, this countermeasure requires too much cost and makes the apparatus expensive.

Further, due to the difference in the characteristics (ejection amount) of the recording head, even if the ink having the same density is used, the recording density may be slightly different, or the intended density (gradation) cannot be recorded. Problems also arise. For example, let us consider a case where the print head B has a discharge amount larger than that of the print head A by about 5%. When the ink having a dye concentration of 0.2% is ejected from the recording head A and the ink having a dye concentration of 4% is ejected from the recording head B, the concentration ratio of the ink itself is 1:20, but on the recording medium. The dye ratio, that is, the concentration ratio is about 1: 2.
It becomes 1. Therefore, in the gradation recording method as described above,
There is a possibility that a state in which the recording density is higher than the low gradation becomes higher than that of the high gradation (reversal of gradation or density).

In order to prevent such gradation reversal, the actual recording density of the combination of dark and light inks used is measured, and the ink combination to be used for each gradation is determined according to the measurement result. However, in order to accurately measure the recording density, a measuring system having a considerable performance is required, and the apparatus becomes complicated and large and expensive. In this case, even if the measurement of the recording density is performed outside the apparatus, the labor becomes complicated, and equipment such as a density measuring device is also required.

The present invention has been made in view of the above circumstances, and provides an ink jet recording apparatus and an ink density correction method for the same, which can record a good gradation image by a simple method with low cost. The purpose is to provide.

[0022]

In order to achieve the above object, the ink jet recording apparatus of the present invention uses a plurality of types of inks having different densities for the same color, and uses inks for recording each pixel. An ink jet recording apparatus for performing multi-gradation recording by changing the type and the number of ink droplets, wherein a first area for recording using an ink whose density is to be determined among the plurality of types of ink, Relative of each ink determined by comparing the densities of the first and second areas with a pattern recording means for recording a density determination pattern in which a second area for recording using ink other than ink is adjacent The pattern recording means includes an input means for inputting information regarding density and a correction means for correcting the recording density based on the information regarding the relative density. In recording the use pattern is recorded with ink droplets equal number of pixels.

Further, the ink density correction method of the present invention which achieves the above object, uses a plurality of types of ink having different densities with respect to the same color, and the type of ink and the ink droplets used when recording each pixel. An ink density correction method for an inkjet recording apparatus that performs multi-gradation recording by changing the number, comprising: a first area for recording using an ink whose density is to be determined among the plurality of types of ink; A relative density of each ink is determined by comparing a density of the first and second areas with a pattern recording step of recording a density determination pattern in which a second area to be recorded using an ink other than ink is adjacent. And a correction step for correcting the recording density based on the relative density. When recording the density determination pattern in the pattern recording step, each pixel is recorded. Recording with the ink droplet number of correct.

That is, in the present invention, a plurality of types of ink having different densities with respect to the same color are used, and the type of ink and the number of ink droplets used for recording each pixel are changed to perform multi-gradation recording. In the inkjet recording device to perform,
Of a plurality of types of ink, a density determination pattern in which a first area to be printed using an ink whose density is to be determined is adjacent to a second area to be printed using an ink other than the ink is printed. Then, the relative density of each ink is determined by comparing the densities of the first and second areas, and the recording density is corrected based on the relative density, but when recording the density determination pattern, each pixel is made equal. Record with a few ink drops.

According to this, since each pixel of the density determining pattern is recorded with the same number of ink droplets, the amount of water and solvent ejected onto the recording medium for recording one pixel is substantially equal. By suppressing the influence of the change in the optical density due to the aggregation of the dye, the relative density of the ink whose density is to be determined can be easily determined with high accuracy by a simple method such as visual inspection.

Therefore, by appropriately determining the relative density of the ink at an appropriate timing, it is possible to always record a good gradation image.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION In the present specification, "recording"
Does (sometimes called "print") not only form significant information such as characters and figures, but also manifest itself so that it can be visually perceived by humans regardless of significance? Images, patterns, widely on recording media, with or without
It also represents a case where a pattern or the like is formed or a medium is processed.

The "recording medium" is not limited to paper used in a general recording apparatus, but is widely applicable to ink such as cloth, plastic film, metal plate, glass, ceramics, wood and leather. Things shall also be represented.

Further, the term "ink" (which may also be referred to as "recording agent") is to be broadly construed in the same way as the definition of "recording (printing)", and is given on a recording medium. , A liquid that can be used for forming an image, a pattern, a pattern, or the like, processing a recording medium, or treating an ink (for example, solidifying or insolubilizing a coloring agent in the ink applied to the recording medium).

[Basic Principle] First, the basic principle of the present invention will be described.

According to the present invention, for each of a plurality of inks of similar colors having different densities, a relative density ratio is simply calculated, that is, each pixel is recorded with a predetermined number of ink droplets by using a combination of different inks. A density determination pattern having one area is printed, the relative density ratio of each ink is determined based on whether the densities of the two areas are equal, and the result is used to print an image.

Specifically, in the density determination pattern, when there are n kinds of ink as D1, D2, ..., Dn from the one with the lowest ink density, each pixel in one area is D1 to D.
Recording with a predetermined number of ink drops from m-1 types of ink up to (m-1), and recording pixels of the other region with a predetermined number of ink drops from m types of ink from D1 to Dm, By recording these two areas adjacently, the densities of both areas can be compared by a simple method such as visual inspection.

The relative density ratio of the m-th ink is determined from the combination of the inks used for recording the areas where the density is recognized to be almost the same, and the relative density ratio of all the inks is determined by performing this in order from the ink with the lowest density. The concentration ratio is determined.

If the ink density for comparison is too low to be easily visually discerned, it is preferable to use the ink having a high density for recording both of the two areas. In this way, the densities of both areas to be compared can be converted into density areas with good visual sensitivity, so that it is easier to compare the densities of the two areas.

The reason why the number of ink droplets used for recording in each pixel of the two areas to be compared here is the same is as follows.

The ink contains various solvents and a dye that imparts color to the ink. When the ink density increases, that is, when the dye density increases, the ink is ejected from the recording head and lands on the recording medium. When doing so, the dyes may aggregate. When the dye aggregates, the interaction causes a change in the optical characteristics of the dye, and the density as an image is lower than that when the dye does not aggregate.

For example, an ink having a dye concentration of 1% is 600
In the case of ejecting 4 drops per 1 pixel of dpi and the case of ejecting 1 drop of ink of 4% dye concentration per 1 pixel of 600 dpi,
Generally, the latter has a lower concentration. For this reason, it is difficult to easily obtain the concentration ratio of both.

To prevent this, the present invention equalizes the number of ink drops used to record one pixel.

For example, one drop ejects 3% of 2% ink per pixel, and the other ejects 2 drops of 1% ink and 4 drops.
Eject one drop of ink. Alternatively, four drops of 2% ink are ejected on one side, and one drop of 4% ink, one drop of 2% ink, and two drops of 1% ink are ejected on the other side. By doing so, the amount of dye per pixel is the same in both cases, and the amounts of water and solvent in the medium are also substantially the same, so even if the dye aggregates, the influence of the agglomeration is almost equal, and the amount of dye is accurate. It is possible to obtain the relative density ratio of the ink.

Further, it is desirable to record the pattern for comparing the densities on a transmissive recording medium. This is because the dye exhibits a substantially constant density regardless of how the dye is fixed and distributed in the depth direction of the medium. On the other hand, in the case of a reflective recording medium, the density tends to be higher when the dye is fixed on the surface of the medium, which makes comparison difficult.

Furthermore, when this comparative pattern is recorded on a transmissive recording medium, the visual sensitivity is sufficiently higher than that of a reflective recording medium, so that it is possible to perform highly accurate density comparison even by visual inspection. As a matter of course, this comparison may be performed using a densitometer or the like.

The number of ink droplets that the recording medium can receive in the recording area of one pixel is greatly influenced by the amount of ink droplets, the recording medium, the recording density, etc., but is generally a value of about 3 to 8. If this value is too large, the problem of ink overflow will occur. Therefore, the number of ink drops used to record each pixel is
It is desirable to keep the number of ink drops within the range that the recording medium can accept.

Further, the concentration ratio of the dye contained in the ink is 1:
2: ...: 2 ^n-1, that is, when the dye density ratio is set so that the relationship of the density Ds of the ink Ds = 2 × D (s-1) is established, the ink droplets used for recording one pixel Even when the number of inks is limited to about 4, it is possible to compare the ink density ratios in various combinations, which is suitable when the ink amount is severely limited.

[First Embodiment] A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

In the embodiments described below, an ink jet printer for recording a chest X-ray medical image on a transmission type film by using a plurality of types of ink for black colors will be described as an example. .

<Schematic Description of Apparatus Main Body> FIG. 12 shows an ink jet printer I as a typical embodiment of the present invention.
It is an appearance perspective view showing the outline of the composition of JRA. In FIG. 12, the carriage HC that engages with the spiral groove 5004 of the lead screw 5005 that rotates via the driving force transmission gears 5009 to 5011 in conjunction with the forward / reverse rotation of the drive motor 5013 has pins (not shown). Then, it is supported by the guide rail 5003 and reciprocates in the directions of arrows a and b.
The carriage HC has an integrated ink jet cartridge I including a recording head IJH and an ink tank IT.
It is equipped with JC.

Reference numeral 5002 denotes a paper pressing plate, which is a carriage H.
The recording paper P is pressed against the platen 5000 in the moving direction of C. Reference numerals 5007 and 5008 denote photocouplers, which are home position detectors for confirming the presence of the carriage lever 5006 in this region and for switching the rotation direction of the motor 5013.

Reference numeral 5016 is a member that supports a cap member 5022 that caps the front surface of the recording head IJH.
Reference numeral 15 is a suction device for sucking the inside of the cap, and performs suction recovery of the recording head through the opening 5023 in the cap. 5
Reference numeral 017 is a cleaning blade, and 5019 is a member that allows this blade to move in the front-rear direction, and these are supported by a main body support plate 5018. Needless to say, a well-known cleaning blade can be applied to this example instead of this form.

Reference numeral 5021 denotes a lever for starting suction for suction recovery, which is a cam 5020 engaging with the carriage.
And the driving force from the driving motor is controlled by a known transmission mechanism such as clutch switching.

The capping, cleaning, and suction recovery are configured so that the desired processing can be performed at their corresponding positions by the action of the lead screw 5005 when the carriage comes to the area on the home position side. As long as the desired operation is performed at the timing, any of the above can be applied.

<Description of Control Configuration> Next, a control configuration for executing the recording control of the above-mentioned apparatus will be described.

FIG. 13 shows an ink jet printer IJRA.
3 is a block diagram showing the configuration of the control circuit of FIG. In the figure showing a control circuit, 1700 is an interface for inputting a recording signal, 1701 is an MPU, 1702 is an MPU1.
ROM storing a control program executed by 701, 1
Reference numeral 703 is a DRAM for storing various data (the above-mentioned recording signal, recording data supplied to the head, etc.). 17
A gate array (GA) 04 controls the supply of print data to the print head IJH, and also controls data transfer between the interface 1700, MPU 1701, and RAM 1703. Reference numeral 1710 is a carrier motor for carrying the recording head IJH, and 1709 is a carrying motor for carrying the recording paper. Reference numeral 1705 is a head driver for driving the recording head, and 1706 and 1707 are motor drivers for driving the carry motor 1709 and the carrier motor 1710, respectively.

The operation of the above control structure will be described. When a recording signal is input to the interface 1700, the gate array 1
A recording signal is converted between the 704 and the MPU 1701 to print data for printing. And the motor driver 1
The recording heads 706 and 1707 are driven, and the recording head is driven according to the recording data sent to the head driver 1705 to perform recording.

Although the control program executed by the MPU 1701 is stored in the ROM 1702 here,
It is also possible to add an erasable / writable storage medium such as an EEPROM so that the control program can be changed from a host computer connected to the inkjet printer IJRA.

As described above, the ink tank IT and the recording head IJH may be integrally formed to form a replaceable ink cartridge IJC, but the ink tank IT and the recording head IJH are separated. It may be configured so that only the ink tank IT can be replaced when the ink is used up.

<Ink and Recording Medium, etc.> The inks used in this embodiment are seven types D0 to D6 shown in Table 1 below, and the main concentration is water, and the relative concentration ratio is 1 as shown in Table 1. : 2: 4: 8: 16: 32 so that the dye is included. Further, various additives such as glycerin and urea are contained in an amount of 0.1 to 10% by weight in order to improve ejection stability.

[0057]

[Table 1]

The recording medium used in this embodiment is
Transparent film with ink receiving layer (Canon CF-
301), and the recording head has a nozzle density of 600 dp.
i, the discharge amount is 8.5 pl.

The limit on the number of ink discharges per pixel in this structure was about 4 to 5.

<Density Determining Pattern> FIG. 1 is a diagram showing an example of the density determining pattern used in the present embodiment. Such a pattern is printed to obtain the actual relative printing density of each ink. The example shown here is a determination pattern for the inks D3 to D6. FIG. 2 is an enlarged view of a part of the determination pattern of FIG. 1, and has comb-teeth-shaped regions a and b which are meshed with each other for easy visual comparison. The area b is recorded with different ink combinations.

FIG. 3 is a diagram showing a combination of inks used to record each part of the determination pattern shown in FIG. 1 and 3, the numbers on the top of each part are
The increase and decrease of the relative density ratio with respect to the dye density ratio shown in Table 1 of each ink are shown. The numbers in each column of FIG. 3 indicate the number of ink drops used to record each pixel of the pattern.

As shown in FIG. 3, in the present embodiment, the pixels of any portion are recorded using the same number of ink droplets (4 droplets), and the recording of the area a is the target of the relative density ratio determination. The ink whose density is lower than that of the ink is used, and the ink for which the relative density ratio is to be determined and the ink whose density is lower than that of the area b are used for printing in the area b. That is, a
The area B is recorded using the combination of inks D1 to D (m-1), and the area b is recorded using the combination of inks D1 to Dm. Therefore, the concentration ratio of Dm can be expressed by using D1 to D (m-1), and the relative concentration of Dm can be determined.

In the present embodiment, such a pattern is recorded, and the relative density of each ink is obtained by visually selecting the portions where the densities of the areas a and b are substantially equal.

More specifically, first, the relative density ratio of the D3 ink is determined. The top row of FIG. 1 is the D3 density determination pattern, and the top row of FIG. 3 is the ink combination used for printing each portion. From these three parts, the part where the two areas a and b are visually recognized to have almost the same density is selected. Usually, in an ink having a relative density ratio that is not so large as the ink of D3, the density change is small, and thus the density is often almost equal in the portion indicated by “X = 0” in FIGS. Also in the embodiment, it is recognized here that the densities of the regions a and b are almost the same. From this result, the relative density ratio of the D3 ink is determined to be "4", which is the same as the dye density ratio. This value is used to determine the relative density ratio after D4.

Next, the density ratio of D4 is obtained. The second line in FIG. 1 is the D4 density determination pattern, and the second line in FIG. 3 is the ink combination used for printing each portion. From this, a portion where the two areas a and b are visually recognized to have almost the same density is selected. In the present embodiment, “1+
It was recognized that the density was almost the same in the part of "X". As described above, regarding D3, it is recognized that the densities are almost the same in the part of "X = 0", and the relative density ratio is determined to be "4". Therefore, the density ratio of D4 is 2 × D3 + 1 = "9"
Is decided.

As described above, when the number above the portion where the density is determined to be almost the same in the density determination pattern (FIG. 1) of the present embodiment is χ, the relative density ratio of the Ds ink is The equation, Ds = 2 × D (s−1) + χ.

As described above, when the density ratio was sequentially determined up to D6 using the pattern of FIG. 1, D1: D
2: D3: D4: D5: D6 = 1: 2: 4: 9: 17:
It became 33.

<Distribution Table> FIG. 4 is a distribution table of six types of ink created by utilizing this result. The number in the ink column in the drawing indicates the number of ink droplets ejected for one pixel, and 0 indicates that the ink is not ejected. The dot number column shows the total number of ink droplets ejected for one pixel,
The total density ratio column is a value obtained by summing the relative density ratios of the respective inks obtained as described above.

The density level column shows values corresponding to 8-bit input image signals (0 to 255: 255 are black). That is, in the present embodiment, 55-value multi-value processing is performed. The value of this density level was obtained by using the relational expression (1) between the amount of dye (total density ratio of ejected ink) on the recording medium and the transmission density (OD).

O. D. = A ₀ + a ₁ d + a ₂ d ² + a ₃ d ³ + a ₄ d ⁴ (1) d: total value of concentration ratio (concentration of D6 is 1) a _{0 to} a ₄ : coefficient, a ₀ = 0. _{05, a 1 = 0.901, a} 2 = -1.235
3 × 10 ^-1 , a ₃ = -3.3643 × 10 ^-2 , a ₄ =-
5.2442 × 10 ^-3 FIG. 5 is a graph showing this curve.

<Data Processing> FIG. 6 is a diagram showing the flow of data processing in this embodiment. In the figure, reference numeral 1 denotes an ink distribution table creation unit, which creates the ink distribution table as shown in FIG. 4 by inputting the relative density ratios of the respective inks previously obtained, and the multi-value processing unit 3 Sent.

The input image data is subjected to γ correction and the like in the second preprocessing section, and further, although not necessary in the present embodiment, color conversion, color distribution and the like are performed as necessary. After this processing is performed, the multi-value quantization processing unit 3 performs the multi-value quantization processing using the distribution table determined in 1. In this embodiment, a general error diffusion process is used in the multi-value quantization process. The data distribution unit 4 distributes the discharge data for each ink.
This ejection data is sent to the six head drivers 5 corresponding to each ink, and an image is recorded.

<Processing for Recording> Here, the operation for recording a chest X-ray medical image on a transmission type film by the ink jet printer of this embodiment will be described with reference to FIG.
And it demonstrates with reference to the flowchart of FIG.

When the recording operation is instructed, it is first determined whether or not the density determination processing using the density determination pattern described above is necessary (step S101). Since the ink ejection characteristics depend on the print head as described above, it is preferable to perform the density determination process after the print head is replaced. Further, since the ejection characteristics also change with the aging of the print head, it is preferable to perform the density determination process at regular intervals in order to maintain the print quality even if the print head is not replaced.

If it is determined that the density determination processing is necessary, the process proceeds to step S102 and the density determination processing is executed. FIG. 15 is a flow chart of the density determination process. Recording of the density determination pattern (step S201), determination of the relative density of each ink based on visual comparison or the like (step S202), and further determination of the relative density of each ink. Creating an ink distribution table based on density (step S
203).

The determination as to whether or not the density determination processing is necessary is preferably performed by the printer side, but the density determination processing may be carried out by the ink jet printer alone, but it is connected to the printer. It may be configured to be executed on a host device that transmits a recording command or recording data. For example, if the host device is a personal computer, instructions for the user are sequentially displayed on the display screen, and the user follows the instructions to record the density determination pattern and input the relative density ratio of each ink. It is possible to configure.

When the density determination process is completed, the recording operation is performed (step S103). When it is determined in step S101 that the density determination process is unnecessary, this recording operation is performed immediately.

The image recorded in this manner did not show inversion of gradation, and was almost comparable to the image output by a general medical laser imager.

Further, in order to evaluate the result of this embodiment, 200 × 2 for each level of 76 which is a multi-valued number.
A batch of 00 pixels in size (about 8.5 mm square) was recorded and its transmission density was measured. The results are shown in the transmission density column of FIG. As you can see from this result,
There was no concentration reversal between levels. Also,
The correlation coefficient when the relationship between the density level and the transmission density was approximated by a straight line was R = 0.99987, which was a very good value.

[First Comparative Example] Table 1 was prepared without performing the work of determining the relative density ratio of the ink, which was carried out in the first embodiment.
The original dye concentration ratio of the ink shown in 1: 2: 4: 8: 1
Recording was performed using an ink distribution table created by using 6:32 as it was as the relative density ratio of the ink.

FIG. 7 is a view similar to FIG. 4, showing an ink distribution table created based on this density ratio. The column of transmission density shows the transmission density measured by recording the batch as in the first embodiment. In this case, for example,
No. 33 and No. 33. When the combinations of No. 34 are compared, the actual transmission density is No. Although the combination of 33 is larger, it corresponds to the lower concentration level, and the reversal of the concentration occurs. Therefore, a favorable image could not be obtained.

[Second Embodiment] The second embodiment of the present invention will be described below. The second embodiment is the above first
The system used in the embodiment is left as it is for about three weeks, and the same processing as in the first embodiment is performed to record and output a chest X-ray medical image on a transmission type film. In the following description, the description of the same parts as those in the first embodiment will be omitted, and the characteristic parts of the present embodiment will be described.

FIG. 8 is a diagram showing a pattern for density determination used in this embodiment. This pattern is the first
1 of the above embodiment, a batch for density measurement is added to the comb-shaped pattern shown in FIG. In the present embodiment, a portion where the densities of the two regions a and b of the comb-teeth pattern are approximately equal to each other is visually selected, and the transmission density of the batch portion is measured by a densitometer.

FIG. 9 is a diagram showing the measurement results of the transmission density of the batch portion of FIG. In the figure, the part indicated by halftone dots is the part where the densities of the two regions a and b were found to be almost equal by measurement, and this is in agreement with the results of visual observation.
From this, the relative density ratio of the ink in this embodiment is
It was determined to be 1: 2: 4: 9: 17: 32.

FIG. 10 is a view similar to FIG. 4, showing an ink distribution table created based on this density ratio.
The column of transmission density shows the transmission density measured by recording the batch as in the first embodiment. As can be seen from this result, no concentration reversal or the like occurred between the levels. When a chest X-ray image was recorded based on this distribution table in the same manner as in the first embodiment, a good gradation image was obtained.

[Second Comparative Example] Table 1 was prepared without performing the work of determining the relative density ratio of the ink, which was carried out in the second embodiment.
The original dye concentration ratio of the ink shown in 1: 2: 4: 8: 1
Recording was performed using an ink distribution table created by using 6:32 as it was as the relative density ratio of the ink.

FIG. 11 is a diagram showing an ink distribution table created based on this density ratio. The column of transmission density shows the transmission density measured by recording the batch as in the first embodiment. In this case, for example, No. 33
And No. When the combinations of No. 34 are compared, the actual transmission density is No. Although the combination of 33 is larger, it corresponds to the lower concentration level, and the reversal of the concentration occurs. Therefore, a favorable image could not be obtained.

[Other Embodiments] It is preferable that the ink density determination process according to the present invention is performed every time the print head is replaced or every fixed period, as described above. Can be configured to start the density determination process from the printer driver or application software installed in the host device that transmits the print command or print data, and the density determination process is executed as part of the printer driver or print utility software. It can also be configured to be performed.

In the above embodiment, the general error diffusion method is used in the multi-value quantization process, but the multi-value error diffusion method, the multi-value dither matrix method, etc. may be used as the multi-value quantization method in the present invention. Various multi-valued methods can be used and are not particularly limited.

The ink jet recording method used in the present invention can be applied to any of the conventionally known ink jet recording systems in which droplets of ink are ejected from nozzles for recording by utilizing various driving principles. Is. As a typical example, in the method described in Japanese Patent Application Laid-Open No. 54-59936, the ink subjected to the action of thermal energy undergoes a rapid volume change, and the action force due to this state change ejects the ink from the nozzle. An inkjet method can be used.

Regarding its typical structure and principle, see, for example, US Pat. Nos. 4,723,129 and 4740.
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 transducer arranged corresponding to the sheet or liquid path in which is stored, which corresponds to the recorded information and gives a rapid temperature rise exceeding nucleate 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.

Due to the growth and contraction of the bubbles, the liquid (ink) is ejected through the ejection openings to form at least one droplet. It is more preferable to make this drive signal into a pulse shape, because the bubble growth and contraction are immediately and appropriately performed, so that the ejection of the 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 constitution of the recording head, in addition to the combination constitution of the ejection port, the liquid passage, and the electrothermal converter (the straight liquid passage or the right-angled liquid passage) as disclosed in the above-mentioned respective specifications, U.S. Pat. No. 4,558,333, US Pat. No. 4,558,333, which discloses a configuration in which the heat-acting surface is arranged in a bending region.
The structure described in the specification of No. 59600 is also included in the present invention. In addition, for multiple electrothermal converters,
Japanese Unexamined Patent Publication No. 59-123670, which discloses a structure in which a common slot is used as a discharge portion of an electrothermal converter, and Japanese Patent Laid-Open No. 59-63, which discloses a structure in which an opening for absorbing a pressure wave of thermal energy is associated with the discharge portion A configuration based on Japanese Patent No. 138461 may be used.

Further, as a full line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, the length can be increased by combining a plurality of recording heads as disclosed in the above-mentioned specification. Either of the structure satisfying the requirement or the structure as one recording head integrally formed may be used.

In addition to the recording head of the cartridge type in which the ink tank is integrally provided in the recording head itself described in the above-described embodiment, the recording head is mounted on the main body of the apparatus to electrically connect with the main body of the apparatus. A replaceable chip-type recording head that enables various connections and supply of ink from the apparatus main body may be used.

Further, it is preferable to add a recovery means for the recording head, a preliminary means, etc. to the structure of the recording apparatus described above because the recording operation can be made more stable. Specific examples thereof include capping means for the recording head, cleaning means, pressurizing or sucking means, an electrothermal converter or a heating element other than this, or preheating means by a combination thereof. Further, provision of a preliminary ejection mode for performing ejection different from recording is also effective for stable recording.

Further, the recording mode of the recording apparatus is not limited to the recording mode of only 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.

Even when the present invention is applied to a system composed of a plurality of devices (for example, host computer, interface device, reader, printer, etc.), a device composed of one device (for example, copying machine, facsimile) Device).

Further, an object of the present invention is to supply a storage medium (or recording medium) recording a program code of software for realizing the functions of the above-described embodiment to a system or apparatus, and to supply a computer of the system or apparatus ( Alternatively, by the CPU or MPU) reading and executing the program code stored in the storage medium,
It goes without saying that it will be achieved. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.
Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also based on the instruction of the program code,
An operating system (OS) running on the computer does some or all of the actual processing,
It goes without saying that the processing includes the case where the functions of the above-described embodiments are realized.

Further, after the program code read from the storage medium is written in the memory provided in the function expansion card inserted in the computer or the function expansion unit connected to the computer, based on the instruction of the program code, , The CPU provided in the function expansion card or the function expansion unit performs some or all of the actual processing,
It goes without saying that the processing includes the case where the functions of the above-described embodiments are realized.

When the present invention is applied to the above storage medium, the storage medium stores the program code corresponding to the above-described flowchart (shown in FIG. 14 and / or FIG. 15).

[0103]

As described above, according to the present invention,
Since each pixel of the density determination pattern is recorded with the same number of ink droplets, the amount of water and solvent ejected onto the recording medium is approximately equal for recording one pixel, so that the optical density changes due to the aggregation of dyes. It is possible to easily determine the relative density of the ink whose density is to be determined accurately and easily by a simple method such as visual inspection while suppressing the influence of.

Therefore, by appropriately determining the relative density of the ink at an appropriate timing, it is possible to always record a good gradation image.

[Brief description of drawings]

FIG. 1 is a diagram showing a pattern for determining a relative density ratio of ink in a first embodiment of the present invention.

FIG. 2 is a detailed view of the pattern of FIG.

FIG. 3 is a diagram showing an ink distribution table used to record the pattern of FIG.

FIG. 4 is a diagram showing an ink distribution table according to the first embodiment of the present invention.

FIG. 5 is a graph showing a relationship between a dye amount and a transmission density on a recording medium.

FIG. 6 is a functional block diagram showing a flow of data processing according to the first embodiment of the present invention.

FIG. 7 is a diagram showing an ink distribution table in a first comparative example.

FIG. 8 is a diagram showing a pattern for determining a relative density ratio of ink in the second embodiment of the present invention.

9 is a diagram showing a measurement result of transmission density of each region of the pattern of FIG.

FIG. 10 is a diagram showing an ink distribution table according to the second embodiment of the present invention.

FIG. 11 is a diagram showing an ink distribution table in a second comparative example.

FIG. 12 is a diagram showing an appearance of a printer which is a preferred embodiment of the present invention.

13 is a block diagram showing a control configuration of the printer of FIG.

FIG. 14 is a flowchart showing a process when recording is performed according to the first embodiment of the present invention.

15 is a flowchart of the density determination process of FIG.

[Explanation of symbols]

1 Ink combination table creation section 2 Pretreatment section 3 Multi-value processing unit 4 Data distribution unit 5 head driver

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Claims (18)

[Claims] 1. An ink jet recording apparatus for performing multi-gradation recording by using a plurality of kinds of inks having different densities for the same color and changing the kind of ink and the number of ink droplets used when recording each pixel. Of the plurality of types of ink, a first area for printing with an ink whose density is to be determined and a second area for printing with an ink other than the ink are adjacent to each other. Pattern recording means for recording a determination pattern; input means for inputting information on the relative density of each ink determined by comparing the densities of the first and second regions; and based on the information on the relative density The pattern recording means records each pixel with an equal number of ink droplets when recording the density determination pattern. An ink jet recording apparatus according to symptoms. 2. The correction unit includes an ink combination determination unit that determines a combination of the type of ink and the number of ink drops to be used corresponding to each gradation value. Inkjet recording device. 3. The second area is recorded with a combination of inks having a lower density than the ink whose density is to be determined, and the first area is recorded with the ink whose density is to be determined and the ink whose density is to be determined. The ink jet recording apparatus according to claim 1 or 2, wherein the ink is recorded with a combination of low density inks. 4. The ink having a darker density than the ink for which the density is to be determined is used for recording in both the first and second areas. The inkjet recording device described. 5. The method according to claim 1, wherein the plurality is n and the ratio of the dye concentrations contained in the n kinds of ink is represented by 1: 2: 4: ...: 2 ^n-1 . 5. The inkjet recording device according to any one of items 4 to 4. 6. The information about the relative density of each ink is represented by an integer ratio with the density of the lowest density ink being 1.
Inkjet recording apparatus according to the item. 7. The density determination pattern includes a plurality of combinations of the first area and the second area, and each second area is recorded with a different ink combination. Item 7. The inkjet recording device according to any one of items 1 to 6. 8. The ink jet recording apparatus according to claim 1, wherein the pattern recording unit records the density determining pattern on a transmissive recording medium. 9. The ink jet recording according to claim 1, further comprising a plurality of recording heads corresponding to the plurality of types of ink, which eject the ink by utilizing thermal energy. apparatus. 10. An inkjet recording apparatus for performing multi-gradation recording by using a plurality of types of ink having different densities for the same color and changing the type of ink and the number of ink droplets used when recording each pixel. An ink density correction method, wherein a first area of the plurality of types of ink is printed using an ink whose density is to be determined, and a second area is printed using an ink other than the ink. A pattern recording step of recording adjacent density determination patterns, a density determination step of determining the relative density of each ink by comparing the densities of the first and second regions, and a recording based on the relative density. A correction step for correcting the density, wherein each pixel is recorded with an equal number of ink droplets when the density determination pattern is recorded in the pattern recording step. Concentration correction method. 11. The method according to claim 10, wherein the correction step includes an ink combination determination step of determining a combination of an ink type and an ink drop number to be used corresponding to each gradation value. Ink density correction method. 12. The second region is recorded with a combination of inks having a lower density than the ink for which the density is to be determined, and the first area is for the ink to be determined for the density and the ink for which the density is to be determined. The ink density correction method according to claim 10, wherein the ink is recorded with a combination of low density inks. 13. The ink according to claim 10, wherein an ink having a darker density than that of the ink whose density is to be determined is used for recording both the first and second areas. Ink density correction method described. 14. The plurality is n, and a ratio of dye concentrations contained in n kinds of ink is 1: 2: 4: ...: 2 ⁿ⁻¹ ,
The ink density correction method according to any one of claims 10 to 13, wherein 15. The ink density correction according to claim 10, wherein the relative density of each ink is represented by an integer ratio with the density of the lowest density ink being 1. Method. 16. The density determining pattern is the first pattern.
16. The ink density correction according to claim 10, wherein a plurality of combinations of the areas and the second areas are included, and each of the second areas is recorded with a different combination of inks. Method. 17. The ink density correction method according to claim 10, wherein the density recording pattern is recorded on a transmissive recording medium in the pattern recording step. 18. A storage medium storing a code of a program for realizing the ink density correction method according to claim 10. Description: