JPH071748A - High-fidelity printing method and ink jet printing cartridge - Google Patents

Abstract

PURPOSE: To largely improve image quality and resolution while minimizing the sacrifice of cost and a printing speed by supplying an ink droplet to the selected pixel position on a printing medium in a reduced amt. over two stages accompanied by different operations of a carriage. CONSTITUTION: In an ink jet printer 10 wherein a printing cartridge 16 housing three separate color pigments (C, Y, M) and a printing cartridge 18 housing a color pigment (K) are mounted on the carriage 14 freely moved along a horizontal rod 12, the cartridges 16, 18 are remodeled so as to supply an ink droplet whose vol. is half that of a usual ink droplet in the case of a 'single position', that is, the same resolution. When the carriage 16 passes on a printing medium firstly, an ink droplet is not applied to each pixel position corresponding to a desired image or a half vol. of an ink droplet is applied thereto. When the carriage passes on the printing medium for the second time, a remaining half- vol. ink droplet is applied if necessary to form an image.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates generally to methods and apparatus for improving ink jet printing, and more particularly for improving image quality and resolution while minimizing the cost and print speed penalty. , Controlling the amount of ink added to each pixel.

[0002]

BACKGROUND OF THE INVENTION The use of inkjet printing systems has grown dramatically in recent years. It is believed that this is due to the significant reduction in price while the resolution and print quality are greatly improved. Inkjet printers today are significantly lower than the prices of comparable products a few years ago,
Provides sufficient print quality for many commercial and home applications. In such a situation,
Research and development for improving inkjet printing quality is ongoing. In general, its print quality falls short of the more expensive techniques of photographic printing, offset printing and gravure printing. Therefore, there remains a problem of improving the print quality of the inkjet printing system without increasing the cost. To the effort to achieve this goal, the drop-on-demand method and most continuous inkjet methods have the fundamental limitation of being binary. That is, it is only possible to add ink to each pixel of the paper (or other output medium) or not to add ink at all. This severely limits the grayscale resolution.

Color inkjet printers are usually
Only three or four color inks (magenta, yellow, cyan and possibly black) are used. Therefore, each pixel can be printed with a very limited range of shades using different combinations of these colors. The range of colors that can be formed in this way, that is, the color resolution is 2 to
If three or more drops of ink are applied, the amount becomes too large, and bleeding and mottle are likely to occur, which is severely restricted. Conventionally, such a constraint is
It has been somewhat mitigated by so-called dither technology. This technique divides the image into a number of square matrices. Each matrix is, for example, 4x
It has a fixed number of pixels, such as 4 pixels or 8 × 8 pixels. Different hues can be obtained by changing the number of pixels to which ink is applied for each matrix. Therefore,
A 4x4 matrix can produce 16 different shades and white (colorless), an 8x8 matrix can obtain 64 shades in addition to white. Therefore, dithering reduces the effective spatial resolution for all but the base system colors. The base system color of a system is a color that can be printed in a single grid. Furthermore, advanced dithering technology and digital halftoning (digital halftoning)
ing) technique, if the ink droplets are relatively large, the image is generally rough and the graininess of the print is visible to the naked eye.

The quality of a printed image can be dramatically improved if the color density of each pixel can be continuously changed. This can be changed almost continuously by using very small pixels so that they cannot be resolved with the naked eye at normal distance. Therefore, for example, an image formed on a grid of 100 pixels for 1 mm has the same appearance as an image of a truly continuous tone as seen in photographic color printing when viewed with the naked eye. become. The question is whether such good resolution can be achieved at low cost.

In the art, each print dot is formed with two ink drops of at least the same color in order to reduce the effect of nozzle clogging or partial inactivity. It is known to eject different ink drops from different nozzles. The second drop of ink is added during the second pass or return of the print head. A technique of this kind is disclosed in U.S. Pat. No. 4,963,882. This "double dot" technique does not improve resolution.

"Gray Scale Printin"
Vaugh entitled "g with Ink Jets"
U.S. Pat. No. 4,494,128 to T., a thermal ink jet system for mixing a vehicle (diluent) with ink during the actual jet printing process to provide a visible change in print density (grayscale). An inner valve device is disclosed. It has been proposed to apply such a system to color mixing in a transducer chamber. Such techniques are difficult to implement in practice.

Hertz et al., US Pat. No. 4,620,
No. 196 discloses a method and apparatus for high resolution inkjet printing. The Hertz patent discloses a fairly complex and therefore expensive system. This patent describes a continuous flow of very small ink drops, 1 per second.
An inkjet printing system of the kind that is ejected at a very high constant frequency of million drops has been disclosed.
An electrical signal called a "print pulse" controls the electrodes surrounding the drop formation point, and accordingly the ink drops produced from the continuous jet are not charged. Then, when such an ink drop passes through the electric field,
The charged ink drops are deflected and enter the catcher,
The ink drops that have not been charged are not deflected and are ejected onto the recording paper. According to the Hertz patent, the amount of ink applied to each pixel is controlled by varying the number of ink drops applied to those pixels. The number of ink drops is controlled by the duration or pulse width of the control signal. This is because the ink drops are fired at a constant velocity. This technique provides high resolution. For example,
In this patent, 0 to 30 ink drops are applied to one pixel to obtain an almost continuous resolution and control the color density.

As stated in the Hertz patent itself, "the principles of this invention appear to be relatively simple, and in fact simple, but their practical application is extremely difficult." The Hertz et al. Patent lists some of the problems with the printing systems described above. For example, the drop diameter must be very small, and the drop generation rate must be generally high and essentially constant. Further, since minute ink droplets are subject to high air resistance, not only individual ink droplets but also ink droplet groups tend to coalesce before reaching the paper, which makes the graininess noticeable. Therefore, to ensure a high drop generation rate, the jet diameter must be small and its velocity must be high. Excitation of the jet drop formation process with ultrasonic waves is essential to ensure a high and constant drop formation rate and to control the drop diameter. What is needed is an electrical device that causes the drops of ink to reach the paper to be slightly charged so that the same charge creates a repulsive force between the drops to counteract the tendency of the drops to coalesce. These and other challenges, and the added complexity they add, make the device very expensive. Therefore, it is desirable to obtain high quality output from low cost inkjet printing systems.

US Pat. No. 4,499,479 to Chee-Shuen et al. Describes grayscale printing using a cylindrical piezoelectric transducer printhead for varying ink drop volume in real time. . That is, the converter is divided into sections that can be activated separately. A drive signal selectively activates one or more of these sections to form an internal pressure wave in response to the print data to form the desired amount of ink drop. The amplitude of this drive signal can be varied to further control the drop volume. Further adjustment can be performed by changing the pulse width of the drive signal. However, the control means for providing such a drive signal is relatively complex. Moreover, this method of segmenting the transducer is not applicable to thermal inkjet printing.

Miyakawa US Pat. No. 4,617,
No. 580 discloses an inkjet printer having a detector that determines whether the print medium is paper or second base paper. If the latter, then this printer
In general, a plurality of ink droplets are attached to one pixel area, and the respective ink droplets are slightly offset from each other in the horizontal direction and / or the vertical direction to improve the application range of the medium required for inkjet printing on the second base paper There is. According to this patent, the ink dots can be shifted vertically by making the feeding pitch of the recording paper fine, and by shifting the delay time of the ejection timing or by reducing the ejection pitch in the horizontal direction. Can be shifted horizontally. Since the second base paper has a low diffusivity and the size of the color dot is smaller with respect to the amount of ink droplets, the ink droplets are slightly displaced to improve the application range for the pixel area. However, reducing the paper feed pitch (vertical direction) and / or finer horizontal resolution (ie, carriage positioning) requires significant improvements in the mechanical assembly involved. Leading to increased costs.

[0011]

OBJECTS OF THE INVENTION It is an object of the present invention to provide a method and apparatus for implementing a method of improving gray scale and color resolution of a thermal ink jet printing system without requiring increased print grid resolution. To do.

[0012]

SUMMARY OF THE INVENTION Accordingly, in accordance with the present invention, the well-known carriage and paper handling electromechanical assembly is substantially used as is. The present invention improves resolution in a given pixel grid by better controlling the total drop volume and / or ink dye concentration.

According to the first aspect of the invention, the nominal amount or "unit amount" of ink is defined as the amount of ink selected for approximately one pixel position on the print medium. That is, this unit amount is a normal amount of one ink droplet ejected from the nozzle of the pen. In order to improve the print quality, the amount of ink drops is reduced below this unit amount, and the printing operation is performed a plurality of times to attach two or more ink drops of such reduced amount to each pixel position. To enable. Thus, a unit amount of ink can be formed (or approximated) by applying at least two reduced amounts of ink drops to the same pixel location.

In one example, the reduced amount is equal to half the unit amount. This has the advantage that the resolution of the print density is increased by allowing the selection of three levels, namely zero, half and unit quantities, rather than the usual binary mode. The increased cost of increasing color (or grayscale) resolution is not as great because print grid resolution (eg 300 DPI) is maintained. Therefore, no modification of the printer mechanism or drive means defining the print grid is required to use the present invention.

A second feature of the invention is the provision of at least two different drop volumes in a printing system. Such two quantities can be implemented in one print cartridge or with multiple print cartridges. As an example, a print cartridge in which one half of the nozzles is configured to eject one-third unit amount of ink drops and the other half is configured to eject two-third unit amount of ink drops. is there. If both drop volumes are available on the same horizontal line ("in-line pen layout" -see Figure 3A), the printhead only needs to make one pass to get four possible ink volumes, namely 0, 1 /
Any one of 3, 2/3, or 3/3 (i) unit ink volume is applied to each grid position, thereby increasing resolution. When the same printhead is passed again, a total of 4/3, 5/3, 6/3 (ii) units of ink is applied to each grid position, for a total of 7 possible levels. Offset pen layout (Fig. 3 (B)
The same 7 levels are possible with 4 passes using (see). If this principle is expanded to further increase the amount of ink droplets and the number of times the print head passes, the dot size per unit area to be printed can be further reduced, and the number of dots can be further increased to further improve the resolution. it can.

A third aspect of the invention is to vary the ink colorant concentration, also called "dye loading",
It is to improve print quality. Dye load is the relative amount of dye or colorant in the printing solution that distinguishes it from the carrier or solution portion of the ink that evaporates as soon as the ink is applied to the medium. The dye loading of the ink affects the color density of the printed dots. Therefore, reducing the dye load in the ink can be used to improve spatial resolution and increase the number of base system colors.

A fourth aspect of the invention is a printing method that utilizes multiple dye loads provided on a single pen. For example, a pen with three chambers can be used to provide three different dye loads for a particular color ink. Three gray levels and two printing operations provide 27 grayscale levels. Three dye densities can be provided for each color in one color system. In the CYM system,
For example, this configuration allows 19,683 dot combinations (27 cyan) x (27 magenta) x (27 yellow), which provides 19,683 basic system colors.

The fifth feature of the present invention is a combination of techniques for reducing the ink amount and the dye load. By controlling these two variables individually, the resolution can be greatly improved even in this case without changing the driving mechanism, hardware and software forming the printing grid. Of course, the advantages of the present invention are applicable to any printer grid size.

The above objects, features and advantages of the present invention, as well as other objects, features and advantages, will be more apparent from the following detailed description of the embodiments with reference to the drawings.

[0020]

【Example】

[Outline of Printer Device] In FIG. 1, reference numeral 10 denotes a discontinuous inkjet printing system. Inkjet printers of this type are well known in the field of printing technology, for example Hewlett-Packard Desk.
There is Jet 550 CTM. A key component of this printer is a bar 1 that extends the full width of the printer 10.
2 is included. A carriage 14 that linearly moves along the horizontal bar 12 is attached to the horizontal bar 12. Figure 1
Although not shown in FIG. 3, means for advancing the carriage along the horizontal bar 12 is provided. However, such means are well known in the art and include stepper motors and gears. The carriage 14 is the print cartridge 1
Designed to receive 6 and 18. The print cartridges 16 and 18 each have separate ink reservoirs. In this example, the print cartridge 16 contains three separate color pigments (C, Y, M),
The print cartridge 18 contains the color pigment (K) of the carriage 14. A plurality of inkjet nozzles are arranged under each print cartridge, and ink stored in the corresponding cartridge passes through these nozzles. The ability to selectively actuate these nozzles to form the desired image on the print medium is well known in the field of ink jet printing.

The printing medium such as paper provided in the medium tray 20 is usually driven by a set of driving rollers (not shown).
It is removed from the media tray 20 and advanced along axis X in a controlled manner. As the print media passes along the X-axis, the carriage 14 includes print cartridges 16 and 1.
It is advanced along a horizontal bar 12 to position 8 on the print medium. Once the print cartridges 16 and 18 are positioned in the desired position, the appropriate nozzles in either or both cartridges are operational. The enabled nozzle forms an ink drop therein, which is then ejected onto the print medium underneath. The carriage 14 is then typically further advanced along the bar 12 by an amount that defines the horizontal resolution of the printer,
This entire process is repeated. After the carriage 14 has moved across the width of the print medium, the print medium is fed by a predetermined amount, usually defined by the vertical resolution of the printer, and the carriage reverses its path along the crossbar 12. Return to.

FIG. 2 shows an example of the structure of the print nozzles on the conventional print cartridge 22. In this example, each nozzle is represented by a small circle. These print nozzles are arranged in six parallel vertical rows (here, vertical means perpendicular to the running of the print cartridge). In this example, there are 16 nozzles in each row, but this number can be selected depending on the design. Each pair of rows, for example row 24 and row 26, is vertically offset from each other by half the distance between adjacent nozzles in the row. This improves the vertical resolution. For example, it is difficult to implement inkjet nozzles that are 1/300 inch apart in one row. Three
00DPI printing involves providing two parallel nozzle rows, such as rows 24 and 26, for each color of ink, with the nozzles in each row being vertically spaced 1 / 150th of one another. Achieved by By offsetting each row by 1/150 inch, one nozzle of the two rows can be activated appropriately on demand 30
A vertical resolution of 0 DPI can be obtained.

Printing With Reduced Ink Droplet A dot is a dot of ink printed on paper or other media. If the dots are made smaller, it becomes difficult to identify individual dots, and the print quality is improved. For example, the smaller the dots, the brighter the tone can be made smoother and less grainy. Increasing the number of dots in an area increases the amount of information displayed in that area of the paper, thereby increasing the number of possible colors and gray scales. Smoother color changes between hues and more uniform midtone colors. In addition, improved draft quality, composite black (compositebl)
improvement of ack, secondary color (secondary col)
or)) becomes clearer, and the degree of freedom in balancing dyes is increased.

First, the unit ink drop volume is defined as the normal volume selected to fill approximately one pixel position on a print medium. To improve print quality, the ink drop volume is reduced below this unit volume, and multiple print operations are used to provide multiple reduced volumes of ink drops for each operation at each grid or pixel position. Add 1 drop. One grid position is the finest division position where the printing device can place dots. For example, a 300 dot / inch (DPI) machine prints at 1 / 300th of each grid position. According to the present invention, a reduced number of dots are printed at each grid position by printing one dot each time the print cartridge passes each grid position. Therefore, the total number of dots printed at each position is less than or equal to the number of printing operations (this is not always the case for multi-ink quantity printing using the inline pen layout described below).

In one example of an embodiment of the present invention, the print cartridge is modified to provide a "unit dose" or half the "normal" drop volume for the same resolution. As the carriage first passes over the print medium, either no ink drops or half the ink drops are deposited at each pixel location, depending on the desired image. When the carriage passes over the print medium a second time, the printer can either re-ink or not drop half the volume of ink at any pixel location. In this way, a combination of three ink droplets can be obtained for each pixel position with two printing operations. That is, there are no ink drops, one drop, and two drops. In a three color system, this method provides a combination of 27 dots. Ie 6
One primary, twelve secondary colors, eight composite black or near neutral (and white).

In FIG. 4, the selected dot combinations are shown on a predetermined rectangular printing grid 30 consisting of a regular array of pixel areas, such as pixels 32, 34. Colors are indicated by the shaded directions as shown for yellow, cyan, and magenta. The drop volume is significantly less than the unit volume that nearly fills one pixel area (one pixel is more completely close by shifting the smaller and smaller nominal dot size vertically and / or horizontally). This "phase shifting" can be done in a pen layout or by changing the dot firing timing, but changing the print grid is generally undesirable.)

In FIG. 4, the four adjacent pixels forming the upper left quadrant 36 of the printing grid 30 each contain a single dot of each color. All three colors are printed after every two movements, for a total of six ink drops. In the upper right quadrant 38, magenta and cyan dots are also 1 in each of the two printing operations.
Dots are printed dot by dot, for a total of four ink drops. One dot of yellow ink and one dot of magenta ink are shown in the lower left quadrant 40, and finally, magenta and cyan dots are shown in the lower right quadrant 42. The lower quadrant can be printed in one or two printing operations. FIG. 4 shows only a few of the many possible dot combinations. The following table 1 lists 27 possible combinations.

[0028]

[Table 1]

It should be noted that the printed image obtained by the selected printing order of the dots of different colors has a slight color shift compared to the case of another order. This effect can be used to provide a range of basic system colors that is larger than those described herein.

Computer source data (image data)
Is usually converted by a printer driver implemented in software.
This driver software uses digital halftoning technology to convert the image data to the resolution of the target output device. That is, the present invention can be applied to a cyan / yellow / magenta printing system of 300 × 300 DPI. Digital halftoning uses 24 bits / pixel (8 bits / pixel) of the source data (in the printer driver).
Color) to 6 bits / pixel. This 6-bit data is 1 for cyan, magenta, and yellow.
Each consists of three 2-bit components. These two
Each one bit controls one-half unit amount of ink drop at one print grid position.

Printing using multiple printing operations has another advantage. This improves the management of ink bleed and makes the dot placement errors of the mechanism and pen less noticeable. The increased cost of implementing this print mode is minimal due to the constant grid resolution. Fine pitch control to shift the dots, as disclosed in the Miyakawa patent, is not required. Despite the problem of increasing the time to print a page, multiple printing operations are already used in many applications for other reasons, such as the so-called "singling" technique. In addition, the print mode selection can be under user control, and the user can disable the high resolution print mode for faster draft quality output. User selections are entered into the driver software to control halftoning.

This principle of the present invention can be used to further reduce the amount of ink to improve printing quality. For example, 1/3 of the unit amount of ink droplets can be printed by three printing operations. Similarly, the ink amount can be reduced to 1/4 of the unit ink drop amount, and in this case, the printing operation is performed four times. A drop volume of 1/4 provides 5 levels of density at each grid location for each primary color ink (4 levels of ink and no ink). Given five levels, a combination of 5 × 5 × 5 or 125 primary color ink drops is obtained at each grid location in a three color system. Therefore, this system has 125 base system colors.

For example, the amount of ink drops may be further reduced to the nominal value of 1
Other modifications, such as reducing to / 8, can also be used. A drop volume of 1/8 provides nine density levels for each primary color, resulting in 9x9x9 for each grid position in nine printing operations (for three color pens).
That is, 729 possible color combinations can be obtained. 1 in a 4-color system (eg, KCMY)
With a drop volume of / 8, a base system color of 9x729, or 6,561, is obtained.

The print quality can be further improved by combining the increase in the resolution of black ink with this ink amount reduction method. Since most of the image information is contained in gray content, this method can be used to obtain a large color quality improvement at a small cost. To explain this, in the 300 DPI color system, increasing the gray resolution to 600 DPI basically provides up to 5 levels of gray-based resolution at each grid or pixel location. As described above, half the unit amount of color dots can be printed in two printing operations. However, with black ink, the amount of ink droplets that can be printed with 0, 1, 2, or 4 dots in a super pixel of 2 × 2 dots that fills a 300 × 300 grid position is 300 DPI ink droplet amount. It is about 1/4. This configuration provides four gray levels for each pixel with the smallest black dot size. Table 2 shows the combinations of dots obtained in each pixel. 50 of these combinations
The above can be used.

[0035]

[Table 2]

Therefore, this reduced ink amount printing method improves color and / or grayscale print quality by reducing the dot size and increasing the number of dots in a region. Importantly, as will be described below, by providing multiple drop volumes, improved print quality can be achieved without linearly increasing the number of printing operations.

[Multiple Ink Volume Printing] Another feature of the present invention is to use a plurality of different ink droplet volumes in a single drop-on-demand printing system. Preferably, multiple different ink drop volumes are used in a single print cartridge, but multiple cartridges are mounted on a single carriage. The usable ink droplet amount is determined in advance. In FIG. 6, a part of the inkjet printer is shown in a perspective view. A modified carriage 70 is attached to the cross rail 72. The carriage 70 includes four print cartridges 62, 64, 66.
And 68 and are configured to carry them. Each cartridge has a single color, eg C, M, Y
Alternatively, it is configured to provide K ink drops. Further, each cartridge is configured to allow selection from at least two different amounts of the corresponding ink, as required.

FIG. 3A shows an example of the configuration of a pen nozzle ("pen layout") for printing a plurality of ink droplet amounts.
Shown in. In FIG. 3A, the nozzles are arranged in a total of three pairs of rows, one row for each color. For example, columns 78 and 80 both eject cyan ink. However, the amount of ink drops ejected from the nozzles in column 78 is less than that from column 80. For example, row 7
Eight nozzles provide ⅛ of the unit volume, row 80 is
Provides a quantity of 8.

The change in ink drop volume need not necessarily be provided by changing the nozzle size or aperture. Using appropriate changes in the internal structure of the cartridge and / or changes in the drive signals that control the cartridge,
The amount of ink drop can be changed. Control of ink drop volume in a thermal inkjet printhead is discussed in US Pat. No. 4,339,762.

The printing method using a plurality of different ink drop amounts makes it possible to widely control the ink drop amount without linearly increasing the number of printing operations. For example,
Half of that dot is 1/3 unit amount, and the other half is 2
A print cartridge that is / 3 unit quantity can be provided. These nozzles can be configured such that both quantities can be used on the same horizon, so that either or both quantities can be printed in a single operation. This is called an inline pen layout and is shown in FIG. Using the pen configured as described above, ink droplet amounts of 0, 1/3, 2/3, and 3/3 can be set to 1
It is possible to print at each grid position in one operation. Alternatively, these nozzles can be configured so that different amounts are vertically offset from each other, as shown in FIG. This is called an offset pen layout. Other configurations such as a diagonal layout are possible. Two printing operations with the offset layout pen provide the four ink level levels described above.

In FIG. 5, a portion of the print grid 44 has three pixel columns, columns 46, 50 and 54. The pixels forming the column 46 each have one dot of ink, such as dot 48, and each dot has about 1/3 of the unit amount of ink. The pixels forming the column 50 each have one dot of ink, such as dot 52, which has about 2/3 of the unit amount of ink. The pixels forming the columns 54 each have two dots of ink, such as multiple dots 48. Dot 56
Is formed by an ink drop 57 of 2/3 unit amount and an ink drop 58 of 1/3 unit amount. Any or all of these dots can be printed in one operation using the inline pen layout described above, or printed in two printing operations using the offset pen layout. This feature of the invention can be applied to select other drop volumes and additional printing operations can be used to obtain smaller dots and larger dots per area. These techniques have been found to significantly improve print quality without changing the underlying print grid resolution.

In another example, one half of the nozzles of the print cartridge are configured to deliver one-eighth the unit volume of ink drops, and the other half deliver three-eighth the unit volume of ink drops. Is configured to. In this case, two printing operations (using an inline pen layout) would result in nine density levels at each grid position, namely 0, 1 /
8, 2/8, 3/8, 4/8, 5/8, 6/8, 7 /
Either 8 or 8/8 unit total ink volume is provided. The same resolution can be achieved by using four printing operations with the offset pen layout. Amount exceeding normal unit amount, ie 10/8
(125%) and 12/8 (150%) can also be obtained with four print operations. These are effective, for example, when printing on the second base paper or other media that requires an increased amount of ink. In one color system, eg CMY system, 1 pixel / 1
If there are 9 levels per color, we can get (9 cyan) x (9 magenta) x (9 yellow) = 729 dot combinations, i.e. the base system color.

There is some freedom in the actual use of dot combinations and in the method of encoding the data to drive the printer. For example, seven or eight of the nine possible ink volumes in the example above can be selected as the ones most frequently used. In this case, the driver software can be configured to provide 3-bit data per color / pixel, thereby specifying one of the selected levels.

The present invention applies to other scan head printing or imaging techniques in which the absolute dot size is quantified and the effective dot size or density increases when larger absolute dots are formed by a plurality of absolute dots. be able to.

Printing With Reduced Dye Load Another feature of the invention is to improve print quality by adjusting the ink density, also referred to as "dye load". First, a standard dye load is selected to form dots with acceptable size and density (and other characteristics) when a unit drop volume of ink of that standard dye load is applied to the medium. Defined as normal or regular dye loading. Thus, a half-dye-loaded ink drop (unit volume) provides only half the dye of a unit dye-loaded ink dot to the paper. The reduced dye loaded dots have a lower optical density than the standard dye loaded dots.

The reduced dye loading has the advantage of increasing density resolution. For example, reducing the dye load to half of the standard dye load would basically mean three dot sizes, ie 0, instead of the normal binary mode.
Provides a semi-dye load or a standard dye load. Depending on the pen layout, to print full density dots (ie two half dye loaded dots) on a pixel,
Two printing operations may be required. However, two print operations are used in many inkjet printer applications for other purposes. In addition, the cost of achieving high resolution is not significant due to the use of reduced dye loading. This is similar to existing printer grid resolutions, for example 300DP, as is the case with technologies that use reduced ink drop volume.
I can be used. Therefore, no modification is required to the standard printer mechanism and drive means that define the print grid.

The reduced dye loading method is particularly beneficial in that it requires no hardware modifications and can be implemented in many inkjet printer systems. The dye-reduced ink can be provided in a replaceable print cartridge and the necessary changes to the printing method are implemented in the dithering software. As described above in relation to ink drop volume, the dye loading is, for example, 1/2, 1/3, 1
/ 4, etc., and the number of printing operations increases correspondingly.

It is particularly beneficial to use multiple different dye loads. It would be advantageous to be able to use such various dye loads in a single print cartridge. According to this method, the resolution (the number of density levels) can be increased without linearly increasing the number of printing operations. Droplets of various dye concentrations can be combined in a single pixel. One example is a system that has three dye loads available and uses two printhead movements.
As a result, it is possible to supply up to two ink droplets of each dye concentration to each grid position.
The dye loading is selected so that one drop of medium density is darker than two drops of lower density and one drop of higher density is darker than two drops of intermediate density.

Twenty-seven density levels can be obtained in two printing operations. The first level is when no drops are applied. The second level consists of only one low density ink drop. The third level corresponds to two low density ink drops that have been overlaid in two printing operations. As described above, two low-concentration ink droplets are at level 4 1
A lower density ink drop is formed than one intermediate density ink drop. Level 5 consists of one medium density ink drop and one low density ink drop. Level 6 consists of two low density ink drops and one medium density ink drop. Level 7
Consists of two medium density ink drops, each applied in a separate movement of the carriage. Level 8 is
It is composed of two intermediate density ink drops and one low density ink drop, and one of the low density ink drop and the intermediate density ink drop is applied in the first printing operation and the second intermediate density ink drop is applied. The drops are applied in the second printing operation.

Level 9 has two low density ink drops and two
One medium density ink drop, and one low density ink drop and one low density ink drop in each of two consecutive printing operations.
Two medium density ink drops are applied. To generate levels 10 to 18, one high density drop is added to levels 1 to 9. To generate levels 19 to 27, a second high density ink drop is added to levels 10 to 18 in the second printing operation. In this way, two print operations on the print medium using three dye densities will produce two for each color.
Seven different levels of color density or gray level can be generated. In a three-color system, this three-dye loading method can be used to obtain (27 cyan) * (27 magenta) * (27 yellow) = 19,683 dot combinations in just two printing operations.

In one operational example of one embodiment of the present invention, high density ink drops have a density of 100% (ie standard dye loading), medium density ink drops are 20%, and low density ink drops are 2.
%. It should be noted that this combination results in a wide dynamic range with a minimum number of drops and printing operations. The specific dye load is
It can be optimized empirically according to the print medium and environmental conditions. By varying the dye loading and the number of printing operations, various ranges of gray levels and color combinations can be obtained. Some examples are shown in Table 3 below.

[0052]

[Table 3]

Returning to FIG. 6, four print cartridges 6
Recall that 2, 64, 66 and 68 are arranged on one carriage. Each cartridge is configured to provide one color, for example C, M, Y or K ink drops. Each cartridge was for example of one color ink of C, M, Y or K. Also, each cartridge has been described as providing at least two different amounts of corresponding ink drops of corresponding ink upon request. In contrast, each cartridge can be configured to provide at least two different dye concentration inks. For example, a three-chamber pen is well known for providing three colors of ink. Alternatively, known ink cartridges containing the same color ink with three different dye concentrations can be used to carry out the method described herein.

[Mixing System-HiFi Ink Drop] Another feature of the present invention is to combine the above-described reduced ink amount technique and reduced dye loading technique. One example is a printing method that uses both a reduced amount of ink drops (eg, 1/4 of a unit amount) and a reduced dye load (eg, 1/2 of a standard dye load). The dot size and density of the dots formed by this printing method are about 1/8 of the normal size. The reduced amount of drops with reduced dye loading will be referred to as "high fidelity" drops. As mentioned above, with multiple hi-fi ink drops, nine density levels are provided in this example. In this embodiment,
Very good color print quality is obtained on a 300 DPI inkjet printer. Other hi-fi ink drops can be selected to achieve even higher resolutions. In general, the hi-fi dot size and density produced by this technique is approximately equal to the product of relative drop volume and relative dye loading. This is explained in Table 4 below using a few examples.

[0055]

[Table 4]

The combination of the reduced ink amount and the reduced dye load is
It is suitable for some applications because it relaxes the resolution condition for each variable. For example, 1/4
Unit drop volume can be difficult to implement due to pen constraints. By reducing the dye load in half, a 1/4 dot size can be implemented using 1/2 unit drop volume.

Other combinations of dye density and print times are possible using the method described above. As the total number of drops in a grid position increases, the size of the drops must be reduced so that the total fluid volume per unit area of the print medium does not exceed the absorption capacity of the medium. 1
In systems where the total number of possible ink drops per pixel (number of print operations x number of dye densities x number of pens) exceeds the capacity of the medium, limit the possible combinations of driver software or system hardware, Can be configured.

FIG. 7 is a flow chart for explaining an embodiment of the present invention in the ink jet printing system. The graphic image data (source data) 82, for example, 24-bit RGB data, is provided to the printer driver 84 by the host system or application software. The printer driver 84 has digital halftoning software for reducing the source data to a desired resolution. As a result, the resulting print data is, for example, 6-bit CMY data or 8-bit CMYK data, or a larger number of bits reflecting the increased resolution of the present invention. A printer control language file can be created. This printer control language file is then used by the inkjet printer 8 of the type described above.
8 and other printer mechanisms.

Printer 88 can be configured to provide one or more reduced drop volumes for printing with reduced drop volumes. In this case, the data 92 representing the usable ink droplet amount is input to the printer driver 84. Printer 88 can also be configured to provide one or more reduced dye loads or ink densities for printing with reduced dye loads. in this case,
Data 94 representing the usable dye density is input to the printer driver 84. If both data 92 and data 94 are provided, hi-fi ink drops can be used. For example, pen layout information 98 such as inline pen layout vs. offset pen layout is also input to the printer driver. Information defining the printer and the ink cartridges installed in the printer can be provided, such as by a "printer setup" routine in the host machine. Alternatively, this information can be read or detected automatically in the printer and provided to the driver as indicated by dashed line 96. In addition, the user or host machine may provide a desired maximum 90 dot display per pixel input to the driver. For example, the user may select a "draft mode" in which the number of dots per pixel is small in order to reduce the number of printing operations, thereby increasing the speed and reducing the ink usage fee instead of decreasing the print quality. You can

As detailed above, the high fidelity printing of the present invention provides for [1] discontinuous drop-on-demand ink jet printing having unit ink drop volumes selected to fill approximately one pixel area on a print medium. A method of printing with reduced ink volume at selected pixel locations in a system; for supplying ink drops disposed on a carriage that traverses a print medium parallel to its surface. Providing a print cartridge having nozzles;
Reducing the drop volume so that the nozzle delivers less than the unit drop volume; depositing a first reduced volume drop at a selected pixel location on the print medium; and Applying a second reduced amount of ink drops to the same selected pixel location on the print medium; applying the second reduced amount of ink drops applies the first reduced amount of ink drops; It is achieved by the movement of the carriage different from the step, and has the following preferred embodiment.

[2] The method of [1] further comprising the step of applying one or more additional reduced amounts of ink drops to the same selected location on the print medium, each additional ink. The drops are deposited during different movements of the carriage, thereby depositing a total ink volume at this selected pixel location equal to an integer multiple of the reduced ink volume.

[3] In the method of [1], the reduced ink drop amount is approximately equal to half the unit amount, and at the selected pixel position in two printing operations, there is no ink and half the unit amount. Ink, or a unit amount of ink, can be selected and printed.

[4] In the method of [1], the print cartridge has at least three nozzles, and each nozzle is configured to supply one of three different color inks. Reducing the amount of ink drops of the three different colors comprises providing reduced ink drops of each of the three different colors on demand, said inking step being selected in the first printing operation. Applying a reduced amount of at most one drop of each color to a pixel position; and adding at least one reduced amount of each color to a selected pixel position in a second printing operation Of ink drops, thereby printing at the same pixel location at a higher grayscale resolution than when printing with a unit amount of ink drops.

In the methods [5] and [4], the reduced amounts of the inks of the three colors are all approximately equal to half the unit amount, and in two printing operations, no ink is applied to the selected pixel position. , Can be printed with half the unit amount, or a selected amount of one unit amount of each color of ink, thereby providing 27 different possible dot combinations at the selected pixel location. To do.

[6] The method of [4] further comprises the step of selecting all the reduced amounts of the three color inks equal to 1 / N of the unit amount, where N is an integer greater than 1. And it is possible to print at each selected pixel position any one of N + 1 different amounts of each color of ink at each selected pixel position, thereby N + 1) ³ different possible dot combinations are provided.

The high fidelity printing of the present invention was also selected for [7] a discontinuous on-demand ink jet printing system having a predetermined printing grid forming an array of pixel locations for printing on the medium. A method of printing a plurality of ink amounts at pixel positions, the method comprising:
Defining a unit drop volume that fills approximately one pixel location on the print medium; providing an ink drop having a first predetermined volume less than the unit volume on demand;
On-demand providing a second ink drop having a second predetermined amount that is less than the first amount; at most one selected pixel location on the medium in a first printing operation on the medium. Applying a first amount of ink drops; and in a second printing operation on the medium, applying at most one second amount of ink drops to the same selected pixel location on the medium; thereby , No ink, a first amount, a second amount, or an amount of ink equal to the selected one of the first amount plus the second amount and printed at this pixel location. It is characterized by improving the gray scale resolution without changing the grid and has the following preferred embodiments.

[8] In the method of [7], the first amount is approximately equal to 2/3 of the unit amount, and the second amount is 1 / of the unit amount.
It is approximately equal to 3, thereby allowing selection from three non-zero total ink volumes in up to two printing operations.

[0068]

[9] In the method of [7], the first amount is approximately equal to 3/8 of the unit amount, and the second amount is 1/1 of the unit amount.
It is approximately equal to 8, thereby allowing selection from 8 non-zero total ink volumes for up to 4 printing operations.

The high fidelity printing method of the present invention is also described in [1
0] A method of printing at a selected pixel location with reduced dye loading in a discontinuous on-demand inkjet printing system having a predetermined printing grid forming an array of pixel locations; A step of selecting a drop amount as a unit amount; a step of selecting a predetermined ink concentration as a standard dye load; a dot having a size that substantially fills a pixel position when a unit amount of standard dye load ink is applied to the pixel position A suitable amount of unit amount and a standard dye concentration for forming an ink on a print medium; providing on demand ink drops each having a reduced dye load less than a standard dye load; a print medium Depositing a first reduced dye loading ink drop at a selected pixel location of the Forming a first dot that is smaller than the dot formed by the load drop; and applying a second reduced dye load drop to the same selected pixel location on the print medium; The step of applying the second drop is accomplished by a different movement of the carriage than the step of applying the first drop, and is characterized in that it improves the grayscale resolution without changing the print grid and is preferred as follows: Has an embodiment.

[11] The method of [10] further comprising the step of applying one or more additional reduced dye loading ink drops at the same selected pixel location on the print medium, each Additional drops are applied with different movements of the carriage.

[12] The method of [10] further comprising the step of providing a selected one of a plurality of different ink dye loads according to demand, each ink dye load being greater than the standard dye load. It is small and improves grayscale resolution printing without linearly increasing the number of printing operations.

[13] In the method of [10], the print cartridge has at least three nozzles, and each nozzle is configured to supply one of three different color inks. The step of providing one of the ink dye loads of the inks comprises the step of providing a reduced dye load ink drop of each of the three different color inks on demand, the step of applying the ink comprising: Applying a maximum of one drop of reduced dye loading of each color to the selected pixel location in the first printing operation, and reducing each color to the selected pixel location in the second printing operation. When printing with a standard dye-loaded ink drop at the same pixel location, which comprises applying up to one drop of dye-loaded ink Ri perform printing at a high color resolution.

[14] In the method of [13], the reduced dye loadings of the three color inks are all approximately equal to 1 / N of the standard dye loading, where N is an integer greater than 1 and N times. Printing at the selected pixel location in any one of N + 1 different dye amounts with each color of ink, without modifying the print grid, Provide (N + 1) ³ different possible color combinations.

The high fidelity printing method of the present invention is also described in [1
5] A method of performing high fidelity printing at selected pixel positions in a discontinuous on-demand inkjet printing system having a predetermined printing grid forming an array of pixel positions; Selecting as a quantity; selecting a predetermined ink density as a standard dye load; when a unit quantity of standard dye load ink is applied to a pixel position, a dot having a size that substantially fills the pixel position is formed on the print medium. A level of unit dye and a standard dye concentration suitable for forming; a on-demand drop of ink, each having a reduced dye load less than the standard dye load; Reducing the amount of each drop to less than a unit amount for printing high fidelity drops;
Applying at most one high fidelity ink drop to a selected pixel location on the print medium; and applying a second high fidelity ink drop to the same selected pixel location on the print media; The step of applying the second drop is accomplished by a different movement of the carriage than the step of applying the first drop, and is characterized in that it improves the grayscale resolution without changing the print grid and is preferred as follows: Has an embodiment.

[16] In the method of [15], the reduced amount is approximately equal to half the unit amount, the reduced dye load is approximately equal to half the standard dye load, and at most 2
Having up to two additional high fidelity ink drops at the same pixel location in up to four additional printing operations, thereby providing up to four gray printing levels per pixel in up to four printing operations .

[17] In the method of [15], the reduced amount is approximately equal to 1/4 of the unit amount, the reduced dye load is approximately equal to half of the standard dye load, and at most 6 additional additions are made. Printing operations up to 6 additional high fidelity ink drops at the same pixel location, thereby providing up to 8 printing operations to provide 9 grayscale levels per pixel.

[18] An ink jet print cartridge of the present invention [18] an ink reservoir for holding ink; coupled to the ink reservoir, each ejecting a first ink drop having a first predetermined amount on demand. And a second nozzle group coupled to the ink reservoir and each configured to eject a second ink drop having a second predetermined amount on demand. Have;
The present invention is characterized in that it enables printing of effective dots having a total ink amount equal to an integer combination of the first amount and the second amount at one pixel position, and has the following preferred embodiment.

[19] In the ink jet print cartridge of [18], the first and second nozzle groups are arranged in an in-line pen layout, whereby the first and second inks are printed during one printing operation of this cartridge. It makes it possible to print up to 1 dot of each of the drops.

[20] In the ink jet print cartridge of [18], the first and second groups of nozzles are arranged in an offset pen layout, whereby the first and second inks are printed during two printing operations of this cartridge. It makes it possible to print up to 1 dot of each of the drops.

While the principles of the invention have been illustrated and described in the embodiments thereof, it will be apparent to those skilled in the art that changes can be made in the construction and details of the invention without departing from such principles. We claim all modifications that fall within the scope of the claims.

[0081]

According to the present invention, the gray scale and color resolution of a thermal inkjet printing system can be improved without the need to increase the print grid resolution. Also, according to the present invention, conventional carriage and paper handling electromechanical assemblies can be used substantially as is. Furthermore, the present invention allows for better control of the total drop volume and / or ink dye concentration to improve the resolution in a given pixel grid.

[Brief description of drawings]

FIG. 1 is a perspective view of a conventional inkjet printer mechanism.

FIG. 2 is a diagram showing a conventional configuration of a nozzle of a thermal inkjet pen.

FIG. 3A is a diagram showing an in-line pen layout for providing a plurality of different ink drop volumes in one inkjet print cartridge, and FIG. 3B is a plurality of different inks in one inkjet print cartridge. FIG. 6 illustrates an offset pen layout for providing drop volume.

FIG. 4 illustrates the use of reduced volumes of ink drops in color printing.

FIG. 5 illustrates the use of multiple different reduced volume drops.

FIG. 6 is a perspective view of an inkjet printer mechanism having multiple pens for providing multiple different ink drop volumes and / or multiple different ink dye densities.

FIG. 7 is a flow diagram illustrating one embodiment of the present invention in an inkjet printing system.

[Explanation of symbols]

 10: Printer 12: Horizontal bar 14: Carriage 16, 18, 22: Print cartridge 20: Media tray 24, 26: Row 30, 44: Print grid 32, 34: Pixel 36: Upper left quadrant of print grid 38: Upper right quadrant 40: Lower left quadrant 42: Lower right quadrant 46, 50, 54: Pixel row 48, 56: Dot 57, 58: Ink drop 62, 64, 66, 68: Print cartridge 70 : Modified carriage 72: Cross rail 78, 80: Row 84: Printer driver 86: Conversion step 88: Inkjet printer 90: Maximum dot number 92, 94: Data 96: Dashed line 98: Pen layout information

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location B41J 3/04 104 H (72) Inventor Joseph M Toger Sun Philomas Hayden Valley Road, Oregon, USA 24901

Claims (5)

[Claims] 1. A discrete drop-on-demand inkjet printing system having a unit drop volume selected to fill an area of about one pixel on a print medium, printing at a reduced ink level at selected pixel locations. A step of providing a print cartridge having nozzles for supplying ink droplets arranged on a carriage that traverses the print medium in parallel to the surface thereof, wherein the nozzles are less than the unit ink droplet amount. Reducing the amount of ink drops to supply the ink, applying a first reduced amount of ink drops to selected pixel locations on the print medium, and the same selected pixels on the print medium. Applying a second reduced amount of ink drops to the position, the step of applying the second ink drop having the first reduced amount. Was achieved by steps and operation of different carriage to give an ink droplet quantity, high-fidelity printing wherein the. 2. A plurality of ink volumes of ink are printed at selected pixel locations in a discontinuous on-demand inkjet printing system having a predetermined print grid forming an array of pixel locations for printing on a medium. Defining a unit drop volume that fills substantially one pixel location on a print medium, providing an ink drop having a first predetermined volume less than the unit volume on demand. On-demand providing a second ink drop having a second predetermined amount less than one amount, a first printing operation on the medium, up to a first one at a selected pixel location on the medium. Applying a volume of one drop and a second printing operation on the medium, depositing at most one second volume of ink on the same selected pixel location on the medium Step, whereby an amount of ink equal to the selected one of no ink, a first amount, a second amount, or a first amount plus a second amount is applied to this pixel. A high fidelity printing method, characterized in that the gray scale resolution is improved without changing the printing grid at the position. 3. A method of printing at a selected pixel location with reduced dye loading in a discontinuous on-demand inkjet printing system having a predetermined print grid forming an array of pixel locations, the method comprising: Step of selecting a predetermined ink drop amount as a unit amount, step of selecting a predetermined ink concentration as a standard dye load, and a size that substantially fills a pixel position when a unit amount of standard dye load ink is applied to a pixel position. A suitable level of unit amount and standard dye concentration for forming dots of fineness on the print medium, each providing on demand an ink drop having a reduced dye load less than the standard dye load , Applying a first reduced dye loading drop at a selected pixel location on the print medium, thereby causing this pixel location Forming a first dot smaller than the dot formed by the standard dye-loaded ink drop on the print medium, and applying a second reduced dye-loaded ink drop on the same selected pixel location on the print medium. The step of applying the second ink drop is accomplished by a different movement of the carriage than the step of applying the first ink drop to improve grayscale resolution without changing the print grid. Fidelity printing method. 4. A method of high fidelity printing at selected pixel locations in a discontinuous on-demand inkjet printing system having a predetermined printing grid forming an array of pixel locations, the method comprising: Amount of ink as a unit amount, a step of selecting a predetermined ink density as a standard dye load, and a dot of a size that almost fills the pixel position when a unit amount of standard dye load ink is applied to the pixel position. Selecting an appropriate level of unit amount and standard dye concentration to form on the print medium, providing on demand ink drops each having a reduced dye load that is less than the standard dye load, reduced Steps to reduce the amount of each dye-loaded drop to less than the unit amount for printing high fidelity drops, maximum At a selected pixel position on the print medium at a selected pixel position on the print medium, and at the same selected pixel position on the print medium at a second high fidelity ink drop. High fidelity printing, characterized in that the step of applying the second drop is accomplished by a different movement of the carriage than the step of applying the first drop, improving the grayscale resolution without changing the print grid. Method. 5. An ink reservoir for holding ink, a first ink reservoir coupled to the ink reservoir and configured to eject a first ink drop each having a first predetermined amount on demand. It is connected to the nozzle group and the ink reservoir,
A second group of nozzles each configured to eject a second drop of ink having a second predetermined amount on demand, at one pixel location, the first amount and the second amount; An ink jet print cartridge, which enables the printing of effective dots having a total ink quantity equal to a combination of integers of quantities.