Patent Publication Number: US-6705699-B2

Title: Image output device for improving image resolution and tone expression

Description:
This application incorporates by reference Taiwan application Serial No. 090110667, filed May 3, 2001. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates in general to an image output device, and more particularly to an image output device for improving image resolution and tone expression. 
     2. Description of the Related Art 
     In recent years, the personal computer has become so popular that the peripheral computer products have developed very rapidly. Most users employ printers to create output images by printing the electrical documents, such as plain text, colorful graphics, or beautiful pictures, which might be downloaded from the Internet or photographed by a digital camera. By balancing the price and quality, the color ink-jet printer is an affordable option for most PC buyers and has thus become the most popular type of printer sold today. 
     In the ink-jet printer, a print head traverses over the surface of the paper and ejects ink onto the paper to form a printed image. The bubble jet and piezoelectric print head technologies are widely applied to ink-jet printers now to produce bubble jet printers and piezoelectric printers. The principal difference between bubble-jet printers and piezoelectric printers is that bubble-jet printers use special heating elements to prepare the ink, and the piezoelectric printers use piezoelectric crystals. In substance, the piezoelectric printer uses the expanding piezoelectric crystals to force ink drops out of the nozzle and onto the paper. Usually, the bubble jet printer includes a heating element, ink, and nozzle. The heating element heats the ink and forms a bubble until the pressure forces it to burst. A drop of ink is then forced out of the nozzle and onto the paper. During printing, it is required that the ink density and dropping location be controlled to form the desired printed image. 
     The printed image is a pattern consisting of a number of ink drops or pixels. The print quality relates to the resolution. Generally speaking, the higher the resolution, the more pixels per square inch an image has, and the better the overall print quality. For example, if the resolution of 600*600 dpi (dot per inch) increases to the resolution of 1200*600 dpi, the ink drop size decreases a half time accordingly. The U.S. Pat. No. 5,726,690 discloses a method for controlling the ink drop size by controlling the pulse width of the delivered firing pulse. However, the variation range of the ink drop size is only 16% by the method, which does not improve the resolution very much. 
     Another key factor of print quality for a color ink-jet printer is the tone expression. The traditional color ink-jet printer uses ink of four colors, M (Magenta), C (Cyan), Y (Yellow), and K (Black). In recent years, the color ink-jet printer uses ink of six colors including M, C, Y, K, light M, and light C, or even uses ink of seven colors by adding light Y. Therefore, the tone expression can enrich the color of the printed image. In a printer having six color inks, the printed image can have 2 5 =32 kinds of color combinations without the shortcoming of half tone simulation and the print quality will greatly improve. Therefore, the key factor of print quality for a color ink-jet printer is the number of the color combinations, that is to say, the tone expression. 
     The following statement is about the improvement on the variation range of the ink drop size (resolution) and the number of the color combination (tone expression) regarding the conventional image output device with ink of four/six colors. 
     Referring to FIG. 1, an arrangement for a nozzle of the conventional image output device with ink of four colors is shown. The conventional image output device with ink of four colors includes a color ink cartridge  110  and a black ink cartridge  140 . The color ink cartridge  110  has a yellow ink tank Y filled with yellow ink  112 , magenta ink tank M filled with magenta ink  114 , and cyan ink tank C filled with cyan ink  116 . The small circles near the ink tanks represent the nozzle of the printhead for ejecting ink. The yellow ink nozzle  122  is capable of ejecting yellow ink  112 , the magenta ink nozzle  124  is capable of ejecting magenta ink  114 , and the cyan ink nozzle  126  is capable of ejecting cyan ink  116 . The black ink cartridge  140  only has a black ink tank K filled with the black ink  142 , and the black ink nozzle  152  is capable ejecting black ink  142 . 
     Referring to FIG. 2, another arrangement for nozzle of the conventional image output device with ink of four colors is shown. The U.S. Pat. No. 6,149,260 discloses an ink jet recording apparatus capable of printing different dot sizes by using a large size nozzle and a small size nozzle to increase the variation range of the ink drop size. As shown in FIG. 2, the conventional image output device with ink of four colors includes a color ink cartridge  210  and a black ink cartridge  240 . The color ink cartridge  210  has a yellow ink tank Y filled with yellow ink  212 , magenta ink tank M filled with magenta ink  214 , and cyan ink tank C filled with cyan ink  216 . The yellow ink nozzles  222 ,  232  are capable of ejecting yellow ink  212 , the magenta ink nozzles  224 ,  234  are capable of ejecting magenta ink  214 , and the cyan ink nozzles  226 ,  236  are capable of ejecting cyan ink  216 . The black ink cartridge  240  only has a black ink tank K filled with the black ink  242 , and the black ink nozzle  252  is capable ejecting black ink  242 . 
     In FIG. 2, the color cartridge  210  has nozzles with a large diameter and a small diameter. The nozzle with small diameter will be driven to eject the small ink drop or light ink drop. The nozzle with large diameter will be driven to eject the large ink drop or dark ink drop. The ejected ink has a proper size and color since the variation range of the ink drop size is increased. However, it requires a larger wafer for forming nozzles with different diameters on one printhead. Besides, the cost of manufacturing the printhead increases and the controlling method becomes more complicated. Although the ink jet recording apparatus is capable of printing in different dot sizes by using two nozzles with different sizes increases the variation range of the ink drop size, it increases the cost of manufacturing the printhead and the complexity of controlling the printhead. 
     Referring to FIG. 3, an arrangement for nozzles of the conventional image output device with ink of six colors is shown. The conventional image output device with ink of six colors includes color ink cartridges  310  and  340 . The color ink cartridge  310  has a yellow ink tank Y filled with yellow ink  312 , magenta ink tank M filled with magenta ink  314 , and cyan ink tank C filled with cyan ink  316 . The yellow ink nozzle  322  is capable of ejecting yellow ink  312 , the magenta ink nozzle  324  is capable of ejecting magenta ink  314 , and the cyan ink nozzle  326  is capable of ejecting cyan ink  316 . The color ink cartridge  340  has a black ink tank K filled with the black ink  342 , light cyan ink tank c filled with cyan ink  344 , and light magenta ink tank m filled with light magenta ink  346 . The black ink nozzle  352  is capable of ejecting black ink  342 , the cyan ink nozzle  354  is capable of ejecting cyan ink  344 , and light magenta ink nozzle  356  is capable of ejecting magenta ink  346 . 
     Comparing FIG. 3 with FIG. 1, the light cyan ink and the light magenta ink are included in the color ink cartridge  340 . This increases the tone expression and therefore enriches the color of the printed image. However, the variation range of the ink drop sizes is limited due to the uniform size of the nozzles. It is still of no help to improve image resolution. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide an image output device for improving image resolution and tone expression by the arrangement for nozzles of the color ink cartridge of the image output device. 
     The invention achieves the above-identified objects by providing an image output device includes two color ink cartridges. The first color ink cartridge has a yellow ink tank Y filled with yellow ink, a first magenta ink tank M filled with magenta ink, and a first cyan ink tank C filled with cyan ink. Besides, the yellow ink nozzle is connected with the yellow ink tank Y for ejecting the yellow ink, the first magenta ink nozzle is connected with the first magenta ink tank M for ejecting the magenta ink, and the first cyan ink nozzle is connected with the first cyan ink tank C for ejecting the cyan ink. The second color ink cartridge has a black ink tank K filled with black ink, a second magenta ink tank M filled with magenta ink, and a second cyan ink tank C filled with cyan ink. Besides, the black ink nozzle is connected with the black ink tank K for ejecting the black ink, the second cyan ink nozzle is connected with the second cyan ink tank C for ejecting the cyan ink, and the second magenta ink nozzle is connected with the second magenta ink tank M for ejecting the magenta ink. When employing the image output device for printing, the color ink cartridge ink having nozzle with small diameter is driven to create small ink drops or light ink drops, and the color ink cartridge having nozzle with large diameter driven to create large ink drops or dark ink drops. 
     Furthermore, the image output device can have two ink color cartridge, both of which provides yellow ink, magenta ink, and cyan ink to achieve the same result by simply using different diameters of the nozzles. The image output device in the invention improves the image resolution and create a six-color tone expression. Moreover, the cost of manufacturing the printhead will not be increased and the controlling method will not become complicated. 
     Other objects, features, and advantages of the invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 (Prior Art) shows an arrangement for nozzle of the conventional image output device with ink of four colors; 
     FIG. 2 (Prior Art) shows another arrangement for nozzle of the conventional image output device with ink of four colors; 
     FIG. 3 (Prior Art) shows an arrangement for nozzle of the conventional image output device with ink of six colors; and 
     FIG. 4 shows an arrangement for printhead nozzles of the image output device according to the first embodiment of the invention; and 
     FIG. 5 shows an arrangement for printhead nozzles of the image output device according to the second embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the first embodiment of the invention, the image output device has a carriage and a motor. The motor drives the carriage to reciprocate along predetermined directions. An ink cartridge is mounted on the carriage and has several nozzles for ejecting ink and forming a number of ink drops. The image output device might be an ink jet printer, fax machine, or multi-function peripheral (MFP). 
     The image output device uses nozzles with different diameters but filled with the same color ink to increase tone expression. In the first embodiment, the image output device has two color ink cartridges. The first color ink cartridge provides yellow ink, magenta ink, and cyan ink, and the second color ink cartridge includes black ink, magenta ink, and cyan ink. In the second embodiment, the image output device has two color cartridges, both of which provide yellow ink, magenta ink, and cyan ink. 
     FIG. 4 shows an arrangement for printhead nozzles of the image output device according to the first embodiment of the invention. The image output device includes two color ink cartridges  410  and  440 . The first color ink cartridge  410  has a yellow ink tank Y filled with yellow ink  412 , a first magenta ink tank M filled with magenta ink  414 , and a first cyan ink tank C filled with cyan ink  416 . Besides, the yellow ink nozzle  422  is connected with the yellow ink tank Y for ejecting the yellow ink  412 , the first magenta ink nozzle  424  is connected with the first magenta ink tank M for ejecting the magenta ink  414 , and the first cyan ink nozzle  426  is connected with the first cyan ink tank C for ejecting the cyan ink  416 . 
     The second color ink cartridge  440  has a black ink tank K filled with black ink  442 , a second magenta ink tank M filled with magenta ink  446 , and a second cyan ink tank C filled with cyan ink  444 . Besides, the black ink nozzle  452  is connected with the black ink tank K for ejecting the black ink  442 , the second cyan ink nozzle  454  is connected with the second cyan ink tank C for ejecting the cyan ink  444 , and the second magenta ink nozzle  456  is connected with the second magenta ink tank M for ejecting the magenta ink  446 . 
     The cyan ink  416  of the first color ink cartridge  410  is the same as the cyan ink  444  of the second color ink cartridge  440 , and the magenta ink  414  of the first color ink cartridge  410  is the same as the magenta ink  446  of the second color ink cartridge  440 . Besides, the diameter of the second magenta ink nozzle  456  is smaller than a diameter of the first magenta ink nozzle  424 , and the diameter of the second cyan ink nozzle  454  is smaller than the diameter of the first cyan ink nozzle  426  as well. Furthermore, the diameter of the yellow ink nozzle  422 , the diameter of the first magenta ink nozzle  424 , and the diameter of the first cyan ink nozzle  426  are the same. In addition, the diameter of the second magenta ink nozzle  456  is the same as the diameter of the second cyan ink nozzle  454  but smaller than the diameter of the black ink nozzle  452 . Further, the diameter of the second magenta ink nozzle  456  is smaller than the diameter of the first magenta ink nozzle  424 , and the diameter of the second cyan ink nozzle  454  is smaller than the diameter of the first cyan ink nozzle  426 . Therefore, ink drops ejected from the second magenta ink nozzle  456  of the second color ink cartridge  440  are smaller than ink drops ejected from the first magenta ink nozzle  424  of the first color ink cartridge  410 , and ink drops ejected from the second cyan ink nozzle  454  of the second color ink cartridge  440  are smaller than ink drops ejected from the first magenta ink nozzle  426  of the first color ink cartridge  410 . 
     In the above-described first embodiment, the differences between the conventional ink cartridge  340  (see FIG. 3) and the ink cartridge  440  of the first embodiment (see FIG. 4) are the kinds of inks and nozzle sizes. In FIG. 4, the light cyan ink  344  and the light magenta ink  346  of FIG. 3 are replaced by cyan ink and magenta ink respectively, and the cyan ink nozzle  354  and the magenta ink nozzle  356  have smaller diameters respectively. That is to say, the color ink cartridge  440  replaces the conventional ink cartridge  340 . 
     The smaller ink drop with the same color looks lighter due to the sense of sight. Therefore, whenever employing the image output device of the first embodiment, the cyan ink nozzle  454  or the magenta ink nozzle  456  of the color ink cartridge  440  is driven to create small ink drops or light ink drops. At the same time, the cyan ink nozzle  426  or the magenta ink nozzle  424  of the color ink cartridge  410  is driven to produce large ink drops or dark ink drops. 
     In the second embodiment of the invention, one color ink cartridge  540  includes yellow ink, magenta ink, and cyan ink replace the color ink cartridge  440  providing black, magenta ink, and cyan ink. The black color can be blended by the red, green, blue color. The relationship between the diameter of nozzle and the color chroma in the second embodiment is similar to the first embodiment. 
     Referring to FIG. 5, an arrangement for printhead nozzles of the image output device according to the second embodiment of the invention is shown. The first color ink cartridge  510  has a first yellow ink tank Y filled with yellow ink  512 , a first magenta ink tank M filled with magenta ink  514 , and a first cyan ink tank C filled with cyan ink  516 . Besides, the first yellow ink nozzle  522  is connected with the first yellow ink tank Y for ejecting the yellow ink  512 , the first magenta ink nozzle  524  is connected with the first magenta ink tank M for ejecting the magenta ink  514 , and the first cyan ink nozzle  526  is connected with the first cyan ink tank C for ejecting the cyan ink  516 . The second color ink cartridge  540  has a second yellow ink tank Y filled with yellow ink  542 , the second magenta ink tank M filled with magenta ink  544 , and the second cyan ink tank C filled with cyan ink  546 . Besides, the second yellow ink nozzle  552  is connected with the second yellow ink tank Y for ejecting the yellow ink  542 , the second magenta ink nozzle  554  is connected with the second magenta ink tank M for ejecting the magenta ink  544 , and the second cyan ink nozzle  556  is connected with the second cyan ink tank C for ejecting the cyan ink  546 . 
     The yellow ink  512  has the same color with the yellow ink  542 , the magenta ink  514  has the same color with the magenta ink  544 , and the cyan ink  516  has the same color with the cyan ink  546 . At least two color nozzles of the color ink cartridge  540  have smaller diameter than the corresponding color nozzles of the color ink cartridge  510 . As shown in FIG. 5, the diameter of the first yellow nozzle  522  and the diameter of the second yellow nozzle  552  are the same, the diameter of the first magenta ink nozzle  524  is larger than the diameter of the second magenta nozzle  554 , and the diameter of the first cyan ink nozzle  526  is larger than the diameter of the second cyan nozzle  556 . 
     Similarly, the diameter of the first magenta nozzle and the diameter of the second magenta nozzle can be the same, and at the same time, the diameter of the first cyan ink nozzle is larger than the diameter of the second cyan nozzle, and the diameter of the first yellow ink nozzle is larger than the diameter of the second yellow nozzle. On the other hand, the diameter of the first cyan nozzle and the diameter of the second cyan nozzle can be the same, the diameter of the first magenta ink nozzle is larger than the diameter of the second magenta nozzle, and the diameter of the first yellow ink nozzle is larger than the diameter of the second yellow nozzle. 
     The invention uses the nozzles with different diameters but filled with the same color ink to increase tone expression. The four colors of ink can create the same tone expression with the six colors of ink and enriches the color of the printed image. Different diameters of the nozzles can increase the variation range of the ink drop size and then improve image resolution. Furthermore, the printhead according to the invention does not require two nozzles with different diameters, as shown in FIG.  2  and therefore does not require a larger wafer for manufacturing the printhead. Besides, the cost of manufacturing the printhead will not increase and the controlling method will not become complicated since there is no need to change the chip for controlling the printhead due to more nozzles. 
     By using the nozzles with different diameters but filled with the same color ink, the invention can reach the advantages: (1) the image resolution is improved and a six-color tone expression is created; (2) the cost of manufacturing the printhead will not increase and the controlling method will not become complicated. 
     While the invention has been described by way of example and in terms of embodiments, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.