Abstract:
To simplify the management of unique information on printing apparatuses, the printing apparatus sends the HS data unique to a particular print head to the computer terminal equipment which, based on the HS data, corrects the print data and sends the corrected print data to the printing apparatus.

Description:
This application is based on Patent Application No. 165615/1998 filed on Jun. 12, 1998 in Japan, the content of which is incorporated hereinto by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a printing system and a printing method in which a printing apparatus prints an image according to print data transmitted from a control apparatus. 
     2. Description of the Prior Art 
     First Conventional Example 
     Generally, a print head used in an inkjet printing apparatus ejects ink through ink paths that form a plurality of nozzles or ink ejection orifices. In the printing apparatus using such a print head, there may be minute variations in shape among the nozzles forming ink paths and also errors in the nozzle shapes during the nozzle forming process. Because of these variations, it is often not possible to produce a uniform image by ejecting inks onto a print medium even when a command signal to form a uniform image is issued. 
     A method for correcting unevenness in print density, the cause of uneven image, and for making the density uniform is already known as head shading (HS). 
     FIG. 1 is a schematic block diagram of an apparatus that actually employs the head shading (hereinafter also referred to as “HS”) technique. The apparatus shown in FIG. 1 incorporates three systems, a reading unit (image exposing unit)  101 , an image processing section  102 , and a print (image forming) section  103 . A conventional HS technology will be described below. 
     In FIG. 1, the reading unit  101  reads an original document and inputs a result of printing to obtain a density pattern required to perform HS. The image processing section  102  performs calculation processing on an image read by the reading unit  101 , such as color correction and value determination processing (n=2, 3, 4 . . . ). The HS processing is also included in these calculation processing. The image forming section  103  takes in data, which was read by the reading unit  101  and processed by the image processing section  102 , and then, based on this data, forms an image on a print medium by each print head  104 . 
     In the printing apparatus of this configuration, the image forming section  103  forms an image on a print medium by using the print heads  104  according to a test pattern that is used to form an image of a specified density. The result of printing is read by the reading unit  101 . The data read by the reading unit  101  is sent to the image processing section  102  where it is used to generate data required to perform HS processing (hereinafter referred to as “HS data”). The HS data  105  is used to correct density-varying spots observed in the printing result produced by each of the print heads  104 . That is, the print heads  104  each have a plurality of ink paths that form nozzles or ink ejection orifices and, when there are variations in the amount of ink ejected from these ink paths, density-varying spots are formed in the printing result. The HS data  105  is used to correct the density-varying spots and make them inconspicuous. That is, the HS data  105  is used as data for directly correcting an image input signal from the reading unit  101  for each print head  104 . Based on the corrected output signal value, the print heads  104  in the image forming section  103  print an image. 
     Second Conventional Example 
     There is a print system which has configured independently of each other the original exposing section (reading unit), the image processing system and the image forming section, like a system consisting of an image scanner, a computer terminal equipment and a printer. As to this system a variety of improvement proposals have been made, which include Japanese Patent Application Laid-Open Nos. 8-156932, 8-156803, 8-156813, 8-156820, 8-156822 and 8-156802. 
     One of these proposals deals with a case where a plurality of printing apparatuses are connected to a computer terminal equipment. In this configuration, correction information on all printing apparatuses which may be connected to the computer terminal equipment is constructed into database and stored in advance in a storage device connected to the computer terminal equipment. When printing, the computer terminal equipment sends a serial number to a printing apparatus to check the detail of the printing apparatus. Based on the result of the check, the computer uses the correction information corresponding to that printing apparatus and performs printing. In this way, the printing apparatus to be operated and the corresponding correction information are matched. Of the above proposals some include date information in the management of the correction information. 
     In the above proposals, however, the correction information unique to a particular printing apparatus exists separately and independently of the printing apparatus. Thus, the user must obtain in advance correction information about all the printing apparatuses that may be connected to the computer terminal equipment and manage these information. Further, as the number of printing apparatuses increases, the correction information on these printing apparatuses is accumulated in the storage device connected to the computer terminal equipment, thus increasing the amount of data stored. An increase in the accumulated data in turn makes erroneous operations and other troubles on the part of the user more likely. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a printing system and a printing method, both capable of simplifying the management of information on individual printing apparatuses. 
     In a first aspect of the present invention, there is provided a printing system comprising: 
     a printing apparatus capable of printing an image according to print data on a print medium by using a print head having a plurality of print elements; and 
     a controller for sending the print data to the printing apparatus; 
     wherein the printing apparatus has first and second holding means for holding first unique information unique to the printing apparatus and second unique information unique to the print head, respectively; 
     wherein the controller includes: 
     first and second registration means capable of registering the first and second unique information sent from the printing apparatus, respectively; 
     a request means for requesting the printing apparatus to send the second unique information when the registered content of the first and second registration means does not agree with the first and second unique information in the printing apparatus; and 
     a conversion means for converting the print data according to the second unique information registered in the second registration means. 
     In the second aspect of the present invention, there is provided a printing method comprising the steps of: 
     sending print data from a controller to a printing apparatus; and 
     printing an image on a print medium according to the print data by using a print head having a plurality of printing elements; 
     wherein the printing apparatus sends unique information unique to the print head to the controller, and the controller converts the print data according to the unique information and sends the converted print data to the printing apparatus. 
     The present invention has stored in individual printing apparatuses correction information unique to each printing apparatus. A controller such as a computer terminal equipment requests unique information as required from a desired printing apparatus connected to it. This can eliminate the work on the part of a user, including preparation and management of unique information corresponding to the individual printing apparatuses. 
     Further, because individual printing apparatuses hold their unique information respectively, the controller such as a computer terminal equipment does not need to pool the unique information on individual printing apparatuses. The storage device on the controller side needs only to hold unique information on the printing apparatuses currently connected to the controller. For example, when one printing apparatus is selectively connected to the controller, only the unique information on that printing apparatus needs to be registered in the controller, thus it is prevented that the amount of data stored in the storage device on the controller side from increasing. 
     The unique information on individual printing apparatuses to be registered in the storage device on the controller side can be changed and updated for each print head. For example, by managing date data, version of information, and serial numbers, it is possible to automatically match the printing apparatuses to their corresponding unique information without the user having to become conscious of their correspondence. 
     As a result, the burden of the user is alleviated, allowing the user to easily establish the correspondence between the printing apparatuses and their unique information and to obtain appropriate printed result easily and reliably. 
     Further, in the invention the unique information corresponding to a print head installed in a printing apparatus is held in the printing apparatus and, at time of printing, the unique information is downloaded from the printing apparatus to the controller. The controller uses the downloaded unique information in the conversion processing such as correction of print data. This enables an overall management of the print heads in the printing apparatuses and their corresponding unique information. 
     Therefore, it is not necessary to manage the unique information on printing apparatuses separately by the printing apparatuses and the controller, as has been done in the conventional printing system. Further, in a storage device connected to the controller such as a computer terminal equipment, there is no need to manage a plurality of unique information, such as HS data of the printing apparatuses to be connected to the controller, as has been required conventionally. 
    
    
     The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic block diagram of a printing system that realizes the conventional head shading; 
     FIG. 2 is a schematic diagram of a print system according to one embodiment of the invention; 
     FIG. 3 is an explanatory diagram showing a communication procedure performed by the printing system of FIG. 2; 
     FIG. 4 is an explanatory diagram showing head shading (HS) correction data used in the embodiment of the invention; 
     FIG. 5 is an explanatory diagram showing reference table numbers in the HS correction data of FIG. 4; 
     FIG. 6 is an explanatory diagram showing HS gamma table used in the embodiment of the invention; 
     FIG. 7 is an explanatory diagram showing table values of the HS gamma table of FIG. 6; 
     FIG. 8 is a perspective view of a color label printing apparatus that can apply the present invention; and 
     FIG. 9 is a side view showing an interior of the color label printing apparatus of FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of this invention will be described by referring to the accompanying drawings. 
     FIG. 2 is a schematic diagram showing a printing system that can apply the present invention. 
     A printing apparatus  201  has installed therein a plurality of print heads  202  formed with a plurality of ink ejection orifices or nozzles. These print heads  202  are controlled by a controller  207 . The printing apparatus  201  also has a DRAM  206 , a ROM  205  and a RAM  203 . The DRAM  206  constitutes an area for buffering print data transferred from a computer terminal equipment  211 . The ROM  205  is an area for storing programs. The RAM  203  constitutes an area for storing HS data to implement the head shading (simply referred to as “HS”). An interface unit  204  communicates with an interface unit  210  of the computer terminal equipment  211  or the controller. These interface units  204  and  210  are usually connected with a cable. 
     In this example, we will take up a case where the printing apparatus  201  is connected to the computer terminal equipment  211  with a cable. 
     FIG. 3 shows the procedure of communication between the computer terminal equipment  211  and the printing apparatus  201  connected to it when printing is performed. 
     First, the computer terminal equipment  211  starts communicating with the printing apparatus  201  and sends a “device ID request” to the printing apparatus  201  to check whether the printing apparatus  201  is properly connected to the computer terminal equipment  211  (step S 302 ). The printing apparatus  201  returns information on the printing apparatus  201  including a serial number to the computer terminal equipment  211  (step S 303 ). Based on the returned signal, the computer terminal equipment  211  decides whether or not the printing apparatus  201  is connected to it (step S 304 ). 
     When it is decided that the printing apparatus  201  is not connected, the computer terminal equipment  211  performs error processing (step S 301 ). When the printing apparatus  201  is confirmed to be connected, the computer terminal equipment  211  checks whether HS data is present in a storage device  208  connected to the computer terminal equipment  211  (step S 306 ). When the HS data is not found, the computer terminal equipment  211  issues an HS data read request to the printing apparatus  201  (step S 312 ). The printing apparatus  201  reads the HS data for all print heads  202  described later from the HS RAM  203  and returns the HS data to the computer terminal equipment  211  (step S 313 ). 
     If the HS data exists in the storage device  208 , the computer terminal equipment  211  compares the serial number returned from the connected printing apparatus  201  with the serial number of the HS data contained in the storage device  208  (step S 307 ). When they do not agree, i.e., when the HS data in the storage device  208  is not for the print heads  202  of the printing apparatus  201  connected to the computer terminal equipment  211 , the processing proceeds to step S 312 . In step S 312 , the computer terminal equipment  211  requests HS data for all print heads  202 , as is done when HS data does not exist in the storage device  208 . In step S 307 , when the serial number of the printing apparatus  201  coincides with the serial number stored in the storage device  208 , the processing proceeds to step S 308 . That is, when the HS data in the storage device  208  is for the print heads  202  of the printing apparatus  201  connected to the computer terminal equipment  211 , the processing proceeds step S 308 . The step  308  requests only header information (hereinafter referred to “HS data ID”) attached to the HS data. 
     Now, HS data and HS data ID will be explained. 
     As shown in FIG. 4, the HS data, which is a combination of an HS data ID section  401  as a header and an HS data section  402 , constitutes correction information for one print head  202 . In the case of a printing apparatus  201  using four print heads  202 , for example, there are four such HS data assigned. The HS data is stored in HS RAM  203  on printing apparatus  201  side. The HS data ID section  401  and the HS data section  402 , combined together, are also called HS correction data  407 . 
     The HS data ID section  401  represents information on the HS data section  402 . That is, the HS data ID section  401  includes date information  405  on year (YY), month (MM) and day (DD) when the HS data section  402  was generated, and version information  406  used to establish matching with HS gamma table  505  described later. The HS data section  402  has the same number of data items as there are nozzles that form one print head  202 . The HS data section  402  contains reference information  404  about correction gamma table that defines each pixel to be formed by each nozzle. The reference information  404  contains, as shown in FIG. 5, table numbers of gamma table (reference table numbers) as data for each pixel that corresponds to a nozzle number (n). The gamma table is used to correct input data on pixel density. In this example, there are a total of 64 reference table numbers  404  from “0” to “63”. At time of HS processing, a gamma table of the corresponding table number is referenced to correct the input data concerning the density of each pixel. The input data is referred to as “input pixel data” and the corrected data as “output pixel data.” 
     Next, the HS gamma table stored in the storage device  208  on the computer terminal equipment  211  side will be explained by referring to FIGS. 6 and 7. 
     The HS gamma table  505 , like the HS correction data  407  described above, has an ID section  503  as a header and a gamma table section  501 . The gamma table section  501  contains gamma tables  502  that correspond to the reference table numbers  404  stored in the HS data section  402 . The gamma tables  502  will be detailed later. The ID section  503  stores date information  504  on year (YY), month (MM) and day (DD) when the HS gamma table  505  was generated, and version information  506 . 
     The version information  506  must agree to the version information  406  of the HS correction data  407 . The reason for this is that the HS correction data  407  is the data used to reference the gamma tables  502 . The second reason is that the HS correction data  407  is updated in the HS RAM  203  of the printing apparatus  201 . The third reason is that the HS gamma table  505  updates device driver information necessary for using the printing apparatus  201 . For these reasons, it is necessary to check, at the start of printing, whether the version of the HS correction data in the storage device  208  that is used for printing matches the version of the HS correction data in the HS RAM  203  of the printing apparatus  201 . 
     In this example, the input pixel data and the output pixel data both have 8 bits for each pixel. Therefore, the gamma tables  502 , as shown in FIG. 7, must have output values from 0 to 255 for the input values from 0 to 255. For this reason, the gamma table section  501  is constructed such that each gamma table  502  has 256 bytes. The value y of the output pixel data is determined by taking the selected gamma table  502  and the input pixel data value x as parameters. Specifications of values and table arrangement are not limited to those described above in this example. 
     Now, returning to FIG. 3, we will explain about the processing after the request for the header section (ID section) of the HS correction data  407  (step S 308 ). 
     In step S 308 , the computer terminal equipment  211  requests an ID of the HS correction data  407  from the printing apparatus  201 . In response to this request, the printing apparatus  201  sends back the HS data ID section  401  (step S 309 ). The computer terminal equipment  211  compares, for each print head  202 , the version information  406  of the HS data ID section  401  returned from the printing apparatus  201  with the version information  506  of the ID section  503  stored in the storage device  208  (step S 310 ). If any of the version information  406 ,  506  disagrees, the computer terminal equipment  211  requests HS data (step S 312 ). In response to the request, the printing apparatus  201  returns the HS correction data  407  for all print heads  202  (step S 313 ). The computer terminal equipment  211  receives the HS correction data  407  and updates the data in the storage device  208 . In this case, even when the version information  406 ,  506  differs, as long as their relationship falls within a predetermined range of history, for example, within a predetermined range of version, they may be determined as being equal. 
     In step S 310 , when all the version information  406 ,  506  agree, the processing proceeds to step S 311 , where the date information  405  and  504  are compared for each print head  202 . Then, for only those print heads  202  for which the date information  405 ,  504  disagree, the computer terminal equipment  211  requests the HS correction data  407  (HS data request (step S 312 )). The computer terminal equipment  211  receives the HS correction data  407  and stores them in the storage device  208 . In that case, even when the date information  405  and  504  differ, as long as their relationship falls within a predetermined range of history, they may be determined as being identical. For example, if the deviation between date information  405  and  504  is within a predetermined period, it is possible not to request the HS correction data  407  corresponding to these information data  405 ,  504 . 
     In this way, the HS correction data stored in the storage device  208  connected to the computer terminal equipment  211  is matched, for each print head  202 , to the HS correction data stored in the HS RAM  203  of the printing apparatus  201 . Then, based on the HS correction data stored in the storage device  208 , the computer terminal equipment  211  corrects print data, i.e., performs HS correction. The printing apparatus  201  receives the corrected print data and prints them out. 
     FIG. 8 is a perspective view of a color label printing system as one form of the printing system that can apply the present invention. 
     The color label printing apparatus, as the printing apparatus  201 , has a paper roll holder  601  for holding a roll of paper  602  as a medium to be printed on. According to the print data received from the computer terminal equipment  211  through a printer cable, the printing apparatus  201  prints on the roll of paper  602 . Designated  603  is an operation panel. 
     FIG. 9 is a side view showing the interior of the color label printing apparatus of FIG.  8 . 
     The color label printing apparatus feeds the roll of paper  602 , a print medium held in the paper roll holder  601 , to a printing apparatus body by paper roll feed rollers  604 . In the printing apparatus body, the paper  602  is carried to the left in the figure, as shown by the arrow, by a transport roller  605  and a transport belt  606 . Four print heads  202  are provided which correspond to four color inks, yellow, magenta, cyan and black. These four print heads  202  combine to form a head unit. The print heads  202  use these color inks supplied from corresponding color ink cartridges and print images on the paper  602 . 
     The print heads  202  have a plurality of ink ejection orifices (not shown) formed in their surface opposing the paper  602  and arranged in a direction crossing the paper feed direction. The print heads  202  also have ink passages (not shown) communicating with individual ink ejection orifices. For each of the ink passages, the print heads are provided with an electricity-heat converter that generates thermal energy used to eject ink droplets. The electricity-heat converter generates heat by an electric pulse applied according to the print data. The heat causes film boiling which in turn generates a bubble, ejecting an ink droplet from the ink ejection orifice. 
     The present invention achieves distinct effect when applied to a recording head or a recording apparatus which has means for generating thermal energy such as electrothermal transducers or laser light, and which causes changes in ink by the thermal energy so as to eject ink. This is because such a system can achieve a high density and high resolution recording. 
     A typical structure and operational principle thereof is disclosed in U.S. Pat. Nos. 4,723,129 and 4,740,796, and it is preferable to use this basic principle to implement such a system. Although this system can be applied either to on-demand type or continuous type ink jet recording systems, it is particularly suitable for the on-demand type apparatus. This is because the on-demand type apparatus has electrothermal transducers, each disposed on a sheet or liquid passage that retains liquid (ink), and operates as follows: first, one or more drive signals are applied to the electrothermal transducers to cause thermal energy corresponding to recording information; second, the thermal energy induces sudden temperature rise that exceeds the nucleate boiling so as to cause the film boiling on heating portions of the recording head; and third, bubbles are grown in the liquid (ink) corresponding to the drive signals. By using the growth and collapse of the bubbles, the ink is expelled from at least one of the ink ejection orifices of the head to form one or more ink drops. The drive signal in the form of a pulse is preferable because the growth and collapse of the bubbles can be achieved instantaneously and suitably by this form of drive signal. As a drive signal in the form of a pulse, those described in U.S. Pat. Nos. 4,463,359 and 4,345,262 are preferable. In addition, it is preferable that the rate of temperature rise of the heating portions described in U.S. Pat. No. 4,313,124 be adopted to achieve better recording. 
     U.S. Pat. Nos. 4,558,333 and 4,459,600 disclose the following structure of a recording head, which is incorporated to the present invention: this structure includes heating portions disposed on bent portions in addition to a combination of the ejection orifices, liquid passages and the electrothermal transducers disclosed in the above patents. Moreover, the present invention can be applied to structures disclosed in Japanese Patent Application Laying-open Nos. 123670/1984 and 138461/1984 in order to achieve similar effects. The former discloses a structure in which a slit common to all the electrothermal transducers is used as ejection orifices of the electrothermal transducers, and the latter discloses a structure in which openings for absorbing pressure waves caused by thermal energy are formed corresponding to the ejection orifices. Thus, irrespective of the type of the recording head, the present invention can achieve recording positively and effectively. 
     The present invention can be also applied to a so-called full-line type recording head whose length equals the maximum length across a recording medium. Such a recording head may consists of a plurality of recording heads combined together, or one integrally arranged recording head. 
     In addition, the present invention can be applied to various serial type recording heads: a recording head fixed to the main assembly of a recording apparatus; a conveniently replaceable chip type recording head which, when loaded on the main assembly of a recording apparatus, is electrically connected to the main assembly, and is supplied with ink therefrom; and a cartridge type recording head integrally including an ink reservoir. 
     It is further preferable to add a recovery system, or a preliminary auxiliary system for a recording head as a constituent of the recording apparatus because they serve to make the effect of the present invention more reliable. Examples of the recovery system are a capping means and a cleaning means for the recording head, and a pressure or suction means for the recording head. Examples of the preliminary auxiliary system are a preliminary heating means utilizing electrothermal transducers or a combination of other heater elements and the electrothermal transducers, and a means for carrying out preliminary ejection of ink independently of the ejection for recording. These systems are effective for reliable recording. 
     The number and type of recording heads to be mounted on a recording apparatus can be also changed. For example, only one recording head corresponding to a single color ink, or a plurality of recording heads corresponding to a plurality of inks different in color or concentration can be used. In other words, the present invention can be effectively applied to an apparatus having at least one of the monochromatic, multi-color and full-color modes. Here, the monochromatic mode performs recording by using only one major color such as black. The multi-color mode carries out recording by using different color inks, and the full-color mode performs recording by color mixing. 
     Furthermore, although the above-described embodiments use liquid ink, inks that are liquid when the recording signal is applied can be used: for example, inks can be employed that solidify at a temperature lower than the room temperature and are softened or liquefied in the room temperature. This is because in the ink jet system, the ink is generally temperature adjusted in a range of 30° C.-70° C. so that the viscosity of the ink is maintained at such a value that the ink can be ejected reliably. 
     In addition, the present invention can be applied to such apparatus where the ink is liquefied just before the ejection by the thermal energy as follows so that the ink is expelled from the orifices in the liquid state, and then begins to solidify on hitting the recording medium, thereby preventing the ink evaporation: the ink is transformed from solid to liquid state by positively utilizing the thermal energy which would otherwise cause the temperature rise; or the ink, which is dry when left in air, is liquefied in response to the thermal energy of the recording signal. In such cases, the ink may be retained in recesses or through holes formed in a porous sheet as liquid or solid substances so that the ink faces the electrothermal transducers as described in Japanese Patent Application Laying-open Nos. 56847/1979 or 71260/1985. The present invention is most effective when it uses the film boiling phenomenon to expel the ink. 
     Furthermore, the ink jet recording apparatus of the present invention can be employed not only as an image output terminal of an information processing device such as a computer, but also as an output device of a copying machine including a reader, and as an output device of a facsimile apparatus having a transmission and receiving function. 
     The present invention has been described in detail with respect to various embodiments, and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and it is the intention, therefore, in the appended claims to cover all such changes and modifications as fall within the true spirit of the invention.