Patent Publication Number: US-7722150-B2

Title: Image recording apparatus and image recording method

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an image recording apparatus and an image recording method, and more particularly, to a configuration of an image recording apparatus, and image forming technology, for forming an image on a recording medium. 
   2. Description of the Related Art 
   An inkjet recording apparatus has been known which forms an image on a recording medium, or the like, by ejecting ink from a head while conveying a recording medium or an intermediate transfer body which is fixed to a conveyance mechanism, such as a conveyance belt. In this inkjet recording apparatus, image deterioration, such as non-uniformities and color deviation, is likely to occur in the image recorded on the recording medium, or the like, when variation occurs in the conveyance speed of the recording medium, or the like, due to vibrations, fluctuations in the conveyance load resistance, or the like. Various technologies have been proposed in order to prevent non-uniformities and color deviation caused by the conveyance of the recording medium, or the like. 
   In the invention described in Japanese Patent Application Publication No. 2004-17458, an encoder is provided which detects slits provided on the edge of a conveyor belt, and ejection from the print head is controlled in synchronism with the output pulse signal output from the encoder, in such a manner that colored inks are ejected in consideration of the actual conveyance speed, thereby preventing color deviation in the sub-scanning direction. 
   In the invention described in Japanese Patent Application Publication No. 2003-211770, the color sequence in a recording device is KCMY, resist marks are recorded onto the recording paper at uniform intervals at the time of printing of the color K (black), the deviation in the movement speed of the recording paper is calculated from information obtained by reading in the resist marks, and the print timing for the colors C, M and Y is controlled on the basis of the calculated deviation in the movement speed of the recording paper, thereby eliminating color deviation caused by eccentricity in the recording paper rollers, or color non-uniformities caused by the density variations in the dots. 
   However, in the invention described in Japanese Patent Application Publication No. 2004-17458, since ejection is controlled in synchronism with an output pulse from the encoder, then a uniform time delay occurs between the detection and ejection, and it is difficult to provide correction for speed variations in cases where the speed variations occur in a short period of time. 
   In the invention described in Japanese Patent Application Publication No. 2003-211770, the behavior of the recording paper during printing and recording of the color K (black) affects positions of the resist marks, and therefore, if a non-uniformity occurs in the color K, then this non-uniformity is also superimposed on the other colors, C, M and Y, and it becomes difficult to eliminate the non-uniformity. For example, non-uniformities arise in the recorded image, as a result of impacts which occur when the recording paper is pinched between the conveyance rollers or separates from the conveyance rollers. 
   SUMMARY OF THE INVENTION 
   The present invention has been contrived in view of these circumstances, an object thereof being to provide an image recording apparatus and an image recording method which do not produce image degradation as a result of non-uniformities or color deviation in the recorded image, even if there is variation in the conveyance speed of the recording medium. 
   In order to attain the aforementioned object, the present invention is directed to an image recording apparatus, comprising: a recording device which deposits an image record substance on a recording medium; a recording medium conveyance device which includes a conveyance medium having a recording medium hold region and conveying the recording medium with respect to the recording device in a conveyance direction while holding the recording medium on the recording medium hold region, the recording medium conveyance device being provided with a determination pattern which is formed outside the recording medium hold region on the conveyance medium and follows the conveyance direction; a determination device which determines the determination pattern while the recording medium is held on the conveyance medium; a calculation device which acquires speed variation data of the conveyance medium in accordance with determination results of the determination device; a storage device which stores the speed variation data acquired by the calculation device; and a record timing correction device which corrects record timing of the recording device in accordance with the speed variation data of the conveyance medium stored in the storage device. 
   In this aspect of the present invention, since sudden speed variation caused in the conveyance medium on which the recording medium is held is corrected on the basis of the speed variation data of the conveyance medium stored in the storage device, then the occurrence of non-uniformities in the recorded image as a result of the sudden speed variation of the conveyance medium is prevented. Furthermore, since the speed variation data stored previously in the storage device is used for correcting the speed variation of the conveyance medium, then no delay arises due to the determination time or the processing time, compared to a system where the speed variation of the conveyance medium is corrected while the behavior of the conveyance medium is determined. 
   Here, the image record substance may be colored ink for forming a color image, resist for forming a pattern shape, or the like. 
   Moreover, the “recording medium” is a medium which receives the image record substance deposited by a recording device, and the recording medium includes various types of media, irrespective of material and size, such as continuous paper, cut paper, sealed paper or other types of paper, or resin sheets, film, cloth, metal sheets, and other materials. 
   The conveyance medium includes, for example, an endless belt wound about a plurality of rollers, or a plate-shaped member which is movable in a prescribed direction by means of a conveyance mechanism. Resin material and metal material are suitably used for the conveyance medium. 
   It is sufficient to provide the determination pattern only at portions corresponding to the region where the recording medium is held on the conveyance medium, the determination pattern following the conveyance direction of the recording medium. Of course, the determination pattern may also be provided throughout the whole of the recording medium in the conveyance direction. 
   A mode is possible where the determination device includes: a determination unit which determines the determination pattern and outputs a determination signal; and a signal processing unit which carries out prescribed signal processing (noise reduction, amplification, and the like) on the determination signal. 
   The “image” referred in the present invention not only mean an image such as a photograph or a picture, but also includes a wiring pattern formed on a printed wiring board, or a mask pattern used to form a three-dimensional shape on a substrate, or the like. 
   Preferably, the above-described image recording apparatus further includes: a supply device which supplies the recording medium to the recording medium conveyance device; and an output device which outputs the recording medium from the recording medium conveyance device, wherein the determination device determines the determination pattern during a period including a time point when the recording medium comes out of contact with the supply device and a time point when the recording medium comes into contact with the output device. 
   In this aspect of the present invention, it is possible to prevent image degradation caused by the speed variation occurring in the conveyance medium when the recording medium separates from the supply device, or the speed variation occurring in the conveyance medium when the recording medium comes into contact with the output device. 
   Preferably, the record timing correction device corrects the record timing of the recording device so as to eliminate an error based on difference between an actual conveyance amount of the conveyance medium and a theoretical conveyance amount of the conveyance medium. 
   In other words, by correcting the cycle of the trigger signal which indicates the record timing, it is possible to make the conveyance amount of the conveyance medium between two record timings coincide with the theoretical conveyance amount. If the actual conveyance distance is greater than the theoretical conveyance distance, then the record timing is corrected in such a manner that the cycle of the trigger signal becomes shorter, and if the actual conveyance distance is shorter than the theoretical distance, then the record timing is corrected in such a manner that the cycle of the trigger signal becomes longer. 
   Preferably, the recording medium conveyed by the recording medium conveyance device when the determination pattern is determined by the determination device, has a type and a size identical to the recording medium used in actual image recording. 
   In this aspect of the present invention, by using the recording medium which is used in actual image recording, when reading in the determination pattern, it is possible to calculate and correct the speed variation of the conveyance medium which occurs during actual image formation, in an accurate fashion, and hence a desirable recording image can be obtained. 
   Here, there are various types of recording media with different materials, different thicknesses, and different shapes, and the like; and, in this aspect of the present invention, the recording medium conveyed in determining the determination pattern may have a type identical to the recording medium used in actual image recording, in respect of at least one of these parameters. 
   Preferably, the determination pattern is formed by a photographic method. 
   In this aspect of the present invention, it is possible to form the determination pattern, with good accuracy, and therefore improvement in the accuracy of determining speed variations are expected. 
   A photographic method is a method which forms a pattern of photosensitive material by exposing photosensitive material through a mask in which holes corresponding to a pattern are formed. One characteristic feature of a photographic method is that it allows the formation of highly fine patterns by changing the magnification optically in the exposure step. For the method of forming the test pattern  37  (determination pattern) used in the present invention, apart from a photographic method in which photosensitive material is exposed, it is also possible to form a pattern of a liquid containing photosensitive material, such as a liquid resin, by means of a mask formed with fine pattern, whereupon the liquid is cured by heating or cooling, or by means of a chemical method. 
   In order to attain the aforementioned object, the present invention is also directed to an image recording apparatus, comprising: a recording device which deposits an image record substance on a recording medium; a recording medium conveyance device which conveys the recording medium with respect to the recording device in a conveyance direction while holding the recording medium; a storage device which stores speed variation data of the recording medium acquired in accordance with determination results of a determination pattern composed of the image record substance deposited on the recording medium by the recording device; and a record timing correction device which corrects record timing of the recording device in accordance with the speed variation data of the recording medium stored in the storage device. 
   In this aspect of the present invention, sudden speed variation occurring in the recording medium, and the speed variation of the recording medium caused by sudden speed variation occurring in the conveyance medium due to stretching or defects in the conveyance medium, or slippage between the recording medium and the conveyance medium, are corrected on the basis of the speed variation data of the recording medium stored in the storage device. Therefore, the occurrence of non-uniformities in the recorded image due to sudden speed variations in the recording medium is prevented. Furthermore, since speed variation data stored previously in the storage device is used for correcting speed variation of the recording medium, then no delay arises due to the determination time or the processing time, compared to a system where speed variation of the recording medium is corrected while the behavior of the conveyance medium or recording medium is determined. 
   Preferably, the above-described image recording apparatus further includes a determination and calculation device which acquires the speed variation data of the recording medium to be stored in the storage device, the determination and calculation device including: a determination unit which determines the determination pattern on the recording medium; a movement unit which moves the recording medium on which the determination pattern is formed and the determination device relatively to each other; and a calculation unit which acquires the speed variation data of the recording medium in a state of being held on the recording medium conveyance device, in accordance with the determination results of the determination unit. 
   In this aspect of the present invention, since the determination pattern is determined at a position outside the conveyance system used for image recording (in other words, the determination pattern is determined in the determination and calculation device that is independent from the recording medium conveyance device), then the determination pattern is determined in a desirable fashion without being affected by vibrations, or the like, of the conveyance system being used for image recording while reading in the determination pattern. 
   The determination and calculation device may be provided inside the image recording apparatus or it may be provided externally to the image recording apparatus. In a mode where the determination and calculation device is provided inside the image recording apparatus, the determination and calculation device may be detachably installed to the image recording apparatus. 
   Preferably, the record timing correction device corrects the record timing of the recording device so as to eliminate an error based on difference between an actual conveyance amount of the recording medium and a theoretical conveyance amount of the recording medium. 
   In other words, by correcting the cycle of the trigger signal which indicates the record timing, it is possible to make the conveyance distance of the recording medium during two record timings coincide with the theoretical conveyance distance. If the actual conveyance distance is greater than the theoretical conveyance distance, then the record timing is corrected in such a manner that the cycle of the trigger signal becomes shorter, and if the actual conveyance distance is shorter than the theoretical distance, then the record timing is corrected in such a manner that the cycle of the trigger signal becomes longer. 
   Preferably, the recording medium on which the determination pattern is formed by the recording device, has a type and a size identical to the recording medium used in actual image recording. 
   In this aspect of the present invention, by using the recording medium which is used in actual image recording, when recording the determination pattern, it is possible to determine and correct the speed variation of the recording medium which occurs during actual image formation, in an accurate fashion, and hence a desirable recording image can be obtained. 
   Preferably, the above-described image recording apparatus further includes: a supply device which supplies the recording medium to the recording medium conveyance device; and an output device which outputs the recording medium from the recording medium conveyance device, wherein: a length P of the recording medium in the conveyance direction, a distance X a  between the output device and an end of the recording device on a side of the output device, and a distance X b  between the supply device and an end of the recording device on a side of the supply device, have at least one of relationships of P≧X a  and P≧X b ; and the determination pattern is formed on the recording medium throughout the length P of the recording medium. 
   In this aspect of the present invention, even in the case of using a recording medium having a size such that the recording medium is being subjected to image recording at the time that the recording medium separates from the supply device or at the time that the recording medium comes into contact with the output device, it is still possible to correct the speed variation of the recording medium occurring in the recording medium when the recording medium separates from the supply device or when the recording medium comes into contact with the output device. 
   Preferably, the image recording apparatus further includes: a supply device which supplies the recording medium to the recording medium conveyance device; and an output device which outputs the recording medium from the recording medium conveyance device, wherein: at least one of following inequality expressions is satisfied:
 
 Q&lt;W+X   a , and
 
 Q&lt;W+X   b ,
 
where X a  is a distance between the output device and an end of the recording device on a side of the output device, X b  is a distance between the supply device and an end of the recording device on a side of the supply device, W is a length of the recording device in the conveyance direction, and Q is a distance between a leading end of a preceding recording medium and a leading end of a subsequent recording medium which is conveyed after the preceding recording medium when a plurality of recording media are conveyed consecutively; and the determination pattern is recorded on each of the plurality of recording media throughout the length of the recording media in the conveyance direction.
 
   In this aspect of the present invention, in a mode where a plurality of recording media are conveyed consecutively and images are recorded thereon, it is possible to correct the speed variation occurring in a recording medium when another recording medium separates from the supply device or comes into contact with the output device. 
   Preferably, the image recording apparatus further includes: a supply device which supplies the recording medium to the recording medium conveyance device; and an output device which outputs the recording medium from the recording medium conveyance device, wherein: the determination pattern is formed on each of n pieces of recording medium throughout lengths of the n pieces of recording medium in the conveyance direction, in a case where the n pieces of recording medium are conveyed consecutively, n being a natural number not less than two; and at least one of following inequality expressions is satisfied:
 
 R   n   &lt;W+X   a , and
 
 R   n   &lt;W+X   b ,
 
where X a  is a distance between the output device and an end of the recording device on a side of the output device, X b  is a distance between the supply device and an end of the recording device on a side of the supply device, W is a length of the recording device in the conveyance direction, and R n  is a distance between a leading end of a first recording medium to be conveyed first and a trailing end of a last recording medium to be conveyed last.
 
   In this aspect of the present invention, in a mode where n pieces of recording media are conveyed consecutively and images are recorded thereon, it is possible to correct the speed variation occurring in a recording medium when another recording medium separates from the supply device or comes into contact with the output device. 
   Preferably, the image recording apparatus further comprises: a supply device which supplies the recording medium to the recording medium conveyance device; and an output device which outputs the recording medium from the recording medium conveyance device, wherein: the determination pattern is formed on each of a first recording medium and a second recording medium following the first recording medium, throughout lengths of the first recording medium and the second recording medium; and following inequality expressions are satisfied:
 
 P   1   ≧X   a   , P   2   ≧X   a   , P   1   ≧X   b   , P   2   ≧X   b , and  P   1   +P   2   +P   d   &lt;X   a   +X   b   +W,  
 
where P 1  is a length of the first recording medium in the conveyance direction, P 2  is a length of the second recording medium in the conveyance direction, P d  is a distance between an end of the first recording medium on a side of the second recording medium and an end of the second recording medium on a side of the first recording medium, X a  is a distance between the output device and an end of the recording device on a side of the output device, X b  is a distance between the supply device and an end of the recording device on a side of the supply device, and W is a length of the recording device in the conveyance direction.
 
   In this aspect of the present invention, by using two pieces of recording media, it is possible to determine the speed variation data corresponding to all of the possible factors of the speed variation, in a mode where a plurality of recording media are conveyed consecutively and images are recorded thereon. 
   Preferably, the recording device includes a plurality of recording heads which deposit different types of image record substances on the recording medium; the recording medium is demarcated into a plurality of regions corresponding to the plurality of recording heads; and the determination patterns are respectively formed on the plurality of regions by the plurality of recording heads. 
   In this aspect of the present invention, since, in a mode where a plurality of recording heads are provided, the record positions of the recording heads at the same timing are mutually different, then by determining the speed variation data for each recording head, it is possible to achieve correction of the speed variation of the recording medium in consideration of the differences in the recording positions on the recording medium of the respective recording heads. 
   The different types of image record substances include inks of different colors. The plurality of recording heads corresponding to the different types of image record substances include recording heads for respective colors. 
   Preferably, the image recording apparatus further comprises: a speed variation position calculation device which calculates a position on the recording medium corresponding to a timing at which the speed variation occurs, in accordance with a position of the recording device in a conveyance path of the recording medium; and a determination control device which controls the determination and calculation device in such a manner that the determination unit selectively determines the determination pattern at the position on the recording medium corresponding to the timing at which the speed variation occurs, in accordance with calculation results of the speed variation position calculation device. 
   In this aspect of the present invention, it is possible to reduce the volume of determination data determined by the determination device, and this contributes to reducing the processing load of the calculation device which acquires the speed variation data, reducing the storage capacity of the storage device which stores the speed variation data, and thus helping to reduce the overall cost of the apparatus. 
   In order to attain the aforementioned object, the present invention is also directed to an image recording apparatus, comprising: a recording device which deposits an image record substance on an intermediate transfer body; a transfer device which transfers an image composed of the image record substance deposited on the intermediate transfer body to a recording medium by causing the intermediate transfer body and the recording medium to move relative to each other while causing the intermediate transfer body and the recording medium to be pressed against each other; a determination device which determines a determination pattern composed of the image record substance on the intermediate transfer body deposited by the recording device; a calculation device which acquires speed variation data of the intermediate transfer body in accordance with determination results acquired by the determination device; a storage device which stores the speed variation data of the intermediate transfer body acquired by the calculation device; and a record timing correction device which corrects record timing of the recording device in accordance with the speed variation data of the intermediate transfer body stored in the storage device. 
   In this aspect of the present invention, in an image recording apparatus which uses a so-called transfer method, in a mode where an image is formed on an intermediate transfer body while transferring an image from the intermediate transfer body to the recording medium, the speed variation occurring in the intermediate body due to the transfer operation is corrected and therefore it is possible to form a desirable image which is free of non-uniformities, on the intermediate transfer body. 
   In an image recording apparatus which uses the transfer method, the speed variation occurring in the recording medium when the recording medium is supplied or when the recording medium is output does not affect image recording onto the image transfer body. 
   Preferably, the recording device forms the determination pattern on the intermediate transfer body in a state where the intermediate transfer body and the recording medium are moved relatively to each other while being pressed against each other. 
   In this aspect of the present invention, since the determination pattern is recorded under the same conditions in the actual image formation on the image transfer body, then it is possible to determine the speed variation occurring in intermediate transfer body during actual image formation, accurately, and therefore the record timing can be corrected in a desirable fashion. 
   Preferably, the record timing correction device corrects the record timing so as to eliminate an error based on difference between an actual conveyance amount of the intermediate transfer body and a theoretical conveyance amount of the intermediate transfer body. 
   In other words, by correcting the cycle of the trigger signal which indicates the record timing, it is possible to make the conveyance distance of the intermediate transfer body during two record timings coincide with the theoretical conveyance distance. If the actual conveyance distance is greater than the theoretical conveyance distance, then the record timing is corrected in such a manner that the cycle of the trigger signal becomes shorter, and if the actual conveyance distance is shorter than the theoretical distance, then the record timing is corrected in such a manner that the cycle of the trigger signal becomes longer. 
   Preferably, the recording medium used when the determination pattern is recorded on the intermediate transfer body, has a type and a size identical to the recording medium used in actual image recording. 
   In this aspect of the present invention, by using the recording medium which is used in actual image recording, when forming the determination pattern, it is possible to determine and correct the speed variation of the intermediate transfer body which occurs during actual image formation, in an accurate fashion, and hence a desirable recording image can be obtained. 
   Preferably, the above-described image recording apparatuses further include an environment conditions measurement device which measures environment conditions including at least one of temperature and humidity in a conveyance path of the recording medium, wherein: the storage device stores the speed variation data in association with the environment conditions; the record timing correction device corrects the record timing of the recording device by reading out the speed variation data corresponding to the environment conditions measured by the environment conditions measurement device, from the storage device. 
   In this aspect of the present invention, even in cases where the thickness or the rigidity of the recording medium changes due to variation in the environmental conditions, such as the temperature and humidity, it is possible to correct the record timing in an appropriate manner. 
   In order to attain the aforementioned object, the present invention is also directed to an image recording method for an image recording apparatus which includes: a recording device which deposits an image record substance on a recording medium; and a recording medium conveyance device which includes a conveyance medium having a recording medium hold region and conveying the recording medium with respect to the recording device in a conveyance direction while holding the recording medium on the recording medium hold region, the image recording method comprising the steps of: determining a determination pattern which is formed outside the recording medium hold region on the conveyance medium and which follows the conveyance direction; calculating speed variation data of the conveyance medium in accordance with determination results of the determination pattern; storing the calculated speed variation data in a storage device; reading the stored speed variation data of the conveyance medium from the storage device; correcting record timing of the recording device in accordance with the read speed variation data; and recording an image on the recording medium with the recording device by depositing the image record substance on the recording medium according to the corrected record timing. 
   Moreover, in order to attain the aforementioned object, the present invention is also directed to an image recording method for an image recording apparatus which includes: a recording device which deposits an image record substance on a recording medium; and a recording medium conveyance device which conveys the recording medium with respect to the recording device in a conveyance direction while holding the recording medium, the image recording method comprising the steps of: determining a determination pattern composed of the image record substance which is deposited on the recording medium by the recording device; calculating speed variation data of the recording medium in accordance with determination results of the determination pattern; storing the calculated speed variation data in a storage device; reading the stored speed variation data of the recording medium from the storage device; correcting record timing of the recording device in accordance with the read speed variation data; and recording an image on the recording medium with the recording device by depositing the image record substance on the recording medium according to the corrected record timing. 
   Further, in order to attain the aforementioned object, the present invention is also directed to an image recording method for an image recording apparatus which includes: a recording device which deposits an image record substance on an intermediate transfer body; and a transfer device which transfers an image composed of the image record substance deposited on the intermediate transfer body to a recording medium by causing the intermediate transfer body and the recording medium to move relative to each other while causing the intermediate transfer body and the recording medium to be pressed against each other, the image recording method comprising the steps of: determining a determination pattern composed of the image record substance which is deposited on the intermediate transfer body by the recording device; calculating speed variation data of the intermediate transfer body in accordance with determination results of the determination pattern; storing the calculated speed variation data in a storage device; reading the stored speed variation data of the intermediate transfer body from the storage device; correcting record timing of the recording device in accordance with the read speed variation data; recording the image on the intermediate transfer body with the recording device by depositing the image record substance on the intermediate transfer body according to the corrected record timing; and transferring the recorded image on the intermediate transfer body to a recording medium with the transfer device. 
   According to the present invention, since sudden speed variation caused by the conveyance medium on which the recording medium is held is corrected on the basis of the speed variation data of the conveyance medium stored in the storage device, then the occurrence of non-uniformities in the recorded image as a result of the sudden speed variation of the conveyance medium is prevented. Furthermore, since the speed variation data stored previously in the storage device is used for correcting the speed variation of the conveyance medium, then no delay arises due to the determination time or the processing time, compared to a system where speed variation of the conveyance medium is corrected while the behavior of the conveyance medium is determined. 
   Moreover, sudden speed variation occurring in the recording medium, or speed variation of the recording medium caused by sudden speed variation occurring in the conveyance medium due to stretching or defects in the conveyance medium, or slippage between the recording medium and the conveyance medium, is corrected on the basis of the speed variation data for the recording medium stored in the storage device, and therefore the occurrence of non-uniformities in the recorded image due to sudden speed variations in the recording medium is prevented. 
   In an image recording apparatus which uses a so-called transfer method, in a mode where an image is formed on an intermediate transfer body while transferring an image from the intermediate transfer body to the recording medium, the speed variation occurring in the intermediate body due to the transfer operation is corrected and therefore it is possible to form a desirable image which is free of non-uniformities, on the intermediate transfer body. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The nature of this invention, as well as other objects and advantages thereof, will be explained in the following with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures and wherein: 
       FIG. 1  is a basic schematic drawing of an inkjet recording apparatus according to a first embodiment of the present invention; 
       FIG. 2  is a plan view of the principal part of the peripheral printing region of the inkjet recording apparatus illustrated in  FIG. 1 ; 
       FIGS. 3A to 3C  are plan view perspective diagrams showing examples of the composition of a print head; 
       FIG. 4  is a cross-sectional diagram showing the three-dimensional structure of a print head; 
       FIG. 5  is a cross-sectional diagram showing the composition of an ink supply system of the inkjet recording apparatus shown in  FIG. 1 ; 
       FIG. 6  is a principal block diagram showing the system configuration of the inkjet recording apparatus shown in  FIG. 1 ; 
       FIGS. 7A and 7B  are diagrams showing the relationship between the conveyance speed of the belt and the ejection timing; 
       FIGS. 8A and 8B  are diagrams for illustrating ejection timing correction according to an embodiment of the present invention; 
       FIG. 9  is a basic schematic drawing of an inkjet recording apparatus according to a second embodiment of the present invention; 
       FIG. 10  is a block diagram showing the system composition of the speed determination block illustrated in  FIG. 9 ; 
       FIGS. 11A and 11B  are diagrams for describing test pattern images recorded by the image recording block in  FIG. 9 ; 
       FIG. 12  is a diagram for describing the consecutive conveyance of a plurality of sheets, in the inkjet recording apparatus shown in  FIG. 9 ; 
       FIG. 13  is a diagram showing the detailed composition of an image recording block shown in  FIG. 9 ; 
       FIGS. 14A and 14B  are diagrams for illustrating the factors of speed variation in a case where one sheet of recording paper is conveyed; 
       FIGS. 15A and 15B  are diagrams for illustrating factors (A) and (B) of the speed variation; 
       FIGS. 16A and 16B  are diagrams for illustrating factors (C) and (D) of the speed variation; 
       FIG. 17  is a diagram showing the detailed composition of another aspect of the image recording block shown in  FIG. 9 ; 
       FIG. 18  is a diagram for describing test pattern determination relating to a second embodiment of the present invention; 
       FIG. 19  is a diagram for describing test pattern recording relating to a second embodiment of the present invention; 
       FIG. 20  is a flowchart of test pattern recording relating to a second embodiment of the present invention; 
       FIGS. 21A to 21K  are diagrams for describing state transitions in test pattern recording relating to a second embodiment of the present invention; 
       FIGS. 22A and 22B  are diagrams for describing the relationship between the speed variation positions and the nozzles; 
       FIG. 23  is a basic schematic drawing of an inkjet recording apparatus according to an application example of the second embodiment of the present invention; 
       FIG. 24  is a basic schematic drawing of an inkjet recording apparatus according to a third embodiment of the present invention; and 
       FIG. 25  is a block diagram showing the system configuration of the inkjet recording apparatus shown in  FIG. 24 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   First Embodiment 
   General Composition of Inkjet Recording Apparatus 
     FIG. 1  is a diagram of the general composition of an inkjet recording apparatus (image recording apparatus) according to an embodiment of the present invention. As shown in  FIG. 1 , the inkjet recording apparatus  10  comprises: a recording unit  12  (recording device) having a plurality of recording heads  12 K,  12 C,  12 M and  12 Y for ink colors of black (K), cyan (C), magenta (M), and yellow (Y), respectively; an ink storing and loading unit  14  for storing inks of K, C, M and Y to be supplied to the respective recording heads  12 K,  12 C,  12 M and  12 Y; a paper supply unit  18  for supplying recording paper  16 ; a decurling unit  20  for removing curl in the recording paper  16  supplied from the paper supply unit  18 ; a suction belt conveyance unit  22  (conveyance device) disposed facing the nozzle face (ink ejection face) of the recording unit  12 , for conveying the recording paper  16  while keeping the recording paper  16  flat; a print determination unit  24  for reading the printed result produced by the recording unit  12 ; a test pattern reading unit  25  (corresponding to a “determination device”) which reads in a test pattern (corresponding to “determination pattern”; not shown in  FIG. 1 , but indicated by reference numeral  37  in  FIG. 2 ) formed on the recording paper supporting surface of a conveyance belt  33  which supports and conveys the recording paper  16 ; and a paper output unit  26  for outputting image-printed recording paper (printed matter) to the exterior. 
   In  FIG. 1 , a magazine for rolled paper (continuous paper) is shown as an example of the paper supply unit  18 ; however, more magazines with paper differences such as paper width and quality may be jointly provided. Moreover, papers may be supplied with cassettes that contain cut papers loaded in layers and that are used jointly or in lieu of the magazine for rolled paper. 
   In the case of a configuration in which a plurality of types of recording paper can be used, it is preferable that an information recording medium such as a bar code and a wireless tag containing information about the type of paper is attached to the magazine, and by reading the information contained in the information recording medium with a predetermined reading device, the type of paper to be used is automatically determined, and ink-droplet ejection is controlled so that the ink-droplets are ejected in an appropriate manner in accordance with the type of paper. A composition may be adopted in which the recording paper information can be input by the user by means of a user interface. 
   The recording paper  16  delivered from the paper supply unit  18  retains curl due to having been loaded in the magazine. In order to remove the curl, heat is applied to the recording paper  16  in the decurling unit  20  by a heating drum  30  in the direction opposite from the curl direction in the magazine. The heating temperature at this time is preferably controlled so that the recording paper  16  has a curl in which the surface on which the print is to be made is slightly round outward. 
   In the case of the configuration in which roll paper is used, a cutter (first cutter)  28  is provided as shown in  FIG. 1 , and the continuous paper is cut into a desired size by the cutter  28 . The cutter  28  has a stationary blade  28 A, whose length is not less than the width of the conveyor pathway of the recording paper  16 , and a round blade  28 B, which moves along the stationary blade  28 A. The stationary blade  28 A is disposed on the reverse side of the printed surface of the recording paper  16 , and the round blade  28 B is disposed on the printed surface side across the conveyor pathway. When cut papers are used, the cutter  28  is not required. 
   The decurled and cut recording paper  16  is delivered to the suction belt conveyance unit  22 . The suction belt conveyance unit  22  has a configuration in which an endless belt  33  is set around rollers  31  and  32  so that the portion of the endless belt  33  (conveyance medium) facing at least the nozzle face of the recording unit  12  and the sensor face of the print determination unit  24  forms a horizontal plane (flat plane). 
   The belt  33  has a width that is greater than the width of the recording paper  16 , and a plurality of suction apertures (not shown) are formed on the belt surface. A suction chamber  34  is disposed in a position facing the sensor surface of the print determination unit  24  and the nozzle surface of the recording unit  12  on the interior side of the belt  33 , which is set around the rollers  31  and  32 , as shown in  FIG. 1 . The suction chamber  34  provides suction with a fan  35  to generate a negative pressure, and the recording paper  16  on the belt  33  is held by suction. In other words, the region of the belt  33  where the suction apertures are formed functions as a region (recording medium hold region) for holding the recording paper  16 . The mode of holding the recording paper  16  on the belt  33  is not limited to a mode using air suction, and it is also possible to adopt other methods, as appropriate, such as electrostatic attraction in which static electricity is generated between the belt  33  and the recording paper  16 , and the recording paper  16  is thereby attracted to the belt  33  by means of an electrostatic force. 
   The belt  33  is driven in the clockwise direction in  FIG. 1  by the motive force of a motor  88  (not shown in  FIG. 1 , but shown in  FIG. 6 ) being transmitted to at least one of the rollers  31  and  32 , which the belt  33  is set around, and the recording paper  16  held on the belt  33  is conveyed from left to right in  FIG. 1 . 
   Since ink adheres to the belt  33  when a marginless print job or the like is performed, a belt-cleaning unit  36  is disposed in a predetermined position (a suitable position outside the printing area) on the exterior side of the belt  33 . Although the details of the configuration of the belt-cleaning unit  36  are not shown, examples thereof include a configuration of nipping with a brush roller, or a water absorbent roller or the like, an air blow configuration in which clean air is blown onto the belt, or a combination of these. In the case of the configuration of nipping with the cleaning rollers, it is preferable to make the line velocity of the cleaning rollers different than that of the belt  33  to improve the cleaning effect. 
   The inkjet recording apparatus  10  may include a roller nip conveyance mechanism, in place of the suction belt conveyance unit  22 . However, there is a drawback in the roller nip conveyance mechanism that the print tends to be smeared when the printing area is conveyed by the roller nip action because the nip roller makes contact with the printed surface of the paper immediately after printing. Therefore, the suction belt conveyance in which nothing comes into contact with the image surface in the printing area is preferable. 
   Paper supply rollers  38 A and  38 B which guide recording paper  16  supplied from a paper supply unit  18 , onto the belt  33 , are provided on the upstream side (between the cutter  28  and the suction belt conveyance unit  22 ) of the suction belt conveyance unit  22  shown in  FIG. 1 , in terms of the conveyance direction of the recording paper  16  (hereinafter, called “paper conveyance direction”). When either the paper supply roller  38 A, which presses against the recording surface (the upper side in  FIG. 1 ) of the recording paper  16  on which the image is recorded, or the paper supply roller  38 B, which presses against the holding surface (the lower side in  FIG. 1 ) of the recording paper  16  which is held by the belt  33 , is caused to rotate, then the recording paper  16  pinched between the paper supply rollers  38 A and  38 B is conveyed to the belt  33  in synchronism with the rotation of the paper supply rollers  38 A and  38 B, and the recording paper  16  is guided to the recording paper holding region on the belt  33 . 
   A paper supply sensor  39  which detects the recording paper  16  (in other words, which judges whether or not the leading end of the recording paper  16  has arrived at the suction belt conveyance unit  22 ) is provided at the furthest upstream position on the paper conveyance path formed by the suction belt conveyance unit  22 . The paper supply sensor  39  is composed of a light source (such as a LED) and a photoreceptor that is disposed across the recording paper  16  from the light source, and it outputs a determination signal which is directly proportional to the amount of light arriving at the photoreceptor. If recording paper  16  is present between the light source and the photoreceptor, then the amount of light incident on the photoreceptor is reduced in comparison with a case where the recording paper  16  is not present, and therefore the presence or absence of recording paper  16  is judged on the basis of the amount of light incident on the photoreceptor (in other words, the magnitude of the determination signal). 
   Furthermore, it is also possible to determine the length of the recording paper  16  in the direction of paper conveyance by storing (counting) the output signal of the paper supply sensor  39  continuously. In other words, the length of the recording paper  16  in the conveyance direction is found by multiplying the conveyance speed of the recording paper  16  by the time taken for the recording paper  16  to pass through the sensing region of the paper supply sensor  39 . 
   It is also possible to dispose a light source and a photoreceptor on the same side of the recording paper  16  in such a manner that the photoreceptor receives the light emitted from the light source and reflected by the recording paper  16 . 
   A temperature and humidity measurement unit  40  is provided at the next stage after the paper supply sensor  39  (on the downstream side in terms of the paper conveyance direction). The temperature and humidity measurement unit  40  is constituted by a temperature measurement section which measures the temperature, a humidity measurement section which measures the humidity, and a signal processing unit which carries out prescribed signal processing, such as noise reduction, amplification, and the like, on the temperature signal output from the temperature measurement section and the humidity signal output from the humidity measurement section. 
   A heating fan  41  is provided at the next stage after the temperature and humidity measurement unit (the downstream side in terms of the paper conveyance direction). This heating fan  41  blows heated air onto the recording paper  16  before printing, and thereby heats up the recording paper  16 . Since the recording paper  16  is thus heated before printing, then the ink will dry more readily after depositing on the paper. 
   The recording unit  12  provided at the next stage after the heating fan  41  (the downstream side in terms of the paper conveyance direction) includes a so-called “full line head” in which a line head having a length corresponding to the maximum paper width is arranged in a direction (main scanning direction) that is perpendicular to the paper feed direction (see  FIG. 2 ). 
   Each of the recording heads  12 K,  12 C,  12 M and  12 Y is constituted by a line head, in which a plurality of ink ejection ports (nozzles) are arranged along a length that exceeds at least one side of the maximum-size recording paper  16  intended for use in the inkjet recording apparatus  10 , as shown in  FIG. 2 . An example of the detailed structure of the recording head is described later. 
   The recording heads  12 K,  12 C,  12 M and  12 Y are arranged in the order of black (K), cyan (C), magenta (M) and yellow (Y) from the upstream side, along the feed direction of the recording paper  16 . A color image can be formed on the recording paper  16  by ejecting the inks from the recording heads  12 K,  12 C,  12 M and  12 Y, respectively, onto the recording paper  16  while conveying the recording paper  16 . 
   The recording unit  12 , in which the full-line heads covering the entire width of the paper are thus provided for the respective ink colors, can record an image over the entire surface of the recording paper  16  by performing the action of moving the recording paper  16  and the recording unit  12  relative to each other in the sub-scanning direction just once (in other words, by means of a single sub-scan). Higher-speed printing is thereby made possible and productivity can be improved in comparison with a shuttle type head configuration in which a recording head moves reciprocally in the main scanning direction. 
   Although a configuration with four standard colors, K M C and Y, is described in the present embodiment, the combinations of the ink colors and the number of colors are not limited to these, and light and/or dark inks can be added as required. For example, a configuration is possible in which recording heads for ejecting light-colored inks such as light cyan and light magenta are added. 
     FIG. 2  is a plan diagram of the principal part of the recording unit  12  and the conveyance system of recording paper  16 , as viewed from the side of the recording surface of the recording paper  16 . As shown in  FIG. 2 , a test pattern  37  (determination pattern) composed of a plurality of rectangular patterns is formed by a photographic method on the belt  33 , to the outside of the recording paper holding region. 
   The plurality of patterns constituting the test pattern  37  have the same shape and are aligned at uniform intervals, following the paper conveyance direction. The test pattern  37  is read in with the test pattern reading unit  25  shown in  FIG. 1 , while the recording paper  16 , which is held on the belt  33 , is conveyed at the same conveyance speed as in actual image recording, in other words, under the same conditions as the image recording conditions, and the speed of the belt  33  is measured from the reading results. 
   The photographic method described above is a method in which a liquid containing a photosensitive material, such as resist (light-sensitive film), is applied to a prescribed position on the belt  33 , the resist is exposed by using a prescribed light source through a mask, and after this exposure process, the unwanted resist is removed, thereby forming a prescribed test pattern (determination pattern). If the photographic method is used, then it is possible to form a highly fine pattern with high precision, by using a mask which is larger than the actual test pattern and altering the magnification optically when carrying out exposure. 
   It is possible to form the test pattern  37  by applying a liquid, such as resin liquid, which does not contain photosensitive material, onto the belt  33  through a mask having the same pattern as the test pattern (by screen printing, for example), and then curing the liquid by means of a heating and cooling, or by means of a chemical method. 
   Although the details are described later, in the inkjet recording apparatus  10  shown in the present embodiment, the speed variation data for the belt  33  (recording paper  16 ) is previously obtained and stored, and ejection control is implemented in order to correct the ink ejection timings during image recording in accordance with this speed variation data. In the present embodiment, it is supposed that no slippage, or the like, occurs between the recording paper  16  and the belt  33 , and the conveyance speed of the recording paper  16  is the same as the speed of the belt  33  in the recording region. 
   From the viewpoint of the visibility of the non-uniformities in the recorded image caused by the variation in the speed of the belt  33 , it is desirable that the arrangement pitch of the test pattern  37  is 100 μm to 1 mm, and the width of each pattern is substantially ½ of the arrangement pitch of the test pattern. 
     FIG. 2  shows a mode where the test pattern  37  is provided in the vicinity of one end portion of the belt  33  in the breadthways direction thereof which is substantially perpendicular to the paper conveyance direction (the lower end portion in  FIG. 2 ), but the test pattern  37  may also be provided on the other end portion of the belt  33  in the breadthways direction thereof (for example, the upper end portion in  FIG. 2 ), or it may be provided on both end portions in the breadthways direction of the belt  33 . 
   Although the present embodiment shows a mode in which the test pattern  37  is formed on the belt  33  by means of a photographic method, it is also possible to adopt a mode in which the test pattern is created by forming slits in the belt  33 . In the mode where the slits are formed in the belt, it is difficult to process holes in order to form slits with high precision, and the deformation of the belt  33  due to the formation of the slits is also a concern. Therefore, a desirable mode is one in which the test pattern  37  is formed by the photographic method. 
   As shown in  FIG. 1 , the ink storing and loading unit  14  has ink tanks for storing the inks of the colors corresponding to the respective recording heads  12 K,  12 C,  12 M and  12 Y, and the respective tanks are connected to the recording heads  12 K,  12 C,  12 M and  12 Y by means of channels (not shown). The ink storing and loading unit  14  has a warning device (for example, a display device, an alarm sound generator, or the like) for warning when the remaining amount of any ink is low, and has a mechanism for preventing loading errors among the colors. 
   Furthermore, the paper supply unit  18  shown in  FIG. 1  is able to ascertain the type of recording paper  16 , and the like, by reading in an information storage body which stores recording paper information (recording medium information), such as the type of recording medium  16 . For example, an IC tag which stores recording paper information, such as the type of recording paper, the quantity (length) of the paper, the date of manufacture, and the like, is attached to the central core portion of recording paper in a rolled form, the information on the IC tag is read out with a reading device installed in the paper supply unit  18 , and the recording paper information thus read out is supplied to the control system (see  FIG. 6 ). 
   The print determination unit  24  according to the present embodiment reads out the image printed on the recording paper  16 , determines the print status (the presence/absence of ejection, variation in droplet ejection, and the like) by carrying out prescribed signal processing, or the like, and thereby functions as a print determination device for the control system (for example, the print controller  80  in  FIG. 6 ). The print determination unit  24  according to the present embodiment is constituted by a line sensor having a row of photoreceptor elements of a greater width than the total width of the belt  33  (the length in the direction perpendicular to the paper conveyance direction). This line sensor has a color separation line CCD sensor including a red (R) sensor row composed of photoelectric transducing elements (pixels) arranged in a line provided with an R filter, a green (G) sensor row with a G filter, and a blue (B) sensor row with a B filter. Instead of a line sensor, it is possible to use an area sensor composed of photoelectric transducing elements which are arranged two-dimensionally. 
   The test pattern reading unit  25  has a light source, such as an LED element, and a photoreceptor element, such as a photoelectric transducing element, provided on the side of the belt  33  where the test pattern is formed, and light is radiated onto the test pattern formed on the belt  33 , by the light source, the light reflected is thereby received by the photoreceptor, and a determination signal which is directly proportional to the amount of incident light is output by the photoreceptor. It is also possible to adopt a composition in which the belt  33  is made of a transparent member (or semi-transparent member), and the photoreceptor element is disposed across the belt  33  from the light source, in such a manner that the light emitted from the light source and transmitted through the belt is received by the photoreceptor. 
   Furthermore, the test pattern reading unit  25  which is used in the present embodiment has a reading resolution which enables it to read each individual pattern of the test pattern  37 . It is also possible to combine the test pattern reading unit  25  with the print determination unit  24 . 
   A post-drying unit  42  is disposed following the test pattern reading unit  25 . The post-drying unit  42  is a device to dry the printed image surface, and includes a heating fan, for example. It is preferable to avoid contact with the printed surface until the printed ink dries, and a device that blows heated air onto the printed surface is preferable. 
   In cases in which printing is performed with dye-based ink on porous paper, blocking the pores of the paper by the application of pressure prevents the ink from coming into contact with ozone and other substance that cause dye molecules to break down, and has the effect of increasing the durability of the print. 
   A heating/pressurizing unit  44  is disposed following the post-drying unit  42 . The heating/pressurizing unit  44  is a device to control the glossiness of the image surface, and the image surface is pressed with a pressure roller having a predetermined uneven surface shape while the image surface is heated, and the uneven shape is transferred to the image surface. 
   Paper output rollers  45 A and  45 B are provided at the stage after the heating and pressurizing unit  44  (in other words, on the downstream side of the suction belt conveyance unit  22  in terms of the paper conveyance direction). The paper output rollers  45 A and  45 B have the same structure as the paper supply rollers  38 A and  38 B described above, and when the recording paper  16  subjected to the complete image recording arrives between the paper output rollers  45 A and  45 B, then the recording paper  16  is output while being pressed between the paper output roller  45 A and  45 B. 
   A paper output sensor  46  which detects the recording paper  16  (namely, which judges whether or not the trailing end of the recording paper  16  has exited from the conveyance belt conveyance unit  22 ) is provided at the stage after the paper output rollers  45 A and  45 B. The paper output sensor  46  adopts the same composition as that of the paper supply sensor  39  described above. 
   The printed matter generated in this manner is outputted from the paper output unit  26 . The target print (i.e., the result of printing the target image) and the determination print image (the image for determining the printing) are preferably outputted separately. In the inkjet recording apparatus  10 , a sorting device (not shown) is provided for switching the outputting pathways in order to sort the printed matter with the target print and the printed matter with the determination print, and to send them to paper output units  26 A and  26 B, respectively. When the target print and the determination print are simultaneously formed in parallel on the same large sheet of paper, the determination print portion is cut and separated with a cutter (second cutter)  48 . The cutter  48  is disposed directly in front of the paper output unit  26 , and is used for cutting the determination print portion from the target print portion when the determination print has been performed in the blank portion of the target print. The structure of the cutter  48  is the same as the first cutter  28  described above, and has a stationary blade  48 A and a round blade  48 B. 
   Although not shown in  FIG. 1 , the paper output unit  26 A for the target prints is provided with a sorter for collecting prints according to print orders. The reference numeral  26 A is a main image output unit and the reference numeral  26 B is a print determination image output unit. 
   Description of Structure of Recording Head 
   Next, the structure of the recording head is described below. The recording heads  12 K,  12 C,  12 M and  12 Y provided for the respective ink colors have the same structure, and a reference numeral  50  is hereinafter designated to any of the recording heads  12 K,  12 C,  12 M and  12 Y. 
     FIG. 3A  is a plan view perspective diagram showing an example of the composition of a recording head  50 , and  FIG. 3B  is an enlarged diagram of a portion of same. Furthermore,  FIG. 3C  is a plan view perspective diagram showing a further example of the structure of a recording head  50 . In order to achieve a high density of the dot pitch printed onto the surface of the recording medium, it is necessary to achieve a high density of the nozzle pitch in the recording head  50 . As shown in  FIGS. 3A to 3C  and  4 , the recording head  50  in the present embodiment has a structure in which a plurality of ink chamber units  53 , each including a nozzle  51  from which ink is output and a pressure chamber  52  connecting to the corresponding nozzle  51 , are disposed in the form of a staggered matrix, and the effective nozzle pitch is thereby made small. 
   More specifically, as shown in  FIGS. 3A and 3B , the recording head  50  according to the present embodiment is a full-line head having one or more nozzle rows in which a plurality of nozzles  51  for ejecting ink are arranged along a length corresponding to the entire width of the recording paper  16  in a direction substantially perpendicular to the paper conveyance direction. 
   Moreover, as shown in  FIG. 3C , a full-line head can be composed of a plurality of short two-dimensionally arrayed head units  50 ′ disposed in a staggered arrangement and combined so as to form nozzle rows having lengths that correspond to the entire width of the recording paper  16 . Furthermore, although not shown in the drawings, it is also possible to connect short heads in a linear fashion. 
   As shown in  FIGS. 3A to 3C , the pressure chamber  52  provided corresponding to each of the nozzles  51  is approximately square-shaped in plan view, and a nozzle  51  and a supply port  54  are provided respectively at either corner of a diagonal of the pressure chamber  52 . Moreover, the respective pressure chambers  52  are each connected via a supply port  54  to the common liquid chamber (not shown in  FIGS. 3A to 3C ; and indicated by reference numeral  55  in  FIG. 4 ). 
   As shown in  FIG. 3B , the plurality of ink chamber units  53  having this structure are composed in a lattice arrangement, based on a fixed arrangement pattern having a row direction which coincides with the main scanning direction, and a column direction which, rather than being perpendicular to the main scanning direction, is inclined at a fixed angle of θ with respect to the main scanning direction. By adopting a structure in which a plurality of ink chamber units  53  are arranged at a uniform pitch d in a direction having an angle θ with respect to the main scanning direction, the pitch P of the nozzles projected so as to align in the main scanning direction is d×cos θ. 
   More specifically, the arrangement can be treated equivalently to one in which the respective nozzles  51  are arranged in a linear fashion at uniform pitch P, in the main scanning direction. By means of this composition, it is possible to achieve a nozzle composition of high density, in which the nozzle columns projected to align in the main scanning direction reach a total of 2400 per inch (2400 nozzles per inch). Below, in order to facilitate the description, it is supposed that the nozzles  51  are arranged in a linear fashion at a uniform pitch (P), in the longitudinal direction of the head (main scanning direction). 
   In a full-line head comprising rows of nozzles corresponding to the entire width of the paper, the “main scanning” is defined as printing one line formed of a row of dots, or a line formed of a plurality of rows of dots in the width direction of the recording paper (the direction perpendicular to the conveyance direction of the recording paper) by driving the nozzles in one of the following ways: (1) simultaneously driving all the nozzles; (2) sequentially driving the nozzles from one side toward the other; and (3) dividing the nozzles into blocks and sequentially driving the nozzles from one side toward the other in each of the blocks. 
   In particular, when the nozzles  51  arranged in a matrix such as that shown in  FIGS. 3A  to  3 C are driven, the main scanning according to the above-described (3) is preferred. On the other hand, “sub-scanning” is defined as to repeatedly perform printing of one line formed of a row of dots, or a line formed of a plurality of rows of dots formed by the main scanning, while moving the full-line head and the recording paper relatively to each other. 
   In other words, “main scanning” is the action of driving the nozzles so as to print a line constituted by one row of dots, or a plurality of rows of dots, in the breadthways direction of the paper, and “sub-scanning” is the action of repeating the printing of a line constituted by one row of dots or a plurality of rows of dots formed by main scanning. When implementing the present invention, the arrangement of the nozzles is not limited to that of the example illustrated. 
     FIG. 4  is a cross-sectional diagram showing the three-dimensional structure of the recording head  50  (the ink chamber unit  53  shown in  FIGS. 3A to 3C ) (namely, a cross-sectional diagram along line  4 - 4  in  FIGS. 3A and 3B ). A piezoelectric element  58  including an individual electrode  57  is bonded to the diaphragm  56  which constitutes the ceiling of the pressure chambers  52 , and the diaphragm  56  also functions as a common electrode for the piezoelectric elements  58 . By applying a drive voltage to the individual electrode  57 , a bending deformation is applied to the piezoelectric element  58 , the pressure chamber  52  is deformed, and ink is ejected from the nozzle  51 . When ink is ejected from the nozzle, ink is supplied to the pressure chamber  52  from the common flow chamber  55 , via the supply port  54 . 
   In the present embodiment, a method is adopted in which ink is pressurized by the deformation of the piezoelectric element  58 . In implementing the present invention, another actuator other than a piezoelectric element can also be used in place of the piezoelectric element  58 . 
   Furthermore, in the present embodiment, a recording head is described in which nozzles are arranged in a matrix configuration, but the nozzle arrangement is not limited to a matrix configuration and it is also possible to use a mode where nozzles are arranged in one row following a direction which is perpendicular to the paper conveyance direction, and a mode where two nozzle rows are arranged in a staggered configuration. 
   The present embodiment describes, as an example, a full line recording head which has an ejection port row of a length corresponding to the breadthways direction of the recording paper  16 , but the present invention may also be applied to a serial head which uses a method in which printing is carried out in the breadthways direction of the recording paper  16  while scanning the recording paper  16  with a short head having a length shorter than the breadthways length of the recording paper  16 , in the breadthways direction of the recording paper  16 , and the printing in the breadthways direction of the recording paper  16  is repeated while conveying the recording paper  16  in the paper conveyance direction. 
   Description of Ink Supply System 
   Next, the general composition of the ink supply system of the inkjet recording apparatus  10  is described below.  FIG. 5  is a conceptual diagram showing the composition of an ink supply system in the inkjet recording apparatus  10 . 
   The ink supply tank  60  is a base tank that supplies ink and is set in the ink storing and loading unit  14  described with reference to  FIG. 1 . The aspects of the ink supply tank  60  include a refillable type and a cartridge type: when the remaining amount of ink is low, the ink supply tank  60  of the refillable type is filled with ink through a filling port (not shown) and the ink supply tank  60  of the cartridge type is replaced with a new one. In order to change the ink type in accordance with the intended application, the cartridge type is suitable, and it is preferable to represent the ink type information with a bar code or the like on the cartridge, and to perform ejection control in accordance with the ink type. 
   A filter  62  for removing foreign matters and bubbles is disposed between the ink supply tank  60  and the recording head  50  as shown in  FIG. 5 . The filter mesh size is preferably equivalent to or less than the diameter of the nozzle and commonly about 20 μm. 
   Desirably, a composition is adopted in which a sub tank (not illustrated) is provided in the vicinity of the recording head  50 , or in an integrated fashion with the recording head  50 . The sub tank has a damper function for preventing variation in the internal pressure of the pressure chamber  52  and the common flow channel  55  and a function for improving refilling characteristics. 
   Possible modes for controlling the internal pressure of the common flow channel  55  by means of the sub tank are: a mode where the internal pressure of the pressure chambers  52  is controlled by the differential in the ink level between a sub tank which is open to the external air and the pressure chambers  52  inside the recording head  50 ; and a mode where the internal pressure of the sub tank and the internal pressure of the pressure chambers  52  are controlled by a pump connected to a sealed sub tank; and the like. Either of these modes may be adopted. 
   Description of Maintenance of Head 
   As shown in  FIG. 5 , a cap  64  forming a device for preventing the drying of the nozzles  51  or increase in the viscosity of the ink in the vicinity of the nozzles  51  is provided in the inkjet recording apparatus  10 , and a blade  66  is provided as a device for cleaning (wiping) the nozzle forming surface on which the nozzles  51  are formed. 
   A maintenance unit including the cap  64  and the blade  66  can be relatively moved with respect to the recording head  50  by a movement mechanism (not shown), and is moved from a predetermined holding position to a position below the recording head  50  as required. 
   The cap  64  shown in  FIG. 5  has a size which enables it to cover the whole of the nozzle forming surface of the recording head  50 . The cap  64  is displaced upwards and downwards in a relative fashion with respect to the recording head  50  by an elevator mechanism (not shown). When the power of the inkjet recording apparatus  10  is switched off or when in a print standby state, the cap  64  is raised to a predetermined raised position thereby placing same in close contact with the recording head  50  (the nozzle forming surface of the recording head  50 ), in such a manner that the nozzle forming surface is covered with the cap  64 . 
   During printing or standby, if the use frequency of a particular nozzle  51  is low, and if a state of not ejecting ink continues for a prescribed time period or more, then the solvent of the ink in the vicinity of the nozzle evaporates and the viscosity of the ink increases. In a situation of this kind, it will become difficult to eject ink from the nozzle  51 , even when the piezoelectric element  58  is operated. 
   Therefore, before a situation of this kind develops (namely, while the ink viscosity is within a range which allows the ink to be ejected by operation of the piezoelectric element  58 ), the piezoelectric element  58  is operated, and a preliminary ejection (“purge”, “blank ejection”, or “liquid ejection”) is carried out toward the cap  64  (ink receptacle), in order to expel the degraded ink (namely, the ink in the vicinity of the nozzle which has increased viscosity). 
   This suction operation is also carried out when ink is loaded into the head for the first time, or in order to remove degraded ink which has increased in viscosity and solidified when the head starts to be used after having been out of use for a long period of time. Since the suction operation is carried out with respect to all of the ink inside the pressure chambers  52 , the ink consumption is considerably large. Therefore, desirably, preliminary ejection is carried out while the increase in the viscosity of the ink is still minor. If an air bubble is present in a pressure chamber  52 , then a pressure loss occurs when the piezoelectric element  58  is operated, and therefore, nozzle suctioning is carried out with the object of removing air bubbles inside the pressure chambers  52 . 
   The blade  66  functions as a wiping device for removing dirt from the nozzle forming surface by moving while pressing against the nozzle forming surface, and a hard rubber material, or the like, is suitable for use in the blade  66 . In other words, the blade  66  has a prescribed strength (rigidity) and a prescribed elasticity, and the surface thereof has prescribed hydrophobic properties such that the ink droplets are repelled from the surface thereof. The blade  66  is constituted of a member which is capable of wiping and removing ink (ink that has solidified on the nozzle forming surface), paper dust, and other foreign matter, which has adhered to the nozzle forming surface. 
   Furthermore, although not shown in  FIG. 5 , the head maintenance mechanism (head maintenance device) of the inkjet recording apparatus  10  includes a blade elevator mechanism (not shown), which moves the blade  66  in the upward and downward directions and thus switches the blade  66  between a state of contact and a state of non-contact with the nozzle forming surface, and a cleaning device which removes foreign matter adhering to the blade  66 . 
   Description of Control System 
   Next, the control system of the inkjet recording apparatus  10  according to the present embodiment is described below.  FIG. 6  is a principal block diagram showing the system composition of the inkjet recording apparatus  10 . The inkjet recording apparatus  10  includes a communication interface  70 , a system controller  72 , a memory  74 , a conveyance drive control unit (motor driver)  76 , a heater driver  78 , a print controller  80 , an image buffer memory  82 , a head driver  84 , and the like. 
   The communication interface  70  is an interface unit for receiving image data sent from a host computer  86 . A serial interface such as USB (Universal Serial Bus), IEEE1394, Ethernet®, wireless network, or a parallel interface such as a Centronics interface may be used as the communication interface  70 . A buffer memory may be mounted in this portion in order to increase the communication speed. The image data sent from the host computer  86  is received by the inkjet recording apparatus  10  through the communication interface  70 , and is temporarily stored in the memory  74 . The memory  74  is a storage device for temporarily storing images inputted through the communication interface  70 , and data is written and read to and from the memory  74  through the system controller  72 . The memory  74  is not limited to a memory composed of semiconductor elements, and a hard disk drive or another magnetic medium may be used. 
   The system controller  72  is a control unit for controlling the various sections, such as the communication interface  70 , the memory  74 , the conveyance drive control unit  76 , the heater driver  78 , and the like. The system controller  72  is constituted by a central processing unit (CPU) and peripheral circuits thereof, and the like, and in addition to controlling communications with the host computer  86  and controlling reading and writing from and to the memory  74 , or the like, it also generates a control signal for controlling the motor  88  of the conveyance system and the heater  89 . 
   The conveyance drive control unit  76  is a driver (drive circuit) which drives the motor  88  of the conveyance drive system in accordance with instructions from the system controller  72 . In addition to the motor  88 , the conveyance drive control unit  76  also controls other motors relating to the conveyance system, such as the paper supply rollers  38 A ( 38 B) and the paper output rollers  45 A ( 45 B). 
   The heater driver  78  drives the heater  89  of the post-drying unit  42  or the like in accordance with commands from the system controller  72 . The heater  89  shown in  FIG. 6  includes heaters such as a heater used in a post-drying unit  42 , as shown in  FIG. 1 , a temperature adjustment heater for each respective recording head  50 , and the like. 
   The print controller  80  has a signal processing function for performing various tasks, compensations, and other types of processing for generating print control signals from the image data stored in the memory  74  in accordance with commands from the system controller  72  so as to supply the generated print control signal (print data) to the head driver  84 . Prescribed signal processing is carried out in the print controller  80 , and the ejection amount and the ejection timing of the ink droplets from the respective recording heads  50  are controlled via the head driver  84 , on the basis of the print data. By this means, prescribed dot size and dot positions can be achieved. 
   The print controller  80  is provided with the image buffer memory  82 ; and image data, parameters, and other data are temporarily stored in the image buffer memory  82  when image data is processed in the print controller  80 . The aspect shown in  FIG. 6  is one in which the image buffer memory  82  accompanies the print controller  80 ; however, the memory  74  may also serve as the image buffer memory  82 . Also possible is an aspect in which the print controller  80  and the system controller  72  are integrated to form a single processor. 
   The head driver  84  drives the piezoelectric element  58  (see  FIG. 4 ) of the recording head  50  of the respective colors on the basis of print data supplied by the print controller  80 . The head driver  84  can be provided with a feedback control system for maintaining constant drive conditions for the print heads. 
   The program storage unit  90  stores control programs for the inkjet recording apparatus  10 , and the system controller  72  reads out the various control programs stored in the program storage unit  90 , as and when appropriate, and executes the control programs. 
   The print determination unit  24  is a block that includes the line sensor as described above with reference to  FIG. 1 , reads the image printed on the recording paper  16 , determines the print conditions (presence of the ejection and variation in the dot formation) by performing desired signal processing, or the like, and provides the determination results of the print conditions to the print controller  80 . According to requirements, the print controller  80  makes various corrections with respect to the recording head  52  on the basis of information obtained from the print determination unit  24 . 
   The test pattern reading unit  25  reads in the test pattern  37  (see  FIG. 2 ) formed on the belt  33 , by means of a sensor, and sends a corresponding read signal to the print controller  80 . The test pattern reading unit  25  includes a reading control unit (reading control device) which controls the reading by the sensor on the basis of a control signal supplied by the print controller  80 . 
   The speed calculation unit  92 , which is one functional block of the print controller  80 , calculates the speed variation data for the belt  33  on the basis of the read signal for the test pattern  37 , and the speed variation data is stored in a speed variation data storage unit  94  attached to the print controller  80 . 
   The speed variation data for the belt  33  stored in the speed variation data storage unit  94  is read out as and when appropriate by the ejection timing correction unit  96 , which is one functional block of the print controller  80 . The ejection timing correction unit  96  corrects the ink ejection timing on the basis of the speed variation data for the belt  33  (the ejection timing correction unit  96  sends a trigger signal indicating a corrected ejection timing to the head driver  84 ), and the ink is ejected at the corrected ejection timing. 
   The determination signals output from the paper supply sensor  39  and the paper output sensor  46  shown in  FIG. 1  are supplied to the system controller  72 , and it is judged whether or not the recording paper  16  is present in the recording paper conveyance path of the belt  33 , in addition to which a recording paper calculation unit (counter)  98 , which is one functional block of the system controller  72 , calculates the length of the recording paper  16  on the conveyance path, and the interval between sheets of recording paper when a plurality of recording papers  16  are conveyed continuously (namely, the distance between the trailing end of a preceding recording paper and the leading end of a subsequent recording paper), on the basis of the determination signal from the paper supply sensor  39 . 
     FIG. 6  shows the memories as separate memories according to the contents of the information stored therein, but these memories can be formed as shared memories or separate memories, accordingly. Moreover, the invention is not limited to a mode where the memories are attached to the system controller  72  and the print controller  80 , and it is also possible to use the internal memory of the processors which constitute the system controller  72  and the print controller  80 . 
   Description of Ejection Timing Correction 
   Next, the correction of ink ejection timing in the recording head  50  is described below. In the inkjet recording apparatus  10  according to the present embodiment, the test pattern  37  formed on the belt  33  is read in with the test pattern reading unit  25 , the speed variation data for the belt  33  is calculated from the read result, this speed variation data is stored, and the ink ejection timing of the recording head  50  is corrected during image recording on the basis of the speed variation data for the belt  33 . 
   The reading in of the test pattern  37  and the calculation of the speed variation data for the belt  33  needs to be carried out once only, when the apparatus is started up, for example. However, desirably, the test pattern  37  is read in and the speed variation data of the belt is calculated and stored, appropriately, when maintenance of the conveyance system, such as replacement of the belt  33 , is carried out, or when recording paper  16  of a type for which speed variation data has not been stored is used, for instance. Moreover, the speed variation data corresponding to environmental conditions, such as the temperature and humidity, may be prepared in advance and the speed variation data to be used may be selected in accordance with the temperature and humidity. The mode of selecting the speed variation data in accordance with the temperature and humidity also includes a mode in which a temperature coefficient (a correction coefficient based on temperature) and a humidity coefficient (a correction coefficient based on humidity) are prepared in advance, and the speed variation data is corrected by multiplying the temperature coefficient and the humidity coefficient. 
   Next, the relationship between the conveyance speed of the belt  33  and the ejection timing is described below.  FIG. 7A  is a diagram showing the conveyance speed of the belt  33  in which there is no speed variation (in other words, the theoretical conveyance speed), and FIG.  7 B is a diagram showing a trigger signal  108  which indicates the theoretical ejection timings (namely, the uncorrected ejection timings). The timings t 1  to t 4  shown in  FIG. 7A  indicate the ejection timings of the recording head  50 . At the respective ejection timings shown in  FIG. 7B , it is possible to carry out ink ejection simultaneously from a plurality of nozzles. 
   Furthermore, the values (namely, the areas of the rectangular shapes indicated by the reference numerals  100 ,  102 ,  104  and  106  in  FIG. 7A ) obtained by integrating the conveyance speed of the belt  33  with respect to the time interval between one ejection timing and the next ejection timing (for example, between t 1  and t 2 ), represent the distances (in other words, the conveyance amount of the recording paper  16 ) moved by the belt  33  between the respective ejection timings. 
   More specifically, the area of the region in  FIG. 7A  indicated by the reference numeral  100  represents the movement distance of the belt  33  from timing to timing t 1 , and similarly, the areas of the regions indicated by the reference numerals  102 ,  104  and  106  respectively represent the movement distances of the belt  33  from t 1  to t 2 , from t 2  to t 3 , and from t 3  to t 4 . 
   The trigger signal  108  shown in  FIG. 7B  is a positive logic pulse signal, and an ink ejection action is carried out at the timings t 1 , t 2 , t 3 , and t 4  of the rising edges (leading edges) of the trigger signal  108 .  FIG. 7B  shows a positive logic pulse signal where the leading edge is taken as the rising edge, but it is also possible to use a negative logic pulse signal where the leading edge is taken to be the falling edge. 
     FIG. 8A  is a diagram showing the conveyance speed of the belt  33  in which there is variation in the speed of the belt  33 . It is extremely rare for the belt  33  to be conveyed ideally (theoretically), as shown in  FIG. 7A , and in actual practice, the speed variation occurs in the belt  33 , for instance, when the recording paper  16  separates from the paper supply roller  38 A (see  FIG. 1 ), or when the leading end portion of the recording paper  16  impacts the paper output roller  45 A (see  FIG. 1 ), and as a result of the occurrence of the speed variation such as that shown in  FIG. 8A , for example, positional displacement occurs in the recording paper  16 . 
   In the inkjet recording apparatus  10  shown in the present embodiment, the effect of the positional displacement of the recording paper  16  with respect to the recording head  50  caused by the speed variation of the belt  33 , can be eliminated by correcting the ejection timing so as to cancel the speed variation of the belt  33  such as that described above. 
   In other words, in the inkjet recording apparatus  10 , the timings at which ink is ejected toward the recording paper  16  held on the belt  33 , which produces the speed variation shown in  FIG. 8A , are changed in such a manner that the movement distance of the belt  33  between the ejection timings coincides with the theoretical movement distance. More specifically, the ejection timing is changed from t 1  to t 11 , in such a manner that the conveyance distance of the belt  33  indicated by the reference numeral  120  in  FIG. 8A  (the actual movement distance of the belt  33 ), becomes equal to the conveyance distance of the recording paper  16  indicated by the reference numeral  100  in  FIG. 7A  (the theoretical movement distance of the belt  33 , indicated by the broken line in  FIG. 8A ). Similarly, the theoretical ejection timings t 2 , t 3 , and t 4  are respectively changed to ejection timings t 12 , t 13 , and t 14 , in such a manner that the movement distances of the belt  33  indicated by the reference numerals  122 ,  124  and  126  in  FIG. 8A , become equal to the movement distances of the belt  33  indicated by the reference numerals  104 ,  106  and  108  in  FIG. 7A , respectively. 
   In other words, when the actual conveyance speed is slower than the theoretical conveyance speed, then the ejection timing is corrected in such a manner that the actual ejection timing is later than the theoretical ejection timing, and on the other hand, when the actual conveyance speed is faster than the theoretical conveyance speed, then the actual ejection timing is corrected in such a manner that the actual ejection timing is earlier than the theoretical ejection timing.  FIG. 8B  shows the trigger signal  128  in which the ejection timings described above have been corrected. 
   When the test pattern  37  is read in, a recording paper which is the same as the recording paper  16  to be used in actual image recording (the same type and the same size) is held on the belt  33 , and the recording paper  16  is conveyed at the same conveyance speed as that used in image recording. In other words, by setting the conveyance of the belt  33  to the same conditions as the image recording conditions, then it is possible to determine accurately the variation in the conveyance speed of the belt  33  which may occur during image recording. 
   Furthermore, in a case where there are a plurality of recording papers  16  used in image recording, or in a case where a plurality of conveyance speeds can be set (for example, in the case of a composition which can be switched between high-speed printing for a low resolution mode and low-speed printing for a high resolution mode), a plurality of the speed variation data associated with the parameters such as the type and size of the recording paper, and the conveyance speed (image recording mode), or the like, are stored in the speed variation data storage unit  94  shown in  FIG. 6 . In the ejection timing correction process, the plurality of speed variation data are read out appropriately in accordance with the above-described parameters. 
   Here, the factors of variation in the speed of the belt  33  are described below. When the recording paper  16  makes contact with (abuts against) the paper output rollers  45 A and  45 B shown in  FIG. 1 , and the recording paper  16  is pinched between the paper output rollers  45 A and  45 B, then the speed variation occurs in the recording paper  16  and therefore the speed variation occurs in the belt  33 , in synchronism with this speed variation of the recording paper  16 . 
   Similarly, when the recording paper  16  separates from the paper supply rollers  38 A and  38 B, the speed variation occurs in the belt  33 , in synchronism with the speed variation occurring in the recording paper  16 . When a plurality of pieces of recording paper  16  are conveyed in a consecutive fashion, there may be cases where image recording onto a subsequent recording paper may be in progress at the timing that the preceding recording paper makes contact with the paper output rollers  45 A and  45 B, depending on the length of the recording paper  16  in the paper conveyance direction. In such cases, the speed variation of the belt  33  caused by the speed variation of the preceding recording paper produces the speed variation in the subsequent recording paper and thus has an effect on the image quality of the subsequent recording paper. Furthermore, if image recording onto the preceding recording paper is in progress at the timing that the subsequent recording paper separates from the paper supply rollers  38 A and  38 B, then the speed variation of the belt  33  caused by the speed variation of the subsequent recording paper  16  has an effect on the image quality of the preceding recording paper. 
   Consequently, in the case of continuous image recording onto a plurality of pieces of paper, it is necessary to determine the speed variation data of the belt  33  under the same conditions as the actual conveyance conditions, by conveying a plurality of pieces of recording paper of the same type and size as those used in actual image recording, and hence to determine the indirect speed variation arising as a result of speed variation of the belt  33  caused by speed variation of another recording paper. Moreover, in the case of continuous image recording onto a plurality of pieces of paper, if the same image is to be recorded using the same size of recording paper, then the speed variation occurring in the belt  33  can be considered to have periodicity (namely, a certain speed variation pattern is repeated), and therefore it is possible to determine a basic pattern of corrected ejection timings based on a basic speed variation pattern and to repeat the basic pattern, thereby canceling the overall speed variation pattern. 
   The inkjet recording apparatus  10  having the composition described above reads in the test pattern  37  provided on the belt  33 , which holds and conveys the recording paper  16 , by means of the test pattern reading unit  25 . From these reading results, the inkjet recording apparatus  10  determines and stores the speed variation data for the belt  33 , and during actual image recording, the ejection timings of the recording head  50  are corrected on the basis of this previously stored speed variation data. Consequently, even if a sudden speed variation occurs when the recording paper  16  separates from the paper supply rollers  38 A and  38 B or when the recording paper  16  receives pressurized contact from the paper output rollers  45 A and  45 B, the ejection timing is corrected accordingly and deviation does not occur in the image formation positions (dot formation positions) on the recording paper  16 . Therefore, image degradation, such as non-uniformities and color deviations in the recorded image, are prevented. 
   Second Embodiment 
   Next, a second embodiment of the present invention is described below. In the second embodiment, a test pattern image (corresponding to a “determination pattern”; not shown in  FIG. 9  and indicated by reference numeral  220  in  FIGS. 11A and 11B ) is formed on recording paper  16  while conveying the recording paper  16  under the same conveyance conditions as the conditions during actual image recording, the recording paper  16  formed with the test pattern image is moved to another conveyance system which is different to the conveyance system for image recording, and the test pattern image on the recording paper  16  is read in while conveying the recording paper  16  formed with the test pattern image by means of the other conveyance system. The speed variation data for the recording paper  16  is calculated from the reading results, and the speed variation data is stored in the prescribed storage unit. During image recording, the speed variation data of the recording paper  16  stored in the storage unit is read out and the ejection timing is corrected accordingly. 
     FIG. 9  is a general schematic drawing showing the general composition of an inkjet recording apparatus  200  according to the second embodiment of the present invention. In  FIG. 9 , items which are the same as or similar to those in  FIG. 1  are labeled with the same reference numerals and description thereof is omitted here. Moreover, the composition apart from the main composition according to the present embodiment is not shown in  FIG. 9 . 
   The inkjet recording apparatus  200  shown in  FIG. 9  has an image recording block  202  which records an image and a speed determination block  204  which determines variation in the conveyance speed of the recording paper  16 . A test pattern image is formed on the recording paper  16  by the image recording block  202 , and the speed determination block  204  then reads in the test pattern image on the recording paper  16 , which is supplied from the image recording block. Moreover, the speed variation data of the recording paper  16  is calculated from the reading results, and the speed variation data is obtained for all the recording heads. The speed variation data of the recording paper  16  thus calculated is stored in a speed variation data storage unit of the image recording block  202 , in association with the respective recording heads. The image recording block  202  subsequently corrects the ejection timings in image recording of the respective recording heads, on the basis of this speed variation data. 
   The image recording block  202  shown in  FIG. 9  has a recording unit  12  including recording heads  12 K,  12 C,  12 M and  12 Y which correspond to respective ink colors of K, C, M and Y, a suction belt conveyance unit  22  which holds the recording paper  16  and conveys the recording paper  16  in the paper conveyance direction, paper supply rollers  38 A and  38 B which introduce the recording paper  16  onto the belt  33  of the suction belt conveyance unit  22 , and paper output rollers  45 A and  45 B which output the recording paper  16  on which an image has been recorded. 
   The suction belt conveyance unit  22  shown in  FIG. 9  has the same composition as the suction belt conveyance unit  22  in  FIG. 1 , namely, a structure in which an endless belt  33  is wound about rollers  31  and  32 , and when the motor  88  is caused to rotate and the rollers  31  and  32  are caused to rotate in the counter-clockwise direction, then the belt  33  moves from left to right in  FIG. 9  (indicated by arrow A in  FIG. 9 ), and the recording paper  16  moves from left to right in  FIG. 9 . 
   Moreover, the speed determination block  204  shown in  FIG. 9  includes: a conveyance system constituted by an endless belt  210  which holds the recording paper  16  on which the test pattern image (denoted with a reference numeral  220  in  FIG. 11A ) composed of colored patterns of K, C, M and Y, has been formed, and which conveys the recording paper  16  in a prescribed direction, rollers  212  and  214  about which the belt  210  is wound, and a motor  216  which drives the roller  214 ; a test pattern reading unit  218 , which is provided so as to oppose the surface holding the recording paper  16  in the conveyance region of the conveyance system, and which reads in a dot pattern formed on the recording paper  16 ; and a recording paper detection sensor  211 , which is provided on the upstream side of the conveyance system in terms of the paper conveyance direction, and which judges whether or not recording paper  16  is present on the belt  210 . 
   The test pattern reading unit  218  shown in  FIG. 9  is constituted by a line sensor having rows of photoreceptor elements having a larger width than the total width of the recording paper  16  (the length in a direction perpendicular to the paper conveyance direction), and the density of the test pattern image is read out with the test pattern reading unit  218 . 
   The line sensor used in the test pattern reading unit  218  may be a color separation line CCD sensor including a red (R) sensor row composed of photoelectric transducing elements (pixels) arranged in a line provided with an R filter, a green (G) sensor row with a G filter, and a blue (B) sensor row with a B filter. If a color separation line CCD sensor is used for the test pattern reading unit  218 , then it is possible to read in the test pattern images formed by the K, C, M and Y inks, for the colors, respectively. Instead of a line sensor, it is possible to use an area sensor composed of photoelectric transducing elements which are arranged two-dimensionally. 
   Moreover, although not shown in the drawings, the image recording block  202  includes a speed calculation unit (see  FIG. 6 ) which determines the speed variation data of the recording paper  16  for each of the recording heads with different colored inks, on the basis of the determination signal obtained from the test pattern reading unit  218  of the speed determination block  204 . A mode is also possible in which the speed calculation unit is provided in the speed determination block  204 . 
   During the conveyance of the recording paper  16  in the speed determination block  204 , it is desirable to ensure a state where there are no impacts caused by the pressurized contact of the rollers, separation from the rollers, or the like, and there is no variation in the speed during conveyance, caused by vibrations, or the like. When the test pattern image is read by the test pattern reading unit  218 , errors will occur in the reading results if there is speed variation in the recording paper  16 ′ on which the test pattern image is recorded, and these errors will affect the results of ejection timing correction. It is therefore preferable to prevent the speed variation of the recording paper and the conveyance system from occurring in the reading region of the test pattern reading unit  218 . 
   To give one example of a mode for avoiding the causes of speed variation in the test pattern reading unit  218 , there is a mode in which the recording paper  16 ′ on which the test pattern image has been recorded is caused to contact the belt  210  tightly by applying an electrostatic force to the belt  210 , and furthermore, the recording paper  16 ′ is conveyed at a conveyance speed which minimizes the vibration during conveyance of the recording paper  16 ′ on which the test pattern image has been recorded. 
   Moreover, it is also possible to compose the speed determination block  204  in such a manner that it is detachable from the inkjet recording apparatus  200 . The speed determination block  204  shown in the present embodiment is used only when calculating the speed variation data for the recording paper  16 , and therefore it may be detached from the inkjet recording apparatus  200  during image recording. 
     FIG. 10  shows the composition of the conveyance system of the speed determination block  204 .  FIG. 10  is a principal block diagram showing the system composition of the speed determination block  204 . It is possible to use the composition of the control system of the inkjet recording apparatus  10  according to the first embodiment of the present invention shown in  FIG. 6 , as the control system of the image recording block  202  in  FIG. 9 , and therefore further description thereof is omitted here. Moreover, the test pattern reading unit  25  and the speed calculation unit  92  shown in  FIG. 6  can be omitted in the control system of the image recording block  202  as shown in  FIG. 10 , and therefore further description thereof is omitted here. 
   As shown in  FIG. 10 , the control system of the speed determination block  204  includes a communication interface  240 , a controller  242 , a memory  244 , a conveyance drive control unit (motor driver)  246 , and the like. 
   The communication interface  240  is an interface unit which receives image data transmitted from an external source. The communication interface  240  may adopt the same composition as the communication interface  70  shown in  FIG. 6 . 
   The memory  244  is a storage device which functions as a calculation region for the controller  242  and as a storage region for temporarily storing data, and data is read from and written to the memory  244  via the controller  242 . The memory  244  is not limited to a memory composed of a semiconductor element, and a magnetic medium, such as a hard disk, or the like, may also be used. 
   The controller  242  is a control unit which governs the control system of the speed determination block  204 , and it is constituted by a central processing unit (CPU) and peripheral circuits thereof, and the like, and in addition to controlling communications with external equipment and controlling reading and writing from and to the memory  244 , or the like, it also generates a control signal for controlling the motor  216  of the conveyance system. The conveyance drive control unit  246  is a driver (drive circuit) which drives the motor  216  of the conveyance drive system in accordance with instructions from the controller  242 . 
   The program storage unit  250  stores control programs for the speed determination block  204 , and the controller  242  reads out the various control programs stored in the program storage unit  250 , as and when appropriate, and executes the control programs. 
   As described above with reference to  FIG. 9 , the test pattern reading unit  218  is a block including a line sensor, and it reads in the test pattern image recorded on the recording paper  16  and supplies the read signal to the speed calculation unit  252 . The test pattern reading unit  218  includes a reading control unit (reading control device) which controls the reading operation by the line sensor. 
   In the speed calculation unit  252 , the speed variation data of the recording paper  16  is calculated on the basis of the read signal from the test pattern reading unit  218 , and the speed variation data is stored temporarily in the memory  244 . The speed variation data of the recording paper  16  temporarily stored in the memory  244  is stored in the speed variation data storage unit of the image recording block  202 , via the controller  242 . A mode is also possible in which the speed calculation unit  252  of the speed determination block  204  is provided in the control system of the image recording block  202 . In this case, it is also possible to adopt a composition in which the read signal obtained from the test pattern reading unit  218  of the speed determination block  204  is supplied to the image recording block  202 . 
   The detection signal output from the recording paper detection sensor  211  shown in  FIG. 9  is supplied to the controller  242 . The controller  242  judges whether or not the recording paper  16  is present on the recording paper conveyance path, as well as deciding the read start timing and the read end timing of the test pattern reading unit  218  on the basis of the determination signal from the recording paper detection sensor  211 . 
   Next, the test pattern image is described specifically.  FIG. 11A  shows a test pattern image  220  formed on the recording paper  16 , and  FIG. 11B  shows an enlarged view of the portion  222  of the test pattern image  220  surrounded by the circle in  FIG. 11A . 
   As shown in  FIG. 11A , the test pattern image  220  is formed over the whole surface of the recording paper  16  by ejecting inks at uniform time intervals, from specified nozzles of the recording heads  12 K,  12 C,  12 M and  12 Y of the respective colors in the recording unit  12 . 
   More specifically, the test pattern image  220  is constituted of: a K ink pattern  220 K which is formed by K ink; a C ink pattern  220 C formed by C ink; an M ink pattern  220 M formed by M ink; and a Y ink pattern  220 Y formed by Y ink. As shown in  FIG. 11A , patterns of the same color are formed following the paper conveyance direction and patterns of different colors are aligned following a direction substantially perpendicular to the paper conveyance direction. 
   As shown in  FIG. 11A , the K ink pattern  220 K, the C ink pattern  220 C, the M ink pattern  220 M and the Y ink pattern  220 Y are formed respectively, following the paper conveyance direction, in separate regions which are divided in the direction substantially perpendicular to the conveyance direction of the recording paper  16 . 
   It is desirable that the recording paper  16  is demarcated into separate regions and the test patterns are formed on the regions for the respective colors of the recording heads, as shown in  FIG. 11A , since this makes it possible to determine speed variation data for the recording paper  16  for each of the recording heads. 
   Depending on the position of the recording head in the recording paper conveyance path, recording may not be affected even when the variation does occur in the speed of the recording paper  16 . Therefore, by obtaining the speed variation data for each recording head, it is possible to avoid correction errors caused by the fact that the recording heads are disposed in different positions in the recording paper conveyance path. 
     FIG. 11B  shows an enlarged view of the test pattern image  220  shown in  FIG. 11A  (the portion surrounded by the circle indicated by the reference numeral  222  in  FIG. 11A ). When the recording paper  16  separates from the paper supply rollers  38 A and  38 B, or when the recording paper  16  receives pressurized contact from the paper output rollers  45 A and  45 B, for instance, then the variation may occur in the conveyance speed of the recording paper  16 , and in such a case, the interval between the patterns becomes non-constant and the test pattern image  220  is recorded at irregular intervals as shown in  FIG. 11B . 
   If the conveyance speed of the recording paper  16  becomes slower than the theoretical conveyance speed, then the interval in the pattern becomes wider than the theoretical pattern interval d (not shown), as indicated by the interval d 1  between lines  224  and  226  (in other words, d 1 &gt;d), whereas if, on the other hand, the conveyance speed of the recording paper  16  becomes faster than the theoretical conveyance speed, then the pattern interval becomes narrower than the theoretical pattern interval, as indicated by the interval d 2  between lines  226  and  228  (in other words, d 2 &lt;d). 
   Next, image recording onto a plurality of pieces of recording paper  16  which are conveyed consecutively is described below.  FIG. 12  is a conceptual diagram showing a state where a plurality of pieces of recording paper  16  ( 16 - 1 ,  16 - 2 ,  16 - 3 , . . . ) are conveyed consecutively and image recording is performed onto these pieces of recording paper.  FIG. 12  shows three pieces of recording paper, but a mode is also possible in which image recording is carried out by conveying two pieces of recording paper, or four or more pieces of recording paper, consecutively. 
   Assuming that the recording paper  16  itself does not deform, the factors of the speed variation of the recording paper  16  are, for example: the acceleration of the recording paper (reference numeral  16 - 3  in  FIG. 12 ) due to the force created by the descent of the paper supply roller  38 A, when the recording paper  16  separates from a state where it is pinched between the paper supply rollers  38 A and  38 B, and the idle roller  38 A descends from the state in  38 A′ indicated by the broken line in  FIG. 12  (a state where it is pushed upwards by an amount corresponding to the thickness of the recording paper  16 ) to the state in  38 A indicated by the solid line; and the speed differential between the belt  33  and the recording paper  16  caused by the load imparted to the recording paper  16  by the force required to push the paper output roller  45 A upwards by an amount corresponding to the paper thickness, when the recording paper  16  (reference numeral  16 - 1  in  FIG. 12 ) is pinched between the paper supply rollers  45 A and  45 B. 
   Furthermore, the speed variation of the recording paper  16  may be caused by the speed variation occurring in the recording paper  16  itself, or the speed variation of the recording paper  16  may be caused by the effects of the speed variation of the belt  33 . 
   The speed variation occurring in the recording paper  16  itself may, for example, be caused by (1) slipping between the recording paper  16  and the belt  33 . Furthermore, the occurrence of the speed variation in the recording paper  16  due to the effects of speed variation of the belt  33  may, for example, be caused by (2) slipping between the belt  33  and the drive roller  32  (drive shaft), or back-lash or slipping in the transmission mechanism (gears, belts, etc.) between the drive motor (reference numeral  88  in  FIG. 9 ) and the drive roller  32 . 
   If the holding force of the recording paper  16  (the adhesive force between the recording paper  16  and the belt  33 ) is weak, then only the speed variation of the recording paper  16  described in (1) above occurs, but if the recording paper  16  is held on the belt  33  by a normal holding force, then both (1) and (2) described above occur and therefore (1) and (2) described above should be taken into account. 
   Furthermore, in the cases where pieces of recording paper  16  are conveyed consecutively as shown in  FIG. 12 , if there is the speed variation of the belt  33 , then the speed variation occurs in the plurality of recording papers  16  held on the belt  33 . When the speed variation in a particular recording paper (for example, the recording paper  16 - 1  in  FIG. 12 ) produces the speed variation in the belt  33 , this speed variation of the belt  33  also produces the speed variation in the other pieces of recording paper (for example, the recording papers  16 - 2  and  16 - 3  in  FIG. 12 ). Consequently, in order to determine the speed variation of the recording paper  16 , it is necessary to determine both the speed variation of the recording paper  16  itself, and the speed variation of the recording paper  16  caused by the speed variation of the belt  33 . 
   It is also possible to use an immobile body (such as a platen) as the conveyance medium for conveying the recording paper  16 . In the case where an immobile body is used as the conveyance medium, since the length of the recording paper  16  is longer than the distance between the paper supply rollers  38 A and  38 B and the paper supply rollers  45 A and  45 B, then the speed variation does not occur in the conveyance body when the paper separates from the paper supply rollers  38 A and  38 B or when the paper is pinched between the paper output rollers  45 A and  45 B. However, wear due to the friction of the recording paper  16  does occur, and maintenance, such as replacement is necessary. Therefore, a desirable mode is one which uses a belt as the conveyance medium. 
   The factors of speed variation of the recording paper  16 , in a case where pieces of recording paper  16  are conveyed consecutively, can be summarized as factors (A) to (D) below. 
   (A) The speed of the recording paper  16  is altered directly due to the recording paper  16  receiving the pressurized contact of (in other words, being pinched between) the paper output rollers  45 A and  45 B. 
   (B) The speed of the recording paper  16  is altered directly due to the recording paper  16  separating from the paper supply rollers  38 A and  38 B. 
   (C) The speed of the recording paper  16  is altered indirectly as a result of variation in the speed of the belt  33  due to another sheet of recording paper receiving the pressurized contact of the paper output rollers  45 A and  45 B. 
   (D) The speed of the recording paper  16  is altered indirectly as a result of variation in the speed of the belt  33  due to another sheet of recording paper separating from the paper supply rollers  38 A and  38 B. 
   In a system where other members which are the cause of load variation, such as other rollers, separating hooks, or the like, are present on the belt  33  (on the conveyance path of the recording paper  16 ), it is desirable that the speed variation of the recording paper  16  is determined by taking account of the load variations caused by these members which are causes of load variation. 
   Next, the factors of speed variation in recording paper  16  according to the length of the recording paper  16  is described below, with reference to  FIGS. 13 to 18 . 
   As shown in  FIG. 13 , the length of the recording unit  12  (the total of the lengths of the recording heads  12 K,  12 C,  12 M and  12 Y in the paper conveyance direction plus the distances between the heads) is taken to be W, the distance between the furthest downstream portion of the recording unit  12  in terms of the paper conveyance direction (the front end portion of the recording unit) and the paper output rollers  45 A and  45 B (the position where the leading end portion of the recording paper  16  starts to receive pressurized contact by the paper output rollers  45 A and  45 B) is taken to be X a , the distance between the furthest upstream portion of the recording unit  12  in terms of the paper conveyance direction (the rear end portion of the recording unit) and the paper supply rollers  38 A and  38 B (the position where the trailing end portion of the recording paper  16  separates from the paper supply rollers  38 A and  38 B) is taken to be X b , and the length of the recording paper  16  in the paper conveyance direction is taken to be P. 
   In a case where there is only one sheet of recording paper  16  on the belt  33  and the relationship of P&lt;X a  is satisfied as shown in  FIG. 14A , then the whole of the recording paper  16  is situated outside the recording region (to the downstream side of the recording region in the paper conveyance direction) at the timing when the leading end portion of the recording paper  16  starts to receive the pressurized contact of the paper output rollers  45 A and  45 B, and therefore the speed variation in the recording paper  16  itself (the speed variation in the recording paper  16  due to the above-described factor (A)) does not affect recording quality. In other words, it is considered that the speed variation in the recording paper  16  itself does not occur during image recording onto the recording paper  16 . 
   Moreover, in a case where there is only one sheet of recording paper  16  on the belt  33  and the relationship of P&lt;X b  is satisfied as shown in  FIG. 14B , then the whole of the recording paper  16  is situated outside the recording region (to the upstream side of the recording region in the paper conveyance direction) at the timing when the trailing end portion of the recording paper  16  separates from the paper supply rollers  38 A and  38 B, and therefore the speed variation in the recording paper  16  itself (the speed variation in the recording paper  16  due to the above-described factor (B)) does not affect recording quality. In other words, it is considered that the speed variation in the recording paper  16  itself does not occur during image recording onto the recording paper  16 . 
   Next, a mode where a plurality of pieces of recording paper  16  are conveyed consecutively is described below. As shown in  FIG. 15A , taking the distance between the leading end portion  260  of a preceding recording paper  16 - 1  and the leading end portion  262  of the subsequent recording paper  16 - 2  to be Q, if the conditions of Q&gt;W+X a  are satisfied, the subsequent recording paper  16 - 2  is situated outside the recording region at the timing when the leading end portion  260  of the preceding recording paper  16 - 1  starts to receive the pressurized contact of the paper output rollers  45 A and  45 B, and therefore the speed variation of the preceding recording paper  16 - 1  does not affect the recording quality of the subsequent recording paper  16 - 2 . In other words, it is considered that the speed variation does not occur in the recording paper (the recording paper  16 - 2  shown in  FIG. 15A ) due to the above-described factor (C). 
   Moreover, as shown in  FIG. 15B , taking the distance between the trailing end portion  264  of the preceding recording paper  16 - 1  and the trailing end portion  266  of the subsequent recording paper  16 - 2  to be R, then if the conditions of R&gt;W+X b  are satisfied, the trailing end portion  264  of the preceding recording paper  16 - 1  is situated outside the recording region (to the upstream side of the recording region in terms of the paper conveyance direction) at the timing when the subsequent recording paper  16 - 2  separates from the paper supply rollers  38 A and  38 B, and therefore the speed variation of the subsequent recording paper  16 - 2  does not affect the recording quality on the preceding recording paper  16 - 1 . In other words, it is considered that the speed variation does not occur in the recording paper (the recording paper  16 - 1  in  FIG. 15B ) due to the above-described factor (D). 
   In the cases shown in  FIGS. 15A and 15B , the speed variation in the recording paper itself does occur due to the above-described factors (A) and (B), for the recording paper that is situated in the recording region (the recording paper  16 - 1  in  FIG. 15A  and the recording paper  16 - 2  in  FIG. 15B ). 
     FIG. 16A  shows a case where there are a plurality of pieces of recording paper  16  ( 16 - 1 ,  16 - 2 ,  16 - 3 ,  16 - 4  and  16 - 5 ) in the recording region. 
   As shown in  FIG. 16A , there are four pieces of recording paper  16 - 1 ,  16 - 2 ,  16 - 3  and  16 - 4  which precede the recording paper  16 - 5 . If the distance Q n  between the leading end portion of the leading recording paper  16 - 1  and the leading end portion of the rearmost recording paper  16 - 5  has the relationship of Q n &lt;W+X a , then the recording quality on the four subsequent pieces of recording paper  16 - 2 ,  16 - 3 ,  16 - 4  and  16 - 5  is affected at the timing when the leading recording paper  16  starts to receive pressurized contact from the paper output rollers  45 A and  45 B. This means that in the case of the recording paper  16 - 5 , the speed variation due to the speed variation (in other words, the speed variation due to the above-described factor (C)) of the other recording papers  16 - 1  to  16 - 4 , occurs a plurality of times. 
   To state this situation in general terms, it is supposed that there are n pieces of recording paper on the belt  33 , and the leading end portion of a specified recording paper  16   i−n  is in contact with the paper output rollers  45 A and  45 B. In this case, if the distance Q n  between the leading end portion of the recording paper  16   i  and the leading end portion of the recording paper  16   i−n  which is n pieces ahead of the recording paper  16   i , has the relationship of Q n &lt;W+X a , then the speed variation occurs in the recording paper  16   i  a number of times equal to the number of pieces of recording paper preceding the recording paper  16   i  (in the present example, n sheets). However, if the distance R n  between the trailing end portion of the recording paper  16   i  and the leading end portion of the recording paper  16   i−n , which is n pieces ahead of the recording paper  16   i , has the relationship of R n &lt;X a , then the speed variation in the recording papers  16   i−1 ,  16   i−2 , . . . preceding the recording paper  16   i  does not affect the recording quality of the recording paper  16   i . 
   Furthermore, in  FIG. 16B , similarly to  FIG. 16A , there are four pieces of recording paper  16 - 2 ,  16 - 3 ,  16 - 4  and  16 - 5  following the recording paper  16 - 1 . If the distance R n  between the leading end portion of the leading recording paper  16 - 1  and the trailing end portion of the rearmost recording paper  16 - 5  has the relationship of R n &lt;W+X b , then the speed variation will occur four times in the leading recording paper  16 - 1 , at the timings when the following four recording papers  16 - 2  to  16 - 5  separate from the paper supply rollers  38 A and  38 B. 
   To state this situation in general terms, it is supposed that there are n pieces of recording paper on the belt  33 , and the trailing end portion of a specified recording paper  16   i+n  is separating from the paper supply rollers  38 A and  38 B. In this case, if the distance R n  between the leading end portion of the recording paper  16   i  and the trailing end portion of the recording paper  16   i+n , which is n pieces behind the recording paper  16   i , has the relationship of R n &lt;W+X b , then the speed variation occurs in the recording paper  16   i  a number of times equal to the number of pieces of recording paper following the recording paper  16   i  (in the present example, n sheets). However, if the conditions of R n &lt;X b  are satisfied, then the speed variations in the recording papers  16   i+1 ,  16   1+2 , . . . , following the recording paper  16   i  do not affect the recording quality on the preceding recording paper  16   i . 
     FIG. 17  shows a mode where the recording heads  12 K,  12 C,  12 M and  12 Y corresponding to the respective colors of K, C, M and Y are provided separately in the recording unit  12 . In the recording unit  12  including line type heads, the recording heads of the respective colors are separated and are disposed at prescribed intervals. As shown in  FIG. 17 , in a mode where a plurality of independent recording heads are provided, the distance X a  between the front end portion of the recording head and the paper output rollers  45 A and  45 B and the distance X b  between the rear end portion of the recording head and the paper supply rollers  38 A and  38 B, are taken into consideration for each respective recording head. 
   It is possible to predict what kind of speed variations will occur when the following parameters are already know: the lengths W K , W C , W M  and W Y  of the respective recording heads  12 K,  12 C,  12 M and  12 Y of the colors K, C, M and Y in the paper conveyance direction; the distances X aK , X aC , X aM  and X aY  from the respective front ends of the recording heads  12 K,  12 C,  12 M and  12 Y (the ends on the upstream side in terms of the paper conveyance direction) to the paper supply rollers  45 A and  45 B; the distances X bK , X bC , X bM  and X bY  from the respective rear ends of the recording heads  12 K,  12 C,  12 M and  12 Y (the ends on the downstream side in terms of the paper conveyance direction) to the paper supply rollers  38 A and  38 B; and the length and number of pieces of the recording paper  16 . 
   As described above, the speed variation data for the recording paper  16  is determined in accordance with the conditions relating to the composition of the recording unit  12 , the size of the recording paper  16  and the number of pieces of recording paper  16 , and the data thus determined is then stored in association with these respective conditions. It is thereby possible to provide desirable correction of the ejection timings in accordance with various recording conditions. 
   Next, the calculation of speed variation data when a plurality of pieces of recording paper  16  are conveyed consecutively, is described below in detail with reference to  FIGS. 18 and 19 . 
     FIG. 18  is a diagram for describing a method of determining the speed variation data for the recording paper  16  due to the aforementioned factors (A) to (D), using two pieces of recording paper  16 - 1  and  16 - 2 . 
   The following parameters are already known: the length W of the recording unit  12  in the paper conveyance direction shown in  FIG. 18 ; the distance X a  between the front end portion of the recording unit  12  (the end on the downstream side in terms of the paper conveyance direction) and the paper output rollers  45 A and  45 B; and the distance X b  between the rear end portion of the recording unit  12  (the end on the upstream side in terms of the paper conveyance direction) and the paper supply rollers  38 A and  38 B. 
   It is possible to determine the speed variation data for the recording paper  16  due to the factors (A) to (D), by determining the speed of two pieces of recording paper  16 - 1  and  16 - 2 . In this case, the recording papers  16 - 1  and  16 - 2  have all of the following relationships:
 
 P   1   &gt;X   a   , P   1   &gt;X   b   , P   2   &gt;X   a   , P   2   &gt;X   b , and  P   1   +P   2   +P   D   &lt;X   a   +W+X   b ,
 
where P 1  is the length of the preceding recording paper  16 - 1  in the paper conveyance direction, P 2  is the length of the subsequent recording paper  16 - 2  in the paper conveyance direction, and P D  is the distance between the trailing end portion of the recording paper  16 - 1  and the leading end portion of the recording paper  16 - 2 .
 
   The length P 1  of the preceding recording paper  16 - 1  in the paper conveyance direction and the length P 2  of the subsequent recording paper  16 - 2  in the paper conveyance direction are known. It is possible to adopt a composition in which these values P 1  and P 2  are input via a user interface, such as a keyboard, or a composition in which these values P 1  and P 2  relating to the recording paper are read in automatically from an information record body in which the recording paper information is stored, when the paper is loaded in the paper supply unit  18  (see  FIG. 1 ). Moreover, the distance P D  between the trailing end portion of the recording paper  16 - 1  and the leading end portion of the recording paper  16 - 2  is measured by using the paper supply sensor  39  and a counter (not illustrated). 
     FIG. 19  shows the details of the test pattern image  220  (test patterns  220 K,  220 C,  220 M and  220 Y) recorded on the recording paper  16 , which is also shown in  FIGS. 11A and 11B .  FIG. 19  shows the nozzle arrangement of the recording heads  12 K,  12 C,  12 M and  12 Y of the respective colors in a simplified view, but in practice, the matrix configuration shown in  FIG. 3A  is adopted. Moreover, the recording of the test pattern image  220  is carried out by means of a single pass operation in which the recording papers  16 - 1  and  16 - 2  are moved (scanned) once only through the recording region of the recording unit  12 . 
   The test pattern image  220  shown in  FIG. 19  is constituted of a Y ink pattern  220 Y, an M ink pattern  220 M, a C ink pattern  220 C and a K ink pattern  220 K, and the patterns of the colors are recorded respectively onto separate regions of the recording paper  16  divided in the direction (the breadthways direction of the recording paper  16 ) perpendicular to the paper conveyance direction. 
   In other words, the test pattern image  220  is recorded onto the recording paper  16  in such a manner that the Y ink pattern  220 Y, the M ink pattern  220 M, the C ink pattern  220 C and the K ink pattern  220 K are aligned in this order in the breadthways direction of the recording paper  16 , from the left-hand side in  FIG. 19 .  FIG. 19  shows a mode where the test patterns for the colored inks are recorded respectively at positions which are staggered by a prescribed interval in the paper conveyance direction, but the present invention is not limited to this, and the test patterns of the colored inks may also be recorded onto the same position in terms of the paper conveyance direction. 
   When recording the test pattern image  220  shown in  FIG. 19 , the ink ejection from the recording heads  12 K,  12 C,  12 M and  12 Y of the respective colors is controlled in such a manner that the inks of respective colors are ejected from specified nozzles in the respective recording heads  12 K,  12 C,  12 M and  12 Y. In the Y head  12 Y, a plurality of nozzles (nozzle group N 1 ) in the region indicated by the reference numeral  270  in  FIG. 19  are used. The nozzle group N 1  includes nozzles which form dots at the same position in terms of the paper conveyance direction on the recording paper  16 , when these nozzles eject ink at the same timing. 
   Similarly, in the M head  12 M, a nozzle group N 2  in the region indicated by the reference numeral  272  is used, in the C head  12 C, a nozzle group N 3  in the region indicated by the reference numeral  274  is used, and in the K head  12 K, a nozzle group N 4  in the region indicated by the reference numeral  276  is used. 
   Since the recording regions of the recording heads  12 K,  12 C,  12 M and  12 Y (the recording region of the recording unit  12 ) have prescribed lengths in the paper conveyance direction, then the inks ejected from the respective recording heads  12 K,  12 C,  12 M and  12 Y at the same timing will be deposited onto the preceding recording paper  16 - 1  or onto the subsequent recording paper  16 - 2 , when the preceding recording paper  16 - 1  and the subsequent recording paper  16 - 2  are present simultaneously on the recording region. In the respective recording heads  12 K,  12 C,  12 M and  12 Y, by simultaneously using the nozzle group N 1  at the front end in the paper conveyance direction and the nozzle group N 4  at the rear end in the paper conveyance direction, it is possible to record test patterns in the case of speed variations due to the above-described factors (A) to (D), onto the preceding recording paper  16 - 1  and the subsequent recording paper  16 - 2 . 
   For example, when the speed variation occurs in the recording paper  16  due to the above-described factor (C), if ink is ejected from the nozzle group N 1  only that is situated at the front end of the recording region, then there may be a case where it is not possible to record the test pattern image that is subjected to the speed variation based on the factor (C), on the subsequent recording paper  16 - 2 . More specifically, if the subsequent recording paper  16 - 2  is not present under the nozzle group N 1  when the preceding recording paper  16 - 1  receives pressurized contact with the paper output rollers  45 A and  45 B shown in  FIG. 18 , then it is not possible to record the test pattern image that is subjected to the speed variation based on the factor (C). Similarly, when the speed variation occurs in the recording paper  16  due to the above-described factor (D), if ink is ejected only from the nozzle group N 4  situated at the rear end of the recording region, then there may be a case where it is not possible to record the test pattern image that is subjected to the speed variation based on the factor (D), on the preceding recording paper  16 - 1 . The recording of the test pattern image shown in the present embodiment is therefore desirable in that problems of this kind do not occur. 
   Moreover, the test pattern image  220  shown in  FIG. 19  has a prescribed length in the paper conveyance direction and is recorded at a prescribed arrangement pitch in the paper conveyance direction. As shown in  FIG. 19 , a desirable mode is one where the width of each pattern (line) is 85 μm, and where the arrangement pitch of the patterns is approximately 170 μm. 
     FIG. 20  is a flowchart showing the sequence of control for the recording of the above-described test pattern image, and  FIGS. 21A to 21K  are conceptual diagrams showing schematic views of respective states of test pattern image recording. Below the test pattern image recording procedure shown in  FIG. 20  is described with reference to  FIGS. 21A to 21K . 
   When test pattern recording starts (step S 10 ), the paper supply rollers  38 A and  38 B and the paper output rollers  45 A and  45 B are started (step S 12 ), and the procedure then advances to step S 14 . 
     FIG. 21A  shows a state where the first sheet of recording paper  16  is supplied to a standby position and the paper supply rollers  38 A and  38 B and the paper output rollers  45 A and  45 B have started to be driven. The recording paper  16 - 1  situated in the standby position is pressed between the paper supply rollers  38 A and  38 B and due to the rotation of the paper supply rollers  38 A and  38 B, the recording paper  16 - 1  is moved in a prescribed conveyance direction. 
   At step S 14  in  FIG. 20 , determination of the leading end portion of the recording paper  16 - 1  is carried out by the paper supply sensor  39 , and if the leading end portion of the recording paper  16 - 1  is not determined (NO verdict), then the determination of the leading end portion of the recording paper  16 - 1  is continued. If, on the other hand, the leading end portion of the recording paper  16 - 1  is determined (YES verdict), then the procedure advances to step S 18 .  FIG. 21B  shows a state where the leading end portion of the recording paper  16 - 1  has been determined by the paper supply sensor  39 . 
   At step S 18  in  FIG. 20 , when the recording paper  16 - 1  arrives at the recording region of the recording unit  12 , then ink is ejected from the recording unit  12 , and a prescribed test pattern image is recorded on the recording paper  16 - 1  (step S 18 ). During recording of the test pattern image, determination of the trailing end portion of the recording paper  16 - 1  is carried out by the paper supply sensor  39  (step S 20 ), and if the trailing end portion of the recording paper  16 - 1  is not determined (NO verdict), then the determination of the trailing end portion of the recording paper  16 - 1  is continued, and if the trailing end portion of the recording paper  16 - 1  is determined (YES verdict), then the procedure advances to step S 24 . 
     FIG. 21C  shows a state at the start of test pattern image recording, and  FIG. 21D  shows a state where the recording paper  16 - 1  is separated from the paper supply rollers  38 A and  38 B during test pattern image recording, thereby producing the speed variation caused by the above-described factor (B). 
   At step S 24  in  FIG. 20 , counting of the interval (distance) P D  between the preceding recording paper  16 - 1  and the subsequent recording paper  16 - 2  (the distance between the trailing end portion of the preceding recording paper  16 - 1  and the leading end portion of the subsequent recording paper  16 - 2 ) is started (step S 24 ). 
     FIG. 21E  shows a state where the trailing end portion of the recording paper  16 - 1  has been determined and the counting of the interval to the subsequent recording paper  16 - 2  has started. The interval between the preceding recording paper  16 - 1  and the subsequent recording paper  16 - 2  is counted by using a counter  280 . 
   During the counting of the interval between the preceding recording paper  16 - 1  and the subsequent recording paper  16 - 2 , determination of the leading end portion of the subsequent recording paper  16 - 2  is carried out (step S 26  in  FIG. 20 ). If, at step S 26 , the leading end portion of the recording paper  16 - 2  is not determined (NO verdict), then the determination of the leading end portion of the recording paper  16 - 2  is continued, and when the leading end portion of the recording paper  16 - 2  is determined (YES verdict), then the counting of the interval between the trailing end portion of the preceding recording paper  16 - 1  and the leading end portion of the subsequent recording paper  16 - 2  is terminated (step S 28 ), and the procedure then advances to step S 32 .  FIG. 21F  shows a state where the leading end portion of the subsequent recording paper  16 - 2  has been determined. 
   At step S 32  in  FIG. 20 , recording of a test pattern image onto the recording paper  16 - 2  is started at a prescribed timing. During the recording of the test pattern image onto the recording paper  16 - 2 , determination of the trailing end portion of the recording paper  16 - 2  is carried out (step S 32 ), and if the trailing end portion of the recording paper  16 - 2  is not determined (NO verdict), then the determination of the trailing end portion of the recording paper  16 - 2  is continued. On the other hand, if, at step S 32 , the trailing end portion of the recording paper  16 - 2  is determined (YES verdict), then the procedure advances to step S 36 . 
     FIG. 21G  shows a state where a test pattern image is being recorded onto the recording paper  16 - 1  and the recording paper  16 - 2 , and  FIG. 21H  shows a state where the trailing end portion of the recording paper  16 - 2  is determined. 
   At step S 36 , measurement of the halt time T END  is started (step S 36 ), and if there is no subsequent recording paper following the recording paper  16 - 2 , then the paper supply rollers  38 A and  38 B are halted (step S 38 ) and the procedure then advances to step S 40 . 
   The halt time T END  of which measurement is started in step S 36  is the period of time from the time at which the trailing end portion of the recording paper  16 - 2  is determined until the trailing end portion of the recording paper  16 - 2  passes the print unit  12 . 
   At step S 40 , it is judged whether or not the halt time T END  has reached a specified time period (more specifically, a time value obtained by dividing the distance from the paper supply sensor  39  to the paper output rollers  45 A and  45 B, by the conveyance speed of the recording paper  16 - 2 ) determined on the basis of the length P 2  of the recording paper  16 - 2  in the paper conveyance direction, and the conveyance speed of the recording paper  16 - 2  (the conveyance speed of the belt  33 ), and if the halt time T END  has not reached the specified time period (NO verdict), then the measurement of the halt time T END  is continued. If, on the other hand, the halt time T END  has reached the specified time period (YES verdict), then test pattern image recording is terminated (step S 42 ), the driving of the paper output rollers  45 A and  45 B is halted (step S 44 ), and test pattern recording ends (step S 46 ). 
     FIG. 21I  shows a state at the time when the preceding recording paper  16 - 1  receives pressurized contact from the paper output rollers  45 A and  45 B. In the state shown in  FIG. 21I , the speed variation occurs in the preceding recording paper  16 - 1  due to the above-described factor (A), and the speed variation occurs in the subsequent recording paper  16 - 2  due to the above-described factor (C).  FIG. 21J  shows a state where the speed variation occurs in the recording paper  16 - 2  due to the above-described factor (A), when the recording paper  16 - 2  receives pressurized contact from the paper output rollers  45 A and  45 B. Moreover,  FIG. 21K  shows a state where the recording paper  16 - 2  has been output. 
   The test patterns thus recorded on two pieces of recording paper  16 - 1  and  16 - 2  are then read in by the test pattern reading unit  218  of the speed determination block  204  shown in  FIG. 9 , and the speed variation data of the recording papers  16 - 1  and  16 - 2  in the image recording block  202  is calculated on the basis of these reading results. The method of calculating the speed variation data uses the same method as that of the first embodiment. 
   In other words, the test pattern image is recorded by means of a prescribed recording method onto a prescribed number of pieces of recording paper  16  having a prescribed size (test pattern recording step), in the image recording block  202  shown in  FIG. 9 , then in the speed determination block  204  shown in  FIG. 9 , the test pattern image is read in by means of the test pattern reading unit  218  (test pattern reading step), and the speed variation data is then calculated (speed variation data calculation step). The speed variation data thus calculated is stored in a prescribed storage unit (speed variation data storage step). 
   Next, the test pattern reading step is described with reference to  FIGS. 22A and 22B .  FIG. 22A  shows test patterns  220 - 1  and  220 - 2  that have been recorded respectively on the recording paper  16 - 1  and the recording paper  16 - 2  in the test pattern recording step shown in  FIGS. 20 and 21A  to  21 K.  FIG. 22B  is a conceptual diagram showing the positions of the nozzle groups recording the test pattern, in the conveyance path of the recording paper  16 . 
   As shown in  FIG. 22A , the test patterns  220 - 1  and  220 - 2  recorded include four regions divided in the direction perpendicular to the paper conveyance direction, and the four regions of the test patterns  220 - 1  and  220 - 2  are recorded by means of the corresponding colored inks ejected from the recording heads  12 K,  12 C,  12 M and  12 Y. 
     FIG. 22B  shows the positions, on the conveyance path of the recording paper  16 , of the nozzle groups N 1  to N 4  of the recording unit  12  (the recording heads  12 K,  12 C,  12 M and  12 Y) which record the test patterns. The nozzle groups N 1  to N 4  include a plurality of nozzles aligned in a direction perpendicular to the paper conveyance direction (see  FIG. 19 ). The positions of the nozzle groups N 1  to N 4  in terms of the conveyance path of the recording paper  16  shown in  FIG. 22B  are previously stored as data in the memory  244  in  FIG. 10 . 
   The nozzle groups N 1  to N 4  in  FIG. 22B  correspond respectively to Y ink, M ink, C ink and K ink. The pattern groups  220 Y- 1  and  220 Y- 2  shown in  FIG. 22A  are recorded by means of Y ink, and the pattern groups  220 M- 1  and  220 M- 2  are recorded by means of M ink. Similarly, the pattern groups  220 C- 1  and  220 C- 2  are recorded by means of C ink and the pattern groups  220 K- 1  and  220 K- 2  are recorded by means of K ink. 
   In the test pattern reading process, each of the above-described factors (A) to (D) is independently analyzed on the basis of the test pattern image  220 , the speed variation data is calculated for each of the factors (A) to (D), and this speed variation data is stored for each of the factors (A) to (D). 
   Since the positions in the conveyance path of the recording paper  16  at which the nozzle groups N 1  to N 4  recording the test patterns  220 - 1  and  220 - 2  are provided, are known in terms of the paper conveyance direction, then it is possible to predict (calculate) the positions on the recording paper  16  at which the speed variation of the recording paper  16  will occur. 
   The test pattern image  220 - 1  recorded on the recording paper  16 - 1  shown in  FIG. 22A  includes: a portion that is subjected to the speed variation caused by the above-described factor (B) at the position indicated by reference numeral  300  in the pattern group  220 K- 1 ; a portion that is subjected to the speed variation caused by the above-described factor (D) at the position indicated by the reference numeral  302  in the pattern group  220 M- 1 ; and a portion that is subjected to the speed variation caused by the above-described factor (A) in the portion indicated by reference numeral  304  in the pattern group  220 K- 1 . 
   The test pattern image  220 - 2  recorded onto the recording paper  16 - 2  includes: a portion that is subjected to the speed variation caused by the above-described factor (B) in the portion indicated by reference numeral  310  in the pattern group  220 K- 2 ; a portion that is subjected to the speed variation caused by the factor (C) in the portion indicated by the reference numeral  312  in the pattern group  220 C- 2 ; and a portion that is subjected to the speed variation caused by the factor (A) in the portion indicated by reference numeral  314  in the pattern group  220 Y- 2 . 
   As shown in  FIG. 22B , symbols X a1  to X a4  indicate the distances between the paper supply rollers  38 A and  38 B and the nozzle groups N 1  to N 4 , respectively; and symbols X b1  to X b4  indicate the distances between the paper output rollers  45 A and  45 B and the nozzle groups N 1  to N 4 , respectively. The distance X a4  from the paper supply rollers  38 A and  38 B to the nozzle group N 4  is equal to the distance X a  from the paper supply rollers  38 A and  38 B to the rear end portion of the recording unit  12  (X a4 =X a ). Moreover, the distance X b1  from the paper output rollers  45 A and  45 B to the nozzle group N 1  is equal to the distance X b  from the paper output rollers  45 A and  45 B to the front end portion of the recording unit  12  (X b1 =X b ). These parameters are stored in the memory  244  in  FIG. 10 . 
   For example, assuming that the ink heads  12 C and  12 K are recording the test pattern image on the recording paper  16 - 1  when the recording paper  16 - 1  separates from the paper supply rollers  38 A and  38 B, it is possible to predict the positions (including the speed variation position  300  shown in  FIG. 22 ) of the portions that are subjected to the speed variation caused by the factor (B) on the recording paper  16 - 1 , as the positions at which the distances from the trailing end of the recording paper  16 - 1  are X a3  and X a4  (the distances in the paper conveyance direction from the paper supply rollers  38 A and  38 B to the nozzle groups N 3  and N 4 ), respectively. 
   Assuming that the ink heads  12 Y and  12 M are recording the test pattern image on the recording paper  16 - 1  when the recording paper  16 - 1  receives the pressurized contact of the paper output rollers  45 A and  45 B, it is possible to predict the positions (including the speed variation position  304 ) of the portions that are subjected to the speed variation caused by the factor (A) on the recording paper  16 - 1 , as the positions at which the distances from the leading end of the recording paper  16 - 1  are X b1  and X b2  (the distances in the paper conveyance direction from the paper output rollers  45 A and  45 B to the nozzle groups N 1  and N 2 ), respectively. The speed variation position  314  at which the test pattern image is disturbed due to the factor (A) and the speed variation position  310  at which the test pattern image is disturbed due to speed variation cause (B), can also be predicted for the recording paper  16 - 2  by a similar method. 
   Moreover, assuming the ink heads  12 Y and  12 M are recording the test pattern image on the recording paper  16 - 1  when the recording paper  16 - 2  separates from the paper supply rollers  38 A and  38 B, it is possible to predict the positions (including the speed variation position  302 ) of the portions that are subjected to the speed variation caused by the factor (D) on the recording paper  16 - 1 , as the positions at which the distances from the trailing end portion of the recording paper  16 - 1  are (X a1 −(P 2 +P D )) and (X a2 −(P 2 +P D )), respectively. In this case these values of (X a1 −(P 2 +P D )) and (X a2 −(P 2 +P D )) can be obtained respectively by subtracting the length P 2  of the recording paper  16 - 2  in the paper conveyance direction and the distance P D  between the trailing end portion of the recording paper  16 - 1  and the leading end portion of the recording paper  16 - 1 , from the distances X a1  and X a2  in the paper conveyance direction from the paper supply rollers  38 A and  38 B to the nozzle groups N 1  and N 2 . 
   Assuming that the ink heads  12 C and  12 K are recording the test pattern image on the recording paper  16 - 2  when the recording paper  16 - 1  comes into pressurized contact from the paper output rollers  45 A and  45 B, it is possible to predict the positions (including the speed variation position  312 ) of the portions that are subjected to the speed variation caused by the factor (C) on the recording paper  16 - 2 , as the positions at which the distances from the leading end portion of the recording paper  16 - 2  are (X b3 −(P 1 +P D )) and (X b4 −(P 1 +P D )), respectively. In this case, these values of (X b3 −(P 1 +P D )) and (X b4 −(P 1 +P D )) can be obtained respectively by subtracting the length P 1  in the paper conveyance direction of the recording paper  16 - 1  and the distance P D  between the trailing end portion of the recording paper  16 - 1  and the leading end portion of the recording paper  16 - 1 , from the distances X b3  and X b4  in the paper conveyance direction from the paper output rollers  45 A and  45 B to the nozzle groups N 3  and N 4 . 
   In other words, the respective parameters described above are stored in advance in the memory  244  (see  FIG. 10 ), and by acquiring data relating to the lengths P 1  and P 2  of the recording papers  16 - 1  and  16 - 2  in the paper conveyance direction, and the distance P D  between the trailing end portion of the recording paper  16 - 1  and the leading end portion of the recording paper  16 - 2 , the main controller  246  in  FIG. 10  can predict (calculate) the positions on the recording papers  16 - 1  and  16 - 2  at which the test pattern image is disturbed due to the speed variation. 
   In the test pattern reading step according to the present embodiment, the speed variation positions (positions at which the speed variation is likely to occur) are predicted, and the test pattern image is read selectively at the speed variation positions. 
   In other words, the test pattern reading unit  218  executes reading control by referring to the data on the speed variation positions calculated (predicted) by the main controller  242  in  FIG. 10 . The speed variation of the recording paper  16  often affects on a certain range of the paper because of phenomena such as elastic deformation of the rollers  31  and  32  in the image recording block  202  shown in  FIG. 9 , slippage between the recording paper  16  and the belt  33 , and vibration of the belt  33 . Consequently, a desirable mode is one in which the periphery of the predicted speed variation position is also read in as a region in which the speed variation is likely to occur. 
   In other words, when reading in the test pattern image corresponding to the position at which the speed variation occurs, the test pattern image is read in over a prescribed range to the front and rear in the paper conveyance direction, centered on the position at which the speed variation occurs. The optimal value of this reading range is determined appropriately in accordance with the composition of the suction belt conveyance unit  22  of the image recording block  202 . 
   The read data for the test pattern image is converted to binary data using a prescribed threshold value, and the speed variation data (see  FIG. 8A ) is then calculated on the basis of this binarized data. The test pattern image is read in selectively, and the calculated speed variation data forms partial data corresponding to the portions of the test pattern that have been read in. 
   Since the position at which the speed variation is to occur is already known (predicted in advance), as described above, then in an actual recording operation, it is possible to calculate the time period from the determination of the leading end position of the recording paper  16  until the occurrence of the speed variation, and the time period until the end of the speed variation. Therefore, it is possible to store the speed variation data in association with the time period from the determination of the leading end portion of the recording paper  16  until the start of correction of the speed variation (the time period from the determination of the leading end position of the recording paper  16  until the start of the speed variation), and the time period until the end of this correction (the time period until the end of the speed variation). 
   When the recording paper  16  for image recording is conveyed, the time period is counted from the determination of the leading end of the recording paper  16 . At the time when the speed variation start time stored in association with the speed variation data has elapsed, then the ejection timing is corrected by correcting the trigger signal on the basis of the speed variation data. Moreover, at the time when the end time of the speed variation has elapsed, then the correction of the trigger signal on the basis of the speed variation data is terminated, and ejection is carried out on the basis of the original trigger signal. The correction data occurs two times to four times during the printing of one sheet, and the ejection timing is corrected accordingly on each occasion. 
   In this way, by adopting a mode in which the positions at which speed variation occurs in the test pattern image are identified, the test pattern image at the positions where the speed variation occurs is read in, and the ejection timing is corrected on the basis of the read results, it is possible to minimize the amount of read data and it is also possible to shorten the reading time and the processing time. Furthermore, it is possible to reduce the data volume of the stored speed variation data, and therefore it is possible to reduce the storage capacity of the speed variation data storage unit  94  shown in  FIG. 6 , and this helps to lower costs. 
   In the inkjet recording apparatus  200  having the composition described above, since the test pattern image  220  is recorded on the recording paper  16  by the image recording block  202 , and the test pattern image  220  recorded on the recording paper  16  is read in by the test pattern reading unit  218  of the speed determination block  204 , then it is possible to accurately determine the speed variation of the recording paper  16  even in a case where a speed differential arises between the recording paper  16  and the belt  33 . Furthermore, since the test pattern recording block and the test pattern reading block are separate, then improved accuracy in reading the test pattern image can be expected. 
   Moreover, in a mode where image recording is carried out by conveying a plurality of pieces of recording paper  16  consecutively, then even if the speed variation occurs in a particular sheet of recording paper as a result of speed variation occurring in the belt  33  due to speed variation of another sheet of recording paper, it is still possible accurately to ascertain the speed variation of that sheet of recording paper. 
   In the case of image recording onto a plurality of consecutive pieces of recording paper, since the test pattern image is read in at the vicinities of the speed variation positions, in respect of each of the factors of speed variation in the recording paper  16 , and speed variation data is calculated for each of the factors of speed variation in the recording paper  16 , then it is possible to shorten the test pattern reading time, as well as contributing to reducing the storage volume required to store the speed variation data. 
   Application Embodiment 
     FIG. 23  shows an application of the second embodiment described above. In  FIG. 23 , items which are the same as or similar to those in  FIG. 9  are labeled with the same reference numerals and description thereof is omitted here. 
   The inkjet recording apparatus  200 ′ shown in  FIG. 23  includes a recording paper identification unit  290  which identifies the type or size of the recording paper  16  in an image recording block  202 ′. At least one of the type and size of the recording paper  16  on which image recording is to be performed is identified by the recording paper identification unit  290 , and it is determined whether or not there is a record of the use of this recording paper  16 . 
   If a specified recording paper used has never been used, then a test pattern image is recorded on that recording paper  16 , the test pattern image is read in by the speed determination block  204 , the speed variation data is calculated from this read result, and the speed variation data is stored in a prescribed storage block. 
   If, on the other hand, there is a past record of use of a specified recording paper, then the corresponding speed variation data is read out from the speed variation data storage unit  94  shown in  FIG. 6 , and the ejection timing is corrected on the basis of the speed variation data thus read out. 
   The recording paper identification unit  290  may have a composition which captures an image of the surface of the recording paper by means of an image pickup element such as a CCD, and identifies the type of the recording paper (for example, the surface properties and color) on the basis of the image pickup results, or it may have a composition which identifies the type of recording paper by means of a sensor which determines the thickness or a sensor which determines the weight, or the like. The aforementioned compositions may also be combined suitably. 
   It is also possible to adopt a composition in which a user inputs recording paper information via a user interface, such as a keyboard, a mouse, a touch panel, or the like. Moreover, a mode may also be adopted, in which an information storage body (IC tag) which stores recording paper information (the type, color, thickness, weight, size, or the like) is provided on the recording paper stacker (in the case of cut paper) or the core of the roll (in the case of continuous paper), so that the recording paper information is read out automatically from the information storage body when the recording paper is installed in the apparatus. 
   According to the present application embodiment, even when there is change in the type and size of the recording paper, ejection timing correction which is suitable to that recording paper is carried out. 
   In the present application embodiment, a mode is adopted where the type of recording paper is identified, but it is also possible to adopt a mode in which speed variation data corresponding to environmental conditions, such as the temperature or humidity, is prepared in advance, and the speed variation data is switched appropriately in accordance with the environmental conditions. By adopting a mode where the speed variation data is switched in accordance with the environmental conditions, it is possible to reduce error in the correction of the ejection timing due to contraction of the recording paper  16  or contraction of the belt  33  based on the environmental conditions. 
   Third Embodiment 
   Next, a third embodiment of the present invention is described below.  FIG. 24  is a conceptual diagram showing the composition of the principal part of an inkjet recording apparatus  300  according to a third embodiment of the present invention, and  FIG. 25  is a block diagram showing a general composition of a control system of the inkjet recording apparatus  300 . Items of the present embodiment which are the same as or similar to those in the first and second embodiments described above are labeled with the same or similar reference numerals and description thereof is omitted here. 
   A so-called transfer method is used in the inkjet recording apparatus  300 , as shown in  FIG. 24 . More specifically, an image is formed by ejecting ink onto an intermediate transfer body  302  from a recording unit  12 , the image forming surface (image forming region)  302 A of the intermediate transfer body  302  is placed in contact with the image recording surface  16 A of the recording paper  16 , and furthermore, the image formed on the intermediate transfer body  302  is transferred to a recording paper  16  by causing the intermediate transfer body  302  and the recording paper  16  to be pressed against each other by means of transfer rollers  304  and  306  while causing the recording paper  16  and the intermediate transfer body  302  to move in unison. 
   In the present embodiment, speed variation occurring in the intermediate transfer body  302  is determined while carrying out transfer to the recording paper  16  from the intermediate transfer body  302 , and the ejection timing is corrected in accordance with the speed variation of the intermediate transfer body  302 . In a mode where image recording onto the intermediate transfer body  302  is carried out, in order to improve productivity, while transferring an image from the intermediate transfer body  302  onto the recording paper  16 , it is possible to prevent image degradation caused by speed variation of the intermediate transfer body occurring as a result of transfer, and therefore desirable image formation is achieved. 
   The intermediate transfer body  302  has a structure in which an endless belt is wound about rollers  308  and  310 , and a transfer roller  304 . When the drive roller  308  is caused to rotate in the clockwise direction by means of the motor  312 , the intermediate transfer body  302  moves in the clockwise direction in synchronism with the rotation of the drive roller  308 . 
   The recording unit  12  has a structure in which recording heads  12 K,  12 C,  12 M and  12 Y corresponding to inks of K, C, M and Y are aligned successively from the upstream side in terms of the direction of movement of the intermediate transfer body  302 , and when the drive roller  308  is caused to rotate in the clockwise direction, the intermediate transfer body  302  moves from left to right in  FIG. 24  through the recording region directly below the recording unit  12  (in the direction from the K ink recording head  12 K to the Y ink recording head  12 Y). A speed reading apparatus  314  which determines the movement speed of the intermediate transfer body  302  is provided on the downstream side of the recording unit  12  in terms of the direction of movement of the intermediate transfer body  302 , and the speed information relating to the intermediate transfer body  302  obtained by the speed reading apparatus  314  is supplied to the control system (the print controller  80  in  FIG. 25 ). 
   When an image is formed on the intermediate transfer body by means of ink ejected from the recording unit  12 , the intermediate transfer body  302  is moved further and the image is moved into a transfer section which includes the transfer rollers  304  and  306 . When the image arrives at the transfer section, the recording paper  16  is supplied to the transfer section by means of paper supply rollers  316 A and  316 B. A position determination sensor  318  which determines the position of the recording paper  16  is provided on the upstream side of the transfer unit in the paper conveyance direction, and the position determination sensor  318  determines whether or not there is a recording paper  16  present immediately before the transfer unit. When the image formed on the intermediate transfer body  302  has been transferred to the recording paper  16  by the transfer section, the recording paper  16  recorded with the image is then output by means of the paper output rollers  320 A and  320 B. 
   As shown in  FIG. 25 , the system controller  72  sends a control signal to the intermediate transfer body drive control unit  330  which controls the motor  312  forming the drive source of the intermediate transfer body  302 . The intermediate transfer body drive control unit  330  controls the speed, and the like, of the intermediate transfer body  302  on the basis of the control signal sent by the system controller  72 . 
   Similarly, the recording paper conveyance control unit  332  controls the drive motor  334  of the paper supply rollers  316 A and  316 B and the paper output rollers  320 A and  320 B, on the basis of the control signal sent by the system controller  72 . 
   Furthermore, the output signal obtained from the speed reading apparatus  314  which determines the speed of the intermediate transfer body  302  is supplied to the speed calculation unit  92 , which is a functional block of the print controller  80 . Moreover, the output signal of the position determination sensor (recording medium determination unit)  318  which determines the position of the recording paper  16  is also supplied to the speed calculation unit  92 . 
   In the speed calculation unit  92 , the speed variation occurring in the intermediate transfer body  302  at the timing when the intermediate transfer body and the recording paper  16  receive the pressurized contact of the transfer rollers  304  and  306  is determined on the basis of the speed information relating to the intermediate transfer body  302  and the position information relating to the recording paper  16 , and speed variation data is created accordingly. The speed variation data created by the speed calculation unit  92  is stored in the speed variation data storage unit  94 , and the ejection timing correction unit  96  reads out this speed variation data, as and when necessary, and corrects the ejection timing accordingly. 
   Next, the correction of the ejection timing according to the third embodiment is described in detail below. Firstly, a test sheet of recording paper  16  is conveyed (recording paper conveyance step). The recording paper to be used for actual image recording (in other words, a recording paper with the same type and size) is used as the test recording paper  16 . 
   The speed (speed variation) of the intermediate transfer body  302  when the test recording paper  16  and the intermediate transfer body  302  are pressed by the transfer rollers  308  and  310  is measured by the speed reading apparatus  314 . The speed variation of the intermediate transfer body  302  is measured by determining a test pattern formed previously on the intermediate transfer body  302  (see  FIG. 2 ), by means of a sensor (test pattern reading step), and then calculating speed variation data for the intermediate transfer body  302  on the basis of the determination result (speed variation data calculation step). 
   Furthermore, alternatively, a test pattern image may be formed on the intermediate transfer body by means of the recording unit  12  (see  FIGS. 11A and 19 ), an imaging apparatus, such as a CCD sensor, is used as the speed reading apparatus  314 , and an image of the test pattern image on the intermediate transfer body  302  is captured by the CCD sensor (test pattern reading step), speed variation data for the intermediate transfer body  302  being calculated on the basis of this imaging result (speed variation data calculation step). 
   In a mode where a test pattern image is formed by ejecting ink from the recording unit  12 , a step for removing the test pattern becomes necessary, and therefore a desirable mode is one in which a test pattern is formed previously at a prescribed position on the intermediate transfer body  302 . 
   In a so-called transfer method, as described in the present embodiment, since a conveyance belt for conveying the recording paper  16  is not necessary (the conveyance system for the recording paper  16  adopts a simplified composition shown in  FIG. 24 , including only paper supply rollers  316 A and  316 B, and paper output rollers  320 A and  320 B), then the speed variation occurring in the recording paper  16  when the recording paper  16  separates from the paper supply rollers  316 A and  316 B or when the recording paper  16  comes under pressurized contact from the paper output rollers  320 A and  320 B, is absorbed by deformation of the recording paper  16 , and therefore it does not affect the speed variation of intermediate transfer body  302 . Consequently, it is sufficient to consider only the speed variation occurring in the intermediate transfer body  302  when the recording paper  16  receives the pressurized contact of the transfer rollers  304  and  306 , and when the recording paper  16  separates from the transfer rollers  304  and  306 . 
   Since the conveyance distance from the transfer rollers  304  and  306  to the recording unit  12  is already known, then it is possible to predict the timing at which speed variation will occur in the intermediate transfer body  302 , on the basis of the timing at which the recording paper  16  receives the pressurized contact of the transfer rollers  304  and  306 , and the length of the recording paper  16 . 
   The embodiments of the present invention described above related to an inkjet recording apparatus  10  which forms color images on a recording paper  16  by ejecting liquid ink droplets onto the recording paper  16 , but the scope of application of the present invention is not limited to an inkjet recording apparatus, and it may also be applied to a liquid ejection apparatus which ejects other types of liquid, such as water, liquid chemicals, treatment liquid, and the like, from ejection holes (nozzles) provided in a head. Furthermore, it may also be applied to an image recording apparatus which forms a prescribed pattern by using a recording body such as resist, on a substrate. 
   It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the invention is to cover all modifications, alternate constructions and equivalents falling within the spirit and scope of the invention as expressed in the appended claims.