Patent Publication Number: US-8985733-B2

Title: Pattern inspection apparatus, pattern inspection method, and printer

Description:
The present application claims priority from Japanese Patent Application No. 2013-072322, filed on Mar. 29, 2013, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a pattern inspection apparatus and a pattern inspection method in which inspection is performed by reading a print pattern printed by a printer, and a printer in which a print pattern is printed and inspection is performed by reading the printed print pattern. 
     2. Description of the Related Art 
     Conventionally, an ink-jet printer is known, in which the printing is performed by discharging ink from a printing head carried on a carriage while reciprocatively moving the carriage in a scanning direction. In a certain ink-jet printer, ink is discharged from certain nozzles while moving a carriage in the scanning direction to thereby print a linear reference pattern extending in the main scanning direction. Subsequently, the recording paper P is transported by a certain distance, and then the ink is discharged from nozzles positioned on the downstream side in the transport direction as compared with the nozzles having been used to print the reference pattern, while moving the carriage in the scanning direction to thereby print an adjusting pattern extending linearly in the scanning direction. Accordingly, an error detecting print pattern, which is composed of the reference pattern and the adjusting pattern, is printed. The printing of the reference pattern and the adjusting pattern as described above is performed a plurality of times while changing the transport distance of the recording paper P, and thus a plurality of error detecting print patterns are printed. The plurality of error detecting print patterns are read by using an optical sensor to acquire densities of the respective error detecting print patterns. In this context, the density of the print pattern is the ratio of the areal size of the pattern portion to which the ink is adhered with respect to the areal size of the portion (white background portion) at which the recording medium is exposed. In this procedure, the acquired density is the lowest in relation to the error detecting print pattern in which the reference pattern and the adjusting pattern are overlapped to the greatest extent. Accordingly, in the ink-jet printer described above, the transport amount, which is provided when the error detecting print pattern having the lowest acquired density, is used as the transport amount to be used during the printing. 
     In relation thereto, in the case of the ink-jet printer in which the printing is performed by discharging the ink from the plurality of nozzles, any abnormality arises in a part of the reference pattern or the adjusting pattern, for example, such that a part of the reference pattern or the adjusting pattern is not printed and/or any dispersion arises in the thickness of the reference pattern or the adjusting pattern. For example, when the printing of the reference pattern and the adjusting pattern is repeatedly performed as in the ink-jet printer described above, the following situation sometimes arises. That is, the ink is not discharged upon the ink discharge performed for the first time during the printing of the reference pattern or the adjusting pattern performed for the first time, and a part of the reference pattern or the adjusting pattern is not printed. Further, the following situation sometimes arises. That is, the discharge speed and/or the volume of the ink discharged from the nozzles is/are fluctuated, and any dispersion arises in the thickness of the reference pattern or the adjusting pattern, on account of the temporarily unstable voltage supplied from a power source to the ink-jet printer, the vibration of the surface on which the ink-jet printer is arranged, and/or the change of the direction of the force applied to the ink contained in the ink-jet head during the acceleration or deceleration of the carriage depending on the movement direction of the carriage. 
     In this way, if any abnormality arises in a part of the reference pattern or the adjusting pattern, the density, which is acquired from the reading result obtained by reading the error detecting print pattern by means of the optical sensor, is consequently different from the density which is to be originally or normally acquired. As a result, it is feared that the error detecting print pattern, which includes any abnormal reference pattern or any abnormal adjusting pattern and which is different from the error detecting print pattern that is to originally have the lowest density, may be judged as the pattern which has the lowest density, and it is impossible to appropriately set the transport amount. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a pattern inspection apparatus, a pattern inspection method, and a printer which make it possible to acquire the density information while excluding the influence exerted, for example, by any abnormality of each of patterns in a print pattern formed by overlapping the two patterns. 
     According to a first aspect of the present invention, there is provided a pattern inspection apparatus configured to inspect a print pattern printed on a medium by a printer, including: 
     a reading mechanism configured to read the print pattern including an overlapped pattern portion in which a first-pattern and a second-pattern are overlapped and a single pattern portion in which one of the first-pattern and the second-pattern is formed without overlapping; and 
     a controller configured to acquire density information of the print pattern based on a result of the reading performed by the reading mechanism and to correct density information of the overlapped pattern portion by using density information of the single pattern portion. 
     According to a second aspect of the present invention, there is provided a pattern inspection method for inspecting a print pattern printed on a medium by a printer, including: 
     reading, by a reading apparatus, the print pattern printed on the medium by the printer, the print pattern including an overlapped pattern portion in which a first-pattern and a second-pattern are overlapped and a single pattern portion in which one of the first-pattern and the second-pattern is formed without overlapping; 
     acquiring density information of the print pattern based on a result of the reading; and 
     correcting density information of the overlapped pattern portion by using density information of the single pattern portion. 
     According to a third aspect of the present invention, there is provided a printer configured to perform printing on a medium, including: 
     a print unit which is configured to print a print pattern on the medium; 
     a read unit which is configured to read the print pattern printed on the medium; and 
     a controller which is configured to control the print unit and the read unit to perform: 
     printing of the print pattern including an overlapped pattern portion in which a first-pattern and a second-pattern are overlapped and a single pattern portion in which one of the first-pattern and the second-pattern is formed without overlapping, by controlling the print unit; 
     acquisition of density information of the print pattern based on a result of the reading; and 
     correction of density information of the overlapped pattern portion by using density information of the single pattern portion. 
     According to the inventions described above, the density information of the overlapped pattern portion is corrected by using the density information of the single pattern portion formed with only the first-pattern or the second-pattern. Therefore, even when any abnormality or the like exists in a part of the first-pattern or the second-pattern, it is possible to exclude the influence of the density change caused by the abnormality or the like. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic arrangement of a printer according to a first embodiment. 
         FIG. 2  shows a schematic arrangement of a print unit provided in the printer shown in  FIG. 1 . 
         FIG. 3  shows a block diagram illustrating a hardware arrangement of the printer. 
         FIGS. 4A ,  4 B and  4 C show steps illustrating a printing procedure for an inspection pattern (pattern for inspection) in the first embodiment. 
         FIGS. 5A ,  5 B and  5 C show steps to be performed after those shown in  FIGS. 4A to 4C , of the printing procedure for the inspection pattern in the first embodiment. 
         FIG. 6A  shows an ink-jet head in which the nozzle arrangement direction is parallel to the transport direction,  FIG. 6B  shows a printing result of the inspection pattern in the case of  FIG. 6A ,  FIG. 6C  shows an ink-jet head in which the nozzle arrangement direction is inclined with respect to the transport direction, and  FIG. 6D  shows a printing result of the inspection pattern in the case of  FIG. 6C . 
         FIG. 7  illustrates the correction of the density of the inspection pattern in the first embodiment. 
         FIGS. 8A ,  8 B and  8 C show steps illustrating a printing procedure for an inspection pattern (pattern for inspection) in a second embodiment. 
         FIGS. 9A ,  9 B and  9 C show steps to be performed after those shown in  FIGS. 8A to 8C , of the printing procedure for the inspection pattern in the second embodiment. 
         FIG. 10  illustrates the correction of the density of the inspection pattern in the second embodiment. 
         FIG. 11  shows an arrangement of a platen and holding members in a third embodiment. 
         FIG. 12A  shows an inspection pattern (pattern for inspection) in the third embodiment, and  FIG. 12B  shows a printing result of the inspection pattern when a part of line pattern is not printed. 
         FIG. 13  shows enlarged first and second-patterns in the third embodiment. 
         FIG. 14  illustrates the density correction in the brightness acquiring area. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     A first embodiment of the present teaching will be explained below. 
     A printer  1  according to a first embodiment (corresponding to a printer of the present teaching) is a so-called multifunction machine which is capable of performing, for example, the reading of an image, as well as the printing on the recording paper P. The ink-jet printer  1  is provided with, for example, a print unit (see  FIG. 2 ), a paper feeding unit  3 , a paper discharging unit  4 , a read unit  5 , an operation unit  6 , and a display unit  7 . The operation of the ink-jet printer  1  is controlled by a controller  50  (see  FIG. 3 ). 
     The print unit  2  is provided at the inside of the ink-jet printer  1 , and the print unit  2  performs the printing on the recording paper P. Detailed arrangement of the print unit  2  will be explained later on. The paper feeding unit  3  is the portion to arrange, for example, a recording paper tray in which the recording paper P to be supplied to the print unit  2  is accommodated. The paper discharging unit  4  is the portion to which the recording paper P having been subjected to the printing by the print unit  2  is discharged. The read unit  5  is, for example, a scanner, and the read unit  5  is the portion to perform the reading of an image. The operation unit  6  is provided with, for example, buttons. A user performs the necessary operation with respect to the ink-jet printer  1  by operating, for example, the buttons of the operation unit  6 . The display unit  7  is, for example, a liquid crystal display, and the display unit  7  displays information which is required when the ink-jet printer  1  is used. 
     Next, the print unit  2  will be explained. As shown in  FIG. 2 , the print unit  2  is provided with a carriage  11 , an ink-jet head  12 , transporting rollers  13 , and a platen  14 . 
     The carriage  11  is reciprocatively movable in the scanning direction by being guided by guide rails  15 . The following explanation will be made while the right side and the left side in the scanning direction are defined as shown in  FIG. 2 . The ink-jet head  12  is carried on the carriage  11 , and the ink-jet head  12  discharges inks from a plurality of nozzles  10  formed on the lower surface thereof. The plurality of nozzles  10  are arranged to form four nozzle arrays  9 , and the respective nozzle arrays  9  are arranged over a length C in the transport direction perpendicular to the scanning direction. The four nozzle arrays  9  are aligned in the scanning direction. The black, yellow, cyan, and magenta inks are discharged from the plurality of nozzles  10  in this order as starting from those which form the nozzle array  9  disposed on the right side in the scanning direction. 
     The transporting roller  13  is arranged on the both sides of the ink-jet head  12  in the transport direction, and the transporting roller  13  transports the recording paper P in the transport direction. The platen  14  is arranged to face the lower surface of the ink-jet head  12 , and the platen  14  supports, at the lower position, the portion of the recording paper P transported by the transporting rollers  13 , the portion facing the ink-jet head  12 . 
     In the print unit  2 , the inks are discharged from the ink-jet head  12  which is moved reciprocatively in the scanning direction together with the carriage  11 , while intermittently transporting the recording paper P in the transport direction by means of the transporting rollers  13 . Thus, the printing is performed on the recording paper P. 
     Next, an explanation will be made about the controller  50  provided to control the operation of the ink-jet printer  1 . As shown in  FIG. 3 , the controller  50  is provided with, for example, a Central Processing Unit  51  (a CPU  51 ), a Read Only Memory  52  (a ROM  52 ), a Random Access Memory  53  (a RAM  53 ), and an ASIC  54 . In the controller  50 , the CPU  51  and the ASIC  54  cooperatively perform the control necessary for the operation of the printer  1 , including, for example, the ordinary printing performed by the print unit  2 , the printing of an inspection image (image for inspection) as described later on, the reading of the image by the read unit  5 , and the processing for the result of reading of the image. Accordingly, the controller  50  operates, for example, as the density acquiring mechanism, the position specifying mechanism, and the inclination detecting mechanism of the present teaching. Only one CPU  51  is shown in  FIG. 3  for the purpose of convenience. However, the controller  50  may include only one CPU  51  and one CPU  51  may perform the processing. Alternatively, the controller  50  may include a plurality of CPU&#39;s  51  and the plurality of CPU&#39;s  51  may perform the processing in a shared manner. Further, only one ASIC  54  is shown in  FIG. 3  for the purpose of convenience. However, the controller  50  may include only one ASIC  54  and ASIC  54  may perform the processing. Alternatively, the controller  50  may include a plurality of ASICs  54  and the plurality of ASICs  54  may perform the processing in a shared manner. 
     In the first embodiment, as described above, the plurality of nozzles  10 , which form the respective nozzle arrays  9 , are arranged in the transport direction. However, the arrangement direction of the nozzles  10  is inclined with respect to the transport direction in some cases at the stage at which the carriage  11  is assembled to the guide rails  15 , for example, due to the production error of, for example, the carriage  11  and/or the guide rails  15 . Accordingly, in the first embodiment, the following inspection is performed, and the direction of the carriage  11  is adjusted in accordance with the inspection result. 
     Specifically, an inspection pattern (pattern for inspection)  100  as shown in  FIG. 5C  is firstly printed. A program, which allows the printer  1  to perform the printing of the inspection pattern  100 , is stored, for example, in the ROM  52  of the controller  50 . A printing procedure of the inspection pattern  100  will be explained. At first, as shown in  FIG. 4A , the black ink is discharged from M pieces of the nozzles  10  as counted from the downstream side in the transport direction, of the plurality of nozzles  10  for forming the nozzle array  9  positioned on the rightmost side in the scanning direction, while moving the carriage  11  in the scanning direction. In this way, a first-partial pattern  111 , which is composed of M pieces of first line patterns  111   a , is printed on the recording paper P. The M pieces of first line patterns  111   a  extend in the scanning direction respectively, and they are arranged at equal intervals in the transport direction. In this case, in  FIG. 3 , only two of the M pieces of nozzles  10  are illustrated for the purpose of convenience, and only three of the M pieces of first line patterns  111   a  are illustrated. The illustration is also made in the other drawings in the same manner as described above. 
     Subsequently, as shown in  FIG. 4B , the recording paper P is transported by a minute distance D (first offset amount of the present teaching) by means of the transporting rollers  13 . Further, the black ink is discharged from M pieces of the nozzles  10  disposed adjacently on the upstream side in the transport direction of the M pieces of nozzles  10  having been used for the printing of the first-partial pattern  111  just before, while moving the carriage  11  in the scanning direction. In this way, a first-partial pattern  111  is printed on the recording paper P. After that, the transport of the recording paper P performed by the transporting rollers  13  and the printing of the first-partial pattern  111  are repeatedly performed in the same manner as described above. As shown in  FIG. 4C , [(N+1)/2] pieces (N is an odd number) of the first-partial patterns  111 , which are aligned in the transport direction, are printed on the recording paper P.  FIG. 4C  shows the situation provided at the point in time at which the printing is performed until the fourth (4=(7+1)/2) first-partial pattern  111  in the case of N=7. It is noted that N represents the number to express what number of first-partial pattern or patterns  111  is/are to be printed, and N can be set to an arbitrary natural number, if necessary. In the following explanation, N pieces of first-partial patterns  111  are referred to as “N blocks of first-partial patterns  111 ” in some cases. 
     Subsequently, as shown in  FIG. 5A , the magenta ink is discharged from M×N pieces of the nozzles  10  as counted from the downstream side in the transport direction of the nozzle array  9  positioned on the leftmost side in the scanning direction, while moving the carriage  11  in the scanning direction, without transporting the recording paper P from the state shown in  FIG. 4C . Accordingly, a second-pattern  102  is printed on the recording paper P. The second-pattern  102  is such a pattern that N blocks of second-partial patterns  112 , each of which is composed of M pieces of second line patterns  112   a , are aligned in the transport direction. The M pieces of second line patterns  112   a  are the patterns formed by the ink discharged from the M pieces of nozzles  10  arranged adjacently. The M pieces of second line patterns  112   a  extend in the scanning direction respectively, and they are arranged in the transport direction. In this case, in the first embodiment, the recording paper P is not transported during the period in which the N blocks of second-partial patterns  112  are printed as described above. That is, in the first embodiment, the second offset amount of the present teaching is zero. In this procedure, the second line patterns  112   a  are printed on the right side in the scanning direction with respect to the first line patterns  111   a  by an amount shorter than the length in the scanning direction of the line patterns  111   a ,  112   a.    
     Subsequently, the transport of the recording paper P by the minute distance D performed by the transporting rollers  13  and the printing of the first-partial pattern  111  are repeatedly performed in the same manner as described above. Thus, as shown in  FIG. 5B , the [(N−1)/2] blocks of first-partial patterns  111 , which are aligned in the transport direction, are printed on the portion of the recording paper P disposed on the upstream side in the transport direction of the [(N+1)/2] blocks of first-partial patterns  111  described above. Accordingly, as shown in  FIG. 5C , the first-pattern  101 , which is formed by aligning the N blocks of first-partial patterns  111  in the transport direction, is printed on the recording paper P. 
     The first-pattern  101  and the second-pattern  102  are printed as described above. Accordingly, as shown in  FIG. 5C , the inspection pattern  100 , which includes the first-pattern  101  and the second-pattern  102 , is printed on the recording paper P. The inspection pattern  100  has an overlapped pattern portion  121 , a first single pattern portion  122 , and a second single pattern portion  123 . 
     The overlapped pattern portion  121  is the portion which is positioned at a substantially central portion of the inspection pattern  100  in the scanning direction and at which the first-pattern  101  and the second-pattern  102  are overlapped with each other. In the overlapped pattern portion  121 , the first-partial pattern  111 , which is printed at the Kth position (K=1, 2, . . . N) (hereinafter simply referred to as “K-th”) from the downstream side in the transport direction, is overlapped with the K-th second-partial pattern  112 . The following explanation will be made assuming that the portion of the overlapped pattern portion  121 , at which the K-th first-partial pattern  111  and the K-th second-partial pattern  112  are overlapped with each other, is referred to as “K-th overlapped portion  121   a”.    
     The first single pattern portion  122  is the portion which is positioned on the left side in the scanning direction of the overlapped pattern portion  121  and which is formed with only the first-pattern  101 . The second single pattern portion  123  is the portion which is positioned on the right side in the scanning direction of the overlapped pattern portion  121  and which is formed with only the second-pattern  102 . 
     Subsequently, the printed inspection pattern  100  is read by the read unit  5  of the printer  1  to thereby acquire the brightness (density information of the present teaching) of the respective portions of the overlapped pattern portion  121  and the single pattern portions  122 ,  123  of the inspection pattern  100  (a step of reading of the present teaching). Specifically, the overlapped pattern portion  121  is comparted into a plurality of areas  131  in each of which only one overlapped portion  121   a  is arranged, and the brightness of the respective areas  131  are acquired. Further, the first single pattern portion  122  is comparted into a plurality of areas  132  in each of which only one first-partial pattern  111  is arranged, and the brightness of the respective areas  132  are acquired. Further, the second single pattern portion  123  is comparted into a plurality of areas  133  in each of which only one second-partial pattern  112  is arranged, and the brightness of the respective areas  133  are acquired. In this procedure, the brightness, which is acquired by reading the inspection pattern  100  by the read unit  5 , is more lowered at the portion at which the density of each of the overlapped pattern portion  121  and the single pattern portions  122 ,  123  is higher. That is, the acquisition of the brightness of each of the overlapped pattern portion  121  and the single pattern portions  122 ,  123  is equivalent to the acquisition of the density of each of the overlapped pattern portion  121  and the single pattern portions  122 ,  123 . 
     Subsequently, the brightness of each of the areas  131  of the overlapped pattern portion  121  is corrected by subtracting the brightness of the corresponding areas  132 ,  133  of the single pattern portions  122 ,  123  from the brightness of each of the areas  131  of the overlapped pattern portion  121  (a step of acquiring a density of the present teaching). Subsequently, the area  131  having the highest brightness is specified on the basis of the density of each of the areas  131  of the overlapped pattern portion  121  after the correction. Thus, the position in the transport direction is specified for the overlapped portion  121   a  which has the largest degree of the overlap between the first line pattern  111   a  and the second line pattern  112   a  (a step of specifying a position of the present teaching). Further, the inclination of the arrangement direction of the nozzles  10  with respect to the transport direction is detected on the basis of the position of the specified overlapped portion  121   a  (a step of detecting an inclination). 
     This procedure will be explained in further detail below. In the first embodiment, the [(N+1)/2]th first-partial pattern  111  is printed, and then the N blocks of second-partial patterns  112  are printed without transporting the recording paper P. On the other hand, in the case of the ink-jet head  12  of the first embodiment, the position in the transport direction of the nozzle  10  for constructing each of the nozzle array is identical in relation to any nozzle array  9 . Therefore, when the arrangement direction of the nozzles  10  is parallel to the transport direction, as shown in  FIG. 6A , the nozzle  10 , which forms the nozzle array  9  disposed on the rightmost side and which is used to print the first line pattern  111   a , is overlapped in the scanning direction with the nozzle  10  which forms the nozzle array  9  disposed on the leftmost side and which is used to print the second line pattern  112   a . Therefore, when the arrangement direction of the nozzles  10  is parallel to the transport direction, as shown in  FIG. 6B , the first line pattern  111   a  and the second line pattern  112   a  are overlapped with each other substantially completely at the [(N+1)/2]th overlapped portion  121   a . Further, the deviation in the transport direction between the first line pattern  111   a  and the second line pattern  112   a  is more increased at the overlapped portion  121   a  separated farther from the [(N+1)/2]th overlapped portion  121   a.    
     On the other hand, as shown in  FIG. 6C , in a case that the arrangement direction of the nozzles  10  is inclined with respect to the transport direction, the nozzle  10  used to print the first line pattern  111   a  and the nozzle  10  used to print the second line pattern  112   a  are deviated from each other in the transport direction. In this situation, the larger the inclination of the arrangement direction of the nozzles  10  with respect to the transport direction is, the larger the deviation amount of the nozzle  10  is. Further, in the first embodiment, the first line pattern  111   a  and the second line pattern  112   a  are printed by using the nozzles  10  for forming the two nozzle arrays  9  separated farthest from each other in the scanning direction, of the four nozzle arrays  9 . Therefore, the deviation amount of the nozzle  10  is maximized. 
     Therefore, in this case, as shown in  FIG. 6D , the degree of overlap between the first line pattern  111   a  and the second line pattern  112   a  is maximized at any overlapped portion  121   a  other than the [(N+1)/2]th overlapped portion. In this situation, when the inclination of the arrangement direction of the nozzles  10  with respect to the transport direction is more increased, the degree of overlap is maximized between the first line pattern  111   a  and the second line pattern  112   a  at the overlapped portion  121   a  separated from the [(N+1)/2]th overlapped portion  121   a . That is, in the case of the inspection pattern  100 , the extent of the inclination of the arrangement direction of the nozzles  10  with respect to the transport direction is indicated by at what overlapped portion  121   a  the degree of overlap is maximized between the first line pattern  111   a  and the second line pattern  112   a.    
     On the other hand, in the overlapped portion  121   a , the larger the degree of overlap between the first line pattern  111   a  and the second line pattern  112   a  is, the larger the areal size of the white background portion at which the recording paper P is exposed is, wherein the white background portion is formed between the first line pattern  111   a  and the second line pattern  112   a.    
     Further, in the first embodiment, the first line pattern  111   a  is printed with the black ink, and the second line pattern  112   a  is printed with the magenta ink. However, the black ink is deeper or darker than the inks of the other colors. Therefore, the portion, at which the first line pattern  111   a  and the second line pattern  112   a  are overlapped with each other, has the color which is close to the color of black. In the case of the brightness value conversion of the color density by the scanner, even when a pattern, in which the black ink is overlapped twice, is read, the brightness value does not become a half. Therefore, the brightness read by the read unit  5  is approximately identical between the portion in which only the first line pattern  111   a  formed with the black ink is arranged and the portion in which the first line pattern  111   a  printed with the black ink and the second line pattern  112   a  printed with the magenta ink are overlapped with each other. 
     When both of the first line pattern  111   a  and the second line pattern  112   a  are printed with the color ink or color inks, such a situation may also arise that the density is higher at the portion in which the first line pattern  111   a  and the second line pattern  112   a  are overlapped with each other as compared with the portion in which the first line pattern  111   a  or the second line pattern  112   a  is arranged singly. In other words, it is feared that the density fluctuation or the density variation of the overlapped pattern portion  121  does not indicate the fluctuation of the degree of overlap between the first line pattern  111   a  and the second line pattern  112   a . In this case, whether or not the density fluctuation of the overlapped pattern portion  121  indicates the fluctuation of the degree of overlap between the first line pattern  111   a  and the second line pattern  112   a  changes depending on the way of adjustment in which to what extent of the brightness the minimum value and the maximum value of the brightness value outputted by the read unit  5  are allowed to correspond. Therefore, for example, it is considered that the scanner is set so that the pattern in which the yellow is used singly and the pattern in which the yellow and the cyan are overlapped with each other have substantially the same brightness value. In this case, when the first line pattern  111   a  is printed with the yellow ink and the second line pattern  112   a  is printed with the cyan ink, then the density fluctuation of the overlapped pattern portion  121  indicates the degree of overlap between the first line pattern  111   a  and the second line pattern  112   a . However, in general, when the adjustment is performed such that the brightness values, which are different from each other as much as possible, are allowed to correspond to the white portion and the black portion, any delicate color difference can be detected at a high resolution in a wide density range. Therefore, the procedure, in which any one of the first line pattern  111   a  and the second line pattern  112   a  is printed with the black ink, is advantageous in relation to the detection accuracy in the read unit  5  described above. 
     As described above, the larger the degree of overlap between the first line pattern  111   a  and the second line pattern  112   a  at the overlapped portion  121   a  is, the higher the brightness read by the read unit  5  is. That is, the brightness of the overlapped portion  121   a  indicates the degree of overlap between the first line pattern  111   a  and the second line pattern  112   a . Therefore, when the position of the overlapped portion  121   a , at which the brightness read by the read unit  5  is the highest (local maximum), is specified, it is possible to acquire the position of the overlapped portion  121   a  at which the degree of overlap between the first line pattern  111   a  and the second line pattern  112   a  is the largest. Further, the inclination of the arrangement direction of the nozzles  10  with respect to the transport direction can be detected from the specified position of the overlapped portion  121   a.    
     However, in the first embodiment, the nozzles  10 , which are used to print the first line pattern  111   a , differ depending on every first-partial pattern  111 . Therefore, a part of the first line pattern  111   a  is not printed in some cases, for example, due to the clog-up of the nozzle  10 , and/or the dispersion arises in the thickness (length in the transport direction) of the first line pattern  111   a  in other cases due to the dispersion of the ink discharge speed and/or the volume. Similarly, a part of the second line pattern  112   a  is not printed in some cases, and/or the dispersion arises in the thickness of the second line pattern  112   a  in other cases. That is, any abnormality sometimes arises in parts of the line patterns  111   a ,  112   a.    
     In such situations, it is feared that the brightness of a part of the overlapped portion  121   a  may differ from the brightness to be originally obtained. Accordingly, in the first embodiment, the brightness of each of the areas  131  of the overlapped pattern portion  121  is corrected by subtracting the brightness of the corresponding areas  132 ,  133  of the single pattern portions  122 ,  123  from the brightness of each of the areas  131  of the overlapped pattern portion  121  as described above. Thus, the position of the overlapped portion  121   a  having the highest brightness is specified by using the brightness of each of the areas  131  of the overlapped pattern portion  121  after the correction. Further, the inclination of the arrangement direction of the nozzles  10  with respect to the transport direction is detected from the specified position of the overlapped portion  121   a . Further, the direction of the carriage  11  is adjusted in accordance with the detected inclination so that the arrangement direction of the nozzles  10  is parallel to the transport direction. 
     As shown in  FIG. 7 , consideration is made while it is assumed by way of example that the brightness is the highest at the fifth overlapped portion  121   a  when no abnormality arises in the line patterns  111   a ,  112   a  on account of the inclination of the arrangement direction of the nozzles  10  with respect to the transport direction. On this assumption, an explanation will be made about a case in which a part of the first line pattern  111   a  of the sixth overlapped portion  121   a  and a part of the second line pattern  112   a  of the third overlapped portion  121   a  are not printed. In this case, at the sixth overlapped portion  121   a , the portion, at which the recording paper P is exposed, has the increased areal size to such an extent that the part of the first line pattern  111   a  is not printed, and the acquired brightness is raised. Further, at the fifth overlapped portion  121   a , the portion, at which the recording paper P is exposed, has the increased areal size to such an extent that the part of the second line pattern  112   a  is not printed, and the acquired brightness is raised. The brightness of the fifth overlapped portion  121   a  is to be originally the highest in relation to the overlapped pattern portion  121 . However, if the correction as described above is not performed, the brightness of the third or sixth overlapped portion  121   a  is the highest. 
     On the other hand, as for the first single pattern portion  122 , the brightness of the sixth first-partial pattern  111  is higher than the brightness of the other first-partial patterns  111 . As for the second single pattern portion  123 , the brightness of the third second-partial pattern  112  is higher than the brightness of the other second-partial patterns  112 . Therefore, if the brightness of the overlapped pattern portion  121  is corrected by subtracting the brightness of the single pattern portions  122 ,  123  from the brightness of the overlapped pattern portion  121 , the relationship of magnitude of the brightness after the correction, which is provided between the N pieces of overlapped portions  121   a  in the overlapped pattern portion  121  after the correction, is the same as the relationship of magnitude of the brightness which is provided between the N pieces of overlapped portions  121   a  when any abnormality does not arise in the line patterns  111   a ,  112   a . That is, when any abnormality arises in a part or parts of the first-pattern  101  and the second-pattern  102 , the influence of the brightness change caused by the abnormality can be excluded from the brightness of the overlapped pattern portion  121 . 
     In the first embodiment, the nozzles  10 , which form the different nozzle arrays  9 , are used in relation to the printing of the first line pattern  111   a  and the printing of the second line pattern  112   a . That is, the nozzles  10  to be used differ between the printing of the first line pattern  111   a  and the printing of the second line pattern  112   a . Therefore, the probability is raised in relation to the occurrence of abnormality in the nozzles  10  when the first line pattern  111   a  and the second line pattern  112   a  are printed, as compared with a case in which the first line pattern and the second line pattern are printed by using the same nozzles  10  (for example, a case in which an inspection pattern  300  is printed in a third embodiment described later on). Therefore, there is a great significance in the correction of the brightness of the overlapped pattern portion  121  with the brightness of the single pattern portions  122 ,  123  as described above. 
     Second Embodiment 
     Next, an explanation will be made about a second embodiment of the present teaching. However, components or parts different from those of the first embodiment will be principally explained below. 
     In the print unit  2  described above, the transporting rollers  13  transport the recording paper P in the transport direction. However, the transport amount of the recording paper P is determined by the rotation amount and the diameter of the transporting roller  13 . On the other hand, in the print unit  2 , as described above, the printing is performed on the recording paper P by discharging the inks from the ink-jet head  12 , while intermittently transporting the recording paper P in the transport direction by means of the transporting rollers  13 . In this procedure, the ideal transport amount L of the recording paper P to be provided by performing the transport operation once is determined by the length C of the nozzle array  9  in the transport direction (see  FIG. 2 ). In the following explanation, the ideal transport amount L to be provided by performing the transport operation once is defined as the amount obtained by subtracting the length F in the transport direction of the range of arrangement of the nozzles  10  used to print each of partial patterns  211 ,  212  from the length C of the nozzle array  9 . There is no need to define the ideal transport amount L, in the above-described way. However, it is preferable to define the ideal transport amount L in the above-described way, because it is possible to maximize the value of L. 
     In this procedure, in the case of the printer  1 , any dispersion arises in the actual diameter of the transporting roller  13  and/or the length C of the nozzle array  9 , for example, due to the influence of the error caused during the production. Therefore, if the rotation amount of the transporting roller  13 , which is to be provided when the recording paper P is transported during the printing, is determined assuming that the diameter of the transporting roller  13  and the length C of the nozzle array  9  are the designed values, then it is feared that the transport amount of the recording paper P is not the adequate transport amount with respect to the length C of the nozzle array  9 , and the quality of the printing may be deteriorated. Accordingly, in the second embodiment, the following inspection is performed at the stage at which the production of the printer  1  is completed, and the rotation amount of the transporting roller  13  is corrected when the recording paper P is transported during the printing. 
     Specifically, an inspection pattern (a pattern for inspection)  200  as shown in  FIG. 9C  is firstly printed. A printing procedure for printing the inspection pattern  200  will be explained. At first, as shown in  FIG. 8A , the black ink is discharged from M pieces of the nozzles  10   a  disposed on the upstream side in the transport direction, of the nozzles  10  for forming the nozzle array  9  positioned on the rightmost side, and thus a first-partial pattern  211 , which is composed of M pieces of first line patterns  211   a , is printed on the recording paper P. The M pieces of first line patterns  211   a  extend in the scanning direction respectively, and they are arranged at equal intervals in the transport direction. 
     Subsequently, as shown in  FIG. 8B , the recording paper P is transported by a predetermined distance Q by means of the transporting rollers  13 , and then the black ink is discharged from the M pieces of nozzles  10   a  described above to print the first-partial pattern  211 . After that, the transport of the recording paper P by the transporting rollers  13  and the printing of the first-partial pattern  211  are repeatedly performed to thereby print a first-pattern  201  formed by aligning N pieces of the first-partial patterns  211  in the transport direction as shown in  FIG. 8C . 
     Subsequently, as shown in  FIG. 9A , the black ink is discharged from M pieces of the nozzles  10   b  separated from the nozzles  10   a  by L on the downstream side in the transport direction. In this way, a second-partial pattern  212 , which is composed of M pieces of second line patterns  212   a , is printed. In this case, before printing the second-partial pattern  212 , the recording paper P is transported by the transporting rollers  13  to a position at which the accumulated or added-up transport amount is L−[(N−1)/2]×D from the position at which the first first-pattern  201  is printed. In the first embodiment, the recording paper P has already been transported by a length of (N−1)×Q during the period in which the first-pattern  201  is printed. Therefore, the transport amount of the recording paper P which is to be transported after printing the first-pattern  210  is L−[(N−1)/2]×D−(N−1)×Q. In this case, D is a minute value as compared with L (for example, D=L/100). The M pieces of second line patterns  212   a  extend in the scanning direction respectively, and they are arranged at equal intervals in the transport direction. In this procedure, the second line pattern  212   a  is printed while deviating the second line pattern  212   a  with respect to the first line pattern  211   a  on the right side in the scanning direction by an amount shorter than the length in the scanning direction of the line patterns  211   a ,  212   a.    
     Subsequently, as shown in  FIG. 9B , the recording paper P is transported by (Q+D) by the transporting rollers  13 , and the black ink is discharged from the M pieces of nozzles  10   b  described above to print the second-partial pattern  212 . In the following procedure, the transport of the recording paper P by the transporting rollers  13  and the printing of the second-partial pattern  212  are repeatedly performed. Accordingly, as shown in  FIG. 9C , a second-pattern  202 , in which N blocks of the second-partial patterns  212  are aligned in the transport direction, is printed. 
     The first-pattern  201  and the second-pattern  202  are printed as described above. Accordingly, the inspection pattern  200 , which is composed of the first-pattern  201  and the second-pattern  202 , is printed on the recording paper P. The inspection pattern  200  has an overlapped pattern portion  221 , a first single pattern portion  222 , and a second single pattern portion  223 . 
     The overlapped pattern portion  221  is the portion which is positioned at a substantially central portion of the inspection pattern  200  in the scanning direction and at which the first-pattern  201  and the second-pattern  202  are overlapped with each other. In the overlapped pattern portion  221 , the first-partial pattern  211 , which is provided at the K-th position (K=1, 2, . . . N), is overlapped with the K-th second-partial pattern  212 . The following explanation will be made assuming that the portion of the overlapped pattern portion  221 , at which the K-th first-partial pattern  211  and the K-th second-partial pattern  212  are overlapped with each other, is referred to as “K-th overlapped portion  221   a”.    
     The first single pattern portion  222  is the portion which is positioned on the left side in the scanning direction of the overlapped pattern portion  221  and which is formed with only the first-pattern  201 . The second single pattern portion  223  is the portion which is positioned on the right side in the scanning direction of the overlapped pattern portion  221  and which is formed with only the second-pattern  202 . 
     Subsequently, the printed inspection pattern  200  is read by the read unit  5  to thereby acquire the brightness (density information of the present teaching) of the respective portions of the overlapped pattern portion  221  and the single pattern portions  222 ,  223  (a step of reading of the present teaching). Specifically, the overlapped pattern portion  221  is comparted into a plurality of areas  231  in each of which only one overlapped portion  2211   a  is arranged, and the brightness of the respective areas  231  are acquired. Further, the first single pattern portion  222  is comparted into a plurality of areas  232  in each of which only one first-partial pattern  111  is arranged, and the brightness of the respective areas  232  are acquired. Further, the second single pattern portion  223  is comparted into a plurality of areas  233  in each of which only one second-partial pattern  212  is arranged, and the brightness of the respective areas  233  are acquired. 
     Subsequently, the brightness of each of the areas  231  of the overlapped pattern portion  221  is corrected by subtracting the brightness of the corresponding areas  232 ,  233  of the single pattern portions  222 ,  223  from the brightness of each of the areas  231  of the overlapped pattern portion  221  (a step of acquiring density of the present teaching). Subsequently, the area  231  having the highest brightness is specified on the basis of the density of each of the areas  231  of the overlapped pattern portion  221  after the correction. Thus, the position in the transport direction is specified for the overlapped portion  221   a  which has the largest degree of overlap between the first line pattern  211   a  and the second line pattern  212   a  (a step of specifying position of the present teaching). Further, the rotation amount of the transporting roller  13  during the printing is adjusted on the basis of the position of the specified overlapped portion  221   a.    
     This procedure will be explained in further detail below. When the diameter of the transporting roller  13  and the length C of the nozzle array  9  are exactly the designed values, the transport distance of the recording paper P, which is provided from the printing position of the K-th first-partial pattern  211  to the printing position of the K-th second-partial pattern  212 , is L−[(N+1)/2]×D+K×D. Therefore, when K=[(N+1)/2] is given, the transport distance of the recording paper P, which is provided from the position of printing of the first-partial pattern  211  to the position of printing of the second-partial pattern  212 , is L. When the length C of the nozzle array  9  is exactly the designed value, then L is the amount obtained by subtracting, from the length C of the nozzle array  9 , the length F in the transport direction of the range of arrangement of the nozzles  10  used to print the respective partial patterns  211 ,  212 , and hence the first line pattern  211   a  and the second line pattern  212   a  are overlapped with each other substantially completely at the [(N+1)/2]th overlapped portion  221   a . Further, the deviation in the transport direction between the first line pattern  211   a  and the second line pattern  212   a  is more increased for the overlapped portion  221   a  separated farther in the transport direction from the [(N+1)/2]th overlapped portion  221   a.    
     On the other hand, when the diameter of the transporting roller  13  and/or the length C of the nozzle array  9  is/are deviated from the designed value or designed values, the degree of overlap between the first line pattern  211   a  and the second line pattern  212   a  is maximized at any overlapped portion  221   a  other than the [(N+1)/2]th overlapped portion  221   a  depending on the deviation amount from the designed value. 
     Therefore, in the second embodiment, the position of the overlapped portion  221   a , at which the degree of overlap between the first line pattern  211   a  and the second line pattern  212   a  is maximized, indicates the transport amount of the recording paper P (rotation amount of the transporting roller  13 ) which is adequate with respect to the length C of the nozzle array  9 . 
     Also in the second embodiment, the larger the degree of overlap between the first line pattern  211   a  and the second line pattern  212   a  is, the higher the brightness read by the read unit  5  is, in the same manner as explained in the first embodiment. Therefore, the position of the overlapped portion  221   a , at which the degree of overlap between the first line pattern  211   a  and the second line pattern  212   a  is maximized, can be acquired by acquiring the position of the overlapped portion  221   a  at which the brightness is the highest. The brightness of the overlapped pattern portion  221  is changed in the same manner as those shown in  FIGS. 6B and 6D , any illustration in the drawing is omitted herein. 
     However, when the inspection pattern  200  is printed as well, then parts of the line patterns  211   a ,  212   a  are not printed in some cases, and/or the dispersion arises in the thicknesses of the line patterns  211   a ,  212   a  in other cases. For example, in the case of the second embodiment, when the inspection pattern  200  is printed with the printer  1  with which the printing has not been performed for a long period, the following situation tends to arise due to the increase in viscosity of the ink. That is, the ink is not discharged from the nozzles  10   a  in some cases and/or the volume of the ink discharged from the nozzles  10   a  is decreased in other cases, when the first-partial pattern  211  to be printed firstly is printed as compared with when the first-partial pattern  211  to be printed secondly or following times is printed. Similarly, the following situation tends to arise. That is, the ink is not discharged from the nozzles  10   b  in some cases and/or the volume of the ink discharged from the nozzles  10   b  is decreased in other cases, when the second-partial pattern  212  to be printed firstly is printed as compared with when the second-partial pattern  212  to be printed secondly or following times is printed. In such situations, it is feared that the brightness of a part of the overlapped portion  221   a  may differ from the brightness to be originally obtained at the overlapped pattern portion  221 . 
     Accordingly, in the second embodiment, as described above, the brightness of the overlapped pattern portion  221  is corrected by subtracting the brightness of corresponding areas  232 ,  233  of the single pattern portions  222 ,  223  from the brightness of each of the areas  231  of the overlapped pattern portion  221 . Further, the position of the overlapped portion  221   a  having the lowest brightness is specified by using the brightness of each of the areas  231  of the overlapped pattern portion  221  after the correction. Further, the rotation amount of the transporting roller  13  is adjusted on the basis of the position of the specified overlapped portion  221   a.    
     As shown in  FIG. 10 , consideration is made while it is assumed that the brightness is the highest at the fifth overlapped portion  221   a  if no abnormality arises in the line patterns  211   a ,  212   a  on account of the deviation of the diameter of the transporting roller  13  and/or the length C of the nozzle array  9  from the designed value or designed values. On this assumption, an explanation will be made about a case in which a part of the first line pattern  211   a  of the first first-partial pattern  211  is not printed and a part of the second line pattern  212   a  of the first second-partial pattern  212  is not printed. In this case, the brightness of the fifth overlapped portion  221   a  is to be originally the highest in relation to the overlapped pattern portion  221 . However, at the first overlapped portion  221   a , the part of the first line pattern  211   a  and the part of the second line pattern  212   a  are not printed. Therefore, the brightness is the highest at the first overlapped portion  221   a.    
     On the other hand, as for the first single pattern portion  222 , the brightness of the first first-partial pattern  211  is higher than those of the other first-partial patterns  211 . As for the second single pattern portion  223 , the brightness of the first second-partial pattern  212  is higher than those of the other second-partial patterns  212 . Therefore, if the brightness of the overlapped pattern portion  221  is corrected by subtracting the brightness of the single pattern portions  222 ,  223  from the brightness of the overlapped pattern portion  221 , the relationship of magnitude of the brightness after the correction, which is provided between the N blocks of overlapped portions  221   a  in the overlapped pattern portion  221 , is the same as the relationship of magnitude of the brightness which is provided between the N pieces of overlapped portions  221   a  when any abnormality does not arise in all of the line patterns  211   a ,  212   a . That is, when any abnormality arises in parts of the first-pattern  201  and the second-pattern  202 , the influence of the brightness change caused by the abnormality can be excluded from the information of the brightness of the overlapped pattern portion  221 . 
     In the second embodiment, the nozzles  10   a  to be used for the printing of the first line pattern  211   a  is different from the nozzles  10   b  to be used for the printing of the second line pattern  212   a . Therefore, the probability is raised in relation to the occurrence of abnormality in the nozzles  10  when the first line pattern  211   a  and the second line pattern  212   a  are printed, as compared with a case in which the first line pattern and the second line pattern are printed by using the same nozzles  10  (for example, a case in which an inspection pattern  300  is printed in a third embodiment described later on). Therefore, there is a great significance in the correction of the brightness of the overlapped pattern portion  221  with the brightness of the single pattern portions  222 ,  223  as described above. 
     Third Embodiment 
     Next, an explanation will be made about a third embodiment of the present teaching. However, components or parts different from those of the first and second embodiments will be principally explained below. 
     In the third embodiment, as shown in  FIG. 11A , a plurality of ribs  61  are arranged on the upper surface of a platen  14  while providing intervals in the scanning direction. A plurality of holding members  62 , which hold the recording paper P from upper positions, are arranged at portions positioned between the plurality of ribs  61  in the scanning direction. The holding members  62  are retained by, for example, an unillustrated frame of the printer  1 . Accordingly, the recording paper P, which is transported by the transporting rollers  13 , is bent by the plurality of ribs  61  and the plurality of holding members  62  to provide such a wavy shape that peak portions Pm protruding upwardly and valley portions Pv protruding downwardly are alternately aligned in the scanning direction in a range R from which the both ends portions in the scanning direction are excluded. Accordingly, the distance G, which is provided between the nozzle  10  of the ink-jet head  12  and the recording paper P having the wavy shape, varies or fluctuates in the scanning direction. 
     In this arrangement, in the print unit  2 , the printing is performed by discharging the inks from the nozzles  10  while reciprocatively moving the carriage  11  in the scanning direction as described above. In this case, in order that any deviation does not arise in the landing position of the ink on the recording paper P between when the carriage  11  is moved to the right side in the scanning direction and when the carriage  11  is moved to the left side, it is necessary to adjust the discharge timing of the ink from the nozzle  10 . The amount of movement of the ink in the scanning direction, which is provided until the ink is landed on the recording paper P after the ink is discharged from the nozzle  10 , is increased/decreased depending on the flight time of the ink. Therefore, the discharge timing of the ink from the nozzle  10 , which is required to land the ink onto a certain position of the recording paper P, differs depending on the distance between the nozzle  10  and the recording paper P. In the third embodiment, as described above, the distance between the nozzle  10  and the recording paper P varies in the scanning direction. Therefore, in order to determine the discharge timing of the ink to be discharged from the nozzle  10 , it is necessary to acquire the distance between the nozzle  10  and each of the portions of the recording paper P. Accordingly, in the third embodiment, the inspection is performed as follows. The distance between the nozzle  10  and each of the portions of the recording paper P is acquired depending on the inspection result. Further, the discharge timing of the ink to be discharged from the nozzle  10  is adjusted depending on the acquired distance. 
     Specifically, at first, an inspection pattern  300  as shown in  FIG. 12A  is printed. The printing procedure for printing the inspection pattern  300  will be explained. The black ink is discharged from the plurality of nozzles  10  for forming a certain nozzle array  9  (see  FIG. 1 ) while moving the carriage  11  to the right side in the scanning direction to thereby print a plurality of first-patterns  301  arranged in the scanning direction. The first-pattern  301  is the pattern which extends linearly or in a straight line form in parallel to the transport direction. In particular, as shown in  FIG. 13 , the first-pattern  301  is the pattern formed such that a plurality of linear first line patterns  301   a  each having a short length, which extend in parallel to the transport direction, are arranged in the transport direction. However, in  FIG. 13 , in order to illustrate the drawing simply, the first line pattern  301   a  and a second line pattern  302   a  are shown more thickly as compared with the actual dimensions. Further, the plurality of first-patterns  301  are printed over a range from which a range R1 positioned at the right end portion is excluded, the range being included in the range R in which the recording paper P has the wavy shape. 
     Subsequently, the black ink is discharged from the nozzles  10  for forming the nozzle array  9  disposed on the rightmost side, while moving the carriage  11  to the left side in the scanning direction to thereby print a plurality of second-patterns  302  which are arranged in the transport direction. The second-pattern  302  is the step-shaped pattern. However, the difference in level or step of the step-shaped pattern is minute. Therefore, the second-pattern  302  looks like a linear pattern inclined with respect to the transport direction as a whole. In  FIG. 12 , the second-pattern  302  is expressed as a diagonal line or oblique line. However, in particular, as shown in  FIG. 13 , the second-pattern  302  is the pattern formed such that the linear second line patterns  302   a  each having a short length, which extend in parallel to the transport direction, are arranged in the transport direction while being deviated from each other in the scanning direction. Further, the second-patterns  302  are printed over a range from which a range R2 positioned at the left end portion is excluded, the range being included in the range R in which the recording paper P has the wavy shape. When the second-pattern  302  is printed, the ink is discharged from the nozzle  10  at such a discharge timing that the point of intersection B between the first-pattern  301  and the second-pattern  302  is disposed at the central portions of the first-pattern  301  and the second-pattern  302 , assuming that the distance between the nozzle  10  and the recording paper P is a certain predetermined distance. 
     The plurality of first-patterns  302  and the plurality of second-patterns  302  are printed as described above, and thus the inspection pattern  300 , which includes the plurality of first-patterns  301  and the plurality of second-patterns  302 , is printed on the recording paper P. The inspection pattern  300  has an overlapped pattern portion  321 , a first single pattern portion  322 , and a second single pattern portion  323 . The overlapped pattern portion  321  is the portion in which the first-patterns  301  and the second-patterns  302  are overlapped with each other, the portion being positioned in the range of the range R from which the ranges R1, R2 are excluded. Intersecting patterns  310 , in each of which the first-pattern  301  and the second-pattern  302  intersect, are formed in the overlapped pattern portion  321 . The first single pattern portion  322  is the portion in which only the first-patterns  301  are formed, the portion being positioned in the range R2. The second single pattern portion  323  is the portion in which only the second-patterns  302  are formed, the portion being positioned in the range R1. 
     Subsequently, the inspection pattern  300  is read by the read unit  50  to thereby acquire the brightness of the respective portions of the inspection pattern (a step of reading the present teaching). This procedure will be explained in further detail below. The overlapped pattern portion  321  is comparted into a plurality of brightness acquiring areas  330  in each of which a predetermined number of the intersecting patterns  310  are included, and the brightness acquiring area  330  is comparted into a plurality of areas  331  which are aligned in the transport direction. Further, the brightness of the respective areas  331  are acquired. Further, each of the single pattern portions  322 ,  323  is comparted into a plurality of areas  332 ,  333  which are aligned in the transport direction, and the brightness of the respective areas  332 ,  333  are acquired. 
     Subsequently, the brightness of the corresponding areas  332 ,  333  of the single pattern portions  322 ,  323  are subtracted from the brightness of the respective areas  331  of the respective brightness acquiring areas  330  to thereby correct the brightness of the respective areas  331  of the respective brightness acquiring areas (a step of acquiring density of the present teaching). 
     In this procedure, the first line pattern  301   a  and the second line pattern  302   a  are overlapped with each other substantially completely at the point of intersection B between the first-pattern  301  and the second-pattern  302  in the intersecting pattern  310 . Further, the first line pattern  301   a  and the second line pattern  302   a  are more deviated from each other in the scanning direction at positions separated farther from the point of intersection B in the transport direction. Accordingly, the thickness of the intersecting pattern  310  is the thinnest at the point of intersection B, and the thickness becomes thicker at positions separated farther from the point of intersection B in the transport direction. Therefore, the brightness of the intersecting pattern  310  is the highest in the area  331  including the point of intersection B, and the brightness is more lowered in the areas  331  separated farther from the point of intersection B in the transport direction. In  FIG. 12 , in order to illustrate the drawing simply, the inclination of the second line pattern  302   a  with respect to the transport direction is enlarged as compared with the actual dimension, and the first line pattern  301   a  and the second line pattern  302   a  are not overlapped with each other at most portions other then the point of intersection B. However, actually, as shown in  FIG. 13 , the inclination of the second line pattern  302   a  with respect to the transport direction is such an inclination that at least parts of the first line pattern  301   a  and the second line pattern  302   a  are overlapped with each other at most portions thereof. 
     On the other hand, in the third embodiment, as described above, the point of intersection B between the first-pattern  301  and the second-pattern  302  is positioned at the central portions thereof when the distance between the nozzle  10  and the recording paper P is the predetermined distance described above. When the distance between the nozzle  10  and the recording paper P is deviated from the predetermined distance, then the formation position of the first-pattern  301  and the formation position of the second-pattern  302  are deviated to the mutually opposite sides in the scanning direction, and thus the point of intersection B is deviated in the transport direction. Therefore, the brightness acquiring area  330 , which includes the predetermined number of intersecting patterns  310 , has the brightness which is the highest at the position obtained by averaging the positions of the points of intersection B in the intersecting patterns  310 . In this case, to what side the point of intersection B is deviated in the transport direction is determined whether the distance between the nozzle  10  and the recording paper P is larger or smaller than the predetermined distance. Further, the deviation amount of the point of intersection B is determined by the difference of the distance between the nozzle  10  and the recording paper P from the predetermined distance, the inclination of the second-pattern  302 , the movement speed of the carriage  11 , and the flight speed of the ink discharged from the nozzle  10 . On the other hand, the inclination of the second-pattern  302 , the movement speed of the carriage  11 , and the flight speed of the ink discharged from the nozzle  10  are controlled by known quantities or amounts. Therefore, the deviation amount of the point of intersection B is the amount corresponding to the distance between the nozzle  10  and the recording paper P. 
     According to the fact as described above, in the third embodiment, the position, at which the brightness of each of the brightness acquiring areas  330  is the highest, indicates the distance between the nozzle  10  and the portion of the recording paper P corresponding to each of the brightness acquiring areas  330 . 
     However, in the third embodiment, the plurality of first line patterns  301   a , which form the first-patterns  301 , are printed by the ink discharged from the different nozzles  10 , and the plurality of second line patterns  302   a , which form the second-patterns  302 , are printed by the ink discharged from the different nozzles  10 . When the inspection pattern  300  is printed, such a situation may arise that parts of the line patterns  301   a ,  302   a  are not printed as shown in  FIG. 12B  due to the clog-up of parts of the nozzles  10 . On the other hand, the dispersion sometimes arises in the thickness between the line patterns  301   a ,  302   a  due to the increased viscosity of the ink contained in parts of the nozzles  10 . In such situations, parts of the acquired brightness of the brightness acquiring areas  330  are different from the brightness to be originally obtained. 
     Accordingly, in the third embodiment, as described above, the brightness of the respective portions of the respective brightness acquiring areas  330  are corrected by subtracting the brightness of the corresponding area portions  332 ,  333  of the single pattern portions  322 ,  323  from the brightness of the respective areas  331  of the respective brightness acquiring areas  330 . The position, at which the brightness of each of the brightness acquiring areas  330  is the highest, is specified by using the brightness of the respective brightness acquiring areas  330  after the correction. The distance between the nozzle  10  and the portion of the recording paper P corresponding to each of the brightness acquiring areas is acquired on the basis of the specified position. Accordingly, it is possible to accurately acquire the distance between the nozzle  10  and each of the portions of the recording paper P. 
     As shown in  FIG. 14 , consideration is made while it is assumed by way of example that the brightness of a certain brightness acquiring area  330  is originally the highest in the fourth area  331  as counted from the upstream side in the transport direction, in accordance with the relationship of the distance between the nozzle  10  and the portion of the recording paper P corresponding to the concerning brightness acquiring area  330 . On this assumption, an explanation will be made about a case in which parts of the line patterns  301   a ,  302   a  arranged in the first areas  332 ,  333  as counted from the upstream side in the transport direction are not printed. In this case, the brightness is the lowest in the first brightness acquiring area  330  as counted from the upstream side in the transport direction. 
     On the other hand, in this situation, the brightness of the first single pattern portion  322  is higher than those of the other portions in the first area  332  as counted from the upstream side in the transport direction. Further, the brightness of the second single pattern portion  323  is higher than those of the other portions in the first area  332  as counted from the upstream side in the transport direction. Therefore, if the brightness of each of the brightness acquiring areas  330  is corrected by subtracting the brightness of the corresponding areas  332 ,  333  of the single pattern portions  322 ,  323  from the brightness of respective areas  331  of the brightness acquiring areas  330 , the relationship of magnitude of the brightness after the correction, which is provided between the respective areas  331  of the respective brightness acquiring areas  330 , is the same as the relationship of magnitude of the brightness which is provided between the respective areas  331  of the respective brightness acquiring areas  330  when the ink is discharged normally from the nozzles  10 . That is, when any abnormality arises in parts of the first-pattern  301  and the second-pattern  302 , the influence of the brightness change caused by the abnormality can be excluded from the information of the brightness of the overlapped pattern portion  321 . 
     Next, an explanation will be made about modified embodiments in which various modifications are applied to the embodiment of the present invention. However, the components or parts, which are the same as or equivalent to those of the embodiment of the present invention, are appropriately omitted from the explanation. 
     In the first and second embodiments, N is an odd number. However, N may be an even number. In this case, in relation to the first embodiment, [(N+1)/2] may be replaced [(N/2)+1], and [(N−1)/2] may be replaced with (N/2). Further, in relation to the second embodiment, [(N+1)/2] may be replaced with (N/2). 
     In the first embodiment, the brightness of the overlapped pattern portion  121  is corrected by subtracting both of the brightness of the first single pattern portion  122  and the brightness of the second single pattern portion  123  from the brightness of the overlapped pattern portion  121 . However, there is no limitation thereto. The brightness of the overlapped pattern portion  121  may be corrected by subtracting only the brightness of any one of the single pattern portions  122 ,  123  from the brightness of the overlapped pattern portion  121 . In this case, the inspection pattern  100  may have only any one of the two single pattern portions  122 ,  123 . 
     Also in this case, it is possible to accurately detect the inclination of the arrangement direction of the nozzles  10  with respect to the transport direction as compared with a case in which the brightness of the overlapped pattern portion  121  is used as it is. However, the black ink is deeper or darker than the magenta ink (color ink). Therefore, when the first line pattern  111   a  is printed with the black ink, and the second line pattern  112   a  is formed with the magenta ink (color ink) as in the first embodiment, then the abnormality of the first line pattern  111   a  more greatly affects the brightness of the overlapped pattern portion  121  as compared with the abnormality of the second line pattern  112   a . Therefore, when the brightness of the overlapped pattern portion  121  is corrected by subtracting only the brightness of any one of the single pattern portions  122 ,  123  from the brightness of the overlapped pattern portion  121 , it is possible to accurately detect the inclination of the arrangement direction of the nozzles  10  with respect to the transport direction by subtracting only the brightness of the single pattern portion  122  printed with the black ink. 
     Similarly, in the second embodiment, the brightness of the overlapped pattern portion  221  may be corrected by subtracting only the brightness of any one of the single pattern portions  222 ,  223  from the brightness of the overlapped pattern portion  221 . Further, in the third embodiment, the brightness of each of the brightness acquiring areas  320  may be corrected by subtracting only the brightness of any one of the single pattern portions  322 ,  323  from the brightness of each of the brightness acquiring areas  320 . 
     Further, the brightness of the overlapped pattern portion may be corrected by using the brightness of the single pattern portion by means of any method other than the method in which the brightness of the single pattern portion is subtracted from the brightness of the overlapped pattern portion. 
     In the first to third embodiments, the predetermined characteristic of the printer  1  is expressed by the position of the portion at which the brightness is the highest (density is the smallest or minimum) in relation to the inspection pattern. However, there is no limitation thereto. The predetermined characteristic of the printer  1  may be expressed by the position of the portion at which the brightness is the lowest (density is the deepest or darkest) in relation to the inspection pattern. 
     In the first to third embodiments, the inspection pattern is comparted into the plurality of areas, the brightness is detected for each of the areas, and the area, in which the brightness is the highest, is selected therefrom. However, there is no limitation thereto. For example, an approximating curve, which fits the change of the brightness value in the plurality of areas, may be calculated by using the values of the brightness of the plurality of areas, and the position, at which the value expressed by the approximating curve is local maximum, may be selected. In this case, the position, at which the brightness is local maximum, can be selected by using the unit which is finer or smaller than the number of the areas comparted to acquire the brightness. 
     In the first embodiment, the first line pattern  111   a  is printed with the black ink, and the second line pattern  112   a  is printed with the magenta ink. However, there is no limitation thereto. The second line pattern  112   a  may be printed with the yellow ink or the cyan ink. Alternatively, the first line pattern  111   a  may be printed with the color ink of any color, and the second line pattern  112   a  may be printed with the color ink having a color different from the color of the first line pattern  111   a.    
     Alternatively, in the first embodiment, all of the nozzles  10  for forming the four nozzle arrays  9  may be the nozzles for discharging the black ink. The first line pattern  111   a  may be printed by discharging the black ink from the nozzles  10  for forming a certain nozzle array  9 , and the second line pattern  112   a  may be printed by discharging the black ink from the nozzles  10  for forming any nozzle array  9  different from the nozzle array  9  used to print the first line pattern  111   a.    
     In the first embodiment, the position of the nozzles  10  in the transport direction are the same in relation to all of the four nozzle arrays  9 . However, the positions of the nozzles  10  in the transport direction may be deviated from each other between the nozzle arrays  9 . For example, the nozzles  10 , which form the nozzle array  9  for discharging the magenta ink, may be deviated in the transport direction by an integral fraction of the length C of the nozzle array  9  or by any other quantity or amount with respect to the nozzles  10  which form the nozzle array  9  for discharging the black ink. In this case, the pattern may be constructed so that the brightness of the central block provides an extreme value in an ideal state while considering the deviation amount. 
     In the first embodiment, the recording paper P is not transported during the period in which the N pieces of second-partial patterns  112  are printed, and the second offset amount of the present invention is zero. However, there is no limitation thereto. The recording paper P may be transported by any second offset amount which is different from the first offset amount (minute distance D) every time when the second-partial pattern  112  is printed. In this case, the recording paper P is transported during the period in which the N pieces of second-partial patterns  112  are printed. Therefore, it is necessary that the recording paper P should be transported to adjust the position before the [(N−1)/2] pieces of the first-partial patterns ill are printed after the N pieces of second-partial patterns  112  are printed. 
     In the first to third embodiments, all of the deviation amounts between the adjoining partial patterns (line patterns in the third embodiment) of the N blocks of partial patterns are constant, and the first offset amount and the second offset amount have the constant values. However, the first offset amount or the second offset amount may differ for each of the adjoining partial patterns. For example, when the offset amount is decreased for the partial pattern disposed in the vicinity of the center of the plurality of partial patterns, and the offset amount is increased for the partial pattern disposed at the position far from the center, then the brightness of any one of the N pieces of partial patterns can provide an extreme value even in the case of an apparatus having large deviation, while securing the adjustment accuracy of the apparatus by adjusting the apparatus to be in such a state that the brightness of the central partial pattern finally provides an extreme value. That is, both of the high adjustment accuracy and the wide adjustment range can be established by using one pattern. 
     In the first to third embodiments, the explanation has been made about the factor of the occurrence of the abnormality in the line pattern, inherent in each of the embodiments. However, the factor of the occurrence of the abnormality in the line pattern is not limited thereto. For example, the abnormality also occurs in the line pattern in some cases when the voltage, which is supplied to the printer  1  from an external power source, is temporarily unstable. In other cases, the abnormality also occurs in the line pattern when the surface, on which the printer  1  is arranged, is greatly vibrated during the printing of the inspection pattern. In the case of the printer  1  in which the printing is performed by discharging the ink from the nozzles  10  while reciprocatively moving the carriage  11  in the scanning direction, the direction of the force applied to the ink contained in the ink-jet head  12  when the carriage  11  is accelerated or decelerated is oppositely directed between the situation in which the carriage  11  is moved to the right side and the situation in which the carriage  11  is moved to the left side. Thus, the abnormality sometimes arises in the line pattern due to the difference in the force applied to the ink contained in the ink-jet head  12 . These factors are the factors common to the first to third embodiments. 
     The inspection pattern to be printed by the printer  1  is not limited to the inspection patterns  100 ,  200 ,  300  of the first to third embodiments. The inspection pattern may be any other pattern including an overlapped pattern portion in which two patterns are overlapped with each other and single patterns in each of which only one of the two patterns is formed. In this arrangement, each of the two patterns is not limited to a pattern formed by a plurality of line patterns. For example, it is also allowable to use, for example, a pattern in which a certain area of the recording paper P is painted over. Further, in this arrangement, the inspection pattern may indicate or express the characteristic of the printer  1  different from those explained in the first to third embodiments. 
     In this case, any condition differs between when the first-pattern is printed and when the second-pattern is printed, for example, such that the discharge speed and/or the volume of the ink discharged from the nozzle  10  differs or differ between when the first-pattern is printed and when the second-pattern is printed, depending on what inspection pattern is printed. Such a pattern can be constructed that the information, which relates to any characteristic of the printer  1  allowed to appear as the difference between the conditions, is acquired by using the deviation of the ink landing position to be caused between the different conditions. Further, in any case, any abnormality arises in a part of the first-pattern and/or a part of the second-pattern, for example, when the voltage supplied to the printer  1  from the external power source is temporarily unstable as described above and/or when the surface, on which the printer  1  is arranged, is greatly vibrated during the printing of the inspection pattern. Therefore, even in such situations, it is possible to exclude the influence of the change of the brightness caused by the abnormality by correcting the information of the brightness of the overlapped pattern portion with the information of the brightness of the single pattern portion. 
     In the first to third embodiments, the inspection patterns  100 ,  200 ,  300  are read by the read unit  5  of the printer  1 . However, there is no limitation thereto. The inspection patterns  100 ,  200 ,  300  may be read, for example, by a scanner provided separately from the printer  1 . In this case, for example, the information of the position of the portion having the highest brightness of the overlapped pattern portion after the correction may be inputted into the printer  1  by operating the operation unit  6  of the printer  1 . 
     The foregoing explanation has been made about the exemplary case in which the present invention is applied when the inspection image is printed by the ink-jet printer provided with the so-called serial type ink-jet head for performing the printing by discharging the ink from the nozzles while moving the carriage in the scanning direction, and the printed inspection image is read. However, there is no limitation thereto. The present teaching is also applicable when an inspection image is printed by an ink-jet printer provided with a so-called line head extending over the entire length in the widthwise direction of the recording paper P, and the printed inspection image is read. Further, the present invention is also applicable when an inspection image is printed by a printer other than the ink-jet printer, including, for example, an industrial printer for discharging any liquid other than the ink from nozzles and a printer such as a laser printer for performing the printing other than the method for discharging the liquid from the nozzles, and the printed inspection image is read.