Patent Publication Number: US-8540336-B2

Title: Apparatus and method for controlling ink supply amount/registration adjustment in printing press

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an apparatus and method for controlling ink supply amount/registration adjustment in a printing press, which simultaneously perform ink supply amount adjustment (color tone adjustment) and registration adjustment of each color in a printing press. 
     Conventionally, not only an image is printed on a printing product printed by a printing press but also a color bar including color patches used to measure the densities of respective colors is printed in the top, bottom, or center margin of the printing product to extend laterally. The density of the printed color patch of each color is automatically measured by laterally moving an automatic scanning colorimeter. The density value of the measured color patch of each color is compared with a reference density value for this color to adjust the opening ratio of an ink fountain key of this color in accordance with the difference between these density values. Thus, the printing product is printed using a reference density value for each color. Note that instead of the density value, the color value may be measured. In this case, the printing product is printed using a reference color value for each color. 
     However, in measuring the color bar on the printed printing product using an automatic scanning colorimeter, the color bar must precisely be placed below the scanning path of the colorimeter. That is, the printing product must precisely be placed on a base on which the colorimeter is mounted to be movable in the X direction (the lateral direction; a direction perpendicular to the conveyance/printing direction) and the Y direction (the upward/downward direction; the conveyance/printing direction or circumferential direction regarding a cylinder), thus inflicting a heavy burden on the operator. 
     To solve this problem, a scanning apparatus which manipulates the color bar using a colorimeter including a line sensor with a upward/downward dimension larger than the width (upward/downward dimension) of the color bar is proposed, as disclosed in Japanese patent Laid-Open No. 8-043205 (literature 1). Literature 1 adopts a measurement scheme of detecting the central position of the color bar in the upward/downward direction using the line sensor to adjust the upward/downward position of the colorimeter in accordance with the detected central position. Using such a measurement scheme, the density value or color value of the color patch of each color in the color bar can precisely be measured as color matching data even if the printing product is not precisely placed on the base. 
     On the other hand, a register mark of each color used to adjust registration of this color is printed in the margin of the printing product printed by the printing press. According to Japanese Patent Laid-Open No. 62-99149, a cruciform register mark printed at a predetermined position for each color is captured by a camera to obtain the amount of positional shift of an image of each color based on a shift between a reference position and the position of the intersection point of the captured register mark for each color. The position of a plate cylinder of each color, which holds a printing plate of this color, and the position, in the skewing direction, of a transfer cylinder for printing paper conveyance, are adjusted as registration error amounts in accordance with the obtained amount of positional shift to match the position of the image of this color with the target position. 
     However, it is a conventional practice to provide the printing press with separate adjusting devices: an ink supply amount adjusting device which uses a color bar, and a registration adjusting device which uses register marks. The ink supply amount adjusting device includes a sensor for measuring color matching data of each patch, and a line sensor for detecting the upward/downward position of the color bar. On the other hand, the registration adjusting device includes a camera for detecting the positions of the register marks. Thus, the entire printing press entails a high cost. Also, the two devices require individual maintenance, thus inflicting a heavy burden on the operator. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an apparatus and method for controlling ink supply amount/registration adjustment in a printing press, which reduce the cost of the entire printing press. 
     It is another object of the present invention to provide an apparatus and method for controlling ink supply amount/registration adjustment in a printing press, which simplify maintenance to relieve the operator&#39;s burden. 
     In order to achieve the above-described objects, according to an aspect of the present invention, there is provided an apparatus for controlling ink supply amount/registration adjustment in a printing press, including a base on which a printing product printed by the printing press is set, a sensor head, sensor head moving means for moving the sensor head laterally and upward/downward on the base, a first detector which is mounted on the sensor head, and measures color matching data of a color patch of each color in a color bar printed in a margin of the printing product, a second detector which detects a position of a register mark of each color, which is printed in a margin of the printing product, and control means for, when the sensor head moves laterally, controlling an ink supply amount of each color in the printing press based on the color matching data of the color patch of each color in the color bar, which is measured by the first detector, and adjusting registration of each color in the printing press based on the position of the register mark of each color, which is measured by the second detector, the sensor head moving means comprising upward/downward position adjusting means for adjusting a upward/downward position of the sensor head, wherein the second detector detects a upward/downward position of the color bar when the color matching data of the color patch of each color in the color bar is measured by the first detector, and the upward/downward position adjusting means adjusts the upward/downward position of the sensor head based on the upward/downward position of the color bar, which is detected by the second detector. 
     According to another aspect of the present invention, there is provided a method of controlling ink supply amount/registration adjustment in a printing press, comprising the steps of measuring color matching data of a color patch of each color in a color bar, which is printed in a margin of a printing product, using a first detector mounted on a sensor head, detecting a upward/downward position of the color bar using a second detector upon defining a moving direction of the sensor head as a measuring direction when the color matching data of the color patch of each color in the color bar is measured by the first detector, adjusting a upward/downward position of the sensor head based on the upward/downward position of the color bar, which is detected by the second detector, controlling an ink supply amount of each color in the printing press based on the color matching data of the color patch of each color in the color bar, which is measured by the first detector, when the sensor head moves laterally, detecting a position of a register mark of each color, which is printed in a margin of the printing product, using the second detector, and adjusting registration of each color in the printing press based on the position of the register mark of each color, which is measured by the second detector. 
     In the present invention, a spectroscopic sensor, for example, is used as the first detector, and an image sensor, for example, is used as the second detector. In this case, the spectroscopic sensor and the image sensor are mounted on the sensor head, and the image sensor exhibits the same function as the conventional line sensor, which is required to detect the upward/downward position of the color bar, during measurement of color matching data of the color patch of each color in the color bar. Also, the image sensor exhibits the same function as the conventional camera, which is required to adjust registration, at the position at which the register mark of each color is detected. 
     Note that in the present invention, when a spectroscopic sensor, for example, is used as the first detector, the color matching data includes, for example, color data measured by the spectroscopic sensor, and the density value or color value obtained from this color data. Alternatively, the density value directly measured by a densitometer which uses a filter may be used as the color matching data. In this manner, the color matching data represents a superordinate concept including all data with which density adjustment or color adjustment (color matching) can be done based on the data. 
     Also, in the present invention, adjusting registration of each color in the printing press means adjusting the position of a plate cylinder of each color, which holds a printing plate of this color, or adjusting the position, in the skewing direction, of a transfer cylinder which conveys a printing sheet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view showing the main part of an inking device (inker) of each color, which is provided in a corresponding one of a plurality of printing units which constitute a printing press to which the present invention is applied; 
         FIG. 2  is a plan view showing a printing product printed by the printing press shown in  FIG. 1 ; 
         FIG. 3  is a plan view showing a set of register marks printed in the margins of the printing product shown in  FIG. 2 ; 
         FIG. 4  is a perspective view showing the outer appearance of a scanner which reads the density value of a color patch of each color in a color bar printed on the printing product shown in  FIG. 2 , and the position of a register mark of each color in the set of register marks printed on this printing product; 
         FIG. 5  is a plan view showing the state in which the printing product is set on a base of the scanner shown in  FIG. 4 , and the moving direction (X and Y directions) of a scanning head which moves on the base; 
         FIG. 6  is a perspective view showing the outer appearance of the scanning head shown in  FIG. 5 ; 
         FIG. 7  is a bottom view of the scanning head shown in  FIG. 5 ; 
         FIG. 8  is a view showing the moving direction (measuring direction) of the scanning head when the density value of the color patch of each color in the color bar printed on the printing product placed on the base of the scanner is measured; 
         FIG. 9  is a block diagram showing the electrical configuration of an apparatus for controlling ink supply amount/registration adjustment according to an embodiment of the present invention; 
         FIGS. 10A and 10B  are block diagrams showing details of a storage unit in the apparatus for controlling ink supply amount/registration adjustment shown in  FIG. 9 ; 
         FIGS. 11A to 11C  are flowcharts showing a process operation executed by a CPU of the apparatus for controlling ink supply amount/registration adjustment shown in  FIG. 9 ; 
         FIG. 12  is a plan view showing the state in which the printing product is precisely placed at a reference set position on the base of the scanner shown in  FIG. 4 ; 
         FIG. 13  is a plan view showing the state in which the printing product is placed on the base of the scanner shown in  FIG. 4  such that it is shifted with respect to the reference set position; 
         FIG. 14  is a block diagram showing the electrical configuration of an ink fountain key control device connected to the apparatus for controlling ink supply amount/registration adjustment shown in  FIG. 9 ; 
         FIGS. 15A and 15B  are flowcharts showing an operation of controlling the opening ratio of each ink fountain key by the ink fountain key control device shown in  FIG. 14 ; 
         FIG. 16  is a block diagram showing the electrical configuration of a registration adjusting device connected to the apparatus for controlling ink supply amount/registration adjustment shown in  FIG. 9 ; and 
         FIGS. 17A and 17B  are flowcharts showing a registration adjustment operation by the registration adjusting device shown in  FIG. 16 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An apparatus for controlling ink supply amount/registration adjustment according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings. 
     [Inking Devices] 
     An inking device (inker) of a printing unit of each color, which constitutes a printing press for four-color printing shown in  FIG. 1 , includes an ink fountain  1 , ink  2  stored in the ink fountain  1 , an ink fountain roller  3 , a plurality of ink fountain keys  4 - 1  to  4 -n juxtaposed in the axial direction of the ink fountain roller  3 , an ink ductor roller  5 , an ink roller group  6 , and a printing plate  7  mounted on a plate cylinder  8 . An image is printed on the printing plate  7 . 
     [Printing Product] 
     In the above-mentioned inking device, the ink  2  in the ink fountain  1  is supplied from the gap between the ink fountain keys  4 - 1  to  4 -n and the ink fountain roller  3 . The ink  2  supplied to the ink fountain roller  3  is further supplied to the printing plate  7  via the ink roller group  6  by the ink feed operation of the ink ductor roller  5 . The ink  2  supplied to the printing plate  7  is printed on a printing sheet via a blanket cylinder (not shown) to obtain a printing product  9  shown in  FIG. 2 . 
     [Color Bar] 
     A band-shaped color bar  9 - 1  is printed in a margin other than image regions  9 A to  9 D to extend laterally. Although the color bar  9 - 1  is printed in the bottom margin (lower margin) of the printing product  9  in this example, it may be printed in the top margin (upper margin) or center margin of the printing product  9 . 
     In general four-color printing, the color bar  9 - 1  is formed by regions S 1  to Sn including color patches (solid patches with 100% dot area) used to measure the densities of respective colors: black, cyan, magenta, and yellow. The regions S 1  to Sn correspond to the key zones of the ink fountain keys  4 - 1  to  4 -n in the printing unit of each color in the printing press. 
     [Register Marks] 
     Register marks  9 - 2  are printed in margins other than the color bar  9 - 1  on the printing product  9 . In this example, a first register mark RM 1  is printed at the right center of the printing product  9 , and a second register mark RM 2  is printed at the left center of the printing product  9 . 
     Each of the register marks RM 1  and RM 2  is formed by four black register marks P 1  to P 4 , two yellow register marks P 5  and P 6 , one magenta register mark P 7 , and one cyan register mark P 8 , as shown in  FIG. 3 . The register marks P 1  to P 8  are printed in a spot pattern so that they are scattered in the register marks RM 1  and RM 2 . A description of register marks printed in a spot pattern in U.S. Pat. No. 5,018,213 is incorporated in this specification. 
     [Scanner] 
     A scanner  10  includes a base  10 - 1  having an upper surface on which the printing product  9  is set, and a scanning unit  10 - 2  which moves on the base  10 - 1 , as shown in  FIG. 4 . A scanning head (sensor head)  10 - 3  shown in  FIG. 5  is provided in the scanning unit  10 - 2 . 
     The scanning unit  10 - 2  moves on the upper surface of the base  10 - 1  in the X direction (laterally) by an X driving mechanism  10 - 4 . The scanning head  10 - 3  moves in the scanning unit  10 - 2  in the Y direction (upward/downward) by a Y driving mechanism  10 - 5 . In this arrangement, the scanning head  10 - 3  moves on the base  10 - 1  in the X and Y directions by the X driving mechanism  10 - 4  and Y driving mechanism  10 - 5  (sensor head moving means), respectively. The printing product  9  is set on the base  10 - 1  upon defining the lateral direction (a direction perpendicular to the printing/conveyance direction) as the X direction, and the upward/downward direction (printing/conveyance direction or circumferential direction regarding a cylinder) as the Y direction. 
     [Scanning Head] 
     Rollers  10 - 31  and  10 - 32  which guide movement in the X direction are provided on the bottom surface of the scanning head  10 - 3 , as shown in  FIGS. 6 and 7 . In measuring the density value of the color patch of each color in the color bar  9 - 1  or detecting the positions of the register marks of each color in the register marks  9 - 2 , the scanning head  10 - 3  is lowered so that the rollers  10 - 31  and  10 - 32  land on the upper surface of the base  10 - 1 . 
     The scanning head  10 - 3  mounts a spectroscopic sensor  11  and an image sensor  12  which constitutes a color camera. The spectroscopic sensor  11  functions as a detector (first detector) for measuring the density value of the color patch of each color in the color bar  9 - 1  printed on the printing product  9 . The image sensor  12  functions as a detector (second detector) for detecting the positions of the register marks of each color in the register marks  9 - 2 . The image sensor  12  also serves as a detector for detecting the upward/downward position of the color bar  9 - 1 . 
     The image sensor  12  has an image sensing region with a upward/downward dimension larger than the width (upward/downward dimension) of the color bar  9 - 1 , and is provided in front of the spectroscopic sensor  11  in the X direction. That is, when the moving direction of the scanning head  10 - 3  in measuring the density value of the color patch of each color in the color bar  9 - 1  is defined as the measuring direction (see  FIG. 8 ), the image sensor  12  is mounted on the scanning head  10 - 3  such that its set position is located downstream of the spectroscopic sensor  11  in the measuring direction. Let d be the distance by which the spectroscopic sensor  11  and the image sensor  12  are spaced apart from each other in the measuring direction. 
     [Apparatus for Controlling Ink Supply Amount/Registration Adjustment] 
     An apparatus  13  for controlling ink supply amount/registration adjustment includes not only the above-mentioned scanner  10  but also a CPU  13 A, a RAM  13 B, a ROM  13 C, a touch panel  13 D, a compact disk device  13 E, a measurement switch  13 F, a display device  13 G, a flexible disk drive, an output device  13 H such as a printer, and a storage unit  13 I, as shown in  FIG. 9 . 
     The apparatus  13  for controlling ink supply amount/registration adjustment also includes a device  13 J for setting the upward/downward position of the color bar  9 - 1 , a device  13 K for setting the measurement interval for the color bar  9 - 1 , a device  13 L for setting the upward/downward position of a measurement point for the left register mark RM 2 , a device  13 M for setting the lateral position of a measurement point for the left register mark RM 2 , a device  13 N for setting the upward/downward position of a measurement point for the right register mark RM 1 , a device  13 O for setting the lateral position of a measurement point for the right register mark RM 1 , and input/output interfaces (I/O, I/F)  13 P to  13 U. 
     The X driving mechanism  10 - 4  for the scanner  10  mentioned above includes a D/A converter  10 - 41 , a motor driver  10 - 42  for laterally moving the scanning head  10 - 3 , a motor  10 - 43  for laterally moving the scanning head  10 - 3 , a rotary encoder  10 - 44  for the motor  10 - 43  for laterally moving the scanning head  10 - 3 , a counter  10 - 45  for measuring the current lateral position of the scanning head  10 - 3 , and a detector  10 - 46  for detecting the origin position of the scanning head  10 - 3  in the lateral direction. 
     The Y driving mechanism  10 - 5  for the scanner  10  mentioned above includes a D/A converter  10 - 51 , a motor driver  10 - 52  for moving upward/downward the scanning head  10 - 3 , a motor  10 - 53  for moving upward/downward the scanning head  10 - 3 , a rotary encoder  10 - 54  for the motor  10 - 53  for moving upward/downward the scanning head  10 - 3 , a counter  10 - 55  for measuring the current upward/downward position of the scanning head  10 - 3 , and a detector  10 - 56  for detecting the origin position of the scanning head  10 - 3  in the upward/downward direction. 
     The apparatus  13  for controlling ink supply amount/registration adjustment is connected to ink fountain key control devices  14 - 11  to  14 -MN of the printing units of the respective colors, and registration adjusting devices  15 - 1  to  15 -M for adjusting registration of the printing units of the respective colors. Each of the registration adjusting devices  15 - 1  to  15 -M is formed by adjusting devices for the skewing, upward/downward, and lateral directions. 
     The storage unit  13 I includes memories M 1  to M 26 , as shown in  FIGS. 10A and 10B . The memory M 1  stores a upward/downward position Yb of the color bar  9 - 1 . The memory M 2  stores a measurement interval L at which the color bar  9 - 1  is measured by the image sensor  12 . The memory M 3  stores the upward/downward position of a measurement point at which the left register mark RM 2  is measured by the image sensor  12 . The memory M 4  stores the lateral position of the measurement point at which the left register mark RM 2  is measured by the image sensor  12 . The memory M 5  stores the upward/downward position of a measurement point at which the right register mark RM 1  is measured by the image sensor  12 . The memory M 6  stores the lateral position of the measurement point at which the right register mark RM 1  is measured by the image sensor  12 . 
     The memory M 7  stores lateral positions x 1  to xm of measurement points at which the color patches of the respective colors are measured by the spectroscopic sensor  11 . The memory M 8  stores the distance d between the spectroscopic sensor  11  and the image sensor  12 . The memory M 9  stores an initial measurement interval L 0  at which the color bar  9 - 1  is measured by the image sensor  12 . The memory M 10  stores the total number Lmax of measurement points at which the color bar  9 - 1  is measured by the image sensor  12 . The memory M 11  stores lateral positions c 1  to cLmax of measurement points at which the color bar  9 - 1  is measured by the image sensor  12 . The memory M 12  stores a basic lateral-to-upward/downward scanning path conversion equation of the color bar  9 - 1 . 
     The memory M 13  stores, as the measurement positions of the scanning head  10 - 3 , the lateral positions x 1  to xm of the measurement points for the respective rearranged color patches, and the lateral positions cl to cLmax of measurement points for the color bar  9 - 1 . The memory M 14  stores the total number Dmax of measurement points obtained by summing up the number of lateral positions x 1  to xm of the measurement points for the respective color patches, and the number of lateral positions cl to cLmax of the measurement points for the color bar  9 - 1 . The memory M 15  stores a lateral-to-upward/downward scanning path conversion equation for measurement of the color bar  9 - 1 . 
     The memory M 16  stores color data measured by the spectroscopic sensor  11 . The memory M 17  stores image data of the color bar  9 - 1  sensed by the image sensor  12 . The memory M 18  stores the upward/downward position of the color bar  9 - 1 , which is obtained from the image data of the color bar  9 - 1  sensed by the image sensor  12 . The memory M 19  stores image data of the right register mark RM 1  sensed by the image sensor  12 . The memory M 20  stores image data of the left register mark RM 2  sensed by the image sensor  12 . 
     The memory M 21  stores the measured density value of the color patch of each color, which is calculated from the color data measured by the spectroscopic sensor  11 . The memory M 22  stores a reference density value for each color. The memory M 23  stores the density difference between the measured density value of the color patch of each color and the reference density value of this color. The memory M 24  stores a density difference-to-ink fountain key opening ratio correction value conversion table of each color. The memory M 25  stores the correction value of the opening ratio of the ink fountain key of each color, which is obtained from the density difference-to-ink fountain key opening ratio correction value conversion table. The memory M 26  stores the modified value of the opening ratio of each ink fountain key in the printing unit of each color. 
     A process operation executed by the CPU  13 A of the apparatus  13  for controlling ink supply amount/registration adjustment will be described next with reference to  FIGS. 11A to 11C . The CPU  13 A obtains various types of input information provided via the interfaces  13 P to  13 U, and executes a process operation in accordance with the program, stored in the ROM  13 C, while accessing the RAM  13 B or the storage unit  13 I. Note that the contents stored in the memories M 1  to M 26  shown in  FIGS. 10A and 10B  will become apparent from the description of the process operation of the CPU  13 A. 
     [Setting of Printing Product on Upper Surface of Base of Scanner] 
     At the start of ink supply amount adjustment and registration adjustment in the printing press, the operator sets the printing product  9  on the upper surface of the base  10 - 1  of the scanner  10 , as shown in  FIG. 12 . At this time, the printing product  9  is set at a reference set position on the base  10 - 1 . 
     [Data Input] 
     Next, the operator uses the position setting device  13 J to input the upward/downward position Yb of the color bar  9 - 1  on the printing product  9  (step S 101  in  FIG. 11A ). The input upward/downward position Yb of the color bar  9 - 1  is stored in the memory M 1 . Note that the upward/downward position Yb of the color bar  9 - 1  is input as that corresponding to the reference set position of the printing product  9 . 
     The operator uses the measurement interval setting device  13 K to input the lateral interval L between the measurement points at which the color bar  9 - 1  is measured by the image sensor  12  (step S 102 ). The input lateral interval L between the measurement points for the color bar  9 - 1  is stored in the memory M 2 . Note that the lateral interval L between the measurement points for the color bar  9 - 1  is larger than the initial measurement interval L 0  stored in the memory M 9  in advance (L&gt;L 0 ). That is, the initial measurement interval L 0  is set in advance as a measurement interval smaller than the measurement interval L input by the operator. 
     The operator uses the position setting devices  13 L,  13 M,  13 N, and  13 O to input the upward/downward and lateral positions of the right and left register marks  9 - 2  on the printing product  9  (step S 103 ). The input upward/downward and lateral positions of the right and left register marks  9 - 2  are stored in the memories M 3  to M 6 . Note that the upward/downward and lateral positions of the right and left register marks  9 - 2  are input as those corresponding to the reference set position of the printing product  9 . 
     The operator instructs to input a measurement point for each color patch. Upon receiving this instruction, the CPU  13 A reads, from the compact disk device  13 E, the lateral positions x 1  to xm of the measurement points at which the color patches of the respective colors in the color bar  9 - 1  are measured by the spectroscopic sensor  11 , and stores them in the memory M 7  (step S 104 ). 
     [Calculation of Lateral Measurement Positions at which Color Bar is Measured by Image Sensor] 
     When data is input in this way, the CPU  13 A calculates the lateral measurement positions at which the color bar  9 - 1  is measured by the image sensor  12  (step S 105 ). 
     In calculating the lateral measurement positions for the color bar  9 - 1 , the lateral position x 1  of the first color patch measurement point is read out from the memory M 7 . Also, the distance d between the spectroscopic sensor  11  and the image sensor  12  is read out from the memory M 8 , and the initial measurement interval L 0  for the color bar  9 - 1  is read out from the memory M 9 . Then, the distance d between the spectroscopic sensor  11  and the image sensor  12  is subtracted from the lateral position x 1  of the first color patch measurement point, and the initial measurement interval L 0  for the color bar  9 - 1  is added to the obtained difference, thereby calculating the lateral position c 1  of the first color bar measurement point. 
     The initial measurement interval L 0  for the color bar  9 - 1  is added to the thus calculated lateral position cl of the first color bar measurement point to calculate the lateral position c 2  of the second color bar measurement point. The same process is subsequently repeated until the lateral position c 10  of the 10th color bar measurement point is calculated. 
     The measurement interval L (L&gt;L 0 ) for the color bar  9 - 1 , which is set by the operator, is read out from the memory M 2  and added to the lateral position c 10  of the 10th color bar measurement point to calculate a lateral position c 11  of the 11th color bar measurement point. In the same way, the lateral positions of the measurement points for the color bar  9 - 1  are calculated until the lateral position xm of the last color patch measurement point is exceeded. 
     The number of measurement points for the color bar  9 - 1  immediately before the lateral position xm of the last color patch measurement point is exceeded is determined as the total number Lmax of measurement points for the color bar  9 - 1 , and stored in the memory M 10 . Also, the lateral positions cl to cLmax of the measurement points for the color bar  9 - 1  until the total number Lmax of measurement points is reached are stored in the memory M 11 . 
     [Generation of Basic Lateral-to-Upward/Downward Scanning Path Conversion Equation] 
     The CPU  13 A generates a basic lateral-to-upward/downward scanning path conversion equation of the color bar  9 - 1  (step S 106 ). That is, the upward/downward position Yb of the color bar  9 - 1  is read out from the memory M 1  to generate a basic lateral-to-upward/downward scanning path conversion equation assuming that the upward/downward position Yb of the color bar  9 - 1  is used with respect to all the lateral positions of the measurement points for the color bar  9 - 1 , and the generated conversion equation is stored in the memory M 12 . 
     [Rearrangement of Lateral Measurement Positions at which Respective Color Patches are Measured by Spectroscopic Sensor, and those at which Color Bar is Measured by Image Sensor] 
     The CPU  13 A reads out the lateral positions x 1  to xm of the measurement points at which the respective color patches are measured by the spectroscopic sensor  11 , which are stored in the memory M 7 , and the lateral positions cl to cLmax of the measurement points at which the color bar  9 - 1  is measured by the image sensor  12 , which are stored in the memory M 11 . The readout positions of the respective measurement points are rearranged in a specific order (in ascending order) from the left end, and the rearranged positions of the respective measurement points are stored in the memory M 13  as the measurement positions of the scanning head  10 - 3  (step S 107 ). At this time, the number of lateral positions x 1  to xm of the measurement points for the respective color patches, and the number of lateral positions c 1  to cLmax of the measurement points for the color bar  9 - 1  are summed up, and the obtained sum is stored in the memory M 14  as the total number Dmax of measurement points. 
     [Measurement of Density Value of Each Color Patch While Adjusting Upward/downward Position] 
     The CPU  13 A reads out the upward/downward position Yb of the color bar  9 - 1  from the memory M 1  to move the scanning head  10 - 3  to the upward/downward position Yb (step S 108 ). In the initial state, the scanning head  10 - 3  is located at the origin position in the lateral and upward/downward directions on the base  10 - 1 . The scanning head  10 - 3  moves from this origin position to the upward/downward position Yb of the color bar  9 - 1 . 
     This movement of the scanning head  10 - 3  is done while the rollers  10 - 31  and  10 - 32  are floated. 
     Thus, the scanning head  10 - 3  quickly moves to the upward/downward position Yb of the color bar  9 - 1 . 
     After the scanning head  10 - 3  moves to the upward/downward position Yb of the color bar  9 - 1 , the CPU  13 A moves it laterally (step S 109 ). This movement of the scanning head  10 - 3  is done while the rollers  10 - 31  and  10 - 32  are landed on the base  10 - 1 . Thus, the distances between the spectroscopic sensor  11  and image sensor  12  and the printing product  9  on the base  10 - 1  are stably maintained constant. 
     In laterally moving the scanning head  10 - 3 , the CPU  13 A reads out the basic lateral-to-upward/downward scanning path conversion equation for the color bar  9 - 1 , which is stored in the memory M 12 , and stores it in the memory M 15  as a lateral-to-upward/downward scanning path conversion equation for measurement. The upward/downward position of the scanning head  10 - 3  is adjusted based on this lateral-to-upward/downward scanning path conversion equation for measurement (step S 110 ). 
     When the scanning head  10 - 3  reaches the measurement position stored in the memory M 13  (YES in step S 111 ), it is checked whether a specific color patch is to be measured by the spectroscopic sensor  11  at this measurement position (step S 112 ). If a specific color patch is to be measured by the spectroscopic sensor  11  at the reached measurement position (YES in step S 112 ), color data of this color patch is measured by the spectroscopic sensor  11 , and the measured color data is stored in the memory M 16  in association with this color patch (step S 113 ). 
     On the other hand, if the color bar  9 - 1  is to be measured by the image sensor  12  at the reached measurement position, the color bar  9 - 1  is sensed by the image sensor  12  (step S 114 ). The sensed image data is stored in the memory M 17 . At this time, if the color bar  9 - 1  has not yet been sensed by the image sensor  12  ten times or more (NO in step S 115 ), the upward/downward position of the color bar  9 - 1  is calculated from the sensed image data and stored in the memory M 18  (step S 116 ). In this calculation, the lower end position of the sensed color bar  9 - 1  is added to its upper end position, and the obtained sum is divided by two to obtain the central position of the color bar  9 - 1  so that the obtained central position is determined as the upward/downward position of the color bar  9 - 1 . 
     Thus, until the number of times of sensing the color bar  9 - 1  by the image sensor  12  reaches  10  while laterally moving the scanning head  10 - 3  (until the image sensor  12  completes measurement of the color bar  9 - 1  at the initial measurement interval L 0 ), the upward/downward position of the scanning head  10 - 3  is adjusted based on the basic lateral-to-upward/downward scanning path conversion equation obtained in step S 106 . 
     If the color bar  9 - 1  has already been sensed by the image sensor  12  ten times or more (YES in step S 115 ), the upward/downward position of the color bar  9 - 1  is calculated from the sensed image data and stored in the memory M 18  (step S 117 ). A lateral-to-upward/downward scanning path conversion equation of the color bar  9 - 1  is obtained again using the least-squares method from the upward/downward position of the color bar  9 - 1 , which is stored in the memory M 18 , to rewrite the lateral-to-upward/downward scanning path conversion equation for measurement of the color bar  9 - 1 , which is stored in the memory M 15  (step S 118 ). 
     Thus, when the color bar  9 - 1  has already been sensed by the image sensor  12  ten times or more while laterally moving the scanning head  10 - 3  (when the image sensor  12  starts measurement of the color bar  9 - 1  at the measurement interval L (L&gt;L 0 ) set by the operator), a lateral-to-upward/downward scanning path conversion equation of the color bar  9 - 1  is obtained again using the least-squares method from the previously calculated upward/downward position of the color bar  9 - 1 . The upward/downward position of the scanning head  10 - 3  is then adjusted based on the lateral-to-upward/downward scanning path conversion equation obtained again. 
       FIG. 12  illustrates an example in which the printing product  9  is precisely placed at the reference set position on the base  10 - 1 . In contrast, if the printing product  9  is not precisely placed on the base  10 - 1 , the set position of the printing product  9  is shifted with respect to the reference set position.  FIG. 13  illustrates an example in which the printing product  9  is placed on the base  10 - 1  such that it is shifted with respect to the reference set position. As shown in  FIG. 13 , until the image sensor  12  completes measurement of the color bar  9 - 1  at the initial measurement interval L 0  (point a), the upward/downward position of the scanning head  10 - 3  is adjusted based on the basic lateral-to-upward/downward scanning path conversion equation (scanning path  101 ). Next, when the image sensor  12  starts measurement of the color bar  9 - 1  at the measurement interval L set by the operator, a lateral-to-upward/downward scanning path conversion equation of the color bar  9 - 1  is obtained again every time a predetermined point (points a, b, c, . . . ) is reached. The upward/downward position of the scanning head  10 - 3  is adjusted based on the lateral-to-upward/downward scanning path conversion equation obtained again (scanning path  102 ). 
     In this manner, when color data of the color patch of each color in the color bar  9 - 1  is measured by the spectroscopic sensor  11  while moving the scanning head  10 - 3  in the X direction, the upward/downward position of the scanning head  10 - 3  is adjusted based on the lateral-to-upward/downward scanning path conversion equation updated at the measurement interval L. This makes it possible to accurately measure color data of the color patch of each color in the color bar  9 - 1  even if the printing product  9  is placed on the base  10 - 1  with relatively low precision. 
     [Sensing of Right and Left Register Marks] 
     When measurement of the total number Dmax of measurement points is completed (YES in step S 119 ), the CPU  13 A reads out the upward/downward and lateral positions of the right register mark RM 1  from the memories M 5  and M 6 , respectively. The scanning head  10 - 3  is moved to the readout upward/downward and lateral positions of the right register mark RM 1 , and the right register mark RM 1  is sensed by the image sensor  12  (step S 120 ). The sensed image data of the right register mark RM 1  is stored in the memory M 19 . 
     This movement of the scanning head  10 - 3  to the upward/downward and lateral positions of the right register mark RM 1  is quickly done while the rollers  10 - 31  and  10 - 32  are floated. After the scanning head  10 - 3  moves to the upward/downward and lateral positions of the right register mark RM 1 , the rollers  10 - 31  and  10 - 32  land on the base  10 - 1 . 
     The CPU  13 A reads out the upward/downward and lateral positions of the left register mark RM 2  from the memories M 3  and M 4 , respectively. The scanning head  10 - 3  is moved to the readout upward/downward and lateral positions of the left register mark RM 2 , and the left register mark RM 2  is sensed by the image sensor  12  (step S 121 ). The sensed image data of the left register mark RM 2  is stored in the memory M 20 . 
     This movement of the scanning head  10 - 3  to the upward/downward and lateral positions of the left register mark RM 2  is also quickly done while the rollers  10 - 31  and  10 - 32  are floated. After the scanning head  10 - 3  moves to the upward/downward and lateral positions of the left register mark RM 2 , the rollers  10 - 31  and  10 - 32  land on the base  10 - 1 . 
     After the right register mark RM 1  and left register mark RM 2  are measured by the image sensor  12 , the CPU  13 A returns the scanning head  10 - 3  to the origin position (step S 122 ). This returning of the scanning head  10 - 3  to the origin position is also quickly done while the rollers  10 - 31  and  10 - 32  are floated. 
     [Adjustment of Ink Supply Amount of Each Color] 
     The CPU  13 A calculates the measured density value of each color patch from the color data of this color patch, which is measured and stored in the memory M 16  (step S 123 ). The measured density value of each color patch is stored in the memory M 21 . 
     The CPU  13 A reads out the reference density value of each color, which is stored in the memory M 22 . The density difference between the readout reference density value of each color and the measured density value of the color patch of this color, which is measured in the memory M 21 , is calculated and stored in the memory M 23  (step S 124 ). 
     The correction value of the opening ratio of the ink fountain key of each color is obtained using the density difference-to-ink fountain key opening ratio correction value conversion table of this color, which is stored in the memory M 24 , from the calculated density difference of the color patch of this color, thereby modifying the opening ratio of the ink fountain key of this color (step S 125 ). The correction value of the opening ratio of the ink fountain key of each color is stored in the memory M 25 , and the modified value of the opening ratio of the ink fountain key of this color is stored in the memory M 26 . 
     [Registration Adjustment of Each Color] 
     The CPU  13 A obtains the position of the right register mark RM 1  of each color from the image data of the right register mark RM 1 , which is stored in the memory M 19  (step S 126 ). The CPU  13 A obtains the position of the left register mark RM 2  of each color from the image data of the left register mark RM 2 , which is stored in the memory M 20  (step S 127 ). 
     Next, the registration error amount of each color in the skewing direction is obtained from the upward/downward positions of the right and left register marks  9 - 2  of this color, and the obtained registration error amounts in the skewing direction are sent to the registration adjusting devices  15 - 1  to  15 -M of the respective colors. The registration adjusting devices  15 - 1  to  15 -M of the respective colors adjust registration of these colors in the skewing direction using the received registration error amounts (step S 128 ). 
     The position of the right register mark RM 1  of each color is corrected using the registration error amount of this color in the skewing direction to obtain the registration error amount of this color in the upward/downward direction from the corrected upward/downward position of the register mark RM 1  of this color. The obtained registration error amounts in the upward/downward direction are sent to the registration adjusting devices  15 - 1  to  15 -M of the respective colors to adjust registration of these colors in the upward/downward direction (step S 129 ). 
     The registration error amount of each color in the lateral direction is obtained from the lateral positions of the right and left register marks  9 - 2  of this color. The obtained registration error amounts in the lateral direction are sent to the registration adjusting devices  15 - 1  to  15 -M of the respective colors to adjust registration of these colors in the lateral direction (step S 130 ). 
     [Ink Fountain Key Control Device] 
     The ink fountain key control device  14 - 11  includes a CPU  14 A, a ROM  14 B, a RAM  14 C, an ink fountain key driving motor  14 D, an ink fountain key driving motor driver  14 E, a rotary encoder  14 F for the ink fountain key driving motor  14 D, a counter  14 G, input/output interfaces  14 H and  14 I, and memories M 31  to M 34 , as shown in  FIG. 14 . The ink fountain key control device  14 - 11  is connected to the apparatus  13  for controlling ink supply amount/registration adjustment via the interface  14 I. 
     The memory M 31  stores the received correction amount of the opening ratio of each ink fountain key. The memory M 32  stores the count value of the counter  14 G. The memory M 33  stores the current opening ratio of each ink fountain key. The memory M 34  stores the target opening ratio of each ink fountain key. 
     The process operation of the CPU  14 A of the ink fountain key control device  14 - 11  will be described next with reference to  FIGS. 15A and 15B . 
     When the correction amount of the opening ratio of each ink fountain key is sent from the apparatus  13  for controlling ink supply amount/registration adjustment to the ink fountain key control device  14 - 11  (YES in step S 201  of  FIG. 15A ), the CPU  14 A stores the sent correction amount of the opening ratio of this ink fountain key in the memory M 31  (step S 202 ). The CPU  14 A sends a reception completion signal of the correction amount of the opening ratio of each ink fountain key to the apparatus  13  for controlling ink supply amount/registration adjustment (step S 203 ). The CPU  14 A reads the current count value from the counter  14 G, and stores it in the memory M 32  (step S 204 ). 
     The CPU  14 A reads out the current count value of the counter  14 G from the memory M 32 . The CPU  14 A calculates the current opening ratio of each ink fountain key from the readout count value, and stores it in the memory M 33  (step S 205 ). 
     The CPU  14 A reads out the correction amount of the opening ratio of each ink fountain key from the memory M 31  (step S 206 ). The CPU  14 A adds this correction amount to the current opening ratio of each ink fountain key in the memory M 33  to calculate the target opening ratio of this ink fountain key, and stores the obtained target opening ratio in the memory M 34  (step S 207 ). 
     The CPU  14 A reads out the current opening ratio of each ink fountain key in the memory M 33  (step S 208 ), and compares it with the target opening ratio of this ink fountain key in the memory M 34  (step S 209 ). If the target opening ratio and the current opening ratio are not equal (NO in step S 209 ), the CPU  14 A confirms whether the current opening ratio is lower or higher than the target opening ratio (step S 210 ). 
     If the current opening ratio of each ink fountain key is lower than the target opening ratio of this ink fountain key (YES in step S 210 ), the CPU  14 A sends a forward rotation command to the motor driver  14 E (step S 211 ). On the other hand, if the current opening ratio of each ink fountain key is higher than the target opening ratio of this ink fountain key (NO in step S 210 ), the CPU  14 A sends a reverse rotation command to the motor driver  14 E (step S 212 ). 
     The CPU  14 A reads the current count value of the counter  14 G (step S 213 ) to calculate the current opening ratio of each ink fountain key using the read count value (step S 214 ). The CPU  14 A reads out the target opening ratio of each ink fountain key from the memory M 34  (step S 215 ), and repeats a series of process operations in steps S 213  to S 216  until the current opening ratio of each ink fountain key and the target opening ratio of this ink fountain key become equal (YES in step S 216 ). 
     If the current opening ratio of each ink fountain key and the target opening ratio of this ink fountain key are equal (YES in step S 216 ), the CPU  14 A outputs a stop command to the motor driver  14 E to stop the rotation of the motor  14 D. 
     [Registration Adjusting Device] 
     The registration adjusting device  15 - 1  includes a CPU  15 A, a ROM  15 B, a RAM  15 C, a registration adjusting motor  15 D, a registration adjusting motor driver  15 E, a potentiometer  15 F for the registration adjusting motor  15 D, an A/D converter  15 G, input/output interfaces (I/O, I/F)  15 H and  15 I, and memories M 41  to M 44 , as shown in  FIG. 16 . The registration adjusting device  15 - 1  is connected to the apparatus  13  for controlling ink supply amount/registration adjustment via the interface  15 I. 
     The memory M 41  stores the received registration error amount. The memory M 42  stores the output value of the potentiometer  15 F for the registration adjusting motor  15 D. The memory M 43  stores the current position of the registration adjusting device  15 - 1 . The memory M 44  stores the target position of the registration adjusting device  15 - 1 . 
     Note that three registration adjusting devices for the skewing, circumferential, and lateral directions, which constitute the registration adjusting device  15 - 1 , have the same configuration. Hence,  FIG. 13  assumes that the registration adjusting device  15 - 1  is a registration adjusting device which performs registration adjustment in one direction. Note that registration adjusting devices for the skewing, circumferential, and lateral directions for each color may be provided as independent devices. 
     When the registration error amount is sent from the apparatus  13  for controlling ink supply amount/registration adjustment (YES in step S 201  of  FIG. 17A ), the CPU  15 A stores the sent registration error amount in the memory M 41  (step S 302 ). The CPU  15 A sends a reception completion signal of the registration error amount to the apparatus  13  for controlling ink supply amount/registration adjustment (step S 303 ). The CPU  15 A reads the current output value from the potentiometer  15 F via the A/D converter  15 G, and stores it in the memory M 42  (step S 304 ). 
     The CPU  15 A reads out the current output value of the potentiometer  15 F from the memory M 42  to calculate the current position of the registration adjusting device using the readout output value, and stores the obtained current position in the memory M 43  (step S 305 ). 
     The CPU  15 A reads out the registration error amount from the memory M 41  (step S 306 ). The CPU  15 A adds this registration error amount to the current position of the registration adjusting device in the memory M 43  to calculate the target position of the registration adjusting device, and stores the obtained target position in the memory M 44  (step S 307 ). 
     The CPU  15 A reads out the current position of the registration adjusting device in the memory M 43  (step S 308 ), and compares it with the target position of the registration adjusting device in the memory M 44  (step S 309 ). If the target position and the current position are not equal (NO in step S 309 ), the CPU  15 A confirms whether the current position is lower or higher than the target position (step S 310 ). 
     If the current position is lower than the target position (YES in step S 310 ), the CPU  15 A sends a forward rotation command to the motor driver  15 E (step S 311 ). If the current position is higher than the target position (NO in step S 310 ), the CPU  15 A sends a reverse rotation command to the motor driver  15 E (step S 312 ). 
     The CPU  15 A reads the current output value from the potentiometer  15 F via the A/D converter  15 G (step S 313 ) to calculate the current position of the registration adjusting device from the read output value (step S 314 ). The CPU  15 A reads out the target position of the registration adjusting device from the memory M 44  (step S 315 ), and repeats a series of process operations in steps S 313  to S 316  until the current position and the target position become equal (YES in step S 316 ). 
     If the current position and the target position are equal (YES in step S 316 ), the CPU  15 A outputs a stop command to the motor driver  15 E to stop the rotation of the motor  15 D (step S 317 ). 
     In this embodiment, a detector which measures color data of the color patch of each color in the color bar  9 - 1  is used as the spectroscopic sensor  11 , a detector which detects the position of the register mark of each color is used as the image sensor  12 , and the image sensor  12  is mounted on the scanning head  10 - 3 , together with the spectroscopic sensor  11 , so as to also serve as a detector which detects the upward/downward position of the color bar  9 - 1 . This makes it possible to integrate a camera required to adjust registration, and a line sensor required to detect the upward/downward position of the color bar. This, in turn, makes it possible to improve the cost performance, and simplify maintenance so as to relieve the operator&#39;s burden. 
     Although the density value (measured density value) of the color patch of each color is obtained from the color data of this color patch, which is measured by the spectroscopic sensor  11 , in the above-described embodiment, the color value of this color patch may be obtained. To obtain the color value of the color patch of each color, the obtained color value (measured color value) is compared with a reference color value to adjust the opening ratio of the ink fountain key of each color in accordance with the color difference between these color values. In addition, the color data need not always be measured using the spectroscopic sensor  11 , and the density value may directly be measured using a densitometer which employs a filter. 
     Also, although register marks printed in a spot pattern are used as the register marks  9 - 2  in the above-described embodiment, cruciform register marks may be used, as a matter of course. 
     Moreover, although not described in the above-mentioned embodiment, when images of the register marks  9 - 2  are to be obtained in practice, the full images of the register marks  9 - 2  are read by the image sensor  12 . On the other hand, when the upward/downward position of the color bar  9 - 1  is to be detected in practice, the image of the color bar  9 - 1  is laterally compressed to reduce the image data. This allows a high-speed process. 
     As has been described above, according to the present invention, since one image sensing means is used for both registration adjustment and detection of the upward/downward position of the color bar, it is possible to reduce the cost and facilitate the maintenance operation by the operator.