JP3683492B2 - Color chart measuring method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color chart measuring method and apparatus for managing ink density in offset printing or the like.
[0002]
[Prior art]
In recent years, a plate making apparatus (print plate recording apparatus) that forms an image on a printing plate based on digital image data, a printing apparatus in which a so-called CTP (Computer-To-Plate) apparatus is incorporated in the machine has been put into practical use. It is disclosed in JP-A-10-272756. Such a printing apparatus is called a digital printing machine, and is suitable for high-mix low-volume printing with a short work time because a printed matter can be obtained directly from image data. In this digital printing machine, the plate making process and the like are automated so that even an unskilled person can easily handle them, but further automation is desired for the ink supply control and the like in the printing process.
[0003]
In the ink supply control in the conventional printing apparatus, it is common to use a separate color stand that measures the taken print sample on a table. In this case, the operator takes out an appropriate print sample and prints it. There is a problem that color measurement must be performed.
[0004]
In order to solve this problem, as disclosed in Japanese Patent No. 2824334, a printing apparatus is disclosed that includes means for capturing an image of a printed matter in a printing apparatus. In this prior art, the printed matter is imaged on the impression cylinder of the printing apparatus to obtain image data, and the ink supply amount is controlled by comparing the image data with reference image data obtained by reading a printed matter as a control reference in advance. I am doing so. In this conventional technique, since an image of a printed matter is captured in the printing apparatus, there is an advantage that an operator does not need to be interposed as in the case of using a color stand.
[0005]
[Problems to be solved by the invention]
However, the above-described conventional technique has a problem that since the image of the entire printed matter is read and compared with the reference image, the amount of image data to be handled increases, and the image data processing takes time. Further, since the reference image must be prepared in advance, it is not suitable for work requiring instantaneous power, such as the above-mentioned multi-product small-number printing.
[0006]
For this reason, the present applicant has considered a color chart measuring apparatus that prints a color chart on a printed material and measures the color chart within the printing apparatus. As described above, the use of the color chart has advantages that the image data to be handled becomes small and that it is not necessary to prepare a reference image in advance. However, the color chart arranged in the margin of the printed material must be a small size, and it is difficult to accurately measure the color chart from the printed printing paper. In particular, if the printing machine is a sheet-fed printing machine, the printing paper is nipped and conveyed only on the leading side. In general, since the color chart is provided on the rear end side of the printing paper, the paper flicker tends to increase in the vicinity of the color chart. According to this, there is a problem that the reading level differs in each part of the color chart due to the flickering of the printing paper accompanying the conveyance.
[0007]
The present invention has been made to solve the above-described problem, and a color chart measuring method and apparatus capable of measuring a color chart with high accuracy even when the reading level of each part of the printing paper changes due to the flapping of the printing paper being conveyed, etc. The purpose is to provide.
[0008]
[Means for Solving the Problems]
The invention according to claim 1 is a color chart measurement method for imaging a color chart on a printing paper having a plurality of color chart areas and measuring color chart information from image data obtained by the imaging, An unprinted area is provided on the printing paper in the vicinity of the color chart area. The printing paper is transported in a state where the leading edge of the printing paper is nipped, and the color chart area of the printing paper being transported is unclear. Imaging a print area; Calculate the color data corresponding to each color chart area from the image data of each color chart area Process and Calculate individual white data corresponding to each color chart area from the image data of the unprinted area adjacent to each color chart area. , For each color chart area Color data for each color chart area based on the corresponding white data The correction And the process to do The
[0010]
Claim 2 The invention described in claim 1 The color chart measurement method according to claim 1, wherein the imaging is performed by an imaging unit including a plurality of imaging elements, and the imaging unit reads a white reference object that is placed in a stationary state before imaging the color chart. In this case, shading correction is performed on captured image data.
[0011]
Claim 3 The invention described in claim 1 Or 2 In the color chart measurement method described in the above, when the color data of each color chart area is c1 and the white data of the corresponding unprinted area is c0, the color density D of each color chart area by the correction is D = −. It is calculated by k * log (c1 / c0). (Where k is the gain coefficient)
[0012]
Claim 4 The invention described in 1 is provided in a printing apparatus that performs multicolor printing of a plurality of colors on a printing paper, images a color chart on the printing paper having a plurality of color chart areas, and uses image data obtained by the imaging. A color chart measuring device for measuring color chart information, A conveying means that conveys the leading edge of the printing paper in a sandwiched state, and an unprinted area is provided on the printing paper in the vicinity of the color chart area; Imaging means for reading an image including a color chart and an unprinted area adjacent to the color chart from the printing paper being conveyed, color data of each color chart area from the obtained image data, and white of an adjacent unprinted area Calculate with data And Paper white correction means for correcting the color data with corresponding white data.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
[Embodiment of color chart]
First, the configuration of the color chart used in the present invention will be described. FIG. 6 is an explanatory diagram showing a specific example of a color chart according to the present invention. In FIG. 6A, an image im representing a printed matter and a color chart cc are printed on the printing paper S, and the position of the color chart cc is a position following the rear end of the image im. Here, the position of the image im on the printing paper S is positioned and arranged at a position separated from the print head side (paper holding side) by a predetermined holding amount f, and the size of the image im (printing direction) Assuming that (size) is m and the width of the color chart cc is r, the area where the color chart cc is arranged is “a point from the top of the printing paper to f + m” to “a point from the same f + m + r”. That is, in general, the amount of adjustment f and the width r of the color chart cc are constant values, so that the area where the color chart cc is arranged can be calculated based on the size m of the image im.
[0014]
FIG. 6B shows a specific example of the color chart cc. In this color chart cc, a plurality of color chart areas cr and reference marks rm1 to rm3 (collectively referred to as rm) provided between the color chart areas cr are arranged in series along the print width direction. It is a design. The color chart area cr is formed by repeatedly arranging a predetermined density of a net area or a solid area for each color in a predetermined order. Therefore, it is possible to determine whether the ink supply amount is excessive or insufficient by measuring the color chart region, calculating the solid density or the halftone percentage, and comparing it with a predetermined value. The arrangement of the color chart regions arranged with the reference mark rm1 interposed therebetween is arranged symmetrically with respect to the reference mark rm1.
[0015]
FIG. 6C is an enlarged view of the reference mark rm. In the present embodiment, the reference mark rm is a positioning mark printed with one color of K color (black), and two bars b having a predetermined length along the printing direction; It consists of a cross mark d provided between the bars b. The position of the horizontal line of the cross mark d is substantially at the center height of the color chart region cr, and the printing direction position of the color chart region cr can be specified. Further, a paper white area hr (see FIG. 6B) that is an unprinted area is provided above the color chart area cr, and the length of the bar b is equal to the width of the color chart area cr. It is set so as to include the paper white area hr. Therefore, if it is the detection range of the bar b in the printing direction, it can be determined as the range of the paper white area hr. In the present embodiment, the reference mark rm1 is provided in the center of the color chart cc, and the reference marks rm2 and rm3 are provided in the vicinity of both left and right ends.
[0016]
[First Embodiment]
Embodiments of a printing apparatus using a color chart and a color chart measuring method according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic side view showing an example of a printing apparatus according to the present invention. First, as shown in FIG. 1, the printing apparatus includes, as printing mechanisms, first and second plate cylinders 1 and 2 for holding a printing plate, and first and second plates for transferring an ink image from each plate cylinder. A second blanket cylinder 3, 4, a pressure cylinder 5 that holds printing paper and an ink image is transferred from both blanket cylinders 3, 4, and a paper feed cylinder 6 that supplies or discharges printing paper to and from the impression cylinder 5 A discharge cylinder 7, dampening water supply means 8 and ink supply means 9 for supplying dampening water or ink to the printing plates on the first and second plate cylinders 1 and 2, and stacked unprinted A paper supply unit 10 that sequentially supplies the print sheets and a paper discharge unit 11 that sequentially stacks the printed print sheets.
[0017]
On the other hand, this printing apparatus has, as a plate making mechanism, a printing plate supply unit 12 that supplies an unexposed printing plate to the first and second plate cylinders 1 and 2, and an image on the printing plate on the plate cylinder. An image recording unit 13 for recording, a developing unit 14 for developing a printing plate on which an image is recorded, and a printing plate discharge unit 15 for discharging a used printing plate are provided. The printing apparatus also detects an image pickup unit 16 that picks up an image on the printed print paper, an encoder unit 17 that detects the rotational position of the impression cylinder 5, and a print paper fed from the paper feed unit 10. The paper detection sensor 18 is provided.
[0018]
Hereinafter, the details of each of the above portions will be described. The first plate cylinder 1 is configured to be movable between a first printing position indicated by a solid line in FIG. 1 and an image recording position indicated by a two-dot chain line by a plate cylinder driving mechanism (not shown). Similarly, the second plate cylinder 2 is configured to be movable between a second printing position indicated by a solid line in FIG. 1 and an image recording position indicated by a two-dot chain line by a plate cylinder driving mechanism (not shown). That is, the first and second plate cylinders 1 and 2 are respectively arranged at the first or second printing position when the printing operation is executed, and are alternately arranged at the image recording position when the plate making operation is executed. Then, the plate making process of the printing plate on each plate cylinder is performed. Each of the first plate cylinder 1 and the second plate cylinder 2 has a circumferential surface capable of holding printing plates for two colors, and the printing plates are fixed at positions facing each other by 180 degrees on the circumferential surface. For this purpose, there is a gripping means (not shown).
[0019]
The first blanket cylinder 3 is configured to rotate in contact with the first plate cylinder 1 at the first printing position, and the second printing is similarly applied to the second blanket cylinder 4. It is configured to rotate in contact with the second plate cylinder 2 at the position. The first and second blanket cylinders 3 and 4 have the same diameter as the first and second plate cylinders 1 and 2, and blankets capable of transferring ink images of two colors from the respective plate cylinders. It is mounted on the circumference.
[0020]
The impression cylinder 5 has a diameter half that of the first and second plate cylinders 1 and 2 and is configured to rotate in contact with both the first and second blanket cylinders 3 and 4. ing. The impression cylinder 5 is provided with a holding means (not shown) capable of holding one printing sheet having a size corresponding to the printing plate. The gripping means can be opened / closed at a predetermined timing by an opening / closing mechanism (not shown) to hold the front end portion of the printing paper. On the other hand, in this embodiment, the pressure drum 5 is provided with the coaxial encoder means 17 so that the rotational position of the pressure drum 5 can be detected. Such an encoder means 17 is generally provided for controlling the rotational position of the impression cylinder 5, and in the present invention, this is used to detect the transport position of the printing paper.
[0021]
The paper feed cylinder 6 and the paper discharge cylinder 7 have the same diameter as the impression cylinder 5, and are provided with a gripping means (not shown) similar to the gripping means provided on the impression cylinder 5. The gripping means for the paper feed cylinder 6 and the paper discharge cylinder 7 are arranged so as to be able to deliver printing paper in synchronization with the gripping means for the impression cylinder 5.
[0022]
The first and second plate cylinders 1 and 2 disposed at the first and second printing positions, the first and second blanket cylinders 3 and 4, the impression cylinder 5, the paper feed cylinder 6 and the discharge cylinder. The paper cylinder 7 is provided with a driving gear (not shown) having the same size as the diameter of each cylinder at each cylinder end, and each gear meshes between the cylinders that contact each other. Therefore, by driving this gear by a print driving motor (not shown), the cylinders can be driven to rotate synchronously.
[0023]
In the printing apparatus according to the present embodiment, the plate cylinders 1 and 2 and the blanket cylinders 3 and 4 have a circumferential length twice that of the impression cylinder 5, so that the plate cylinders 1 and 2 and the blanket cylinders 3 and 4 are 1 Each time it rotates, the impression cylinder rotates twice. Accordingly, when the impression cylinder 5 is rotated twice while holding the printing paper, the first and second plate cylinders 1 and 2 can perform multicolor printing of a total of four colors of 2 colors + 2 colors.
[0024]
Two sets of dampening water supply means 8 are arranged for each of the plate cylinders 1 and 2 at the first and second printing positions, and are selective to the two printing plates on each of the plate cylinders 1 and 2. Can be supplied with dampening water. The dampening water supply means 8 includes a water boat that stores dampening water and a dampening water roller group that pumps up the dampening water in the water boat and passes it to the printing plate surface. The roller that contacts the plate surface is configured to contact or separate from the plate cylinder surface by a cam mechanism (not shown). If the printing plate is a type of printing plate that does not require fountain solution, the fountain solution supply means 8 is not necessary.
[0025]
Two sets of ink supply means 9 are arranged for each of the plate cylinders 1 and 2 in the first and second printing positions, and are selectively different for the two printing plates on the plate cylinders 1 and 2. Color ink can be supplied. The ink supply means 9 includes an ink fountain means capable of adjusting the amount of ink discharged for each of a plurality of regions in the printing width direction, and a plurality of ink kneaded inks supplied from the ink fountain means and supplied to the printing plate surface. Among the ink rollers, at least a roller that contacts the printing plate surface is configured to contact or separate from the plate cylinder surface by a cam mechanism (not shown). The ink of each ink supply means 9 is, for example, arranged for the first plate cylinder 1 with K (black) and M (magenta) ink supply means 8, and for the second plate cylinder 2. Thus, ink supply means 8 for C color (cyan) and Y color (yellow) are arranged. It should be noted that some of the dampening water supply means 8 and the ink supply means 9 are configured so that they can be withdrawn from their movement paths as the first and second plate cylinders 1 and 2 move.
[0026]
The paper feeding unit 10 takes out printing paper one by one from a pile on which unused printing paper is stacked and passes it to the paper feeding cylinder 6. In this embodiment, the paper feeding unit 1 is turned on every two rotations of the paper feeding cylinder. Operates to supply twice-printed paper. The paper feeding unit 10 is provided with a paper detection sensor 18 that optically detects the passage of the printing paper. Such a paper detection sensor 18 is generally provided for detecting a paper jam or two-sheet taking. In the present embodiment, the pressure is detected according to the detection result of the paper detection sensor 18. It is possible to determine whether the printing paper is fed to the cylinder 5 or the feeding cylinder 6 or not. On the other hand, the paper discharge unit 11 receives printed paper from the paper discharge cylinder 7 and stacks it. Details of the paper discharge unit 11 will be described later together with the configuration of the imaging unit 16.
[0027]
Next, the plate making mechanism of this printing apparatus will be described. In this printing apparatus, when the plate making operation is executed, the first and second plate cylinders 1 and 2 are alternately moved to the image recording position. At this image recording position, a friction roller (not shown) is configured to abut on the plate cylinder and rotate.
[0028]
The printing plate supply unit 12 includes a cassette roll in which a roll-shaped unexposed printing plate is shielded and stored, a conveyance roller and a conveyance guide for conveying the drawn printing plate to the plate cylinders 1 and 2, and the printing plate in a sheet form Cutting means. In this embodiment, a silver salt sensitive material is used as the printing plate, and an image is recorded by laser light. The printing plate supply operation procedure is as follows. First, the front end of the printing plate drawn out from the cassette roll is sandwiched between gripping means (not shown) of the printing cylinders 1 and 2, and the printing cylinders 1 and 2 are rotated in this state to perform printing. The plate is wound on the plate cylinders 1 and 2, and then the printing plate is cut to a predetermined length and the rear end of the printing plate is held by the other gripping means.
[0029]
The image recording unit 13 records the image im and the color chart cc by exposing the printing plate by turning on / off the laser beam. In this embodiment, laser light emitted from a laser transmission source (not shown) is subjected to main scanning along the axial direction of the plate cylinder by a polarizer such as a polygon mirror (not shown), and the printing plate surface is rotated by rotating the plate cylinder. It is configured to perform sub-scanning. The scanning method may be a type in which a plurality of laser beams are provided in the plate cylinder axis direction and main scanning is performed as the plate cylinder rotates. The printing plate and the image recording unit 13 may record not only an image by exposure but also an image by heat or electric discharge machining.
[0030]
The developing unit 14 develops the printing plate exposed by the image recording unit 13. In this embodiment, the developing unit 14 is configured to draw up the processing liquid stored in a processing tank (not shown) by a coating roller and apply the processing liquid to the printing plate to perform the developing process. And a lifting means (not shown) that moves to a position close to the plate cylinder. If an image recording method that does not require development processing is employed, the developing unit 14 may be omitted.
[0031]
In this printing apparatus, the first and second plate cylinders 1 and 2 are moved to the image recording position, and the plate making operation is performed by supplying the printing plate and recording and developing the image. When the plate making operation is completed, the first and second plate cylinders 1 and 2 can be arranged at the first and second printing positions to perform the printing operation.
[0032]
On the other hand, the printing apparatus can automatically discharge the printing plate after the printing operation is completed. In this embodiment, the printing plate discharge unit 15 includes a peeling unit that peels the printing plate from the plate cylinder at the image recording position, a conveyance unit that conveys the peeled printing plate, and a used printing plate that has been conveyed. A discharge cassette.
[0033]
Next, the configuration of the imaging unit 16 and the paper discharge unit 11 according to the present invention will be described with reference to FIG. FIG. 2 is a schematic side view of the vicinity of the paper discharge unit 11. First, the paper discharge unit 11 is hung between the paper discharge cylinder 7 and two gears 7 ′ having substantially the same diameter as the paper discharge cylinder 7 (along with the vertical direction on the paper surface of FIG. 2). An endless chain 20, a plurality of gripping means 21 for transporting the printing paper S conveyed by the two chains, and a stack of the printing paper S transported by the gripping means 21. The sheet discharge table 22.
[0034]
At both ends of the paper discharge cylinder 7, gear portions (not shown) for engaging with the chain 20 are provided, and two gears 7 'having substantially the same diameter are arranged opposite to the gear portions. . An endless chain 20 is wound around the gear portion of the discharge cylinder 7 and the gear 7 ′. The length of the chain 20 is set to an integral multiple of the circumferential length of the paper discharge cylinder 7.
[0035]
The gripping means 21 has a claw member that can be opened and closed to pinch the leading edge of the printing paper S, and a plurality of gripping means 21 are fixed across the two chains. The arrangement interval of the gripping means 21 on the chain 20 corresponds to the circumferential length of the paper discharge cylinder 7. On the other hand, each gripping means 21 is configured to open and close in synchronization with a gripping means (not shown) provided on the paper discharge cylinder 7 by a cam mechanism (not shown). S is received, and the printing paper S is conveyed and discharged on the paper discharge tray 22 as the chain 20 rotates.
[0036]
The paper discharge table 22 is a pallet-like member on which a plurality of printing papers S can be stacked, and is moved up and down by lifting means (not shown). That is, as the printing paper S is discharged, the paper discharge tray 32 is sequentially lowered, so that the discharge height of the printing paper S can be made constant and the printing paper S can be discharged smoothly.
[0037]
In the paper discharge unit 11, the leading edge of the printing paper S is nipped and conveyed by the gripping means 21, so that the trailing edge of the printing paper S is conveyed in an unfixed state. For this reason, flapping of the printing paper S occurs with conveyance. In the present embodiment, in order to suppress the flapping of the printing paper S, a suction roller 23 that stabilizes the conveyance state of the printing paper S is provided on the front side of the paper discharge tray 22.
[0038]
The suction roller 23 has a number of fine suction holes on its surface and is connected to a vacuum pump (not shown). The suction roller 23 has a roller axis parallel to the gripping means 21 spanned between the two chains 20 so that the top of the roller is positioned at substantially the same height as the lower passage position of the chain 20. Is arranged. The suction roller 23 is configured to be driven to rotate in accordance with the passing speed of the gripping means 21 or to be rotatable. Therefore, the printing paper S is conveyed while being attracted to the surface of the suction roller 23 when passing over the suction roller 23. Absent. Instead of the suction roller 23, a suction plate member that sucks the printing paper S in a plane may be employed.
[0039]
The imaging unit 16 includes an illumination unit 24 that illuminates the conveyed printing paper, and an imaging unit 25 that captures an image on the illuminated printing paper and obtains image data. The illumination unit 24 is arranged along the suction roller 23 and includes a plurality of linear light sources that illuminate the printing paper S on the suction roller 23, and is provided between the chain 20 traveling up and down. An imaging slit is formed at the center of the light source.
[0040]
The imaging means 25 includes a housing 26 for shielding light and dust, and a mirror 27, a lens 28, and a CCD line sensor 29 disposed inside the housing. The image pickup means 35 picks up an image of the printing paper on the suction roller 23 through the slit of the illumination means 24, and incident light of the image turned back by the mirror 27 passes through the lens 28 and is a CCD line sensor. Light is received at 29. The CCD line sensor reads an image corresponding to three colors of RGB. In this embodiment, as the printing paper is conveyed, the image on the printing paper is sequentially read line by line.
[0041]
In the present embodiment, two image pickup means 25 are provided along the vertical direction of the paper surface of FIG. 2, and the image in the width direction of the print paper S is divided into two images. Yes. This configuration will be described with reference to FIG. FIG. 5 is an explanatory diagram showing a state in which two image pickup means 25 are provided along the print width direction. As shown in FIG. 5, the two image pickup means 25R and 25L are arranged so as to divide the color chart cc in the print width direction, and the image pickup means 25R and 25L are provided with the CCD line sensor 29. It is incorporated so that the reading directions match. In addition, the areas to be imaged by the imaging units 25R and 25L partially overlap at the center. And it arrange | positions so that the reference mark rm1 may be located in this overlapped area | region. According to this embodiment, it is possible to align the read image data read by the two imaging means 25R and 25L with the reference mark rm1.
[0042]
On the other hand, the reference marks rm2 and rm3 are provided in the vicinity of the left and right ends of the printing paper. The image pickup means 25R can pick up the reference marks rm1 and rm2, and the image pickup means 25L can pick up the reference marks rm1 and RM3. . Thus, since the two reference marks rm are imaged on each of the imaging means 25R and 25L, the inclination amount of the color chart cc can be obtained by detecting the positions of the reference marks rm1 to rm3. That is, when the color chart cc on the printing paper is printed with an inclination or when the printing paper is inclined, the image of the color chart cc in the read image data is also inclined. Even in this case, the inclination can be corrected by detecting the positions of the reference marks rm1 to rm3.
[0043]
In consideration of the inclination correction as described above, it is desirable that the positions of the reference marks rm2 and rm3 are arranged as much as possible in the width of the printing paper S. In the present embodiment, the position is set in accordance with the minimum width printing paper Smin usable in the printing apparatus. In this case, there is an advantage that a constant color chart cc is always formed regardless of the size of the printing paper S.
[0044]
Next, the control unit of the printing apparatus will be described with reference to FIGS. FIG. 3 is a block diagram of the entire printing apparatus, and FIG. 4 is a functional block diagram showing the functional block diagram of the block diagram. As shown in the block diagram of FIG. 3, the printing apparatus includes a control terminal 30 for editing image data and instructing a printing operation to the printing apparatus, and a print control unit for controlling each part of the printing apparatus. 31, each of which is connected by a LAN or the like.
[0045]
The control terminal 30 is a computer system having a CPU and memory for performing calculations, a display device such as a CRT, an input device such as a keyboard and a mouse, and a storage device such as a magnetic disk for storing various image data and programs. Yes, provided outside the printer body. The control terminal 30 prepares print image data representing a printed matter by directly creating image data or editing image data received from another image data creation device.
[0046]
The print control unit 31 is a computer system including a CPU board or the like provided inside the printing apparatus main body, and controls each part of the printing apparatus via various I / Fs. The color chart measurement control unit 32 for processing the read image data imaged by the imaging unit 25 and measuring the color chart is constituted by a separate substrate with respect to the print control unit 31, and the print control unit 31 is connected. The color chart measurement control unit 32 is also a computer system composed of a CPU board or the like, and is configured to receive detection signals from the encoder unit 17 and the paper detection sensor 18 in addition to connection to the imaging unit 25. .
[0047]
Next, the configuration of the control unit according to the present invention will be functionally described with reference to FIG. The control terminal 30 stores color chart data storage means 40 for storing image data representing the color chart cc prepared in advance (hereinafter referred to as color chart data cd), and the stored color chart data cd as print image data. a color chart adding unit 41 for adding to pd, a RIP processing unit 42 for generating binary image data pd2 by RIP processing (raster-image-processing) the print image data pd to which the color chart data cd is added, and Is provided. In the present embodiment, the color chart adding means 41 automatically performs processing according to a predetermined arrangement condition such as “adding the color chart cc to a position following the rear end of the print image im”. The operator may manually determine the position of the color chart cc. The image data pd2 created by the RIP processing unit 42 is sent to the image recording unit 13 via the print control unit 31.
[0048]
On the other hand, the control terminal 30 also includes color chart arrangement position calculation means 43 that calculates the position to which the color chart cc is added. For example, if the arrangement condition is “add the color chart cc to a position following the rear end of the print image im”, the color chart arrangement position calculation unit 43 calculates the predetermined amount f and the print image data pd. The position of the color chart cc on the printing paper S can be calculated by adding the image size m. Here, the image size m may be obtained from the print image data pd by the control terminal 3, or may be obtained from a preceding image data creation device (not shown) that created the print image data pd. The calculated arrangement position of the color chart is sent to the color chart measurement control unit 32 via the print control unit 31 as color chart position data id. When the operator arranges the color chart cc at an arbitrary position, the calculation may be performed based on the relative position where the color chart cc is arranged with respect to the print image data pd.
[0049]
Next, the color chart measurement control unit 32 stores a reading period setting unit 44 that sets a reading area of the imaging unit 25 based on the color chart position data id, and a reading that stores the read image data rd read by the imaging unit 25. An image data storage means 45, a reference mark detection means 46 for detecting the position of the reference mark rm from the read image data rd, and a color chart for calculating the actual position of each color chart region cr based on the detected position of the reference mark rm. Real position calculation means 47, read image data read means 48 for reading out image data at the real position, paper white correction means 49 for performing correction based on the white reference of the print paper based on the read image data, and each color chart Color chart information display for calculating color chart information such as color density and halftone percentage of area cr And it means 50.
[0050]
In the reading period setting unit 44, the imaging unit 25 reads a reading region including the color chart cc on the printing paper S based on the color chart position data id, the encoder signal of the encoder unit 17, and the paper detection signal of the paper detection sensor 18. The reading period is set as follows. Here, by first counting the encoder signal of the encoder means 17, it can be determined in which of the paper discharge sections 11 the printing paper S is located. Accordingly, the reading period setting unit 44 determines the timing at which the reading area including the color chart cc defined in the color chart position data id is at the reading position of the imaging unit 25 from the count of the encoder signal, and the imaging unit 25 Command to start and end reading.
[0051]
However, since this printing apparatus is configured to supply and discharge printing paper every two rotations of the impression cylinder 5, the printing paper is actually conveyed only once every two rotations. Therefore, in the present embodiment, in accordance with the paper detection signal from the paper detection sensor 18, control is performed so that imaging is performed only when the printing paper S is conveyed under the imaging unit 25. Actually, the color chart is measured every predetermined number of samplings. As described above, the reading period setting unit 44 determines the conveyance position of the printing paper according to the rotation position of the impression cylinder 5 when the impression cylinder is rotated by the paper detection signal. The reading period is instructed to the image pickup means 25 in prediction. The reading area of the image pickup means 25 is set larger than the width of the color chart cc so that there is no problem even if a slight deviation occurs.
[0052]
In response to a command from the reading period setting unit 44, the imaging unit 25 reads an image on the printing paper S, and the read image data rd thus read is stored in the read image data storage unit 45. The read image data storage means 45 comprises two sets of memories respectively corresponding to the image pickup means 25R and 25L, and the read image data rd read by the image pickup means 25L is stored in reverse from the rear of the memory at the time of storage. The As a result, the read image data obtained from the image pickup means 25R and 25L can be read in the same procedure. In the above description, when the read image data rd is stored, one is stored from the rear of the memory. However, the reading direction of one CCD line sensor 29 may be arranged in reverse.
[0053]
The reference mark detection unit 46 detects the reference mark rm by image processing from the stored read image data rd. First, a pixel arrangement pattern at the center of the cross mark d sandwiched between the bars b in the reference mark rm is obtained in advance. For example, FIG. 6D shows an example of a pixel arrangement pattern in the direction A at the center of the cross mark d in FIG. In this example, the width of the bar b is represented by three black pixels, the white line between the bar b and the cross mark d is represented by two white pixels, and the horizontal line of the cross mark d is represented by five black pixels. Yes. The reference mark detection means 46 collates the pixel arrangement pattern shown in FIG. 6D by shifting one pixel at a time in order to determine whether or not the read image data in the memory is included. Such a method is individually performed in the orthogonal XY directions on the memory storing the read image data rd. Then, the position where the pixel arrangement pattern exists can be taken as a histogram for each of XY, and the position with the highest histogram can be set as the position of the reference mark rm. This method is an example of pattern recognition, and other methods may be employed as long as the position of the reference mark rm can be determined.
[0054]
First, the color chart actual position calculating unit 47 calculates the distance between the detected two reference marks rm. Thereby, the inclination of the color chart cc can be detected. FIG. 7 is an explanatory diagram for explaining the inclination correction of the color chart cc. In this example, the distance in the Y direction (shift in the printing direction) between the two reference marks rm1 and rm2 is h, and the distance in the X direction (in the printing width direction). The distance between the reference marks rm1 and rm2 which is (distance) is w and is known in advance is L. Assuming that the target color chart area crx is at a known distance x from the reference mark rm1, the target color chart area crx uses the position of the reference mark rm1 as the origin as a reference point in the X direction. The position of x · h / L in the w / L and Y directions is the actual position in the read image data rd. In this way, if at least two reference marks rm are read by the imaging means 25, the inclination of the color chart cc can be corrected.
[0055]
The read image data reading means 48 reads the read image data in the memory corresponding to the actual position, and here, the corresponding image data of the color chart area cr and the image of the paper white area hr immediately above it. Read data and. Note that image data is read out in a predetermined minute size area, but this is performed by designating a predetermined address space on the memory. Therefore, in the present embodiment, this is handled by performing an address operation by the tilt correction on a predetermined read address. For example, in the example described above, x · w / L may be added to the X-direction address and x · h / L may be added to the Y-direction address with respect to the predetermined read address. The actual position of the paper white area hr is defined by the bar b that constitutes each of the reference marks rm. The position in the print width direction of the paper white area hr is the same position as each corresponding color chart area cr, and the position in the print direction can be determined at a predetermined line position within the detection range of the bar b. .
[0056]
The paper white correction unit 49 creates white data from the read image data of the paper white area hr, and corrects the color data calculated from the color chart area cr based on the white data. If the color data is C1, the white data is C0, and the desired color density is D, then D = −k · log (C1 / C0). (Where k is a gain coefficient) In this embodiment, white data serving as a white reference is obtained from the adjacent paper white area hr for each of the color chart areas. There is an advantage that appropriate colorimetry can be performed even if the image pickup level changes in various places on the printing paper due to the occurrence of lifting or the like.
[0057]
The color chart information calculation means 50 calculates color chart information in the color chart region cr, for example, a halftone percentage in addition to the color density D. Further, based on the obtained color density D, the ink density may be converted into YMCK ink density, or may be converted into the ink key opening amount of the ink fountain means if necessary.
[0058]
The color chart information of the color chart thus obtained is used for adjusting the supply amount of ink and fountain solution. That is, the color chart measurement control unit 32 or the print control unit 31 compares the measured color chart information with a preset reference value to determine whether ink or dampening water is excessive or deficient. Ensure proper supply control.
[0059]
Next, the operation of the printing apparatus according to the present embodiment will be described using the flowchart of FIG. FIG. 8A is a flowchart showing the entire process of printing work, and FIG. 8B is a flowchart showing the color chart measuring process. First, in FIG. 8A, various settings are made in step S1 in the printing work process. For example, designation of print image data pd to be used, setting of the number of prints, and the like. Further, color chart data cd is added to the print image data pd in advance. The position where the color chart is added is calculated as color chart position data id. The print image data pd with the color chart cd added is subjected to RIP processing to generate image data pd2. The generation of the image data pd2 may be performed in real time in accordance with the exposure of the printing plate.
[0060]
In the next step S2, an image is formed on the printing plate. First, one of the plate cylinders 1 and 2 moves to the image recording position, and an unexposed printing plate is mounted. An image is exposed based on the image data pd2. After the exposure is completed, development processing is performed by the developing unit 14. This plate making process is performed alternately by the plate cylinders 1 and 2. In step 3, a printing operation is performed based on the prepressed printing plate. That is, the fountain solution is supplied to the printing plates on the plate cylinders 1 and 2, and then the color ink corresponding to each plate is supplied. The ink image on the printing plate is transferred to the blanket cylinders 3 and 4 and transferred onto the printing paper fed to the impression cylinder 5.
[0061]
In step S4, it is determined whether or not the number of printed sheets has reached the desired amount. If not achieved, the color chart measurement in step S5 is performed for each predetermined number of samplings. This color chart measurement will be described later using the flow of FIG. In step S6, the supply amount of ink or dampening water is adjusted based on the color chart information obtained by the measurement in step S5, and the process returns to step S3.
[0062]
Next, the color chart measurement process according to the present invention will be described. In FIG. 8B, first in step P1, the reading period is set by the reading period setting means 44 based on the color chart position data id calculated in step S1. In Step P2, the imaging means 25R and 25L start reading with the start of this reading period. In step P3, it is determined whether the imaging means is 25R or 25L. If the imaging means is 25R, the process proceeds to step P4. If the imaging means is 25L, the process proceeds to step P5. In step P4, the read image data rd is stored in the forward direction in the memory of the read image data storage means 45. In step P5, the read image data rd is stored in the reverse direction in the memory of the read image data storage means 45.
[0063]
When the storage of the read image data rd is completed, in step P6, the read image data rd in each memory is subjected to image processing to detect the reference mark rm. In the next step P7, the distance between the detected reference marks rm is calculated, and the inclination amount of the read color chart cc is calculated. In step S8, the actual position of each color chart area is calculated based on the obtained tilt amount, and the address for reading the image data in the memory is corrected.
[0064]
In step P9, image data in the color chart area cr is read from the address position corrected by the inclination correction. In step P9, the image data is also read from the paper white area hr adjacent to the color chart area cr. In Step P10, white data serving as a white reference is determined based on the image data of the paper white area hr, and thereby the color density of the color chart area cr is corrected. In step P11, color chart information is calculated. In step P12, it is determined whether there is a next color chart region cr to be measured. If the color chart area cr to be measured still remains, the process returns to step P8 and the measurement is repeated.
[0065]
In the printing apparatus according to the first embodiment, since the area including the color chart is read from the printing paper being conveyed and the color chart information is measured, the apparatus can be configured compactly and the image data to be handled There is an advantage that it can be reduced. In particular, in the case of a printing apparatus equipped with a printing plate recording apparatus, the reading area can be set from the information on the position where the color chart is arranged. For example, it is appropriate even if the arrangement position of the color chart changes due to different image sizes. Can respond.
[0066]
[Second Embodiment]
In addition to the first embodiment, in the second embodiment, the shading correction of the CCD line sensor 29 is further performed. In this embodiment, the procedure is as follows.
[0067]
First, a white reference object prepared in advance is placed on the suction roller 23 in a stationary state. Alternatively, a white reference object may be formed on the surface of the suction roller 23. Note that the static state is set so as not to cause a difference in reading level due to fluttering during conveyance. The stationary white reference object is read by the imaging means 25, and white reference data W is obtained for each element of each CCD line sensor 29. On the other hand, black reference data (data corresponding to the dark current of each element) B of each element is obtained. This completes preparations for performing shading correction. This preparation may be appropriately performed at the time of factory shipment, maintenance, or before work, and is not necessarily performed along with all operations.
[0068]
In this state, when an image is actually read by the CCD line sensor 29, the read data Sp of each element is subjected to shading correction such that Sp ′ = (Sp−B) / (WB). Is called. This data correction may be performed before and after storing captured image data in steps P4 and P5 in FIG. 8B, for example.
[0069]
[Other embodiments]
(1) In the first embodiment, the image pickup unit 25 is provided in the paper discharge unit 11 from which the print paper S is discharged and conveyed, but the print paper S conveyed on the impression cylinder 5 and the paper discharge cylinder 7 is read. You may arrange as follows.
[0070]
(2) In the first embodiment, the color chart data cd is added by the control terminal 30, but the color chart that has undergone RIP processing on print image data that has been RIP processed in advance by the print control unit 31 or the like. Data may be added.
[0071]
(3) In the first embodiment, two imaging means 25 are arranged side by side, but one or three or more may be arranged.
[0072]
(4) In the first embodiment, the color chart cc is arranged on the rear end side of the image im, but may be provided on the head side. Further, the color chart cc may be arranged not at a position immediately after the image im but at a predetermined distance or a fixed position on the printing paper.
[0073]
【The invention's effect】
Claim 1 4 According to the invention described in (1), paper white correction can be performed by using image data in an unprinted area corresponding to each color chart area, so that a difference in reading level caused by printing paper fluttering or floating is corrected. be able to.
[0074]
Also, Claim 1 to 4 According to the invention described in (4), it is particularly suitable for measuring a color chart while conveying printing paper.
[0075]
Claim 2 Since the shading correction is performed based on the stationary white reference object, the accuracy of the color chart measurement can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic side view showing an example of a printing apparatus according to the present invention.
FIG. 2 is a schematic side view illustrating a paper discharge unit and an imaging unit in the printing apparatus.
FIG. 3 is a block diagram illustrating a configuration of a control unit of the printing apparatus.
4 is a functional block diagram functionally showing the block diagram of FIG. 3. FIG.
FIG. 5 is an explanatory diagram illustrating a positional relationship between an imaging unit and a reference mark on a color chart.
FIG. 6 is an explanatory diagram showing a configuration of a color chart.
FIG. 7 is an explanatory diagram for explaining inclination correction of an inclined color chart.
FIG. 8 is a flowchart showing the operation of the printing apparatus.
[Explanation of symbols]
1 First plate cylinder
2 Second plate cylinder
3 The first blanket cylinder
4 Second blanket cylinder
5 impression cylinder
6 Feeding cylinder
7 Discharge cylinder
9 Ink supply means
11 Paper discharge unit
13 Image recording unit
17 Encoder means
18 Paper detection sensor
22 Output tray
23 Suction roller
25 Imaging means
29 CCD line sensor
30 Control terminal
31 Print control unit
32 Color chart measurement controller
40 Color chart data storage means
41 Color chart data adding means
42 RIP processing section
43 Color chart arrangement position calculation means
44 Reading period setting means
45 Read image data storage means
46 Reference mark detection means
47 Color chart actual position calculation means
48 Reading image data reading means
49 Paper white correction means
50 Color chart information calculation means
S printing paper
im image
m Image size
f Barking amount
cc color chart
cr color chart area
hr Paper white area
rm fiducial mark
b Bar (reference mark)
d Cross mark (reference mark)
cd color chart data
id Color chart position data
pd print image data
pd2 Binarized print image data
rd read image data

Claims (4)

A color chart measurement method for imaging a color chart on a printing paper having a plurality of color chart areas and measuring color chart information from image data obtained by imaging,
On the printing paper, an unprinted area is provided close to the color chart area,
Transporting in a state where the leading edge of the printing paper is sandwiched;
Imaging a color chart area and an unprinted area of the printing paper being conveyed;
A step of calculating the color data corresponding to each color chart area from the image data of the color chart area,
Calculating a separate white data corresponding to each color chart area from the image data of the non-printed area adjacent to each color chart area, of the color chart area based on the corresponding white data to each of the color chart area and the step of correcting the color data,
Tona Ru color chart measurement method. The imaging is performed by imaging means comprising a plurality of imaging elements,
2. The color chart measurement according to claim 1, wherein the imaging unit reads a white reference object placed in a stationary state in advance before imaging the color chart and performs shading correction on the captured image data. Method. If the color data of each color chart area is c1, and the white data of the corresponding unprinted area is c0,
The color chart measuring method according to claim 1 or 2, wherein the color density D of each color chart region by the correction is calculated by D = -k * log (c1 / c0) . (Where k is the gain coefficient) Provided in a printing device that performs multi-color printing of multiple colors on printing paper,
Image color chart on printing paper with multiple color chart areas,
A color chart measuring device for measuring color chart information from image data obtained by imaging,
Transport means for transporting the printing paper in a state of sandwiching the leading end thereof;
An unprinted area is provided on the printing paper in the vicinity of the color chart area, and an imaging unit that reads an image including the color chart and the unprinted area in the vicinity of the color chart from the printing paper being conveyed; ,
Paper white correction means for calculating the color data of each color chart area from the obtained image data and the white data of the adjacent unprinted area, and correcting the color data with the corresponding white data;
It features and be Luke color chart measuring device Rukoto to have a.

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