JP2002127373A - Method and device for measuring color chart - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for measuring a color chart which make it possible to read the color chart with accuracy even when a printing paper to be conveyed flutters. SOLUTION: The present invention is a device for taking a photograph of a color chart on a printing paper having a plurality of color chart areas and measuring a color chart information from an image data rd obtained by taking a photograph of the color chart. The device includes an image pickup means 25 for reading out an image having the color chart and an unprinted area adjacent to the color chart from the printing paper during conveying, a calculating means 50 for calculating a color chart area and a white data of the unprinted area adjacent to the color chart area from the obtained image data rd and a paper whiteness correcting means 49 for correcting the color data based on corresponding white data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring a color chart for controlling ink density in offset printing or the like.

[0002]

2. Description of the Related Art In recent years, a plate making apparatus (printing plate recording apparatus) for forming an image on a printing plate based on digital image data,
Printing apparatuses incorporating a so-called CTP (Computer-To-Plate) apparatus in the machine have been put into practical use.
It is disclosed in Japanese Patent Publication No. 0-272756. Such printing devices are called digital printing machines,
Since prints can be obtained directly from image data, it is suitable for multi-product small-volume printing, which requires a short working time. In this digital printing machine, a plate making process and the like are automated so that even an unskilled person can easily handle them. However, further automation of ink supply control and the like in the printing process is desired.

In the ink supply control of the conventional printing apparatus, it is common to use a separate color stand for measuring the taken-out print sample on a table. In this case, an operator prepares an appropriate print sample. There is a problem that it is necessary to take out and measure the color of the printed matter.

[0004] To solve this problem, Japanese Patent No. 282
As disclosed in Japanese Patent No. 4334, there is disclosed a printing apparatus including means for capturing an image of a printed matter in the printing apparatus. According to this conventional technique, image data is obtained by imaging a printed matter on an impression cylinder of a printing apparatus, and an ink supply amount is controlled by comparing this image data with reference image data which is a reference of a printed matter which is a reference for control in advance. Like that.
According to this conventional technique, an image of a printed matter is captured in the printing apparatus, and therefore, there is an advantage that an operator does not need to intervene as in the case of using a light booth.

[0005]

However, in the above-mentioned prior art, since the image of the entire printed matter is read and compared with the reference image, there is a problem that the image data to be handled becomes large and it takes time to process the image data. . In addition, since the reference image must be prepared in advance, it is not suitable for an operation requiring an instantaneous power as in the above-described printing of a large number of small copies.

For this reason, the present applicant has considered a color chart measuring apparatus which prints a color chart on a printed material and measures the color chart in a printing apparatus. In this way, if a color chart is used, the image data handled becomes smaller,
There is also an advantage that it is not necessary to prepare a reference image in advance. However, the color chart arranged in the margin of the printed matter must be small in size, and it is difficult to accurately measure the color chart from the conveyed printing paper. In particular, if the printing press is a sheet-fed printing press, the printing paper is conveyed while nipping only the leading side. In general, since the color chart is provided on the rear end side of the printing paper, the flutter of the paper tends to increase near 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 flapping of the printing paper accompanying the conveyance.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a color chart measurement method capable of measuring a color chart with high accuracy even when the reading level of each part of the printing paper changes due to flapping of the printing paper during transportation. It is intended to provide a method and apparatus.

[0008]

According to the first aspect of the present invention, a color chart on a printing sheet having a plurality of color chart areas is imaged, and color chart information is measured from image data obtained by the imaging. A color chart measuring method, wherein color data corresponding to each color chart area is calculated from image data of each color chart area, and each color chart area is calculated from image data of an unprinted area adjacent to each color chart area. The color data of each color chart area is corrected based on the corresponding white data when calculating individual white data corresponding to each color chart area and calculating the color chart information from each color chart area. And

According to a second aspect of the present invention, there is provided the color chart measuring method according to the first aspect, wherein the color chart is imaged while the printing paper is conveyed.

According to a third aspect of the present invention, there is provided the color chart measuring method according to the second aspect, wherein the imaging is performed by an imaging unit including a plurality of imaging elements, and the imaging unit performs imaging of the color chart. The method is characterized in that a white reference object placed in a stationary state in advance is read before shading correction of image data of a captured image is performed.

According to a fourth aspect of the present invention, there is provided the color chart measuring method according to any one of the first to third aspects, wherein color data of each color chart area is c1, and white data of a corresponding unprinted area is c1. Assuming that c0, the color density D of each color chart area by the correction is D = −k * log
It is characterized by being calculated by (c1 / c0). (However, k is a gain coefficient)

According to a fifth aspect of the present invention, there is provided a printing apparatus for performing multi-color printing of a plurality of colors on a printing paper, wherein a color chart on the printing paper having a plurality of color chart areas is imaged, and the imaging is performed. A color chart measuring device that measures color chart information from the obtained image data, and an imaging unit that reads an image including a color chart and an unprinted area adjacent to the color chart from a printing paper being transported. Computing means for computing color data of each color chart area from the image data obtained, and white data of an adjacent unprinted area, and paper white correcting means for correcting the color data by corresponding white data. Features.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [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 the color chart according to the present invention. In FIG. 6A, an image im representing a printed material 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, it is assumed that the position of the image im on the printing paper S is positioned and arranged at a position separated by a predetermined grip amount f from the printing leading side (paper grip side), and the size of the image im (printing direction). If the size) is m and the width of the color chart cc is r, the color chart c
The area where c is located is “f + m from the top of the printing paper” to “f + m + r”. That is,
Generally, since the edge amount f and the width r of the color chart cc are constant values, the area where the color chart cc is arranged can be calculated based on the size m of the image im.

FIG. 6B is a diagram showing a specific example of the color chart cc. In the color chart cc, a plurality of color chart areas cr and reference marks rm1 to rm3 (generally referred to as rm) provided between the color chart areas cr are serially arranged along the printing width direction. It is a designed pattern. The color chart area cr is obtained by repeatedly arranging a halftone area or a solid area having a predetermined density for each color in a predetermined order. Therefore, by measuring the color chart area and calculating the solid density and the halftone percentage, and comparing them with predetermined values, it is possible to determine whether the ink supply amount is excessive or insufficient. The reference mark rm1
Are arranged point-symmetrically with respect to the reference mark rm1.

FIG. 6C is an enlarged view of the reference mark rm. In the present embodiment, the reference mark rm is a mark for positioning printed in one color of K color (black), and has 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 height of the center of the color chart area cr, and the print direction position of the color chart area cr can be specified. A paper white area hr (see FIG. 6B) serving as an unprinted area is provided above and adjacent to the color chart area cr, and the length of the bar b is determined by the width of the color chart area cr. And is set to include the paper white area hr. Therefore, if the detection range of the bar b in the printing direction, it can be determined that the range is the paper white region hr. In this embodiment, the reference mark rm1 is the color chart c
In the center of c, reference marks rm2 and rm3 are provided near the left and right ends.

[First Embodiment] An embodiment 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 a first and second plate cylinders 1 that hold a printing plate as a printing mechanism.
2, first and second blanket cylinders 3 and 4 for transferring ink images from respective plate cylinders, and impression cylinders 5 holding the printing paper and transferring the ink images from both blanket cylinders 3 and 4. And a feed cylinder 6 and a discharge cylinder 7 for supplying or discharging printing paper to and from the impression cylinder 5, and supplying dampening water or ink to the printing plates on the first and second plate cylinders 1 and 2, respectively. The apparatus includes a dampening solution supply unit 8 and an ink supply unit 9, a paper supply unit 10 that sequentially supplies stacked unprinted printing papers, and a paper discharge unit 11 that sequentially loads printed printing papers.

On the other hand, this printing apparatus has a plate making mechanism,
A printing plate supply unit 12 for supplying an unexposed printing plate to the first and second plate cylinders 1 and 2; an image recording unit 13 for recording an image on a printing plate on the plate cylinder; And a printing plate discharging unit 15 for discharging a used printing plate. The printing apparatus includes an imaging unit 16 that captures an image on a printed printing sheet, and an encoder unit 1 that detects a rotational position of the impression cylinder 5.
7 and a paper detection sensor 18 for detecting print paper fed from the paper feed unit 10.

Hereinafter, the details of each of the above components will be described.
The first plate cylinder 1 is driven by a plate cylinder driving mechanism (not shown) as shown in FIG.
Is configured to be movable between a first printing position indicated by a solid line and an image recording position indicated by a two-dot chain line, and the second plate cylinder 2 is similarly driven by a plate cylinder driving mechanism (not shown). It is configured to be movable between a second printing position indicated by one solid line and an image recording position indicated by a two-dot chain line.
That is, the first and second plate cylinders 1 and 2 are arranged at the first or second printing position when performing the printing operation, and are alternately arranged at the image recording position when performing the plate making operation. The plate making process of the printing plate is performed on each plate cylinder. Each of the first plate cylinder 1 and the second plate cylinder 2 has a peripheral surface capable of holding a printing plate for two colors, and fixes each printing plate at a position facing 180 degrees on the peripheral surface. (Not shown).

The first blanket cylinder 3 is configured to rotate in contact with the first plate cylinder 1 in the first printing position, and the second blanket cylinder 4 is similarly rotated in the first printing position. The second printing cylinder 2 is configured to rotate in contact with the second plate cylinder 2 at the printing position 2. The first and second blanket cylinders 3 and 4 have the same diameter as the first and second plate cylinders 1 and 2, and are used to transfer blankets capable of transferring ink images of two colors from each plate cylinder. It is mounted on the peripheral surface.

The impression cylinder 5 includes the first and second plate cylinders 1,
It has a diameter of 1/2 and is configured to rotate in contact with both the first and second blanket cylinders 3,4. The impression cylinder 5 is provided with a not-shown gripper capable of holding one printing sheet having a size corresponding to the printing plate. The holding means can be opened and closed at a predetermined timing by an opening / closing mechanism (not shown) to hold the front end of the printing paper. On the other hand, in this embodiment, the impression cylinder 5 is provided with encoder means 17 coaxially, whereby the rotational position of the impression cylinder 5 can be detected. Incidentally, such an encoder means 17 is generally provided to control 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.

The paper feed cylinder 6 and the paper discharge cylinder 7 have the same diameter as the impression cylinder 5 and are provided with not-shown grip means similar to the grip means provided on the impression cylinder 5. The gripping means of the paper feeding cylinder 6 and the paper discharging cylinder 7 are arranged so as to be able to transfer the printing paper in synchronization with the gripping means of the impression cylinder 5.

First and second plate cylinders 1 and 2 arranged at the first and second printing positions, first and second blanket cylinders 3 and 4, impression cylinder 5, and feed cylinder 6 and the paper discharge cylinder 7, each of the cylinders is provided with a drive gear (not shown) having the same size as the diameter of each cylinder at the cylinder end, and each gear meshes between the abutting cylinders. . Therefore, by driving this gear by a printing drive motor (not shown), the respective cylinders can be rotationally driven synchronously.

In the printing apparatus of the present embodiment, since the plate cylinders 1 and 2 and the blanket cylinders 3 and 4 have twice the circumference of the impression cylinder 5, the plate cylinders 1 and 2 and the blanket cylinder 3 The impression cylinder makes two rotations each time 4 makes one rotation. Accordingly, when the impression cylinder 5 rotates twice while holding the printing paper, multicolor printing of a total of four colors of two colors + two colors can be performed from the first and second plate cylinders 1 and 2.

Two sets of dampening solution supply means 8 are provided for each plate cylinder 1 and 2 at the first and second printing positions, respectively. On the other hand, a dampening solution can be supplied selectively. The dampening water supply means 8 includes a watercraft storing the dampening water, and a dampening water roller group that pumps up the dampening water in the watercraft and transfers it to the printing plate surface.
At least one of the dampening solution rollers that comes into contact with the printing plate surface is configured to come into contact with or separate from the plate cylinder surface by a cam mechanism (not shown). If the printing plate does not require dampening water, the dampening water supply means 8 is not required.

Two ink supply means 9 are provided for each of the plate cylinders 1 and 2 at the first and second printing positions, respectively. Ink of different colors can be supplied. The ink supply means 9 includes an ink fountain means capable of adjusting the ink ejection amount for each of a plurality of regions in the printing width direction, and a plurality of inks kneaded from the ink fountain means and supplied to the printing plate surface. Of the ink rollers, at least the roller that contacts the printing plate surface is configured to contact or separate from the plate cylinder surface by a cam mechanism (not shown). For the ink of each ink supply means 9, for example, K (black) and M (magenta) ink supply means 8 are arranged for the first plate cylinder 1, and are supplied to the second plate cylinder 2. In addition, C (cyan) and Y (yellow) ink supply means 8 are arranged. In addition,
Some of the dampening solution supply means 8 and the ink supply means 9 are configured so as to be able to be evacuated from their movement paths as the first and second plate cylinders 1 and 2 move.

The paper feed unit 10 takes out print paper one by one from a pile of unused print paper and transfers it to the paper feed cylinder 6. In this embodiment, the paper feed cylinder rotates twice. It operates to supply the printing paper once every time. The paper supply 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 pick-up, but in the present embodiment, the pressure is determined according to the detection result of the paper detection sensor 18. It can be determined whether the printing paper is fed to the cylinder 5 or the paper feeding cylinder 6 or not. On the other hand, the paper discharge unit 1
Reference numeral 1 denotes a printer that receives printed paper from the paper discharge cylinder 7 and stacks it. The details of the paper discharge unit 11 will be described later together with the configuration of the imaging unit 16.

Next, the plate making mechanism of the printing apparatus will be described. In this printing apparatus, when performing a plate making operation, the first and second plate cylinders 1 and 2 are alternately moved to an image recording position. At this image recording position, a friction roller (not shown) is configured to be in contact with the plate cylinder to rotate.

The printing plate supply unit 12 includes a cassette roll for storing the unexposed printing plate in a light-shielded state, a transport roller and a transport guide for transporting the drawn printing plate to the plate cylinders 1 and 2, and the printing plate. Cutting means for cutting the sheet into a sheet shape. In this embodiment, a silver salt sensitive material is used as a printing plate, and an image is recorded by a laser beam. The printing plate supply operation procedure is as follows. First, the leading end of the printing plate pulled out from the cassette roll is clamped by gripping means (not shown) of the plate cylinders 1 and 2, and the plate cylinders 1 and 2 are rotated in this state to perform printing. The plate is wound on plate cylinders 1 and 2,
Thereafter, the printing plate is cut at a predetermined length, and the rear end of the printing plate is held by the other holding means.

The image recording section 13 turns on / off the laser light.
Exposure is performed on the printing plate by f to record the image im and the color chart cc. In this embodiment, a laser beam emitted from a laser source (not shown) is main-scanned in 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. The sub-scanning is configured.
The scanning method may be such that a plurality of laser beams are provided side by side in the plate cylinder axis direction and the main scanning is performed in accordance with the rotation of the plate cylinder. Further, the printing plate and the image recording section 13 may be not only those that record images by exposure, but also those that record images by heat or electric discharge machining.

The developing section 14 develops the printing plate exposed by the image recording section 13. In this embodiment, the developing unit 14 has a configuration in which a processing liquid stored in a processing tank (not shown) is pumped up by an application roller and applied to a printing plate to perform a developing process. And a lifting means (not shown) which moves to a position close to the plate cylinder. If an image recording method that does not require a developing process is adopted, the developing unit 14 may be omitted.

In this printing apparatus, the first and second plate cylinders 1 and 2 are moved to an image recording position, and a plate making operation is performed by supplying a printing plate and recording and developing an image. When the plate making operation is completed, the first and second plate cylinders 1 and 2 are moved to the first position.
And a printing operation can be performed by arranging them at the second printing position.

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 separating unit that separates the printing plate from the plate cylinder at the image recording position, a conveying unit that conveys the separated printing plate, and a conveyed used printing plate. And a discharge cassette for discharging the paper.

Next, the imaging unit 1 according to the present invention will be described with reference to FIG.
6 and the configuration of the paper discharge unit 11 will be described. In addition,
FIG. 2 is a schematic side view of the vicinity of the paper discharge unit 11. First, a paper discharge unit 11 is wound around the paper discharge cylinder 7 and two gears 7 ′ (approximately vertically arranged on the paper surface of FIG. 2) having substantially the same diameter as the paper discharge cylinder 7. Endless chain 20, a plurality of grippers 21 transported by these two chains and transporting the printing paper S, and these grippers 21
Tray 2 for stacking the printing paper S transported by the printer
Consists of two.

At both ends of the paper discharge cylinder 7, gears (not shown) for engaging with the chains 20 are provided, and two gears 7 'having substantially the same diameter are arranged opposite to the gears. Have been. An endless chain 20 is looped around the gear portion of the paper discharge cylinder 7 and the gear 7 '. The length of the chain 20 is set to a length that is an integral multiple of the circumference of the paper discharge cylinder 7.

The holding means 21 has an openable / closable claw member for holding the leading end of the printing paper S.
1 is fixed between the two chains. The arrangement interval of the holding means 21 on the chain 20 corresponds to the circumferential length of the paper discharge cylinder 7. On the other hand, each holding 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).
The printing paper S is conveyed with the rotation of the chain 20 and discharged on the paper discharge table 22.

The paper discharge tray 22 is a pallet-like member on which a plurality of printing papers S can be loaded, and is moved up and down by a lifting means (not shown). That is, as the print sheet S is discharged, the discharge table 32 is sequentially lowered, so that the discharge height of the print sheet S is constant, and the discharge operation of the print sheet S can be performed smoothly.

In the paper discharge section 11, the leading end of the printing paper S is conveyed while being clamped by the gripping means 21, so that the rear end of the printing paper S is carried in an unfixed state. For this reason, the printing paper S flaps with the conveyance. In the present embodiment, in order to suppress the fluttering of the printing paper S, a suction roller 23 for stabilizing the transport state of the printing paper S is provided on the front side of the paper discharge tray 22.

The suction roller 23 has many fine suction holes on its surface, and is connected to a vacuum pump (not shown). The suction roller 23 has a gripper 21 whose roller axis extends between the two chains 20.
, And the roller is positioned such that the top of the roller is positioned at substantially the same height as the position below the chain 20. In addition, the suction roller 23 is configured to be driven to rotate in accordance with the passage speed of the grip means 21 or to be rotatable only. Accordingly, when the printing paper S passes over the suction roller 23, the printing paper S is conveyed while being sucked on the surface of the suction roller 23.
The printing paper S does not flutter in the upper part of FIG. Instead of the suction roller 23, a suction plate member that sucks the printing paper S in a planar manner may be employed.

The image pickup section 16 includes an illuminating means 24 for illuminating the printing paper being conveyed, and an imaging means 25 for picking up an image on the illuminated printing paper to obtain image data. The illuminating means 24 is arranged along the suction roller 23 and includes a plurality of linear light sources for illuminating the printing paper S on the suction roller 23. The illuminating means 24 is provided between the vertical movement of the chain 20. Note that a slit for imaging is formed in the center of the light source.

The imaging means 25 includes a housing 26 for shielding light and dust, 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 illuminating means 24. The incident light of the image turned back by the mirror 27 passes through the lens 28 and passes through the CCD line sensor. The light is received at 29.
The CCD line sensor reads an image corresponding to three colors of RGB. In this embodiment, the image on the printing paper is read sequentially line by line as the printing paper is transported.

In this embodiment, the imaging means 2
Reference numeral 5 denotes two images 5 arranged side by side in the direction perpendicular to the paper surface of FIG. 2 so that an image in the width direction of the printing paper S is divided into two and captured. This configuration will be described with reference to FIG. FIG. 5 is an explanatory diagram showing a state in which two imaging units 25 are provided side by side along the print width direction. As shown in FIG. 5, the two image pickup units 25R and 25L are arranged so as to divide the color chart cc in the print width direction to pick up an image, respectively.
It is incorporated so that the reading directions of the CD line sensor 29 match. In addition, the imaging areas of the imaging units 25R and 25L partially overlap each other at the center. The reference mark rm1 is arranged so as to be located in the overlapping area. According to this embodiment, the position of the read image data read by the two imaging units 25R and 25L can be adjusted by the reference mark rm1.

On the other hand, the reference marks rm2 and rm3 are provided near the left and right ends of the printing paper.
In R, the reference marks rm1 and rm2 can be imaged, and in the imaging means 25L, the reference marks rm1 and RM3 can be captured.
Can be imaged. Thus, each imaging means 25R,
Since two reference marks rm are imaged in 25L, the inclination amount of the color chart cc can be obtained by detecting the positions of the respective reference marks rm1 to rm3.
That is, when the color chart cc on the printing paper is printed with an inclination or when the conveyance of the printing paper is inclined, the image of the color chart cc in the read image data is also inclined. Even if the reference mark rm
The inclination can be corrected by detecting the positions of 1 to rm3.

Considering the inclination correction as described above,
It is desirable that the positions of the reference marks rm2 and rm3 be located as close to the width of the printing paper S as possible. In the present embodiment, the printing paper S having the minimum width that can be used for the printing apparatus is used.
The position is set according to min. In this case, there is an advantage that a constant color chart cc may be always formed regardless of the size of the printing paper S.

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 block diagram in a functional configuration. As shown in the block diagram of FIG. 3, the printing apparatus includes a control terminal 3 for editing image data and instructing a printing operation to the printing apparatus.
0, a print control unit 31 for controlling each unit of the printing apparatus
And each is connected by a LAN or the like.

The control terminal 30 includes 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. This is a computer system provided outside the printing apparatus main 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.

The print control unit 31 is a computer system including a CPU board and the like provided inside the printing apparatus main body, and controls each section of the printing apparatus via various I / Fs. The color chart measurement control unit 32 for processing the read image data picked up by the image pickup unit 25 and measuring the color chart is constituted by a separate substrate from the print control unit 31. 31. This color chart measurement control unit 32 is also C
A computer system including a PU board and the like, which is configured to receive detection signals from the encoder unit 17 and the paper detection sensor 18 in addition to the connection with the imaging unit 25.

Next, the configuration of the control section 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 (hereinafter referred to as color chart data cd) representing a color chart cc prepared in advance, and stores the stored color chart data cd in print image data. a color chart adding unit 41 for adding the color chart data cd to the print image data pd to which the color chart data cd is added;
ster-image-processing) and perform binary image data pd
And a RIP processing unit 42 for generating the second RIP. In the present embodiment, the color chart adding means 41 determines a predetermined arrangement condition, for example,
Is added automatically to the position following the rear end of the color chart cc, but 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.

On the other hand, the control terminal 30 transmits the color chart c
The color chart arrangement position calculating means 43 for calculating the position to which c is added is also provided. The color chart arrangement position calculating means 43 determines that the arrangement condition is “color chart c
c is added to the position following the trailing edge of the print image im, the predetermined edge amount f and the image size m of the print image data pd are added, and the color chart cc on the print paper S is added. The position can be calculated. 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 position of the color chart is sent to the color chart measurement controller 32 via the print controller 31 as color chart position data id. When the operator places the color chart cc at an arbitrary position, the calculation may be performed based on the relative position of the color chart cc to the print image data pd.

Next, the color chart measurement control section 32 includes a reading period setting means 44 for setting a reading area of the imaging means 25 based on the color chart position data id,
A read image data storage unit 45 for storing read image data rd read by the imaging unit 25;
A reference mark detecting means 46 for detecting the position of the reference mark rm from the color chart; a color chart actual position calculating means 47 for calculating the actual position of each color chart area cr based on the detected position of the reference mark rm; Read image data reading means 48 for reading image data, paper white correction means 49 for performing correction based on the white reference of printing paper based on the read image data, and each color chart area c
a color chart information calculating means 50 for calculating color chart information such as the color density and halftone percentage of r.

The reading period setting means 44 images the reading area including the color chart cc on the printing paper S based on the color chart position data id, the encoder signal of the encoder means 17 and the paper detection signal of the paper detection sensor 18. The reading period is set so that 25 reads. here,
First, by counting the encoder signal of the encoder 17, it is possible to know where the printing paper S is located in the paper discharge unit 11. Therefore, the reading period setting means 44
The timing at which the reading area including the color chart cc defined by the color chart position data id is at the reading position of the imaging means 25 is determined from the count of the encoder signal, and the reading start and end commands are issued to the imaging means 25. .

However, since the printing apparatus feeds and discharges the printing paper every two rotations of the impression cylinder 5, the printing paper is actually conveyed only once every two rotations. Accordingly, in the present embodiment, control is performed such that imaging is performed only when the printing paper S is being conveyed below the imaging unit 25 in accordance with a paper detection signal from the paper detection sensor 18. Actually, the measurement of the color chart is performed every predetermined number of samplings. As described above, the reading period setting unit 44 performs the rotation of the impression cylinder when the printing paper S is determined to be the time when the printing paper S passes below the imaging unit 25 based on the paper detection signal.
This is for predicting the transport position of the printing paper according to the rotational position of the impression cylinder 5 and instructing the image pickup unit 25 to read the image. The reading area of the image pickup means 25 is set to be larger than the width of the color chart cc so that there is no problem even if a slight displacement occurs.

The imaging unit 25 reads an image on the printing paper S in response to a command from the reading period setting unit 44, 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 is composed of two sets of memories respectively corresponding to the image pickup means 25R and 25L, and the read image data r read by the image pickup means 25L.
d is stored in reverse from the back of the memory at the time of storage.
This makes it possible to read out the read image data obtained from the imaging units 25R and 25L in the same procedure. In the above description, when storing the read image data rd, one is stored from the back of the memory.
9 may be arranged with the reading direction reversed.

The reference mark detecting means 46 detects the reference mark rm from the stored read image data rd by image processing. First, a pixel array 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 array pattern in the direction A at the center of the cross mark d in FIG. In this example, for simplicity, the width of the bar b is represented by 3 pixels in black, the space between the bar b and the horizontal line of the cross mark d is represented by 2 white pixels, and the horizontal line of the cross mark d is represented by 5 black pixels. I have. The reference mark detecting means 46
Checks whether or not the pixel array pattern of FIG. 6D is included in the read image data on the memory by shifting one pixel at a time. Such a method is individually performed in the orthogonal XY directions on the memory storing the read image data rd. Then, a position where the pixel array pattern exists is plotted in a histogram for each of XY, and a position having the highest histogram can be set as a position of the reference mark rm. Note that this method is an example of pattern recognition, and another method may be adopted as long as the position of the reference mark rm can be determined.

The color chart actual position calculating means 47
First, the distance between the two detected reference marks rm is calculated from the positions of the two marks. This gives the color chart cc
Can be detected. FIG. 7 is an explanatory view for explaining the inclination correction of the color chart cc. In this example, the distance between the two reference marks rm1 and rm2 in the Y direction (displacement in the printing direction) is h, and the distance in the X direction (in the printing width direction). Distance) is w, and the distance between the reference marks rm1 and rm2 that are known in advance is L. Here, 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 reference.
The position of x · w / L in the X direction and x · h / L in the Y direction is the real position in the read image data rd. As described above, at least two reference marks r
By reading m, the inclination of the color chart cc can be corrected.

The read image data reading means 48 reads the read image data in the memory corresponding to the actual position. Here, the corresponding color chart area cr is used.
And the image data of the paper white area hr immediately above it. The reading of the image data is performed in a predetermined small-sized area. This is performed by specifying a predetermined address space on the memory. Therefore, in the present embodiment, this is dealt with by performing an address operation based on the tilt correction on a predetermined read address. For example, in the case of the above-mentioned example, x.w / L with respect to an X-direction address with respect to a predetermined read address
, And x · h / L may be added to the Y-direction address. Note that the range of the actual position of the paper white area hr is determined by the bars b constituting the reference marks rm.
The position in the printing width direction of the paper white region hr is the same position as the corresponding color chart region cr, and the position in the printing direction can be set to a predetermined line position within the detection range of the bar b. .

The paper white correction means 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. For example, if the color data is C1, the white data is C0, and the desired color density is D,
D = −k · log (C1 / C0) (Where k is a gain coefficient) In this embodiment, a paper white area h adjacent to each color chart area is provided.
Since white data serving as a white reference is obtained from r, there is an advantage that appropriate colorimetry can be performed even if the imaging level changes in various places on the printing paper due to, for example, flapping or floating of the printing paper.

The color chart information calculating means 50 calculates color chart information of the color chart area cr, for example, halftone percentage in addition to the color density D. Further, based on the obtained color density D, it may be converted into the ink density of YMCK or, if necessary, into the opening degree of the ink key of the ink fountain means.

The color chart information of the color chart thus obtained is used for adjusting the supply amounts of ink and dampening water. That is, the color chart measurement control unit 32
Alternatively, 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 insufficient, and controls an appropriate supply amount of ink or dampening water. To do.

Next, the operation of the printing apparatus according to the present embodiment will be described with reference to the flowchart of FIG. FIG. 8A is a flowchart showing the entire process of the printing operation, and FIG. 8B is a flowchart showing the color chart measuring process. First, in FIG. 8A, in the printing operation process, various settings are made in step S1. For example, there are designation of print image data pd to be used and setting of the number of prints. The 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 to which the color chart cd has been added is subjected to RIP processing to obtain image data pd2.
Is generated. The generation of the image data pd2 may be performed in real time in accordance with the exposure of the printing plate.

In the next step S2, an image is formed on the printing plate. First, one of the plate cylinders 1 and 2 is moved to an image recording position, and an unexposed printing plate is mounted. Then, the image is exposed based on the image data pd2. After the completion of the exposure, the developing unit 14 performs a developing process. This plate making process is performed alternately by each of the plate cylinders 1 and 2. In step 3, a printing operation is performed based on the printing plate that has been made. That is, fountain solution is supplied to the printing plates on the plate cylinders 1 and 2, and then ink of a color corresponding to each plate is supplied. The ink images on this printing plate were blanket cylinders 3, 4
Is transferred to the printing paper fed to the impression cylinder 5.

In step S4, it is determined whether or not the number of printed sheets has reached a desired amount. If the number has been reached, this operation is terminated.
If not achieved, every predetermined number of samples,
The color chart measurement in step S5 is performed. This color chart measurement will be described later using the flow of FIG.
In step S6, the supply amounts of ink and dampening water are adjusted based on the color chart information obtained in the measurement in step S5, and the process returns to step S3.

Next, the steps of color chart measurement according to the present invention will be described. In FIG. 8B, first, in step P1, a 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, at the start of the reading period, the imaging units 25R and 25L start reading. In step P3, the imaging means is 25R,
It is determined which one of 25L is used, and if the imaging means is 25R, the process proceeds to Step P4, and if it is 25L, the process proceeds to Step P5. In this step P4, the read image data rd is stored in the memory of the read image data storage means 45 in the forward direction. In step P5, the read image data r is stored in the memory of the read image data storage means 45 in the reverse direction.
d is stored.

When the storage of the read image data rd is completed, in step P6, the read image data rd in each memory is read.
Is processed to detect the reference mark rm. In the next step P7, the distance between the detected reference marks rm is calculated, and the amount of inclination 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 from which the image data in the memory is read is corrected.

In step P9, the image data of 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 the color density of the color chart area cr is corrected accordingly. Then, in step P11, the calculation of the color chart information is performed. In Step P12, it is determined whether there is a next color chart area cr to be measured.
Here, if the color chart region cr to be measured still remains, the process returns to Step P8 to repeat the measurement.

In the printing apparatus according to the first embodiment, the area including the color chart is read from the printing paper being conveyed to measure the color chart information, so that the apparatus can be made compact. There is an advantage that less image data needs to be handled. In particular, if the printing apparatus is provided with a printing plate recording apparatus, the reading area can be set from the information on the position where the color chart is arranged. Can respond.

[Second Embodiment] In addition to the first embodiment, in the second embodiment, shading correction of the CCD line sensor 29 is further performed. In this embodiment, the following procedure is performed.

First, a white reference material prepared in advance is placed on the suction roller 23 in a stationary state. Alternatively, a white reference material may be formed on the surface of the suction roller 23. The stationary state is used to prevent a reading level difference due to flapping during conveyance. The stationary white reference object is read by the imaging unit 25, and each C is read.
White reference data W is obtained for each element of the CD line sensor 29. On the other hand, black reference data B (data corresponding to dark current of each element) B of each element is obtained in advance. This completes the preparation for performing shading correction. This preparation may be appropriately performed at the time of factory shipment, maintenance, or before work, and need not necessarily be performed in association with all operations.

In this state, when an image is actually read by the CCD line sensor 29,
The read data Sp of each element is as follows: Sp ′ = (Sp−B)
/ (WB) shading correction is performed. This data correction is performed, for example, at step P in FIG.
4. It may be performed before and after storing the captured image data in P5.

[Other Embodiments] (1) In the first embodiment, the image pickup means 25 is provided in the paper discharge unit 11 where the print paper S is discharged and conveyed, but the impression cylinder 5 and the paper discharge cylinder 7 It may be arranged to read the printing paper S conveyed above.

(2) In the first embodiment, the control terminal 3
Although the color chart data cd is added by 0, the RIP-processed color chart data may be added to the print image data that has been RIP-processed in advance by the print control unit 31 or the like.

(3) In the first embodiment, the imaging means 2
Although two are arranged side by side, one or three or more may be arranged.

(4) In the first embodiment, the color chart cc is arranged at the rear end of the image im, but may be arranged at the top. Further, the color chart cc may not be arranged at a position immediately after the image im, but may be arranged at a position separated by a predetermined distance or at a fixed position on printing paper.

[0073]

According to the first, fourth, and fifth aspects of the present invention, it is possible to perform paper white correction using image data of an unprinted area corresponding to each color chart area. It is possible to correct a difference in the reading level due to the lifting or the like.

According to the second aspect of the present invention, it is particularly suitable for the case where the color chart is measured while the printing paper is being conveyed.

According to the third aspect of the invention, 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 showing 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.

FIG. 4 is a functional block diagram functionally showing the block diagram of FIG. 3;

FIG. 5 is an explanatory diagram showing 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 tilt correction of a tilted color chart.

FIG. 8 is a flowchart illustrating an operation of the printing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st printing cylinder 2 2nd printing cylinder 3 1st blanket cylinder 4 2nd blanket cylinder 5 Impression cylinder 6 Paper supply cylinder 7 Discharge cylinder 9 Ink supply means 11 Discharge part 13 Image recording part 17 Encoder means REFERENCE SIGNS LIST 18 paper detection sensor 22 paper ejection tray 23 suction roller 25 imaging means 29 CCD line sensor 30 control terminal 31 print control unit 32 color chart measurement control unit 40 color chart data storage unit 41 color chart data addition unit 42 RIP processing unit 43 color chart Arrangement position calculating means 44 Reading period setting means 45 Read image data storage means 46 Reference mark detecting means 47 Color chart actual position calculating means 48 Read image data reading means 49 Paper white correction means 50 Color chart information calculating means S Printing paper im Image m Image size f Amount of mouth cc Color char cr color chart area hr paper white areas rm reference mark b bar (reference mark) d cross marks (reference marks) cd color chart data id color chart position data pd print image data pd2 2 binarized print image data rd read image data

Claims (5)

[Claims] 1. A color chart measuring method for imaging a color chart on a printing sheet having a plurality of color chart areas and measuring color chart information from image data obtained by the imaging, comprising: The color data corresponding to each color chart area is calculated from the image data, and the individual white data corresponding to each color chart area is calculated from the image data of the unprinted area adjacent to each color chart area, When calculating color chart information from each color chart area, a color chart measurement method is characterized in that color data of each color chart area is corrected based on corresponding white data. 2. A color chart measuring method, wherein a color chart is imaged while the printing paper is conveyed. 3. The image pickup is performed by an image pickup unit including a plurality of image pickup devices, and the image pickup unit reads an image obtained by reading a white reference object arranged in a stationary state before image pickup of a color chart. 3. The color chart measurement method according to claim 2, wherein data shading correction is performed. 4. The color data of each color chart area is represented by c
1. Assuming that the white data of the corresponding unprinted area is c0, the color density D of each color chart area by the above correction is D =
4. The color chart measurement method according to claim 1, wherein the calculation is performed by -k * log (c1 / c0). (However, k is a gain coefficient) 5. A printing apparatus provided in a printing apparatus for performing multi-color printing of a plurality of colors on printing paper, picking up an image of a color chart on the printing paper provided with a plurality of color chart areas, and performing color printing from image data obtained by the shooting A color chart measuring device for measuring chart information, comprising: an imaging unit that reads an image including a color chart and an unprinted area adjacent to the color chart from a printing paper being transported; and each color chart from the obtained image data. A color chart measuring device comprising: an arithmetic unit for calculating color data of an area and white data of an adjacent unprinted area; and a paper white correction unit for correcting the color data by corresponding white data. .