JP2003004533A - Colorimetric method and device for printed material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a colorimetric device capable of measuring colors of a printed image more precisely than by the conventional colorimetric device. SOLUTION: A colorimetric device 20 comprises a camera 24 for photographing a printed image of a printed material, a display monitor 30, and a control device 28 for receiving the printed image from the camera 24 and producing the printed image on the display monitor 30. The control device 28 calculates the RGB-to-XYZ conversion matrix and the RGB-to-Lab conversion matrix, and determines the color differences between the Lab values in an inspection region and reference values.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color measuring method and a color measuring device for printed matter.

[0002]

2. Description of the Related Art As an apparatus for measuring the color of a printed image of a printed matter, an online method for inputting the printed image from the printed matter fed at a constant speed and measuring the color of the printed image, and a static state of the printed matter There is an offline method in which a print image is input and the color of the print image is measured.

The off-line system includes a color difference meter based on a stimulus value direct reading system equipped with an XYZ sensor and a spectrocolorimeter based on a spectroscopic colorimetry system equipped with a spectroscopic sensor.

In these off-line type color measuring devices,
Highly accurate color measurement is possible, but there is a drawback that the color measurement speed is low. Therefore, at present, an on-line type color measuring device capable of performing high-speed color measurement is generally used.

As an example of such an on-line type color measuring device, a color measuring device disclosed in Japanese Patent Laid-Open No. 7-203476 is shown in FIG.

An RGB analog signal of a print image of a printed matter picked up by the color camera 1 is transmitted to the Lab conversion circuit 2 and converted into a digital value corresponding to the Lab value in the Lab conversion circuit 2.

The color difference calculation circuit 6 calculates a color difference ΔE from the Lab value converted by the Lab conversion circuit 2 and the L ₀ a ₀ b ₀ value of the reference color output from the reference color registration operation control unit 10. Output.

The color difference ΔE is calculated according to the following equation (1).

[0009] _{ΔE = ((L-L 0} ) 2 + (a-a 0) 2 + (b-b 0) 2) 1/2 (1) color difference Delta] E calculated by the arithmetic circuit 6 gradation conversion circuit 7
The gradation is converted by.

Next, the digital-analog conversion circuit 8
Thus, the digital signal from the gradation conversion circuit 7 is converted into an analog signal.

The first image synthesizing circuit 9 synthesizes the analog signal from the digital-analog converting circuit 8 and the synchronizing signal included in the video signal from the color camera 1 and outputs it as a monochromatic image signal to the monochromatic image processing device 15. To do.

In this color measuring device, the reference color is registered
(1) area designating means for designating a desired area on a monitor screen displaying a captured image, (2) registration period designating means for designating a period for registering a reference color, or
(3) In the area designated by the area designating means, either the color range of the video signal included in the period designated by the registration period designating means, or the color range already stored in the color range storing means. This is performed using a color range storage unit that newly stores the colors included in the range as a reference color range.

More specifically, the video signal from the color camera 1 is combined with the output of the window generating circuit 11 in the second image combining circuit 14, and the monitor TV 16 displays it.
The original image and window are displayed. The user operates the cursor button 13 while watching the image on the monitor TV 16 to move the window to a desired area on the screen and specify an area for which the reference color is to be set.

Next, when the user presses the registration button 1, the range of all colors Lab included in the period in which the registration button 1 is pressed in the area set by the window is instructed by the reference color registration operation control unit 10. Are stored in the reference L memory 3, the reference a memory 4, and the reference b memory 5, respectively. When the registration button 1 is released, the reference color registration operation control unit 10
Reads the contents of each of the memories 3, 4, 5, and L, a, b
The median value of each range is calculated and output to the color difference calculation circuit 6 as reference color data.

[0015]

In the above-described color measuring device, the Lab conversion circuit 2 converts the RGB value of the video signal transmitted from the color camera 1 into the Lab value according to the following equation (2). Done.

[0016]

[Table 1]

That is, the conversion of the RGB value of the video signal transmitted from the color camera 1 into the Lab value is performed via the conversion matrix X.

However, in the conventional colorimetric device, since the conversion matrix X has a fixed value, it is not always possible to accurately obtain the change in the color difference corresponding to the actual change in the color. The conventional color measurement device has a problem that the color of printed matter cannot be managed with high accuracy.

The present invention has been made in view of the above problems, and is a colorimetric apparatus and a colorimetric apparatus capable of colorimetrically measuring a printed image of a printed matter with higher accuracy than a conventional colorimetric apparatus. An object of the present invention is to provide a method and a program for operating a color measuring device.

[0020]

In order to achieve this object, the present invention provides a process of obtaining RGB average values in a predetermined inspection area of a printed matter having a pattern that changes periodically.
A process of aligning a predetermined area of the pattern, a process of normalizing the color of white as a reference, a process of obtaining an RGB average value of the predetermined area, and integrating data for a plurality of visual fields,
A colorimetric method for a printed matter is provided, which comprises a step of obtaining RGB values in a predetermined area.

In the present invention, a first step of inputting a print image of a printed matter on a display monitor, a second step of designating a part of the print image as a measurement range, and a measurement range of the print image in the measurement range. A third step of obtaining an RGB average value and a field having an RGB value closest to the RGB average value from a database in which a plurality of fields having an RGB value, a Lab value and an XYZ value as a set are stored in advance. And a fifth step of extracting N fields (N is a positive integer of 1 or more) having a Lab value closest to the Lab value of the field extracted in the fourth step. And a linear multiple regression analysis from the RGB value and the XYZ value of the field extracted in the fourth step and the N fields extracted in the fifth step. A sixth step of calculating a first matrix for converting RGB values into XYZ values, and the field extracted in the fourth step and the fifth step using the first matrix as an initial matrix. A seventh step of calculating a second matrix for converting RGB values into Lab values by nonlinear multiple regression analysis from the RGB values and Lab values of the selected N fields; the second matrix, and the RGB average value; From the first L in the measurement range of the printed image
An eighth step of calculating an ab value, a ninth step of designating a part of the print image in a range other than the measurement range as an inspection range, and an RGB average value in the inspection range of the print image are obtained. The tenth step and the second step
Eleventh step of calculating the Lab value of the inspection range of the printed matter and the twelfth step of calculating the difference between the Lab value of the inspection range of the printed matter and the first Lab value as a color difference by the matrix of And a colorimetric method for printed matter.

The colorimetric method further includes a step of capturing a white plate together with the print image when capturing the print image, and normalizing the RGB values of the print image with the white color of the white plate as a reference. It is preferable to provide.

This colorimetric method preferably further comprises a step of issuing an alarm when the color difference exceeds a threshold value.

In this colorimetric method, when the color difference exceeds the threshold value, the color difference is calculated according to the difference between the color difference and the threshold value.
Preferably, the method further comprises the step of adjusting the amount of ink for forming the printed image.

Further, according to the present invention, a printed matter comprising a camera for picking up a printed image of the printed matter, a display monitor, and a control device for receiving the printed image from the camera and displaying the printed image on the display monitor. In the colorimetric device, the control device obtains an RGB average value in a predetermined inspection region of a printed matter having a pattern that periodically changes, aligns the predetermined region of the pattern, and a white color as a reference. The present invention provides a colorimetric apparatus for printed matter, which is to normalize the above, obtain the RGB average value of the predetermined area, integrate the data for a plurality of visual fields, and obtain the RGB value of the predetermined area.

Also, the present invention is a printed matter comprising a camera for picking up a printed image of the printed matter, a display monitor, and a control device for receiving the printed image from the camera and displaying the printed image on the display monitor. In the color measurement device, the control device obtains an RGB average value in a part of the print image designated as a measurement range,
A field having an RGB value closest to the RGB average value is extracted from a database in which a plurality of fields each having a value, a Lab value, and an XYZ value as a set are stored in advance, and the field is closest to the Lab value of the field. La
N fields (where N is a positive integer of 1 or more) having b values are extracted, and RGB values are XY by linear multiple regression analysis from the RGB values and XYZ values of the (N + 1) fields.
A first matrix to be converted into a Z value is calculated, and the RG of the (N + 1) fields is defined by using the first matrix as an initial matrix.
A second matrix for converting RGB values into Lab values is calculated from the B value and the Lab value by non-linear multiple regression analysis, and the first matrix in the measurement range of the print image is calculated from the second matrix and the RGB average value. A Lab value is calculated, an RGB average value in a portion of the print image designated as an inspection range is calculated, and a Lab value of the inspection range of the printed matter is calculated by the second matrix, and the inspection range of the printed matter is calculated. To provide a colorimetric apparatus for a printed matter, which calculates the difference between the Lab value of the above and the first Lab value as a color difference.

The colorimetric device further includes a white plate that is imaged together with the print image when the print image is captured, and the control device uses the white color of the captured white plate as a reference. It is preferable to normalize the RGB values of the printed image.

The colorimetric device further includes an alarm device for issuing an alarm. When the color difference exceeds a threshold value, the control device activates the alarm device to issue an alarm. It is preferable.

In this color measuring device, the control device is
The control device is connected to an ink amount adjustment mechanism that adjusts the amount of ink for forming the print image, and the control device, when the color difference exceeds a threshold value, the color difference and the threshold value. It is preferable to control the ink amount adjusting mechanism to adjust the amount of ink according to the difference.

Further, the present invention is a printed matter comprising a camera for picking up a printed image of the printed matter, a display monitor, and a control device for receiving the printed image from the camera and displaying the printed image on the display monitor. A program for operating the control device in a color measuring device, comprising: a process for obtaining, in the control device, an RGB average value in a predetermined inspection region of a printed matter having a pattern that periodically changes, and a predetermined region of the pattern. The process of aligning
A program for executing a process of normalizing a color with a reference white color to obtain an RGB average value of the predetermined region and a process of integrating data for a plurality of visual fields to obtain an RGB value of the predetermined region. I will provide a.

The present invention also provides a printed matter comprising a camera for picking up a printed image of the printed matter, a display monitor, and a control device for receiving the printed image from the camera and displaying the printed image on the display monitor. A program for operating the control device in the color measuring device,
A step of obtaining an RGB average value in a part of the print image designated as a measurement range by the control device;
A process of extracting a field having an RGB value closest to the RGB average value from a database in which a plurality of fields each having a B value, a Lab value, and an XYZ value as a set are stored, and a Lab value of the field. N having the Lab value closest to (N is a positive integer of 1 or more)
Of the fields, the step of calculating a first matrix for converting RGB values into XYZ values by linear multiple regression analysis from the RGB values and XYZ values of the (N + 1) fields, and the first matrix As an initial matrix,
+1) converting RGB values into Lab values from the RGB values and Lab values of the 1 field by non-linear multiple regression analysis
Of the matrix, the second matrix and the RGB
The first in the measurement range of the printed image from the average value
Lab value of the printed image, a step of obtaining an RGB average value in a portion of the print image designated as an inspection range, and a step of calculating the Lab value of the inspection range of the printed matter by the second matrix. And a step of calculating a difference between a Lab value in the inspection range of the printed matter and the first Lab value as a color difference.

[0032]

1 is a block diagram of a colorimetric device 20 according to an embodiment of the present invention.

The colorimetric apparatus 20 according to this embodiment includes a color camera 24 for picking up a print image of a printed matter 22 fed at a constant speed in the horizontal direction, and a length measuring encoder 26 for measuring the length of the printed matter 22. And the color camera 24
Controller 28 for receiving the video signal of the print image from the printer and the trigger signal from the encoder 26 for length measurement, the display monitor 30 for displaying the video signal sent from the controller 28, and the alarm transmission signal from the controller 28. And an alarm device 32 for issuing an alarm when receiving.

As the color camera 24, either an area sensor camera or a line sensor camera can be used.

A printing device 70 for printing an image on the printed matter 22 is arranged upstream of the length measuring encoder 26. The printing sheet 72 conveyed from the roll 71 passes through the four impression cylinders 73a, 73b, 73c and 73d. Each of the impression cylinders 73a, 73b, 73c, 73d has a plate cylinder 7
4a, 74b, 74c, 74d are in contact with each other and are rotating, and part of each of the plate cylinders 74a, 74b, 74c, 74d is filled with ink.
It is adapted to be immersed in the ink container 36, the third ink container 38, and the fourth ink container 40. These first to fourth ink containers 34, 36, 38 and 40 are respectively the first to fourth ink valves 34a and 34a, which serve as ink amount adjusting mechanisms.
After the ink amount is adjusted in 36a, 38a, 40a, each ink tank 75a, 75b, 75c, 75
A predetermined amount of ink is supplied from d.

For example, in the first ink container 34, cyan,
The second ink container 36 is magenta, and the third ink container 38 is
Is filled with yellow ink, and the fourth ink container 40 is filled with black ink.

The control device 28 includes a central processing unit 42, a first memory 44, a second memory 46, and a third memory 48.
The fourth memory 50, the fifth memory 52, the sixth memory 54, the seventh memory 56, the eighth memory 58, the ninth memory 60, and the tenth memory 62.

The first memory 44, the second memory 46, the third memory 48, the fourth memory 50, the fifth memory 52, the sixth memory 54, the seventh memory 56, the eighth memory 58, the ninth memory 60 and the tenth memory. Each of the memories 62 is a central processing unit 42.
It is connected to the.

A measurement database is stored in the first memory 44. This measurement database uses a camera to measure the R of each of the 100 reference samples in advance.
The GB value was measured, and the Lab of each sample was measured with a spectroscope.
Value and XYZ value are measured, RGB value of each sample, La
It is composed of 100 fields having a b value and an XYZ value as a set.

The central processing unit 42 receives a video signal from the color camera 24 and a trigger signal from the length measuring encoder 26.

Further, the central processing unit 42 transmits a video signal to the display monitor 30 and displays the video indicated by the video signal on the display monitor 30. Further, the central processing unit 42 issues an alarm transmission signal to the alarm device 32 so that the alarm device 32 issues an alarm.

The central processing unit 42 includes the first to fourth units.
Control signals are transmitted to the ink valves 34a, 36a, 38a, 40a, respectively. First to fourth ink valves 34
a, 36a, 38a, 40a adjust the opening degree of the valve according to this control signal, and the first to fourth ink containers 3
The amount of ink supplied to the ink cartridges 4, 36, 38, 40 is adjusted.

The printing sheet 72 is printed with a predetermined pattern by the printing device 70 and then conveyed as a printed matter 22 to the downstream side.

The colorimetric apparatus 20 according to this embodiment having the above structure operates as follows.

The printed matter 22 according to the present embodiment has a periodic pattern.

The length-measuring encoder 26 sends a trigger signal to the central processing unit 42 every time the printed matter 22 is fed by a fixed length. The central processing unit 42 operates the color camera 24 in synchronization with this trigger signal. That is, in synchronization with the trigger signal, the image of the pattern printed on the printed matter 22 is captured, and the video signal representing the image is received from the color camera 24.

As shown in FIG. 2, the color camera 24 is
When the image of the printed matter 22 is imaged, the white plate 42 is also imaged together with the image.

The central processing unit 42, which has received the video signal from the color camera 24, compares the position of the printed matter 22 with the reference position and performs the position matching by pattern matching. By performing this alignment, it is possible to eliminate the influence of the left and right blurring of the printed matter 22.

Further, the central processing unit 42 performs time integration and makes a predetermined improvement on the image as follows.

Prior to the measurement, the lens of the color camera 24 is capped, and the RGB average values B _R , B _G , and B _B of arbitrary small areas are obtained as inspection areas. That is, the black level is measured before the color inspection of the image.

After the start of measurement, that is, the color camera 24
For pattern matching after removing the lid from the lens
After performing the alignment, the measured part of the image and the white plate
The RGB average value of 42 small areas is calculated. Image under test
Smp the RGB average value of the part _Ri, Smp_Gi, Smp_Bi,
The RGB average value of the white plate 42 is W_Ri, W_Gi, W_BiAnd

Then, the RGB values Smp _Ri ', Smp _Gi ', Smp _Bi 'of the portion to be measured are calculated according to the following correction equation (3).
Ask for.

[0053]

[Table 2]

Next, the above procedure is repeated N times (N is an integer of 2 or more), and R of the measured portion is calculated according to the following equation (4).
The GB average values Smp _Ri '(with upper bar), Smp _Gi ' (with upper bar), and Smp _Bi '(with upper bar) are obtained.

[0055]

[Table 3]

When obtaining the RGB average values, the data of the predetermined inspection areas N of the periodic pattern is not added every time, but the oldest measurement value is subtracted from the time density sum and the latest The calculation amount is reduced by adding the measured value.

In this way, after performing the time integration of the RGB average values of N visual fields (N inspection areas) of a periodic pattern, the central processing unit 42 transmits a video signal to the display monitor 30,
The image of the design of the printed matter 22 captured by the color camera 24 is displayed on the display monitor 30.

In the case of the off-line method, the color camera 24 captures a sample image and then transmits the video signal to the central processing unit 42. In the case of the off-line method, the color measurement device 20 does not need to include the length measurement encoder 26.

The operator designates an arbitrary area from the image of the picture displayed on the display monitor 30 by using a pointing device such as a mouse. The area designated in this way is hereinafter referred to as a measurement range.

The central processing unit 42 obtains the RGB average values of the measurement range designated in this way. This RGB average value is stored in the second memory 46.

The video signal sent from the color camera 24 includes the picture of the printed matter 22 and the image of the white plate 42. Therefore, the central processing unit 42 uses the captured white plate 42 as a reference for the RG of the image of the design.
After normalizing the B value, the RGB average value of the measurement range is obtained.

When the color camera 24 captures a picture of the printed matter 22, a strobe may be used to ensure brightness. However, since the brightness provided by the strobe is not always constant, the difference in strobe brightness can be determined by normalizing the RGB values of the image of the pattern with the white color of the white plate 42 as a reference as described above. It is possible to compensate.

Next, the central processing unit 42 extracts one field F1 having the RGB value closest to the RGB average value of the measurement range from the measurement database stored in the first memory 44.

That is, R value, G value, B of RGB average value
When the value respectively _{R 0, G 0, B 0} , R value R ₁ as ΔRGB represented by the following formula (5) is minimized, G value G _1,
Extract one field having RGB values with B value B ₁ .

ΔRGB = ((R ₀ −R ₁ ) ² + (G ₀ −G ₁ ) ² + (B ₀ −B ₁ ) ² ) ^1/2 (5) The extracted field F1 is stored in the third memory 48. Is stored.

Then, the central processing unit 42 has N (N is a positive integer of 1 or more, for example, N = 30) field F having the Lab value closest to the Lab value of the field F1.
2 to F (N + 1) are extracted.

[0067] That is, when Lab values of the fields F1 to respectively _{L 0, a 0, b 0} , L value ΔLab that is minimized as represented by the following formula (6) L _1, a value a _1, b Value b
Extract N fields that have Lab values with ₁ .

ΔLab = ((L ₀ −L ₁ ) ² + (a ₀ −a ₁ ) ² + (b ₀ −b ₁ ) ² ) ^1/2 (6) The extracted fields F2 to F (N + 1) are It is stored in the fourth memory 50.

Next, the central processing unit 42 performs a linear multiple regression analysis, and (N + 1) fields F1 to F (N +) stored in the third memory 48 and the fourth memory 50.
From the RGB value and the XYZ value of 1), a first matrix for converting the RGB value into the XYZ value is calculated.

That is, a 3 × 4 matrix A that satisfies the following expression (7) is calculated as the first matrix.

[0071]

[Table 4]

The first matrix A is stored in the fifth memory 52.

Then, the central processing unit 42 obtains the first matrix A stored in the fifth memory 52, which is obtained from the equation (7).
Non-linear multiple regression analysis is performed using as an initial matrix, and stored in the third memory 48 and the fourth memory 50 (N + 1).
RGB values and L of the fields F1 to F (N + 1)
A second matrix for converting RGB values into Lab values is calculated from the ab values.

That is, a 3 × 4 matrix B that satisfies the following equation (8) is calculated as the second matrix.

[0075]

[Table 5]

This second matrix B is stored in the sixth memory 54.

Next, the central processing unit 42 uses the second matrix B stored in the sixth memory 54 and the RGB average value of the measurement range stored in the second memory 46 to obtain the Lab value Lab ₁ in the measurement range. To calculate.

Lab value Lab thus calculated
₁ is stored in the seventh memory 56.

Next, the operator of the color measuring device 20 according to the present embodiment actually measures the color from the image of the picture displayed on the display monitor 30 by using, for example, a mouse or other pointing device. Specify the inspection range as the area.

The central processing unit 42 obtains the RGB average values of the inspection range thus designated. This RGB average value is stored in the eighth memory 58.

Next, the central processing unit 42 uses the second matrix B stored in the sixth memory 54 to calculate the Lab value Lab ₂ of the inspection range.

Lab value Lab thus calculated
₂ is stored in the ninth memory 60.

Next, the central processing unit 42 reads the Lab value Lab ₁ in the measurement range from the seventh memory 56, and further reads the Lab value Lab ₁ in the inspection range from the ninth memory 60.
After reading the ab value Lab ₂ , both Lab values Lab ₁
And Lab ₂ are calculated as the color difference ΔE according to the following equation (7).

ΔE = ((L ₁ −L ₂ ) ² + (a ₁ −a ₂ ) ² + (b ₁ −b ₂ ) ² ) ^1/2 (9) In the formula (9), L ₁ , a ₁ , B ₁ are the L value, the a value, and the b value of the Lab value Lab ₁ in the measurement range, respectively,
L ₂ , a ₂ , and b ₂ are Lab values L in the inspection range, respectively.
These are the L value, a value, and b value of ab ₂ .

The color difference ΔE thus calculated is the tenth
It is stored in the memory 62.

The threshold value E _T of the color difference ΔE is preset in the central processing unit 42 by the operator of the colorimetric device 20 according to this embodiment.

The central processing unit 42 compares the color difference ΔE calculated as described above with the threshold value E _T.

When the color difference ΔE is smaller than the threshold value E _T (ΔE <E _T ), the central processing unit 42 determines that the printed matter 22
It is judged that the color of the picture of is accurately displayed, and printed matter 2
Continue the color measurement of the pattern in 2.

On the other hand, when the color difference ΔE is equal to the threshold value E _T or the color difference ΔE is larger than the threshold value E _T (ΔE ≧ E _T ), the central processing unit 42 determines that It is determined that the color of the pattern 22 does not appear accurately, and an alarm transmission signal is transmitted to the alarm device 32.

The alarm device 32, which has received the alarm transmission signal from the central processing unit 42, issues an alarm to the operator of the color measuring device 20. This alarm allows the operator to take necessary measures such as stopping the operation of the color measuring device 20.

Alternatively, when the color difference ΔE is equal to the threshold value E _T or the color difference ΔE is larger than the threshold value E _T (ΔE ≧ E _T ), the central processing unit 42 activates the alarm device 32. Instead of being operated, a control signal is sent to the first to fourth ink valves 34a, 36a, 38a, 40a, and according to the difference between the color difference ΔE and the threshold value E _T , the first to fourth ink valves 34a, It is also possible to adjust the opening degree of 36a, 38a, 40a.

As a result, the amount of the insufficient ink or the excessive ink is adjusted, and the color management of the pattern of the printed matter 22 can be automatically performed.

When the color difference ΔE is equal to the threshold value E _T or the color difference ΔE is larger than the threshold value E _T , the alarm device 32 is activated, or the first to fourth ink valves 34a, Whether to adjust the opening degree of 36a, 38a, 40a can be set such that the operator of the colorimetric device 20 selects one in advance and the central processing unit 42 performs the selected operation. .

As described above, in the conventional colorimetric device, since the conversion matrix X for converting the RGB value into the Lab value is a fixed value, the change in the color difference corresponding to the actual change in the color is not necessarily high. The accuracy could not be calculated.

On the other hand, according to the colorimetric apparatus 20 of this embodiment, the first matrix A and the second matrix B are obtained each time colorimetry is performed, so that it is possible to cope with the actual change in color. It is possible to obtain the change in color difference with high accuracy. That is, it is possible to perform color management of the print image of the printed matter with higher accuracy than that of the conventional color measurement device, specifically, with the same level of accuracy as the off-line spectrocolorimeter.

The operation of the control device 28 in the above-described embodiment can also be performed through a program stored in a storage medium in a computer-readable state.

[0097]

As described above, in the conventional colorimetric device, since the conversion matrix X for converting the RGB values into the Lab values is a fixed value, the change in color difference does not always correspond to the actual change in color. Could not be obtained with high accuracy.

On the other hand, according to the colorimetric apparatus or the colorimetric method of the present invention, the first matrix and the second matrix are obtained each time colorimetry is performed, so that it is possible to cope with the actual change in color. It is possible to obtain the change in color difference with high accuracy. That is,
It is possible to perform color management of a print image of a printed matter with higher accuracy than a conventional color measurement device, specifically, with the same level of accuracy as an off-line spectrocolorimeter.

[Brief description of drawings]

FIG. 1 is a block diagram of a color measurement device according to an embodiment of the present invention.

FIG. 2 is a plan view showing a white plate used when capturing an image of a printed matter.

FIG. 3 is a block diagram of a conventional color measurement device.

[Explanation of symbols]

20 Color Measuring Device According to One Embodiment of the Present Invention 22 Printed Material 24 Camera 26 Encoder for Length Measurement 28 Control Device 30 Monitor for Display 32 Alarm Devices 34, 36, 38, 40 Ink Containers 34a, 36a, 38a, 40a Ink Valve 42 White plates 44, 46, 48, 50, 52, 54, 56, 58, 6
0, 62 memory 70 printing device 71 roll 72 printing sheet 73a, 73b, 73c, 73d impression cylinder 74a, 74b, 74c, 74d plate cylinder

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G06T 1/00 510 B41F 31/02 F 5C079 H04N 1/46 33/14 G 1/60 H04N 1/40 D 7/18 1/46 Z (72) Inventor Ryoichi Soga 2951 Ishikawa-cho, Hachioji-shi, Tokyo 4 F-term in Nireco Co., Ltd. (reference) 2C250 EA02 EA25 EB40 EB43 EC05 2G020 AA08 DA05 DA14 DA34 DA35 DA36 DA43 DA65 5B057 AA11 BA11 CE16 CE18 CH01 CH11 DA07 DA15 DA16 DB02 DB06 DB09 5C054 AA01 AA05 EF01 FC15 FF06 HA05 5C077 MP08 PP32 PP36 PP46 PQ12 PQ18 PQ22 SS01 SS06 5C079 HB01 HB05 HB08 HB11 LA02 LA10 MA01 MA11 MA17 NA29

Claims (16)

[Claims] 1. A process of obtaining an RGB average value in a predetermined inspection region of a printed matter having a periodically changing pattern, a process of aligning the predetermined region of the pattern, and a color normalization by a reference white color. And calculating the RGB average value of the predetermined area, and integrating the data for a plurality of visual fields to obtain the R of the predetermined area.
A process for obtaining a GB value, and a colorimetric method for printed matter, which comprises: 2. A first step of inputting a print image of a printed matter to a display monitor, a second step of designating a part of the print image as a measurement range, and an RGB average value in the measurement range of the print image. Third step of obtaining, and extracting a field having an RGB value closest to the RGB average value from a database in which a plurality of fields having a set of RGB value, Lab value and XYZ value are stored in advance. 4 and the Lab of the field extracted in the fourth step
A fifth step of extracting N fields (N is a positive integer of 1 or more) having a Lab value closest to the value, the field extracted in the fourth step and the field extracted in the fifth step. RG of N fields
A sixth step of calculating a first matrix for converting RGB values into XYZ values by linear multiple regression analysis from the B value and the XYZ value, and extracted in the fourth step using the first matrix as an initial matrix. And a seventh step of calculating a second matrix for converting RGB values into Lab values by nonlinear multiple regression analysis from RGB values and Lab values of the N fields extracted in the fifth step. Eighth calculating a first Lab value in the measurement range of the print image from a second matrix and the RGB average value
A ninth step of designating a part of the print image in a range other than the measurement range as an inspection range; a tenth step of obtaining an RGB average value in the inspection range of the print image; By the second matrix, L of the inspection range of the printed matter is obtained.
An eleventh step of calculating an ab value, a Lab value in the inspection range of the printed matter, and a first La
A twelfth step of calculating a difference from the b value as a color difference, and 3. The method further comprises a step of capturing a white plate together with the print image when capturing the print image, and normalizing RGB values of the print image with reference to the white color of the white plate. The color measuring method of the printed matter according to claim 2. 4. When the color difference exceeds a threshold value,
The color measuring method for the printed matter according to claim 2, further comprising a step of issuing an alarm. 5. When the color difference exceeds a threshold value,
The color measurement method for a printed matter according to claim 2, further comprising a step of adjusting an amount of ink for forming the print image according to a difference between the color difference and the threshold value. 6. A color measuring device for a printed matter, comprising: a camera for capturing a printed image of the printed matter; a display monitor; and a control device for receiving the print image from the camera and projecting the printed image on the display monitor. Then, the control device obtains an RGB average value in a predetermined inspection region of a printed material having a pattern that changes periodically, aligns the predetermined region of the pattern, and normalizes the color with white as a reference. Then, the RGB average value of the predetermined area is obtained, the data is integrated for a plurality of visual fields, and the R of the predetermined area is calculated.
A colorimetric device for printed matter for obtaining a GB value. 7. A color measuring device for a printed matter, comprising: a camera for capturing a printed image of the printed matter; a display monitor; and a control device for receiving the printed image from the camera and displaying the printed image on the display monitor. The control device obtains an RGB average value in a part of the print image designated as a measurement range, and a database in which a plurality of fields each having an RGB value, a Lab value, and an XYZ value as a set are stored in advance. A field having an RGB value closest to the RGB average value, and extracting N fields (N is a positive integer of 1 or more) having a Lab value closest to the Lab value of the field, A first matrix for converting RGB values into XYZ values is calculated by linear multiple regression analysis from RGB values and XYZ values of (N + 1) fields. , Using the first matrix as an initial matrix, calculating a second matrix for converting RGB values into Lab values by nonlinear multiple regression analysis from the RGB values and Lab values of the (N + 1) fields, A first Lab value in the measurement range of the print image is calculated from a matrix and the RGB average value, an RGB average value in a part of the print image designated as an inspection range is obtained, and by the second matrix, L of the inspection range of the printed matter
The ab value is calculated, and the Lab value of the inspection range of the printed matter and the first La are calculated.
A colorimetric apparatus for printed matter, which calculates a difference from a b value as a color difference. 8. The image forming apparatus further comprises a white plate that is imaged together with the print image when the print image is captured, and the control device sets the RGB of the print image based on the white color of the captured white plate. The colorimetric apparatus for printed matter according to claim 7, wherein the value is normalized. 9. An alarm device for issuing an alarm is further provided, and when the color difference exceeds a threshold value, the control device activates the alarm device to issue an alarm. The color measuring device for printed matter according to claim 7. 10. The control device is connected to an ink amount adjustment mechanism that adjusts the amount of ink for forming the print image, and the control device controls when the color difference exceeds a threshold value. 8. The color measuring device for a printed matter according to claim 7, wherein the color difference is controlled by controlling the ink amount adjusting mechanism in accordance with a difference between the color difference and the threshold value. . 11. A colorimetric apparatus for printed matter, comprising: a camera for picking up a printed image of printed matter; a display monitor; and a control device for receiving the printed image from the camera and displaying the printed image on the display monitor. A program for operating the control device, wherein the control device is configured to determine an RGB average value in a predetermined inspection region of a printed matter having a pattern that periodically changes, and to align the predetermined region of the pattern. The process of performing, the process of normalizing the color of the reference white color to obtain the RGB average value of the predetermined region, and the process of integrating the data for a plurality of fields of view to obtain the R of the predetermined region.
A program for executing the process of obtaining a GB value and. 12. A colorimetric apparatus for printed matter, comprising: a camera for picking up a printed image of printed matter; a display monitor; and a control device for receiving the printed image from the camera and displaying the printed image on the display monitor. It is a program for operating the control device, wherein the control device obtains an RGB average value in a part of the print image designated as a measurement range, and a set of RGB value, Lab value and XYZ value as a set. A process of extracting a field having an RGB value closest to the RGB average value from a database in which a plurality of fields having the plurality of fields are stored in advance; and N pieces having a Lab value closest to the Lab value of the field (N is A step of extracting (1 or more positive integer) fields, and RGB values and XY of the (N + 1) fields Calculating a first matrix for converting RGB values into XYZ values by linear multiple regression analysis from the values, and using the first matrix as an initial matrix, the nonlinearity is obtained from the RGB values and the Lab values of the (N + 1) fields. Calculating a second matrix for converting RGB values into Lab values by multiple regression analysis; and calculating a first Lab value in the measurement range of the print image from the second matrix and the RGB average value. A step of obtaining an RGB average value in a portion of the print image designated as an inspection range, and L of the inspection range of the printed matter by the second matrix.
calculating the ab value, the Lab value of the inspection range of the printed matter, and the first La
A program for executing the process of calculating the difference from the b value as a color difference, and 13. The control device according to claim 12, further comprising a step of normalizing RGB values of the print image with reference to white color of a white plate taken together with the print image. The listed program. 14. The colorimetric device for printed matter further comprises an alarm device for issuing an alarm. When the color difference exceeds a threshold value, the control device activates the alarm device to generate an alarm. 13. The program according to claim 12, further executing the process of issuing. 15. The control device is connected to an ink amount adjustment mechanism that adjusts the amount of ink for forming the print image, and when the color difference exceeds a threshold value, the control device. 13. The program according to claim 12, further comprising: controlling the ink amount adjusting mechanism according to the difference between the color difference and the threshold value to further adjust the amount of ink. 16. A computer-readable storage medium storing the program according to claim 11.