KR19990060565A - Print Quality Evaluation System - Google Patents

Abstract

The present invention relates to a system for evaluating a print quality. The present invention relates to a printing quality evaluation system, which more accurately and repeatedly measures a printing density, a print dot, and a printing scale, which determine a quality of a printed matter, at an arbitrarily set position within a system, and measures the measured values again. It is to provide an integrated print quality evaluation system that can process quality factors and present the results.

In order to achieve the above object, the present invention provides a measuring head portion having a means for measuring the above-mentioned basic print quality more accurately, and a measuring head portion at high speed and precisely at the top of the sample while stably seating the sample. It consists of a table unit including three axes to move, and an operating system unit analyzing and analyzing the quality factors provided from the measuring head unit as measured values.

Description

Print Quality Evaluation System

The present invention relates to a print quality evaluation system, and more particularly, by measuring the print density, print dot and scale for determining print quality in a single system to provide comprehensive print quality information, thereby obtaining optimal print quality. And a print quality evaluation system.

In general, a printing job is to reproduce a large amount of originals to be copied by transferring ink onto paper or other media.

The quality of the printed matter is determined by the degree of transfer of the printing ink and its shape. The degree of transfer of the ink on the printed matter is interpreted as the print density, and the transfer type of the ink is interpreted by the microanalysis through image analysis.

In addition, since the separation is basically printed through a color separation process, accurate printing accuracy becomes an essential element in the reproduction of the original.

These printing characteristic values are currently measured using an independent measuring instrument. In terms of density, a color densitometer is generally used. For printing halftone analysis, halftone characterization using image analysis is used. In the case of printing alignment, visual judgment or image analysis of an enlarged sample image is common.

However, the existing print job is difficult to maintain a certain quality because the print quality is judged by the producer's supervision, it is virtually impossible to repeat a certain quality of the print job, the dimensions of the print or the position of the print is not properly made If not, the print image transferred to the print medium during printing is not properly printed due to mismatching, and an improvement is needed to provide objective information on the print quality factor and to allow repeated measurement.

The present invention has been devised in view of this point, and it is possible to repeatedly measure more accurately and repeatedly the printing density, print dot and printing alignment which determine the quality of printed matters at a randomly set position in one system, and measure the measured value again. The objective is to provide an integrated print quality evaluation system that can treat multiple quality factors and present the results.

In order to achieve the above object, the present invention provides a measuring head portion having a means for measuring the above-mentioned basic print quality more accurately, and a measuring head portion at high speed and precisely at the top of the sample while stably seating the sample. It consists of a table unit including three axes to move, and an operating system unit analyzing and analyzing the quality factors provided from the measuring head unit as measured values.

1 is a perspective view showing the configuration of a print quality evaluation system according to the present invention;

2 is an exploded perspective view showing a measuring head of the printing quality evaluation system according to the present invention;

3 is a flowchart showing a method of detecting a measurement position of a color bar using a printing quality evaluation system according to the present invention;

4 is a view showing an effective printing concentration detection method of a color bar of a printing quality evaluation system according to the present invention;

5 is a view showing a print scale analysis of the print quality evaluation system according to the present invention.

* Explanation of symbols for main parts of the drawings

10 measuring head portion 11 compressed air distributor

12 laser displacement sensor 13 laser indicator

14 Camera 15 Color Density Meter

16 housing 17 support bracket

18: rubber ring 20: table portion

21: 3 axis 22: Seating plate

23: vacuum hole 30: operating system

C: Color Bar

The present invention provides a measurement head unit 10 including means for measuring a print density and obtaining an image for printing halftone and printing registration, and while measuring the sample on the upper surface stably, the measurement head unit 10 The table unit 20 includes three axes 21 freely moving on the upper part of the sample, and the operating system unit 30 processes the information on the print quality factor input from the measuring head unit 10 as measured values. Characterized in that consisting of.

In a preferred embodiment of the present invention, the measuring head portion 10 is a compressed air distributor 11 for injecting compressed air to the bottom of each sensor between the bottom surface and the upper surface of the table portion 20, and the table portion (2) The laser indicator 13 for setting an accurate measurement position on the upper surface of the sensor, the laser displacement sensor 12 for compensating the measurement object and the lower surface of the head portion 10 to maintain a constant distance, and the measurement object. It is characterized by consisting of two cameras 14 having different magnifications from which an image is obtained, a color densitometer 15 for measuring print density at a measurement position set on a printed matter, and a housing 16 for wrapping them together. .

Further, the position of the corner of the color bar C is detected through the print images obtained from the cameras 14, and the size of the color bar pieces is corrected at this position to determine the start and end points of the color bar C or the measurement section. It is characterized by obtaining.

In addition, the effective print density value of the color bar (C) is obtained by partitioning the color bar (C) into pieces of color bars divided into several pieces, and inferring the highest frequency value with respect to the print density values measured in each divided section. It is characterized by.

This will be described in more detail with reference to the accompanying drawings.

FIG. 1 is a perspective view showing the configuration of a print quality evaluation system according to the present invention, and FIG. 2 is an exploded perspective view showing a measurement head part of the print quality evaluation system according to the present invention.

The system according to the present invention, while stably fixing the sample to be measured and the measurement head unit 10 including a density measuring means for measuring the print density and a means for measuring the print halftone and print alignment using the image The table portion 20 includes three axes configured to allow the measuring head portion 10 to move in a plane from the top of the sample and to adjust the height thereof, and from the print density and the print image obtained by the measuring head portion 10. It is composed of an operating system unit 30 to analyze the print quality factor and give it as a measured value.

The measuring head portion 10 includes density measuring means for detecting a density, two cameras 14 for providing an image for measuring a printing dot and printing accuracy, and a table portion of the measuring head portion 10. A laser indicator 13 for determining a position on a plane of the 20, a laser displacement sensor 12 for measuring a distance between the measuring head 10 and the upper surface of the table 10 so as to maintain a constant height, Each of the sensors 12 and 13 comprises a compressed air distributor 11 for attaching compressed air at a predetermined inclination angle from the lower surface to the upper surface of the table 20, and a housing 16 for enclosing them in one. have.

In particular, the density measuring means is to use a color densitometer 15 made of a known technique that can measure the print density, the same effect as using a color difference meter, spectrophotometer, CCD sensor, etc. as a print density meter Will be obtained.

Here, the concentration measurement is measured using a color bar (C). Even if an abnormal measurement value is obtained using the color bar (C), the effective concentration value using the mode value in the center portion is obtained. The color bar C will be described later.

The two cameras 14 use differently magnified charge doped device cameras equipped with a magnification lens and a luminaire for measuring the print dot and the print fit, and in particular, image processing. Are illuminated by an optical fiber extended from a halogen lamp to obtain a suitable printed image.

In a preferred embodiment of the present invention, the camera 14 preferably uses 100 to 300 magnifications and 5 to 30 magnifications, respectively, in order to obtain a clearer image for printing dots and print matching.

In addition, each of the cameras 14 is installed in the housing 16 via the support bracket 17. At this time, the support bracket 17 is inaccurate due to the vibration generated by the movement of the measuring head 10. The rubber ring 18 is inserted and installed to prevent an image from being obtained.

The camera 14 installed as described above reads an image from the measuring head unit 10 at the set measuring position, and then transmits the image to the operating system 30 as data for analyzing the print quality factor. Will be swallowed.

The laser indicator 13 is a visible means for designating a position to be measured by the measuring head unit 10 moving along the X and Y axes of the table unit 30 under the control of the operating system unit 30.

That is, the laser indicator 13 does not operate as a control means of the system of the present invention, but when the user arbitrarily designates the measurement position, the laser indicator 13 visually shows the designated position on the table.

The laser displacement sensor 12 measures the position set around the reference position defined in the table portion 20 using the directivity and temporal energy of the laser light, and if the sample is not in the correct position or the measurement head portion 10 If is not in the correct position to provide a signal for this to the operating system unit 30 to perform a parallel effect.

In addition, the laser displacement sensor 12 compensates the position of the measuring unit and the proper height Z-axis when the densitometer 15 and the two cameras 14 provided in the measuring head 10 measure a sample or input an image. Given.

That is, even if the distance from the lower surface of the densitometer 15 and the camera 14 to the upper surface of the sample is a predetermined position, the focal length may be changed due to deformation or deformation of the sample, and the laser displacement sensor 12 may The cause is compensated by changing the focal length.

Here, the compensation of the scattering at the focal length is made by the laser displacement sensor 12 as well as the compressed air and the lower end of the cable by the vacuum pressure. The vacuum pressure is such that the sample is entirely seated on the upper surface of the table portion 20. The laser displacement sensor 12 determines the position of the three axes according to the phase of Z in real time, and the compressed air is a table portion 20 in which the sample is uneven or deformed at the measurement position of the camera 14. Prevented from being lifted from.

Therefore, the laser displacement sensor 12 determines the position of the measurement head unit 10 by measuring the focal length more accurately, and also measures the flatness of the upper surface of the table unit 20 on which the measurement sample is seated. Can be lowered.

The compressed air distributor 11 includes a distribution pipe which receives compressed air from the compressed air supply means made of known technology and injects the compressed air between the measuring head 10 and the table 20, wherein the compressed air A certain angle is injected at a position where the extension line extending from the center vertical line of each measuring means and the table portion 20 are in contact with each other.

The compressed air injected in this way allows the print medium deformed by moisture, temperature, humidity, etc. at the measurement position to be properly seated on the table 20, thereby enabling more accurate and stable measurement.

Particularly, the distribution pipe injected from the compressed air distributor 11 uses a pipe having a diameter of 3 to 5 mm, and expands the inner diameter of the tip by about 10 to 20% so as to be widely sprayed onto the printing medium, thereby ensuring stable seating of the sample. It is desirable to be able to prevent the sample from being damaged by the high pressure compressed air.

The housing 16 has a hollow rectangular parallelepiped shape, and one side lower end is cut into a predetermined size.

Here, the housing 16 is provided with a color density meter 15 in the longitudinal direction therein, the laser indicator 13 and the two cameras 14 are installed on the lower side of the other side facing the table 20. have.

In addition, the laser indicator 13 is installed at the cut portion and the above-described area to provide a visual position with respect to the measurement position of the measurement head unit 10.

The housing 16 formed as described above combines the other components constituting the measuring head portion 10 as one, and in this state, three axes of the table portion 20 to move along the X, Y, and Z axes. It is connected to 21 and installed.

The table portion 20 is provided with a three-axis 21 to allow the measuring head portion 10 to move freely along the Z-axis along with the X-axis, Y-axis together with the seating plate 22 on which the measurement sample is seated. .

In addition, the seating plate 22 is the upper surface is precision processed for the stability of the sample, the upper surface of the vacuum hole 23 is formed at regular intervals is connected to the vacuum means not shown, this vacuum hole ( 23) is formed with a diameter of about 1 ~ 2mm at intervals of 30 ~ 70mm.

In particular, the seating plate 22 may be manufactured by using various sizes, and the vacuum area may be set in multiple stages so as to be suitable for various printed sizes. In the present invention, the standard paper size is 4 · 6 (788 × 1092 mm). ), 4 · 6 halves (788 × 545mm), national version (636 × 939mm), B3 (350 × 480mm), but there is no particular limitation on this.

Here, the three axes use the XYZ axis device made of a known technique to move left, right, up, down based on one end of the seating plate 22, the position information obtained from this axis is a three-dimensional It is sent to the operating system through, and can be moved to the correct detection position by receiving a compensation for the position detection.

Therefore, when the sample is placed on the seating plate 22, the table portion 20 more stably fixes the sample by the generation of the vacuum pressure through the vacuum hole 23. In this state, the measuring head portion ( 10) is coupled to the three axis 21 to be free to move in three dimensions under the control of the operating system (30).

The operating system unit is related to software, and controls the measuring head unit 10 to move to a measurement position arbitrarily determined by a user, or converts an input value obtained from each measuring unit into a control value to further increase the measurement degree in the measuring section. do.

In particular, the operating system is responsible for the control of the motion and the input and output of the control value from each sensor 12, 13, and also to obtain and process the data from the measurement sensor (densimeter and camera) to return as a control value or Will print the result.

The measurement head unit 10 thus obtained obtains a print quality factor for the color bar C on the measurement sample placed on the seating plate 22 by an image recognition technique using the camera 14. ) Consists of a series of different colors or shapes in succession of square-shaped pieces of color bars, and is the basis for interpreting factors that determine print quality.

In a preferred embodiment of the present invention, the color bar edge position detection of the camera for detecting the measurement position uses a low magnification camera.

On the other hand, the process of obtaining the color bar (C) with reference to the accompanying drawings 3 and 4 First of all, the user roughly determines the approximate position of the start and end of the measurement section to be input to the operating system unit 30 .

As a result, the camera 14 obtains an image including a portion of the color bar C having a rectangular band shape at a predetermined position.

In order to detect the position of a starting point in the image thus obtained, the lower right end of the color bar C is referred to as the reference point (0,0), and color information at an arbitrary point A (x ₁ , y ₁ ) is obtained.

With the point A and the point x ₁ fixed, the height of y ₁ is increased upward for each section to obtain color information at each point, and the color information is sent to the operating system unit 30 to be compared and analyzed. .

At this time, when the pixel PIXEL: m having a rapidly changing y ₁ value is detected by the operating system unit 30, the pixel m is divided into pixel sections again, and the y ₁ value is changed again as described above. The position where the color information value changes abruptly is found, which is the pixel 1 (p) at the edge of the color bar C.

In a preferred embodiment of the present invention, the smaller the length of the pixel m, the more accurate the point can be found.

Subsequently, the pixel 2 (q) is found by finding the position of y _{2 in} the same manner as described above with the position of the X axis moved to x ₂ .

When the detected pixels 1 (p) and 2 (q) are combined and solved, a straight line equation is obtained. The straight line equation becomes a horizontal line of the color bar C.

In the same way, while moving the position of x by the pixel size while fixing y ₁ , pixel 4 (s) obtained by shifting the position of x in pixel 3 (r) and y ₂ by the pixel is obtained, and this pixel 3 ( The equation of a straight line with r) and pixel 4 (s) can be obtained.

Therefore, the equation of the straight line passing through the pixel 1 (p) and the pixel 2 (q) is the horizontal axis of the color bar C, and the equation of the straight line passing through the pixel 3 (r) and the pixel 4 (s) is the color bar. It becomes the vertical axis of (C), and the starting contact pixel (c ₁ ) where these two equations overlap is the starting point of the color bar (C).

In the same way, when the end point of the color bar is found, the end point pixel c ₂ is obtained as shown in the attached drawing 4.

Subsequently, a straight line passing through the center point pixels c ' ₁ and c' ₂ obtained by subtracting the half length of the height of the color bar C from the y values of the poetic point pixel c ₁ and the end point pixel c ₂ is obtained. This straight line is the measuring path in the system of the present invention.

Hereinafter, a method of obtaining an effective concentration value of a color bar piece according to the present invention using the specific path and the attached drawing 4 degrees as follows will be described.

First, from the configuration information of the color bar (C) to obtain the actual distance from the position of both ends of the color bar by the method of detecting the overall length of the color bar (C) and the measurement section position, and then compare the two distance values to the printing process Compensation for errors due to deformation

In this case, a measurement value for each color bar piece is obtained according to the configuration information of the color bar (C), and the effective measurement value for the color bar piece in the center portion of the divided section not including the adjacent color bar pieces is obtained. In order to take the mode, the mode is obtained, and this value is registered as the representative value of the color bar piece.

As an example, Table 1 shows the measured values of the effective concentration values of the color bars using the system according to the present invention. In FIG. 4, the concentration representatives of cyan at the first pitch P ₁ of the color bars C are shown. Chi is showing.

TABLE 1

From this data, it is found that the effective concentration of cyan is in the range of 0.96 to 0.98, and the effective concentration can be obtained by averaging the detected values for each section.

Therefore, the highest frequency value that maintains a constant level in the center section of the color bar piece can be obtained as the effective concentration value in this section, so that even if an error occurs due to contamination or damage, the effective color density Will be obtained.

Here, the minimum demand frequency is set to obtain an optimal color density due to damage or deterioration of color bar pieces.

The minimum required frequency is obtained by the following equation.

Minimum Required Frequency = [(A-B) × c × r × t]

A is the width of the colored bar piece (mm)

B is the horizontal length of the densitometer measuring diameter (mm)

c is the number of measurements per unit distance (times / mm)

r is the peninsula (0 ~ 1)

t is the tolerance (0 ~ 1)

In a preferred embodiment of the present invention, the minimum required frequency is used as (color bar piece length-2 mm) × 5pt / mm × 0.98 × 0.7.

In particular, the measured concentration is not simply expressed as the print density but is expressed as a print quality factor related to the print density, which is halftone area ratio, dot spread, print contrast, color error, grayness, gray scale reconstruction, and interval density variation. , GATF color hexagon and optimal print density analysis.

For quality factors related to these print densities, see 'Quality and Productivity in the Graphic Arts', Miles Southworth and Donna Southworth, (Graphic Arts Publishing, 1989, Chap. 19, 1-26), and 'Colour Control in Lithougraphy', Kelvin Tritton (Pira International, 1993, Chap. 3, 41-56, Chap. 7, 106-123).

In general, the halftone image with the area ratio of about 30 to 40% is suitable, but there are no special limitations, and the magnification for obtaining the printed image dot size varies depending on the resolution. It is usually between 150 and 300 times.

In the system of the present invention, a halogen light source and an enlarged lens barrel are processed and mounted on a predetermined CCD camera 14 to obtain a printed image point, the Hilogen light source is extended to an optical fiber, and then a circular enlarged lens tube is evenly distributed in the measurement area. By configuring the light source to shine, a printing network image is obtained.

The print quality characteristics obtained through the print dot analysis include the sharpness of the print dot image, the area ratio of perfect score (Area%), the circular dot circularity, the image density deviation between dots, and the image density roughness in the dot dots ( Intensity Roughness in dot).

Related publications include 印刷 品質 評價 法 の 硏 究, 高 柳 茂 直, 三 ● 重工 技 報, Vol. 20, No. 1, 1983-1, Evaluation of Offset Print Quality on Coated Papers by means of Instrumental Measurement, Y. Kohara, S. Takahashi, JPA Technology, 35, 8, 1992, Kara- 印刷 物 作成 工程 でIt is well represented in No.2, Skills, Japanese Journalism, and No. 26.

In addition, the present invention includes a print scale, the print scale is obtained in the same configuration as the print network analysis, except for using a low magnification of the sensor used to measure this, and generally for the print scale 5 to 30 magnifications are used.

In general, when an image is obtained from the camera 14 with respect to a standard measurement object (Scale) having a physical specific size, and compared with the actual size of the standard measurement object with respect to the image obtained by the monitor, the actual object of the monitor pixel The magnitude gets the reference value.

In this state, the measurement is performed using the alignment indicator, and the system of the present invention provides two modes for automatic measurement and manual measurement.

In the case of manual measurement, an enlarged image of any print alignment indicator printed together on the printed matter is provided to the user directly through the camera 14, so that the user can easily detect the alignment error.

Further, in the case of automatic measurement, the original image of the R, G, B mode obtained from the camera 14 in order to extract each print ink component from the image picked up by the camera 14 for the target measurement object having a certain shape. Will be converted to C, M, Y, K mode.

In this case, when the respective color images C, M, and Y are added to the K color image, a characteristic composition image for each printing ink component is obtained, and the composition image (C, M, Y, K) _{Obtain an} intensity profile or histogram peak parallel to the X and Y axes to obtain the center coordinate value (x _CMYk y _CMYk ) for each ink, and then the center coordinate value of the K column. Based on (x _K , y _K ), a matching error is detected from the position difference with respect to the center coordinate value of each printing color.

By compensating by manually or automatically operating the print alignment control system according to the detected error value, high quality printed matter can be obtained.

Print alignment is an important factor in determining the print quality of color prints that are separated by color separation process, and a device capable of digitizing or controlling the alignment error between print inks is shown in US Pat. No. 4,596,468, UK 2,109,544.

Meanwhile, in the system of the present invention, two cameras 14 having different magnifications are used for the print dot analysis and the print size analysis, but one camera 14 having a variable magnification lens capable of adjusting the magnification is used. It is also possible to obtain these printing characteristic elements.

Accordingly, the present invention provides a measurement head unit for measuring the main factors for determining the print quality in one operating system, and the height of the measurement head unit can be freely moved on the plane while the sample is settled stably. It consists of a table section including three axes configured, and an operating system section that controls these and directly analyzes the print density and print image obtained from the measurement head section and converts them into various print quality factors. In addition, it is possible to obtain control values and fluctuations quickly and accurately with respect to an arbitrarily set measurement position, and to have a work which is duplicated from the obtained information.

Claims (4)

A measurement head section 10 including means for measuring printing density and obtaining an image for printing halftone and printing registration, and the measurement head section 10 stably seating the measurement sample on the upper surface thereof. Table portion 20 including a three axis (21) to move freely in the upper portion of, and the operating system unit 30 for processing the information about the print quality factor input from the measuring head portion 10 as a measurement value Print quality evaluation system, characterized in that. The method of claim 1, wherein the measuring head portion 10 of the compressed air distributor 11 for injecting compressed air to the lower portion of each sensor between the bottom surface and the upper surface of the table portion 20, and the table portion 2 of the From the laser indicator 13 for setting the correct measurement position on the upper surface, the laser displacement sensor 12 for compensating the measurement object and the lower surface of the head portion 10 to maintain a predetermined interval, and from the measurement object A print quality evaluation system comprising: two cameras (14) having different magnifications for obtaining an image, a densitometer (15) for measuring density at this arbitrarily set position, and a housing (16) for wrapping them together. The method according to claim 1, wherein the reference position point detection for repeated measurement of the measuring system is bent to detect the corner position of the color bar C through the printed image obtained from the camera 14, and the color bar at this position. A print quality evaluation system, characterized in that the correction of the size of a piece to obtain the start and end points of a color bar (C) or a measurement section provides a reference point for the obtained position for any other set measurement position. The effective print density value of the color bar (C) is divided into color bar (C) into pieces of color bars divided into several pieces, and the highest frequency value with respect to the print density values measured in each divided section. Print quality evaluation system, characterized in that obtained by extracting.