JPH06222002A - Method and equipment for measuring unevenness of luster and print - Google Patents

Abstract

PURPOSE:To measure the unevenness of luster quantitatively. CONSTITUTION:Outer surface of an object 23 is irradiated with visible light emitted from one light source 21 and reflected light is received by a TV camera 24 which produces a two-dimensional image having gray scale distribution. When the two-dimensional image is subjected to Fourier transform and then inverse Fourier transform by an image analyzer 20, gray scale of the image is subjected to bi-polarization using enhancement coefficients over a specific wavelength range. Bright and dark parts constituting a closed section are regarded as uneven luster parts and the areas thereof are calculated individually and the distribution parameters of the area are outputted as measurement results.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gloss unevenness and print unevenness measuring method and apparatus for quantitatively measuring gloss unevenness and print unevenness on a product surface as one item of quality.

[0002]

2. Description of the Related Art In recent years, in addition to the strength of the gloss of the product surface, the gloss and the unevenness of the printed coated paper or film have become important in terms of the quality of the product.
For example, the "feel" of coated paper, the "flow mark" on the surface of molded plastic, and the "vividness" of automobile coating.

The surface feeling of the coated paper will be described. That is, it is said that the more the product has a uniform glossiness, the better the surface feeling. The evaluation has hitherto been made by an inspector visually observing the unevenness of gloss in the submillimeter region of the coated paper surface. In addition, the following inspection method has also been proposed, in which the appearance of a product is imaged by an imaging device such as a television camera, and the distribution of the brightness level (reflected light intensity) of the product appearance is calculated from the imaging result.

One of them is a modification of a chromatographic scanner, in which a luminous flux of 0.4 mmφ is scanned on the surface of coated paper at an incident reflection angle of 75 °, and the standard deviation of the intensity of reflected light is related to the visual order. (H. Fujiw)
ara et. al. , 1990 TAPPI Coa
t. Conf. Proc. , 209 (1990)).

The other is to analyze the surface reflection two-dimensional image of the printing paper input from the CCD camera to examine the correlation with the average visual order, and to find the correlation with the intensity of reflected light, that is, the variation coefficient of gradation. It's a good thing. But,
It is said that there were many cases where the uneven glossiness of white paper did not correlate <M. A. MacGregor et. a
l. , 1991 TAPPI Coat. Conf. P
roc. , 495 (1991)>.

Next, the print unevenness of the printed coated paper will be described. The print unevenness is originally such that the ink density at a certain portion of the printed matter to be printed uniformly is different from the surrounding ink density. It is said that. Further, since the printing portion where the print unevenness is likely to appear is the halftone portion having a uniform ink density, the print unevenness is conventionally evaluated by the visual judgment of the halftone portion of the printed matter by the inspector. Further, various measuring methods and devices for detecting print unevenness have also been proposed.

One of the methods is to calculate the area ratio of each halftone dot in the printed halftone portion and obtain the coefficient of variation (Takao Arai, Paper and Paper Cooperative Journal 43 57 (198).
9)).

In addition, there is a method in which a series of halftone dots in a printed halftone portion is line-scanned by an image analyzer and the regularity of the shading profile is digitized and used as a parameter of print unevenness (T. Koskinen et.
al, Paperi JaPuu 74 45 (199
2)).

[0009]

However, in the inspection of uneven gloss and uneven printing by visual inspection, personal subjectivity is apt to be included in the evaluation and lack of quantitativeness. Therefore, a professional inspector is required to objectively judge pass / fail. Need a large number.

On the other hand, the above-mentioned optical inspection method for uneven gloss has the following drawbacks.

For the measurement of the optical unevenness of gloss, quantification is attempted by the reflected light intensity distribution, but there is a drawback that it does not necessarily correspond to the result of visual judgment. In particular, the blank surface feeling (surface feeling before printing) is strong in diffuse reflected light, and the uneven glossiness due to specular reflected light is weakened, and the optical inspection method for examining the reflected light intensity distribution has a large error.

Further, regarding the optical inspection method of the print unevenness, only the light and shade of the ink density is measured, which may not coincide with the visual evaluation.

Therefore, in view of the above points, the present invention provides a method and apparatus for measuring uneven glossiness, which can quantify and show the uneven glossiness measurement result based on the magnitude and distribution of uneven glossiness rather than the intensity distribution of light. Another object of the present invention is to provide a method and apparatus for measuring print unevenness that improves the accuracy by measuring the size and distribution of the dark and light portions of the ink density rather than the dark and light of the ink density.

[0014]

In order to achieve such an object, the invention of claim 1 takes an image of an object to be inspected by an image pickup device, and an image analysis device closes the image obtained as an image pickup result. An image area of a bright portion or a dark portion forming a section is detected as the uneven gloss portion of the inspection target, the area of each of the detected closed section image areas is calculated, and the distribution of each of the calculated areas is calculated. It is characterized in that the calculation result is used as a quantified measurement result of uneven gloss.

According to a second aspect of the present invention, the lightness or darkness of the image pickup result is emphasized when detecting the image area of the bright portion or the dark portion forming the closed section.

According to a third aspect of the present invention, an image pickup means for picking up an image of an object to be inspected, and an image area of a bright part or a dark part forming a closed section in an image obtained as a result of the image pickup is defined as a gloss of the object to be inspected. Detection means for detecting the uneven portion,
A first calculation unit that calculates the area of each of the detected closed-section image regions, and a distribution of each of the calculated areas is calculated by calculating the distribution of each of the calculated areas. And a second calculation means for outputting the measurement result of the uneven glossiness.

According to a fourth aspect of the present invention, an image of an inspection target is picked up by an image pickup device, and the image analysis device sets an image area of a bright portion or a dark portion forming a closed section in the image obtained as an image pickup result of the inspection target. It is detected as an uneven printing area, the area of each of the detected closed-section image regions is calculated, the distribution of each of the calculated areas is calculated, and the calculation result is used as the quantified uneven printing measurement result. Characterize.

According to a fifth aspect of the present invention, the lightness or darkness of the image pickup result is emphasized when detecting the image region of the bright portion or the dark portion forming the closed section.

According to a sixth aspect of the present invention, an image pickup means for picking up an image of an inspection target, and an image area of a bright portion or a dark portion forming a closed section is printed from the image obtained as a result of the image pickup of the inspection target. Detection means for detecting the uneven portion,
A first calculation unit that calculates the area of each of the detected closed-section image regions, and a distribution of each of the calculated areas is calculated by calculating the distribution of each of the calculated areas. A second calculation means for outputting as a measurement result of print unevenness is provided.

[0020]

According to the first and third aspects of the invention, the inventor of the present invention has found that the unevenness of the gloss of the product appearance causes a difference in lightness and darkness, so that a bright portion or a dark portion forms a closed section in the captured image. Then, the measurement result of uneven gloss is quantified by calculating the area distribution of the image of this closed section.

According to the second aspect of the present invention, the uneven gloss portion can be accurately identified by emphasizing the lightness and darkness of the image pickup result.

According to the third and fifth aspects of the present invention, since the print unevenness on the printing surface of the product causes a difference in the density of the ink density, the bright portion or the dark portion forms a closed section in the captured image. The inventor further discovered and quantified the print unevenness measurement result by calculating the area distribution of the image of the closed section.

According to the fourth aspect of the present invention, uneven printing can be accurately identified by emphasizing the lightness and darkness of the image pickup result.

The printing unevenness is for observing the ink density, to be precise, the unevenness of the dot density, and depends on the diffuse reflection light from the surface of the printed matter. On the other hand, the minute gloss unevenness on the printed surface of the coated paper is due to the specular reflection light, which is obviously different from the unevenness due to the diffuse reflection light which is a factor of the printing unevenness.

[0025]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows the basic construction of an embodiment of the present invention.

In FIG. 1, reference numeral 1000 denotes an image pickup means for picking up an image of the inspection object.

Reference numeral 1100 is a detection means for detecting an image area forming a closed section from the image obtained as a result of the image pickup as the uneven glossy portion of the inspection object.

Reference numeral 1200 is a first calculating means for calculating the area of each of the detected closed section image regions.

Reference numeral 1300 is a second calculating means for calculating the distribution of each of the calculated areas and outputting the calculation result as the measurement result of the uneven glossiness.

As will be described later, the functions of the detecting means 1100 and the first and second calculating means 1200, 1300 are realized by the arithmetic function of the image analysis processing device.

FIG. 2 shows a schematic structure of a measuring device to which the present invention is applied.

In FIG. 2, a light source 21 in an image pickup device (image pickup means 1100 in FIG. 1) 10 is attached to an inspection object 23.
Light is projected through the polarization filter 22. The light reflected by the object 23 is received by the television camera 24 via the polarization filter 25. The television camera 24 converts the received light into an image signal for each pixel, and the image analysis device 2
Output to 0.

Visible monochromatic light or white light is preferably used for the light source 21 used in this embodiment. Further, the incident light on the surface of the object 23 is preferably parallel light or light in a state close to parallel light. If the light is not parallel light or light close to parallel light, uneven gloss may be difficult to capture over the entire image. The incident angle is preferably 15 ° to 35 °, but is not limited to this.

In the present embodiment, the reflected light received by the television camera 24 is −10 ° to +1 with respect to the value of the incident angle.
It is preferable to capture at a reflection angle of 0 °. If it deviates from this range, it becomes difficult to capture the specularly reflected light, which is the main component of gloss.

By passing the incident light and the reflected light through the polarization filters 22 and 25 having the same phase, the diffuse reflected light is blocked,
Transmits specularly reflected light. Therefore, uneven gloss is emphasized more.

The television camera 24 used in this embodiment refers to a device for obtaining a two-dimensional (planar) image of the object 23, and what is used is one that can capture the change in brightness and darkness with respect to the position in the plane by an electric signal. Good. C as commercially available
Although there are a CD camera, a video camera, and the like, it is preferable to use a CCD camera in which light and dark and electric signals have a linear relationship. The focal length of the lens of the TV camera is 0.5 mm or less when the image resolution is expressed by the size of the surface of the object,
And the measurement area of the object corresponding to the whole image is 2 x 2 mm
It is preferable to select the above.

The present invention is characterized by an image signal analysis method, and the image analysis processing relating to the present invention will be described.

The image signal for one screen obtained by the television camera 24, that is, the brightness value (gradation expression) for each pixel is stored in the memory in the image analysis device 20 and then read by the central processing unit. The image is analyzed in the following processing steps.

(1) Fourier transform is applied to the two-dimensional image by the following equation.

[0041]

[Equation 1]

The result of the Fourier transform shows the intensity distribution for each frequency band and is called a power spectrum.

(2) When the inverse Fourier transform of the Fourier transform result is performed, the portion corresponding to the specific wavelength range that can be recognized by the naked eye is multiplied by the enhancement coefficient to obtain an enhanced image in which the lightness and darkness of the two-dimensional image at the time of image pickup is enhanced. . The inverse Fourier transform formula is represented by the following formula.

[0044]

[Equation 2]

(3) In the obtained emphasized image, an image area portion in which a white portion corresponding to a light portion or a black portion corresponding to a dark portion forms a closed section is detected as a gloss unevenness portion, and the detected closed section is detected. The area, average area, standard deviation, coefficient of variation, or number of white or black portions per unit area for each of the regions is calculated as a gloss unevenness determination parameter corresponding to visual evaluation. Further, these parameter values quantitatively represent the degree (distribution) of uneven gloss.

Here, the white portion and the black portion refer to independent closed partition areas having gradations corresponding to white and black, respectively.

For reference, the formulas for calculating the above parameters are used.
The formula is shown below. Further, it goes without saying that the image analysis apparatus when executing this process operates as the detection means 1100, the second calculation means 1200, and the second calculation means 1300 of FIG.

[0048]

[Equation 3]

[0049]

[Equation 4]

[0050]

[Equation 5]

The lower limit of the specific wavelength range is 0.
It is preferable to set the wavelength range such that the wavelength range is 004 to 2.0 mm and the upper limit is 2.0 to 200 mm. The lower limit is 0.
If it is out of the range of 004 to 2.0 mm, it is different from the resolution of human vision, and it becomes impossible to obtain an effective measurement value. Also, if the upper limit is outside the range of 2.0 to 200 mm, it is different from the size perceived by humans as a difference, and an effective measurement value cannot be obtained.

The emphasis coefficient in the equation (2) is preferably 2 to 50 times. If it is less than 2 times, the polarization of light and darkness cannot be obtained, and if it exceeds 50 times, the uneven shape does not match the visually recognized one, and it becomes difficult to obtain an effective measurement value.

When the above arithmetic processing is calculated by a computer, a two-dimensional image is divided into a set of pixels, and the gradation of each pixel is input by digitizing an image signal.

In the image analysis processing described above, the operation of Fourier transforming and inverse transforming a two-dimensional image to obtain a white portion or a black portion is a region setting which is conventionally called a "threshold" and which tends to be arbitrary. Since it can be set under the same conditions for all samples, measurement values with good reproducibility and reliability can be obtained.

The method and apparatus for quantitatively measuring the unevenness of gloss of the object to be inspected are suitable as a method for replacing the conventional method of visually judging the unevenness of gloss of the product surface, and do not require any arbitrary operation. It has the feature that quantitative values with good reproducibility and reliability can be easily obtained without being influenced by the experience and judgment of the person.

Therefore, according to the present invention, the minute gloss unevenness of the coated paper, the white surface and the printed surface as well as the minute gloss unevenness of the molded plastic surface, various coated surfaces, and other articles in which the appearance and smoothness of the surface are important are quantified. The present invention provides a method and device useful for clinical evaluation.

The measurement results of the uneven glossiness actually performed will be introduced for reference. The coated paper samples are commercially available glossy fine coated papers for sheet offset (4 types of A0 to A3,
5 groups, 33 samples) were used.

The device shown in FIG. 2 was used as the device for measuring the uneven glossiness of white paper. White visible parallel light (light irradiation device HT-
2: Nikon) is polarized and irradiated onto the surface of the coated paper at an incident angle of 25 ° with respect to the normal line, and the reflected light of the same 25 ° is passed through a polarization filter of the same phase as the incident light and a CCD camera. (SONY: CE-75).

The photographing area of the surface of the object per pixel is 4
The measurement area was 0 × 40 μm and 10 × 10 mm.
The data were taken at 4 points per sample, and the arithmetic mean thereof was used as the value.

The brightness of each pixel was converted into a digital gradation by an A / D converter. 256 tones from black to white
The level was divided into 0 and black was set to 0 and white was set to 255. The amount of light was set so that the gradation distribution of the sample with the highest glossiness in each group of coated paper samples does not reach the gradation level 255.

Image analysis (Image analysis device IP-1000:
Asahi Chem. Ind. ) Conditions,
After the two-dimensional Fourier transform of the original image, the specific wavelength range that can be recognized by the naked eye at the time of the inverse transform is multiplied by the enhancement coefficient to emphasize the unevenness of light and dark in the image. An image before emphasis and an image after emphasis are shown in FIG. In the gradation of the image in which unevenness is emphasized, the range of 0 to 1 is defined as <black part>, and the range of 254 to 255 is defined as <white part>. After the area of each of the black part (dark part in the original image) and the white part (bright part in the original image) was obtained, its standard deviation was calculated.

With respect to the visual level, 7 to 18 specialists involved in paper quality evaluation inside and outside the company gave a ranking, and the arithmetic mean value of the ranking was taken as the visual average ranking. The order of ranking was given as integers such as 1, 2, 3, ...

18 of commercially available A2 gloss paper (79 g / m ² ).
The results of the human visual evaluation ranking are shown in FIG. 5 and 6 show the relationship between the average rank of the visual evaluation and the area standard deviation of the highlighted white part and black part corresponding to the uneven gloss of the coated paper.
In this case, the emphasized wavelength range at the time of inverse Fourier transform is 0.4 to
The value was 8.0 mm and the emphasis coefficient was 10 times. 5 and 6
As is clear from the above, the correlation coefficient is r =
In the case of −0.48 and the black part, r = 0.97 was obtained. By the way, the correlation between the average rank of visual evaluation and the variation coefficient of gradation is r
= 0.72, and r = -0.35 in the case of standard deviation of gradation. From these results, it can be seen that the visual evaluation of glossy paper is made by observing the dark portion of the uneven gloss rather than the bright portion. In addition, the area standard deviation of the black portion is considered to be the dominant factor for the visual sense rather than the parameter representing the gradation distribution.

7 to 10 show the relationship between the average rank of the visual evaluations, the average area per white portion and the black portion, and the density. The size of the dark area and the number per unit area and the visual evaluation have a very high correlation.

An attempt was made to identify the boundary condition of the emphasis range at the time of inverse Fourier transform. The lower limit of the range is shown in FIG.
Shows the correlation coefficient for the upper limit of the range. From both figures, it is understood that the optimum emphasized wavelength range is 0.4 to 8.0 mm.
Further, when the emphasis coefficient in that range was examined at 5 to 20 times, it was confirmed that 10 times was optimal (Fig. 1).
3).

The average area of the black portion and its standard deviation were obtained by the same measurement method for other types of commercially available gloss paper for sheet offset, and the correlation coefficient with the average rank of visual evaluation was calculated. The results are shown in Table 1 below. The correlation coefficient of the standard deviation shows a value of 0.90 to 0.97, which shows that there is a good correlation. The correlation coefficient of the average area of the black portion was 0.89 to 0.97, indicating a similar good correlation, but if anything, the correlation coefficient with the standard deviation showed a higher value.

[0067]

[Table 1]

FIG. 14 shows a schematic structure of a measuring apparatus according to the second embodiment of the present invention.

In FIG. 14, light from the light sources 121 and 121 'in the image pickup device 10 is projected onto the inspection object 123 through the polarization filters 122 and 122'. The light reflected by the object 123 is polarized by the polarization filter 125.
The light is received by the television camera 124 via. The television camera 124 converts the received light into an image signal for each pixel and outputs it to the image analysis device 120.

Visible monochromatic light or white light is preferably used for the light source 121 used in this embodiment. The incident light on the surface of the object 123 may be parallel light or diffused light and is not particularly limited. In the present embodiment, it is preferable that the reflected light received by the television camera 124 captures diffuse reflected light. By passing the reflected light through the polarizing filters 122 and 122 '(122 and 122' are in phase) of the incident light and the polarizing filter 125 whose phase is changed by 90 °, the diffuse reflected light is transmitted and the specular reflected light is blocked. Therefore, uneven printing is emphasized.

The television camera 124 used in the present embodiment refers to a device for obtaining a two-dimensional (planar) image of the object 123, and what is necessary is to use an electric signal to capture the change in shading of print unevenness with respect to the position within the plane. May be used. Although there are CCD cameras, video cameras and the like that are commercially available, it is preferable to use a CCD camera in which the brightness and the electric signal have a linear relationship. The focal length of the lens of the TV camera is 0.5 when the image resolution is expressed by the size of the object surface.
It is preferable to select such that the measurement area of the object corresponding to the entire image is 2 × 2 mm or more. The image analysis of the present embodiment is performed by the Fourier analysis according to the equation 1 as in the first embodiment. That is, the image signal for one screen obtained by the television camera 124, that is, the brightness value (gradation expression) for each pixel is the image analysis device 120.
After being stored in the internal memory, it is read out by the central processing unit and subjected to image analysis in the following processing steps.

(1) Fourier transform is applied to the two-dimensional image by the equation (1).

The result of the Fourier transform shows the intensity distribution for each frequency band and is called a power spectrum.

(2) By multiplying the portion corresponding to the specific wavelength range that can be recognized by the naked eye when the inverse Fourier transform is performed on the result of the Fourier transform by the above equation 2, the emphasis coefficient is obtained.
An emphasized image in which the lightness and darkness of the two-dimensional image at the time of image pickup is emphasized is obtained.

(3) In the obtained emphasized image, an image area portion in which a white portion corresponding to a light portion or a black portion corresponding to a dark portion forms a closed section is detected as a print uneven portion, and the detected closed section is detected. The area, average area, standard deviation, variation coefficient, or number of white or black portions per unit area for each of the regions is calculated as a print unevenness determination parameter corresponding to visual evaluation. Further, these parameter values quantitatively represent the degree (distribution) of print unevenness.

Here, the white portion and the black portion refer to independent closed partition areas having gradations corresponding to white and black, respectively.

The above equations 3 to 5 are used to calculate the above parameters. As the above-mentioned specific wavelength range, it is preferable to set the wavelength range such that the lower limit is 0.004 to 2.0 mm and the upper limit is 2.0 to 200 mm. If the lower limit is out of the range of 0.004 to 2.0 mm, it is different from the human visual resolution, and it becomes impossible to obtain an effective measurement value. Also, if the upper limit is outside the range of 2.0 to 200 mm, it is different from the size perceived by humans as a difference, and an effective measurement value cannot be obtained.

In the second embodiment, the emphasis coefficient in the equation 2 is preferably 2 to 500 times. If it is less than 2 times, the polarization of light and darkness of the original image cannot be obtained, and if it exceeds 500 times, the shape of the unevenness does not match what is visually recognized, and it becomes difficult to obtain an effective measurement value. More preferable range is 30 to 3
It is 00 times.

When the above arithmetic processing is calculated by a computer, a two-dimensional image is divided into a set of pixels, and the gradation of each pixel is input by digitizing an image signal.

Among the image analysis processes described above, the operation of Fourier transforming and inverse transforming a two-dimensional image to obtain a white part or a black part is a region setting which is conventionally called "threshold" and which tends to be arbitrary. Since it can be set under the same conditions for all samples, measurement values with good reproducibility and reliability can be obtained.

The method and apparatus for quantitatively measuring the print unevenness of the inspection object are suitable as a method for replacing the conventional method for visually judging the print unevenness on the product surface, and do not require any arbitrary operation. It has the feature that quantitative values with good reproducibility and reliability can be easily obtained without being influenced by the experience and judgment of the person.

Therefore, the present invention is useful for quantitatively evaluating the print unevenness of coated paper, as well as the print unevenness of plastics, film surfaces, molded plastic surfaces, various coated surfaces, and other surfaces for which printability is important. Method and apparatus.

The actual measurement results of the print unevenness are introduced for reference. The printed coated paper sample is a commercially available A2 gloss-quality fine coated paper for sheet offset (basis weight 1
27.9 g / m ² , 10 samples), and a halftone portion printed by a four-color printing unit type printing machine was used.

The apparatus shown in FIG. 14 was used as the apparatus for measuring the printing unevenness of the printing coated paper. White visible light is polarized and irradiated onto the surface of the printing coated paper at an incident angle of 45 ° with respect to the normal, and the reflected light of the same 0 ° is passed through a polarizing filter with a phase different from the incident light by 90 °. It was detected by a CCD camera (SONY: CE-75).

The photographing area of the surface of the object per pixel is 1
The measurement area was 00 × 100 μm and 25 × 25 mm. The data were taken at 4 points per sample, and the arithmetic mean thereof was used as the value.

The brightness of each pixel was converted into a gray scale digitized by an A / D converter. 256 tones from black to white
The level was divided into 0 and black was set to 0 and white was set to 255. The light intensity is E
The gradation distribution of the P-printed paper sample was set so as not to reach the gradation level 255.

Image analysis (Image analysis device IP-1000:
Asahi Chem. Ind. ) Conditions,
After the two-dimensional Fourier transform of the original image, the specific wavelength range that can be recognized by the naked eye at the time of the inverse transform is multiplied by the enhancement coefficient to emphasize the unevenness of light and dark in the image. In the gradation of the image in which unevenness is emphasized, the range of 0 to 1 is <black part>, 254-2
The range of 55 was defined as <white part>. After the area of each of the black part (dark part in the original image) and the white part (bright part in the original image) was obtained, its standard deviation was calculated.

Regarding the visual level, 12 specialists involved in paper quality evaluation inside and outside the company ranked and the arithmetic mean value of the ranking was taken as the visual average rank. The order of ranking was given as integers such as 1, 2, 3, ...

Table 2 shows the results of the visual evaluation ranking of 12 persons in the multicolor halftone portion of the commercially available A2 printing coated paper. FIG. 15 shows the relationship between the average rank of the visual evaluation and the average area of the highlighted black portion corresponding to the print unevenness of the coated paper. In this case, the emphasis wavelength range at the time of inverse Fourier transform was 1.2 to 6.2 mm, and the emphasis coefficient was 160 times. As is clear from FIG. 15, the correlation coefficient was r = 0.95. 16 shows the relationship between the average rank of the visual evaluation and the area standard polarization of the black portion. The dark area distribution and the visual evaluation have a very high correlation.

With respect to the commercially available sheet-offset coated papers for sheet offset of A0 to A3, the uneven printing in the halftone part of a single color (black, indigo and red) is emphasized in the wavelength range 0.8.
.About.4.0 mm, the enhancement coefficient was 80 to 240 times, and the same measurement was performed to obtain the average area of the black portion and its standard deviation. When the correlation coefficient between those values and the average rank of visual evaluation was calculated, the results of Tables 3 to 5 were obtained.

[0091]

[Table 2]

[0092]

[Table 3]

[0093]

[Table 4]

[0094]

[Table 5]

In addition to this embodiment, the following example can be realized.

(1) In the first and second embodiments, the processing up to the measurement of gloss unevenness and print unevenness has been described, but the appearance inspection can be automatically performed using the measurement results.
In this case, the presence or absence of abnormality is determined by comparing the parameter value obtained as the measurement result with a predetermined threshold value. At this time, it is advisable to display the inspection result and an image emphasizing the imaging result on the display.

(2) In order to visually output the measurement result of uneven gloss or uneven print, the following forms can be used.

(A) The calculated parameter value is numerically output by a display device or a printer.

(B) The calculated parameter value is graphically output by a display device or a printer.

(C) The uneven glossiness or the degree of printing is converted into a numerical value by a numerical arithmetic expression using a plurality of parameter values,
A message such as "large", "medium", or "small" of uneven gloss or printing is displayed according to the numerical value.

(3) In the present embodiment, detailed processing for detecting the image area of the closed section portion from the image was not described, but this processing can be performed by using various well-known methods as contour line extraction processing. Good.

(4) When it is desired to clarify the boundary of the uneven gloss or uneven print portion, it is advisable to emphasize the outline forming the closed section.

[0103]

As described above, according to the present invention, it is possible to quantitatively measure unevenness in gloss, so that the degree of unevenness in gloss can be known.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing a basic configuration of an embodiment of the present invention.

FIG. 2 is a structural diagram showing the structure of an embodiment of the present invention.

FIG. 3 is a diagram showing an imaging result and an example of an image subjected to an emphasis process.

FIG. 4 is a diagram showing the results of measurement and evaluation by visual inspection.

FIG. 5 is a diagram showing the relationship between the average order of visual observation and the standard deviation of uneven areas of uneven gloss.

FIG. 6 is a diagram showing the relationship between the visual average order and the standard deviation of uneven gloss dark areas.

FIG. 7 is a diagram showing a relationship between a visual average rank and a gloss unevenness bright area.

FIG. 8 is a diagram showing a relationship between a visual average rank and a dark area with uneven gloss.

FIG. 9 is a diagram showing a relationship between a visual average rank and a density of uneven glossy bright portions.

FIG. 10 is a diagram showing the relationship between the average visual ranking and the density of dark areas with uneven gloss.

FIG. 11 is a diagram showing a relationship between a lower limit of the size of a dark area and a correlation coefficient (visual average-dark area standard deviation).

FIG. 12 is a diagram showing the relationship between the upper limit of the size of the dark area and the correlation coefficient (visual average−dark area standard deviation).

FIG. 13 is a diagram showing a relationship between an emphasis coefficient and a correlation coefficient at the time of Fourier transform.

FIG. 14 is a block diagram showing a structure of a second embodiment.

FIG. 15 is an explanatory diagram showing a relationship between a black area average area and a visual average rank.

FIG. 16 is an explanatory diagram showing a relationship between a black area average area and a visual average rank.

[Explanation of symbols]

 10,110 Imaging device 20,120 Image analysis device 21,121,121 'Light source 22,25 Polarization filter 23,123 Object 24,124 Television camera 122,122', 125 Polarization filter

Claims (6)

[Claims] 1. An image of an inspection target is picked up by an image pickup device, and an image area of a bright part or a dark part forming a closed section is detected as an uneven glossy part of the inspection target by an image analysis device. Then, the area of each of the detected closed-section image regions is calculated, the distribution of each of the calculated areas is calculated, and the calculation result is used as a quantified measurement result of the gloss unevenness. Measuring method. 2. The uneven glossiness measuring method according to claim 1, wherein, when detecting an image region of a bright portion or a dark portion forming the closed section, the lightness and darkness of an imaging result is emphasized. 3. An image pickup device for picking up an image of an inspection target, and an image region of a bright portion or a dark portion forming a closed section is detected as a gloss uneven portion of the inspection target from an image obtained as a result of the image pickup. Detecting means, first calculating means for calculating the area of each of the detected closed partition image regions, and calculating each distribution of the calculated area, thereby calculating each distribution of the calculated area, A gloss unevenness measuring device, comprising: a second calculation means for outputting the calculation result as a gloss unevenness measurement result. 4. An image of an inspection object is picked up by an image pickup device, and an image area of a bright portion or a dark portion forming a closed section is detected as an uneven print portion of the inspection object by an image analysis device. Then, the area of each of the detected closed-section image regions is calculated, the distribution of each of the calculated areas is calculated, and the calculation result is used as a quantified print unevenness measurement result. Measuring method. 5. The print unevenness measuring method according to claim 4, wherein when detecting an image region of a bright portion or a dark portion forming the closed section, the lightness and darkness of an image pickup result is emphasized. 6. An image pickup unit for picking up an image of an inspection target, and an image area of a bright portion or a dark portion forming a closed section is detected as a print uneven portion of the inspection target from an image obtained as a result of the image pickup. Detecting means, first calculating means for calculating the area of each of the detected closed partition image regions, and calculating each distribution of the calculated area, thereby calculating each distribution of the calculated area, A print unevenness measuring apparatus comprising: a second calculation unit that outputs the calculation result as a print unevenness measurement result.