JPH05332755A - Smoothness measuring device - Google Patents

Abstract

(57) [Summary] [Purpose] The measurement result changes when the sample surface position changes,
An object of the present invention is to provide a smoothness measuring device, which has improved the problem of the conventional method that it takes time to measure at one location. [Structure] A means for projecting a circular pattern on the surface from a position of 10 degrees or less with respect to the normal to the surface of the sample and photographing the specular reflection image, and means for image-analyzing the electric signal from the photographing means are provided. A smoothness measuring device characterized by the above. [Effect] The smoothness of the glossy sheet surface is non-contact,
It can measure at high speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring device for measuring the smoothness of a glossy sheet surface at high speed without contact.

[0002]

2. Description of the Related Art A non-contact method for measuring the smoothness of a glossy and relatively smooth surface of paper, film, coating film, etc.
(1) As described in JP-A No. 62-235512, the surface is irradiated with oblique light from a large angle of incidence of 45 degrees or more with respect to the normal line, and the intensity distribution of specular reflection light is measured. Or a method of analyzing a shadow reflecting surface irregularities caused by oblique light, (2) spatial light of a rectangular wave pattern projected and imaged on the surface as described in JP-A-58-97608. Method to analyze intensity distribution, (3)
There is known a method of directly measuring unevenness of a surface with a non-contact displacement sensor using laser light or the like.

[0003]

In the conventional method in which the incident angle with respect to the normal line is as large as 45 degrees or more, due to a large undulation of the sample surface or a change in the sample surface position during movement,
The problem is that the measured values fluctuate greatly as the distance between the surface and the light source or detector changes. Further, the method of analyzing the projected rectangular wave pattern has drawbacks that the evaluation of the unevenness is limited to a specific direction, and that it takes time to measure because the detection spot is continuously scanned.

The method of directly measuring the unevenness of the surface with the non-contact displacement sensor has an advantage that the size of the unevenness of the surface can be actually measured, but when measuring a sample moving at a constant speed, the sample surface The problem was that it was strongly affected by position changes. Another problem is that the amount of information that can be obtained from one sensor at a time is limited because the measurement spot is small.

An object of the present invention is to provide a smoothness measuring apparatus which improves the problems of the conventional method such as (1) the measurement result changes when the position of the sample surface changes, and (2) it takes time to measure one point. Is to provide.

[0006]

[Means for Solving the Problems] In order to solve the above problems, various investigations were made on the type of light to be irradiated onto the sample surface, the type of detector to receive light, irradiation conditions, detection conditions, etc. We have found the equipment elements and their arrangement conditions that can obtain a stable detection signal even for a sample that moves while vibrating. At the same time, a method for analyzing the detection signal at high speed was also examined and a preferable direction was found.

That is, means for projecting a circular pattern on the surface from a position of 10 degrees or less with respect to the normal to the surface of the sample, and means for photographing the specular reflection image, and means for image-analyzing the electric signal from the means for photographing. With the smoothness measuring device characterized by being provided, it is possible to measure the smoothness of the glossy sheet surface, which is the object of the present invention, in a non-contact manner and at a high speed without being influenced by the sample position fluctuation. It became possible.

The light source of the present invention includes a halogen lamp,
A tungsten lamp, a strobe light, a laser or the like can be used. Further, in a halogen lamp or the like, it is possible to install a filter between the lamp and the sample and use only light of a certain specific wavelength or wavelength range.

The circular pattern projected on the sample surface is projected and imaged by disposing a semitransparent plate and a lens having a predetermined pattern between the light source and the sample. The size of the projected image can be changed according to the size of the unevenness to be measured, and in consideration of the correspondence with the visual evaluation result, a diameter of 1 to 10 mm is preferable. The difference in optical density between the projected image and the surroundings may be 0.5 or more, and the optical density of the projected image may be higher or lower than the surroundings.

As means for photographing the projected image, there are an image pickup tube such as a carnicon or a vidicon or a solid-state image pickup device (CC
A television camera using D) can be used. The TV camera is preferably installed at a position where it can receive specularly reflected light of projection light. The projection of the circular pattern and the installation position of the TV camera are
It should be installed at a position of 10 degrees or less with respect to the normal line of the sample surface.

As a means for analyzing an image, a digital image processing device which digitizes an electric signal from a television camera, transfers it to an image memory, and processes various data under computer control can be used. As a data processing method, a Fourier analysis of a grayscale image, a shape analysis of an image binarized by a predetermined method, or the like can be used.

Among these, it is particularly preferable to obtain the area (A) and the perimeter (P) of the binarized image,
It is an image analysis unit that quantifies the degree of deterioration of the captured image with respect to the projected image using the smoothness index (S) represented by (Equation 1).

[Equation 2] S can be used as it is as a smoothness index, or smoothness can be evaluated by the ratio (S / S _s ) of the index (S) of the measurement sample to the index (S _s ) of the reference mirror surface.

[0013]

According to the present invention, means for projecting a circular pattern on the surface from a position of 10 degrees or less with respect to the normal to the surface of the sample and photographing the specular reflection image, and image analysis of the electric signal from the photographing means. By using the smoothness measuring device characterized by including the means, the smoothness of the glossy sheet surface can be measured at high speed without contact.

[0014]

Embodiments of the present invention will be described with reference to the drawings.
The present invention is not limited to the embodiments. Figure 1
In the figure, the block diagram of the smoothness measuring device is shown. The sample 1 is conveyed by the feed roller 2. A CCD camera 7 equipped with an illuminating device composed of a halogen lamp light source 4, a circular pattern plate 5, a lens 6 and a magnifying lens 8 is installed at a position opposed to the normal line 18 of the sample by 5 degrees. Here, the halogen lamp is a stabilized DC power supply 3
Is lit by.

The electric signal from the CCD camera 7 is sent to the image analysis device 9, A / D converted into a digital image, and then subjected to a predetermined analysis. The result is the CRT device 1
0 or output to the printer 11.

FIG. 2 is a conceptual diagram of a projection pattern. A projection optical path 12 and a detection optical path 13 having a circular pattern on the sample 1 are shown. The circular pattern is projected into a slightly distorted ellipse 14,
The length of its major axis was 20 mm. Line X on the surface of sample 1
A distribution 15 is obtained when the brightness of the digital image is measured with a spot of 0.1 mm square along −Y. By binarizing with a luminance value that allows the top of the distribution 15 and the other portions to be separated, a binary image as shown in FIGS. 3 and 4 is obtained. FIG. 3 shows a principle diagram of image analysis when the sample surface is close to a mirror surface. Further, FIG. 4 shows a principle diagram of image analysis in the case of resin-coated paper. Note that this apparatus can also project a plurality of circular patterns at the same time.

FIGS. 3 and 4 show the principle of image analysis. An image taken by a CCD camera has a pixel size of 0.1 m
It is digitized under the condition corresponding to m-square and binarized by the above-mentioned method. Area of figure of the obtained binary image (A)
16 and the perimeter (P) 17 which is the length of the contour line, and the smoothness index (S) represented by the following mathematical formula 3
Ask for.

[Equation 3]

The apparatus of the present invention is installed in a coating machine for extruding and coating a low-density polyethylene resin containing 10% of titanium dioxide to a thickness of 30 μm on various sheets at a line speed of 100 m / min. The results of measuring the sex are shown in Table 1.

[0019]

[Table 1]

In Table 1, the smoothness index is a value obtained from (Equation 1). The visual evaluation was performed by comparing the smoothness of the sample after coating with a standard sample in which the smoothest sample near the mirror surface was 1, and the sample with poor smoothness was 5. The results in Table 1 show that the tendency of the smoothness index continuously measured on a coating machine matches the visual evaluation value of the sample after coating extremely well.

[0021]

From the above results, the smoothness measuring device of the present invention is a means for projecting a circular pattern on the surface from a position of 10 degrees or less with respect to the normal line of the sample surface and photographing the specular reflection image thereof. , A means for analyzing an image of an electric signal from the photographing means is provided, and by using the smoothness measuring device of the present invention, the smoothness of the surface of the sheet having gloss can be non-contacted. , It became clear that it can measure at high speed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a smoothness measuring device.

FIG. 2 is a conceptual diagram of a projected image.

FIG. 3 is a principle diagram of image analysis. (When the surface is close to the mirror surface)

FIG. 4 is a principle diagram of image analysis. (For resin-coated paper)

[Explanation of symbols]

 1 Sample 2 Feed roller 3 Stabilizing DC power supply 4 Halogen lamp light source 5 Circular pattern plate 6 Lens 7 CCD camera 8 Magnifying lens 9 Image analysis device 10 CRT device 11 Printer 12 Projection optical path of circular pattern 13 Circular pattern detection optical path 14 Projection pattern 15 Luminance distribution 16 Area of binary image 17 Perimeter of binary image 18 Normal

Claims (2)

[Claims] 1. A means for projecting a circular pattern on the surface from a position of 10 degrees or less with respect to a normal to the surface of the sample and photographing a specular reflection image of the circular pattern, and means for image-analyzing an electric signal from the photographing means. A smoothness measuring device comprising: 2. The area (A) and the perimeter (P) of the photographed circular pattern are obtained, and the degree of deterioration of the photographed image with respect to the projected image is quantified by the smoothness index (S) represented by the following mathematical formula 1. The smoothness measuring apparatus according to claim 1, further comprising image analysis means for performing the smoothing. [Equation 1]