JP3511881B2 - Crystal grain size measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal grain size measuring device for measuring a crystal grain size on a metal surface by image processing,
In particular measuring the particle size of the spangle precipitated on the plating surface
Regarding the device .

[0002]

2. Description of the Related Art For example, surface-treated steel sheets, which are widely used as exterior and interior materials for automobiles, exterior materials for household appliances, and construction materials, have rust-proof and corrosion-resistant properties on the surface of cold-rolled thin steel sheets. Plating with an alloy containing zinc, iron, aluminum, and tin as the main components for the purpose of strengthening, and then coating the surface with a coating material such as colorless or extremely pale yellow chromate to enhance rust prevention. The surface-treated steel sheet produced in accordance with the present invention, which is particularly used for automobiles and household appliances, is surface-coated with a coating material having a high affinity for paints, and then applied with coating.

Recently, due to the progress of plating technology,
It has become possible to manufacture surface-treated steel sheets with extremely excellent corrosion resistance, and particularly for household electrical appliances exterior materials and construction materials, surface-treated steel sheets using Al-Zn alloy plating that does not require painting have already been commercialized. .

In such a surface-treated steel sheet which does not require coating, crystal grains called spangles are inevitably deposited on the surface of the steel sheet during the cooling process after the plating agent is applied, so that the plated steel sheet surface is colorless or polar. There is a problem in that the appearance quality through the light yellow coating film is impaired, and attempts have been made to suppress the deterioration in appearance quality by making the grain size of the crystal grains uniform. The grain size here is the average value of the diameter of a circle having a size corresponding to the area of the crystal grain.

On the other hand, from the viewpoints of feedback control and inspection of the crystal grain size, attempts have been made to realize automatic measurement of the crystal grain size on the production line, and Japanese Patent Application Laid-Open No. 5-45138 discloses the measured surface. After the image is picked up by using an image pickup device such as a camera, it is binarized and a cumulative value of a predetermined width is calculated from projection data of orthogonal two directions in the binarized image information, and the cumulative value of each direction is further determined according to a predetermined threshold value. There is disclosed a crystal grain size measuring device which binarizes the grain size and calculates the grain size based on the number of points changing from 0 to 1 in the binarized information and the size of the surface to be measured.

[0006]

However, in the crystal grain size measuring device as described above, when the difference in density between the spangle and other crystal grains is small, the grain boundary is unclear when the captured image data is binarized. Therefore, there is a problem that the crystal grain size cannot be accurately measured.

The inventor of the present application paid attention to the fact that all kinds of crystal grains, including crystal grains to be measured such as spangles, on the plating surface are dendritic crystals having a unique optical directivity. When the plated surface is irradiated with light as described above, only the reflected light from the spangle is captured by the image sensor, so that the background of the imaging area is made substantially black and only the spangle is made substantially white at the stage of imaging. I knew what I could do.

The present invention has been made in view of the above findings, and the light emitted from the light source to the surface to be measured is reflected on the surface of the crystal grain to be measured, such as spangle, and the reflection direction thereof is reflected. By providing an image pickup device in the image pickup device, the object of the present invention is to provide a crystal grain size measuring device capable of accurately measuring the crystal grain size of spangle even when the difference in density between spangle and other crystal grains is small. To do.

[0009]

A crystal grain size measuring apparatus according to a first aspect of the present invention captures an image of a surface of an object to be measured using an imager,
In a crystal grain size measuring device for measuring the grain size of the crystal grain by calculating the grain size of a predetermined type of crystal grain deposited on the surface to be measured from the image pickup result, a quantization for quantizing the image pickup result.
Means and the quantization result of the quantizing means to a predetermined brightness threshold
Binarization based on the above
And a binarizing / identifying means for identifying
Counting for counting the identified pixels of the predetermined type of crystal grain
And an area corresponding to the counting result of the counting means
Corresponding to the area calculation means and the calculation result of the area calculation means
Diameter calculating means for calculating the diameter of a circle, and the diameter calculating means
Particle size calculating means for calculating the particle size based on the calculation result
And a light irradiation means for irradiating the surface to be measured with light, and the light irradiation means.
The amount of light from the projection means is compared with that of the crystal grains of the predetermined type to be imaged.
Of the image sensor in order to clarify the difference in density with other crystal grains of
The light amount increasing / decreasing means for increasing / decreasing according to the
Each time the amount of light is increased or decreased, calculation is performed by the particle size calculation means.
Deviation calculator for calculating the deviation between said particle size and a predetermined value
Stage, and the above-mentioned illumination device that minimizes the calculation result of the deviation calculating means.
And a light quantity selection means for selecting the light quantity of the projection means .

[0010]

The crystal grain size measuring apparatus according to the second aspect of the present invention uses the image pickup device to image the surface of the object to be measured, and calculates the grain size of a predetermined type of crystal grain deposited on the surface to be measured from the imaged result. In a crystal grain size measuring apparatus for measuring the grain size of the crystal grains, a quantizing means for quantizing the image pickup result, and binarizing the quantizing result of the quantizing means based on a predetermined brightness threshold value. A binarization / identification means for identifying the predetermined type of crystal grains, a counting means for counting the pixels of the predetermined type of crystal grains identified by the binarization / identification means, and a counting result of the counting means Area calculation means for calculating the area according to
Diameter calculation means for calculating the diameter of a circle corresponding to the calculation result of the area calculation means, particle size calculation means for calculating the particle size based on the calculation result of the diameter calculation means, and light to the surface to be measured. Light irradiating means for irradiating, and the measured object
Illumination angle to the surface or the measured surface of the imager
The optical axis angle, and the angle changing means for changing in accordance with the sensitivity of the imager so as to clarify the shading difference between the predetermined type of grains and other grains to be imaged, said that the angle changing means
Deviation calculation means for calculating a deviation between the particle size calculated by the particle size calculation means and a predetermined value each time the irradiation angle of the light irradiation means or the optical axis angle of the imaging device is changed ; Deviation performance
Irradiation angle of the light irradiation means that minimizes the calculation result of the calculation means
Characterized in that it comprises a time or angle selecting means for selecting the optical axis angle of the imager.

[0012]

[0013]

The crystal grain size measuring device according to the third aspect of the present invention is an image pickup device.
Image the surface of the object to be measured with a measuring instrument and
To calculate the grain size of a certain type of crystal grain that precipitates on a fixed surface
In the crystal grain size measuring device for measuring the grain size of the crystal grain by
A quantizing means for quantizing the imaging result, and the quantizing means
The quantization result of the means is binarized based on a predetermined brightness threshold
Binarization for identifying the above-mentioned predetermined type of crystal grain by
/ Discriminating means and the location discriminated by the binarizing / identifying means
Counting means for counting pixels of a fixed type of crystal grain, and the counting hand
Area calculation means for calculating an area according to the counting result of the step,
The diameter of the circle corresponding to the calculation result of the area calculation means is calculated.
Based on the calculation result of the diameter calculating means and the diameter calculating means
Particle size calculating means for calculating the particle size, and to the surface to be measured
The light irradiation means for irradiating light and the light quantity of the light irradiation means are photographed.
Concentration of the predetermined type of crystal grains and other crystal grains to be imaged
Increase or decrease according to the sensitivity of the imager to clarify the difference
The light amount increasing / decreasing means and the light irradiation means for illuminating the surface to be measured.
Angle of incidence or optical axis angle of the imager with respect to the measured surface
, The predetermined type of crystal grains to be imaged and other crystal grains
In order to clarify the difference in density between the
Further, the angle changing means and the light quantity increasing / decreasing means change the light quantity.
Each time it increases or decreases, and the angle changing means is the light irradiation means.
Each time the irradiation angle of or the optical axis angle of the imager is changed ,
A deviation calculating means for calculating a deviation between the particle diameter and the predetermined value which is calculated by the particle-diameter calculation means, Starring the deviation calculating means
Quantity of the light irradiation unit that calculation results is minimized and the light irradiation
Select the irradiation angle of the shooting means or the optical axis angle of the imager
A light quantity / angle selecting means is provided .

The crystal grain size measuring apparatus according to the fourth invention is the first
To any of the crystal grain size measuring devices of the third invention ,
Threshold changing means for changing the brightness threshold, and the brightness threshold
Further comprising a threshold selection means for selecting
Stage, each time the threshold value changing means changes the luminance threshold, as the deviation between the particle diameter and the predetermined value which is calculated by said deviation calculation means selects a brightness threshold becomes minimum
Characterized in that there.

[0016]

[0017] In the crystal grain size measuring apparatus according to the first aspect of the present invention, shooting
The image information of the surface to be measured captured by the imager is quantized.
This quantization result is binarized based on a predetermined brightness threshold.
By doing so, certain types of crystal grains such as spangles
Of spangles identified from other grains
Pixels are counted and the area is calculated according to the counting result.
The diameter of the circle corresponding to the calculation result of is calculated, and this calculation result
The crystal grain size of spangle is calculated based on the fruit. Change
In addition, the amount of light from the light irradiation means that irradiates the surface to be measured is imaged.
Clarify the difference in shade between spangles and other crystal grains
Therefore, it is calculated each time it is increased or decreased according to the sensitivity of the imager.
A deviation between the spangle crystal grain size and a predetermined value is calculated.
Then, these calculations are repeated as the amount of light increases or decreases.
The light amount with the smallest deviation is selected from the calculated particle size.
Is selected .

[0018]

In the crystal grain size measuring apparatus according to the second aspect of the invention, the image information of the surface to be measured which is picked up by the image pickup device is quantized, and the quantized result is binarized based on a predetermined brightness threshold value. By doing this, a specified type of crystal grain such as spangle is identified from other crystal grains, the pixels of the identified spangle are counted, the area corresponding to the count result is calculated, and the diameter of the circle corresponding to this calculation result is calculated. Then, the crystal grain size of the spangle is calculated based on this calculation result. Furthermore, the irradiation angle of the light irradiation means for irradiating the light to the surface to be measured or
Varying in accordance with the sensitivity of the imaging device in order to clarify the shading difference between the spangle and other grains optical axis angle of the imager is captured
Each being further, deviation between the grain size and the predetermined value of the computed spangle is calculated. And these operations are illuminated
Repeated in response to changes in the irradiation angle of the shooting means or the optical axis angle of the imaging device, the deviation from the calculated particle size is minimized.
The irradiation angle of the light irradiation means or the optical axis angle of the image pickup device is selected.

[0020]

[0021]

[0022] In the crystal grain size measuring apparatus according to the third invention, shooting
The image information of the surface to be measured captured by the imager is quantized.
This quantization result is binarized based on a predetermined brightness threshold.
By doing so, certain types of crystal grains such as spangles
Of spangles identified from other grains
Pixels are counted and the area is calculated according to the counting result.
The diameter of the circle corresponding to the calculation result of is calculated, and this calculation result
The crystal grain size of spangle is calculated based on the fruit. Change
In addition, the amount of light from the light irradiation means that irradiates the surface to be measured is imaged.
Clarify the difference in shade between spangles and other crystal grains
Therefore, every time it is increased or decreased according to the sensitivity of the image pickup device, and the irradiation angle of the light irradiation means or the optical axis angle of the image pickup device is imaged.
Image to clarify the difference in density between the single crystal and other crystal grains
Calculated spang each time it is changed according to the sensitivity of the vessel
The deviation between the crystal grain size of the aluminum and the predetermined value is calculated. And
These calculations are performed to increase or decrease the light amount of the light irradiation means and the irradiation angle or
Is repeated according to the change of the optical axis angle of the image pickup device, and the amount of light of the light irradiation means that minimizes the deviation from the calculated particle size
And the irradiation angle or the optical axis angle of the imager is selected.

[0023] In the crystal grain size measuring apparatus according to the fourth invention, the
In any of the crystal grain size measuring devices of the first to third inventions, the crystal of the crystal is changed every time the brightness threshold value used for binarization is changed.
The deviation between the particle size and the predetermined value is calculated. Then, these calculations are repeated and calculated according to the change of the brightness threshold .
The brightness threshold that minimizes the deviation is selected .

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. Hereinafter, the present invention will be described in detail with reference to the drawings showing an embodiment thereof. FIG. 1 is a block diagram showing the configuration of the crystal grain size measuring apparatus according to the first embodiment.

In FIG. 1, reference numeral 1 denotes an object to be measured, which is made of, for example, an Al—Zn plated steel plate after surface coating, and the surface to be measured 11 is located on the surface 11 to be measured. A light source 2 whose irradiation angle θ and light amount can be adjusted is provided, and an imager 3 such as a camera and a CCD is provided on the same side so as to face the surface 11 to be measured. Imager 3
The picked-up image data of is given to the image processing device 4,
The image processing device 4 calculates the crystal grain size on the surface 11 to be measured. It is desirable to use a linear light source or a surface light source as the light source 2 in order to irradiate the surface 11 to be measured with a uniform amount of light.

The image processing device 4 binarizes the image data input from the image input unit 41 and the image input unit 41 as an interface of the image pickup device 3 provided with an A / D converter, a frame memory and the like 2 A binarization processing unit 42, a preprocessing unit 43 that performs preprocessing such as noise removal and hole filling, and a crystal grain size calculation unit 44 that calculates the crystal grain size based on the binarized data after the preprocessing are provided. Become. The crystal grain size calculation unit 4
The crystal grain size calculated in 4 can be displayed on a display device (not shown) and can also be used as a feedback value to a control device for controlling the crystal grain size.

FIGS. 2 and 3 are schematic views showing an example of a picked-up image of the surface 11 to be measured, and in particular, FIG. 2 does not use the light source 2 in the crystal grain size measuring apparatus having the above-mentioned configuration and natural light is emitted. FIG. 3 shows an image pickup result when the surface to be measured 11 is irradiated.
3A and 3B respectively show imaging results by the crystal grain size measuring device according to the present invention.

In FIG. 2, the darkest black portion (cross hatching portion) is the spangles s, s, ..., As shown in FIG. 2, in the image captured by natural light, the spangles s, s ,. The hatched portion) has a small difference in density and the captured image in this state is captured by the image processing device 4
It is difficult to accurately measure the crystal grain size as described above even when the light source 2 is set to a light source 2 set to a predetermined irradiation angle θ and a predetermined light amount, which will be described later. As shown in FIG. 3, the measured surface 11 is provided by providing
It is possible to increase the difference in density between the spangles s, s, ... (Cross hatching portion) and other crystal grains (white portion) at the stage of imaging.

FIG. 4 is a graph showing the relationship between the irradiation angle θ when an Al-Zn plated steel sheet is used as the DUT 1 and the measurement error of the crystal grain size obtained from the captured image at that time. The irradiation angle θ (°) is arranged on the axis, and the crystal grain size measurement error (mm) is arranged on the vertical axis. In addition, FIG.
6 is a graph showing the relationship between the illuminance w of the surface 11 to be measured by the light source 2 and the measurement error of the crystal grain size obtained from the captured image when the n-plated steel plate is the object to be measured 1; Is the illuminance w (kLux), and the vertical axis is the crystal grain size measurement error (m
m) are arranged respectively.

In these graphs, first, with either one of the irradiation angle θ and the illuminance w fixed at an appropriate value within the measurable range of the particle size, the other value is adjusted to obtain a captured image. While observing with a display device, the other value is fixed at a value at which the spangle and other crystal grains can be clearly distinguished as shown in FIG. 3, and the one value is measured while changing the other value. Is.

As shown in FIGS. 4 and 5, the irradiation angle θ is 13 ° <θ <23 ° and the illuminance w is 13 kLux <w <25.
When kLux, the crystal grain size measurement error is ± 0.1m each
It is m, which means that the measurement accuracy is sufficiently high for practical use. Therefore, not only Al-Zn plated steel sheet,
The relationship between the irradiation angle θ and the illuminance w as described above is experimentally measured with respect to the DUT 1 having the same crystal structure, and the light source 2 is controlled so that the irradiation angle θ and the illuminance fall within this range.
By setting the optical axis angle of each crystal grain in the captured image obtained by the image pickup device 3, the difference in shade between the specific crystal grain and the other crystal grain is increased, and the original light distribution of each crystal grain is obtained. Only specific crystal grains can be extracted by emphasizing the difference in sex.

FIG. 6 is a flow chart showing the processing procedure of the particle size calculation in the image processing apparatus 4. First, the captured image data as shown in FIG. 3 given from the image pickup device 3 to the image input unit 41 is quantized (step 1) and binarized by the binarization processing unit 42 as shown in FIG. 7 (step 2). .

FIG. 7 is a schematic diagram showing the result of binarizing the captured image shown in FIG. 3 by the image processing device 4. The irradiation angle θ of the light emitted from the light source 2 to the surface 11 to be measured within the above-described range, and the illuminance w on the surface 11 to be measured by this irradiation light.
7 is preset, only the spangles s, s, ... Can be extracted in white from the captured image data of the surface 11 to be measured.

Next, the binarized image data is subjected to pre-processing such as noise removal and hole filling (step 3), and then FIG.
The number of pixels forming the white portion corresponding to the spangle as shown in (4) is calculated (step 4), the area is calculated based on this number of pixels (step 5), and the diameter of the circle corresponding to this area is calculated ( Step 6). It is confirmed whether steps 4 to 6 have been performed for all spangles (step 7), and if they have been performed for all spangles, the average value of the diameters calculated in step 6 is calculated (step 8). Let this be the crystal grain size of spangle.
If all spangles have not been processed in step 7, steps 4 to 7 are repeated.

FIG. 8 is a graph showing the measurement accuracy of the crystal grain size measuring apparatus according to the present invention, where the horizontal axis is JIS G 0.
The average particle size measurement value (mm) measured by the method according to 551 is arranged, and the vertical axis corresponds to the horizontal axis and the average particle size measurement value (measured by the crystal grain size measuring device according to the present invention ( mm) are arranged respectively.

As shown in FIG. 8, the relationship between the measured values of the average grain sizes on the horizontal axis and the vertical axis converges on a substantially straight line, and the crystal grain size measuring apparatus according to the present invention has a specific crystal grain and other grains. It can be seen that even if the difference in density from the crystal grains is small, only specific crystal grains can be extracted to measure the crystal grain size with high accuracy.

In the above embodiment, the irradiation angle θ of the light source 2 onto the surface 11 to be measured can be changed. However, the present invention is not limited to this, and the light source 2 is fixed at a predetermined irradiation angle θ. It goes without saying that the optical axis angle of the image pickup device 3 with respect to the measured surface 11 can be changed according to the above.

Further, although the grain size of specific crystal grains such as spangles is measured after the surface coating treatment, it goes without saying that the grain size may be measured before the surface coating treatment. , The measurement target is not limited to the spangle.

Embodiment 2. FIG. 9 is a block diagram showing the configuration of the crystal grain size measuring apparatus according to the second embodiment. In FIG. 9, a light source 2 that is capable of adjusting the irradiation angle θ and the amount of light to the measured surface 11 is provided on the measured surface 11 side of the measured object 1 by the light source control device 5, and on the same side. , C
An imager 3 including a CD is provided so as to face the surface 11 to be measured. Image data captured by the image pickup device 3 is supplied to the image processing device 4, and the image processing device 4 calculates the crystal grain size on the surface 11 to be measured.

The light source 2 is supported by a support frame (not shown) so that the irradiation angle θ can be changed within the range of 0 ° to 90 °. As the light source 2, any shape such as a spot, a line, a surface, or a ring can be used, but the measured surface 11 is irradiated with a uniform light amount, and the influence of shading in the imaging visual field by the imaging device 3 is exerted. It is desirable to use a line light source or an area light source in order to minimize As the light source 2, a white light source such as halogen, metal halide, or xenon can be used, but it is preferable to use a white light source having a relatively long life and about 100 W or more. It goes without saying that the illuminance on the surface 11 to be measured varies depending on the distance between the light source 2 and the surface 11 to be measured, the size of the imaging field of view, and the like. Further, when the surface 11 to be measured moves, a stroboscopic type capable of instantaneous light emission is used to suppress image blurring.

The light source control device 5 for adjusting and controlling the irradiation angle θ and the light amount of the light source 2 has the irradiation angle θ and the light amount instruction values from an external input means such as a ten-key pad, and the image processing device 4 stored in advance. By inputting the input binarization threshold value (luminance threshold value) and the spangle crystal grain size (crystal grain size true value) obtained in advance in the standard sample of the DUT 1, the optimum irradiation angle θ, light amount, 2 In addition to calculating the binarization threshold value and adjusting and controlling the light source 2, the binarization threshold value that has been computed is supplied to the image processing device 2 and a trigger signal is supplied to the image processing device 2 during this computation. As mentioned above,
When the stroboscopic light source 2 is used, it is desirable that the light emitting period, the pulse width, etc. can be controlled in addition to the irradiation angle θ and the light amount. When the irradiation angle (incident angle) θ of the light source 2 controlled by the light source control device 5 is an acute angle, for example, when measuring the crystal grain size of spangles deposited on the surface 11 to be measured, the optical characteristics of the spangles are measured. The reflected light at the spangle can be increased and emphasized by the light quantity of the light source 2 and the image processing device 4.
It is not a steady effect due to the threshold value of binarization in.

The image pickup device 3 for picking up the surface 11 to be measured is a general CCD equipped with a full frame memory (for one screen), and is provided sufficiently distant from the surface 11 to be measured.
It is desirable to have a zoom lens whose zoom magnification (zoom ratio) can be manually or automatically adjusted according to the measurement of a minute spangle crystal grain size. Further, when the light from the light source 2 is on or near the optical axis where the surface 11 to be measured is regularly reflected (broken line a in FIG. 9), halation occurs in the imaged image, and the imaged object to be measured is imaged. Since an apparent deformation occurs in the spangle of the surface 11, the imager 3 is provided on the optical axis perpendicular to the surface 11 to be measured (broken line b in FIG. 9).

The image processing device 4 includes an A / D converter (not shown) and the like, and prior to optimizing parameters to be described later such as control parameters of the light source 2 and measurement parameters of the image processing device 4, the light source control device 5 is provided. In accordance with the trigger signal given from the image pickup device 3, the picked-up image data of the measured surface 11 given from the image pickup device 3 is A / D converted, and binarized based on the binarization threshold given from the light source control device 5, It has a function of performing processing (noise removal, hole filling, etc.) and calculating the crystal grain size based on the pretreatment result, and feeds back the calculation result (crystal grain size measurement value) to the light source control device 5.
When performing a stable continuous calculation of the crystal grain size after setting the above-mentioned parameters, the internal timer calculates the crystal grain size in a predetermined cycle without a trigger signal from the light source control device 5. Do.

FIG. 10 and FIG. 11 are flowcharts showing the process of determining the irradiation angle θ, the light amount, and the binarization threshold value in the light source control device 5. First, each input value is temporarily set (fixed) to the irradiation angle θ and the binarization threshold value (step 1,
2) The light amount is adjusted (changed) to a preset initial value (step 3), and a trigger signal is output to the image processing device 4 to calculate the spangle crystal grain size in this state (step 4). Next, the crystal grain size measurement value fed back from the image processing device 4 is stored in an internal memory (not shown) together with the corresponding light amount, and it is confirmed whether or not the measurement of the crystal grain size with all the light amounts is completed (step 5). When the measurement of the crystal grain size is not completed for all the light amounts, the light amount is changed in a preset increment and steps 3 to 5 are repeated.

In step 5, when the measurement of the crystal grain size with all the light quantities is completed, the error between each crystal grain size measurement value stored in the internal memory and the input crystal grain size true value is calculated. Each is calculated (step 6), and the light quantity corresponding to the smallest error is selected from these (step 7).

This time, the amount of light selected in step 7 is fixed, the irradiation angle θ is adjusted to a preset initial value (step 8), and image processing is performed to calculate the spangle crystal grain size in this state. A trigger signal is output to the device 4 (step 9). Then, the crystal grain size measurement value fed back from the image processing device 4 is used as the corresponding irradiation angle θ.
It is also stored in the internal memory together with whether or not the measurement of the crystal grain size at all irradiation angles θ is completed (step 1
0). When the measurement of the crystal grain size at all irradiation angles θ has not been completed, the irradiation angle θ is changed in a preset increment and steps 8 to 10 are repeated.

Then, in step 10, when the measurement of the crystal grain size at all irradiation angles θ is completed, each crystal grain size measurement value stored in the internal memory and the input crystal grain size true value are stored. Are calculated (step 11), and the irradiation angle θ corresponding to the smallest error is selected from these (step 12).

Next, the irradiation angle θ selected in step 12 is fixed, and it is confirmed whether or not the minimum error in step 12 exceeds a preset threshold value (step 1).
3).

If the minimum error in step 12 does not exceed the threshold value, the binarization threshold value is adjusted to a preset initial value (step 14) to calculate the spangle crystal grain size in this state. First, the binarization threshold value is output to the image processing device 4 (step 15), and then the trigger signal is output to the image processing device 4 (step 1).
6). Next, the crystal grain size measurement value fed back from the image processing device 4 is stored in an internal memory together with the corresponding binarization threshold value, and whether or not the measurement of the crystal grain size with all the binarization threshold values is completed is performed. Confirm (step 17). When the measurement of the crystal grain size is not completed for all the binarization thresholds, the binarization threshold is changed by a preset increment and steps 14 to 17 are repeated.

Next, in step 17, when the measurement of the crystal grain size at all the binarization threshold values has been completed, each crystal grain size measurement value stored in the internal memory and the input crystal grain size. The error from the true value is calculated (step 18), and the binarization threshold value corresponding to the smallest error is selected from these (step 19). When the minimum error exceeds the threshold value in step 13, or after step 19, the process ends.

In the above determination process, the irradiation angle θ is first fixed and the light amount is changed, and then the light amount is fixed and the irradiation angle θ is changed. However, conversely, the light amount is first fixed. It is also possible to change the irradiation angle θ and then fix the irradiation angle θ to change the light amount.

With the above-described structure, stable measurement can be performed based on the obtained optimum irradiation angle θ, light quantity, and binarization threshold, and the parts corresponding to those of the first embodiment can be obtained. Are denoted by the same reference symbols and description thereof will be omitted.

FIG. 12 shows Step 3 of FIGS. 10 and 11 when the Zn-55% Al plated steel plate is used as the DUT 1.
Is a graph showing the relationship between the illuminance w of the measured surface 11 corresponding to the amount of light changed in step 6 and the crystal grain size measurement error obtained from the captured image at that time, and the abscissa represents the illuminance w (kLux) The crystal grain size measurement error (mm) is arranged on the vertical axis. Further, FIG. 13 shows the irradiation angle θ changed in step 8 to step 11 of FIGS. 10 and 11 when the Zn-55% Al plated steel plate is used as the DUT 1, and obtained from the captured image at that time. 2 is a graph showing the relationship between the measured crystal grain size error and the irradiation angle θ on the horizontal axis.
(°) and the crystal grain size measurement error (mm) are arranged on the vertical axis.

As shown in FIGS. 12 and 13, for example, when the set crystal grain size measurement error is within ± 0.1 mm, the illuminance w is 12 kLux to 25 kLux and the irradiation angle θ.
The optimum value is obtained in the range of 13 ° to 23 °. The binarization threshold value in the image processing device 4 at this time was 80.

FIG. 14 shows the true value of crystal grain size and the image processing apparatus 4.
2 is a graph showing the relationship with the crystal grain size measurement value obtained in Fig. 4, in which the abscissa axis is the crystal grain size true value (mm), and the ordinate axis is the crystal grain size measurement value (mm) corresponding to the abscissa axis. Are arranged respectively.

As shown in FIG. 14, the error of the measured crystal grain size with respect to the true crystal grain size is about ± 0.1 mm, and it can be seen that it has sufficient practicality.

Regarding the method of obtaining the true value of the crystal grain size,
This will be described with reference to FIG. FIG. 15 is an explanatory diagram for explaining how to determine the true value of the crystal grain size, and shows a part of the spangles s, s, ... 15, a line segment AA having an arbitrary length and direction is set on the surface 11 to be measured, and the number of spangles s, s, ... Crossed by the line segment AA is visually counted. And
The true value of the crystal grain size can be obtained by dividing the length of the line segment AA by the number of the above-mentioned spangles s, s, ....

Third Embodiment FIG. 16 is a block diagram showing the configuration of the crystal grain size measuring apparatus according to the third embodiment.
In FIG. 16, the crystal grain size measuring apparatus is
Steel plate (measurement object) that is transported to the next process after plating 1
It is provided to measure the crystal grain size of spangles deposited on the surface (surface to be measured) 11 of.

The strip-shaped steel plate 1 is conveyed by two rollers r, r, and the illumination probe 21 for irradiating the steel plate 1 in the middle of these rollers r, r emits light (incident angle) θ. Is supported by a support frame (not shown) so that it can be changed in the range of 0 ° to 90 °, and the illumination probe 21 is connected to the light source 2 via an optical fiber 22.

As the illumination probe 21, any shape such as spot, line, surface, ring, etc. can be used, but for the same reason as in the first embodiment, it is set to a shape such as a line light source or a surface light source. Is desirable. Furthermore, in the present embodiment, since the surface 11 to be measured moves as the steel sheet 1 is conveyed, a stroboscopic type capable of instantaneous light emission is used to suppress image blur. The light emission cycle can be fixed at a preset cycle, but in the present embodiment, the camera control unit 53 connected to the light source 2 adjusts the light emission cycle according to the variation in the transport speed of the steel plate 1. Has become.

The camera (image pickup device) 3 is connected to the image freezer 31 for adjusting the image pickup cycle.
1 determines an image pickup cycle in accordance with the conveyance speed of the steel plate 1 and the light emission cycle of the light source 2 so as to reduce the image pickup shake, outputs a trigger signal for making the camera 3 pick up an image, and is picked up by the camera 3. The processed image is processed in frame units, and the processing result is given to the image processing unit 4. When the light emission period of the light source 2 is sufficiently smaller than the conveying speed of the steel plate 1, the image blurring is small, and thus the image freezer 31 can be omitted.

The image processing section 4 is composed of a microprocessor, quantizes the image data of the surface 11 to be measured, which is given from the image freezer 31, and quantizes the quantized image data on the CRT.
42 to display the captured image data, and
Further, this image data is binarized, pre-processed (noise removal, hole filling, etc.), and the crystal grain size is calculated based on the pre-processing result, and then the calculation result (crystal grain size measurement value) is calculated.
Give to. Further, the image processing unit 4 stores the calculation result and the captured image data in the image storage unit 43 as needed.

The camera control unit 53 is composed of a microprocessor different from the image processing unit 4, and the crystal grain size measurement value given from the image processing unit 4 is transmitted via the communication control unit 52 including a modem, a router, etc. It is designed to be sent to a host computer (not shown). Similarly, information on the transport speed of the steel sheet 1 is received from the host computer via the communication control unit 52, and the camera control unit 53 gives this information on the transport speed to the camera 3. The camera control unit 53 further outputs the above operating state to the CRT 51.

The transmission of the camera control section 53 to the host computer can be made to coincide with the image pickup cycle of the camera 3, and the average value of the crystal grain size measurement values from a predetermined number of image pickup images is calculated, It is also possible to adopt a configuration in which this is sent out at the imaging cycle of the predetermined number of times. However, the transmission speed depends on the processing speeds of the image processing unit 4 and the camera control unit 53, but in reality, the fluctuation of the spangle crystal grain size in the transport direction of the steel sheet 1 is not abrupt, and therefore several H
A period corresponding to z to several tens Hz is practically sufficient.

In the present embodiment, Al-Z
Although the steel plate 1 is imaged while being conveyed to the next step after the n-plating process, the imaging position is not limited to this. However, with quick feedback of the measured grain size,
In order to avoid the measurement error of the crystal grain size due to the flapping of the conveyed steel plate 1, the plate elongation, etc., it is desirable that the imaging position be as close to the solidification completion position as possible after the plating pot. In order to stabilize the pass line of steel plate 1,
It is desirable that one of the rolls r, r is in the vicinity thereof.

FIG. 17 is a flow chart showing the processing procedure of the crystal grain size calculation in the image processing section 4. First, the image data given from the image freezer 31 is quantized (step 1) and binarized using a threshold value set in advance by the procedure as described in the second embodiment (step 2), 2
Preprocessing such as isolated point removal and hole filling, which is a general image processing method, is performed on the binarized image data (step 3). Next, the number of pixels in the portion corresponding to the spangle is calculated (step 4), and the area corresponding to this pixel is calculated based on this number of pixels and the actual size value of one pixel calculated in advance (step 5), The diameter of the circle corresponding to the calculated area is calculated (step 6). Then, it is confirmed whether or not steps 4 to 6 have been performed for all spangles (step 7), and if they have been performed for all spangles, spangles having a small diameter are excluded based on a preset threshold value. (Step 8: area removal). The average value of the diameters of the spangles remaining without being removed in step 8 is calculated (step 9), and this is used as the crystal grain size of spangles.
If all spangles have not been processed in step 7, steps 4 to 6 are repeated.

The threshold in step 8 is the same as the above-mentioned grain size measurement in the state where no spangle is precipitated (zero spangle), and the measured value at this time is used.

FIG. 18 is an explanatory view for explaining the removal of isolated points in the preprocessing of step 3 described above, and schematically shows the state after binarization in step 2. In FIG. 18, the imaging area of the surface to be measured 11 has a grid shape, and each rectangular area divided by the grid represents one pixel. In each pixel, the spangle after binarization is indicated by "1", and the other portions are indicated by "0", but due to factors such as dust on the surface 11 to be measured, some noise at the time of imaging, etc. The part may be displayed as "1". So, in this isolated point removal, "1"
When the eight pixels surrounding the pixel are all "0" and the pixel is replaced with "0", the influence as described above can be eliminated.

FIG. 19 is an explanatory view for explaining filling in the preprocessing of the above-mentioned step 3, and schematically shows the state after the binarization in step 2 as in FIG. In FIG. 19, consecutive "1" pixel groups indicate a spangle, and surrounding "0" pixel groups indicate the other part. However, for the same reason as the above-described removal of isolated points, the pixel group of "0" may be mixed in the pixel group of spangle. Therefore, by focusing on the pixel of “0” surrounded by the pixel group of “1” or the pixel group and replacing the pixel or pixel group of “0” with “1”, the above influence is eliminated. can do.

FIG. 20 is a graph showing the relationship between the result of measuring the spangle crystal grain size of the steel sheet 1 by the crystal grain size measuring apparatus according to the third embodiment and the corresponding transport speed of the steel sheet 1. The measured length of the steel sheet 1 (length in the conveying direction: km) is arranged on the axis, and the crystal grain size measurement value (mm) corresponding to the horizontal axis and the conveying speed (m / min) are arranged on the vertical axis. There is. Further, on the graph of the crystal grain size measurement value, the result of obtaining the crystal grain size true value at an arbitrary measurement length interval is plotted by the X mark. Further, as the steel plate 1 to be measured, a steel plate 1a having a plate thickness of 0.7 mm is first used, and when the measurement length is about 0.58 km, it is switched to a steel plate 1b having a plate thickness of 1.3 mm.

As shown in FIG. 20, it can be seen that the measured crystal grain size agrees with the true crystal grain size regardless of the change in the transport speed.

The present embodiment is configured as described above, and the portions corresponding to those of the second embodiment are designated by the same reference numerals and the description thereof will be omitted.

Fourth Embodiment FIG. 21 is a block diagram showing the configuration of the crystal grain size measuring apparatus according to the fourth embodiment.

In FIG. 21, the movable mechanism portion 34 is arranged in parallel with the conveying direction of the steel plate 1 and is provided with a beam 341 movably provided in a direction of approaching and separating from the steel plate 1 (a hollow arrow direction). , A guide screw 342 that is screwed into a screw hole that penetrates the beam 341 in the direction of the hollow arrow and is screwed into the screw hole. A motor 33 that rotates the guide screw 342 guides its output shaft. It is provided coaxially with the screw 342. A camera 3 is provided in the middle of the beam 341 so as to face the steel plate 1.

In the middle of the beam 341, the rangefinder 3
2 is provided to face the steel plate 1. This rangefinder 32
Is to irradiate the surface of the steel plate 1 with a laser, and optically measure the distance (measurement distance) between the camera 3 and the surface of the steel plate 1 based on the reflected light thereof.
This measurement result is given to the image processing unit 4. In addition, rangefinder 3
In addition to the above-mentioned laser type, a general distance measuring means such as a contact type, an ultrasonic type, an eddy current type, etc. can be used for 2, but it is a non-contact type so as not to scratch the steel plate 1. Expression is preferred.

The image processing unit 4 has the same function as the image processing unit 4 of the third embodiment, and after calculating the crystal grain size based on the preprocessing result and the distance measurement result from the distance meter 32. Then, the calculation result (measurement value of crystal grain size) is displayed as the camera control unit 53.
Give to.

FIG. 22 is a flow chart showing the processing procedure of the crystal grain size calculation in the image processing section 4. First, quantization, binarization, and preprocessing are performed as in steps 1 to 3 of FIG. 17 in the third embodiment (steps 1 to 3). Then, the distance measurement result (measurement distance) by the distance meter 32 is read (step 4), and the actual size of one pixel is calculated based on the read result (step 5). Then, step 4 in FIG.
9 to 9 are performed (steps 6 to 11).

FIG. 23 is an explanatory diagram for explaining the calculation of the actual size of one pixel in step 5 described above. Figure 2
3, p represents the size of one pixel, and 1,1
Indicates a steel plate. Although the steel plate 1 is normally at the position b (reference position), the distance between the surface of the steel plate 1 which is the surface 11 to be measured and the camera 3 (measurement distance) changes due to flapping, fluctuations in thickness, and the like. The size of the spangle of the surface 11 to be measured, which is calculated based on the size of the pixel, needs to be corrected according to the variation in the above-described measurement distance. When the steel plate 1 is at the reference position b, the reference position b and the camera 3
The distance between and is Db (reference measurement distance), and the size of one pixel at that time is Xb (reference pixel size). Then, for example, when the steel plate 1 is moved to the position s as shown in FIG. 23,
D is the distance between the position b measured by the distance meter 32 and the camera 3.
The actual size Xs of one pixel when s can be obtained by the formula Xs = (Xb / Db) · Ds. The reference measurement distance Db,
The reference pixel size Xb can be easily obtained in advance by actual measurement.

FIG. 24 is a graph showing the relationship between the results of measuring the spangle crystal grain size of the steel sheet 1 by the crystal grain size measuring apparatus according to the fourth embodiment and the corresponding measurement distances. Measured length of steel plate 1 (length in conveyance direction: km)
Are arranged, and the vertical axis indicates the measured crystal grain size (m
m) and the measurement distance deviation (mm) from the reference measurement distance as described above are respectively arranged. Further, on the graph of the crystal grain size measurement value, the result of obtaining the crystal grain size true value at an arbitrary measurement length interval is plotted by the X mark.

As shown in FIG. 24, it can be seen that the measured crystal grain size agrees with the true crystal grain size regardless of the variation in the measurement distance.

The present embodiment is configured as described above, and the portions corresponding to those of the third embodiment are designated by the same reference numerals and the description thereof will be omitted.

[0082]

As described in detail above, according to the crystal grain size measuring apparatus according to the first aspect of the present invention, the difference in shade between a predetermined type of crystal grain (spangle) to be imaged and other crystal grains is further clarified .
That it can, spangle and other crystals that are imaged
It is possible to select the optimum amount of light to clarify the difference in light and shade of grains.
Therefore, the accurate calculation result of the crystal grain size can be stably obtained from the captured image .

[0083]

Further, according to the crystal grain size measuring apparatus of the second aspect of the present invention, it is possible to further clarify the shade difference between the predetermined type of crystal grain (spangle) to be imaged and the other crystal grain, and the image is captured. Of the optimum light irradiation means or the image pickup device to clarify the difference in density of spangles and other crystal grains .
The optical axis angle can be selected, and the accurate calculation result of the crystal grain size can be stably obtained from the captured image.

[0085]

[0086]

Further, according to the crystal grain size measuring apparatus of the third aspect of the present invention, it is possible to further clarify the difference in shade between the predetermined type of crystal grain (spangle) to be imaged and other crystal grains.
Difference in density of spangles and other crystal grains imaged
The optimum light amount and irradiation angle of the light irradiation means or
It can be selected optical axis angle of the imager and Do Ri, positive from a captured image
An accurate calculation result of the crystal grain size can be stably obtained .

Further, according to the crystal grain size measuring apparatus of the fourth invention, a predetermined type of crystal grain (spangle) to be imaged.
The present invention has excellent effects such as the selection of an optimum brightness threshold value that makes clear the difference in density between the crystal grain and other crystal grains .

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a crystal grain size measuring apparatus according to the present invention.

FIG. 2 is a schematic diagram showing an example of a captured image of a surface to be measured captured under natural light.

FIG. 3 is a schematic diagram showing an example of a captured image of a surface to be measured, which is captured by a crystal grain size measuring apparatus according to the present invention.

FIG. 4 is a graph showing a relationship between an irradiation angle θ when an Al—Zn plated steel sheet is used as a measured object and a measurement error of a crystal grain size obtained from a captured image at that time.

FIG. 5 is a graph showing the relationship between the illuminance w of the surface to be measured when an Al—Zn plated steel sheet is used as the object to be measured, and the measurement error of the crystal grain size obtained from the captured image at that time.

FIG. 6 is a flowchart showing a processing procedure of particle size calculation in the image processing apparatus.

FIG. 7 is a schematic diagram showing a binarization result of the captured image shown in FIG.

FIG. 8 is a graph showing the measurement accuracy of the crystal grain size measuring apparatus according to the present invention.

FIG. 9 is a block diagram showing a configuration of a crystal grain size measuring device according to a second embodiment.

FIG. 10: Irradiation angle θ, light quantity, 2 in the light source control device
It is a flowchart which shows the determination process of a threshold value.

FIG. 11: Irradiation angle θ, light quantity, 2 in the light source control device
It is a flowchart which shows the determination process of a threshold value.

FIG. 12 shows steps 3 to 6 of FIGS. 10 and 11 when a Zn-55% Al plated steel plate is used as the DUT 1.
The illuminance of the measured surface corresponding to the amount of light changed in
It is a graph which shows the relationship with the crystal grain size measurement error obtained from a captured image at that time.

FIG. 13: Steps 8 to 1 of FIGS. 10 and 11 when a Zn-55% Al plated steel plate is used as the DUT 1.
3 is a graph showing the relationship between the irradiation angle changed in 1 and the crystal grain size measurement error obtained from the captured image at that time.

FIG. 14 is a graph showing a relationship between a true crystal grain size and a crystal grain size measurement value obtained by an image processing apparatus.

FIG. 15 is an explanatory diagram for explaining how to determine a true value of a crystal grain size.

FIG. 16 is a block diagram showing a configuration of a crystal grain size measuring apparatus according to a third embodiment.

FIG. 17 is a flowchart showing a processing procedure of a crystal grain size calculation in the image processing unit.

FIG. 18 is an explanatory diagram for explaining isolated point removal in the preprocessing of step 3 described above.

FIG. 19 is an explanatory diagram for explaining hole filling in the preprocessing of step 3 described above.

FIG. 20 is a graph showing the relationship between the result of measuring the spangle crystal grain size of the steel sheet by the crystal grain size measuring apparatus according to the third embodiment and the corresponding transport speed of the steel sheet.

FIG. 21 is a block diagram showing a configuration of a crystal grain size measuring device according to a fourth embodiment.

FIG. 22 is a flowchart showing a processing procedure for calculating a crystal grain size in the image processing unit.

FIG. 23 is an explanatory diagram for explaining calculation of an actual size of one pixel in step 5 described above.

FIG. 24 is a graph showing the relationship between the result of measuring the spangle crystal grain size of a steel sheet by the crystal grain size measuring apparatus according to the fourth embodiment and the corresponding measurement distance.

[Explanation of symbols]

1 DUT 2 light sources 3 imager 4 Image processing device 11 Surface to be measured 41 Image input section 42 Binarization processing unit 43 Pretreatment section 44 Particle size calculator

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-11-72317 (JP, A) JP-A-7-294452 (JP, A) JP-A-59-99304 (JP, A) JP-A-54- 128756 (JP, A) JP-A-7-139930 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01B 11/00-11/30 G01N 15/02 G01N 21/00- 21/958 G01N 33/20

Claims (4)

(57) [Claims] 1. The grain size of the crystal grain is measured by imaging the surface of the object to be measured with an imager and calculating the grain size of a predetermined type of crystal grain deposited on the surface to be measured from the imaging result. In a crystal grain size measuring device , a quantizing means for quantizing the imaging result and a quantizing result of the quantizing means based on a predetermined brightness threshold value.
The predetermined type of crystal grains are identified by binarization.
Binarizing / identifying means, and the predetermined type of crystal grain identified by the binarizing / identifying means
Means for counting the number of pixels, and area calculation for calculating an area according to the counting result of the counting means
Means and a diameter of a circle corresponding to the calculation result of the area calculation means.
And a diameter calculation means for calculating the particle diameter based on the calculation result of the diameter calculation means.
Grain size calculating means, light irradiating means for irradiating the surface to be measured, and light amount of the light irradiating means, and the crystal of the predetermined type to be imaged
The image is taken to clarify the difference in density between the grain and other crystal grains.
The light quantity increasing / decreasing means that increases / decreases according to the sensitivity of the container, and the particle size control means each time the light quantity increasing / decreasing means increases / decreases the light quantity.
The deviation between the particle size calculated by the calculation means and the predetermined value is calculated.
Deviation calculation means for calculating, and the light irradiation means for minimizing the calculation result of the deviation calculation means
And a light amount selecting means for selecting the light amount of the crystal grain size measuring device . 2. The grain size of the crystal grain is measured by imaging the surface of the object to be measured using an imager and calculating the grain size of a predetermined type of crystal grain deposited on the surface to be measured from the imaged result. In a crystal grain size measuring device, a quantizing means for quantizing the imaging result, and a binarization of the quantizing result of the quantizing means on the basis of a predetermined luminance threshold to identify the predetermined type of crystal grain. Binarization / identification means, counting means for counting the pixels of the predetermined type of crystal grains identified by the binarization / identification means, and area calculation means for calculating an area according to the counting result of the counting means A diameter calculation means for calculating the diameter of a circle corresponding to the calculation result of the area calculation means, a particle size calculation means for calculating the particle size based on the calculation result of the diameter calculation means, and a light irradiating means for irradiating light, said light irradiating means Irradiation angle or the imaging of the measuring surface
An optical axis angle with respect to the surface to be measured of the device, an angle changing means for changing the optical axis angle according to the sensitivity of the image pickup device in order to clarify the difference in density between the crystal grains of the predetermined type to be imaged and other crystal grains, The angle changing means is the irradiation angle of the light irradiation means or the photographing
Each time the optical axis angle of the imager is changed , the particle size calculating means is used.
Deviation calculating a deviation between the particle diameter and the predetermined value calculated Ri
Arithmetic means, said light irradiating means the operation result of said deviation calculation means is minimum
Crystal grain size measuring apparatus, characterized in that it comprises a angle selection <br/>-option means for selecting the optical axis angle of the illumination angle or the imager. 3. A surface of an object to be measured is imaged by using an imager.
Then, based on the imaging results, the specified types of crystal grains that precipitate on the surface to be measured
The grain size of the crystal grain is measured by calculating the grain size of
In the crystal grain size measuring device, a quantizing means for quantizing the imaging result, and a quantizing result of the quantizing means based on a predetermined brightness threshold value.
The predetermined type of crystal grains are identified by binarization.
Binarizing / identifying means, and the predetermined type of crystal grain identified by the binarizing / identifying means
Means for counting the number of pixels, and area calculation for calculating an area according to the counting result of the counting means
Means and a diameter of a circle corresponding to the calculation result of the area calculation means.
And a diameter calculation means for calculating the particle diameter based on the calculation result of the diameter calculation means.
Grain size calculating means, light irradiating means for irradiating the surface to be measured, and light amount of the light irradiating means, and the crystal of the predetermined type to be imaged
The image is taken to clarify the difference in density between the grain and other crystal grains.
Light amount increasing / decreasing means that increases / decreases in accordance with the sensitivity of the measuring device, and the irradiation angle of the light irradiation means to the measured surface or the imaging
Before imaging the optical axis angle of the imager with respect to the measured surface
Clarify the difference in shade between the specified type of crystal grain and other crystal grains
Therefore, the angle changing means for changing the light quantity according to the sensitivity of the image pickup device, each time the light quantity increasing / decreasing means increases / decreases the light quantity, and the angle changing means changes the irradiation angle of the light irradiation means or the imaging.
A deviation calculation for calculating the deviation between the particle size calculated by the particle size calculation means and a predetermined value each time the optical axis angle of the container is changed.
Calculation means and the light irradiation means for minimizing the calculation result of the deviation calculation means
Of light and the irradiation angle of the light irradiation means or the image pickup device
Further comprising a light intensity / angle selection means for selecting the optical axis angle
A crystal grain size measuring device characterized by: 4. Further comprising threshold changing means for changing the brightness threshold and threshold selecting means for selecting the brightness threshold.
For example, the threshold selecting means, every time the threshold value changing means changes the luminance threshold, as the deviation between the particle diameter and the predetermined value which is calculated by said deviation calculation means selects a brightness threshold becomes minimum claims 1 to 3 Neu, characterized in that
Crystal grain size measuring apparatus according to Zureka.