JP2695338B2 - Hardness measuring method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hardness measuring method.

[0002]

2. Description of the Related Art Conventionally, a method of marking a square quadrilateral indentation on a measurement sample with a predetermined pressure and measuring the diagonal length of the indentation to specify the hardness of the measurement sample has been conventionally related to a Vickers hardness tester. The device disclosed in Japanese Patent Publication No. 3-34819 is well known as a device for performing such a measuring method.

In this conventional apparatus, since the indentation is read by using a one-dimensional image pickup element, it takes a long time to read the indentation image, and the diagonal length is likely to be different from the visual measurement. There is.

In order to solve such a problem, the inventors of the present invention have stated that "it is possible to move in the X, Y and Z directions orthogonal to each other, and Z
A two-dimensional image sensor and a movable stage rotatable about a rotation axis parallel to the direction, and a plurality of objective lenses and indenters having different imaging magnifications are equidistant from the rotation axis. The revolver provided at the position of 1 is disposed between the moving stage and the image pickup device so as to be rotatable about the rotation axis parallel to the Z direction and movable in the Z direction, and the measurement sample installed on the moving stage. After making an indentation on the
Rotate the revolver and select the objective lens with the proper magnification,
A magnified image of the indentation is formed on the light-receiving surface of the image sensor with the selected objective lens, the indentation image is read, the diagonal length of the indentation image is measured, and the hardness of the measurement sample is calculated. "Fully automatic hardness measurement method Is intended for practical use.

In this measuring method, the process from setting the measurement sample on the moving stage to calculating the hardness is automatically performed. Since a two-dimensional image pickup device is used to read the indentation image, a measured value that is in good agreement with the visual measurement can be obtained, but the amount of information to be handled is large, and therefore devising is necessary to perform high-speed automatic measurement.

A factor important in realizing high-speed automatic measurement is "immediately forming an indentation image of an appropriate size at an appropriate position on the light-receiving surface of a two-dimensional image pickup device". In the above measurement method, "the objective lens and the indenter are located at the same distance from the rotation axis of the revolver", so that the objective lens can be set at a position right above the indentation in principle by rotating the revolver. Although it is possible, in reality, it is inevitable that the positional relationship between the indentation and the objective lens is incorrect due to a mechanical positional error between the indenter and the objective lens, a revolver rotation angle error, or the like.

Even if the displacement of the positional relationship is actually small, when an enlarged image is formed on the light receiving surface by the objective lens, it is enlarged on the light receiving surface. As the hardness of the measurement sample increases, the size of the indentation formed becomes smaller. Therefore, in order to form an indentation image of an appropriate size for such a small indentation, it is necessary to increase the magnification of the objective lens. There is
Uncertainty of the image formation position of the indentation image on the light receiving surface becomes a great obstacle to high-speed measurement.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a novel hardness measuring method which enables high-speed automatic measurement.

[0009]

The hardness measuring method according to the present invention includes a moving stage which is movable in X, Y and Z directions orthogonal to each other and is rotatable about a rotating shaft parallel to the Z direction.
A revolver having a plurality of objective lenses having different imaging magnifications and an indenter equidistant from the rotation axis by making a two-dimensional image pickup device face each other in the Z direction. , Is arranged so as to be rotatable around the rotation axis parallel to the Z direction and movable in the Z direction, and after forming an indentation by the indenter on the measurement sample installed on the moving stage, the revolver is rotated to make it appropriate. Select an objective lens of magnification, form a magnified image of the indentation on the light-receiving surface of the image sensor with the selected objective lens, read the indentation image, measure the diagonal length of the indentation image, and measure the hardness of the measurement sample. "Calculate" is a fully automatic hardness measurement method. The “rotation axis” of the moving stage and the “rotation axis” of the revolver may be aligned with each other or may be offset from each other.

According to the method of claim 1, "after selecting an objective lens having an appropriate magnification, the entire light-receiving surface of the image pickup device is used as an AF area (autofocus area: an area for capturing data for performing autofocus). By roughly autofocusing, binarizing the image sensor output in a roughly focused state, searching the indentation position based on that data, and re-setting an AF area around the indentation that is slightly larger than the indentation In this way, the hardness is calculated by setting the measurement area in a slightly larger area than the enlarged indentation image and measuring the diagonal length of the indentation image based on the data in this measurement area. It is characterized by

In the above description, "selecting the objective lens" means "rotating the revolver so that the objective lens occupies the position occupied by the indenter when the indentation was formed". Of course, this objective lens selection is made within a mechanical error range. Moreover, the selected objective lens has “appropriate magnification” means that the size of the indentation image formed on the light-receiving surface of the image pickup element by the selected objective lens is the size (area ratio) required for measurement accuracy. 1/1 of the entire light-receiving surface of the image sensor
(About 5 to 1/100).

"Rough autofocus" means
The autofocus has a step of about the focal depth width of the selected objective lens, and the "fine autofocus" is the autofocus with a step of about a fraction of the focal depth width.

In the method according to claim 1, a specific method for searching for the indentation position in a roughly focused state is to "binarize the image sensor output in the roughly focused state and to obtain the longest black in the scanning direction. Select the raster that continues in the area,
A method (claim 2) in which the center of the black region in this raster is the center of the indentation may be used, or "the light receiving content of all the light receiving surfaces of the image pickup device is binarized in a roughly focused state, and the black region is Select the area of the expected area of the indentation ± 50%, specify the square root of the area of the selected area and the ratio of the perimeter as a parameter for identification, identify a pattern close to a square as the indentation, and specify the center coordinates of the specified indentation. The method of “determining” (claim 3) may be used.

In the method according to the first aspect, there are basically two methods for automatically selecting an objective lens having an appropriate magnification. The first method is a method that uses calculation.
Generally, the hardness of a measurement sample for which hardness is measured is not unknown at all, and even if the exact hardness is unknown, the magnitude of the hardness is often known in advance. In such a case, the size of the indentation formed on the measurement sample can be roughly predicted in advance. Therefore, depending on the expected size of the indentation, the imaging magnification for forming an indentation image of an appropriate size on the light receiving surface is calculated by calculation, and an objective lens having an imaging magnification close to this calculation result is calculated. To choose.

The second method is a method that does not rely on such calculation. This method is the method according to claim 4,
“After forming an indentation on a measurement sample, first select a low-magnification objective lens and perform rough autofocus and fine autofocus to measure the diagonal length of the indentation image.
The measured diagonal line length determines whether or not it has a predetermined size, when the diagonal line length does not have the predetermined size, select a high-magnification objective lens than the selected objective lens, This is a method of selecting an objective lens with an appropriate magnification by repeating the process from rough autofocus to length determination of the diagonal length. ”

[0016] in carrying out the method of the fourth aspect, when the selection of the high magnification objective lens is made, it may be adjusted the position of the measurement sample (claim 5).
Alignment of the measurement sample, "After performing rough autofocus, row <br/> Nau prior to the setting the AF area for fine autofocus" in the auto focus process may be (Claim 6).

[0017]

First, the outline of the hardness measurement, which is the premise of the present invention, will be described with reference to a concrete apparatus example.

FIG. 4 (a) schematically shows only an example of a hardness measuring device for carrying out the present invention. In the figure, reference numeral 10 denotes a moving stage, reference numeral 20 denotes a revolver, reference numeral 3
0 is an illumination system, and reference numeral 40 is a CC as a two-dimensional image sensor.
D camera, reference numeral 50 indicates an image processing unit. Reference numeral 6
Reference numeral 0 represents a display, reference numeral 70 represents a revolver / indenter driving device, reference numeral 80 represents a stage controller, and reference numeral 90 represents a computer. These are all appropriately supported by supporting means (not shown).

The moving stage 10 is an X-direction stage 10X which is displaced in the X direction corresponding to the direction orthogonal to the drawing of FIG. 4A, and a Y which is displaced in the Y direction corresponding to the left-right direction in the figure.
Direction stage 10Y and Z corresponding to the vertical direction in FIG.
It is configured by combining Z-direction stages 10Z that are displaced in the direction, and is entirely rotatable about a predetermined Z-axis (rotating shaft) parallel to the Z-direction. The step motor MX is operated to move the X-direction stage 10X in the X direction, and the step motors MY and MZ are operated to displace the Y and Z direction stages 10Y and 10Z in the Y and Z directions, respectively. To rotate the entire moving stage 10 around the Z axis, the step motor Mθ is operated. The measurement sample 0 is the X-direction stage 10X of the moving stage 10.
Placed on top.

In FIG. 4 (a), the chain line indicated by symbol S indicates the "reference axis" in the hardness measuring device. The reference axis S is fixedly set in the measuring device space parallel to the Z direction, which is the moving direction of the Z direction stage 10Z placed on the moving stage 10, and coincides with the Z axis described above in this device example.

The revolver 20 comprises a body 21 having a rotation axis 25 parallel to the reference axis S, and a fixed indenter 23 and a plurality of objective lenses 22, which are rotatable around the rotation axis 25. , Can also be moved in the direction of the rotary shaft 25 (direction parallel to the reference axis S). The rotation axis 25 is set at a predetermined distance: H from the reference axis S.

The revolver 20 is rotated / moved by a revolver / indenter drive unit 70. The revolver / indenter driving device 70 drives the stepper motor for rotating the revolver 20 around the rotation shaft 25, the motor for displacing the revolver 20 in the direction of the rotation shaft 25, and the indenter 23 when the indentation is formed. Indenter drive device 23A
And

In this example, the body 21 of the revolver 20 is provided with one indenter 23 and two objective lenses 22. The objective lens 22 and the indenter 23 are shown in FIG.
As shown in (a), the tip end of the indenter 23 and the objective lenses 22A, 22 are provided symmetrically with respect to the rotation axis 25.
The distance of the optical axis of B from the rotation axis 25 is the above distance:
It is set to H. The arrangement of the indenter and the objective lens in the revolver is not limited to this example, and as shown in FIG. 5B, in addition to the indenter 23, a plurality of objective lenses 22A, 22B,
22C or the like may be provided. If necessary, two or more indenters may be provided on the revolver main body. Indenter 2
The tip of 3 forms a regular tetragonal pyramidal tip with an apex angle of 90 degrees.

Each lens 22A, 22B of the objective lens 22
Have different imaging magnifications, one of which has a low magnification and the other has a high magnification.

Returning to FIG. 4A, CC is on the reference axis S.
A D camera 40 is provided, and the revolver 20 and the CC
The illumination system 30 is provided between the camera and the D camera 40.
The illumination system 30 includes a light source lamp 32, a collimating lens 33, and a semi-transparent mirror 34 disposed in a casing 31. The semi-transparent mirror 34 is located on the reference axis S and is inclined by 45 degrees with respect to the reference axis S. The casing portion where the reference axis S passes is formed in the window. As shown in the figure, when the light source lamp 32 is caused to emit light when the objective lens 22 is selected and located at the reference axis S position, the light is collimated by the collimator lens 33, reflected by the semitransparent mirror 34, and passed through the objective lens 22. And illuminates the measurement sample 0. The reflected light from the measurement sample 0 passes through the objective lens 22 and the semi-transparent mirror 34 and the CCD camera 40.
Incident on the light receiving surface of. Depending on the objective lens, the illumination light flux from the illumination system may not be a parallel light flux.

For hardness measurement, as shown in FIG. 4 (b), "indentation formation" is performed after "sample setting", followed by "objective lens selection", and hardness is calculated by "imaging / calculation". The procedure is as follows.

In the "indentation formation", the indenter driving device 23A is driven by the revolver / indenter driving device 70 to drive the indenter 23.
Is moved toward the measurement sample 0, and the indenter 23 is applied at a predetermined pressure.
It is carried out by pushing the tip of the sample into the surface of the measurement sample 0, and a square 4 as shown in FIG.
A quadrilateral indentation AK is formed. Indentation A is shown in FIG.
It is a cross-sectional shape of K. According to the tip shape of the indenter 23, the angle γ in the drawing at the indentation AK is 90 degrees.

Since the pressure for pushing the tip of the indenter 23 is constant at a "predetermined pressure", the larger the hardness of the measurement sample 0, the smaller the pressure AK formed. Therefore,
When the size of the indentation AK is measured by the diagonal lines L1 and L2, the size of the diagonal lines L1 and L2 and the hardness of the measurement sample have an inversely proportional correspondence relationship, and the hardness can be calculated according to this correspondence relationship.

The pressure applied to the indenter and the pressing time are set appropriately in advance according to the sample to be measured. That is, as described above, in general, the hardness of the measurement sample can be preliminarily estimated. Therefore, the indenter pressure and the pressing time are set appropriately in accordance with the hardness.

When the indentation is formed, the indenter 23 is returned to the revolver 20 side, and then the revolver 20 rotates to select the objective lens 22. With this selection, 2
The optical axis of one of the two objective lenses 22 having an appropriate imaging magnification is matched with the reference axis S.

Subsequently, the illumination system 30 illuminates the measurement sample 0, the indentation image is read by the CCD camera 40, the diagonal length of the indentation is calculated from the output of the CCD camera 40, and the hardness of the measurement sample 10 is calculated based on the diagonal length. To do. A conventionally known calculation algorithm can be appropriately used for the calculation calculation for calculating the hardness from the diagonal length. The calculated hardness is output as the hardness of the measurement sample.

The features of the present invention are mainly as follows.
This is the acquisition of indentation data in the imaging / calculation process in FIG. That is, in measuring the diagonal length from the indentation image, a measurement area slightly larger than the indentation image is set, and the measurement is performed using only the data in this measurement area. In this way, the diagonal length can be determined with much less data than in the case where the data of the entire light receiving surface of the image sensor is used for measuring the diagonal length.

Further, autofocusing for forming the indentation image on the light receiving surface of the image pickup element is performed by rough autofocusing and fine autofocusing. In fine autofocusing, the AF area is slightly larger than the indentation image. Since it is set, the amount of data required for autofocus is small.

[0034]

EXAMPLES Specific examples will be described below.

FIG. 1 is a flow chart showing the procedure of an embodiment of the method of claim 1. The hardness measurement procedure starts with the "measurement sample setting step" in which the measurement sample is placed on the moving stage. Of course, the measurement sample is installed manually. The position where the measurement sample is set is marked on the moving stage. When the measuring sample is set according to this mark and the measurement start button is pressed, the moving stage is activated and the measuring sample is automatically moved to the position shown in FIG. It is moved to the position of the reference axis S in a).

Subsequently, in the "indentation forming step", only the indenter in the revolver is driven to form the indentation. The pressing force of the indenter and the pressing time are adjusted according to the measurement sample. Here, for the sake of simplicity of explanation, the number of indentations formed is one.
Suppose it is an individual.

Next, in the "objective lens selection step", the objective lens of appropriate magnification is selected by rotating the revolver. In this embodiment, the size of the indentation formed is roughly predicted to calculate the appropriate magnification (performed by the computer 90 of the apparatus of FIG. 4A), and the objective lens is selected based on the result. .

In the next "AF step", rough autofocusing is performed based on data from the entire light receiving surface of the CCD camera which is a two-dimensional image pickup device. Then, the "indentation search step" is performed in the roughly focused state as a result. In this embodiment, the search process is performed according to the procedure shown in FIG. That is, after performing the rough autofocus as described above, the position of the indentation is roughly searched. That is,
The output of the entire light receiving surface of the CCD camera is binarized in a roughly focused state.

In a roughly focused state, the "concave portion" on the surface of the measurement sample becomes a high density portion. Therefore, when the output of each pixel is binarized in this state, the above concave portion becomes a "black" region. Further, in this state, the largest concave portion on the surface of the measurement sample is an indentation. Therefore, when the raster having the longest "black" region in the scanning direction of the CCD camera is selected, it is considered that the raster approximately passes through the center of the indentation.
Therefore, the center of the largest "black" area in this raster approximately gives the center of the indentation. Also, the length of the "black" area gives an approximate size of the indentation.

In this way, since the position and size of the indentation can be specified with considerable accuracy, the AF area is set based on the position and size of the indentation specified in this way (see "AF area setting step in FIG. 1"). )). At this time, since the surface of the measurement sample is in a rough focus state, the size of the indentation image does not change significantly even if fine autofocus is performed thereafter. Therefore, based on the approximate size of the indentation determined as described above, an appropriate AF according to the size of the indentation is obtained.
The area can be set.

Fine autofocusing is performed using the data in the AF area set in this way. Then, in the fine focus state resulting from the fine autofocus, a measurement area slightly larger than the impression image is set around the impression image (“measurement area setting step”). As this measurement area, an AF area for detailed autofocus may be used as it is.

Hereinafter, the diagonal length of the indentation image is measured based on the data in the measurement area, and the hardness of the measurement sample is calculated. The calculation in this step may be performed by appropriately using a conventionally known one.

FIG. 2B shows the procedure of another example of the "indentation image retrieval step". When rough focus is achieved by rough autofocus, scratches on the surface of the measurement sample within the light-receiving surface,
There is a possibility that an image of dust or the like attached to the surface is also formed. Therefore, in this procedure, C
The output of each pixel of the CD camera is binarized (Fig. 2 (b)),
The noise component is removed by erasing an image having an area smaller than the expected area of the indentation image as an image other than the indentation.

Next, the noise-removed image information is "black".
Labeling is performed by sequentially numbering the patterns of the areas. The labeled pattern may include "things other than the impression image". Therefore, for each of the labeled patterns, the one whose area is included in the region of the expected area of the impression image ± 50% is selected. For each selected pattern, the ratio of the square root of the area to the perimeter is used as an identification parameter, and this parameter is 1 /
Select a value close to 4. As shown in FIG. 6A, the shape of the indentation is close to a square. If the length of one side of the square is a, the square root of the area is a and the perimeter is 4a, so that in the square, the parameter: a / 4a is 1/4. Therefore, the above parameters are calculated for each of the patterns selected as described above, and one having a value close to 1/4 is specified as an indentation image. Then, the center coordinates of each of the identified indentation images are calculated.

Selection of information necessary for these processes is shown in FIG.
The image processing section (a) performs the necessary calculation by fetching the information from the image processing section 50 into the computer 90.

FIG. 3 is a flow chart showing the procedure of an embodiment of the method of claim 4. For ease of explanation, FIG.
As described above, it is assumed that the revolver is provided with two objective lenses with high and low imaging magnification. After forming the indentation, first, an objective lens having a low imaging magnification is selected.
Then, the rough autofocus and the fine autofocus described above are performed to realize a fine focus state, the diagonal length of the indentation is measured from the data in the measurement area, and the measured diagonal length is a predetermined value. A computer (computer 90 in FIG. 1A) determines whether or not the size, that is, the size capable of ensuring the measurement accuracy. When the measured diagonal length is sufficiently large, the hardness is calculated based on the measured value.

If the measured diagonal length is less than the predetermined value, the image forming magnification of the objective lens is insufficient. Therefore, the objective lens having a high image forming magnification is selected again, and rough autofocus and close inspection are performed. Repeat autofocus and measure the diagonal length to calculate the hardness. Even when three or more objective lenses are mounted on the revolver, a proper objective lens can be automatically selected by the same process as above.

It should be noted that the position of the indentation is positioned so as to be closer to the reference axis S between the rough autofocus and the fine autofocus described above, and at the time of reselection of the objective lens in selecting the objective lens. Correction may be performed. By doing so, the accuracy of the alignment function in the moving stage and the revolver can be set loosely.

In the above-described example, the number of indentations formed on the measurement sample is one, but the present invention can be applied to the case where the number of indentations formed on the same measurement sample is two or more. In this case, an appropriate objective lens may be selected for one indentation, and the process of calculating the hardness described above may be repeated for each indentation. At that time, the respective indentations are successively brought to the position of the reference axis S by the moving stage.

[0050]

As described above, according to the present invention, a novel hardness measuring method can be provided. Since this method is configured as described above, in a hardness measurement method that performs the hardness calculation after setting the measurement sample fully automatically, there is little data for fine autofocus and the diagonal length measurement of the indentation image. Is possible, and high-speed and accurate hardness measurement is possible.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a hardness measuring method of the present invention.

FIG. 2 is a flow diagram illustrating an embodiment of the method of claims 2 and 3.

FIG. 3 is a flow diagram illustrating an embodiment of the method of claim 4;

FIG. 4 is a view conceptually showing an example of a hardness measuring device for carrying out the present invention.

FIG. 5 is a diagram for explaining a revolver.

FIG. 6 is a diagram for explaining an indentation formed on the surface of a measurement sample.

Claims (6)

(57) [Claims] 1. A movable stage movable in X, Y, and Z directions orthogonal to each other, and a movable stage rotatable about a rotation axis parallel to the Z direction, and a two-dimensional image sensor face each other in the Z direction. At most, a revolver provided with a plurality of objective lenses having different imaging magnifications and an indenter at positions equidistant from the rotation axis is provided around the rotation axis parallel to the Z direction between the moving stage and the image sensor. The selected objective lens is arranged so as to be rotatable and movable in the Z direction, and after forming an indentation by the indenter on the measurement sample installed on the moving stage, the revolver is rotated to select an objective lens with an appropriate magnification. A magnified image of the indentation is formed on the light-receiving surface of the image sensor by using to read the indentation image, measure the diagonal length of the indentation image, and calculate the hardness of the measurement sample. Select a lens After that, the entire light-receiving surface of the image sensor is roughly used as an AF area for auto-focusing, and the image sensor output is binarized in a roughly focused state. The data is used to search the indentation position, and the indentation position is searched for around the searched indentation. The AF area slightly larger than the indentation is reset to perform fine autofocus, and in the fine focus state, an area slightly larger than the enlarged indentation image is set as the measurement area, and the indentation is based on the data in this measurement area. A hardness measuring method, characterized by measuring the diagonal length of an image to calculate the hardness. 2. The hardness measuring method according to claim 1, wherein the output of the image pickup device is binarized in a roughly focused state, the raster having the longest black region in the scanning direction is selected, and the center of the black region in this raster is selected. A hardness measuring method, characterized in that a portion is set as a central portion of the indentation, and an AF area for fine autofocus is set based on the central portion according to the size of the indentation. 3. The hardness measuring method according to claim 1, wherein the light receiving contents of all the light receiving surfaces of the image pickup device are set to 2 in a roughly focused state.
The value is selected, and the black area is selected to have an expected area of indentation ± 50%, and the ratio of the square root of the area of the selected area to the perimeter is used as a parameter for identification to identify a pattern close to a square as an indentation. The hardness measuring method is characterized in that the center coordinates of the indentation are obtained, and a fine AF area for autofocus is set around the center coordinates. 4. The hardness measuring method according to claim 1, 2 or 3, after forming an indentation on a measurement sample, first selecting a low-magnification objective lens to perform rough autofocus and fine autofocus. , Measuring the diagonal length of the indentation image and determining whether or not the measured diagonal length has a predetermined size. When the diagonal length does not have the predetermined size, the selected objective lens A hardness measuring method comprising selecting an objective lens having a higher magnification and repeating the process from the rough autofocusing to determining the length of a diagonal line to select an objective lens having an appropriate magnification. 5. A hardness measurement method according to claim 4, wherein, when the selection of the high magnification objective lens is performed, and adjusting the position of the measurement sample, hardness measurement method. 6. The method according to claim 1 or 2 or 3 or 4 or 5 hardness measurement method described, rough after performing autofocus, AF area for after adjusting the measurement sample position, fine autofocus The hardness measuring method is characterized by setting.