JP2695337B2 - 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 device, it takes a long time to focus the objective lens on the measurement sample on which the indentation is formed, and it takes a long time to measure the hardness. There is a problem.

In order to solve such a problem, the present inventors have stated that "they are movable in the X, Y and Z directions orthogonal to each other and Z
A revolver having a movable stage rotatable about a rotation axis parallel to the direction and a two-dimensional image sensor facing each other in the Z direction and having an objective lens and an indenter at positions equidistant from the rotation axis, After the movable stage and the image sensor are arranged so as to be rotatable about the rotation axis parallel to the Z direction and movable in the Z direction, an indentation is formed by an indenter on the measurement sample installed on the movable stage. , The revolver is rotated to select the objective lens, the magnified image of the indentation is formed on the light receiving surface of the image sensor by the objective lens, the indentation image is read, and the hardness of the measurement sample is calculated. 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. When the objective lens is selected, autofocus is performed to form an image of the indentation on the light receiving surface of the image pickup device.

At this time, assuming that the entire light receiving surface of the image pickup device is an AF area (autofocus area: an area for fetching a signal for performing autofocus processing), a small "scratch" on the surface of the measurement sample or the same adheres to the surface. There is a problem that "dust" or the like affects the autofocus and causes an error in the autofocus. In addition, when autofocusing with fine steps is performed based on the information of the entire light receiving surface, there is a problem in that autofocusing takes time because a large amount of information is handled.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and the autofocus is not easily affected by scratches and dust on the surface of the measurement sample, and the autofocus can be shortened in time. The object is to provide a new hardness measuring method.

[0007]

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 three-dimensional image pickup device facing each other in the Z direction, and a revolver provided with an objective lens and an indenter at positions equidistant from the rotation shaft, the rotary shaft parallel to the Z direction between the moving stage and the image pickup device. It is arranged so as to be rotatable around and movable in the Z direction, and after the indentation is formed on the measurement sample installed on the moving stage by the indenter, the revolver is rotated to select the objective lens, and the indentation The magnified image is formed on the light-receiving surface of the image sensor to read the indentation image and calculate the hardness of the measurement sample. "This is a fully automatic hardness measurement method. The “rotation axis” of the moving stage and the “rotation axis” of the revolver may be aligned or may be offset from each other.

According to the method of claim 1, "after selecting an objective lens, the entire light-receiving surface of the image pickup device is used as an AF area for rough autofocusing, and the image pickup device output is binarized and scanned in a roughly focused state. Select the raster with the longest black area in the direction, and set the center of the black area in this raster as the center of the indentation, and based on this center, the AF area for indentation forms the indentation image according to the size of the indentation. The area including the image position and slightly wider than the impression image is set as the AF area for fine autofocus,
The indentation image is formed on the light receiving surface of the image pickup device.

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".

Since the objective lens and the indenter are arranged at positions equidistant from the "rotational axis" of the revolver, the indenter was formed when the indentation was formed by forming the indentation on the measurement sample and then rotating the revolver. If the objective lens occupies the position, the image formation position of the indentation image is uniquely determined except for mechanical error.Therefore, it may be possible to set the AF area fixedly in advance in the control program. However, the measurement sample may move on the moving stage for some reason after the indentation is formed.

As described above, if the AF area is set according to the size of the indentation after the center portion of the indentation is detected after the rough autofocusing, mechanical error, position variation of the measured sample, etc. Accurate autofocus is possible regardless of.

Depending on the measurement conditions, a plurality of indentations may be formed on the measurement sample, and the hardness may be calculated for each of the indentations formed. In such a case, it is necessary to "select the objective lens after forming indentations at predetermined positions on the measurement sample installed on the moving stage, and then move the moving stage to bring the indentation to the optical axis position of the objective lens. Repeat the process of measuring hardness with all indentations. ”

As described above, in the case of "forming a plurality of indentations on the surface of the sample", "when the hardness is measured for each indentation after selecting the objective lens, the indentation group is brought to the image forming area of the objective lens. The area where the black area has an expected area of indentation ± 50% is obtained by binarizing the received light content of all the light-receiving surfaces in a roughly focused state by roughly autofocusing the entire light-receiving surface of the image sensor as an AF area. Select, and specify the square root of the area of the selected area and the perimeter as a parameter for identification to identify a pattern close to a square as an indentation, find the center coordinates of the indentation specified, and change the indentation to be measured each time. , A around the center coordinates of the indentation
The F area is set and the AF area is set around this center coordinate where autofocusing is performed "(claim 2).

The above "rough autofocus"
Is an autofocus whose step is about the focal depth of the selected objective lens, and “fine autofocus” is an autofocus whose step is about a fraction of the above focal depth.

[0015]

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. 5 (a) schematically shows only an essential part of an example of a hardness measuring apparatus 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. 5A, 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. Further, in order 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. 5 (a), the chain line indicated by the symbol S indicates the "reference axis" in the hardness measuring device. The reference axis S is fixedly set in the measuring device space in parallel to the Z direction, which is the moving direction of the Z-direction stage 10Z that can be placed on the moving stage 10, and in this device example, the "rotating shaft" Z of the stage described above. Aligns with the axis.

The revolver 20 includes a main body 21 having a "rotation axis" 25 parallel to the reference axis S, an indenter 23 and an objective lens 2.
2 are fixedly provided, are rotatable around the rotary shaft 25, and are also movable in the direction of the rotary shaft 25 (direction parallel to the reference axis S). The rotary shaft 25 is set apart from the reference shaft S (the rotary shaft of the moving stage 10) by a predetermined distance H.

The rotation and movement of the revolver 20 are performed by a revolver and indenter driving device 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
Have means for operating.

In this example, the body 21 of the revolver 20 is provided with one indenter 23 and one objective lens 22. The objective lens 22 and the indenter 23 are shown in FIG.
As shown in (a), it is provided in axial symmetry with respect to the rotating shaft 25, and the distance between the tip of the indenter 23 and the optical axis of the objective lens 22 from the rotating shaft 25 is set to the distance H. The arrangement of the indenter and the objective lens in the revolver is not limited to this example, and as shown in FIG. 6B, a plurality of objective lenses 22A, 22B, 22C may be provided in addition to the indenter 23. If necessary, two or more indenters may be provided on the revolver main body. The tip of the indenter 23 has a vertical angle of 90.
It forms a regular quadrangular pyramid-shaped point.

Returning to FIG. 5A, 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. When the objective lens 22 is selected as shown in the figure and the light source lamp 32 is caused to emit light 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. Illuminate the measurement sample 0. The reflected light from the measurement sample 0 enters the light receiving surface of the CCD camera 40 via the objective lens 22 and the semi-transparent mirror 34.

For hardness measurement, as shown in FIG. 5 (b), after "sample setting", "indentation formation" is performed, and then the objective lens is selected by "revolver rotation", and "imaging / calculation" is performed.
The hardness is calculated by the procedure.

The indentation is formed by the revolver / indenter driving device 7
0 is operated to move the indenter 23 toward the measurement sample 0, and the tip of the indenter 23 is pushed into the surface of the measurement sample 0 at a predetermined pressure. A square quadrilateral indentation AK is formed as shown in a). FIG. 7B is a sectional shape of the indentation AK. Depending on the tip shape of the indenter, the angle γ in the figure is generally 90 degrees.

Since the pressure for pushing the tip of the indenter 23 is constant at a "predetermined pressure", the indentation AK formed becomes smaller as the hardness of the measurement sample 0 increases. Therefore, the indentation A
If the size of K 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 a 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 measurement sample. That is, since the hardness of the measurement sample is generally "preliminary", the appropriate indenter pressure and pressing time are set accordingly.

When the indentation is formed, the indenter 23 is returned to the revolver 20 side, and then the objective lens 22 is selected by rotating the revolver 20. With this choice,
The optical axis of the objective lens 22 is matched with the reference axis S.

Next, the illumination system 30 illuminates the measurement sample 0,
After autofocusing, the objective lens 22 is the CCD camera 4
The indentation image formed on the light receiving surface of 0 is read by the CCD camera 40, the diagonal length of the indentation is calculated by the output of the CCD camera 40, and the hardness of the measurement sample 10 is calculated based on the diagonal length. For the calculation calculation for calculating the hardness from the diagonal length, a conventionally known calculation program can be appropriately used. The calculated hardness is output as the hardness of the measurement sample.

The feature of the present invention resides in the autofocus which is a part of the image pickup / calculation process in the above-described measurement process. After rough autofocus, an AF area slightly larger than the indentation image is set in the image forming portion of the indentation. However, fine autofocusing is performed "based only on the information in the AF area".

[0029]

1 and 2 are views for explaining one embodiment of the method of claim 1. FIG. 1A shows the “procedure outline” of the embodiment. The execution of the measurement process is
This is performed by the apparatus example described with reference to FIG.

First, in the "measurement sample setting step", the measurement sample 0
Is installed on the moving stage. The position on which the measurement sample 0 is set is marked on the moving stage. When the measurement sample is set according to this mark, the computer 90, which is the control means, controls the moving stage 10 by the stage controller 80 to set the measurement sample 0. It is moved to the position of the reference axis S.

Subsequently, in the "indentation forming step", the indentation is formed by the indenter 23. As described above, the hardness of the sample to be measured is roughly known, and the pressure applied to the indenter and the indenter pressing time are stored in the computer 90 so that the size of the indentation formed is appropriate. Is set. Since the indentation is formed in this way, the size of the indentation formed can be expected to some extent. Subsequently, in the "objective lens selection step", the revolver is rotated and the objective lens 2
The two optical axes are aligned with the reference axis S. The “appropriate size of the indentation” means that the CC is magnified by the objective lens.
The size of the indentation image formed on the light receiving surface of the D camera is about 1/100 to 1/15 of the light receiving surface in terms of area ratio.

Following this, autofocus is executed, but prior to that, the "AF area setting step" is executed. An area indicated by reference numeral 1 in FIG. 1B is a CCD.
The entire light receiving surface of the camera is shown, and this figure shows a state in which the vicinity of the indentation forming portion of the measurement sample 0 is imaged on the light receiving surface 1. In the image-forming state, in the light-receiving surface area 1, the image IA of the indentation formed on the measurement sample 0 and the scratch K on the surface are formed.
1, K2, K3, etc., dust Ho, etc. will be imaged. These scratches K1, K2, K3, etc., dust Ho, etc. generate noise signals for autofocus, which causes errors in autofocus, and in some cases, autofocus failure.

Therefore, according to the first aspect of the invention, after rough autofocusing, an AF area DAF which is slightly wider than the indentation image IA is set around the indentation image IA, and the "AF step" is performed.
Then, fine autofocusing is performed only on signals from the AF area DAF. The AF area is set by controlling the image processing unit 50 by the computer shown in FIG.

When the objective lens 22 is selected, the imaging magnification is 1
Computer 90 (Figure 5 (a))
First, the revolver / indenter driving device 70 moves the revolver 20 along the rotation axis 25, and the revolver 20 is arranged at a position (which is determined by a relative positional relationship with the CCD camera 40) corresponding to the imaging magnification. Computer 90
Based on the control of 1., the Z direction stage 10Z of the moving stage 90 is driven by the stage controller 80, and the moving sample 10 including the measurement sample 0 is moved in the Z direction in predetermined steps. At each step, the output from the CCD camera 40 is taken into the image processing unit 50, and the AF area DA
The autofocus program is executed only for signals from inside F.

Since the size of the indentation is also set to an appropriate size as described above, the size of the AF area to be set may be uniquely determined, but in this example, the size of the indentation (predictably The size is adjusted accordingly.

Various methods are known for autofocus, and a known method may be used as a specific method. For example, the maximum and minimum of all pixel outputs in the AF area DAF of the CCD camera 40 are obtained, and the Z-direction stage 10Z
Thus, the maximum and minimum difference is calculated each time the measurement sample 0 moves in the Z direction by one step, and the Z direction stage 10Z may be controlled so as to find the position where the calculation result is maximum.

In this way, when the autofocus operation is completed, an enlarged image IA of the indentation marked on the measurement sample 0 is formed on the light receiving surface of the CCD camera 40. Subsequently, in the "hardness measuring step", 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 calculated diagonal length. As a calculation for calculating the hardness from the diagonal length, a conventionally known calculation is used. The calculated hardness is output as the hardness of the measurement sample.

In actuality of such hardness measurement, there is a "mechanical error" or "the measured sample slightly moves from the initial position due to some cause" on the moving stage.
Sometimes. Considering such a point, the size of the AF area set as described above has a margin with respect to the “deviation of the actual indentation image position from the theoretical position” due to the mechanical error or the movement of the measurement sample. Must be set.
Then, the probability that scratches, dust, or the like that cause an autofocus error will enter the inside of the AF area set according to the indentation also increases. Therefore, it is desirable to set the AF area as small as possible according to the impression image.

In order to do this, the procedure is as shown in FIG. That is, after the indentation is formed, first, the entire area of the light receiving surface of the CCD camera, that is, the "entire screen" is set as the AF area and rough autofocus is performed. (In this rough autofocus process, one step in the Z direction is appropriate. To make it bigger). Then, the position of the indentation is roughly measured 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-mentioned concave portion becomes a "black" region. In this state, the "largest concave portion on the surface of the measurement sample" is an indentation. Therefore, when a raster having the longest “black” region in the scanning direction of the CCD camera, which is a two-dimensional image pickup device, is selected, this raster is considered to pass approximately 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 indentation position and size specified in this way. 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, it is possible to set an appropriate AF area according to the size of the indentation.

In the embodiment described above, it was premised that the number of indentations formed on the surface of the measurement sample was 1, but as described above, depending on the measurement situation, a plurality of indentations may be formed on the same measurement sample. In some cases, it is formed and the hardness is calculated for each indentation. The procedure of one embodiment in such a case is shown in FIG.

In this embodiment, when a measurement sample is set, first, a predetermined number of indentations are formed. The number of indentations formed and the formation positions are entered in advance in the computer,
By moving the moving stage, the measurement sample is moved relative to the indenter to sequentially form the indentations.

After forming a predetermined number of indentations, the objective lens is selected. Then, the process from setting the AF area to calculating the hardness is repeated for each indentation. If the number of indentations formed on the surface of the measurement sample is relatively small (2 to 3) and all the images of the indentations are within the light-receiving surface of the CCD camera at one time, move the moving stage after selecting the objective lens. Without operating, AF is performed for each indentation on the light receiving surface of the CCD camera.
The area should be set. At this time, when the AF area is set for one indentation image, autofocus is performed on this indentation image and the diagonal line of the indentation is measured to calculate the hardness. The same process is then repeated for another indentation image.

The AF area for each indentation can be uniquely set according to the data (the position where the indentation is formed and the expected size of the indentation) at the time of forming the indentation. It is desirable to set an AF area of a size that is slightly larger than the size of the indentation, and doing so increases the probability that scratches and dust will enter the set area. Therefore, even when a plurality of indentations are formed on the surface of the measurement sample, the AF area should be set as small as possible according to each indentation. In the invention described in claim 2, this is performed as follows.

Referring to FIG. For the sake of concreteness of the description, three indentations are formed on the surface of the measurement sample, and when the objective lens is selected, as shown in FIG.
It is assumed that K1, IK2, and IK3 can form an image on the light receiving surface 1 of the CCD camera.

In this case, first, the entire light receiving surface 1 is used as an AF area to roughly perform autofocus. As a result, a state close to that shown in FIG. 4B is realized. A on the entire light-receiving surface
Since auto-focusing is performed as the F area, in a roughly focused state, there is a possibility that an image such as a scratch on the surface of the measurement sample or dust adhering to the surface is also formed in the light receiving surface. In this state, the output of each pixel of the CCD camera is “binarized” (FIG. 4A), and a “noise removal” step is performed to erase an image having an area smaller than the expected area of the impression image.

Next, the noise-removed image information is used to sequentially number the patterns in the "black" area. The labeled pattern may include "things other than the impression image". Therefore, with respect to each of the labeled patterns, a region whose area is the expected area of the impression image ± 50% is selected.

With respect to the pattern of each selected region, the ratio of the square root of the area to the perimeter is used as an identification parameter, and one having this parameter close to ¼ is selected.
As shown in FIG. 7A, the shape of the indentation is close to a square.
When the length of one side of the square is a, “the square root of the area is a” and “the perimeter is 4a”. Therefore, in the square, the identification parameter: a / 4a becomes 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. The information necessary for these processes is selected by the image processing unit of FIG. 5A, and the necessary calculation is performed by fetching the information from the image processing unit 50 into the computer 90.

The indentation image identified as described above (see FIG. 4)
(B) IK1, IK2, IK3), and when the position and size are obtained, first, the impression image IK1 is taken and A
The F area DAF1 is set to perform fine autofocusing, the indentation image IK1 is formed on the light receiving surface, and the diagonal length thereof is measured to calculate the hardness. This process is called indentation image I
Repeat for K2 and IK3.

In this way, accurate hardness measurement is realized.

[0051]

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 in which the hardness is calculated automatically after setting the measurement sample, the image of the indentation formed on the measurement sample is automatically received by the two-dimensional image sensor. The autofocus imaged on the surface is not easily affected by scratches and dust on the surface of the measurement sample, and accurate autofocus can be performed, so that accurate hardness measurement is possible. Also, by setting the autofocus step to two types, large and small, performing a rough autofocus with a large step, specifying the position of the indentation, and then performing a fine autofocus with a small step to shorten the desired indentation. It can be brought to a state where it can be easily imaged in time, and the speed of measurement can be improved.

[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 chart illustrating a characteristic part of the method of claim 1;

FIG. 3 is a flow diagram illustrating the method of claim 2.

FIG. 4 is a diagram illustrating a characteristic part of the method of claim 2;

FIG. 5 is a diagram conceptually showing an example of a hardness measuring device for carrying out the present invention.

FIG. 6 is a diagram for explaining a revolver.

FIG. 7 is a diagram for explaining an indentation formed on the surface of a measurement sample.

[Explanation of symbols]

 1 Light receiving surface of two-dimensional image sensor IK Image of indentation formed on light receiving surface K1 Image of scratch on measurement sample surface Ho Image of dust adhering to measurement sample surface

Claims (2)

(57) [Claims] 1. A movable stage, which is movable in X, Y, and Z directions orthogonal to each other, and is rotatable about a rotation axis parallel to the Z direction, and a two-dimensional image sensor are opposed to each other in the Z direction. At the very least, a revolver equipped with the objective lens and indenter at positions equidistant from the rotation axis can be rotated and moved in the Z direction with the rotation axis parallel to the Z direction between the moving stage and the image sensor. After forming an indentation by the indenter on the measurement sample installed on the moving stage, the revolver is rotated to select the objective lens, and an enlarged image of the indentation is picked up by the objective lens to obtain the light receiving surface of the image pickup device. In the fully automatic hardness measurement method, in which the indentation image is read by imaging on the top and the hardness of the measurement sample is calculated, after selecting the objective lens, the entire light-receiving surface of the image sensor is set as the AF area.
And then roughly auto focus to get a rough focus.
In this state, the image sensor output is binarized and
Select the raster with the longest continuous black area and
-The center of the black area in the
The size of the indentation as the AF area for the indentation based on the core.
Depending on the size, including the image formation position of the indentation image
A hardness measuring method, characterized in that a region is set, a fine autofocus is performed, and an indentation image is formed on a light receiving surface of the image pickup device. 2. A movable stage, which is movable in X, Y, and Z directions orthogonal to each other, and is rotatable about a rotation axis parallel to the Z direction, and a two-dimensional image sensor are opposed to each other in the Z direction. At the very least, a revolver equipped with the objective lens and indenter at positions equidistant from the rotation axis can be rotated and moved in the Z direction with the rotation axis parallel to the Z direction between the moving stage and the image sensor. After forming an indentation by the indenter on the measurement sample installed on the moving stage, the revolver is rotated to select the objective lens, and an enlarged image of the indentation is picked up by the objective lens to obtain the light receiving surface of the image pickup device. In the fully-automatic hardness measurement method in which the hardness of the measurement sample is calculated by reading the indentation image by imaging on the top, the indentation is formed at each predetermined position of the measurement sample installed on the moving stage, and then the objective lens is selected. This is a hardness measurement method in which the process of bringing the indentation to the optical axis position of the objective lens by the movement of the moving stage and measuring the hardness is repeated for all the indentations. When performing hardness measurement, after bringing the indentation group to the image formation area by the objective lens, roughly autofocusing is performed with the entire light-receiving surface of the image sensor as the AF area. Binarize the contents, select the area where the black area is the expected area of the indentation ± 50%, specify the square root of the area of the selected area and the perimeter as a parameter for identification, and specify a pattern close to a square as the indentation. The feature is to find the center coordinates of each specified indentation, and set the AF area around the center coordinates of the indentation each time the measurement target indentation is changed to perform autofocus. Hardness measurement method to be.