JP2005337973A - Hardness testing machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the measuring precision of hardness by accurately forming the image data in the vicinity of the outer edge of a cavity by performing the automatic control of light in a hardness testing machine. <P>SOLUTION: The hardness testing machine 1 is constituted so as to calculate the hardness of a sample S by forming the cavity to the surface of the sample S by an indenter 34 and measuring the dimension of the cavity and equipped with an illuminator 33 for illuminating the surface of the sample S, a CCD camera 31 for imaging the surface of the sample S illuminated by the illuminator 33 to form the image data of the cavity and the peripheral part of the cavity, an automatic light control means for automatically adjusting the quantity of the irradiation light of the illuminator 33 so that the brightness of the light (reflected light) reflected by the surface of the sample S irradiated from the illuminator 33 to enter the CCD camera 31 is converged into a predetermined range and a measuring means for measuring the dimension of the cavity from the image data formed by the CCD camera 31. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hardness tester, and more particularly to a hardness tester that measures the hardness of a sample based on the size of a recess formed on the surface of a predetermined sample.

  Conventionally, various hardness testers such as a Brinell hardness tester, a Vickers hardness tester, a Knoop hardness tester, etc., that measure the hardness of the sample based on the size of a recess formed on the surface of a predetermined sample. Has been proposed and put into practical use. For example, a Vickers hardness tester is equipped with a hardness measuring unit having a regular quadrangular pyramid indenter, and the diagonal length of a depression formed by pushing the indenter into the surface of a sample is measured with an optical microscope or the like. The hardness is calculated based on the diagonal length.

In the hardness tester as described above, when the diagonal length of the dent is measured, focusing is performed on the surface of the sample on which the dent is formed. In recent years, the optical microscope has a moving means for moving the objective lens or sample up and down, and an automatic focusing means for controlling the moving means, so that the optical microscope can be automatically focused. A testing machine has been proposed (for example, see Patent Document 1).
JP 2002-310869 A (first page, FIG. 1)

  By the way, in the conventional hardness tester as described in Patent Document 1, light is irradiated on the surface of the sample using an illuminating device such as a halogen lamp, and the light reflected on the surface of the sample is CCD (Charge Coupled). A predetermined image information is generated by detection by an imaging device such as a device, and automatic focusing is performed based on the image information.

  Here, when the illumination device has a large amount of light, the luminance of the light reflected from the surface of the sample (reflected light) increases, but the luminance of the reflected light exceeds the luminance range that can be expressed by the imaging device. In some cases, the image information of the depression on the surface of the sample and the image information of the peripheral portion of the depression may not be generated accurately.

  For example, when a CCD capable of expressing the luminance of 256 gradations (0 to 255) is employed as the imaging device, the luminance of the reflected light near the outer edge of the recess formed on the surface of the sample can be expressed by the CCD. If the upper limit of luminance (255) is exceeded, the image information in the vicinity of the outer edge of the indentation will be inaccurate. When the diagonal length of the dent is measured using such inaccurate image information (for example, see FIG. 7), the measured values (d1, d2) become shorter than the actual dimensions (D1, D2), and the hardness of the sample is reduced. An error also occurs in the calculation result.

  An object of the present invention is to improve the accuracy of hardness measurement by accurately generating image information near the outer edge of a dent by performing automatic light control in a hardness tester.

In order to solve the above problems, the invention described in claim 1
A hardness tester (Vickers hardness test) for calculating the hardness of the sample by forming a recess (K) on the surface of a predetermined sample (S) using an indenter (34) and measuring the size of the recess In machine 1)
An illumination device (33) for illuminating the surface of the sample;
An imaging device (CCD camera 31) that images the surface of the sample illuminated by the illuminating device and generates image information of the depression and the peripheral portion of the depression;
Automatic dimming that automatically adjusts the amount of light emitted from the illumination device so that the brightness of reflected light that is irradiated from the illumination device and reflected by the surface of the sample and incident on the imaging device converges within a predetermined range. Means (CPU 10a and automatic light control program);
Measurement means (CPU 10a and hardness measurement unit control program) for measuring the size of the indentation based on the image information generated by the imaging means;
It is characterized by providing.

  According to the first aspect of the present invention, the amount of light emitted from the illumination device is automatically adjusted by the automatic light control means, and reflected light (light that is irradiated from the illumination device and reflected by the surface of the sample and incident on the imaging device). ) Can be converged within a predetermined range. For example, by converging the brightness of the reflected light within the brightness range that can be expressed by the imaging device, the entire surface of the sample can be accurately imaged, and image information such as the outer edge of the indentation is accurately generated. be able to. As a result, the dimensions of the indentation can be measured accurately, and the calculation accuracy of the hardness of the sample can be improved.

The invention according to claim 2 is the hardness tester according to claim 1,
The automatic light control means includes
The brightness of the reflected light is set to be less than the maximum brightness that can be expressed by the imaging apparatus.

  According to the second aspect of the present invention, the brightness of the reflected light is set to be less than the specific upper limit brightness (the maximum value of brightness that can be expressed by the imaging device) by the automatic light control means. Therefore, since the depression on the surface of the sample and the peripheral portion of the depression can be accurately imaged, the image information of the outer edge portion of the depression can be accurately generated. As a result, the dimension of the indentation (for example, the length of the diagonal line) can be accurately measured, so that the hardness of the sample can be accurately calculated.

The invention according to claim 3 is the hardness tester according to claim 1 or 2,
The automatic light control means includes
The brightness of the reflected light is set to be equal to or higher than the minimum brightness necessary for measuring the size of the recess by the measuring means.

  According to the invention described in claim 3, the automatic light control means sets the brightness of the reflected light to be equal to or higher than a specific lower limit brightness (minimum value of brightness necessary for measuring the size of the dent by the measurement means). Therefore, even if the illumination light quantity is reduced for the purpose of power saving and the brightness of the reflected light is reduced, the brightness of the reflected light does not become less than the lower limit brightness. It can be measured. Accordingly, it is possible to realize the measurement of the size of the dent and the calculation of the hardness of the sample while realizing power saving.

  According to the first aspect of the invention, the light intensity from the illumination device can be automatically adjusted by the automatic light control means so that the brightness of the reflected light can be converged within a predetermined range. Therefore, the calculation accuracy of the hardness of the sample can be improved.

  According to the second aspect of the present invention, since the brightness of the reflected light can be set to be lower than the specific upper limit brightness by the automatic light control means, the depression on the surface of the sample and the surrounding area of the depression can be accurately imaged. Thus, the image information of the outer edge portion of the recess can be generated accurately. As a result, since the dimension of the indentation can be accurately measured, the hardness of the sample can be accurately calculated.

  According to the invention described in claim 3, since the automatic light control means can set the brightness of the reflected light to be equal to or higher than the specific lower limit brightness, even when the irradiation light quantity of the lighting device is reduced for the purpose of power saving. Since the brightness of the reflected light does not become less than the lower limit brightness described above, the size of the recess can be reliably measured by the measuring means. As a result, it is possible to realize the measurement of the size of the dent and the calculation of the hardness of the sample while realizing power saving.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, the Vickers hardness tester 1 will be described as an example of the hardness tester according to the present invention.

  First, the configuration of the Vickers hardness tester 1 according to the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a perspective view for explaining the overall configuration of the Vickers hardness tester 1, and FIG. 2 is an explanatory diagram for explaining the configuration of the main body 2 of the Vickers hardness tester 1. FIG. 2 is a block diagram showing a functional configuration of the Vickers hardness tester 1.

  The Vickers hardness tester 1 includes a main body 2, a hardness measurement unit 3, an elevating mechanism 4, a sample fixing device 5, an XY stage 6, and the like. The Vickers hardness tester 1 includes a control device 10, a monitor 11, a keyboard 12, a mouse 13, and the like outside the main body 2.

  As shown in FIG. 2, the hardness measuring unit 3 includes a CCD camera 31 that can move in the vertical direction (Z direction in FIG. 2), an AF control mechanism 32, an illumination device 33 that illuminates the surface of the sample S, an indenter 34, The objective lens 35 includes a turret 36 that can be switched between the indenter 34 and the objective lens 35 by rotation.

  The CCD camera 31 is an imaging device according to the present invention, acquires reflected light on the surface of the sample S through the objective lens 35, and converts the reflected light into an electrical signal to generate image information on the surface of the sample S. To the control device 10. In the present embodiment, a CCD camera 31 capable of 8-bit (256 gradation) sampling is employed. That is, the CCD camera 31 can express 256 levels of luminance from 0 (luminance 0%: black) to 255 (luminance 100%: white) for each pixel.

  The AF control mechanism 32 realizes an automatic focusing operation by raising and lowering the CCD camera 31 under the control of the control device 10.

  The illuminating device 33 illuminates the surface of the sample S by irradiating light. The illumination device 33 is electrically connected to the control device 10, and the amount of irradiation light is automatically adjusted by executing an automatic light control program by the CPU 10 a of the control device 10.

  The elevating mechanism 4 is connected to the sample fixing device 5, and the operator operates the handle 4 a to raise and lower the sample fixing device 5 in the vertical direction (Z direction in FIG. 2) to bring the sample S into a predetermined focusing position. To move to.

  The sample fixing device 5 is a device for fixing the sample S, and can be moved in the vertical direction by the elevating mechanism 4 described above. The sample S is detachably fixed to the sample fixing device 5 by a fastening member (not shown).

  The XY stage 6 moves in an XY plane perpendicular to the vertical direction (Z direction in FIG. 2) under the control of the control device 10. The XY stage 6 horizontally moves the sample fixing device 5 arranged on the upper part and the sample S detachably fixed to the sample fixing device 5 in both XY directions, and the sample is moved below the hardness measuring unit 3. Position S.

  As shown in FIG. 3, the control device 10 includes a CPU 10 a that is connected to each unit and integrally controls the entire device, a ROM 10 b that stores a control program for controlling each unit, and various data generated by executing various programs. It has a RAM 10c that functions as a work area for temporary storage.

  The CPU 10a moves the XY stage 6 so that a predetermined area on the surface of the sample S is located directly below the CCD camera 31 by executing an XY stage control program stored in the ROM 10b.

  Further, the CPU 10a executes an automatic light control program stored in the ROM 10b, and thereby based on the brightness of light acquired by the CCD camera 31 (light reflected from the surface of the sample S and incident on the CCD camera 31). Thus, the luminance of the reflected light (hereinafter simply referred to as “reflected light”) on the surface of the sample S is set within a predetermined range by automatically adjusting the irradiation light amount of the illumination device 33. That is, the CPU 10a and the automatic light control program are automatic light control means in the present invention.

  Further, the CPU 10a executes an automatic focusing program stored in the ROM 10b, thereby controlling the AF control mechanism 32 on the basis of image information obtained by the CCD camera 31 of the hardness measuring unit 3, and the CCD camera 31. Is raised and lowered to perform automatic focusing on the surface of the sample S.

  Further, the CPU 10a executes a hardness measurement unit control program stored in the ROM 10b, thereby pressing the indenter 34 against the surface of the sample S with a predetermined test force to form a recess, or generated by the CCD camera 31. The diagonal length of the indentation is measured based on the image information of the surface of the sample S to be measured, and the hardness of the sample S is calculated based on the diagonal length of the indentation measured. That is, the CPU 10a and the hardness measurement unit control program are measurement means in the present invention.

  In this embodiment, in order to measure the diagonal length of the indentation of the sample S by executing the hardness measurement unit control program, the luminance of each pixel of the image information generated by the CCD camera 31 is set in 256 levels. It must be “30” or more.

  Further, the CPU 10a causes the monitor 11 to display image information on the surface of the sample S generated by the CCD camera 31, the calculation result of the hardness of the sample S calculated by executing the hardness measurement unit control program, and the like.

  The monitor 11 is a display unit that visualizes the image information of the surface of the sample S acquired by the CCD camera 31 and displays the calculation result of the hardness of the sample S. The keyboard 12 and the mouse 13 are input means for an operator to input various setting conditions.

  Next, the hardness measurement operation by the Vickers hardness tester 1 according to the present embodiment will be described with reference to FIGS. FIG. 4 is a flowchart for explaining the hardness measurement operation in the present embodiment.

  First, the user fixes the sample S whose hardness is measured to the sample fixing device 5 (sample fixing step: S1). Then, the CPU 10a of the control device 10 moves the XY stage 6 horizontally by executing an XY stage control program in accordance with an input signal generated by operating the keyboard 12 or the mouse 13, and the surface of the sample S is indented by the hardness measuring unit 3. It arranges in the position which opposes.

  Next, the CPU 10a of the control device 10 executes a hardness measurement unit control program, thereby pressing the indenter 34 of the hardness measurement unit 3 against a predetermined position on the surface of the sample S and applying a predetermined test force for a certain period of time. A recess is formed on the surface of the sample S (recess formation step: S2). Thereafter, the CPU 10a of the control device 10 rotates the turret 36 of the hardness measuring unit 3 and arranges the objective lens 35 above the recess.

  Next, the CPU 10a of the control device 10 executes the hardness measurement unit control program, thereby illuminating the surface of the sample S with the illuminating device 33 and the vicinity of the indentation on the surface of the sample S by the CCD camera 31 through the objective lens 35. A part is imaged and image information is acquired. Then, the acquired image information is displayed on the monitor 11 (image information display step: S3). FIG. 5 shows the display screen 11 a of the monitor 11 displaying the image information of the surface of the sample S.

  Next, the CPU 10a of the control device 10 executes an automatic light control program, and based on the brightness of the reflected light (light irradiated from the illumination device 33 and reflected by the surface of the sample S and incident on the CCD camera 31), The irradiation light amount of the illumination device 33 is automatically adjusted. By this automatic adjustment, the brightness of the reflected light is converged to be lower than the specific upper limit brightness and higher than the specific lower limit brightness (automatic light control step: S4). Here, the “upper limit luminance” means the maximum luminance value (255) that can be expressed by the CCD camera 31, and the “lower limit luminance” means the minimum luminance value (necessary for measuring the diagonal length of the dent ( 30).

  Here, the effect of the automatic light control step S4 will be specifically described with reference to FIG. FIG. 6A is a graph showing the relationship between the change in the irradiation light amount level of the illumination device 33 and the change in the measured diagonal length of the sample S. FIG. 6B is a graph showing the relationship between the change in the irradiation light amount level of the illumination device 33 and the change in the calculated value of the hardness of the sample S. In FIG. 6A, “D1” is a measured value of the diagonal length of the indentation K in the image information on the surface of the sample S shown in FIG. 5, and “D2” is FIG. 2 is a measured value of the diagonal length of the indentation K in the horizontal direction in the image information of the surface of the sample S shown in FIG.

  As shown in FIGS. 6A and 6B, when the irradiation light quantity level is 10 or less, the measured diagonal length and the calculated hardness are constant. On the other hand, when the irradiation light quantity level exceeds 10, the measured value of the diagonal length decreases and the calculated value of hardness increases. As described above, the measured value of the diagonal and the calculated value of the hardness change as the irradiation light amount level increases for the following reason. That is, when the irradiation light level increases, the brightness of the reflected light near the outer edge of the recess formed on the surface of the sample S exceeds the maximum brightness value (255) that can be expressed by the CCD camera 31, so that the vicinity of the outer edge of the recess. This is because the image information becomes inaccurate.

  In order to solve the above problems, in the automatic light control step S4, the brightness of the reflected light is adjusted to a specific upper limit brightness (maximum brightness that can be expressed by the CCD camera 31) by automatically adjusting the irradiation light amount level to 10 or less. (255)).

  In the present embodiment, in order to measure the diagonal length of the depression of the sample S by executing the hardness measurement unit control program, the luminance of each pixel of the image information generated by the CCD camera 31 is set in 256 steps. It must be “30” or more.

  Therefore, in the automatic light control step S4, the brightness of the reflected light is adjusted to a specific lower limit brightness (minimum brightness value (30) necessary for measuring the diagonal length of the dent) by automatically adjusting the irradiation light amount level to 7 or more. ) It is set above. FIG. 5 shows image information of the surface of the sample S when the irradiation light quantity level is set to “10”.

  Following the automatic light control step S4, the user operates the handle 4a of the elevating mechanism 4 while moving up and down the sample fixing device 5 and the sample S while visually recognizing the display screen 11a of the monitor 11. The surface of the sample S is placed at the in-focus position with a predetermined distance from the lens 35 (manual focusing step: S5).

  When the surface of the sample S is placed at the in-focus position, the CPU 10a of the control device 10 executes the auto-focus program, thereby controlling the AF control mechanism 32 based on the acquired image information to control the CCD camera 31. The sample is moved up and down to focus on the surface of the sample S (automatic focusing step: S6).

  Next, the user operates the keyboard 12 and the mouse 13 to cause the CPU 10a of the control device 10 to execute the hardness measurement unit control program, and the CCD camera 31 of the hardness measurement unit 3 causes the depression K (see FIG. 5). The length of the diagonal line is automatically measured (recess dimension automatic measurement step: S7). And CPU10a of the control apparatus 10 calculates the hardness of the sample S from the length of the measured diagonal of a hollow (hardness calculation process: S8).

  In the Vickers hardness tester 1 according to the present embodiment, the amount of irradiation light of the illumination device 33 is automatically adjusted by automatic dimming means (CPU 10a and automatic dimming program), and reflected light (reflected on the surface of the sample S). Thus, the brightness of the light incident on the CCD camera 31 can be converged within a predetermined range.

  That is, the light intensity level of the illumination device 33 is adjusted to 10 or less by the automatic light control means, and the brightness of the reflected light is made less than a specific upper limit brightness (the maximum brightness value (255) that can be expressed by the CCD camera 31). Can be set. Therefore, since the depression on the surface of the sample S and the peripheral portion of the depression can be accurately imaged, the image information of the outer edge portion of the depression K can be accurately generated. As a result, the diagonal length of the indent can be accurately measured, so that the hardness of the sample can be accurately calculated.

  Further, the light intensity level of the illumination device 33 is adjusted to 7 or more by the automatic light control means, and the brightness of the reflected light is set to a specific lower limit brightness (minimum brightness value (30) necessary for measuring the diagonal length of the recess). ) Can be set above. Therefore, even when the illumination light amount is reduced for the purpose of power saving and the luminance of light incident on the imaging device is reduced, the reflected light luminance does not become less than the lower limit luminance described above. Can be reliably measured. Accordingly, it is possible to realize the measurement of the diagonal length of the dent and the calculation of the hardness of the sample while realizing power saving.

  In the above embodiment, the 8-bit sampling type CCD camera 31 capable of expressing 256 levels of luminance for each pixel is employed as the imaging device, but a 10-bit sampling type capable of expressing 1024 levels of luminance for each pixel. A CCD camera can also be employed. In such a case, the light intensity of the illuminating device 33 is adjusted in the automatic light control step S4 so that the luminance of the reflected light is set to be less than the maximum luminance value (1023) that can be expressed by the 10-bit sampling CCD camera. .

  In the above embodiment, in order to measure the diagonal length of the depression of the sample S, the luminance of each pixel of the image information generated by the CCD camera 31 needs to be “30” or more in 256 steps. However, if the diagonal length of the dent of the sample S can be measured even at a lower luminance by upgrading the program or the like, the irradiation light amount of the illumination device 33 is further reduced to further save power. be able to.

  In the present embodiment, an example in which the present invention is applied to the Vickers hardness tester 1 has been shown. However, another hardness test in which a recess is formed on the surface of the sample and the hardness is measured according to the size of the recess. The present invention can also be applied to a machine (for example, a Brinell hardness tester or a Knoop hardness tester).

  In addition, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as the object of the present invention can be achieved.

1 is a perspective view showing an overall configuration of a Vickers hardness tester according to an embodiment of the present invention. It is explanatory drawing for demonstrating the structure of the main body of the Vickers hardness tester shown in FIG. It is a block diagram for demonstrating the functional structure of the Vickers hardness tester shown in FIG. It is a flowchart for demonstrating the hardness measurement operation | movement of the Vickers hardness tester shown in FIG. It is a figure which shows the state which displayed the image information of the surface of a sample on the monitor of the Vickers hardness tester shown in FIG. (A) is a graph which shows the relationship between the irradiation light quantity level of the illuminating device of the Vickers hardness tester shown in FIG. 1, and the measured value of the diagonal length of a hollow. (B) is a graph which shows the relationship between the irradiation light quantity level of the illuminating device of the Vickers hardness tester shown in FIG. 1, and the calculated value of hardness. It is a figure which shows the example of the image information (thing near the outer edge of a hollow is inaccurate) of the surface of a sample.

Explanation of symbols

1 Vickers hardness tester 10a CPU (automatic light control means, measuring means)
31 CCD camera (imaging device)
33 Illuminator 34 Indenter K Recess S Sample

Claims (3)

In a hardness tester that calculates the hardness of the sample by forming a recess on the surface of a predetermined sample using an indenter and measuring the size of the recess,
An illumination device for illuminating the surface of the sample;
An imaging device that images the surface of the sample illuminated by the illuminating device and generates image information of the depression and a peripheral portion of the depression;
Automatic dimming that automatically adjusts the amount of light emitted from the illumination device so that the brightness of reflected light that is irradiated from the illumination device and reflected by the surface of the sample and incident on the imaging device converges within a predetermined range. Means,
Based on the image information generated by the imaging means, measuring means for measuring the size of the recess,
A hardness tester comprising: The automatic light control means includes
The hardness tester according to claim 1, wherein the brightness of the reflected light is set to be less than a maximum value of brightness that can be expressed by the imaging apparatus. The automatic light control means includes
The hardness tester according to claim 1 or 2, wherein the brightness of the reflected light is set to be equal to or greater than a minimum brightness value necessary for measuring the size of the recess by the measuring means.