JPS6212851B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring the size of a hardness test depression made on the surface of a solid material.

The principle of determining the size of the indentation produced by a hardness tester by means of an optoelectronic device is well known. For example, German patent no.
According to OS2331124, the surface being indented is illuminated by a light beam in a specified direction. The portion of the light beam incident on the recess is reflected in a direction different from that of the light reflected from the unrecessed surface. This phenomenon is used to generate a light image of the depression and its surrounding area. The optical image is quantitatively evaluated using a scanning technique that counts the number of pixels that make up the optical image.

One drawback of these scanning methods is that they must rely on magnified images of the depression. Therefore, the quantitatively measured results are related to the magnification rate of the magnifying device. This magnification factor must be known and must be constant. Furthermore, since the enlarged image of the depression is scanned, the scanning area becomes larger, which causes problems in the linearity of the scanning. If the lens has aberrations, the shape of the optical image will not necessarily match the shape of the depression, so measurement errors will also occur due to the aberrations of the lens.

It is an object of the present invention to be able to directly measure the indentation created by a hardness tester without using an optical device that forms a light image, without changing optical parameters, and in which all indentation elements are It is an object of the present invention to provide a method that allows measurement while being pressed against a test object under a test load. In this method, measurements are taken by transmitting illumination light through an element that is indented.

A method for achieving this object is described in claim 1. It also describes important features of the method of the invention.

The diameter of the light beam irradiated onto the surface to be tested is selected according to the area of the depression to be measured. In order to obtain a suitable measurement accuracy, the ratio between the diameter of the light spot and the diameter of the depression (better the ratio between the area of the light spot and the area of the depression) must be chosen appropriately. Generally, an area ratio of at least about 1:100 is considered to be a sufficient ratio. If the area of the depression is quite small (0.01-0.1 mm ² ), the use of a light source producing monochromatic coherent light is indicated, for example a laser with a beam expander and a converging lens. Using such a laser, it is possible to obtain a light spot with a diameter of less than 50 microns and a beam convergence angle of 2 degrees at a relatively long focal length. If such a light source is used, the distance between the converging lens and the test object may not be very precise. In this case, it is not necessary to use a normal focus adjustment device.

When measuring large depressions (1-10 ^mm2 ), non-coherent light is usually sufficient to generate a sufficiently small spot of light.

A suitable photosensitive element such as a photocell, photoconductive element or a conventional selenium photocell is used to measure the intensity of the reflected light. The photosensitive elements are sized and positioned to receive light reflected from the recess or from areas (of predetermined area) surrounding the recess. In this case, care must be taken to minimize the incidence of scattered light coming from other directions on the photosensitive element.

Two basic modes of operation are possible when implementing the novel measurement technique according to the invention.

() Measure the diameter of one or more of the depressions to determine hardness. This first mode of operation is primarily applicable to measuring relatively large conical and spherical depressions. If the test object is an anisotropic material, it is better to measure two orthogonal diameters of the depression.

() In a particularly useful construction of the measuring device realizing the second mode of operation, it is emphasized that the well-known basic definition of the indentation hardness is based on the area of the indentation to be measured. In the case of a Bitkers depression, the difference between the area calculated from the length of the diagonal and the actual area is 25 if the depression has a strong asteroid shape (pin cushion shape).
%.

According to the invention, the area can be measured with the indenting element away from the test object and with the indenting element pressed against the test object.

According to the invention, the area can be measured with the indenting element away from the test object and with the indenting element pressed against the test object.

Another object of the invention is to provide a measuring device for applying the technology having the features set out in claim 8. Various examples of such devices suitable for measuring both the length and area of depressions are set out in claims 9 to 22.

From the description of embodiments of the invention that follows, it will be seen that the apparatus implementing the method of the invention does not require any calibration. The numerical value obtained as a result of the measurement is independent of parameters such as optical magnification, amplification, resistance or capacitance, etc.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

First, with reference to FIGS. 1 and 2, the principle for determining the area or diameter of a depression made for hardness testing will be explained.

FIG. 1 shows a simple embodiment consisting of a cylindrical member 1. FIG. This cylindrical member 1 is placed on the surface of a test piece M, and a depression E is formed on the surface at a position on or near the axis of the cylindrical member 1.
For example, a sharp and slightly converging beam of light, such as a focused laser beam, is formed by three rays A ₁ ,
The surface M of the specimen is irradiated as indicated by A ₂ and A ₃ . This light beam is passed through a scanner (not shown) before reaching the lower part of the tubular member 1. The scanner deflects its light beam in two directions: an X direction, as indicated by the arrow, and a Y direction, which is perpendicular to this X direction and the plane of the paper in which FIG. 1 is drawn. The light beam is incident on the surface M of the test piece at right angles, and the light beam is parallel to the surface M of the test piece without changing the direction of incidence of the light beam to avoid measurement errors due to angular deviation. be moved. Since the surface of the depression E is assumed to be substantially mirror-like, the light ray A is reflected from the surface of the depression almost as if it were reflected by a mirror. This condition is achieved in most metals. The light rays A ₁ , A ₂ incident on the conical or pyramidal depressions are reflected laterally and impinge on a photosensitive layer 2 provided on the inner wall of the tubular member 1 near its open end. This photosensitive layer 2 can consist of a photocell, a photoconductive element, a photovoltaic cell (for example a selenium photovoltaic cell). A diffusion layer 3 can be provided on the surface of the photosensitive layer 2 in order to cause the light beam reflected from the surface of the depression to be incident over a wide area of the photosensitive layer 2. The photosensitive layer 2 is connected to an electronic circuit and a measuring unit.

Light incident on a surface of a test piece other than the indentation will be reflected in the same direction as the incident direction if that surface is sufficiently smooth. Therefore, the light travels upward parallel to the axial direction of the cylindrical member 1 and does not enter the photosensitive element 2.

The light beam incident on the surface M of the specimen has a diameter D
The light beam is deflected by moving at a constant speed in the X direction within the range of . Depending on the intensity of the reflected light, the photosensitive layer 2 generates a voltage E(t) as shown in the left part a of FIG. Even if the travel distance X of the light beam is replaced by the time t on the abscissa, the shape of this voltage does not change.

Points P ₁ and P ₂ correspond to the two edges of the depression E.
The lateral dimension of the depression E can be calculated from the time difference Δt if the deflection speed of the light beam is constant and known. Assuming that the light beam is moved by one line width in the Y direction for each movement in the will occur. When the entire area including the depression is scanned in this way, the area A of the depression can be calculated using the following equation.

A=b _y v _x Σ(Δt) () where b _y is the width of the scanning line. The light beam deflection mechanism and voltage pulse processing device will be explained in detail later.

The method described above can in principle be applied not only to conical or pyramidal depressions, but also to spherical depressions such as those made with a Brinell hardness tester. An example of an apparatus for measuring spherical depressions is shown in FIG. FIG. 3 shows only the slightly conically shaped cylindrical member 11 of the device, which is placed on the surface M of the specimen. This member 11 is placed so that the recess EB is on or near the central axis of the member 11, and a light beam that can be deflected in both the X and Y directions is irradiated from above the member 11.

The two positions of the central ray of the incident light beam are indicated by the symbols A ₄ and A ₅ . The light reflected from the depression is spread over a relatively large angular range due to the spherical shape of the depression. The limits of this angular range follow the rules for the Brinell hardness test. According to the rules, the depression should not be smaller than 0.25D _k and should not be larger than 0.6D _k . Note that D _k is the diameter of the element forming the spherical depression. Therefore, the photosensitive layer 12 with the diffusion layer 13 must be shaped accordingly. Since the light directly reflected from the central part of the depression does not reach the photosensitive layer 12, a "hole" appears in the voltage curve, but this "hole" can be filled with an electronic processing circuit. The other measurement operations are the same as those described for measuring conical and pyramidal depressions.

The embodiment described above is quite simple and suitable for carrying out many hardness tests. However, it should be noted that the surface of the specimen generally does not have ideal reflector properties. Typically, the incident light is reflected in more than one direction, i.e., due to the roughness of the input surface or the machining and finishing marks that the specimen has undergone on its surface. , scattered. Light that is diffusely reflected from a rough surface has low contrast, i.e., the second
The voltage ratio E _nax /E _r in the figure becomes smaller. In order to prevent this reduction in contrast, elements can be used in the measuring device to make the voltage ratio as high as possible even under such conditions.

In addition, light that is diffusely reflected from the surface of the test piece may enter the photosensitive layer. In this connection,
It should be mentioned that the edges of the depressions are not always sharp. Those edges of the depressions often have some degree of rounding, as indicated by the symbol W in FIG. 4, due to the collection of material displaced during the depression. The periphery of the depression E formed on the surface M of the test piece is slightly raised as shown in an exaggerated manner in FIG. The light ray _A6 incident on this raised ivy portion is reflected in a different direction than the light ray reflected from the depression itself. For example, compare rays A ₆ and A ₇ . For this purpose, only light incident within a specified angle range can enter the photosensitive layer.
It is advantageous to provide a directional element in the photosensitive layer. By doing this, light arriving at different angles is deflected in other directions, absorbed, or simply reflected, depending on the type of angle-limiting element used.

An angle limiting element is included in the device shown in FIG. The measuring device shown in FIG. 4 also has a cylindrical member 21. The measuring device shown in FIG. This cylindrical member 21 is placed on top of the dimpled surface of the specimen. A deflectable light beam is incident from above the cylindrical member 21 . The various positions of the light beam are indicated by rays A ₆ to _{A 9} .

Immediately below the insert 24 in the lower part of the cylindrical member 21 a vitreous body 25 is placed. This glass body 25 has a hole in the center and a conical outer surface. _The apex angle γ of this conical shape is determined by the critical angle α _krit α _krit = arcsin1 _/ n _gk ( ) is very close to . In addition, n
_gk is the refractive index of the glass constituting the vitreous body. The light rays A ₇ and A ₈ reflected by the depressions pass through the light diffusion layer 23 and reach the photosensitive layer 22 . Rays of light reflected from the rounded edge W of the depression
A ₆ is the critical angle α _krit on the outer surface of the vitreous body 25
The light enters at a larger angle α, is totally reflected, and is finally absorbed by the light absorption layer 26 attached to the upper surface of the glass body 25.

In principle, the glass body 25 and the cylindrical member 2
It is possible to utilize said space to construct a multiple reflection pattern, such that an incident light beam travels back and forth through the space between the photosensitive layer 1 and impinges on an infinite number of points on the photosensitive layer. In that case, the diffusion layer 23 may not be provided. Further, when the photodetecting element is composed of a vacuum cell (photocell), there is no need to provide a diffusion layer.

Another very effective way of limiting the incidence of scattered light into the photosensitive layer is to provide an angular filter that allows only the rays falling within a narrow limited range to be incident on the photosensitive layer. Such an angular filter is shown in FIG. In order to simplify the illustration, FIG. 5 shows the surface M of the test piece with the indentation E, the photosensitive layer 32, the diffusion layer 33, the angle filter 35, and some light rays. Only necessary elements are shown.

The angle limiting element is composed of an annular glass body 35. The cross-sectional shape of this glass body is similar to that of a Porro prism. A Porro prism is transparent to light rays incident at right or nearly right angles to its base (hypotenuse). After being totally reflected twice by the two short sides, the rays exit the bottom of the prism at the same angle as they entered the bottom of the prism. A ray of light incident on the bottom of a prism at an angle of incidence greater than a certain angle of incidence will exit from one of the short sides of the prism and thus disappear. The angular range through which light travels can be calculated from the following equation.

±β=±(45°−arcsin1/n) () where n is the refractive index of the glass. for example,
If a prism is made of glass with a refractive index n = 1.485, the angular range through which light is transmitted is β = ±
It becomes 2.7°. Also, when n=1.603, β=±6.4
It becomes ゜.

This angle limiting principle is used in the "Porro ring" shown in FIG.
The cross-sectional shape of the rotationally symmetrical glass body 35 is triangular, that is, the two conical surfaces that intersect on the outside are at right angles, and the inner conical surface and the outer conical surface are
Intersect at 45 degrees. An annular photosensitive layer 32 provided with a diffusion layer 33 is attached to the upper part of the inner conical surface F ₃ . The ray A ₁₀ reflected from the depression E is the surface
The light exits from _F3 and enters the photosensitive layer 32. Light ray incident on the surface M of the test piece other than the depression E
A ₁₁ etc. give rise to scattered rays B′, B″, for example. If these reflected rays are not contained within the angular limits given by the above equation (), then when leaving the Porro ring the surface F ₁ , does not pass through F ₂ .

The angle φ/2 formed by the inner conical surface F ₃ with respect to the surface M of the specimen is related to the cone angle φ of the indentation if the indentation is conical, or to the cone angle φ of the indentation if the indentation is a Bitkers indentation. Vertical angle φ
related to. If necessary, elastic recovery effects that occur when the indenting element is removed from the surface of the specimen can be taken into account. The apex angle of the indentation after the indentation element is removed from the surface of the test specimen is smaller than the apex angle of the indentation when the element is pressed against the surface of the test specimen. As mentioned above, the measurement technique of the present invention can be used to measure the area of an indentation while the indentation element is pressed against the surface of the specimen. This is the preferred and more accurate technique for several reasons, including:

1 According to the original definition of indentation hardness, the quantity to be measured is the area of the indentation while the indenting element is pressed against the surface of the specimen. As far as metals are concerned, the difference between the area of the indentation when the test load is fully applied and the area of the indentation at no load, i.e. after the indenting element has been removed from the surface of the specimen, is at most a few %. However, when it comes to plastic materials, the difference can be large.

2. Measurements made while the indenting element is pressed against the surface of the specimen take much less time. This is because there is no effort to remove the applied load, to remove the indenting element from the indented surface, or to place an area measuring device over the indentation. Therefore, measurements are taken immediately after the specified loading time for the hardness test has elapsed. Rapid hardness testing of large numbers of parts is currently widely used in industry. Therefore, no matter how short the time can be, it is important.

3. The contour of the indentation is better discernible when the indenting element is pressed against the surface of the specimen than after it has been removed from the surface of the specimen. This can be understood if one assumes that the edges of the depression have a constant radius of curvature, as shown in FIG.

4 Correct hardness measurements based on the area of the depressions are also possible in the case of plastics.

5. Light scattered from unrough surfaces does not significantly interfere with measurements. In this regard, the depressions themselves have a certain degree of dampening effect.

6. Since no elastic recovery of the depth of the indentation can occur as long as the load is applied, narrow limits can be placed on the permissible angle of the light beam that can reach the photosensitive element of the device.

FIG. 6 shows an embodiment for measuring the area of an indentation while the indentation element is pressed against the surface of the test piece. The cylindrical member 4 is a transparent slab 44 with parallel major surfaces made of a strong material such as fused alumina, quartz or special glass.
It is inserted into the lower end of 1. A transparent recessed element 48 is placed opposite the underside of this slab 44. This dimple element is made of a transparent hard material such as diamond, sapphire or fused alumina. Its diameter D _E corresponds to the maximum diameter D _M of the measuring part. The sides of the recessed element are surrounded by another transparent object 45. A light diffusion layer 43 is attached to the outer surface of this object, and a photosensitive layer 42 is attached to the surface of this light diffusion layer.

The test load P is transmitted from the tubular member 41 via the slab 44 to the indentation element 48 . No force should be transmitted to the transparent object 45. transparent object 4
5 is made of transparent plastic or glass;
A recessing element 48 is molded into this object 45 . If the recessed element 48 has a square cross section, the transparent body 45 can be constructed in four parts if desired. A recessed subassembly ready for installation and easy to replace includes the element 48, the surrounding glass body 45 and the photosensitive layer 42 with the light diffusing layer 43 in an annular support. It can be made by attaching it to. The annular support can be provided with a threaded groove so that the subassembly can be threadedly attached to a hardness testing machine.

The total reflector at the interface between the recessed element 48 and the object 45 surrounding it is directed to the glass object 45 after being reflected from the recess at a nominal angle α ₂ =φ−
This does not occur with ray A ₁₂ incident at 90°. The conditions for preventing total reflection at the interface are as follows.

α ₂ <α _krit = arcsin(n ₄₅ /n ₄₈ ) () In this equation, n ₄₅ and n ₄₈ are the refractive indices of the object 45 and the indentation element, respectively.

The light ray A ₁₂ is reflected by a mirror surface 46 provided between the slab 44 and the glass object 45 and then enters the photosensitive layer 42 .

Now, considering the light ray _A13 incident on the surface of the specimen outside the depression E, the following conditions must be met in order to prevent this light ray from being totally reflected at the interface between the depression element and the air. Must be.

α ₁ =1/2(180°−φ)<α _krit () The Bitkers pyramidal indentation element is made of diamond. Since the refractive index of diamond is equal to 2.415, the critical angle is 24.46° according to equation (). Since the apex angle of the pyramid is equal to 136°, α ₁ = 22
It is ゜. Therefore, the incident ray is transmitted,
It is reflected from the surface M of the specimen and then re-enters the indentation element in such a way that most of the light energy contained in the ray A ₁₃ is returned to the black central hole of the tubular member 41 . The light energy returned to the black center hole of the cylindrical member 41 is ultimately absorbed there.

The lower surface of the transparent object 45 is coated with an opaque light absorbing layer 47 . Furthermore, in order to prevent external light from entering the photosensitive layer 42, which would reduce the contrast, a movable tube or a sleeve made of rubber, for example, can be fitted on the outside of the cylindrical member 41. This is not shown in FIG.

Special conditions exist if the specimen is transparent (eg transparent glass, transparent plastic). In that case, α ₁ = 0.5 (180° − φ) > α _krit
We have to find the conditions. Total internal reflection then occurs at the surface of the indentation element bordering the air, and the light is transmitted through the indentation, ie the area where the indentation element is in contact with the surface of the specimen. The voltage curve shown in FIG. 2 is then reversed. In this case, instead of measuring the length of time Δt during which the light is intensified, the length of time Δt' during which the light is weakened is measured. In this case, the area A of the depression can be found from the equation A=b _y v _x Σ(Δt') instead of equation (1). This measurement method can also be applied to black opaque objects such as graphite and black opaque plastics.

Totally reflective dimpled elements, such as 120° diamond cones, can also be used for hardness testing of metals. This is possible because almost all metals reflect only a portion of the incident light. The mirror-finished steel surface reflects 59% of light in the 600nm wavelength range and 45% of light (ultraviolet radiation) in the 300nm wavelength range. Pushing such a totally reflective dimple element into the steel surface results in a bright edge (due to total internal reflection at the diamond-air interface) and a specular reflection at the diamond-steel interface. A relatively dark central area (due to the glaucoma) can be seen. In this case, the measurement conditions are particularly good because no light scattering occurs.

Comparable light reflection conditions exist when testing translucent or opaque plastics using a 120° diamond cone.

It may be advantageous to carry out measurements with a modification of the example shown in FIG. The revised example is not shown. The modified example uses a diamond indentation element with an apex angle of 136°. Then ()
The formula gives the refractive index n ₄₅ >1.744 of the glass object 45. The material suitable for making the object 45 is n=
1.923 zirconium silicate (ZrO ₂ SiO ₃ ). However, because the difference in refractive index is even larger,
Ray A ₁₂ is incident on mirror surface 46 at a relatively small angle of incidence. Therefore, the photosensitive layer 42 can be attached to the bottom surface of the object 45 rather than the outer surface. Furthermore,
In this case, the light ray reflected from the surface M of the test piece
A ₁₃ is subjected to multiple reflections within the dimple element 48 before it returns to the hole in the tubular member 41 and exits the dimple element 48 somewhere on the underside of the object 45 .

7, 8 and 10 show a complete embodiment of the invention for measuring the area of a depression, highlighting a scanning device which seems particularly suitable from a technical point of view. In this embodiment, a light beam deflected in two mutually perpendicular directions is limited in its lateral movement distance to the order of the diameter of the depression. A test device designed to measure depressions with an area of about 1 mm ² is suitable for handling a scanning area of about 4 mm ² . By reducing the scan area to such a small size, linearity problems are virtually eliminated. At the same time, the light beam is translated by a mechanical-optical scanning mechanism. This avoids angular errors entering the numerical measurements that can occur with scanning devices that utilize rotating mirror scanning mechanisms.

7 and 8 show the main components of a mechanical-optical scanning device for deflecting a light beam. The scanning device has a light source 52, such as a laser, which produces a narrow, slightly convergent light beam A. One end of the shaft of the motor 53 is directly connected to a glass plate 54, and the other end is connected to a second glass plate 58 via reduction gears 55, 56, 57. Since the two glass plates 54 and 58 having rotation axes perpendicular to each other are rotated by one and the same motor,
The rotational speed ratio of the glass plates is constant. Due to the reduction gears 55, 56, 57, the rotational speed of the second glass plate 58 is much lower than the rotational speed of the first glass plate 54. The parts described above are fixed to the frame 59. The bottom of this frame contacts the stop 51, and the hole F in the stop 51 limits the scanning area.

A light beam A generated from a light source 52 passes through two glass plates 54 and 58 and a hole F in a stop 51, and enters a test piece M including a depression E. A cylindrical member 1, 11, 21 or 41 is provided between the stop 51 and the surface M of the specimen. The cylindrical members are provided with a photosensitive layer and an optical element for polarizing the reflected light beam. The connections between the photodetector and the electronics are not shown in FIGS.

A plane-parallel glass plate deflects the light beam by a value given by:

Here, n _p is the refractive index of the glass plate, φ is the rotation angle equal to the angle of incidence, and t _p is the thickness of the glass plate.
The deflection speed when a=0 can be obtained from equation ().

V _x(y) = (1-1/n _p1 (2))2πn ₁ (2)t _p1 (2)(
) where n ₁ is the rotational speed (rpm), n _p1 is the refractive index, and t _p1 is the thickness of the first glass plate, ie, the element that deflects the beam in the X direction. The thicker the glass plate and the higher its refractive index, the seventh
The linearity requirement is met for a given deflection distance a _F determined by the scanning area F shown in the figure.

The two glass plates 54, 58 perform linear deflections a _x (t) and a _y (t) within the limits determined by the width of the scanning area F. Due to constant rotational speed n ₁ >>n ₂ constant deflection speeds v _x , v _y are also obtained. When the two glass plates 54, 58 are rotated, a light spot generated on the surface M of the specimen by the light beam A traverses the scanning area F including the depression E. As a result, a photodetector built into the measuring device generates a voltage E(t) having the waveform shown in FIG.

FIG. 9 shows an example of a circuit configuration of an electronic device for measuring voltage E(t). Voltage E controls gate circuit 61. This gate circuit is a counting circuit 68
is combined with The voltage E(t) generated by a photosensitive element, e.g. a photocell and its auxiliary circuitry, is amplified and then applied to a trigger circuit 64 having elements for setting a threshold voltage E _S . E
As long as (t)> _ES , the gate circuit 61 is open and the frequency generated from the pulse generator 67 is
Pass a pulse that is _z . _The number of pulses passing through the gate circuit 61 is N= _ztd . This t
_d is the time that the gate circuit 61 is open, and t _d =
Σ(Δt). Therefore, N is proportional to the area A of the depression.

A pulse of frequency _z is generated as follows. A motor 53 (FIGS. 7 and 8) drives a generator 65 at a rotational speed n ₁ so that a signal with a main frequency _g = μ ₁ n ₁ is generated. The signal generated by the generator 65 is applied to a frequency multiplier 66 with a multiplication factor of _μ2 . Finally, a signal of frequency μ _{2 g} is applied to pulse shaping circuitry 67 . Then, the output of the pulse shaping network 67 has a frequency _z = μ _{2 g} =
It consists of a series of short pulses μ ₁ μ ₂ n ₁ =mn ₁ .
These pulses pass through a gate 61 to a counting circuit 6
given to 8. If N is equal to the number of pulses counted, the corresponding area of the indentation is A=
kN. This area is displayed by the readout device 69. It is preferable to configure the electronic device shown in FIG. 9 so that the coefficient k in the formula for determining the area A of the depression is equal to a power of 10. small computer circuit 70
By adding , you can directly specify the desired hardness value or print out the value.

By combining _the formula ( ₎ for calculating the _area A of the recess, _the formula () for calculating the deflection _{speed v} The area A of can be found. Note that in the equation representing the width b _y of the scanning line, p ₁ is the number of flat surfaces of the rotating glass body 54 used to deflect the light beam in the X direction. In the embodiment shown in FIGS. 7 and 8, p ₁ =2. When a hexagonal prism is used instead of a plane-parallel glass plate, p ₁ =6. The number p ₁ also indicates how many times the scanning in the X direction is performed during one rotation of the glass body 54. Here, v _x , v _y =
Assuming constant, n ₁ ≫ n ₂ , t _d = N/ _z , _z =
Since mn is ₁ , the area A of the depression can be found as follows.

A=v _x b _y /mn ₁・N =4π ² n ₂ /p ₁ nm ₁ (1-1/n _p1 ) (1-1/n _p2 )t _p1 t _p2 N=kN Thickness t of glass plate _p1 and t _p2 are unchangeable and can be measured accurately, the refractive indices n _p1 and n _p2 of the glass used in the glass plate are known and cannot be changed, and if gears are used, the rotational speed ratio It should be noted that n ₂ /n ₁ is fixed, the number of surfaces p ₁ is a fixed number, and the frequency multiplication factor m is also unchanged. This frequency multiplication factor m is a power of two. Therefore, as mentioned above, the area of the depression can be written as A=kN.
This coefficient k is a computable invariable.

The electronic device shown in Figure 9 includes an oscilloscope 7.
1 are combined. This oscilloscope displays the shape of the indentation, which allows us to draw some conclusions about the properties of the specimen.

One additional variable remains in the electronic device shown in FIG. This variable is the trigger threshold voltage E _S . If the residual voltage caused by the light scattered from the surface of the specimen is F _r , then the average voltage is equal to 1/2 (E _r +E _nax ).

It is possible to automatically adjust E _S by electronics so that the trigger threshold voltage E _S is always approximately equal to this average voltage. This is "electronic interpolation"
It is called. In this way, the uncertainty caused by the finite slope of the voltage E(t) curve is largely eliminated. Because the diameter of the light spot irradiated on the depression is finite and the curvature of the edge of the depression is finite, it is important that the rising and falling angles of the E(t) curve are less than 90 degrees. This can be seen from Figure 2.

Finally, a simple example for measuring the diameter of a recess under load is shown in FIG. A test load P is applied to the cylindrical member 80. The cylindrical wall 81 of this cylindrical member terminates in a plate carrying an indentation element 88 in contact with the surface M of the specimen. A light source (laser) 82 is a cylindrical member 8
It is provided inside 0. This light source can be moved in the X direction by means of a micrometer screw 84. A light beam A generated from a light source 82 passes through an indentation element 88 to a surface M of the specimen. Even if the light source 82 is moved in the X direction, the light beam A
Light beam A is directed through the center of recessed element 88 by controlling the direction of the light beam so that it passes through the apex of recessed element 88 .

Light reflected from the depressions is incident on the photosensitive layer (not shown) in the same manner as described with reference to FIG. The resulting voltage E(x)
is amplified and then applied to the voltmeter 85. An XY recorder can be used in addition to or instead of a voltmeter. The shape of the E(x) curve is the same as shown on the left side of Figure 2a.

It is a matter of choice what type of micrometer is utilized for this measurement purpose. In its simplest construction, this measuring device uses a standard screw-type micrometer. For more complex and expensive devices, a motor-driven micrometer combined with a digital reader is used.

In a variant of the device shown in FIG. 10, the light source can be fixed. In that case the light beam is deflected by a rotatable plane-parallel glass plate. A transparent drum is attached to the rotating shaft of the glass plate. The surface of the drum is provided with optical grating lines. A fixed optical grating made with the same line spacing as the grating lines is provided on the outside of the glass drum. Light beams generated from fixed light sources are directed through these optical gratings. The transmitted light beam is received by a photocell. The photocell is connected to electronic equipment including an amplifier and trigger circuit and pulse counter. As the drum is rotated, a number of pulses is generated that is proportional to the deflection distance Δx of the light beam. The drum can be turned by hand,
By counting the number of pulses within the range given by the E(x) curve as described above, it is possible to determine the diameter of the depression very precisely.

[Brief explanation of the drawing]

1 is a longitudinal sectional view of the measuring device for carrying out a first embodiment of the method of the invention for measuring the area of a depression, with parts of the measuring device placed on the surface of a test piece; FIG.
FIG. 3 is a waveform diagram showing the output voltage of the photocell as a function of time; FIG. 3 is a diagram similar to FIG. FIG. 4 is a view similar to FIG. 1 of parts of an apparatus for carrying out the third embodiment of the method of the present invention, and FIG. 5 is an angle at which reflected light can reach the photocell in an apparatus for measuring the area of a depression. FIG. 6 is a view similar to FIG. 1 showing parts of an apparatus for carrying out a fourth embodiment of the method of the invention; FIG. 7 is a hardness test 8 is a schematic diagram of the mechano-optical part (scanning mechanism) of an apparatus useful for measuring the area of a depression made by a device; FIG. 8 is a schematic diagram showing a portion of the scanning mechanism shown in FIG. 7; , FIG. 9 is a schematic block diagram showing the entire measuring device including the electronic part, and FIG. 10 is a longitudinal sectional view of a part of an embodiment of the device applicable to measuring the diameter of a recess. 1, 11, 21... Cylindrical member, 2, 12, 2
2, 32, 43... photosensitive layer, 13, 23, 33...
...Light diffusion layer, 45...Transparent object, 48,88...
Recessing element, 50... Motor, 52, 82...
...Light source, 54, 58... Glass plate, 61... Gate circuit, 64... Trigger circuit, 65... Generator,
66...Frequency multiplier, 67...Pulse generator, 6
8...Counting circuit, 69...Reading device.

Claims (1)

[Claims] 1. A method for measuring the size of a hardness testing depression formed by an indentation element on a solid surface, the method comprising: directing a focused light beam having a diameter smaller than the diameter of the depression into the solid surface; projecting onto a surface in a direction perpendicular thereto; translating the light beam laterally in at least one direction by an amount that traverses the recess at least once; and the direction of the projected light beam. measuring the intensity of reflected light reflected from the recess in a direction at an angle to the recess, and utilizing changes in the intensity of the reflected light that occur when the light beam crosses the edge of the recess; It consists of recording the start and end points of the lateral travel path of the light beam, the distance between these two points corresponding to the distance between the two edges of the recess, thereby determining the length of the travel path. A method for measuring the size of a hardness test indentation, characterized in that: 2. In the method described in claim 1,
A method characterized in that the light beam is moved at a constant speed, the time corresponding to the distance between the two points is measured, and the sum of this time is determined. 3. A method for measuring the size of a hardness test depression formed by a transparent indentation element on a solid surface, the method comprising: continuing to apply a load to the transparent indentation element; and comparing the diameter of the indentation. projecting a focused light beam having a small diameter through the transparent indentation element in a direction perpendicular thereto to the solid surface; and directing the light beam in at least one direction by an amount that traverses the indentation at least once. measuring the intensity of reflected light reflected from the recess in a direction at an angle to the direction of the projected light beam; The process consists of recording the start and end points of the lateral movement path of the light beam by using changes in the intensity of reflected light that occur when the light beam crosses, and the distance between these two points is determined by the distance between the two edges of the recess. A method for measuring the size of a hardness test indentation, characterized in that the length of the travel path is determined by the distance between the indentations. 4. A device for measuring the size of a hardness test depression formed by an indentation element on a solid surface, comprising a light source 52 that generates a light beam, and the light beam is incident at right angles to the solid surface M to be measured. a device for focusing and directing the light beam, a deflection device 54, 58 for deflecting the light beam in a plane perpendicular to the direction of travel of the light beam, and only the reflected light reflected by the surface of the recess. a photodetecting device 2, 12, 22, 32 configured to mainly receive the light and measuring the intensity of the received light; and an amplifier 63 that amplifies the signal from the photosensitive element 62 in this photodetecting device. A trigger circuit 64 with an adjustable threshold voltage level E _S and a pulse generation circuit 67
a gate circuit 6 which performs the function of allowing or blocking passage of the pulse flow in response to the amplified signal from the amplifier 63;
1, and a signal generator 65 that is driven in synchronization with the deflection operation of the deflection device and generates a signal, and a frequency multiplier 66 multiplies the generated signal to obtain a frequency. is proportional to the pulse from the pulse generation circuit 67, and the gate circuit 61.
a counting circuit 68 for counting the pulses that have passed through the recess, and a readout device 69 for displaying the area of the recess, which corresponds to the scanning of the recess, and is given information on the total number of pulses that have passed, or a built-in calculation device; a reading device 70 for displaying the hardness number calculated by the device; and a video display tube 71 synchronized with the signal from the signal generator 65 and whose brightness is changed by the trigger circuit 64 to visualize the scanning of the depression. A device that measures the size of indentations for hardness testing. 5. The apparatus according to claim 4, which includes a cylindrical member, which can be brought into contact with the surface to be measured M, and which allows the light beam to pass through. The inner diameter of this cylindrical member is larger than the maximum diameter of the recess to be measured, and the cylindrical member 1, 11, 21, 41, 8
A coaxial annular portion is formed inside the photosensitive element 1, and the photosensitive elements 2, 12, 22, 32, 42 are disposed outside the area through which the light beam passes through the annular portion.
, which element is coupled to said amplifier 63. 6. The device according to claim 5, characterized in that the light-receiving surfaces of the photosensitive elements 2, 12, 22, 32, and 42 are provided with a diffusion layer that causes light scattering or light diffusion. Device. 7. In the device according to claim 5 or 6, the cylindrical member 21, 41 has an optical function inside the device 25, 26, 35, 4.
5, 47, and is adapted to deflect or block unnecessary light directed toward the photosensitive element. 8. In the device according to claims 4, 5, 6 and 7, the light beam passes through two rotating glass plates 5 having at least two parallel planes.
4, 58 or a prism, the rotational axes of the two rotating glass plates or prisms are perpendicular to the direction of propagation of the light and perpendicular to each other, and the rotation is caused by at least one motor 53. Furthermore, the movement of the light spot on the surface to be measured M is restricted by the diaphragm 51, and the deflection speed of the light spot in one direction is greater than the deflection speed in the second direction perpendicular to it. A device characterized by: 9 A device for measuring the size of a hardness test depression formed by a transparent indentation element on the surface of a solid, the indentation element being made of a transparent material and the indentation element through the indentation element during the measurement. A device that applies weight to the surface and a light source 5 that generates a light beam
2; a device for focusing and directing the light beam so that it is incident through the indentation element at right angles to the solid surface to be measured; and a device for focusing and directing the light beam in a plane perpendicular to the direction of travel of the light beam. Deflection devices 54 and 58 for deflecting, a photodetector 42 configured to mainly receive only the reflected light reflected on the surface of the recess and for measuring the intensity of the received light, and this photodetector. Photosensitive element 6 in the device
2 and a trigger circuit 64 with an adjustable threshold voltage level E _S in response to the amplified signal from said amplifier 63 for the flow of pulses from a pulse generating circuit 67. a trigger circuit 64 that controls the gate circuit 61 that functions to allow or block the passage of the pulse flow; and a signal generator 65 that generates a signal by being driven in synchronization with the deflection operation of the deflection device. A signal generator 6 whose frequency obtained by multiplying the generated signal by a frequency multiplier 66 is proportional to the pulse from the pulse generation circuit 67.
5 and a counting circuit 68 for counting the pulses that have passed through the gate circuit 61, the readout for displaying the area of the recess, which is provided with information on the total number of pulses that have passed, corresponding to the scanning of the recess. A device 69 or a readout device 70 for displaying the hardness number calculated by a built-in arithmetic device, and a reading device 70 for displaying the hardness number calculated by the built-in arithmetic device, and the brightness is changed by the trigger circuit 64 in synchronization with the signal from the signal generator 65 to scan the recess. A device for measuring the size of a depression for hardness testing that can be displayed on a visual display tube 71. 10. The device according to claim 9, wherein the recessing element is a transparent cylindrical light-transmitting body 4.
4, the light beam can pass through the light passage, and the test load is applied via a push rod abutting the upper surface of the light passage. 11. In the device according to claim 9 or 10, the beam is configured to traverse two rotating glass plates 54, 58 or prisms having at least two parallel planes, the two rotating glass plates 54, 58 or prisms having at least two parallel planes. The rotational axes of the plates or prisms are perpendicular to the direction of propagation of the light and perpendicular to each other, the rotation is provided by at least one motor 53, and the movement of the light spot on the surface to be measured M is controlled by the diaphragm. 51, characterized in that the speed of deflection of the light spot in one direction is greater than the speed of deflection in a second direction perpendicular thereto.