Non-contact type error reduction measurement method and non-contact type error reduction measurement device for cylindrical rod material with oil film

Abstract

To provide a non-contact type error reduction measurement method and a non-contact type error reduction measurement device for measuring a diameter dimension of a cylindrical rod material with an oil film, which include only three light sources and a photographing device that photographs the light sources.SOLUTION: The measurement method and the measurement device are configured such that a first light source and a second light source are arranged symmetrically left and right with the circular section of a cylindrical rod material therebetween; a cylindrical rod material with an oil film is irradiated with light from each light source; a third light source and a photographing device are installed in a vertical direction with respect to a virtual straight line for connecting the light sources with the circular section of the cylindrical rod material therebetween; reflected light reflected from the cylindrical rod material with the oil film and transmission light are photographed; an inter-peak distance between reflected light of the first light source and reflected light of the second light source included in the distribution of the reflected light and the transmission light and an inter-edge distance are acquired by the transmission light from the third light source; and a diameter dimension of the cylindrical rod material with the oil film is measured by using these distances.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a non-contact error-reducing measurement method and a non-contact error-reducing measurement device for a cylindrical bar with an oil film. [Background technology]

[0002] 2. Description of the Related Art Conventionally, dimensional measurements are carried out to confirm whether or not the dimensions of manufactured products conform to specifications before they are shipped.

[0003] There are contact measurement methods for measuring dimensions, such as micrometers, calipers, and depth gauges, which directly contact the object to be measured, but contact measurement methods vary depending on the person performing the measurement, as their measurement skills, contact position, angle, and force vary. Also, when measuring metal products, the rust-preventive oil applied to the surface may adhere to the measuring device itself, or the product itself may be scratched by contact with the measuring device.

[0004] Therefore, in recent years, non-contact measurement methods have been adopted, which use laser light or other devices to measure three-dimensional information about the object being measured, and from the acquired data, can measure various dimensions such as the external dimensions and surface roughness of the manufactured product.This reduces the variation in measurements depending on the person taking the measurement, eliminates contact with the measuring equipment, and prevents damage to the product itself during measurement.

[0005] However, when measuring products with an oil film using a non-contact measurement method using laser light, the measurement includes the thickness of the oil film, which causes measurement errors in the diameter of circular cross sections of cylindrical rods with an oil film, etc. This leads to various problems, such as increased labor for removing and reapplying the oil film, and deterioration of the metal due to the removal of the oil film.

[0006] To solve these problems, Patent Document 1 discloses a measurement system that includes an air supply device that can supply airflow to the optical axis position of the measurement laser light, and reduces the thickness of the oil film at the measurement point using air, thereby reducing measurement errors caused by the oil film.

[0007] Next, Non-Patent Document 1 discloses a measurement method and device in which a first light source and a second light source are arranged symmetrically on either side of the circular cross section of a cylindrical rod, light from each light source is irradiated onto the cylindrical rod with an oil film, a camera is installed perpendicular to an imaginary line connecting the light sources, the light reflected from the cylindrical rod with an oil film is photographed, the peak distance between the reflected light from the first light source and the reflected light from the second light source contained in the distribution of the reflected light is obtained, and this is used to measure the diameter dimension of the cylindrical rod with an oil film. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-326769 [Non-patent literature]

[0009] [Non-Patent Document 1] Kai Nakano, Reduction of Oil Film-Induced Errors in Non-Contact Measurement of Stainless Steel Rods Using Reflected Light Distribution, Kyushu Institute of Technology, 2021, Graduation Thesis Summary of the Invention [Problem to be solved by the invention]

[0010] However, in Patent Document 1, a laser beam is installed in an NC processing machine to measure whether the shape of the workpiece has been processed to a predetermined value during or after processing, so it is not suitable for measuring the diameter of a cylindrical bar as a final product. Also, in Non-Patent Document 1, a first light source and a second light source are arranged symmetrically on either side of the circular cross section of the cylindrical bar, and a vertically installed imaging device is used to capture reflected light to determine the edge-to-edge distance taking into account the peak-to-peak distance and the oil film thickness, but calculation of the edge-to-edge distance is not stable using only reflected light from light sources arranged symmetrically on the left and right.

[0011] The present invention has been made in consideration of the above circumstances, and aims to provide a non-contact error-reducing measurement method and a non-contact error-reducing measurement device for measuring the diameter of a cylindrical bar material with an oil film, which are composed only of a light source and a photographing device for photographing it. [Means for solving the problem]

[0012] In order to solve this problem, the inventors have conducted extensive research and have come up with the following invention.

[0013] This is a measurement method for measuring the diameter of a cylindrical bar with an oil film, and is characterized in that a first light source and a second light source are arranged symmetrically on either side of the circular cross section of the cylindrical bar in the circular cross section plane of the cylindrical bar with an oil film, light from each light source is irradiated onto the cylindrical bar with oil film, a camera and a third light source are installed perpendicular to the imaginary line connecting the light sources, with the circular cross section of the cylindrical bar between them, and the reflected light reflected from the cylindrical bar with oil film and the transmitted light from the third light source are photographed, and the peak distance between the reflected light from the first light source and the reflected light from the second light source included in the distribution of the reflected light and the edge-to-edge distance due to the transmitted light from the third light source included in the distribution of the transmitted light are obtained, and these are used to measure the diameter of the cylindrical bar with an oil film.

[0014] Furthermore, the distribution of reflected light and the distribution of transmitted light are preferably obtained by photographing the reflected light and transmitted light when light from each light source is irradiated onto a cylindrical rod with an oil film using an imaging device, converting the acquired image into a grayscale image, and then, based on the data acquired from the grayscale image, obtaining a graph in which the vertical axis represents the grayscale value and the horizontal axis represents the pixel value in the horizontal direction of the grayscale image, and eliminating errors caused by the oil film from this graph.

[0015] Next, the diameter of the cylindrical rod with the oil film is determined by using the distribution of reflected light and the distribution of transmitted light, and calculating the peak distance 2X p and edge-to-edge distance 2X r Using the distances, the refractive index n of the oil film and the X coordinate X of point B are calculated using the sine theorem for the triangle OAB consisting of the center O of the circular cross section of the cylindrical rod and the reflected light AB in the oil film. p and the radius X including the thickness of the oil filmr Therefore, it is preferable to determine the radius r of the cylindrical bar using Equation 1.

number

[0016] This is a measuring device that uses a non-contact error reduction measurement method to measure the diameter dimensions of a cylindrical bar with an oil film while reducing measurement errors.The device is characterized by the fact that, in the circular cross-sectional plane of the cylindrical bar with an oil film, a first light source and a second light source are arranged symmetrically on either side of the circular cross-section of the cylindrical bar, and a camera and a third light source are installed perpendicular to the imaginary line connecting the light sources, sandwiching the circular cross-section of the cylindrical bar.

[0017] Furthermore, the first and second light sources preferably use reflected light parallel lasers that are phase-aligned and capable of maintaining a constant intensity, and the parallel lasers are arranged symmetrically on the left and right sides of the circular cross section of the cylindrical rod with an oil film on the circular cross section of the cylindrical rod; and the third light source preferably uses transmitted light parallel lasers, and is arranged perpendicular to the virtual line connecting the first and second light sources, with the camera and third light source on either side of the circular cross section of the cylindrical rod. [Effects of the Invention]

[0018] By using the non-contact error reduction method of the present invention, it is possible to measure the diameter dimension of the circular cross section of a cylindrical bar with an oil film while reducing errors caused by the oil film by using three light sources and a photographing device. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram illustrating an overview of a non-contact error reduction measurement device. [Figure 2] FIG. 10 is a diagram showing a comparison of the reflected light distribution and the path diagrams of incident light and reflected light. [Figure 3] FIG. 1 is a diagram illustrating the paths of incident and reflected light relative to a cylindrical rod. [Figure 4] 10 is an image captured of reflected light emitted from a first light source and a second light source. [Figure 5]10 is an image captured of reflected light emitted from a first light source and a second light source, and transmitted light emitted from a third light source. [Figure 6] 1 is a diagram showing the distribution of transmitted light and the path of incident light. [Figure 7] FIG. 1 is a diagram illustrating the paths of incident and reflected light relative to the circular cross-sectional plane of a cylindrical rod with an oil film. [Figure 8] This is an enlarged view of the right-angled triangle OBC that can be created in the path diagram for a cylindrical bar with an oil film. [Figure 9] This is an enlarged view of the triangle OAB that can be created in the path diagram for a cylindrical bar with an oil film. [Figure 10] This is an image of reflected and transmitted light from a 2.994 mm diameter stainless steel cylindrical rod with an oil film. [Figure 11] This is a distribution diagram of reflected light from a stainless steel cylindrical bar with a diameter of 2.994 mm and an oil film. [Figure 12] This is an image of reflected and transmitted light from a stainless steel cylindrical rod with an oil film, 8.181 mm in diameter. [Figure 13] This is a distribution diagram of reflected light from a stainless steel cylindrical bar with an oil film and a diameter of 8.181 mm. [Figure 14] This is an image of reflected and transmitted light from a 10.044 mm diameter stainless steel cylindrical rod with an oil film. [Figure 15] This is a distribution diagram of reflected light from a stainless steel cylindrical bar with a diameter of 10.044 mm and an oil film. DETAILED DESCRIPTION OF THE INVENTION

[0020] The non-contact error reduction measurement method and non-contact error reduction measurement device for a cylindrical bar with an oil film according to the present invention will be described below.

[0021] 1. Non-contact error reduction measurement method The non-contact error reduction measurement method used in the present invention, as shown in the schematic diagram of the non-contact error reduction measurement device in Figure 1, involves arranging the first light source 3 and the second light source 4 (Figure 1) symmetrically on either side of the circular cross section of the cylindrical bar 1 on the circular cross section of the oil film 2 in the plane of the circular cross section of the cylindrical bar 1. Light from each light source is irradiated onto the cylindrical bar with the oil film 2. An image capture device 5 and a third light source 6 are placed on imaginary line 11 perpendicular to imaginary line 10 connecting the light sources, sandwiching the circular cross section of the cylindrical bar 1. Images of the reflected and transmitted light from the oil film-covered cylindrical bar shown in Figures 2 and 4 are captured. The peak-to-peak distance between the reflected light from the first light source 3 and the reflected light from the second light source 4 and the transmitted light contained in the light distribution are obtained, and the edge-to-edge distance can be calculated from the transmitted light. The diameter calculation method described in the embodiment of the present invention assumes that the oil film 2 is applied to a uniform thickness.

[0022] 1-1 Reflected light distribution The reflected light distribution according to the present invention is achieved by arranging a first light source 3 and a second light source 4 symmetrically on either side of the circular cross section of the cylindrical rod (the xy plane shown in Figure 2) on the circular cross section plane of the oil film-covered cylindrical rod, and irradiating the cylindrical rod with light from each light source with light, thereby obtaining reflected light 7 refracted by the oil film, as shown in Figures 2 and 4. The reflected light with the highest illuminance among the reflected light generated by each light source (hereinafter simply referred to as the "peak") is used to determine the peak-to-peak distance (the distance between 7 shown in Figure 2) and the edge-to-edge distance (the distance between 8 shown in Figure 4) from the outer peripheral edge 8 of the oil film as viewed from the circular cross section of the oil film-covered cylindrical rod (hereinafter the outer peripheral edge of the cylindrical rod and the oil film are referred to as the "edge").

[0023] Using the diagram of the path of light relative to the cylindrical rod shown in Figure 3, we will explain the incident angle at which the peak occurs, assuming that the center of the circular cross section of the cylindrical rod is O, an arbitrary point on the circumference of the circular cross section that the incident light comes into contact with is A, and the intersection point with an imaginary line drawn perpendicularly from point A toward the x-axis that passes through the center O of the circular cross section of the cylindrical rod is D, and the angle between the lines OA and OD is θ (0≦θ≦π / 2).

[0024] Incident light parallel to the line OD strikes point A at an angle of incidence θ and is reflected at an angle of reflection θ according to the law of reflection, with the angle between the incident light and the reflected light being 2θ. Furthermore, the camera that captures reflected light captures the vertical component of the reflected light, so if we calculate θ when the intensity of the reflected light is λ, and the following equation 2 is maximized, θ is 45°, so when the angle of incidence is 45°, the illuminance of the reflected light reaches its maximum, reaching its peak.

[0025]

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[0026] The peak-to-peak distance is preferably determined by photographing reflected light at an incident angle of 45°, converting the image into a grayscale image, and based on the obtained data, creating a distribution of reflected light as shown in Figure 2, with the vertical axis representing the row containing the pixel value closest to 255 in grayscale value and the horizontal axis representing the pixel values in the horizontal direction of the grayscale image. From this graph, the distance between the data with the highest pixel values is obtained and used as the peak-to-peak distance.

[0027] 1-2 Transmitted light distribution The transmitted light distribution according to the present invention is achieved by arranging the first light source 3 and the second light source 4 symmetrically on either side of the circular cross section of the cylindrical bar (the xy plane shown in Figure 2) in the circular cross section plane of the oil-filmed cylindrical bar, and arranging the third light source 6 and the photographing device 5 perpendicular to the imaginary line l0 connecting the first light source 3 and the second light source 4 at a position where the oil-filmed cylindrical bar is sandwiched between them, and irradiating transmitted light from the third light source, thereby enabling the outer peripheral edge of the cylindrical bar to be measured more clearly as shown in Figure 5 than when irradiating reflected light only from the first light source 3 and the second light source 4 shown in Figure 4.

[0028] The transmitted light distribution is preferably used to photograph light 8 passing through a cylindrical rod with an oil film as shown in Figure 6, and to determine the edge-to-edge distance generated by the third light source 6 from the outer peripheral edge of the oil film as viewed from the circular cross-sectional direction of the cylindrical rod shown in Figure 6.

[0029] 1-3 Calculation method for diameter dimensions To calculate the diameter, the circular cross section of the oil-filmed cylindrical rod and the light path diagram shown in Figure 7 were used. The refractive index of oil is n, and the incident angle of the reflected light in the oil film is θ y , the outgoing angle of the reflected light is θ x The radius of the cylindrical rod is r, and the radius of the cylindrical rod with the oil film, taking into account the thickness of the oil film, is X r It is also assumed that the oil film is applied to the cylindrical rod with a uniform thickness, and the reflected light shown in Figure 6 is at its peak.

[0030] First, from Figure 7, the refractive index n of the oil film is calculated by the angle of incidence of the reflected light in the oil film, θ y , the outgoing angle of the reflected light is θ x Using the law of refraction, we obtain the following equation 3.

[0031]

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[0032] Next, let us explain using the right-angled triangle OBC in Figure 8. Point B is the point of emergence of the reflected light that is refracted in the oil film, and point C is the intersection of a line drawn from point B parallel to the x-axis and the y-axis. Then, ∠BOC=θ x So, OB=X r , CB=X p Using the trigonometric theorem, we obtain the following number 4.

[0033]

number

[0034] Next, using the triangle OAB in Figure 9, point A is the point where the refracted incident light in the oil film comes into contact with the cylindrical rod, and ∠OAB=135°+θ x -θ y , ∠OBA=θ y , OB=X r , OA=r, so use the sine law to find the circular cross-sectional radius r of the cylindrical rod for ∠OBA and ∠OAB, and use equation 4 to find sinθ y Substituting for , we get the following numbers 5 and 6.

[0035]

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[0036]

number

[0037] And, sin(135°+θ) in the denominator of Equation 6 x -θ y ) and calculate it using the addition theorem, we get the following number 7.

[0038]

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[0039] Furthermore, cos(θ x -θ y ), sin(θ x -θ y ) and calculate each of them using the addition theorem, we get the following number 8.

[0040]

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[0041] Next, from the interrelationship of trigonometric functions, cosθ x , cosθ y When we solve for each of these, we get the following number 9.

[0042]

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[0043] Equation 8 is obtained by substituting Equation 4 and Equation 9, and finding the refractive index n and the radius X including the oil film. r , the x-coordinate of the emission point of the peak reflected light X p When expressed using the formula, we get the following number 10.

[0044]

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[0045] Furthermore, sin(135°+θ x -θ y ) is the refractive index n, and the radius X including the oil film r , the x-coordinate of the emission point of the peak reflected light X p When expressed using this formula, we get the following formula 11.

[0046]

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[0047] Then, by substituting this equation (11) into equation (6) for finding r and rearranging it, we can calculate the formula for deriving the radius of the cylindrical bar with an oil film shown in equation (1), and it becomes possible to find the diameter dimension 2r.

[0048] 2. Non-contact error reduction measurement device This is a measuring device that uses the non-contact error reduction measurement method of the present invention to measure the diameter dimension of a cylindrical bar with an oil film while reducing measurement errors.In the circular cross-sectional plane of the cylindrical bar with an oil film shown in Figure 1, a first light source 3 and a second light source 4 are arranged symmetrically on either side of the circular cross-section 1 of the cylindrical bar, and a third light source and a photographing device 5 are arranged perpendicular to the imaginary line l0 connecting the light sources, facing each other and sandwiching the cylindrical bar with an oil film.By photographing the reflected light incident from the light source and the transmitted light from the third light source, it becomes possible to measure the diameter dimension using the error reduction measurement method.

[0049] 2-1.Light source The light sources arranged in the non-contact error reduction measurement device according to the present invention preferably use reflected light collimated lasers for the first and second light sources, and preferably use transmitted light collimated lasers for the third light source, because the use of collimated lasers makes it possible to utilize the characteristics of reflected light and transmitted light and maintain a constant light intensity.

[0050] The positions of the light sources are preferably such that the first light source 3 and the second light source 4 are arranged symmetrically on either side of the circular cross section of the cylindrical bar, and the imaginary line l0 connecting the light sources passes through a point at which the angle it forms with the center O of the circular cross section plane of the cylindrical bar is 0°. Furthermore, it is even more preferable that the imaginary line l0 connecting the light sources passes through a point at which the angle it forms with the center O of the circular cross section plane of the cylindrical bar is 45°, as this maximizes the illuminance of the reflected light.

[0051] Next, it is preferable that the third light source be arranged symmetrically on an imaginary line l1 that is perpendicular to the imaginary line l0 and passes through the center O of the circular cross-sectional plane of the cylindrical bar, with the camera and the third light source sandwiched between them and sandwiched between the circular cross-section of the cylindrical bar.

[0052] 2-2. Imaging equipment The imaging device 5 placed in the non-contact error reduction measurement device is preferably a line scan camera that can capture both reflected light from the oil-coated cylindrical bar and transmitted light irradiated onto the oil-coated cylindrical bar. Using a line scan camera allows the entire side of the cylindrical bar to be imaged in one shot, and by illuminating it uniformly, a wealth of surface information can be obtained, including foreign matter, shallow dents, and air bubbles adhering to the surface of the object being measured. The imaging device can also be changed as needed, as long as it can capture both reflected and transmitted light with high precision. [Example]

[0053] The first and second light sources were positioned on an oil-free stainless steel cylindrical bar with a diameter of 2.994 mm measured using a micrometer, so that the imaginary line connecting the light sources passed through the point where the angle between them and the center O of the circular cross-sectional plane of the cylindrical bar was 0°.The third light source and camera were placed on the imaginary line passing through the center O of the circular cross-sectional plane of the cylindrical bar, sandwiching the cylindrical bar between them, and the peak-to-peak distance and edge-to-edge distance used in the non-contact error reduction method were measured 10 times. [Example]

[0054] The peak-to-peak distance and edge-to-edge distance used in the non-contact error reduction method were measured 10 times in the same manner as in Example 1 for a stainless steel cylindrical bar material without an oil film and having a diameter of 8.181 mm measured using a micrometer. [Example]

[0055] The peak-to-peak distance and edge-to-edge distance used in the non-contact error reduction method were measured 10 times in the same manner as in Example 1 for a stainless steel cylindrical bar material without an oil film and having a diameter of 10.044 mm measured using a micrometer. [Example]

[0056] Oil was applied to a stainless steel cylindrical rod having a diameter of 2.994 mm measured using a micrometer, and the diameter of the cylindrical rod with the oil film was measured using the non-contact error reduction method as in Example 1. [Example]

[0057] Oil was applied to a stainless steel cylindrical rod having a diameter of 8.181 mm measured using a micrometer, and the diameter of the cylindrical rod with the oil film was measured using the non-contact error reduction method as in Example 1. [Example]

[0058] Oil was applied to a stainless steel cylindrical rod having a diameter of 10.044 mm measured using a micrometer, and the diameter of the cylindrical rod with the oil film was measured using the non-contact error reduction method as in Example 1.

[0059] [Evaluation of peak value] In Examples 1 to 3, the cylindrical rod was irradiated with light using Civil Laser's parallel laser (spot size: 20 mm) as the first and second light sources. The third light source was a Civil Laser's parallel laser (spot size: 30 mm) with a divergence angle of 0.02 rad. Images were then taken using a Teledyne DALSA Linea Mono 16K 71 kHz CLHS (model: LA-HM-16K07A) camera. The acquired light distribution map was used to evaluate whether the reflected light had its brightest peak value at a 45° angle with the center O of the circular cross section of the cylindrical rod. The true value was the diameter measured using a micrometer. The results of comparing Examples 1 to 3 are shown below.

[0060] The results obtained in Examples 1 to 3 are shown in Table 1. The results in Table 1 include the peak-to-peak distance, edge-to-edge distance, and the cosine value of the angle between the center O of the circular cross section of the cylindrical bar, and are the average of 10 measurements for each diameter.

[0061] From Table 1, it can be seen that the cosine value of the angle formed with the center O of the circular cross section of the cylindrical bar material in Examples 1 to 3 is 0.707 for Example 1, 0.706 for Example 2, and 0.707 for Example 3. When these values are compared with the theoretical value of cos45° = 0.7071, the relative errors from the theoretical value are all small in Examples 1 to 3, which indicates that the peak-to-peak distance can be measured using the reflected light reflected from the 45° angle with the center O of the circular cross section of the cylindrical bar as the peak.

[0062] [Table 1]

[0063] [Evaluation of error reduction measurement methods] In Examples 4 to 6, the cylindrical rod was irradiated with light using Civil Laser's parallel laser (spot size: 20 mm) as the first and second light sources. The third light source was a Civil Laser's parallel laser (spot size: 30 mm) with a divergence angle of 0.02 rad. Images were then taken using a Teledyne DALSA Linea Mono 16K 71 kHz CLHS (model: LA-HM-16K07A) camera. The true value, which was the evaluation standard, was the diameter measured using a micrometer, and the refractive index of the oil applied to the cylindrical rod was n = 1.4. The results of comparing Examples 4 to 6 are shown below.

[0064] The results of Examples 4 to 6 are shown in Figures 10 to 15. Figures 10 to 15 show photographed images of reflected light and transmitted light, and light distribution maps of reflected light and transmitted light, respectively. Table 2 also shows the measurement results of Examples 4 to 6.

[0065] The photographed images of reflected and transmitted light and the light distribution of reflected and transmitted light shown in Figures 10 and 11 are the measurement results of a 2.994 mm diameter stainless steel cylindrical bar with an oil film in Example 4. From the light distribution diagram of reflected and transmitted light in Figure 11, the peak-to-peak distance and edge-to-edge distance shown in Table 2 can be determined to be 2.121 mm and 3.018 mm, respectively, and the diameter dimension is determined to be 3.018 mm using the error reduction measurement method. The difference from the true value is also 0.6 μm, demonstrating that highly accurate measurements can be performed.

[0066] Next, Figures 12 and 13 show the measurement results of an oil-filmed stainless steel cylindrical bar with a diameter of 8.181 mm in Example 5. From the light distribution diagram of reflected light and transmitted light in Figure 13, the peak-to-peak distance was determined to be 5.785 mm and the edge-to-edge distance was determined to be 8.186 mm, as shown in Table 2. The diameter determined using the non-contact error reduction measurement method was 8.181 mm. The difference from the true value was 0.5 μm, demonstrating that highly accurate measurements can be performed.

[0067] Furthermore, Figures 14 and 15 show the measurement results for a 10.044 mm diameter stainless steel cylindrical bar with an oil film from Example 6. From the light distribution diagram of reflected light and transmitted light in Figure 15, the peak-to-peak distance and edge-to-edge distance shown in Table 2 were determined to be 7.103 mm and 10.049 mm, respectively. The diameter measured using the non-contact error reduction measurement method was 10.049 mm. The difference from the true value was 0.3 μm, demonstrating that highly accurate measurements can be performed. These results demonstrate that measurements can be performed with reduced measurement error.

[0068] [Table 2] [Industrial Applicability]

[0069] By using this invention, it is possible to perform non-contact error-reduced measurement of the diameter of a cylindrical bar with an oil film. As a result, it is no longer necessary to remove and reapply the oil film from the cylindrical bar using only three light sources and a camera, which reduces the number of manufacturing processes and improves manufacturing efficiency. In addition, the measurement equipment only requires three light sources and a camera, which reduces excessive capital investment. [Explanation of symbols]

[0070] 1 cylindrical bar 2 Oil slick 3 1st light source 4 Second light source 5. Imaging equipment 6 Third light source 7 Peak of reflected light from oil film 8. Oil film outer edge l0 Imaginary line connecting light sources l1 Imaginary line connecting the third light source and the camera

Claims

1. This is a measurement method for measuring the diameter of a cylindrical bar with an oil film, a first light source and a second light source are arranged symmetrically on either side of the circular cross section of the cylindrical bar on a circular cross section plane of the oil film-covered cylindrical bar, light from each light source is irradiated onto the oil film-covered cylindrical bar, a photographing device and a third light source are installed perpendicular to an imaginary line connecting the light sources, with the circular cross section of the cylindrical bar on either side, photographing the light reflected from the oil film-covered cylindrical bar and the light transmitted from the third light source, obtaining the peak distance between the reflected light from the first light source and the reflected light from the second light source contained in the distribution of the reflected light, and the edge-to-edge distance due to the transmitted light from the third light source contained in the distribution of the transmitted light, and using these to measure the diameter dimension of the oil film-covered cylindrical bar.

2. The non-contact error reduction measurement method according to claim 1, wherein the distribution of reflected light and the distribution of transmitted light are obtained by photographing the reflected light and transmitted light when a cylindrical rod with an oil film is irradiated with light from each light source using an imaging device, converting the acquired image into a grayscale image, and then, based on the data acquired from the grayscale image, obtaining a graph in which the vertical axis represents the grayscale value and the horizontal axis represents the pixel value in the horizontal direction of the grayscale image, and eliminating errors caused by the oil film from this graph.

3. The diameter of the cylindrical rod with the oil film is determined by using the distribution of reflected light and the distribution of transmitted light, and the distance between peaks is 2× ｐ and edge distance 2X ｒ Using these distances, the refractive index n of the oil film and the X coordinate X of point B are calculated using the sine law for the triangle OAB formed by the center O of the circular cross section of the cylindrical rod and the reflected light AB in the oil film. ｐ and the radius X including the thickness of the oil film ｒ 2. The non-contact error reduction measurement method according to claim 1, wherein the radius r of the cylindrical bar is calculated using Equation 1. [Equation 1]

4. This is a measuring instrument that uses a non-contact error reduction measurement method to measure the diameter dimensions of a cylindrical bar with an oil film while reducing measurement errors, and is characterized in that, in the circular cross-sectional plane of the cylindrical bar with an oil film, a first light source and a second light source are arranged symmetrically on either side of the circular cross-section of the cylindrical bar, and a photographing device and a third light source are installed perpendicular to the imaginary line connecting the light sources, sandwiching the circular cross-section of the cylindrical bar.

5. 5. The non-contact measuring device of claim 4, wherein the first and second light sources are formed by using reflected light parallel lasers that are phase-aligned and capable of maintaining a constant intensity, and the parallel lasers are arranged symmetrically on the left and right sides of the circular cross section of the cylindrical rod material in a circular cross section plane of the oil-filmed cylindrical rod material, and the third light source is formed by using a transmitted light parallel laser, and the imager and the third light source are arranged perpendicular to an imaginary line connecting the first and second light sources, with the circular cross section of the cylindrical rod material in between.

Images