JP2001201443A - Lighting system for non-contact extensiometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting system for a noncontact extensiometer which is simple in constitution, enabling the stable and certain imaging of the marked line applied to the surface of a test piece, regardless of the shaper of the test piece. SOLUTION: The lighting system of the non-contact extensiometer is equipped with a diffusion illumination light source 20, which is a light source for illuminating the test piece S mounted on a tester main body to be subjected to a tensile test and has a sufficiently wide lighting surface with respect to the surface region of the test piece S, for uniformly illuminating the surface to which marked lines R1, R2 are applied of the test piece S from many directions. More specifically, the diffusion illumination light source consisting of a straight pipe fluorescent lamp (light source body) 21 provided along the extension direction of the test piece and the diffusion plate 22 interposed between the light source body, and the test piece and diffusing and transmitting the light emitted from the light source body is provided. Especially, the diffusion plate is formed into a curved shape, so as to surround the surface to which marked lines are applied of the test piece.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating device suitable for being incorporated in a non-contact extensometer for optically detecting a reference line attached to a test piece subjected to a tensile test.

[0002]

2. Related Background Art A tensile test of a test piece is performed by measuring the elongation of the test piece while applying a tensile load to the test piece by a tester body supporting both ends of the test piece. Particularly recently, as shown in FIG. 1, a surface of a test piece S is attached in parallel with a predetermined distance in the direction of its extension.
The elongation of the test piece S is measured in a non-contact manner by imaging the marked lines R1 and R2 with the cameras 1 and 2, respectively, and obtaining the positional displacements of the marked lines R1 and R2 from the images. Has also been done.

That is, this type of non-contact extensometer is attached to a test piece S by light sources 3 and 4 attached to the sides of first and second cameras 1 and 2 as shown in FIG. 1, for example. Each of the marked lines R1 and R2 is illuminated to capture an image of each marked line R1 and R2. The cameras 1 and 2 are supported by moving stages 5 and 6, respectively, and the moving stages 5 and 6 are provided with feed screws 7 driven by pulse motors 7 and 8, respectively.
The test pieces S are meshed with each other, and are moved (up and down) in the direction of extension in accordance with the extension of the test piece S to adjust the position.

The images of the reference lines R1 and R2 captured by the cameras 1 and 2 are taken into an arithmetic processing unit 13 including a CPU via image processing units 11 and 12 and are subjected to predetermined image processing. Then, the position of the mark image in each image is detected. At this time, information such as the images of the marking lines R1 and R2 and the positions of the marking lines images detected from these images are displayed on the display 14 as appropriate. Further, the position control units 15 and 16 are controlled in accordance with the position of the detected mark image.
The pulse motors 7 and 8 are driven by the
2, the imaging positions of the marking lines R1 and R2 are adjusted.

The arithmetic processing unit 13 obtains, for example, the position of the center of gravity of the marked line image in the image picked up by each of the cameras 1 and 2, and the cameras 1, 2 so that the position of the center of gravity becomes the center of the image. Control the position of.
Then, as shown in FIG. 2, the movement amount of the first camera 1 due to the elongation of the test piece S is C _H, and the movement amount of the second camera 2 is C _L.
From, which is intended to determine the elongation of E between marked lines R1, R2 of the test piece S as E = C _H -C _L.

[0006]

The test piece S to be subjected to the tensile test is not necessarily a flat member, but is often provided as a pipe or a round bar. Incidentally, in the case of a flat plate-shaped test piece S, the flatness of the surface with the marked lines R1 and R2 is kept almost constant even when the test piece S is stretched by applying a tensile load, but the shape of the pipe or round bar is In the test piece S, the surface shape (diameter of the peripheral surface) of the stretched portion changes greatly, and warpage may occur. Then, a change in the surface shape or a warp causes a shadow on the surface of the test piece S, which appears as a large luminance unevenness in an image of the marked lines R1 and R2. Such luminance unevenness hinders stable detection of a marked line image in an image, and causes an increase in detection error and a decrease in measurement accuracy.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a stable and reliable marking line attached to the surface of a test piece regardless of the shape of the test piece. It is an object of the present invention to provide an illumination device for a non-contact extensometer that enables imaging and effectively prevents a decrease in measurement accuracy.

[0008]

According to the present invention, there is provided a lighting device for a non-contact extensometer which is mounted on a tester main body and illuminates a test piece to be subjected to a tensile test. In particular, a light source provided along the direction in which the test piece extends so as to uniformly illuminate the marked surface of the test piece from multiple directions, and a light source body and the test piece interposed between the light source and the test piece. A diffused plate such as a so-called frosted glass or translucent acrylic plate is interposed in and diffuses light emitted from the light source body, and forms a sufficiently large surface light source with respect to the surface area of the test piece. It is characterized in that it is a diffused illumination light source for uniformly illuminating the surface of the test piece. The surface is uniformly illuminated regardless of the change in the surface shape due to the elongation of the test piece.

Preferably, the light source is provided with a reflector for reflecting the light emitted from the light source toward the diffuser plate.
As described in (1), the diffusion plate is provided in a curved shape so as to surround the surface of the test piece on which the marked line is provided.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A non-contact extensometer lighting device according to an embodiment of the present invention will be described below with reference to the drawings. The illumination device of this non-contact extensometer basically includes, as shown in FIG. 1, mark lines R1 and R2 attached to a test piece S to which a tensile load is applied, which is attached to a material testing machine main body. 2 and is incorporated in the main body of the material testing machine for imaging, and as shown in FIGS. 3 (a) and 3 (b), the surface area of the test piece S is sufficient. It is characterized in that it is realized as a diffuse illumination light source 20 which forms a wide surface light source and uniformly illuminates the surface of the test piece from multiple directions. FIG. 3A is a perspective view of a main part of the non-contact extensometer, and FIG. 3B shows a plan configuration thereof.

Thus, the diffuse illumination light source (illumination device) 20
Is the direction in which the test piece S is stretched when a tensile load is applied;
That is, a plurality of straight tube fluorescent lamps 21 which are rod-shaped light sources provided side by side along the axial direction of the rod-shaped test piece S, and the straight tube fluorescent lamp (light source) 21 and the test piece S A diffusion plate 22 made of a translucent acrylic plate is interposed therebetween and diffuses and transmits the light emitted from the straight tube fluorescent lamp 21. The diffusion plate 22 forms a slit 23 forming a field of view of the test piece S by the cameras 1 and 2, and has two semicircular arc-shaped curved shapes provided so as to surround the surface of the test piece S. It consists of a plate member. The diffuser plate 22 is provided so that the test piece S is not directly illuminated by the light emitted from the straight tube fluorescent lamp 21 and over a sufficiently large area with respect to the surface area of the test piece S. The test piece S is configured to have a large area when viewed from the test piece S side so as to uniformly illuminate a surface area of the test piece S on which the reference lines R1 and R2 are provided as a surface light source.

The diffusing plate 22 functions as a surface light source that diffuses and transmits the light received from the straight tube fluorescent lamp 21 to uniformly scatter the diffused light over the entire area from multiple directions. The diffusing plate 22 irradiates diffused light along the surface of the test piece S, in particular, from each part forming a semicircular surface along the circumferential direction of the rod-shaped test piece S toward the surface of the test piece S. Thereby, the surface of the test piece S is uniformly illuminated over a wide range.

Thus, the surface of the test piece S is illuminated by such a diffuse illumination light source 20, and the marking lines R1 and R2 attached to the surface of the test piece S are imaged by the cameras 1 and 2, respectively. According to the non-contact extensometer which detects the marked line image and detects the elongation of the test piece S, even if the test piece S is formed of a pipe-shaped or rod-shaped member, The marked lines R1 and R2 can always be detected stably and reliably. That is, since the entire surface of the pipe-shaped or rod-shaped test piece S is uniformly illuminated by the diffuse illumination light source 20 serving as a surface light source, even if the surface shape of the test piece S is deformed due to its elongation, the illumination is performed. No light shading occurs.

Accordingly, the mark R picked up by the cameras 1 and 2
There is no luminance unevenness in an image including 1, R2, and therefore, it is possible to stably and reliably detect a mark image from the image. Moreover, since the brightness itself of the images captured by the cameras 1 and 2 is stable over the entire image, the mark lines R1 and R1 attached to the test piece S by using black paint or the like.
The image of R2 can be perceived as information having high contrast, and can be detected with high accuracy without being affected by luminance unevenness. As a result, it is possible to suppress the detection error and maintain the measurement accuracy sufficiently high. In particular, simply by providing the diffuse illumination light source 20 as described above, it is possible to simply and effectively guarantee the measurement accuracy.

As the diffused illumination light source 20, for example, as shown in FIG. 4A, a diffused light source using a flat diffusion plate 22a may be used. Also, as shown in FIG. 4B, a reflector 24 is provided behind the straight tube fluorescent lamp 21, and the light emitted from the straight tube fluorescent lamp 21 is diffused and diffused by the reflector 24. The test piece S may be illuminated by adding the irregularly reflected light to the scattered light diffusely transmitted through the diffusion plate 22 (22a). By providing such a reflector 24, light emitted from the straight tube fluorescent lamp 21 can be effectively used, and its illumination efficiency can be increased.

Further, as shown in FIG. 4C, for example, a diffused illumination light source 20 in which a plurality of light emitting diodes 25 are arranged in a predetermined surface area to form a surface light source is formed. It may be arranged along. In this case, the plate-like base 26 on which the plurality of light emitting diodes 25 are disposed is realized by a flexible member, and the degree of curvature of the light emitting surface forming the surface light source is determined by the size (thickness; It is desirable to be configured so that it can be variably set according to the curvature). If the curvature of the light emitting surface forming the surface light source can be changed in this way,
Irrespective of the size of the test piece S, the surface of the test piece S can be easily and uniformly illuminated.

Further, as shown in FIG. 4D, the light emitted from the light source 27 is guided through an optical fiber bundle 28,
It is also possible to configure the surface light source 29 by arranging the emission end faces of the plurality of optical fibers constituting the optical fiber bundle 28 in a matrix so as to surround the peripheral surface of the test piece S. In this case, it is also effective to incorporate a microlens into each of the emission end faces so that the light emitted from the emission end faces of the respective optical fibers is diffused with a predetermined spread.

Although not particularly shown, light emitted from the rod-shaped light source is diffused by using a rod lens, or a diffused reflection plate arranged in a lattice is provided on the front surface of the light source, and the light emitted from the light source is emitted. It is also possible to spread. Further, it is of course possible to uniformly illuminate the entire surface of the test piece S by illuminating diffuse light from surface light sources provided obliquely above and below the test piece S with respect to the axial direction.

The present invention is not limited to the above embodiment. Here, the non-contact extensometer configured to image the two marked lines R1 and R2 attached to the test piece S using the two cameras 1 and 2 has been described as an example. The same can be applied to an extensometer that measures elongation while simultaneously capturing images of two marked lines R1 and R2.
Further, the above-mentioned diffuse illumination light source 20 may be incorporated in a camera provided movably in the direction in which the test piece S extends, or may be fixedly incorporated in the tester main body. However, when incorporating the test piece into the tester main body, the test piece S
In view of the displacement width of the reference lines R1 and R2 due to the extension of the light, the diffuse illumination light source
It is necessary to set the size of 0, that is, the size of the surface emitting area. In addition, the present invention can be variously modified and implemented without departing from the gist thereof, such as the material of the diffusion plate and the type of the light source body.

[0020]

As described above, according to the present invention, a sufficiently large surface light source is formed on the marked surface area of the test piece to uniformly illuminate the surface of the test piece from multiple directions. Since the diffused illumination light source is provided, the surface can always be uniformly illuminated irrespective of a change in the surface shape due to the elongation of the test piece having various shapes, and the generation of shadows due to the illumination light can be prevented. As a result, it is possible to simply and stably capture an image of the marking line attached to the surface of the test piece in a simple manner, reduce the detection error of the marking line, and maintain a sufficiently high measurement accuracy. And the like.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part of a non-contact extensometer.

FIG. 2 is a diagram for explaining a detection operation of a mark line attached to a test piece in the non-contact extensometer shown in FIG.

FIG. 3 is a view showing a main part configuration of a lighting device for a non-contact extensometer according to an embodiment of the present invention, showing an example of a diffused illumination light source.

FIG. 4 is a diagram showing a typical modified example of a diffuse illumination light source.

[Explanation of symbols]

 S test piece R1, R2 reference line 20 diffused illumination light source 21 straight tube fluorescent lamp (light source) 22 diffuser 24 reflector 25 light emitting diode 26 substrate 27 light source 28 optical fiber bundle 29 surface light source

Claims (3)

[Claims] An illumination device for a non-contact extensometer for imaging a mark attached to a test piece subjected to a tensile test and optically detecting the extension of the test piece from the displacement of the mark. A light source provided along the direction in which the test piece extends, and a diffusion plate interposed between the light source and the test piece to diffuse and transmit light emitted from the light source. The illumination device for a non-contact extensometer according to claim 1, wherein a surface of the test piece on which the mark is provided is uniformly illuminated from multiple directions. 2. The illumination device for a non-contact extensometer according to claim 1, wherein the light source includes a reflector that reflects light emitted from the light source toward the diffusion plate. . 3. The diffusing plate has a curved shape so as to surround a surface of the test piece on which the marked line is provided.
A lighting device for a non-contact extensometer according to claim 1.