Optical extensometer
By using optical extensometers with components such as single octahedral prisms and telecentric lenses, measurement preparation is simplified and measurement accuracy is improved, solving the problems of complex debugging and insufficient accuracy of optical extensometers in the prior art.
Patent Information
- Application Number
- CN202421046785.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-14
- Publication Date
- 2024-12-17
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Existing optical extensometers require tedious installation, calibration and commissioning preparation before each measurement, and the use of multiple optical components leads to complex and time-consuming operation.
Using an optical extensometer including a single structure symmetric octahedral prism, telecentric lens, digital camera and computer, the octahedral prism is installed in a fixed device, and the optical axis coincides with the overall optical path, simplifying the optical path structure and passing through the telecentric Lens and digital cameras enable high-precision measurements.
It reduces the commissioning preparation work before each measurement, is convenient to operate, and realizes high-precision strain measurement, eliminates false strain caused by off-plane displacement of the sample being measured, and improves measurement efficiency and accuracy.
Smart Images
Figure CN222188211U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of optical extensometer measurement, in particular to an optical extensometer. Background Art
[0002] Extensometers can be divided into contact extensometers and non-contact video (optical) extensometers. Among them, contact extensometers are widely used in many traditional instrument industries, including mechanical extensometers and resistive electronic extensometers. However, contact measuring instruments may cause damage to the measured object, thus affecting the measurement results.
[0003] Compared with traditional contact extensometers or strain gauges, video (optical) extensometers have many advantages and are increasingly widely used in many fields of scientific research and engineering technology. For example, CN202010417825.9 discloses a laser extensometer device for a split Hopkinson bar, including a metal specimen, an incident bar, a transmission bar, a laser transmitter, a dimming convex lens, a right-angle prism, an incident end convex lens, an incident end laser detector, a transmission end convex lens, a transmission end laser detector, a beam splitter, a beam splitting end convex lens, and a beam splitting end laser detector, using multiple optical elements such as lenses and prisms.
[0004] For example, CN202010659710.0 discloses a high-precision biaxial optical extensometer utilizing multiple rhombic prisms, including: a digital camera, a telecentric lens, four rhombic prisms, a fixed plate, a tripod and a data processing device, in which four rhombic prisms are also used.
[0005] However, the above optical extensometers require the use of multiple prisms and lenses, and preparation work such as installation, calibration, and debugging must be performed before each measurement. There are many optical components and the preparation work is time-consuming. Utility Model Content
[0006] In order to solve the technical problem of tedious debugging and preparation work before each measurement of an extensometer caused by using multiple optical elements, the utility model provides an optical extensometer.
[0007] To achieve the above-mentioned purpose, the utility model provides the following technical solutions: an optical extensometer, comprising a prism, a fixing device, a telecentric lens, a digital camera and a computer, wherein the telecentric lens is connected to the digital camera, and the digital camera is electrically connected to the computer.
[0008] The number of prisms is one, and the prism is an octahedral prism with symmetrical structure. The octahedral prism has two acute-angle vertices and four non-acute-angle vertices. The surface formed by the four non-acute-angle vertices is a symmetry surface, and the symmetry surface is a square. The center point of the symmetry surface coincides with the midpoint of the line connecting the two acute-angle vertices, and is perpendicular to the line connecting the two acute-angle vertices. The two prism surfaces located on both sides of the symmetry surface and opposite to each other are parallel and equal in size, and the two prism surfaces located on both sides of the symmetry surface and adjacent to each other are perpendicular and equal in size. The octahedral prism is installed in a fixing device. After installation, the optical axis of the octahedral prism coincides with the optical axis of the overall optical path of the optical extensometer.
[0009] The sample to be tested is located on the side of the prism away from the digital camera, and four target points are arranged on the sample to be tested.
[0010] Preferably, the four target points are respectively a first target point and a fourth target point set in a height direction of the measured sample, and a second target point and a third target point set in a width direction of the measured sample.
[0011] Preferably, when observing from the reverse direction of the optical axis of the vertical octahedral prism, the sample to be measured is located on the right side of the prism, the digital camera is located on the left side of the prism, and the two acute-angle vertices are respectively located on the left and right sides of the symmetry plane.
[0012] The four facets on the right side of the symmetry plane of the octahedral prism are respectively the first facet, the second facet, the third facet and the fourth facet; the four facets on the left side of the symmetry plane of the octahedral prism are respectively the fifth facet, the sixth facet, the seventh facet and the eighth facet; the first target point is horizontally projected on the first facet, the fourth target point is horizontally projected on the third facet, the second target point is horizontally projected on the second facet, and the third target point is horizontally projected on the fourth facet.
[0013] Preferably, the device further comprises a tripod, and the digital camera is mounted on the tripod.
[0014] Compared with the prior art, the beneficial effects of the utility model are:
[0015] Firstly, since the utility model has only one octahedral prism, the utility model reduces the number of optical elements such as prisms and lenses required by existing extensometers to one, and only needs to be installed once for long-term use, the operation process is convenient, and the debugging preparation work before each measurement is greatly reduced; secondly, the octahedral prism can easily receive the light emitted by the four target points on the measured sample, and the transformation from measuring unidirectional strain to achieving bidirectional high-precision strain measurement is simply and conveniently realized; coupled with the use of telecentric lenses, digital cameras and computers, the false strain caused by the off-plane displacement of the measured sample can be effectively eliminated, thereby achieving high-precision strain measurement. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 This is an overall optical path diagram of an embodiment of the utility model;
[0017] Figure 2 It is the axonometric drawing of an octahedral prism;
[0018] Figure 3 This is the axonometric view of the octahedral prism from another angle;
[0019] Figure 4 This is a perspective view of an octahedral prism.
[0020] Figure 5 This is the light path diagram of the first target point incident, refracted and emitted on the octahedral prism.
[0021] In the accompanying drawings, the components represented by the reference numerals are listed as follows:
[0022] 1 is the sample to be measured, 2 is the first target point, 3 is the second target point, 4 is the third target point, 5 is the fourth target point, 6 is the fixing device, 7 is the octahedral prism, 8 is the telecentric lens, 9 is the digital camera, 10 is the tripod, 11 is the computer, 12 is the first facet, 13 is the second facet, 14 is the third facet, 15 is the fourth facet, 16 is the symmetry face of the octahedral prism, 17 is the fifth facet, 18 is the sixth facet, 19 is the seventh facet, and 20 is the eighth facet. DETAILED DESCRIPTION
[0023] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.
[0024] The utility model will now be further described in detail with reference to the accompanying drawings.
[0025] like Figure 1 and Figure 2 As shown, in this embodiment, an optical extensometer is provided, including a fixing device 6, an octahedral prism 7, a digital camera 9, a telecentric lens 8, a tripod 10 and a computer 11, wherein the telecentric lens 8 is connected to the digital camera 9, and the digital camera 9 is electrically connected to the computer 11.
[0026] The octahedral prism 7 has a symmetrical structure. The octahedral prism 7 has two acute-angled vertices and four non-acute-angled vertices. The surface formed by the four non-acute-angled vertices is a symmetry plane 16. The symmetry plane 16 is a square. The center point of the symmetry plane 16 coincides with the midpoint of the line connecting the two acute-angled vertices, and is perpendicular to the line connecting the two acute-angled vertices. The two edge faces located on both sides of the symmetry plane 16 and opposite to each other are parallel and equal in size, and the two edge faces located on both sides of the symmetry plane 16 and adjacent to each other are perpendicular and equal in size.
[0027] The octahedral prism 7 is installed in the fixing device 6. After installation, the optical axis of the octahedral prism 7 coincides with the optical axis of the overall optical path of the optical extensometer. The optical axis of the octahedral prism 7 coincides with the line connecting the two acute-angle vertices. The optical axis of the overall optical path of the optical extensometer is as shown in FIG. Figure 1 The telecentric lens 8 is shown by the dotted line.
[0028] For the convenience of description, the octahedral prism 7 is divided into left and right sides with the symmetry plane 16 of the octahedral prism 7 as the boundary. When observed from the reverse direction of the optical axis of the octahedral prism 7, the sample 1 to be measured is located on the right side of the prism, the digital camera 9 is located on the left side of the prism, and the two acute-angle vertices are respectively located on the left and right sides of the symmetry plane 16.
[0029] After installation, the side of the octahedral prism 7 close to the sample 1 is called the right side. When looking at the right side from the symmetry plane 16, the first prism face 12, the second prism face 13, the third prism face 14 and the fourth prism face 15 are arranged in the counterclockwise direction. Figure 4 As shown; the side of the octahedral prism 7 close to the telecentric lens 8 is called the left side, and the left side is viewed facing the symmetry plane 16. In the counterclockwise direction, there are the fifth prism face 17, the sixth prism face 18, the seventh prism face 19 and the eighth prism face 20. The first prism face 12 and the fifth prism face 17 are located on the opposite sides of the symmetry plane 16, and are located on the opposite sides of the line connecting the two acute angle vertices.
[0030] The sample 1 to be tested is located on the side of the octahedral prism 7 away from the digital camera 9, that is, on the right side of the octahedral prism 7. The sample 1 to be tested is provided with four target points. The first target point 2 and the fourth target point 5 are arranged in the height direction of the sample 1 to be tested, and the second target point 3 and the third target point 4 are arranged in the width direction of the sample 1 to be tested. The shapes of the samples 1 to be tested are different. Some have flat surfaces, some have uneven surfaces, some have regular cross sections, and some have irregular cross sections. The utility model has wide requirements for the selection of target points, and the placement posture adjustment of the sample 1 to be tested is also very convenient. The four target points can be On the same plane or not, the first target point 2 and the fourth target point 5 may be located on the same plumb line or not; the second target point 3 and the third target point 4 may be located on the same horizontal line or not; as long as the first target point 2 is horizontally projected on the first facet 12, the fourth target point 5 is horizontally projected on the third facet 14, the second target point 3 is horizontally projected on the second facet 13, and the third target point 4 is horizontally projected on the fourth facet 15, cumbersome point selection rules and adjustment steps are avoided.
[0031] The octahedral prism 7 is installed in the middle position of the fixing device 6. Figure 1The figure is a schematic diagram of the effect after installation. The octahedron prism 7 and the fixture 6 have precise installation position marks and processing positioning lines. According to the positioning lines, it is very convenient to adjust the symmetry plane 16 of the octahedron prism 7 to a position perpendicular to the horizontal plane. When installing the prism, it can ensure that the optical axis of the octahedron prism 7 coincides with the optical axis of the overall optical path of the optical extensometer. It only needs to be installed once and can be used for a long time. The operation process is convenient, which greatly reduces the preparation work before each measurement.
[0032] See also Figure 2 and 3 , the arrow in the figure indicates the transmission direction of the light path, and the light path of the first target point 2 is taken as an example for description. In order to highlight the light path of the first target point 2, the solid line in the figure indicates the incident light and the outgoing light of the first target point 2 at the octahedral prism 7, to show that the light path of the first target point 2 passes through the left and right parts of the octahedral prism 7; the light paths of the second to fourth target points 3, 4 and 5 through the octahedral prism 7 are similar thereto, and the dotted lines in the figure indicate the left and right parts of the light paths of the second to fourth target points 3, 4 and 5 at the octahedral prism 7.
[0033] Figure 2 , Figure 3 and Figure 5 In the embodiment, the light emitted from the first target point 2 on the sample 1 to be measured is incident on the first facet 12 of the octahedral prism 7. Since the octahedral prism 7 used in the utility model has the following characteristics: the facets opposite to each other on the left and right sides are parallel and equal in size, such as the first facet 12 and the fifth facet 17 are parallel to each other and have equal areas; the facets adjacent to each other on the left and right sides are perpendicular and equal in size, such as the first facet 12 and the seventh facet 19 are perpendicular to each other and have equal areas; and after installation, the optical axis of the octahedral prism 7 coincides with the optical axis of the overall optical path of the optical extensometer. Therefore, after the light emitted from the first target point 2 on the sample 1 to be measured is incident on the first facet 12 of the octahedral prism 7, the light is translated a certain distance ( Figure 2 , Figure 3 , the light path in the octahedral prism 7 is not drawn), and then emerges from the fifth prism face 17, and the emerged light is incident on the telecentric lens 8 again; the light paths of the second to fourth target points in the left and right parts of the octahedral prism 7 are similar thereto, the light emitted by the second target point 3 is incident on the second prism face 13, and emerges from the eighth prism face 20; the light emitted by the third target point 4 is incident on the fourth prism face 15, and emerges from the sixth prism face 18; the light emitted by the fourth target point 5 is incident on the fourth prism face 14, and emerges from the seventh prism face 19, and the emerged light rays are also incident on the telecentric lens 8 again, and their light paths are not described in detail here.
[0034] Figure 4 3 is a perspective view of the octahedral prism 7, in which solid lines indicate that the marked facets are not blocked relative to the viewer, and dashed lines indicate that the marked facets are blocked relative to the viewer.
[0035] Figure 5 This is a light path diagram of the first target point 12 when it is incident on and out of the octahedral prism 7 and is twice refracted in the octahedral prism 7; the light paths of other target points when they are incident on and out of the octahedral prism 7 and are twice refracted in the octahedral prism 7 are similar to those of the first target point 12 and are omitted.
[0036] In other embodiments, a tripod 10 is also used, the telecentric lens 8 is mounted on a digital camera 9 , and the digital camera 9 is mounted on the tripod 10 .
[0037] The digital camera 9 is placed on the tripod 10 to ensure that the digital camera 9 can be stably supported and the position of the digital camera 9 can be adjusted within a certain range.
[0038] The light rays of the first to fourth target points 2, 3, 4 and 5 emitted by the octahedral prism 7 are incident on the telecentric lens 8, and the telecentric lens 8 forms images of the first to fourth target points 2, 3, 4 and 5 on the surface of the sample 1 to be measured. In a traditional lens, due to the field of view, the change in the distance between the object and the lens will cause the magnification of the image to change, which produces the so-called off-plane error or perspective error. The telecentric lens 8 can make the light rays reflected or transmitted from the object to the lens parallel, that is, the main light ray on the object side is parallel to the optical axis, so that it can be ensured that within a certain object distance range, the image size of the object will not change due to the change in distance. Specifically, the telecentric lens 8 places an aperture stop at the focus of the image side, and only the light rays parallel to the optical axis can pass through this stop and reach the imaging plane. Therefore, no matter how far the object is from the telecentric lens 8, its size on the imaging plane remains unchanged. By utilizing the constant magnification characteristic of the telecentric lens 8, the measurement error caused by the off-plane displacement of the sample 1 to be measured can be eliminated. The telecentric lens 8 is a prior art and will not be described in detail here.
[0039] The telecentric lens 8 images the first to fourth target points 2, 3, 4 and 5 on the surface of the sample 1 to be tested based on the received light, and the digital camera 9 forms a digital image based on the images of the first to fourth target points 2, 3, 4 and 5. The first to fourth target points 2, 3, 4 and 5 are respectively located at the upper, lower, left and right four positions of the image chip of the digital camera 9. In the captured digital image, the fields of view of the first to fourth target points 2, 3, 4 and 5 each occupy one quarter, so as to realize the simultaneous acquisition of images of the four target areas.
[0040] The computer 11 acquires four field images of the first to fourth target points 2 - 5 in real time, calculates corresponding displacement information, and then calculates uniform strain information of the surface of the sample 1 under test in combination with the gauge information of the corresponding target points.
[0041] The optical extensometer of the utility model uses an octahedral prism 7 to form a long gauge length. The opposite reflection surfaces on the left and right sides of the octahedral prism 7 are parallel and equal in size, the adjacent reflection surfaces on the left and right sides are perpendicular and equal in size, and the optical axis of the octahedral prism 7 coincides with the optical axis of the overall optical path of the optical extensometer. The extensometer reduces the number of optical elements required to be used from multiple to one, and can be used for a long time after only one installation. The requirements for target point selection are wide. The octahedral prism 7 can easily receive the light emitted by the four target points on the sample 1 to be measured, and the transformation from measuring unidirectional strain to achieving bidirectional high-precision strain measurement is simply and conveniently realized. The placement posture adjustment of the sample 1 to be measured is also very convenient, which greatly reduces the preparation work before each measurement; combined with the imaging of the telecentric lens 8, plus the use of the digital camera 9 and the computer 11, the false strain caused by the off-surface displacement of the sample 1 to be measured is effectively eliminated, thereby achieving high-precision strain measurement.
[0042] The above description is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.
Claims
1. An optical extensometer, comprising a prism, a fixing device (6), a telecentric lens (8), a digital camera (9) and a computer (11), wherein the telecentric lens (8) is connected to the digital camera (9), and the digital camera (9) is electrically connected to the computer (11). It is characterized in that The number of the prisms is one, and the prism is an octahedral prism (7) of symmetrical structure. The octahedral prism (7) has two acute-angled vertices and four non-acute-angled vertices. The surface formed by the four non-acute-angled vertices is a symmetry surface (16). The symmetry surface (16) is a square. The center point of the symmetry surface (16) coincides with the midpoint of the line connecting the two acute-angled vertices, and is perpendicular to the line connecting the two acute-angled vertices. Two prism surfaces located on both sides of the symmetry surface (16) and opposite to each other are parallel and equal in size. Two prism surfaces located on both sides of the symmetry surface (16) and adjacent to each other are perpendicular and equal in size. The octahedral prism (7) is installed in the fixing device (6). After installation, the optical axis of the octahedral prism (7) coincides with the optical axis of the overall optical path of the optical extensometer. The sample to be measured (1) is located on a side of the prism away from the digital camera (9), and four target points are arranged on the sample to be measured (1).
2. An optical extensometer according to claim 1, characterized in that: The four target points are respectively a first target point (2) and a fourth target point (5) arranged in the height direction of the measured sample (1), and a second target point (3) and a third target point (4) arranged in the width direction of the measured sample (1).
3. An optical extensometer according to claim 2, characterized in that: When viewed from the reverse direction of the optical axis of the vertical octahedral prism (7), the sample (1) to be measured is located on the right side of the prism, the digital camera (9) is located on the left side of the prism, and the two acute-angle apexes are located on the left and right sides of the symmetry plane (16) respectively; The four right side faces of the symmetry plane (16) of the octahedral prism (7) are respectively a first facet (12), a second facet (13), a third facet (14) and a fourth facet (15); the four left side faces of the symmetry plane (16) of the octahedral prism (7) are respectively a fifth facet (17), a sixth facet (18), a seventh facet (19) and an eighth facet (20); the first target point (2) is horizontally projected onto the first facet (12), the fourth target point (5) is horizontally projected onto the third facet (14), the second target point (3) is horizontally projected onto the second facet (13), and the third target point (4) is horizontally projected onto the fourth facet (15).
4. An optical extensometer according to claim 1, characterized in that: It also includes a tripod (10), on which the digital camera (9) is mounted.
Citation Information
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