CN212692801U - An Optical Extensometer Based on Lens Imaging and Biprism Reflection - Google Patents
An Optical Extensometer Based on Lens Imaging and Biprism Reflection Download PDFInfo
- Publication number
- CN212692801U CN212692801U CN202021544028.9U CN202021544028U CN212692801U CN 212692801 U CN212692801 U CN 212692801U CN 202021544028 U CN202021544028 U CN 202021544028U CN 212692801 U CN212692801 U CN 212692801U
- Authority
- CN
- China
- Prior art keywords
- lens
- prism
- imaging
- sample
- camera
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 230000003287 optical effect Effects 0.000 title claims abstract description 38
- 238000003384 imaging method Methods 0.000 title claims abstract description 25
- 238000012545 processing Methods 0.000 claims abstract description 7
- 238000006073 displacement reaction Methods 0.000 abstract description 32
- QNRATNLHPGXHMA-XZHTYLCXSA-N (r)-(6-ethoxyquinolin-4-yl)-[(2s,4s,5r)-5-ethyl-1-azabicyclo[2.2.2]octan-2-yl]methanol;hydrochloride Chemical compound Cl.C([C@H]([C@H](C1)CC)C2)CN1[C@@H]2[C@H](O)C1=CC=NC2=CC=C(OCC)C=C21 QNRATNLHPGXHMA-XZHTYLCXSA-N 0.000 abstract description 20
- 238000005259 measurement Methods 0.000 abstract description 18
- 230000015572 biosynthetic process Effects 0.000 abstract description 5
- 238000000034 method Methods 0.000 description 7
- 238000000926 separation method Methods 0.000 description 6
- 238000012360 testing method Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 3
- 238000000691 measurement method Methods 0.000 description 3
- 238000010998 test method Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 2
- 230000000007 visual effect Effects 0.000 description 2
- 230000004308 accommodation Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000013519 translation Methods 0.000 description 1
Images
Landscapes
- Length Measuring Devices By Optical Means (AREA)
Abstract
The utility model discloses an optical extensometer based on lens imaging and biprism reflection, which comprises a digital camera, an imaging lens, a first rhombic prism, a second rhombic prism and a data processing device; two rhombic prisms are arranged between the imaging lens and the sample to be tested, one reflecting surface of each rhombic prism faces to the lens direction of the digital camera, and the digital camera is connected with the data processing device. The utility model discloses an optics extensometer makes the hardware set up more conveniently, and the demarcation of gauge length is more accurate, and this optics extensometer hardly receives the influence of sample off-plane displacement, realizes the strain measurement of high resolution and high accuracy based on single ordinary camera lens formation of image.
Description
Technical Field
The utility model relates to an optical extensometer especially relates to an optical extensometer based on camera lens formation of image and biprism reflection.
Background
The strain measurement has great significance for measuring the mechanical properties of various materials and designing structures. Currently, in a commonly used strain measurement method, such as a contact method of a resistance strain gauge, an electronic extensometer or an optical fiber strain gauge, components need to be installed on a tested sample during measurement, and damage is easily caused, so that the methods are not suitable for detection of small-size and large-deformation materials, particularly flexible materials, and the methods are the field of non-contact measurement methods which can show a large body. Non-contact strain measurement methods are mainly represented by optical (video) extensometers, and respective video extensometers are currently introduced by manufacturers of internationally known testing machines, such as MTS, Instron. However, the strain measurement accuracy of the optical extensometer is often not high, which limits its application mainly due to two reasons: firstly, a sample inevitably generates certain out-of-plane displacement under the actual test condition, and according to a pinhole camera model, false displacement and false strain are generated on the image plane of an imaging system, so that the strain measurement precision and resolution are greatly reduced; secondly, the extensometer gauge length is usually not able to exceed the camera resolution due to the limitation of the camera resolution.
The existing optical extensometer is not convenient enough when adjusting a light path, has the defects of higher cost and constant magnification by adopting telecentric lens imaging, cannot be flexibly adjusted and has no universality; when a common lens is used for imaging, a rigid sheet needs to be adhered to the surface of a sample to be measured, and the operation is still complex.
SUMMERY OF THE UTILITY MODEL
Utility model purpose: the utility model aims at providing a calibration of gauge length is more accurate, do not receive sample off-plane displacement's influence, high resolution and high accuracy based on camera lens formation of image and the optical extensometer that the double prism reflects.
The technical scheme is as follows: the utility model discloses an optical extensometer based on lens imaging and double prism reflection, which comprises a digital camera, an imaging lens, a first rhombic prism, a second rhombic prism and a data processing device;
two rhombic prisms are arranged between the imaging lens and the sample to be tested, one reflecting surface of each rhombic prism faces to the lens direction of the digital camera,
the upper target point on the surface of the tested sample is reflected twice by the upper oblique square prism in sequence, and the lower target point is reflected twice by the lower oblique square prism in sequence and then is respectively incident into the left half lens and the right half lens of the common lens; the common lens simultaneously images the upper target area and the lower target area on the surface of the reflected tested sample, and a digital image is formed on the target surface of the digital camera; the digital camera simultaneously shoots two target areas to obtain a digital image, the shot digital image is transmitted to the data processing module, the information of each target area occupies half of the target surface of the digital camera, and the simultaneous acquisition of two separated target images by a single common camera is realized; the two target points of the optical extensometer are respectively taken on the horizontal middle lines of the left and right areas of a digital image.
Further, the two rhombic prisms are the same in size. Two 45-degree inclined planes of each rhombic prism are coating surfaces so as to increase the reflection performance.
The two rhombic prisms form an X shape and are positioned at the same height. The imaging lens is a fixed focus lens or a zoom lens.
Has the advantages that: compared with the prior art, the utility model has the advantages of it is as follows showing:
(1) nondestructive measurement: compared with contact measurement technologies such as an electronic extensometer, a strain gage and the like in the industrial field, the utility model adopts the optical measurement technology, does not need to be in direct contact with a sample to be measured, has no additional mass, does not damage the sample, and does not limit the deformation of the sample;
(2) little influence by out-of-plane displacement: the arrangement of the two rhombic prisms can enable two target points which are far away from each other to be reflected and converged into a common lens through an optical path, the target points are selected at the horizontal central line of an image, and the off-plane displacement cannot cause the vertical false displacement and the false strain of the target points;
(3) the measurement precision is improved: the strain measurement precision of the optical extensometer is limited by the size of the selected gauge length, and the gauge length cannot exceed the resolution of the digital camera, so that the strain measurement precision is limited, and the arrangement of the two rhombic prisms can amplify the distance between two target points by several times, so that the measurement precision of uniform strain is greatly improved;
(4) the adjustment is convenient: when the separation of field of view is realized to four speculum devices in existence, need the angle of deflection of every speculum of meticulous regulation one by one, accommodation process is more troublesome, and the utility model discloses in only having used two rhombus prisms, greatly simplified the realization step of field of view separation, and easily integrated as a whole measuring device, directly be connected with the camera lens, need not to measure at every turn and all adjust.
Drawings
Fig. 1(a) - (b) are schematic views of the measurement of the optical extensometer of the present invention; FIG. 1(a) is an overall view of an optical extensometer, and FIG. 1(b) is a layout view of two rhombic prisms;
fig. 2 is an image schematic diagram of a single rhombic prism of the present invention;
fig. 3 is a schematic diagram illustrating the calibration of the distance between two target points (i.e., the gauge length) according to the present invention;
fig. 4(a) - (b) are schematic diagrams illustrating the principle of eliminating the out-of-plane displacement according to the present invention, fig. 4(a) is a pinhole model, and fig. 4(b) is an equivalent radial false displacement generated on a dashed circle.
Detailed Description
The technical solution of the present invention will be further explained with reference to the following examples.
As shown in fig. 1(a), the optical extensometer based on lens imaging and double prism reflection of the present invention includes an oblique prism 6 and an oblique prism 7 corresponding to two target points 2 respectively, a housing 8 and a fixed cover plate 9 for fixing the two prisms, a digital camera 3, a common lens 4, a camera tripod 5 and a data processing device.
Firstly, selecting an upper target area and a lower target area of an optical extensometer on a sample 1 to be tested, wherein the upper target area and the lower target area respectively comprise two target points 2; arranging a first oblique prism 6 and a second oblique prism 7 according to a figure 1(b), fixing the first oblique prism and the second oblique prism in a concave shell 8 one above the other, wherein two 45-degree inclined planes of each prism and the surface of a sample 1 to be tested form 45 degrees (an imaging schematic diagram of the oblique prism is shown in a figure 2), the lower reflecting surface of the oblique prism 6 and the upper reflecting surface of the oblique prism 7 are positioned at the same height and are arranged in a staggered way, and the lower reflecting surface of the oblique prism 6 and the upper reflecting surface of the oblique prism 7 are just corresponding to the middle position of the common lens 4, after the front cover plate 9 is covered, only the light rays of the upper reflecting surface of the oblique prism 6 and the lower reflecting surface of the oblique prism 7 can be allowed to pass through, so that the light rays emitted by a first target point are translated downwards by a distance to enter the common lens and are reflected by the two reflecting surfaces of the lower oblique prism 7, the light rays emitted by a second target point are translated, the two groups of light rays are respectively imaged on the left half image surface and the right half image surface of the camera.
A common lens 4 and a digital camera 3 are arranged on a camera tripod 5, and the optical axis of the common lens 4 is vertical to the surface of the sample to be tested by adjusting the tripod; connecting a concave shell 8 provided with a prism to the front part of a common lens 4, using the common lens 4 to image two target points on the surface of a sample 1 to be tested, and eliminating measurement errors caused by the out-of-plane displacement of the sample 1 to be tested by utilizing the characteristic that the points of the common lens 4 on a horizontal central line are not subjected to the out-of-plane displacement; the digital camera 3 is used for simultaneously imaging two target points 2 on the surface of the sample 1 to be tested and forming a digital image, and the two target points 2 are respectively positioned at two sides of an image chip of the digital camera 3 so as to realize the simultaneous acquisition of images of two target areas; the tripod 5 capable of bearing the digital camera ensures that the digital camera 3 can be stably borne, so that the position of the digital camera 3 can be adjusted within a certain range.
The utility model discloses an optical extensometer and strain test method based on camera lens formation of image and separation of diclinic prism visual field can eliminate by the false displacement and the false strain that are aroused by the test appearance off-plane displacement, and false displacement and strain produce the principle as shown in figure 4. The ordinary camera imaging follows a pinhole model as shown in fig. 4(a), and if the target point is set to a point a on the surface of the sample to be tested, which is far from the optical axis, a point a on the image surface is imaged. When the surface of the sample to be tested generates small out-of-plane displacement close to the lens, the point A is moved to the point B, and the point B with a certain distance from the point a on the image surface is imaged according to the pinhole model. Under the condition that a tested sample is not deformed, the same point generates image displacement on an image surface only by the out-of-plane displacement of the tested sample, namely, false displacement, and corresponding strain data can be calculated according to the displacement data, namely, false strain. When the target point A is closer to the optical axis, the false displacement is smaller, the false displacement of a point on the optical axis is just zero, namely the point is not influenced by the off-plane displacement, but the point with the characteristic is only one in the whole image and cannot be used for two target points of the optical extensometer, so that the analysis on the equivalent radial false displacement generated on the dotted line circle in the figure 4(b) shows that the point on the horizontal center line of the image has the false displacement in the horizontal direction without vertical false displacement under the action of the off-plane displacement, and therefore, the two target points C and D are selected on the horizontal center line in the left and right image fields, the vertical false displacement and the false strain cannot be generated, and therefore, the vertical strain measurement precision of the optical extensometer can be improved.
The embodiment of the utility model discloses a high accuracy optical extensometer and strain test method based on ordinary camera lens formation of image and diclinic prism, the light translation characteristic that utilizes diclinic prism will be tested two target points 2 far away on appearance surface and drawn close to the record in a digital image, greatly increased the distance between two target points in the optical extensometer, be favorable to improving strain measurement resolution and measuring accuracy.
The embodiment of the utility model discloses an even strain test method based on above-mentioned optical extensometer, including following step:
step 4, adjusting the aperture and the focal length of the camera to enable the camera to image clearly; placing a ruler with scales on the surface of a sample, and shooting upper and lower target areas of the ruler to obtain a digital image; calculating to obtain the pixel distance generated by the separation of the view fields according to the scale mark readings of the left and right areas of the image and the proportional relation;
In step 2, after the double-oblique-square prism and the front cover plate are installed on the concave shell, repeated installation is not needed in later strain measurement, and the concave shell is connected to the front end of the lens through threads, so that the preparation time of an experiment is greatly saved.
The utility model discloses use ordinary camera lens and diclinic prism separation visual field to being tested two specific target points on appearance surface and form images, compare with traditional single camera, the interval of two target points is the interval of two prisms promptly, has obtained enlargeing doubly, and the vertical displacement of target point does not receive the influence of off-plane displacement to can greatly improve optical extensometer and be used for the measurement accuracy and the resolution ratio of meeting an emergency.
The object distance of the camera is 500mm, the distance between target points in the image is 1600 pixels, if the tested sample has 0.1mm out-of-plane displacement in the testing process, the strain error of 0.1/500 to 200 mu epsilon can be generated by adopting common lens imaging; even if out-of-plane displacement is not generated, the strain precision of the optical extensometer is only (0.01+0.01)/1600 ═ 12.5 mu epsilon; on the other hand, when the scale distance s is increased to 8000 pixels by using the biprism view field separating device of the present embodiment, the strain accuracy of the optical extensometer can be improved to (0.01+0.01)/8000 ═ 2.5 μ ∈.
Claims (5)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202021544028.9U CN212692801U (en) | 2020-07-30 | 2020-07-30 | An Optical Extensometer Based on Lens Imaging and Biprism Reflection |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202021544028.9U CN212692801U (en) | 2020-07-30 | 2020-07-30 | An Optical Extensometer Based on Lens Imaging and Biprism Reflection |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN212692801U true CN212692801U (en) | 2021-03-12 |
Family
ID=74900329
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202021544028.9U Active CN212692801U (en) | 2020-07-30 | 2020-07-30 | An Optical Extensometer Based on Lens Imaging and Biprism Reflection |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN212692801U (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111829448A (en) * | 2020-07-30 | 2020-10-27 | 河海大学 | An optical extensometer and uniform strain measurement method based on lens imaging and double prism reflection |
| CN111829448B (en) * | 2020-07-30 | 2025-04-11 | 河海大学 | An optical extensometer based on lens imaging and dual prism reflection and uniform strain testing method |
-
2020
- 2020-07-30 CN CN202021544028.9U patent/CN212692801U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111829448A (en) * | 2020-07-30 | 2020-10-27 | 河海大学 | An optical extensometer and uniform strain measurement method based on lens imaging and double prism reflection |
| CN111829448B (en) * | 2020-07-30 | 2025-04-11 | 河海大学 | An optical extensometer based on lens imaging and dual prism reflection and uniform strain testing method |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Schwenke et al. | Opto-tactile sensor for 2D and 3D measurement of small structures on coordinate measuring machines | |
| JP3511450B2 (en) | Position calibration method for optical measuring device | |
| JP5829381B2 (en) | Method and apparatus for measuring relative position of specular reflection surface | |
| TW488145B (en) | Three-dimensional profile scanning system | |
| CN110806182A (en) | High-precision optical extensometer and measurement method based on telecentric lens | |
| CN101169601B (en) | Focusing leveling measuring system | |
| CN108332946B (en) | In-situ detection method of reflection focal length in turning of microlens array mold | |
| CN111964600A (en) | High-precision dual-axis optical extensometer and measurement method based on bidirectional field separation | |
| CN106767545A (en) | A kind of high accuracy high-space resolution angel measuring instrument and angle measurement method | |
| US20080137061A1 (en) | Displacement Measurement Sensor Using the Confocal Principle | |
| CN113614617A (en) | Collimator | |
| CN112683382B (en) | Structure three-dimensional vibration measurement system and method based on monocular vision | |
| CN1979091A (en) | Optical measuring system | |
| CN102012215A (en) | Digital image-based noncontact optical strain measurement method and strain gauge | |
| CN109556528B (en) | Single-camera three-dimensional video extensometer and measuring method | |
| CN110702036A (en) | A complex beam angle sensor and a small aspheric topography detection method | |
| CN111829445A (en) | A High Precision Optical Extensometer Based on Biprism | |
| CN212692801U (en) | An Optical Extensometer Based on Lens Imaging and Biprism Reflection | |
| CN101033949A (en) | Strain measurement method and device of object based on misplace relative theory | |
| CN111829448B (en) | An optical extensometer based on lens imaging and dual prism reflection and uniform strain testing method | |
| CN111829446A (en) | A high-precision dual-axis optical extensometer utilizing multiple rhombus prisms | |
| CN114322812A (en) | Monocular three-dimensional high-speed measurement method, optical path system and calibration method thereof | |
| CN111829448A (en) | An optical extensometer and uniform strain measurement method based on lens imaging and double prism reflection | |
| Yoshizawa et al. | Development of an inner profile measurement instrument using a ring beam device | |
| JP2007315865A (en) | Three-dimensional displacement measuring device and measuring method |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| GR01 | Patent grant | ||
| GR01 | Patent grant |