Single camera three-dimensional video extensometer and measurement method
A three-dimensional video and measurement method technology, applied in measurement devices, instruments, optical devices, etc., can solve the problems of complex dual-camera calibration process, limited use, increased hardware costs, etc., and achieve the effect of overcoming the inability to measure out-of-plane displacement.
Active Publication Date: 2019-04-02
NANJING UNIV OF SCI & TECH
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[0002] As a commonly used testing tool, video extensometers are widely used in the testing of mechanical properties of materials. Conventional single-camera video extensometers can only measure two-dimensional in-plane deformation, and small out-of-plane displacements will cause large measurement errors, thereby affecting test accuracy.
The 3D video extensometer based on dual cameras requires a camera synchronization device, which increases the hardware cost
And the calibration process of dual cameras is very complicated, which limits its use in 3D video extensometers
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[0017] The scheme of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.
[0018] Such as figure 1 As shown, a single-camera three-dimensional video extensometer includes an industrial camera 8, a high-resolution lens 7, a tripod 9, a computer 10, and a front coated mirror 5 with at least two marking points 6 attached thereto. 1, 2, 3 and 4 in the figure are universal testing machines: 1 is a column, 2 is a beam, 3 and 4 are upper and lower chucks.
[0019] The industrial camera 8 is arranged on the tripod 9, the high-resolution lens 7 is arranged in front of the industrial camera 8, and the high-resolution lens 7 faces the front coated mirror 5; the front coated mirror 5 is arranged beside the object to be measured. And the lens can clearly observe the object under test and its virtual image in the mirror. Prepare speckles on the surface of the object to be measured.
[0020] In the unloaded and arbi...
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The invention discloses a single camera three-dimensional video extensometer and a measurement method. The measurement method comprises the following steps of calibrating the internal parameter of a camera by using a plane calibration plate; preparing a speckle on the surface of an object to be detected, fixing a reflector adhered with identification points close to the speckle, and collecting thespeckle real image of the object to be detected under an initial state and the speckle virtual image in the reflector; loading the object to be detected during a test process, solving a rotation matrix of a camera coordinate and a mirror surface coordinate under any state and a normalized translation vector during a loading process by using the internal parameter of the camera and the corresponding image coordinates of the real image and the virtual image, and computing a translation vector coefficient by using an actual distance between any two points in the reflector; and computing three-dimensional space coordinates of two points to be detected on the surface of the substance, namely achieving computation on displacement and strain between the two points to be detected. According to the method provided by the invention, the three-dimensional displace and strain computation can be achieved by using a single camera, and the method has the advantages of non-contact and being high in measurement accuracy, simple in equipment, convenient and practical.
Description
technical field [0001] The invention relates to the field of optical measurement experiment solid mechanics, in particular to a single-camera three-dimensional video extensometer and a measurement method. Background technique [0002] As a commonly used testing tool, video extensometers are widely used in the testing of mechanical properties of materials. Conventional single-camera video extensometers can only measure two-dimensional in-plane deformation, and small out-of-plane displacements will cause large measurement errors, thereby affecting test accuracy. . The 3D video extensometer based on dual cameras requires a camera synchronization device, which increases the hardware cost additionally. And the calibration process of dual cameras is very complicated, which limits its use in 3D video extensometers. Contents of the invention [0003] The purpose of the present invention is to provide a single-camera three-dimensional video extensometer and measurement method, wh...
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IPC IPC(8): G01B11/16
CPCG01B11/162
Inventor 刘聪刘晓鹏徐志洪康新
Owner NANJING UNIV OF SCI & TECH