This paper presents a multi-carrier frequency spatial phase shift digital shearing speckle interferometry method which is capable of the first derivative and microdeformation synchronously. The dynamic deformation of the composite defects is carried out by thermal loading.The shear speckle interferometry is used to locate the defect position and holography was used to measure microdeformation of the defect. In Michelson shearing device, an optical fiber is used to introduce a reference beam,two shear images form a shear fringe pattern, and the reference beam introduced is combined with one of the shear patterns to generate a hologram. The spatial phase shifting technique is used to obtain the frequency domain after Fourier transform, holograms and shearograms are obtained at the same time. In this paper, the direct synchronous measurement of microdeformation and first derivative of deformation is realized without the need of numerical integration process. Finally, the experimental results show that the proposed method can quickly obtain the shear fringe image, which represents the first derivative of the deformation to position the defect in the composite material, and the hologram is filtered, unwrapped and 3D displayed to obtain accurate micron scale deformation values.
In speckle metrology, speckle fringe pattern includes phase information, in order to get the contains less noise in the dynamic measurement of the original speckle fringe pattern, allowing for more efficient to extract phase information,A new method is proposed to improve the quality of the original speckle pattern by changing the average speckle size on the digital shear speckle. The quantitative relationship between the optical path system parameters F number and magnification factor and the speckle size on the image surface was analyzed, and the digital shear speckle interferometry experiment based on the space carrier phase shift technology changed F number and magnification factor respectively for verification.Experimental results show that the shape of variables for fixed value, system magnification is 1, the imaging lens F value is 4.5, The average speckle size was 5.841 μm, and the image was best when it was closest to 5.86 μm, as a lens F number is 2, system magnification of 3.5, The average speckle size was 5.841 μm, and the image was best when it was closest to 5.86 μm, after filtering is cosine algorithm, the speckle fringe pattern is the most clear.It is proved that when the speckle size on the image plane is closest to the size of pixel, the quality of the speckle stripe is the best.
Recently, a non-cooperative method of roll angle measurement using digital speckle pattern interferometry (DSPI) is introduced. Mechanism was deduced and the mathematic model of roll angle measurement was established. The novel method also enjoys some other advantages, such as high-accuracy, stand-off, non-contact, and full-field measurement. However, this method is only used for precise measurement of very small roll angle which is up to a few milliradians due to the limitation of DSPI’s measuring range. In this article, a means of range enlargement for DSPI roll angle measurement is introduced. With this means, large roll angle can be divided into a number of small angles which are measured in sequence. Therefore, the large angle is then determined by calculating the sum of these small angles. The proposed method of roll angle is characterized by high-resolution and large-range measurement.
The velocity of warhead fragment is the key criteria to determine its mutilation efficiency. But owing to the small size, larger quantity, irregular shape, high speed, arbitrary direction, large dispersion of warhead fragment and adverse environment, the test of fragment velocity parameter is very difficult. The paper designed an optoelectronic system to measure the average velocity of warhead fragments accurately. The apparatus included two parallel laser screens spaced apart at a known fixed distance for providing time measurement between start and stop signals. The large effective screen area was composed of laser source, retro-reflector and large area photo-diode. Whenever a moving fragment interrupted two optical screens, the system would generate a target signal. Due to partial obscuration of the incident energy and the poor test condition of the explosion, fragment target signal is easily disturbed. Therefore, fragments signal processing technology has become a key technology of the system. The noise of signal was reduced by employing wavelet decomposition and reconstruction. The time of fragment passing though the target was obtained by adopting peak detection algorithm. Based on the method of search peak in different width scale and waveform trend by using optima wavelet, the problem of rolling waveform was solved. Lots of fragments experiments of the different types of the warheads were conducted. Experimental results show that: warhead fragments capture rate of system is better than 98%, which can give velocity of each fragment in the density of less than 20 pieces per m2.
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