Dynamic Holographic-Electronic Speckle-Pattern Interferometry

1993 ◽  
Vol 60 (4) ◽  
pp. 866-874 ◽  
Author(s):  
M. A. Ahmadshahi ◽  
Sridhar Krishnaswamy ◽  
S. Nemat-Nasser
Keyword(s):  
High Speed ◽  
Speckle Pattern ◽  
Processing System ◽  
Ccd Camera ◽  
Electronic Speckle Pattern Interferometry ◽  
Relative Deformation ◽  
Full Field ◽  
Speckle Patterns ◽  
Fringe Patterns ◽  
Laser Light Source

The development of a nondestructive, full-field, quantitative optical technique, and its feasibility to study dynamic deformations of opaque and diffusively reflecting solids under transient loads, are discussed. The technique involves recording a sequence of dynamically changing two-beam speckle interference patterns (also called holographic speckle patterns) of a rapidly deforming body which is doubly illuminated by a laser light source. The time sequence of speckle patterns is recorded by means of a high-speed camera on an ultra-sensitive 35-mm film. The developed negatives are then digitized by a CCD camera into an image processing system. An initial speckle pattern corresponding to the undeformed state of the object is taken as the reference, and subsequent speckle patterns are digitally subtracted (reconstructed) from it to produce time- varying fringe patterns corresponding to the relative deformation of the test object. In order to gain confidence that the technique can be used to record truly transient deformation, it is tested here on a vibrating plate at resonance, thereby obtaining the evolution of the fringe pattern during 1/2 cycle of deformation corresponding to 160 μs.

Full-Field Laser Vibrometer for Instantaneous Vibration Measurement and Non-Destructive Inspection

2010 ◽  
Vol 437 ◽  
pp. 407-411 ◽  
Author(s):  
James M. Kilpatrick ◽  
Vladimir B. Markov
Keyword(s):  
High Speed ◽  
Fiber Optic ◽  
Speckle Pattern ◽  
Vibration Measurement ◽  
Electronic Speckle Pattern Interferometry ◽  
Laser Vibrometer ◽  
Full Field ◽  
The Matrix ◽  
Interferometric Sensor ◽  
Non Destructive

We describe a system for real-time, full-field vibrometry, incorporating features of high-speed electronic speckle pattern interferometry (ESPI) and laser Doppler velocimetry (LDV). Based on a 2D interferometric sensor array, comprising 16×16 parallel illumination and detection channels, the matrix laser vibrometer (MLV), captures full-field data instantaneously, without beam scanning. The instrument design draws on the advantages of scale offered by modern telecommunications fiber optic and digital electronics. The resulting architecture, comprising a compact measurement probe linked by fiber optic umbilical to a remote electronics unit, facilitates practical application to the full-field study of transient vibrations and rapid non-destructive inspection of composite materials.

Experimental Investigation on the Instability of Al Sheet in Hydraulic Bulging Based on ESPI

2011 ◽  
Vol 264-265 ◽  
pp. 84-89
Author(s):  
Yan Liu ◽  
Zhong Jin Wang
Keyword(s):  
Strain Rate ◽  
Strain Localization ◽  
Speckle Pattern ◽  
Electronic Speckle Pattern Interferometry ◽  
Three Dimension ◽  
Full Field ◽  
Localized Necking ◽  
Diffuse Necking ◽  
Fringe Patterns ◽  
Hydraulic Bulging

Electronic speckle pattern interferometry (ESPI) was applied to hydraulic bulging to analyze the entire deformation process, especially the instability evolution of Al 1060 sheet. Speckle patterns of the specimens were captured continuously to record the deformation fields. The development of full-field strain rate during bulging was represented by the fringe patterns real-timely. The emergence of the defect and its subsequent transformation into groove and crack were revealed clearly by the aberration region in the fringe patterns. The onset of diffuse necking and localized necking were determined by the strain rate distribution curves calculated based on the fringe patterns. Results indicate that ESPI is a satisfying method to analyze the instability and fracture of sheet metals even in three dimension deformation. The growth of micro-crack caused a banded weak region. Diffuse necking occurred in the weak region due to strain localization. A groove generated in the banded weak region and then extended along the length direction. The remarkable strain localization in the groove indicated the onset of localized necking. The thickness of the groove decreased quickly and finally caused fracture. The accurately and quickly determined necking strains would lead to a safer FLD.

Study on Displacement Measurement for Induced Strain Field Based on Digital Speckle Pattern Interferometry Method

2013 ◽  
Vol 273 ◽  
pp. 510-514
Author(s):  
Jing Liu ◽  
Hui Zhang ◽  
Jun Li ◽  
Da Chuan Chen ◽  
Yan Kun Tang
Keyword(s):  
Strain Field ◽  
High Speed ◽  
Speckle Pattern ◽  
Measuring Method ◽  
Full Field ◽  
Digital Speckle Pattern Interferometry ◽  
Level Measurement ◽  
On Line ◽  
Interferometry Method ◽  
Digital Speckle

Digital Speckle Pattern Interferometry ( DSPI for short ) method has become one of the most practical worthy techniques for speckle measuring methods with the high-speed development of optic-electronical technique, image processing technology and electronic computer technology. There is a lot of advantages about it, such as uncomplicated operation, non-contacting, advanced automatic level, measurement on-line and extensive using. In this thesis, the displacement variation of the induced strain field for driving by piezoelectric ceramics can be measured by using this method. Thus we can come to a conclusion that digital speckle pattern interferometry is a new measuring method for extracting small-signal. It also provides a powerfully theoretical and experimental platform for study of automated, full-field, high-precision and nondestructive measurement.

Phase Algorithm Integrating Direct-Correlation and Four-Step Phase-Shifting for Electronic Speckle Pattern Interferometry

2013 ◽  
Vol 448-453 ◽  
pp. 3696-3701
Author(s):  
Yan Bin He ◽  
Xin Zhong Li ◽  
Min Zhou
Keyword(s):  
High Speed ◽  
Speckle Pattern ◽  
Phase Shifting ◽  
Electronic Speckle Pattern Interferometry ◽  
High Speed Camera ◽  
Dynamic Measurements ◽  
High Quality ◽  
Correlation Algorithm ◽  
Phase Map

A phase-shifting algorithm, called a (4,4) algorithm, which takes four phase-shifting interferograms before a specimen is deformed and four interferograms after a specimen is deformed, is presented first. This method is most widely used for phase extraction. Its drawback limited it to be used in dynamic measurements. Also shown is an algorithm called a (4,1) algorithm that takes four phase-shifting interferograms before a specimen is deformed and one interferogram after a specimen is deformed. Because a high-speed camera can be used to record the dynamic interferogram of the specimen, this algorithm has the potential to retain the phase-shifting capability for ESPI in dynamic measurements. The quality of the phase map obtained using (4,1) algorithm is quite lower compared to using (4,4) algorithm. In order to obtain high-quality phase map in dynamic measurements, a direct-correlation algorithm was integrated with the (4,1) algorithm to form DC-(4,1) algorithm which is shown to improve significantly the quality of the phase maps. The theoretical and experimental aspects of this newly developed technique, which can extend ESPI to areas such as high-speed dynamic measurements, are examined in detail.

Electronic Speckle Pattern Interferometry Applied to the Displacement Measurement of Sandwich Plates with Single ‘Fully Potted’ Insert

2004 ◽  
Vol 20 (4) ◽  
pp. 273-276 ◽  
Author(s):  
S. J. Huang ◽  
H. L. Lin
Keyword(s):  
Speckle Pattern ◽  
Fem Analysis ◽  
Electronic Speckle Pattern Interferometry ◽  
Sandwich Plates ◽  
Destructive Testing ◽  
Displacement Fields ◽  
Full Field ◽  
Out Of Plane ◽  
Plane Displacement ◽  
Non Destructive

AbstractThe construction and operation of electronic speckle pattern interferometer (ESPI) applied to single-inserted sandwich plates have been earliest presented in this paper. Proposed ESPI has advantages of full-field and non-destructive testing, which can measures microscopic out-of-plane displacement in the elastic region without wasting specimen. For validation purpose, the finite element method (FEM) analysis was conducted. By comparing the results of ESPI and FEM displacement fields around the inserts that a convincing agreement is revealed. The effect of potting material diameter on the displacement of single-inserted sandwich plates was obtained by the ESPI and FEM.

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