These include temporal and spatial phase shifting interferometry, temporal and spatial phase unwrapping, and calculation of strain fields from the phase maps. A digital speckle pattern interferometer based on a novel custom complementary metaloxidesemiconductor cmos array detector is descri bed. The entire analysis process has been examined from its initial stages of video resolution and digitisation, through to the representation of phase data within. Phase stepping shearography and electronic speckle pattern interferometry d findeis, j gryzagoridis, m matlali department of mechanical engineering university of cape town, rondebosch, 7700, south africa tel. A singlemode optical fiber mounted in the center of the systems aperture stop creates a sphericalwave reference beam. University of vigo for discussions about phase unwrapping software. It was later realized that speckle patterns could carry information about the objects surface deformations. Vibration isolation techniques suitable for portable electronic speckle pattern interferometry dirk findeis, jasson gryzagoridis, david reid rowland. This paper presents a holographic interferometer technique for measuring transparent 2d or quasi 2 d density fields. Psi has existed in its basic form for less than 3 decades, and may be regarded as temporal. Phase shifting speckle interferometry for determination of.
In 1970, the french astronomer antoine labeyrie showed that fourier analysis speckle interferometry can obtain information about the highresolution structure of the object from the statistical properties of the speckle patterns. The interference phase has to be recovered with phase shifting methods 2628, requiring additional experimental effort phase shifting unit. Speckle imaging describes a range of highresolution astronomical imaging techniques based on the analysis of large numbers of short exposures that freeze the variation of atmospheric turbulence. Its drawback limited it to be used in dynamic measurements. Automated fringe pattern analysis in experimental mechanics. Digital speckle pattern interferometry dspi is a competitive optical tool for full field. The image quality of digital shearography can be improved by introducing phase stepping. 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.
Recent developments and applications in electronic speckle pattern. Speckle interferometry experiments with a digital photocamera. The paper shows how, in speckle interferometry, the phase information can be retrieved from a single intensity pattern provided that the speckle field captured from the object at the reference conditions is fully resolved in its components of mean intensity, modulation and phase. Digital evaluation of interferograms request pdf researchgate. Thermomechanical behaviour of a pwb by speckle interferometry.
Widearea imaging of ultrasonic lamb wave fields by. Universal optical setup for phaseshifting and spatial. Vibration isolation techniques suitable for portable. Digital phase stepping speckle interferometry maas, a. Phase stepping technique with an electrooptic crystal in digital speckle pattern interferometry. Phase shifting speckle interferometry katherine creath speckle patterns have high frequency phase data, which make it difficult to find the absolute phase of a single speckle pattern. The software also displays the real time subtraction of the images, thus the correlation. Contrary, phase stepped interferometry is less influenced by speckle noise, but needs at least three phase shifted frames at reference and object condition, or one frame with accordingly reduced. Electronic speckle pattern interferometry espi has been widely used for vibration amplitude. Electronic speckle pattern interferometry wikipedia. Digital phase stepping speckle interferometry digital phase stepping speckle interferometry maas, a. Digital interferometry is a new concept for optical interferometry, which combines the high sensitivity of conventional optical interferometry with the robustness of digital modulationdemodulation techniques to achieve a breakthrough combination of sensitivity, ease of use and flexibility. However, it has been during the last 15 years that espi, boosted by the availability of affordable and increasingly powerful digital image processing systems, has grown into one of the leading optical measurement techniques, receiving new names such as tv holography or digital speckle pattern interferometry.
The flexibility of the cmos detector is used to identif y regions of interest with fullfield time averaged measurements and then to. For digital speckle interferometry, the fast fourier analysis usually applied to interference fringe systems suffers from a limited spatial resolution because of the inherent granulation disturbance. Vibrationobservation techniques for digital specklepattern. High precision deformation measurement by digital phase shifting holographic interferometry ming chang, chingpiao hu, philip lam, and james c.
Digital speckle pattern interferometry dspi is a competitive optical tool for fullfield deformation measurement. A photograph is made of the speckle pattern before deformation, and a. Butters and leendertz developed the technique of speckle pattern interferometry in 1970, and since then, speckle has been exploited in a variety of other applications. Shape measurement using phase shifting speckle interferometry. Interferometry is a family of techniques in which waves, usually electromagnetic waves, are superimposed, causing the phenomenon of interference, which is used to extract information. Digital speckle pattern interferometry and related techniques. Speckle interferometry using fiber optic phase stepping. This paper investigates the effect of partial speckle decorrelation due to the transverse component of the object displacement on the phase measurement using statistical optical theory. Determination of the zeroorder fringe position in digital.
Squeezing interferometry for optical phase extraction in. Recent applications for dynamic length measurements target a velocity greater than 1 ms. Keep it simple dont use too many different parameters. Squeezing interferometry for optical phase extraction in digital speckle pattern interferometry. The two main types of dspi, phaseshifting dspi psdspi and. Digital phase stepping speckle interferometry sciencedirect. Digital speckle pattern interferometry dspi is the generic name for a class of important interferometric techniques such as tv holography, electronic holography or phase shifting pattern interferometry, all of which involve similar optical and electronic principles. The object displacements on a a 256256grid are calculated by subtracting the phases of the speckle. Electronic speckle pattern interferometry espi is an optical technique which enables interferometric measurements of surface displacements on almost any surface and material.
A detailed investigation has been carried out into the application of digital phase stepping techniques in the computer analysis of electronic speckle pattern interferometry fringe data. Abstractelectronic speckle pattern interferometry espi is a wholefield non contact. Digital holography dh is usually free of misinterpretation, but when an expression like imageplane digital. Munich tum in the framework of the open access publishing program. Electronic speckle pattern interferometry espi and digital shearography have been shown to be of great value for the nondestructive testing of the integrity of materials and manufactured components.
The phase stepping can be accomplished with a mirror guided by lead zirconate titanate. A common technique for achieving this is temporal phase stepping. A new versatile electronic speckle pattern interferometer for. The temporal evolution of the dynamic deformation of a test object is measured us ing interframe phase stepping. Electronic speckle pattern interferometry espi espi on the other hand, records the surface displacement of an object in response to the applied force. Wyant a digital phase shifting technique capable of quantitatively determining the phase. Phase shifting speckle interferometry for determination of strain and youngs modulus of mineralized. A digital speckle pattern interferometer was built utilizing a 100 x 100 element reticon diode array interfaced to an hp9836c desktop computer. The fringe patterns are obtained by subtraction of the speckle patterns recorded in two different states. Use of spatial phase shifting technique in digital speckle. With selfdeveloped programs, both the psdspi and scdspi modes. Speckle interferometry nanophotonics and metrology lab epfl. Statistical analysis of phase stepping digital speckle pattern interferometry statistical analysis of phase stepping digital speckle pattern interferometry zheng, wen 19930205 00.
Phase stepping phase stepping or, phase shifting is a technique long used in interferometry, with early applications to speckle interferometry by creath 1. This is done by applying phase shifting techniques to speckle interferometry, which will quantitatively determine the phase of doubleexposure speckle. To verify theoretical predictions, experiments have been performed using a solidstate linear detector array to measure 1d surface heights. Electronic speckle pattern interferometry espi, also known as tv holography, is a technique which uses laser light, together with video detection, recording and processing to visualise static and. An automated analysis system based on ibmpc microcomputer and pcvisionplus frame grabber is developed which is able to acquire quantitative displacement information with high speed and accuracy. Stroboscopic phase stepping digital speckle pattern interferometry. Digital phase stepping speckle interferometry, proceedings. Temporal polarization phaseshifting for digital speckle. We discuss a simple experiment for detecting small deformations by speckle interferometry. The object displacements on a a 256256grid are calculated by subtracting the phases of the speckle field. Temporally resolved phasestepped speckle interferometry of.
Digital phase stepping speckle interferometry, proceedings of. Fabrication of a simple and easytomake piezoelectric. The entire analysis process has been examined from its initial stages of video resolution and digitisation, through to the representation of phase. Simple digital phasemeasuring algorithm for lownoise. Digital speckle pattern interferometry dspi and digital shearography ds are well known optical tools for qualitative as well as quantitative measurements of displacement components and its derivatives of engineering structures subjected either static or dynamic load. Creath, phaseshifting speckle interferometry, appl. Electronic speckle pattern interferometry espi non.
Dspi processes speckle patterns in a computer rather than with a frame grabber and analog electronics as in espi. The object displacements on a 256256 grid are calculated by subtracting the phases of the speckle field before and after deformation. Phase stepping shearography and electronic speckle pattern interferometry d findeis, j gryzagoridis, m matlali department of mechanical engineering university of cape town, rondebosch, 7700, south. Phaseshifting speckle interferometry usystem accounts. The phase at this point is measured, digitally, before and after the surface moves. The main advantage of this technique is to demodulate by means. Pdf phase stepping shearography and electronic speckle. Universal optical setup for phase shifting and spatialcarrier digital speckle pattern interferometry sijin wu1, mingli dong1, yao fang1 and lianxiang yang1,2 abstract background. The speckle interferometry technique has been used in this work in order to determine the thermomechanical behaviour of printed wiring board pwb circuits of a radio integrated with tape player and speakers. The purpose of the present work is the use of squeezing interferometry technique to provide an optical phase mapping from dspi fringes. Using shearography to detect damage in gas pipelines.
Phase stepping and phase unwrapping techniques are used to calculate the phase distribution. High precision deformation measurement by digital phase. Statistical analysis of phasestepping digital speckle. To be able to study the realization of such a field at a certain moment of time, the field is frozen on a holographic plate. Vibrationobservation techniques for digital speckle. Universal optical setup for phaseshifting and spatialcarrier digital. The theoretical values of statistical phase errors are derived under the inplane and outofplane displacement sensitive arrangement when using the phase subtracting method. Digital phasestepping holographic interferometry in. Digital speckle pattern interferometry dspi is a competitive optical tool for fullfield.
Espi can be used in arrangements where fringes will represent lines of either inplane or outofplane displacement. Realization and accuracy of a phaseshifting speckle. Fermi 6, 50125 firenze, italy received 12 september 2003. Figure 2 schematics illustrating typical optical arrangements for the principal speckle interferometry techniques, espi and shearography. This method is another version of the phase shifting differential digital speckle interferometer psddspi,8,9 which uses two reference. Abstract a digital speckle interferometric technique for deformation measurement using phase stepping and image processing is presented.
The speckle interferometry technique has been used in this work in order to determine the thermomechanical behaviour of printed wiring board pwb circuits of a radio integrated with tape. Phase stepping shearography and electronic speckle pattern. It is based on an averaging procedure with shifted images obtained before and after a load is applied. They can be divided into the shiftandadd image stacking method and the speckle interferometry. This method is most widely used for phase extraction. Digital speckle pattern interferometry dspi and digital. For one and a half decade, software for interferometric fringe evaluation has. Digital recording and numerical reconstruction of holograms. Phase algorithm integrating directcorrelation and fourstep. The object displacements on a 256256 grid are calculated by subtracting the phases of the speckle. Electronic speckle pattern interferometry espi, also known as tv holography, is a technique which uses laser light, together with video detection, recording and processing to visualise static and dynamic displacements of components with optically rough surfaces.
As a result, it was decided to begin a new project, the aim of which is to develop a small portable electronic speckle pattern interferometry inspection system. This technique is a complement to the phase shifting methods. Vibration observation is a major application of digital speckle pattern interferometry dspi, which is a variation on electronic speckle pattern interferometry espi. Speckle patterns have high frequency phase data, which make it difficult to find the absolute phase of a single speckle pattern. In this paper, computer image processing techniques for the extraction of numerical data of vibration amplitude are presented using stroboscopic phase stepping speckle interferograms. Use of spatial phase shifting technique in digital speckle pattern. Speckle interferometry experiments with a digital photocamera maurizio vannonia and giuseppe molesinib istituto nazionale di ottica applicata, largo e. A method for determining the position of the zeroorder fringe in a metrological experiment with digital speckle pattern interferometry is proposed. Separate search groups with parentheses and booleans. This paper describes a technique that combines ideas of phase shifting interferometry psi and twowavelength interferometry twli to extend the phase measurement range of conventional singlewavelength psi. Wen zheng and yushan tan stroboscopic phasestepping digital speckle pattern. Abstractelectronic speckle pattern interferometry espi is a wholefield noncontact. During the reconstruction of the density field from the hologram the length of the path traversed by the reconstruction beam is diminished in. The application of phase stepping to the analysis of espi.
365 651 1240 1009 442 694 309 1389 667 754 265 718 1334 1205 1537 862 336 576 125 16 332 255 119 1302 1348 831 261 611 889 767 1283 487 902