Phaseshifting interferometry psi has high precision and has been widely used in optical shop testing because of its robust and reliable measurement results even though it suffers from the wellknown 2. In this study, phaseshifting speckle interferometry techniques were adapted for measuring the strain and elastic modulus of small, millimetersized, wet dentin samples loaded in compression. A phase shifting dynamic speckle interferometry system which allows the recording of a sequence of interferograms at a frequency of 1 khz was recently developed. The addition of electronics, computers, and software to interferometry has enabled enormous improvements to optical metrology. High accuracy phase measurement in phaseshifting speckle. For this purpose, the measured speckle field displacement is compensated by lateral shifting in one of the recorded interferograms in subareas 3. Phase shifting electronic speckle pattern interferometry. A digital specklepattern interferometer was built utilizing a 100 x 100 element reticon diode array interfaced to an hp9836c desktop computer. A phase shifting interferometric imaging ellipsometer. Afterwards, the phase difference data is recalculated by an sps algorithm from the decorrelation compen. Pdf phaseshifting algorithms for electronic speckle.
The noncontact and fullfield measurement allows the calculation of the three dimensional distribution of the displacement and strainstress of the object under test as. A reliability test was performed by subtracting two phase maps taken digital phase shifting speckle interferometry 239 fig. Temporal and spatial phase shifting in electronic specklepattern interferometry are compared quantitatively with respect to the quality of the resultant deformation phase maps. The proposed approach, called throughout the paper onestep, can be applied for studying phenomena. Squeezing interferometry for optical phase extraction in. Optotune laser speckle reducers remove local interferences and significantly reduce speckle noise in laser systems by dynamically diffusing the laser beam. A method for accurately measuring information about the deformation of a rough surface object using a phase shifting speckle interferometer with a television camera and a computer is considered. The light emitted by a laser is split into two beams by a beam splitter. Phase shifting interferometry avoids the need to track. Speckle interferometry, squeezing interferometry, phase shifting, phase unwrapping. This paper will show the different steps required to get a procedure optical mounting and computing software enabling the use of lclv in the output beam of the laser coupled with a 3d speckle interferometry setup. Pdf spatially phaseshifted digital speckle pattern.
Universal optical setup for phaseshifting and spatial. Universal optical setup for phaseshifting and spatialcarrier digital speckle pattern interferometry sijin wu1, mingli dong1, yao fang1 and lianxiang yang1,2 abstract background. Using a programmable interferometer for digital phase. The spatially phase shifted digital speckle pattern interferometer spsdspi is a speckle pattern interferometer in which the four phaseshifted interferograms are captured simultaneously in a. Phase shifting speckle interferometry with nematic liquid crystal light valve. Digital speckle pattern interferometry dspi is a whole field optical method for non contact and nondestructive surface analysis. Application of digital image correlation techniques in.
On the basis of an analysis of the noise in sawtooth fringes a figure of merit is defined and measured for various inplane and outofplane sensitive electronic speckle pattern interferometry configurations. Sps electronic specklepattern interferometry that is caused by lateral speckle displacement. Interferometry and its applications in surface metrology. A new method has been developed to remove noise from the deformation phase map obtained by a phaseshifting electronic speckle pattern interferometry. Use of spatial phase shifting technique in digital speckle pattern interferometry dspi and digital shearography ds. In this case, the intensity change of the speckle by phase shifting varies randomly in space because of the statistical property of the speckle. In this case, the intensity change of the speckle by phaseshifting varies randomly in space because of the statistical property of the speckle. Temporal phase shifting is carried out using a pockels cell in the reference beam and phase extraction is performed using a standard fourframe algorithm. The test fixture uses an m12 steel fastener and aluminum joint. 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. Phase shifting speckle interferometry for determination of strain and youngs modulus of mineralized biological materials.
A mechanically stable laser diode speckle interferometer. Variational phase recovering without phase unwrapping in. Wavefront reconstruction in phaseshifting interferometry. Rp photonics encyclopedia laser speckle, pattern, laser. An imaging ellipsometer has been developed which employs phase shifting interferometry to characterize the ellipsometeric parameters. 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. This method is most widely used for phase extraction. A phaseshifting electronic speckle pattern shearing interferometer with a very simple shearing device is proposed. Rp photonics encyclopedia interferometers, types, operation.
High speed electronic speckle pattern interferometry espi. Image processing of corona virus using interferometry. A set of innovative phaseshifting algorithms developed to facilitate metrology based on electronic speckle pattern interferometry. Interferometry has been a timehonored technique for surface topography measurement. Interferometric measurements of surface shape are relative measurement techniques in which the shape of a known surface is compared with that of an unknown surface, and the difference is displayed as a series of interference fringes. Temporal and spatial phase shifting in electronic speckle pattern interferometry are compared quantitatively with respect to the quality of the resultant deformation phase maps.
A simple phase shifting lateral shearing interferometer. Second, measurements can be taken at every element in the photodetector array directly yielding optical pathlength differences on a regularly spaced grid. Sps electronic speckle pattern interferometry that is caused by lateral speckle displacement. Its now considered as a powerful tool for industrial measurements. Does anyone out there know of open source software which can be used for speckle interferometry with normal digital cameras. Nematic liquid crystals valves lclv are also called slm spatial light modulator or lcvr liquid crystal variable retarder. Universal optical setup for phase shifting and spatialcarrier digital speckle pattern interferometry sijin wu1, mingli dong1, yao fang1 and lianxiang yang1,2 abstract background. Eighth international conference on correlation optics. Psi has existed in its basic form for less than 3 decades, and may be regarded as temporal. This is a phenomenon that occurs when coherent light. A digital speckle pattern interferometer was built utilizing a 100 x 100 element reticon diode array interfaced to an hp9836c desktop computer. Electronic speckle pattern interferometry espi is an optical technique which enables interferometric measurements of surface displacements on almost any surface and material. However, for a computer to analyze this information. The method here enables the measurement of phase distributions corresponding to the difference in displacements of two nominally identical specimens subjected to similar common rotation steps.
Development of matlab filtering techniques in digital. Phaseshifting interferometry overcomes these limitations. A phaseshifting algorithm, called a 4,4 algorithm, which takes four phaseshifting interferograms before a specimen is deformed and four interferograms after a specimen is deformed, is presented first. Optical interferometry is beneficial to measure 3d surface profiles of specimens as one of the nondestructive measurement techniques.
Offering a compact size, integrated drive electronics, and vibrationless speckle reduction, optotune laser speckle reducers are ideal for beam homogenization, 3d scanning, metrology. This article is brought to you for free and open access by the centre for industrial and engineering optics at email protected it has been accepted for inclusion in articles by an authorized administrator of email protected for more. A matlab software is developed for image acquisition and phase data calculations that yield the outofplane surface deformation caused by the bolt preload. Mar 01, 2005 in this study, phase shifting speckle interferometry techniques were adapted for measuring the strain and elastic modulus of small, millimetersized, wet dentin samples loaded in compression. This is done by applying phaseshifting techniques to speckle interferometry, which will quantitatively determine the phase of doubleexposure. Electronic speckle pattern interferometry espi is a wellknown application of the speckle effect. Digital holography dh is usually free of misinterpretation, but when an expression like imageplane digital. A simple phaseshifting lateral shearing interferometer.
Phase shifting speckle interferometry katherine creath speckle patterns have high frequency phase data, which make it difficult to find the absolute phase of a sin. A phaseunwrapping algorithm can be used to retrieve. Recent developments and applications in electronic speckle. Speckle interferometry for displacement measurement and hybrid stress analysis 151 the speckle pattern contains lots of noise and th e noise must be filtered out before the phase unwrapping process. This would also reduce many of the errors inherent in espi. Derivation of algorithms for phaseshifting interferometry using the concept of a datasampling window. For miniature screw applications, however, a plastic joint is used. Second, measurements can be taken at every element in the photodetector array directly yielding optical pathlength differences on a. First, phaseshifting interferometry does not rely on. Two partially reflective glass plates are used to introduce the shear in this new interferometer. Unlike usual methods, it estimates almost noisefree phase values directly from the distributions of the intensity differences of four interference patterns by a leastsquares fit. Speckle patterns have high frequency phase data, which make it difficult to find the absolute phase of a single speckle pattern.
Development of matlab filtering techniques in digital speckle. Singleshot imaging of twowavelength spatial phaseshifting. For a finite number of recorded interferograms, the individual. In that case the mean speckle size approximately equals the pixel size of the ccd or cmossensor. Measurements with electronicdigital speckle pattern interferometry espidspi gives object surface deformation, displacement, slope, etc.
This is done by applying phaseshifting techniques to speckle interferometry, which will quantitatively determine the phase of doubleexposure speckle measurements. Spatial versus temporal phase shifting in electronic speckle. Interferometry is an important investigative technique in the fields of astronomy, fiber optics, engineering metrology, optical metrology, oceanography, seismology, spectroscopy and its. On the basis of an analysis of the noise in sawtooth fringes a figure of merit is defined and measured for various inplane and outofplane sensitive electronic specklepattern interferometry configurations.
Phase shifting interferometry overcomes these limitations by not relying on finding fringe centers, but rather by collecting intensity data from every point of the ccd image sensor. Phase shifting speckle interferometry for determination of. A singlemode optical fiber mounted in the center of the systems aperture stop creates a sphericalwave reference beam. The paper presents an algorithm able to retrieve the phase in speckle interferometry by a single intensity pattern acquired in a deformed state, provided that the integrated speckle field is resolved in the reference condition in terms of mean intensity, modulation amplitude and phase. The reflection coefficients of the coatings were 0. The methods reported in literature have some limitations in respect to the experimental setup. Electronic speckle pattern interferometry espi is a wholefield noncontact optical metrology technique for displacement measurement, based on the optical physics of surfacegenerated laser speckle. Phaseshifting interferometry psi method has drawn much attention in many areas of applications because of its high precision in optical measurements1, 2. Phase shifting speckle interferometry with nematic liquid. Automated fringe pattern analysis in experimental mechanics. Phase algorithm integrating directcorrelation and four.
Phase algorithm integrating directcorrelation and fourstep. Phaseshifting interferometry avoids the need to track. Noise attached in the interference fringes can have catastrophic effects on. Phaseshifting interferometry for determining optical surface. Digital speckle pattern interferometry dspi is a competitive optical tool for fullfield deformation measurement. Phaseshifting speckle interferometry katherine creath speckle patterns have high frequency phase data, which make it difficult to find the absolute phase of a sin. High speed phaseshifted speckle pattern interferometry for. Image processing of uniform objects and modified apertures was outlined 10 14.
This paper reports on the application of phase shifting interferometry to digital speckle interferometry. Despite considerable technical challenges, the measurements were performed on samples that were fully immersed in water. A novel optical method for realtime control of bolt. Iv 28 jan 2020 variational phase recovering without phase unwrapping in phaseshifting interferometry ricardo legardasaenza, alejandro tellez quinonesb, carlos britoloezaa. A phaseshifting dynamic speckle interferometry system which allows the recording of a sequence of interferograms at a frequency of 1 khz was recently developed. An interferogram contains an enormous amount of information. Measurement principles of espi dantec dynamics precision. A method for accurately measuring information about the deformation of a rough surface object using a phaseshifting speckle interferometer with a television camera and a computer is considered.
It is apparent that, increasing the deformation, the speckle decorrelation causes nodata points and the deformation map assumes the typical aspect of riddled sheet. Both speckle interferometry and shear speckle interferometry allow electronic detection with phase shifting and automation with enhanced accuracy is possible. Traditionally, interferograms were measured by locating the center of a fringe and then tracing along the fringe. Apr 22, 2008 nematic liquid crystals valves lclv are also called slm spatial light modulator or lcvr liquid crystal variable retarder. A reliability test was performed by subtracting two phase maps taken digital phaseshifting speckle interferometry 239. Polarization phase shifting shearography for optical metrological applications hence, it is necessary to differentiate the slope data to obtain curvature information. Polarization phase shifting shearography for optical. Digital speckle pattern interferometry and related techniques.
While speckle seams to be the standard, im happy to use other systems as well, but dont have easy access to lasers etc. Osa phase shifting speckle interferometry for dynamic. Use of spatial phase shifting technique in digital speckle. Speckle interferometry is a highly sensitive tool used for making fullfield, noncontact measurements of surface properties at the microscale. Leastsquares fitting of the phase map obtained in phase. This is done by applying phase shifting techniques to speckle interferometry, which will quantitatively determine the phase of doubleexposure speckle measurements. This method utilizes the temporal domain to collect a series of interferograms by adjusting the phase of the reference beam. It can be used to measure surface displacement 2 and related parameters including dis1, placement derivative 3, strain 45, shape and slope 6, 7, curvature and twist 8, and vibration 10. If collimated light is used for illumination and a telecentric imaging system is used, or the camera is far enough, the sensitivity vector is always radial and with. A phase unwrapping algorithm can be used to retrieve. High speed phaseshifted speckle pattern interferometry. Speckle interferometry for displacement measurement and. Phaseshifting interferometry for determining optical.
32 1173 262 591 450 256 665 557 362 782 1444 1583 515 1442 529 272 1237 689 1290 1149 435 614 680 405 895 211 982 820 818 179 409 1403 1266 926