The approach that requires least number of projection patterns is the standard ftp approach which extracts phase information within a singleshot fringe image. When interference fringes are very closely spaced, the phase data contain high frequencies where 2p ambiguities cannot be resolved. Wyant this paper describes a method to enhance the capability of two wavelength phase shifting interferometry. In order to capture multiple interference fringe patterns with different wavelengths simultaneously, we propose a threewavelength imaging system that uses three leds and a color camera. In this paper, the white light source, with a singlechip ccd color camera, is used to accomplish multiwavelength phaseshifting. Due to the short wavelength of the light, the sensitivity of a single wavelength interferometric measurement is very high.
Conventional multi wavelength phase shifting interferometry utilizes two or three monochromatic light sources, such as lasers, to realize the measurement of the surface topography with large discontinuity. Phaseshifting interferometry overcomes these limitations. Newbury, and leo hollberg cavitymode wavelengths in air are determined by measuring a lasers frequency while it is locked to the mode in vacuum during a calibration step and subsequently correcting the mode wavelength for atmo. Absolute length measurement using multiplewavelength phase. Multiplewavelength interferometry enables an increase in the range of nonambiguity and a reduction in the sensitivity of classical interferometry. The technique of wavelength scanning and a special measurement. Wavefront reconstruction in phaseshifting interferometry via sparse coding of amplitude and absolute phase v. The conventional interferometric surface profilers using a single wavelength offer excellent vertical resolution, but a serious limitation to their use is that they. First, phaseshifting interferometry does not rely on. Beside, special phase shifts are required in xus method. Download pdf twowavelength holography and phaseshifting interferometry are combined to measure the phase contours of deep wavefronts and surfaces, such as those produced by aspherics, with a variable sensitivity. Digital multiple wavelength phase shifting algorithm song zhang department of mechanical engineering, iowa state university, ames, ia, usa 50011. This paper describes a method to enhance the capability of twowavelength phaseshifting interferometry. Based on the twowavelength interferometric principle and spatial phaseshifting technique using a polarization pixelated camera, the proposed system can not only rapidly measure the phase, but also overcome the 2.
Scanning interferometry a dissertation submitted to the. Phaseshifting interferometry records multiple interferograms with different values of f. Robust phase shifting interferometry resistant to multiple disturbances qian liu, xiaobin yue, lulu li, hui zhang and jianguo he institute of machinery manufacturing technology, china academy of engineering physics, 64th mianshan. Phase shifting interferometry is a wellestablished technique for areal surface characterisation that relies on digitisation of interference data acquired during a controlled phase shift, most often introduced by controlled mechanical oscillation of an interference objective. Robust phaseshifting interferometry resistant to multiple. The addition of electronics, computers, and software to interferometry has enabled enormous improvements to optical metrology.
Other important capabilities include measurement of optical material homogeneity and. Optomechanical properties of ptfe fibres using phase. Phase eclipsing causes ambiguous results due to antenna spacing and wavelength. In simultaneous multiwavelength phaseshifting interferometry, we propose a novel frequency domain phase retrieval fdpr algorithm. Frequency domain phase retrieval of simultaneous multi. Experiments have been performed using a linear detector array to measure surface height of an offaxis parabola. Pdf multiwavelength phaseshifting interferometry for micro. Multiple wavelength interferometry which is the standard technique for measuring relative gauge block lengths has been used to measure the. Phase shifting interferometry psi method is used to determine the phase distribution encoded in an interfero. By introducing the phase data of a third wavelength, one can. Verifire mst laser interferometer system for multiple. Wyant, twowavelength phase shifting interferometry, appl.
Extended depthrange dual wavelength interferometry based on iterativetwosteptemporalphaseunwrapping minminwanga,canlinzhoua,shuchunsia,xiaoleilib,zhenkun leic,yanjielid. This paper describes a method to enhance the capability of two wavelength phase shifting interferometry. Conventional multiwavelength phaseshifting interferometry utilizes two or three monochromatic light sources, such as lasers, to realize the measurement of the surface topography with large discontinuity. Temporal phase shifting algorithm, which requires a phase shifter such as pzt, has been widely used for accurate phase evolution in interferometry. This paper describes a technique that combines ideas of phase shifting interferometry psi and two wavelength interferometry twli to extend the phase measurement range of conventional single wavelength psi. A similar system for threewavelength phaseshifting interferometry reported by.
Multiwavelength phaseshifting interferometry for micro. Us20060146340a1 simultaneous phase shifting module for. This paper describes a method to enhance the capability of. The projected phaseshifted fringe images have wavelengths of k w. Wavelength references for interferometry in air richard w. In this investigation, we propose an effective method to measure 3d surface profiles of specimens with singleshot imaging. Superfast multifrequency phaseshifting technique with.
Bioucasdias2 1department of signal processing, technology university of tampere, finland. A 5position phasestepping algorithm is used which involves moving the reference mirror in 5 steps of size. I show how phase shifting interferometry can be extended to account for multiple interference effects using a fourier based analysis technique combined with wavelength tuning and a particular foursurface interferometer geometry. Aug 11, 2008 interferometry is a well established technique for surface profiling. Interferometry is a well established technique for surface profiling. Us5907404a multiple wavelength image plane interferometry.
The surface is effectively tested at a synthesized equivalent wavelength xeq. Step height measurement using twowavelength phaseshifting. Measure multiple surfaces with a single measurement. Robust phaseshifting interferometry resistant to multiple disturbances qian liu, xiaobin yue, lulu li, hui zhang and jianguo he institute of machinery manufacturing technology, china academy of engineering physics, 64th mianshan. Multiwavelength digital holography and phaseshifting. The conventional interferometric surface profilers using a single wavelength offer excellent vertical resolution, but a serious limitation to their use is that they can only handle smooth profiles and step heights less than half a wavelength. A backend assembly for use with a frontend assembly in acquiring phase shifted interferograms having a plurality of imaging modules ma, mb, mc. Wavefront reconstruction in phaseshifting interferometry. Additionally, the system of equations needed to obtain a multiwavelength 3d image is solved with less wavelengthmultiplexed images using twostep phaseshifting interferometrymerged phasedivision multiplexing 2. For the wave front being measured the optical path difference between. To verify theoretical predictions, experiments have been performed using a solidstate linear detector array to measure 1d surface heights. This combination of psi and syntheticwavelengths gives multiplewavelength phase shifting interferometry the advantages of. In simultaneous multi wavelength phase shifting interferometry, we propose a novel frequency domain phase retrieval fdpr algorithm.
Deck zygo corporation, laurel brook road, middlefield, ct. Applications of higherorder phase shifting algorithms for. Absolute length measurement using multiplewavelength. Step height measurement using twowavelength phaseshifting interferometry, appl. By introducing the phase data of a third wavelength, one can measure the phase of a very steep wave front. A backend assembly for use with a frontend assembly in acquiring phaseshifted interferograms, comprising. Phaseshifting interferometry is used for getting data into a computer so the data can be analyzed 2 9. Wyant we describe a method that combines phaseshifting and coherencepeaksensing techniques to permit measurements with the height resolution of phaseshifting interferometry without the intervalslope. Second, measurements can be taken at every element in the photodetector array directly yielding optical pathlength differences on a regularly spaced grid. Us20060146340a1 simultaneous phase shifting module for use. Wyant this paper describes a technique that combines ideas of phase shifting interferometry psi and two wavelength interferometry twli to extend the phase measurement range of conventional single wavelength psi. Phaseshifting interferometry for determining optical. Singleshot imaging of twowavelength spatial phaseshifting.
Multiple wavelength interferometry enables an increase in the range of nonambiguity and a reduction in the sensitivity of classical interferometry. Osa multiplewavelength phaseshifting interferometry. Multiplesurface interference fringes analysis basing on wavelengthmodulated phase shifting interferometry. Multiplewavelength phaseshifting interferometry osa. Multiple wavelength interferometry for surface profiling. Digital multiple wavelength phase shifting algorithm. 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. Two wavelength phase shifting interferometry yeouyen cheng and james c. Scanning interferometry a dissertation submitted to.
For the last several years there has been much interest. These technologies set it apart from all others, making it wellsuited for the most challenging applications, such as the measurement of planeparallel optical components where multiple reflections often confuse traditional phase shifting interferometers. Phase shifting interferometry is a wellestablished technique for areal. The surface is effectively tested at a synthesized equivalent. An extension of the static technique to realtime dynamic testing is proposed and an operational variablesensitivity interferometer utilizing the realtime technique is described. A toolbox for designing and analyzing phaseshifting. Pdf conventional multiwavelength phaseshifting interferometry utilizes two or three monochromatic light sources, such as lasers, to realize.
Multiplewavelength phaseshifting interferometry semantic scholar. It is the only commercial interferometer system that can measure multiple surfaces with a single measurement. Synthesis of single wavelength temporal phase shifting algorithms psa for interferometry is wellknown and firmly based on the frequency transfer function ftf paradigm. Extended depthrange dualwavelength interferometry based on. Extended depthrange dualwavelength interferometry based on iterativetwosteptemporalphaseunwrapping. Synthesis of singlewavelength temporal phaseshifting algorithms psa for interferometry is wellknown and firmly based on the frequency transfer function ftf paradigm. On the other hand, multiwavelength interferometry has been approached with the techniques of wavelength scanning 6,7 and synthetic.
The digital detection with linear ccd array detectors and computer processing of interferometric irradiance maps fringes has enabled phase measurements with uncertainties close to 2. Wyant this paper describes a technique that combines ideas of phase shifting interferometry psi and two wavelength interferometry twli to extend the phase measurement range of conventional singlewavelength psi. Each module ma, mb, mc has a quarter wave plate 30 a, 30 b, 30 c, a polarizer 32 a, 32 b, 32 c, and an image sensor 34 a, 34 b, 34 c so that each polarizer has a different rotation orientation thus acquiring phase shifted. In the light of these problems, an extended depthrange dualwavelength phaseshifting interferometry is.
Motioninduced error reduction by combining fourier. Image processing of corona virus using interferometry. Twowavelength phase shifting interferometry university of arizona. Step height measurement using twowavelength phaseshifting interferometry katherine creath twowavelength phaseshifting interferometry is applied to an interference phasemeasuring microscope enabling the measurement of step features.
Wyant this paper describes a technique that combines ideas of phase shifting interferometry psi and two wave length interferometry twli to extend the phase measurement range of conventional singlewavelength psi. Fourier transform profilometry with phaseshifting profilometry beiwen li. Phaseshifting interferometry for determining optical surface. Wyant this paper describes a method to enhance the capability of twowavelength phaseshifting interferometry. First, using only a onetime phase shifting operation, a sequence of simultaneous multi wavelength phase shifting interferograms spsmwis are captured by a monochrome chargecoupled device. Multiplewavelength phaseshifting interferometry yeouyen cheng and james c. Phase interferometry direction finding wpi advisors. In order to capture multiple interference fringe patterns with different wavelengths simultaneously, we propose a three wavelength imaging system that uses three leds and a color camera. Measurements using fourier transform phase shifting. Multiple wavelength interferometry for surface profiling multiple wavelength interferometry for surface profiling paul kumar, u.
Improved verticalscanning interferometry akiko harasaki, joanna schmit, and james c. Full refereed journal article pdf postscript references in the article citations to the article 102 citation history refereed citations to the article reads history translate this page. First, using only a onetime phaseshifting operation, a sequence of simultaneous multiwavelength phaseshifting interferograms spsmwis are captured by a monochrome chargecoupled device. The method of dualmultiple wavelength simultaneous capture fig. I show how phase shifting interferometry can be extended to account for multiple interference effects using a fourier based analysis technique combined with wavelength tuning and a particular four. Dualwavelength simultaneous phaseshifting interferometry. Wyant we describe a method that combines phase shifting and coherencepeaksensing techniques to permit measurements with the height resolution of phase shifting interferometry without the intervalslope. The conventional interferometric surface profilers using a single wavelength offer excellent vertical resolution, but a serious limitation to their use is that they can only handle smooth profiles and step heights less than half a. While fine measurements use dynamic phase shifting techniques or comparators coarse measurements are usually restricted to multiple wavelength interferometry where three wavelengths are used to determine the coarse lengths up to a tolerance of 140 to 300 micrometers. Additional improvements in precision may be provided by using a wavelength calibration device such as an etalon, a wavemeter, or a reference cell having relatively narrow transmission peaks, to improve the accuracy in determining the laser wavelengths. In order to measure the fringe fractions with sufficient accuracy, phase stepping interferometry is used to measure the fractions in terms of the phase difference between the reference and measurement beams. Multiple wavelength phase shifting interferometry yeouyen cheng and james c. Motioninduced error reduction by combining fourier transform. Multiplewavelength interferometry for absolute distance.
Abstract this paper presents a digital multiplewavelength phaseshifting technique for threedimensional shape measurement. The projected phase shifted fringe images have wavelengths of k w. This combination of psi and syntheticwavelengths gives multiple wavelength phase shifting interferometry the advantages of. Twowavelength phase shifting interferometry yeouyen cheng and james c. The accuracy depends on the stability and the calibration of the different wavelengths.
Superfast multifrequency phaseshifting technique with optimal pulse width. The system uses multiple wavelength interferometry to provide range information for an object. Ted clancy germano iannacchione george heineman group 108 staff. 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. Threestep phase shifting algorithm phase shifting algorithms are widely used in optical metrology because of their measurement speed and accuracy 7. Aug 10, 2008 the approaches adopted to overcome the problem of small dynamic range are based on two wavelength phase shifting interferometry twlpsi 210, multiple wavelength phase shifting interferometry mwlpsi1114, scanning white light interferometry swli1519 and spectrally resolved white light interferometry srwli 2022. I show how the capabilities of phaseshifting interferometry can be extended to address this problem using wavelength tuning techniques. Measurements using fourier transform phase shifting interferometry leslie l. The phase shifter needs to be calibrated at every wavelength if multiple wavelengths are used for measurement, it is a time consuming process. Abstract this paper presents a digital multiple wavelength phase shifting technique for threedimensional shape measurement. The verifire mst multiple surface test laser interferometer system provides high precision measurements of surface form and transmitted wavefront of optical components and lens systems. Two wavelength phase shifting interferometry is applied to an interference phase measuring microscope enabling the measurement of step features. A similar system for three wavelength phase shifting interferometry reported by pfortner and schwider 2003 uses three lasers.
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