Pmd even has the potential to challenge interferometry. Covers the basics of frozen fringe, live fringe and time averaged holography is simple geometries. The local slope of the sample is encoded in the deformation of the observed pattern 4. Qualifying parabolic mirrors with deflectometry burke. Deterministic manufacturing of precision freeforms tim lynch, kate medicus, matt brunelle, brian myer, todd blalock, joey lawson, and jessica degroote nelson sbir rights notice dec 2007 these sbir data are furnished with sbir rights under contract nos. Hariharan di y ision of applied physics csiro sydney, australia 2 1. Phase measuring deflectometry is a highly precise and full field metrology technique for specular surfaces based on the distortion of known reference patterns observed as a reflection at the surface under test. Ep2063260a1 fourier transform deflectometry system and. Elimination of parasitic reflections for objects with high.
Quantitative deflectometry challenges interferometry. An iterative optimization calibration method for stereo. Iterative surface construction for blind deflectometry intuitive optical. Canabal 14 proposed a cross fringe pattern for moire deflectometry, with a phaseshift in two directions separately, so some pixels are always modulated with low intensity for one direction.
The method relies on rays leaving a source, being deflected by a uut, and then being recorded by a camera. Quantitative deflectometry is a new tool to measure specular surfaces. Qualifying parabolic mirrors with deflectometry phasemeasuring deflectometry is a fullfield gradient technique that lends itself very well to testing reflective optical surfaces. Principles of interferometry 3 placement of the source now produces much less displacement of the fringe patterns as a fraction of the fringe separation d fig. Uncalibrated deflectometry with a mobile device on extended. Moire deflectometry produces result that appears similar to an interferometry technique, in which the object to be tested either phase object or specular surface is mounted in the course of a collimated beam followed by a pair of transmission gratings placed at a distance from each other. Interferometry can measure the distance of atomic layers and the distance of stars. The intrinsic features of deflectometry incoherence, source encoding, high dynamical range, simplicity, and scalability enable new sensors and unexpected applications. Digital holography and threedimensional imaging, 2009. A trial for a reliable shape measurement using interferometry. In the past, the industrys interest has been focussed mainly on the detection of defects and ripples, since it is easy to achieve sensitivity in the nm range.
Principles of interferometry interferometry primer evolution of solarmass stars eso garching, march 25, 2010 chris haniff astrophysics group, cavendish laboratory, university of cambridge, uk 1. In this paper, we demonstrate the development of a pointcloud metrology method. Typically, liquid crystal displays are employed to provide the required patterns. Interferometry conference paper in proceedings of spie the international society for optical engineering 8788. We will demonstrate that deflectometry is a novel imaging principle with a wide spectrum of new applications. To meet the need of onmachine metrology in optical manufacturing, a compact and snapshot dualmode interferometric system is proposed for surface sha.
Review of phase measuring deflectometry sciencedirect. Pdf threedimensional shape measurements of specular. Two ways of understanding interferometry optics put a mask over an aperture. Pdf phase measuring deflectometry pmd acquires the two components of the local. The spectrum of measurable surfaces ranges from flat to freeform surfaces with steep slopes, with a size ranging from. To combine both results, it should be global, precise and reliable measurement. As motivated in the last paragraph, this occurs when the angular separation is. The major challenges, the existing solutions and the remaining limitations in pmd technique are addressed to provide some suggestions for potential future investigations. A camera observes the image of a sinusoidal grating via reflection at the surface under test. Optical interferometry in astronomy 793 is resolved by an interferometer if the fringe contrast goes to zero at the longest baseline. Pdf fast and accurate deflectometry with crossed fringes. Deflectometry enables to measures the local slope of specularly reflecting objects with high information efficiency. This specifically, because in contrast to interferometry, pmd does not display retrace errors. Request pdf deflectometry challenges interferometry.
Fast and accurate deflectometry with crossed fringes. Quantitative deflectometry challenges interferometry springerlink. Interferometry introduction interferometers are devices employed in the study of interference patterns produced by various light sources. Instantaneous phase shifting deflectometry loft, large optics. The present invention relates to a fourier transform deflectometry system 1 and method for the optical inspection of a phase and amplitude object 2 placed in an optical path between a grating 3 and an imaging system 4, at a distance h of said grating 3. However, in practice, the inspection of specular surfaces imposes special challenges. I will present the concept of combination of interferometry and deflectometry and some preliminary experimental results. Experiment 4 the michelson interferometer 4 3 experiment in the following experiments, you will calibrate the movement of m 1 with the hene laser and use the interferometer to accurately measure. One beam is reflected from the reference mirror, and the other one. Request pdf quantitative deflectometry challenges interferometry phasemeasuring deflectometry pmd has been developed at erlangen to measure spatially resolved slope data of specular. Assuming that the given extended source sodium vapor lamp is monochromatic, use eq. Dynamic metrology and data processing for precision freeform. However, up to now deflectometry has not been considered as a viable competitor to interferometry, especially for the qualification of optical components. Deflectometry rivals interferometry gerd hausler institute of optics, information and photonics maxplanck research group university of erlangennurnberg, germany gerd.
Deflectometry, iterative, blind, freeform, metrology, scots. Deflectometric methods that are capable of providing fullfield topography data for specular freeform. However, the limiting factor is the inherent small dynamic range of nulling interferometry. Nov 14, 2009 deflectometry offers a wide spectrum of applications. The intrinsic features of deflectometryincoherence, source encoding, high dynamical range, simplicity, and scalabilityenable new sensors and unexpected applications. By presenting recent developments and measurement examples from different applications, we will show that deflectometry is now heading to become a serious competitor to interferometry. Damage detection using holography and interferometry. For instance, in process surface measurements could be made with orthodox interferometric null testing. Quantitative rainbow schlieren deflectometry as a temperature diagnostic for spherical flames nasatm2004212955 june 2004 national aeronautics and space administration glenn research center prepared for the 42nd aerospace sciences meeting and exhibit sponsored by the american institute of aeronautics and astronautics reno, nevada, january 5. Principles of interferometry interferometry primer evolution of solarmass stars eso garching, march 25, 2010 chris haniff astrophysics group, cavendish laboratory, university of cambridge, uk 1 march 2010. Request pdf deflectometry challenges interferometry the competition gets tougher. Quantitative rainbow schlieren deflectometry as a temperature.
The spectrum of measurable surfaces ranges from flat to freeform surfaces with steep slopes, with a size ranging from millimeters to several meters. Meanwhile, pmd is well established to control the manufacturing of aspheric eyeglasses. Optical interferometers are the instruments that rely on interference of two or more superimposed re. This could be avoided by introducing an extra nshift for each direction with a. Due to a lack of research, these displays are used without sufficient calibration. The reason is that, despite the unparalleled local sensitivity provided by deflectometric methods, the global height accuracy attainable with this measurement technique used to be limited to several microns over a field of 100 mm. Astrophysics group, cavendish laboratory, university of. Compact snapshot dualmode interferometric system for on. Improving the calibration of phase measuring deflectometry by. Hausler, deflectometry challenges interferometrythe competition gets tougher. The smaller the slit separation, the larger the source size that can be probed using interferometry. These are one of the most common optical tools, that are used for precision measurements, surface diagnostics, astrophysics, seismology, quantum information, etc. Alternatively, deflectometry is a nonnull test method which has been shown to provide surface metrology accuracy similar to commercial interferometry systems for freeform optics 7,1012.
The reason is that, despite the unparalleled local sensitivity provided by deflectometric methods, the global height accuracy attainable with this measurement technique used to be limited to. Use the instructors help to align the interferometer. Pointcloud noncontact metrology of freeform optical surfaces jianing yao, alexander anderson, and jannick p. Decker national aeronautics and space administration glenn research center cleveland, ohio 445 1. The intrinsic features of deflectometry made this technique popular over the last years 1, 2, 3.
Deflectometry challenges interferometry the competition. N68936 15 c 0018, n6893616c0020, n6893615c0011, and n6893616c0017. They are conveniently divided into two main classes. Abstract as a low cost, fullfield threedimensional shape measurement technique with high dynamic range, phase measuring deflectometry pmd has been studied and improved to. Introduction some major goals of structural testing are the detection of local damage and, more recently, the general evaluation of structural health. Pointcloud noncontact metrology of freeform optical surfaces. Deflectometric methods that are capable of providing fullfield topography data for specular freeform surfaces have been around for more than a decade.
It is possible to measure structures quantitatively in the nanometer regime. Deflectometry for the inspection of specular surfaces for surfaces used in the manufacturing industry or surfaces which just need to look good, such as, e. Phase measuring deflectometry pmd 1 has been used to measure specular reflective surfaces such as eye glasses or wafers 3. Phase measuring deflectometry pmd is one of the optical 3d. Phasemeasuring deflectometry pmd has been developed at erlangen to measure spatially resolved slope data of specular surfaces 1, 2 and 3. In interferometry, only a small area can be measured, which is almost parallel to the reference surface. Principles and theory of radar interferometry september 19, 2004 igarss 04 tutorials paul a rosen jet propulsion laboratory ieee is an authorized ceu provider of the international association for continuing education and training. Deflectometry challenges interferometry the competition gets tougher. Similar to interferometry, phase measuring deflectometry pmd was proposed primarily for specular surfaces 3 4 5, but different from interferometry, pmd is an incoherent method with a capability of providing fullfield topography data for freeform surfaces 6. Damage detection using holography and interferometry arthur j. Time averaged holography a p p l i e d o p tic s g r o u p d e p a r t ment o f p h y s i c. We will discuss deflectometry from the physicists and from the information theoretical point of view.
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