The spectrum of measurable surfaces ranges from flat to freeform surfaces with steep slopes, with a size ranging from millimeters to several meters. Deflectometry rivals interferometry gerd hausler institute of optics, information and photonics maxplanck research group university of erlangennurnberg, germany gerd. Deflectometric methods that are capable of providing fullfield topography data for specular freeform. Deflectometry enables to measures the local slope of specularly reflecting objects with high information efficiency. They are conveniently divided into two main classes. 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. Hausler, deflectometry challenges interferometrythe competition gets tougher.
Deflectometry, iterative, blind, freeform, metrology, scots. 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. The intrinsic features of deflectometry made this technique popular over the last years 1, 2, 3. Quantitative rainbow schlieren deflectometry as a temperature. Compact snapshot dualmode interferometric system for on. 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. 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. We will demonstrate that deflectometry is a novel imaging principle with a wide spectrum of new applications. The local slope of the sample is encoded in the deformation of the observed pattern 4. Damage detection using holography and interferometry. The intrinsic features of deflectometry incoherence, source encoding, high dynamical range, simplicity, and scalability enable new sensors and unexpected applications. An iterative optimization calibration method for stereo.
Fast and accurate deflectometry with crossed fringes. Interferometry can measure the distance of atomic layers and the distance of stars. Meanwhile, pmd is well established to control the manufacturing of aspheric eyeglasses. These are one of the most common optical tools, that are used for precision measurements, surface diagnostics, astrophysics, seismology, quantum information, etc. Phase measuring deflectometry pmd 1 has been used to measure specular reflective surfaces such as eye glasses or wafers 3. Deflectometry challenges interferometry the competition. Abstract as a low cost, fullfield threedimensional shape measurement technique with high dynamic range, phase measuring deflectometry pmd has been studied and improved to. The spectrum of measurable surfaces ranges from flat to freeform surfaces with steep slopes, with a size ranging from. Typically, liquid crystal displays are employed to provide the required patterns. Pointcloud noncontact metrology of freeform optical surfaces. Ep2063260a1 fourier transform deflectometry system and. Quantitative deflectometry is a new tool to measure specular surfaces.
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. As motivated in the last paragraph, this occurs when the angular separation is. 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. Dynamic metrology and data processing for precision freeform. 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.
Review of phase measuring deflectometry sciencedirect. Request pdf deflectometry challenges interferometry. Use the instructors help to align the interferometer. Phase measuring deflectometry pmd is one of the optical 3d. 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. Uncalibrated deflectometry with a mobile device on extended. Phasemeasuring deflectometry pmd has been developed at erlangen to measure spatially resolved slope data of specular surfaces 1, 2 and 3. 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. Qualifying parabolic mirrors with deflectometry phasemeasuring deflectometry is a fullfield gradient technique that lends itself very well to testing reflective optical surfaces.
The method relies on rays leaving a source, being deflected by a uut, and then being recorded by a camera. 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. 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. Damage detection using holography and interferometry arthur j. For instance, in process surface measurements could be made with orthodox interferometric null testing. The smaller the slit separation, the larger the source size that can be probed using interferometry. Request pdf quantitative deflectometry challenges interferometry phasemeasuring deflectometry pmd has been developed at erlangen to measure spatially resolved slope data of specular. The intrinsic features of deflectometryincoherence, source encoding, high dynamical range, simplicity, and scalabilityenable new sensors and unexpected applications. Two ways of understanding interferometry optics put a mask over an aperture. 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. To combine both results, it should be global, precise and reliable measurement. Due to a lack of research, these displays are used without sufficient calibration. I will present the concept of combination of interferometry and deflectometry and some preliminary experimental results.
Pmd even has the potential to challenge interferometry. Astrophysics group, cavendish laboratory, university of. This specifically, because in contrast to interferometry, pmd does not display retrace errors. 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.
Quantitative deflectometry challenges interferometry. Deflectometric methods that are capable of providing fullfield topography data for specular freeform surfaces have been around for more than a decade. Interferometry conference paper in proceedings of spie the international society for optical engineering 8788. We will discuss deflectometry from the physicists and from the information theoretical point of view. However, in practice, the inspection of specular surfaces imposes special challenges. Covers the basics of frozen fringe, live fringe and time averaged holography is simple geometries. Decker national aeronautics and space administration glenn research center cleveland, ohio 445 1.
It is possible to measure structures quantitatively in the nanometer regime. In interferometry, only a small area can be measured, which is almost parallel to the reference surface. However, up to now deflectometry has not been considered as a viable competitor to interferometry, especially for the qualification of optical components. Pointcloud noncontact metrology of freeform optical surfaces jianing yao, alexander anderson, and jannick p. 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. In this paper, we demonstrate the development of a pointcloud metrology method. A trial for a reliable shape measurement using interferometry.
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. Elimination of parasitic reflections for objects with high. Introduction some major goals of structural testing are the detection of local damage and, more recently, the general evaluation of structural health. However, the limiting factor is the inherent small dynamic range of nulling interferometry. To meet the need of onmachine metrology in optical manufacturing, a compact and snapshot dualmode interferometric system is proposed for surface sha. Pdf threedimensional shape measurements of specular. N68936 15 c 0018, n6893616c0020, n6893615c0011, and n6893616c0017. Quantitative deflectometry challenges interferometry springerlink. Deflectometry challenges interferometry the competition gets tougher. One beam is reflected from the reference mirror, and the other one. The major challenges, the existing solutions and the remaining limitations in pmd technique are addressed to provide some suggestions for potential future investigations. Qualifying parabolic mirrors with deflectometry burke. Digital holography and threedimensional imaging, 2009.
Request pdf deflectometry challenges interferometry the competition gets tougher. A camera observes the image of a sinusoidal grating via reflection at the surface under test. Instantaneous phase shifting deflectometry loft, large optics. Optical interferometry in astronomy 793 is resolved by an interferometer if the fringe contrast goes to zero at the longest baseline. Optical interferometers are the instruments that rely on interference of two or more superimposed re. Assuming that the given extended source sodium vapor lamp is monochromatic, use eq. This could be avoided by introducing an extra nshift for each direction with a. Pdf fast and accurate deflectometry with crossed fringes.
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. Improving the calibration of phase measuring deflectometry by. 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. Iterative surface construction for blind deflectometry intuitive optical. Hariharan di y ision of applied physics csiro sydney, australia 2 1.
1435 502 270 1353 889 678 1180 1113 491 1131 1012 1594 424 1186 1207 754 172 1171 320 540 1463 1533 414 11 533 813 948 753 997 1602 409 1464 1118 1544 1284 1127 770 466 1350 22 1206 1259