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PROF. GERD HÄUSLER   Telephon +49 9131 85 28382
Flying Triangulation (FlyTri)
3D-Microscopy: Structured-Illumination Microscopy and Microdeflectometry
Phase-measuring deflectometry (PMD)
 Flying Triangulation (FlyTri)

With Flying Triangulation we can measure the 3D topography of an object surface “on the fly”. Fields of application are twofold: On the one hand, measurements of complex or large objects such as sculptures or rooms, which require an excessive repositioning of the sensor. on the other hand, measurements of faces, teeth, or other body parts, where an uncontrolled motion of the object relative to the sensor is unavoidable.

FlyTri enables a motion-robust and freely hand-guided acquisition of objects by combining a simple sensor with complex algorithms. With a measurement uncertainty of 30 µm on a volume of measurement of 20 mm x 15 mm x 15 mm the sensor works at the physical limits. The sensor is scalable, from a measurement of teeth to an acquisition of large rooms.

further information:
related papers
Introductory review on ‘Flying Triangulation’: a motion-robust optical 3D measurement principle | 2014
Robust pattern indexing methods for „Flying Triangulation“ | 2012
Medical Applications enabled by a motion-robust optical 3D sensor | 2012
Calibration of "Flying Traingulation" | 2012
Sparse Active Triangulation Grids for Respiratory Motion Management | 2012
Marker-less Reconstruction of Dense 4-D Surface Motion Fields using Active Laser Triangulation for Respiratory Motion Management | 2012
Options and limitations of "Flying Triangulation" | 2011
Optimized data processing for an optical 3D sensor based on Flying Triangulation | 2013
Single-shot 3D sensing with improved data density | 2014
Hand – guided 3D surface acquisition by combining simple light sectioning with real-time algorithms | 2014
Flying Triangulation – Towards the 3D Movie Camera | 2014
Consequences of EEG electrode position error on ultimate beamformer source reconstruction performance | 2014
Management of head motion during MEG recordings with Flying Triangulation | 2013
Improved EEG source localization employing 3D sensing by "Flying Triangulation" | 2013
Joint Surface Reconstruction and 4-D Deformation Estimation from Sparse Data and Prior Knowledge for Marker-Less Respiratory Motion Tracking | 2013
Flying Triangulation - A Motion-Robust Optical 3D Sensor For The Real-Time Shape Acquisition Of Complex Objects | 2013
3D body scanning with "Flying Triangulation" | 2011
“Flying Triangulation”: A motion-robust optical 3D sensor principle | 2009
Detection and correction of line indexing ambiguities in Flying Triangulation | 2013
"Flying Triangulation" - a new optical 3D sensor enabling the acquisition of surfaces by freehand motion | 2009
A new registration method to robustly align a series of sparse 3D data | 2009
Flying triangulation—an optical 3D sensor for the motion-robust acquisition of complex objects | 2012
3D face scanning with "Flying Triangulation" | 2010
How precise is "Flying Triangulation" | 2010
"Flying Triangulation" – Acquiring the 360° Topography of the Human Body on the Fly | 2010
A 3D-Sensor for intraoral metrology | 2009
 3D-Microscopy: Structured-Illumination Microscopy and Microdeflectometry

We work on information-theoretically efficient full-field sensors for the inspection of technical surfaces with a depth sensitivity at the nanometer scale. The sensors use spatially and temporally incoherent illumination, are not based on interferometry and have no confocal pinholes.

Structured-Illumination Microscopy (SIM): A sinusoidal grating is projected in the focal plane of the microscope. By local contrast evaluation, SIM delivers the 3D-topography of smooth surfaces with a depth uncertainty of a few nanometers. At rough surfaces, the principally achievable uncertainty is determined by speckle noise and depends on the aperture (as in all triangulation systems).

Microdeflectometry (µPMD): A sinusoidal grating is projected by the micro-objective at a remote distance from the focal plane. The specular (smooth) object is located at the focal plane. A local tilt will cause a local phase shift of the grating mirror image. So this phase shift intrinsically encodes the local slope of the object. This unique feature makes the sensor the proper tool to measure local defects. Height variations in the order of one nanometer can be detected, with simple hardware.

Both sensors exploit the same technology, so they can easily be combined in one single microscope. The low noise, the high angular dynamic range, and the high depth of field allow for microscopic images with a quality similar to SEM images - with the further advantage to display quantitative 3D-data.

related papers
Structured-illumination microscopy on technical surfaces: 3D metrology with nanometer sensitivity | 2011
Full-field macroscopic measurement of specular, curved surfaces with SIM | 2011
Fast acquisition of 3D-data with Structured Illumination Microscopy | 2011
Microdeflectometry and Structured Illumination Microscopy – New Tools for 3D-Metrology at Nanometer Scale | 2010
Tuning Structured Illumination Microscopy (SIM) for the Inspection of Micro Optical Components | 2010
Information efficient and accurate Structured Illumination Microscopy (SIM) | 2010
3D-microscopy with large depth of field | 2009
Microdeflectometry in transmission | 2009
Microdeflectometry—a novel tool to acquire three-dimensional microtopography with nanometer height resolution | 2008
 Phase-measuring deflectometry (PMD)

With phase-measuring deflectometry we are able to measure the slope - and by numerical integration the topography - of reflecting surfaces. We project fringes on a ground glass screen and observe the pattern, using the object as a mirror. Any slope deviations of the object lead to distortions of the fringe pattern observed by the camera.
To calculate the local curvature of aspheric lenses, we measure the slope of the surface and calculate the first derivative. This process is much less noise sensitive than the evaluation from shape data. The image on the right shows the surface astigmatism of a progressive eyeglass lens, measured with PMD. The curvature maps have an accuracy of better than 0.02D calculated on an area of only 3x3mm².
The method is scalable from large objects like painted car bodies or windscreens, over eyeglass lenses and wafers down to microlenses.

related papers
Deflectometry: 3D-Metrology from Nanometer to Meter | 2009
Deflektometrie macht der Interferometrie Konkurrenz | 2009
Can deflectometry work in presence of parasitic reflections? | 2009
Object tilt - a source of systematic error in transmission deflectometry | 2009
Deflectometric measurement of large mirrors | 2014
Deflectometry vs. interferometry | 2013
New Holistic Self-Calibration Method for Deflectometric Sensors | 2010
Object reconstruction by deflectometry | 2012
Deflectometry for Ultra Precision Machining - Measuring without Rechucking | 2011
Deflektometrische Selbstkalibrierung für spiegelnde Objekte | 2011
Deflectometry challenges interferometry: the competition gets tougher! | 2012
Machine-Integrated Measurement of Specular Free-Formed Surfaces Using Phase-Measuring Deflectometry | 2009
Generalized Hermite interpolation with radial basis functions considering only gradient data | 2007
Phasenmessende Deflektometrie | 2009
Microdeflectometry in transmission | 2009
Measuring the refractive power with deflectometry in transmission | 2008
Sub-micron profilometry on macroscopic free-form surfaces | 2008
Microdeflectometry—a novel tool to acquire three-dimensional microtopography with nanometer height resolution | 2008
Shape reconstruction from gradient data | 2008
Zauberspiegel, Brillengläser und Wasserhähne - alte Probleme neu beleuchtet | 2007
Fast and robust 3D shape reconstruction from gradient data | 2007
Höhe, Neigung oder Krümmung? | 2006
Shape reconstruction of 3d-objects from noisy slope data | 2005
Vision and Modeling of Specular Surfaces | 2005
Full-Field Shape Measurement of Specular Surfaces | 2005
Absolute Phase Measuring Deflectometry | 2004
Absolute Phasenmessende Deflektometrie | 2004
Richtungscodierte Deflektometrie | 2004
Phase Measuring Deflectometry: a new approach to measure specular free-form surfaces | 2004
Measurement of Eye Glasses with Phase Measuring Deflectometry | 2003
Calculating curvatures from discrete slope data | 2003
Metric Calibration of "Phase Measuring Deflectometry" | 2002
Reaching the Physical Limits of Phase Measuring Deflectometry | 2002
Phase Measuring Deflectometry - Simulation of the Sensor | 2001
Physical limits of phase mesuring deflectometry | 2001
Phase Measuring Deflectometry - a new method to measure reflecting surfaces | 2000
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