Combination of non-destructive test methods for damage documentation of monuments

Transcription

1 Combination of non-destructive test methods for damage documentation of monuments Color & Space in Cultural Heritage (COSCH) WG 2: Spatial object documentation Mainz, Fraunhofer Institute for Factory Operation and Automation (IFF) Magdeburg, Germany

2 outline introduction project overview 3d data acquisition and evaluation 3d object reproduction IR data acquisition and evaluation 3d-IR data fusion current work & summary 1

3 Fraunhofer IFF optical 3d metrology in the production application of 2d and 3d measurement principles industrial in-line systems 40% contract research, 30% industrial joint research, 30% publicly funded research quality assurance in production automotive, railway and aerospace industries digitizing factories and cultural goods core competencies efficient data evaluation methods, data fusion intrinsic / extrinsic multi-sensor calibration 2

4 Measurement and Testing Technology main focus automated 3d data acquisition and inline evaluation automated comparisons against nominal geometries (CAD) state-of-the-art technologies for large data analysis data visualization and logging virtual / augmented reality combined with optical 3d metrology measuring assistance systems for worker support / manual production 3

5 project overview project goals: 2d, 3d and IR measurement of cultural goods documentation of defects over time 3d damage cartography, visualizations geometrical comparisons (deviations over time) 3d digital copies, reproduction locations: Halberstadt and Magdeburg cathedral in collaboration with: BAM Federal Institute for Materials Research and Testing, Berlin IDK Inst. for Diagnosis and Conservation on Monuments in Saxony/Saxony-Anhalt, Halle 4

6 project overview requirements & challenges: 2d-, 3d-, IR data acquisition and fusion high 3d precision <<0.5mm accessibility extraneous light (sun), shadowing effects technologies: 3d measurement arm (Faro Technology) flexible kinematic system (radius: 1.2m) optical triangulation sensor,120 lines/sec d points/line (Fraunhofer IFF) IR-camera 640x480 (Infratec VarioCam) digital camera: Canon EOS 450 D 5

7 3d data acquisition duration: 6 hours (+3h preparation + post-processing) object dimension: ~1700mm x 600mm 3d points: ~242mio. 3d uncertainty: < 80μm outlier removal homogenization: 0.5mm triangles: ~14mio. statue in the Magdeburg cathedral 6

8 3d reproduction real & digital conservation of the statue contactless and more precise alternative to plaster casts rapid prototyping, 3D printing/ sintering original photograph digital 3D reconstruction 3D print reconstruction 7

9 Combination of non-destructive test methods quality of reproductions comparison and geometric differences between 3D scan vs. reproductions plaster cast: multiple segments + grinding = higher deviations 3D scan vs. 3D print 3D scan vs. plaster cast mm 8

10 thermography active/impulse thermography: fan heater, halogen lamps, flash lights observing the cooling reaction test setup: IR-camera/lens: VarioCam / 30 mm (interchangeable lens) object distance: 1.81 m heating time: 1 min. measuring time: 1.5 min resolution: 1.5mm / pixel 9

11 comparison: 3D data und thermograms plates, porous regions and loose plates become visible observation over time June 2009 March mm 10

12 data fusion mutual verification and assistance of 3D and IR data intrinsic IR sensor calibration with checker board 2D-3D mapping using implicit landmarks surface damages can be detected, measured and visualized IR data and 3D data correlate! pewter plates for calibration 3d mapping and difference mapping of thermograms. 11

13 case study: Madonna with child (Halberstadt cathedral) texture, 3d model and thermogram of head and hand regions. 12

14 current work 800 years old plaster grooves at the Magdeburg cathedral 2d and 3d measurement optical stereo sensor resolution: 1628 x 1236 px² meas. field: 140 x 120 mm² visualization and emphasis of structures restoration Capturing and visualizing plaster grooves. 13

15 summary scanning with measurement arm and 3d laser triangulation capturing geometric damages reproducing physical copies with high precision thermography for defects underneath the surface capturing cavities / hollow areas data fusion to combine 3d and IR data current work: measuring plaster grooves future work: 3d cartography of deformations with high time resolution 14

16 contact phone: Fraunhofer Institute for Factory Operation and Automation IFF Business Unit of Measurement and Testing Technology Sandtorstrasse 22, Magdeburg, Germany 15