Manufacturing Metrology Team
1
Manufacturing Metrology Team ComparaƟve study of cost effecƟve laser and DLP projectors for fringe projecƟon Amrozia Shaheen 1 , Petros Stavroulakis 1 , Richard Leach 1 1 Manufacturing Metrology Team, Faculty of Engineering University of Noƫngham, NG8 1BB, UK Email: amrozia.shaheen1@noƫngham.ac.uk Abstract Commercially available projectors are subject to gamma non‐linearity, lack of depth‐of‐focus (DOF), system vibraƟon and noise which distort the fringe paƩerns and introduce significant errors in the phase measurement. In this work, we will compare a low‐cost DLP and a laser projector in terms of gamma performance and DOF, and assess which projector type performs beƩer for fringe projecƟon applicaƟons. Our study finds that the focus‐free eye‐safe laser projector provides more con‐ sistent high‐quality sinusoidal paƩerns and has a much longer DOF and is, therefore, recommended for pracƟcal implementaƟon in fringe projecƟon systems. Results Methodology Gamma‐correcƟon: Laser (Laser Beam Pro, C‐200) projector DLP (ICODIS‐G1 Mini) projector Raspberry‐Pi camera SoŌware for data acquisiƟon DOF: A camera‐projector assembly Checkerboard paƩern Rail SoŌware for image processing Fig. 3 Comparison of gamma curves Fig. 2 SchemaƟc illustraƟon of DOF A lookup table is used to compensate for the non‐linear sinusoidal behaviour of the fringes. The gamma curve is ac‐ quired by projecƟng mulƟple grayscale values on an imaging target and capturing by a camera. The DOF is measured by determining the maximum of the Fourier transform of the region‐of‐interest. 3D Metrology Conference ‐ 3DMC, 16‐18 October 2018, Hamburg Germany Fig. 1 SchemaƟc diagram of the gamma‐correcƟon Fig. 5 AŌer gamma‐correcƟon (laser) Conclusions The laser projector has the following upsides, Eye‐safe class‐1 laser Focus free Longer DOF Requires less gamma correcƟon Outperforms a DLP projector Recommended in high‐speed 3D applicaƟons Future work IntegraƟng the a‐priori informaƟon and fusion of different opƟcal tech‐ niques Sources of error CalibraƟon Traceability UlƟmately, designing a high‐speed 3D opƟcal imaging system Fig. 7 Phase image before gamma‐correcƟon (DLP) Fig. 8 AŌer gamma‐correcƟon (DLP) Fig. 6 Comparison of DOF Acknowledgements The authors would like to acknowledge the support provided by the Marie‐ Skłodowska‐Curie InnovaƟve Training Network (ITN), funded by the European Union under Horizon 2020 programme, Grant Agreement N o 721383. Horizon‐2020 Grant Agreement No 721383 Fig. 4 Phase image of a flat plane before gamma‐correcƟon (laser)
Transcript of Manufacturing Metrology Team
Manufacturing Metrology
Team Compara ve study of cost effec ve laser and DLP projectors for fringe projec on
Amrozia Shaheen1, Petros Stavroulakis1, Richard Leach1
1Manufacturing Metrology Team, Faculty of Engineering
University of No ngham, NG8 1BB, UK
Email: amrozia.shaheen1@no ngham.ac.uk
Abstract Commercially available projectors are subject to gamma non‐linearity, lack of depth‐of‐focus (DOF), system vibra on and noise which distort the fringe pa erns and introduce significant errors in the phase measurement. In this work, we will compare a low‐cost DLP and a laser projector in terms of gamma performance and DOF, and assess which projector type performs be er for fringe projec on applica ons. Our study finds that the focus‐free eye‐safe laser projector provides more con‐sistent high‐quality sinusoidal pa erns and has a much longer DOF and is, therefore, recommended for prac cal implementa on in fringe projec on systems.
Results
Methodology Gamma‐correc on:
Laser (Laser Beam Pro, C‐200) projector
DLP (ICODIS‐G1 Mini) projector
Raspberry‐Pi camera
So ware for data acquisi on
DOF:
A camera‐projector assembly
Checkerboard pa ern
Rail
So ware for image processing
Fig. 3 Comparison of gamma curves
Fig. 2 Schema c illustra on of DOF
A lookup table is used to compensate for the non‐linear sinusoidal behaviour of the fringes. The gamma curve is ac‐quired by projec ng mul ple grayscale values on an imaging target and capturing by a camera. The DOF is measured by determining the maximum of the Fourier transform of the region‐of‐interest.
3D Metrology Conference ‐ 3DMC, 16‐18 October 2018,
Hamburg Germany
Fig. 1 Schema c diagram of the gamma‐correc on
Fig. 5 A er gamma‐correc on (laser)
Conclusions The laser projector has the following upsides,
Eye‐safe class‐1 laser
Focus free
Longer DOF
Requires less gamma correc on
Outperforms a DLP projector
Recommended in high‐speed 3D
applica ons
Future work Integra ng the a‐priori informa on
and fusion of different op cal tech‐niques
Sources of error
Calibra on
Traceability
Ul mately, designing a high‐speed 3D op cal imaging system
Fig. 7 Phase image before gamma‐correc on (DLP)
Fig. 8 A er gamma‐correc on (DLP) Fig. 6 Comparison of DOF
Acknowledgements The authors would like to acknowledge the support provided by the Marie‐Skłodowska‐Curie Innova ve Training Network (ITN), funded by the European Union under Horizon 2020 programme, Grant Agreement No 721383.
Horizon‐2020 Grant Agreement No 721383
Fig. 4 Phase image of a flat plane before gamma‐correc on (laser)
