Using Laser Projectors for Augmented...
Transcript of Using Laser Projectors for Augmented...
Using Laser Projectors for Augmented Reality
Björn Schwerdtfeger
2Using Laser Projectors for Augmented Reality - B. Schw erdtfeger
Outline
• Applications
– Quality assurance
– Maintenance
• Problems
– 1) Projecting on arbitrary surfaces
– 2) Accuracy and sources of error
– 3) Where to mount the projector
• Current system
– Setup
– Accuracy evaluation
• Summary
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Applications 1: Quality Assurance in Series Production
Inspection of welding points on white bodies
– E.g car doors
– Each 25th door
– Varying points (due to previous quality )
– Different methods of inspection
• e.g viewing, ultrasound, destructive testing
Using Laser Projectors for Augmented Reality - B. Schw erdtfeger
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Applications 2: Maintenance Support
• Display of the maintenance workflow
• Requirements
– Mobile
– Quick and easy set-up
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Problems
• 1) Projection on arbitrary surfaces
• 2) Accuracy and sources of error
• 3) Where to mount the projector
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Problem: 1) Projection on Arbitrary Surfaces
• General
– Requires presence of a surface
– Public display
• Photometric and Optical
– Bright illuminated workplaces
– Metallic raw objects (e.g. white body)
• reflecting light mainly in the specular direction
• minimal amount of light is reflected omnidirectional
towards arbitrary viewer positions
• Geometric issues
– Deep dents, significant surface structure
– Requires a pre-distorted projection
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Problem: 1) Projection on Arbitrary Surfaces
Hybride Display
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where-to-act
what-to-do
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Problem: 2) Accuracy and Sources of Error
• Accuracy depends on distance between projector and object rather than user and object
• E.g. 1 cm Accuracy required
– projection distance 2 meters -> requires 5 mrad ≈ 0.3°
• Sources of error
– Intrinsic calibration
– Extrinsic calibration (tracking)
• use inside-out (better rotation)
• instead of outside-in (better translation)
– Cheap laser scanners
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Problem: 3) Where to Mount the Projector
• Occlusion
– By user (standing in the line of projection)
– By object itself (protruding parts)
• Solutions
– Optimized projector placement (next Slide)
– Smart projection (not yet solved)
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Problem: 3) Where to Mount the Projector
• Head/shoulder-mounted projector
– Unlimited field of projection
– No occlusion problems
– Has to be light-weight
• Accurate scanners are heavy
• Needs accurate and fast tracking
– Acceptability
• Room mounted
– Slow but robust tracking
– No weight limitations
– Limited field of projection
– Occlusion problem
– Potentially expensive
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Current System
• Tripod mounted: balances some tradeoffs
• Still movable - reconfigurable
– does not suffer from limited range of a room-mounted setup
• More weight possible
– scanning
– extra sensing hardware
• No fast tracking required
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Current System
• Inside-out tracking
– Theoretically better than outside-in
• Fish-eye camera
– Tracked object always in Fiels of view
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Camera
Scanner
Laser
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Current System: Accuracy Evaluation
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Outside-In Tracking vs. Inside-Out Tracking
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Current System: Accuracy Evaluation
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Current System: Accuracy Evaluation
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Outside-In Tracking
ART Target
(Laser)
Laser Projection (Intrinsics)
ART
Origin
Projection
TargetProjection
TargetProjection Target
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Current System: Accuracy Evaluation
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Inside-Out Tracking
Camera
Laser Projection (Intrinsics)
Marker
Projection
TargetProjection
TargetProjection Target
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Current System: Accuracy Evaluation
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Error: 5 mrad ≈ 0.3°Extrema of the
Projection Field
Extrema of the
Tracking System
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Current System: Accuracy Evaluation
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• Conclusion:
• In theory
• Inside-Out should outperform the Outside-In
• In practice
• having a large tracking area...
• A different setup will look different.... come and see it
next door