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Large depth-of-field 3D shape measurement using an electrically tunable lens
Optics Express
|November 6, 2019
Summary
This study introduces an electrically tunable lens to significantly expand the depth-of-field (DOF) for 3D shape measurement systems. The new method achieves high-accuracy, real-time 3D reconstruction over a large depth range.
Area of Science:
- Optics and Photonics
- Metrology
- Computer Vision
Background:
- Conventional 3D shape measurement systems are limited by a shallow working volume due to the restricted depth-of-field (DOF) of standard lenses.
- This limitation hinders applications requiring measurement of objects at varying distances.
Purpose of the Study:
- To substantially enlarge the depth-of-field (DOF) in 3D shape measurement systems.
- To enable high-accuracy, real-time 3D shape reconstruction over an extended depth range.
Main Methods:
- Utilizing an electrically tunable lens synchronized with image acquisition and fringe pattern projection to capture in-focus phase-shifted patterns.
- Developing a phase unwrapping framework incorporating geometric constraints from camera focal length settings.
- Pre-calibrating the system across different focal distances for accurate 3D shape reconstruction.
Main Results:
- A prototype system demonstrated high-quality 3D measurements within a depth range of approximately 1,000 mm (400 mm - 1400 mm).
- Achieved a high measurement accuracy with a low error rate of 0.05%.
- Successfully demonstrated real-time 3D shape measurement of moving objects.
Conclusions:
- Electrically tunable lenses offer a viable solution to overcome DOF limitations in 3D shape measurement.
- The proposed system provides a robust and accurate method for extended-range, real-time 3D metrology.
