Fringe Pattern Switching for Fast Phase Unwrapping
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Solution Overview
Problem
The phase shift method for three-dimensional shape measurement using a projector and camera is inefficient due to the long analysis period required for phase unwrapping, particularly when using Fourier transform in existing systems.
Innovation Solution
A measurement system that switches between first and second pattern lights with varying fringe patterns, allowing for precise phase unwrapping by relating the fringes to multiple pixels, and includes a projection section with a laser light source for high-definition imaging, enabling faster analysis and accurate measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Fourier transform is used for phase unwrapping, then measurement precision is maintained, but measurement time becomes excessively long
Solution Approach 1:
The patent divides the phase unwrapping process into two distinct stages: first performing phase unwrapping on the first fringe pattern light to obtain initial phase information, then using this information to guide phase unwrapping of the second fringe pattern light. This segmentation allows each stage to be optimized independently, reducing overall computation time while maintaining precision.
Solution Approach 2:
The patent performs preliminary phase unwrapping on the first fringe pattern light before processing the second fringe pattern light. The phase information obtained from the first pattern serves as prior knowledge that simplifies and accelerates the subsequent phase unwrapping process, eliminating the need for computationally intensive Fourier transform on the complete dataset.
2Measurement precision
If multiple fringe patterns are projected, then measurement accuracy is improved, but measurement complexity increases
Solution Approach 1:
The patent employs periodic projection of alternating first and second fringe pattern lights with different spatial frequencies. This periodic action allows the system to collect complementary phase information from multiple patterns while using simple switching logic rather than complex simultaneous multi-pattern projection, thereby improving accuracy without proportionally increasing system complexity.
Solution Approach 2:
The patent changes the spatial frequency parameter of the projected fringe patterns by using two distinct patterns: a first pattern with lower spatial frequency for robust initial phase estimation, and a second pattern with higher spatial frequency for enhanced precision. This parameter variation improves measurement accuracy while the switching mechanism keeps the overall system complexity manageable.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces the measurement period and enhances accuracy by allowing quick and precise phase unwrapping, enabling high-speed analysis and precise determination of object coordinates for robot control and picking applications.
Implementation Method 1
a projection section that switches first pattern light having a fringe pattern to second pattern light having a fringe pattern
Implementation Method 2
an imaging section that has a plurality of pixels and images each of the first pattern light and the second pattern light projected on the object to be measured
Data Source
AI summary
A measurement system includes a projection section that switches first pattern light having a fringe pattern to second pattern light having a fringe pattern containing a greater number of fringes than the first pattern light and vice versa and projects the selected light on an object to be measured, an imaging section that has a plurality of pixels and images the first pattern light and the second pattern light projected on the object to be measured, a phase shift section that shifts the phase of the first pattern light and the second pattern light projected by the projection section on the object to be measured, and an analysis section that analyzes results of the imaging performed by the imaging section by relating the fringes contained in the first pattern light and the second pattern light to the plurality of pixels.