3D Measurement Method Using Gray Code Sawtooth Fringes
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Solution Overview
Problem
Existing structured light measurement methods face challenges with low solution accuracy of absolute phase in spatial coding and low processing speed in time coding, particularly due to the need for numerous calculations and pattern projections.
Innovation Solution
A three-dimensional measurement method that converts sawtooth fringe levels into Gray code, acquires sawtooth slope coefficients, and fuses them into target fringe patterns, allowing for reduced pattern projections and pixel-by-pixel phase solving without tangent and arctangent calculations, improving accuracy and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spatial coding method is used, then measurement speed is improved, but absolute phase solution accuracy deteriorates
Solution Approach 1:
The patent combines spatial coding and time coding methods into a hybrid approach. It uses spatial coding for initial phase estimation to maintain speed, then applies time coding with phase shifting for accurate absolute phase solution. The integration of both methods allows the system to achieve both fast measurement speed and high absolute phase accuracy simultaneously.
Solution Approach 2:
The patent performs preliminary phase estimation using spatial coding before conducting the final absolute phase measurement. By pre-processing the phase information through spatial coding, the system reduces the computational burden and improves the accuracy of subsequent absolute phase calculations, resolving the contradiction between speed and accuracy.
2Measurement precision
If time coding method is used, then spatial resolution and measurement accuracy are improved, but processing speed deteriorates
Solution Approach 1:
The patent applies time coding with phase shifting only to the extent necessary for obtaining accurate phase information, rather than using it for the entire measurement process. By selectively applying time coding where needed and combining it with faster spatial coding methods, the system achieves high spatial resolution without the excessive processing time required by pure time coding approaches.
3Measurement precision
If sinusoidal phase-shift coding method is used, then spatial resolution is improved, but processing speed deteriorates due to numerous calculations
Solution Approach 1:
The patent replaces the computationally intensive tangent and arctangent calculations with an optimized algorithm that uses lookup tables and simplified mathematical operations. This substitution maintains the high spatial resolution achieved by sinusoidal phase-shift coding while dramatically reducing the computational burden and processing time required.
4Measurement precision
If multiple projection patterns are used, then measurement accuracy is improved, but measurement time increases
Solution Approach 1:
The patent uses periodic phase-shifting patterns with optimized frequency and timing to achieve accurate measurements with fewer projection patterns. By carefully designing the periodicity and sequence of projected patterns, the system extracts maximum measurement information from each projection, reducing the total number of patterns needed and thereby decreasing measurement time while maintaining accuracy.
Data Source
AI summary
A three-dimensional measurement method comprises: converting a total number of levels of sawtooth fringes into a Gray code and acquiring a sawtooth slope coefficient; fusing the coefficient into a sawtooth fringe image to generate a target sawtooth fringe pattern; projecting each target sawtooth fringe pattern to a surface of a to-be-measured object through a projector, and collecting a deformed target sawtooth fringe pattern on the surface through a camera; solving a Gray code of each sawtooth fringe collection pattern at each pixel point according to a differential property of adjacent pixels in each sawtooth fringe collection pattern and solving a fringe level and a wrapped phase at each pixel point; calculating an absolute phase at each pixel point according to the fringe level and the wrapped phase at each pixel point, and reconstructing a three-dimensional point cloud through triangulation ranging to obtain a three-dimensional model of the to-be-measured object.