Color-Encoded Fringe Pattern for 3D Shape Measurement
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Solution Overview
Problem
Existing three-dimensional shape measurement techniques using sinusoidally modulated fringe patterns face accuracy issues due to 2π ambiguity in phase computation and interference from multiple colors in color-encoded patterns, which reduces measurement accuracy.
Innovation Solution
The method involves projecting sinusoidally modulated fringe patterns with color-encoded features, where each fringe has a colored line with a narrow width and a uniform fringe color, providing uniform illumination and differentiation information to determine fringe orders and compute an unwrapped phase map for accurate depth distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If color-encoded fringe patterns with multiple colors are used to assist fringe order determination, then the ability to resolve 2π ambiguity is improved, but measurement accuracy deteriorates due to interference from different reflectance responses to different colors
Solution Approach 1:
The patent extracts only the necessary color information (single colored line per fringe) rather than using multiple colors across the entire fringe pattern. This extraction approach provides sufficient fringe order determination capability while eliminating the harmful interference from multiple colors that have different reflectance responses.
Solution Approach 2:
The patent applies local quality by placing a colored line only at a specific location within each fringe rather than coloring the entire fringe. This localized color application provides the necessary differentiation information for fringe order determination while minimizing the overall color interference in the measurement system.
2Loss of information
If colored lines are added to fringes for differentiation, then fringe order determination is improved, but the uniformity of illumination is worsened
Solution Approach 1:
The patent makes different parts of the fringe pattern serve different functions: the majority of the fringe provides uniform illumination for accurate intensity measurement, while a narrow colored line at a specific location provides differentiation information. This local quality differentiation resolves the contradiction between providing fringe order information and maintaining illumination uniformity.
3Loss of information
If the width of colored lines in fringes is increased to improve visibility, then fringe differentiation is improved, but spatial resolution is compromised
Solution Approach 1:
The patent applies partial action by using a narrow colored line that provides just sufficient differentiation information without excessive width that would compromise spatial resolution. The colored line width is optimized to be narrow enough to preserve resolution while still providing adequate signal for fringe order determination.
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 enhances measurement accuracy by minimizing interference and ambiguity, allowing for precise computation of fringe orders and depth distribution without compromising spatial resolution.
Implementation Method 1
projecting one or more fringe patterns onto an object and then computing a depth distribution of the object's shape based on one or more distorted fringe images reflected from the object
Data Source
AI summary
This invention discloses using one or more color-encoded fringe patterns for optically, three-dimensionally measuring an object's shape. In one embodiment, a color-encoded fringe pattern comprising a plurality of fringes that are modulated in intensity is configured as follows. An individual fringe selected from the fringes comprises a colored line at a location on the fringe width. The colored line has a line width that is substantially narrower than the fringe width in order that the colored line has a substantially similar intensity over the line width. The individual fringe excluding the colored line has a fringe color that is substantially uniform over the individual fringe. The fringe color is substantially different from the line color. Fringe colors of all the fringes are substantially similar, thereby enabling a major portion of the color-encoded fringe pattern to provide a substantially-uniform illumination color for projection onto the object.