Portable Structured Light Module Using Pattern Shifting
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Solution Overview
Problem
Conventional Structured Light Illumination (SLI) systems are computationally heavy and have large footprints, making them impractical for real-time measurements in small spaces, such as within the mouth or ear of a mammal, inside machinery, or within pipelines, due to the need for sophisticated electronically-driven signal processing and dedicated projector units for each SLI pattern.
Innovation Solution
A portable SLI module with a novel optical technique using a linear or rotating pattern shifting device and polarizing beam splitter, which projects a superimposed SLI pattern composed of dual-frequency sinusoids, allowing for real-time 3D surface measurement without the need for extensive computational processing or large physical separation between the camera and projector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional SLI systems use dedicated projector units for each SLI pattern, then measurement precision is improved, but device complexity and physical size increase
Solution Approach 1:
The patent combines multiple SLI pattern projection capabilities into a single projector unit by superimposing dual-frequency sinusoidal patterns. Instead of using separate dedicated projector units for each pattern, the invention merges multiple pattern types (different frequencies and phases) into one projection system, reducing device complexity while maintaining measurement precision through the mathematical properties of the superimposed patterns
Solution Approach 2:
The single projector unit is designed to project multiple types of SLI patterns simultaneously by generating superimposed dual-frequency sinusoidal patterns with varying phases. This multi-functional projector can perform the work of multiple dedicated projectors, allowing the system to measure different surface characteristics using a universal projection device
2Measurement precision
If conventional SLI systems use sophisticated electronically-driven signal processing, then measurement precision is improved, but computational complexity and processing time increase
Solution Approach 1:
The patent uses periodic dual-frequency sinusoidal patterns that are projected sequentially with different phase shifts. The periodic nature of these patterns allows for efficient temporal encoding of depth information, where the phase difference between the two frequencies can be extracted through simpler computational methods compared to conventional single-frequency approaches, reducing processing time while maintaining precision
Solution Approach 2:
The invention changes the frequency parameter of the projected light patterns by using dual-frequency sinusoids instead of single-frequency patterns. This parameter change enables the system to encode multiple measurement channels in a single projection, allowing for more efficient signal processing and reduced computational complexity while achieving the same measurement precision
3Measurement precision
If dedicated projector units are used for each SLI pattern, then measurement precision is improved, but the physical footprint and device size increase
Solution Approach 1:
The patent merges multiple dedicated projector units into a single compact projector that can generate superimposed dual-frequency sinusoidal patterns. This consolidation dramatically reduces the physical footprint of the system while maintaining the measurement precision that would otherwise require multiple separate projection devices working in coordination
4Measurement precision
If conventional SLI systems are designed for large-scale applications, then measurement precision is improved, but adaptability to small spaces is reduced
Solution Approach 1:
The patent creates a universal measurement system that can adapt to various application scales through the use of dual-frequency sinusoidal patterns. The same compact device can be used for both large-scale industrial applications and small-scale medical applications (such as intra-oral scanning), providing versatility across different size requirements while maintaining high measurement precision through the mathematical properties of the projected patterns
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
Enables high-resolution, real-time 3D surface measurements in various environments, including small spaces, with reduced computational complexity and physical size, allowing for efficient data acquisition and minimal disruption.
Implementation Method 1
a portable module adapted for operation by-hand and comprising: a light source; a linear pattern shifting device which, in operation, shifts a projected light pattern in a linear fashion from the light source
Implementation Method 2
The polarized, projected SLI pattern light then travels on, to be redirected (by reflection, for example) to illuminate the 3-D surface of interest
Implementation Method 3
The spatial shift is preferably achieved by means of thermal actuation
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A surface measurement module for 3-D image acquisition of a subject-under-inspection. The module having: (a) a casing to house a pattern shifting device having a fixed-pattern optic through which light from a light source is passed, an output of the pattern shifting device being directed at a polarizing beam splitter and the polarized output of the splitter directed through a lens assembly comprising at least one lens element; (b) a reflector to direct the polarized output exiting the lens assembly, to illuminate a surface of the subject-under-inspection; (c) a scattered light illumination off the surface is directed back through the lens assembly for capture by an image sensor; and (d) the casing also housing the polarizing beam splitter, the lens assembly, and the image sensor. The output of the fixed-pattern optic comprises a multi-frequency pattern. The pattern shifting device may be a linear or rotating type.