3D Surface Data Acquisition Using Spatial Light Modulator
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Solution Overview
Problem
Existing methods for obtaining 3D surface data face limitations such as dependence on precise mechanical movements, modulo 2π ambiguity, limited precision due to surface reflectivity variations, and slow data acquisition times, especially when dealing with moving objects.
Innovation Solution
The method involves projecting two or more 2D images with distinct wavelength bands along a first optical axis onto an object surface, using spatial light modulators to create varying light intensity patterns, and recording reflected images to calculate 3D surface data by comparing object data with calibration data obtained from a planar surface, allowing for accurate measurements even with varying reflectivity and over extended ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase-shifting techniques are used to achieve good resolution, then measurement precision is improved, but device complexity increases due to sophisticated moving mechanisms
Solution Approach 1:
The patent replaces mechanical moving mechanisms with a spatial light modulator that projects multiple wavelength bands simultaneously. Instead of physically moving the object or grating, the system uses optical modulation to create phase-shifted patterns, eliminating complex mechanical components while maintaining measurement precision.
Solution Approach 2:
The patent employs periodic modulation of light intensity across multiple wavelength bands to encode depth information. By projecting sequences of patterns with different phase shifts across multiple wavelength bands, the system achieves precise measurements without mechanical movement, using temporal periodicity instead.
2Length of stationary object
If Moiré contouring techniques are used to increase measurement range, then measurement range is improved, but measurement precision deteriorates due to modulo 2π ambiguity
Solution Approach 1:
The patent adds a spectral dimension by using multiple wavelength bands simultaneously. This spectral multiplexing allows the system to resolve the modulo 2π ambiguity inherent in single-wavelength Moiré techniques, enabling both extended measurement range and maintained precision through wavelength discrimination.
Solution Approach 2:
The patent combines multiple wavelength bands into a composite illumination scheme. By projecting patterns across multiple spectral bands and analyzing their combined interference patterns, the system overcomes the limitations of single-wavelength approaches, achieving both extended range and preserved precision.
3Ease of operation
If color coding with projections of color stripes or color dots is used, then ease of operation is improved, but measurement precision deteriorates due to limited number of stripes or dots and surface reflectivity variations
Solution Approach 1:
The patent changes the parameter of light wavelength to create distinct bands that are less sensitive to surface reflectivity variations. By using multiple wavelength bands with specific spectral characteristics, the system maintains ease of operation while improving precision through wavelength-based discrimination that compensates for reflectivity changes.
4Adaptability or versatility
If fringe projections using dynamic light modulation devices are used, then adaptability is improved, but productivity deteriorates due to limited response time
Solution Approach 1:
The patent replaces dynamic light modulation devices with a spatial light modulator that can rapidly switch between multiple wavelength bands. This substitution eliminates the response time limitations of conventional dynamic modulators, enabling faster data acquisition while maintaining adaptability through programmable pattern projection.
5Length of stationary object
If projections of patterns with continuously varying wavelengths are used, then measurement range is improved, but measurement precision deteriorates due to detector wavelength detection limitations
Solution Approach 1:
The patent segments the continuous wavelength spectrum into discrete wavelength bands. By using distinct, separable wavelength bands instead of continuously varying wavelengths, the system achieves precise detector response at each band while maintaining extended measurement range through the combination of multiple discrete bands.
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 enables accurate and fast acquisition of 3D surface data, achieving precise results in less than 1000 μs, even for moving objects, with improved immunity to surface reflectivity variations and ambiguity issues.
Implementation Method 1
using spatial light modulators to create varying light intensity patterns
Implementation Method 2
When projected on the object surface, each projected image generates a reflected image along approximately a second optical axis
Implementation Method 3
The reflected image is recorded by an image sensing unit
Data Source
AI summary
The concept includes projecting at the object surface, along a first optical axis, two or more two-dimensional (2D) images containing together one or more distinct wavelength bands. The wavelength bands vary in intensity along a first image axis, forming a pattern, within at least one of the projected images. Each projected image generates a reflected image along a second optical axis. The 3D surface data is obtained by comparing the object data with calibration data, which calibration data was obtained by projecting the same images at a calibration reference surface, for instance a planar surface, for a plurality of known positions along the z-axis. Provided that the z-axis is not orthogonal to the second optical axis, the z-axis coordinate at each location on the object surface can be found if the light intensity combinations of all predefined light intensity patterns are linearly independent along the corresponding z-axis.