Multi-Wavelength Pattern Light for Stereo Distance Measurement
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Solution Overview
Problem
Existing distance measuring devices using stereo cameras struggle to accurately measure distances on surfaces with low reflectance or high light absorption rates due to difficulties in capturing appropriate dot patterns when the laser light wavelength aligns with these properties, leading to inadequate stereo correspondence point searching.
Innovation Solution
A distance measuring device that projects pattern light with multiple types of light regions having different wavelength bands, ensuring that even if the object surface has low reflectance or high light absorption in certain bands, the pattern can be accurately captured by the cameras, allowing for precise stereo correspondence point searching and distance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a single wavelength laser light is projected onto the object surface, then the dot pattern can be generated with high intensity, but the pattern cannot be accurately captured when the object surface has low reflectance or high light absorption at that wavelength
Solution Approach 1:
The single wavelength laser light is segmented into multiple wavelength bands (first, second, and third wavelength bands). By dividing the illumination into multiple spectral segments, the system ensures that at least one segment will be adequately reflected by the object surface regardless of its specific absorption characteristics at any single wavelength.
Solution Approach 2:
The system changes the wavelength parameter of the projected light by incorporating multiple wavelength bands. This parameter diversification allows the illumination to adapt to different object surface properties, ensuring reliable pattern capture by selecting wavelengths that are not absorbed by the object.
2Device complexity
If a single wavelength laser light is used, then the device configuration remains simple, but the stereo correspondence point searching becomes inaccurate on surfaces with wavelength-dependent reflectance properties
Solution Approach 1:
The illumination system is segmented to emit multiple wavelength bands instead of a single wavelength. This segmentation enables the system to overcome wavelength-dependent absorption by object surfaces, thereby improving stereo correspondence point searching accuracy without excessively complicating the overall device architecture.
Solution Approach 2:
The projector is designed with multi-functionality by incorporating multiple wavelength bands into a single illumination system. This universal approach allows the same projector to effectively illuminate various types of object surfaces with different reflectance properties, improving measurement precision across diverse applications.
3Reliability
If multi-wavelength pattern light is projected, then accurate pattern capture is achieved on surfaces with varying reflectance properties, but the device complexity increases due to multiple light sources or filters
Solution Approach 1:
The projector system segments the illumination into multiple wavelength bands using practical methods such as multiple laser diodes or a single laser with wavelength modulation. This segmentation achieves reliable pattern capture on diverse surfaces while maintaining reasonable system complexity through efficient optical design.
Solution Approach 2:
The patent merges multiple wavelength bands into a single projected pattern by combining multiple laser light sources or modulating a single laser source. This merging approach maintains the simplicity of a unified projection system while incorporating the benefits of multi-wavelength illumination for reliable pattern capture.
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
The device achieves accurate distance measurement by maintaining the specificity of pixel blocks through the distribution pattern of light regions with varying wavelength bands, enhancing the accuracy of stereo correspondence point searching and distance measurement even on surfaces with challenging reflectance properties.
Implementation Method 1
even if the object surface has low reflectance or a high light absorption rate in a certain wavelength band
Implementation Method 2
the surface of an object may have a low reflectance or a high light absorption rate in a certain wavelength band
Data Source
AI summary
A distance measuring device includes: a first imager and a second imager provided so as to be aligned such that fields of view thereof overlap each other; a projector configured to project pattern light in which a plurality of types of light regions having wavelength bands different from each other are distributed in a predetermined pattern, onto a range where the fields of view overlap; and a measurer configured to measure a distance to an object surface onto which the pattern light is projected, by performing a stereo correspondence point searching process on images respectively acquired by the first imager and the second imager.