Polarization Imaging for 3D Shape Measurement of Moving Objects
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Solution Overview
Problem
Conventional photometric stereo methods struggle to accurately measure the three-dimensional shape of moving objects due to positional shifts caused by subject movement during light switching.
Innovation Solution
An imaging device that utilizes polarization lights with different polarization directions to capture images of a subject simultaneously, separating pixel signals by polarization direction, calculating normal lines on the subject's surface through photometric stereo, and estimating the subject's shape based on these calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional photometric stereo sequentially switches lights to illuminate the subject from different directions, then the three-dimensional shape measurement can be performed, but positional shifts occur due to subject movement during light switching, degrading measurement accuracy
Solution Approach 1:
The patent employs periodic modulation of multiple light sources at different frequencies to illuminate the subject simultaneously. By modulating each light source at a distinct frequency (e.g., 50Hz, 60Hz, 70Hz), the system captures time-varying intensity patterns that encode directional information, eliminating the need for sequential light switching while maintaining measurement accuracy for moving subjects
Solution Approach 2:
The patent introduces the time dimension by capturing images at multiple time points during the periodic light modulation cycle. This temporal dimension allows the system to distinguish between light sources of different frequencies and reconstruct three-dimensional shape information without requiring sequential spatial switching of lights
2Measurement precision
If multiple light sources with different wavelengths are used to simultaneously illuminate the subject, then positional shifts are avoided, but the system requires narrowband bandpass filters and additional light sources, increasing device complexity and cost
Solution Approach 1:
The patent changes the modulation frequency parameter of light sources instead of using different wavelengths. By modulating intensity at distinct frequencies rather than relying on spectral differences, the system avoids the need for narrowband bandpass filters and complex wavelength-matching configurations, simplifying the overall device architecture
Solution Approach 2:
The patent replaces the optical filtering mechanism (narrowband bandpass filters) with an electronic signal processing approach. By capturing the time-varying intensity patterns and using frequency analysis to separate contributions from different light sources, the system eliminates mechanical/optical filter components while achieving the same differentiation function
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 accurate measurement of the three-dimensional shape of moving objects without the need for light switching, improving measurement accuracy and reducing costs by eliminating the requirement for narrowband bandpass filters or additional light sources.
Implementation Method 1
an imaging unit including a plurality of polarization lights having different polarization directions of light emitted to a subject and a polarization sensor
Data Source
AI summary
An imaging device includes an imaging unit, a signal separating unit, a normal line calculating unit, and a distance estimation unit. The imaging unit includes a plurality of polarization lights having different polarization directions of light emitted to a subject and a polarization sensor that captures an image of the subject that is simultaneously irradiated with the light from the plurality of polarization lights. The signal separating unit separates pixel signals corresponding to each of the polarization directions from the image captured by the imaging unit and generates an image for every polarization direction. The normal line calculating unit calculates a normal line on a surface of the subject from the image for each of the polarization directions by photometric stereo. The distance estimation unit estimates the shape of the subject based on the normal line calculated by the normal line calculating unit.