3D Measurement Reliability via Luminance Gradient Analysis
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Solution Overview
Problem
Existing three-dimensional measurement methods using spatial coding struggle with precision due to measurement errors caused by blur, reflectance, and external light, leading to unreliable determination of boundary positions between bright and dark portions in stripe pattern light.
Innovation Solution
A three-dimensional measurement apparatus and method that calculates reliability by determining the angle formed between line segments from intersecting luminance curves of projected stripe pattern light and its reversed pattern, allowing for precise measurement point validation and improved precision through simultaneous calculation of boundary positions and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spatial coding method with stripe pattern light is used for three-dimensional measurement, then measurement speed and efficiency are improved, but measurement precision deteriorates due to blur, reflectance, and external light affecting boundary position determination
Solution Approach 1:
The patent applies feedback by calculating reliability values for each measurement point based on the luminance gradient magnitude and using this reliability information to validate or reject measurement points. The system feeds back the reliability assessment to determine whether to accept the measured boundary position, thereby improving measurement precision while maintaining the efficiency of the spatial coding method.
Solution Approach 2:
The patent changes the parameter of reliability calculation by introducing a new parameter (reliability value) that is calculated from the luminance gradient magnitude. This parameter change allows the system to distinguish between reliable and unreliable measurement points, resolving the contradiction between measurement speed and precision by enabling selective validation of measurement results.
2Measurement precision
If reliability calculation is performed to improve measurement precision, then measurement accuracy is improved, but computational cost increases
Solution Approach 1:
The patent extracts only the essential information needed for reliability calculation by using the luminance gradient magnitude at boundary positions. Instead of performing complex analysis on the entire luminance curve, the method extracts the gradient magnitude as a sufficient statistic for reliability assessment, thereby reducing computational cost while maintaining measurement precision.
Solution Approach 2:
The patent uses a computationally inexpensive reliability calculation method that can be quickly computed and discarded after use. The reliability value is calculated using a simple formula based on luminance gradient magnitude, making it a 'cheap' computational object that can be generated and used without significant energy expenditure, thus resolving the contradiction between precision and computational cost.
3Area of stationary object
If boundary positions are determined from luminance values affected by blur and reflectance, then measurement coverage is improved, but measurement reliability deteriorates
Solution Approach 1:
The patent substitutes the traditional mechanical approach of directly using luminance values for boundary detection with an optical gradient-based method. By replacing the direct luminance thresholding method with a luminance gradient magnitude calculation, the system can identify boundary positions more reliably even in the presence of blur and reflectance, thus maintaining measurement coverage while improving reliability.
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 proposed solution enables easy and precise calculation of measurement reliability, enhancing the accuracy of three-dimensional shape measurement by filtering out points with low reliability and providing reliable range image data, thus improving measurement precision and reducing computational costs.
Implementation Method 1
a projector (402) which projects stripe pattern light formed by alternately arranging bright and dark portions onto an object (407)
Implementation Method 2
a camera (403) which captures an image of reflected pattern light of the object (407) on which the stripe pattern light is projected
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A three-dimensional measurement apparatus for calculating three-dimensional shape information of a target object, comprising: capturing means for capturing reflected pattern light of stripe pattern light formed by alternately arranging a bright portion and a dark portion as first image data, and capturing reflected pattern light of reversed stripe pattern light formed by reversing the bright portion and the dark portion of the stripe pattern light as second image data; determination means for determining a boundary position between the bright portion and the dark portion based on the first image data and the second image data; and reliability calculation means for calculating a reliability indicating accuracy of the boundary position from a correlation between a first luminance gradient of the first image data and a second luminance gradient of the second image data.