Specular Surface Shape Measurement via Reflectance Mapping
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Solution Overview
Problem
Conventional stereo methods fail to measure the three-dimensional shape of objects with specular surfaces, such as glass, due to difficulties in recognizing the same point in two directions, making it challenging to accurately determine the shape of glass products.
Innovation Solution
A shape measuring apparatus and method that calculates inclination angles at specific positions on a specular surface by capturing images before and after the object's movement, comparing these angles to determine the height direction coordinate, allowing for the measurement of three-dimensional shapes even on specular surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional stereo method is used to measure three-dimensional shape, then measurement can be performed on general objects, but measurement fails on objects with specular surfaces due to inability to recognize the same point in two directions
Solution Approach 1:
The patent introduces a pattern (such as a grid or texture) as an intermediary element that is reflected off the specular surface. This pattern serves as a mediator between the light source and the measurement system, enabling the extraction of surface normal information through reflectance mapping. The pattern's known geometry allows calculation of surface orientation even on highly reflective surfaces where direct point recognition fails.
Solution Approach 2:
The patent replaces the conventional mechanical/stereo vision approach with an optical physics-based approach using reflectance mapping. Instead of relying on geometric triangulation from multiple camera views, the system uses the physical laws of reflection to determine surface normals by analyzing how light reflects off the specular surface at different angles.
2Measurement precision
If multiple captured images are processed to determine height direction coordinate, then three-dimensional shape can be measured on specular surfaces, but calculation complexity increases
Solution Approach 1:
The patent divides the measurement process into discrete, manageable segments: (1) capturing multiple images at different object positions, (2) extracting pattern information from each image, (3) calculating inclination angles based on pattern displacement, and (4) determining height direction coordinates through comparison. This segmentation allows complex measurements to be performed through a series of simpler, standardized operations.
Solution Approach 2:
The patent transitions from two-dimensional image processing to three-dimensional shape reconstruction by utilizing the height direction coordinate as an additional dimension. By calculating inclination angles from pattern displacement in the image plane and mapping these to spatial coordinates, the system reconstructs the three-dimensional surface geometry from two-dimensional image data.
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 three-dimensional shapes on specular surfaces, leading to the production of high-quality glass products with reduced warpage and defects.
Implementation Method 1
captured by reflecting a pattern disposed at a fixed position to the specular surface of the object to be measured
Data Source
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AI summary
Provided is a technique capable of measuring the three-dimensional shape of even an object having a mirror surface by applying a stereo method. A shape measuring device (1) comprises: a pattern position specifying unit (pre-movement pattern position specifying unit, post-movement pattern position specifying unit) (20); an imaging position calculation unit (pre-movement imaging position calculation unit, post-movement imaging position calculation unit) (30); a pixel region specifying unit (second pixel region specifying unit) (40); a tilt angle calculation unit (pre-movement tilt angle calculation unit, post-movement tilt angle calculation unit) (50); a height-direction coordinate determination unit (60); and an output unit (80).