Shape Measurement Apparatus with Region-Specific Calibration Data
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Solution Overview
Problem
Conventional shape measurement techniques for specular objects suffer from calculation errors due to positional differences between measurement points, which become significant in automated optical inspection systems where apparatus size reduction and wider fields of view are necessary.
Innovation Solution
A shape measurement apparatus that switches data sets used for normal line calculation based on the position of measurement points, using a storage unit with pre-generated data sets for reference positions within the field of view, and an illumination unit with varying spectral distributions to accurately calculate three-dimensional shapes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the apparatus size is reduced and field of view is widened to improve inspection efficiency, then productivity increases, but measurement precision deteriorates due to increased calculation errors in normal line calculation
Solution Approach 1:
The patent divides the field of view into multiple regions, each with its own calibration data set. This segmentation allows the system to maintain high measurement precision in each region while supporting a wide overall field of view, thus resolving the contradiction between productivity and measurement precision.
Solution Approach 2:
The patent applies different calibration data sets to different regions of the field of view. Each region has customized calibration parameters that are optimized for its specific characteristics, enabling accurate normal line calculation across the entire wide field of view without compromising precision due to the reduced apparatus size.
2Measurement precision
If the distance l from field center to light source is increased to reduce calculation error, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent performs calibration measurements in advance to pre-compute and store calibration data sets for different field regions. This preliminary action eliminates the need for complex real-time calculations during actual inspection, reducing device complexity while maintaining high measurement precision.
Solution Approach 2:
The patent creates multiple calibration data sets that copy and adapt the optimal calibration parameters for different field regions. Instead of using a single complex calibration system, the system uses multiple simplified region-specific calibration data sets, reducing overall device complexity.
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 significantly reduces calculation errors, enabling accurate three-dimensional shape measurement while allowing for apparatus size reduction and wider fields of view without compromising accuracy.
Implementation Method 1
an illumination unit that emits light onto a measurement target object disposed on a stage
Data Source
AI summary
The shape measurement apparatus calculates a characteristic amount for a plurality of points of interest on a surface of a measurement target object, based on an image obtained by image capturing with a camera, calculates an orientation of a normal line based on a value of the characteristic amount by referencing data stored in advance in a storage device, and restores the three-dimensional shape of the surface of the measurement target object based on a result of the calculation. The storage device stores a plurality of data sets generated respectively for a plurality of reference positions arranged in a field of view of the camera, and the data set to be referenced is switched depending on a position of a point of interest.