Multi-Axis Measurement Apparatus for Surface Normal and Position Data
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Solution Overview
Problem
Existing methods for determining dimensional and geometric properties of measurement objects face challenges in achieving high measurement speed and resolution while being cost-effective, particularly due to limitations in 3D scanning technologies such as fringe projection and photometric stereo methods which are sensitive to noise and unsuitable for high-gloss surfaces.
Innovation Solution
An apparatus comprising a housing body with integrated first and second measurement arrangements, which record positions and surface normals respectively, combined using third measurement values to correct systematic errors and enhance measurement accuracy, allowing for high-speed and high-resolution data acquisition without the need for temporal synchronization of measurement arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photometric stereo method is used to determine surface normals, then measurement accuracy for local inclination is improved, but measurement errors increase due to violation of point-like light source assumption
Solution Approach 1:
The patent changes the fundamental parameter of light source modeling from point-like sources at infinity to extended sources with finite distances. By introducing realistic light source geometry parameters (size, position, intensity distribution), the system maintains measurement precision while eliminating the systematic errors caused by the unrealistic point-source assumption in traditional photometric stereo methods.
2Measurement precision
If multiple measurement arrangements are used to improve measurement resolution, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple measurement functions into an integrated system where a housing body simultaneously holds multiple measurement arrangements (first for positional data, second for surface normals, third for pose determination). This consolidation achieves high measurement resolution through data fusion while managing device complexity through unified structural integration and coordinated operation of the combined measurement system.
3Measurement precision
If fringe projection method is used for 3D scanning, then spatial coordinates are obtained, but measurement errors increase for high-gloss surfaces due to image noise sensitivity
Solution Approach 1:
The patent applies a composite measurement approach that combines multiple measurement methods (fringe projection for positional data, photometric stereo for surface normals, and pose determination) to create a composite measurement system. This composite approach leverages the strengths of each method while compensating for their individual weaknesses, particularly reducing image noise sensitivity for high-gloss surfaces by fusing data from multiple measurement arrangements.
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 apparatus achieves increased measurement resolution and accuracy, enabling subpixel coordinate measurements and faster scanning speeds, particularly effective for objects with complex surfaces like holes and sharp edges, while being cost-effective and compact.
Implementation Method 1
Some methods are based on triangulation, in which the measurement object is recorded with one or more cameras and the evaluation of the camera images is based on trigonometric relationships.
Implementation Method 2
A publication by R. J. Woodham entitled 'Photometric Method for Determining Surface Orientation from Multiple Images,' published in Optical Engineering, 19(1), 1980, the entire disclosure of which is incorporated by reference, describes a method by which the respective local inclination of the measurement object surface can be determined at a plurality of measurement points by illuminating the surface successively from different directions.
Implementation Method 3
a third measurement arrangement, which defines a further coordinate system and is configured to record third measurement values, wherein the third measurement values represent a respective current pose of the housing body relative to the further coordinate system
Data Source
AI summary
An apparatus for determining at least one of dimensional and geometric properties of a measurement object has a first measurement arrangement, which records first measurement values. The first measurement values represent respective positions of first selected measurement points relative to a first coordinate system. The apparatus has a second measurement arrangement, which records second measurement values. The second measurement values represent respective surface normals at second selected measurement points. The first and second measurement arrangements are arranged spatially fixedly with respect to one another on a housing body. The apparatus further has a third measurement arrangement, which records third measurement values. The third measurement values represent a respective current position of the housing body relative to a further coordinate system. The evaluation unit is configured to combine the first measurement values and the second measurement values positionally correctly using the third measurement values.