Machine Vision Absolute Measurement via Deviation Matrix Calibration
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Solution Overview
Problem
Conventional machine vision systems struggle to perform absolute measurements, requiring expensive and wear-prone mechanical methods for precise object positioning, especially when measuring different types of objects or large numbers of objects, as they excel in relative measurements but falter in providing absolute scale values.
Innovation Solution
A machine vision system that uses a reference object measured by a coordinate measurement machine to compute a deviation matrix, allowing for the calculation of absolute scale values from machine vision measurements by comparing target objects to the reference object through a difference matrix and determined coordinate matrix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical positioning methods (measurement jigs, reference objects) are used to achieve absolute measurements, then measurement accuracy is improved, but measurement speed decreases and device complexity increases
Solution Approach 1:
The system performs preliminary calibration by measuring a reference object with a coordinate measurement machine to obtain reference measurement data before actual production measurements. This pre-established reference data enables subsequent machine vision measurements to directly compute absolute scale values without requiring mechanical positioning during production measurements, thus improving measurement speed while maintaining accuracy.
Solution Approach 2:
The invention replaces mechanical positioning systems (measurement jigs, physical reference objects) with a computational approach using machine vision and coordinate transformation. Instead of mechanically positioning objects for absolute measurements, the system uses image processing and mathematical transformation of reference data to achieve absolute scale measurements, eliminating mechanical wear and positioning time.
2Measurement precision
If multiple coordinate measurement machines are used to measure different types of objects, then measurement accuracy is maintained, but device complexity and cost increase
Solution Approach 1:
The system creates a universal measurement approach where a single machine vision system can measure different types of objects by using their respective reference object data. The coordinate transformation method is universally applicable to various object types, eliminating the need for multiple specialized coordinate measurement machines while maintaining measurement accuracy across different object categories.
Solution Approach 2:
The system creates digital copies of reference objects through coordinate measurement machine scanning, storing their geometric data in a database. These digital reference models are then used for comparing and measuring actual production objects via machine vision, replacing the need for physical reference objects and multiple measurement machines.
3Measurement precision
If a large number of cameras are used to increase measurement coverage, then measurement completeness is improved, but device complexity and cost increase
Solution Approach 1:
The system transitions from relying on multiple cameras capturing two-dimensional images to using a single or few cameras capturing three-dimensional point cloud data. By utilizing the depth information and spatial coordinates directly from the camera images through coordinate transformation, the system achieves comprehensive 3D measurement without needing multiple cameras positioned around the object.
Data Source
AI summary
A machine vision system capable of measuring differences on an absolute scale is disclosed. In the machine vision system, a reference object is accurately measured using a reference measurement arrangement, such as a coordinate measurement machine. In the measurement, a set of determined virtual points are measured. The reference measurement is used for computing a deviation matrix between a determined coordinate matrix and the reference measurement results that is later used for computing absolute scale values from machine vision measurements.