Coordinate Measuring Machine Autofocus Interval Strategy
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Solution Overview
Problem
Existing coordinate-measuring machines face challenges in accurately and efficiently determining the focused image distance of optical sensors, particularly when dealing with large catchment regions, which results in slow focusing and reduced reproducibility.
Innovation Solution
A method is proposed that involves specifying a catchment region with a maximum interval length, determining a minimum interval length based on the lens's depth of field, and incrementally reducing interval lengths to ensure the plane of best focus is within the interval, allowing for high-speed autofocusing with precise and reproducible results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the optical sensor is moved slowly through a large catchment region to ensure accurate focus determination, then measurement precision is improved, but productivity deteriorates due to extended focusing time
Solution Approach 1:
The catchment region is divided into multiple sub-regions or intervals, allowing the focusing process to be segmented into discrete evaluation points. This enables systematic sampling of the focus value curve at strategically selected positions, balancing measurement accuracy with reduced evaluation time compared to continuous scanning.
Solution Approach 2:
The system performs preliminary actions by pre-defining the catchment region boundaries and determining evaluation intervals before the actual focusing measurement begins. This preparatory setup allows for optimized measurement paths and reduces the time required during the actual focusing operation by avoiding real-time decision-making about measurement points.
2Productivity
If the optical sensor is moved quickly through the catchment region to improve productivity, then focusing speed is improved, but measurement precision deteriorates due to insufficient sampling
Solution Approach 1:
The system pre-calculates and defines the evaluation intervals and measurement points within the catchment region before executing the focusing measurement. This preliminary setup enables high-speed execution during the actual measurement while ensuring that critical sampling points are not missed, thus maintaining measurement precision despite increased speed.
Solution Approach 2:
The system replaces continuous mechanical scanning with discrete digital evaluation at pre-determined intervals. By substituting continuous motion-based measurement with interval-based sampling, the system achieves faster focusing determination while maintaining sufficient measurement precision through strategic point selection.
3Adaptability or versatility
If the catchment region size is increased to accommodate arbitrary workpiece positions, then adaptability is improved, but device complexity increases due to larger search space
Solution Approach 1:
The system segments the enlarged catchment region into manageable intervals or sub-regions, allowing the control device to systematically evaluate focus values at defined points within each segment. This segmentation approach enables the system to handle arbitrary catchment region sizes without proportionally increasing complexity, as the evaluation process is broken down into standardized steps.
Solution Approach 2:
The system manages the expanded search space by dynamically adjusting evaluation parameters such as interval length and sampling density based on the specific catchment region requirements. This parameter adaptation allows the system to maintain efficient operation across varying catchment region sizes, preventing complexity from scaling linearly with region size.
Data Source
AI summary
The present invention relates to a method for ascertaining a focus image distance of an optical sensor, which is provided with a lens, of a coordinate-measuring machine onto a workpiece to be measured, wherein the optical sensor and the workpiece are movable relative to one another in a Z direction such that a distance in the Z direction between the workpiece and the optical sensor is variable. The present invention furthermore relates to a corresponding coordinate-measuring machine and to a computer program product.