CMM Probe Zero Positioning via Interferometer Feedback
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Solution Overview
Problem
Existing measuring devices face limitations in measurement accuracy due to uncertainties in calibrated standards and gauge blocks, as well as inaccuracies from the probe unit itself, leading to reduced measurement precision.
Innovation Solution
A measuring device with two probe units and a control unit that defines a reference plane by having the probe elements touch each other, allowing for precise measurement without calibrated bodies, and uses interferometer arrangements to determine distances with high precision, accounting for environmental influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibrated standards or gauge blocks are used to define zero position, then a reference position can be established, but measurement accuracy is limited by the uncertainty of these reference objects
Solution Approach 1:
The patent introduces an interferometer as an intermediary measurement system that serves as a mediator between the probe element and the reference objects. The interferometer measures the position of the probe element with high precision independently of the calibrated standards, thereby eliminating the uncertainty propagation from reference objects to the final measurement
Solution Approach 2:
The patent replaces the mechanical contact-based measurement system with an optical interferometry system. Instead of relying on mechanical gauge blocks and calibrated standards, the system uses laser interferometry to measure the position of the probe element, substituting mechanical reference objects with optical field-based measurement
2Measurement precision
If probe units are used to detect length measurements, then workpiece dimensions can be measured, but additional measurement inaccuracies arise from the probe unit itself
Solution Approach 1:
The patent implements a feedback mechanism where the interferometer continuously monitors the position of the probe element and provides precise position information back to the measurement system. This feedback allows for real-time correction of probe unit inaccuracies and enables accurate measurement even when the probe unit itself has manufacturing tolerances
Solution Approach 2:
The patent substitutes the mechanical position sensing mechanism within the probe unit with an optical interferometric sensing system. The interferometer optically tracks the position of the probe element, replacing mechanical position encoders or scales that would be subject to similar accuracy limitations
3Measurement precision
If calibrated standards with high precision are used, then measurement accuracy improves, but the complexity and cost of the measuring device increases
Solution Approach 1:
The interferometer serves as an intermediary that decouples the measurement accuracy from the complexity of calibrated standards. Rather than requiring multiple precision-calibrated reference objects of various shapes and sizes, the interferometer provides a single, universal high-precision measurement method that works with simple probe elements
Solution Approach 2:
The patent employs simple, easily manufacturable probe elements that do not require expensive calibration certificates or traceability to national standards. These simple probe elements can be replaced if needed without significant cost, replacing the need for expensive, fragile, and complex calibrated reference objects
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 enables highly precise measurements by eliminating the need for calibrated standards and accurately determining distances, while also correcting for environmental factors, thereby enhancing measurement accuracy.
Implementation Method 1
an interferometer arrangement (25) is assigned to each carrier part (15, 33). Each interferometer arrangement (25) has a laser interferometer (26) which emits a laser measuring beam (L1, L2)
Data Source
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AI summary
The invention relates to a measuring device (10) and a method for operating it. The measuring device (10) has two measuring units (12), (13), each with a sensing unit (16), (35). Each sensing unit has a sensing element (18), (37). Each sensing element (18), (37) has an outer sensing side (18a) or (37a) in a probing direction (x) and an inner sensing side (18i) or (37i) opposite the outer sensing side. To define a zero position or a reference plane (B) perpendicular to the probing direction (x), the two sensing elements can be brought into contact with their respective outer sensing sides (18a), (37a) or their respective inner sensing sides (18i), (37i). As soon as one of the two touch units (16) or (35) detects the contact between the associated touch surfaces (18a), (37a) or (18i), (37i), a reference plane (B) is defined as the zero position in the probing direction (x) by the point of contact between the two touch elements.This allows the zero position to be set easily and accurately without calibrated standards or gauge blocks.