Confocal White Light Sensor Calibration on Coordinate Measuring Machines
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Solution Overview
Problem
Confocal white light sensors on coordinate measuring machines face challenges in maintaining measurement accuracy due to changes in their operating state, such as manufacturing tolerances and environmental conditions, which affect the focus distance and require complex reference measurements for calibration.
Innovation Solution
A method where the confocal white light sensor is coupled to a coordinate measuring machine, and measurement signals are generated relative to a reference body, allowing the position measurement system to determine the focus distance accurately, enabling precise measurement of object distances without the need for additional calibration steps, and allowing for the use of different sensors with stored linearization parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If confocal white light sensors are used on coordinate measuring machines, then measurement capability is provided, but measurement accuracy deteriorates due to changes in operating state and focus distance variations
Solution Approach 1:
The patent performs reference measurements preliminarily to determine the relationship between measurement signals and actual distances before actual measurements. This preliminary calibration stores linearization parameters that compensate for operating state variations, ensuring measurement accuracy without requiring repeated calibration during operation.
Solution Approach 2:
The patent changes the parameter representation by storing linearization parameters that describe the relationship between measurement signals and actual distances. These parameters are used to transform raw sensor signals into accurate distance measurements, compensating for variations in focus distance and operating conditions.
2Measurement precision
If complex reference measurements are performed for calibration, then measurement accuracy is maintained, but device complexity and calibration time increase
Solution Approach 1:
The patent extracts the essential calibration information into linearization parameters that are stored and reused. Instead of performing complex reference measurements repeatedly, the system extracts the relationship between measurement signals and actual distances into compact parameter sets, simplifying the calibration process while maintaining accuracy.
Solution Approach 2:
The reference measurements and determination of linearization parameters are performed preliminarily before actual measurement operations. This preliminary calibration step establishes the transformation relationship once, and the stored parameters are then used for all subsequent measurements, reducing overall system complexity.
3Adaptability or versatility
If different confocal white light sensors are used on the same machine, then sensor versatility is improved, but recalibration requirements increase complexity
Solution Approach 1:
The patent creates a universal calibration approach where linearization parameters are determined for each sensor individually but stored in a common data structure. This allows different sensors to be interchanged and used with the same coordinate measuring machine using the same software and parameter storage mechanism, achieving universality in the system architecture.
Solution Approach 2:
The patent copies the linearization parameter determination process for each sensor, creating individual parameter sets that can be stored and retrieved independently. Each sensor undergoes the same calibration procedure, and the resulting parameters are copied into the system's data storage, enabling easy sensor replacement without reprogramming.
4Ease of operation
If focus distance changes occur, then operating flexibility is improved, but measurement accuracy deteriorates
Solution Approach 1:
The patent implements feedback by using the position measurement system to monitor the actual distance between the sensor and reference body, then using this information to determine and store linearization parameters. This feedback loop ensures that focus distance variations are compensated for, maintaining measurement accuracy despite changes in operating conditions.
Solution Approach 2:
The patent compensates for focus distance changes by transforming the raw measurement signals using stored linearization parameters. These parameters encode the relationship between signal intensity and actual distance, allowing the system to maintain measurement accuracy even when focus distance varies during operation.
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 simplifies the operation of confocal white light sensors, ensures high measurement accuracy, and allows for the use of various sensors on the same machine without requiring extensive recalibration, reducing complexity and improving reproducibility.
Implementation Method 1
The focusing optical unit effects dispersion of the radiation, i.e., chromatic aberration occurs. As a result, the radiation components of the different wavelengths are focused at different distances to the focusing optical unit.
Implementation Method 2
If an object that reflects radiation back in the direction of the sensor is located in the respective focus (focal point or focal line), the sensor detects radiation of the wavelength with maximum intensity that was back-reflected in the focus.
Data Source
AI summary
A method for operating a confocal white light sensor on a coordinate measuring machine including a sensor carrier configured to couple a coordinate measurement sensor that is movable in a straight movement direction relative to a base of the coordinate measuring machine is provided. A confocal white light sensor is coupled to the sensor carrier and oriented in the straight movement direction toward a reference body. The sensor carrier and the reference body are moved relative to one another in the straight movement direction, and a measurement signal representing a distance between the confocal white light sensor and the reference body is generated at different movement positions. Information relating to a relationship between measurement signals of the confocal white light sensor and an actual distance of the white light sensor to a measurement object is obtained and a measurement value of the object distance is generated.