Optical Positioning Device Abbe Error Reduction
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Solution Overview
Problem
Existing optical position measuring devices for XY tables face challenges in achieving high precision due to significant Abbe distances between the effective measuring point and the tool center point, leading to measurement errors from tilting and guide deviations, especially in the Z-direction.
Innovation Solution
An optical position measuring device with a scanning system that splits a light beam into two partial beams, which are deflected and recombined using additional deflection elements to ensure the effective measuring point is positioned away from the scanning head, allowing for minimal Abbe distances and precise alignment with the tool center point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the effective measuring point is positioned close to the scanning head, then the device complexity is reduced, but the measurement precision deteriorates due to large Abbe distances causing errors from tilting and guide deviations
Solution Approach 1:
The patent extends the measurement from a single point to a plane by using multiple scanning heads arranged in a specific geometry. This dimensional extension allows the effective measuring plane to be positioned close to the tool center point in three-dimensional space, eliminating large Abbe distances while maintaining reasonable device complexity through systematic arrangement of components.
Solution Approach 2:
The patent introduces a neutral pivot point as an intermediary concept that serves as the effective measuring point for the entire system. By positioning this neutral pivot point at the tool center point through careful arrangement of multiple scanning heads, the system eliminates measurement errors from tilting and guide deviations without requiring complex individual head positioning.
2Measurement precision
If three stationary scanning heads are used to shift effective measuring points to the tool center point, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The patent makes each scanning head serve multiple functions: each head not only measures position in its primary direction but also contributes to defining the effective measuring plane and provides redundancy for error compensation. This multi-functionality reduces the need for additional specialized components, thereby limiting the increase in device complexity while achieving high measurement precision.
Solution Approach 2:
The patent combines the measurement functions of multiple scanning heads into a unified effective measuring plane that coincides with the tool center point. By merging the measurement data and geometric contributions of all scanning heads, the system achieves high precision measurement without requiring each individual head to be independently positioned with extreme precision, thus limiting complexity increase.
3Ease of manufacture
If the effective measuring plane is positioned far from the tool center point in the Z-direction, then the ease of manufacture is improved, but the measurement precision deteriorates due to large Abbe distances
Solution Approach 1:
The patent creates a dynamic effective measuring plane that can be positioned at different Z-heights by adjusting the arrangement and positioning of the scanning heads. This dynamic positioning capability allows the effective measuring plane to be brought close to the tool center point in the Z-direction, eliminating large Abbe distances while maintaining ease of manufacture through adjustable rather than fixed positioning.
Solution Approach 2:
The patent changes the geometric parameters of the scanning head arrangement to position the effective measuring plane at the desired Z-height coincident with the tool center point. By adjusting parameters such as the vertical positioning of scanning heads and the angles of their measurement beams, the system achieves both ease of manufacture and high measurement precision without large Abbe distances.
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 configuration significantly reduces Abbe distances to nearly zero, enhancing measurement accuracy and allowing for simpler, less costly guide systems, while maintaining high precision in positioning despite tilting and guide deviations.
Implementation Method 1
In order to generate high-resolution position signals, such optical position measuring devices preferably use interferential scanning principles, in which a beam of rays emitted by a light source is split into at least two partial beams of rays and are superimposed in an interfering manner after the scale has been acted upon once or several times.
Implementation Method 2
a beam of rays emitted by a light source undergoes splitting into two partial beams of rays via the splitting grating, the partial beams of rays then propagate in the direction of a grating on the opposite side of the scanning plate and are each deflected in the direction of the optical axis
Data Source
Figure 1
Figure 2
Figure 3a
AI summary
The present invention relates to an optical position measuring device for detecting the relative position of a physical dimension and at least one scanning head, which are movable relative to each other along at least one measuring direction. The optical scanning is designed such that the effective measuring point of the scanning is located at a defined distance in the direction away from the physical dimension that is oriented away from the scanning head (Fig. 2).