Optical Position Measuring Device With Spatially Limited Reference Marking
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Solution Overview
Problem
Existing optical position measuring devices face challenges in referencing measuring graduations without disturbing the actual position measurement, particularly when using position correction tables, which is essential for high-precision applications.
Innovation Solution
The optical position measuring device incorporates a first measuring standard with a spatially limited marking that generates a signal drop at a defined position, allowing for referencing without impairing the position measurement, and a second reference marking that is only activated when the first scale is in its specified position, enabling accurate referencing of both measuring graduations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reference marking is integrated into the measuring scale, then referencing can be performed, but the position signals are adversely affected
Solution Approach 1:
The measuring scale is divided into two distinct parts: the measuring graduation (first measuring graduation) and the reference marking (first marking). The reference marking is spatially limited and integrated into the scale structure, while the measuring graduation extends over the full measurement range. This segmentation allows the reference marking to be activated only at specific positions without continuously interfering with position measurement signals.
Solution Approach 2:
The reference marking has different optical properties compared to the measuring graduation. It is designed with specific local characteristics (different structure) that enable it to generate a signal drop when illuminated, while the measuring graduation maintains uniform properties for continuous position measurement. This local differentiation allows the reference marking to be distinguished and activated only when needed.
2Measurement precision
If referencing is performed for each measuring graduation in devices with independently movable scales, then accurate position determination is achieved, but the complexity of the referencing process increases
Solution Approach 1:
The optical path and detection system are designed to handle both the first measuring graduation and the second measuring graduation through a unified referencing approach. The single marking recognition unit processes signals from both scales, and the evaluation unit coordinates the referencing of both measuring graduations simultaneously, reducing the overall system complexity despite needing to reference multiple independent scales.
Solution Approach 2:
The reference marking on the first scale serves a dual function: it acts as both a reference for the first measuring graduation and as a trigger to activate the second reference marking on the second scale. This multi-functionality reduces the number of independent reference systems needed and simplifies the referencing process for devices with multiple independently movable scales.
3Productivity
If the full measuring range is maintained available, then measurement capability is preserved, but referencing cannot be performed without disrupting position measurement
Solution Approach 1:
The reference marking is designed to generate a signal drop only at specific periodic positions along the measurement range, rather than continuously. The spatially limited reference marking is positioned such that it is illuminated and activates only when the scanning beam reaches that specific location, allowing position measurement to continue uninterrupted at all other positions while still enabling periodic referencing.
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 solution allows for accurate referencing of measuring graduations without disrupting the position measurement, ensuring highly accurate position determination and correcting grid errors, while maintaining the full measuring range availability.
Implementation Method 1
The first marking (15) is designed in such a way that it results in a signal drop in the detected signals at the at least one defined position along the first measurement direction
Implementation Method 2
a beam of rays incident from the light source being split at the first measuring graduation into two partial beams of rays, the partial beams of rays propagating in the direction of the transmitted-light grating of the second measuring graduation and experiencing diffraction there
Implementation Method 3
the diffracted partial beams of rays in the direction of the Reflector propagate the second measurement graduation and experience a back-reflection there
Implementation Method 4
the diffracted partial beams of rays propagate in the direction of the first measurement graduation, where a superimposition of the partial beams of rays d he relative position of the two material measures can be generated
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
The present invention relates to an optical position measuring device. This device comprises a first physical element having a first measuring scale and movably arranged along a first measuring direction. The first physical element has a spatially limited first marking at at least one defined position along the first measuring direction, which differs from the first measuring scale. Furthermore, the position measuring device comprises a second physical element having a second measuring scale and movably arranged along a second measuring direction. The second physical element has a second reference marking at at least one position, which can only be used to generate at least one second reference signal at a reference position of the second physical element if the first physical element is in the defined position along the first measuring direction specified by the first marking (Fig. 1).