Optical Position Measuring Device with Chirped Reference Marking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical position measuring devices with divergent illumination do not effectively utilize chirped reference markings to generate high-resolution reference signals, and are sensitive to changes in scanning distance and contamination.
Innovation Solution
An optical position measuring device with a material measure and a scanning unit using divergent illumination, featuring mirror-symmetrically arranged reference marking subfields with locally variable graduation periods, and a detector arrangement with elements whose center distances change in the same direction as the graduation periods, ensuring high-resolution reference pulse generation with reduced sensitivity to scanning distance and contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If divergent illumination is used in optical position measuring devices, then the system can operate without collimated beams, but the generation of high-resolution reference signals using chirped reference markings is not effective and the system becomes sensitive to scanning distance changes and contamination
Solution Approach 1:
The detector arrangement is designed with locally varying properties - the spacing between detector elements changes across the array to match the chirped graduation periods in the reference marking. This local adaptation allows each detector element to optimally receive and process the corresponding spatial frequency component of the reference signal, enabling high-resolution reference signal generation despite divergent illumination
Solution Approach 2:
The system changes the spatial arrangement parameter of the detector elements - the center distances between adjacent detector elements are varied to correspond to the locally variable graduation periods. This parameter matching compensates for the divergent beam effects and enables effective chirped reference marking utilization
2Device complexity
If divergent illumination is used with conventional detector arrangements, then the system is simpler to implement, but it becomes sensitive to changes in scanning distance between scale and scanning unit
Solution Approach 1:
The detector arrangement uses variable spacing between elements that corresponds to the chirped reference marking structure. This parameter matching creates a relationship where the detection geometry adapts to the reference marking, reducing sensitivity to scanning distance variations
3Object-affected harmful factors
If single-field scanning is used, then contamination sensitivity is reduced, but the signal amplitude and immunity to interference are lower
Solution Approach 1:
The detector arrangement is optimized for single-field scanning by matching the detector element spacing to the local graduation periods. This local optimization ensures that the entire illuminated field of the reference marking contributes effectively to signal generation, maximizing signal amplitude and interference immunity while maintaining contamination resistance
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
The solution generates high-resolution reference signals with large amplitudes, high immunity to interference, and low signal noise, effectively using the entire illuminated field of the reference marking.
Implementation Method 1
The scanning means comprise at least one light source that radiates divergently in the direction of the material measure
Implementation Method 2
The position measuring device is based on what is known as an interferential scanning principle, in which the first grating in the scanning beam path is collimated, i.e. it is illuminated with a parallel beam of rays. The displacement-dependent scanning signals in the form of the incremental and reference signals are obtained from the constructive and destructive superimposition of several partial beams of rays
Implementation Method 3
a detector arrangement with elements that are arranged along the measuring direction
Data Source
Figure 1
Figure 2~3
Figure 4a~4c
AI summary
The present invention relates to an optical position measuring device for detecting the position of two objects that are movable relative to each other in at least one measuring direction. The position measuring device has a material measure connected to one of the two objects, said measure comprising an incremental scale extending in the measuring direction, and at least one reference marking at a reference position. The reference marking comprises two reference marking partial fields being disposed mirror-symmetrically relative to a reference marking symmetry axis, each of said partial fields consisting of a structure, extending in the measuring direction, having a locally changing graduation period. The position measuring device further has a scanning device connected to the other of the two objects, wherein scanning means are associated with the scanning device, said means being used for generating at least one reference signal at the reference position. The scanning means comprise at least one light source that emits in a divergent manner in the direction of the material measure, and a detector arrangement having elements that are disposed along the measuring direction such that starting from a central detector arrangement symmetry axis and extending in the measuring direction, the center distances between adjacent elements change in the same direction as they do starting from the reference marking symmetry axis of the graduation periods of the structures in the reference marking partial fields.