Optical Positioning Device Scanning Grid Segmentation
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Solution Overview
Problem
Existing optical position measuring devices face challenges in reliably detecting fine stripe patterns due to increased sensitivity to contamination and inhomogeneities, particularly linear contamination, which affects the accuracy of incremental signal generation.
Innovation Solution
The design incorporates a scanning grid with periodically arranged blocks of grid sections, each causing beams to be deflected in multiple spatial directions, with detector elements positioned to capture these deflections in a separate detection plane, reducing contamination susceptibility and enhancing signal modulation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the stripe pattern periodicity is reduced to achieve higher resolution, then measurement precision is improved, but the width of photodiodes must be reduced below manufacturing minimums
Solution Approach 1:
The scanning grid is divided into multiple grid sections (first, second, third, fourth grid sections) arranged in a specific pattern. Each grid section deflects light beams in different spatial directions, enabling the system to detect fine stripe patterns without requiring excessively narrow photodiodes. This segmentation allows the photodiode width to remain above the manufacturing minimum while achieving high measurement precision through the combined output of multiple detector elements.
2Measurement precision
If a scanning grid with multiple grid sections is used to detect fine stripe patterns, then measurement precision is improved, but sensitivity to contamination of the measuring scale increases
Solution Approach 1:
The patent arranges grid sections and detector elements in specific spatial configurations with defined deflection angles. By orienting grid sections at different angles and positioning detector elements in corresponding spatial directions, the system creates a geometric arrangement where contamination effects on the measuring scale are distributed across multiple detection paths. This dimensional arrangement reduces the impact of linear contamination on any single measurement channel.
3Object-affected harmful factors
If grid sections are arranged exclusively in the measuring direction with specific periodicity, then susceptibility to contamination is reduced, but device complexity increases
Solution Approach 1:
The scanning grid is designed as a periodic structure where identical or similar grid section patterns are repeated across different blocks. Each grid section performs the same fundamental function of deflecting light beams, but their collective arrangement in multiple spatial directions enables the system to simultaneously achieve contamination resistance and high-resolution detection. This universal repeating pattern simplifies manufacturing while maintaining the required functionality.
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 enables reliable scanning of very fine stripe patterns with high efficiency and reduced sensitivity to contamination, resulting in stable and accurate incremental signal generation.
Implementation Method 1
Each grid section has a periodic grid structure, which causes the beams of rays propagating through this grid section to be deflected in several spatial directions
Data Source
Figure 1a
Figure 1b
Figure 1c~1d
AI summary
An optical position measuring device for generating n > 1 phase-shifted, displacement-dependent incremental signals with respect to two objects moving relative to each other in a measuring direction is described. This device consists of a scale and a scanning unit with a scanning grating arranged in a scanning plane and several detector elements downstream of the scanning grating. The interaction of the beams emitted by a light source with the scale and optional additional gratings in the scanning beam path results in a fringe pattern with the fringe pattern periodicity TPS in the scanning plane. The scanning grating for generating all incremental signals consists of several blocks arranged periodically in the measuring direction with the scanning grating periodicity TPAG = TPS.Each block comprises n grating sections of width bx = TPAG/n, arranged exclusively in the measurement direction, and each grating section has a periodic grating structure that deflects the beams propagating through this grating section in several spatial directions, with the resulting spatial directions of the grating sections differing within a block. Detector elements are arranged in the different spatial directions in a detection plane, the detection plane being located in a region where the beams emanating from the scanning grating are completely spatially separated (Figure 1c).