Grating Boundary Line Stair Approximation for Optical Position Measuring Devices
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Solution Overview
Problem
The production of lattice structures with curved boundary lines in optical position measuring devices is challenging due to the limitations of electron beam or laser beam writers, which work in orthogonal coordinate systems, leading to approximated boundary lines with abrupt edge roughness, causing wavefront disturbances and reduced measuring accuracy.
Innovation Solution
A grating structure with boundary lines approximated by stair lines consisting of orthogonal stair line sections, where the distance between stair step points varies based on the angle between the boundary line and the stair line section, minimizing edge roughness and avoiding abrupt changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If curved boundary lines of division areas are approximated by step lines using orthogonal coordinate systems, then the lattice structure can be manufactured using electron beam or laser beam writers, but abrupt changes in edge roughness occur at section boundaries
Solution Approach 1:
The curved boundary line is divided into multiple sections, where each section is approximated by step lines. The key innovation is that adjacent sections overlap, creating a transition zone where the step lines gradually change position. This segmentation with overlap allows the boundary to be manufactured using orthogonal coordinate systems while avoiding abrupt edge roughness changes.
Solution Approach 2:
The invention introduces dynamic adjustment of the step line positions in the transition zones. Instead of fixed step lines, the position of step lines varies continuously in the overlap regions, creating a dynamic approximation that adapts to the curved boundary shape. This dynamic approach eliminates abrupt changes in edge roughness while maintaining manufacturability.
2Ease of manufacture
If the boundary lines are approximated by step lines to enable manufacturing, then wavefront disturbances occur that impair measurement accuracy
Solution Approach 1:
By segmenting the boundary line approximation into overlapping sections, the invention reduces the magnitude of abrupt changes in each transition zone. The overlapping structure distributes the approximation error across multiple zones, preventing large wavefront disturbances that would occur with single-step approximations.
Solution Approach 2:
The invention changes the parameters of the step line approximation by allowing variable step positions in transition zones rather than fixed positions. This parameter variation smooths the edge roughness profile, reducing wavefront disturbances and improving measurement accuracy while maintaining the ability to manufacture using orthogonal coordinate systems.
Data Source
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AI summary
The present invention relates to a grid structure for an optical position measuring device. This grid structure comprises division areas that have at least one boundary line which is oriented neither completely orthogonal nor completely parallel to the two coordinate axes of an orthogonal reference coordinate system. The boundary line is at least partially approximated by a stepped line consisting of successive, orthogonally oriented first and second step line segments, which adjoin each other at step points and are oriented parallel to the two coordinate axes of the reference coordinate system. The stepped line is fitted between two approximation parallels that run at equal intervals on both sides of the boundary line, with the step points lying on the approximation parallels (FIG. 4).