Optical Position Measuring Device Scanning Grating
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Solution Overview
Problem
Existing optical position measuring devices face contamination issues with scanning gratings, leading to impaired functionality, especially under harsh conditions, and existing protective measures increase system volume and susceptibility to tilting.
Innovation Solution
The optical position measuring device features scanning gratings on the side of the scanning plate facing the scale, with alternating grating materials of different refractive indices and hardness, and a continuous planarization layer or protective layer to ensure easy cleaning and compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the scanning grid is protected by means of a glass plate, then contamination is prevented, but the overall size of the scanning unit increases
Solution Approach 1:
The protective function is merged with the scanning plate itself by creating a planar front surface that serves both as the structural plate and as the protective element. The scanning grid is integrated onto this plate, eliminating the need for a separate protective glass plate while maintaining protection against contamination.
Solution Approach 2:
The protective function is extracted from a separate component (glass plate) and integrated into the scanning plate structure itself. The planar front surface of the scanning plate becomes the protective element, removing the need for additional protective components and reducing overall volume.
2Reliability
If the scanning grid is positioned on the side of the scanning plate facing away from the scale, then protection is improved, but the overall size increases and tilting susceptibility increases
Solution Approach 1:
Instead of positioning the scanning grid on the back side of the scanning plate (away from the scale), the invention inverts this arrangement by placing the scanning grid on the front side (facing the scale). This inversion maintains a compact design while reducing tilting susceptibility, as the scanning grid is now closer to the scale and less affected by angular deviations.
3Ease of operation
If the scanning grid is cleaned using ultrasonic cleaning method, then contamination is removed, but the scanning grid may be damaged
Solution Approach 1:
The invention changes the physical parameters of the scanning grid by using materials with different hardness values for the grid lines and background. This parameter change makes the grid more resilient to cleaning processes, allowing for effective contamination removal while preventing damage to the grid structure.
Solution Approach 2:
The scanning grid is constructed using composite materials with different hardness properties - harder materials for the grid lines and softer materials for the background. This composite structure provides both the necessary optical contrast and the mechanical resilience required for safe cleaning without damage.
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 design makes the scanning gratings less susceptible to dirt, allows for easy cleaning, reduces tilting sensitivity, and maintains a compact system structure, ensuring reliable operation under harsh conditions.
Implementation Method 1
at least the first grid material has a different refractive index and a different hardness compared to the second grid material
Implementation Method 2
Beams of light emitted from a light source along a scanning beam path illuminate the scale and the scanning grid
Data Source
Figure 1
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AI summary
The present invention relates to an optical position measuring device for detecting the position of two objects moving relative to each other. The position measuring device comprises a scale connected to one of the two objects and a scanning unit connected to the other object. This scanning unit has at least one scanning plate with at least one scanning grating arranged on a support body. The scanning grating is located on the side of the scanning plate facing the scale, with beams of light emitted from a light source along a scanning beam path striking the scale and the scanning grating once or several times. The surface of the scanning plate facing the scale is planar. The scanning grating comprises at least a first and a second grating material arranged alternately, with at least the first grating material having a different refractive index than the second grating material.