Scanning Plate Anti-Reflection Layer Segmentation
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Solution Overview
Problem
Existing scanning plates for optical position measuring devices face challenges in effectively suppressing disruptive reflections, which can falsify position measurements, and current anti-reflection coatings require complex processing steps.
Innovation Solution
A scanning plate with a substrate featuring a thin anti-reflection layer of low absorption coefficient materials like silicon or germanium, applied using thin-film technology, is designed such that the layer is only present on the grating bars and not in the gaps, reducing disruptive back reflections without adding complexity to the etching process for grating production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an anti-reflection layer is applied to the entire surface of the scanning plate, then disruptive reflections are suppressed, but the production process becomes more complex
Solution Approach 1:
The anti-reflection layer is segmented to be applied only on specific functional areas (grating bars and windows) rather than the entire surface. This is achieved by applying the layer to a master pattern and transferring it selectively, avoiding the need for complex masking processes while reducing disruptive reflections in critical areas.
Solution Approach 2:
The anti-reflection coating is applied locally only where needed - on the grating bars and window areas - rather than uniformly across the entire scanning plate surface. This localized application suppresses disruptive reflections in functional areas while simplifying the overall production process by avoiding unnecessary coating in non-functional areas.
2Object-affected harmful factors
If the anti-reflection layer is continuous across the grating area, then reflections are suppressed, but diffraction efficiency decreases
Solution Approach 1:
The anti-reflection layer is segmented into discrete regions corresponding to grating bars and windows, with gaps between them. This segmentation allows the layer to suppress reflections on the grating bars while leaving the gaps open to maintain proper light diffraction patterns, thus preserving diffraction efficiency.
Solution Approach 2:
The anti-reflection coating is applied with local quality - present on grating bars where reflection suppression is needed, and absent from gaps where diffraction functionality is critical. This selective application optimizes both reflection suppression and diffraction efficiency.
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 significantly reduces unwanted reflections in the grating areas while maintaining high diffraction efficiency and simplifying the production process, ensuring accurate position measurements and improved signal quality.
Implementation Method 1
The surface has an anti-reflection layer that is interrupted in the area of the gaps. The anti-reflection layer comprises a layer of a material with a low absorption coefficient and high real refractive index (at a wavelength of approx. 1 μm), such as silicon or germanium
Implementation Method 2
The anti-reflection layer comprises a layer of a material with a low absorption coefficient and high real refractive index (at a wavelength of approx. 1 μm)
Implementation Method 3
the surface has at least one region with a grid formed from gaps and webs, the gaps being formed in the substrate
Implementation Method 4
Gratings are arranged both on the scale and on the scanning plate, which split the light into different orders of diffraction or combine it again and cause it to interfere
Implementation Method 5
the light from a light source in the scanning head is guided through a scanning plate onto a scale
Implementation Method 6
reflected from there back to the scanning head and detected in one or more detectors
Data Source
Figure 1~2
Figure 3
AI summary
A scanning plate for an optical position measuring device is disclosed, comprising a substrate (SUB) with a transmission-operated surface (O) having various functional areas (G, F, R). The surface (O) has at least one area with a grid (G) formed from gaps (L) and ribs (S), wherein the gaps (L) are formed in the substrate (SUB). The surface (O) has an antireflective coating (AR) which is interrupted in the area of the gaps (L).