Optical Encoder Grid Plate Black Plating SNR
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Solution Overview
Problem
Existing optical encoder grid plates face challenges in achieving a high signal-to-noise ratio (SNR) due to the formation of recesses by etching, which results in a significant difference in level between the mirror surface and the recess bottom, leading to diffused reflection and reduced precision, and the thin black plating layer is prone to peeling.
Innovation Solution
The optical encoder grid plate uses a metal base material with a black plated layer, where the average surface roughness is between 0.008 µm to 0.05 µm and the black plated layer thickness is set between 0.3 µm to 3 µm, formed without etching, to enhance plating properties and reduce peeling, thereby improving the SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If recesses are formed by etching to create low reflection surfaces, then the optical encoder grid plate can detect displacement, but the difference in level between mirror surface and recess bottom becomes 10 μm or greater causing diffused reflection and lowered S/N ratio
Solution Approach 1:
The patent extracts the harmful etching process that creates large depth differences and replaces it with a plating process. By removing the etching step and using black plating on a flat surface, the invention eliminates the machined taper and large depth differences while maintaining the optical encoding function.
Solution Approach 2:
The patent changes the key parameter from depth-based differentiation (etching creating 10 μm or greater depth differences) to surface property differentiation (plating creating reflection vs. absorption properties on the same plane). This parameter change from geometric depth to surface optical property resolves the contradiction by maintaining functionality while eliminating harmful depth differences.
2Measurement precision
If black plating is applied to form light absorption grids, then the grid pattern can be created, but the thin plating layer is prone to peeling
Solution Approach 1:
The patent changes the plating thickness parameter from thin (prone to peeling) to a specific optimal range of 0.3 μm to 3 μm. This parameter optimization ensures sufficient adhesion strength while maintaining the optical absorption function. The controlled thickness range prevents peeling while achieving the required light absorption for grid detection.
3Illumination intensity
If the black plated layer is made thin as thin as 10 μm or less to improve optical properties, then light absorption is enhanced, but the plating becomes weak and prone to peeling
Solution Approach 1:
The patent optimizes the plating thickness parameter within the range of 0.3 μm to 3 μm, which is thicker than the conventional 10 μm or less approach. This parameter optimization balances two competing requirements: sufficient thickness for mechanical strength and adhesion, while maintaining thinness for effective light absorption in the visible and near-infrared ranges used by optical encoders.
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 approach results in an optical encoder grid plate that is strong against peeling, has excellent plating properties, and achieves a high SNR by minimizing the difference in level between the reflection surface and the grid, eliminating side edges, and maintaining precision in grid width.
Implementation Method 1
the grids are formed by a black plated layer... having light absorption grids formed a surface of the base material using plating
Implementation Method 2
a base material whose one of surfaces is the reflection surface... irradiation light reflected by a reflection surface is received
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3(a)~3(d)
AI summary
A producing method of an optical encoder grid plate in which the optical encoder grid plate is used as an optical encoder which detects a displacement amount or a displacement direction, and by receiving reflection light reflected by the reflection surface, the optical encoder grid plate includes a base material 20 and grids, metal is used as the base material 20, and grids 30 are formed by a black plated layer, average roughness Ra of the metal surface 21 is in a range from 0.008 µm to 0.05 µm, the black plated layer is made thinner than 3 µm. The present invention provides the optical encoder grid plate having the above-described configuration which is strong against peeling and which has excellent plating property, and has a high SN ratio, and the invention also provides the producing method of the optical encoder grid plate.