Reflective Optical Scale Protective Layer for Higher Encoder Reflectivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The reflection coefficient of the light incident in the high reflection region of reflective type optical scales is degraded due to surface roughening and etching residue when a low reflection layer is formed directly on a high reflection layer, despite the use of a protective layer.
Innovation Solution
A reflective type optical scale is designed with a high reflection layer, a protective layer, and a low reflection layer arranged in a specific thickness direction, where the thickness of the protective layer is adjusted to satisfy the formula d=mλ/[2n*cos{Arcsin(sin(θ/n)} to enhance the reflection coefficient in the high reflection region, and the protective layer is made of an organic material to prevent surface roughening during etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a low reflection layer is formed directly on a high reflection layer, then the structure is simple and easy to manufacture, but the surface of the high reflection layer is roughened and etching residue remains, degrading the reflection coefficient
Solution Approach 1:
A protective layer is introduced as an intermediary between the high reflection layer and the low reflection layer. This protective layer prevents direct contact between the etching solution and the high reflection layer, thereby preventing surface roughening and etching residue formation while maintaining the simplicity of the overall structure.
2Manufacturing precision
If a protective layer is arranged between the high reflection layer and the low reflection layer, then surface roughening is prevented, but the reflection coefficient of the light incident in the high reflection region is degraded
Solution Approach 1:
The thickness of the protective layer is precisely controlled to satisfy the formula: d = m×λ/[2n×cos{Arcsin(sin(θ/n))}] where d is the thickness, m is an integer, λ is the wavelength of incident light, n is the refraction index, and θ is the incident angle. This parameter optimization ensures that the protective layer protects the surface while maintaining high reflection coefficient through constructive interference of reflected light.
3Manufacturing precision
If the thickness of the protective layer is increased to better protect the high reflection layer, then surface protection is improved, but the reflection coefficient is further degraded due to increased light absorption and interference
Solution Approach 1:
The thickness of the protective layer is precisely optimized to satisfy the formula: d = m×λ/[2n×cos{Arcsin(sin(θ/n))}] where d is the thickness, m is an integer, λ is the wavelength of incident light, n is the refraction index, and θ is the incident angle. This parameter optimization ensures that the protective layer protects the surface while maintaining high reflection coefficient through constructive interference of reflected light.
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
The solution improves the reflection coefficient in the high reflection region by aligning the phases of reflected light, reducing surface roughness, and inhibiting irregular reflections, thereby enhancing detection accuracy and signal strength.
Implementation Method 1
a protective layer 2, and a low reflection layer 3 arranged in a patterned shape, in a thickness direction, in this order... the thickness of the protective layer 2 satisfies the specified range... the reflection coefficient of the light incident in the high reflection region is improved
Implementation Method 2
when d (μm) designates a thickness of the protective layer 2, and θ (°) designates an incident angle of an incident light to the protective layer 2... n is a refraction factor of the protective layer 2... below formula (1) is satisfied
Data Source
AI summary
A reflective type optical scale for encoder including: a high reflection layer, a protective layer, and a low reflection layer arranged in a patterned shape, in a thickness direction, in this order. There are a low reflection region where the low reflection layer is arranged, and a high reflection region where the protective layer is exposed, and when d (μm) designates a thickness of the protective layer, and θ (°) designates an incident angle of an incident light to the protective layer, below formula (1) is satisfied.d=mλ/[2n*cos {Arcsin(sin θ/n)}] (1)(In the formula, n is a refraction factor of the protective layer, Δ is a wavelength (μm) of the incident light, and m is a number satisfying 0<m≤0.3 or p−0.3≤m≤p+0.3 (p is an integer that is 1 or more and 3 or less.)