Oscillating Mirror Reflectance via Refractive Index Optimization
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Solution Overview
Problem
Optical scanning mirrors face challenges in achieving high reflectance and minimizing substrate deformation due to the need for a thin substrate and reduced film thickness, as they oscillate and operate at various incident angles, unlike fixed mirrors which can have thicker substrates and more films without deformation.
Innovation Solution
The optical scanning device incorporates a mirror with a thin substrate and a multilayer film configuration comprising a metal film, a low-refractive index film, and a high-refractive index film, optimized to enhance reflectance and reduce incident angle dependence, using atomic layer deposition and sputtering techniques to control film thickness and material selection for improved reflectance across the visible light range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the number of films stacked on the substrate is increased to achieve high reflectance, then the reflectance is improved, but the total thickness of the films increases causing substrate deformation
Solution Approach 1:
The patent changes the refractive index parameter of the films by using a low-refractive index material (SiO2 with refractive index of 1.46) in combination with a high-refractive index material (TiO2 with refractive index of 2.4). This parameter change allows achieving high reflectance with fewer film layers, thereby reducing total film thickness and preventing substrate deformation while maintaining the desired optical performance
Solution Approach 2:
The patent employs a composite multilayer film structure combining materials with different refractive indices (SiO2 and TiO2). This composite structure creates optical interference effects that enhance reflectance without requiring a large number of layers, thus achieving high reflectance while keeping the total film thickness small enough to avoid substrate deformation
2Ease of operation
If a thin substrate is used to enable mirror oscillation, then the oscillation capability is improved, but the substrate becomes more susceptible to deformation when films are stacked
Solution Approach 1:
By changing the refractive index parameter and using a low-refractive index material (SiO2), the patent reduces the number of film layers needed to achieve high reflectance. This parameter change ensures that even with a thin substrate designed for oscillation, the total film thickness remains small enough to prevent substrate deformation
Solution Approach 2:
The patent applies local quality by selectively using low-refractive index material (SiO2) in specific positions within the multilayer structure. This localized application of low-refractive index films helps control the overall film thickness and its impact on the thin substrate, enabling both oscillation capability and high reflectance
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 achieves higher reflectance and reduced incident angle dependence for both p-polarized and s-polarized light, allowing for efficient laser beam scanning with reduced power consumption and minimizing substrate deformation risks, while maintaining a compact film structure.
Implementation Method 1
a metal film formed on the substrate
Implementation Method 2
a dielectric multilayer film formed by stacking a low-refractive index film and a high-refractive index film alternately on the metal film
Data Source
AI summary
An optical scanning device includes a mirror that oscillates to scan incident visible light. The mirror includes a substrate, a metal film formed on the substrate, and an reflection enhancing film stacked on the metal film.