Concavo-convex Optical Element for Directional Near-Infrared Reflection
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Solution Overview
Problem
Existing optical elements fail to selectively directionally reflect light in specific wavelength bands while transmitting other wavelengths effectively, leading to heat island phenomena and reduced transparency due to specular reflection and degradation issues.
Innovation Solution
An optical element with a concavo-convex surface featuring a wavelength-selective reflective layer comprising a metal layer, a protective metal oxide layer, and a high refractive index layer, which selectively directionally reflects light in a specific wavelength band while transmitting other wavelengths, using materials like niobium oxide to reduce stress and prevent degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a reflective layer is provided on flat window glass to shield near-infrared light, then heat ray reflecting properties are improved, but specular reflection causes light to reach outdoor buildings or ground and increase ambient temperature
Solution Approach 1:
The patent applies a concavo-convex surface structure to the window glass, transforming the flat surface into a curved microstructure. This curvature causes incident sunlight to be reflected in multiple directions rather than specularly, directing heat rays upward toward the sky while maintaining visible light transmission. The micro-concave and micro-convex portions create diffuse reflection patterns that prevent heat accumulation in urban areas.
Solution Approach 2:
The invention adds a spatial dimension to light reflection by creating a three-dimensional concavo-convex surface topology. Instead of reflecting light in a single plane (specular reflection), the multi-dimensional surface structure redirects near-infrared light vertically toward the sky, separating the reflection direction from the incident light direction and eliminating the heat island effect.
2Illumination intensity
If a wavelength-selective reflective layer is provided to maintain transparency in visible region, then visible light transmission properties are improved, but the structure becomes complex with multiple layers
Solution Approach 1:
The patent applies different surface characteristics to different regions of the window glass at a microscopic level. The concavo-convex surface creates local variations in light interaction, where micro-concave portions and micro-convex portions independently handle light reflection and transmission. This local differentiation allows the entire surface to function as both a reflective and transmissive element simultaneously, eliminating the need for separate laminated layers.
Solution Approach 2:
The invention changes the surface geometry parameter from flat to concavo-convex, transforming the optical properties of the glass. By modifying the surface topology rather than adding material layers, the glass achieves wavelength-selective reflection and transmission properties. The microstructure parameters (concave/convex dimensions, spacing, and depth) are optimized to reflect near-infrared while transmitting visible 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 achieves directional reflection of specific wavelengths with higher intensity than diffuse reflection, maintaining transparency and reducing heat absorption, thereby mitigating heat island effects and enhancing energy efficiency.
Implementation Method 1
the wavelength-selective reflective layer selectively directionally reflects light in a specific wavelength band while transmitting light other than that in the specific wavelength band
Implementation Method 2
specular reflection of incident sunlight can only be performed
Implementation Method 3
light coming from the sky and specularly reflected reaches another outdoor building or the ground and is changed into heat by absorption
Implementation Method 4
a high refractive index layer provided on the protective layer and containing a metal oxide other than zinc oxide as a primary component
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3A~3B
AI summary
An optical element includes: a first optical layer having a concavo-convex surface; a wavelength-selective reflective layer provided on the concavo-convex surface of the first optical layer; a second optical layer provided on the concavo-convex surface on which the wavelength-selective reflective layer is provided so as to fill the concavo-convex surface, and in the optical element described above, the wavelength-selective reflective layer includes a metal layer, a protective layer provided on the metal layer and containing a metal oxide as a primary component, and a high refractive index layer provided on the protective layer and containing a metal oxide other than zinc oxide as a primary component, and the wavelength-selective reflective layer selectively directionally reflects light in a specific wavelength band while transmitting light other than that in the specific wavelength band.