Flat Metasurface Mirror for Stable Wide-Angle Light Deflection
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Solution Overview
Problem
Existing optical systems, particularly in ultra-short throw projectors, face challenges with large mirror surfaces that occupy significant space and are prone to temperature-induced distortions due to their curved shapes, leading to reduced image quality.
Innovation Solution
A metasurface optical element with a flat plate shape that incorporates a transmission surface with nanostructures and a reflective surface, allowing for adjustable refractive indices and deflection angles, effectively replacing curved mirrors to save space and maintain image quality despite temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a curved mirror surface is used to cover the entire area of an incident light beam, then the mirror can achieve the desired optical performance, but the mirror volume increases and occupies significant space
Solution Approach 1:
The patent creates a flat metasurface that copies the optical function of a curved mirror by using sub-wavelength periodic structures with controlled refractive indices. The metasurface replicates the wavefront shaping capability of a curved mirror without requiring the physical curvature, thereby achieving the same optical performance in a flat, space-saving configuration
Solution Approach 2:
The patent replaces the mechanical curved mirror surface with a metasurface that uses sub-wavelength periodic structures to control light propagation. Instead of relying on the physical curvature of a mirror, the optical function is achieved through the refractive properties of the metasurface structures, substituting mechanical geometry with optical physics
2Volume of stationary object
If a concave mirror is reduced in thickness to reduce the size and weight, then the mirror becomes more compact, but the heat capacity is reduced and temperature changes cause shape distortion and image quality degradation
Solution Approach 1:
The patent changes the fundamental parameter of the optical element from a curved reflective surface to a flat metasurface with controlled refractive indices. This parameter change allows the element to maintain its optical function while being insensitive to temperature-induced shape changes, as the metasurface structure does not rely on the curvature of a bulk material that can thermally expand or deform
3Volume of stationary object
If a flat metasurface is used to replace a curved mirror, then space is saved and temperature drift is suppressed, but the refractive index control precision must be maintained to ensure proper light deflection
Solution Approach 1:
The patent applies local quality by varying the refractive index of the metasurface at different locations. The sub-wavelength periodic structures have different filling factors or geometries in different regions, creating spatially varying refractive indices that precisely control the wavefront shaping and light deflection functions required for the optical application
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 metasurface optical element reduces system size and weight, maintains image formation stability, and enhances light deflection capabilities, enabling wider field angles and lower costs by using a flat surface equivalent to complex curved mirrors.
Implementation Method 1
a transmission surface that transmits light and on which a plurality of nanostructures are continuously arranged, the nanostructures being arranged with a density based on which a refractive index of the metasurface for the light is adjusted
Implementation Method 2
a mirror surface having a flat plate shape and reflecting the light that has passed through the metasurface
Data Source
AI summary
A metasurface optical element is a single optical element and includes a metasurface and a mirror surface. The metasurface includes a transmission surface that transmits light and on which a plurality of nanostructures are continuously arranged, the nanostructures being arranged with a density based on which a refractive index of the metasurface for the light is adjusted. The mirror surface has a flat plate shape and reflects the light that has passed through the metasurface. A dimension d of the nanostructures in a horizontal direction relative to the transmission surface and a wavelength λ of the light satisfy λ≥d. The optical element causes the light deflected by the metasurface to be reflected by the mirror surface so that the light is deflected in a direction different from an incident direction of the light.