Decorative Sheet for Concealing External Light Elements
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Solution Overview
Problem
Existing devices with external light elements, such as cameras or sensors, are difficult to make inconspicuous due to their external appearance, particularly when using half mirrors, which limits design flexibility and visibility.
Innovation Solution
A decorative sheet comprising a circularly polarized light reflecting layer with cholesteric liquid crystal layers, λ/4 plates, and a linear polarizer, designed to reflect specific circularly polarized light components and absorb others, making the element using external light inconspicuous by reducing visible reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a half mirror is used to make the camera inconspicuous, then the camera becomes less visible, but the design flexibility is limited and the appearance looks like a mirror
Solution Approach 1:
The patent changes the optical parameters by using circularly polarized light reflecting layers with specific wavelength selective reflecting properties. The layer reflects left or right circularly polarized light while transmitting the other type, creating inconspicuous appearance without the limitations of half mirrors. The integral reflectivity is controlled at 30% or higher at specific wavelengths (630nm, 550nm, 450nm) to achieve the desired effect.
Solution Approach 2:
The patent employs a composite structure consisting of multiple layers: a circularly polarized light reflecting layer (including cholesteric liquid crystal layers), λ/4 plates, and a linear polarizer. This composite material approach enables sophisticated control of light properties, allowing the camera to be inconspicuous while maintaining design flexibility and avoiding the mirror-like appearance problem.
2Object-affected harmful factors
If a half mirror is used to reduce visibility, then the camera becomes less conspicuous, but it is difficult to apply various designs to the half mirror portion
Solution Approach 1:
The patent modifies the optical parameters by using circularly polarized light reflecting layers that can be tuned to reflect specific wavelengths (630nm, 550nm, 450nm) with integral reflectivity of 30% or higher. This parameter control allows the camera to be inconspicuous while enabling various design applications beyond the limitations of half mirrors.
Solution Approach 2:
The patent introduces a circularly polarized light reflecting layer as an intermediary between the camera and the observer. This layer, composed of cholesteric liquid crystal layers and optical films, mediates the light interaction to make the camera inconspicuous while allowing flexible design applications, unlike direct half mirror usage.
3Object-affected harmful factors
If the circularly polarized light reflecting layer has high integral reflectivity, then the camera becomes more inconspicuous, but the specular reflectivity should be controlled to avoid glare
Solution Approach 1:
The patent precisely controls optical parameters by setting integral reflectivity at 30% or higher at wavelengths 630nm, 550nm, and 450nm while controlling specular reflectivity to be 30% or lower. This parameter optimization achieves inconspicuousness without creating glare, resolving the contradiction between the two reflectivity requirements.
Solution Approach 2:
The patent applies different reflectivity characteristics to different aspects of light interaction: high integral reflectivity for overall light reflection to make the camera inconspicuous, while low specular reflectivity for direct reflection control to avoid glare. This local quality differentiation resolves the contradiction between inconspicuousness and glare prevention.
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 effectively conceals the external light elements by minimizing visible reflections, enhancing design flexibility and reducing the element's visibility from various angles, while maintaining adequate transmission for the element's functionality.
Implementation Method 1
the circularly polarized light reflecting layer includes one or more cholesteric liquid crystal layers having wavelength selective reflecting properties
Implementation Method 2
A decorative sheet comprising a circularly polarized light reflecting layer, a λ/4 plate A, a linear polarizer, and a λ/4 plate B in this order
Data Source
AI summary
Provided are a decorative sheet for making the element using external light, for example, a camera or a sensor inconspicuous to an observer and an optical device and an image display device that include the above-described decorative sheet. The decorative sheet including a circularly polarized light reflecting layer, a λ/4 plate A, a linear polarizer, and a λ/4 plate B in this order, in which the circularly polarized light reflecting layer includes one or more cholesteric liquid crystal layers having wavelength selective reflecting properties, in a case where an integral reflectivity at a wavelength λ nm is represented by I-R(λ), I-R(630), I-R(550), and I-R(450) of the circularly polarized light reflecting layer are 30% or higher, and an angle between a slow axis of the λ/4 plate A and an absorption axis of the linear polarizer and an angle between a slow axis of the λ/4 plate B and the absorption axis of the linear polarizer are 45°±10°, respectively.