Multi-layer Dielectric Spectral Filter for Circadian Light
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing eyewear filters fail to selectively transmit and block specific circadian-active blue and green light wavelengths, leading to interference with the body's natural circadian rhythm due to broad spectral filtering and material limitations, such as dye- and pigment-based filters that allow undesired spectral content to seep through and degrade under high light or temperature exposure.
Innovation Solution
A multi-layer dielectric spectral filter with alternating high and low refractive index layers is designed to allow 98-100% transmission of light within the 455-560 nm range while blocking 80-100% of other spectral content, using materials like titanium dioxide and silicon dioxide to achieve precise spectral shaping and maintain high transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dye- or pigment-based filters are used to block blue light, then some spectral filtering is achieved, but the filters allow undesired spectral content to seep through and degrade under high light or temperature exposure
Solution Approach 1:
The patent employs a composite multi-layer dielectric structure consisting of alternating high-index (e.g., titanium dioxide, zinc sulfide) and low-index (e.g., silicon dioxide, magnesium fluoride) material layers. This composite architecture enables precise spectral filtering through constructive and destructive interference effects, achieving superior selectivity compared to single-material dye or pigment filters while maintaining high stability under various environmental conditions.
Solution Approach 2:
The patent systematically varies critical parameters including layer thickness (optimized to quarter-wave multiples at target wavelengths), refractive index contrast between alternating layers, and number of periods in the multi-layer stack. By tuning these parameters, the filter achieves precise control over transmission and reflection characteristics at specific wavelengths while maintaining robustness against degradation from light exposure and temperature variations.
2Manufacturing precision
If broad spectral filtering is used to block blue light, then some protection is provided, but circadian-active wavelengths cannot be selectively transmitted
Solution Approach 1:
The patent divides the filtering function into multiple discrete dielectric layers, each contributing to the overall spectral response. By segmenting the filter into alternating high-index and low-index layers with specific thicknesses, the design achieves sharp spectral transitions at target wavelengths (e.g., blocking below 450 nm while transmitting 455-495 nm circadian-active blue light). This segmented approach provides precise wavelength selectivity that cannot be achieved with broad-spectrum filters.
Solution Approach 2:
The patent assigns different optical properties to different regions of the filter structure. Each dielectric layer is engineered with specific local characteristics (refractive index, thickness) optimized for its position in the stack. This local optimization enables the filter to exhibit dramatically different transmission characteristics at different wavelengths, achieving high selectivity for circadian-active wavelengths while blocking other spectral regions.
3Illumination intensity
If existing filters are used to block blue light, then general light reduction is achieved, but transmission efficiency in the circadian-active range cannot be maximized
Solution Approach 1:
The patent converts the typically harmful effect of light reflection into a beneficial filtering mechanism. By designing the multi-layer dielectric structure with alternating refractive indices, the filter creates constructive interference for desired circadian-active wavelengths (enhancing transmission) and destructive interference for undesired wavelengths (achieving blocking). This approach transforms what would be wasted reflected light into a selective spectral filtering mechanism that simultaneously maximizes desired transmission and blocks harmful spectral content.
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 enables targeted exposure to circadian-active light, improving the body's natural timing and sleep-wake cycle by selectively channeling blue and green light, maximizing activation of sensitive photoreceptors, and reducing interference from artificial lighting, thus enhancing circadian function and visibility in various lighting conditions.
Implementation Method 1
The spectral filter includes a multi-layer stack of dielectric material with alternate high and low indices of refraction such that a layer having a high index of refraction is positioned above or below a layer having a low index of reflection
Implementation Method 2
a multi-layer stack of dielectric material with alternate high and low indices of refraction
Implementation Method 3
The spectral filter is configured to block 80-100% of the spectral content in each of the contiguous blocking regions
Data Source
AI summary
Methods and devices are described that rely on interference filter designs to provide a precise and granular spectral behavior by allowing emissions of circadian-active blue and green light to reach a viewer. An example wearable device includes one or more windows positioned to allow light from a light source to propagate toward a position of a wearer's eyes, and a spectral filter that includes a coating positioned on one or more sections of the one or more windows. The spectral filter includes a multi-layer stack of dielectric material with alternate high and low indices of refraction. The number of the layers and a thickness of each layer are selected to provide designed transmission and blocking characteristics to allow circadian-active spectra to reach the wearer's eyes while blocking spectral content other than the circadian-active spectra. The designed transmission and blocking characteristics include a contiguous transmission region and two contiguous blocking regions.