Dielectric Filter Assembly with Air-Gap Spacer for Spectral Resolution
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Solution Overview
Problem
Dielectric filters, such as interference filters, exhibit strong angular dependence under diffuse light conditions, leading to spectral broadening and reduced spectral resolution due to shifting transmittance wavelengths.
Innovation Solution
A filter assembly is designed with a spacer, such as an air-gap, between the incident medium and the dielectric filter, which reduces the effective refractive index and minimizes spectral shift and smearing by controlling the working distance and using a medium of lower refractive index.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dielectric filter is used under diffuse light conditions, then spectral selection is achieved, but spectral broadening and reduced spectral resolution occur due to angular dependence
Solution Approach 1:
The patent introduces an incident medium with high refractive index (such as oil or glass) as an intermediary between the light source and the dielectric filter. This intermediary modifies the angular distribution of incident light, effectively reducing the range of angles that reach the filter and thereby minimizing spectral broadening while maintaining spectral selection capabilities
Solution Approach 2:
The patent changes the refractive index parameter of the medium through which light enters the filter system. By using a high refractive index incident medium, the effective angular spread of light is reduced, which compensates for the angular dependence of the dielectric filter and maintains sharp spectral features
2Quantity of substance
If the field of view is increased to accommodate diffuse light, then more light is collected, but spectral shift increases
Solution Approach 1:
The high refractive index incident medium acts as a mediator that allows broader angular acceptance while controlling the effective angle range. The medium's optical properties transform wide-angle diffuse light into a narrower angular distribution at the filter interface, enabling both increased light collection and maintained spectral position accuracy
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 proposed filter assembly significantly reduces spectral shift and smearing, enhancing spectral resolution and improving the transmission profile, especially under diffuse light conditions with high refractive index incoming media.
Implementation Method 1
A filter assembly is designed with a spacer, such as an air-gap, between the incident medium and the dielectric filter, which reduces the effective refractive index and minimizes spectral shift and smearing
Implementation Method 2
Interference filters consist of multiple thin film layers of dielectric material having different refractive indices. Constructive or destructive interference of the incoming light reflected at the interfaces of the layers is used to select one or more spectral bands or lines for transmission
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
A filter assembly comprises an incident medium (10), a spacer (30), at least one dielectric filter (50) and an exit medium (70). The spacer (30) is arranged between the incident medium (10) and the at least one dielectric filter (50) such that the incident medium (10) and the at least one dielectric filter (50) are spaced apart by a working distance (32) and thereby enclose a medium of lower index of refraction than the incident medium (10). The at least one dielectric filter (50) is arranged on the exit medium (70).