Angled Interference Filters Offset Ripple Effects
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Solution Overview
Problem
Existing interference filters used in optical measuring instruments suffer from reduced measurement precision and accuracy due to design limitations and manufacturing tolerances, which result in ripples affecting the filtering effect.
Innovation Solution
An optical filtering assembly is designed with two interference films having different optical path differences, achieved by alternately stacking layers of high and low refractive index materials, to improve the filtering effect by offsetting ripple effects and enhancing precision and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single interference film is used for light filtering, then the device structure is simple, but the measurement precision is reduced due to ripple effects
Solution Approach 1:
The single interference film is divided into multiple interference films (first interference film and second interference film) with different optical path differences. Each film produces ripple effects at different wavelengths, and when combined, these ripple effects offset each other, resulting in a smoother spectrum and improved measurement precision.
Solution Approach 2:
Multiple interference films with different optical path differences are combined to form a composite filtering system. The films use the same materials but are designed with different thicknesses to achieve different optical path differences, creating a composite structure that eliminates ripple effects while maintaining filtering functionality.
2Reliability
If the optical path difference is increased to improve filtering effect, then the filtering performance is enhanced, but the ripple effects become more pronounced
Solution Approach 1:
The ripple effects generated by the first interference film are counterbalanced by the ripple effects generated by the second interference film. By designing the films with different optical path differences, the ripple peaks of one film align with the ripple valleys of the other, causing mutual cancellation and producing a smoother overall spectrum.
Solution Approach 2:
The harmful ripple effects are converted into a beneficial filtering mechanism. Instead of trying to eliminate ripples entirely, the design uses multiple films to generate ripples at different wavelengths that offset each other, transforming the harmful interference pattern into a useful wavelength-selective filtering effect with reduced artifacts.
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 provides a smoother spectrum distribution, improving the precision and accuracy of optical measuring instruments by effectively filtering light and reducing the influence of ripples.
Implementation Method 1
Depending upon thickness distributions and optical constants of the both kind of films, a ray carries out constructive interference and destructive interference while passing through the multilayer film
Implementation Method 2
The interference filter has a multilayer film in which two kinds of films having different optical constants are alternately stacked
Data Source
AI summary
An optical filtering assembly comprises a first interference film and a second interference film. The first interference film comprises multiple first film layers and multiple second film layers. The first film layers and the second film layers are alternately stacked. The second interference film comprises multiple third film layers and multiple fourth film layers. The third film layers and the fourth film layers are alternately stacked. An optical constant of the first film layers is same as an optical constant of the third film layers, and an optical constant of the second film layers is same as an optical constant of the fourth film layers, and an Optical Path Difference (OPD) produced in the first interference film is different from an OPD produced in the second interference film.