Parallelogram Filter Array Sidewalls Reduce Stray Light
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Solution Overview
Problem
Filter arrays face challenges with stray light leakage and increased element size due to angled illumination, which existing techniques like optically absorbing adhesives and surface roughening are ineffective in addressing, especially when total internal reflection occurs at substrate surfaces and adhesive bonds.
Innovation Solution
The design features optical filter elements with parallelogram-shaped substrates and slanted sidewalls, allowing for angled illumination that reduces light scattering and reflection, and accommodates exit aperture shifts through lateral offsetting, thereby minimizing stray light and maintaining structural rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If filter elements are bonded with straight sidewalls, then manufacturing is simpler, but stray light leakage increases due to total internal reflection at substrate surfaces
Solution Approach 1:
The patent applies asymmetry by changing the sidewall geometry from straight (vertical) to slanted (angled). The slanted sidewalls are configured at a specific angle that prevents total internal reflection of stray light, thereby reducing optical cross-talk between adjacent filter elements while maintaining manufacturing feasibility through standard dicing processes.
Solution Approach 2:
The patent changes the geometric parameter of the sidewall angle from 90 degrees (straight) to a slanted angle. This parameter change optimizes the optical path of stray light, ensuring that reflected light does not enter adjacent filter elements, thus reducing stray light leakage while preserving structural integrity.
2Measurement precision
If filter elements are illuminated at an angle, then optical path length increases improving spectral resolution, but element size increases due to lateral shift of exit aperture
Solution Approach 1:
The patent addresses the lateral shift issue by introducing angular dimension through slanted sidewalls. The slanted geometry compensates for the lateral displacement of light paths, allowing angled illumination to achieve increased optical path length (improving spectral resolution) without proportionally increasing the footprint area of the filter elements.
3Quantity of substance
If more filter elements are packed in a given size, then array density increases, but optical cross-talk increases due to stray light from adjacent elements
Solution Approach 1:
The slanted sidewall design creates an asymmetric optical path that directs stray light away from adjacent filter elements. This geometric asymmetry effectively reduces optical cross-talk, enabling higher array density by allowing more filter elements to be packed in a given size without significant interference between neighboring elements.
4Object-affected harmful factors
If slanted sidewalls are used, then stray light is reduced, but manufacturing complexity increases due to angled dicing and bonding
Solution Approach 1:
The patent manages manufacturing complexity by optimizing the slanted angle parameter. The specific angle is chosen to balance optical performance (stray light reduction) with manufacturing feasibility, allowing standard dicing and bonding equipment to be used with minimal modification, thus achieving stray light reduction without excessive increase in manufacturing complexity.
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
This approach effectively reduces optical losses and cross-talk, enabling more filter elements in a given size while maintaining structural integrity, by using slanted sidewalls that match the angle of incidence, thus improving the efficiency and compactness of the filter array.
Implementation Method 1
Optical filters with high spectral selectivity can be manufactured using a stack of layers with alternating layers of two (or more) constituent materials having different refractive index values. Such filters are sometimes called interference filters
Implementation Method 2
Some embodiments are designed to be illuminated at an angle-of-incidence theta, and reduce stray light generated by total internal reflection at the filter element substrate surfaces
Implementation Method 3
an optical filter array comprises optical filter elements each including a parallelogram-shaped substrate with parallel light entrance and light exit surfaces and parallel slanted sidewalls slanted at an angle
Data Source
AI summary
Optical filter elements each include a parallelogram-shaped substrate with parallel light entrance and light exit surfaces and parallel slanted sidewalls slanted at an angle, and an interference filter disposed on one or both of the light entrance surface and the light exit surface. The optical filter elements are bonded together at the slanted sidewalls to form the optical filter array. Light is filtered by illuminating the optical filter array at an angle θ equal to or corresponding to the angle of the slanted sidewalls. In some embodiments the angle of the slanted sidewalls corresponds to the angle-of-incidence θ by Snell's law.