Patterned Dark Mirror Coatings for Infrared Spectrometer Slit Masks
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Solution Overview
Problem
Current slit mask technologies are limited in handling curved lines at the micron scale and are not suitable for infrared applications, as they do not provide the necessary reflectance or transmissive properties, and separate optical filters and slit masks require complex alignment and mounting procedures.
Innovation Solution
A bi-directional dark mirror coating is developed using photolithography on a custom double-sided substrate integrated with a commercial infrared filter substrate, allowing for a multifunctional optical device that transmits light in desired directions while absorbing stray light, and is fabricated using a lift-off procedure to pattern slits and deposit dark mirror coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate optical filters and slit masks are used, then each component can be optimized independently, but complex alignment and mounting procedures are required, increasing device complexity
Solution Approach 1:
The patent combines the optical filter and slit mask into a single integrated component. The filter substrate serves as the base for depositing dark mirror coatings that form the slit mask pattern, eliminating the need for separate mounting and alignment procedures while maintaining the optical performance of both components
Solution Approach 2:
The integrated component performs multiple functions simultaneously: the filter substrate provides wavelength selection while the deposited dark mirror coatings provide slit mask functionality. This multi-functional design replaces two separate components with one that does both jobs
2Manufacturing precision
If diamond saws are used to cut slits in metal for slit masks, then smooth straight lines can be achieved, but curved lines at 10's of micron size scale cannot be handled
Solution Approach 1:
The patent replaces mechanical cutting methods (diamond saws) with a deposition-based approach. Photoresist patterns are formed using photolithography, and dark mirror coatings are deposited conformally on the substrate, allowing both straight and curved slit geometries to be created without mechanical cutting limitations
Solution Approach 2:
The invention changes the fundamental manufacturing parameter from mechanical removal (cutting) to material deposition. This allows arbitrary geometries including curved lines to be created by controlling the photoresist patterning and deposition process rather than being constrained by mechanical tool paths
3Ease of manufacture
If common materials are used in slit masks, then manufacturing is simplified, but the reflectance or transmissive properties required for infrared applications are not achieved
Solution Approach 1:
The patent uses a composite structure consisting of a filter substrate with deposited dark mirror coating layers. This composite material system provides both the mechanical support of the substrate and the specialized optical properties of the deposited coatings, achieving the required infrared reflectance and transmissive properties
Solution Approach 2:
The dark mirror coatings are applied locally to specific regions of the filter substrate to create the slit mask pattern. Different regions have different optical properties: coated regions provide high reflectance for stray light suppression while uncoated regions maintain transmissivity for the desired spectrum
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 solution enables the creation of a custom spectrometer slit mask that effectively transmits light in defined locations while absorbing stray light, reducing reflectance to less than 2% and minimizing ghost reflections, thereby improving the optical performance and reducing manufacturing costs.
Implementation Method 1
patterning one or more slits on a substrate with photolithography
Implementation Method 2
absorbing stray light, reducing reflectance to less than 2%
Data Source
AI summary
A patterned dark mirror coating is developed and fabricated for a custom spectrometer. By combining the photolithography process with a custom double-sided dark mirror coating integrated with a commercial infrared (IR) filter substrate, a multifunctional optical device is fabricated. The lithographic patterning of a dark mirror allows a single device to transmit light in a desired direction and absorb light everywhere else.