Umbrella-Type Absorber Recesses for Infrared Bolometer
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Solution Overview
Problem
Conventional bolometer-based focal plane arrays have limited absorption capabilities due to the resistive absorption layer thickness and thermal design, allowing a significant percentage of incident infrared radiation to pass through without being absorbed.
Innovation Solution
The introduction of an absorber layer with recesses or channels increases resistivity and absorption capability by altering the radiation propagation path, reducing thermal mass, and enhancing the sheet resistance of the absorber layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the absorber layer is made thicker to increase absorption capability, then the absorption of incident radiation improves, but the thermal mass increases leading to slower response time
Solution Approach 1:
The absorber layer is designed with a porous structure containing multiple recesses and channels. This porous configuration increases the effective surface area and absorption capability while maintaining reduced thermal mass, thereby improving radiation absorption without significantly increasing response time.
Solution Approach 2:
The invention transitions from a conventional planar absorber to a three-dimensional structure with recesses and channels. This dimensional change allows the absorber to trap and multiple-pass infrared radiation through the structure, enhancing absorption capability while the hollow spaces reduce overall thermal mass for faster thermal response.
2Reliability
If the absorber layer thickness is increased to improve absorption, then the sheet resistance increases, but the fabrication complexity and thermal mass also increase
Solution Approach 1:
The porous absorber structure achieves high sheet resistance through increased surface area and multiple radiation passes within the recesses and channels, rather than simply increasing layer thickness. This approach attains the desired electrical properties without proportionally increasing fabrication complexity or thermal mass.
Solution Approach 2:
The absorber layer is segmented into multiple recesses and channels rather than being a solid continuous layer. This segmentation increases the effective path length for radiation absorption and sheet resistance while allowing for modular fabrication processes that can reduce overall complexity compared to depositing uniformly thick layers.
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 design significantly improves the absorption of incident radiation, reducing the percentage of reflected radiation and increasing the sheet resistance of the absorber, leading to enhanced performance in infrared detection.
Implementation Method 1
an absorber having a top side defining a recess in the absorber. The recess is adapted to affect the propagation path of a portion of radiation received by the absorber such that the radiation portion is absorbed by the absorber
Implementation Method 2
The recess is adapted to affect the propagation path of a portion of radiation received by the absorber such that the radiation portion is absorbed by the absorber rather than exiting the absorber
Implementation Method 3
Each bolometer includes a transducer element that has an electrical resistance that varies as a result of temperature changes produced by the incident infrared radiation
Data Source
AI summary
A pixel structure for use in an infrared imager is provided. The pixel structure includes a substrate and a bolometer. The bolometer includes a transducer that has a spaced apart relationship with respect to the substrate and has an electrical resistance that varies in response to changes in the temperature of the transducer. The bolometer also includes an absorber that has a spaced apart relationship with respect to the transducer and has a thermal connection to the transducer permitting radiation absorbed by the absorber to heat the transducer. The absorber has a top side defining a recess or channel in the absorber. The recess or channel is adapted to effect the propagation path of a portion of radiation received by the absorber such that the radiation portion is absorbed by the absorber rather than exiting the absorber. The recess or channel also decreases the thermal mass of the bolometer.