Infrared Thermal Sensor Beams with Variable Width for Stress Reduction
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Solution Overview
Problem
Existing thermal infrared sensors face challenges in optimizing signal-to-noise ratio (SNR) and mechanical stress due to varying beam lengths and thermocouple designs, especially in sensors with non-rectangular membranes and low vacuum conditions.
Innovation Solution
The design incorporates a plurality of beams with different lengths and a constant width-to-length ratio for thermocouples, oriented non-radially to reduce stress and enhance SNR, with a filling factor less than 50% and a pressure range of 500 Pa to 20 kPa, using a circular membrane and a polygonal cavity for improved thermal and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If beams are made long and narrow to minimize heat loss, then thermal insulation improves, but mechanical strength deteriorates
Solution Approach 1:
The patent applies local quality by making each beam have a non-uniform cross-section along its length. The beam width varies continuously or in steps, being narrower at the membrane end and wider at the substrate end. This allows the beam to have lower thermal conductivity where needed (near the membrane) while maintaining sufficient mechanical strength where the load is higher (near the substrate).
Solution Approach 2:
The patent changes the geometric parameters of the beams, specifically the width parameter, along the length of the beam. By varying the width parameter continuously or in discrete steps, the beam achieves optimal balance between thermal insulation (narrower sections) and mechanical strength (wider sections).
2Measurement precision
If the membrane is made large to maximize infrared light reception, then detection sensitivity improves, but mechanical stress increases
Solution Approach 1:
The patent segments the membrane into multiple sections divided by grooves or channels. This segmentation reduces the overall mechanical stress on the membrane by creating smaller, more manageable sections that can expand and contract independently, while still maintaining a large total area for infrared detection.
Solution Approach 2:
The patent introduces grooves or channels at specific locations on the membrane surface, creating local variations in the membrane structure. These features reduce stress concentration in critical areas while preserving the overall membrane area for infrared reception.
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 configuration results in a significant improvement in signal-to-noise ratio and reduced mechanical stress, providing a more reliable and efficient infrared radiation detection system.
Implementation Method 1
each beam of the plurality of beams comprising at least one thermocouple arranged therein or thereon for measuring a temperature difference (ΔT) between the membrane and the substrate
Implementation Method 2
a membrane arranged in said cavity for receiving infrared radiation (IR) through a window or aperture
Data Source
AI summary
An infrared thermal sensor for detecting infrared radiation is described. It comprises a substrate and a cap structure together forming a sealed cavity. A membrane is suspended therein by a plurality of beams, each beam comprising at least one thermocouple arranged therein or thereon for measuring a temperature difference between the membrane and the substrate. At least two beams have a different length and each of the thermocouples have a substantially same constant width to length ratio such that the thermal resistance measured between the membrane and the substrate is substantially constant for each beam, and such that the electrical resistance measured between the membrane and the substrate is substantially constant for each beam. The beams may be linear, and be oriented in a non-radial direction.