Plasmonic Lens for MEMS Infrared Sensor
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Solution Overview
Problem
Bolometer devices for infrared radiation detection suffer from inefficiency due to dispersed radiation on non-absorber components, leading to increased costs and complexity, as existing focusing devices are expensive and made from materials like germanium, exceeding the cost of the bolometer itself.
Innovation Solution
A semiconductor device with a substrate, cap wafer, and lens layer is developed, where the lens layer defines grooves and an opening over the absorber to focus infrared radiation directly onto the absorber, enhancing efficiency and reducing production costs by using a semiconductor-based design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a known focusing device made from germanium is used to focus infrared radiation onto the absorber, then the efficiency of infrared radiation absorption is improved, but the cost of the device increases significantly (exceeding the cost of the bolometer by at least an order of magnitude)
Solution Approach 1:
The patent replaces expensive germanium focusing devices with a cost-effective semiconductor-based lens structure that can be fabricated using standard CMOS processes. The lens is formed from silicon or silicon dioxide layers that are already present in the bolometer device, eliminating the need for costly germanium components while maintaining focusing functionality.
Solution Approach 2:
The semiconductor layer serves multiple functions: it acts as both the substrate for the bolometer device and as the focusing lens for infrared radiation. The same silicon or silicon dioxide layer that provides structural support also provides the optical focusing function, eliminating the need for separate expensive focusing components.
2Ease of manufacture
If infrared radiation is allowed to disperse on the substrate and non-absorber portions, then the device structure is simplified, but the efficiency of the bolometer device decreases since the absorber is exposed to only a portion of the incident infrared radiation
Solution Approach 1:
The patent introduces a lens structure with specific local optical properties that focuses infrared radiation onto the absorber region. The lens creates a localized concentration of infrared energy at the absorber position, while other regions of the device remain structurally simple without requiring complex radiation-blocking structures.
3Measurement precision
If photonic detectors are used instead of thermal detectors, then sensitivity and response time are improved, but the device requires cryogenic cooling which increases cost, complexity, weight, and power consumption
Solution Approach 1:
The patent applies the lens concept from visible light optics to infrared radiation, creating a semiconductor-based optical system that enables thermal detectors to achieve focused radiation detection comparable to photonic detectors, but without requiring cryogenic cooling infrastructure.
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 semiconductor device significantly increases the efficiency of infrared radiation absorption by the bolometer, reducing costs and simplifying fabrication, while maintaining or improving performance compared to prior art.
Implementation Method 1
The lens layer is supported by the cap layer. The lens layer defines a plurality of grooves and an opening located over the absorber
Implementation Method 2
In use, infrared radiation incident upon the bolometer device is absorbed by the absorber element, and the heat generated by the absorbed radiation is transferred to the transducer element
Implementation Method 3
a transducer element that has an electrical resistance that varies with temperature
Data Source
AI summary
A portable thermal imaging system includes a portable housing configured to be carried by a user, a bolometer sensor assembly supported by the housing and including an array of thermal sensor elements and at least one plasmonic lens, a memory including program instructions, and a processor operably connected to the memory and to the sensor, and configured to execute the program instructions to obtain signals from each of a selected set of thermal sensor elements of the array of thermal sensor elements, assign each of the obtained signals with a respective color data associated with a temperature of a sensed object, and render the color data.