Frequency Modulation IR Sensor Using Phase Change Material
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Solution Overview
Problem
Uncooled long wave-infrared (LWIR) detectors suffer from low detectivity due to high thermal noise at room temperature, while cooled detectors are expensive and limited by cryogenic cooling requirements.
Innovation Solution
A frequency modulation-based LWIR detection scheme using a phase change material (PCM) like vanadium dioxide, which undergoes an insulator-to-metal transition, creating an oscillating circuit that detects changes in oscillation frequency induced by IR radiation, thereby enhancing detectivity and reducing noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If uncooled detectors are used to operate at room temperature, then ease of operation and cost are improved, but detectivity deteriorates due to high thermal noise
Solution Approach 1:
The patent employs a phase change material (PCM) layer that undergoes an insulator-to-metal transition in response to absorbed infrared radiation. This phase transition creates a significant change in electrical resistance, which is detected as a change in oscillation frequency. The phase transition mechanism enables the detector to achieve high detectivity at room temperature by converting thermal energy into a measurable electrical signal with high sensitivity, thereby resolving the contradiction between easy operation and measurement precision.
Solution Approach 2:
The patent utilizes an oscillating circuit that generates periodic electrical oscillations. When infrared radiation is absorbed by the PCM layer, it causes a change in the oscillation frequency of the circuit. This frequency modulation approach converts the detected signal into a frequency domain measurement, which is inherently more resistant to noise and provides higher detectivity. The mechanical vibration principle is applied through the oscillating electrical circuit that modulates its frequency in response to thermal changes induced by IR radiation.
2Measurement precision
If cooled detectors are used to achieve high detectivity, then measurement precision is improved, but device complexity and cost increase due to cryogenic cooling requirements
Solution Approach 1:
The patent employs a phase change material (PCM) layer that undergoes an insulator-to-metal transition in response to absorbed infrared radiation. This phase transition creates a significant change in electrical resistance, which is detected as a change in oscillation frequency. The phase transition mechanism enables the detector to achieve high detectivity at room temperature by converting thermal energy into a measurable electrical signal with high sensitivity, thereby resolving the contradiction between easy operation and measurement precision.
Solution Approach 2:
The patent utilizes an oscillating circuit that generates periodic electrical oscillations. When infrared radiation is absorbed by the PCM layer, it causes a change in the oscillation frequency of the circuit. This frequency modulation approach converts the detected signal into a frequency domain measurement, which is inherently more resistant to noise and provides higher detectivity. The mechanical vibration principle is applied through the oscillating electrical circuit that modulates its frequency in response to thermal changes induced by IR radiation.
3Ease of operation
If amplitude modulation detection is used to detect photocurrent changes, then ease of operation is improved, but measurement precision deteriorates due to Johnson noise, thermal noise, and shot noise
Solution Approach 1:
The patent utilizes an oscillating circuit that generates periodic electrical oscillations. When infrared radiation is absorbed by the PCM layer, it causes a change in the oscillation frequency of the circuit. This frequency modulation approach converts the detected signal into a frequency domain measurement, which is inherently more resistant to noise and provides higher detectivity. The mechanical vibration principle is applied through the oscillating electrical circuit that modulates its frequency in response to thermal changes induced by IR radiation.
Solution Approach 2:
The patent employs a phase change material (PCM) layer that undergoes an insulator-to-metal transition in response to absorbed infrared radiation. This phase transition creates a significant change in electrical resistance, which is detected as a change in oscillation frequency. The phase transition mechanism enables the detector to achieve high detectivity at room temperature by converting thermal energy into a measurable electrical signal with high sensitivity, thereby resolving the contradiction between easy operation and measurement precision.
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 solution achieves high detectivity comparable to cryogenically cooled detectors at room temperature, with a noise equivalent power of less than 3 pW·Hz−1/2 and detectivity of 10^9 Jones, suitable for applications in IR spectrometers and cameras.
Implementation Method 1
the phase change of the PCM layer periodically and detect a frequency modulation (FM) of the oscillation signal based upon the IR radiation received by the PCM layer
Implementation Method 2
using a phase change material (PCM) like vanadium dioxide, which undergoes an insulator-to-metal transition
Implementation Method 3
Frequency modulation based IR sensing and imaging and related methods
Implementation Method 4
detect changes in the oscillation signal based upon IR radiation received by the PCM layer
Data Source
AI summary
An IR sensor comprises a substrate, a rear reflector on the substrate, a supporting layer a PCM layer carried by the supporting layer, and first and second electrically conductive contacts carried by the substrate and coupled to opposing sides of the PCM layer. The IR sensor also includes a circuit coupled to the first and second electrically conductive contacts and configured to apply an electrical bias signal to the PCM layer to generate an electrical oscillation, and detect the frequency modulation (FM) of the oscillation signal based upon IR radiation received by the PCM layer.