MEMS Infrared Resonant Sensor Array Noise Reduction

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Solution Overview

Problem

Uncooled infrared sensor arrays, such as microbolometers, suffer from high noise levels due to Johnson and thermal fluctuation noise, limiting their sensitivity and dynamic range.

Innovation Solution

A method utilizing MEMS infrared resonant sensors, which transmit a periodic chirp to determine the resonant frequency shift of each pixel, allowing for the calculation of incident power levels, thereby reducing noise and enhancing sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by stationary object

If microbolometers are used as uncooled IR sensors, then the sensor array can operate without cooling, but the noise level increases due to Johnson and thermal fluctuation noise

Engineering Contradiction:

Improvecooling requirementVSAvoidnoise level

Core Design Contradiction:

Use of energy by stationary objectVSObject-generated harmful factors

Solution Approach 1:

The patent replaces the conventional microbolometer sensing mechanism with a MEMS resonant sensor that uses mechanical resonance at microwave frequencies. The resonant sensor detects infrared radiation through changes in resonant frequency rather than temperature-dependent electrical resistance, eliminating Johnson and thermal fluctuation noise while maintaining uncooled operation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating parameter from electrical resistance measurement (microbolometer) to resonant frequency measurement (MEMS sensor). By operating at microwave frequencies and measuring frequency shifts rather than resistance changes, the system achieves lower noise levels while remaining uncooled.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by stationary object

If microbolometers are used, then uncooled operation is achieved, but sensitivity is limited due to high noise levels

Engineering Contradiction:

Improvecooling requirementVSAvoidsensitivity

Core Design Contradiction:

Use of energy by stationary objectVSMeasurement precision

Solution Approach 1:

The patent replaces the microbolometer's electrical resistance-based detection with a MEMS resonant sensor that measures frequency shifts. This substitution provides superior sensitivity because frequency measurements can be made with high precision, and the resonant mechanism is inherently more sensitive to small energy inputs than resistance changes in uncooled conditions.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs mechanical vibration at resonant frequencies to enhance sensitivity. The MEMS resonator is driven at its natural frequency, and incident infrared radiation causes measurable shifts in the resonant frequency. This resonant amplification effect provides high sensitivity without requiring cooling.

Inventive Principle:

Principle #18Mechanical vibration

3Use of energy by stationary object

If microbolometers are used, then uncooled operation is enabled, but dynamic range is limited due to high noise levels

Engineering Contradiction:

Improvecooling requirementVSAvoiddynamic range

Core Design Contradiction:

Use of energy by stationary objectVSProductivity

Solution Approach 1:

The patent replaces the microbolometer system with a MEMS resonant sensor system that measures frequency shifts. This substitution extends the dynamic range because frequency measurements can resolve smaller changes and accommodate larger signals without saturation, providing both enhanced minimum detectable power and maximum measurable power capabilities in an uncooled configuration.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

MEMS infrared resonant sensors achieve lower noise levels, limited only by thermal fluctuation noise, thereby increasing sensitivity and dynamic range of the sensor arrays.

Implementation Method 1

MEMS infrared resonant sensors have lower noise because they are only limited by thermal fluctuation noise

Methodology Applied

Scientific EffectThermal fluctuation noise:

Data Source

PatentUS10288487B2Apparatus and method for MEMS resonant sensor arrays

Publication Date: 2019.05.14 HONEYWELL INTERNATIONAL INC

AI summary

A method is provided. The method comprises: transmitting a periodic chirp to at least two pixels of a MEMS sensor array; determining a resonant frequency of each MEMS resonant sensor receiving the periodic chirp; determining the change in resonant frequency of each MEMS resonant sensor receiving the periodic chirp; determining a power level incident upon each pixel receiving the periodic chirp. In one embodiment, the method further comprises calibrating the MEMS sensor array. In another embodiment, calibrating comprises generating a reference resonant frequency for each MEMS resonant sensor. In a further embodiment, determining the power level comprises determining a difference between the determined resonant frequency and the reference resonant frequency.