Infrared Detector Thermopile Frequency Division Multiplexing
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Solution Overview
Problem
Conventional infrared (IR) detectors, such as microbolometer and thermopile-based detectors, face challenges with noise aliasing and increased noise from amplifiers, which affect the signal-to-noise ratio and predictability of noise patterns, limiting camera performance.
Innovation Solution
The implementation of a Frequency Division Multiplexing (FDM) approach in IR detectors, where all thermopiles in a column or row are modulated with unique orthogonal carriers, allowing for simultaneous activation and demodulation, reducing electronic noise and increasing signal strength while minimizing amplifier noise impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional infrared detectors use single thermopile or microbolometer configuration, then device complexity is low, but signal-to-noise ratio deteriorates due to noise aliasing and amplifier noise
Solution Approach 1:
The detector array is divided into multiple columns, with each column containing multiple thermopiles that can be independently modulated. This segmentation allows different columns to be modulated at different frequencies, enabling frequency division multiplexing and reducing noise aliasing while maintaining a manageable device structure
Solution Approach 2:
Each column of thermopiles is modulated with a unique periodic carrier signal at a specific frequency. This periodic modulation allows the thermal output to be converted into AC signals that can be demodulated, reducing the impact of amplifier noise and improving the signal-to-noise ratio
2Reliability
If all thermopiles are activated simultaneously with unique orthogonal carriers, then signal strength increases, but device complexity increases due to modulation and demodulation requirements
Solution Approach 1:
Each column is modulated with a unique periodic carrier signal, allowing simultaneous activation of all thermopiles while maintaining distinguishable signals through frequency differentiation. This periodic modulation enables signal strengthening without requiring complex individual control circuits for each thermopile
Solution Approach 2:
The modulation scheme is designed with predetermined orthogonal carrier frequencies assigned to each column before operation. This preliminary configuration simplifies the modulation process by establishing fixed frequency assignments, reducing the real-time control complexity while enabling simultaneous signal generation from all thermopiles
3Reliability
If noise is averaged over longer integration time, then signal-to-noise ratio improves, but productivity decreases due to longer measurement time
Solution Approach 1:
The periodic modulation allows the system to extract signal information at the modulation frequency through synchronous demodulation. This enables effective noise filtering and signal-to-noise ratio improvement without requiring long integration times, as the modulated signal can be rapidly demodulated and processed
Solution Approach 2:
The orthogonal carrier frequencies are predetermined and assigned to different columns before measurement begins. This preliminary frequency assignment allows the system to process multiple columns simultaneously through frequency-based separation, improving measurement speed while maintaining signal-to-noise ratio through the inherent noise rejection of frequency division multiplexing
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 FDM approach enhances the signal-to-noise ratio by averaging noise over a longer integration time, reducing the influence of amplifier noise and improving camera performance by maintaining a high signal-to-noise ratio similar to single thermopile detectors.
Implementation Method 1
Thermopiles include a number of thermocouples that convert thermal energy from the object into electrical energy
Implementation Method 2
An IR detector is generally defined as a photodetector that responds to IR radiation
Data Source
AI summary
An infrared (IR) detector including a plurality of thermal sensing elements for generating an image of an object is provided. The IR detector comprises a first thermal sensing element and includes a thermopile and a first switch. The thermopile is configured to receive at least a portion of a thermal output from the object and to provide a modulated electrical output indicative of at least a portion of the received thermal output. The first switch is operatively coupled to the thermopile and is configured to provide a bypass in the event the thermopile is damaged such that remaining thermal sensing elements of the plurality of thermal sensing elements are capable of providing an electrical output therefrom.