Infrared Detector FDM Noise Reduction
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Solution Overview
Problem
Conventional IR detectors, such as microbolometer and thermopile-based detectors, face challenges with noise aliasing and unpredictable noise patterns, which affect image quality and camera performance due to the use of time division multiplexing (TDM) and low noise amplifiers, leading to increased noise and reduced signal-to-noise ratio.
Innovation Solution
The implementation of a Frequency Division Multiplexing (FDM) approach, where each thermopile in the array is modulated with an oscillating carrier at a unique frequency, allowing for simultaneous activation of all thermopiles and the use of dedicated amplifiers for each column or row, effectively reducing electronic noise and improving signal strength by averaging noise over a longer integration time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If time division multiplexing (TDM) is used to activate thermopiles sequentially, then device complexity is reduced, but noise aliasing increases and signal-to-noise ratio deteriorates
Solution Approach 1:
The patent segments the thermopile array into multiple groups, where each group is modulated by a dedicated oscillating carrier signal at a unique frequency. This segmentation allows simultaneous activation of all thermopiles while maintaining individual signal identification through frequency differentiation, thereby eliminating noise aliasing issues associated with TDM while preserving device complexity benefits.
Solution Approach 2:
The patent employs periodic oscillating carrier signals to modulate each thermopile group. These periodic signals enable simultaneous activation of all thermopiles while allowing the system to process multiple signals through frequency division, thus improving signal-to-noise ratio without requiring sequential activation that complicates device operation.
2Object-affected harmful factors
If low noise amplifiers are used to reduce electronic noise, then noise level decreases, but device complexity and cost increase
Solution Approach 1:
The patent introduces oscillating carrier signals as intermediaries between the thermopiles and the amplifiers. By modulating thermopile outputs with these carriers, standard amplifiers can effectively process the signals while the modulation scheme itself filters out electronic noise, eliminating the need for specialized low noise amplifiers and reducing device complexity.
Solution Approach 2:
The patent changes the frequency parameter of the signal by modulating each thermopile group with a unique carrier frequency. This frequency division allows standard amplifiers to handle multiple signals simultaneously without being overwhelmed by noise, as each signal can be processed at its specific frequency band, thereby reducing amplifier complexity requirements.
3Productivity
If all thermopiles are activated simultaneously, then productivity increases, but noise management becomes unpredictable
Solution Approach 1:
The patent segments the thermopile array into multiple frequency-groups, each modulated by a dedicated oscillating carrier at a unique frequency. This segmentation enables simultaneous activation of all thermopiles for high productivity while making noise management predictable through frequency-based signal separation and identification.
Solution Approach 2:
The patent applies frequency modulation as a parameter change technique, assigning unique carrier frequencies to different thermopile groups. This approach enables simultaneous operation of all thermopiles for improved productivity while making noise patterns predictable and manageable through frequency domain analysis and filtering.
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 significantly reduces electronic noise variance and maintains a high signal-to-noise ratio, enabling improved image quality and camera performance by making noise more predictable and manageable, thus overcoming the limitations of TDM and amplifier noise.
Implementation Method 1
Each thermal sensing element is further configured to generate an electrical output signal that is indicative of at least a portion of detected thermal output and to modulate the electrical output signal with the at least one oscillating signal to generate a modulated output signal
Implementation Method 2
Thermopiles include a number of thermocouples that convert thermal energy from the object into electrical energy
Data Source
AI summary
In at least one embodiment, an infrared (IR) detector for generating an image of an object is provided. The IR detector includes a plurality of thermal sensing elements that are arranged in an array of M columns and N rows. Each thermal sensing element is configured to receive at least one oscillating signal and detect at least a portion of a thermal output from the object. Each thermal sensing element is further configured to generate an electrical output signal that is indicative of at least a portion of detected thermal output and to modulate the electrical output signal with the at least one oscillating signal to generate a modulated output signal that is indicative of at least a portion of the image of the object.