Thermal Image Sensor PWM Feedback for Gain and Offset Correction
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Solution Overview
Problem
Thermal image sensors, such as microbolometers, face variations in offset and gain due to temperature changes, aging, and non-linearity, leading to inconsistencies and mismatches in data, which existing methods struggle to accurately correct during analog to digital conversion.
Innovation Solution
A method and system that utilize pulse width modulated (PWM) signals to control currents from thermal image sensors for gain and offset correction, where a PWM signal generated in response to digital feedback from an analog to digital conversion circuit is used to adjust the current from a detector and a reference source, ensuring accurate representation of stimuli during analog to digital conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional analog to digital conversion is used without feedback control, then the conversion process is simple, but offset and gain variations cause inaccuracies in digital values representing thermal stimuli
Solution Approach 1:
The patent implements a feedback mechanism where the digital output from the analog to digital conversion circuit is fed back to control PWM signals that adjust the detector current and reference current. This closed-loop feedback system dynamically corrects offset and gain variations, improving measurement precision while managing complexity through systematic control architecture.
Solution Approach 2:
The system performs self-correction by using its own digital output to generate control signals that automatically adjust its input currents. The feedback loop enables the conversion circuit to self-regulate offset and gain errors without external intervention, improving accuracy while maintaining autonomous operation.
2Measurement precision
If PWM feedback control is implemented for offset and gain correction, then accuracy of thermal image data is improved, but the control system complexity increases
Solution Approach 1:
The feedback control system serves multiple functions simultaneously: it corrects offset errors, adjusts gain variations, and maintains detector consistency across different operating conditions. By consolidating these correction functions into a unified PWM control architecture, the system achieves comprehensive accuracy improvement without proportionally increasing complexity.
Solution Approach 2:
The system dynamically changes the parameters of the PWM control signals (pulse width, frequency) based on the digital feedback to adjust the detector current and reference current. This parameter modulation enables precise control of offset and gain corrections, improving data consistency while using well-established PWM techniques to manage complexity.
3Measurement precision
If real-time offset and gain adjustment is performed using feedback, then signal-to-noise ratio is enhanced, but processing time and system complexity increase
Solution Approach 1:
The feedback control operates continuously alongside the analog to digital conversion process, with the digital output immediately fed back to adjust the currents for the next conversion cycle. This continuous real-time correction enhances signal-to-noise ratio without introducing discrete processing delays, as the adjustment is an ongoing process integrated into the conversion workflow.
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
This approach effectively adjusts offset and gain in real-time, improving the accuracy and consistency of digital values from thermal image sensors, reducing noise and enhancing the signal-to-noise ratio, thereby improving the quality of thermal imaging data.
Implementation Method 1
controlling a current (IACT) from a detector of a thermal image sensor with a first pulse width modulated (PWM) signal (PWMACT) for gain control
Implementation Method 2
controlling a current (IREF) from a reference source of the thermal image sensor with a second PWM signal (PWMFEEDBACK) for gain control and for offset correction, wherein the second PWM signal (PWMFEEDBACK) is generated in response to a digital output (DQ) that is fed back
Implementation Method 3
providing a current (ISUM), which is the sum of the current (IACT) and the current (IREF), to the analog to digital conversion circuit
Data Source
AI summary
Methods and systems for thermal image sensing are disclosed. A method involves controlling a current (IACT) from a detector of a thermal image sensor with a first pulse width modulated (PWM) signal (PWMACT) for gain control, controlling a current (IREF) from a reference source of the thermal image sensor with a second PWM signal (PWMFEEDBACK) for gain control and for offset correction, wherein the second PWM signal (PWMFEEDBACK) is generated in response to a digital output (DQ) that is fed back from an analog to digital conversion circuit, and providing a current (ISUM), which is the sum of the current (IACT) and the current (IREF), to the analog to digital conversion circuit.