Bolometer Offset Correction via Joule Heating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional bolometric infrared detectors face issues with uniformity in image response due to variability in bolometer resistance, leading to offset and gain variations, which reduce the dynamic range and sensitivity of the detector, and existing offset correction methods either require costly calibration or mechanical shutters, or suppress static scene information.
Innovation Solution
A method and device that corrects bolometer resistance variability by injecting a current to shift resistance values based on temperature-dependent offsets before readout, using a signal shaping circuitry with readout biasing, common-mode rejection, and integrating circuits to maintain thermal information and enhance sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If offset correction tables are used with factory calibration, then offset variation is corrected, but manufacturing cost and calibration time increase significantly
Solution Approach 1:
The patent replaces the mechanical shutter system with an electronic solution using a heating circuit that applies Joule heating to the bolometer substrate. This electrical/thermal system substitutes for the mechanical moving parts, eliminating the need for physical shutter mechanisms while achieving the same offset correction function through temperature-controlled calibration.
Solution Approach 2:
The patent changes the temperature parameter of the bolometer substrate by applying controlled heating current. By varying the substrate temperature and measuring the resulting resistance changes, the system performs calibration and offset correction without requiring mechanical shutters or complex external equipment, thus reducing manufacturing costs and calibration complexity.
2Measurement precision
If mechanical shutter is used for offset correction, then offset variation is corrected at ambient temperature, but device complexity and fragility increase due to moving parts
Solution Approach 1:
The patent replaces the mechanical shutter system with an electronic solution using a heating circuit that applies Joule heating to the bolometer substrate. This electrical/thermal system substitutes for the mechanical moving parts, eliminating the need for physical shutter mechanisms while achieving the same offset correction function through temperature-controlled calibration.
Solution Approach 2:
The bolometer substrate serves its own calibration function by using its inherent thermal properties. The heating circuit applies current directly to the substrate, which then self-regulates its temperature and resistance characteristics to perform offset correction, eliminating the need for external mechanical correction devices.
3Measurement precision
If mechanical shutter is used for reference image acquisition, then offset correction is achieved, but energy consumption increases and detector is unavailable during correction
Solution Approach 1:
The patent enables continuous offset correction by applying heating current to the bolometer substrate during normal operation. Unlike mechanical shutter methods that require stopping detection to acquire reference images, this approach maintains continuous detection while simultaneously performing offset correction through ongoing thermal regulation, ensuring the detector remains available throughout the correction process.
4Device complexity
If bolometer resistance variability is not corrected, then device complexity remains low, but image uniformity and dynamic range deteriorate
Solution Approach 1:
The patent changes the temperature parameter of the bolometer substrate by applying controlled heating current. By varying the substrate temperature and measuring the resulting resistance changes, the system performs calibration and offset correction without requiring mechanical shutters or complex external equipment, thus reducing manufacturing costs and calibration complexity.
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 increases the residual dynamic response, reduces variability in formed images, and allows for higher temperature operation without the need for mechanical shutters or extensive calibration, improving sensitivity and maintaining image quality.
Implementation Method 1
The present invention relates to the field of infrared imaging and pyrometry using bolometers
Implementation Method 2
a readout biasing circuitry capable of biasing the bolometer at a predetermined voltage in order to make current flow through the latter
Implementation Method 3
a common-mode rejection circuitry capable of generating a common-mode current
Data Source
AI summary
A device for detecting infrared radiation comprising an array of bolometers for detecting radiation; and in order to read each bolometer, a signal shaping circuitry comprising: a circuitry capable of biasing the bolometer at a predetermined voltage in order to make current flow therethrough; a circuitry capable of generating a common-mode current; and a circuitry capable of integrating the difference between the current that flows through the bolometer and the common-mode current. According to the invention, the device comprises a circuitry capable of injecting current into each bolometer in order to shift its resistance by a predetermined quantity that depends on its offset, current injection being performed prior to readout biasing of the bolometer and the shift being performed according to the direction in which the bolometer's resistance varies as a function of temperature. In addition, correction circuitry is capable of shifting the resistances of bolometers towards a common value.