Thermal Imaging Shutter Calibration via LED Heating
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Solution Overview
Problem
Passive shutters in thermal imaging systems cannot correct for both pixel responsivity and DC offset variations over time due to their inability to control temperature, limiting the performance of thermal imagers, especially with detector technologies like long wave cooled detectors, while active shutters disrupt imaging with significant downtime.
Innovation Solution
A system and method using a shutter that moves between optical and non-optical positions, with non-contact heating by a blue LED to achieve two temperature data sets, allowing for in situ calibration of both offset and gain corrections with minimal downtime and maintaining the benefits of passive shutters such as low mass and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a passive shutter is used for in situ calibration, then the shutter can be thinner, lighter, faster, and consume less power, but it cannot control or change the temperature of the shutter, thereby not allowing both responsivity and DC offset levels to be corrected
Solution Approach 1:
The patent applies preliminary action by pre-heating the shutter blade to a known temperature before calibration. The system performs a first calibration at the shutter's initial temperature, then heats the shutter to a second temperature, and performs a second calibration. This preliminary heating action enables the passive shutter to provide temperature-controlled calibration data without requiring active temperature control during operation.
Solution Approach 2:
The patent changes the temperature parameter of the shutter blade from its initial state to a heated state using a heat source. By controlling the heating process and measuring at two distinct temperatures, the system extracts both responsivity and DC offset calibration parameters from a passive shutter that would otherwise provide only single-temperature data.
2Adaptability or versatility
If an active shutter with TEC is used for calibration, then both responsivity and DC offset can be corrected, but imaging is interrupted for time periods in the region of 30 seconds
Solution Approach 1:
The patent performs calibration measurements in advance at two different temperatures. The shutter is heated to a second temperature, calibration data is collected, then the shutter returns to its initial temperature and a second calibration is performed. These preliminary calibration actions are stored and applied during imaging, eliminating the need for lengthy real-time calibration interruptions.
Solution Approach 2:
The system performs calibration periodically at predetermined temperatures rather than continuously. By pre-heating the shutter to calibration temperatures and collecting data in periodic bursts, the system minimizes imaging interruption while maintaining calibration accuracy.
3Weight of moving object
If a passive shutter is used, then the shutter blade can be thinner and lighter allowing faster motion and reducing the gap required between the detector and the lens, but there is no ability to control or change the temperature of the shutter
Solution Approach 1:
The patent introduces a heat source as an intermediary component that temporarily heats the passive shutter blade to predetermined temperatures for calibration purposes. This intermediary heating mechanism enables temperature control during calibration without requiring the shutter itself to be an active, temperature-controlled component, thus maintaining the lightweight design.
4Temperature
If an active shutter system is used, then temperature control is achieved, but the system is more complex, consumes more power, and costs more
Solution Approach 1:
The patent performs temperature control actions preliminarily - heating the shutter to calibration temperatures before data collection - rather than maintaining continuous active temperature control. This approach achieves the necessary temperature control for calibration while using a simpler passive shutter design without integrated TEC and control electronics.
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
Enables quick and efficient in situ calibration with reduced downtime, achieving imaging performance comparable to active shutters while maintaining the practical advantages of passive shutters, including low mass, low power consumption, and cost-effectiveness.
Implementation Method 1
positioning the shutter adjacent a heat source for a predetermined time thereby changing the temperature of the shutter to a predetermined second temperature
Implementation Method 2
the shutter being moveable from a first position to a second position, the shutter being disposed in the optical path of the imaging system in the first position and outside of the optical path in the second position
Data Source
AI summary
A system and method for calibrating an imaging system includes a shutter that is moveable in to the optical path of the imaging system to generate an image of the shutter surface, which is flat and uniform. The shutter can be moved in and out of the optical path between first and second positions. The shutter is heated while in the second position and then returned to the first position. Data sets generated at two different temperatures enable the image generated by the imaging system in normal use to be to be adjusted for responsivity and variation in DC offset of the specific pixel array.