Compact PMMW Camera Calibration Target Using Segmented Thermal Blocks
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Solution Overview
Problem
Existing calibration techniques for passive millimeter wave (PMMW) cameras require large and cumbersome hot and cold targets that need to be mechanically moved in front of the focal plane array (FPA) for calibration, which is impractical for cameras with large fields-of-view, especially in environments with significant temperature changes.
Innovation Solution
A compact thermal calibrator using two thermally conducting blocks separated by a thermo-electric (TE) cooling device, which heats one block and cools the other, allowing for selective scanning of calibration targets across the FPA, providing hot and cold temperatures without the need for large mechanical movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large hot and cold targets are used for calibration, then calibration accuracy is achieved, but device size and mechanical complexity increase significantly
Solution Approach 1:
The calibration target is segmented into two separate blocks (hot block and cold block) that can be independently positioned. Each block is much smaller than traditional full-field targets, allowing them to be moved sequentially across the FPA rather than requiring large mechanical structures. This segmentation enables compact design while maintaining calibration capability.
Solution Approach 2:
Instead of moving large targets laterally across the entire FPA area, the invention uses a scanning approach where small targets are moved along a single dimension (scanning direction) to sequentially illuminate different receiver elements. This dimensional reduction in movement requirements significantly simplifies the mechanical system.
2Temperature
If traditional calibration targets are used, then temperature calibration is achieved, but space requirements and device size increase
Solution Approach 1:
The hot block and cold block are merged into a single integrated calibration device housing, sharing common structural support, positioning mechanisms, and control systems. This consolidation achieves the full temperature calibration range using a compact footprint rather than requiring separate large-scale target systems.
Solution Approach 2:
The invention replaces the need for large mechanical target structures with a scanning mechanism that moves small thermal blocks across the FPA. The calibration function is achieved through controlled thermal radiation from compact blocks rather than large physical targets, dramatically reducing space requirements.
3Measurement precision
If separate hot and cold targets are mechanically moved, then receiver calibration is achieved, but operation time and procedural complexity increase
Solution Approach 1:
The calibration system uses dynamic scanning motion to sequentially present hot and cold targets to different receiver elements in a continuous sequence. This dynamic approach allows calibration of all receivers in a single scanning pass rather than requiring static positioning and multiple setup changes, significantly reducing calibration time.
Solution Approach 2:
The scanning mechanism continuously moves the thermal blocks across the FPA without interruption, maintaining continuous calibration action across all receiver elements. This eliminates idle time between calibrating different receivers and ensures the calibration process flows continuously, maximizing efficiency.
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 efficient and space-saving calibration of PMMW cameras by providing a compact solution for generating calibration targets, reducing the size and space requirements for calibration, and accommodating temperature changes, thus improving the calibration process.
Implementation Method 1
a thermal calibrator including two thermally conducting blocks separated by a thermo-electric (TE) cooling device that cools one of the blocks and heats the other block
Implementation Method 2
PMMW cameras are well known in the art that passively receive and process millimeter wave radiation from a scene and provide imaging through thermal resolution of objects in the scene
Data Source
AI summary
A calibration system for a passive millimeter-wave (PMMW) camera. The calibration system includes a thermal calibrator having a first thermally conducting body, a second thermally conducting body, a first black body target mounted to a front surface of the first conducting body, a second black body target mounted to a front surface of the second conducting body, and a thermo-electric (TE) cooling device having a hot side and a cold side. The hot side of the TE cooling device is thermally attached to the first conducting body and the cold side of the TE cooling device is thermally attached to the second conducting body.