Thermal Imager Protective Grid Uniform Attenuation
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Solution Overview
Problem
Industrial thermal imaging devices in explosion-proof housings face non-uniform attenuation patterns due to generic protective grids, leading to degraded radiometric performance and image quality, as these grids are not designed considering the specific thermal imager's lens geometry and position.
Innovation Solution
Designing a protective grid with a specific geometry and pattern that accounts for the thermal imager's lens input pupil size and position, using a quadratic or irregular pattern with a constant pitch and bar width, and adjusting the grid geometry to maintain a constant ratio, ensuring predictable and uniform attenuation across the field of view, which can be compensated with a single transmissivity factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a generic protective grid is used in the explosion-proof housing, then the window is protected from the external environment, but the thermal imager experiences non-uniform attenuation patterns that degrade radiometric performance
Solution Approach 1:
The protective grid is designed with non-uniform bar spacing where the spacing varies across the grid surface. The spacing is specifically optimized for different regions of the field of view, with tighter spacing in regions where attenuation would otherwise be excessive and wider spacing in regions where attenuation is insufficient. This local variation in grid structure creates a uniform overall attenuation pattern across the entire field of view, preserving radiometric performance while maintaining protection.
2Ease of manufacture
If a protective grid with uniform bar spacing is used, then the grid structure is simple and easy to manufacture, but the attenuation pattern is non-uniform across the field of view
Solution Approach 1:
The grid employs varying bar spacing across different regions rather than uniform spacing throughout. This allows each region to be optimized for its specific attenuation requirements while maintaining a relatively simple overall grid structure that can be manufactured using standard techniques. The non-uniform spacing pattern is designed to compensate for the angular dependence of attenuation, creating uniform overall performance.
3Strength
If the protective grid bars are spaced closely together, then the mechanical strength of the grid is increased, but the field of view is more blocked and attenuation is non-uniform
Solution Approach 1:
The grid uses region-specific bar spacing where closely spaced bars are positioned in regions requiring higher mechanical strength or where excessive transmission would cause over-attenuation, while more widely spaced bars are used in regions where sufficient transmission is needed. This localized optimization allows the grid to achieve both adequate mechanical strength and uniform attenuation characteristics across the entire field of view.
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 solution achieves a more uniform attenuation pattern with minimal variance, reducing temperature reading errors to ±2% or less, while maintaining mechanical strength and manufacturability, thereby enhancing the radiometric performance and image quality of thermal imagers.
Implementation Method 1
The protective grid causes a strong, non-uniform attenuation pattern in the FOV thereby making the thermal measurements of the thermal imager non-radiometric
Data Source
AI summary
A protective enclosure for a thermal imager having a window and protective grid. The protective grid (204) is designed in relation to the lens (201) of the thermal imaging device such that the grid pattern geometry and size accommodate the thermal imaging device's pupil size (203).