IR Optical Metrology System Background Radiation Compensation
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Solution Overview
Problem
Current IR optical measurement systems face challenges in accurately determining the modulation transfer function (MTF) due to high IR background radiation and signal/noise ratio issues, especially in the far IR region, which affects the precision of MTF calculations.
Innovation Solution
A video-based metrology system that compensates for IR background radiation and thermal management, using a computer-controlled system with a graphical user interface to perform real-time two-dimensional image analysis and MTF calculations, employing bandpass filters, gold reflective coatings, and thermal masses to maintain target temperatures and minimize heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If IR background radiation is present during measurement, then the measurement can be performed continuously, but the signal-to-noise ratio deteriorates and MTF calculation precision is reduced
Solution Approach 1:
The system performs preliminary measurement of background IR radiation by blocking the light source and capturing images of the target without illumination. These background images are processed to determine background radiation levels before the actual MTF measurement begins, allowing for compensation during continuous measurement.
Solution Approach 2:
The system continuously monitors and compensates for background IR radiation by comparing current background levels with reference values and adjusting the measurement calculations accordingly. This feedback mechanism maintains measurement precision despite varying background conditions during continuous operation.
2Measurement precision
If thermal management features are added to minimize IR background, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent introduces an intermediary blocking mechanism (occluder) that can be positioned in the optical path to prevent IR background radiation from reaching the detector. This simple mechanical intermediary effectively isolates the measurement system from thermal interference without requiring complex active thermal management systems.
Solution Approach 2:
Instead of using complex active thermal control systems (coolers, heaters, or temperature-controlled enclosures), the patent substitutes a mechanical blocking approach using an occluder that can be positioned to block IR radiation. This mechanical solution achieves thermal isolation with minimal system complexity.
3Productivity
If real-time image analysis is performed, then productivity increases, but computational requirements and system complexity increase
Solution Approach 1:
The image analysis process is segmented into distinct functional stages: background radiation determination, image capture, image processing, and MTF calculation. By dividing the computational workload into separate modules that can process data independently and in parallel, the system achieves real-time performance without requiring a single complex computational system.
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 system enables accurate and efficient measurement of IR optical components' performance by minimizing IR background interference and thermal noise, allowing for precise MTF determination and improved optical system characterization.
Implementation Method 1
bandpass filters
Implementation Method 2
gold reflective coatings
Implementation Method 3
thermal management
Implementation Method 4
thermal masses to maintain target temperatures
Implementation Method 5
IR camera having an image detector
Data Source
AI summary
A system for quickly measuring and displaying in real-time a variety of performance characteristics of IR optical components such as lenses, or the like. The system is video based and is under the control of a computer which uses a windowing software program to provide the user with a graphical user interface by which the various components of the system and test lenses may be characterized and operated on through functions available via the interface. The system has features for compensating for the presence of IR background radiation that may be present during a measurement cycle and for drift in the video imager. Thermal management features are included to minimize IR background.