Rotatable Shuttered Mirror for Stray Light Control in Thermal Sensors
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Solution Overview
Problem
Conventional sensor systems face challenges in maintaining image quality and calibration accuracy due to stray light from thermal reference sources, which can cause false hot spots and vibration issues during Non-Uniformity Calibration (NUC) of Focal Plane Arrays (FPAs), especially when searching for hot targets against cold backgrounds.
Innovation Solution
A sensor system with a rotatable mirror and shroud that selectively blocks channels to prevent stray light from reaching the FPA, allowing for continuous thermal reference source operation while maintaining image quality, using a shroud that can rotate 360 degrees and is designed to minimize vibration and Wave Front Error (WFE).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermal reference source is kept on continuously to maintain NUC readiness, then calibration repeatability is improved, but stray light degrades image quality
Solution Approach 1:
A shutter mechanism is introduced as an intermediary component between the thermal reference source and the focal plane array. This shutter acts as a controllable mediator that can selectively block or permit the passage of infrared radiation, allowing the TRS to remain on for calibration repeatability while preventing stray light from degrading image quality during normal operation.
Solution Approach 2:
The shutter is designed to be dynamically controllable, transitioning between open and closed states based on operational requirements. This dynamic control allows the system to switch between calibration mode (shutter open) and imaging mode (shutter closed), resolving the contradiction between maintaining continuous calibration readiness and preventing stray light interference.
2Object-affected harmful factors
If a non-integrated powered shutter is used to cover TRS emission, then image quality is improved, but cost and complexity increase
Solution Approach 1:
The shutter function is merged with the existing beam switching mirror mechanism. The same mirror assembly that performs beam switching also performs the shutter function by positioning itself to block or permit TRS emission. This integration eliminates the need for a separate powered shutter mechanism, reducing system complexity and cost while maintaining the ability to block stray light.
Solution Approach 2:
The beam switching mirror is given multiple functions: it performs both beam switching (directing infrared radiation to different detectors) and shuttering (blocking TRS emission when not needed). This multi-functionality reduces the overall component count and system complexity while achieving the desired stray light blocking capability.
3Object-affected harmful factors
If the fold mirror is pivoted away from the center of gravity to block TRS ray path, then stray light is blocked, but vibration and Wave Front Error increase
Solution Approach 1:
Instead of physically moving the heavy fold mirror away from its center of gravity (which causes vibration and WFE), a lightweight shutter component is introduced that can be positioned to block the TRS ray path. This shutter copy performs the blocking function without the adverse mechanical effects of moving the main mirror, effectively decoupling the blocking function from the vibration-problematic mirror pivoting.
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 effectively shields the FPA from stray light, maintaining high calibration accuracy and image quality by allowing the thermal reference source to remain active without degrading image quality, while reducing vibration and improving beam switching precision.
Implementation Method 1
a shroud optionally painted with light absorbing paint that provides shielding from stray light for a sensor
Implementation Method 2
a body having a reflective surface, wherein the body is rotatable about a longitudinal axis
Data Source
AI summary
Methods and apparatus for a sensor system having a structure having a reflective surface, wherein the structure is rotatable about a longitudinal axis. Channels provide respective paths from an entry into the channels to the reflective surface. A shroud selectively block ones of the channels to provide an operational configuration and a calibration configuration.