NVIS-Compatible HUD Combiner Alignment Detector
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Solution Overview
Problem
Traditional combiner alignment detectors (CADs) using 850 nm infrared light are incompatible with night vision imaging systems (NVIS) due to high spectral sensitivity, causing stray infrared light to overwhelm HUD symbology and pose a distraction and safety concern.
Innovation Solution
Implementing a CAD system that pulses IR emitters at extremely low duty cycles (less than 2%) to reduce averaged time-based radiance, allowing existing open air CADs to be compatible with NVIS by using low-duty cycle pulse-width modulation, which maintains alignment detection functionality without interfering with NVIS performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional open air CAD uses 850 nm infrared light, then alignment detection functionality is achieved, but NVIS compatibility is lost due to high spectral sensitivity causing distraction and safety concerns
Solution Approach 1:
The patent applies periodic action by pulsing the infrared emitter at extremely low duty cycles (less than 2%) rather than continuous operation. This pulsed operation reduces the averaged time-based radiance to levels compatible with NVIS while maintaining sufficient signal strength for alignment detection during the pulse windows.
Solution Approach 2:
The patent changes the operational parameters of the infrared emitter by implementing low-duty cycle pulse-width modulation. This parameter change reduces the average radiance output while maintaining the peak intensity needed for detection, thereby resolving the contradiction between detection functionality and NVIS compatibility.
2Measurement precision
If continuous IR emission is used for alignment detection, then detection signal strength is sufficient, but stray infrared light overwhelms HUD symbology when viewed through NVIS goggles
Solution Approach 1:
By switching from continuous emission to periodic pulsed emission at duty cycles less than 2%, the system maintains strong detection signals during pulse windows while reducing overall stray light intensity to NVIS-compatible levels.
Solution Approach 2:
The system uses partial action by emitting infrared light only during brief pulse windows rather than continuously. This partial emission provides sufficient signal for alignment detection during the pulse duration while keeping the overall light exposure below NVIS interference thresholds.
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 enables CAD systems to operate effectively with NVIS, reducing IR light interference and maintaining opto-mechanical functionality, ensuring clear HUD symbology and compatibility across various environmental conditions, including day and night and extreme temperatures.
Implementation Method 1
Traditional methods of single or dual-axis alignment detection work by reflecting a beam of 850 nanometer (nm) infrared (IR) light off of a mirror which is attached to the combiner and onto a photodiode array which senses the location of the IR beam
Implementation Method 2
reflecting a beam of 850 nanometer (nm) infrared (IR) light off of a mirror
Implementation Method 3
onto a photodiode array which senses the location of the IR beam
Data Source
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AI summary
A system and method. The system may include a head-up display (HUD). The HUD may include a positionable combiner optical element (COE) (106) and a combiner alignment detector (CAD) configured to conform images displayed on the positionable COE with a view through the positionable COE. The CAD may include a mirror (112) that moves with the positionable COE, an infrared (IR) emitter (120) configured to emit IR pulses onto the mirror with a duty cycle of less than 1% such that an average time-based radiance of the IR pulses is compatible with a night vision imaging system (NVIS) (1102), and an IR detector (118) configured to receive the IR pulses reflected off of the mirror.