Night Vision Photocathode Control for Fast Bright Flash Recovery
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Solution Overview
Problem
Night vision equipment is vulnerable to detrimental effects from bright flashes, such as muzzle flashes, which can overwhelm the image intensifier tube and lead to prolonged recovery times, disrupting the user's vision.
Innovation Solution
A digital power supply with a processor that implements an automatic brightness control procedure, which senses excessive current, shuts down the photocathode, stores the previous voltage settings, and re-enables them after a short delay to quickly recover from bright light events, reducing the flash response time to less than 50 milliseconds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If automatic brightness control procedure continuously adjusts voltage to photocathode, then brightness control is maintained, but recovery time from bright flash is prolonged
Solution Approach 1:
The patent extracts the automatic brightness control procedure from continuous operation and isolates it during flash recovery. When a bright flash is detected, the ABC procedure is temporarily disabled, allowing the system to recover without interference from continuous brightness adjustment attempts. This extraction resolves the contradiction by separating the brightness control function from the flash recovery period.
Solution Approach 2:
The patent applies preliminary action by storing the voltage value before the flash occurs and preparing the system for quick recovery. The voltage value is captured and preserved in advance, so when the flash ends, the system can immediately restore the previous operating state without needing to re-establish control, significantly reducing recovery time.
2Productivity
If photocathode remains active during bright flash, then continuous operation is maintained, but image quality deteriorates
Solution Approach 1:
The patent applies preliminary anti-action by detecting the bright flash condition and immediately counteracting its harmful effects. When excessive current indicating a flash is detected, the system shuts down the photocathode to prevent saturation and damage, then restores it after the flash passes. This preemptive response protects image quality while maintaining continuous operational capability.
3Adaptability or versatility
If voltage to photocathode is adjusted during flash, then brightness adaptation occurs, but recovery stability is reduced
Solution Approach 1:
The patent stores the voltage value before the flash occurs, preserving the stable pre-flash state. During recovery, this stored value is restored, providing a stable reference point. This preliminary preservation of the voltage state ensures that recovery is stable and predictable, while the system maintains adaptability by being ready to adjust to new lighting conditions after recovery.
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
This approach enables night vision equipment to recover from bright flashes more quickly, minimizing the impact on image quality and user experience, allowing for faster adaptation to changing light conditions.
Implementation Method 1
Visible and infrared energy, for example, may impinge upon the photocathode and be absorbed in the cathode active layer, thereby resulting in generation of electron/hole pairs
Implementation Method 2
As the electrons bombard the input surface of the MCP, secondary electrons are generated within the MCP. That is, the MCP may generate several hundred electrons for each electron entering the input surface
Implementation Method 3
As the multiplied electrons exit the MCP, the electrons are accelerated through the vacuum cavity toward a phosphor screen (or other anode surface)
Data Source
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AI summary
A methodology, for night vision equipment, includes enabling an automatic brightness control (ABC) procedure for a light intensifier having a photocathode that automatically selects a voltage to be applied to the photocathode, sensing current being drawn by the anode, when the current being drawn by the anode exceeds a predetermined threshold, shutting down the photocathode, disabling the ABC procedure, and storing, as a stored voltage value, a value of a voltage that had been selected by the ABC procedure when the current exceeded the predetermined threshold. After a first predetermined period of time, applying a voltage to the photocathode in accordance with the stored voltage value, and after a second predetermined period of time re-enabling the ABC procedure and selecting the stored voltage value as the voltage to be applied to the photocathode.