Image Intensifier Tube Electrode Design for Aberration Correction
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Solution Overview
Problem
Magnetic focus image intensifiers suffer from field curvature aberration and ion damage issues, leading to non-uniform resolution and reduced quantum efficiency, limiting their application in critical fields.
Innovation Solution
The design includes a photocathode, electrodes, and a scintillating screen, where the electrodes generate varying electric fields to uniformly accelerate electrons and create a repulsive field to prevent ion back-bombardment, ensuring uniform focus and reducing damage to the photocathode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a short magnetic solenoid is used to generate magnetic field, then device length is reduced, but magnetic field uniformity deteriorates causing field curvature aberration
Solution Approach 1:
The patent applies local quality by creating non-uniform electric fields in different regions of the tube. The electric field strength is varied along the tube axis and across different radial positions, with stronger fields near the photocathode and weaker fields near the anode. This localized variation in field strength compensates for the non-uniform magnetic field from the short solenoid, correcting field curvature aberration while maintaining a compact device length.
2Reliability
If uniform electric and magnetic fields are used for electron acceleration and focusing, then electron focusing is achieved, but device length increases due to required solenoid length
Solution Approach 1:
The patent employs parameter changes by varying the electric field strength as a function of position along the electron acceleration path. Instead of using a uniform electric field that would require a long solenoid for uniform magnetic field, the electric field parameters are adjusted to create stronger acceleration near the photocathode and weaker acceleration near the anode. This parameter variation enables effective electron focusing and aberration correction within a shorter tube length.
3Measurement precision
If photoelectrons are accelerated through magnetic field with transverse velocity, then electrons make integer turns for focusing, but off-axis electrons travel longer paths causing field curvature aberration
Solution Approach 1:
The patent addresses focus uniformity by implementing local quality through position-dependent electric field strength. Off-axis electrons experience different electric field strengths compared to on-axis electrons, with the field configuration specifically designed to compensate for their longer travel paths. This localized field adjustment ensures that electrons from different field positions arrive at the anode simultaneously, achieving uniform focus 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
This configuration achieves improved resolution uniformity across the field of view and enhanced resistance to ion damage, extending the operational life of the image intensifier tube.
Implementation Method 1
a photocathode configured to emit electrons in response to incident illumination
Implementation Method 2
a plurality of electrodes configured to accelerate the electrons emitted from the photocathode along an acceleration path defined by the electrodes to the scintillating screen
Implementation Method 3
a scintillating screen configured to emit illumination in response to incident electrons including at least a portion of the emitted electrons received from the photocathode via the acceleration path
Data Source
AI summary
The disclosure is directed to image intensifier tube designs for field curvature aberration correction and ion damage reduction. In some embodiments, electrodes defining an acceleration path from a photocathode to a scintillating screen are configured to provide higher acceleration for off-axis electrons along at least a portion of the acceleration path. Off-axis electrons and on-axis electrons are accordingly focused on the scintillating screen with substantial uniformity to prevent or reduce field curvature aberration. In some embodiments, the electrodes are configured to generate a repulsive electric field near the scintillating screen to prevent secondary electrons emitted or deflected by the scintillating screen from flowing towards the photocathode and forming damaging ions.