Electron-Bombarded Sensor Ring Electrode Focusing
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Solution Overview
Problem
Current electron-bombarded CCD and CMOS imaging sensors face challenges in achieving high spatial resolution, low landing energy, and high gain, particularly due to issues like electron and photon scattering, arcing risks, and non-uniformity caused by proximity focus designs, which limit their application in low-light imaging and increase the risk of damage to the sensors.
Innovation Solution
The implementation of novel ring electrode structures and magnetic field generators to accelerate and focus photoelectrons at low electric fields, with distances between the photocathode and sensor optimized to achieve low landing energies (2 keV or below), and the use of deflection fields to direct photoelectrons to an off-axis sensor, enhancing resolution and reducing arcing risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If proximity focus design is used to simplify structure and reduce power requirements, then device complexity and power consumption are reduced, but resolution and uniformity deteriorate due to electron scattering and non-uniform electric fields
Solution Approach 1:
The electrode structure is segmented into multiple zones with different potentials. The first electrode has a first potential and the second electrode has a second potential, creating distinct electric field regions that control electron trajectories differently in various spatial zones, thereby improving resolution while maintaining structural simplicity
Solution Approach 2:
Different regions of the electrode structure are assigned different electrical properties. The electrodes create locally optimized electric fields that account for the non-flat sensor surface, providing uniform acceleration and focusing across the entire detection area despite varying local geometries
2Measurement precision
If higher accelerating voltage is applied to improve resolution, then spatial resolution improves, but landing energy increases causing sensor damage and reduced lifetime
Solution Approach 1:
The system dynamically adjusts electron acceleration in two stages: first accelerating electrons to high energy for resolution, then decelerating them before impact to preserve the sensor. This dynamic control of electron energy allows high-resolution imaging without sensor damage
Solution Approach 2:
The electric field configuration performs preliminary acceleration of electrons to high energies for improved resolution, then prepares for deceleration before sensor impact. This preliminary action sequence ensures both high resolution and sensor protection
3Ease of manufacture
If transmission mode photocathode is used to simplify design, then manufacturing is simplified, but quantum efficiency deteriorates compared to reflective mode
Solution Approach 1:
The system changes the operational parameters of the transmission mode photocathode by implementing specific electric field configurations and acceleration voltages that optimize electron emission and collection efficiency, thereby improving quantum efficiency while maintaining the manufacturing simplicity of transmission mode
4Measurement precision
If non-flat sensor surface is accommodated to allow back-thinning, then quantum efficiency improves, but resolution uniformity deteriorates due to varying electron acceleration distances
Solution Approach 1:
The electric field configuration is optimized for local conditions at different positions on the sensor. The first and second electrodes create field distributions that compensate for the non-flat surface geometry, ensuring uniform electron acceleration and focusing across the entire detection area despite varying local distances
Solution Approach 2:
The solution moves from considering only the one-dimensional electron acceleration distance to incorporating the three-dimensional spatial configuration of electrodes and sensor surface. By designing electrode geometry and potential distribution in multiple dimensions, the system compensates for surface non-flatness and achieves uniform resolution
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 results in high-resolution electron optics with low landing energy, improved sensor lifetime, and reduced arcing risks, enabling high-quality low-light imaging while accommodating sensor non-flatness, thus overcoming the limitations of traditional proximity focus designs.
Implementation Method 1
A photocathode is disposed on an inside surface of the first end wall and is configured to emit photoelectrons in response to low light signals
Implementation Method 2
a magnetic field generator is utilized to generate a focusing lens effect on the photoelectrons
Implementation Method 3
ring electrodes are utilized to accelerate the photoelectrons as they leave the photocathode
Data Source
AI summary
An electron-bombarded detector for detecting low light signals includes a vacuum tube structure defining a cylindrical vacuum tube chamber, a photocathode disposed at a first end of the vacuum tube chamber, a sensor disposed at a second end of the vacuum tube chamber, ring electrodes disposed in the vacuum tube chamber for generating an electric field that accelerates emitted photoelectrons toward the sensor, and a magnetic field generator configured to generate a symmetric magnetic field that applies a focusing lens effect on the photoelectrons. The ring electrodes and magnetic field generator are operating using one of a reduced distance focusing approach and an acceleration/deceleration approach such that the photoelectrons have a landing energy below 2 keV. The use of reflective mode photocathodes is enabled using either multi-pole deflector coils, or ring electrodes formed by segmented circular electrode structures. Large angle deflections are achieved using magnetic or electrostatic deflectors.