Surface Charge Distribution Measurement Using Potential Saddle Point
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Solution Overview
Problem
Current methods for measuring surface charge distribution on electrophotographic photoreceptors are limited by dark decay, which causes rapid loss of electric charges, and existing calculation methods suffer from low accuracy due to cancellation errors in space field calculations, leading to lengthy computation times.
Innovation Solution
A method and device that measure surface charge distribution by irradiating the sample with a charged particle beam, using a potential saddle point and electromagnetic field analysis to determine the space and surface charge distribution, reducing computation time and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If small cell sizes are used in space field calculations to improve measurement precision, then calculation accuracy improves, but calculation time increases significantly
Solution Approach 1:
The patent extracts and measures the potential at the saddle point specifically, rather than calculating the entire space field distribution. By focusing measurement on this critical point and using it to determine surface charge distribution, the method avoids the need for fine meshing of the entire calculation domain, thus reducing calculation time while maintaining accuracy
Solution Approach 2:
The patent performs preliminary identification of the saddle point position and uses it to guide the measurement process. By pre-locating this critical point and using it as the basis for charge distribution determination, the method eliminates the need for iterative full-field calculations with small cell sizes
2Productivity
If the number of measurements and calculation steps is reduced to shorten measurement time, then productivity improves, but measurement precision deteriorates
Solution Approach 1:
The patent extracts the critical information from a single saddle point measurement rather than requiring multiple measurements across the entire field. This extraction of essential information enables rapid measurement while maintaining the precision needed to determine surface charge distribution accurately
Solution Approach 2:
The patent uses the potential distribution pattern (with its characteristic saddle point) as a signature or copy of the surface charge distribution. By measuring this characteristic pattern at the saddle point, the method can infer the complete charge distribution without direct measurement of every point, thus achieving both speed and precision
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
Enables high-resolution measurement of surface charge distribution in a short period with improved accuracy, reducing the number of computation steps and measurement times required.
Implementation Method 1
Secondary electrons generated from incident electrons are pushed back by this electric field so that less amount of the electrons can reach a detector
Implementation Method 2
A field distribution is formed in a space over the surface of a sample in accordance with the charge distribution on the sample surface
Data Source
AI summary
A surface charge measuring distribution method includes the steps of irradiating a sample with a charged particle beam and charging a sample surface in a spot-like manner, irradiating the charged sample with the charged particle beam to measure a potential at a potential saddle point formed above the sample, selecting one of preset multiple structure models and a tentative space charge distribution associated with the selected structure model, calculating a space potential at the potential saddle point by electromagnetic field analysis using the selected structure model and tentative space charge distribution, comparing the calculated space potential and measured value to determine the tentative space charge distribution as a space charge distribution of the sample when an error between the space potential and the measured value is within a predetermined range, and calculating a surface charge distribution of the sample by electromagnetic field analysis based on the determined space charge distribution.