Detector Circuit for Programmable Dark Current Compensation
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Solution Overview
Problem
Digital imaging devices suffer from distortion due to dark current, which is indistinguishable from photo current and consumes a part of the detector's capacity, leading to inaccurate image representation and increased gaps between active imaging areas.
Innovation Solution
Implementing a programmable current source to supply a neutralizing charge that counters the effect of dark current, allowing for more accurate photo current representation and reducing the need for guard rings, thereby minimizing image distortion and pixel gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a detector substrate is used to detect radiation, then radiation detection capability is improved, but dark current causes distortion and reduces measurement precision
Solution Approach 1:
The patent applies preliminary anti-action by introducing a neutralizing charge before reading the detector signal. The circuit adds a compensation charge equal in magnitude but opposite in sign to the expected dark current, thereby counteracting the dark current effect before it can distort the measurement. This is achieved through a capacitor that stores a neutralizing charge and is coupled to the detector substrate, allowing the dark current distortion to be cancelled out in the final reading.
2Measurement precision
If guard rings are added to reduce dark current effects, then measurement precision is improved, but device complexity and area increase
Solution Approach 1:
The patent extracts the dark current compensation function from the physical detector structure (guard rings) and implements it through an electrical compensation mechanism. Instead of adding complex guard ring structures around the detector pixels, the invention removes the need for such structures by using a capacitor to store and apply a neutralizing charge that electronically compensates for dark current, thereby simplifying the overall device structure while maintaining measurement precision.
3Object-affected harmful factors
If guard rings are used to counter dark current, then dark current distortion is reduced, but the area of active imaging regions decreases due to increased gaps
Solution Approach 1:
The patent extracts the dark current management function from the spatial guard ring structures and relocates it to an electrical compensation mechanism. By using a capacitor to store and apply neutralizing charge, the invention eliminates the need for physical guard rings that would consume valuable imaging area, thereby maintaining full active imaging coverage while still compensating for dark current effects through electrical means.
4Device complexity
If a fixed charge compensation method is used, then dark current counteraction is simplified, but adaptability to varying dark current levels is reduced
Solution Approach 1:
The patent applies dynamics by making the charge compensation adaptive rather than fixed. The capacitor is configured to store a neutralizing charge that can be adjusted based on the actual dark current levels, which may vary with temperature, radiation dose rate, and detector aging. This dynamic adaptation allows the compensation mechanism to remain effective under varying operating conditions without requiring complex real-time control circuitry.
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 enhances image accuracy by eliminating or reducing the impact of dark current, allowing for smaller gaps between active imaging areas and straightening bias voltage field lines, resulting in less distorted images.
Implementation Method 1
The detector substrate is made of a photo-conductor material which converts incoming radiation into electronic signals
Implementation Method 2
the imaging system further comprises at least one programmable current source, arranged to provide a neutralizing charge to the capacitor
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
Some embodiments include an imaging system comprising a detector substrate, at least one detector circuit comprising a capacitor coupled with the detector substrate, the capacitor arranged to collect an electrical charge from the detector substrate, and the imaging system further comprises at least one programmable current source, arranged to provide a neutralizing charge to the capacitor, and the imaging system is configured to select a value for the neutralizing charge in dependence of a frame number.