Radiation Detector Circuit Using Frame-Based Dark Current Compensation
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Solution Overview
Problem
Digital high-energy radiation imaging devices face 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 potential curvature of electric field lines causing image distortion.
Innovation Solution
A programmable current source is used to provide a neutralizing charge to counteract the dark current, allowing for more accurate representation of photo current and reducing image distortion by eliminating or minimizing the effect of dark current, potentially eliminating the need for guard rings and reducing pixel gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a detector substrate is used to collect electrical charge from incoming radiation, then radiation detection capability is improved, but dark current accumulates in the capacitor causing image distortion and reducing measurement precision
Solution Approach 1:
The patent applies feedback control to measure the dark current that accumulates in the capacitor and actively compensates for it by subtracting the measured dark current signal from the total signal. This converts the harmful dark current into a measurable quantity that can be used to correct the measurement error, thereby improving photo current measurement accuracy while accounting for the dark current's presence
Solution Approach 2:
The patent implements a feedback mechanism where the dark current is continuously measured during the integration period and fed back to the signal processing circuitry. This feedback signal is then used to adjust and correct the final image signal, creating a closed-loop system that actively compensates for dark current accumulation and maintains measurement precision over time
2Manufacturing precision
If guard rings are added to reduce dark current effects, then image distortion is reduced, but device complexity and pixel gap requirements increase
Solution Approach 1:
The patent extracts and separates the dark current measurement and compensation function from the traditional guard ring structure. Instead of using physical guard rings to contain dark current, the invention measures the dark current electrically and compensates for it through signal processing, thereby eliminating the need for complex guard ring structures and reducing device complexity while maintaining image quality
Solution Approach 2:
The patent replaces the mechanical/physical guard ring structure with an electrical/electronic dark current compensation system. Instead of using physical barriers (guard rings) to manage dark current, the invention uses electronic measurement and signal processing to compensate for dark current effects, substituting a simpler electronic system for a more complex mechanical structure
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 effectively reduces image distortion by accurately representing the photo current, allowing for smaller pixel gaps and improved image quality by neutralizing the dark current's impact, resulting in more precise and 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
A programmable current source is arranged to provide a neutralizing charge to the capacitor
Data Source
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.