Per-Pixel Detector Bias Control via Floating Gate Injection
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Solution Overview
Problem
Detector bias non-uniformity across an imaging array affects the performance and yield of infrared imagers, leading to unusable pixels and degraded image quality, particularly due to variations in detector and transistor characteristics.
Innovation Solution
A pixel circuit with a floating gate injection device that controls the flow of charge from an integration capacitor to a detector, allowing for per-pixel bias voltage adjustment through a control voltage stored on the gate of the floating gate device, which can be individually programmed to address non-uniformity issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed bias voltage is used for the detector, then the circuit design is simple, but detector bias non-uniformity across the array degrades performance and yield
Solution Approach 1:
The patent implements per-pixel bias control by storing a unique control voltage VT in the floating gate of each pixel's injection transistor. This allows each pixel to have customized bias characteristics tailored to its specific detector and transistor parameters, resolving the non-uniformity issue while maintaining overall system simplicity
Solution Approach 2:
The control voltage VT is pre-programmed into the floating gate during or after fabrication based on measured detector and transistor characteristics. This preliminary customization enables each pixel to operate optimally without requiring complex real-time adjustment circuitry during operation
2Reliability
If per-pixel bias control is implemented, then detector performance uniformity is improved, but device complexity increases
Solution Approach 1:
The floating gate structure serves as an intermediary that stores the control voltage VT and translates it into the appropriate bias condition for each pixel's injection transistor. This mediator approach enables per-pixel customization without requiring complex control circuitry for each pixel
Solution Approach 2:
The patent changes the electrical parameter (control voltage VT) stored in the floating gate to adjust the bias characteristics of each pixel. By modifying this single parameter during programming, optimal performance is achieved for each pixel without changing the physical structure or adding complex 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
This solution improves imaging performance and yield by allowing each pixel to operate optimally, reducing the impact of detector and transistor variations, and maintaining optimal bias conditions, thereby enhancing the overall imaging quality.
Implementation Method 1
The floating gate injection device has a gate, a source electrically coupled to the detector at a first node, and a drain electrically coupled to the integration capacitor. The gate has a control voltage (VT) stored therein to set to a per-pixel bias gate voltage
Data Source
AI summary
A pixel includes a detector that changes its operating characteristics based on incident energy, an integration capacitor arranged to discharge stored charge through the detector based on changes in the operating characteristics, and an floating gate injection device disposed between the photo-diode and the integration capacitor that controls flow of the charge from the integration capacitor to the detector. The floating gate injection device has a gate, a source electrically coupled to the detector at a first node, and a drain electrically coupled to the integration capacitor. The gate has a control voltage (VT) stored therein to set to a per-pixel bias gate voltage to control a detector bias voltage of the detector at the first node.