Hybrid Image Sensor Charge Injection via Assisted Direct Injection
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Solution Overview
Problem
Hybrid image sensors face inefficiencies in charge injection due to parasitic capacitance and depletion, leading to non-linearity and lag in response to incident light, primarily because the skimming gate operates in a sub-threshold mode with slow settling times and low current injection efficiency.
Innovation Solution
The implementation of 'Assisted Direct Injection' (ADI) techniques, which include Charge Leveling and Charge Pump operations, to stabilize voltage across the photosensitive film and compensate for parasitic capacitance, ensuring proportional charge injection and reducing lag and non-linearity by initializing and resetting potential wells and injecting additional charge carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the skimming gate operates in sub-threshold mode to enable global shutter functionality, then the device complexity is reduced and ease of operation is improved, but charge injection efficiency deteriorates and lag increases
Solution Approach 1:
The patent applies preliminary action by filling the potential well at the pixel electrode with charge carriers before the actual photocharge acquisition begins. This pre-filling operation ensures that the well is ready to efficiently collect photocharges without delay, thereby improving charge injection efficiency while maintaining the global shutter functionality enabled by sub-threshold skimming gate operation.
2Device complexity
If the skimming gate operates in sub-threshold mode, then device complexity is reduced, but settling time increases and response speed deteriorates
Solution Approach 1:
The patent performs preliminary filling of the potential well with charge carriers before photocharge acquisition. This pre-initialization of the potential well eliminates settling delays during the actual measurement phase, allowing the skimming gate to operate in the simpler sub-threshold mode without sacrificing response speed.
3Ease of manufacture
If parasitic capacitance is present at the pixel electrode, then manufacturing is simplified, but charge injection linearity deteriorates and non-linearity increases
Solution Approach 1:
The patent applies preliminary action by pre-filling the potential well with charge carriers before photocharge acquisition. This pre-charging operation compensates for the effects of parasitic capacitance, ensuring that the well is properly initialized and that subsequent charge injection remains linear and accurate, despite the presence of parasitic capacitance from simplified fabrication.
4Use of energy by moving object
If the potential well is not pre-filled with charge carriers, then energy consumption is reduced, but charge injection efficiency deteriorates and lag increases
Solution Approach 1:
The patent performs preliminary filling of the potential well with charge carriers before photocharge acquisition. While this requires additional energy input, it significantly improves charge injection efficiency by ensuring the potential well is properly initialized and ready to efficiently collect photocharges, thereby reducing lag and improving overall system productivity.
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
ADI techniques enhance charge injection efficiency, eliminate lag, and maintain signal linearity by stabilizing voltage and compensating for capacitance depletion, resulting in improved photo-response consistency across varying light levels.
Implementation Method 1
a photosensitive medium configured to convert incident photons into charge carriers
Data Source
AI summary
Imaging apparatus (20) includes a photosensitive medium (22) and a bias electrode (32), which is at least partially transparent, overlying the photosensitive medium. An array of pixel circuits (26) is formed on a semiconductor substrate (30). Each pixel circuit includes a pixel electrode (24) coupled to collect the charge carriers from the photosensitive medium; a readout circuit (75) configured to output a signal indicative of a quantity of the charge carriers collected by the pixel electrode; a skimming gate (48) coupled between the pixel electrode and the readout circuit; and a shutter gate (46) coupled in parallel with the skimming gate between a node (74) in the pixel circuit and a sink site. The shutter gate and the skimming gate are opened sequentially in each of a sequence of image frames so as to apply a global shutter to the array and then to read out the collected charge carriers via the skimming gate to the readout circuit.