Per-Pixel Gain ROIC Architecture for High Dynamic Range Imaging
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Solution Overview
Problem
Conventional readout integrated circuits (ROICs) face challenges in efficiently handling wide dynamic range scenes due to fixed gain settings, which lead to saturation issues and reduced sensitivity, particularly at low signal levels, increasing power consumption and noise contributions.
Innovation Solution
A reconfigurable ROIC architecture that utilizes per-pixel gain selection based on Received Signal Strength Indicator (RSSI) bits, allowing for on-the-fly adaptations by adjusting the gain of each pixel sensor, thereby maximizing the full-scale photo-diode dynamic range and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fixed gain settings are used in conventional ROICs, then device complexity is reduced, but dynamic range performance deteriorates due to saturation issues and reduced sensitivity at low signal levels
Solution Approach 1:
The patent implements dynamic gain adjustment by introducing a gain control circuit that modifies the gain setting based on detected signal levels. The system transitions from a static fixed gain architecture to a dynamic one where gain can be adjusted in real-time according to scene requirements, resolving the contradiction between adaptability and complexity by making the system flexible only when needed.
Solution Approach 2:
The patent changes the gain parameter dynamically based on signal level detection. By monitoring the input signal strength and adjusting the gain parameter accordingly (increasing gain for low signals, decreasing for high signals), the system achieves extended dynamic range performance without requiring a completely complex restructured architecture.
2Measurement precision
If high gain is used to improve sensitivity at low signal levels, then signal-to-noise ratio improves, but saturation occurs at high signal levels
Solution Approach 1:
The patent employs feedback mechanisms where the gain control circuit continuously monitors the output signal level and adjusts the gain setting accordingly. When high signal levels are detected, the circuit provides feedback to reduce gain, preventing saturation. When low signal levels are detected, feedback triggers increased gain to improve SNR, thus resolving the contradiction between measurement precision and saturation resistance.
Solution Approach 2:
The gain control circuit automatically adjusts gain settings based on detected signal levels without external intervention. The system serves itself by detecting its own operating conditions and making appropriate gain adjustments, eliminating the need for manual gain selection and ensuring optimal performance across varying signal conditions.
3Adaptability or versatility
If per-pixel gain adjustment is implemented, then intra-scene dynamic range is enhanced, but device complexity increases
Solution Approach 1:
The patent segments the image sensor into multiple regions or pixels, each capable of independent or semi-independent gain adjustment. By dividing the sensor array and applying gain control at segmented levels (pixel-level, block-level, or region-level), the system achieves enhanced intra-scene dynamic range while managing complexity through modular organization rather than requiring fully independent control for every single pixel.
Solution Approach 2:
The gain control circuit is designed to serve multiple functions: it can operate in automatic mode for wide dynamic range scenes, manual mode for specific applications, and can adapt to different lighting conditions. This multi-functionality allows a single circuit design to handle various scenarios, reducing the need for multiple specialized circuits and thereby managing complexity while providing versatile dynamic range enhancement.
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 approach enhances intra-scene dynamic range, reduces power consumption, and improves signal-to-noise ratio (SNR) by allowing per-pixel gain adjustments, preventing saturation and increasing sensitivity across varying signal levels.
Implementation Method 1
The image sensors convert incident electromagnetic radiation to electrical signals that may be represented as digital images
Data Source
AI summary
An imager device includes a pixel sensor configured to receive and convert incident radiation into a pixel signal and a readout circuit configured to receive the pixel signal from the pixel sensor, generate a received signal strength indicator (RSSI) value based on the pixel signal, and generate a digital signal based on the RSSI value and the pixel signal.