Image Sensor Dynamic Range Enrichment via Overlapped Readout
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Solution Overview
Problem
CMOS imaging sensors face limitations in dynamic range due to signal chain constraints, leading to increased noise and reduced scalability to higher resolutions, with existing solutions either increasing circuit complexity or requiring additional camera processing, which adds cost and complexity.
Innovation Solution
A method and apparatus that enhance dynamic range by taking additional exposures during signal readout, controlled by a timing controller, and combining these exposures with base exposure signals using algorithms such as scaling and filtering, while maintaining low noise and scalability through on-chip processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If additional exposures are taken during signal readout to enhance dynamic range, then dynamic range is enriched by up to 20×log(2N) dB, but readout time and processing complexity increase
Solution Approach 1:
The patent performs additional exposures during the signal readout period of previous rows, utilizing time that would otherwise be wasted. By the time row 0's signal needs to be read, rows 1-4 have already completed their exposures and are ready for readout, effectively parallelizing operations to avoid time loss.
Solution Approach 2:
The patent maintains continuous useful action by overlapping the exposure phase of subsequent rows with the readout phase of previous rows. This ensures that the sensor array is always either exposing or reading, eliminating idle time and maximizing productivity.
2Loss of information
If additional signal processing and memory storage are implemented to combine exposures, then dynamic range is enhanced, but device complexity increases
Solution Approach 1:
The patent divides the dynamic range enhancement process into discrete segments: base exposure signal, additional exposure signals from different rows, and their weighted combination. This segmentation allows independent optimization of each component and simplifies the overall architecture by breaking down the complex task into manageable parts.
Solution Approach 2:
The patent makes the additional exposure signals serve multiple functions: they extend dynamic range for their native row while also providing enhancement data for previous rows. This multi-functionality reduces the need for separate processing paths and minimizes overall device complexity.
3Ease of manufacture
If on-chip processing is used to maintain scalability to higher resolutions, then manufacturing cost is reduced, but circuit complexity increases
Solution Approach 1:
The patent merges the dynamic range enhancement functionality with the existing readout circuitry by integrating additional exposure capture and signal combination operations into the standard signal path. This consolidation avoids adding separate processing subsystems and keeps the architecture scalable.
Solution Approach 2:
The patent introduces dynamic timing control to coordinate multiple exposures and readout operations. The timing controller dynamically adjusts exposure durations and readout schedules based on row index and signal readiness, enabling flexible operation without hardwiring complex control logic.
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 effectively enriches the dynamic range of CMOS imaging sensors by up to 20×log(2N) dB, extending the nominal 12-bit range to 16 bits, with minimal added complexity and power consumption, maintaining high performance and reducing noise, and is compatible with both rolling and global shutter operations.
Implementation Method 1
Each pixel element Pi,j of the imager includes a photodetector
Data Source
AI summary
A method and apparatus for an electronic image sensor having a base exposure, followed by a second or multiple exposures that are formed during signal readout. A timing controller controls the signal readout, such that as each line is read, the second and subsequent exposures are subsequently added to the base exposure to enrich the dynamic range. The image sensor may further include an analog-to-digital converter and noise suppression to further enhance the efficacy of the dynamic range enrichment. The system may also include additional signal processing and scaling functions.