Image Sensor Pixel Unit Time-Overlapped Sampling
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Solution Overview
Problem
Current image sensors face challenges in temporally correct sampling due to their relatively short exposure time acting as a low-pass filter, leading to aliasing effects and inadequate sampling frequency, which is particularly problematic in applications requiring high-frequency signal capture like video-based driver assistance systems.
Innovation Solution
A pixel unit for image sensors is designed with a multiplexer unit and storage devices to generate and buffer multiple time-limited integral values of signals, allowing for time-overlapped sampling and reconstruction of images, effectively adapting the low-pass filter to achieve temporally correct sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the exposure time is extended to capture high-frequency light signals, then the signal capture capability is improved, but temporal aliasing effects (rolling shutter, wagon wheel artifacts) occur due to incorrect sampling
Solution Approach 1:
The pixel unit is segmented into multiple storage units (first storage unit, second storage unit, etc.) that separately buffer time-limited integral values of multiplexer signals generated at different time instants. This segmentation allows the system to capture multiple temporal samples within a single exposure period, enabling correct temporal sampling of high-frequency light signals without aliasing effects.
2Reliability
If multiple storage units are added to enable time-overlapped sampling, then temporal sampling accuracy is improved, but device complexity increases
Solution Approach 1:
The multiplexer unit serves multiple functions: it generates multiple multiplexer signals from a single processing signal, enables time-overlapped sampling across different storage units, and facilitates temporal reconstruction of light signals. This multi-functionality reduces the need for separate dedicated components for each sampling function, thereby limiting the increase in device complexity.
3Productivity
If the exposure time is shortened to increase frame rate, then productivity is improved, but measurement precision of light signals deteriorates
Solution Approach 1:
The pixel unit continuously generates multiple multiplexer signals at different time instants during the exposure period and buffers their time-limited integral values in separate storage units. This continuous sampling approach allows the system to maintain high frame rates while capturing sufficient temporal information to reconstruct light signals with high precision, even with short exposure times.
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 enables aliasing-free sampling and improved optical flow quality by ensuring the sampling frequency meets the Nyquist-Shannon criteria, reducing aliasing effects and allowing for longer exposure times without compromising frame rates, thus enhancing image quality in applications with rapid scene changes.
Implementation Method 1
a possibly complex photodiode for converting a light signal into a processing signal
Data Source
AI summary
A pixel unit for an image sensor. The pixel unit includes a photodiode for converting alight signal into a processing signal, a multiplexer unit that is designed for using the processing signal to generate at least a first multiplexer signal and a second multiplexer signal that deviates therefrom, and a storage device having at least a first storage unit for buffer storing a time-limited integral value of the first multiplexer signal and a second storage unit for buffer storing a time-limited integral value of the second multiplexer signal. The pixel unit makes possible a time-overlapped sampling of the first multiplexer signal and of the second multiplexer signal.