High Dynamic Range Imager Rolling Shutter Integration
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Solution Overview
Problem
Conventional semiconductor imagers face challenges in capturing images over a high dynamic range of brightness levels, leading to issues of overexposure at high brightness and underexposure at low brightness due to the light sensitive element producing excessive or insufficient photo-generated charges.
Innovation Solution
The imager employs both short and long integration periods for each pixel, allowing different rows to be at various stages of integration, with parallel signal paths for reading analog pixel signals and generating corresponding digital values that are linear functions of incident light, using a modified pixel reading circuit with separate sample and hold circuits and differential amplifiers for each integration period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single integration period is used for each pixel, then the pixel reading circuit is simple, but the imager cannot capture high dynamic range of brightness levels
Solution Approach 1:
The patent divides the integration period into multiple segments (first integration period and second integration period) to capture different brightness ranges. The pixel array is divided into first and second pixel arrays, with different rows undergoing different integration periods simultaneously, enabling high dynamic range capture while maintaining manageable circuit complexity through systematic segmentation.
Solution Approach 2:
The patent introduces a temporal dimension by implementing multiple integration periods sequentially. Different rows are assigned different integration periods (first and second integration periods) that overlap in time, adding a time-based dimension to the traditional spatial pixel array structure, thereby enabling high dynamic range without proportionally increasing circuit complexity.
2Measurement precision
If a long integration period is used, then low brightness conditions are improved, but high brightness conditions cause overexposure
Solution Approach 1:
The patent implements dynamic integration periods where different rows of the pixel array undergo different integration durations simultaneously. The first integration period and second integration period are temporally overlapping and can be adjusted independently, allowing the system to adapt to varying brightness conditions across different regions of the image without fixed constraints.
Solution Approach 2:
The patent changes the integration period parameter dynamically across different rows and time periods. By varying the integration period length based on the specific brightness conditions being captured, the system optimizes measurement precision for both low and high brightness conditions, preventing overexposure in bright areas while maintaining sensitivity in dark areas.
3Adaptability or versatility
If a short integration period is used, then high brightness conditions are prevented from overexposing, but low brightness conditions result in underexposure
Solution Approach 1:
The patent segments the pixel array into first and second pixel arrays with different integration periods. The first integration period is optimized for high brightness conditions while the second integration period is optimized for low brightness conditions, allowing each segment to operate at its optimal parameter setting without compromising the other.
Solution Approach 2:
The patent employs dynamic integration periods that can be independently controlled for different rows. By making the integration period adjustable and variable across different spatial regions and time periods, the system adapts to local brightness conditions, preventing overexposure in bright areas while avoiding underexposure in dark areas.
4Adaptability or versatility
If multiple integration periods are implemented for each pixel, then high dynamic range is achieved, but the pixel reading circuit complexity increases
Solution Approach 1:
The patent segments the pixel array into distinct first and second pixel arrays that can be processed independently through separate reading circuits. This segmentation allows multiple integration periods to be handled in parallel by different circuits, reducing the complexity burden on any single pixel reading circuit while achieving high dynamic range through the combined output of multiple circuits.
Solution Approach 2:
The patent resolves the complexity issue by adding a temporal and spatial dimension to the integration periods. Instead of having multiple integration periods compete for resources within a single pixel reading circuit, the system distributes different integration periods across different pixel arrays and time slots, effectively moving the complexity problem to a higher dimensional space where it can be managed more efficiently.
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 the imager to maintain linear operation across a wide dynamic range, minimizing kTC noise and ensuring that pixel output signals are suitable for high and low brightness conditions, with the ability to process digital values from both integration periods to produce a representation of the image with improved dynamic range.
Implementation Method 1
The light sensitive element 101 produces and stores charge related to the amount of incident light
Data Source
AI summary
A high dynamic range imager operates pixels utilizing at least a short integration period and a long integration period. The pixel reading circuits of the imager are adapted to process pixel signals corresponding to the integration periods in parallel. The pixel signals are converted into digital values in parallel. The digital values are each linear functions of the incident light and therefore suitable for use with conventional color processing algorithms. A pipelined rolling shutter operation may be employed where the short integration period of one row of pixels is performed simultaneously with the long integration period of another row of pixels.