Per-Pixel Exposure Control for High Dynamic Range Image Sensors
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Solution Overview
Problem
Conventional image sensors, particularly CMOS sensors, face challenges in achieving high dynamic range imaging due to limited well-capacity and fixed exposure times, requiring multiple successive exposures and compromising on frame rate and spatial resolution.
Innovation Solution
A highly-programmable exposure control and read out architecture that allows individual in-frame exposure control for each pixel cell across the pixel array, using multi-bit resolution and eliminating the need for multi-frame combinations or down-sampling, enabling improved charge integration and high frame rate with high spatial resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple successive exposures are used to achieve HDR, then dynamic range is improved, but frame rate deteriorates
Solution Approach 1:
The patent implements per-pixel programmable exposure control that allows each pixel to have a different exposure time within a single frame. This dynamic control enables the system to capture both bright and dark regions simultaneously with optimized exposure times, achieving HDR效果 without requiring multiple frames, thus maintaining high frame rate while improving dynamic range
Solution Approach 2:
The patent applies different exposure times to different pixels based on their local lighting conditions. Bright regions use shorter exposure times to avoid saturation, while dark regions use longer exposure times to capture sufficient signal. This local optimization allows simultaneous capture of high and low light levels in a single frame, resolving the contradiction between dynamic range and frame rate
2Illumination intensity
If multiple successive exposures are used to achieve HDR, then dynamic range is improved, but spatial resolution deteriorates
Solution Approach 1:
By implementing dynamic per-pixel exposure control within a single frame, the patent eliminates the need for multiple frame captures. This ensures that all pixels capture image data at the same moment, avoiding misalignment issues that would degrade spatial resolution, while still achieving HDR through localized exposure time optimization
Solution Approach 2:
The patent applies local exposure time optimization to each pixel based on its specific lighting conditions without requiring multiple frames. This local control approach maintains consistent spatial positioning across all pixels, preserving spatial resolution while achieving the desired dynamic range enhancement
3Device complexity
If fixed exposure times are used, then device complexity is reduced, but adaptability to varying light conditions deteriorates
Solution Approach 1:
The patent changes the exposure time parameter on a per-pixel basis within a single frame, allowing adaptation to different light conditions. By programming different exposure times for different pixels, the system achieves high adaptability to varying illumination levels without requiring complex multi-frame capture mechanisms, thus balancing device complexity with adaptability
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 solution achieves optimal operation of each pixel cell, providing high dynamic range imaging without sacrificing frame rate or spatial resolution, effectively addressing the limitations of traditional image sensors.
Implementation Method 1
a photodiode adapted to accumulate image charge in response to incident light
Data Source
AI summary
A method of controlling a pixel array includes reading out image data from pixel cells of a row i of the pixel array with second transfer control signals that are coupled to be received by transfer transistors included in the pixels cells of the row of the pixel array that is being read out. Exposure times for pixel cells are independently controlled in other rows of the pixel array that are not being read out with first transfer control signals coupled to be received by transfer transistors included in the pixel cells in the other rows of the pixel array that are not being read out while the image data is read out from the pixel cells of row i of the pixel array.