Imaging Device Pixel Architecture for Extended Dynamic Range
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Solution Overview
Problem
Conventional imaging devices with global electronic shutter functions face challenges in extending dynamic range and increasing focus detection speed, and they suffer from image quality degradation due to varying exposure times in moving image photography, leading to jerky motion and unnatural subject motion.
Innovation Solution
The imaging device employs a configuration where each pixel includes a photoelectric conversion unit, a holding unit, and an amplifier unit, allowing for the output of signals based on charges generated during different exposure periods, with specific transfer transistors managing the accumulation and transfer of charges to optimize exposure times and reduce image saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If exposure time is changed in each frame to handle luminance changes, then dynamic range is extended, but image quality degrades due to jerkiness and unnatural motion
Solution Approach 1:
The pixel array is divided into a first pixel array and a second pixel array, where the first pixel array captures images during a first exposure period and the second pixel array captures images during a second exposure period. This segmentation allows different exposure times to be applied to different regions, extending dynamic range while maintaining consistent temporal sampling across the entire scene to prevent jerkiness.
Solution Approach 2:
The first and second pixel arrays simultaneously capture images at different exposure times before the frames are combined. By performing the exposure simultaneously at different times rather than sequentially varying exposure within a single array, the system captures the scene state at consistent temporal intervals, preventing motion artifacts while achieving extended dynamic range through the combination of differently exposed images.
2Adaptability or versatility
If multiple exposures with different lengths are used, then dynamic range is extended, but focus detection speed decreases
Solution Approach 1:
The pixel array is segmented into first and second pixel arrays that simultaneously perform exposures of different lengths. This allows the system to capture both short-exposure and long-exposure images at the same time, enabling fast focus detection using the short-exposure images while the long-exposure images extend the dynamic range, without the sequential delay that would slow down focus detection.
3Duration of action of moving object
If charge is accumulated only in the photoelectric conversion unit, then exposure time is limited, but charge overflow occurs with long exposures
Solution Approach 1:
The patent introduces a spatial dimension to charge storage by providing separate first and second pixel arrays that simultaneously perform exposures of different durations. The first pixel array handles short exposures while the second pixel array handles long exposures, effectively adding a temporal dimension to the charge accumulation process. This prevents charge overflow in long exposures by directing those exposures to a dedicated pixel array, while maintaining the ability for extended exposure times through the second array without affecting the first array's short-exposure capability.
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 configuration enables the extension of dynamic range and improvement in focus detection speed, while maintaining image quality by synchronizing exposure times across frames, reducing jerky motion and unnatural subject motion in moving images.
Implementation Method 1
a photoelectric conversion unit that generates charge by photoelectric conversion
Data Source
AI summary
An imaging device includes pixels including a photoelectric conversion unit, a holding unit holding charge transferred from the photoelectric conversion unit, and an amplifier unit outputting signal based on the charge. The pixels output a first signal based on charge generated in a first exposure period and a second signal based on charge generated in a second exposure period of different length. In the first exposure period, the photoelectric conversion unit accumulates the generated charge, and charge held by the holding unit is transferred to the amplifier unit. The second exposure period includes a period of accumulating the generated charge only in the photoelectric conversion unit and a period of holding the generated charge in the photoelectric conversion unit and the holding unit. In the period of accumulating the generated charge only in the photoelectric conversion unit, the charge held by the holding unit is transferred to the amplifier unit.