Image Sensor Dynamic Exposure Control for High Dynamic Range
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Solution Overview
Problem
Conventional image sensors face challenges in automatically adjusting exposure time based on light intensity, leading to issues like blown-out highlights and limited dynamic range.
Innovation Solution
The image sensor incorporates a light receiving element with a semiconductor structure that includes a first and second conductivity type semiconductor layer, insulation, and a gate electrode, allowing for automatic adjustment of exposure time through a current readout unit and voltage control, enabling dynamic range expansion without manual exposure time control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If exposure time is lengthened to improve sensitivity, then more light is accumulated, but charge exceeds upper limit value causing blown-out highlights
Solution Approach 1:
The patent applies dynamics by making the exposure time variable rather than fixed. The exposure time is dynamically adjusted based on the intensity of incident light, automatically shortening when light intensity is high and extending when light intensity is low, thereby preventing blown-out highlights while maintaining sensitivity
Solution Approach 2:
The patent implements feedback control where the exposure time is automatically adjusted based on detection of light intensity and accumulated charge levels. The system monitors the charge accumulation in real-time and modifies exposure parameters accordingly to maintain optimal imaging conditions
2Reliability
If exposure time is shortened to prevent blown-out highlights, then highlight accuracy is improved, but sensitivity decreases and dynamic range is limited
Solution Approach 1:
The patent uses dynamic exposure time adjustment that adapts to varying light conditions. Rather than using a fixed short exposure time, the system dynamically extends or shortens exposure based on actual light intensity, thereby maintaining both sensitivity and highlight accuracy
Solution Approach 2:
The patent changes the exposure time parameter based on detected light intensity and charge accumulation levels. By adjusting this critical parameter dynamically, the system expands its dynamic range and maintains sensitivity across varying lighting conditions while preventing highlight saturation
3Device complexity
If manual exposure time control is used to maintain simplicity, then device complexity is low, but automatic adaptation to light intensity is lost
Solution Approach 1:
The patent implements self-service by enabling the imaging system to automatically adjust its own exposure time based on detected light conditions. The system monitors incident light intensity and charge accumulation, then autonomously modifies exposure parameters without requiring manual intervention, thereby maintaining simplicity while gaining 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 allows for automatic exposure time adjustment, expanding the dynamic range of the image sensor up to 120 dB, improving image quality by preventing blown-out highlights and enhancing sensitivity.
Implementation Method 1
When sensing incident light, each photodiode generates electric current
Implementation Method 2
The at least one light receiving element receives light incident on a junction between the first semiconductor layer and the second semiconductor layer
Data Source
AI summary
A light receiving element includes a first semiconductor layer of a first conductivity type to which a first potential is to be applied, a second semiconductor layer of a second conductivity type formed on the first semiconductor layer, first and second regions of the first conductivity type formed in an upper portion of the second semiconductor layer, a first electrode that is located on the first region and is to be subjected to application of a second potential, a second electrode located on the second region, an insulation layer formed on the second semiconductor layer between the first and the second regions, and a gate electrode that is formed on the insulation layer and is to be subjected to application of a gate voltage. A current readout unit detects, as a pixel signal reflecting an amount of light received, a current flowing from the first region to the second region.