Imaging System Pixel Group Exposure Control for Distance Measurement
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Solution Overview
Problem
Conventional imaging sensors face challenges in capturing images with uniform signal-to-noise ratios across dark and light areas, leading to inaccurate distance measurements due to varying illumination and reflectivity, resulting in a larger spread of distance measurements for dark areas.
Innovation Solution
The imaging system employs pixel groups with programmable memory elements and a trigger generator to control exposure time, allowing for different accumulation cycles for dark and light areas, thereby enhancing the signal-to-noise ratio and reducing the difference between signal-to-noise ratios in images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If short exposure time is used, then saturation of light areas is avoided, but signal-to-noise ratio of dark areas becomes much lower
Solution Approach 1:
The imaging sensor is divided into multiple pixel groups, each capable of independent exposure control. This segmentation allows different accumulation cycles to be applied to different regions, enabling light areas to use shorter exposure times while dark areas use longer accumulation times, thus resolving the contradiction between avoiding saturation and maintaining signal-to-noise ratio.
Solution Approach 2:
The system dynamically adjusts the number of accumulation cycles for each pixel group based on local illumination conditions. The trigger generator controls the reset signals and transfer signals to enable dynamic exposure time adjustment, allowing the system to adapt exposure parameters in real-time to different scene conditions, thereby resolving the fixed exposure time limitation.
2Measurement precision
If long exposure time is used, then signal-to-noise ratio of dark areas is improved, but saturation occurs in light areas
Solution Approach 1:
Different pixel groups are assigned different numbers of accumulation cycles according to their local illumination characteristics. Dark areas receive more accumulation cycles to improve signal-to-noise ratio, while light areas receive fewer cycles to avoid saturation. This local quality differentiation resolves the contradiction by tailoring exposure parameters to specific scene regions.
3Device complexity
If uniform exposure time is used for all pixel groups, then device complexity is reduced, but difference of signal-to-noise ratio between dark and light areas increases
Solution Approach 1:
The trigger generator serves multiple functions: it generates reset signals, transfer signals, and controls the accumulation cycles for all pixel groups. This multi-functional design enables differentiated exposure control across pixel groups without requiring separate control circuits for each region, thus resolving the contradiction between device complexity and measurement precision uniformity.
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 precise measurement of electromagnetic radiation from both dark and light areas, reducing the spread of distance values and improving the accuracy of distance measurements.
Implementation Method 1
the photodiode is configured to accumulate a charge when it is electromagnetically irradiated
Data Source
AI summary
Imaging system includes pixel groups and a trigger generator to generate reset signals and a transfer signal. Each pixel group includes pixels and a programmable memory element to store a first or a second value. Each pixel includes a pixel circuit with a photodiode and a storage capacitance. The pixel circuit, the trigger generator, and the memory element are interconnected to permit the photodiode to be held at a constant voltage when the trigger generator sends the reset signal to the pixel circuit. When the reset signal is switched off, the photodiode accumulates a charge while being irradiated. When the transfer signal is received, the charge is transferred to the storage capacitance. The memory element blocks the transfer signal from arriving on all the pixel circuits when it has stored the first value and passes the transfer signal to all the pixel circuits when it has stored the second value.