Pixel Photosites with Multiple Integration Times
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Solution Overview
Problem
Imaging devices with matrix networks of photosites face challenges in capturing clear signals under varying light intensities, as high-intensity light can saturate photosites, requiring longer exposure times or larger pixel sizes, which compromise image quality.
Innovation Solution
The implementation of pixels with multiple photosites of different light sensitivities, where charges are accumulated for distinct integration times, allowing for the selection of unsaturated signals across a wide range of light intensities, and post-processing to normalize and digitize the signals effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the exposure time is extended to capture low-intensity light, then the signal strength is improved, but photosite saturation occurs under high-intensity light
Solution Approach 1:
The pixel is divided into multiple photosites with different integration times. Each photosite is optimized for specific light intensity ranges, allowing the system to segment the dynamic range capture task across multiple specialized sensors rather than using a single photosite for all conditions.
Solution Approach 2:
The integration time parameter is varied across different photosites within the same pixel. By having photosites with different integration times (e.g., short, medium, long exposure), the system can adapt to different light intensities without saturation by selecting the appropriate photosite based on current lighting conditions.
2Adaptability or versatility
If multiple photosites with different integration times are implemented, then the dynamic range is improved, but the pixel size increases
Solution Approach 1:
Multiple photosites with different integration times are merged within a single pixel structure, sharing common readout circuitry and control logic. This combining approach allows the system to achieve extended dynamic range while maintaining compact pixel dimensions by reusing shared resources rather than implementing completely separate sensor structures.
Solution Approach 2:
The pixel structure is designed with multi-functionality, where a single pixel contains photosites that can handle different light intensity conditions. The shared readout circuitry and control mechanisms serve multiple photosites with different integration times, making the pixel structure universally capable of handling various imaging conditions without requiring separate dedicated structures for each function.
3Use of energy by moving object
If multiple photosites are coupled together to increase sensitive area, then the sensitivity to low-intensity light is improved, but the image definition is reduced
Solution Approach 1:
The sensitive area is segmented into multiple photosites with different integration times rather than combining them into a single large photosite. This segmentation allows each photosite to maintain its own charge storage and readout capabilities, preserving spatial resolution while still benefiting from the combined sensitivity of multiple photosites through intelligent signal selection.
Solution Approach 2:
Different photosites within the pixel are assigned different integration times based on their local quality characteristics. Each photosite is optimized for specific light intensity ranges, with longer integration times for low-intensity conditions and shorter times for high-intensity conditions, allowing local optimization without compromising overall image definition.
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 imaging devices to capture unsaturated signals across a wide range of light intensities, preventing saturation and maintaining image quality without increasing pixel size, thus enhancing sensitivity and definition.
Implementation Method 1
The imaging device makes use of the photoelectric effect. The photons sensed by a photodiode of a photosite are converted into electron/hole pairs.
Data Source
AI summary
A method for controlling a pixel may include first and second photosites, each having a photodiode and a charge-transfer transistor, a read node, and an electronic read element, all of which are common to all the photosites. The method may include an accumulation of photogenerated charges in the photodiode of the first photosite during a first period, an accumulation of photogenerated charges in the photodiode of the second photosite during a second period shorter than the first period, a selection of the signal corresponding to the quantity of charges accumulated in the photodiode of a photosite having the highest unsaturated intensity or else a saturation signal, and a digitization of the selected signal.