CMOS Image Sensor Pixel Layout for Flicker Pulse Detection
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Solution Overview
Problem
CMOS image sensors face challenges in accurately capturing images of light sources with varying pulse rates, as existing technologies struggle to match the detection rate of the sensor with the pulse rate of the light source, leading to missed pulses and inaccurate image representation.
Innovation Solution
The implementation of a CMOS image sensor design that includes large photodiodes (LPDs) and small photodiodes (SPDs) with different capture rates, along with a flicker reduction layer that absorbs or reflects incident light, allowing for increased detection duration while reducing the risk of saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the detection duration is increased to capture more light pulses, then the accuracy of image capture improves, but the photodiode becomes saturated more easily, reducing reliability
Solution Approach 1:
The pixel array is divided into two distinct types of pixels: first pixels with first photodiodes having a first detection duration, and second pixels with second photodiodes having a second detection duration. This segmentation allows different regions to handle different pulse rates, resolving the contradiction between capturing enough pulses (longer detection) and avoiding saturation (shorter detection).
Solution Approach 2:
Different pixels are assigned different detection durations based on their local requirements. First pixels are configured with one detection duration while second pixels have another, allowing each region to be optimized for its specific function - some areas prioritize capturing low-frequency pulses while others handle high-frequency signals without saturation.
2Device complexity
If a single detection duration is used for all pixels, then device complexity is reduced, but the sensor cannot accurately capture light sources with varying pulse rates, worsening measurement precision
Solution Approach 1:
The pixel array is segmented into first pixels and second pixels with different detection durations, enabling the sensor to handle multiple pulse rates simultaneously. This segmentation resolves the contradiction by allowing specialized regions rather than requiring a complex adjustable mechanism for each pixel.
Solution Approach 2:
The image sensor achieves multi-functionality by incorporating pixels with different detection durations, allowing a single sensor to accurately capture both low-frequency and high-frequency light pulses without requiring separate sensors or complex adjustable mechanisms.
3Manufacturing precision
If all pixels have the same detection duration, then manufacturing precision requirements are simplified, but the sensor fails to handle varying pulse rates effectively, reducing adaptability
Solution Approach 1:
The manufacturing process is segmented to create two types of pixels with different detection durations. This approach maintains relatively simple manufacturing requirements compared to creating fully adjustable pixels, while still achieving the adaptability to handle various pulse rates through the segmented architecture.
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 design enhances the detection duration of the image sensor, reducing the likelihood of missing pulses from light sources and improving the accuracy of captured images by allowing the sensor to handle a wider range of pulse rates.
Implementation Method 1
a flicker reduction layer that absorbs or reflects incident light
Implementation Method 2
a flicker reduction layer that absorbs or reflects incident light
Implementation Method 3
As the photodiode receives incident light, an electrical charge is induced in the photodiode. Each photodiode generates electrons proportional to the amount of light incident on the pixel.
Data Source
AI summary
An image sensor includes a substrate. The image sensor includes a first photodiode (PD) having a first size in the substrate. The image sensor further includes a second PD having a second size in the substrate, wherein the first size is different from the second size. The image sensor further includes a first layer, wherein the first layer comprises a metal material or a dielectric material, and the first layer defines sidewalls of a first recess aligned with the first PD. The image sensor further includes a second layer in the first recess, wherein a portion of the first layer aligned with the second PD is free of the second layer, and the second layer overhangs the first layer.