Pixel Layout for HDR Photoelectric Conversion With Lower Signal Loss
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Solution Overview
Problem
In photoelectric conversion devices, signal loss occurs due to light entering the floating diffusion near the center of pixels, particularly when high-sensitivity and low-sensitivity photoelectric conversion units are arranged close to each other, leading to inefficiencies in charge transfer and image generation.
Innovation Solution
A photoelectric conversion device configuration with a substrate featuring a first and second high-sensitivity photoelectric conversion unit aligned in a direction, and a third low-sensitivity unit positioned along the outer circumference, along with a microlens and transfer transistors, reduces signal loss by minimizing light incidence on transfer transistors and the floating diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the floating diffusion is arranged between high-sensitivity and low-sensitivity photoelectric conversion units, then charge transfer can be achieved, but light enters the floating diffusion causing signal loss
Solution Approach 1:
The patent relocates the floating diffusion from a central position to a peripheral position along the outer circumference of the pixel. This spatial reconfiguration in the planar dimension separates the light collection path from the charge transfer path, allowing light to be guided to photoelectric conversion units without entering the floating diffusion, thereby eliminating signal loss while maintaining charge transfer functionality.
Solution Approach 2:
The patent introduces a microlens as an intermediary optical element that guides light from the incident surface to the photoelectric conversion units. The microlens focuses and directs light rays away from the floating diffusion region, enabling efficient light collection while preventing light from entering the floating diffusion, thus resolving the conflict between charge transfer and signal preservation.
2Adaptability or versatility
If high-sensitivity and low-sensitivity photoelectric conversion units are arranged close to each other, then high-dynamic range imaging can be achieved, but light guidance to the center causes signal loss
Solution Approach 1:
The patent redistributes photoelectric conversion units and the floating diffusion along the peripheral region of the pixel in a planar configuration. This spatial arrangement allows multiple photoelectric conversion units with different sensitivities to be positioned along the outer circumference, enabling high-dynamic range imaging while directing light away from the centrally located floating diffusion to prevent signal loss.
Solution Approach 2:
The patent assigns different sensitivities to different photoelectric conversion units positioned at specific locations along the outer circumference. High-sensitivity units and low-sensitivity units are strategically placed to optimize their respective functions, with each unit's characteristics matched to its position and light reception characteristics, thereby achieving high-dynamic range imaging without compromising signal integrity.
3Productivity
If transfer transistors are positioned near the center of the pixel, then charge transfer is efficient, but light enters the transfer transistors causing signal loss
Solution Approach 1:
The patent repositions transfer transistors from central locations to peripheral locations along the outer circumference of the pixel. This spatial relocation separates the charge transfer function from the light collection path, allowing transfer transistors to efficiently collect charges from photoelectric conversion units while being positioned outside the primary light guidance path, thus preventing light from entering the transistors and causing signal loss.
Solution Approach 2:
The patent uses the microlens system as an intermediary to control light paths, directing light away from peripheral components including transfer transistors. The microlens focuses light onto photoelectric conversion units while creating optical isolation from surrounding components, enabling transfer transistors to be positioned efficiently without compromising signal integrity by preventing light contamination.
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 enhances charge transfer efficiency and reduces signal loss, enabling improved high-dynamic range imaging and phase difference detection, even under high-intensity light conditions.
Implementation Method 1
a microlens arranged over the substrate commonly to the first photoelectric conversion unit, the second photoelectric conversion unit, and the third photoelectric conversion unit
Implementation Method 2
a first photoelectric conversion unit, a second photoelectric conversion unit, and a third photoelectric conversion unit each arranged in the substrate and configured to generate charges based on incident light
Data Source
AI summary
In a photoelectric conversion device, a first photoelectric conversion unit and a second photoelectric conversion unit are arranged so as to be aligned in a first direction in a plan view with respect to a substrate, the sensitivity of a third photoelectric conversion unit is lower than the sensitivity of the first photoelectric conversion unit and lower than the sensitivity of the second photoelectric conversion unit, and the third photoelectric conversion unit is arranged along a part of the outer circumference of a region including the first photoelectric conversion unit and the second photoelectric conversion unit in the plan view.