Phase-Detection Pixel Overflow Path for Higher Saturation Charge
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Solution Overview
Problem
Conventional imaging elements experience a decrease in saturation charge amounts for photoelectric conversion sections when generating phase difference signals, leading to a narrowed detectable range and reduced convenience.
Innovation Solution
An imaging element with a pixel structure that includes photoelectric conversion sections, an intra-pixel separator, an overflow path, an overflow gate, a charge holding section, and charge transfer sections to manage and transfer charges effectively, preventing charge overflow and maintaining image signal linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the potential barrier of the semiconductor region between two photoelectric conversion sections is lowered to move charges between sections, then charge transfer between sections is improved, but the saturation charge amount of each photoelectric conversion section decreases
Solution Approach 1:
The pixel is divided into two independent photoelectric conversion sections with separate charge storage regions, allowing each section to maintain its own saturation charge amount while providing a dedicated overflow path for charge transfer between sections
Solution Approach 2:
An overflow path with an overflow gate is introduced as an intermediary mechanism between the two photoelectric conversion sections. This mediator allows charge transfer when needed while maintaining separate charge storage capacities, resolving the contradiction between charge transfer capability and saturation charge amount
2Adaptability or versatility
If the saturation charge amount is increased to widen the detectable phase difference range, then the detectable range is improved, but charge overflow to adjacent pixels occurs causing image signal errors
Solution Approach 1:
The overflow path extracts excess charges from the photoelectric conversion section before they can overflow into adjacent pixels. By providing a dedicated escape route for overflow charges, the system can handle larger charge amounts without causing image signal errors
Solution Approach 2:
The potential harmful charge overflow to adjacent pixels is converted into a beneficial feature by directing it through a controlled overflow path. The overflow that would normally cause errors is now utilized to transfer charges between sections for phase difference detection
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
The solution enhances the saturation charge capacity and linearity of image signals, widening the phase difference detectable range and improving convenience by effectively managing charge overflow within the imaging element.
Implementation Method 1
a pixel including a plurality of photoelectric conversion sections that is formed on a semiconductor substrate and performs photoelectric conversion of incident light from a subject to generate a charge
Data Source
AI summary
To prevent a decrease in a saturation charge when a phase difference signal is generated. A pixel includes a plurality of photoelectric conversion sections that is formed on a semiconductor substrate and performs photoelectric conversion of incident light from a subject to generate a charge. An intra-pixel separator separates the plurality of photoelectric conversion sections. An overflow path in the intra-pixel separator transfers charges overflowed in the plurality of photoelectric conversion sections to each other. An overflow gate in the pixel and adjusts a potential of the overflow path. A pixel separator is disposed at a boundary between the pixels. A charge holding section holds the generated charge. A charge transfer section is disposed one-by-one for the plurality of photoelectric conversion sections and transfers the generated charge to the charge holding section. An image signal generating section generates an image signal on the basis of the generated charge.