Shared Pixel Isolation Gate for Phase Detection Linearity

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Solution Overview

Problem

Existing phase detection autofocus systems in imaging devices suffer from poor low light performance and signal linearity issues due to inadequate isolation between photodiodes in recta shared pixels, which affects both autofocus accuracy and imaging quality.

Innovation Solution

Implementing a variable potential barrier controlled by a control gate between the photodiodes of recta shared pixels, allowing for high isolation in autofocus mode and low isolation in imaging mode, using a control gate to adjust the separation ratio and promote accurate phase detection and signal linearity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If great isolation between photodiodes is provided, then phase detection autofocus accuracy is improved, but signal linearity deteriorates due to charge overflow to floating diffusion

Engineering Contradiction:

Improvephase detection autofocus accuracyVSAvoidsignal linearity

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies the dynamics principle by making the isolation barrier height variable rather than fixed. A control gate is introduced that can dynamically adjust the potential barrier height between photodiodes based on operating mode. During autofocus mode, the barrier is raised to provide high isolation for accurate phase detection. During imaging mode, the barrier is lowered to allow charge sharing between photodiodes, maintaining signal linearity and preventing overflow to floating diffusion.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If physical masks are used to separate pixels, then phase detection capability is enabled, but low light performance deteriorates

Engineering Contradiction:

Improvephase detection capabilityVSAvoidlow light performance

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The patent applies parameter changes by modifying the electrical potential parameters rather than using physical masks. Instead of fixed physical separators that block light, the invention uses controllable potential barriers that can be raised or lowered electronically. This allows the system to achieve pixel separation for phase detection when needed, while maintaining full light sensitivity during imaging operations by lowering the barriers.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If recta shared pixels are used for phase detection, then autofocus points can be provided across all image areas, but isolation control between sub-pixels becomes critical for dual-mode operation

Engineering Contradiction:

Improveautofocus coverageVSAvoidisolation control mechanism

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies universality by designing recta shared pixels that can function in multiple modes. The same pixel structure serves both phase detection autofocus and imaging functions. The control gate mechanism enables the pixel to adapt its isolation characteristics based on the required operation, making a single pixel type versatile enough to replace dedicated autofocus and imaging pixels.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 enables accurate phase detection autofocus and improved signal linearity in imaging mode by maintaining high isolation during autofocus operations and reducing isolation during imaging, enhancing overall performance of the imaging device.

Implementation Method 1

control of the signal isolation between the individual photodiodes of a recta phase detection pixel is enabled by the creation of a variable potential barrier. More particularly, a control gate is disposed adjacent to the potential barrier between the individual photodiodes

Methodology Applied

Scientific EffectPotential barrier control: Electric Field

Implementation Method 2

Each recta shared pixel can include first and second (e.g. left and right or top and bottom) sub-pixels or photodiodes

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Data Source

PatentUS20250318293A1Imaging sensor and device with gate controlled isolation between shared pixels

Publication Date: 2025.10.09 SONY SEMICON SOLUTIONS CORP

AI summary

An imaging device including a plurality of recta shared pixels in which a potential barrier between the photoelectric conversion units of the recta shared pixels is controlled by a control gate. In a default mode, a first voltage is supplied to the control gate to establish an amount of separation between the photoelectric conversion units of the recta shared pixels that is lower or the same as or only slightly larger than the separation established by an intra-pixel separation structure. In another mode, a second voltage is supplied to the control gate to establish an amount of separation between the photoelectric conversion units of the recta shared pixels that is greater than in the default mode. The default mode is maintained during image acquisition, while the other mode is applied only during generation of charge by the photoelectric conversion units during phase detection autofocus operations.