Parabolic PDAF Pixel Structure for Low-Light Phase Detection

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Solution Overview

Problem

Existing PDAF pixels in digital cameras face challenges in generating accurate phase disparity signals, particularly under low light conditions, and their placement on color channels can impact image quality.

Innovation Solution

The use of parabolic-shaped microlenses in PDAF pixels, oriented differently to generate phase disparity signals in horizontal and vertical directions, and placement on green or blue color channels with potential replacement of blue filters by green filters, enhances autofocus performance and maintains image quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If PDAF pixels are placed on color channels in traditional configurations, then autofocus functionality is provided, but image quality degradation occurs

Engineering Contradiction:

Improveautofocus functionalityVSAvoidimage quality

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies local quality by placing PDAF pixels specifically on green color channels rather than uniformly distributing them across all color channels. This localized placement optimizes the balance between autofocus functionality and image quality, as green channels provide sufficient luminance information for focus detection while minimizing impact on overall image quality.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent inverts the traditional approach by replacing blue color filters with green color filters in PDAF pixel locations. This inversion allows the PDAF pixels to function effectively for autofocus while maintaining better image quality, as green filters provide superior luminance response compared to blue filters.

Inventive Principle:

Principle #13The other way round (Inversion)

2Device complexity

If conventional microlens configurations are used in PDAF pixels, then device simplicity is maintained, but phase disparity signal accuracy deteriorates under low light conditions

Engineering Contradiction:

Improvepixel structureVSAvoidphase disparity signal accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent employs parabolic-shaped microlenses instead of conventional spherical microlenses in PDAF pixels. The parabolic curvature optimizes light focusing properties, improving the accuracy of phase disparity signal generation particularly under low light conditions, while maintaining relatively simple device structure.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 improves autofocus accuracy and signal-to-noise ratio, enabling fast and accurate focus across varied scenes and lighting conditions while minimizing image quality degradation.

Implementation Method 1

a photodiode

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 2

a color filter disposed on the photodiode

Methodology Applied

Scientific EffectOptical absorption: Absorption (EM radiation)

Implementation Method 3

a parabolic-shaped microlens disposed on the color filter and oriented in a direction that generates an angular response

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS12568705B2Phase detection autofocus pixel

Publication Date: 2026.03.03 APPLE INC

AI summary

Embodiments are disclosed for a Phase Detection Autofocus (PDAF) pixel, including a photodiode; a color filter disposed on the photodiode; and a parabolic-shaped microlens disposed on the color filter and oriented in a direction that generates an angular response, such that a phase disparity signal is generated in a horizontal or vertical direction of an imaging plane or both directions.