Phase Detection Autofocus Grid with Low Refractive Index Material

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Solution Overview

Problem

Optical image sensors face challenges in phase detection autofocus due to unwanted total internal reflection from composite grids, which reduces angular response sensitivity of phase detection pixels, affecting autofocus performance.

Innovation Solution

Incorporating a composite grid with smaller openings for phase detection components and a low refractive index material, vertically misaligned with microlenses, to reduce reflection and enhance angular discrimination, and using a dielectric grid structure with a refractive index smaller than the color filters to minimize internal reflection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a composite grid is used in optical image sensors, then light sensing and crosstalk reduction are improved, but unwanted total internal reflection occurs that reduces angular response sensitivity of phase detection pixels

Engineering Contradiction:

Improveangular response sensitivityVSAvoidunwanted total internal reflection

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent changes the refractive index parameter of the grid material by using a low refractive index dielectric material instead of conventional higher refractive index materials. This parameter change reduces the refractive index contrast between the grid and surrounding media, thereby minimizing total internal reflection and improving angular response sensitivity of phase detection pixels

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material structures including dielectric grid layers with specific refractive indices, color filters, and phase detection components arranged in a composite grid system. This composite structure allows optimization of optical properties to reduce unwanted reflection while maintaining light sensing and crosstalk reduction functions

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If phase detection pixels are incorporated to enable autofocus, then focus detection capability is improved, but angular response sensitivity is reduced due to internal reflection

Engineering Contradiction:

Improveautofocus capabilityVSAvoidangular response sensitivity

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

By changing the refractive index parameter of the grid material to a lower value, the patent reduces internal reflection effects that otherwise degrade angular response sensitivity, thereby enabling phase detection pixels to maintain high measurement precision while providing autofocus capability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The low refractive index dielectric grid material acts as an intermediary between the microlens array and the photodiode layer, mediating the optical path to reduce unwanted reflection while allowing phase detection components to function effectively for autofocus

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Improves angular response and sensitivity of phase detection pixels, allowing for more precise autofocus by reducing unwanted reflection and increasing the critical angle, resulting in sharper intensity response curves and better focus detection.

Implementation Method 1

unwanted total internal reflection from composite grids, which reduces angular response sensitivity of phase detection pixels

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

a low refractive index material, vertically misaligned with microlenses, to reduce reflection and enhance angular discrimination, and using a dielectric grid structure with a refractive index smaller than the color filters to minimize internal reflection

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS9905605B2Phase detection autofocus techniques

Publication Date: 2018.02.27 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

The present disclosure relates to an image sensor having autofocus function and associated methods. In some embodiments, the integrated circuit has a photodiode array with a plurality of photodiodes disposed within a semiconductor substrate and a composite grid overlying the photodiode array and having a first plurality of openings and a second plurality of openings extending vertically through the composite grid. The integrated circuit further has an image sensing pixel array with a plurality of color filters disposed in the first plurality of openings. The integrated circuit further has a phase detection pixel array having a plurality of phase detection components that are smaller than the plurality of color filters and that have a low refractive index (low-n) material with a refractive index (n) smaller than a refractive index of the plurality of color filters, wherein the phase detection components are disposed in the second plurality of openings.